Nr3en2022

Prof.

Assoc.prof.

Assoc.prof.

Prof.

Prof.

Prof. Mircea

Prof. Pascu Mihai

Lect.

Radu

- MINING REVUE

AJOURNALOF MININGAND ENVIRONMENT

Scientific committee:

Prof. Iosif ANDRAȘ, University of Petrosani, Romania PhD. Eng. Marwan AL HEIB, Ecole des mines de Nancy, INERIS, France Assist. prof. Adam BAJCAR, Poltegor-Instytut, Poland PhD. Eng. Iosif Horia BENDEA, Politechnico di Torino, Italy Assoc. prof. Boyko BEROV, Bulgarian Academy of Sciences, Bulgaria

Prof. Essaid BILAL, Centre Sciences des Processus Industriels et Naturels (SPIN), France Prof. Lucian BOLUNDUȚ, University of Petrosani, Romania Prof. Ioan BUD, Technical University of Cluj-Napoca (North Center of Baia Mare), Romania

Prof. Nam BUI, Hanoi University of Science and Technology, Vietnam PhD. Eng. Constantin Sorin BURIAN, INSEMEX Petrosani, Romania

Prof. Eugen COZMA, University of Petrosani, Romania PhD. Eng. György DEÁK, National Institute for Research and Development in Environmental Protection Prof. Nicolae DIMA, University of Petrosani, Romania

Prof. Carsten DREBENSTEDT, TU Bergakademie Freiberg, Germany

Prof. Ioan DUMITRESCU, University of Petrosani, Romania

PhD. Eng. George-Artur GĂMAN, INSEMEX Petrosani, Romania

Prof. Ioan GÂF-DEAC, Dimitrie Cantemir Christian University Bucharest, Romania

Ph.D. Eng. Edmond GOSKOLLI, National Agency of Natural Resources, Albania

Prof. Andreea IONICĂ, University of Petrosani, Romania

Prof. Sair KAHRAMAN, Hacettepe University, Turkey

Prof. Sanda KRAUSZ, University of Petrosani, Romania

Prof. Krzysztof KOTWICA, AGH University of Science and Technology Krakow, Poland

Prof. Maria LAZAR, University of Petrosani, Romania

Prof. Monica LEBA, University of Petrosani, Romania

Prof. Roland MORARU, University of Petrosani, Romania PhD. Eng. Vlad Mihai PĂSCULESCU, INSEMEX Petrosani, Romania

Prof. Sorin Mihai RADU, University of Petrosani, Romania

Prof. Ilie ROTUNJANU, University of Petrosani, Romania

Prof. Mihaela TODERAȘ, University of Petrosani, Romania

Assoc. prof. Sorin Silviu UDUBAȘA, University of Bucharest, Romania

Prof. Ioel VEREȘ, Technical University of Cluj-Napoca, Romania

Assoc. prof. Zoltan Istvan VIRÁG, University of Miskolc, Hungary Prof. Florin Dumitru POPESCU, University of Petrosani, Romania

CONTENTS

Rickard HANSEN

The throttle effect blower fan versus exhaust fan 1

Zoltán VIRÁG

Finite element analysis of a cutting and hauling mining adapter 21

Mihai Valentin HERBEI, Roxana Claudia HERBEI, Florin SALA

Assessment of the tilt phenomenon and the tilt distance of the land as an effect of coal mining, Jiu Valley basin, Romania 28

Daniela CIOLEA, Vasile BOBEI, Marius BERCA

Research on fog guns for dust reduction at coal field Roșiuța Quarry 39

Laurențiu-Ștefan POPESCU, Adrian CEPTUREANU

Geophysical analysis on the geomechanical characteristics of the soil for choices of the drilling rig, in the area of Târgu Ocna, Bacău County, Romania 48

Vasile BOBEI, Daniela CIOLEA

Aspects regarding the use of coal in the production of electrical and thermal energy 59

Ioan BOROICA, Marius CUCĂILĂ, Simona CUCĂILĂ, Nicolae DIMA

Researches on mining cadastre: past, present and future perspectives.

The case of a former mining town: Borșa, Maramureș County 65

Gheorghe Marian VANGU

The use of drones in mining operations 73

Mădălina (Barbu) DELAYAT, Maria LAZĂR, Sabin IRIMIE, Sabina IRIMIE

Eco energetic efficiency comparative analysis of steam power plants versus micro hydropower plants 83

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 1 20

THE THROTTLE EFFECT BLOWER FAN VERSUS EXHAUST FAN

Rickard HANSEN1*

1Sustainable Minerals Institute, The University of Queensland, Brisbane, Australia, rickard.hansen@uq.edu.au

DOI: 10.2478/minrv 2022 0016

Abstract: One of the risks connected to fires underground is the throttle effect which may cause unforeseen smoke spread. This paper investigates the throttle effect for a blower fan and an exhaust fan case in a mine drift. The aim of the paper is to perform a parametric study on the throttle effect, varying influencing parameters such as the heat release rate and fan flow velocity. Data from fire experiments in a model scale mine drift and results from CFD simulations were used during the study. It was found that the differences between the two fan cases were significant both in magnitude and occasionally in direction. For the base cases the throttle effect as well as the backlayering were more severe in the exhaust fan case. When increasing the heat release rate to 116 kW an increasing backlayering resulted, but the throttle effect was found to increase for the exhaust fan case and decrease for the blower fan case. The throttle effect decreased in the blower fan case as the gas density decrease levelled off, but the flow velocity increased even further, causing an increase in the downstream mass flow rate. This finding was confirmed by similar experimental results in model scale mine drifts. The resulting mass flow rate induced by the fire plume changes was found to be higher than the externally imposed increase of the fan flow velocity. When increasing the distance between the fire and the exhaust fan, the backlayering increased and the throttle effect decreased

Keywords: Throttle effect, mine drift, exhaust fan, blower fan, backlayering, CFD, mine fire, underground mine

1. Introduction

An occurring fire in a mine section underground will entail several risks and hazards, where the smoke production and smoke spread will generally present the dominating risk. One of the hazardous characteristics of the smoke spread is the transient nature where the fire will be a driving force and one of the phenomena the throttle effect. With an increasing heat release rate of a fire in a mine drift and resulting temperature increase, disturbances and changes in the air flow may occur which is termed the throttle effect. The changes and disturbances may result in difficulties and unwanted impact during the crucial evacuation phase and ensuing fire and rescue operation.

This paper focuses on the variations of the throttle effect and its impact for a blower fan positioned upstream of the fire case versus an exhaust fan positioned downstream of the fire case in a mine drift. What are the differences between the two cases? How will the level of impact varywith increasing heat release rate for the two cases? How will the distance between the fire and the exhaust fan affect the occurring throttle effect? Understanding and knowing the differences in the throttle effect for the two cases will improve the pre planning of fires underground and the safety of an ongoing fire and rescue operation underground.

The throttle effect was investigated through a parametric study using a qualitative approach where a CFD (Computational Fluid Dynamics) tool was used to obtain data for the study. Conducting a parametric studywould allowfor athorough investigation onthe influence of various parameters on the twothrottle effect cases. By using a CFD tool, various parameters can be isolated and studied individually in an otherwise complex process. The experimental data which this study is based on and used as input for the CFD simulations, were obtained from model scale fire experiments with varying heat release rates and with a longitudinal ventilation flow (blower fan) [1]. The data was selected as the conditions of the experiments fitted the scope of this study and the data constituted the basis for an earlier validation study of a CFD tool versus the throttle effect [2].

Corresponding author: Rickard Hansen, Ph.D MSc Eng., The University of Queensland, Brisbane, Australia, rickard.hansen@uq.edu.au

The purpose of this paper is to investigate the nature of the throttle effect and its impact on the surroundings when comparing a blower fan case with an exhaust fan case and varying influencing parameters such as the heat release rate.

Few works have dealt with the throttle effect in an underground mine, where a majority of the works has been based on simplified fire conditions (for example steady state heat release rates and gas burner experiments). An exhaust fan was used during experiments by Hwang and Chaiken [3] to analyse the changes in the ventilation air flow in a duct during a fire. The volumetric flow rate of the exhaust fan was assumed to be constant during the experiments. With increasing convective heat losses from the fire gases, the ratio of the intake air velocity prior to the fire to the intake air velocity during the fire was found to decrease. The decrease was explained to be due to the increase in the fire gas density. Further duct fire experiments with an exhaust fan were conducted by Lee et al [4], investigating the throttle effect and the occurring backlayering. Maintaining constant speed for the exhaust fan, resulted in a 50% decrease in the mass flow rate compared with the initial mass flow rate due to the throttle effect. Litton et al [5] investigated the throttle effect further, conductingexperiments inan intermediate scale tunnel with an exhaust fan and a large scale gallery with a blower fan. The fire source in the intermediate scale tunnel consisted of a gas burner with heat release rates ranging from 8.5 to 120 kW. The heat release rates of the fire source in the large scale gallery ranged from approximately 300 kW to 5900 kW. It was found that the impact of the throttle effect was distinct, with a 10 11% maximum reduction in the total air flow and a 29% reduction in the intake air flow. Using a model scale mine drift, Hansen [6] conducted fire experiments to investigate the cause of the throttle effect, its impact, and variations. During the experiments a blower fan was used to provide the longitudinal ventilation flow. The fire source consisted of a single or multiple piles of wooden pallets distributed along the mine drift. It was found that the reduction in the mass flow rate downstream of the fire was caused by a larger decrease in the fire gas density (caused by the heating from the fire) compared with the increase in the flow velocity.

Earlier CFD studies in underground mines have mainly dealt with the smoke and fire spread along a mine entry [7 9], or the backlayering and critical velocity in a mine section [10 12]. Hansen [13] conducted CFD studies on the fire gas temperatures and fire gas velocities along a mine drift, comparing the modelling results with experimental data from full scale fire experiments. A CFD modelling study was also conducted by Vaitkevicius et al. [14] to demonstrate the impact of the throttle effect on tunnel fires. Hansen [2] investigated the ability of a CFD tool to predict and reproduce the throttle effect for fire scenarios underground. The CFD results were validated against experimental data from fire experiments in a model scale mine drift.

No earlier study has dealt with the differences in the throttle effect for a blower fan case versus an exhaust fan case. This study is limited to blower fan and exhaust fan cases with a constant flow velocity.

In the ensuing chapters, the mass flows and throttle effect in a mine drift with a burning object are described. Model scale fire experiment and the set up of the CFD simulations are described together with the resulting data from the CFD simulations. The simulation results are analyzed and discussed with respect to the mechanisms and parameters involved, and the resulting impact on the surroundings.

2. Mass flows in a mine drift and the throttle effect

Prior to an occurring fire in a mine drift, the longitudinal ventilation flow will largely dictate the flow rates and flow directions in the mine drift. Disturbances may occur due to for example changes in wind conditions or occurring temperature changes, but by and large a uni directional and a largely non transient flow can be expected in the mine drift. At the onset of a fire underground, increased disturbances can be expected. The smoke from the initial fire will rise and spread along the direction of the ventilation flow, but with increasing heat release rate an inflow of air towards the base of the fire source and a counter current flow of fire gases at the ceiling level (i.e., backlayering) can be expected. The backlayering flow of hot fire gases will cool off when mixing with the cooler ventilation air flow in the opposite direction and descend towards the floor and veer back towards the fire. Other than the ventilation flow velocity and the heat release rate, the heightoftheminedriftwillalsohaveanimpactonthemassflowinthenearvicinityofthefire.Withincreasing mine drift height, the rising smoke will undergo increased cooling and result in a lower vertical temperature gradient. This in turn will result in a lower degree of smoke stratification, a longer time before a hot fire gas layer is established at the ceiling level and a longer time before any backlayering occurs. In the near field of the fire both upstream and downstream a transient and multi directional flow situation will thus occur.

In the far field of the fire, the distance to the fire will largely influence the mass flow situation and the occurring smoke spread and smoke stratification. With an increasing downstream distance to the fire, the cooling of the flowing fire gases will be noticed by the decreasing fire gas temperature, lower vertical

temperature gradient and decreasing smoke stratification. Other than the distance to the fire, the cooling of the fire gases will be influenced by parameters such as the roughness of the rock surface and the ventilation flow velocity. Furthermore, with increasing distance downstream of the fire, the multi directional flow will become more of a uni directional flow. Fig 1 depicts schematic mass flows in a mine drift with longitudinal ventilation flow, with a backlayering present.

Figure 1. Schematic mass flows (mass flow directions marked by red arrows) in a mine drift with longitudinal ventilation flow

In conjunction with the ongoing fire, the gases at the site of the fire will heat up, decrease in density, rise towardstheceiling,andcausebuoyancyforcesatthefiresite.Withincreasingheatreleaserateandtemperature differences, the buoyancy forces will increase as well. With increasing buoyancy forces and temperatures, the passing air masses will heat up and increase in volume, causing a throttle effect which is noticed by a blockage in the ventilation flow at the site of the fire and a reduced mass flow rate. For a blower fan positioned upstream of the fire and set at a constant flow velocity, the reduced mass flow rate downstream of the fire site can be explained by a larger decrease in the gas density compared with the increase in the downstream flow velocity. With an increasing flow velocity comes an increase in the volume flow downstream of the fire.

In the case of an exhaust fan positioned downstream of the fire and set at a constant flow velocity, the reduced mass flow rate will be due to the decreased density of the heated fire gas masses. With increasing distance between the fire site and the exhaust fan, the cooling of the fire gas will increase and thus also the density which in turn will decrease the throttle effect.

An earlier study pointed out a mass injection parameter as an influencing parameter on the throttle effect [3]. The mass injection parameter is defined as the ratio between the mass flow emitted from the fire mass loss of the fire during combustion to the mass flow from the intake. A latter study using data from full scale fire experiments in an underground mine found that an average of 2% of the mass flow downstream originated from the fire [6]. The mass flow injected from the fire will only be a small fraction and have negligible influence on the throttle effect. For further reading on the throttle effect, see paper by Hansen [6].

3. Methodology

This study relies heavily on CFD simulations to investigate the influence of various parameters on the throttleeffect cases. Prior totheCFD simulations, datafroma model scalefireexperiment was obtained where the CFD tool had earlier been validated against the experimental results. The experimental conditions of the model scale experiments were largely kept during the investigative simulations, but where the ventilation flow velocity, the heat release rate, position of fan and length of mine drift were varied.

3.1 Fire experiment in a model-scale mine drift

Full scale fire experiments are frequently found to be very costly and very resource intensive, whereas model scale fire experiments have the advantage of being more cost efficient and resource efficient.

A model scale mine drift was used for twelve fire experiments, when investigating the fire spread and the fire behaviour of a single and multiple fuel items along the mine drift. The fuel items consisted of either a single pile of scaled down wooden pallets or multiple piles positioned at certain positions.

A longitudinal ventilation flow was provided throughout all experiments, where the flow velocity was set to either 0.3 m/s, 0.6 m/s or 0.9 m/s throughout the different experiments. A constant volumetric flow rate was provided by an electrical axial fan attached to the entrance of the model scale mine drift, thus presenting a blower fan case. The mine drift was in scale 1:15, with a length of 10 m, a width of 0.6m and a height of 0.4m. Fig 2 displays the long section layout of the model scale mine drift with two piles of wooden pallets and the attached thermocouples, probes, and other instruments. The first pile of pallets was positioned at the same location in all experiments, i.e., on the weight scale marked with a “W” in Fig 2. Not seen in the figure is an

exhaust duct found at the end of the mine drift. Downstream of the fuel items is a thermocouple pile named “pile B” in Fig 2, where the thermocouples positioned at different heights would provide a good picture of the vertical temperature distribution and thus also on the cooling and stratification of the fire gases. At pile B, a bi directional probe would measure the centreline pressure difference, together with the temperature measurement providing input to the downstream centreline flow velocity calculations. At the entrance of the mine drift, a bi directional probe and a thermocouple would provide the input for the corresponding upstream centreline flow velocity calculations.

A report by Hansen and Ingason [15] provides an in depth description of the experiments.

Figure 2. The long section layout of the model scale mine drift with attached thermocouples, probes and instruments [16]

Among the total of twelve experiments, three experiments were conducted with a single pile of wooden pallets. The difference between the three experiments laid in the ventilation flow velocity, 0.3 m/s, 0.6 m/s or 0.9 m/s. When modelling the mass flows in the mine drift it is important to use an accurate heat release rate of each pile of pallets and as the total heat release rate of the experiments involving multiple piles of pallets can only to some extent be correctly allocated to the individual piles, thus only the experiments involving a single pile were of interest in the ensuing analysis. Furthermore, as pile B was found to be positioned upstream of the hydrodynamically fully developed region in the 0.6 m/s and 0.9 m/s cases, focus would be on the 0.3 m/s case. Measurements taken in the hydrodynamically fully developed region is desirable as the pressure gradient and shear stress in the flow will be in balance and any localized eddies will have decayed.

The resulting heat release rate curve of the experiment involving a single pile of pallets and a ventilation flow velocity of 0.3 m/s can be found in Fig.3. The heat release rate was calculated based on recorded data at pile B and using a method by Newman [17]. Please observe that Fig 3 also contains the initial two minutes of recorded data prior to ignition. The maximum heat release rate can be seen to occur after approximately 2 minutes after ignition.

release rate (kW)

(min)

Figure 3. The heat release rate curve of model scale fire experiment involving a single pile of wooden pallets and a longitudinal ventilation velocity of 0.3 m/s

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Fig 4 displays the measured mass flow rate downstream of the fire at pile B for the experiment during the initial eight minutes (capturing the growth phase, maximum heat release rate and parts of the decaying phase). A time averaged mass flow was calculated to facilitate comparison. Same as for Fig 3, the initial two minutes prior to ignition are included. Fig 4 displays a decreasing mass flow rate approximately one minute after ignition, which coincides with the rapidly increasing heat release rate seen in Fig 3. The lowest mass flow rate isrecordedapproximatelytwo minutesafter ignition,coincidingwiththemaximumheat releaserate.Themass flow rate can be seen to increase again after approximately 2.5 minutes after ignition, coinciding with the start of the decaying phase seen in Fig 3.

Mass flow rate (kg/s)

(min)

Figure 4. The measured mass flow rate at pile B for the experiment involving a single pile of wooden pallets and a longitudinal ventilation velocity of 0.3 m/s

3.2 CFD simulations

CFD models are commonly used when modelling and predicting parameters such as ventilation flows and heat transfer during a fire, due to its capability to model complex geometries and fire characteristics. As CFD modelling will be very time consuming and demanding in computational resources with increasing size of the modelleddomain,anyCFD modellingwillgenerallybeconductedforalimitedpartofthemine.ACFD model divides the computational domain into a three dimensional mesh of multiple cells. For each cell the fundamental laws of fluid mechanics and heat transfer found in the laws of conservation mass, momentum and energy are applied. For further reading on CFD modelling of fires, see Yeoh and Yuen [18].

An earlier modelling study was performed of the throttle effect in the model scale mine drift, where the CFD results were analysed and validated against the experimental data from the model scale fire experiments [2]. During the study the Fire Dynamics Simulator (FDS) version 6.7.5 was chosen as CFD model due to its capability of modelling low speed, thermally driven flow [19].

Whenperformingthe simulations,the simulatedtime was set toeight minutes includingthetwo minutes prior to ignition as this would capture the critical stages of the fire, i.e., the growth phase, peak heat release rate and the start of the decaying phase.

The burning pile of wooden pallets was modelled using the heat release rate per unit area (HRRPUA) model as pyrolysis model and the heat release rate curve in Fig.3 as input to the HRRPUA model. The surface areas of the pallets exposed to the surrounding air defined as burning surfaces were calculated and used as input when describing the ramped heat release rate per unit burning area as a function of time.

An earlier study [13] had pointed out the radiative heat transfer fraction as a potential error source when modelling the fire gas temperature, but when increasing the radiative fraction from the default value of 0.35 (solving the radiation transport equation for a grey gas) to 0.45 it was found that the output results were more or less identical for the two different radiative fraction values.

The impact of the boundary layer on the turbulent flow was investigated in the simulations by applying a so called wall model in some simulations, simulating the turbulent transport close to any surface. It was found that the wall model did not result in any improved predictions of the output results.

The measured average ventilation velocity at the upstream bi directional probe prior to the fire was used as the input ventilation velocity in the simulations, as the measured flow velocity displayed erratic behaviour during the fire due to increased eddy formations.

28,

Initially, the temperature and the velocity measuring points in the simulations were positioned in accordance with the thermocouples at pile B and the bi directional probe (see Fig 2). When analysing the simulation results it was found that a single measuring point to model the downstream flow velocity raises some questions on the output results, as uncertainties and differences compared with the experimental results were detected. Applying an average flow velocity based on multiple measuring points would account for the variations along the cross section and the thermal stratification. When using multiple measuring points for both the temperature and the velocity, it was found that the uncertainties and differences were significantly reduced.

The modelled and experimental mass flow rate for the experiment involving a single pile of wooden pallets and a longitudinal ventilation velocity of 0.3 m/s can be found in Fig 5. The modelled mass flow rate is seen to end prior to the eight minutes mark. The reason behind this time difference is the experimental heat release rate occurring earlier than the recorded data further downstream from which the heat release rate was calculated from. When accounting for the time difference, the difference was calculated by dividing the distance between the fire and the measuring point by the average ventilation flow velocity. When comparing the measured (from experiment) mass flow rate with the modelled mass flow rate, it can be seen that the modelled results match the measured mass flow rate very well except for the latter part approximately five minutes into the simulation.

At this stage the mass flow rate has undergone a phase with minimum mass flow rate and has started to regain in magnitude. The measured mass flow rate can be seen to eventually attain the same levels as prior to thefirewhereasthemodelledmassflowrateincreasesat alowerrate.IntheanalysisofHansen[2]thequestion whether the mass flow rate would regain in magnitude this fast was investigated. It was found that the mass flow rate measurements in the duct downstream of pile B indicated that the initiation of the throttle effect took place later and the mass flow rate would regain the same levels as prior to the fire after almost eight minutes. As the measured mass flow rate at pile B was based on only one measuring point and the mass flow rate in the duct would be expected to have a uniform appearance due to the high degree of mixing, the confidence in the modelled mass flow rate increased.

The modelled mass flow rate can be seen to start the descent after approximately three minutes somewhat later than the measured mass flow rate. This delay can be attributed to the approximation when calculating the time difference mentioned above, where using an average ventilation flow velocity may cause an offset. The modelled mass flow rate also displays a hump (i.e., an increase followed by a sudden decrease) just prior to the initiation of the throttle effect, which is not seen in the measured mass flow rate. In the analysis of Hansen [2] it is found that the hump appearance is caused by the sudden increase in the modelled flow velocities at the two highest measuring points at pile B. The model thus failed to fully predict the extent of the mass flow rate and thermal stratification during the critical stage when the throttle effect initiates.

Given the difficulties of the CFD model to accurately predict the thermal stratification and, by extension, the throttle effect, Hansen [2] recommends using the CFD model mainly for qualitative analysis of the throttle effect. Thus, in the ensuing study predominantly a qualitative approach is used.

flow rate

measured and the modelled mass flow rate at pile B for the experiment involving a single pile of wooden pallets and a longitudinal ventilation velocity of 0.3 m/s.

The simulations in this paper were largely based on the same input data as the simulated fire experiment which was validated in the study of Hansen [2] a fire in a model scale mine drift involving a single pile of wooden pallets and a longitudinal ventilation velocity of 0.3 m/s. The differences laid in the investigated parameters, the measuring points, the mesh grid size, and the use of the HVAC feature. The investigated influencing parameters varied for the different simulations were the heat release rate, the longitudinal flow velocity and the distance between the fire and the exhaust fan. The ramped heat release rate was scaled to obtain a desired maximum heat release rate, retaining the appearance of the heat release rate curve. Measuring points were positioned 0.1 m, 3.1 m, 3.5 m, and 8.7 m downstream of the entrance, obtaining data upstream of the fire, across the fire (burning pile positioned between 3.1 m and 3.5 m downstream of the entrance), and downstream of the fire. At each distance, measuring points were positioned 0.04 m, 0.12 m, 0.2 m, 0.28 m, and 0.36mfromthefloor,allowingforthe studyofthevariousparametersinthe different five segments where the lowest segment would be from floor to 0.04 m and the highest segment from 0.36 m to ceiling. At each position, the temperature, flow velocity, background pressure, and pressure perturbation were measured. The background pressure and pressure perturbation were used to obtain the total pressure at the location. The mesh grid size in the study by Hansen [2] was 0.02 m, while in this study a finer mesh grid was selected where the grid size was decreased to 0.01 m. To simplify the CFD simulations and decrease the run time of the simulations, the HVAC (Heating, Ventilation and Air Conditioning) feature of FDS was applied. The sections prior to and after the mine drift where uni directional flow can be expected were therefore defined as duct segments, connected to the CFD region consisting of the mine drift. The multi scale modelling approach of a longer mine drift will reduce the length of the CFD region and thus also the run time. The one dimensional HVAC feature solves the continuous flow in the duct, applying conservation equations for the mass, energy, and momentum. For further information on the HVAC feature, see Fire Dynamics Simulator user’s guide [19].

4. Results and discussion

Below, the results and analysis on the base cases forthetwo types of fans, the influence of the heat release rate, the longitudinal flow velocity and corresponding full scale values can be found.

As the results from the CFD modelling oscillated considerably in some cases, the time averaged mass flows and pressure differences were therefore calculated and is presented in some of the ensuing work to facilitate the comparison and analysis.

Thepresented,modelledresultsinthegraphsbelowdonotincludetheinitialtwominutespriortoignition.

To facilitate the analysis of the impact of heat release rate, ventilation velocity and distance between fire and exhaust fan, the output results were normalized by dividing it by the corresponding results from the base casein question.The mass flow rate and flow velocitycould have negative values(flows in the counter current direction) and the quotient of two negative values would result in a positive value. Two negative values resulting in a quotient smaller than one would indicate a decreasing trend despite that in effect an increasing trend exists in the co current direction. Thus, the resulting normalized values were manually checked to detect any misleading results.

Astheflowsbothupstreamanddownstreamofthefirewerenotuni directional,analysingsolelyalumped total mass flow rate or average flow velocity would in many cases be insufficient. Thus, the mass flow rates, andflowvelocitieswerealsoanalysedusingthemassflowratesandflowvelocitiesoftheindividual segments, the total mass flow rate of segments upstream of the fire with a counter current flow direction and the total mass flow rate of segments downstream of the fire with a co current flow direction. The data from segments upstream of the fire and with a counter current flow direction will be of interest as this will include a mass flow in an undesired direction. The downstream data will be of interest as this will include a mass flow in a desired direction, critical for the smoke extraction operation.

4.1 Base cases

The blower fan case and exhaust fan case constituting the base cases had a maximum heat release rate of 58 kW and a longitudinal flow velocity at the fans of 0.168 m/s. The blower fan was positioned at the very entrance to the mine drift from the HVAC duct and the exhaust fan at the end of the mine drift prior to the HVAC duct. The maximum heat release rate and longitudinal flow velocity were 50% of the corresponding values for the experiment involving a single pile of wooden pallets as initial simulations for the exhaust fan case resulted in severe backlayering. Thus, to obtain fairly overall uni directional mass flow in the co current direction in the base case simulations, the maximum heat release rate and the corresponding flow velocity were halved.

Fig 6 displays the modelled total mass flow rates of the blower fan case and Fig 7 the exhaust fan case. As seen in Fig 6, the modelled upstream (3.1 m from entrance) mass flow rate of the blower fan case increases somewhat but the corresponding mass flow rate for the exhaust fan case remains more or less constant after an initial and temporary dip (a similar dip is seen in the blower fan case but shorter in time and lower in magnitude). The increased mass flow rate in the blower fan case is due to an increased mass flow rate of the lower four segments (each segment is connected to the corresponding vertical measuring point 3.1 m downstream of the entrance) which exceeds the negative mass flow rate of the uppermost segment as seen in Fig 8. The mass flow rate of the uppermost segment is negative due to backlayering occurring. The larger increase in the mass flow rate of the lower four segments is due to an increased flow velocity but where also the decrease in the density of the flowing gas (due to an increasing temperature) is considerably lower compared with the decreased gas density of the uppermost segment. Even though the flow velocity of the uppermost segment is significantly higher than the flow velocity of the lower four segments, the decrease in the gas density is even higher. The initial dip in the upstream mass flow rate is caused by the gradient of the decreasing mass flow rate of the uppermost segment is larger than the gradient of the increasing mass flow rate of the lower four segments. The larger gradient of the mass flow rate of the uppermost segment is due to a more rapid increase in the flow velocity compared with the slower decrease in the density and the initially slower temperature increase in the fire gases. The more or less constant upstream mass flow rate of the exhaust fan case is caused by the decrease of the mass flow rate of the uppermost segment being equivalent in magnitude with the increase of the mass flow rate of the lower four segments. The initial dip in the mass flow rate is caused by the same phenomenon as described above for the blower fan case.

