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Revista Minelor Mining Revue AN INTERNATIONAL JOURNAL OF MINING AND ENVIRONMENT Vol. 23 No. 4 / 2017 ISSN-L 1220 – 2053 / ISSN 2247 -8590

Published by: University of Petroşani


REVISTA MINELOR - MINING REVUE EDITORIAL BOARD Editor in chief: Prof. Ilie ONICA Associate editors: Lect. Paul Dacian MARIAN Lect. Lavinia HULEA Senior editors: Prof. Dumitru FODOR Prof. Nicolae ILIAŞ Prof. Mircea GEORGESCU Scientific committee: Prof. Iosif ANDRAS - University of Petroșani, Romania Ph.D eng. Marwan AL HEIB - Ecole des Mines de Nancy, INERIS, France Prof. Victor ARAD - University of Petroșani, Romania Prof. Lucian BOLUNDUȚ - University of Petroșani, Romania Prof. Ioan BUD - Universitatea Tehnică Cluj-Napoca, Romania Prof. Mihai Pascu COLOJA - Universitatea de Petrol și Gaze din Ploiești, Romania Prof. Ştefan COVACI - University of Petroșani, Romania Prof. Eugen COZMA - University of Petroșani, Romania Prof. Nicolae DIMA - University of Petroșani, Romania Prof. Carsten DREBENSTEDT - TU Bergakademie Freiberg, Germany Prof. Ioan DUMITRESCU - University of Petroșani, Romania Ph.D ing. George-Artur GĂMAN - I.N.C.D. INSEMEX Petroşani, Romania Prof. Ioan GÂF-DEAC - Universitatea Dimitrie Cantemir Bucureşti, Romania Ph.D eng. Edmond GOSKOLLI - National Agency of Natural Resources, Albania Prof. Mircea GEORGESCU - University of Petroșani, Romania Prof. Monika HARDIGORA - Technical University of Wroclaw, Poland Prof. Andreea IONICĂ - University of Petroșani, Romania Prof. Alexandr IVANNIKOV - Moscow State Mining University - Rusia Prof. Oleg I. KAZANIN - National Mineral Resources University of Sankt Petersburg, Rusia Prof. Vladimir KEBO - Technical University of Ostrava, Czech Rep. Assoc.prof. Charles KOCSIS - University of Nevada, Reno, U.S.A. Prof. Sanda KRAUSZ - University of Petroșani, Romania Prof. Maria LAZĂR - University of Petroșani, Romania Prof. Monica LEBA - University of Petroșani, Romania Prof. Per Nicolai MARTENS - RWTH Aachen University, Germany Prof. Roland MORARU - University of Petroșani, Romania Prof. Jan PALARSKI - Silesian University of Technology - Gliwice, Poland Prof. George PANAGIOTU - National Technical University of Athens, Greece Prof. Lev PUCHKOV - Moscow State Mining University, Russia Prof. Pavel PAVLOV - University of Mining and Geology St. Ivan Rilsky Sofia, Bulgaria Prof. Sorin Mihai RADU - University of Petroșani, Romania Prof. Ilie ROTUNJANU - University of Petroșani, Romania Ph.D eng. Raj SINGHAL - Int. Journal of Mining, Reclamation and Environment, Canada Prof. Mostafa Mohamed TANTAWY - Assiut University, Egypt Prof. Mihaela TODERAȘ - University of Petroșani, Romania Prof. Lyuben TOTEV - University of Mining and Geology Sofia, Bulgaria Prof. Ingo VALMA - Tallin University of Technology, Estonia Assoc.prof. Ioel VEREȘ - University of Petroșani, Romania Prof. Yuriy VILKUL - Technical University of Krivoi Rog, Ukraine Prof. Işik YILMAZ - Cumhuriyet University, Turkey Acad. Dorel ZUGRĂVESCU - Geodynamics Institute of the Romanian Academy, Romania


CONTENTS

Sorin Mihai RADU, Ioel Samuel VEREȘ, Valeriu PLEȘEA, Ioan CUCU Metallic support with reinforced elements for the execution of underground excavations found in difficult geo-mechanical conditions

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Dacian-Andrei FLOAREA, Ilie ONICA, Ramona-Rafila MARIAN Surface deformation prognosis in the case of Paroșeni Mine using the profile function and the 3D finite element method

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Dacian-Paul MARIAN Analysis of surface behavior as a result of underground mining of two coal seams

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Alecsandru Valentin TOMUȘ, Mircea GEORGESCU Calculation of methane emissions from a landfill with a view to optimally sizing the collection, evacuation and elimination system after closure and cleanup

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Adriana DONEA (CIOCAN), Camelia BĂDULESCU Use of dolomite limestone in the domestic wastewater treatment

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METALLIC SUPPORT WITH REINFORCED ELEMENTS FOR THE EXECUTION OF UNDERGROUND EXCAVATIONS FOUND IN DIFFICULT GEO-MECHANICAL CONDITIONS Sorin Mihai RADU*, Ioel Samuel VEREȘ**, Valeriu PLEȘEA***, Ioan CUCU**** Abstract The execution of underground mines, namely the works carried out for the opening of the mine and for the preparation of the coal deposit which is the raw material used by heating power plants to create conventional energy, is carried out for different geo-mechanical conditions of the location, beginning with the light ones, with the existence of fixed rocks on the outline to more difficult ones characterised by the presence of unstable rocks and a high degree of changeability in time. For such difficult conditions of the location of the underground mining the present common metallic support built from simple metallic elements used temporarily in an elastic-sliding regime no longer represents an efficient solution both from a technical and economical point of view, being exposed during the enhancement of the loads on the outline of the excavation for accentuated stress and deformation, favouring the sensitively high increase of material and man-hours consumption, exaggerated expenses required for mining / maintenance works during their entire life span. Considering the increase of the efficiency of the support activity of the underground mine in such difficult geo-mechanical conditions, a new metallic support is described hereinafter based on doubling its basic elements. The main operation principle of the new metallic support consists of a temporary behaviour in a first step, when its operation is an elastic-sliding operation followed by a final behaviour when the operation of the support is final, operation obtained by ending the sliding movement of the basic elements and aligning them with the metallic reinforcements. Key words: metallic support construction, bearing capacity, interaction mechanism, rock deformation, metallic reinforcements, laminated profiles, attachment flange, operational characteristic of the support relaxation curve of the rock 1. Introduction Within the actual construction presented, the metallic sliding support, used 80% of the cases when carrying out underground excavations, respectively mine galleries, is composed of metallic elements (beam and the 2 props) made of laminated profiles with different shapes of the transversal section and weight per meter belonging to the same reduced class, to average, respectively up to 24 Kg/m, which overlap with openings between the shoulders (the case of the old national made laminated profiles) or without openings by connecting them completely (the case of imported laminated profiles). Depending on the geomechanical conditions of the location of the underground excavation, the metallic support employed, for which the connection of the elements (beam and the props) is made with the use of attachment flanges, involves the placement of the frames / reinforcements supports at distances up to * Prof.eng.Ph.D, University of Petroșani ** Assoc.prof.eng.Ph.D, University of Petroșani *** Eng.Ph.D S.C.Coming Industry Petroșani **** Eng.Ph.D stud. S.C. Lanț Minier Petroșani 2

1.0 m. Considering the case of difficult sites, with excessive pressures on the outline of the mine work where the geo-mechanics of the massif is affected by the presence of rocks which have a reduced resistance and a high degree of alterability and instability in time at the action of disturbing agents, with a view to take over the stress and ensure the stability of the excavation, this classic support lacking heavy laminated profiles depending on weight (weights higher than 25 kg/m of profile), implies the placement of metallic reinforcement at reduced distances of minimum 0.3 m, influencing the exaggerated increase consumption of materials, man-hours and maintenance costs. Following the non-correlation of the actual technological excavation requirements and considering the technical-economic efficiency criterion that regards the lack of application for such difficult geo-mechanical areas for the placement of heavy laminated profiles, the finding of a new adequate construction for the support, respectively a support with reinforced elements, is required, based on the increase of the bearing capacity of the metallic reinforcements manufactured for the presently used laminated

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profiles as long as the connection is made at the level of the basic metallic elements of the metallic resistance reinforcements. 2. The construction of the support with reinforced elements Considering its constructive form and size, the new support construction may be adapted for the

execution of underground excavations from simple profiles to double or triple ones, which may be open at the base – the case of GSM, GDM, and GTM profiles or closed circular type profiles – the case of profiles foreseen with bedstone elements such as GSMV, GDMV, and GTMV, respectively the simple circular profile GSIM or the double circular profile GDIM.

Fig.1 Double construction metallic support reinforcements: a – GDM profile (straight walls and arched roof); b – circular profile; 1 – main supporting elements (base); 2 – metallic support reinforcements; u – the sliding length of the elements The new support construction presented in Figure 1 a and b implies the use of base metallic elements made of laminated profiles usually used for mine galleries, the connection of which is made without any space between the shoulders at the level of the collar (for the Bulgarian THN 21 laminate and the “U” type Polish flanges), which are foreseen with resistance reinforcements executed from the same type of laminate attached to the base elements with attachment flanges which has the form of a demountable construction assembly [4], [5]. By using this new type of supporting construction, the increase with over 50% of the actual bearing capacity is foreseen in the conditions of a controlled sliding and stiffening of the elements by carrying out the connection between the head of the elements and that of the resistance reinforcements. Therefore, the dimensioning and the use of the exact length for the resistance reinforcements is made considering the dual interaction mechanism i.e. “massif – support” in order to ensure the sliding race of the base metallic elements during the operation of the construction within the elastic-sliding field and the start of the rigid operation regime during which the bearing capacity records its maximum values ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

The connection and attachment of the main supporting elements is made over distances of 400 mm, with the help of a new type of flanges which shall be used as well for the connection/attachment of the reinforcements to the base. 3. The interaction between different types of supports and the surrounding rock In order to explain the operating principle of the reinforced support, Figure 2 exemplifies the classic principle of the interaction between the support and the surrounding rock, taking into consideration different types of behaviour in the non-elastic field. [1], [2]. This representation of the classic interaction mechanism highlights the fact that the expansion of the rock and the development of the non-elastic area reduces on one hand the load on the support, load which decrease as the radius of the area increases, and on the other hand leads to the reduction of the resistance of the rock [2], [3], [4]. Considering the obtained results, the hypothesis according to which an area of nonelastic deformities is formed around the horizontal mine work is therefore confirmed, area which is strictly dependent on the geo-mechanical characteristics of the surrounding rock, as well as 3


on the expansion phenomenon as a result of the breaking of the rocks respectively the appearance of fissures and crushed rocks in the immediate vicinity of the outline of the mine work.

