World Coal December 2021

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ISSUE 4 2021 - VOLUME 30 NUMBER 4

ANSWERING MINING’S TOUGHEST QUESTIONS

Fletcher values what their customers say. Since 1937, Fletcher has been answering some of underground mining’s toughest questions. At Fletcher we provide more than solutions, we provide an atmosphere for an open dialogue with customers ® to ensure their operations are reaching maximum efficiency. Is your operation facing obstacles that mass produced equipment isn’t addressing?

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ISSUE 4 2021 03 Comment

CONTENTS 34 Unlocking Load And Haul Efficiencies Simon van Wegen, Komatsu, USA, outlines how to unlock load and haul efficiencies by better integrating and analysing data.

05 World News 10

Powering Eastern Europe

Dr Stephen Mills, International Centre for Sustainable Carbon, UK, provides insight into the role coal will play in powering Eastern European countries.

17

Underestimating The Missing Link Of Longwall Automation

37

Surface Mining For Cleaner Coal

41

The Magic of Coal Preparation Plants: Part Two

Karol Bartodziej, FAMUR, Poland, considers the importance of automated face advancing units when trying to achieve longwall automation.

21

Developing Shotcrete Solutions

Donald O Connor and Bryce Nhlapho, Minova, explain how recent developments in shotcrete solutions have helped provide secondary support to mining operations across the globe.

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In part two of a two-part article, Dr Andrew Vince, Elsa Consulting Group, Australia, explores a potential future threat to the magic of coal preparation plants.

44

29 Blasting The Surface

Geoff Stevenson, Orica, Australia, discusses how wireless blasting can benefit surface mining operations.

Fugitive Material: A Preventable Enemy Of Bulk Conveying

Todd Swinderman, Emeritus/Martin Engineering, USA, examines how fugitive material can be managed in order to improve safety in the workplace and dramatically reduce the cost of operation.

Driving Efficiency In Underground Mining

Andreas Westphalen, Caterpillar, Germany, explores how high-torque drive systems can offer increased efficiency and reliability in underground mining.

Dr Erik Zimmermann, Wirtgen GmbH, Germany, provides insight into how surface miners can help coal operations become more environmentally responsible.

49

Preventing Production Stoppages

Benoit Pluchon, Standard Industrie Singapore, discusses how product stoppages due to material build-up can be prevented.

53 The Formula For Storage-Facility Success Rebecca Long Pyper, Dome Technology, USA, identifies the requirements needed in order to establish a successful coal storage facility.

WORLD COAL

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ON THE COVER

ISSUE 4 2021 - VOLUME 30 NUMBER 4 ISSUE 4 2021

The rough conditions of underground longwall mining place high demands on the reliability, efficiency, and capacity of the equipment used. The economic development towards higher operating performance drives technological progress. Therefore, Caterpillar is currently developing a modular system of high torque drives (HTD) for armoured face conveyors: permanent magnet excited synchronous motors (PMSM) of different outputs, supplied by medium voltage frequency converters. The Cat HTD system will be characterised by high efficiency, high rated torque, and significantly reduced rated speed to improve productivity in longwall mining. To find out more, visit: Cat.com/mining www.worldcoal.com OFC_Issue4_WCL_2021.indd 1

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MANAGING EDITOR James Little

james.little@worldcoal.com SENIOR EDITOR Callum O’Reilly

callum.oreilly@worldcoal.com DEPUTY EDITOR Will Owen

will.owen@worldcoal.com EDITORIAL ASSISTANT Jessica Casey

jessica.casey@worldcoal.com SALES DIRECTOR Rod Hardy

rod.hardy@worldcoal.com SALES MANAGER Ryan Freeman

ryan.freeman@worldcoal.com PRODUCTION Kyla Waller

kyla.waller@worldcoal.com ADMINISTRATION MANAGER Laura White

laura.white@worldcoal.com DIGITAL ADMINISTRATOR Lauren Fox

lauren.fox@worldcoal.com DIGITAL EVENTS COORDINATOR Louise Cameron

louise.cameron@worldcoal.com VIDEO CONTENT ASSISTANT Molly Bryant

molly.bryant@worldcoal.com World Coal (ISSN No: 0968-3224, USPS No: 020-997) is published four times per year by Palladian Publications Ltd, GBR, and distributed in the USA by Asendia USA, 17B S Middlesex Ave, Monroe NJ 08831. Periodicals postage paid New Brunswick, NJ, and additional mailing offices. POSTMASTER: send address changes to World Coal, 701C Ashland Ave, Folcroft PA 19032. Annual subscription (monthly) £110 UK including postage, £125 overseas (airmail). Two-year discounted rate (monthly) £176 UK including postage, £200 overseas (airmail). Claims for non-receipt of issues must be made within four months of publication of the issue or they will not be honoured without charge.

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DEPUTY EDITOR WILL OWEN

COMMENT

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OP26 – the 26th United Nations Climate Change conference – was recently held at the SEC Centre in Glasgow, Scotland, UK, from 31 October – 13 November 2021. It appears set to go down in history as a milestone event of the early 21st century fight against climate change, albeit with a variety of different connotations and points of significance attached to it. Indeed, the UK Prime Minister, Boris Johnson, has called the Glasgow climate deal a “game-changing agreement”, whereas critics argue that the deal does not go far enough and will not meet the key summit goal of limiting global warming to 1.5˚C by the end of the century.1 With regards to the global coal industry, it has become apparent that, on one hand, many around the world, including Prime Minister Johnson, view the commitments made by major players at COP26 as yet more nails in its coffin – the publication of a ‘Global Coal to Clean Power Transition Statement’ by 52 nations, five sub-nationals, and 26 other organisations being hailed as one of the largest.1, 2 However, if one takes the time to dig (or mine) beneath the surface layers of these commitments, it is clear there is still life in coal yet. For example, as has been noted by Prakash Sharma, Wood Mackenzie’s Asia Pacific Head of Markets and Transitions, “China and India insisted the wording of the final text [of the COP26 climate deal] was amended to ‘phase down’ rather than ‘phase out’ coal-fired power”.3 This subtle, but nonetheless critical, change in semantics will mean all the difference to the coal industry moving forward. As is emphasised by Sharma in Wood Mackenzie’s ‘COP26 key takeaways’, this change in wording concedes the reality that, at present, as well as in the near-to-medium future, the aim of some countries will remain energy supply security, rather than environmental goals, “at least until other clean baseload supply options are commercially available at the scale that’s needed to replace coal in power generation”.3 Scharma’s points regarding viability in relation to commercial availability and scale, are particularly poignant, and will no doubt be music to the ears of major coal players. The need for a properly staged and considered transition from coal to renewables is being made ever clearer, fuelled by the fact that the current availability of renewables and transition energy sources makes the immediate cessation of coal production and coal-fired power generation a highly impractical course of action. In the words of Ian Macfarlane, Queensland Resources Council Chief Executive, “the world needs [coal] more than ever to support the transition to a cleaner, greener, and more sustainable future”.4 With the ‘death of coal’ postponed for a little while yet, I would like to invite you to enjoy this latest issue of World Coal magazine, which features a regional report from the International Centre for Sustainable Carbon on Eastern Europe, and a range of technical articles on roof bolting & bolter miners; truck & shovel mining; drill & blast; IPCC & surface miners; conveyors & dust control; washing, cleaning & separation; longwall mining; and domes & silos. Furthermore, don’t forget to visit www.worldcoal.com for all the latest industry news and developments. 1. 2. 3. 4.

Faulkner, D., ‘COP26: Climate deal sounds the death knell for coal power – PM’, BBC, (15 November 2021), https://www.bbc.co.uk/news/uk-59284505 Kettle, J., ‘Is the end of coal in sight?’, Wood Mackenzie, (17 November 2021), https://www.woodmac.com/news/opinion/ is-the-end-of-coal-in-sight/ ‘Wood Mackenzie weighs in on COP26 key takeaways’, Wood Mackenzie, (15 November 2021), https://www.woodmac.com/ press-releases/wood-mackenzie-weighs-in-on-cop26-key-takeaways/ ‘Qld’s high quality coal industry here for the long haul: QRC’, Queensland Resources Council, (19 November 2021), https://www.qrc.org.au/media-releases/qlds-high-quality-coal-industry-here-for-the-long-haul-qrc/

April 25-27, 2022 Central Bank Center Lexington, KY

The Coal Preparation Society of America (CPSA) is bringing back the Coal Processing Technology Conference and Exihibition to Lexington, Kentucky. A new venue, the Central Bank Center adjacent to Rupp Arena will house the event. Also new, it will be a joint conference with the Society of Mining Engineers, Central Appalachian Section with parallel technical sessions and more choices.

•

Three days of workshops, keynote and technical sessions The majority of our exhibitors along with some new ones will be back on the • Two days of exhibits in 33,000 sq. floor which is nearly 80% booked. Check out the latest floor plan at www. ft. of space coalprepsociety.org under the events tab and book a booth with the exhibitor application. Lunches will be served on the exhibit floor thanks to our sponsors: • One of the best venues around, Elgin and FLSmidth. centrally located between the Appalachian and Illinois Basins Monday, April 25 is exhibitor setup and features two workshops as part of our technical program (total of 7 Professional Development Hours): • Pumps 101 - Topics include the fundamentals, selection, what affects performance, wear modes, and the best maintenance practices of slurry pumps. • Coal Prep 101 - Topics include a review of coal properties important to utilization, coal sizing, cleaning and dewatering operations. Tuesday, April 26, the conference begins with a keynote address by Joe Craft, President of Alliance Coal. The exhibit hall opens after the keynote and following a quick tour of the exhibit hall, join us for lunch and our annual membership meeting where you will learn what new programs and training opportunities the CPSA will be offering to further the knowledge of coal preparation. The technical sessions begin Tuesday afternoon with both the SME/CAS and the CPSA having paper presentations on timely topics. A detailed technical program can also be found at www.coalprepsociety.org Our Members Night Out also returns Tuesday evening to the Buffalo Trace Distillery. It will be held in their newly rennovated Giants Hall and will feature distillery tours, bourbon tasting, hors d’oeuvres, dinner and Byron Trimble, a very funny comedian to close out the night. It is a great networking opportunity so reserve a seat or an entire table but do so soon because this event always sells out and space is limited. Wednesday, April 27 there are morning and afternoon technical sessions with a lunch program that will include a few surprises. Our presenters in the technical sessions will talk about advances in coal preparation, slurry impoundments and new technologies in mining and processing among other topics. Planning for this exciting event is well underway with more details about the program to come as it is finalized. Frequent updates will be available at www.coalprepsociety.org. You can also register for the conference and exhibition ($50 which includes lunches and refreshments), book your seat(s) at Members Night Out, sign up to exhibit and/or advertise in our quarterly journal. Should you have any questions, please contact Mel Laurila (qcinc@aol.com) or Kathryn Dew (coalprotec@gmail.com).

IN BRIEF RUSSIA

On 11 November 2021, the Board of Directors of National Transportation Co. appointed Mikhail Kuznetsov as the company’s CEO. Kuznetsov has been on the Board of Directors of JSC SUEK since 2020.

SOUTH AFRICA

Edenville Energy Plc has provided an update regarding the company’s Rukwa Coal Project in southwest Tanzania for October 2021, as it continues to ramp up production and sales to a targeted output of 3000 tpm of washed coal later this year. In October 2021, the company mined 2240 t of run of mine coal and produced 1024 t of washed coal through its wash plant, representing an increase of over 150% on the September 2021 figures.

MEXICO Allegiance Coal Ltd has announced the first New Elk cargo of metallurgical coal was loaded and sailed week commencing 08 November from the Port of Guaymas in northern Mexico, to China. The event marks a significant achievement for Allegiance, returning the New Elk Mine in southern Colorado to production just five months earlier. The company acknowledges the efforts of its workforce at the New Elk Mine, along with Union Pacific Rail, its sales agent, M Resources, and its customs agent at the Port of Guymas, Segrove. Focus is now on executing the next cargo more quickly and more efficiently as production at the mine continues to improve. Meanwhile, the Black Warrior Mine in Alabama loaded its first barge the weekend of 13 – 14 November, as it starts to move coal to the McDuffie Terminal in the Port of Mobile for the second cargo set to sail in the first 10 days of December.

WORLD NEWS

RUSSIA SUEK invests in Cat system upgrades at

Russian V. D. Yalevskogo Mine

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aterpillar will deliver a complete armoured face conveyor system upgrade to Siberian Coal Energy Company, SUEK, for its V. D. Yalevskogo Mine, located in the Kemerovo region, Siberia, Russia. The order includes the Cat® AFC PF6 Armoured Face Conveyor, BSL PF6 Beam Stage Loader, SK1114 Crusher Station, SMB 1600/3500 Belt Return Units, and a steering system including 45 sets for 225 roof supports, plus a spare parts package. The armoured face conveyor and belt return are powered by three, 1200-kW Cat CST65 drive systems, offering 2133 kN (479 415 ft-lb) short-duration, maximum torque output. Specially designed for long, high-capacity faces, the controlled start transmission (CST) drive systems provide no-load motor start-up, synchronised soft-start and heavy-load start-up capabilities, as well as accurate load sharing and instant, effective overload protection. The longwall panel at the Yalevskogo Mine averages a 3.8 m (12.5 ft) seam height and 400 m (1312 ft) face length. With a minimum targeted productivity of at least 4400 tpy, the mine’s targeted average production is up to approximately 5 million tpy of a thermal coal. Installation and technical support will be provided by Cat dealer, Vostochnaya Technika. The complete armoured face conveyor system has an anticipated late-2Q22 delivery date.

AUSTRALIA Golding and CS Energy sign

Kogan Creek Mine contract extension

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RW Holdings Ltd has advised that its wholly owned subsidiary, Golding Contractors Pty Ltd, has signed a contract with Aberdare Collieries Pty Ltd, a subsidiary of CS Energy Pty Ltd, to extend the current contract mining agreement (CMA) beyond 30 June 2022. Under the terms of the CMA, the term is extended four years until 30 June 2026, with an option for CS Energy to extend the contract for up to another four years. The contract value for the initial four-year extension is approximately AUS$150 million. The contract extension represents the third mining contract term and life-of-mine to date for Golding and CS Energy at Kogan Creek Mine, with Golding performing the civil works in 2006 before mining commenced in 2007. Under this new arrangement, all major plant equipment will be supplied by Golding, requiring a total new capital spend of approximately AUS$11 million in the first year. All the remaining fleet required is currently operating on site and is owned by Golding. Golding will continue to employ approximately 70 people at the mine, most of which live in the local Chinchilla or broader South East Queensland regions.