Mass flow rate (kg/s)

Figure

Mass flow rate (kg/s)

Figure

Upstream of fire Downstream of fire

(min)

The modelled upstream and downstream total mass flow rate in mine drift blower fan case

(min)

Upstream of fire Downstream of fire

upstream and downstream total mass flow rate in mine drift exhaust fan case

Mass flow rate (kg/s)

Mass flow

segment

(min)

Figure 8. The modelled upstream mass flow rates of the uppermost segment and lower four segments respectively blower fan case

For both the blower fan case and the exhaust fan case, the average cross sectional upstream flow velocity decreased with a fire occurring in the mine drift. The flow velocity decrease was significantly higher for the exhaust fan case, where the average flow velocity reversed in direction and attained a magnitude higher than prior to the fire.

As seen from Fig 6 and Fig.7, the throttle effect is more severe for the exhaust fan case (i.e., the downstream mass flow rate was reduced to a larger degree and the ratio of the downstream mass flow rate to the upstream mass flow rate was lower in the exhaust fan case). Fig.9 displays the upstream mass flow rate of thesegmentswithacounter current flowdirection,wherethemassflowrateintheundesireddirectionislarger in the exhaust fan case and thus experiencing a larger degree of backlayering. Fig.10 displays the effect of a more severe throttle effect for the exhaust fan case, where the downstream mass flow rate of the segments with a positive flow direction is considerably larger for the blower fan case.

The negative total downstream mass flow rates for both cases are mainly caused by a flow in the negative directionforthethree lower segments, asseenin Fig.11 (measuringpoint is 8.7 mdownstreamof theentrance) for the blower fan case. Even though the flow velocities of the upper two segments are very high (noted by an increase in the average downstream flow velocity), the higher gas densities at the three lower segments (seen in Fig.12) result in a negative mass flow rate for the cross section. The lower negative mass flow rate of the blower fan case compared with the exhaust fan case is due to the significantly higher flow velocities at the upper two segments for the blower fan case.

Mass flow rate (kg/s)

flow

of

segments with

Exhaust fan

counter current flow direction

Mass flow rate (kg/s)

(min)

Exhaust fan Blower fan

The negative flow velocity direction of the lower three segments is caused by the ventilation flow passing on the sides of the burning pile and being steered back towards the fire, adding a three dimensional aspect to the mass flows in the mine drift. This flow is more pronounced for the blower fan case, where the flow velocities at the lower three segments were higher and the densities were more or less equal to the ambient gas density compared with the exhaust fan case with lower velocities and lower densities. Given the position of the two types of fans versus the downstream flow field, the higher flow magnitude for the blower fan case could be expected. With increasing distance to the measuring station, the negative flow direction would eventually cease.

For the exhaust fan case, the average cross sectional downstream flow velocity decreased with a fire occurring in the mine drift. The decrease was significantly lower compared with the decrease in the upstream flow velocity, approximately one third compared with the upstream velocity which is in line with the findings of Litton et al [5]. For the blower fan case the opposite occurred, i.e., the average flow velocity increased with an occurring fire.

Flow velocity (m/s)

(min)

m height

m height

m height 0.28 m height

m height

Figure 10. The modelled downstream mass flow rates of the segments with a co current flow direction

Figure 11. The flow velocity downstream of the fire blower fan case

Gas density (kg/m

(min)

Figure 12. The gas density downstream of the fire blower fan case

0.04 m in height 0.12 m in height 0.2 m in height 0.28 m in height 0.36 m in height

The upstream flow velocity at the uppermost segment where backlayering occurred differed significantly between the two cases, where the flow velocity in the negative direction was significantly higher for the exhaust fan case as seen in Fig 13. Despite a higher gas density for the blower fan case, the significantly higher flow velocity of the exhaust fan case resulted in much higher mass flow rate. The upstream counter current flow velocity at the uppermost segment was approximately 1.5 times higher in the exhaust fan case compared with the blower fan case. As previously noted, a more severe backlayering would thus result in the exhaust fan case.

Flow velocity (m/s)

t (min)

Figure 13. The upstream flow velocity at the uppermost segment

The absolute upstream pressure difference was calculated using the pressure results at 0.1 m and 3.1 m respectively from the entrance. The absolute pressure differences were calculated to obtain positive values for the analysis. The absolute pressure difference across the fire was calculated using the pressure results at 3.1 m and 3.5 m respectively from the entrance. The absolute downstream pressure difference was calculated using the pressure results at 3.5 m and 8.7 m respectively from the entrance.

Fig 14 displays the absolute pressure differences for the blower fan case and Fig 15 for the exhaust fan case. The distinctly higher pressure difference downstream of the fire in the blower fan case is caused by the higher gas temperatures which result across the fire zone and the increased magnitude of the average flow velocity downstream of the fire. These observations are in line with the findings by Litton et al [5]. The same conclusion can be drawn regarding the higher pressure differences upstream of the fire in the exhaust fan case. An increased magnitude in the average flow velocity foremost due to the significantly higher flow velocity at the uppermost segment and the increased gas temperature at the uppermost segment due to significant backlayering. The changed direction of the average upstream flow velocity was noted by the negative values of the upstream pressure difference prior to calculating the absolute value.

Absolute pressure difference (Pa) t (min)

Pressure difference upstream of fire

Pressure difference across fire

Pressure difference downstream of fire

Absolute pressure difference (Pa) t (min)

4.2 Varying heat release rate

Pressure difference upstream of fire

Pressure difference across fire

Pressure difference downstream of fire

When varying the heat release rate, the maximum heat release rate was set to 50% of the heat release rate of the corresponding base case (i.e., reduced to 29 kW) as well as 200% (i.e., increased to 116 kW).

A decreasing heat release rate will result in an increase in the upstream total mass flow rate compared to the base case for both the exhaust fan case and the blower fan case, which is caused mainly by a reduced backlayering. The reduction in the backlayering is caused by an increasing mass flow rate (and flow velocity) in the third segment from the floor and a decreasing counter current mass flow rate and flow velocity of the uppermostsegment whichinturnwillbecausedbyadecreasingmomentumofthefireplumeduetodecreasing heat release rate. Fig 16 displays a larger reduction of the normalized upstream negative mass flow rate for the blower fan case compared to the exhaust fan case, resulting in a larger reduction of the backlayering for the blower fan case. Downstream of the fire, the total mass flow rate will be similar to the base cases, the throttle effect will decrease and the normalized mass flow rate in the co current direction will decrease at a similar magnitude for the two fan cases, which is expected due to a decreasing momentum of the fire plume. The similar decrease in magnitude of the normalized mass flow rate for the two fan cases, could be explained by the decreasing mitigating effect of the flow velocity. This will be due to the flow velocity of the hot gases approaching the pre set flow velocity of the exhaust fan downstream. As the downstream mass flow rate was

Figure 14. The absolute pressure differences of the blower fan case

15. The absolute pressure differences of the exhaust fan case

significantly higher for the blower fan base case (see Fig 10), the significant differences between the two fan cases will remain for a decreasing heat release rate. In the exhaust fan case, the decrease is foremost seen in the mass flow rate decrease and flow velocity decrease in the second highest segment, whereas in the blower fan case both uppermost segments displayed similar decreases.

An increasing heat release rate will result in an increasing backlayering for both fan cases, where the increase will be larger for the blower fan case as seen in Fig 17. The increased backlayering in the blower fan case will be compensated by a distinct increase in the mass flow rate and flow velocity of the lower three segments, resulting in an increase in the mass flow rate across the entire cross section. This distinct increase in the lower three segments is not seen in the exhaust fan case, resulting in a decrease in the total mass flow rate. The normalized downstream mass flow rate decreased, and the throttle effect increased for the exhaust fan case with increasing heat release rate. Whereas, for the blower fan case the throttle effect decreased, and the normalized mass flow rate increased. Thus, the two fan cases displayed completely different results when increasing the peak heat release rate from 58 kW to 116 kW. Why did the blower fan case start to display decreasing throttle effect, when the opposite occurred when increasing the peak heat release rate from 29 kW to58kW?Intheblowerfancase,thethrottleeffectiscausedbythelarger decreaseinthegasdensitycompared with the increase in the downstream flow velocity.

Normalized mass flow rate t (min)

Blower fan

fan

Figure 16. The normalized upstream mass flow rates of the segments with a flow direction opposite to the ventilation flow for a decreasing heat release rate

mass flow rate t (min)

Blower fan

fan

Figure 17. The normalized upstream mass flow rates of the segments with a counter current flow direction for an increasing heat release rate

Fig 18 and Fig.19 display the downstream flow velocities and gas densities of the uppermost segment and for the three different peak heat release rates. When increasing the peak heat release rate from 58 kW to 116 kW, the gas density decrease can be seen to level off but the flow velocity increases even further and thus causing an increase in the downstream mass flow rate. Thus, for higher heat release rates, the blower fan case actually starts to display decreasing throttle effect and increasing downstream mass flow rates. An earlier analysis predicted increasing throttle effect with increasing heat release rate for a blower fan case [6]. The analysis only included the incipient phase and the growth phase of the fire as these phases are generally of most interest as they will include the evacuation and possibly the critical initial fire suppression and rescue operations. The fully developed phase with the highest temperatures and heat release rates were therefore not included in the analysis. Fig 20 displays the mass flow ratio as a function of the dimensionless heat release rate of the experiment described in chapter 3.1, having a peak heat release rate of 116 kW and where all phases of thefire experiment are included. The highest dimensionless heat release rates were recorded duringthe fully developed phase of the fire and for the higher dimensionless heat release rates the mass flow ratio can be seen to increase (i.e., decreasing throttle effect). The same phenomenon occurred in the other fire experiments as well, where the peakheat release rate exceeded 116 kW in all cases. So based on experimental results and CFD modelling, the throttle effect reverses and starts to decrease for higher heat release rates. For the exhaust fan case, the gas density did not start to level off and the increase of the flow velocity was similar as when increasing the peak heat release rate from 29 kW to 58 kW. The downstream mass flow rate of segments with a co current flow direction increased in the blower fan case when increasing the peak heat release rate to 116 kW, whereas the mass flow rate for the exhaust fan case displayed only a minor increase as seen in Fig.21. Thus, for higher heat release rates the smoke extraction of the blower fan will be significantly higher than the exhaust fan. The higher increase for the blower fan case is due to increasing co current mass flow rate and flow velocity of the upper three segments, whereas in the exhaust fan case only the second highest segment contributes with an increase.

Flow velocity (m/s)

(min)

Figure 18. The downstream flow velocities of the uppermost segment for the three different heat release rates blower fan

Gas density (kg/m

(min)

Figure 19. The downstream gas densities of the uppermost segment for the three different heat release rates blower fan

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The changes in absolute pressure difference differs between the two fan cases. In the exhaust fan case, the highest pressure differences are found upstream of the fire and where an increasing heat release rate will foremost lead to increasing flow velocities and gas temperatures at the uppermost segment, and in turn increased pressure differences. In the blower fan case, the highest pressure differences are found downstream. When decreasing the heat release rate compared to the base case the pressure difference decreases, and when increasing the peak heat release rate to 116 kW, the pressure difference also decreases. The latter decrease could be related to the increasing mass flow rate.

Mass flow ratio Dimensionless heat release rate

Figure 20. The mass flow ratio as a function of the dimensionless heat release rate of the experiment described in chapter 3.1 [6].

mass flow rate

(min)

Figure 21. The normalized downstream mass flow rates of the segments with a co current flow direction for an increasing heat release rate.

4.3 Varying longitudinal flow velocity

When varying the longitudinal flow velocity, the flow velocity at each fan was set to 125% of the flow velocity of the corresponding base case (i.e., increased to 0.21 m/s). The longitudinal flow velocity was not increased any further to reduce the risk of numerical instability.

The increased flow velocity resulted in a slightly increased upstream mass flow rate, upstream flow velocity and decreased backlayering for both fan cases. The magnitude of the changes is similar for the two fan cases. In the exhaust fan case, all segments displayed an increased mass flow rate and foremost the lower segments and the highest segment displayed an increased flow velocity in the co current direction. Whereas in the blower fan case, foremost the lowest segment displayed increasing mass flow rate and the highest segment slightly lower values than the base case. The flow velocity in the co current direction increased foremost in the lower segments and the highest segment for the blower fan case.

Thetotaldownstreammassflowrateandaverageflowvelocityincreasedtoaminorextentwithincreasing fan flow velocity, where the mass flow and flow velocity increase were foremost detected in the lower segments for both fan cases. The throttle effect was found to decrease to a minor extent in both fan cases. The downstream mass flow rate of segments with a co current flow direction displayed only a minor increase for bothfancasesasseeninFig 22,wheretheaverageincreasewasonly2%.Nosegmentdisplayedanysignificant deviation from the base cases. The downstream flow velocity of segments with a co current flow direction was much higher for both fan cases when increasing the heat release rate compared to when increasing the fan flow velocity, which could at least partially be explained by the larger increase when doubling the heat release rate compared to the 25% increase in the fan flow velocity. When comparing the downstream mass flow rates in Fig 21 and Fig.22, the normalized mass flow rates when the heat release rate was increased were significantly higher than when the fan flow velocity was increased.

Eventhougha100%increaseoftheheatreleaserateishigherthana25%increaseof thefanflowvelocity, the resulting downstream mass flow rate induced by the changes in the fire plume is clearly higher than the mass flow rate due to the externally imposed increase of the fan flow velocity. These findings are in line with earlier experimental observations where the ventilation flow velocity was found to have a weak effect on the occurring throttle effect [6]. The larger impact of the changing fire plume and the ensuing increase in the volume flow will underline the poor performance of an exhaust fan set at a constant flow velocity as it will resist the increased volume flow. Even if increasing the exhaust fan flow velocity, the measure seems to have limited effect when studying Fig.22. The exhaust fan flow velocity will have to be increased considerably to attain similar mitigating effects on the throttle effect as a blower fan with a lower fan flow velocity. Furthermore, when countering the backlayering phenomenon by increasing the fan flow velocity, the mitigating effect on the throttle effect will be minor in both fan cases.

The changes in absolute pressure difference for both fan cases were found to be significantly lower compared to the differences when varying the heat release rate. The differences in magnitude compared to the base cases were almost negligible in the downstream case, which could be attributed to lower flow velocity increases.

mass flow rate

(min)

Blower fan

fan

normalized downstream mass flow rates of the segments with a co current flow direction for an increasing longitudinal flow velocity

4.4 Increasing distance between fire and exhaust fan

The modelled domain was extended so that the distance between the fire and the exhaust fan (and the downstream measuring point) was increased by 3 m.

When increasing the distance between the fire and the exhaust fan, the resulting upstream mass flow rate and flow velocity are slightly lower than the base case, but the difference is only a few percentages. The upstream mass flow rate of segments in the counter current direction displays a smaller increase. The mass flow rates of the individual segments largely follow the corresponding results of the base case. The flow velocity of the second highest segment displays a decrease, whereas the remaining segments follow the base case values.

The resulting total downstream mass flow rate, the mass flow rate of segments with a co current flow direction (see Fig.23) and the average flow velocity displayed a slight increase with an increasing distance. The throttle effect was found to decrease with increasing distance. The negative flow velocities of the second lowest andthirdsegment fromthefloordecreasedinmagnitudewithincreasingdistanceaspredictedinchapter 4.1. The cooling effect on the flowing gas with an increased distance can be seen in Fig.24 with an increase in the average gas density at the exhaust fan. The modelled surface roughness in the simulations was defined as a smooth surface, whereasthe rocksurface alonga mine drift will have rough characteristics which will further increase the cooling of the flowing gases [20].

Normalized mass flow rate t (min)

Normalized average gas density t (min)

Figure 23. The normalized downstream mass flow rates of the segments with a co current flow direction for an increasing distance between the fire and the exhaust fan

Figure 24. The normalized downstream average gas density for an increasing distance between the fire and the exhaust fan

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The increased cooling of a rough rock surface will increase the downstream mass flow rate of segments with a co current flow direction, decrease the throttle effect and increase the smoke extraction efficiency of the exhaust fan. Ensuring an adequate distance and cooling effect between any potential fire position and an exhaust fan will be an efficient tool when increasing the smoke extraction performance of the fan. Unfortunately, when increasing the smoke extraction capacity downstream of the fire the upstream mass flow rate of segments in the counter current direction increases as well. This dilemma will have to be accounted for in the planning of the smoke extraction of the mine section in question. The upstream absolute pressure difference for the exhaust fan case was lower than the base case, which will be attributed to lower upstream flow velocities.

4.5 Full scale values

A well defined similarity exists between the model scale results and the corresponding full scale results, allowing for a translation of the model scale results by using the theory of dimensionless groups [21 23]. Equations (1 2) contain the scaling models for the heat release rate and the flow velocity. The index F seen in equations (1 2) relates to the full scale (i.e., 15 in this case) and the index M relates to the model scale (i.e., 1 in this case). A model scale length of 1 m would therefore be equivalent to 15 m in full scale.

Heat release rate:

Flow velocity:

where �� is the heat release rate [kW],

is the flow velocity [m/s] and �� is the length [m].

Calculating the equivalent full scale heat release rates using equation (1), a model scale heat release rate of 29 kW corresponds to approximately 25.3 MW in full scale, 58 kW correspondsto approximately 50.5 MW and 116 kW corresponds to approximately 101.1 MW. A 25.3 MW peak heat release rate is close to the peak heat release rate of a drilling rig fire [24]. A 50.5 MW fire will most likely involve several larger mining vehicles to attain such high peak heat release rate. A fire underground with a peak heat release rate of 101.1 MW would imply a catastrophic fire with very high fuel load, possibly involving a fuel tanker. In the simulations, backlayering was found to be more severe in the exhaust fan case, but where a larger increase in the backlayering would occur for the blower fan case when increasing the heat release rate from 58 kW to 116 kW. Thus, a more severe backlayering will generally be more probable and be expected in an exhaust fan case but for fires with extremely high heat release rates the worsening conditions for a blower fan case will have to be accountedforinthe design of thesmoke evacuationsystem. Thethrottle effect was foundto besignificantly higher in the exhaust fan case for the 29 kW and 58 kW fires and where the differences between the two fan cases increased even further when increasing the heat release rate from 58 kW to 116 kW as the throttle effect started to reverse in the blower fan case. Thus, when attaining very high heat release rates the choking conditions caused by the throttle effect will deteriorate even further for the exhaust fan case whereas it will take a directly opposite course in the blower fan case.

Calculating the equivalent full scale flow velocities using equation (2), a model scale flow velocity of 0.168 m/s corresponds to approximately 0.65 m/s in full scale and 0.21 m/s corresponds to approximately 0.81 m/s. These full scale flow velocities are low ventilation velocities for a mine drift and would explain the high degree of backlayering in the simulations.

The increased distance when extending the modelled domain between the fire and the exhaust fan would be equivalent to 45 m. When studying the results in Fig 23, the long extension would seem to have limited cooling effect but given the extensive cooling effect of the rough rock surface a considerably larger cooling effect can be expected for a 45 m extension.

5. Conclusions

A study on the variations of the throttle effect and its impact for a blower fan case versus an exhaust fan case in a mine drift was performed. Experimental data from fire experiments in a model scale mine drift and modelling results from a CFD model were used when analysing the throttle effect and mass flow phenomena of the two fan cases.

The differences between thetwo fan cases were found to be significant, both in magnitude and occasionally indirection.Itwasfoundthatforthebasecasesthethrottleeffectwasmoreseverefortheexhaustfancase,which was due to significantly lower downstream flow velocities at the upper two segments for the exhaust fan case. For the exhaust fan case, the average downstream flow velocity decreased with a fire occurring. The decrease was significantly lower compared with the decrease in the upstream flow velocity. For the blower fan case the opposite occurred, i.e., the average flow velocity increased with an occurring fire. A more severe backlayering resulted in the exhaust fan case, where the upstream counter current flow velocity at the uppermost segment was approximately 1.5 times higher in the exhaust fan case compared with the blower fan case.

When decreasing the heat release rate to 29 kW the backlayering decreased as well and with a larger reduction of the backlayering for the blower fan case. The reduction is caused by an increasing mass flow rate and flow velocity in the middle segment and a decreasing counter current mass flow rate and flow velocity of the uppermost segment. The throttle effect was found to decrease at a similar magnitude for the two fan cases.

When increasing the heat release rate to 116 kW an increasing backlayering resulted for both fan cases and where the increase will be larger for the blower fan case. The throttle effect was found to increase for the exhaust fan case and decrease for the blower fan case. The throttle effect decreased in the blower fan case as the gas density decrease was found to level off, but the flow velocity was found to increase even further and thuscausinganincreaseinthedownstreammassflowrate.Thisfindingwasconfirmedbysimilar experimental results in model scale mine drifts. A model scale heat release rate of 116 kW would correspond to approximately 101.1 MW in full scale, which would imply a very severe fire in terms of intensity.

When increasing the fan flow velocity to 0.21 m/s, the backlayering decreased and the throttle effect decreased to a minor extent for both fan cases. The resulting downstream mass flow rate induced by the changes in the fire plume was higher than the mass flow rate due to the externally imposed increase of the fan flow velocity. The larger impact of the changing fire plume and the increase in the volume flow will underline the poor performance of an exhaust fan set at a constant flow velocity.

When increasing the distance between the fire and the exhaust fan, the backlayering increased and the throttle effect decreased. With increasing surface roughness of the rock surface and distance between fire and exhaust fan, an increased cooling and further decreased throttle effect can be expected.

The results from the study will increase the understanding of the throttle effect phenomenon for the two different fan cases as well as serving as an aid during the planning of the smoke ventilation system underground. This will increase the safety of an ongoing fire and rescue operation underground.

Acknowledgements

The author would like to thank and acknowledge the support from the Sustainable Minerals Institute, The University of Queensland.

References

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Heat release rates of multiple objects at varying distances Fire Safety Journal, vol.52, pp. 1 10.

[2] Hansen R., 2021

Modelling the throttle effect in a mine drift Journal of Sustainable Mining, vol 20, pp 277 295

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Effect of Duct Fire on the Ventilation Air Velocity. Report of Investigations 8311 Bureau of Mines United States Department of Interior.

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Interaction Between Duct Fires and Ventilation Flow: An Experimental Study. Combustion and Technology, vol. 20, pp. 59 72.

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Calculating Fire Throttling of Mine Ventilation Airflow. Report of Investigations 9076 Bureau of Mines United States Department of Interior.

[6] Hansen R , 2020

Mass flow during fire experiments in a model scale mine drift with longitudinal ventilation. Mining Technology, vol. 129, pp. 68 81. https://doi.org/10.1080/ 25726668.2020.1766302.

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[7] Edwards J.C., Hwang C.C., 1999

CFD analysis of mine fire smoke spread and reverse flow conditions. NIOSH.

[8] Edwards J.C., Hwang C.C., 2006

CFD modelling of fire spread along combustibles in a mine entry SME annual meeting and exhibit, St. Louis, MO

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Modeling carbon monoxide spread in underground mine fires. Applied Thermal Engineering, vol. 100, pp. 1319 26.

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Experimental and modelling investigation of the effect of ventilation on smoke rollback in a mine entry. NIOSH.

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Smoke reversal interaction with diagonal airway its elusive character. NIOSH.

[12] Friel G.F., Yuan L., Edwards J.C., Franks R.A , 2006.

Fire generated smoke rollback through crosscut from return to intake experimental and CFD study. NIOSH.

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Modelling temperature distributions and flow conditions of fires in an underground mine drift Geosystem Engineering, vol. 23, pp. 299 314.

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Investigating the Throttling Effect in Tunnel Fires Fire Technology, vol. 52, pp. 1619 1628.

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Model scale fire experiments in a model tunnel with wooden pallets at varying distances Research report SiST 2010:8. Mälardalen University. Västerås, Sweden.

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Computational Fluid Dynamics in Fire Engineering, Theory, Modelling and Practice. Academic Press, Oxford.

[19] McGrattan K., Hostikka S., Floyd J., McDermott R., Vanella M , 2020.

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The influence of rough rock surface on the heat losses of fire gases in a mine drift Proceedings of the 5th World Congress on Mechanical, Chemical, and Material Engineering (MCM’19), Lisbon, Portugal.

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This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

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FINITE ELEMENT ANALYSIS OF A CUTTING AND HAULING MINING ADAPTER

Zoltán VIRÁG1*

1University of Miskolc, Institute of Mining and Geotechnical Engineering, Miskolc, Hungary, gtbvir@uni miskolc.hu

DOI: 10.2478/minrv 2022 0017

Abstract: A recently completed research focused on the development of a low volume mining production and transportation prototype machine By developing this new mining adapter, the number of machines used in the mine can be reduced. Its application in dimensional stone mining can reduce the expenses of mining companies After the block stone has been cut around, the stone material can be moved with the machine The cutting forces and power requirements are calculated for the chain speeds used in production. This paper shows the static stress analysis of two kinds of possible structures of the dimension stone mining adapter. Finite element analysis was used to determine the displacements and the effective stress distribution of the adapter.

Keywords: dimensional stone, mining adapter, chainsaw, cutting force, FEA

1. Introduction

A recently completed research focused on the development of low volume limestone mining production and transportation machine The goal of the development is to optimize the mining of dimensional stone by rethinking the use of production and transportation based on a construction loadall machine. The aim of the project is the exploitation of Leitha limestone in the Soproni Mountains. This stone is currently mined in two mines (Szentmargitbánya and Fertőrákos). All over the world, limestone has been a popular building material for thousands of years. This stone was already used by the Celts and the Romans, but it became an important buildingmateriallater.Itwasverypopular becausethisstonewaseasytomineandtransport.Itwastransported in huge quantities to nearby major cities. Most of the houses in Bratislava, Sopron and Vienna are built of this stone, and buildings, monuments and statues made of this limestone can be found in almost every settlement in the area. These structures are under the protection of monuments, so they can only be renovated with the original building material. That is why it is important to continuously develop this area of technology as well.

Manytechnologiesfordimensional stoneproductionhave been developed over the years.The best known are the following: the creation of blocks by drilling and rock sawing, use of rock setting wedges placed in small diameter holes, cleavage of stone blocks using chemical swelling energy, and block production with a large borehole blasting technology. Since rock sawing is the most gentle production technology, where no unwanted cracks appear in the stone, we have developed our machine for this method of winning.

Chainsaws are often used in dimensional stone quarries, so questions constantly arise in terms of creating the best operating conditions. There are few studies of mining chainsaws in the scientific literature, and most studies focus on monitoring and measuring performance. An example of this is the definition of standardized cutting forces and cutting angles and the identification of important parameters like the depth of cut and feed rate per single tool [1]. Another paper deals with aspects of tool lacing for chainsaw machines and explains how the cutting performance of these machines can be increased and the tool wear reduced [2].

The mining machine for cutting and transportation can reduce the number of mining equipment in the dimensional stone quarries (see Figure 1). Its main goal is planned to reduce the expenditures of mining companies, which contain costs of maintenance and mining operations [3]. The main goal of the paper is to investigate the power requirement of the cutting tool for cutting and to examine the adapter structure by the finite element method.

* Corresponding author: Zoltán Virág, Assoc. Prof., University of Miskolc, Miskolc, Hungary, (H 3515 Miskolc Egyetemváros, gtbvir@uni miskolc.hu)

2. The mining prototype

2.1 The basic machine of the prototype

The mining prototype machine is based on a JCB 540 170 Construction Loadall (see Figure 2). This vehicle is used in many areas for a variety of works due to its high load capacity and unique design. It has a highly maneuverable drive that makes it easy to use in tight spaces. The machine has two four wheel steers modes for working in confined spaces, and the crab steer for maneuvering close to walls. Adaptive Load Control automatically controls and adjusts hydraulic operation to help maintain thelongitudinal stability of the vehicle. This machine is very energy efficient, consuming up to 7% less fuel than the previous ones. It makes this vehicle more environmentally friendly than its competitors. The economic engine of the loadall can be adapted to lower quality diesel oils, so the machines can be used in different working areas [4].

Its multi functional applicability is ensured by the high performance hydraulic system. To perform the various tasks, the built in system provides a system operating pressure of 260 bar and the main pump capacity of 90+72 l/min. Two front stabilizers are installed to increase the stability and lifting capacity of the machine. The adapter is in place of the forklift by the end of the boom.