Fig.2 The classic interaction mechanism between the massif and the support system: 1-the relaxation curve of the rock; 2-the elastic behaviour of the rock; 3-the elastic-plastic behaviour; 4-the plasticrigid behaviour; 5-the characteristic curve of the support; OD1-the theoretic radial movement; M – the balance point between the rock and the support Following the influence of the support (curve 5 from the diagram) on the displacement of the rocks on the outline of the mine work (curve 1) highlights the fact the installation of the support determines the reduction of the deformations (u), but in the same time the increase of the load on the outline (p). In time, the deformations increase to the limit of elasticity of the used support. Thus in order to ensure a better stability of the work the mechanism of the interaction between the support and the rock involves running through two distinct steps:  Step I, when the behaviour of the support needs to be elastic, and the displacement of the rocks to occur in certain limits of the stresses on the outline of the mine work, together with the assurance of their reduction and redistribution;  Step II, when the behaviour of the support needs to be a rigid one in order to allow the reduction of the movement assuring therefore the normal functionality of the mine work together with an increased bearing capacity. The conditions of an adequate interaction within the “rock-support” system are not completely met by either the presently used supports or by the elastic sliding type of supports, the operation of which is exclusively temporary, or by the rigid supports made of bricks or prefabricate reinforced concrete characterised by a definitive operation. 4

Therefore, considering the metallic sliding supports the applicability of which records a value of over 80% for the execution of horizontal mine works in Jiu Valley, the mechanism of the interaction is partially carried out, this type of support ensuring an almost continuous slide and a relatively limited bearing capacity (120 – 170 kN), depending on the type of laminate used for the execution and the characteristics of the steel used. Considering the classic metallic structures, the bringing to a halt the deformation of the rocks on the outline of the excavation, carried out in difficult geo-mechanical conditions with the achievement of the balance between the operating characteristic of the support and of the rock for load and stress values equal at least to the superior bearing capacity of the used metallic support, might be possible through the introduction and application of heavy laminated profiles due to their weight for the manufacture of metallic support elements (figure 3), belonging to the TH series profiles (44, 46). This could thus bring forward the significant increase of the consumption of raw materials and man hours for the execution and installation of the support, with highly increased expenses which are not economically justified for the present excavation conditions [1], [5]. In the case of definitive supports, the situation becomes more critical through their completely rigid behaviour, this type of support encourages the intensification of much larger strains on the outline of the mine work without any movement of the rocks and respectively their reduction and redistribution. In such cases, the increase and intensification of the strains on the outline of the mine work, exceeding the resistance to breaking of the construction material produces therefore the destruction of the support, for the rehabilitation of which high consumptions of materials and man hours are necessary, which increased expenses compared to those required for a metallic sliding support. One ideal support solution for the execution of the underground excavations in difficult geomechanical conditions would be the one where the installation in first step of a temporary support made of simple construction metallic reinforcements, and after a certain time interval pre-established taking into account a series of technical and technological parameters of the excavation as well as of the support and of the rocks met on site, the rigid support should be applied. In this case as well, the application of this solution, which uses combined supports, requires an increased period of maintaining the underground excavation in service (over 15 years) besides important initial costs for the application of the support, generated by the consumption of materials and extremely increased man-hours. Revista Minelor / Mining Revue - no. 4 / 2017


Fig.3 The diagram for the rock-support interaction considering the temporary operation: a –the working characteristic of the metallic support in the usual actual construction; b-the working characteristic of the metallic support built from superior laminated profiles according to weight; B – contact spot between the support and the rock; BC –the pre-tensioning interval (loading) of the support; CD – the sliding interval (discharge) of the support; A, A1 – balance points in the rock-support system (A- the case of the actual metallic support; A1 – the case of the superior bearing support made of heavy laminated profiles) 4. Working characteristics of the support with reinforced elements In order to eliminate the constructive and functions inconveniences met in the case of usual classic supports, the researches were directed to find at the level of the support, such as the elastic metallic support as well as the rigid concrete or masonry support, modular solutions which award the possibility to retrieve the level of the same type of support two operation modes, namely an elastic one (elasto-plastic) occurring in a first step, followed by a rigid operation mode. All these in mind, at the level of the definitive rigid masonry or prefabricated concrete elements support, the solution using drilled bricks placed on the extra-back of the basic support, in order to be sacrificed (destroyed) during the deformation of the rocks, until the stress is reduced to maximum values equal to the minimum bearing capacity of the basic support. Considering the same interaction principles with the surrounding rock, at the level of the elastic-sliding metallic support, in order to assign the support and the operation in a rigid mode, the reinforced elements were therefore conceived. Therefore, together with the initial role of elastic

ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

operation of the support given by the cyclic charge and discharge through the sliding of the basic elements the support also has the role of rigid operation once all the elements are butt joined with the resistance reinforcements. The operation of the reinforced support and the highlight of the two steps and working modes is presented graphically in figure 4 [3], [4]. According to the interaction diagram it is therefore noticed that the reinforced elements the working characteristic of which is represented considering curve c on the diagram and which have a superior bearing capacity compared to the actual present support (curve a), similar to the support from heavy laminated profiles (reinforced) according to weight (curve b) ensure the balance with the massif in the contact point A2 with the relaxation curve of the rock, point which is situated at a superior level and corresponds to a superior rock pressure which is equal with the bearing capacity of the support, for a deformation of the rock and respectively sliding of the support (u) with more reduced values compared to the classic usually used support.

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Fig. 4 Graficul de interacțiune rocă – susținere metalică: A1, A2 – puncte de echilibru între susținere și masivul de rocă (rigidizarea susținerii); C,D – puncte limită de pretensionare (încărcare) și, respectiv de descărcare prin culisare ale susținerii la nivel de ciclu; Pmi, Pmf - presiunile inițială și, respectiv finală exercitate de rocă (portanța susținerii); (u) –deformarea rocii. One of the characteristics of the new support construction with reinforced elements is the prognosis of the sliding of the basic elements and the stiffening of the support anticipating how a controlled bearing capacity of the support might be obtained considering the specific conditions of the location of the mine galleries, the type of material used for the execution and the type and dimensions of the profiles used for the galleries. „This paper was carried out through programme 2 – The increase of Romanian economic competitiveness through research, development and innovation, sub-programme 2.1 – Competitiveness through research, development and innovation “Innovation Circles” — PN- IIIP2-2.1-CI-2017-0629, carried out with the support of MEN – UEFISCDI, Project no. 63/2017”

References 1. Leţu, N., Pleşea, V., Butulescu, V., Semen, C-tin Eficientizarea susţinerii lucrărilor orizontale la minele din Valea Jiului. Ed. POLIDAVA, Deva, 2001, ISBN 973 – 99458 – 7 – 2, pg. 201 2. Pleşea, V. Proiectarea şi construcţia susţinerii lucrărilor miniere subterane din sectorul carbonifer, Ed. UNIVERSITAS, Petroşani, 2004, ISBN 973 – 8260 – 68 – X, pg. 251. 1. 2.

3. Todorescu, A. Gaiducov, V. Presiunea minieră. Stabilitatea și fiabilitatea construcțiilor miniere subterane. Editura Tehnică, București, 1996.

3.

4. 5.

4. Vereș, I.S., Radu, S.M., Nan, S.M., ș.a. Construcție performantă de susținere a excavațiilor miniere subterane amplasate în condiții geomecanice dificile. Proiect nr.63/01.07.2017 derulat prin MEN – UEFISCDI, Petroșani, 2017.

6.

5. Vereș, I.S., Radu, S.M., Pleșea, V., ș.a. Tehnologie competitivă de susținere a excavațiilor miniere subterane aliniată la condițiile de performanță ridicată în exploatarea și utilizarea cărbunelui pentru producerea de energie. Programul Parteneriate în Domenii Prioritare. Contract de finanțare nr. 51/01.07.2014.

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SURFACE DEFORMATION PROGNOSIS IN THE CASE OF PAROȘENI MINE USING THE PROFILE FUNCTION AND THE 3D FINITE ELEMENT METHOD Dacian-Andrei FLOAREA*, Ilie ONICA**, Ramona-Rafila MARIAN*** Abstract: The paper refers to the analysis of the measurements from the surface terrain deformation at Paroseni Mine and data approximation with a profile function – of predictive and comparative analysis with the results obtained from finite element modeling in 3D. Key words: subsidence, horizontal displacement, coal seam, underground mining, profile function, numerical modelling, finite element 1. Monitorring the surface terrain deformation in the case of Paroșeni Mine The monitoring of the land deformation phenomenon, as a result of the underground mining at Paroșeni Mine, is accomplished by an alignment consisting of a total of 63 points, with a total length of 1,600 m, the purpose of which is to monitor the access road to the return station of the waste dump funicular. In the above mentioned area, seam 3 and 5 were extracted; seam no. 3, in the panels 1, 2 and 3, from block V and panels 1, 2, 3, and 4 from block VI, and seam no. 5, in the panel 6, block III and panel 6 and 7, in block V (figure 1).

The monitoring period ran from June 2011 to May 2015, and, due to the fact that part of the initial points had disappeared during this period, in the graphic representation of the subsidence trough, only the points existing over the entire duration of monitoring of the surface subsidence phenomenon have been taken into account. The development of the subsidence trough over time, based on the measurements carried out, is shown in figure 2. Also, the time evolution of the maximum subsidence, resulting from the processing of the data collected from the field, is shown in figure 3.

