Longwall - The road ahead


Published on

Published in: Technology
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Longwall - The road ahead

  1. 1. Longwall Mining – The Road Ahead DLR.Prasad* Lolla Sudhakar** M. Venkat Ramana Rao*** SYNOPSIS: The gap between demand and supply is more than 50MT for the previous financial year and as per the projections of Planning commission it may increase to 260MT by end of 2011-12. Hence, bulk producing and safer technology implementation has become inevitable. In the past two decades the increased demand for coal was met by opening more number of opencast mines. With the depletion of shallow reserves its high time that most modern high productive technologies for working deeper deposits is the need of the future. The successful and proven technology for working deeper deposits world over is Longwall technology. In this race to increase the production levels, coal companies in India are planning to introduce bulk producing high tech longwalls in some of their projects. This paper attempts to deal with longwall experiences in India and various steps taken by SCCL to promote this technology in its future deep shaft projects for long term sustenance of coal mining industry. INTRODUCTION India is the third largest coal producer in the world. With hard coal reserves of around 240 billion tonnes, out of which 90 billion tonnes are proven, Indian coal offers a unique eco-friendly fuel source to domestic energy market for the next century and beyond. In World’s hard coal production scenario, 70 percent of coal comes from underground mining. Out of the total underground production 70% is contributed by mechanized longwall constituting about 50% of the total hard coal production. Scenario in India is just the reverse. Total annual coal production in India is about 340 million tonnes (m.t) out of which nearly 80% is from Opencast Mines. Coal India produces about 90% of total Indian coal production and SCCL’s share is about 10%. Coal production has to be increased by over 500 m.t in the next 15 years, Public sectors companies are expected to increase their production level by over 250 m.t by 2011-12, a gap of over 260 m.t which still remains would have to met by imports or induction of private capital. The proven technology for production and productivity all over the World is Longwall. Longwall mining in the world is moving towards increased face dimensions, least cost per tonne, higher productivity and lesser face transfer periods. The production from each face is ranging from 1 million tonnes per annum (mtpa) to 4 mtpa, though there are certain extremes of 8 mtpa. ------------------------------------------------------------------------------------------------------------------------------- * Chief General Manager, Corporate Planning, ** Additional Manager, Mech. Cell, Corporate Planning ** Under Manager, Corporate Planning THE SINGARENI COLLIEIRES COMPANY LIMITED, KOTHAGUDEM
  2. 2. The trend for the past three decades (during post nationalized period) in India of meeting the increased demand of coal by opening more number of open cast mines cannot continue indefinitely. Especially this assumes greater significance in view of the higher (Two and a Half times) Reserves/Production ratio of underground mineable reserves when compared to opencastable reserves. Environmental degradation, problems in diverting forestland may further limit the expansion of open cast mines. The increasing trend in the consumption of coal requires the construction of new mines and expansion of existing mines. The future challenges are confined not only to increase the coal production but also to increase the coal recovery, productivity, health and safety conditions and to minimize environmental disturbances resulting from the production processes. In view of long gestation period for deep underground mines it is time that appropriate strategies for meeting demand of coal from underground mines are put into operation. For bulk production of coal from underground mining, particularly at greater depths, the proven technology world over is Long wall. To compensate the diminishing production from opencast mines, longwall faces are to be planned with minimum production capability of 1 million tonnes per annum. PRESENT SCENARIO: Most of the world coal production is coming from Opencast mines as the reserves amenable for open pit mining are more compared to underground and the technology is limited with lot of constraints for extracting coal from underground. The safest and highly productive technology world over is longwall. For example in 2003-04 Australia has produced around 74MT of coal by operating 24 longwall faces and plans to produce 100MT in this financial year. World wide and also in India the reserves amenable for opencast mining may lost for few decades but the situation in SCCL is different. Most of the reserves present with in a depth of 300m are fast depleting by the operation of opencast mines and may lost with in 10 to 15 years. Hence, the future option is only to go for underground mining with safe and bulk production. Depth – Wise coal reserves of Andhra Pradesh as on 01.01.2005 in million tonnes is given below. TYPE OF DEPTH(m PROVED INDICATED INFERRED TOTAL COAL ) 0-300 5467 2229 102 7798 NON-COKING 300-600 2796 2832 553 6181 600-1200 -- 1018 1929 2947 TOTAL 0-1200 8263 6079 2584 16926 2