Figure 1. The dimensional stone mine with an old rock saw machine

Figure 2. Construction Loadall vehicle with the prototype mining adapter

2.2 The prototype adapter

The small volume mining adapter designed in the project is suitable for extracting one cubic meter of dimensional stone, primarily limestone quality. In the present study, the conceptual design of the prototype adapter is clarified in one cylinder (see Figure 3) and two cylinder (see Figure 4) versions.

Figure 4. The model of the adapter with two cylinders

Based on the mining technology, the adapter can be divided into two main units. One is the chainsaw unit combined with a work consisting of hydraulic cylinders for feeding The other is a hydraulic rotation unit that allows the adapter to be rotated 90° in both directions. The individual structure of the rock chainsaw is built on special cutting elements. The manufacturer developed the chainsaw specifically for limestone rock grade (see Figure 5). The cutting teeth forming the chain follow each other in a specific order and form a chain sequence of 7 teeth, which reduces the chip area in this way. The dimensions of the cutting tool are extremely important, as they have a great influence on the already high cutting forces and loads [5, 6]. Reducing the chip area reduces stresses, which is important because high loads can have an undesired effect on the mechanics [7,8].

The other unit of the mining tool is used to support and stiffen the first main machine unit during slotting. This unit provides stability and elevation of the object table made of a special alloy with an excavated stone block in a direction perpendicular to the front. The blocks slide on wear resistant carbide plate components that are complemented by several modular elements that are subject to heavy wear in mining applications [9].

Figure 5. A chainsaw sequence

Figure 3. The model of the adapter with one cylinder

3. Cutting forces and cutting power

Determining the properties of the mined stone is important for the design of the mining adapter to be developed.Intheinitial phaseoftheresearch,animportant taskduring designistodeterminethecuttingforces and power requirements. The following numerical examples show a brief calculation for the chain speeds used in production

Based on the experience gained during our previous rock cutting tests, the average specific cutting force is determined [10]. For limestone, the cutting force is calculated with a value of Fcutting = 24 N/mm2 Chain speeds specified by the manufacturer are vchain = 0.4, 0.9, 1.2 and 2.1 m/s. The teeth pitch is lpitch = 0.1 m. The cutting length of the adapter is lcutting = 1.2 m. The chip area is a constant Achip= 6 mm2 The number of cutting chain parts working at the same time is

The overall cutting force is calculated as

where Achip is the chip area. The power demand is

Since we do not examine the chain friction and the efficiency of the machine separately during the calculations, based on our many years of practical experience, it is worth increasing the power by 25% to the required power requirement for safe operation. The calculated cutting forces and cutting powers for different chain speeds are shown in Table 1.

Table 1. Cutting forces and cutting powers.

Chain speed [m/s]

Cutting force for one tooth [N]

Overall cutting force [N]

Cutting power [W] Increased cutting power [W] 0,4 144 1728 691 2 864 0,9 144 1728 1555 2 1944 1,2 144 1728 2073 6 2592 2,1 144 1728 3628 8 4536

The results shown in Table 1 can be provided by the prototype machine.

4. Finite element analysis

Another special task is the design of the basic structure of the prototype adapter. Initially, we examined two constructs, a one cylinder (see Figure 3) and a two cylinder (see Figure 4) versions The greatest load on the adapter occurs during the transport of excavated stone when it loads the object table with its full weight. Finite element analysis is used to determine stresses and displacements of the adapter. This first type of prototype adapter is designed for a 1 m3 limestone which has a maximum density of 2500 kg/m3 For safety reasons, this highest density was taken into account in our calculations. The FE model is designed in such a way that the distributed load due to the weight of the stone acts on the object table, and the ends of the beams are connected to a totally rigid connector. The results are shown with both retracted and extended booms in Figures 6 to 13.

Figure 6. Effective stress distribution in the adapter (one cylinder) with retracted boom.

Figure 7. Displacements in the adapter (one cylinder) with retracted boom.

Figure 8. Effective stress distribution in the adapter (one cylinder) with extended boom.

Figure 9. Displacements in the adapter (one cylinder) with extended boom.

Figure

Effective stress

adapter (two cylinder) with

boom.

Figure

Figure

Displacements in the adapter (two cylinder) with retracted boom.

Effective stress

(two cylinder) with

boom

Figure

(two cylinder) with

Revista Minelor Mining Revue vol. 28, issue 3 / 2022 ISSN L 1220 2053 / ISSN 2247 8590 pp. 21 27

The results in the figures show maximum stress of 103 MPa and a maximum displacement of 12.26 mm, which are appropriately small values for the structure. The results show that the maximum stress is displayed on the lower cylinders when the boom is retracted, while it is displayed on the upper stiffener when extended. The largest displacement is seen at the end of the adapter as expected. Owing to the two upper closed section booms, both constructions are suitable, but the two cylinder version has been implemented to avoid jamming due to asymmetry during extending of the boom (see Figure 2).

5. Conclusions

Locally available, high quality limestone is needed for the proper reconstruction of historic buildings and monuments. Rock sawing is the gentlest production method, where no unwanted cracks appear in the stone. That is why the idea came up to design mining equipment with a chain saw for dimensional limestone. The machine can provide the cutting force and power required for rock sawing, which have been calculatedat different chainspeedsusedindimensional limestonemining. Thetransport oftheexcavatedstone generates the greatest load for the adapter. The results of the finite element analysis used to determine the stresses and displacements of the adapter confirmed that both design versions are adequate. The two cylinder version was implemented to avoid jamming of the extending boom. The following step is a comprehensive testing period of the adapter, which is essential for further development. During the on site cutting test, the dynamic stress of the machine units will be examined in extreme cases to determine more precise parameters.

References

[1] Romoli, L. 2018

Cutting force monitoring of chain saw machines at the variation of the rake angle, International Journal of Rock Mechanics and Mining Sciences, 101, pp. 33 40.

[2] Hekimoglu, O.Z. 2014

Studies on increasing the performance of chain saw machines for mechanical excavation of marbles and natural stones, International Journal of Rock Mechanics and Mining Sciences, 72, pp. 230 241.

[3] Virag, Z., Fülöp, V., Molnár, J. 2018

Initial steps to develop a cutting and hauling adapter for dimension stone mining, Annals of the University of Petrosani: Mechanical Engineering, 20, pp. 121 126.

[4] Kovács, Gy., Gubán, M. 2017

Planning of Optimal Fuel Supply of International Transport Activity, Periodica Polytechnica Transportation Engineering, 45 (4), pp. 186 195

[5] Tomus, O. B., Rada, A. C. 2017

Study of the cutting forces and specific cutting resistance from the point of view of the cutting direction relative to stratification of the coal seam, Annals of the University of Petrosani: Mechanical Engineering, 19, pp. 143 148.

[6] Virág, Z., Szirbik, S. 2012

Examination of an optimized replaceable cutting tooth of excavator, Geosciences and Engineering, 1 (1), pp. 337 342.

[7] Andras, I., Radu, S. M., Andras, A 2016

Study Regarding the Bucket Wheel Excavators Used in Hard Rock Excavations, Annals of the University of Petrosani: Mechanical Engineering, 18, pp. 11 22.

[8] Andras, A., Radu, S. M., Brînaș, I., Popescu, F. D., Budilică, D. I., Korozsi, E. B. 2021

Prediction of Material Failure Time for a Bucket Wheel Excavator Boom Using Computer Simulation, Materials, 14 (24), 7897

[9] Kovács, Gy. 2019

Optimization of structural elements of transport vehicles in order to reduce weight and fuel consumption, Structural Engineering and Mechanics, 71 (3), pp. 283 290.

[10] Ladányi, G., Sümegi, I., Virág, Z. 2007

Laboratory rock cutting tests on rock samples from Visonta South Mine, AnnalsoftheUniversityofPetroşani,Mechanical Engineering, 9, pp. 209 218

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 28 38

ASSESSMENT OF THE TILT PHENOMENON AND THE TILT DISTANCE OF THE LAND AS AN EFFECT OF COAL MINING, JIU VALLEY BASIN, ROMANIA

Mihai Valentin HERBEI1 , Roxana Claudia HERBEI2 , Florin SALA3*

1University of Life Sciences “King Michael I” Timișoara, Remote Sensing and GIS dept., Timișoara, Romania, mihai_herbei@yahoo.com

2University of Petrosani, Cartography, Mining Surveying and Real Estate dept., Petrosani, Romania, roxanaherbei@upet.ro

3University of Life Sciences “King Michael I” Timișoara, Soil Science and Plant Nutrition dept., Timișoara, Romania, florin_sala@usab tm.ro

DOI: 10.2478/minrv 2022 0018

Abstract: The aim of the study was to evaluate the phenomenon of land tilting and the tilting distance as a secondary effect of surface coal mining in the Jiu Valley area, Romania. To evaluate the tilting phenomenon, through the two considered elements (inclination Lt, tilting distance Td) 16 control points (CP1 to CP16) were used whose coordinates were measured in the Stereographic 1970 projection system, the 1975 Black Sea elevation system at an initial moment (t0) and at the current moment (t1). The static method was used by GPS technology to measure the elevations of the control points. Through descriptive statistical analysis, a general characterization of the set of recorded values was obtained, and the ANOVA test confirmed the safety of the data and the presence of variance in the data set. From the analysis of the recorded values, a Spline type model was obtained that described the variation of Lt in relation to Td, under conditions of statistical safety ( 0137302ε

). Regression analysis facilitated the obtaining of equation type models, which described the variation of Lt and Td in relation to the X, Y and Z coordinates of the control points (t0, t1), under conditions of statistical certainty (R2 =0.697, p=0.014 for Td variation according to Z0 and Z1; R2 =0.722, p=0.0094 for Td in relation to X0 and Z0). According to PCA, PC1 explained 61.303% of variance, and PC2 explained 38.697% of variance. The cluster analysis facilitated the obtaining of a dendrogram based on Euclidean distances, regarding the grouping based on the similarity of the control points in relation to the studied phenomenon, under conditions of statistical safety (Coph. corr.=0.957).

Keywords: Land tilt, tilt distance, coal mining, Spline model, regression analysis

1. Introduction

The exploitation of different categories of resources from the earth's crust can be done with different technologies, depending on the type of resources and their location in the deposits formed in relation to the surface of the soil, in surface quarries or in underground mines, with major implications on ecosystems and the environment in whole [1], [2], [3].

For a long period of time, coal represented an important energy resource, which facilitated the development of human society, was exploited in different technical and efficient conditions, with socio economic but also environmental impact, and currently approaches regarding the sustainable exploitation of coal are of interest [4], [5], [6], [7], [8].

Mining greatly affects the morphology of the land surface and soil structure, and the restoration of the vegetation on the affected lands, within a complex of measures, as a post exploitation process, is an effective way to restore natural balances, to preserve habitats and mitigate the ecological and social impact economic [9], [10], [11].

* Corresponding author: Florin Sala, Professor Ph.D, University of Life Sciences “King Michael I” Timisoara, (Calea Aradului Street, 119, 300645, Timisoara, Romania, florin_sala@usab tm.ro)

The lands and soil in the areas affected by mining were also studied from pedogenetic, morphological, physical, chemical, biological and microbiological perspectives, as a detectable effect of mining activities, but also from the perspective of the effect on vegetation, agriculture, quality of life, but and by ecological restoration and reconstruction [12], [13], [14], [15].

The reduction of soil fertility and soil degradation were evaluated in relation to land subsidence in the specific conditions of some coal mining areas [16].

The areas affected by coal mining have been studied and evaluated through the prism of specific elements of land surface modification (eg sinking, sliding, tilting, categories of use, economic use, etc.) in order to characterize the extent of the phenomena, to make forecasts, to provide data and information for an adequate management of the affected areas [17], [18], [4], [19].

At the same time, the affected areas were studied for the purpose of their recovery, ecological and socio economic reintegration by re vegetating the lands affected and disturbed by mining in order to make hay, pastures or cultivated lands [20], by restoring the landscape post mining [21], reforestation [22], etc.

For this purpose, the use of germplasm adapted to local or zonal Eco physiological conditions can be considered [23], different methods were used based on genetically modified plants, adapted for such places [24], the promotion of green technologies in the recovery and re cultivation of affected lands [25], the use of techniques based on mycorrhization of the planted biological material [26].

In the context of the interest for these categories of land, the study proposed to evaluate the phenomenon of tilting and the distance of the tilting of the land as an effect of coal mining, in the area of the Jiu Valley, Romania.

2. Materials and method

In order to evaluate the tilt of the land and the distance from the tilt, as a secondary effect of the mining activities (coal mines), an area in theJiu Valley, Romania, was considered for the study. 16 control points (CP) were identified, for which the coordinates were measured in the Stereographic projection system 1970, the Black Sea elevation system 1975 at a time t0 (reference time) and at a time t1, in order to capture possible differences betweentheinitial values(t0)andthe final ones (t1).The area under study, with an area of 95403.89 ha, is located in the Jiu Valley, Romania, with a general presentation of the terrain tilt in figure 1.

Figure 1. Map of Slope, Jiu Valley, Romania

The tilt of the land and the distance from the tilt were studied, phenomena that appear as consequences of the mining operations in the area under consideration.

Underground mining has the effect of moving and deforming the land following the extraction of useful mineral matter.

These land surfaces, affected by underground exploitations, require monitoring in time and the realization of real time forecasts for the purpose of integrated management measures to protect the land surface and the existing constructions on it, to mitigate the manifestation of this phenomenon and ensure a sustainable development in the respective areas, these being generally mono industrial areas and disadvantaged areas. In the conditions of the present study, the tilt of the land surface and the tilt distance were analyzed.

The tilt of the surface represents the inclination of an area the segment between two tracking points on the surface, relative to its initial position. This represents the differential variation of the vertical movement and is determined by the ratio between the differences in the dips of two consecutive observation landmarks and the horizontal distance between them, equation (1). Tilt is a deformation of the surface due to subsidence and has nothing in common with the physical tilt of the land surface.

D SS

(1)

where: Si the sinking of the current landmark; Si+1 sinking the next landmark; di,i+1 the horizontal distance between the two landmarks.

The tilt distance (Td) represents the horizontal component of the point displacement vectors. It is the horizontal displacement of a point compared to its predecessor, located in the zone of influence of the exploitation. It is determined by the difference between the current distance and the same distance initially measured (before the sinking phenomenon), equation (2).

DDD (2)

where: Di,i+1 the horizontal distance between the two landmarks at the current measurement; D0i,i+1 the horizontal distance between the same two landmarks at the "zero" measurement.

For the area proposed for tracking the inclination and the distance to the inclination, of the land surface in the Maleia mining area, the stable area and the area that is subject to movement were defined. Two types of landmarks were also considered: some for horizontal and vertical movements and others only for vertical movements. Four pairs of landmarks were placed in the stable area to determine horizontal and vertical movements.

Land surface movement tracking landmarks and topo geodetic measurements were performed using GPS technology, L1/L2 Topcon dual frequency receivers. The GPS measurement method used for geodetic accuracy is the static method.

PAST software [27], and Wolfram Alpha (2020) [28] were used to process the recorded data.

3. Results and discussion

For the characterization of the land in the study area, respectively the phenomenon of land tilting and the tilting distance, 16 control points were considered for which the elevations were measured.

The data on the elevations at two different moments of measurement (t0 and t1), table 1, were useful for evaluating the phenomenon of land tilt and the tilt distance, values that are presented in table 2. The general aspect of the framing area of the study area, regarding the tilt of the land, Jiu Valley, Romania, is presented in figure 1.

The ANOVA test confirmed the safety of the data and the presence of variance in the data set collected in the study (p<<0.001, F>Fcrit, for Alpha=0.001), table 3.

The land tilting phenomenon (Lt) in relation to the tilting distance (Td) was described by a spline type model, under statistical safety conditions, table 4, for which the values were calculated with equation (3).

Revista Minelor Mining Revue vol. 28, issue 3 / 2022 ISSN L 1220 2053 / ISSN 2247 8590 pp. 28 38

Table 1. Statistical description of the values recorded at the control points, the study area, Jiu Valley, Romania Statistical parameter t1 (current measurement) t0 (reference measurements) X 1 Y 1

0 Y 0

N 16 16 16 16 16 16

Min 373708.6 435197.4 647,994 373708.6 435197.4 648.0599

Max 375838.1 436735.4 830.6045 375838.1 436735.4 830.6333

Mean 375023.5 436133 763.6769 375023.5 436133.1 763.6596 Std. error 178.0901 112.8642 15.27511 178.0889 112.8628 15.27544

Variance 507457.3 203813.2 3733.262 507450.6 203808.1 3733,423 Stand. dev 712.3603 451.4567 61.10043 712.3556 451.4511 61.10175

Median 375150.9 436153.9 774.9239 375150.9 436153.9 774.4535 25 prcntil 374537.5 435992.3 703.3972 374537.5 435992.3 703.4014 75 prcntil 375557.1 436509 824.0965 375557.1 436509 824.1838 Coeff. var 0.189951 0.103514 8.000822 0.18995 0.103512 8.001175

Table 2. Data regarding the tilt of the land in the study area, Jiu Valley, Romania

Control point Tilt parameters

Land tilt (mm/m) Tilt distance (m) PC1 0 0

PC2 0.27764 19089.539 PC3 0.09200 635870.481 PC4 4.45942 11526.168 FP5 4.77032 219985.336 FP6 4.88820 195961.784 FP7 0.02978 1222115.108 FP8 2.24968 32715.694 PC9 0.00391 1993147.689 PC10 0.09710 683839.294 PC11 0.70407 49852.956 PC12 0.04838 1366331.720 PC13 0.16614 432770.403 PC14 0.11568 414932.795 PC15 0.03310 1480455,999 PC16 0.03605 809905.344

Table. 3. ANOVA test Source of Variation SS df THX F P values F crit Between Groups 6.44E+12 7 9.19E+11 19.08644 5.98E 17 3.766975 Within Groups 5.78E+12 120 4.82E+10 Total 1.22E+13 127

Table 4. Statistical values related to the spline model, to describe the tilt phenomenon in relation to the tilt distance Trials data Lt in relation to Td No xi yi ysi ei Ii/1 PC1 0 0 0.15635 0 1.00000 PC2 19090 0.27764 0.85167 2.06753 5.44720 PC3 6.36E+05 0.09200 0.09188 0.00135 0.58763 PC4 11526 4.45940 3.87570 0.13089 24.78862 FP5 2.20E+05 4.77030 4.75790 0.00260 30.43108 FP6 1.96E+05 4.88820 4.87470 0.00276 31.17813 FP7 1.22E+06 0.02978 0.02978 0.00013 0.19044 FP8 32716 2.24970 2.06230 0.08330 13.19028 PC9 1.99E+06 0.00391 0.00391 0.00000 0.02501 PC10 6.84E+05 0.09710 0.09699 0.00109 0.62036 PC11 49853 0.70407 0.74682 0.06072 4.77659 PC12 1.37E+06 0.04838 0.04837 0.00008 0.30940 PC13 4.33E+05 0.16614 0.16271 0.02065 1.04068 PC14 4.15E+05 0.11568 0.11994 0.03683 0.76713 PC15 1.48E+06 0.03310 0.03310 0.00006 0.21170 PC16 8.10E+05 0.03605 0.03604 0.00047 0.23049 0.137302

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The graphical distribution of the tilt values in relation to the tilt distance, according to the Spline model, is shown in figure 2.

Figure 2. Tilt in relation to tilt distance, spline model, Valea Jiului, Romania

Taking into account the overall aspect of the area under study, and the variation of the values recorded for the inclination and the distance to the inclination of the land in the specific conditions of the Jiu Valley, Romania, an analysis was made of the variance of these elements (Lt, Td) in relation to with the elevation values of the 16 control points (PC1 to PC16).

The multiple regression analysis was used, which analyzed the variation of the studied elements Lt and Td according to the quotas at the reading times t0 and t1. Based on this analysis, models of variation of Lt and Td were found, under statistical safety conditions only in relation to X0 , Z0 and Z1 . The models found were of the form f(X0,Z0 ) and f(Z0,Z1 ).

The variation of the Lt Parameter according to Z0 and Z1 was described by equation (4), under general statistical safety conditions (p=0.056). The 3D graphical representation is shown in figure 3, and the graphical representation in the form of isoquants is shown in figure 4. For the minimum tilt of the land, the optimal values for x (Z0) and y (Z1) were found in the amount of xeight = 695.3124464, and for yeight =695.2819745.

where:

Z

y Z1; a, b, c, d, e, f coefficients of the equation (4); a= 9.42472457; b= 9.23983431; c= 129.11873162; d= 129.12611575; e= 18.66456825; f = 0.

graphic representation of the Tilt variation

relation to

of the land in the study

in the form of isoquants

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Similarly, multiple regression was used to find out the variation of the tilt distance (Td) according to the values of the X0, Z0 and Z1 elevations. The result was equation (5) which described in statistical safety conditions (R2 =0.697, p=0.014) the variation of Td according to Z0 and Z1. The 3D graphical distribution is shown in figure 5. The graphical distribution in the form of isoquants is shown in figure 6. For the minimum tilt distance (Td) of the land, the optimal values for x (Z0) and y (Z1) were found in the quantum of xeight =805.038805, and for yeight =805.0132269.

Td (5) where: x Z0; y Z1; a, b, c, d, e, f coefficients of the equation (5); a= 5501184.92280514; b= 5681441.05912441; c= 144823270.924133; d= 144826425.708353; e= 11182621.1588526; f = 0.

Lookingat thevariationofTdaccordingtoX0andZ0 ,themultipleregressionanalysisresultedinequation (6) under statistical safety conditions (R2 =0.722, p=0.0094). The 3D graphical distribution is shown in figure 7, and the distribution in the form of isoquants is shown in figure 9. For the minimum tilt distance (Td) of the land, the optimal values for x (X0) and y (Z0) were found in the quantum of xeight =375397.8685, and for yeight = 777.1035984.

From the analysis of the values but also of the 3D graphic distribution, it was found that under the study conditions, the variation of Td in relation to X0 and Z0 was very strongly influenced by the elevation Z0 (y axis, fig. 7) for which the value was found optimal yeight = 777.1035984. Under the same conditions, the ratio of the X 0 rate to the Td variation was negligible.

Td (6) where: x X0; y Z0; a, b, c, d, e, f coefficients of the equation (6); a= 0.01676537; b= 182.73301809; c= 5999.10099842; d= 2898613.41143636; e= 8.47798735; f = 0.

Figure 5. 3D graphic representation of the Td variation in relation to the x(Z0) and y (Z1) elevations of the land in the study area.

Figure 6. Distribution in the form of isoquants of Td values depending on x (Z0) and y (Z1) in the study area

Figure 7. 3D graphic representation of the Td variation in relation to the x (X0) and y (Z0) elevations of the land in the study area

Figure 8 . Distribution in the form of isoquants of Td values depending on x (X0) and y (Z0) in the study area

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According to PCA, the distribution diagram of the control points was obtained in relation to the land tilt phenomenon, through the prism of the two elements considered, Lt and Td, figure 9. PC1 explained 61.303 % of variance, and PC2 explained 38.697 % of variance. From the analysis of the distribution of control points, it was found the orientation and association of some points with Lt (PC4, PC6), the association of some points with Td (PC9,PC15,PC12,PC7),as well astheintermediateor independent positioning(egPC5) of other pointscontrol.

The cluster analysis led to the grouping of the control points, as a trial point, in relation to the tilting phenomenon, under conditions of statistical safety (Coph. corr. =0.957), figure 10. In the case of the obtained dendrogram, based on the Euclidean distances, the independent positioning of the PC5 point and the association of the other points in several clusters and sub clusters were found, in relation to the degree of similarity for the studied inclination phenomenon.

From the analysis of the dendrogram in figure 10 and the SDI values (table 5), it was found a high level of similarity of the control points in relation to the phenomenon of land tilt, through the prism of the studied elements. High level of similarity was registered at control points PC15 and PC16, PC1 and PC9, PC12 and PC16, PC12 and PC15. The set of SDI values obtained for all control points is presented in table 5.

Figure 9. PCA diagram regarding the distribution of control points in relation to the tilting phenomenon and the tilting distance

Figure 10. Dendrogram of the grouping of control points (CP) in relation to the phenomenon of land tilt in the studied area, Jiului Valley, Romania

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Table 5. SDI values regarding the similarity of control points in relation to the phenomenon of land tilt

PC1 PC2 PC3 PC4 FP5 FP6 FP7 FP8 PC9 PC10 PC11 PC12 PC13 PC14 PC15 PC16

PC1 0.278 0.092 4 459 4 770 4 888 0.030 2 250 0.004 0.097 0.704 0.048 0.166 0.116 0.033 0.036 PC2 0.278 0.186 4.182 5.048 4.611 0.307 1.972 0.282 0.375 0.426 0.229 0.444 0.393 0.245 0.242

PC3 0.092 0.186 4 367 4 862 4 796 0.122 2 158 0.096 0.189 0.612 0.044 0.258 0.208 0.059 0.056

PC4 4 459 4 182 4 367 9 230 0.429 4 489 2 210 4 463 4 557 3 755 4 411 4 626 4 575 4 426 4 423

FP5 4.770 5.048 4.862 9.230 9.659 4.741 7.020 4.766 4.673 5.474 4.819 4.604 4.655 4.803 4.806

FP6 4 888 4 611 4 796 0.429 9 659 4 918 2 639 4 892 4 985 4 184 4 840 5 054 5 004 4 855 4 852

FP7 0.030 0.307 0.122 4 489 4 741 4 918 2 280 0.026 0.067 0.734 0.078 0.136 0.086 0.063 0.066

FP8 2.250 1.972 2.158 2.210 7.020 2.639 2.280 2.254 2.347 1.546 2.201 2.416 2.365 2.217 2.214

PC9 0.004 0.282 0.096 4 463 4 766 4 892 0.026 2 254 0.093 0.708 0.052 0.162 0.112 0.037 0.040

PC10 0.097 0.375 0.189 4 557 4 673 4 985 0.067 2 347 0.093 0.801 0.145 0.069 0.019 0.130 0.133

PC11 0.704 0.426 0.612 3 755 5 474 4 184 0.734 1 546 0.708 0.801 0.656 0.870 0.820 0.671 0.668

PC12 0.048 0.229 0.044 4.411 4.819 4.840 0.078 2.201 0.052 0.145 0.656 0.215 0.164 0.015 0.012

PC13 0.166 0.444 0.258 4 626 4 604 5 054 0.136 2 416 0.162 0.069 0.870 0.215 0.050 0.199 0.202

PC14 0.116 0.393 0.208 4 575 4 655 5 004 0.086 2 365 0.112 0.019 0.820 0.164 0.050 0.149 0.152 PC15 0.033 0.245 0.059 4.426 4.803 4.855 0.063 2.217 0.037 0.130 0.671 0.015 0.199 0.149 0.003

PC16 0.036 0.242 0.056 4 423 4 806 4 852 0.066 2 214 0.040 0.133 0.668 0.012 0.202 0.152 0.003

The spatial and temporal interaction between coal extraction in surface quarries, land cover and changes in the use of directly affected or neighboring land surfaces have been taken into account in some studies, with the aim of sustainable mining [29].

In order to optimize the recovery measures of the lands affected by mining, the content and the variation of the content of nutrients in the soil were taken into account and studied in relation to possible categories of land use [30].

Land instability as a result of mining works was studied in relation to different factors (type of rocks, humidity conditions) that generated certain physical and mechanical characteristics and led to land instability [31].

Soil erosion has been studied in relation to agricultural and mining activities, from the perspective of the threat to the balance of ecosystems [32].

The Valea Jiului area, Romania, presented interest for study from different ecological, economic and social perspectives. The water quality was studied from the perspective of the content of heavy metals and some chemical compounds that affect its various uses [33]. Similar research was carried out regarding the quality of water and some sediments in the Cavnic mining area and the Lapus river [34].

Polluting aspects with heavy metals, associated with mining activities in the exploitation of some resources of interest have been evaluated in different mining basins around the world [35], [36].

In the context of the high interests given to the areas and land surfaces affected by coal mining, for the purpose of their monitoring, their ecosystem integration, socio economic valorization, the present study contributed to an analysis regarding the tilt and tilt distance and provided information and approach models for the purpose of adequate management of these land categories.

4. Conclusions

The approach used in the present study facilitated the analysis and evaluation of the phenomenon of land tilting and the tilting distance, as a secondary effect of coal mining in Jiu Valley, Romania.

Models of the type of mathematical equations were obtained that described the phenomenon of tilting and the tilting distance in relation to 16 control points, whose elevations were measured at different times (t1 and t0).