Fig.1 Alignment of subsidence monitoring at Paroșeni Mine * Eng.Ph.D E.M. Lupeni ** Prof.eng.Ph.D, University of Petroșani *** Eng.Ph.D stud., University of Petroșani

ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

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Fig.2. Subsidence graph resulted from measurements at Paroseni Mine [1], [2]

Fig.3. The evolution in time of the maximum subsidence measured at Paroseni Mine [1], [2] For the statistical approximation of subsidence trough produced by the underground mining of the coal seams 3 and 5, in the mentioned panels, the profile function (1) was used for the prediction of subsidence: (1) W x  = a  x b  e  c  x where: x is the distance measured from the limit or the subsidence trough to the reference point. The value of the regression coefficients a, b and c, of the function (1) in the case of maximum subsidence, from the Paroseni Mine, is the following: a  1.777  10 ; b  2.517 ; c  3.974  10 ; 3

3

and the determination coefficient is R  0.995 . Using this profile function the maximum calculated subsidence is 1,614mm, in relation to the one measured, of 1,638 mm (resulting in a very good estimate of the measurements). Figure 4 shows the graph of this function compared to the maximum subsidence resulted 2

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from the processing of the data collected from the field. The time evolution of the maximum subsidence resulting from the processing of the data collected from the field, compared to the maximum subsidence resulting from the use of the profile function is shown in figure 5. During this period, the surface subsidence speed is between 124 mm/month in the first monitoring period and 3 mm/month in the last period. It can also be noticed that during the winter period – November 2011 – May 2012 (the period between the 23rd month and the 32nd month of monitoring), September 2013 – May 2014 (month 48 to month 56 of monitoring period), subsidence speed is significantly reduced from 124 mm/month in the first monitoring period to 6 mm/month, which may lead to the wrong conclusion that the phenomenon has entered in the final phase (the extinguishing phase). Revista Minelor / Mining Revue - no. 4 / 2017


Fig.4. Maximum measured subsidence and maximum predicted subsidence at Paroseni Mine [1], [2]

Fig.5. The evolution in time of the maximum measured and predicted subsidence at Paroseni Mine [1], [2] 2. The influence of the time factor on the surface subsidence in the case of Paroșeni Mine After the determination of the coefficients a, b and c of the prognosis function (1), the graphical representation of these coefficients was made (fig. 6) resulting a number of issues, namely: - The evolution of the three coefficients is nonlinear over time; - The approximation functions whose regression coefficients are closer to 1 are the linear ones and have the expressions: at   a1  t  a2 (2)

bt   b1  t  b2

(3)

ct   c1  t  c2

(4)

where: t is time; a1, a2,…, c2 – regression coefficients of linear functions (2), (3) and (4). - From the new regression function of coefficients a, b and c, which are dependent parameters,

ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

explained, are part of it the pairs of regression coefficients (a1, a2), (b1, b2), and (c, c2); the value of these regression coefficients for function (5), in the case of Paroseni Mine, is shown in the table 1. Consequently, the new subsidence prognosis function obtained for the Paroseni Mine, which takes into account both the distance measured from the limit of the subsidence trough and time, has the form: W ( x, t )   a1  t  a2   x b1 t  b2  ec1 t  c2  x (5) where: is the distance measured from the limit of the subsidence trough to the reference point; t – time. The value of the average determining factor 2  0,897 . of the function (5) is Rmed The comparative graphical representation of the subsidence curves predicted with function (5) and the measured subsidence curves, in time, is shown in figure 7.

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a)

b)

c) Fig. 6. Evolution over time of the regression coefficients a, b and c and the regression functions of the regression coefficients a(t), b(t) and c(t) Table 1. The values of regression coefficients for function (5) [1], [2] Coefficient Value Coefficient Value Coefficient Value . -5 a1 3 10 b1 0,0129 c1 5.10-5 a2 0,0007 b2 3,5289 c2 0,0072 R2 0,5263 R2 0,6393 R2 0,8782

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Fig.7. The comparative chart of the measured subsidence with those predicted with the new profile function [1], [2] Using the new profile function, the maximum calculated subsidence is 1,647 mm, against the measured one, which is 1,638 mm – resulting a very good estimation of the profile function, for the subsidence prognosis in the case of Paroseni Mine. 3. Numerical modeling of the surface subsidence phenomenon at Paroșeni Mine Owing to the fact that the alignment used to monitor the subsidence phenomenon at Paroseni Mine is situated largely outside the excavated fields (fig. 1), they considered as necessary and very important issues to carry out a three-dimensional modelling of the area to capture the development of this phenomenon as close as possible to reality. For the numerical modelling of the situation presented in figure 1, from Paroseni Mine, they used the CESAR-LCPC finite element software, with the CLEO3D processor [8]. Numerical modelling with the finite element method involves the passage of certain stages, namely [7], [8], [9]: - Building the model; - Initializing the model and editing the geomechanical features; - Imposing boundary conditions and editing the characteristics to load the model; - Launching in calculations and getting results. In order to determine the land surface displacement, in the area of the monitoring emplacement where the land is affected by the underground mining of the coal seam no. 3 and 5, a ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

3D model with “mining voids” was designed, whose rocks are considered homogeneous and isotropic, taking into account the hypothesis of elastic behaviour of the massif [3]. This stage of model designing required the following phases: a) building the geometry of the model; b) establishing the areas of interest; c) meshing of the model [7], [8], [9]. At this stage, in order that the boundaries of the model would not affect the results, a very large model was created (Fig. 8), taking into account a distance of 500 m, measured from the ends of the model to the edge of the panels (extracted spaces). Thus, a model with the following dimensions resulted: X=3,169 m; Y=3,426 m; Z=580m. Following the meshing of the model with triangular finite elements, using a linear interpolation function, a number of 38,095 nodes and 71,262 volume elements were obtained. This simplified mod of modelling has been chosen, because of the very large dimensions, which also required (although simplified) the generation of a large number of elements, with consequences on computing resources. In this stage, the initial conditions of the model were settled, which refer to: a) the geomechanical characteristics of the different groups of elements; whether those elements are active or not in the initial situation of the model; c) model load mode [8]. The geo-mechanical characteristics taken into account are summarized in table 2.

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a) b) Fig. 8. Construction of the model with finite elements, under the conditions of Paroseni Mine [1], [2] a) Establishing the areas of interest (regions); b) Meshing with finite element Table 2. The values of the geo-mechanical characteristics of rocks and coal [6], [10] Rock characteristic Symbol UM Rock Coal Apparent specific weight

a

kg/m3

2 663

1 450

Young modulus of elasticity

E

kN/m2

5 035 000

1 035 000

Poisson ratio

adim.

0,19

0,13

Cohesion

C

kN/m

6 130

1 300

Internal friction angle

o

55

50

In this model, the load of the model was considered to be geostatic, for mining depth of the coal seam no. 3 of 480 m and seam no. 5, 410 m. Regarding the limit conditions of the model (Fig. 9): the upper part of the model was considered to be free, without constraint; as for the lower limit, the condition has been set that the model is locked vertically (vertical displacement w  0 ), and on the horizontal to be free (horizontal displacement after the two axes u  0 ; v  0 ); for the sides of the model, the vertical movement was made free ( w  0 ) and the horizontal locked ( u  0 ; v  0 ) In order to perform the calculation related to this model (Fig. 8), a number of general calculation parameters have been established, such as: a) the number of increments; b) the maximum number of iterations per increment (50 iterations/increment); c) permitted tolerance (1%); d) method of calculation (initial strain method) [8]. After calculation, the results were displayed in a graphical form both on the surface of the model and on certain predefined sections of the model or on certain routes imposed by the user (Fig. 10). The results obtained refer to both displacements – vertical displacements, or subsidence (w), and horizontal displacements (u and v) – as well as to

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2

the state of tensions developed in the massive, from the mining void to the surface. From the analysis of the obtained results (shown graphically in Figure 11), one may notice that, as far as the 3D numerical modelling is concerned, the subsidence trough appeared on the surface has a similar shape to that measured in the monitoring station, the maximum subsidence being 1,730 mm, a value relatively close to the maximum measured subsidence, whose absolute value is 1,638 mm. Also, the maximum subsidence obtained from 3D modelling is slightly higher than the maximum subsidence calculated with the profile function (5) of 1,663 mm. Analysing the time evolution of the maximum subsidence measured at Paroseni Mine, (figure 5), and the maximum subsidence represented in figure 11, one may conclude that the subsidence phenomenon is in the extinguishing phase, and the final subsidence on the studied route according to the prognosis will be around 1,730 mm. The horizontal displacement U, along the xaxis, obtained from the finite element model at Paroseni Mine, is in the range of -400 mm +500 mm (figure 12) and the horizontal displacement V along the y-axis is maximum 226 mm (figure 13).

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Fig. 9. Imposing boundary conditions, for the model of Paroseni Mine

Fig. 10. Drawing on the model the subsidence monitoring station from surface [1], [2]

Fig. 11. Comparative graphical representation of the measured maximum subsidence, predicted with the profile function and predicted by numerical modelling [1], [2]

Fig. 12. Horizontal displacement U in the 3D model with finite elements, along the monitoring alignment [1], [2] ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, PetroĹ&#x;ani, Romania

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Fig. 13. Horizontal displacement V in the 3D model with finite elements, along the monitoring alignment [1], [2] 4. Conclusions Monitoring the surface deformation phenomenon in the case of Paroșeni Mine, was performed on certain routes (determined by the interest of the mine), by topographical methods (middle geometric levelling and/or trigonometric levelling). The maximum measured subsidence represents 1,638 mm in the case of Paroșeni Mine. The statistical and mathematical approximation of the measurements carried out at Paroșeni Mine, over a period of time, was accomplished through a profile function of the subsidence prognosis, specific to the Jiu Valley Mining Basin, which well estimated the measurements made over time, namely 1,614 mm. For the mining conditions of Paroșeni Mine, a 3D modelling with finite elements was carried out using the CESAR-LCPC software. The maximum subsidence value obtained on the occasion of the measurement alignment was 1,730 mm, which well estimates the field measurements. Also, the value of the horizontal displacements resulting from the numerical modelling was: U  400  500 mm along the x axis; V  226 mm along the y axis. References 1. Floarea, D.A Cercetări privind stabilitatea terenurilor stratificate şi a obiectivelor de la suprafaţă în cazul exploatării stratelor groase de cărbune din bazinul minier Valea Jiului, Teză de doctorat, Universitatea din Petroşani, 2017. 2. Floarea, D.A Stabilitatea terenurilor şi construcţiilor aflate sub influenţa exploatării subterane. Studii de caz din bazinul minier Valea Jiului, Ed.Universitas, Petroşani, 2017.