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WORLD COAL ISSUE 4 2021

DIARY DATES POWERGEN International 26 – 28 January 2022 Dallas, USA www.powergen.com

International Mining and Resources Conference (IMARC) 31 January – 02 February 2022 Melbourne, Australia & Virtual https://imarcglobal.com

IME 2022

15 – 18 February 2022 Kolkata, India www.miningexpoindia.com

MINEXCHANGE 2022 SME Annual Conference & Expo 27 February – 02 March 2022 Salt Lake City, USA www.smeannualconference.com

Future of Mining Australia 2022

28 – 29 March 2022 Sydney, Australia https://australia.future-of-mining.com

Coal Processing Technology (CoalProTec) Conference & Exhibition 2022 25 – 27 April 2022 Lexington, USA www.coalprepsociety.org/ViewEvent. aspx?ID=7

Electra Mining Africa

05 – 09 September 2022 Johannesburg, South Africa www.electramining.co.za

To stay informed about the status of industry events and any potential postponements or cancellations of events due to COVID-19, visit World Coal’s events page: www.worldcoal.com/events

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WORLD COAL ISSUE 4 2021

WORLD NEWS

SOUTH AFRICA New investments to extend

Kangra Mine life beyond 2031

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oal mining company Kangra, a subsidiary of mining investment company Menar, is nearing the completion of the construction of the Twyfelhoek Adit, which forms part of the Kusipongo coal reserve. Construction started on 6 April 2021 and is on course to be completed by mid-December 2021, with the first coal expected by 1Q22. Twyfelhoek has met all the regulatory requirements. The company has allocated a capital budget of ZAR 153.6 million to establish the shaft and the project is progressing well. The access road to the Adit was completed on 13 September 2021, and the powerlines and water reticulation connection will be completed by mid-December 2021. Agreements were reached with affected families living within 500 m of the mine to be relocated, and Kangra is in the process of building the families new homes using local contractors, with the construction due to be completed by 1Q22. Kangra also invested in new and reconditioned mining equipment to the value of ZAR 45 million to mine the Kusipongo reserves. As part of the mine’s social and labour plan commitments, a project will commence in 1Q22 to supply water to the Donkerhoek community.

RUSSIA Vostochnaya Mining Company implements

radio communication

V

ostochnaya Mining Co. is switching to digital operational radio communications at its key mining asset, the Solntsevsky coal mine. The system has been introduced to systematise and unify the key production processes of dispatching the mining and transport complex. The system helps to collect critical information when responding to or preventing emergency situations. The system provides not only control of technological processes, but also significantly increases the efficiency of production management. At the cut, a solution consisting of modern walkie-talkies, mobile applications, dispatch and control platforms was applied. This solution provides versatile services, including instant one-to-one and one-to-many, full duplex calls. In addition, the use of digital communication has expanded the geographic boundaries of interaction; a specialist, brought into the new system, can now interact from anywhere in the world. The project was implemented jointly with Haiter LLC and MTS PJSC. This is the first project for Haiter LLC in the Russian market of the Hytera Hytalk PoC solution (radio communication works through the public 4G network). The company has adapted the control and dispatching consoles for VGK LLC.

WORLD NEWS

JAPAN Mitsubishi Heavy Industries completes IGCC plant construction

A

consortium led by Mitsubishi Heavy Industries, Ltd (MHI) has completed the construction of an integrated coal gasification combined cycle (IGCC) plant in the town of Hirono, in Fukushima Prefecture’s Futaba District. The new plant has been formally handed over to the customer, Hirono IGCC Power GK. Operation of the new facility, which is a high-efficiency, clean commercial power plant incorporating the world’s most advanced coal gasification technologies, got underway on 19 November 2021. The project called for the creation of one of the world’s largest IGCC configurations, roughly twice the scale of the previously completed Nakoso Unit 10 (former IGCC demonstration plant). The new facility is the second IGCC plant of such large scale in commercial use, following the installation constructed for Nakoso IGCC Power GK that went into operation in Fukushima Prefecture’s Iwaki City in April 2021. The Hirono project was completed with integration of next-generation thermal power generation technologies from MHI – including Mitsubishi Power – and three group companies. Mitsubishi Power, a power solutions brand of MHI, manufactured the core air-blown IGCC system, including the coal gasification furnace;

Mitsubishi Heavy Industries Engineering, Ltd (MHIENG) was in charge of the gas refining equipment; Mitsubishi Electric Corporation oversaw production of generators and electrical equipment; and Mitsubishi Heavy Industries Power Environmental Solutions, Ltd was responsible for the wastewater treatment equipment. The Hirono IGCC plant adopts a high-efficiency gas turbine combined cycle (GTCC) system, integrating gas and steam turbines. Coal is gasified in a gasification furnace at a high temperature under high pressure; sulfur, ash, and the like are separated out and removed; and the refined gas is used as fuel to drive the gas turbine. Combusted waste gas is fed to a waste heat recovery boiler, and the generated steam is used to operate the steam turbine. Power generation efficiency is 48%. This high efficiency contributes to reduction of carbon emissions. The IGCC plant construction project undertaken by Hirono IGCC Power GK incorporates the hopes and expectations of all stakeholders that the new plant, featuring the world’s most advanced thermal power generation technologies, will contribute to the creation of the local industrial infrastructure, and thereby to Fukushima’s regional recovery.

INDONESIA Cokal provides BBM Project update

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okal Ltd has completed the purchase of the Batu Luhung site for its permanent jetty for the BBM project and has completed LiDAR and bathymetric surveys of the site. BBM has appointed consultants to design the coal stockpiles, conveyors, barge loader, fuel storage, power supply, laboratory, weighbridge, and office. A temporary crossing of the Mohing River has been established to enable road clearing to proceed ahead while the Mohing River bridge is being built. Construction commenced on the Mohing River bridge, the biggest bridge on this road, and is proceeding to plan. BBM has deployed additional equipment to upgrade the road to access its coal mining areas, while at the same time upgrading the road profile to be suitable for use as a long-term coal haulage road. Upgrading will require the team to widen

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WORLD COAL ISSUE 4 2021

the road, reduce road gradients, spread sub-base rock where required, compact the sub-base, and improve drainage to final standard. After the Mohing River bridge has been constructed, only one major bridge will be required in the last 26 km of road to the mine. The most difficult section of the road reconstruction is now behind the company. Land compensation has been prioritised so road clearing can proceed unhindered. This is a major element of construction in Kalimantan to ensure indigenous villagers are fairly compensated for the impact on their agricultural land. Two teams are working simultaneously to speed up the process. Cokal has signed an MoU with other users of the road to conduct a joint survey for the road from 52 km to 4 km, which is the intersection road to BBM’s jetty at Batu Luhung.

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10

Dr Stephen Mills, International Centre for Sustainable Carbon, UK, provides insight into the role coal will play in powering Eastern European countries.

E

astern Europe has a complex history and continues to be shaped by both internal and external forces. There are many influential factors at work, such as: political and economic alignments, disputes over territory and land annexation, and split loyalties between major players – such as the European Union (EU) and Russia. Countries such as Bulgaria, Czech Republic, Croatia, Hungary, Poland, Romania and the Slovak Republic are already EU Member States, whereas other ‘candidate countries’ – including Albania, Montenegro, North Macedonia, Serbia, and Turkey – are in the process of integrating EU legislation into national law. Others, such as Bosnia and Herzegovina (BiH) and Kosovo,

are considered potential candidate countries. For membership, countries must fully transpose and implement EU legislation by the time of accession, although under certain circumstances, time/scope-limited transitional measures may be granted; for example, in areas of industrial pollution and air quality. However, there is a requirement to eventually fall in with EU plans to decarbonise and meet prevailing emission limits. For full membership, candidate countries must agree to the EU’s plan for carbon neutrality by 2050. The elimination of coal power, plus a greater reliance on renewables, is seen as a major component in this process, one that wealthier western member states are increasingly adopting. However, some Eastern European countries

11

are poorer and continue to rely on electricity generated by hard coal and lignite-fired power plants. Unlike their western counterparts, many lack the resources to fully replace their coal capacity with affordable alternatives. Various new coal power projects have been proposed, but even when based on modern high efficiency, low emission (HELE) technologies, some have met considerable opposition. Even proposals for improving and modernising existing plants have faced resistance. Many coal plants in the region need upgrading and equipping with new emission control systems in order to meet EU emission requirements, but, because of the anti-coal stance of the EU and others, it has become increasingly difficult to procure project finance. This has helped increase China’s influence, and Chinese finance and construction capabilities have been used to support various new coal developments in the region.

Why coal power persists in the region

It is clear that coal use is declining in many European economies, driven mainly by EU

Figure 1. İsken Sugözü 1210 MW power plant in Turkey. The plant’s two units burn approximately 3 million tpy of imported hard coal. It was the first coal-fired power plant built and operated by the private sector. Source: STEAG.

Figure 2. The 1.44 GW Afşin-Elbistan B lignite-fired power plant in Turkey. The plant has 12 units with a total installed capacity of 2.33 GW. Source: Turkish Coal Enterprises, TKI.

12

WORLD COAL ISSUE 4 2021

and national policies promoting the greater deployment of renewables and natural gas, and higher carbon prices under the EU’s Emissions Trading Scheme. These measures have prompted a number of countries to introduce plans to phase out coal for power generation. In 2020, coal provided only 13% of the EU’s electricity, a level surpassed by the combined generation from wind and solar. Coal’s share of EU power supply is now lower than most major economies. Further reductions are expected, with 14 EU Member States announcing plans to eliminate coal power generation between 2025 and 2030. Many Eastern European countries have traditionally relied on hard coal and/or lignite for at least part of their electricity supply, and although some aspire to decarbonise their power sectors, others intend to continue its use. The reasons for this focus on cost and ease of availability, diversification of energy sources, security of supply, driving economic and/or social development, plus a lack of affordable large scale alternatives. Other factors at play – cited by BiH, Kosovo, Serbia, Montenegro, Turkey, and Ukraine – include scepticism over the reliability and cost-effectiveness of intermittent renewables, as well as concerns over job losses in the mining sector. The significant uptake of renewables and the phasing out of fossil fuels is likely to have a disproportional impact in parts of Eastern Europe, compared with western economies. Coal and lignite are the main indigenous energy resources in some, hence their importance. Many have much of their energy tied to non-renewable sources, making any major switch a real challenge. Although the EU is attempting to unify national energy policies between Western and Eastern Europe, there are concerns that this will damage the economies and hinder further development in parts of the latter.

The future for coal power in the region

Fossil fuels are currently used to generate 61% of the electricity in Albania, BiH, Kosovo, Montenegro, North Macedonia, and Serbia. Although some regional governments have pledged to follow the EU’s path towards carbon neutrality by 2050, in many cases, this has yet to be reflected in concrete actions, as some countries push ahead with plans to refurbish existing coal-fired generating capacity or commission new plants. However, EU legislation, such as the ‘Industrial Emissions Directive’ and its predecessor, the ‘Large Combustion Pollution Directive’, is having an impact on coal power in the region, and some older coal plants are likely to be closed within the next few years. Approximately 10 units in Serbia, Montenegro and BiH, with a

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combined capacity of approximately 1 GW, are currently operating under the opt-out mechanism of the directive. It allows exemption of individual plants from the compliance regime, although they can only operate for a maximum of 20 000 hours

between 1 January 2018 and 31 December 2023. Most are older, small capacity, low efficiency, subcritical units. They also emit high levels of pollutants which is a particular issue. Individual countries are at different stages in addressing air

Table 1. Prospects for coal power in selected countries

Country

Coal power proposals Technologies Comments proposed

Ukraine

Two 600 MW projects proposed, with several others under consideration.

Serbia

Kosovo

New SC unit on line by mid-2020s. Other projects proposed.

Proposed SC (but project now in some doubt).

CFBC, USC

Possibly SC or USC

The country already has SC capacity operating. It also has plans to modernise some older plants.

Lignite-fired plants generate approximately 70% of the country’s electricity. Government intends to continue use of lignite for power generation. Some existing capacity being upgraded and modernised.

Possibly SC

Bosnia and Up to four new Herzegovina proposals. Several projects underway.

SC

Aim to modernise and Montenegro extend life of existing Subcritical plant.

North Macedonia

Proposed 300 MW lignite-fired plant.

Belarus

Government suggests that up to 1 GW of coal power could be developed.

Turkey

Major project under construction – 1.3 GW due online in 2021. Many others at various stages of development.

Subcritical

Possibly SC

USC

Key CFBC – circulating fluidised bed combustion SC – supercritical USC – ultrasupercritical

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WORLD COAL ISSUE 4 2021

Existing lignite-fired plants need modernising – programme already underway. New proposed SC unit would replace older, outdated capacity. Government considers coal essential for maintaining the security and affordability of electricity, and economic development. Need for new capacity, plus modernisation of some existing units. Government will continue operating country’s single lignite power plant. Output considered as vital in maintaining reliable and affordable electricity supply. Lignite is the country’s main energy resource. Two main lignite and hard coal plants provide 60 – 70% of the country’s electricity. Several existing units to be modernised and possibly equipped with flue gas desulfurisation.

Almost entirely reliant on Russia for its energy. Ways to diversify energy mix being considered. The country’s first nuclear power plant is partly online, but efforts are also underway to further develop local energy resources, including brown coal.

Around 70% of electricity provided by fossil fuels. Coal and lignite are the main indigenous energy resources. Government aims to reduce high energy import dependence via greater use of indigenous coal.