The PCA analysis facilitated obtaining a distribution of control points in relation to the affinity to the two studiedelements(inclinationanddistancetoinclination),whichconfirmedthat theapproachmethodfacilitates the clear detection of points in the field for the purpose of high level highlighting fidelity of the analyzed phenomenon.

The cluster analysis facilitated the obtaining of a dendrogram of grouping the control points in relation to the degree of similarity to the manifestation of the studied inclination phenomenon.

Revista Minelor Mining Revue vol. 28, issue 3 / 2022

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Acknowledgements

The authors thankto the GEOMATICS Research Laboratory, Universityof Life Sciences "KingMichael I" from Timisoara, for the facility of the software use for this study.

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This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

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ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 39 47

RESEARCH ON FOG GUNS FOR DUST REDUCTION AT COAL FIELD ROȘIUȚA QUARRY

Daniela CIOLEA1*,Vasile BOBEI2, Marius BERCA3

1University of Petrosani, Petrosani, Romania, danielaciolea@upet.ro

2Oltenia Energy Complex, Tg. Jiu, Romania, vasile.bobei@ceoltenia.ro

3Oltenia Energy Complex, Tg. Jiu, Romania, marius.berca@ceoltenia.ro

DOI: 10.2478/minrv 2022 0019

Abstract: In order to comply with the provisions of the normative acts in the field of air quality (STAS 12574/1987 maximum allowed concentrations of sedimentable powders [1]), it was proposed to build a water mist dedusting facility within the coal deposit to stop the dust emissions at the source. The installation must ensure long term operation in harsh conditions, with resistance to wear and minimal maintenance: operating time 12 14 hours/day, 365 days/year. The dedusting plant is composed of the water house, the distribution network, the fog production plants and the electricity supply plant. The process used to create the mist is based on the use of high pressure pumps. The equipment consists of fog guns equipped with high pressure water spray nozzles and dispersion fans that are purchased fully equipped including a remote control installation; 6 spray guns were provided.

Keywords: dust emissions, sedimentable powders, installation, equipment

1. General data

The technological flow at Roşiuţa Quarry was followed and the land for the area meant to continue the works in the existing license perimeter was checked. It was observed that [2]:

The surface of Roşiuţa mining perimeter, approved by the exploitation license, is 1866.50 ha, of which 787.70 ha are for the continuation of the lignite exploitation works;

The excavation is carried out with 7 (seven) excavators with a rotor type ERc 1400x30/7;

The exploitation works consist in the extraction of coal from layers V XII of lignite; Exploitation is done in parallel blocks, with a width of 40 45 m;

There are no coal self ignition foci in the layer; No areas with landslides were identified; No mirrors of water or waste were identified;

No protected species of flora or fauna were identified on the site;

In the areas adjacent to the site, the quarry activity is not audible; 70% of the targeted households are already expropriated by Oltenia EC; the village of Runcurelu is not connected to utilities (water, gas, sewage, streets, etc.), and the proposed village hearth has all these facilities; Dozens of ecologically rehabilitated hectares were identified, in a forestry regime by Oltenia EC; Fog guns, to blur the powders.

In the perimeter intended for the continuation of the works at Roşiuţa Quarry, forest vegetation was identified, mature trees which include the following species: beech, hornbeam, acacia, hornbeam, hornbeam, hornbeam and oak, practically nothing special and irreplaceable for the next stage that follows the exploitation of the energy resource, more precisely, the area concerned can and will be ecologically rehabilitated at the appropriate time.

Roşiuţa Quarry is located in a typically hilly area. The total area from which fertile soil can be mechanically harvested represents about 45.84 ha out of a total of 787.70 ha. In this context, the uncovered soil will be used immediately by depositing it as fertilizing material on the landscaped surfaces of the dumps.

* Corresponding author: Daniela Ionela Ciolea , Assoc.Prof.Eng. Ph D, University of Petrosani, Romania, 20 Univeristatii str., 332006 Petrosani, Romania, danielaciolea@upet.ro, 0251542580/int. 236

Revista

Through the implementation of the project, there is no expansion of Roşiuţa Quarry outside the license perimeter, just maintaining of the production capacity within the same mining perimeter, cf. HG 1294/2007.

From the framing plans and also fromthe field research, we found that the distance from the area intended for the continuation of the works at Rosiuţa Quarry to the protected area ROSCI0045 Jiu’s corridor represents over 21 km East and over 6 km West from the RO SCI 0366 Motru River.

The water mist dedusting facility within Roșiuța coal deposit is intended for stopping the dust emissions at the source (Figure 1).

2. Project characteristics

The reasons, on the basis of which, the need for not carrying out the environmental impact assessment was established, are the following ones:

a) The project falls within the provisions of Law no. 292/2018 regarding the assessment of the impact of certain public and private projects on the environment, Annex no. 2, point 10. a) Development projects of industrial units/areas and point 13. a) Any changes or extensions, other than those provided for at point 24 of annex no. 1 [3];

b) From the analysis of the control list for the framing stage, it follows that the project does not have a significant impact on the environment;

c) The points of view expressed in writing by the TAC members were not of a nature to lead to the continuation of the environmental impact assessment procedure;

d) From the analysis of the criteria in Annex no. 3 of Law no. 292/2018 results that it is not necessary to carry out the environmental impact assessment. [3]

Project characteristics [2], [4]:

a) The size and design of the entire project: the land area occupied by the existing constructions, access roads and areas for other functions is So=100220 m2;

Areas of land occupied by the proposed objectives of the investment: New constructions = 649.56;

The permanently occupied area 649.56 m2;

Water household L=35.00m, l=15.00m =525.00 m2 ;

Access road to the GA premises L=30.00m, l=3.00m = 90.00m; Water cannons 2 pieces L=1.30m, W=1.60m = 14.56 m2;

Bedrooms 5 pieces W=2.0m, L=2.0m = 20.00 m2;

Temporarily occupied lands L=650 m; l=0.85m = 552.5,00 m2;

Figure 1. The water mist dedusting facility within Roșiuța coal deposit for stopping the dust emissions at the source

The surface temporarily occupied for the execution of the water supply networks will be restored according to the current configuration.

In order to comply with the provisions of the normative acts in the field of air quality (STAS 12574/1987 maximum allowed concentrations of sedimentable powders [1]), it was proposed to build a water mist dedusting facility within the coal deposit to stop the dust emissions at the source (fig. 1). The installation must ensure long term operation in harsh conditions, with resistance to wear and minimal maintenance: operating time 12 14 hours/day, 365 days/year.

The dedusting plant is composed of the water house, the distribution network, the fog production plants and the electricity supply plant.

The existing fencing is made for the entire coal depot with a bordered wire mesh fence mounted on precast concrete posts, concrete foundation, and wire mesh panels.

The well cabin the water supply will be made by connecting to the existing underground source in the premises. The well cabin is a valve chamber with a diameter of Dn=1500, mounted buried, above the well, inside are mounted the pump, armatures and related equipment.

Technological water storage tank, above ground, with a capacity of 20 m3, equipped with a metal tower type support system, on a continuous reinforced concrete foundation, will be installed on the site by redistribution from Roșiuța Quarry. The tank will be protected with mineral wool insulation and, externally, with galvanized sheet.

The pump station cabin: modular construction, self supporting, removable, it will be placed on a cushion of well compacted ballast,the wallsandtheroof willbemade of insulated sandwich panelssheet/polyurethane foam/sheet, concrete floor, lighting installation with fluorescent lamps, the heating is done electrically with the help of a convector. For forced ventilation, a fan and two ventilation grills with dimensions of 0.20 m x 0.20 m each are provided. The pumps, the buffer tank and the control panel will be mounted inside. The cabin will be provided on the outside with four reflectors for perimeter lighting.

Fog production guns are of the type with wide local emission (storage area, loading point, distribution node), freely levitating fog is used i.e. water particles with a diameter of up to 65microns, carried by the flow of air of a fan at the dust emission points.

The process used to create the mist is based on the use of high pressure pumps. The equipment consists of fog guns equipped with high pressure water spray nozzles and dispersion fans that are purchased fully equipped including a remote control installation.

6 (six) spray cannons mounted as follows:

The guns being mobile, and with a degree of freedom on the area of stack no. 1 at a radius of 30 60 m, the emission of coal dust resulting from the loading process is stopped directly at the source, by positioning the water jet near the work point. In this way, the spraying flow rate can be optimized and implicitly the volume of water sprayed on the coal stack can be reduced. In order to make the activity more efficient, coal from stack 2 can be extracted from the deposit only after advance gaps have been made in stack 1

4 pieces of fog installations mounted on a frame with large wheels and a handling system with a hook, on the alignment of the warehouse at a distance of

2 fixed installations (one in the area of the coal crusher with a radius of 50 m and one in the area of the angular station with a radius of 50 m) which will be mounted on spatial metal poles mounted on an isolated foundation with a simple concrete block and concrete bearing reinforced in the block, which ensures a high propagation height and thus reducing the possibility of propagation of the small fraction of coal driven by air currents. (1 piece in the area of the coal crusher with a radius of 50 m and 1 piece in the area of the corner station with a radius of 50 m).

Pipes for mobile installations ensure a working radius of 75 m and are made of pressure hoses with DN20 and working pressure of PN10, mounted with a quick clamping system (with clip).

The turbines have the following characteristics:

Turbine with a range of 50 60 m;

Production of wet fog with a minimum of 30 nozzles and particles of 30 50μm;

Turbine with 2 speeds, 1500 rpm and 1000 rpm, with low noise (maximum 63 dB(A)), with rotation at 1800 in the horizontal plane and displacement on a curve of min 500 in the vertical plane;

Working pressure 20 bars;

Blown air volume 30000 50000 m3/h;

Power supply at a voltage of 0.4kV; Radio command with 100 meter coverage; 3 water flows selectable by radio control, with water consumption between 16 and 100 liters / minute;

Minimum water pressure at turbine inlet 3 bars; Maximum weight 500 kg; Water networks.

The adduction that feeds the tank in the water household is made of high density polyethylene with De 90 mm and length of L=18m. The route of the adduction is reduced and makes the connection between the catchment and the water household.

Technological networks in the premises they are the networks that ensure the connection between the storage basin and the pump station as well as the draining, overflow and tank supply pipes.

The technological water network in the coal deposit is a network that provides water for the spraying installations at a working pressure of 4 bars (prescribed in the technical book of the machine); the main pipe was dimensioned at 10 bar for further equipment and system expansion. Flexible connections (rubber hoses are sized at 4 bars and are SN1 type with Pn6 and Dn20mm). Depending on these dimensions, the sectorization fittings are dimensioned (ball valve DN20 and quick clamping couplings with Dn20 fastening).

The lengths of the pipelines by diameter within the network are as follows: 63x3.6 mm, L= 230 m; 90x5.7mm, L= 70 m; 110x6.6 mm, L= 102 m; 125x7.1 mm, L= 165 m.

The total length of the distribution pipes is 565m. The diameter of the pipes is between 63mm and 125mm.

Electrical installations of the water utility:

The electricity supply will be made at the voltage of 0.4 kV from the power house of the coal crusher, located about 450 m from the position where the general distribution board will be located.

The estimated energy situation is: Pi=61.6 kW (Pc=49.28 kW). The electrical connection will be made through a CYY 3x50+25 mm2 copper electrical cable of approximately 250 m to the TDG general distribution board located on the external wall of the pumping station building in a place with easy access in case of intervention and which will be provided on the input with automatic load switch with thermal and electromagnetic protection, differential protection against residual currents and protection against atmospheric over voltages.

Roads and platforms in the premises.

A ballasted, compacted road was provided inthe premises for access to the pump station cabin, a road with a carriageway width of 3.00 m.

b) Cumulation with other existing and/or approved projects: the project is cumulated with the investment "Continuation of mining works in the license perimeter of Roșiuța". The exploitation of the lignite deposits is carried out on the basis of the ANRM Bucharest Exploitation License no. 3497/24.06.2002, approved by GD no. 1294/24.10.2007 published in the Official Gazette 738/31.10.2007.

Roșiuța coal depot in operation has the following equipment:

Loading machine type KSS 5600 1 pc;

Depositing machine type ASG 6000 1 pc; Conveyor belt circuit with a total length of 3,067 m.

c) Use of natural resources, especially soil, land, water and biodiversity: the dedusting facility will use water from the existing underground source. The resulting waste water will be collected from the platform and the landscaped area of the warehouse and will be discharged through the drains of the concrete platforms of the warehouse in Roșiuța Valley.

d) The amount and types of waste generated/managed: the resulting waste will be temporarily stored selectivelyin spacesspecially arrangedfor wastecategories until theyare taken over byauthorized companies;

e) Pollution and other negative effects: the impact on the environment produced by the proposed execution activities will be reduced becausethe equipment and machineryused will beefficient, appropriate and modern. The purpose of the dedusting installation to be built is to comply with the provisions of the normative acts in the field of air quality STAS 12574/1987 maximum allowed concentrations for sedimentable powders [1].

f) Risks of major accidents and/or disasters relevant to the project in question, including those caused by climate change, according to scientific information: all measures will be taken to prevent accidents from occurring.

g) Risks for human health (for example, due to water contamination or atmospheric pollution): it is estimated that during the execution period of the works, the project will generate an insignificant impact on the population and human health. The realization of the project has a beneficial purpose for the population in the area, by reducing dust emissions from the activity of the coal deposit.

3. Location of the project

a) The current and approved use of the land [2], [4]:

The proposed investment will be carried out on the land privately owned by S Oltenia EC SA, the current use is construction yards, the destination is in PGU industrial zone, according to Town Planning Certificate no. 28/11/03/2019 issued by Motru City Hall. The area is intended for mining constructions coal storage.

The coal deposit of Rosiuta Quarry is part of the shipping delivery Sector and its activity is the transportation, storage and loading of coal.

The coal deposit is located in the western area of Roşiuţa Quarry. It consists of two prismatic bodies, arranged symmetrically with respect to the TMC406 and TMC407 belts, the belts on which the two machines drive: KsS 5600/5600*40 and AsG 6000*40 warehouse.

The dimensions of the prismatic bodies are 40m x 320m x 10m, respectively approximately 2 x 60 thousand t; the total projected capacity is 120 thousand t.

In certain cases, by pushing with classic machines, a maximum of 200 thousand t can be stored.

The stack located on the left side of the central axis borders on the southwest with the households of Rosiuţa village.

At this time, Roșiuta coal depot is in operation, and has the following equipment:

Loading machine type KSS 5600 1 pc;

Depositing machine type ASG 6000 1 pc;

Conveyor belt circuit with a total length of 3,067 m.

b) The richness, availability, quality and relative regeneration capacity of natural resources, including soil, land, water and biodiversity, in the area and its subsoil: not the case.

c) The absorption capacity of the natural environment, paying special attention to the following areas:

1. Wetlands, riparian areas, river mouths: not the case.

2. Coastal areas and the marine environment: not applicable.

3. Mountain and forest areas: not the case.

4. Natural areas protected by national, community, international interest: this is not the case.

5. Classified or protected areas according to the legislation in force: Natura 2000 sites designated in accordance with the legislation on the regime of natural protected areas, conservation of natural habitats, flora and fauna; the areas provided for by the legislation regarding the approval of the National Territorial Development Plan Section III protected areas, the protection areas established according to the provisions of the legislation in the field of water, as well as the one regarding the nature and size of sanitary and hydrogeological protection areas: it is not case.

6. The areas where there have already been cases of non compliance with the environmental quality standardsprovidedbynationallegislationandattheEuropeanUnionlevelandrelevant fortheproject orwhere such cases are considered to exist: at the limit of the functional area of the coal deposit of Roșiuța quarry, in the vicinity of protected areas (housing), exceeding the maximum allowed value of 17 g/m²/month for the sedimentable dust indicator, according to STAS 12574/1987 [1], were recorded.

7. Areas with a high population density: not the case.

8. Historically, culturally or archaeologically important landscapes and sites: not applicable.

4. Types and characteristics of potential impact

The significant effects that the project may have on the environment analysed in relation to the criteria established in points 1 and 2, considering the impact of the project on environmental factors and taking into account:

a) The importance and spatial extent of the impact for example, the geographical area and the size of the population that may be affected: the planned works will not have a negative impact on the population and human health during the construction period as well as during the operation period of Roșiuța coal deposit. When the dust removal facility is put into operation, the impact will be positive; the purpose of the project is to reduce dust emissions from the activity of the coal deposit.

b) The nature of the impact: the impact on the environment will be positive through the implementation of the dust removal facility;

c) Cross border nature of the impact: it is not the case;

d) The intensity and complexity of the impact: considering the location and the proposed works, the negative impact will be reduced strictly to the area of the location of the proposed works;

e) Probability of impact: insignificant.

f) The expected onset, duration, frequency and reversibility of the impact: the period of operation of the coal deposit is correlated with the Exploitation License no. 3497/2002 NAMR Bucharest.

g) Cumulation of the impact with the impact of other existing and/or approved projects: the impact is cumulated with the impact of the activity in the coal deposit; the realization of the project will lead to the reduction of the negative impact;

h) The possibility of effective reduction of the impact: during the execution period of the project, the impactisreduced,locally.Therealizationoftherespectivedustremoval plantprojectisdoneinordertoreduce the impact on air quality and to comply with the provisions of the normative acts. II. The reasons, on the basis of which, the need for not carrying out the appropriate evaluation was established, are as follows: the proposed project does not fall under the scope of art. 28 of GEO 57/2007 regarding the regime of natural protected areas, conservation of natural habitats, flora and fauna, approved with amendments and additions by Law no. 49/2011, with subsequent amendments and additions.

The location of the project for the continuation of the mining works at Roşiuţa Quarry is in areas with mineral energy resources and is located outside the protected natural areas, at very large distances from them. Fromthe framingplans, it can beseenthat the distancefromtheareaintendedforthe continuation of the works at Roşiuta Quarry to the protected area RO SCI 0045 Jiu’s corridor is min. 21000 m East and over 6000 m West from RO SCI 0366 Motru River.

The site ROSCI0366 Motru River is declared a natural protected area of community interest (SCI) by the Order of the Minister of Environment and Forests no. 2387/2011 for the amendment of the Order of the Minister of Environment and Sustainable Development no. 1964/2007 regarding the establishment of the protected natural area regime of sites of community importance, as an integral part of the European Natura 2000 ecological network in Romania.

The surface of the Natura 2000 Site ROSCI0366 is 1921 ha, comprising various forms of ownership and administration, located on two distinct sectors of the Motru River course:

a) The first sector, starts downstream from Baia of Aramă, near the town of Apa Neagră and extends for a length of 14.7 km, reaching the town of Cătunele; at the level of this perimeter, without a doubt, the most valuable area is that of Cheilor Glogovei, where Motru river crosses a winding course of approximately 2 km, guarded by steep, wooded slopes;

b) The second sector, approximately 32 km long, starts downstream from the town of Văgiuleşti and runs along a smooth flowing route, until close to the confluence with Jiu river, the banks preserving traces of valuable riparian formations, such as forests of the meadow, of the flooded meadows, the dead arms (zatoane).

In this context, Roşiuţa Quarry located in the village of Roşiuţa, Motru Municipality, Gorj County, which islocatedat adistanceofover 6kmfromMotruRiverandover 21kmfromJiuRiver,hasnonegativeinfluence on the two protected area sectors.

The mining works to be carried out at Rosiuţa Quarry will not reduce the distances between the mining perimeter existing at this moment and the limit of the two protected areas of community interest.

We specify that the project the continuation of the works at Roşiuţa Quarry, does not fall under the scope of art. 28 of GEO 57/2007.

The reasons on the basis of which the need for not carrying out the assessment of the impact on water bodies are as follows: the proposed project does not fall under the provisions of art. 48 and 54 of the Water Law no. 107/1996 [5], with subsequent amendments and additions, according to SWG Gorj address no. 3502/CI/06.05.2019;

The conditions for the realization of the project:

The technical project submitted to the documentation will be fully respected;

The environmental legislation in force and the conditions stipulated in the regulatory acts issued by other authorities will be respected;

Environmental factors will not be affected during the implementation of the project;

Unclogging and maintenance of drainage sections of rainwater collection channels;

The activity carried out on the site must not lead to a deterioration of air quality by exceeding the limit values established by Law 104/2011 on ambient air [6], for specific quality indicators, as well as compliance with the provisions of STAS 12574/1987 Air from protected areas Conditions of quality maximum allowed concentrations, for the sedimentable powders indicator 17 g/m2/month [1];

During the works, efficient machines will be used that do not produce loss of polluting substances during operation and that do not generate noise above the admissible limits;

Measures will be taken to avoid pollution caused by accidental leaks of fuels, lubricants, other chemical substances that could contaminate the soil during the execution of the works;

It is forbidden to leave the premises of the site organization with the means of transport with the wheels/body of vehicles loaded with mud, in order to avoid its entrainment on public roads;

The work schedule will be structured in optimal time intervals, so as to limit the discomfort created by the operation of specific machines near homes;

During the execution of the works, the necessary conditions will be ensured so that the noise limits stipulated by SR 10009/2017 Acoustics are respected. Admissible limits of the noise level in the ambient environment and the provisions of H.G. no. 1756/2006 regarding limiting the level of environmental noise emissions produced by equipment intended for use outside buildings;

The space where the waste resulting from the proposed works will be temporarily stored will be properly arranged; The selective collection of waste resulting from the works, storage and disposal depending on their nature, will be done by specialized/authorized companies, according to the legal provisions;

Site organization the contractor will take measures to set up the material storage spaces, will have absorbentmaterialstoallowquickinterventionintheevent ofaccidental pollutioncausedbymachinery/means of transport;

After the completion of the construction works, the temporarily occupied areas affected by the execution of the works will be cleaned and the land brought back to its original state.

Compliance with the provisions of O.U.G. no. 195/2005 on environmental protection, approved with amendments and additions by Law no. 265/2006 with subsequent amendments and additions; [7], [8]

According to the provisions of art. 43, paragraph (3) and (4) of Annex no. 5 to Law no. 292/2018, upon completion of the project, you will notify the E.P.A. Gorj [9] in order to verify compliance with the provisions of the decision on the recruitment stage; The protocol drawn up following the control will be attached and will be an integral part of the reception protocol upon completion of the works;

When the facilities were put into operation, the review of the environmental authorization was also requested.

In the Environmental Agreement no. 5/2016 [9], measures are specified for the prevention, reduction and, where possible, compensation of significant negative effects on the environment.

Thus they provide:

Measures and conditions that must be respected during the realization of the project;

Measures during exploitation and the effect of their implementation;

Measures for closing/demolition/decommissioning and rehabilitating the land for further use, as well as the effect of their implementation;

Measures for the protection of water quality, air quality, protection against noise and vibrations, in the field of soil and subsoil, in the field of biodiversity;

The environmental monitoring plan, indicating the environmental components to be monitored. Practically, all measures to protect environmental factors were taken into account in accordance with the legislation in force;

Figure 2. A number of 5 installations are required on the side facing the inhabited area and two installations positioned at the corner station respectively in the area of the coal crusher

In order to create efficient installations, the following technological installation for dust control was proposed and implemented (fig. 2 and fig. 3):

Theinstallationonthesideofthewarehouse,towardstheinhabitedarea,offogproductionfacilitieswhich, in order to be effective, must be located at a maximum distance of 70 m between the axes on the side of the warehouse and those in the coal flow directing areas (lane intersection) at the distance of 85 m.

In order to be effective, the technical characteristics that must be ensured are 50 m radius with a possibility of positioning in the horizontal plane of 1800, and in the vertical plane of 500 to ensure the movement of the sprayed water jet over the level of the stack (10 m).

For this purpose, to cover the size of the warehouse at the boundary of the property towards the residential area for the size of the warehouse LxW =324 m x 40 m, 5 fog production guns are required in the case of using stationary installations.

From the calculation, a number of 5 installations are required on the side facing the inhabited area and two installations positioned at the corner station respectively in the area of the coal crusher, fig. 3.

Figure 3. Image of the operation of the sedimentable dust retention facility

Spatial support pillars are metal pillars; the pole is mounted on an isolated foundation with plain concrete block and block reinforced concrete bearing. The plan size of the foundation block is 1.30 m x 1.60 m calculated for difficult and sensitive soils to wetting.

A 1300 mm x 1600 mm 20 mm thick plate was embedded in the concrete at the top for placing the space pillar.

On the plate, there are oval holes for fixing buttons and technological holes for pouring concrete. The pillar is a spatial metal construction made of a pipe with a diameter of 121 x 6 695 cross linked with a thick plate of 100 x 8 480, the distance between the axes of the pillars is 600 mm.

5. Conclusions

1. By placing the mobile water spray installation at the minimum limit in relation to the sources of dust production, dust emission iscompletelyeliminated(removal machine, depositingmachine, angular station and crusher).

2. Positioning at the minimum limit also requires a scheme for exploitation in the warehouse, with extraction in the field, so that the permanent positioning of the fog production facilities near the warehouse machines (KSS and ASG) can be ensured even when they are working on stack no. 2.

3. The fixed installations (stationary guns) are positioned on poles with a high height so that the sprayed water jet covers the entire area generating coal dust;

4. The fixedinstallations were mounted onthespace polesto which quickaccess ladders (fire fighter type) were attached.

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5. The moisture content of the coal is very little influenced by the water sprayed from the misting plants. Thehourlyvolumeforthetwoinstallationsworkingsimultaneouslyonthecoalstackismax.5.5m3 (maximum volume according to the technical book).

In 10 hours of continuous operation, the 2 installations spray max. 55 m3 of water, water directed to the loading area (KSS wheel) and discharge point (ASG).

If we consider that the volume of coal loaded daily is 10,000 t/day (4 sets), we observe that humidity increases as a percentage compared to the volume of coal transported by 0.55%, a percentage that is compared to the natural humidity of the coal; this increase in humidity in reality is smaller, as part of the amount of sprayed water evaporates and the rest accumulates on platforms from where it is directed through the drainage systems of the warehouse.

The addition of water as a result of the wetting process is eliminated in the transport operations unloading stored at the beneficiary.

6. Installations working in the area of the corner station and the coal crusher do not affect the quality of the coal, the waters accumulate on the platforms from where they are naturally directed to the discharge areas.

7. For the acoustic excess that is registered in the area of the houses, it is proposed to install sound absorbing panels with a height of 3.5 m, at the property limit of the houses.

References

[1] *** , 1987

Maximum allowed concentrations of sedimentable powders

[2] Ciolea D.I., 2021

Judicial technical expertise in Ds. no. 14675/3/2017, Bucharest Court Archive

[3] *** , 2018

Law no. 292/2018 regarding the assessment of the impact of certain public and private projects on the environment

[4] *** , 2017

Minutes Documentation Expertise in the field for Ds. no. 14675/3/2017 16.04.2018/ 02.07.2021.

[5] *** , 1996

The Water Law no. 107/1996

*** , 2011

The Law on ambient air quality no. 104/2011.

*** , 2006

OUG 195/2005 regarding environmental protection, additions by the Law 256/2006

*** , 2007

OUG 114/2007 amending and supplementing GEO 195/2005 on environmental protection. [9] *** www.apmgj.anpm.ro

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 48 58

GEOPHYSICAL ANALYSES ON THE GEOMECHANICAL CHARACTERISTICS OF THE SOIL FOR CHOICES OF THE DRILLING RIG, IN THE AREA OF TÂRGU OCNA, BACĂU COUNTY, ROMANIA

Laurențiu Ștefan POPESCU*1 , Adrian CEPTUREANU2

1University of Petrosani, Petrosani, Romania, laurentiu@geoscan.ro 2Geoscan Service S.R.L., Plopeni, Romania, adrian@geoscan.ro

DOI: 10.2478/minrv 2022 0020

Abstract: As part of the company Geoscan Service S.R.L., I was contacted to investigate the possibility of using resistivity, refraction seismic data and MASW seismic to identify the stratification up to 15m deep so that the client could choose the type of drilling rig for installing the conductor in order to drill two water injection wells. The main problem in the choice of geophysical methods was the lack of detailed geological data for calibrating the obtained results, as the presence of groundwater, the thicknesses of the deluvial layer and the bedrock. The choice of geophysical methods and the work procedure are carried out according to the international standards in force, ASTM D6429 99 "Standard guide for Selecting Surface Geophysical Methods", ASTM D5777 00 "Standard guide for Using the Seismic Refraction Method for Subsurface Investigation, "Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization", STAS 1242/7 84 "Geophysical research of the land by seismic methods".