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3. Floarea, D., Marian, D.P., Cozma, E., Onica, I. Using numerical modeling in the anaslyis of surface deformation as effect of underground mining of coal seam at Paroşeni mine, Romania, Proceeding of the 15th International Multidisciplinary Scientific GeoConference & EXPO - SGEM 2015a, Sofia, Bulgaria, June 16-25 2015, Book1, Science and Technologies in Geology, Exploration and Mining, Vol.II, 2015a. 4. Floarea D., Marian D.P., Fissgus K.G., Vereş I., Ştefan N. Ground Stability Study for a Subsidence Affected Area at Paroşeni Coal Mine, Romania, Freiberger Forschungsforum; 64. Berg-und Hüttenmännischer Tag, Scientific Reports on Resource Issues, Freiberg, 2016. 5. Marian, D.P Analiza stabilităţii terenului de la suprafaţă sub influenţa exploatării stratelor de cărbuni cu înclinare mică şi medie din bazinul valea Jiului, Teză de doctorat, Petroşani, 2011. 6. Marian, D.P. Urmărirea topografică şi analiza deformării suprafeţei terenului afectat de exploatarea subterană, Ed.Universitas, Petroşani, 2012. 7. Onica, I. Introducere în metode numerice utilizate în analiza stabilităţii excavaţiilor miniere, Editura Universitas, Petroşani, 2001. 8. Onica, I. Introducere în modelarea cu elemente finite. Stabilitatea excavaţiilor miniere, Editura Universitas, Petroşani, 2016. 9. Onica, I., Marian, D.P. Aplicaţii ale metodei elementelor finite în analiza stabilităţii terenurilor şi structurilor subterane, Ed. Universitas, Petroşani, 2016. 10. Onica, I., Marian, D.P. Ground Surface Subsidence as Effect of Underground Mining of the Thick Coal Seams in the Jiu Valley Bassin, Archives of Mining Sciences, Vol.57(2012), No.3, p.547-577

Revista Minelor / Mining Revue - no. 4 / 2017


ANALYSIS OF SURFACE BEHAVIOR AS A RESULT OF UNDERGROUND MINING OF TWO COAL SEAMS Dacian-Paul MARIAN* Abstract The underground mining of a deposit leads inevitably to the deformation of the surface as well as to the destruction of the objectives located in the area of influence of the extraction. The problem of surface deformation as a result of underground mining has occupied and still occupies an important place in the mining field scientific research. Solving this problem makes it possible to predict the effects of the underground mining on the surface and offers the possibility of taking appropriate measures to protect the objectives located in the area of influence of the extraction. This paper analyzes the problem of surface deformation as a result of the simultaneous extraction of two horizontal coal seams, through applying the influence function method. Key words: underground mining, subsidence, horizontal displacement, prognosis, influence function. 1. Generalities The need to study the phenomenon of surface deformation as a result of underground mining of useful mineral substances has occurred with the development of mining and, in particular, with the transition from a predominantly surface extraction (open-pit) to underground mining [3], [5]. The subsidence phenomenon is still being studied and will be studied in the future as it is a topical issue grounded upon the need to protect surfaces and constructions from surface or underground mining works, communication paths, utility networks, etc. [2]. In the case of the underground mining of two or more nearby seams, the problem of reducing the mining effects is very difficult. Thus, the objectives located in the area of influence of the extraction can be protected by a harmonic extraction of the seams, with the aim of reducing the tension and compressive stresses appearing on the surface. Otherwise, through a misalignment of the panel, these stresses may increase, leading to the destruction of the objectives located in the area of influence of the extraction [4]. In order to reduce the tensions appeared on the surface, it is necessary to extract the two seams concomitantly, with the offsetting of the panels. The gap between the panels, from the nearby seams, must take into account that deformations whose size exceeds the permissible limits must be compensated by the deformations of the sign contrary which are born in the rock massif.

* Lect.eng.Ph.D University of Petroșani

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2. Influence function method The influence function methods (figure 1) are based on the prognosis of the subsidence trough with the help of the influence area theory around the point of extraction [1], [6]. These methods can be applied to the extracted areas of different forms, but they are more difficult to calibrate and verify than the profile function methods [7], [10]. These are methods used to determine the influence exerted at the surface by the partial elements of the extracted area.

Fig. 1. The influence of extracting the base element Q Different forms of influence functions were obtained by several researchers of subsidence events including - Bals 1932 Bayer, 1945; Sann 1949 Knothe 1957 Kochamanski 1957 Ehrhardt and Sauer 1961; Brauner 1973; Zich 1993, etc. [3], [8], [9]. In our case, for the surface deformation prognosis due to underground mining, the influence function method developed by Knothe (also known as Knothe-Budryk method) was applied. 15


This method is based on the Gaussian distribution of probabilities. According to this method, the math function is [6]: (1) 3. Analysis of the influence of the concomitant underground mining of two seams on surface To analyze the behavior of the surface as a consequence of the simultaneous extraction of two coal seams, the influence function method was applied. With this in view, we considered the extraction of two horizontal coal seams of equal thickness (m = 10m), situated at a mining depth of 90m from each other, with a depth of extraction of the upper seam of 300m (figure 2).

In order to study the influence of the underground mining of the two coal seams on the surface, 11 cases were considered. Thus, in the first case, we considered that the panels P1 and P2 are extracted on the two seams, with sizes of 100m each, vertically arranged one above the other so that the centers of the two panels coincide (see Figure 2). For the other analyzed cases, the two panels were offset with 20m, reaching in the last phase (case 11) at a distance between the central points of the two panels of d = 200m (with a distance between the edges of the panels of xa= 100m, figure 3).

Fig. 3. The position of the two panels for the last analyzed case

Fig. 2. The layout of the coal seams for the considered case

The third dimension of the excavation has been chosen so as not to affect the way that surface moves in the area of interest. Following the calculations performed, subsidence and horizontal displacement were predicted for all 11 studied cases.

Fig. 4. Subsidence curves predicted for the 11 cases studied 16

Revista Minelor / Mining Revue - no. 4 / 2017


Fig. 5. Horizontal displacement curves predicted for the 11 cases studied Figure 4 shows the subsidence curves predicted by the influence function method and Figure 5 displays the predicted curves of horizontal displacement. The analysis of the predicted subsidence and horizontal displacement curves shows that the maximum subsidence and horizontal displacement decreases with the lag of the two panels, but the sizes of the subsidence trough are larger (the area affected by the underground mining is bigger). From the safety point of view of the buildings, it can be said that under the considered

conditions, the ideal case is where the gap between the two panels is maintained at approximately d = 150-160m (namely x = 50-60m). In this case, we may observe that the subsidence in the central area of the subsidence trough is approximately constant and the horizontal displacement in this area is minimal, therefore the tensile and compressive stresses are minimal. For a better image of the surface movement, figures 6 and 7 show the subsidence and horizontal displacements, predicted for the case when da= 100m, in a 3D representation.

Fig. 6. Predicted subsidence trough for the extraction of the two panels for d = 160m

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Fig.7. Predicted horizontal displacement for the extraction of the two panels, for d = 160m 4. Conclusions The influence function method belongs to the empirical methods group applied for the prognosis of the surface deformation due to underground mining. Unlike the profile functions method, this method can be applied and operated in the case of several extracted areas, or in the case of the extracted areas with difficult configurations. The applying of the influence function method in the case of the current paper resulted in an overview of the deformation of the surface as a result of underground mining of two panels, located on two horizontal coal seams of equal thickness (m = 10m), placed at a depth of 90m apart, with a mining depth of the top seam of 300m. To observe how the mutual position of the two panels influences the deformation of the surface, 11 situations were analyzed (in the first case the two panels are vertically arranged one above the other, and for the other situations the distance between the centers of the two panels was gradually increased with 20m for each case). Analyzing the results obtained, we may assert that in all analyzed cases a common subsidence trough emerged at surface, resulted from the superposition of the effects of the two extracted panels. In the case when the distance between the two panels is wider (estimated to be approximately x = 200m), two subsidence troughs would result on the surface for the extraction of each panel. It can also be seen that if the two panels are perfectly superimposed, subsidence reaches a maximum value of approx. 8200mm (for given conditions) and the horizontal displacement is approx. 400mm. With the lag of the two panel centers, the maximum subsidence decreases, but the affected area is larger. 18

References 1. Fissgus K.G. Ingineria subsidențelor în minerit, Editura Universitas, Petroșani, 2011; 2. Floarea D.A., Marian, D.P., Onica,I., Cozma, E. Necessity of Following up the Land Surface Deformation for Closed Mining Areas, Proceeding of the 15tth International Multidisciplinary Scientific GeoConference & EXPO - SGEM, Vol. II, Sofia, Bulgaria, 2015; 3. Marian, D.P. Analiza stabilităţii terenului de la suprafaţă sub influenţa exploatării stratelor de cărbuni cu înclinare mică şi medie din bazinul Văii Jiului, Teză de doctorat, Petroşani 2011; 4. Marian, D.P., Onica, I., Cozma E. Sensibility Analysis of the Subsidence Parameters at the Variation of the Main Geo-Mining Factors, Revista Minelor, Vol. 17, nr. 3/2011. 5. Marian, D.P. Urmărirea topografică şi analiza deformării suprafeţei terenului afectat de exploatarea subterană, Editura Universitas, Petroşani, 2012, ISBN 978-973-741-264-5. 6. Marian, D.P., Onica, I., Marian, R.R., Floarea D.A. Surface subsidence prognosis using the influence function method in the case of Livezeni Mine, Revista minelor, Vol. 23, nr. 1/2017. 7. Onica, I., Cozma, E., Marian, D.P. Analysis of the Ground Surface Subsidence in the Jiu Valley Coal Basin by using the Finite Element Method, Proceeding of the 11th International Multidisciplinary Scientific Geo-Conference & EXPO - SGEM 2011, Sofia, Bulgaria, June 19-25 2011, ISSN: 1314-2704.

Revista Minelor / Mining Revue - no. 4 / 2017


8. Onica, I., Marian, D.P. Ground surface subsidence as effect of underground mining of the thick coal seams in the Jiu Valley Basin, Archives of Mining Sciences, Vol. 57, nr. 3, Polonia 2012, ISSN: 0860-7001;

10. Ortelecan, M. Studiul deplasării suprafeţei sub influenţa exploatării subterane a zăcămintelor din Valea Jiului, zona estică, Teză de doctorat, Universitatea din Petroşani, 1997.