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pollution in terms of national strategies, policy development, funding, monitoring, and reporting. The environmental impact of coal-fired power generation in the region and beyond has been highlighted as an area of concern, with emissions of sulfur dioxide (SO2), nitrogen oxide (NOX), and particulates frequently above permitted limits – particularly in BiH, Serbia, and North Macedonia. There are 16 major lignite power plants in the Western Balkan countries of Albania, BiH, North Macedonia, Montenegro, Serbia and Kosovo, that were famously cited for emitting as much SO2 and particulates in 2016 as all the EU’s 250 coal power plants. 1 Clearly, emissions to air are not restricted by national borders, and trans-boundary dispersion is an international issue. Most Eastern European countries have signed up to the EU’s Energy Community Treaty that came into force in 2006. This aims to integrate energy markets in the region with that of the EU, and apply appropriate environmental legislation in the energy sector – including commitments to reduce pollutant emissions from coal plants. However, emissions from some plants often exceed the ceiling agreed, and there have been numerous cases of non-compliance that have not been rectified by successive governments. During the past few years, some older lignite-fired capacity has been closed and a number of plants have been equipped with new emission control systems, such as flue gas desulfurisation (FGD) and improved particulate control devices. There are also proposals or projects in development aimed at improving efficiency and cleaning up other facilities. However, not all environmental upgrading projects have progressed smoothly. For example, there have been problems with an FGD unit added to the Kostolac B plant in Serbia. In other cases, the pandemic has delayed project progress. Thus, trial operations of a new FGD unit at the Ugljevik power plant in BiH were halted temporarily, only resuming in July 2020 when Mitsubishi Hitachi Power Systems Ltd staff were able to return.

What happens next?

In contrast to most other European countries, a number of new coal projects have been proposed or are in development in the region (Table 1), although during the past five years, others have been deferred or abandoned, largely on grounds of profitability, funding issues, and possible environmental impact. Efforts to eliminate coal power have been tabled by several aspiring EU members, hoping to replace it mainly with more intermittent renewables. However, depending on the national circumstances, this may raise issues of affordability and reliability of electricity supply.

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Increased grid interconnection between neighbours can help alleviate electricity shortages when they occur, although it does little to improve energy independence or reduce the cost of energy imports. So, despite the EU’s planned coal phase-out, the transition is unlikely to go so smoothly in a number of Eastern European economies. Several have long relied on coal for at least part of their electricity, and are likely to continue doing so for some time. For example, Serbia gets approximately 70% of its electricity from its six main lignite-fired power plants, with much of the balance coming from hydro. The Serbian government has made it clear that it intends to continue using the country’s reserves of lignite for power generation, as it considers this key to maintaining a secure, stable, and affordable electricity supply. As part of this, some existing capacity is being upgraded and modernised and there are also several projects proposed that could potentially add considerably to lignite-fired capacity; some of this is likely to adopt HELE technology. Further Chinese involvement seems likely in the development of at least some of these projects. In various cases, proposals for new modern HELE-based projects have been abandoned or delayed as finance for coal power projects from European and other investors has dried up. Ironically, had such projects proceeded and modern, clean, HELE technology been used to retire outdated generating capacity, issues of localised pollution would have been significantly reduced and system reliability greatly increased. Now, a number of countries are scrambling to update and clean up older capacity that ideally would have been replaced already. Some countries face conflicting requirements. For example, most aspire to eventually become full EU Member States, requiring them to fall into line with EU plans to remove coal from the bloc’s power sector. However, cost and energy security, among other factors, suggest that coal/lignite will retain a role in a number of economies for some years. It will be interesting to see how some candidate members of the EU intend to achieve carbon neutrality and the eventual elimination of coal, whilst providing an effective supply of electricity to their respective populations and industrial sectors. Despite the outdated and polluting coal-fired capacity still operating, in reality, for some, it may remain the only reliable cost-effective option.

References

1. ZANDER, E., ‘EU action on Western Balkans’ chronic coal pollution is a unique opportunity to improve health and productivity’, Health and Environment Alliance (HEAL), https://www.env-health.org/press-release-eu-action-on-weste rn-balkans-chronic-coal-pollution-is-a-unique-opportunity-toimprove-health-and-productivity/ (2019).

Karol Bartodziej, FAMUR, Poland, considers the importance of automated face advancing units when trying to achieve longwall automation.

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or many years, achieving longwall automation has been a goal of mine authorities and machinery manufacturers. Nowadays, the number of longwalls mined with the use of an electrohydraulic control system for powered roof supports is relatively high, and shearers that can automatically perform one or more cuts are also increasingly popular. However, the use of an electrohydraulic control system for powered roof support is not enough to make a longwall unmanned. In fact, there is an element of the longwall system that is not being addressed at all.

Overcoming the beam stage loader Automated face advancing

While the longwall face can progress on its own due to electrohydraulic control of the machines, the beam stage loader (BSL) remains in its static position and must be moved manually by the operator. As an example, one of the solutions to this problem is FAMUR’s UPZP-1200 automated face advancing unit. It has two cylinders and the construction of the belt conveyor’s turning section allows the BSL to be pulled up synchronously to the machines working the longwall.

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The key role is played by the unit’s control algorithm, which interacts with the control system of machines by detecting their status and the length of the extended shifter cylinder pushing out the armoured face conveyor (AFC) adjacent to the BSL in real time. In case the face advancing unit is unable to perform an automatic movement, it alerts the operator of the need for them to take control and sends a signal to the control system for powered roof supports to stop performing an automatic repositioning cycle, so that the operator can remove the problem.

The ‘master-slave’ mode

The unit control system operates in a ‘master-slave’ mode, where the unit is controlled by the control system of the longwall powered roof support, subjecting itself to its operation cycle. As a result, there is no need to interfere with the control system of powered roof support; only the standard information that such systems exchange with SCADA visualisation systems is used. This means that the use of products, such as the UPZP-1200 unit, is possible without involving the programming team of the roof support control system’s manufacturer. The system can operate as a ‘slave’ element for the central control system. The prepared communication interface enables the visualisation of its operating and alarming states, as well as the possibility of controlling the UPZP-1200 unit. If, on the other hand, the user wishes to implement the UPZP-1200 unit as a system that is not linked to the central SCADA, a computer with FAMUR’s SmartMine application will be provided, where the user can supervise the operation of the system.

Mechanical structure Figure 1. UPZP-1200 overlapping station – conveyor belt return part, and vertical stabilising cylinders.

Figure 2. UPZP-1200 – station feed cylinders, and a BSL discharge part.

Another element of the UPZP-1200 unit is its mechanical structure. Due to the mechanical solutions, the automation system is as simple as possible. The design effectively prevents stalls of the BSL during progression cycles and enables operation even when the BSL is subjected to bends in each axis. The overlapping station has a number of features facilitating automation, e.g. the passage of cables and hoses between the lower and upper part of the unit through a cable gland, which makes them self-guiding to prevent damages during operation. In addition, the latching holes, against which the cylinders are locked are designed in such a way to be self-cleaning, in order to prevent the accumulation of excavated material, which helps to ensure that the system is self-operating. The length of the unit together with the BSL is selected according to the daily progress of mining – e.g. in the Shigetai mine, the conveyor allowed for 20 m of adjustment in automatic mode. Due to this configuration, manual intervention in the system to move the belt return (lower) part of the unit takes place only once a day during maintenance shift. The operation of the cylinders is supported by a set of proximity sensors detecting the point when the cylinders can lock against the lower part of the unit and detecting irregularities in locking, e.g. due to clogging of the latching holes with excavated material. If the system detects an anomaly, it attempts to reposition the cylinders and if it cannot lock them properly, it signals the operator of the problem and enters manual control mode.

Radio remote control Figure 3. UPZP-1200 – flexible part of a BSL entering the belt return (lower) part.

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An additional feature of the UPZP-1200 unit is the operation of each cylinder in manual mode using a radio remote control. This significantly increases safety

in relation to standard overlapping stations, where the operator controls the operation cycle by switching hydraulic valves mounted on the station itself. In such a configuration, the station’s movement can pose a danger to the operator. Operation using radio remote control allows the operator to freely choose their position so that they can work safely. The operation cycle of the UPZP-1200 unit starts with the stable expansion of the cylinders stabilising the return (lower) part of the unit in relation to the floor, roof, and walls. As a result, the return part of the unit is a stable track needed for the process of pulling up the discharge (upper) part of the unit. The turning section is equipped with guides with a series of holes which the bolts of the feed cylinder pins enter, pulling up the discharge section of the unit. The feed cylinders start their operation cycle from the maximal spreading of the cylinders. Due to a set of sensors, the system detects holes against which the cylinder can interlock. After stable locking against the belt return part (lower) of the UPZP-1200, the system is ready to pull up the BSL. When the roof supports in the longwall start to push the AFC conveyor, the UPZP-1200 receives information about this activity and pulls the BSL forward, adjusting the pulling rate to the rate of AFC movement. Upon completing this operation, the system re-extends the cylinders and interlocks them to be ready for the next cut of the machine.

contemporary communication protocols. Both the communication protocol and the interface are matched for a specific installation. The implementation of the UPZP-1200 overlapping station at the Shigetai mine was very unusual. Commissioning of the unit took place in 2Q20, during the period of the worldwide COVID-19 outbreak. Due to air traffic blockages and the inability to obtain visas to China for FAMUR service representatives, the implementation of this system had to take place without their presence on site. Timing and synchronisation of operation between HNDZ systems and the FAMUR overlapping station were done remotely. The installation of this unit at the Shegetai mine was also unusual for another reason. The UPZP-1200 unit had to cooperate with a longwall system with a rather unusual mining method. In the place of a standard roadheader with two long arms, a Heilong’s (Mikrus’s) GUŁ-500 cutting and loading head was used. This system has a non-standard operation cycle – when the

Case study: China

Due to its versatility, the UPZP-1200 unit control system can be configured to work with any electrohydraulic control system for powered roof support. For example, during the implementation of this unit at the Chinese Shigetai mine in the Shanxi province, the unit cooperated with machines controlled by the system of the Chinese company, HNDZ, where the exchange of information between them took place in the Modbus protocol. The native transmission protocols in the system are Modbus, OPC and MQTT, but the control system architecture is versatile enough to cooperate with most of the

C i n c i n n a t i D u a l S p r o c k e t Conveyor Chains are proven to be be t t e r than o t h e r mining chains. Tons better, in fact. Tests confi rm our c h a i n s d e l i v e r 2 0 p e r c e n t m o r e s t r e n g t h . T h e r e s u l t i s g r e a t e r d u r a b i l i t y, m a x i m u m availability and a t r o u b l e - f r e e s e r v i c e l i f e . T h a t ’s how we del i ver the l owest cost per ton. For 90 years, Cincinnati has proven to be THE STRONGEST LINK.

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cutting and loading head arrives at the end of the longwall it almost completely gets into the main gate or rail gate gallery, after which the GUŁ-500 makes a full step forward into a coal face, and then starts the next cut. Therefore, the control algorithm of UPZP-1200 unit had to take into account the additional factor of the frontal sumping of GUŁ-500’s head and react appropriately to anomalies in this process, so as not to interrupt automatic operation. As the GUŁ-500 head goes almost entirely into the main gate, the AFC also is abnormally long and goes deeply into the side galleries. Therefore, the

BSL is located virtually at the very opposite face to the longwall. Due to the ergonomics of longwall operation, the belt conveyor receiving the excavated material is on the other hand located at the opposite side of the transportation tunnel. In order to solve this problem, the BSL had to be designed in such a way that its standard layout is snake-shaped, passing from one side of the transportation tunnel to the opposite side. In spite of this unusual design, the UPZP-1200 and the BSL enable an automatic progression cycle in line with the operation cycle mining the longwall. GUŁ-500 is a machine designed for thin coal seams with thicknesses from 1.2 m. Anyone who has worked on such a low longwall, or at least had to walk through it on their knees, knows how difficult and dangerous such conditions are for human labour. Therefore, it is not surprising that, in order to minimise the presence of people in the mining area, such longwalls are much more frequently subject to automated mining than higher longwalls.

Conclusion

Figure 4. UPZP-1200 – feed cylinders interlocked against the belt return (lower) part.

Figure 5. Vertical stabilising cylinder extended against the floor and ceiling, in the maingate tunnel.

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The development of technology in the field of mining automation could be compared to the development of many items; it has already been forgotten that a lot of these items did not appear suddenly as a finished product, but are the result of gradual evolution in a given field. Take, for example, smartphones. First, all the component technologies had to emerge, such as the development of a way to produce electronic components, then a specific design of radio transmitters, a charging system, a display or even a specific user interface, which are now taken for granted and cannot imagine that someone could have designed it differently. Therefore, history has repeatedly shown that the inventions that are used today were very rarely the work of a single author, and were most often a series of relatively small innovations that, when put together, produce the desired end result. This is also the case with longwall automation. The aforementioned electrohydraulic control system for powered roof supports, or shearers capable of cutting automatically, are all significant milestones on the road to full longwall automation. Just as a smartphone would not be such an indispensable product if not for the development of touchscreens, one cannot afford to have missing links in mining technology, which would cause that the final effect of longwall automation is lost because it has to be supported by manual work. Although it will probably take a few more years to see the autonomous operation, it must be stated with certainty that, as the numerous geological challenges are a separate area of problems waiting to be solved and hindering the automatic operation of the machines themselves, the use of automatic overlapping stations, such as the UPZP-1200, is one of those necessary milestones required for unmanned mining.

Developing shotcrete solutions G

Donald O Connor and Bryce Nhlapho, Minova, explain how recent developments in shotcrete solutions have helped provide secondary support to mining operations across the globe.

lobally, the mining industry faces relentless pressure to simultaneously improve safety and productivity. Nimbleness in adopting new technologies is a key to facing that challenge. In recent years, Minova has developed several shotcrete solutions that are used across the globe to provide secondary support to mining operations. Its recent innovation, TekCrete Fast M, is an ultra-fast, high-strength shotcrete that is sprayed onto the rock requiring support. Originally developed

to stabilise earthquake or bomb-damaged buildings to allow rescuers to enter safely, the product has been adapted for use in mining by the addition of dust-reducing agents to minimise dust when spraying underground. It is supplied as a dry powder that is sprayed using a dry shotcrete pump. Consistent with its original time-critical mission, TekCrete Fast M has fast strength development and high ultimate strength. Within 15 minutes, compressive strength reaches 1000 psi (6.9 MPa)

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and final strength exceeds 6700 psi (46 MPa). The high strength means that a much thinner coating is needed – typically only 12 – 15 mm. This reduces the volume of material required and provides rapid area coverage. In contrast, even one hour after spraying, conventional shotcrete shows essentially zero strength, and final strength seldom reaches even 28 MPa – meaning it requires a much thicker application.