Keywords: seismic investigations, geophysics, MASW, refraction, resistivity, applied geophysics

1. Introduction

Considering the current technical development that led to the possibility of using non intrusive indirect measurement techniques (from the ground surface), we chose two complementary geophysical methods: seismic (refractions and MASW) and resistivity (VES vertical electrical sounding). The purpose of the investigations was to provide precise information so that the optimal technical economic variant of the drilling rig could be chosen for drilling the conductor of the two water injection wells. The choice of the two geophysical methods was made to analyze two different sets of data: from seismic data the speeds of P and S waves that respond mainly to the density of the rocks they cross, and from VES data the resistivity which is a result of the rocks' resistance to the passage of electric current, mainly due to natural humidity.

The initial information made available consisted only of the location of the two rigs prepared for drilling. Given theconfidentialityofthedata,thepreciseposition of the boreholesandthe final beneficiaryof the works will not be detailed in this article.

The work area is located near the city of Târgu Ocna, Bacău County, Romania, at the southern limit of Tazlău Cașin depression with Nemira Mountains. From a geological point of view, the area is part of the Carpathian flysch unit made up of Paleogene formations arranged in Tarcău and Kliwa folds.

The choice of geophysical investigation methods took into account the following considerations:

1. The required investigation depth of 15m;

2. Estimation of existing lithological complexes in the area. For this, the 1:200000 geological maps of the Geological Institute of Romania were used, thus the study locations were included in Tarcău map composed of Paleogene formations mainly sandstones and limestones. Considering the purpose of the geophysical investigations,theresults must delimitthedeluvialsedimentarylayer fromthebedrockandthestiffnessdegree of the lithological complexes up to 15m deep.

author: Laurențiu Ștefan Popescu, Eng. Ph D student, University of Petrosani, Romania,

Universitatii str., 332006 Petrosani, Romania, laurentiu@geoscan.ro

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3. The landscape of the perimeters to be investigated: quasi horizontal, considering the fact that the drilling platforms had already been set up. The two perimeters are located in a hilly area, so we considered the fact that the top of the bedrock has a slope similar to the slope of the land. Based on this reasoning, two complementary geophysical methods were chosen so that the results of the measurements are conclusive according to the client's requirements. The two methods chosen are electrometry as the vertical electrical sounding method and seismic as the refraction method and MASW (Multi Channels Analysis of Surface Waves Survey). [1], [2], [3], [4]

2. Geophysical methods

2.1 Seismic method

Geophysics studies the behavior of waves propagating inside materials. A seismic signal changes according to the characteristics of the medium it travels through. Waves can be generated artificially with a batteringram,hammer,etc.Theseismicsignal canbedecomposedintoseveralphases,eachofwhichidentifies the movement of particles driven by seismic waves. The phases can be:

P Longitudinal: compression depth wave;

S Transverse: shear depth wave;

L Love: surface waves composed of P and S waves;

R Rayleigh: Surface wave composed of elliptical and retrograde motion.

Rayleigh waves “R”

In the past, studies on seismic wave propagation focused on the propagation of depth waves (P, S) considering surface waves as a "noise" of the seismic signal to be analyzed. However, recent studies have allowedthecreationofadvancedmathematical models fortheanalysisofsurfacewavesinmediawithdifferent stiffness.

For this project, a SYSMATRACK Seismograph equipment with 2 channels and24 4.5Hzgeophones and 10Hz trigger was used. The seismic source used was an 8kg seismic hammer.

Signal analysis using the MASW technique

According to the fundamental hypothesis of linear physics (Fourier's Theorem) signals can be represented as the sum of independent signals, called harmonics of the signal. These harmonics, for one dimensional analyses, are sine and cosine trigonometric functions, and behave independently without interacting with each other. Focusing our attention on each harmonic component, the final result in the linear analysis is equivalent to the sum of the partial behaviors corresponding to the individual harmonics. Fourier analysis (FFT spectral analysis) is the fundamental tool for spectral characterization of the signal. The analysis of Rayleigh waves, by means of the MASW method, is carried out by the spectral processing of the signal in the transformed domain where it is possible, in an easy way, to identify the signal relative to Rayleigh waves compared to other types of signals, noting, moreover, that the speed with which Rayleigh waves propagate is a function of frequency. The speed frequency relationship is given by the dispersion spectrum. The dispersion curve identifiedinthef kdomainiscalledtheexperimentaldispersioncurveandrepresentsthemaximumamplitudes of the spectrum in the given domain.

Data processing

Starting from a synthetic geotechnical model characterized by thickness, density, Poisson's ratio, S wave speed and P wave speed, it is possible to simulate the theoretical dispersion curve that connects speed and wave length according to the relationship:

By changing the parameters of the synthetic geotechnical model, an overlap of the theoretical dispersion curve with the experimental one can be obtained: this phase, called inversion, allows the determination of the velocity profile in environments with different stiffness.

Modes of vibration

Both in the theoretical and in the experimental inversion curve, the various configurations of ground vibrations can be identified. The modes for Rayleigh waves can be: deformations in contact with air, nearly zero deformations at mid wavelength, and zero deformations at high depths.

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Rayleigh waves decay at a depth approximately equal to the wavelength. Short wavelengths (high frequencies) allow the survey of shallow areas, while long wavelengths (low frequencies) allow surveys at great depths.

Table 1. Vp Vs velocities of the main sedimentary rock types according to Geol 615: Geostatistics University of Mississippi

Type of rock P waves velocity (Vp) m/sec S waves velocity (Vs) m/sec limestones 2500 6000 3100 sandstones 1400 4000 2400 gravel, sand 400 2300 80 880 clay 200 2200 100 1500 soil 100 500 50 180

Seismic refraction studies allow the interpretation of the subsurface stratigraphy through the physical principle of the refraction of the incident seismic wave on a discontinuity, detected between two bodies with different mechanical properties (refraction horizon).

The basic requirement for conducting seismic refraction studies is one for which the succession of layers to be investigated is characterized by an increase in seismic velocity with increasing depth. In this way, up to 4 or 5 different refraction horizons can be analyzed. The processed seismic data resulting from the survey, it will be compared with Vp Vs velocities of the main sedimentary rock types according to the Geostatistics University of Mississippi (Table 1) and with regional or local geological data.

Surveys are based on the measurement of elastic wave travel times for which, assuming extended discontinuity surfaces compared to the wavelength or, at any rate, with weak curvature; the wave fronts are represented by relative seismic waves. The analysis is based on Fermat's principle and Snell's law.

Fermat's principle states that the wave travels the distance between the seismic source and the receiver followingthe minimumpropagationtime. Given a plane separatingtwo media withdifferent elastic properties, the seismic wave is the one that propagates along a plane perpendicular to the discontinuity containing both source and receiver.

Snell's law is a formula that describes the refraction modes of a seismic wave in the transition between two media characterized by different wave speeds or, equivalently, by different refractive indices. The angle formed between the surface of the discontinuity and the seismic ray is called the angle of incidence θi while that formed between the refracted ray and the surface normal is called the angle of refraction θr. The mathematical formula is: where v1 and v2 are the velocities of the two media separated by the surface of the discontinuity.

2.2 Geo-electrical method

The geo electrical measurements were carried out by the method of resistivity, using the procedure of vertical electrical sounding (VES), according to the standards in force.

The principle of the method used consists in injecting into the basement a current of known intensity (I) by means of two current electrodes(A, B) and measuringthe potential difference(ΔV) with the help of another pair of potential electrodes (M, N).

Apparent resistivity is calculated using the relationship: a=kV/I [m] where k is a constant that depends on the geometry of the device and is obtained using the expression: k=2∏a

Fortheexecutionofverticalelectricalsounding,Schlumberger typesymmetricalquadripoledeviceswere used, with a maximum emission line of 40m for investigation depths of maximum 20m considering a device constant AB/2.

The resistivity processed data will be compared with the values of the resistivity of the main types of sedimentary rocks according to the Geostatistics University of Mississippi (Table 2) and with regional or local geological data.

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Table 2 Resistivity of the main types of sedimentary rocks according to Geol 615: Geostatistics University of Mississippi

Type of rock Resistivity (ohmmeters) Type of rock Resistivity (ohmmeters) limestone 100 10 000 drilling fluid 4.5 sandstones 100 1 000 marl 100 1 000 compact sandstone 1000 10000 salt 1012 1014 Gravel, sand 100 10 000 oil 109 1016 clay, silty clay 1 100 sweet water 10 100 wet plastic clay 20 Sea water 0.1 1 soil 1 10

3. Field data acquisition

We carried out the three geophysical investigations: refraction and MASW seismic profiling, and vertical electrical sounding (VES) for both locations required for investigation. The field acquisition was done as presented in figures 1 3.

Seismic data acquisition was done using the following configuration:

Number of geophones: 24 (fixed range)

Distance between geophones: 2.5m

Investigation depth: 15m

Orientation: SW NE

Number of Stations: 1 (24 geophones/Station)

Source type: hammer, 8kg

Distance between sources: variable

Number of sources: 3

Sampling interval: 0.000133 s

Recording length: 0.681s

Figure 1 Seismic profile PS1

Figure 2. Seismic profile PS2

Figure 3. Vertical electrical sounding

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In order to acquire geo electrical data, a rectilinear device was drawn with the distance between the A B electrodes increasing, every 5m (increasing equidistance 10 15 20 25 30 35 40m), and the distance between the M N electrodes was kept fixed at 0, 70m.

4. Geophysical data processing

4.1 Raylaigh (MASW) surface waves processing

Data processing was performed using the EasyMASW software.

Data loading Recordings (fig. 4)

No. records 24

Total recording sampling time [msec] 681.0

Spacing of geophones [m] 2.5

Recording sampling time [msec] 133.0

Figure 4. Seismic recording

Spectral analysis The spectral analysis phase is necessary to determine the experimental dispersion curve.

Spectral analysis (fig. 5)

Minimum processing frequency [Hz] 4.5

Maximum processing frequency [Hz] 30

Minimum processing speed [m/sec] 1

Maximum processing speed [m/sec] 800 Speed range [m/sec] 1

Figure 5 Example of synthetic model curves

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In this phase, it is necessary to define a synthetic model of the terrain on which the subsequent processing will be based. The parameters to be defined are: number of layers; minimum research thickness; initial research thickness; maximum research thickness; volumetric weight; volumetric weight in saturated state; the presence of water; Poisson's ratio; minimum admissible wave speed for the layer; wave speed for the first attempt; maximum admissible wave speed for the layer.

4.2 Compressional waves P processing

The data processing was carried out with the help of EasyRefract software:

Data import (fig. 6)

Figure 6 Loading recordings

Data filtration (fig. 7)

Figure 7. Filtration process

Choosing the first arrivals (fig. 8)

Figure 8 Choosing the time for the first arrival

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Calculation of speed curves (fig. 9)

Figure 9 Calculation of speed curves

5. Geophysical data interpretation

5.1 Surface waves Rayleigh interpretation (MASW)

The MASW data have been represented in two different ways: Depth (m) vs. Vs (m/s) according to fig. 10 and 11; Tables containing dynamic parameters for every seismic complex (tables 3 and 4).

Figure 10. Vs velocity model PS1 profile

Figure 11 Vs velocity model PS2 profile

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Table 3 Seismic data MASW interpretation

Profile Description Depth [m] Thickness [m] Volumetric weight [kg/mc]

Poisson’s coefficient Water table presence

Vp [m/sec] Vs [m/sec]

PS1 Complex 1 2.81 2.81 2000.0 0.25 No 281.6 162.6 Complex 2 5.55 2.74 2100.0 0.25 No 371.6 214.5 Complex 3 15.55 10.00 2200.0 0.25 No 658.2 380.0

PS2 Complex1 9.99 9.99 2000.0 0.25 No 444.1 256.4 Complex 2 12.66 2.67 2100.0 0.25 No 780.4 450.6 Complex 3 15.59 2.93 2200.0 0.25 No 1036.8 598.6

Table 4 Other geotechnical parameters

Profile Depth [m] Thickness [m] Vs [m/s] Vp [m/s] Density [kg/mc] Poisson’s coefficient G0 [MPa] Ed [MPa] M0 [MPa] Ey [MPa]

NSPT Qc [kPa]

PS1 2.81 2.81 162.60 281.63 2000.00 0.25 52.88 158.64 88.13 132.20 22 268.72 5.55 2.74 214.54 371.59 2100.00 0.25 96.65 289.96 161.09 241.64 32 1081.94 15.55 10.00 379.99 658.17 2200.00 0.25 317.67 953.01 529.45 794.17 N/A N/A

PS2 9.99 9.99 256.37 444.05 2000.00 0.25 131.46 394.37 219.09 328.64 75 2648.60 12.66 2.67 450.56 780.40 2100.00 0.25 426.31 1278.94 710.52 1065.79 N/A N/A 15.59 2.93 598.62 1036.842200.00 0.25 788.35 2365.06 1313.92 1970.88 N/A N/A

Description of the parameters used in tables 3 and 4:

Vs: S waves velocity;

Vp: P waves velocity;

G0: Shear deformation module;

Ed: Edometric module;

M0: Volumetric compressibility module;

Ey: Young module;

Ey: Young module;

NSPT: normal standard penetration test;

Qc: conventional pressure

Results PS1

Depth [m] 15.00

Vs,30 [m/sec] 475.47

Soil category B

Type B soil: Soft rocks or very dense large grained soil deposits or very consistent small grained soils with thicknesses greater than 30 m, characterized by a gradual improvement in mechanical properties with depth and values of Vs,30 between 360 m/s and 800 m/s (NSPT,30 > 50 in large grained soils and with,30 > 250 kPa in small grained soils).

Results PS2

Depth [m] 15.00

Vs,30 [m/sec] 695.09

Soil category B

Type B soil: Soft rocks or very dense large grained soil deposits or very consistent small grained soils with thicknesses greater than 30 m, characterized by a gradual improvement in mechanical properties with depth and values of Vs,30 between 360 m/s and 800 m/s (NSPT,30 > 50 in large grained soils and with,30 > 250 kPa in small grained soils).

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Following the processing of the frontal wave data using the previously presented steps, we made velocity maps of the P Vp frontal wave variations for the two profiles PS1, PS2 (seismic vertical sections) presented in fig. 12 and 13.

Figure 12 P waves velocity model PS1

Figure 13 P waves velocity model PS2

5.3 Interpretation of geo electric data

After processing the geo electric resistivity data, we obtained tables of values of the resistivity variation with depth, shown in the tables 5, 6 and 7.

Table 5 SEV1 values No. ρ (ohmm) Thickness (m) Depth (m)

1 20.5 1.99 1.99 2 3.64 1.73 3.72 3 82.1 3.18 6.90 4 36.4 10.8 17.7 5 10587

Table 6 SEV2 values No. ρ (ohmm) Thickness (m) Depth (m)

1 10.7 1.52 1.52 2 150 1.71 3.23 3 2.25 3.69 7.19 4 3.59 2.64 9.83 5 2964

Table 7 SEV3 values No. ρ (ohmm) Thickness (m) Depth (m)

1 96.1 1.34 1.34 2 6.25 0.89 2.23 3 38.3 3.70 5.93 4 2.91 5.04 11 5 12671

We choose a resistivity model made by 4 resistivity complexes with different values (according to tables 5, 6 and 7). Analyzing the resistivity values, we considered that the lithology up to 15m depth has a high water content with high porosity and/or permeability specific to soft to medium rocks.

6. Conclusions

Following the interpretation of the seismic and resistivity data, two important lithological complexes resulted, as follows:

the complex located up to 5 6m deep with the speed of p waves between 500 600 m/s, of s waves between 160 260 m/s and resistivity variations between 3.60 6.25 ohmm.

The complex located below 5 6m depth with the speed of p waves between 1327 1356 m/s, of s waves between 658 1036 m/s and resistivity variations between 2.90 36.4 ohmm.

For the S wave application plan according to Eurocode 8, the lithological complex below 5 6m depth is described as soil type B: soft rocks or very dense large grained soil deposits or very consistent small grained soils with thicknesses greater than 30 m, characterized by a gradual improvement of mechanical properties with depthand values ofVs,30 between 360 m/s and800 m/s (NSPT,30> 50 inlarge grained soils and with,30 > 250 kPa in small grained soils).

By analyzing the entire set of geophysical data, without having access to direct data, it was concluded that up to 15m depth there are two complexes characterized both seismically and by resistivity as having high porosity, with a relatively high content of bound water, with relatively low seismic wave velocities Vs and Vp. So a low density geological material that can be penetrated by percussion drilling methods, without more costly mud circulation drilling rigs that involves higher mobilization and execution costs.

Consequently, the client for whom the works described above were carried out made the decision to drill with a percussion hydraulic installation, the method with minimal drilling costs.

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As a final conclusion, the seismic and resistivity geophysical methods used together give conclusive results for the analysis of the lithology and geo mechanical parameters of the strata through which direct investigations are requested.

Acknowledgements

Professor Ilie ONICA, Ph.D.

References

[1] Subjender Reddy A.

Geophysical survey for subsurface investigation. Part 1: Engineering Applications, www.academia.edu/7814943/Geophysical_Surveys_for_Subsurface_Investigation

[2] Hoover D.B., Klein D.P., Campbell D.C., 1995

Geophysical methods in exploration and mineral environmental investigations

[3] Watson K., Fitterman D., Saltus R.W., McCafferty A., Swayze G., Church S., Smith K., Goldhaber M., Robson S., McMahon P., 2001

Application of geophysical techniques to minerals related environmental problems, U.S. Geological Survey

[4] Gandhi S.M., Sarkar B.C., 2016

Essentials of mineral exploration and evaluation

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 59 64

ASPECTS REGARDING THE USE OF COAL IN THE PRODUCTION OF ELECTRICAL AND THERMAL ENERGY

Vasile BOBEI1 , Daniela CIOLEA2*

1Oltenia Energy Complex, Tg. Jiu, Romania, vasile.bobei@ceoltenia.ro

2University of Petrosani, Petrosani, Romania, danielaciolea@upet.ro

DOI: 10.2478/minrv 2022 0021

Abstract: Globally, coal was and remains one of the main primary energy resources, being the cheapest option for power generation. Coal deposits are available in large quantities, its exploitation being done with more stable prices and less sensitive to a series of international events, but it has the disadvantage of significant additional costs, due to the technologies required to reduce emissions in the environment. Romania, one of the most important coal producing countries in Europe, has a long tradition in the mining industry and has important coal reserves, which can ensure the continuity of production for more than 150 years. Unfortunately, after 1989, coal production in our country almost halved, mainly due to the decrease in mining activity and the reduction of coal consumption (both by industry, such as steel and households for the heat consumed from power plants based on of coal). At the moment, Romania mainly imports coal, but the share of imported coal also decreased to a quarter compared to 1990.

Keywords: coal, energy, production of electrical energy, environmental protection

1. Introduction

The protecting and preservation of the environment, although they are global problems of humanity, must be, first of all, a concern of national, economic and socio human interest, with a determining role in the sustainable development strategy of society.

Technical progress brings with it, in addition to benefits for human beings, many disadvantages, such as pollution, which threatens to destroy the environment. The electricity production industry is a strategic sector for any state that wants economic, social, strategic and political development at the level of the 21st century.

Currently, Romania a member country of the European Union must make the most of its geostrategic advantages, its energy potential and, last but not least, the possibility of becoming an important transit corridor from Eastern producers to Western consumers.

At the same time, however, the energy sector and especially thermal power plants, which use coal as fuel, have a major impact on all environmental components in the area adjacent to them (atmosphere, water, soil, flora and fauna, food and living space), so that they are considered among the main sources of environmental pollution.

2. Environmental legislation in the field of the energy sector

The energy sector has the greatest impact on the environment through the emissions produced, energy's contribution being assessed at around 80% to environmental pollution and, as a result, to the phenomenon of global warming.

At the European and international level, there are concerns regarding the development of optimal strategies and actions to reduce environmental pollution. Two of the main directives that regulate the legal framework for reducing environmental pollution are: Directive 2008/1/EC (IPPC) on the Prevention and Integrated Control of Pollution and Directive 2001/80/EC (LCP) on the Limitation of Air Emissions of some pollutants from Large Combustion Plants.

Corresponding author: Daniela Ionela Ciolea, Assoc.Prof.Eng. Ph D, University of Petrosani, Romania, 20 Universitatii str., 332006 Petrosani, Romania, danielaciolea@upet.ro, 0251542580/int. 236

Revista Minelor Mining Revue vol. 28, issue 3

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Directive 2001/80/EC (LCP), transposed into Romanian legislation by H.G. no. 440/2010 defines Large Combustion Installations and aims to reduce air emissions of some pollutants from burning fuels in them, while the IPPC Directive (transposed into our legislation by O.U.G. no. 34/2002), aims to protect the environment as a whole and proposes that any polluting facility should have a permit (authorization), which can be issued if the activity in question is based on best available techniques (BAT).

These two directives, to which five others are added, are brought together in Directive 2010/75/EU (IED) Industrial Emissions Directive, which entered into force on 01.01.2016. The transposition of the directive into Romanian legislation was achieved through Law 278/2013 on industrial emissions and has the general objective of reducing polluting emissions into the atmosphere, water, soil, as well as waste from agriculture and industry, with the aim of achieving the highest level of environmental and health protection.

The main objectives of the current European framework for energy and climate policy to be achieved by 2020 are:

Reduction of greenhouse gas emissions (20%);

Improvements in the field of energy efficiency (20%).

The new energy climate policy framework for 2030 will also take into account the recently adopted EuropeanStrategyon EnergySecurity.Thus,thepillarofthe2030frameworkforpromotingsecurityofenergy supply will be structured based on:

1. Exploitation of new sources of sustainable energy;

2. Diversification of countries and supply routes with regard to fossil fuel imports (strengthening competition in energy markets by increasing liberalization, by completing the internal energy market and developing energy transport infrastructure);

3. Improving the energy intensity of the economy in a cost effective way and generating energy savings by improving the energy performance of buildings, products and processes.

4. Animportantrole inthenew 2030architecture will be anew monitoringframework, whichwill include national plans for a competitive, safe and sustainable energy.

Even if the European Union manages to change its energy mix in favor of renewable sources and substantially reduce its energy consumption, it will still remain dependent on fossil resources for the foreseeable future: coal, oil, natural gas. Because of this, it is in the general interest to develop technologies that reduce the carbon dioxide emissions of combustion plants. The capture and storage of CO2 emissions is a promising solution, but such technologies are not yet commercially tested.

However, despite the commitment to reduce greenhouse gas emissions from 1990 levels by 20% by 2020, coal fired power plants in the European Union have in recent years started operating again at high capacity.

The factors that have made coal attractive again are related to:

1. The strong decline of its price on international markets as a result of the increase in American natural gas production and the direction of extracted coal mainly abroad.

2. In the confrontation between the price of natural gas and the price of coal, the latter comes out victorious, European natural gas prices being the highest in the world.

3. The failure of the European carbon tradingplatform(ETS), thecentral instrument of the E.U. to combat climate change. The European Commission is trying to fundamentally reform the market for carbon dioxide certificates. Until this action is taken, the ETS remains unable to penalize the use of coal plants.

4. Russia's military aggression against Ukraine.

Romania has undertaken commitments regarding the limitation of pollutant emissions into the air from large combustion installations (IMA), according to Directive 2001/80/EC, achieving staggered transition periods until 2013, by category of pollutants emitted into the atmosphere (carbon dioxide sulfur, nitrogen oxides and dusts), respectively 2017 for the further reduction of nitrogen oxide emissions. These transition periods highlight the fact that the respective large combustion plants have a significant effect on air quality, as it is necessary to implement measures to reduce polluting emissions and that the level of investment required is very high and difficult for the beneficiary to bear.

Most thermal energy capacities are not yet equipped with high performance installations to reduce pollution, as a result SO2 and NOx emissions are above the maximum values accepted in the European Union.

In the last 10 years, some thermal power plants representing approximately 10% of the installed power have been modernized/re technologized, and work to comply with environmental requirements is underway at most thermal plants.

All thermal energy groups that remained in operation after 2014 must comply with the environmental requirementsestablished byOrder no. 859/29.09.2005 fortheapproval of the National Planfor the Reduction ofSulfurDioxide,NitrogenOxidesandDustEmissionsfromLargeCombustionPlants.Failureofthesegroups

to observe the deadlines for complying with the European Union rules date will lead to the prohibition of their operation after the expiration of these deadlines.

3. The use of coal in the production of electricity and thermal energy

On a global scale, coal was and remains one of the main primary energy resources, being the cheapest option for power generation. Coal deposits are available in large quantities, being spread evenly in different geographical areas of the globe, but the large scale use has brought with it the considerable degradation of the environment and the reduction of the optimal territory for habitation.

Coal, compared to oil and natural gas, has the advantage of a more stable price and less sensitive to a series of international events; on the other hand, it has the disadvantage of significant additional costs, due to the extraction technologies and the technologies required to reduce emissions in the environment.

Coal, despite its poor environmental credentials, remains a staple in the energy supply of countless countries. (World Energy Resources 2013 World Energy Council Report). [1]

However, the latest data show that coal is currently used to produce 40% of the world's total electricity, and its use has increased by more than 50% in the last 10 years. Forecasts show a decrease in this proportion, while, in absolute values, its use will increase (http://www.energynomics.ro/ro/analize/centralele pe carbune raman viabHe din perspectiva costurilor /). [2]

Even if countries in Europe and North America try to switch to alternative energy sources, the reductions are cancelled by the big economies, most of them coming from Asia, which mainly use coal, and have important reserves of this fuel.

Coal also plays a very important role in covering the base load of electricity consumption. The increase in the popularityof coal is veryclear fromthe analysis of today's consumption comparedto 20 years ago. Also, the world's coal reserves fell by 14% between 1993 and 2011, while energy production increased by more than 68% during the same period. (World Energy Council, World Energy Resources (WER) 2013, Published 2013, ISBN: 978 0 946121 29 8, available at: http://www.worldenergy.org/publications/ 2013/worldenergy resources 2013 survey/). [3]

The world's known coal reserves of 909,000 thousand tons are unevenly distributed in the world, most of the reserves being: 28% in North America; 28.4% in Asia; 27.2% in Europe (in particular, in the Russian Federation, Ukraine and Poland).

The large volume of existing coal reserves in the world makes this raw material an important and sustainable energy resource for the future, which could be make possible through:

a. Long term planning of the use of coal in the future in the sense of its use over the period of several generations;

b. Makinglong termprofitsandrecoveringthecapital invested byentrepreneursin: thermal and electrical plants, metallurgical plants, transport infrastructure, logistics, etc.;

c. Carryingout research onthe use and savings of coal resources, not onlyin the area of interest of applied sciences, but also in that of fundamental sciences.

In Europe, coal represents 5% of the world's coal reserves, being vital for it to cover its main needs.

In the European Union, superior coal (anthracite and coal) is mined in the Czech Republic, Germany, Poland, Romania, Spain and Great Britain. Poland produces more coal than all the other 26 EU member states combined.

Lower coal (lignite and lignite) is mined in Bulgaria, the Czech Republic, Germany, Greece, Hungary, Poland, Romania, Slovakia, Slovenia and Spain.

Europe is able to cover a significant proportion of its coal requirement from its own resources. Poland and Germany are the leaders in coal production, together producing two thirds of the European Union's production, followed bytheCzech Republic and Greece. The Czech Republic, Greece, Spainand Great Britain also produce large amounts of coal within the European Union. The countries of south eastern Europe, such as Hungary, Romania and Bulgaria, also produce important amounts of coal. Coal is also obtained in other states of the European Union, such as Slovakia and Slovenia, and also in the associated countries and on the way to become part of the European Union.

The development of imports is of vital importance for meeting the needs of coal in the European Union. About 200 million tons of coal equivalents are imported every year to cover the needs. Imports are made from South Africa, Colombia, Ukraine and Mozambique.

With a total demand of around 750 million tons ofcoalequivalent, EuropeincludingRussia, isthe world's third largest coal consumer after North America and China, showing that Europe accounts for over 15% of

global coal consumption. In the 28 countries of Europe, in the future, coal will cover a fifth of the primary energy needs.

The European Union is already the world's largest importer of oil, natural gas and coal. The consumption of primary resources in EU is as follows: oil 41%, natural gas 22%, coal 16%, nuclear energy 15%, and renewable sources 6%. The EU's current energy dependence on external sources is 50%. Reserves are concentrated in a few countries. About half of the EU's natural gas consumption comes from just three countries(RussianFederation,Norway,Algeria), and45%ofoilimportscomefromtheMiddleEast.Ifcurrent trends continue, gas imports will increase by up to 80% over the next 25 years. [4]

A worrying conclusion is that, if the European Union (EU) fails to make its energy sector more efficient, in the next 20 30 years, approximately 70% of the EU's energy demand will be covered by imports, some of which will come from regions threatened by insecurity.