9. Onica, I., Cozma, E., Marian, D.P., Ștefan, N. Prognosis of the Maximum Subsidence and Displacement of the Ground Surface in the Jiu Valley Coal Basin, Proceeding of the 14th International Multidisciplinary Scientific Geo-Conference & EXPO SGEM 2014, Vol. III, Sofia, Bulgaria, June 17-26 June 2014, pag. 465-472, ISBN 978-619-7105-09-4, ISSN:1314-2704.

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CALCULATION OF METHANE EMISSIONS FROM A LANDFILL WITH A VIEW TO OPTIMALLY SIZING THE COLLECTION, EVACUATION AND ELIMINATION SYSTEM AFTER CLOSURE AND CLEANUP Alecsandru Valentin TOMUȘ*, Mircea GEORGESCU** Abstract This paper displays a general procedure for calculating methane emissions emitted in a landfill, referring to the particular case of the deposit of Bârcea Mare waste investment, which is part of the centre for the integrated management of waste (CMID) in Hunedoara County. Key words: emissions of methane, mixed waste landfill 1. Introduction The implementation and functioning of ecological deposits in Romania is done according to the local strategy of each county,” regarding the integration in the context of the new waste management policies at a local and national level”. The goal of these investments is to achieve beneficial correlations with forecasts of future developments in waste management resulting from the activity of the local economic units and of the inhabitants. Investment opportunity consists in identifying the best technical closure solutions and greening of the organic deposits and in providing the legal framework for the financing of the required works. In order to establish the optimum technical solutions for the collection and evacuation of deposit gas, it is necessary to previously calculate the quantities of gas to be emitted by the waste landfill. 2. Mixed waste landfill in Bârcea Mare [3]

The landfill is located approximately in the centre of Hunedoara County, at about 10 km from the municipalities of Deva and Hunedoara and at about 9 and 7 km from the towns of Călan and Simeria. (Fig.1). The landfill extends over a total area of 26.2 ha. At present, only the first alveolus has been currently built, with a projected total capacity of 1,236,800 m3, of which a minimum capacity of 1,050,000 m3 representing the real storage capacity. The capacity of the 1st alveolus is estimated for a period of waste storage of about 7 years, at a waste height of approximately 23 m (considered from the level of the perimeter access road). The 1st alveolus has been built as pits whose basis surface represents 17,920 sqm, while the inner surface of the embankments represents 44,580 sqm. In order to avoid the infiltration of surface water to the body of the alveolus, it is surrounded by a perimeter embankment covering three sides (N, S, E) and an intercellular embankment built along the Western side. Channels for collecting pluvial water have been built in the perimeter afferent to the embankments. The inter-alveolar embankment is to be incorporated into the waste mass, when the 2nd alveolus is going to be operational (Fig.2).

Fig.1. Landfill location at Bârcea Mare * Eng.Ph.D University of Petroșani ** Prof.eng.Ph.D University of Petroșani

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Fig.2. Location of landfill at Bârcea Mare Revista Minelor / Mining Revue - no. 4 / 2017


3. Calculation of methane emissions from a waste landfill The standard ecological is established for a total planned capacity (TPC) with a view to serve the inhabitants of a given area. The following types of waste are accepted at entrance: - municipal mixed waste; code: 20.03.01; - inert waste; code: 17.09.04; - street waste; code: 20.03.03; - mud from the treatment plant afferent to the projected landfill; code: 20.03.04. The estimation of methane emissions from the eco-friendly landfill is done through the default method [1] (developed by Bingemer-Crutzen), using the formula: QCH4= TDG  FDG  FCM  FCOD  FCODCH4  F

  16

 R 1  OX  t/yr

12

where: TDG - total quantity of waste, t/year; TDG= 365·q·n q – average rate of urban waste: 0, 925kg/place/year n – number of inhabitants FDG– fraction of urban solid waste (t/year), which entered the landfill. It is considered that only about 91% of the waste produced are going to enter the landfill: FDG= 0,91·TDG FCM – methane correction factor that depends on the method of storage and landfill’s depth FCM = 0,6 FCOD - fraction of degradable organic carbon; depends on waste composition. FCOD = 0,4A + 0,17B + 0,15C + 0,3 If A - paper, cardboard, textiles content, 8% B - leaves, grass content, 6% C - vegetables, fruit content, 16 % D - wood content, 4% then: FCOD = 0,4 • 0,08 + 0,17 • 0,06 + 0,15 • 0,16 + 0,3 • 0,04 = 0,008 FCODCH4– degradable organic carbon fraction converted into biogas FCODCH4 = 0,014t + 0,28 t – temperature in the anaerobic area of the waste layer. A constant temperature t = 350C should be considered, so that: FCODCH4 = 0,014 • 35 + 0,28 = 0,77 F – fraction of methane in deposit gas: 0,6 R – retrieved methane fraction:1 OX – methane oxidation factor. It is considered that in the case of the upper layer of waste, where oxygen is present, methane oxidation occurs. Because this factor is not unanimously accepted, it is considered equal to 0.

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4. The application of the calculation methodology for the landfill methane emissions at Bârcea Mare For instance, one may calculate the estimated gas emissions from the 1st alveolus of the standardized waste landfill at Big Bârcea, an investment which is part of the centre for the integrated waste management (CMID) of Hunedoara County, which has a total of residents n=471,613, on 01.07.2015, according to the National Institute of Statistics. Consequently: TDG =365·0,925 · 471.613 = 159.228.339 kg/year  159.228 t/year FDG= 159.228 · 0,91= 144.897,48  144.900 t/year

 16   11  0 =  12 

And QCH4= 144.900  0.6  0,008  0.77  0.6

107,11 100 t/year = 0,275 t/day The daily volume of methane emissions will be: VCH4=

Q CH4 d CH4

m3

where: d CH4 - relative density of methane: 0,424 kg/m3 = 0,000424 t/m3 so: VCH4= 0,275 = 648,585 m3/day 0,000424 This quantity will be evacuated by a series of vertical collecting tubes, located so that each of them covers a warehouse area with a radius of 22 m. Number of collecting tubes will be:

St piece S dfc where: St - total area of the 1st alveola: 62.500 m2 S - the area afferent to one collecting tube: dfc n=

π·r2 = 3,14·222 = 1520 m2 so: n = 62.500 = 41,11  42 pieces

1.520

Under these circumstances, the amount of methane evacuated by a collecting tube will be: V Vtc= CH4 = 648,585 = 15,44 m3/day

n

42

Taking into account an average rate of methane emission in time k = 0.085 m3 · year-1, one may estimate the annual emissions of methane, considered from the moment the landfill enters into operation (2018) until the end of the 30-year monitoring period, after the year when waste would no longer be deposited (2046). Considering that the duration of waste depositing in the 1st alveolus is estimated at 7 years, the maximum emission of gas from the deposit will occur in the year following its closure, namely in the 8th year. Beginning with the 9th year, the emissions from the deposit will fall gradually, until exhaustion at the end of the monitoring period (Table 1). 21


Table 1. Calculating the daily and annual quantities of methane emissions Year Evacuation points / alveolus piece 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2056 2057 2058 2059 2060

42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

ALVEOLUS 1 Daily

Anual

ALVEOLUS 2 ALVEOLUS 3 The amount of gas generated m3 Daily Anual Daily Anual

ALVEOLUS 4 Daily

Anual

TOTAL LANDFILL EMISSIONS m3 Daily Anual

On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total On 1 Total point point point point point point point point point point 8,29 9,06 9,90 10,82 11,83 12,93 14,13 15,44 14,13 12,93 11,83 10,82 9,90 9,06 8,29 7,59 6,95 6,36 5,82 5,32 4,87 4,45 4,07 3,72 3,40 3,11 2,84 2,59 2,37 2,17 1,98 1,81 1,66 1,52 1,42 1,30 1,19

348 380 416 455 497 543 593 648 593 543 497 455 416 380 348 319 292 267 245 224 205 187 171 156 143 131 120 109 100 91 83 76 70 64 60 55 50

3026 3307 3614 3949 4318 4719 5157 5636 5157 4719 4318 3949 3614 3307 3026 2770 2537 2321 2124 1942 1778 1624 1486 1358 1241 1135 1037 945 865 792 723 661 606 555 518 475 434

127.084 138.700 151.767 165.939 181.368 198.217 216.445 236.520 216.445 198.217 181.368 165.939 151.767 138.700 127.084 116.284 106.465 97.487 89.211 81.637 74.623 68.255 62.420 57.090 52.180 47.692 43.624 39.837 36.500 33.244 30.438 27.773 25.389 23.285 21.742 19.918 18.235

8,29 9,06 9,90 10,82 11,83 12,93 14,13 15,44 14,13 12,93 11,83 10,82 9,90 9,06 8,29 7,59 6,95 6,36 5,82 5,32 4,87 4,45 4,07 3,72 3,40 3,11 2,84 2,59 2,37 2,17 1,98 1,81 1,66 1,52 1,42 1,30 1,19

348 380 416 455 497 543 593 648 593 543 497 455 416 380 348 319 292 267 245 224 205 187 171 156 143 131 120 109 100 91 83 76 70 64 60 55 50

3026 3307 3614 3949 4318 4719 5157 5636 5157 4719 4318 3949 3614 3307 3026 2770 2537 2321 2124 1942 1778 1624 1486 1358 1241 1135 1037 945 865 792 723 661 606 555 518 475 434

127.084 138.700 151.767 165.939 181.368 198.217 216.445 236.520 216.445 198.217 181.368 165.939 151.767 138.700 127.084 116.284 106.465 97.487 89.211 81.637 74.623 68.255 62.420 57.090 52.180 47.692 43.624 39.837 36.500 33.244 30.438 27.773 25.389 23.285 21.742 19.918 18.235

8,29 9,06 9,90 10,82 11,83 12,93 14,13 15,44 14,13 12,93 11,83 10,82 9,90 9,06 8,29 7,59 6,95 6,36 5,82 5,32 4,87 4,45 4,07 3,72 3,40 3,11 2,84 2,59 2,37 2,17 1,98 1,81 1,66 1,52 1,42 1,30 1,19