Case study: Africa

TekCrete Fast M was recently used by the Minova Africa team, who were requested to develop a rock-reinforcing solution as part of the rehabilitation of a main conveyor drive at a coal mine in Mpumalanga, South Africa. The project was a great success, and was completed ahead of the eight-month planned schedule, with no injuries occurring during its duration.

Project scope

The strata in the immediate roof of a main conveyor belt line passing through an old mined-out area of a coal storage facility was deteriorating and required rehabilitation. The worsening condition of the roof posed a high risk to employees working in the vicinity of the belt. Additionally, there was the risk of damage to the belt, due to falls of ground.

Figure 1. Mining roof post application with Tekcrete Fast M.

Figure 2. TekCrete Fast M application at Minova Africa’s testing facility.

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Scaling of the side walls and the old roof support posed major hazards. The roof had to be first stabilised before new permanent resin bolt support was installed, as the operators were exposed to hazardous and unpredictable conditions. The project required a system to immediately stabilise the rock, providing protection to the rehabilitation crews, and to build sufficient enough strength so that it was part of the permanent reinforcement of the roof strata. Minova identified the rapid-setting, fast coverage rate, and high ultimate strength of TekCrete Fast M as the core of its solution.

The solution

Minova supported the customer with product training and its expertise in the application of TekCrete Fast M, built up in previous local and international projects. The project also included the erection of scaffolding over the conveyor belt to spray TekCrete Fast M. The fast setting of the product required the development of new methods for on-site quality control. The strength of conventional shotcrete is measured by spraying the material into cube moulds, that are then taken to a specialist laboratory on surface for compressive testing. This inevitably introduces a delay between spraying and testing, sometimes of several hours or as long as days. This method was too slow to produce meaningful data on the hardening of TekCrete Fast M, where the strength increase takes place within the first few hours. An in-situ test method was found, using the depth of penetration and pull-out resistance of a nail fired into the sprayed material, to give a strength index that was correlated to laboratory-measured compressive strength. TekCrete Fast M acted as a critical barrier between high-risk roof conditions and the people, enabling them to safely and systematically re-support the length of the belt. The belt drive was refurbished and provides a long-term solution to safely transport coal. This was not the first time that the company had worked with the same customer to provide a solution that delivered immediate and tangible benefits to the mining operations. Some years ago, the customer was grappling with resin bolting cycle times that were constraining mining rates. Minova proposed using a faster-setting resin capsule. After months of laboratory development and site testing, they delivered a decrease of 15 seconds per bolt, which highly increased the efficiency of the mine. The additional time gained by speeding up rock bolting with resin capsules, allowed the customer to gain an extra month’s bolting time in each year. This enabled bolting to catch up with mining rates and even allowed the customer to consider additional bolting operations, such as reinforcing the coal ribs

with glass-fibre reinforced plastic (GFRP) bolts.

Challenges One of the challenges faced was the need to reduce the cost of the nuts, which was as high as the GFRP bolts. The company has re-evaluated its supply chain to provide savings to its customer and deliver a substantially more cost-effective product without detriment to its performance. Minova Africa’s focus was to provide a one stop shop solution to their customer. With streamlined supply chain, the mine could then focus on the operations element. Thanks to the securing of the continuous supply of products, the customer was given peace of mind and allowed them to focus on their daily tasks.

The results

TekCrete Fast M is now regularly used on a variety of underground and opencast coal mines throughout Africa. The product is supported by field technical service advisors who help to plan the project and provide ongoing support such as training, quality assurance for the users. With the help of Minova’s sister company, GroundProbe, the application of sprayed cement has become easier and more efficient. GroundProbe has developed specialist laser scanning hardware and software to estimate the quantity of TekCrete Fast M required for a particular application. The system also provides continuous monitoring of the thickness during the project. This provides the customer with peace of mind that the design thickness is being correctly applied without over application. This in turn helps to keep the cost close to budget and minimises product waste. The company is working on further improving the product by developing a

full portfolio of coatings that are based on this technology. The future uses will include structural concrete repair and trowel-on application for smaller tasks. This will enable users to benefit from the unique properties of the material without having to purchase or hire full scale application equipment.

Conclusion

The confluence of deep expertise in materials science and understanding of the needs of mining has resulted in a stream of solutions that are providing immediate and real benefits to mining opetrations .

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underground mining Andreas Westphalen, Caterpillar, Germany, explores how high-torque drive systems can offer increased efficiency and reliability in underground mining.

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nderground mining places high demands on the reliability, efficiency, and capacity of the machinery. The economic development toward higher operating performance drives technological progress. When coal is extracted in longwall mining, a chain scraper conveyor transports the raw material extracted by the mining machine to the end of the longwall. Conventionally, the drive is implemented at both ends of the chain scraper conveyor by means of two-pole squirrel cage asynchronous motors that include reduction gears.

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Cat face conveyors with controlled start transmission (CST) technology have established themselves on the market. Equipped with a slip clutch, the CST gearbox allows for the load-free motor start-up and heavy-load start of the conveyor using the motor stalling torque, as well as the load sharing required for distributed drives by targeted use of the slip clutch. Currently, Caterpillar is developing a modular system of high-torque drives (HTD): permanent magnet excited synchronous machines (PMSM) of different outputs – from 300 – 1600 kW – supplied

by medium-voltage converters. The HTD system is characterised by high efficiency, high-rated torque ranging from 9000 – 70 000 Nm, and significantly reduced rated speeds of 300 – 600 rpm. Its modular design allows the new technology to be used underground for other drive applications beyond face conveyors. HTD system technology offers new degrees of freedom and opens new possibilities for the raw materials industry. Due to the slower speed and modified gear ratio, the moment of inertia visible on the gear output shaft is reduced by a

factor of eight. As a result, system damage from conveyor blockages will be less severe or virtually non-existent. Another advantage from this new technology: instead of using only the narrow working area of the asynchronous machine between the stalling point and the synchronous point, the HTD system provides a complete torque-speed map by using frequency inverters. Depending on the selection, the new drive system offers precise control over torque or speed. This precision enables smoother starting and

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braking processes, targeted speed ramps, rapid intervention in the event of a fault, improved load sharing between the head and tail gates, creep, and reverse travel. The conveying rate can be optimally adapted to the production rate, and necessary speed adjustments can be made when encountering difficult geological conditions to avoid damage to the system. In general, the HTD system is more efficient and reliable than conventional drive technology. It offers lower energy consumption and less cooling capacity, plus system component wear is reduced due to a simpler gearbox with fewer rotating parts.

Conveyor start-up

The start-up process of a chain scraper conveyor is a special event due to the process, but it must be carried out safely and reliably. A classic distinction is made between a smooth and a heavy-load start-up. The smooth start-up serves to protect the system and increases the service life. The aim is to introduce the force into the chain in a controlled manner without peaks and fluctuations during acceleration. In the case of a heavy-load start-up with fully loaded or even overloaded conveyors, however, the drive must be able to provide the maximum possible and permissible chain tractive force. The qualitative load curve shown in Figure 1a

shows the required torque over the motor speed that is passed through during start-up until the nominal speed is reached. When the conveyor is started, three components act on the chain force and thus on the motor torque: The mass of the chain as a dead load on one side and the load as a payload on the other lead to a friction force directed against the movement, which must be overcome (sliding friction). After a prolonged standstill, residual loads can bake into the conveyor and lead to a greatly increased static friction. The force required to accelerate the masses to be moved.

Conventionally, underground asynchronous machines are used as conveyor drives. They have established themselves as an efficient, reliable, and safe drive variant. However, in terms of its characteristics, the load torque is higher than the pull-up torque of the motor (Figure 1b) to manage the task at hand. For this reason, an additional technical system component is required for a heavy-load start. Cat conveyors are equipped with CST technology for this purpose. A slip clutch in the gearbox separates the motor from the load, so that the motor can run up freely to the nominal speed at the beginning. When the coupling closes, the motor comes into contact with the load, and the heavy-load conveyor start can be carried out with the help of the available stalling torque of the motor. There is a compromise for the system – a longer start-up time. To protect the electrical power network, the motors of the chain scraper conveyor start in stages. Prior to the conveyor starting, the CST coupling’s hydraulic components Figure 1. a) Load characteristics of a chain scraper conveyor; b) Torque-speed characteristic of an asynchronous motor; and c) Torque-speed characteristic are then prefilled, and the couplings diagram of a PMSM. are closed in a time-based way and coordinated with each other to keep the slack chain accumulation low, among other things. Only then does the conveyor start. Another issue with conventional technology is that motor currents rise sharply when a stalling torque is used. On the one hand, high motor currents are only allowed for three seconds for operational reasons, so the conveyor must have broken away by then. On the other hand, a voltage drop occurs Figure 2. The torque curve of a CST drive (blue), as well as the speed (green), during in weak electrical networks, causing the heavy-load start of a conveyor (simulation). The torque builds up at the output the effectively available torque to because of the timed closing of the CST coupling. If it exceeds the breakaway torque, the conveyor accelerates to operating speed within a short amount of time. drop. The high reduction ratio of

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the gearbox (typically 33:1), the rapidly rotating masses, and the high moments of inertia related to the load require measures to protect the system components in the event of a fault, such as a blockage. Figure 2 shows a torque time curve and CST drive speed during a heavy-load start, which was obtained with the digital twin of a chain scraper conveyor. The breakaway of the conveyor is based on a torque ramp. The actual acceleration phase is quite short and lasts approximately three seconds. The chain is locally stretched to different degrees and accelerated to operating speed. In the initial phase, significant torque fluctuations occur, which decay over time.

start does not differ qualitatively from a smooth start-up, something that cannot be achieved through conventional technology. Figure 5 compares a smooth start-up with a heavy-load start, as recorded on a motor test bench. In both cases, the measurement data of the speed and motor current (as a measure of torque) show a smooth acceleration process to the

HTD systems

The Cat HTD system (Figure 3) consists of a PMSM with slow rotation compared to Figure 3. High-torque drive Cat HTD4100. an asynchronous machine, a medium-voltage converter, and a gearbox with a much smaller reduction ratio, typically 6:1. The reduced mass moment of inertia is considerably smaller by a factor of eight than of the CST drive, eliminating the need for design measures to protect components in the event of a fault. Compared to the asynchronous motor, the availability of a torque-speed map (Figure 1c) through an inverter drive offers a Figure 4. The torque curve of a HTD (blue), as well as the speed (green), during the significant advantage. For a start, the simulated heavy-load start of a conveyor. When the speed is specified, the torque required for acceleration is built up. The gradient of the speed ramp determines the load does not have to be separated time until the operating speed is reached. from the motor, and the necessary torque is available from zero speed. To obtain an optimum ratio of torque to current, the reluctance torque of the machine is used. The HTD system masters the handled load profile without further difficulties (the load profile and the PMSM characteristic in Figure 1). In the heavy-load start shown in Figure 4, the simulated torque and speed obtained are plotted over time. In contrast to the CST technique, the start-up is speed-controlled. The controlled acceleration phase over the selected 10 seconds runs more smoothly regarding the torque behaviour; the amplitude of the initial torque oscillation due Figure 5. Measurement data for the starting behaviour of a HTD against a load of to the breakaway has decayed 100% (top) or 200% (bottom); the motor current (blue) is shown as a measure of the significantly, becoming both torque and the speed (green). Regardless of the size of the load, there is a smooth smaller and faster. The heavy-load acceleration process.

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maximum permissible operating speed due to the load. With this behaviour, the HTD system exceeds the previous catalogue of requirements for conveyor drives, because the previous technology cannot reconcile a reduction of the load peaks and chain force oscillations with the introduction of the maximum possible and permissible chain force.

Conveyor blockage

Although unlikely, hard blockage occurrences do happen in the field. In such a case, the individual components of the conveyor are strongly stressed, especially if the blockage occurs close to the drive. If a face conveyor is equipped with a cross frame, this represents a potential source for such a blockage. With CST technology, the moments of inertia of the motor and gearbox drive line components are clearly dominant overall in comparison to the rest (Figure 6). In the case of a hard blockage, large dynamic forces act on the weakest link

– the conveyor chain. The safety equipment must therefore be designed to prevent chain breakage as far as possible. Otherwise, production downtime will occur, resulting in high costs for the plant operator. With CST technology, the coupling is opened after a blockage is detected, and the motors are switched off. The separation of the drive line from the chain prevents the fast-rotating drive masses from damaging the chain. The simulation with the digital twin (Figure 7 – blue curve) shows that the introduced force is limited to approximately 4000 kN. However, a single chain strand cannot be prevented from being torn (breaking force 2800 kN) in an extreme case with an asymmetric twin inboard chain strand. A symmetrical double chain strand can withstand the peak force without damage. However, this is not the case with a conveyor drive with a fast-rotating asynchronous motor, frequency inverter, and rigid gearbox (VFD) without additional safety equipment (Figure 7 – green curve). There, the dynamic forces caused by the rotating masses break through and destroy the entire chain assembly. The HTD technology, which has a similar structure in principle but significantly lower moments of inertia in the drive line, offers better protection than other drive technologies, since the peak force remains below the critical limit for a single chain strand (Figure 7 – red curve).

Figure 6. Comparison of the moments of inertia related to the output shaft of the individual conveyor components for CST and HTD technology (HG: head gate, TG: tail gate, UR: upper run, BR: bottom run). In comparison, CST technology is clearly dominated by the moments of inertia of the motor and gearbox. In the case of a blockage, they can have a negative effect on the other components.

Figure 7. Chain forces during a hard blockage for different drive systems (simulation). With VFD technology, the force peak triggered by the blockage exceeds the breaking force of the twin inboard chain assembly. The slip clutch of the CST technology significantly limits the peak force. The HTD technology is characterised by the fact that the force peak remains below the chain breaking force in the considered blockage case.

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Summary

HTD drive systems offer the most advantages when system and component properties are prepared: smooth start-up even with heavy loads, overload and blockage protection, precise load sharing, creep mode, and reverse travel. In addition, the HTD drive offers great potential regarding its reliability and availability with fewer rotating parts, no overload coupling, constant condition monitoring, less wear, and lower maintenance costs. It also offers productivity advantages over its service life through lower energy consumption, and total cost advantages over the life cycle through lower total cost of ownership.