Coal certainly limits Europe's dependence on energy imports. Coal also reduces Europe's vulnerability to the energy crisis thanks to its own coal reserves and a well functioning world market for this raw material. The average percentage of 29% of the share of coal use in electricity production hides major differences between the member states of the European Union (Poland, with 90% of electricity production based on coal. France 5%, Sweden 1%).

Romania has a diverse, but quantitatively reduced, range of primary energy resources, fossils and minerals: crude oil, natural gas, coal, uranium ore, as well as an important exploitable potential of renewable resources.

The importance of the energy sector (resources energy industry consumption), a strategic sector for any state, is best emphasized by the fact that, also in the case of Romania, energy represents a product with great economic, social, strategic and political value.

Romania has a long tradition in the mining industry and has important coal reserves that can ensure the continuity of production for more than 150 years.

The situation of geological coal resources in the records of the National Agency of Mineral Resources (ANRM) is presented as follows (table no. 1):

Table 1. National coal resources

Resource type Exploitation perimeters (thousands of tons) Concessioned perimeters (thousands of tons)

Total (thousands of tons) Coal

Lignite

Romania is one of the most important coal producing countries in Europe, after Poland, Great Britain, Germany and the Czech Republic, and one of the largest producers of lignite after Germany, Poland and the Czech Republic.

According to data from the International Energy Agency (IEA), Romania ranks 17th in the world in terms of coal production. (The Global Methane Initiative, Country overview, available at https://www.globalmethane.org/documents/toolsres_coal_overview_ch29.pdf). [5]

Coal production has almost halved in 20 years, mostly due to a decline in mining activity and a reduction in coal consumption (both by industry, such as steel, and by households for heat from coal fired power plants).

4. Decarbonisation of the energy sector

Component C6. Energy, within Pillar I. The green transition of the National Recovery and Resilience Plan, aims to address the main challenges of the energy sector in Romania regarding the decarbonization of the energy system and air pollution, respectively ensuring the green transition and digitalization of the energy sector, through promoting the production of electricity from renewable sources, energy efficiency and future technologies.

Setting this target is motivated by the fact that, in the energy sector, coal is the main responsible for air pollution, which includes greenhouse gas emissions.

Reform 1 provides, in the first stage, the adoption by June 30th, 2022 of the Law on the decarbonization of the energy sector, which creates the legal framework necessary for the measures and actions that must be taken to carry out the entire process and which includes:

The calendar for the definitive and irreversible closure of the energy groups based on lignite and coal; The calendar for definitive and irreversible closure of lignite quarries and coal mines;

Support measures for the definitive and irreversible closure of lignite and coal based electricity production capacities;

Support measures for the definitive and irreversible closure of lignite quarries and coal mines;

Measures to mitigate the social consequences of the definitive and irreversible closure of lignite and coal based electricity production capacities and related quarries and mines;

Sources of financing of state aid measures;

Measures for the coordination and implementation of the decarbonization process; Sanctions;

Energy crisis;

Considering the gradual elimination of the production of coal fired power plants, in order to ensure the continuity and safety of the electricity supply, as well as the safe and stable operation of the National Energy System, the commissioning of new capacities for the production of electricity from renewable sources and naturalgaspreparedforhydrogenblendingisofutmostimportance.Additionally,inordertocoverthecapacity deficit created by the elimination of coal from the energy mix, the commissioning of new hydroelectric production capacities and nuclear energy capacities is considered by 2030.

The decrease in the nominal electric power of lignite and coal based electricity generating capacities is achieved this year, according to the provisions of the National Recovery and Resilience Plan (PNRR), through the definitive and irreversible withdrawal from operation of 660 MW, based on lignite:

• Rovinari 3 energy group 330 MW;

• Turceni 7 energy group 330 MW;

The year 2025 represents a new stage, provided for in the PNRR, regarding the definitive and irreversible closure of the total energy capacity installed based on lignite and coal, through the definitive and irreversible shutdown of the following groups totaling 1,425 MW:

• The energy group, based on lignite, Rovinari 6 330 MW;

• The lignite based energy group, Turceni 4 330 MW;

• The lignite based energy group, Ișalnița 7 315 MW;

• The energy group, based on lignite, Govora 3 50 MW;

• The energy group, based on lignite, Govora 4 50 MW;

• The energy group, based on lignite, Craiova II 1 150 MW;

• The energy group, based on lignite, Craiova II 2 150 MW;

• Termo Service Iași II, based on coal 50 MW.

The definitive and irreversible closure of the lignite based production capacities related to Complex Energetic Oltenia S.A. are also included in its Restructuring Plan, approved by the European Commission on 26.01.2022.

The final closure of the last energy groups based on lignite and coal, remaining after the year 2025, with a total capacity of 1,140 MW, will be carried out by December 31, 2030, as follows:

• The energy group, based on lignite, Rovinari 4 330 MW 31.12.2030;

• The energy group, based on lignite, Rovinari 5 330 MW 31.12.2030;

• Energy group, based on lignite, Turceni 5 330 MW 31.12.2029;

• Coal based energy group, Paroșeni 4 150 MW 31.12.2030.

The definitive and irreversible closure of lignite quarries and coal mining operations will be correlated with the definitive and irreversible closure of electricity production capacities.

Final closure and greening works will be carried out at the quarries where the lignite mining activity ceases, considering the fact that the lignite mining activity had an impact on the environmental components, the most affected being the soil. The cessation of mining activity, the definitive and irreversible closure of lignite quarries and the restoration of the environment will be done in accordance with the provisions of the Mining Law no. 85/2003, with subsequent amendments and additions and directly applicable rules.

Given that the approval of the National Recovery and Resilience Plan implies compliance by the Romanian authorities with the conditions, objectives and reforms aimed in the energy sector, and given the fact that the European Commission requires compliance with the coal replacement calendar, the economic operators who own coal based electricity generation capacities are obliged to meet the established closure deadlines, even if the European Commission does not authorize the state aid measures. [6]

5. Conclusions

The energy sector has important effects, direct or indirect, on a local, regional or global scale on environmental components. The environmental impact of electricity production activities differs depending on the stage of transformation and the type of primary energy.

The impact that coal fired power plants have on environmental components can be: climatic, on underground and surface water, on soil, on vegetation, on human health or aesthetics.

At the European and international level there are concerns regarding the development of optimal strategies and actions to reduce environmental pollution. Thus, Directive 2010/75/EU (IED) Industrial Emissions Directive, transposed into Romanian legislation by Law 278/2013, which entered into force on 01.01.2016, has as its general objective the reduction of polluting emissions into the atmosphere, water, soil, as well as waste from agriculture and industry, with the aim of achieving the highest level of environmental and health protection.

References

[1] *** , 2013

World Energy Council Report, World Energy Resources

[2] *** , 2021 http://www.energynomics.ro/ro/analize/centralele pe carbune raman viabile din perspectiva costurilor/ [3] *** , 2013 http://www.worldenergy.org/publications/ 2013/worldenergy resources 2013 survey/ [4] S.C. Eryza Proiect S.R.L., 2010 Technical Project regarding the closure of the slag ash deposit in the town of Bejan, Hunedoara County [5] *** , 2015 https://www.globalmethane.org/documents/toolsres_coal_overview_ch29.pdf

[6] Ministry of Energy in Romania, 2022 Background note regarding the Emergency Ordinance

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 65 72

RESEARCHES ON MINING CADASTRE: PAST, PRESENT AND FUTURE PERSPECTIVES. THE CASE OF A FORMER MINING TOWN: BORȘA, MARAMUREȘ COUNTY

Ioan BOROICA1 , Marius CUCĂILĂ

, Simona CUCĂILĂ

, Nicolae DIMA4

1University of Petrosani, Petrosani, Romania, ioanboroica@muzeulmaramuresului.ro

University of Petrosani, Petrosani, Romania, mcucaila@yahoo.com

Ministry of National Education, Bucharest, Romania, simona.cucaila@edu.gov.ro

University of Petrosani, Petrosani, Romania, nicolaedima@upet.ro

DOI: 10.2478/minrv 2022 0022

Abstract: After the cessation of mining activities, concerns for mining cadastre research are only sporadic. The present study aims at bringing up to date the evolution of the mining cadastre in the Romanian provinces with a mining book regime, territories that were until 1918 within the structure of the former Habsburg Empire. (Austro Hungary since 1867). Several stages can be distinguished in the evolution of the mining cadastre in the areas shown. From the 16th century until 1854 the principles and methods of the mining cadastre were set up. Between 1854 and 1924 the provisions of the Austrian General Mining Law of 1854 were followed. From 1924 to 1948, the mining cadastre provisions provided for in the mining law of 1924 and other specific regulations are applicable. After 1948, under the conditions of a statist regime, the mining record did not respect the principles of the mining cadastre previously assessed. After 1990, the new mining cadastre only partially takes over the classical principles and methods of the mining cadastre. The way of applying the mining cadastre was focused upon in the town of Borșa, a mountainous place where farmers had not formed cooperatives and where intensive mining was carried out until 2007. With the cessation of mining in Baia Borșa, the mining cadastre was reduced to inventories of some mining assets and sporadic cadastre registrations of some premises and settling ponds. The study analyzes the current situation and proposes some integrated solutions, mediated by GIS technology, aiming the introduction of the mining cadastre in correlation with the introduction of the general cadastre. In this context, GIS technology offers modeling tools that, for example, can assess the degree of suitability of the land for construction.

Keywords: mining, stable cadastre, concretual cadastre, Baia Borșa mining area

1. Introduction

Historical legal background of mining cadastre within the Romanian provinces of the former Habsburg Empire

Theminingcadastreistheoldesttechnicalorspecializedcadastrecreatedtoregulatetherelationsbetween the different public and private entities involved in mining activities and also to secure mining possessions and activities. Securing starts from the exploration stage, as the right of preference is only applied to those mining possessions registered and described in the records of the mining cadastre. Legal and technical prescriptions specific to the mining cadastre were gradually established within the historical Romanian provinces of the former Habsburg Empire. They were included within the mining legislation applicable in the mentioned provinces, consisting of ordinary and special mining laws. Until 1850 the mining legislation in Transylvania was made up of ordinances, imperial rescripts, constitutions, regulations and imperial patents of historical and practical interest. For Galicia, of which Bucovina was a part, the imperial patents are of interest.

Within the Habsburg Empire the mining evolution preceded the development of mining law and the mining cadastre. The main principles, methods and techniques, derived from German inspired mining law, were already established by the beginning of the 19th century. Their codification began as early as the 16th

Corresponding author: Marius Cucăilă, Eng. Ph D, University of Petrosani, Romania, 20 Universitatii str., 332006 Petrosani, Romania, mcucaila@yahoo.com

century. It introduced the concept of investiture which involves the granting on behalf of the sovereign by the mining authorities of the right of concession to explore and exploit mineral substances in a fief an area of land that actually belonged to allodial property. A variety of mineral resources were the object of the concession.

The right to exploit mineral resources definitely determined through exploration works was granted to the first discoverer following a petition by the mining authority. The petitioner should have previously applied for and obtained an exploration permit registered within the exploration register. The petition had to contain information regarding the identification of the petitioner and the location of exploration area with the assigned name and the mention of the type of mineral resource. The petition had to include information about the petitioner, the location and the assigned name of the perimeter and the type of mineral resource. Registration in the mining book confers a special legal regime according to the prescriptions of both mining and civil law. Only those evaluated as exploitable under profitable conditions were granted, thus becoming reserved minerals. Next came the surveying of a ground size reduced area of an three dimensionally featured earth's crust, withstandardizedlength, widthanddepth.Therewerealso grantedthelandsfor ore processingfacilities, as well as the main gallery right. With the investiture and the transcription of this record within the mining cadastre registers of the Mining Court, the granting decision was sent to the petitioner. [1]

The specific provisions of mining law of the various provinces of the Habsburg Empire were unified and systematized by the Austrian General Mining Law of 1854, the legislator still allowing the existence of particular rules established by statutes and regulations. Unlike the previous legal provisions, it distinguishes twostagesinexplorationwork:prospectingandexploration.Accordingtotheprovisionsofthelaw,themining cadastre works, especiallythose concerningthe miningbook, are to be preceded bymineral resource discovery works based on exploration permits. The mining authority of first instance issued two types of permits at the entrepreneur's request: general and exclusive. An exploration permit had to be obtained for each type of activity. For the first type of work, a permit was requested for a"general research area" whose boundaries were determined at the discretion of the petitioner. For the second type, an exclusive exploration area is requested related to anexclusive exploration sign. This was a landmark, which becomes the center of a circular perimeter with a radius of 424.812 m (224 Viennese fathoms). Confirmation of fixing the landmark was made by the mininglocalauthority. It gave the right to request a concessionfor arectangular area of45,116.4squaremeters (12,544 square fathoms). This was called a mining precinct, with an orientation that generally had to take into account the spatial arrangement of mineral ores. Private mining statutes may bend the pre established surface rule.

The license of exploitation works is done by the concession of a mining precinct where exploration works have been carried out. By granting the concession, the surface property is separated from the underground property, being considered as new possession. A translation of the subsurface property to the ground surface by assignation of visible boundary marks is also carried out. By concession, the ownership was granted following an inspection by the mining authority. This one ascertains the existence and exploitability of mineral resources. Another stage in granting the right of concession is the surveying and laying out the boundaries on the surface or even inside the mine. It is executed by the mining authority for the mining boundaries, relative to the opening point. A parallelepiped with unlimited height and depth is delimited, with the previously specified base area whose width cannot be less than 106 m. The mining statutes grant other types of mining boundaries. All surface constructions, workshops and installations that are used for the exercise of rights deriving from the concession deed belong to mining properties

The main role in the management of the mining cadastre and implicitly the mining book was adjudicated to the mining authority of first instance, in this case the mining captaincies or their branch offices and also mining courts. They had the obligation to register all granted concessions in a standardized public register. Each type of concession or investiture is recorded, respectively precincts or sub surfaces, the intermediate spaces mining fields. Three pages were reserved for each concession. The actual mining book represented, in the view of the mining legislation, an instrument of record of the mining cadastre under the administration of the mining court, as an authority that registers and verifies the legality of registrations of mining possessions

Theregistrationswereorderedbytheexecutiveminingauthorityrepresentedmainlybytheminingcaptaincies. Once the investiture was granted and transcribed within the mining cadastre registers of the Mining Court, the granting decision was sent to the petitioner. The concession once obtained, the entrepreneurial shareholder must assume some obligations. The mining activities were permanently supervised by the mining authorities.

The Austrian General MiningLaw onlypartiallysolves the problemof interoperabilitybetween thestable cadastre introduced after 1850 and the mining cadastre by impelling the preparation of topographic survey plans at the cadastral scale 1:2880. It does not mention the compulsoriness to frame the topographic surveying

works into the local or higher order geodetic network. The phrase “stable” means that the tax remains stable even if the owner changes. [2]

The provisions of the Austrian General Mining Law regarding the mining cadastre were maintained in force after the Great Union, from 1918 until the promulgation of the Mining Law of 1924. It was based on the provisions of the Constitution of March 28th, 1923. According to the fundamental law, underground resources belong to the state, thus amending the existing legislation by nationalizing the underground, admitting, however, that the rights won in the past will be maintained. The new Mining Law, as amended in 1929 and 1937, took over in part the mining cadastre principles of the Austrian Mining Law. It was due to the fact that part of the mining leaseholds in interwar Romania were located within the Romanian provinces derived from the former Austro Hungarian Empire with a mining book regime. Thus, the duality of the institutions that manage the entries in the mining book is kept up.

The attainment of the mining property was done by granting the concession. It gives the right to mine on the basis of a license for a certain type of minerals, within a bounded perimeter on the ground and underground for certain period of time. The granting of the concession is done after the prospecting and exploration works in order to discover exploitable ores. They were to be executed based on a license by the Geological Institute or private entrepreneurs. Following these steps, the state chooses an explorer, to whom it grants an exclusive explorationpermitthat gives himthe right tocarryoutminingworks, excludingother entrepreneurs. Bounding the mining area was assimilated to mining cadastre works. It was necessary to precisely bind the mining area and represent it on topographical plans or map it. The geometric shape of the leaseholds had to have square or rectangular geometries. Their sides had to be oriented to the N S and E W directions according to the site astronomical meridian. They had to have the geometric proportions of dimensions similar to those established by law for different types of minerals. The location of the leaseholds was conditioned by the existence of a number of definite exploration points attesting the existence of an ore that can be profitably mined. The property right of the mine and its specified by the law annexes is acquired after the publication of the license deed in a journal of the Council of Ministers. It was accompanied by a specification detailing the main types of mining activities to be developed within the mining area. By granting the concession, the mining rights are separated from the surface right, without excluding the land owners. They had the right to participate as shareholders. The mine and its annexes are considered immovable property that cannot be merged or subdivided without the prior authorization of the mining authorities.

The possession is secured by registering the properties in the mining book, a tool for advertising mining rights and duties. They were established at territorial courts and the regional mining authority. The law included provisions and procedures regarding the recognition and validation of so called earned rights. It regulated the relations between the State, having the capacity of grantor and the assignees prior to the new law, as well as of previously acquired exploration rights. It had significance for the Romanian provinces of the former Habsburg Empire which provided for a deadline that was extended several times.

Although there was the question of achieving a correlation between the works of the general cadastre and that of the mining cadastre, i.e. all the cadastre works to be coordinated by a single institution, this remained a desideratum in the interwar period. The mining cadastre works were drawn up by mining engineers and other licensedpersonnel,butwithoutaunitarycommon methodologywiththe specificworksofthe generalcadastre. [3]

This system of granting leaseholds for exploration and mining works and the procedures of registration within the mining book was maintained until 1948, with the nationalization of mining enterprises.

During the communist regime, one cannot speak of a proper mining cadastre, as it was applied until 1948. Statism is also reflected in the new Mining Survey Regulation, according to which the mining surveying activity is carried out in the mining areas where the mining was carried out by state mining enterprises.

After 1990, the new socio economic reality led to the resumption of enactment in the parliamentary regime of the exploitation of mineral resources. The concession and the granting for managing for a limited period, with the possibility of extension, remain the main ways of exploiting mineral resources by the state. It is not explicitly stated that the concession bound the rights over the underground mineral resources compared to those of the surface. Only the ways of acquiring the use and access to the lands on which mining is carried out is set forth. According to Law 85 of 2003, the mining book is a constituent of the extractive cadastre. The data to be entered into the mining book refer to the land surfaces associated with the leasehold, the topographical situation of the mining works, the state of the mineral resources or reserves and those of production.

The mining book is open for each area of exploration or mining based on a license. The purpose of its institution is to ensure the rights publicity and charges of any kind encumbering the mining properties, which thus become opposable to third parties. In the new legislation, the bipartite system of the mining book held by

both the mining authority and the judicial authority was abandoned. It is exclusively in charge of the executive authority: National Agency of Mineral Resources with its territorial structures. They are made up of cadastral inspectorates, subordinated to the General Directorate for territorial inspection and supervision of mining activitiesandoiloperations.Theminingbookisdrawnupforeachminingareaandmainlyincludesthegeneral record book and the mining book, which includes a series of registers and the entered records.

2. Material and methods

2.1 Study area

Borșa is a town located in a mountainous area at the south eastern end of the county including, as a result of the administrative reform of 1968, the village of Baia Borșa, which became Băile Borșa neighborhood. The town area is 419.13 km². It was a non cooperative area with an important mining activity and primary processing of some non ferrous ores. Until 2007, the year the mines were closed, the country's 8th largest mining state company operated here. The area of mining interest is located especially on the right side of Țâșla River.

Figure 1. Map of Maramures county from 1980 with the demarcation of Baia Borșa mining area. (Source: National Archives, Maramureș County Service, NA, AMMS) It is also valid today

2.2 Historical data on background of mining within Băile Borșa.

The beginning of mining in Baia Borșa is not known but it appears to have its origins in the Bronze Age. Written evidence of the existence of mining comes froma 1780 copy of a report drawn up in 1551 on two field visits by an official of the Montanist Court Chancellery. At the end of the 18th century, mining activities were resumed, the main investor being the Ministry of Finance or the Treasury and some private investors. In the absolutist decade, Manz Ritter von Mariensee became the main investor in Baia Borșa mining, who acquired the main mining assets in 1859. Mining went into decline for ten years with bankruptcy proceedings after Manz's death. The mining properties were purchased by Hubert Franz Franzbender, the owner director of the Chemical ProductsFactoryfromBocicoiulMare.Since1893,partoftheminesfromBaiaBorșawaspurchased by the Hungarian Swiss joint company, "Klotid”. Before the World War I, beginning with 1905, a mixed Hungarian and Anglo Austrian company started sporadic mining exploration works. During the war, mining was controlled by the army. Mining continued intermittently until 1927 when the Pyrit Company called for their cessation. The properties and mining rights at Baia Borșa were purchased in 1928 by Minopirit but without carrying out important mining activities within the area. [4] After nationalization, the new communist regime established in 1948 initiated an ambitious investment program within Borșa and Baia Borșa that led to an unprecedented development of mining in the area. In 1952, Baia Borșa Mining Enterprise was founded, which continued its activity under different names until 2007.

2.3 The evolution of mining cadastre works in Baia Borșa mining interest area

Some documents from the years 1852 1859 of the Baia Borșa mining court, which became the Mining Sub Captaincy, refer to mining cadastre works. They were made based on the prescriptions of the mining law of the time. Among the records are the petitions for granting or renewing the miningconcessions of some local investors or mining associations, sale purchase or lease deeds of some mines. Between 1856 and 1867, cadastralworkswerecarriedouttointroducethestablecadastre,inparallelwiththat ofthe concretual cadastre. They also provide information on the mining cadastre. Within the framework of the stable cadastre, permanent constructions, some hydro technical facilities, roads were mapped. They were located in the area of Burloaia stream, in the major bed of Tâșla River as well as in Baia Borșa. After 1859, mining cadastre activities were carried out according to the provisions of the Austrian General Mining Law under the control and supervision of Baia Mare Mining Captaincy. Mining ceased for various reasons by the end of the 19th century. The resumption of mining activities is reflected in the entries in the mining cadastre records. In particular, circular exploration areas will be recorded in the mining book. In the interwar period, the control of mining cadastre activities was entrusted to the VII Mining Inspectorate, Baia Mare. During the World War II, the Hungarian administration set up in 1942 a Mining Captaincy in Baia Mare that would control the mining within Maramureș area. Until the enactment of the Mining Act of 1924 Pyrit applied for annual extensions of the validity of exploration permits. It was only in 1927 that they requested and obtained, in 1929, the validation in principle of the mining rights of exploration and mining by a specialized panel of judges from the Maramureș Court. Minopirit wanted to secure its mining rights after having acquired the mining properties from Pyrit Company. Thus, in 1931, it requested the renewal of exploration rights for 80 circular perimeters out of the 86 that the former company had obtained. It requested the granting of new exploration permits within the limits of 27 rectangular perimeters with an area of 2070.55 ha within Baia Borșa area. In 1936, the Ministry of Industry and Commerce approves the renewal of exploration rights only for some circular perimeters included within seven rectangular perimeters. The Ministry appreciated the request as it was formulated as a tendency to grab areas with exclusive exploration rights. Thus, it approved only those perimeters that can constitute a reserve for the existing exploitation perimeters. During the period 1948 1989, the most intense mining activity wascarriedout.Minetopographyworkswerecarriedoutonthesurfaceandunderground.Giventheconditions of a statist regime of soil and subsoil ownership, one cannot speak of a proper mining cadastre. The mining activities had consequences on the mining cadastre after 1990. [5]

2.4 The current cadastre in the area of mining interest Baia Borșa

The setting up of the mining heritage of Baia Borșa Mining Company after 1948 was done in several ways:

Nationalizations: the inventory of the assets of the former Minopirit Company transferred, beginning with 1952, to the Mining Company Baia Borșa. It consisted of plots within built up area of Baia Borșa (the mining colony), buildings and facilities as well as the Borșa train station area (land, constructions, preparation facilities, and funicular).

Another source was the transfer to the administration of Baia Borșa Mining Company of some forest areas managed by the Forestry Offices of the area. Most of the forests in Baia Borșa came from the expropriation of compossesoral forests, of the commune and of private owners.

Expropriations by the communist authorities of private lands for the future industrial or mining sites and for the construction of settling ponds and tailings dumps within Baia Borșa area. A correlation was made between the historical cadastre, the “concretual” cadastre and the topographic surveys for the lands proposed for expropriation. The “concretual” cadastre is a form of fiscal cadastre introduced after 1850 based on expeditious fields surveys including parcels with the same land use. The expropriation documentation was drawn up by the topographical service of Baia Borșa Mining Company.

Surface constructions, development works and underground mining works were supported by an ambitious program of investments within Baia Borșa mining enterprise.

Until now, the mining cadastre works for the mining interest area had as their object the registration in the general cadastre records of the main mining premises. Sometimes the sporadic cadastre and several technical cadastres compete for the same surface. In Borșa town, no systematic cadastre works have been carried out so far. Thus, through the sporadic cadastre, certain mining areas were occupied, areas that maintain their importance even if the mining activity has ceased.

Figure 2.Topographical plan with the location of some plots proposed for expropriation in 1952 for the location of the industrial premises, (Source NA, AMMS)

Carrying out works for the introduction of the general or systematic cadastre is a necessity in the area of mininginterest in Baia Borșa. Accordingtothe methodologyfor introducingthe systematic cadastrefor Borșa, 56 cadastral sections were designed by the National Agency for Cadastre and Real Estate Advertising. The design of the cadastral sectors was done relatively arbitrarily without taking into account the physical geographical realities of the area and the existing cadastral works.

To facilitate the introduction of the mining cadastre in correlation with that of the systematic cadastre, the following aspects must be taken into account:

1.InthetownofBorșa,the“concretual”cadastreisinuse,whichwasintroducedsimultaneouslyorshortly after the completion of the stable cadastre works. The stable cadastre works were carried out between 1856 and 1867. An important cadastral material consisting of maps made on a scale of 1:2880 and records of parcels and owners was created. The connection between the two types of cadastre is made through correspondence registers between cadastral and topographical numbers. [6]

2. Part of the lands located in the area of mining interest was subject to the reconstitution of property rights through the agrarian reform laws after 1991. Most of these lands are forests that were nationalized by the communist regime. By retrocession, the forestry regime achieved through the forest cadastre is maintained.

3. Miningcadastre works were carried out mainlythrough sporadic cadastre worksfor some of the mining premises and settlingponds. For example theroads andaccess areas to manholes ofsome closed mine galleries were included within the reverted forest property.

3. Results and discussions

By means of the systematic cadastre it will be possible to clarify ownership relationships and ownership structures of the area. In support of the complete introduction of the mining cadastre correlated with the systematic cadastre, several solutions can be proposed:

1. The analysis and processing in GIS or CAD environments of the cadastral material resulting from the stable cadastre offers the possibility to make the connection between the “concretual” cadastre and the layout of the plots in the field. Processing in ArcGIS Pro involved scanning the cadastral plans, geo referencing and mosaickingthem. Tofacilitate geo referencing, a gridwas created withthe use ofcontrol pointsthrough which the correspondence between stable points in the field and those on the map is made.

The digital map of Borșa resulting from the mosaicking of 192 map sections can be used for: the restoration of the border limits of Borșa town since the current ones were set arbitrarily; the design of cadastral sectors based on the toponymy criterion, since the toponymy coverage of the territory is more stable and easy to use; reconstitution of parcel boundaries in uncertain and litigious situations; predictions for the possible number of parcels within a cadastral sector based on the ownership structure identified on the stable cadastral maps.

2. Making correlations mediated by ArcGIS Pro between the competing cadastres: the historical cadastre, the sporadic cadastre, the forest cadastre and other technical cadastres in support of the introduction or continuation of mining cadastre works. These correlations can be made through a database in ArcGIS Pro. [7] Raster or spatial data from different sources can be integrated into the database. They allow the realization of different analyses or modelling.

Figure 3. Topographical plan with the location of some land proposed for expropriation in 1982 for the expansion of the settling pond D3 (Source NA, AMMS)

Analysis and modeling in the GIS environment provides the possibility for potential investors to make predictions in the evaluation of land according to their suitability for building. A classification of land in Borșa town according to favorability and readiness for construction can be achieved through modeling in a GIS environment.