348 380 416 455 497 543 593 648 593 543 497 455 416 380 348 319 292 267 245 224 205 187 171 156 143 131 120 109 100 91 83 76 70 64 60 55 50

3026 3307 3614 3949 4318 4719 5157 5636 5157 4719 4318 3949 3614 3307 3026 2770 2537 2321 2124 1942 1778 1624 1486 1358 1241 1135 1037 945 865 792 723 661 606 555 518 475 434

127.084 138.700 151.767 165.939 181.368 198.217 216.445 236.520 216.445 198.217 181.368 165.939 151.767 138.700 127.084 116.284 106.465 97.487 89.211 81.637 74.623 68.255 62.420 57.090 52.180 47.692 43.624 39.837 36.500 33.244 30.438 27.773 25.389 23.285 21.742 19.918 18.235

8,29 9,06 9,90 10,82 11,83 12,93 14,13 15,44 14,13 12,93 11,83 10,82 9,90 9,06 8,29 7,59 6,95 6,36 5,82 5,32 4,87 4,45 4,07 3,72 3,40 3,11 2,84 2,59 2,37 2,17 1,98 1,81 1,66 1,52 1,42 1,30 1,19

348 380 416 455 497 543 593 648 593 543 497 455 416 380 348 319 292 267 245 224 205 187 171 156 143 131 120 109 100 91 83 76 70 64 60 55 50

3026 3307 3614 3949 4318 4719 5157 5636 5157 4719 4318 3949 3614 3307 3026 2770 2537 2321 2124 1942 1778 1624 1486 1358 1241 1135 1037 945 865 792 723 661 606 555 518 475 434

127.084 138.700 151.767 165.939 181.368 198.217 216.445 236.520 216.445 198.217 181.368 165.939 151.767 138.700 127.084 116.284 106.465 97.487 89.211 81.637 74.623 68.255 62.420 57.090 52.180 47.692 43.624 39.837 36.500 33.244 30.438 27.773 25.389 23.285 21.742 19.918 18.235

8,29 9,06 9,90 10,82 11,83 12,93 14,13 23,73 23,19 22,83 22,65 22,65 22,83 23,19 32,63 30,78 29,78 29,01 28,47 28,15 28,06 36,47 34,85 33,50 32,41 31,58 30,99 30,65 30,55 27,96 25,58 23,40 21,41 19,58 17,94 16,41 15,02 12,65 11,57 10,59 9,68 8,88 8,12 7,43 5,70 5,21 4,77 4,36 4,01 3,67 3,36 1,98 1,81 1,66 1,52 1,42 1,30 1,19

348 380 416 455 497 543 593 996 973 959 952 952 959 973 1.344 1.293 1.251 1.218 1.196 1.182 1.179 1.532 1.463 1.407 1.361 1.326 1.302 1.287 1.283 1.174 1.074 983 899 822 753 689 631 531 486 445 407 373 341 312 239 219 200 183 168 154 141 83 76 70 64 60 55 50

3.026 3.307 3.614 3.949 4.318 4.719 5.157 8.662 8.464 8.333 8.267 8.267 8.333 8.464 11.688 11.235 10.870 10.589 10.392 10.275 10.242 13.311 12.720 12.227 11.830 11.527 11.311 11.187 11.151 10.205 9.337 8.541 7.815 7.147 6.548 5.990 5.482 4.617 4.223 3.865 3.533 3.241 2.964 2.712 2.081 1.902 1.741 1.591 1.464 1.340 1.226 723 661 606 555 518 475 434

127.084 138.700 151.767 165.939 181.368 198.217 216.445 363.781 355.145 349.984 347.307 347.307 349.984 355.145 490.688 471.857 456.527 444.723 436.451 431.539 430.160 559.180 534.250 513.555 496.845 484.121 475.077 469.865 468.332 428.627 392.141 358.795 328.215 300.161 275.020 251.565 230.257 195.925 177.368 162.345 148.394 136.130 124.480 113.902 87.381 79.869 73.124 66.839 61.473 56.261 51.509 30.438 27.773 25.389 23.285 21.742 19.918 18.235

LEGEND MAXIMUM EMISSION FROM ALVEOLAUS MAXIMUM EMISSION FROM LANDFILL EMISSION FROM ALVEOLUS DURING THE MONITORING PERIOD EMISSION FROM ALVEOLUS AT THE END OF THE PERIOD OF MONITORING NOTE: - MAXIMUM EMISSION OF GAS FROM ALVEOLI, ONE YEAR AFTER THEIR CLOSURE; - MAXIMUM EMISSION OF GAS FROM THE LANDFILL WILL OCCUR IN YEAR 2039, ONE YEAR AFTER THE OPENING OF THE 4TH ALVEOLUS.

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5. Conclusions The amount of methane produced by the 1st alveolus at Bârcea Mare solid waste landfill was calculated through the recommended IPCC default method. The estimation was made in accordance with the available data regarding the population and the rate of generation of the solid waste in Hunedoara County. As compared with the theoretical values resulting from calculations, the amounts of biogas that will come out from the 4 alveoli to be constructed on the landfill are sufficient enough in order to be retrieved, treated or used in controlled combustion processes. Meanwhile, the quantities emitted justify the drilling, within the waste mass, of biogas download wells, namely 42 pieces per each alveolus.

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References 1. Bingemer, H.Q., Crutzen, P.J. Production of methanefrom solid waste, Journal of Geophysical Research 87 (D2), pages 2181-21287. 1987 2. Nicolic, V. Producerea şi utilizarea biogazului, Chiminform Data, Bucureşti, 2005 3. Consorțiul EPEM Grecia / ISPE Romania Sistem de Management Integrat al Deșeurilor in Județul Hunedoara, Studiu de fezabilitate – județul Hunedoara, 2013

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USE OF DOLOMITE LIMESTONE IN THE DOMESTIC WASTEWATER TREATMENT Adriana DONEA(CIOCAN)*, Camelia BĂDULESCU** Abstract: The fields of dolomite limestone using are extremely varied as it can be employed in metallurgy, construction materials, chemical and glass industry, as well as multiple usages in agriculture and environmental protection. This paper focuses on the use of the dolomite from Budureasa area, Bihor County, in the process of purifying domestic wastewater from Glina Station near Bucharest, in order to reduce the content of nitrogen and phosphate ions in the raw domestic water below the limit permitted by the rules in force regarding their discharge into the emissary. Key words: Dolomite limestone, brucitic dolomite limestone, domestic waste water, anionic ions, phosphate ions 1. Introduction Magnesium-bearing minerals, widespread on the surface of the globe, are very important and are used in multiple fields, representing a potential "savior" of the planet. As a result of processing operations that reveal reactive magnesium oxide (reactive magnesia), magnesium minerals can be a basic source in various fields of activity. Magnesium is widely distributed in nature in the form of combinations, making up 2% of the Earth's crust. Thus, it is found in magnesite deposits (magnesium carbonate - MgCO3) and especially dolomite (double calcium and magnesium carbonate, MgCO3 · CaCO3). Very common are carnalite (potassium chloride and magnesium chloride - Mg, Cl2 · KCl · 6H2O), kieserite (magnesium sulphate - MgSO4 · H2O), then different magnesium silicates - such as olivine (Mg,

Fe) SiO4], serpentine, talc, asbestos as well as aluminosilicates such as spinel, MgO.Al2O3 (V. Brana, 1967). In soil, there are always combinations of calcium and magnesium coming from the disintegration of minerals. Many magnesium salts are dissolved in sea water or salty lakes, to which they give a bitter taste. Also, many mineral springs contain dissolved magnesium sulphate. 2. Areas of use of dolomitic limestone Magnesite, dolomite and seawater are the most common sources for making metallic magnesium and its compounds, though brucite and olivine are also used. Depending on the magnesia and magnesia content (magnesium oxide), the main industrial minerals are shown in table 1.

Table 1 – The main magnesium minerals with industrial value MgO, % Mineral Chemical formula

Nr.

Mg, %

1

41,68

69,12

Brucite

Mg(OH)2

2

34,5

57,3

Forsterite (peridot series)

Mg2SiO4

3

30,0

49,7

Peridot (Mg-Fe)

(Mg,Fe)2SiO4

4

28,8

47,8

Magnesite

MgCO3

5

26,3

43,6

Serpentine

3(Mg,Fe)O 2SiO2 2H2O

6

11,96

19,83

Bischofit

MgCl2·6(H2O)

7

8,75

14,51

Carnallite

(K,Mg)Cl3·6(H2O)

As a result of the magnesia ore processing operations with significant economic value, there are several salable finished products that are used in different economic areas. The final products are usually obtained by thermal treatment applied to the * Eng.Ph.D stud. University of Petroșani ** Prof.eng.Ph.D University of Petroșani 24

rough magnesium ore at well-established temperature ranges, which give the calcined material different physical and chemical properties. Magnesium oxide (or magnesia) resulting from the thermal treatment of various magnesium minerals, depending on the calcination temperature, may have different names (and different compositions), and the fields of use are different. Revista Minelor / Mining Revue - no. 4 / 2017


The three magnesia forms obtained successively at increasing temperatures are: calcined caustic magnesia (CCA - caustic-calcined magnesia); burned or sintered magnesia (DBM); melted magnesia (FM - fused or electro-fused magnesia) (Schulze - Rettmer, R, 2010). The main areas of use of these three basic products, available at variable prices, are:  For CCM : - Extraction of metallic magnesium; - Production of molten magnesia; - Production of special cements (eco-products); - Electrical insulation; - Paper industry; - As a fertilizer in agriculture and animal feed; - Stabilizer for the production of synthetic rubber; - Uranium production; - Protection of the environment (waste water treatment and desulphurization of combustion gases).  For DBM: obtaining basic refractory bricks;  For FM: thermal insulation, electrical insulation (electric furnaces and installations) 2.1. Domains of use in the industrial field a) In metalurgy limestone is widely used and is one of the necessary technological products that participate in most ore extraction processes. Calcium is used as a foundry in the production of iron and steel, and dolomite for the production of refractory bricks used in furnaces or for the production of refractory mixtures and refractories which are resistant to high temperatures. The limestone introduced into the furnace also has the role of iron ore desulphurization. b) Large quantities of limestone or lime are used in the manufacture of cement, which, depending on the manufacturing recipe, is included in the composition of different types of cements. c) The production of lime is an extremely important industrial field, because many types of activity use the calcium and magnesium source under this form of product, resulting from the thermal processing of different types of limestone associated with dolomite or brucite. 2.2. The use of dolomite limestone in agriculture In agriculture, dolomite limestone are used as fertilizers in acid soil detoxification and deoxidation, as mineral mixtures in animal feed (nutritional supplement) or as Ca and Mg in some crops of important vegetables, fruit trees and vines. It is important to note that just a few years ago (2013), a Romanian product called DelCaMag (or DEL-CA-MAG) was launched on the market, which produces amazing results in Romanian agriculture and beyond. This product is dolomite by ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