W

Geoff Stevenson, Orica, Australia, discusses how wireless blasting can benefit surface mining operations.

ireless initiating systems allow for groups of in-hole primers to be wirelessly initiated by a firing command that communicates through rock, air, and water. This eliminates the need for down-wires and surface-connecting wires, enabling completely wireless mining methods and blasting techniques that are safe and reliable

– further reducing risks and operating costs while, at the same time, increasing productivity benefits. This significant step-change in blasting technology has fundamentally shifted the industry’s approach to blasting and mining and opens up opportunities for a much wider array of markets and mining applications.

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Wireless blasting

Since the launch of Orica’s WebGenTM 100, the world’s first wireless initiating system, in early 2017, Orica has successfully completed more than 2500 blasts using the wireless technology in both underground and surface mines around the world. Now, Orica has announced the second generation of this technology. Built to deliver market-leading safety and reliability, the new WebGen 200 incorporates world-first wireless technology; engineered with enhanced capabilities and security to meet the extremes of mining conditions, with greater versatility to adapt to the needs of both surface and underground customers pushing the boundaries of mining. Orica’s new technology has been designed in line with customer needs and feedback, as they look to further improve safety and productivity across their operations. WebGen 200 will be available as four product variants and includes a wider range of booster weights; opening up new segments, applications and opportunities, in both surface and underground mining. It is a critical enabler to Orica’s vision of transforming how drill and blast is used to unlock mining value across the value chain, utilising integrated digital and automated technologies to create safer and more productive operations for customers.

Figure 1. AvatelTM at Epiroc’s factory in Örebro, Sweden.

Figure 2. A WebGen Specialist assembling a WebGen 200 Surface primer ready for encoding.

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WORLD COAL ISSUE 4 2021

The system leverages advancements in digital technology to deliver sophisticated features including digital inventory management, delay adjustments before blasting, an improved user interface and increased quality assurance. Reliability is front and centre, with the primers able to endure even greater dynamic pressure and the ability to sleep the product in the ground longer.

Elevating surface and underground mining operations

WebGen 200 Surface and WebGen 200 Surface Pro are designed for surface mining applications, with the latter designed for extreme blasting conditions, allowing for the use of innovative blasting techniques, such as: multi-stratum blasting, mining schedule flexibility, and lightning risk reduction. The WebGen 200 Underground Pro is suited to production blasting, while the WebGen 200 Underground Dev has been designed for mechanical assembly and handling, and enables the automation of underground development charging with AvatelTM. The WebGen 200 Encoder has been ergonomically designed for easier handling – the primer is now placed in a side opening without the need for alignment, and the DRXTM is encoded using near field communication (NFC). This can be completed with or without the booster attached for either batch or at-hole encoding. The encoding tablet is a Juniper Systems Mesa3 with the Windows 10 operating system, which can be removed from the encoder body as required. The new encoder takes advantage of WiFi, NFC, and RFID for data exchange and to streamline workflow, and also programs every individual WebGen primer via an encrypted code specific to the mine site. The encoder is a key component in managing the safety and security of the system, and programs each wireless primer with three important pieces of information. The first code is a unique blast identity number (BID), which is exclusive to the mine site and is assigned to specified groups of primers, which will sleep, wake, and fire together as a single blast. The second code is the blast proximity identity (BPI), which is recovered from an RFID beacon that is in the blast location. The third code is the DRX ID (UID) and it is linked to delay time and hole ID, and allows the all-new capability of deleting primers or changing the delay times of primers in a blast; it also records component IDs for blast inventory management (BIM). The BIM senses an RFID tag in the DRX and is traced to a blasthole; soon, it will also be possible for cases of detonators and primers to be scanned going in and out of magazines (and other sensitive locations) – during encoding, they too will be associated with a blast hole. Also coming soon is a

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misfire detection system, which will trigger an alert if a misfire has occurred in a blasthole. There are five antennas available with the wireless blast system, which means the effective transmission range for the firing signals can be more closely controlled to the work area. The antennas have been designed for more convenient handling, with hinged joints to reduce bulk where needed, and they are further hardened to withstand mine site conditions. The new hardware, software, and primers come together as a versatile and reliable system that is easily integrated into any operation to allow miners to think differently about their ways of working and operations.

Breaking new ground in surface mining

While WebGen 100 was initially positioned for use in underground applications, it is now increasingly being adopted in surface mining to complete successful surface blasts across three continents. WebGen 200 presents an opportunity to overcome one of the industry’s most constraining limitations, which is the relatively fragile physical connection to each primer in

Figure 3. WebGen 200 fully wireless initiating system has no downlines and surface connections to the detonator.

a blast. Wired systems have a large physical footprint and are susceptible to damage at every point along the connecting lines, so removing this barrier significantly increases reliability. The potential for misfires, due to downline damage in wired systems, has commonly led to the application of redundant initiation systems and can prevent loading of adjacent blast patterns, due to possible fly-rock damage. These contributing factors increase blasting costs, reduce mine efficiency, and limit blast productivity. Wired systems in priming, loading, stemming, and tie-in activities require precautionary measures to protect wired connections, adding to manpower needs and cycle time. WebGen 200’s fully wireless technology simplifies bench operations in surface mining with no tie-in process, and reduces on-bench resources, inventory, and misfires that occur due to line damage or cut-offs, slumping, or operator error. Stemming costs are also reduced and back-up inventory is eliminated through this wireless system. The absence of downlines also removes the interaction between heavy vehicles and people, in order to protect initiating systems and reduce exposure to on-bench hazards. The elimination of the tie-in process means spotters are not required to protect downlines nor exposed to dust and dangers from stemming operations. The second generation also paves the way for innovative mining practices to be considered, such as turning a WebGen 200 loaded blast strip into a temporary haul road, providing greater scheduling flexibility to operations. This enables haul trucks and other mining equipment to tram over the loaded blastholes, providing improved efficiencies in the load and haul process; and greater productivity to mine operations through flexibility in mine pit scheduling, delivering increased vertical advance in surface mining operations. With increased flexibility in pit planning and blasted inventory, mine operations enabled by WebGen 200 can prime and load larger single blasts, as well as eliminate firing window variability.

Untethered blasting opportunities

Figure 4. Wireless blasting reduces mine operation downtime during lightning events – eliminating all potential initiation pathways and risk of unplanned explosion.

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Being truly wireless means benches with stemmed holes loaded with WebGen 200 primers have no wires or signal tubes on the surface – all explosive materials are located within the blastholes in the ground. This eliminates the most likely hazards associated with vehicle interactions with explosives. Other situations considered potentially hazardous were also investigated. Detailed theoretical and practical investigations have concluded that heat and pressure are rapidly attenuated by

the ground; therefore, fire, heavy equipment forces, and rockfall impacts will not have any effect on the primers or Orica bulk explosives, due to the absence of downlines and surface connecting wires. The magnetic field induced by high current trailing cables does not carry the correct digital code to wake up and fire a WebGen unit, and the magnetic field will be too weak to cause corruption of the DRX that might lead to a misfire. Along with WebGen 200, a number of operational controls will be necessary to ensure there is no risk, including priming practice, blast demarcation, and changes to excavation practices.

Lightning risks and delays a thing of the past

The wireless blast technology enables the elimination of lightning-induced explosion hazards in loaded blastholes, including any holes that remain unstemmed, by removing the initiation pathway provided by downlines and surface connecting wires. In the event of approaching lightning storms, a mining exclusion zone is placed around the loaded blast or, in some cases, the blast is cut short and immediately fired. With the removal of all initiation systems from the bench surface, mine operations no longer require a wide lightning exclusion zone to continue safe operations, thereby avoiding long periods of inactivity or causing the firing window variability that is subject to the use of conventional initiating systems. With bulk explosives and initiating systems at a minimum safe depth of 3 m below the surface, and with the absence of lead wires, the temperature, pressure, and electric charge associated with a lightning strike has no significant effect on the explosives loaded in the blast holes; rather, the energy is rapidly attenuated by the earth. The magnetic field induced by lightning will not carry the correct digital code required to activate a WebGen unit for firing, so in the event of lightning in the vicinity, the bench will still need to be cleared of personnel, but there will be no explosion risk.

Bringing mining efficiencies to the surface

The technology can also improve productivity in surface mining by loading multiple decks in a single pass. This approach offers improved utilisation of drill and blast and load and haul capacity. In the case of drill and blast, the second generation technology allows for bench preparation to be reduced and drill metres to be increased through fewer relocations of the drill. Explosive loading is faster and scheduling blasts are no longer constrained by the drill and blast process. The load and haul operations are also more productive, with continuous access to broken stock, less relocation of equipment, and a smaller overall active footprint. Along with WebGen 200, additional operational controls will be required, which include more accurate drilling, monitoring explosives deck location, monitoring stemming, and primer location; and an

excavation management plan that ensures standoffs and relative levels are maintained, supported through technologies that are currently in use.

Case study: Brazil

Salobo Mine (Vale, Brazil) was interested in eliminating safety related damage to lead wires during stemming and reducing the loading crew’s exposure to dust and heavy vehicles. Two demonstration blasts were planned – one of 350 holes and a second of 190 holes. These blasts were able to demonstrate: The elimination of safety incidents related to wire damage, which is a critical requirement for the operation. Removal of interaction between heavy vehicles and people during stemming. The elimination of exposure to dust during stemming and lead wire damage. A 50% reduction in stemming time, as manoeuvrability was unhindered by lead wires. While WebGen also allows the elimination of lightning exclusion zones around loaded blasts, this was not able to be assessed as no lightning events occurred during the trial period. Once the loading of the second blast was completed, the loading equipment (mobile manufacturing units – MMUs) were driven over a temporary road which ran diagonally through blast holes on the bench. The objective was to demonstrate that loaded WebGen blasts can be safely used as roads without impacting on blast performance. Vale and Orica are currently exploring opportunities to further assess the benefits that WebGen would bring to scheduling flexibility and overall production from the pit.

Moving the mining industry forward

The WebGen 200 development programme is progressing according to plan, with comprehensive product verification and validation testing now complete. Field trials of the WebGen 200 system began in September 2021 and will be completed by December 2021, across multiple mining segments and regions in Australia, Canada, Latin America, and Europe.

Conclusion

Artificial intelligence and advanced machine learning capability will interpret real-time data to design even more predictable blasts. As operations become more digitally connected, more workflows will become fully automated. As mines go even deeper, and ore becomes even harder to reach, ongoing advances in automation, digitisation, wireless blasting technology, and data analysis will deliver not just better returns, but also better environmental and social outcomes.

ISSUE 4 2021 WORLD COAL

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s the coal industry continues to deal with fluctuating coal prices, it is critical to improve operational efficiencies in order to maintain profitability goals. A tighter integration and smarter analysis of the big data now available can be a strong contributor here – especially in load and haul process route optimisation, payload compliance, and fleet uptime and longevity.

Data solutions

Traditionally, mining companies have looked to a combination of on-board control systems and original equipment manufacturer (OEM)-agnostic technologies, in order to assist in improving individual load and haul tasks. Onboard control systems provide critical data, such as machine health and payload. And, OEM-agnostic technologies offer real-time information for payload optimisation, machine guidance, fleet management, and a range of other tasks.

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While each control system or technology can provide value on its own, it is the integration of these onboard control systems and OEM-agnostic systems that empower valuable insights for faster and more-informed decisions. Mines that push ahead in this area can expect significant benefits, such as: Consistent operations with increased safety. Optimised dispatching and real-time decision-making. A next-level competitive advantage with cost savings and reduced cycle times. Optimisation across the load and haul process. Maximisation of the entire value chain. OEMs, such as Komatsu, are focused on creating, connecting, and transforming data and systems to better manage the ever-increasing complexity of mining operations. In partnering with their customers, Komatsu provides expertise and integrated solutions that can

Simon van Wegen, Komatsu, USA, outlines how to unlock load and haul efficiencies by better integrating and analysing data.

do just that. The company’s smart mining approach is designed to accommodate any mining operation regardless of equipment, technology, or data maturity. Centred around the load and haul process, these data solutions services focus on boosting productivity, increasing efficiency, while remaining focused on safety. With a range of holistic solutions that translate data into insights using connected cloud and edge data, these insights identify patterns and actions to continuously improve the load and haul process, as well as the entire value chain.

Load up on payload results

Both underloading and overloading haul trucks can negatively impact the production of mining operations: an underloaded truck reduces efficiency and productivity, while an overloaded truck can create higher maintenance costs. In order to avoid both scenarios, operators require real-time payload information.

Komatsu’s Integrated Payload Management solution leverages a mine’s existing equipment and technology to deliver just that. Integrating all payload systems across all makes of equipment provides a comprehensive view for operators, and empowers full collaboration between personnel using truck and shovel payload management systems. An example of the optimised payload process shows the on-board truck payload system communicating the target payload information through the fleet management system to the shovel operator (Figure 1). The shovel operator then loads the truck to its optimal target load, adjusting for any carryback. An Australian coal mine has benefited from the Integrated Payload Management solution with the help of local Komatsu experts. Working collaboratively with the operations team to integrate their existing on-board controls systems and OEM-agnostic technologies, the mine was able to improve payload accuracy by 5%.

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Phase 2: implementation Once the assessment is completed, the recommendations are implemented, such as route modifications and operator training. Phase 3: sustainable results It is important to be able to continuously test and improve. Figure 1. Visual representation of the optimised payload management process through the So, Komatsu’s team creates a integration of on-board and OEM-agnostic technologies. digital simulation of the road network and compares the set targets and baseline performance metrics against the real-time data. If reality does not match the plan, the mine is alerted so corrective actions can be taken. Mines using truck cycle optimisation are seeing results. Komatsu and partner customers have achieved up to 23% improvement in truck cycle times.