The analysis involves making spatial correlations between the component layers of the created database. The resulting model respects the statistical and scientific rigors, while also allowing an adequate evaluation of the cost of land suitable for construction and mining developments. Land use, geo morphometric factors, accessibility and restrictive factors such as watercourses were taken into account in the creation of the model. The first stage of the analysis consisted in the acquisition of the data, followed by their symbolization within some thematic layers.

The vector data were transformed into raster type structures, necessary for spatial modeling. The resolution of all grids that were included in the model was 10 m. In the next step, the initial raster data were reclassified, thus the raster values were ordered according to the favorability for construction. With the help of "Weighted Overlay" tool, spatial modeling could be done to obtain a thematic layer. This thematic layer reflects the suitability and favorability of land for construction and implicitly for mining developments. Each rasterisassignedaweight inthemodelaccordingtotheimportancethatthefavorableconditionshavereported, respectively favorable or unfavorable. To these are added any restrictions regarding the arrangement of industrial and mining buildings.

Figure 4. Mosaic digital map of the stable cadaster of Borșa town.

Figure 5. Historical cadastral sectors in relation to the sectors proposed by NACREA within Baia Borșa area

Figure 6. Map of Borșa town with the zoning of the suitability for construction works

4. Conclusions

The extensive studyof the material resultingfromthe miningcadastre and extractive activities, in particular theoneconcerningthemininginterestareainBorșa,canbringboththeoreticalandpracticalbenefits.Themining cadastre is the oldest technical cadastre and the first three dimensional one. The classical principles and methods of the mining cadastre were observed until the imposition of the communist regime. In this new situation, under the conditions of a statist regime, mining cadastre works were partially assimilated with mining topography works. However, the connection with the historical cadastre was not ignored, especially in the case of expropriations. Unlike the historical cadastre, in the case of the mining cadastre after 1990, the principles of the classic mining cadastre were only partially adopted. Given that most mining activities have been stopped in nowadays Romania, concerns for theoretical or technical aspects have become peripheral. In the mining project, theextractivecadastreworksareimportantinallitsphases.Thepresentresearchfocusesonthenecessarymining cadastre works for the mining resumption. At this stage, the identification of legal mining lands, their inventory and registration in the cadastral records is mandatory. To the same extent, the problems of property relations in the areas that can be affected by the activities of the mining project must be solved, so an integrated solution of thecadastralproblemsintheareasofmininginterestisneeded.Equally,theproblemsofpropertyrelationswithin the areas potentially affected by the activities of the mining project must be solved, so an integrated solution of the cadastral problems in the areas of mining interest is needed. GIS technology provides technical support and also for scientific analysis in introducing and continuation of mining cadastre work. The conclusions of this research are limited by the material accessible to the research. The opening for scientific research of the documents resulting from the mining activities, in the present case the documents created by Baia Borșa Mining Enterprise, will allow the realization in a GIS or CAD environment of some three dimensional modeling of the mineral deposits. It will be possible to evaluate the ore reserves as well as the virtual reconstruction of the underground mining works. Such modeling will facilitate the exploration and opening works in case of the resumption of mining works in the studied area. Complex analyzes in GIS environment of mining fields will be able to be performed for reserve evaluation and optimization of mining operations.

References

[1] Tausch G., 1837

Il dirito minerale dell Impero Austriaco sistematicamente compilato ed ilustrato dal dott. p.1 7, 37, 43 46

[2] Stoian G., Gheorghiade V., 1924

Romanian Mining laws new and old. Laws of annexed counties before 4 July 1924 (in Romanian) Bucharest, 1924, p. 87 89

[3] Ministerul Industriei și Comerțului, 1937

Regulation of mining laws from 24 March 1937 (in Romanian), Bucharest 1937

[4] Boroica I., 2021

Past mining activities in Băile Borșa, Maramureș, until 1948 (in Romanian) Țara Bârsei Revistă de cultură, p.161 172, ISSN 1583 3119. Tara barsei.ro/wp content/uploads/2021/12/book TB 2021_INT_ 27 nov_mic.pdf

[5] National Archives, Maramureș County Service

The Baia Borșa state mining company archival fund, The Baia Mare Directorate of Mines and Metallurgical Plants Archival Fund, Baia Borșa Mining Captaincy Archival Fund, Geological Mining Inspectorate Archival Fund (in Romanian)

[6] Boroica I., 2022

Cadastre within the paradigms of society development from historical Maramureș (in Romanian), Revista română de istorie economică, Tomul I 2022, Presa Universitară Clujeană, p.173 106 http://www.rriejournal.ro/wp content/uploads/2022/09/Ioan Boroica.pdf

[7] Allen D.W., 2019

Focus on Geodatabases in ArcGIS Pro, Esri Press, 260 p. ISBN 978 1 5894 8445 0

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 73 82

THE USE OF DRONES IN MINING OPERATIONS

Gheorghe Marian VANGU1*

1University of Craiova, Faculty of Agronomy, Craiova, Romania, marian_vangu@yahoo.com

DOI: 10.2478/minrv 2022 0023

Abstract: This paper presents the possibilities and benefits of using drones in mining operations. In the first part of the paper, aspects regarding the concept, the constructive elements of autonomous aerial vehicles, legislative provisions for the use of drones, elements of flight safety and the security of people are clarified. In the second part of the paper, the possibilities of practical use of drones in mining operations, the benefits and the types of expected results are presented. Keywords: drone, UAV, UAS, mining, security, photogrammetry

1. Introduction

Currently, more and more business sectors are adopting modern methods and technologies for collecting, processing and analyzing data of interest. These include aerial scanning methods and techniques, aerial photogrammetry, use of UAS, GIS type applications, etc. Thus, all these methods and technologies have penetrated even the miningfield, a field that presents both a dynamic activity and a high level of risks to which personnel are subjected.

Drones are one of the modern methods increasingly used in mining [1] and offer the possibility of fast, safe and cost effective data collection. Thus, access to mining operations located in remote locations and hard to reach places is facilitated, at the same time offering the possibility of constant monitoring and the adoption of quick and documented decisions, which ensure the normal development of the activity and the increase of mining efficiency. Based on the data thus collected, surveyors and engineers can issue forecasts regarding the development andexpansionofmines,makerapidassessmentsofareasandworkingconditions,thusimproving the safety of mining personnel.

The increasing use of unmanned aerial vehicles (UAVs) may improve the productivity and profitability of remote sensing operations in the mining industry. The objective of this paper is to enable stakeholders to identify possible opportunities for adoption, improvement and innovation of drone applications in mining [2].

Over time, various studies have been carried out on the use of UAVs in the mining field, among which we mention: case studies on surface mapping, 3D modeling, land damage assessment, monitoring of the environment and the level of pollution [1], scenarios of UAV use in the land reclamation phase [3], studies on UAV based structures in motion (SfM Structure from Motion), translated into a methodology that can be applied to the mapping and analysis of dikes and dams [4].

Park, S. and Choi, Y. [5] centralized 65 research articles on the use of UAVs in mining and made a structuring according to their applicability, as seen in figure 1.

This paper tries to answer the question: how can drones be used in the 3 main phases (exploration, exploitation and reclamation) of a mining operation [2], what are the benefits and how can it be promoted and encouraged the use of drones in mining.

2. Drone Overview, definition, characteristics, legislation and security, flight safety

In recent years, drones have proven their usefulness and efficiency in more and more fields of activity, from mining and surveying to the organizing air shows [5]. However, to fully understand the benefits, dangers and responsibilities of using drones, both technical and legislative aspects must be defined and known.

Faculty of Agronomy, University of Craiova, Craiova, Romania, (University of Craiova, 19 Liberty Street, +40 741040424, marian_vangu@yahoo.com)

Corresponding author: Gheorghe Marian Vangu, As eng.ec. Ph.D stud. / Land Surveying, Management, Mechanization Department

2.1 Drone vs. UAV vs. UAS

Giventhatincurrentlanguagetheterm"drone"isusedgenericallytodefinearemotelycontrolledvehicle, the correct definition of the terms is required [6], as follows:

Drone a vehicle that can move autonomously, without the intervention of the human factor (without having a pilot on board, but they can be controlled remotely). Although drones can travel through air, water, or land, this article refers strictly to air travel.

UAV (Unmanned Aerial Vehicle) represents a narrowing of the types of drones and is limited to aerial vehicles that have the ability to travel autonomously or remotely controlled, without having a pilot on board [6], [7], [8]. At the same time UAV refers strictly to the flight vehicle itself, without covering other components (physical or logical) that can interact with the UAV. Any UAV is a drone, but not every drone is a UAV.

Unmanned aerial vehicles (UAVs) have become favored instruments for remote sensing applications [9], are capable of sustaining flight without onboard human involvement and are remotely controlled either manually or by a computerized piloting program [2].

It should be noted that unmanned helicopters and gliders are assimilated to drones as they are known by the majority of the population (multi engine).

UAS (Unmanned Aerial System) includes all the components of a flight system [6], [8]: the flight vehicle, radio control, GNSS sensors, accessories used, the human factor (pilot and/or operator), photo/video cameras, additional loads, telemetry systems, software components etc. Thus, UAV is a component of UAS.

2.2 Components

A UAS consists of several components and accessories, depending on the way of manufacture, the purpose of use or the field of activity. Thus, the most common components of a UAS, but not limited to these, are:

TheactualUAV,asaflyingdevicewithoutapilotonboard,but withtheabilitytotravel autonomously or remotely controlled. It strictly includes manufacturing elements and does not include any elements subsequently attached by the operator. UAVs can be mass produced (known as commercial drones) or home built.

Figure 1. Process of the literature search and classification [5]

Radio control, as a tool for directing the UAV by the pilot. The radio control has various characteristics: it can operate on various frequencies, it may or may not include a graphic display, it can be used simultaneously with another control device (UAV controlled by two pilots, especially in pilot training courses), it includes a rechargeable battery, etc.

Photo / video camera and light filters, if attached outside the manufacturing process. If commercial UAVsusuallyincludeastandardcamera,UAVsusedinspecializedfieldsusespecialattachedcameras (multispectral, LIDAR, thermal imaging, etc.).

GNSS sensors, additional batteries, etc., if attached outside the manufacturing process.

The software component, which includes any software product used to plan, conduct, control or supervise a flight. These software products can be installed and run on mobile (phone, tablet) or laptop/desktop devices and are interconnected with the software component of the UAS.

Pilot/operator, refers to the human or legal factor. The pilot is the person who actually flies the UAV, and the operator is the natural or legal person who benefits from the results of the flight. For example, if an employee performs a photogrammetric flight while on duty, that employee is the pilot and the employer is the operator.

Other components: telemetry elements, launch pads, night flight lights, FPV (First Person View) goggles, etc.

2.3 Legislation and security

Considering the use of UAVs both in industrial sectors and especially by the general population, the need to regulate their use has arisen. Thus, regulations were drawn up (at European and national level) with the aim ofensuringtheprotectionofthepopulation.WithreferencetotheterritoryofRomania,theauthoritiesinvolved in the development and implementation of these regulations are EASA (European Union Aviation Safety Agency) and AACR (Romanian Civil Aviation Authority).

Figure 2. A.UAV (Unmanned Aerial Vehicle) [7], B.UAS (Unmanned Aerial System) [8]

Figure 3. Unmanned Aerial System Subsystems [8]

At the national level, AACR must ensure the necessary environment and conditions [10] for:

registration of UAV operators;

training and examination of UAV pilots;

defining and updating geosecurity areas;

issuing authorizations and certificates necessary for UAV operations;

permanent supervision of UAV operations, including checks and audits;

continuous promotion of safety in the use of UAVs.

When referring to the assurance of security and the level of risk presented in use, both the types of operations carried out and the classification of UAVs must be taken into account [6], [10].

Table 1. Categories of operations Category Risk Details

Subcategory

A1 operations near isolated persons are allowed.

Overflying uninvolved persons must be avoided, and overflying crowds of people is prohibited;

Flight within the visual line of sight (VLOS Visual Line of Site);

Maximum altitude 120 m.

Open Low

Does not require a flight permit issued by the AACR; Supervision of operations is the responsibility of local authorities.

A2 operations at a horizontal safe distance for non involved persons are allowed; Flight within the visual line of sight (VLOS Visual Line of Site);

Maximum altitude 120 m.

A3 operations without non involved persons. Flight within the visual line of sight (VLOS Visual Line of Site);

Horizontal safety distance 150 m from residential or commercial areas; Maximum altitude 120 m.

Specific High

Requires obtaining a flight authorization before flying, unless the operation is covered by a standard scenario found in the annex to EU regulation 2019/947.

Operations are overseen by the AACR.

Requires UAV certification;

Requires pilot licensing;

Certificated Major

Requires obtaining a flight permit from the AACR.

Assessing the risk of the intended operation by applying the SORA (Specific Operations Risk Assessment) methodology or an equivalent methodology.

Predefined Risk Assessment (PDRA Predefined Risk Assessment) it includes the most common scenarios, so that the flight guidance issued by EASA can be followed and applied.

Type 1 operations: international flight of certified cargo drones

Type 2 operations: drone operations in urban or rural environments using predefined routes

Type 3 operations similar to type 2 operations, but involves the presence of a pilot on board the drone

In addition to the category of operation to be carried out, the restrictions imposed by the class in which the drone was assigned must also be taken into account. EASA regulations provide for the classification and labeling of drones in the following classes: C0, C1, C2, C3, C4, privately built). Considering that currently there are many UAVs that have not been classified and labeled accordingto these regulations, until 01.01.2023 they can be used as follows:

28,

Table 2. Limitations of open operations, valid until 01.01.2023

UAS Operational

Class Total mass Subcategory Restrictions

Operator / Pilot

Registration of the operator Competences for remote pilot Minimum age

Private construction < 250 g A1 (may also fly in the A3 category)

No identification class

250 < 500 g

No hovering over uninvolved people; No flying over crowds of people.

No, if the UAV has no camera No training necessary No age limit

No flying over crowds of people;

A2 (may also fly in the A3 category)

2 kg < 25 kg A3

Keeps a horizontal distance of 50 m from non involved persons.

No flying near people;

Fly outside urban areas (minimum 150m).

YES

Reads the user manual; Conducts training and examination at AACR (according to subcategory).

16 500 g < 2 kg

Table 3. Limitations of open operations, starting with 01.01.2023

UAS Operational Operator / Pilot

Class Total mass Subcategory Restrictions

May fly over non involved people;

Registration of the operator Competences for remote pilot Minimum age

No training necessary No age limit

May not fly over crowds of people.

No, if the UAV has no camera

Private construction < 250 g A1 (may also fly in the A3 category)

C0

No hovering over uninvolved people;

No flying over crowds of people.

No hovering over uninvolved people;

C2 900 g < 4 kg

A2 (may also fly in the A3 category)

Maintains a horizontal distance of 30 m from non involved persons (this can be reduced to 5 m if the “reduced speed” function is activated).

No flying near people;

YES

Reads the user manual; Conducts training and examination at AACR

YES

Reads the user manual; Carries out and declare individual practical training; Conduct training and examination at AACR.

16

Reads the user manual. 16 C1 250 < 900 g

C3 C4

Private construction 4 kg < 25 kg A3

Fly outside urban areas (minimum 150m).

YES

Reads the user manual; Conducts training and examination at AACR

16

16

2.4 Flight safety

In order to ensure safety conditions during operations involving the use of UAVs, both legislative provisions and good practice recommendations must be observed. These include the appropriate training of participating personnel, technical conditions, meteorological conditions, environmental conditions, UAV flight performance etc.

A basic principle of flight safety is MEUH (Meteorology, Environment, UAS, Human) [6] Meteorology weather conditions can influence both the performance of the equipment used (UAV, radio control, radio signal, photo/video cameras, etc.) and the capacity of the human factor (pilot, observer). The main environmental (climatic) factors are:

Wind, characterized by speed and direction; updrafts and downdrafts that can form due to temperature differences or existing vertical walls must also be taken into account. Wind speed conditions must be correlated with UAV flight performance.

Temperature, with direct influence on the flight equipment, on its lift and on the pilot. The flight temperature must be correlated with the technical specifications of the equipment (UAV, radio control). Low temperatures increase the air density and implicitly the lift of the UAV, but decrease the battery performance and therefore the flight autonomy. Increased temperatures decrease the density of theairandgenerateadditional effortontheengines,whichleadstoincreasedconsumptionandreduced flight range. At the same time, high temperatures have harmful effects on batteries, which can cause their sudden discharge or even their explosion.

Precipitation, which varies depending on the form it can take (rain, snow, hail, etc.), intensity and duration. Precipitation can destroy equipment quickly, by causing an electrical short circuit, or over time, by corroding various wires or circuits. At the same time, precipitation influences the pilot’s ability to properly maneuver the UAV, decreases the degree of visibility and reduces the range of the radio control.

Fog may cause ice to form on the propellers, which can lead to reduced lift and the UAV crashing. Environment refers to all conditions existing in the flight area. Among these we mention:

Geosecurity areas are areas where flying is not allowed, these are usually areas used for civil and military air traffic. These are areas where traffic is strictly regulated by the AACR.

Altitude relative to sea level, the altitude of the flight area may affect the performance of the UAV, especially through atmospheric rarefaction with increasing altitude.

Terrain profile may cause problems due to existing obstacles, bumps that may generate turbulence and the type of surfaces that may generate atmospheric instability.

Electromagnetic interference presents the risk of breaking the connection between the UAV and the remote control, which can cause it to be lost or crashed.

UAS refers to all the technical aspects and capabilities of the equipment, from checking the charge level of the accumulators to knowing the technical characteristics of the equipment (user’s manual).

Human referstothepossiblepeopleinvolvedornotinvolved: pilot,operator,observer,peopleontheground, people in the air, etc. For the assessment of the pilot’s condition, it is recommended to use the “I’M SAFE” methodology [10], which is embodied in a checklist with the following:

llness even a minor condition may cause errors of judgment and operation;

Medication may lead to decreased pilot performance. Thus, the possible side effects that can be given by the administered medication must be evaluated;

Stress may affect the performance of the pilot, who may feel lack of energy or who cannot concentrate enough;

Alcohol even a small amount of alcohol consumed may affect the pilot’s reflexes and reaction times;

Fatigue represents one of the most dangerous factors that may cause piloting errors, the crash of the UAV or even injury to people;

Emotions anger, fury, depression, anxiety, etc. are manifestations that may reduce the pilot’s level of attention and ability to concentrate and that can encourage destructive behavior.

Hence, we can conclude that flight safety refers both to the protection of the equipment and especially to the security of the people involved or not involved, on the ground or in the air.

3. The use of drones in mining

Although sensor equipped UAVs are relatively new to the mining industry, their use has grown and diversified, covering geological modeling, surface and underground mining mapping, mining exploration, exploitation and rehabilitation, etc. [2].

Professionals who started using drones in their current mining activities quickly realized the added value they bring to mining [11]. The use of drones in mining enables efficient management of large mining sites and quarries, providing fast, accurate and comprehensive data. Thus, both the dynamic supervision of operations, but also the effective coordination of work teams and keeping them safe is possible. It should be stated that the data provided by drones can be used in real time (e.g., performing a reconnaissance or surveillance flight) or after some post processing steps (e.g., performing a photogrammetric flight). By using drones in mining, engineers no longer have to focus on measurement and data collection activities in the field and can focus on data analysis and interpretation.

3.1 UAV mining operations

The main uses of drones in mining are [1], [5], [11]:

Monitoring, surveillance, inspection: mining is one of the most dangerous industries for the human factor (directly productive workers). Current mining operations present various and numerous hazards such as: rock falling, gas leaks, high humidity, floods, dust explosions and other events that may pose risks to mining personnel. Drones equipped with various sensors (from RGB or thermal cameras to gas detectors) can be used for: real time monitoringand inspection of mine shafts, mining equipment inspection, detonation surveillance, etc.

Topography and mapping: in the mining industry, geolocation is of particular importance, so the mapping of sites must be redone or updated periodically, which requires a significant consumption of resources (especially time and people). By using drones and specific software products, aerial mappingofsitescanbecarriedoutbyacquiringrawdataduringaphotogrammetricflight,processing them and obtaining photogrammetric products (orthophotoplan, 3D models, thematic maps, level curves, etc.). The classic photogrammetry method can also be used (which involves a flight with a traditional piloted plane), but in the case of using drones, the costs are significantly lower, and the resolution obtained is clearly superior.

Storage and warehousing: In mining as in other fields, inventory management is a cumbersome and essential task that can streamline or completely block the operation of a mining site (and the units that depend on the supplied resources). Inventory management refers both to the obtained products (main or secondary), but also to residual products. A constant challenge is the ever changing heights and irregularly shaped deposits, making it difficult to accurately determine volumes by conventional techniques and methods. At the same time, these techniques and methods are based on direct measurements carried out in the field, which presents risks for personnel. Based on the data acquired with drones and by applying photogrammetric methods, 3D models, digital terrain models, digital elevation models, etc. can be generated, products that allow various analyzes and calculations (including volumetric) to be performed.

Hauling road management and optimization: haulage road networks are essential to the efficiency and productivity of mining operations. To ensure reliable and consistent transport, the state and quality conditions of the roads must be constantly ensured. Through the use of drones, rapid and frequent visual assessments of transport routes can be made (either in real time by telemetry methods or after the flight by photogrammetric methods). Based on the acquired and processed data, relevant information on transport roads (lengths, slopes, turning angles, etc.) can be obtained, information that supports engineers and builders for their preparation, design, development and maintenance.

Mining exploration: Mining exploration operations carried out in the traditional way present one of the highest risks to personnel. With the technological evolution and the use of drones in mining, mining exploration methods have been adapted, so that today they include the use of drones and photogrammetric methods based on which high resolution orthophotoplans, 3D models, multispectral analysis, etc. are obtained and used.

Monitoring settling or tailings dams: the use of drones for monitoring and inspecting tailings dams removes anydanger topersonnel who would otherwisebe exposedtothe risks of applyingtraditional monitoringmethods[1]. Aerialimageryprovides the human factor withtheopportunitytofrequently

observe site components such as tailings dam slopes or tailings slide slopes. The use of drones eliminates the need for manual measurements, so personnel no longer have to travel to risky locations. By analyzing digital data, mining companies can maintain the structural integrity of tailings dams and prevent them from collapsing.

Hydrological and sediment monitoring: permanent monitoring of unwanted water and sediment flows can avoid the interruption of mining operations caused by them. Drones can be used for real time monitoring or data acquisition. Later, by processing this data, digital elevation models are generated that provide the user with a realistic perception of the situation. Also, based on the digital models obtained, scenarios and hydrological simulations (flood scenarios) can be. As it can be seen, the use of drones in mining can be structured into two types of scenarios: flights with the visualization and evaluation of data in real time (by telemetric methods) and flights for the acquisition of photogrammetric data (for further processing). The first type of flight is considered dynamic, it can be done quickly, it does not require detailed planning, it allows the recording of photo video data for later viewing, and the user has immediate access to the data. To carry out the second type of flight (photogrammetric), it is necessary to go through some stages, as follows: setting objectives, flight planning, flight and data collection, data processing, generation of photogrammetric products (orthophotoplan, various digital models), use effective of the photogrammetric products. In this case it can be seen that the user has access to the data of interest only after processing the raw data purchased.

3.2 Sensors used in mining

Technological evolution, innovation and development of various types of sensors have facilitated their integration with UAVs and use for mining operations. Depending on the type of data to be collected and environmental conditions, various sensors can be used by attaching to the UAV. The most used sensors in mining are [11]:

Infrared Sensors (IR, Infrared Sensors) arerelativelycheapsensorsandareusedtodetectobstacles. They are sensors that work on heat detection and have the advantage that they can be used even in conditions of fog, smoke, day, night, etc., but they have limitations in conditions of dense dust or high temperatures.

Ultrasonic sensors (US, Ultrasonic sensors) are relatively cheap sensors that rely on high frequency sound waves to detect obstacles. They have the disadvantage of not being able to be used in sound absorbing environments and have a shorter range than other sensors.

RGB sensors (Red Green Blue) is the most common sensorand is used for RGB image acquisition. When choosing a camera, both its technical capabilities and the capabilities of the drone (autonomy, load capacity) must be taken into account.

Stereo cameras are cameras equipped with two or more lenses to generate three dimensional images. They have the advantages of generating high resolution and accurate images, but have limitations when used in foggy, smoky or dusty environments.

Laser Range Finders (LRFs) are expensive sensors used to detect and avoid obstacles. They are not suitable for use in conditions of fog, smoke, dust or other similar conditions.

Ultra Wideband Radar (UWB) is based on the emission of electromagnetic waves in the radio spectrum, the wavelength of which is longer than in the case of IR. It has the advantage that radio waves propagate more easily than visible light in fog, smoke, dust or other similar conditions.

Hyperspectral sensors based on the assessment of reflected radiation as a series of narrow and continuous wavelength bands. These sensors can provide information that is not accessible through traditional methods.

Magnetic sensors are based on the accurate assessment of the magnetic field. At the same time, they have the ability to evaluate interferences and changes in the magnetic field. It should be noted that in order to obtain three dimensional gradients of the magnetic field, it is necessary to use four magnetometers.

Sensors for the visible and near infrared spectral range (VNIR, Visible and Near Infrared spectral range) present the advantage of having small dimensions and weight. They can be used to evaluate the surface moisture conditions of quarries, tailing ponds, underground spaces, walls, surfaces, etc.

Air quality monitoring sensors are sensors specially developed for air quality assessment and monitoring, detection of various gases, monitoring of dust clouds, etc.

3.3 The benefits of using UAVs in minig

The use of drones for topography in mining presents numerous advantages, among which we mention:

Fast data collection: The use of drones allows rapid data collection, almost 30 times faster than through traditional practices carried out by personnel. At the same time, saving and reusing flight plans reduces the time spent in the field and ensures accurate data collection from the area of interest (including by making flights over the same surface, but at different times).

Improved data accuracy: being specially designed equipment, surveying drones for mining operations have the ability to accurately capture data both in terms of image resolution and their geo positioning at the time of data acquisition. Thus, in the data post processing stages georeferenced digital results with high precision can be obtained

Quality and structure of the data: the use of drones allows the rapid acquisition of data (photos, photograms, videos) with high resolution. Thus, both the direct (visual) interpretation of the data by the human factor is possible, but also their subsequent processing and the obtaining of photogrammetric products such as: orthophoto plane, point cloud, DEM, DSM, level curves etc.

Increased efficiency: byusingdrones,miningoperationshavebecomemoreproductiveandefficient. The efficiency of these operations is mainly ensured by: reduction of data collection times, high quality of collected data, quick data access (especially in scenarios of using cloud services with real time data transfer) and decision making fast and documented.

Workers’ safety: drone operations can be planned and simulated from the office stage, so that any observed risks can be eliminated. At the same time, the operations of mapping, surveying, inspection and monitoring of mining operations are carried out remotely, so that the operator/pilot is permanently safe, and the presence of other people is not necessary

Low costs: in order to be able to establish the profitability of using drones in mining, it is necessary to evaluate several aspects,such as: the initial level of investment in UAV equipment and specialized software products (which is quite high), the reduction of the time data collection and processing, increasing staff safety and avoiding possible work accidents, increasing the frequency of data collection, accuracy of collected data, etc. Thus, by balancing the costs with the benefits of using drones in mining, we can conclude that their use is also justified from a financial point of view

4. Conclusions

Withtheevolutionoftechnology,autonomousaerialvehicleshavefoundtheirusefulnessinvariousfields of activity, including mining. Even though the use of drones has many advantages and benefits, there has been a need to regulate how and where they are used to ensure the safety and security of those involved and those not involved.Thus, bothat the European and national level, regulations have been developed and implemented that classify the type of operations, the type of UAV, the protection and security areas and which detail the

sensors on

Revista Minelor Mining Revue vol. 28, issue 3 / 2022 ISSN L 1220 2053 / ISSN 2247 8590 pp. 73 82

conditions that must be met for the safe performance of a flight. Compliance with legislative requirements and good practice guidelines ensures the success of UAV operations.

In mining operations, drones are mainly used to carry out photogrammetric flights and acquire data to be processed to obtain the final products: orthophotoplan, DEM, 3D models, thematic maps, etc. The main uses of drones in mining are: monitoring and surveillance, surveying and mapping, storage and warehouse management, hauling road management and optimization, mining exploration, monitoring settling or tailing dams, hydrological monitoring.