Delniţa (Harghita County), which has a special peculiarity that makes it unique (at least at European level) (Ecological Farming Magazine "Eco Ferma", 2014). Delniţa Dolomite has an amorphous structure, translated by the fact that between calcium and magnesium ions there is a much weaker connection than in crystalline dolomite, which favors dissolution processes in the soil or gastric juice of animals, favoring a much faster assimilation of them. The beneficial effects of Delniţa dolomite were evaluated by the team of researchers from the National Research and Development Institute for Pedology, Agro-Chemistry and Environmental Protection - ICPA Bucharest. According to them, using DELCAMAG increases crop yield by 30%. The study refers to fruit trees, potatoes, vines, linen or celery. "The documentary study on dolomite deposit at Delniţa, Harghita County, in connection with its importance for agriculture" by ICPA, shows that using dolomite is a 100% natural solution that can be used to increase productivity for a number of important crops for the economy such as fruit trees, potatoes or vines. According to the study, the use of dolomite as a calcium and magnesium for soil cultivated with plants gives them resistance to breakage and dropping, owing to their essential role in the development of the root system and strains. Dolomite does not exert phytotoxic effects on plants, even in larger quantities (being considered as the only ion with this property) and its absence influences negatively the absorption of phosphoric ions and nitrates. "Mineral maintains calcium pectin time longer in the pulp of fruit, ensuring greater resistance to conservation and induction of positive effects on plant resistance to disease and pest attack," says study (www.eco-ferma.ro, 2014). Dolomite is used as a dietary supplement in farmed animals (cattle, sheep, poultry), calcium and magnesium intake favoring the absorption of nutrients in feed by altering the permeability of cell membranes and having an important role in developing the bone system and increasing resistance to various diseases. 2.3. The use of dolomite limestone in the environmental protection In the protection of the environment, dolomite limestone or their derivatives are used in the:  Treatment of combustion gases from thermal power plants (desulphurisation)  Neutralizing acid waters  Treatment of household waste water  Recovery of heavy metals from industrial waste water 25


At the level of 1973, there were 42 FDG units (Flue Gas Desulfurization) applied to thermopower plants in Japan and the USA. In 2000, 278 economically developed countries operated 678 FDG units, operating in thermo-electric plants producing approximately 229 GigaWatt (Rubin E., Yeh S. et al., 2004). An alternative to removing sulfur from the combustion gases is removing sulfur from the fuel before or during combustion. The hydrodesulphurization of the fuel before use is carried out by a fluidized bed of lime during combustion. The lime reacts with SO2, causing it to form sulfates, which become part of the ash. This elemental sulfur is then separated and the ash can subsequently be used, for example, for the production of agricultural products. Safety is one of the greatest benefits of this method, as the whole process takes place at atmospheric pressure and ambient temperature (Official Paqell website). In the process of neutralization of acidic waste water, but also for the recovery of heavy metals from different types of industrial waste water, limestone and especially dolomite limestone with brucite are very used, and there are some clear advantages of the presence of brucite, Mg (OH)2 in limestone material. (Simandl, G.J., Paradis, S., & Irvine, M.,2007). At present, magnesium as a metal or in various compounds that may result from dolomite or dolomite limestone calcination with brucite has a very wide range of uses and is becoming a highly sought after and profitable product to be produced and marketed. The cessation of the non-ferrous ore extraction activity at national level has turned the attention of this area to the resources indispensable to the sector with the highest growth in recent years, namely: construction. According to the National Mineral Resources Agency, the most valuable mineral resources are the limestone deposits, limestone being the raw material necessary for the production of cement and lime, silico-calco-sodic glass, the mosaic for ornamental works, decorative concrete, as well as aggregates used in road construction. Starting from the many fields of use and resources existing in our country, all researches aiming at a superior valorization of magnesiumbearing minerals is of particular economic importance.

3. Research regarding the use of Dolomite limestone with brucite from Budureasa area, Bihor County, in the domestic residual waters treatment The most valuable deposits that can provide a viable source of reactive magnesium oxide that can be recovered are the dolomite limestone [Mg (OH) 2], which exist in Romania. In our country, at the beginning of the nineteenth century, brucite appeared as a substance almost unknown both in terms of its economic and of mineralogical valorization. Then, the only deposits on the territory of Romania, the ones in the Bihor Mountains, the Budureasa - Pietroasa area, were highlighted. (Panaiotu C.E., 2005). As a mineral, brucite is relatively easy to identify optically, the minerals it includes (moulder, gibbsite, gypsum, talc) appear in different types of rocks or mineral associations. The pure brucite has the appearance of a micaceous, uniaxial and local appearance of fibrotic development. The variety of ferrobrucit (formerly, "amakinit") has a brownishyellow color, showing the same birchiness as pure brucite, as can be seen in figure 1. Generally, brucite develops on dolomite (Ca and Mg carbonate), periclaz (Mg oxide) and forsterit (Mg silicate), in conditions of increased water activity. In turn, it transforms relatively easily into hydrogenous and less in serpentine minerals (Petrulian N., 1973).

Fig.1. Brucite

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Revista Minelor / Mining Revue - no. 4 / 2017


3.1. Physic-chemical characteristics of the Dolomite limestone with brucite, from Budureasa area, Bihor County For laboratory tests regarding the use of dolomite limestone in household waste water

treatment, which consists in the reduction of the nutrient content (nitrates and phosphates), bruciticdolomite limestone was used, having the chemical composition presented in tables 2 and 3.

Table 2 The results of the general chemical analysis on the brucite limestone sample (macroelements)

ELEMENT

LD

VALUES (%)

SiO2 TiO2 Al2O3 MnO Fe2O3 MgO CaO Na2O K2O P2O5 P.C. LD – detection limit

0,01 0,01 0,01 0,01 0,01 0,01 0,01 0,01 0,01 0,05 0,10

0,42 0,01 0,03 0,02 0,13 23,18 33,12 0,09 0,06 0,18 42,28

Table 3 The results of the general chemical analysis on the brucite limestone sample (microelements)

ELEMENT Li Be V Cr Co Ni Cu Zn As Rb Sr Y Zr Nb Mo Cd Sn Sb Te Cs Ba W Pb Bi Th U Tl Ga Se

LD

VALUES (%*10-4)

0,2 0,2 1,0 0,1 0,5 0,5 0,1 1,0 0,1 0,1 1,0 0,1 1,0 0,1 0,1 0,1 0,4 0,5 0,01 0,1 1,0 0,25 1,0 0,1 0,1 0,1 0,2 0,1 0,1

0 0 5 1,9 29,3 2,7 14,2 42 0 0,2 86 1,1 11 0,6 0,3 0,4 3,6 0,5 0 0 10 0 15 0,1 0,4 0,4 0 0 0,1

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Analyzing the results of the general chemical analysis, it can be seen that, as expected, the largest share is held by calcium and magnesium oxide. Thermo-differential and thermo-gravimetric analysis was performed on a sample of material (figure 2) in the furnace, at 1000oC with a heating rate of 10oC / min.

Fig.2. Thermo-differential and thermo-gravimetric curves The weight loss recorded by the TG curve corresponds to the enthalpy variations recorded by the DTA curve through the endothermic effects characteristic of brucite, calcite and dolomite traces. The endothermic effect at 420°C represents the dehydroxylation of brucite by the loss of a water molecule marked by the first weight loss step on the TG curve shown in the figure. The endothermic effect at 880°C indicates the decomposition of calcium carbonate - calcite and the elimination of carbon dioxide through the second weight loss step on the thermo-gravimetric curve. The endothermic effect at 800°C indicates the presence of dolomite (traces). The results of this type of analysis indicate the presence of these minerals in the following proportions: Brucite – 23.2%; Calcite - 42.7%. Knowing the decomposition temperatures of the component minerals is particularly important for the processing steps when it is desired to highlight a particular mineral in order to recover it through various technological processes. Aspectul general al calcarului dolomitic la micro The general appearance of the dolomite limestone on the electron microscope presented on different scales (200, 100, 20 and 5 microns) in figure 3 (a, b, c, d) reveals that the main component minerals are dissociated at this level of shredding of the material. In the figure denoted by (d) a 20-

28

micron particle of brucite is observed, white patches representing ultrafine calcine or dust particles, but not particle-bound, they change their position during "bombardment" X-ray beam sample (INCDMRR Bucharest, 2005).

Fig.3. The general aspect of the sample on the electron microscope The results of the granulometric analysis after three shredding operations (two successive crushing with jaw crushers and a chopping up to 23 mm in the disk mill) are presented in Table 4. From the cumulative rejection curve shown in figure 4 it can be seen that the weight of intermediate material (0.4-0.04 mm) is relatively reduced after the three shredding operations, the material being composed of a homogeneous mixture of coarse granules with ultra-fine particles. The lower hardness and density of brucite compared to other mineral species leads from the outset to the idea of its selective crushing, since as found in the magnesium oxide content on granulometric classes, the brucite concentrates in the ultrafine fraction (below 0, 04 mm), the MgO content in this class being 28.56%, 6% higher than the average content of the entire sample that is 22.56%. The distribution of brucite on grain-size classes is very interesting in that the whole material can be divided into three granulometric layers with the average MgO content distributed as follows: the material between 0.44-2 mm has an average content of 21.84% MgO, the material between 0.04-0.4 mm has an average content of 17.24% MgO and the ultra fine material -0.04 mm has a MgO content of 28.56%.