Shift from reactive to proactive

Further optimising the efficiency of loading and hauling is not enough if haulage equipment is unreliable. To address this, Komatsu has a focused remote health monitoring (RHM) solution. The RHM programme creates a more integrated Figure 2. Utilising data in digital simulation and scenario assessments, mines can continuously refine haul routes to reduce haulage cycle asset health management ecosystem, giving times, move more material, and reduce equipment interactions. mines a more comprehensive picture of their operations. It combines real-time data insight, OEM Tuning the truck haulage cycle equipment knowledge specialists, and cloud-hosted big Ensuring that the load and haul process is not a data analytics. bottleneck in the value chain is essential. Eliminating With RHM, Komatsu and mines track critical issues such as poor road conditions, traffic congestion, machine and production data and then use it to prevent speed restrictions, long route layouts, and inconsistent unplanned downtime and better prepare for planned operator practice can help to reduce cycle times, downtime by monitoring machine health. In some cases, accelerate productivity, and reduce light-vehicle it could be machine data alone identifying an imminent interaction for additional safety (Figure 2). issue or a deviation in production performance. Komatsu’s truck cycle optimisation solution enables Because the monitoring is remote, operations benefit mines to make more informed decisions to achieve from Komatsu expertise on site or at the factory or excellent haul cycle rates and safety. By utilising data in service centre. digital simulation and scenario assessments, mines can With RHM, the integration of multiple data sources continuously refine haul and vehicle routes to reduce and systems, such as MineCare and Komtrax Plus, helps haulage cycle times, move more material, and reduce customers minimise downtime with proactive and equipment interactions. Komatsu can help establish real-time alarms. Operations using Komatsu RHM have key performance indicators (KPIs) for truck speed and seen machine availability increase by more than 5%, continuously monitor results against baseline targets to and mean time between failures increasing by more ensure optimisation is ongoing. than 150%.

Implementing truck cycle optimisation Phase 1: assessment Includes simulation and evaluation of a mine’s baseline performance targets and metrics to quantify areas for opportunity. Komatsu mining teams work with mine personnel to develop an action plan to optimise the road network.

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Creating value together

Each solution plays an integral part in further optimising the load and haul process. While many mining companies own mining assets with on-board controls and OEM-agnostic technologies, companies, such as Komatsu, are working with customers to maximise the value of their systems through integration and innovation.

Dr Erik Zimmermann, Wirtgen GmbH, Germany, provides insight into how surface miners can help coal operations become more environmentally responsible.

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oday, more than ever before, industrial processes pivot on sustainability and environmentally compatible technologies. The prioritisation of these aspects is also becoming increasingly important in opencast coal mining. Conventional mining methods for the extraction of primary resources include, for example, ‘rip-and-stack’ and ‘drill-and-blast’. Here, too, mining companies are making every effort to achieve environmental compatibility. In particular, they have already consistently reduced the exhaust gas emissions of the

machines deployed and the environmental effects of blasting. Despite these successes, the fulfillment of the intended objectives is becoming increasingly difficult. A simple and economically viable way of reducing the exhaust gas emissions of the machine fleets deployed is to simply mine the same volume of materials with fewer machines. This lowers the specific fuel consumption per tonne of material mined. The environmental effects of blasting can be minimised by reducing the explosive energy released

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in the blasting process to a minimum, and keeping the number of blasting operations as small as possible.

Benefits of surface miners

This is precisely where surface miners can help bring significant advantages. As the first step in the process chain, they can play a decisive role in the realisation of more efficient, safer, and more environmentally friendly opencast mining of primary resources. They selectively mine coal – as well as other raw materials, such as: limestone, salt, bauxite, iron ore, and gypsum – with an absolute minimum of interburden. This results in products with a high degree of purity that can be loaded from the surface miner’s belt conveyor system directly into transport vehicles, or stockpiled for loading at a later stage of the mining operation.

Figure 1. Cutting drum of a 220 SM 3.8 for coal mining.

The use of surface miners can effectively eliminate the need for drilling and blasting. In comparison to conventional equipment, a further advantage is that the machines can also be used in urban environments. The mining process produces level surfaces that serve as stable roadways and facilitate fast and safe transport of material. Another contrast to conventional equipment is that there is also a considerable reduction of environmental impact in the form of vibration, dust and noise, and a simultaneous improvement of safety at opencast mines.

Selective mining of pay minerals

As the surface miner moves forward, a cutting drum fitted with numerous picks rotates against the direction of travel (up-cut method), cutting layers of material from the rock formations and crushing it in the drum housing. Depending on the method selected, there are now two different loading options. For example, in the ‘cut-to-ground’ method, the mined material is deposited directly behind the machine for loading into transport vehicles by wheeled loaders at a later stage of the mining operation. The second option is direct loading into transport vehicles by means of the machine’s belt conveyor. Here, the primary conveyor receives the material from the drum housing and transports it to the rear of the machine, where it is then transferred to the slewing and height-adjustable discharge conveyor. The discharge conveyor either loads the material directly into transport vehicles (direct loading), or discharges it alongside the surface miner (side casting). The discharge height can be adjusted to the height of the transport vehicles. An automatic levelling system ensures that the machine maintains the exact cutting depth, allowing even thin seams or layers to be selectively mined with maximum precision. The use of surface miners, such as those offered by Wirtgen, is accompanied by the following characteristic process benefits:

Selective mining

Figure 2. Comparison: amount of equipment.

Thin seams interspersed with intermediate rock layers can be mined precisely and economically. Surface miners ensure high-quality run-of-mine material by adjusting the cutting depth in millimetre precision. � Higher quality of the mined material. � Better stripping ratio due to reduced dilution. � Increased processing plant recovery.

Blast-free-mining

� Environmentally friendly mining Figure 3. Surface miner operating principle.

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– due to no vibration and fly rock, reduced dust, fumes, and noise.

etter drainage, with less water seepage into floor. B Easier slope reclamation. Improved safety due to no usage, handling, or storage of explosives. Effective mining close to residential areas, public roads, or pipelines is possible. Reduced amount of work for permission and documentation of explosives. Improved slope stability, and thus less rock fall. No oversize rock handling caused by poor blasting. Higher pit availability – due to no production delays and stoppages caused by blasting.

Cut, crush, and load in a single operation

Streamlining the mining operation. Simplification of production planning. Simplification of administration and maintenance. Higher pit availability – due to reduced time losses in-between mining steps. Reduced number of mobile equipment and thus lower emissions and operating costs – due to reduced maintenance, health and safety equipment, personnel, and fuel. Lower mining unit costs (US$/t). Potentially saving the primary crushing stage.

Reduced haulage costs

reation of smooth and levelled surfaces. C Smaller on-highway trucks can be used.

educed haul road maintenance. R Smooth surfaces allow for faster haulage. Less wear and tear on truck tyres. Smooth and consistent loading operation. Less wear and tear on truck bodies, frame, suspension, and tyres. Loading consistent to design payload.

Maximum reserve extraction

Improved deposit exploitation, improved stripping ratio, and increased reserve base due to: Increased slope stability and higher slope angle. Buffer/safety zones can be mined additionally. Additionally mined thin seams.

Conventional opencast mining vs use of surface miners

In addition to blasting operations, the most significant environmental effects of opencast mining are due to the use of a whole variety of different machines. Reducing the number of machines deployed leads to lower carbon dioxide (CO2) emissions. Studies and tests have been conducted at a number of opencast coal mining sites over a period of several years. Comparisons with conventional opencast mining show that the use of surface miners is accompanied by a significant reduction

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in the amount of equipment usually required. They can cut, crush, and load materials in a single operation and, in some cases, can even eliminate the need of the primary crushing stage. On average, a Wirtgen 4200 SM, for example, can reduce the number of machines otherwise required for conventional mining by 65%. At the mines in question, the average fuel consumption of the machine fleets was reduced by around 50% and, in some cases, the resulting fuel savings were even more significant. In view of this, the use of surface miners is a relatively simple solution for reducing CO2 emissions and achieving emission reduction targets while maintaining the same production rate.

Surface miners in use around the globe

In the course of time, more than 600 Wirtgen Surface Miners have been deployed in a wide range of mining scenarios. Of these, almost 200 are used for coal mining.

Case study: Talcher, India

Bhubaneswari Coal Mines Ltd (BCML) has been mining coal near the town of Talcher in the Indian state of Odisha since the 1990s. Mining operations at the Bhubaneswari coal mine are conducted 24 hours a day to constantly supply the nearby coal-fired power stations with the fuel they need for

Figure 4. When working in windrowing mode, the cut material is deposited directly behind the machine.

Figure 5. Direct loading onto trucks is usually the most economical method if the material is to be transported over distances of more than approximately 250 m.

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generating electricity. The opencast mine has an output of 25 million tpy of coal with an unconfined compressive strength of up to 35 MPa. The use of surface miners eliminates the need for drilling and blasting, as well as offering further advantages. It increases the safety in the opencast mine by eliminating the need for storing and handling explosives; improved slope stability and a lower incidence of rockfalls also contribute to greater safety. Surface miner technology also allows for uninterrupted mining, as the mine no longer needs to be closed while blasting is in progress. In addition, it eliminates the time and effort required for obtaining blasting permits and the laborious documentation this entails. In Talcher, the coal is mined using the windrowing method, which means that the machine can work continuously without having to wait for transport vehicles.

Case study: Farmington, USA

In Farmington, a 4200 SMi Surface Miner has replaced the three mining machines previously used at the mine and enables a noticeable reduction of noise, dust, and exhaust gas emissions. In contrast to the crawler dozers and wheeled loaders, which created considerable amounts of dust, the dust generated by the surface miner in the cutting process is captured and bound by an integrated water spray system. A comparative analysis of the two mining methods also reveals that the fuel consumption when working with surface miners is approximately 80% lower than it was with the previously used method. The lower number of machines deployed at the mine also has a positive effect on risk management, as fewer machines mitigate the risk of accidents in the mine. In Farmington, the surface miner mines up to 2300 tph of coal and, in addition to the positive aspects mentioned above, reduces the overall mining costs per tonne by 60%.

Conclusion

Surface miners, such as the Wirtgen Surface Miner portfolio, can help offer solutions for every application. For example, the company’s portfolio all have the central drum design in common, where the cutting drum unit is located centrally under the machine, resulting in optimum weight distribution. As a result, the machine’s weight force can be used optimally for the cutting process. No other concept offers comparable results when mining rock with a rotating cutting drum. Surface miners are used for mining coal and a wide variety of raw materials. Whether small quantities in small opencast mines in confined spaces, continuous operation in large opencast mines with several machines, or for routing work and large infrastructure projects, a surface miner can help operations reduce exhaust gas emissions and make coal mining more environmentally responsible.

In part two of a two-part article, Dr Andrew Vince, Elsa Consulting Group, Australia, explores a potential future threat to the magic of coal preparation plants.

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he first part of this two-part article, published in Issue 2 2021 of World Coal, discussed how the ‘magic’ of coal preparation plants (CPP)s can obtain money for ‘nothing’ through incremental accounting, incremental ash equalisation (IAE) and near gravity capture. It was concluded that CPPs incur small relative costs, and yet enable high prices to be obtained for saleable coal. In addition, it was also found that they enable highly leveraged incremental accounting practices to be utilised, whilst also affording significant yield increases via straightforward operational setting optimisation, which can include significant near gravity capture, to obtain money for ‘nothing’. Whilst the three concepts discussed in the first article (incremental accounting, IAE, and near gravity capture) are applicable to all CPP operations, the magnitude of the effects is largest for situations mainly relating to the production of low (~ 10%) ash coal. This is because of the location of the highest peaks on the associated washability histogram chart (Figure 1 and 2). For coking coal and coal which is suitable for pulverised coal injection (PCI) in blast furnaces,1 separations in Australia typically occur with cut points in the 1.40 – 1.45 RD range (indicated by Figure 1 and 2); the proportion of near gravity material is, also typically, very high.

Impending potential market threat from hydrogen blast furnace concept

Towards the end of 2019, significant advances in blast furnace technology for the commercial production of iron, the precursor of steel, were announced.2 These are possibly significant to the market for metallurgical coal, with the potential to reduce demand for PCI coal in the short term, and possibly coking coal in the longer term. In brief, blast furnaces produce molten iron (Fe) from iron ore (as haematite [Fe2O3] or as magnetite [Fe3O4]) by using

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a horizontal layered packed bed, typically comprising alternate layers of lump iron ore, coarse screened coke, flux (e.g. coarse limestone lump), and agglomerated fines.3,4 As the name suggests, the process is sustained by blasting hot air through the packed bed which consumes the bed. The bed is replaced, batchwise, with feed at the top of the blast furnace. This is shown diagrammatically in Figure 3. In very simplistic terms, the iron ore is reduced to iron by reaction with carbon in the coke and PCI: 2Fe2O3 + 3C = 4Fe + 3CO2 or Fe3O4 + 2C = 3Fe + 2CO2

Figure 1. Mass percent of material between ±0.10 units of RD of consideration.

Figure 2. Yield washability histogram.

Figure 3. Diagram of iron blast furnace alternating coke, iron ore, flux and agglomerated fines layers (after GEERDES, M., et al.3).

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Carbon enables the oxygen to be removed from the ore via the formation of carbon dioxide (CO2). The alternate approach – to replace the use of carbon based reductants with hydrogen – has major apparent ecological/greenhouse and process simplification benefits. Along with eliminating CO2 production, there is also a benefit from removing the use and cost of coke oven and pulverising plants. With hydrogen, reduction of iron ore occurs via chemical reactions, without involving carbon in any form. In very simplified terms: Fe2O3 + 3H2 = 2Fe + 3H2O or Fe3O4 + 4H2 = 3Fe + 4H2O The by-product from both of these reactions is water. Another major synergy of the hydrogen blast furnace technology is that, in concept at least, the application would use pre-existing major blast furnace capital items. Such an outcome would be very economically synergistic, thus there is no surprise that development in this area is advancing quickly and involving large organisations, including: thyssenkrupp, SSAB, and AcelorMittal. This threat to the metallurgical coal market seems to have been lost in the simultaneous emergence of the global COVID-19 pandemic. The threats do have major implications to the metallurgical coal market. Namely, that existing blast furnace technology can be used by replacing all/some of PCI coal with hydrogen. There are obvious extensions to prime reduction of iron ore (haematite or magnetite) with hydrogen, where there are other technical barriers to be overcome. The net effect is the removal of the oxygen not as CO2, as is achieved when using coke, but as water (H2O). The implication to the topics described in this article, and the first in this two-part series, is that the reduction in the market for low ash PCI and coking coal could lead to an inevitable demand increase in alternative markets, such as thermal coal. This would mean that the need to operate CPPs at low separation RDs would diminish, as it would likely make better economic sense to produce thermal coal. Producing thermal coal simply involves increasing the cut points used in CPPs. As can be seen from the data shown in Figure 1 and 2, this would have the effect of not only increasing yield, but also moving the separations to areas of low near gravity levels. In short, the operation of a CPP producing thermal coal at high cut points is simpler and much less technically demanding than operating with low cut points. A major consequence of this is the virtual elimination of the magical characteristics of significant benefits of the presence of near gravity capture, and the concurrent benefit reduction from IAE. However, the

benefits of incremental accounting will remain. The need for highly metallurgically efficient coal preparation plant operations would be significantly diminished.