The benefits of using drones in mining operations are both economic (quick and cheap data collection, increasing efficiency, reducing costs) and operational (ensuring personnel safety, monitoring hard to reach areas, accuracy and quality of data collected)

References

[1] Ren, H., Zhao, Y., Xiao, W., Hu, Z., 2019

A review of UAV monitoring in mining areas: current status and future perspectives, International Journal ofCoal Science & Technology, https://doi.org/10.1007/s40789 019 00264 5

[2] Loots, M., Grobbelaar, S., van der Lingen, E., 2022

A review of remote sensing unmanned aerial vehicles in the mining industry, Journal of the Southern African Institute of Mining and Metallurgy, vol. 122, no. 7, pp. 387 396, http://dx.doi.org/10.17159/2411 9717/1602/2022

[3] Buczyńska, A., 2020

Remote sensing and GIS technologies in land reclamation and landscape planning processes on post mining areas in the Polish and world literature, AIP Conference Proceedings 2209, 040002 (2020); https://doi.org/10.1063/5.0000009

[4] Dering, G.M.; Micklethwaite, S.; Thiele, S.T.; Vollgger, S.A.; Cruden, A.R., 2019

Review of drones, photogrammetry and emerging sensor technology for the study of dykes: Best practises and future potential, Journal of Volcanology and Geothermal Research, Volume 373, 15 March 2019, Pages 148 166, https://doi.org/10.1016/j.jvolgeores.2019.01.018

[5] Park, S., Choi, Y., 2020

Applications of Unmanned Aerial Vehicles in Mining from Exploration to Reclamation: A Review, MDPI Minerals Journal, https://doi.org/10.3390/min10080663

[6] Luxembourg Directorate of Civil Aviation, 2022 LearningZone, UAS Remote Pilot Open Category A1+A3 [UAS OPEN A1+A3]

[7] Chamola, V., Kotesh, P., Agarwal, A., Gupta N., Guizani, M., 2021

A Comprehensive Review of Unmanned Aerial Vehicle Attacks and Neutralization Techniques, Ad Hoc Networks, Volume 111, 102324, https://doi.org/10.1016/j.adhoc.2020.102324

[8] Singhal, G., Bansod, B., Mathew, L., 2018

Unmanned Aerial Vehicle Classification, Applications and Challenges: A Review, Computer Science, Environmental Science, Mathematics

[9] Muchiri, N., Kimathi, S., 2016

A review of applications and potential applications of UAV, Proceedings of the 2016 Annual Conference on Sustainable Research and Innovation, IEEE, vol. 7. pp. 280 283

[10] Autoritatea Aeronautică Civilă Română, 2022 Manual pentru pregătire și certificare pilot la distanță categoriile A1/A3, A2

[11] Shahmoradi, J., Talebi, E., Roghanchi, P., Hassanalian, M., 2020

A Comprehensive Review of Applications of Drone Technology in the Mining Industry, MDPI Drones Journal, https://doi.org/10.3390/drones4030034

This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above mentioned CC BY SA 4.0 license.

Revista Minelor Mining Revue

ISSN L 1220 2053 / ISSN 2247 8590 vol. 28, issue 3 / 2022, pp. 83 92

ECO ENERGETIC EFFICIENCY COMPARATIVE ANALYSIS OF STEAM POWER PLANTS VERSUS MICRO HYDROPOWER PLANTS

Mădălina (Barbu) DELAYAT1, Maria LAZĂR2* , Sabin IRIMIE3 , Sabina IRIMIE4

1National College “Ion C. Bratianu”, Pitești, Romania, madigeo2003@yahoo.com

2University of Petrosani, Petrosani, Romania, marialazar@upet.ro

3University of Petrosani, Petrosani, Romania, sabinirimie@upet.ro

4University of Petrosani, Petrosani, Romania, sabinairimie@upet.ro DOI: 10.2478/minrv 2022 0024

Abstract: Global warming and climate changes, as well as the contribution of fossil fuel to the accentuation of these phenomena are realities almost unanimously accepted. Therefore, the reduction of the coal ratio in the energy mix and its replacement with forms of energy without emissions is being discussed more and more frequently. Nevertheless, it is important that the impact generated in the environment by the alternative energy sources related to energy production does not exceed the shortcomings created by the steam power plants, as it seems to be the case of micro hydropower plants (MHC) located on the superior flow of mountain rivers. As it is difficult to compare the impact on the environment generated by two completely different energy sources, two indictors were defined and used in this sense that consider their ecological, economic and social performance. As a result of the evaluation of the impact and of the comparison criteria, the two indicators were used in the two chosen case studies, resulting that a steam power plant that operates in cogeneration has a superior eco energy efficiency to a micro hydropower plant. Thus, following the carried out studies, we believe that MHC can be recommended only under special circumstances such as providing electric power to areas difficult to reach without them injecting the produced energy into the National Energy System (SEN). Keywords: ecoenergetic efficiency, impact, environment, social and ecological efficiency

1. Introduction

Theantagonismexistingbetweenthecontinuousincreaseoftheenergydemandbasedonthedemographic explosion and the necessity to reduce emissions generated by fossil fuels, when globally about 40% of the energy is provided by them, is felt all over the world [1] Hydroenergy represents the type of renewable energy used most frequently, as micro hydropower plants have a lower carbon footprint, often being promoted as an answer to the significant reduction of greenhouse gas emissions and implicitly to the mitigation of the effects of climate changes [2]. Nevertheless, the micro hydropower plants’ negative effects on the environment must not be underestimated even if they are promoted as energy sources with low impact on the environment [3, 4]. Although the micro hydropower plants have a small capacity, they affect the natural flow of rivers which, normally, provide large quantity of water resulted from the melting of snow during spring and summer and low quantities of water determined by low rainfall during winter and autumn, thus the mountain rivers being given a unique dynamic character. The change of this natural dynamic negatively affects the flora and fauna of the aquatic system, as well as the riparian ecosystems. At the same time, water storage dams limit the river’s natural dynamics, as downstream of the storage lake the river is left with a low water flow, upstream it is affected the transportation of sediments and the water volume in the storage lakes varies according to the demands of the energetic system. Inthecurrentcontext,characterizedbyanalarmingincreaseofcomplexespollutioncausedbytheprocurement of energy from burning coal, major attention must be paid to steam power plants and to the analysis of the desirability to reduce the dependence on fossil fuel used as basis for raw material. The energy installations that use coal as fuel influence the environment affecting the ecological balance not only in the emplacement areas,

Prof.Eng. Ph D, University

Petrosani, Romania,

str.,

Romania, marialazar@upet.ro

but also imposing a complex impact on all environmental factors in the neighboring area. Also, there is a significant volume of information and studies regarding the fact that steam power plants using coal issue significant quantities of carbon dioxide, sulphure dioxide and nitrogen oxide, dust and powder, these polluting agents having concerning consequences on the environment and on human health. Considering the important rolethe steampower plantshave intheenergeticmix due totheir safetyin comparison with renewablesources, at national, European and global level, the alternance of the two categories of resources must be done in a fair manner both for the general population and for the environment. Consequently, the energy mix of the future shall imposeontheenergyproducersahighdegreeofflexibilitytobecompensatedbythefluctuatingcharacter of the renewable resources, the steam power plants using coal being capable to provide this advantage. For the complex analysis of the two types of energy production that would allow the actual identification of the energy resource that operates favorably in a certain geographic area, in accordance with the environment and efficient for the general population, the case studies were defined, namely the micro hydropower plants on Buda and Capra creeks in the superior basin of Argeş river, and the steam power plant at Govora and its coal supplier, Berbeşti mining basin.

2. Materials and Methods

The major environmental problems generated by energy production based on fossil fuel, among which we could mention the increase of greenhouse effect, global warming and climate changes, prompted contemporary society to identify and implement alternative technologies on ever larger scales, in order to reduce greenhouse gas emissions. However, at least on medium term, the energy obtained based on renewable resources cannot cover consumption, therefore energy obtained from coal shall represent about one third of the population’s production in the future as well.

Under these circumstances the question arises regarding the desirability for small scale hydroenergetic facilities to ensure reduced quantities of energy affecting extremely valuable and sensitive ecosystems in the superior hydrographic basins of water courses.

The evaluation of the impact of various energy sources on the environment is a very important and complex process as any technology produces indirect effects besides the direct effects for which it was implemented and they must be managed accordingly in order to optimize the technology and to reduce significantly the impact on the environment.

The research required the use of an adequate evaluation method of the global impact generated by the production of energy on the environment, as well as the definition and use of criteria and/or indicators for comparisonfromtheecological,economicandsocialpoint ofviewoftwocompletelydifferent energysources.

2.1. Global impact index

The method of the global impact index represents an adaptation of the Rojanschi method, which makes it possible to identify the status of the environment based on a report that is executed by the comparison of the ideal status with the ideal status under the conditions of implementing a certain project [5]

For the assessment of the environment’s status both under ideal circumstances, and under natural circumstances, as well as in case this is affected by anthropic activities, after analyzing the environmental components affected byvarious projectactivities,reliabilityscores are granted accordingtothe level ofimpact on these components. The most frequently used reliability scale includes scores from 1 to 10, so that 1 corresponds to an extremely serious state of degradation of the targeted environmental factors and 10 represents the natural state, unaffected by the anthropic activities.

Considering the reliability scores that define the environment in its initial state and in case of implementing a certain project, two polygons are built, the first representing the ideal state, and the second representing the actual state of the environment affected by the impacts generated by the respective project. Subsequently the global impact index can be calculated, Iig, by dividing the surfaces of the obtained polygons.

The method of the evaluation of the global impact index has a few advantages from among which we could mention the fact that it provides a general overview of the environment’s status, it allows for a comparativeanalysisofdifferent projectsand/or areasbystudyingthembased onthe same indicators,it allows for the analysis of the dynamics in time of a certain area. By using this method several environmental components can be analyzed, such as water, air and soil quality, the general population’s health status, the deficit of plant and animal species. [6].

2.2. Comparison indicators of the two energy sources in the context of impact generated on the environment

Establishing comparison indicators between the two energy sources, namely the energy produced by micro hydropower plants and steam power plants is important and it is aimed at providing information for the decision making factors so that the most appropriate energy technologies are validated and, implicitly, adopted in accordance with the available resources.

Also, the proposed indicators are important because they allow for the prevision of the effect on the environment of the two energy production activities, they allow for measures to be taken for the reduction of elimination of the negative effects that might occur, they can help at the timely initiation of measures that would allow for the reduction or elimination of the possible unwanted connected effects.

The importance of these indicators also resides in the fact that they allow for the comparison of two or more completely different energy production sources, from the impact generated on the environment’s point of view. Thus, two indicators were defined, explained and calculated that can represent a useful tool for the decision making factors in terms of establishing the structure of the energetic mix.

2.2.1. Eco energetic efficiency indicator (K1)

In the specialized literature the term of energetic efficiency is used only in reference with the methods used to save energy [7, 8]. Basically, the gain of the same benefit by using less energy is targeted.

The area refers to the construction industry, namely better external thermal insulation of buildings, the transportindustry, namelymore efficient cars fromtheenergypoint of view, the electrical appliances’ industry with efficient energy technologies or energy saving light bulbs.

Although energy saving has a great economic impact, it is equally important that the energy efficiency term is regarded from a different point of view, not approached so far by the specialized national and international literature, namely the necessity to establish certain relationships between obtaining a certain amount of electric power from various sources and the impact’s magnitude on the environment’s components caused by the respective energy production.

For this purpose a comparison indicator was defined that considers both real (actual) energy production or the installed power of a power plant and the quantification of the changes on the environment, which allows for the comparison of different energy sources and the validation of the one that implies minimum costs for the environment and which was called eco energetic efficiency indicator.

The eco energetic efficiency indicator K1 is an indicator that represents the ratio between annual production (Pa) of a power plant and the global impact index (Iig) produced by its operation.

K1 = Pa / Iig, (1) Pa annual production Iig global impact index

This indicator allows for the distribution of the impact units to the total obtained energy production, the higher its value, the better the eco energetic efficiency of an energy production method.

2.2.2. The social and ecological efficiency indicator (K2)

Considering that between benefits and costs there must be established a direct and balanced ratio we devised an indicator used to divide the number of beneficiaries of a certain energy quantity to the impact generated on the environment by the production of the energy.

This indicator noted K2 and called social and ecological efficiency indicator may answer the need to validate only those projects that provide energy for as large a number of persons as possible with minimum damage for the environment.

For this purpose, it was necessary to answer the challenge to analyze the two energy sources in question, establishing double benefits in relation with each of them, for man and for the environment, in the end identifying which of the analyzed energetic technologies is more efficient from the social and ecological point of view.

The social and ecological efficiency indicator (K2) is an indicator that represents the ratio between the number of people provided with energy and the number of consumers that benefit of energy (Pb) and the global impact index (Iig).

K2 = Pb / Iig, (2) Pb Number of beneficiaries Iig Global impact index

The social and ecological efficiency indicator allows for the distribution of impact units to the number of serviced consumers. The higher its value, the greater is the social and ecological efficiency for the analyzed energy production forms.

3. Results

3.1. The comparison of the global impact index for MHC, CET and EMB

The determination of the global impact index value allows for an ample comparison between the impact generated on the environment by the two different energy production sources, mentioning that to the direct impact of the steam power plant (CET) Govora the indirect impact is added generated by the exploitation of brown coal that is used for the operation of the steam power plant in question. The values obtained for the global impact index are [9]:

• Micro hydropower plant (MHC) Iig = 1,87

• Steam power plant (CET) Govora Iig = 2,36

• Berbeşti mining operation (EMB) Iig = 2,60

In figure 1 the real states of the environmental components were simultaneously overlapped under the circumstances of operating the three analyzed projects, namely the micro hydropower plants from the superior basin of Argeș river, the steam power plant in Govora and Berbeşti mining operation of brown coal that supplies this steam power plant.

Based on the chart considerations can be made regarding the degree to which these projects influence the environmental categories considered for the determination of the global impact.

Air quality is affected most by the operation of Govora steam power plant, followed by the brown coal exploitation in Berbeşti mining operation. The operation of the micro hydropower plants contributes in a reduced manner to the affectation of the environmental factor [9].

The soil suffers a major impact as a result of the mining operation, closely followed by the steam power plant’s operation. Micro hydropower plants generate a relatively small impact on the pedological mantle.

Water is almost equally influenced by all three analyzed projects, namely the mining operation, the steam power plant and the micro hydropower plants, the differences between them being insignificant.

The ecosystems suffered as a result of the mining operation, followed by the steam power plant and by the micro hydropower plants, the differences being also very small.

The relief is changed essentially by the brown coal’s quarry mining, the changes generated by the steam power plant and the micro hydropower plants on it being small.

As far as the population is concerned, it is affected in a larger degree by the steam power plant and by the brown coal’s exploitation and in a lesser degree by the operation of the micro hydropower plants.

Figure 1. Global impact generated by the three analyzed projects [9]

Ecosisteme

Populatie

3.2. The determination of the comparison indicators

A proper energetic mix can be established only by a coherent strategy that would consider its own energetic resources, the operational safety of the SEN, the efficient operation of the power market, the efficiency of the electric power production and consumption and a bearable price of electric power for industrial and domestic consumers.

As a result of the carried out analyses, a table was drawn up that shows the synthetic and comparative image of the results obtained, calculated and presented, alternatively for the two different energy sources, hydroenergy and thermal energy (table 1).

Table 1. Comparison criteria for the two forms of energy production. No. Indicator value MHC CET

Installed power

production (2017)

degree of SEN supply

impact index

Sale price

In order to determine the energetic efficiency indicators in relation with the global impact, the appropriate global impact index shall be considered and the global impact index for the coal supplier, namely Berbeşti mining operation.

3.2.1. The eco energetic efficiency indicator

The eco energetic efficiency indicator calculated for the micro hydropower plants on the tributaries of Argeș river, namely Capra and Buda creeks, represent the ratio between the annual production of the MHC, calculated for 2017 in this particular case, and the global impact index generated by the micro hydropower plant, K1 MHC = Pa / Iig, according to formula 1.

A micro hydropower plant on Capra and Buda creeks recorded oscillating productions during 2017 (between 1.12 MWh and 1.22 MWh), the maximum value was considered, and for the two strings of micro hydropower plants a yearly average production Pa = 128,24 GWh was obtained.

Knowing the value of the global impact index discovered in the previous chapter, as well as the value of the annual production for the micro hydropower plant on the two tributary of Argeș river, Capra and Buda creeks, the eco energetic efficiency indicator was calculated for the micro hydropower plants K1 MHC = Pa / Iig = 68.

The eco energetic efficiency indicator for Govora steam power plant and Berbeşti mining operation, whichprovidestherawmaterialrequiredforoperation,wascalculatedasratiobetweenthesteampowerplant’s annual production(for Pathe annual productionvaluesfor 2017 wasconsidered)and the global impact indexes generated by the operation of Govora steam power plant and by Berbeşti mining operation were determined.

According to Table 1, for 2017, for all four trimesters, the situation of electric and thermal power production in high efficiency cogeneration at CET Govora is as follows: total annual quantity of energy produced was 723000 MWh/year, and the delivered quantity was 531000 MWh/year.

The obtained values were replaced in the formula of the ecoenergetic efficiency indicator (1) presented above and a total calculated value for CET Govora and Berbești mining operation was obtained

K2 = Pb / Iig, K1 CET+EMB = Pa / Iig = 723 GWh / 4,96 = 145 (3)

Accordingtothecalculationsitisnoticedthattheeco energeticefficiencyindicatorobtainedforthemicro hydropower plants is K1 MHC = 68, smaller than the one obtained for the Govora steam power plant, even if for this the general impact on the environment of Berbeşti mining operation was considered, K1 CET+EMB = 145, which shows that the eco energetic efficiency of the steam power plant related to production is higher.

If for the K1 eco energetic efficiency indicator a superior value is determined, it shows that the impact exerted by the operation of the respective energy source on the components of the environment is smaller and, therefore, the operation of the respective plant’s location and operation is much more efficient.

28,

This is possible as we consider the energy production related to the environmental costs that materialize in the changes that occur at the level of the main environmental components; they are quantized in the form of the global impact index on the environmental components.

Relating the two eco energetic efficiency indicators obtained before, there resulted an eco energetic efficiency for the Govora steam power plant of about 2.1 times higher than that of the 12 micro hydropower plants located on Buda and Capra creeks.

Basically, the operation of the steam power plant, even under the given circumstances, is 2.1 times more efficient for the population and for the environment than the location o the micro hydropower plants in the superior hydrographic basin of the two creeks.

Although the micro hydropower plants are less polluting for the environment and for the population, by its low annual energy production related to the environmental costs and to the major remnant changes to the environmental components: relief, fish population, water flow and quality, vegetation and man, they are less efficient from the eco energetic point of view.

3.2.2. Social and ecological efficiency indicator

According to the statistics supplied by ANRE (National Energy Regulatory Authority) for 2017, Romania had an average electric power consumption of approximately 0.6 MWh/person/year. According to this value, our country occupies the last place in the EU 28 from this point of view, having the lowest electric power consumption per capitainthe EuropeanUnion, namely2.6 timessmaller than the EUaverage UE which is 1.6 MWh/person/year.

The 0.6 MWh represent approximately 600 kWh. This is the value allotted for own, individual consumptionofaninhabitant in our country, obtainedbythe National EnergyRegulatoryAuthoritybyrelating the number of consumed and recorded kilowatts according to the electric power bills to the number of beneficiaries. Therefore, the approximately 600 kWh represent the total value for electric power consumed personally by an inhabitant in Romania in a household, during a calendar year. Dividing the 600 kWh consumed in one year to 12 months there results a monthly domestic consumption per inhabitant of approximately 50 kWh.

Energy consumption of which every person in our country benefits from the public domain is added to this individual domestic consumption. Here the following were included public street lighting and the maintenance of public infrastructures, electric power consumption in hospitals, schools and other public institutions, commercial areas and consumers from the industrial area of which all Romanians benefit equally.

This value of the total energy consumption of each person in the country was obtained by relating the total annual energy consumption of our country to the total population of Romania in the respective year.

According to the data supplied by the National Institute of Statistics during 2017 our country had a total energy consumption of 54.6 TWh, which represents an average of 54600000 MW [10].

Relating this value to Romania’s population in 2017, which was of approximately 19 million inhabitants, an average consumption of 2.87 MWh per inhabitant, namely 2870 kWh for one person in our country for one year was obtained. The average annual consumption was rounded to approximately 3 MWh/year in order to simplify calculations.

As a result, one inhabitant in our country uses for one month an average quantity of electric power of approximately 250 kWh, this value was obtained by dividing the annual consumption to 12 months (the obtained value of 239 kWh/person/month was rounded to 250 kWh).

According to formula 2, the social and ecological efficiency indicator K2 MHC is an indicator that represent the ration between the total number of beneficiaries that benefit of the entire quantity of energy produced by the micro hydropower plants in the Arges areas (Pb) in a certain year (the data obtained during 2017 were considered) as well as the value of the global impact index (Iig) which was calculated before (K2 MHC = Pb / Iig).

Considering the average production of the micro hydropower plant on Capra and Buda creeks of 117734 MWh and the number of persons served from the annual production of all micro hydropower plants situated on Argeș River, of approximately 39244 that benefit og the hydropower produced by the micro hydropower plants, the index for social and ecological efficiency was calculated

2 MHC = Pb / Ig = 39244 / 1.87 = 20986

Revista Minelor Mining Revue vol. 28, issue 3 / 2022 ISSN L 1220 2053 / ISSN 2247 8590 pp. 83 92

The social and ecological efficiency indicator for Govora steam power plant was calculated in a similar manner, namely the ratio between the total number of consumers that benefit of the entire quantity of energy produced by Govora steam power plant in the reference year 2017, namely 177 000 persons and the global impact index and the following was obtained

K2 CET+EMB = Pb / Iig = 177000 / 4,96 = 35685 (5)

Indicator K2 MHC has a smaller value than K2 CET, that shows that the social and ecological efficiency of the steam power plant is higher, considering the ration between the number of persons that benefit of the produced energy and the environmental costs, namely of the global impact generated on the environmental components, in comparison with indicator K2 MHC.

It is considered that the operation of the steam power plant under the current circumstances is 1.7 times more efficient for the population that benefits ofthe produced energyand for the environment thanthe location of the micro hydropower plants on the two tributaries of Argeș River, which although it presents an inferior impact on the environment due to the reduced number of beneficiaries of the produced energy is significantly less efficient.

Moreover, in order to synthesize the arguments in the previous paragraphs and in order to highlight more efficiently the use of the proposed indicators and the comparative obtained results the charts in figures 2 and 3 were built.

Figure 3. Ratio [CET+EMB]/MHC for the performance afferent to the compared versions

The achieved visualizations also allow for a quicker evaluation of the advantages and disadvantages specific for the analyzed and compared sources.

Figure 2. Energetic (K1), social (K2), ecological (Iig) performance for the compared versions

Interpreting the chart in figure 2, we notice the following:

• The energetic and social performances of the version CET+EMB are superior compared to the version MHC;

• The difference in performances, highlighted above, is significantly amplified if we consider the two EMB specific aspect superior energy return rate of coal and the social aspects concerning the productive use of the human resource;

• The ecological performances afferent to the MHC version are superior compared to the CET+EMB version.

Once again, the analysis of the chart in figure 3 shows the following aspects:

• The performance ratio [(CET+EMB)/MHC] for energy and society is favorable to coal;

• The performance ratio [(CET+EMB)/MHC] for environment of favorable to the hydropower version (in order to mark this, we used the sign to note the ration RIig);

• In addition, in order to note the superiority of the CET+EMB energy version compared to the MHC version, the sum of RK1 + RK2 is represented in figure 3, and we may conclude that, in this particular case, the version using coal is superior to the hydropower version.

4. Discussions

Consideringthatinthecurrent periodtheentireworldwitnessesaprofoundstructuralchange oftheglobal energetic system, one must not lose sight of the idea promoted by the 2009/28/CE Directive, namely the use of energy from renewable sources. This establishes a mandatory target that, by the end of 2020, 20% of the final energy consumption should come from renewable sources, giving the member states the freedom to decide on what type of renewable energy to promote and under what circumstances [11]

For these reasons, knowing the implications of micro hydrological arrangements are of paramount importance in respect of the effects generated on the environment, thus being necessary to identify methods to limit such investments, especially in areas where extremely valuable and sensitive ecosystems are to be found.

Equally, attention must be given to steam power plants and mining operations, which transform and influence the natural environment irrevocably exercising power pressure on nature and on its resources, but which can be refurbished and modernized in order to integrate the enlarged concept of sustainable development, especially as by gaining the status of member country of the European Union with full rights since 2007, Romania is subjected to the obligation to adopt European norms for environmental protection and, implicitly, for monitoring its quality.

Analyzing by comparison the two different energetic sources a clearer view was obtained of the situation regarding environmental quality and current social and economic aspects involved by the location of the presented micro hydropower plants in mountain regions and the operation of traditional steam power plants.

From the analysis of the results obtained by determining the three indicators proposed for the comparison of the two different energetic sources we find that the micro hydropower plants with a small capacity have a major influence on the environmental components. Therefore, we must not overlook the many negative environmental aspects such as the change of the creeks’ flow, change of the riverbed, long term affectation of the aquatic and riparian ecosystems, which under the conditions of the operation of the micro hydropower plants cannot be improved. A complex analysis is required in terms of opportunity of location of the micro hydropower plants on small mountain rivers as they have an efficiency of 71% and produce a fairly small quantity of energy injected directly in the National Energetic System.

From the eco energetic efficiency’s point of view, the operation of the analyzed micro hydropower plants leads to the destruction of certain valuable and extremelysensitive ecosystems while providinga small amount ofenergyincomparisonwiththegeneratedimpact.At thesametime,thenumerouswaterdamsandthevolume of water stored in lakes limit the river’s natural dynamics; this quantity varies in accordance with the requirements of the energetic system. There results a small water flow downstream of the storage lake and the changeofthesediments’ transportupstream.Forthelocationofamicrohydropowerplant andtheorganization of the storage lake it is important to study some of the multiple use possibilities of the respective hydro energetic organization namely, besides the main energetic purpose recreational and sport activities should intervene in addition such as fishing, rafting, tourism, boating, supply with drinking water of the isolated households and water catching for irrigations. Also, this poses problems in terms of supply of the National Energetic System with energy due to the efficiency and the unpredictable character of production.

28,

By comparison, the steam power plant at Govora that uses coal as fuel influences the environment deeply affecting the ecological balance in the area where it is located and generates a complex impact on the environmental factors.Ifweconsiderthehighenergeticproductionandtheconstanteffortssupportedbymajor investments in modernization and the provision of rigorous maintenance of the cogeneration power plant, the existing measures and those applicable in the future for the limitation of the impact on the environment, we may suppose that the steam power plant has an increased eco energetic efficiency and it may continue to present a significant segment of the energetic mix, due to the safety it offers in comparison with the renewable sources.

Steam power plants have superior energetic efficiency by energetic production in cogeneration, provided they are modernized, refurbished and maintained rigorously, having as priority ecological criteria that can provide a higher degree of protection for population, as well as the involved environmental factors, by actual reduction of emissions.

5. Conclusions and remarks

The conclusions of the present paper may be divided into two categories, namely conclusions regarding the quality of the environment in the two areas subjected to analysis and conclusions regarding the results shown by the two indicators proposed to be used for the comparison of different energetic sources.

As the micro hydropower plant and the steam power plant represent two different energetic sources due to their operating method, used raw material and manifestation of the impact on the environment, the identification of comparison methods regarding the magnitude of their influence on society and environment with all its components was a challenge.

Evenifthesteampower planthashigheremissionbyitssuperiorproductionofenergy,superiorefficiency supportedbycogenerationandlargenumber ofbeneficiaries,it hasincreasedenergeticefficiencyandprovides safety in supplying the National Energetic System and a proper management of the carbon dioxide emissions is required in order to limit the impact on the environment, substantial material investments, refurbishment and modernization of the existing installations and highly selective exploitation of the raw materials.

In the current European context priority must be granted to renewable energy sources and to the technologies that have the smallest negative impact on the environment and biodiversity, capitalizing the advantage related to certain geographical or climate situations in order to ensure the obtaining of a beneficial result for the population. At the same time, increased attention must be paid to coal based energy, more eco efficient than micro hydro power plants, considering that it is one of the few sources of safe energy that can guarantee the energy security of the country, especially in the conditions of the crisis triggered by the war between Russia and Ukraine.

References

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[2] Quaranta E., Bódis K., Kasiulis E. et al., 2022

Is There a Residual and Hidden Potential for Small and Micro Hydropower in Europe? A Screening Level Regional Assessment. Water Resour Manage 36, https://doi.org/10.1007/s11269 022 03084 6

[3] Crnobrnja Isailović J., Jovanović I., Ilić M., Ćorović J., Čubrić T., Stojadinović D., Ćosić N., 2021

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