Revista Minelor / Mining Revue - no. 4 / 2017


Table 4 Granulometric analysis of the fine material Rejections, qi Cumulated rejections Σqi, % grams % 20 1,61 1,61 33 2,65 4,26 104 8,37 12,63 251 20,22 32,85 106 8,53 41,38 129 10,38 51,76 117 9,43 61,19 28 2,25 63,44 28 2,25 65,69 79 6,36 72,05 25 2,01 74,06 322 25,94 100,00 100,00

Granulometric class (mm) +2 2-1,6 1,6-1,25 1,25-0,8 0,8-0,63 0,63-0,4 0,4-0,2 0,2-0,16 0,16-0,125 0,125-0,074 0,074-0,040 -0,040 Total/average

Content MgO, % 21,514 21,742 22,265 22,216 21,476 21,717 19,646 17,796 17,466 14,594 13,462 28,566 22,56

cumulated rejections, %

The granulometric curve 100 80 60 40 20 0 0

0.04 0.0740.125 0.16 0.2

0.4 0.63 0.8 1.25 1.6

2

3

d, mm

Fig.4. Granulometric curve on a representative sample 3.2. Laboratory research regarding the use of dolomite limestone in the household waste water treatment For the laboratory waste water treatment trials, three types of dolomite limestone were used: dolomite crude limestone, calcined dolomite limestone and magnesium oxide-rich concentrate. The granulometry of the material differed according to the type of material, as follows: - The crude dolomitic limestone was crushed under 10 mm; - Calcined dolomite limestone was crushed under 3 mm; - Impure magnesium oxide was obtained by carbon dioxide solubilization of calcined dolomite limestone, having micronized dimensions. The content of magnesium and calcium oxides that will react with nitrate and phosphate ions in domestic waste water are increasing after calcination and CO2 solubilization operations (fig.5). Magnesium required for precipitation should not be added as a precipitating reagent. Research done at the University of Petrosani aims to use

ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, Petroşani, Romania

dolomite (CaMgCO3) to generate the necessary magnesium ion. Magnesium dissolving occurs only to a small extent (R. Sârbu, 2015) The solubility product allows a magnesium solubility of 0.005 mol / l. Magnesium dissolves in greater proportion as a result of the reaction with carbon dioxide: Ps = [Mg2+][CO3+2] =2,610-5 Mg(CO3) + CO2 + H2O = Mg(HCO3)2

Fig.5. The variation of MgO and CaO (%) contents from the three material types 29


The struvite formed in this reaction, in the case it is not contaminated by heavy metals, can be used successfully as a chemical fertilizer with phosphorus and ammonium. Two types of household waste water taken from the 2nd stage effluent from the Glina Waste Water Treatment Plant were used for rinsing tests. The conditioning of the domestic waste water with the three types of magnesium mineral component was done at 10 minutes, after which the two products were obtained by filtration: purified water and solid material. After the pre-conditioning

phase, the solutions obtained were filtered and then subjected to chemical analysis. Besides the above-mentioned aspect, through conditioning, with magnesium minerals, the noticeable odor of the domestic waste water predominantly from the nitrogen-containing nutrient content has been significantly reduced. Laboratory tests were performed according to the scheme shown in figure 6. The results of the chemical analyzes performed on the used and obtained products are summarized in table 5.

Fig.6. The flow sheet of the laboratory research

Contents, % Solution feed (S1) Solution 2 (S 2) Solution 3 (S3) Contents, % Solid feed (1) Solid (2) Solid (3)

Table 5. Results using raw, roasted dolomite and magnesia Mineral: raw dolomite Mg Ca NO3PO4-3 2,12 39,83 1,2 23,77 19,5 29,1 sld 9,1 22,4 22,84 sld 7,85 CaO 35,62 22,24 22,91

Contents, % Solution feed (S1) Solution 2 (S 2) Solution 3 (S3)

MgO Ca 11,32 25,46 33,02 15,9 31,28 16,38 Mineral: roasted dolomite Mg Ca NO32,12 39,83 1,2 24,85 17,17 sld 7,1 16,1 sld

Contents, % Solid feed (1) Solid (2) Solid (3)

Mg 8,03 18,45 18,25

CaO 39,36 22,75 22,2

30

Mg 6,83 19,92 18,87

MgO 13,31 30,58 30,25

Ca 28,13 16,26 15,87

PO4-3 23,77 6,8 3,1

CCOMn 14,147

CCOMn 14,147

Revista Minelor / Mining Revue - no. 4 / 2017


Contents, % Solution feed (S1) Solution 2 (S 2) Solution 3 (S3)

Mg 2,12 0,03 0,13

Contents, % Solid feed (1) Solid (2) Solid (3)

Mg 14,9 15,08 10,53

Mineral: magnesia Ca NO339,83 1,2 130,5 sld 13,63 sld MgO 24,7 25 17,45

From the results of the chemical analyzes carried out on the solutions and products of the mineral materials used, the following facts can be concluded: 1. The content of nitrogenous and phosphate ions in the household raw water decreases significantly after 10 minutes (solution 2), through conditioning it with the magnesia purification products, as can be seen in figures 7 and 8;

Ca 20,65 17,28 20

PO4-3 23,77 4,13 2,78

CCOMn 14,147

CaO 28,89 24,18 27,98

2. Significant differences are found between the three types of mineral materials used, dolomite limestone calcined at 650oC and MgO-rich concentrate resulting in higher net results over the same time period of use. It is obvious that the Mg ions are released by the calcination operation to reduce the phosphate and nitrate ions to the limit for the evacuated effluent 5 mg / l for PO43- and 1 mg / l for NO3-.

Fig.7. Variation of nitrate and phosphate ion contents in waste water (mg / l) treated with different types of magnesium mineral substances (solution 2)

Fig.8. Variation of nitrate and phosphate ion contents in wastewater (mg / l) treated with different types of magnesium mineral substances (solution 3) ISSN-L 1220-2053 / ISSN 2247-8590 Universitas Publishing House, PetroĹ&#x;ani, Romania

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4. Conclusions Dolomite, in all its natural forms of presentation in nature, is an economically attractive mineral, because the multiple areas of use impose it on the market, and the recovery technologies are not very complicated and require no major investments, unless extraction is desired of dolomite of metallic magnesium. Dolomite is enriched by the presence of brucite (magnesium hydroxide), which, due to its special properties, leads to an increase in the content of MgO reactive, which determines the widening of the range of uses, both in industry, but also in agriculture or environmental protection, turning dolomite with brucite into a universal panacea to protect the environment. Budureasa, Bihor County displays the largest limestone quarry in Europe, estimated at about 110 million tons, with MgO content ranging between 20-25%, which is the subject of this research. Following the household wastewater treatment tests from Glina Station near Bucharest, using three limestone varieties, it was found that the nitrogen and phosphate ions in the raw domestic water fall below the permissible limit for discharge into the emissary.

References 1. * * * DELCAMAG folosit cu succes ca amendament pentru solurile acide, Revista de Agricultură Ecologică “Eco Ferma”, septembrie 2014. 2. * * * The brucite of Kuldur deposit, Russian Mining Chemical Company, from http://www.brucite.ru/eng/, 2005. 3. * * * www.eco-ferma.ro, Revista de agricultură ecologică, sept. 2014. 4. * * * THIOPAQ Oil & Gas process description and flow diagram – official Paqell website. 5. * * * Teste tehnologice de laborator pentru prepararea rocilor brucitice din zăcământul Budureasa în vederea obţinerii unui concentrat de brucit - Contract: 5/2005 INCDMRR Bucureşti. 6. Brana V. Zăcămintele nemetalifere din România, Ed. Tehnică, Bucureşti, 1967. 7. Panaiotu C.E. Resurse minerale și sisteme depoziționale asociate – Roci carbonatice, Note de curs, Universitatea București, Facultatea de Geologie&Geofizică, 2005 8. Petrulian N. Zăcăminte de minerale utile – Ed. Tehnică, Bucureşti, 1973. 9. Rubin, Edward S.; Yeh, Sonia; Hounshell, D.A.; Taylor, Margaret R. Experience curves for power plant emission control technologies. International Journal of Energy Technology and Policy, 2004. 10. Sârbu, R. Tehnici avansate de epurare a apelor, Note de curs, 2015 11. Schulze-Rettmer, R. The simultaneous chemical precipitation of ammonium and phosphate in the form of magnesium ammonium phosphate. Water Science Technology. 2010. 12. Simandl, G.J., Paradis, S., & Irvine, M. Brucite – the mineral of the future. Geoscience Canada, 2007. 13. Simandl, G.J., Simandl, J., Debreceni, A. Hydromagnesite-magnesite resources: potential flame retardant material. Geological Fieldwork - Victoria, British Columbia: British Columbia Ministry of Energy and Mines, 2001.

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Aims & Scope Revista Minelor - Mining Revue publishes original and advanced research papers, new developments and case studies in mining engineering and technologies aiming new and improved techniques also suitable for civil applications. The journal covers all aspects of mining, environmental issues and technologies relating to exploration, exploitation and processing of mineral resources, mining survey, computers and simulation, performance improvement, cost control and improvement, all aspects of safety improvement, rock mechanics and interface between mining and law. Environmental issues specially identified for coverage include: Environmental impact assessment and permitting; mining and processing technologies; waste management and waste minimization practices; mine site closure, decommissioning and reclamation; acid mine drainage. Mining issues to be covered include: Design of surface and underground mines (economics, geotechnical, production scheduling, ventilation); mine optimization and planning; drilling and blasting technologies; material handling systems; mine equipment. Computers and microprocessors and artificial intelligence based technology used in mining are also covered. The papers have a wide ranging and interdisciplinary topic choice. The editors will consider papers on other topics related to mining and environmental issues. All published research articles in this journal have undergone rigorous peer review, based on initial editor screening and anonymous refereeing by independent expert referees. Subject coverage Mining exploration,Mine planning and design,Drilling and blasting,Mining survey, Materials handling - excavation, haulage and disposal,Mining rock mechanics and ground control, Mine drainage,Mining process control and optimization, Computers, micro-processors and artificial intelligence based technology used in mining,Mine information technologies, Mining mechanization, automation and robotics, Reliability, maintenance and overall performance of mining systems, Emerging technologies in mining and mineral engineering, Interaction between minerals, systems, people and other elements of mining and mineral engineering, Simulation of mining systems, Mining health and safety, Environmental impact assessment, Mineral economics, Business systems in mining engineering, Risk assessment and management in mining and mineral engineering, Mining sustainable development

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