Concluding remarks

Exploitation of the money for ‘nothing’ concept of incremental accounting, IAE, and near gravity material capture of coal preparation provides for significantly high returns to any coal mining operation. Overall, mine site profits are highly leveraged to yield to the extent that any small yield improvement creates profits like magic. For parallel streamed plants, equalising incremental ash has been well known to be an imperative to maximising yield. When undertaken with a raw coal that exhibits high levels of near gravity the benefits are considerably magnified. However, as the knife cuts both ways, it is essential that CPP yield is constantly maximised and attention in this area by operational personnel will be handsomely rewarded by higher profits. When this happens, it is truly magical. Whilst the competing blast furnace technologies under development provide major threats to the existing market for low ash metallurgical coals, the higher ash coal markets would likely remain. These involve naturally separating in areas of low near gravity, and so are less sensitive to any plant inefficiencies, and there would be little opportunity to capture further near gravity material. If these threats from hydrogen blast furnace

technology are realised, only the benefits from incremental accounting and IAE would remain. This is because low ash (~ 10%) specifications for coal would be replaced by those more typical of thermal coal (> ~ 20% ash). Such higher ash targets render CPPs much easier to operate and far less sensitive to the negative yield impact of any decreased metallurgical processing efficiencies. Whilst this discussion has been based on neglecting imperfections in unit operations, the concepts are valid and therefore real. It does appear magical that seemingly real money for nothing is created by CPPs, when money matters are viewed from an incremental basis. This aspect of the magic will likely remain if the looming threat of the hydrogen blast furnace manifests itself on the metallurgical market, but it is considered that the magic described via IAE and near gravity capture would be significantly reduced.

References

1. ISHII, K., Advanced pulverized coal injection technology and blast furnace operation, (2000). 2. ‘World first in Duisburg as NRW economics minister Pinkwart launches tests at thyssenkrupp into blast furnace use of hydrogen,’ thyssenkrupp, www.thyssenkrupp.com/en/newsroom/press-releases/ world-first-in-duisburg-as-nrw-economics-minister-pinkwart-launchestests-at-thyssenkrupp-into-blast-furnace-use-of-hydrogen-17280.html [accessed 8 January 2021]. 3. GEERDES, M., CHAIGNEAU, R., KURUNOV, I., LINGIARDI, O. and RICKETTS, J., Modern blast furnace iron making, 3rd ed., (2015). 4. BISWAS, A. K., Principles of blast furnace iron making, (1981).

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Todd Swinderman, Emeritus/Martin Engineering, USA, examines how fugitive material can be managed in order to improve safety in the workplace and dramatically reduce the cost of operation.

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ost conveyors have some amount of material loss from spillage, leakage, dust and carryback emissions, collectively called fugitive materials. The loss can range from 3% of the cargo for poorly operated and maintained systems to less than 0.1% for world-class operations. The lost material manifests itself as degraded component life, resulting in workers being exposed to hazards and reduced product quality. While fugitive materials cannot be totally eliminated from bulk material handling conveyors, the problem can be managed. The root causes are often obvious, but rarely addressed. Rather, the standard approach is to treat the symptoms. The symptoms of a failure to control fugitive materials include: Unplanned downtime. Excessive cleaning costs. Regulatory actions. Poor public relations. Safety incidents. Addressing these symptoms with workable long-term root cause solutions will improve availability, housekeeping, safety, and company cash flow.

Types of fugitive material

The nature of fugitive material problems from any conveyor is indicated by the location and particle sizes of the accumulations. Fugitive materials are generally categorised into: spillage, leakage, dust, and carryback.

Spillage

Spillage is cargo that escapes the belt, accumulating on either side of the conveyor and characterised by a range of particle sizes similar to the cargo. Piles of spillage can accumulate quite rapidly and can occur intermittently from plugged chutes, overloaded belts and mistracking, or continuously from poorly designed or inadequately maintained transfer points. Inclined loading zones can also have material roll backward, causing spillage out the back of the transfer point.

Leakage

Leakage of bulk material can happen from worn skirtboard wear liners and seals or gaps in chutes and hoppers. Leakage tends to slowly accumulate in piles of small, mostly uniform particles created by the dimensions of the leak. Leakage frequently falls from overhead and collects on top of transfer points and equipment below, so its source may not be obvious.

Dust

Dust is the fine particles, usually less than the diameter of a human hair, that are created during processing and the degrading action as the bulk material moves through a conveyor system. Fine airborne dust is emitted at locations where the cargo becomes airborne and is emitted from open inspection doors, missing covers, worn skirtboard seals, and the exit of transfers. Because dust particles are very small, when dry they are easily dispersed by wind and blanket wide areas, but the sources are often visually obvious. In processing involving hot materials, the fumes given off often saturate dust particles and cause them to build up inside chutes and on equipment.

Carryback

Carryback is fine material that sticks to the belt surface or becomes lodged in the cracks and crevices of the carrying side of the belt. Carryback material collects on components that the carrying side of the belt touches and eventually dries out, dropping beneath the system along the return path. Carryback accumulations tend to range from pyramid shaped piles of dry dust particles to puddles of muck. In severe cases, large chips of material form thick layers of buildup on return rollers and are thrown off of return rollers as they dry and break up.

Issues created by design

Bulk material handling projects are often capital projects because of the significant cost and the expected life of the equipment. Control of fugitive material requires attention to detail in the design stage that is often not considered.

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Figure 1. Spillage from transfer point causing slip, trip, and fall hazard.

Figure 2. Crusher dust containing silica.

Figure 3. Transfer point designed for fugitive material control, with three dust curtains maintained close to the cargo.

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This is as a result of the additional design time (capital cost) required and the perception that fugitive material control costs are hard to quantify, and therefore hard to justify design improvements. In new projects, careful thought must be given to capacity calculations, the angle of incline, transfer point design, and access for cleaning and maintenance. To improve fugitive material control, it is advisable to derate the capacity to 80 – 90% of the theoretical capacity and use slower belt speeds. A common spillage problem is created during rainy periods when the angle of incline is appropriate for dry cargo, but not for wet material. Loading at less than a 5˚angle and reducing the angle of incline will reduce flooding and material rollback at the tail. Designing a skirtboard enclosure that is longer and taller, with the proper number and placement of dust curtains, will help control dust emissions. Designing access for cleaning and maintenance can shorten downtime for these activities by 33%, and can significantly reduce exposure to hazards that can result in safety incidents. If future capacity increases are likely, they should be planned for in the initial design. In most cases, adding 10% to the design time of a project will allow for these details to be designed into the project, with little impact on the overall equipment cost, but a huge return on the investment over time. Quite often existing conveyor systems are ‘upgraded’ to increase capacity or handle alternate bulk materials. An upgrade is often actually a downgrade, because control of increased fugitive emissions was not considered in the upgrade plans and short cuts taken in the original design have left minimal space for changes. A common ‘upgrade’ is to increase the speed of the belt. Fugitive material problems are roughly proportional to the speed of the conveyor (or tonnage), so if the belt speed is doubled, the fugitive material problem and costs may also double. In addition, an upgrade often results in less capacity, rather than more, because of changed material trajectories resulting in chute plugging and increased wear, both requiring increased downtime or reduced throughput to keep running.

Issues created by fugitive material

Because of the large number of variables in handling bulk materials – both in the bulk materials themselves and in the condition of the conveyors – it is physically, financially, and statistically impossible to reduce fugitive emissions to zero over a long period of time. Accumulations of fugitive materials are often an indication of an underlying culture of ‘production first’. In this environment, frequent cleaning is an accepted necessity to keep production running. Many safety incidents occur during cleaning and many fatalities have occurred trying to clean with the conveyor operating: piles of spillage on waking surfaces present slip, trip, and fall hazards; accumulations of carryback and buildup that falls when cleaning a chute, or spillage of cargo from overhead conveyors, can increase the risk of blunt trauma or crushing hazards; safety incidents range

from minor first aid to lost-time cases; a common lost-time event is a muscular skeletal injury manifested as a back or shoulder injury. These sprains and strains are often hard to diagnose and on average result in a multi-week recovery. Control of fugitive materials to the point where cleaning is seen as a periodic housekeeping task rather than a daily production-enabling strategy should be the goal. The need to clean to keep running is one obvious cause of unplanned downtime. Another less obvious productivity thief is the large role fugitive materials play in reducing equipment life, which leads to more frequent outages for maintenance than necessary. Idler bearings are particularly susceptible to contamination from dust. Material escaping under the wear liners and skirtboard seals leads to shorter belt life, due to belt grooving under the seals. The belt (because of its total mass) and idlers (because of their numbers) are expensive and time consuming to replace. There are additional hidden costs that are often overlooked when justifying improvements to control fugitive materials. Working in a dusty atmosphere reduces worker productivity, in some studies as much as 20%, if respirators must be worn. The leading cause of death in industry is from disease, not accident. Respiratory illness from exposure to even nuisance dust often leads to workers being put on long-term disability, increasing worker compensation costs. A dirty operation also attracts the attention of regulators and neighbours. A reputation as a dirty place to work reduces the pool of employees

who are willing to work in such an environment, and those already employed often suffer from low morale. Fugitive materials are often a root cause of catastrophic events. Many dusts present fire and explosion risks, in addition to health and safety concerns. The destructive power of dust explosions is well documented in industries such as coal mining, grain processing, and sugar production. Static discharge into a dusty atmosphere is a common cause of many of these fires and explosions. What is often harder to detect is the chain of events that led up to a conveyor belt fire. In many cases, a frozen idler bearing is the heat source that ignites the grease, in turn causing the belt to catch fire. In other cases, mistracking belts caused by spillage or carryback built up on pulleys creates friction between the belt and structure that can actually cut steel beams in two, or create enough heat to become an ignition source. Friction is another common root cause of major incidents.

Detecting and measuring fugitive materials

Indirectly, safety switches and conveyor parameter sensors create data outputs from problems created by fugitive materials, and thus can provide some measurement or indication of problems to come. In many operations, acceptable fugitive material control performance means keeping the emissions to a level that allows cleaning or maintenance during scheduled routine production outages or maintenance time. Through good design techniques, well trained operators and

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predictive maintenance practices, most conveyor systems can go weeks without a need to shut down just for cleaning, without causing a safety problem or significant production loss. The application of indicators – such as belt wander switches, zero speed switches, and plugged chute detectors – has been practiced for as long as there have been conveyors. These devices are often purposely defeated due to false trips or other signals that

Figure 4. Buildup causes belt mistracking, which leads to belt and structural damage and a potential safety incident.

interrupt production. The bulk material handling industry is starting to adapt sensor technology to the rigors of bulk material handling to better monitor conveyor performance and provide proactive warnings of problems that are developing. For example, wireless technology can gather data from numerous sensors without the need for hard wiring, and fibre optics are being used to detect heat rise in idler bearings. Many conveyor components that were simply considered ‘dumb’ brute force devices, such as belt cleaners, are now being remotely monitored and controlled to improve cleaning effectiveness and provide indications of malfunction. In new designs, case study data can be used to estimate the potential size of the fugitive material problem and costs associated with not addressing the issues. With existing operations, the information needed to justify improvements may at first seem difficult to quantify. In reality, as few as five independent observations of the problem can provide facts that represent the problem with a reliability of over 90%.1 While some company data or information may not be kept or readily available, there are many resources completing the picture of the costs of fugitive materials and the benefits to be derived from implementing controls.2 Measuring the amount of fugitive materials can be as easy as laying a tarp under the transfer point or conveyor return run and weighing the accumulations over a period of days. The same observation and measurement techniques can be used to judge the success or failure of mitigation efforts. There are even ways to empirically judge the extent of the problems and determine whether or not the changes are having the desired effects.3

Conclusion

Figure 5. Damaged idler roll shell because bearings failed from fugitive materials penetrating the bearing seal.

Because the problem of fugitive material has been around since conveyors first came into use, in the minds of many operators, fugitive material is merely a sign that the plant is producing – i.e. ‘We’re making money, so there’s dust and spillage.’ However, fugitive material leads to major issues that can and should be addressed. Managing fugitive material is a more economically and operationally sound choice than merely chalking it up as ‘the cost of doing business’. The effect that spillage, dust, and carryback have on an operation is a tangible reminder of unnecessary inefficiency. By working with experts, installing modern solutions to age-old conveyor problems and practicing state of the art maintenance, operators can significantly improve safety in the workplace and dramatically reduce the cost of operation.

References

Figure 6. Coal carryback accumulation causes bearing failure, which can lead to a belt fire.

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1. HUBBARD, D. W., How to Measure Anything, Finding the Value of Intangibles in Business, (2010). 2. SWINDERMAN, R. T. et al, ‘FoundationsTM: The Practical Resource For Cleaner, Safer, More Productive Dust & Material Control’, Martin Engineering, (2009), 4th edn., pp.492 – 504. 3. COSCIONE, M. P., ‘Measurement of Fugitive Material for Belt Cleaning Assessment’, ENCOM, https://www.academia. edu/30665866/Measurement_of_Fugitive_material_for_belt_ cleaning_equipment_assessment

Benoit Pluchon, Standard Industrie Singapore, discusses how product stoppages due to material build-up can be prevented.

M

aterial build-ups in the production process often lead to reduced plant productivity and higher cleaning costs, as well as increased safety risks to maintenance staff. Such issues can be avoided by undertaking measures,

including blockage and build-up removal and silo and hopper cleaning. Having developed expertise in both these areas, Standard Industrie International has helped a number of plants across the world improve their productivity; reduce cleaning

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costs and lower accident risks. Since 1978, the company has been a leading group in the engineering and manufacturing of industrial equipment specialised in the handling, storage, and transportation of bulk materials. Its solutions help improve production performance and efficiency, reduce maintenance costs and risks, and ensure a safer working environment. Among these solutions is the AIRCHOC® air cannon which, placed on silos or hoppers, acts preventively on the material inside to prevent it from clogging, as a result of regular shots. It is an economical solution that uses air only when the shots are activated. With a wide range (tank capacity from 4 – 400 l), this solution is suitable for

many sectors interacting with bulk cargo, including sectors handling coal.

Case study: Indonesia The problem

A frequently encountered problem was the blockage of two coal bunkers during the rainy season when the humidity level is very high.

Temporary solution

The client implemented the following solutions: The operators attempted to unblock the coal bunkers by using hammers and metal bars to hit the hopper at the accumulation place. Installing liners on the inside to reduce the fixation of coal on the walls.

Solution

Figure 1. Airchoc ACC3SDX dn 150 mm 100 l – ATEX zone 20.

After the problem continued to persist, four AIRCHOC ATEX devices were installed on each of the two hoppers to solve the clogging problem (Figure 1). An ATEX version was chosen in order to avoid explosion risks. A switch was also installed for each hopper at the customer’s request in order to manually start the Airchoc operations 4 – 5 times a day, sequenced by a control panel (Figure 2). This frequency of shots ensures efficient and constant cleaning of the air pipes. An air filter on each hopper was also installed to neutralise fine carbon dust. This prevents them from being deposited on the AIRCHOC mechanism and preserves air quality.

Results

Figure 2. Control panel COFS8230 with special switch (on/off) and electrical operated release device ATEX ELESDA1322.

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The customer was satisfied with the result of the installation of the air cannons, as they allowed them to cease the ‘manual’ unclogging of these two hoppers during the rainy season. AIRCHOC is thus used in many other applications. It is regularly installed on raw material storage units (sand, powders, flours, grains, wood chips, peat, straw, mulch, etc.) all around the world, and can also be found at the end of the process on fly ash or lime silos. The company’s technical teams study the clogging factors, the behaviour of the clogged product, the inclinations of the storage unit, the productivity issues, etc. This complete diagnosis allows for the establishment of an optimal installation recommendation according to the environment of use (various risks, high heat zone, corrosiveness, type of fuels burnt). The recommended solution will also consider the need for precise orientation of the shot, the number of shots, the diameter of the blow pipe according to the available pressure, the volume of the tank, and the blow pipe length.

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Silo cleaning service and safety

In case the plant faces reduced collection capacity, the use of the pneumatic GIRONET, proposed by the company will help to clean the silos and allow for the restoration of the full storage capacity. The articulated arm of the GIRONET rotates at 360˚ and eliminates the rat holing problems. This solution meets stringent safety standards – it avoids having any human presence inside silos, therefore enabling an increase in the capacity of collection, which in turns helps to avoid supply disruptions. The GIRONET is effective on any type of blockage, product or storage unit, and can be used without stopping production. In addition, declogging with the POWERNET will solve bridging problems through the safe breaking down of the clogged material to help it flow more freely. The POWERNET is used before the GIRONET when the storage unit is completely blocked.

Case Study: Bavarian power station

As an example relating to the silo cleaning activity, Standard Industrie recently carried out an intervention in a coal power station located in Bavaria. This plant contacted Standard Industrie to perform a complete cleaning of its five coal storage hoppers. The purpose of the operation was to make the hoppers safe for scaffolding and work. The cleaning technique used was the ATEX GIRONET. Build ups, as well as bridging piling up in three of a range of five coal hoppers, were reducing the flow of coal to the boiler.

To compensate for the reduction in storage capacity, it was necessary to operate with continuous discharge; this seriously affected the boiler capacity and production plans. One of the main reasons the plant decided to appoint Standard Industrie for the cleaning of the three silos was the safety factor offered by the Gironet solution – i.e. it meant no human intervention was necessary inside the silo. Cleaning operations are performed from the top of the silo, without putting people at risk inside the silo (Figure 3). Moreover, Standard Industrie offered an Atex solution in the form of its ATEX GIRONET using brass chains. No real adaptations of the hoppers needed to be made, as the cleaning GIRONET operators installed the GIRONET on existing 500 x 500 mm openings. The existing hoppers could easily support the weight of one person and the equipment. Air pressure was available so everything was here to do the job quickly and safely. After five days of interventions, the three hoppers had been cleaned, and a total of 10 t of material was extracted. The customer can now resume operation of the boiler with less risks of up and downs.

Case study: South African power station

In another power station in South Africa, the GIRONET was implemented to clean the coal build up all around the extraction. The 7 m rotating and articulated robust arm goes through the hole and gets attached to a mast which is fixed on to the structure of the bunker making the whole unit safe and secure.

Results No personnel inside the bunker means there is no risk of fatal accidents. All sections of the 36 coal bunkers can be cleaned to maintain the delivery of coal to the boilers. This solution benefits the performance of the power station globally.

Conclusion

Figure 3. The Gironet, placed on top of the silo, for safe cleaning.

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Over the years, many industries have successfully replaced manual cleaning with an air cannon. Manual cleaning unnecessarily requires qualified personnel and high levels of supervision; moreover, extra safe measures have to be taken and sometimes may lead to unplanned shutdown, which involves loss of production. This type of human intervention is both difficult and dangerous, and can cause serious or even fatal accidents. In addition, the advantages it offers include: effective declogging of the structure without interrupting the production process; elimination of the risk of feed restrictions, blockages and production downtime, proportionally to the installed equipment; increased safety of the principle; and a fast return on investment.

Rebecca Long Pyper, Dome Technology, USA, identifies the requirements needed in order to establish a successful coal storage facility.

T

he sophistication of coal storage keeps increasing. Once considered dirty and environmentally hazardous, structures are now built with tight emissions control, minimal-to-zero product interaction with the outside world, and the innovative utilisation of byproducts that used to be destined for landfills. Coal is a resilient industry that keeps adapting to stay relevant. Even as the industry sees proactive change, a few things remain the same: one of which

is that domes are well suited for coal storage. To help coal companies plan the ideal project, Dome Technology relies on a simple rule of thumb: the type of coal determines the reclaim, and the type of reclaim determines the dome shape.

Coal types and reclaim options

With sub-bituminous coal, storage and handling requirements are stringent. Based on volatility, coal companies must decide how they will maintain access to the pile for handling potential

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fires and hot spots. A doughnut-shaped pile is a good option for storing sub-bituminous coal. The pile is placed and reclaimed using a stacker reclaimer; this model allows access to the pile and can work particularly well during the cleanout, which happens every couple of weeks. A monitoring system on the inbound conveyor is another must, so that hot coal is rejected before being placed in the storage. Fugitive dust cleanup is also essential to proper storage and the avoidance of fire and explosion concerns. A kidney-shaped pile can also work well. The stacker creates a pile that tapers off on the side, and the filling arm’s swing is 230 – 250˚. This shape provides ample access to the pile, so while it might not make the most of a dome’s capacity, it does provide peace

Figure 1. A stacker reclaimer is an effective, efficient reclaim system for sub-bituminous coal.

of mind and safety when managing and monitoring a volatile product. With bituminous and lignite coal, stacking and reclaim options are expansive. From front-end loaders to a stacker reclaimer or drag chain, coal producers can be choosy, balancing low cost with sophistication. Rotary plows with cone-shaped piles are an effective reclaim option, and so are tall domes with a live-bottom floor to keep product rotating.

Reclaim options and complementary dome types

For a reclaim system to work best, the dome must be built to complement it. Sub-bituminous storage is safest within a hemispherical dome with easier hot-spot access from the inside of the storage, but the inside shape of the dome must be engineered accurately too. For instance, with a stacker reclaimer, the shell is built to account for the reclaim arm being fully extended without scraping the dome wall. Typically, the dome is built with a short stem wall and a pedestal upon which the stacker reclaimer sits. This model can leave pockets of product behind on the floor, so the dome floor is often built with a slope to ensure product can be mostly reclaimed to the tunnel hopper instead of building up in hard-to-reach spaces. Bituminous, anthracite, or lignite coal all benefit from stacker or live reclaim. When a 100% live reclaim system is selected, the dome can be taller and smaller in diameter – an ideal model for sites with less construction space. For example, a hemispheric dome with short stem walls is recommended if a stacker is selected.

Case study Every coal dome is customised, so reclaim and dome type work hand in hand. For one potential customer working with bituminous coal, Dome Technology recommended four tall domes with 80% live reclaim that feeds three below-grade tunnels and affords the ability to clean out the rest with front-end loaders. With these domes holding 60 000 t apiece, the company could achieve its intended goal of moving 4 million tpy, or approximately 76 000 tpw, as a result of a solid plan at the front end.

Dust control: The benefits of a sealed envelope

Figure 2. China Coal chose six domes for its Hulusu and Menkeqing facilities.

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A reinforced-concrete storage dome is a natural choice for companies eager to minimise environmental impact. Dust is a concern with many stored products, but it cannot escape a monolithic concrete dome since joints or seams do not exist. Inside, the truss-free interior discourages dust build up, and a host of dust-control systems exist in the marketplace to manage dust production. Automatic dust-collection systems can be designed to convey dust back into the product stream. Sealed and seamless, a dome keeps product inside and prevents interaction with the environment. This envelope is multi-layered; a dome is built using

the shotcrete method, so concrete is sprayed in place without any construction joints. On the exterior, a high-strength PVC membrane covers the entire structure. Between the membrane and the concrete, urethane foam protects the life of the structure, as well as the stored product. The PVC membrane ensures completely waterproof protection for the reinforced concrete shell and, consequently, the material stored within. A mould-resistant UV-protective resin coats both sides of the membrane, providing long-term protection from these two common sources of degradation. No other silo option offers this type of waterproof protection, and this exterior requires almost zero superficial maintenance. Domes are always built without rivets, fasteners or mechanical connections found in other storage, thus eliminating potential sources for leaks and rust. This comprehensive approach to waterproofing promises long-lasting protection for stored product and the structure itself. The double curvature of a dome provides strength at all points of the structure, even near the apex. With strength at the top, a coal company has no problem securing adequate space for dust-collection systems.

Structural strength

The dome itself can survive a disaster other types of storage might not, and will likely reward companies with insurance-premium savings. A dome has inherent strength other bulk-storage structures do not. Should an earthquake, tsunami, hurricane or tornado occur, the structure has a better chance of survival than a traditional building. In a deflagration event, a dome’s round shape channels energy out with less structural damage. Historically, square and rectangular explosion venting has been the norm in storing products prone to deflagration, but Dome Technology’s team has pioneered a round hybrid model that started to be installed on projects in 2016. Whether a pre-manufactured rectangular panel or a metal cladding piece, a squared-off panel creates a weak spot. Round panels are preferable because there are no sharp corners for stress concentration in the structure. This allows for a release of pressure, protecting the structure. The proprietary explosion vents are comprised of a circular geodesic steel lattice covered with the same PVC fabric used in the dome construction process. The panel is anchored to the dome with explosion-venting relief screws that remain secure during the design dead, live, and wind loads. But in the event of a deflagration event, the screws release the panel and allow for the release of the excessive internal pressure. The system is watertight and meets the required operational design loads. When an explosion occurs, the fabric accepts the load and transfers it uniformly around the ring’s circumference. Because it is circular, the load going to each of the fasteners can be predicted

really well. If it was rectangular, the pressure going to each fastener could be different and more difficult to estimate. Each explosion vent is unique to the project. Dome Technology’s engineering team uses discrete finite element modelling and computational fluid dynamics to model the potential explosion event, in addition to determining the amount of open area required for the blast panels, such that the pressure only gets to a certain level before fasteners release.

Case study: China

When Dome Technology CEO, Bradley Bateman, met with China Coal management, it was clear what the company wanted: a high live-reclaim system at an economical price – and good looks would not hurt either. China Coal sought storage facilities for both its Hulusu and Menkeqing coal mines, located 15 miles apart in north China’s Inner Mongolia province. Based on their ability to keep out outside moisture, a series of domes was a more economical solution than traditional silos. Moreover, in the land of the yurt, another factor was the aesthetics and the way they would look. Dust buildup is always a concern with coal storage, and China Coal takes it seriously. Since domes are built without the use of interior supports, dust build-up on trusses is not a concern. Secondary explosions – the kind caused when initial explosions shake loose accumulated coal dust – are less likely because the

Figure 3. This image shows how floor angles can assist in product reclaim. In this drawing, coal flows to three hoppers.

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support-free domes have no ledges for dust to build up on. One of the major dome advantages, and one aspect Coal China liked, is the prevention of fire, due to there being no interior shelves to collect dust. Other design features are also key to fire prevention. To render the pile of coal inert, China Coal has the ability to seal the domes at the top and bottom, in order to cut off oxygen sources and pump nitrogen inside to lower the existing oxygen level. With a thermal scanner over the belt on the inbound receiving side, infrared cameras can check the temperature of coal on the belt, in order to make sure no off-specification product enters the dome. A linear heat cable monitors for fire on the belt, as well as examining bearings in case one is throwing sparks; this cable might detect a fire travelling along the belt length before it reaches the thermal scanner. A product unique to combustion-prone materials, this system shuts down conveyance and alerts facility management of the fire. Depending on the setup, workers can either extinguish the fire, or an existing fire-suppression system takes care of the problem. In summary, today, visitors to one of China Coal’s mines will see three domes housing 60 000 t of coal each, and, in the distance, three identical domes at the

company’s other mine. An innovative material-handling system gives China Coal the ability to move product fast. Inside each dome, a full hopper system similar to a series of funnels situated side by side allows coal to flow through the structure under its own weight rather than by loader. Other design details also add value, especially since the possibility of coal self-igniting in the dome was one of China Coal’s main concerns, according to Zhao Jiapeng, China Coal. The exterior PVC membrane prevents moisture from contributing to spontaneous combustion. Secondary explosions are less likely because the domes have no ledges for dust to accumulate upon. China Coal can also render the pile of coal inert by sealing the dome and pumping nitrogen to lower the oxygen level. The project wrapped in August 2015.

Conclusion

Domes, such as those offered by Dome Technology, allow companies to build storage that meets green regulations now and into the future. The dome is an out-of-the-box, customised solution for companies hoping to grow business, while acting as a better steward of the environment.

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