  3. 3. SELECTION OF TECHNOLOGY: - Since the Opencast reserves are fast depleting in SCCL, the future is only underground mining. - More method of workings like working with SDLs, LHDs, Blasting Gallery method, Longwall, etc are available to work upto a depth of 400m. - The existing huge locked up coal can be extracted by adopting the above mentioned technologies. - Except longwall in all other technologies the rate of production is comparatively low to meet the future demands. - Hence, a method of extracting developed pillars by longwall –called ‘Oblique Longwall’ can be seriously thought for implementing on a large scale. - Presently available safe and more productive method of mining beyond the depth of 300m is only longwall. Hence, SCCL is giving a serious thought on achieving the world standard production by implementing longwall in some of its future projects. LONGWALL MINING – A PROVEN TECHNOLOGY: For economic survival of the nation, not only the physical targets of coal production are to be fulfilled, but also is to be produced at competitive costs. In formulating an overall strategy on the means and measures of raising the quantum of production, a major consideration will be that of choice of technology. Longwall mining, with its accompanying advantages of higher extraction, increased safety and higher established as a mining method for coal seams of 1-5m thickness, although the initial investment for longwall mining panel is substantially higher than that for bord & pillar method. In other words this method assumes greater importance because much of high quality coal found in deeper seams can be mined out only by Longwall mining method. India was not a late starter in its approach towards this technology. Longwall mining had limited success so far. However in view of the necessity for exploiting deeper deposits and for the reasons like Demand-Supply, Reserves etc., there is no doubt that Longwall Mining will be the need of the day & future. Hence it is imperative to invite foreign collaboration into Indian mining field on a large scale and for longer period for not only producing higher outputs but also to enrich our experience so as to compete with the world standards. INDIAN LONGWALL MINING - PAST EXPERIENCES In seventies, the mining community of India at large, forced by the technological developments in the competitive oil industry, was forced to make substantial progress in terms of productivity and cost reduction. During this period there were many innovative initiatives and successful projects, which gave the required boost to the mining industry. With this tempo the industry marched forward for considerable period. It will not be out 3
  4. 4. of place to mention that during those eventful years there was overall development in all mining technologies irrespective of their contribution to the overall quantity of production. Further, sufficient thought, innovation and development took place in all direction. The longwall technology was also give the required attention along with others and ambitious projects were envisaged. Unfortunately, this tempo could not be continued as a result of exploration shallower deposits. The introduction of first mechanized powered support longwall caving face in August 1978 at Moonidih marked a major step forward in the introduction of advanced technology mining system in India coal Industry. In between 1978 to 1985, a number of first generation mechanized longwall packages were introduced in Moonidih colliery (total 3 longwall packages, first one installed in August 1978, second one in July 1980 and third one in October 1985 of Jhanjra Coal field, Seetalpur colliery (One longwall package installed in October 1982) and Dhemomain colliery (one longwall package installed in November 1982) of Raniganj Coalfield, Pathakhera colliery (One longwall package installed in September 1982) of Satpura coal basin and GDK-7/VK-7 mines of Singareni Collieries Company Limited (One longwall package in each mine, first one installed in September 1983 and the second one installed in June 1985) of Pranahita Godavari Valley Coal field. In SCCL, Longwall technology was introduced at GDK-7 Incline in 1983 and after successful completion of two faces equipment was shifted to GDK-9 Incline where the Longwall face collapsed due to inadequacy of support capacity. In GDK-11A initially 3 longwall faces have planned with 450T capacity supports, which also failed due to underrating of supports. Later in GDK-10A Incline Longwall method is introduced with increased capacity of powered supports (from 450 to 800T) where it worked successfully by producing 3.5MT of coal. First time in PVK, 2-Chinese Longwall sets are introduced to work the Top seam coal, performance of these sets are good to some extent, but effected by lot of breakdowns of Shearer and other connected machinery with poor metallurgy. In VK-7 Incline first Longwall face was introduced in 1984 with 360T capacity, in due course of time the face length is reduced to 90m 150m to suit the underrated capacity of supports. JK-5 Incline Longwall experiences are also in the similar lines with further successful experiments in working under caved goaf and working in inclined seams (1 in 3). The faces at SCCL in GDK-7 and VK-7 did well in comparison with the other faces, which experienced caving difficulties. The supports, which were underrated, got damaged. Among various designs of longwall cutter loader, the Anderson-Shearer type has been found to be the most successful. In early nineties, higher capacity longwall powered supports were provided for the faces at Churcha (seam V) in SECL, Jhanjra (RVII seam) in ECL, JK-5 (Queen seam), GDK-11A 3sets (seam-1), GDK-10A (seam-1) and PVK (Queen seam)-2sets. 4
  5. 5. Churcha longwall face, which was worked with 680T supports, yielded promising results initially but collapsed at a distance of 189m from barrier mainly due to dynamic weighting. The Jhanjra project represents a totally unique situation. The depth of mining was less than 50m in most of the panels with thickness of hard cover as low as 16m at some locales. This project, which was started in collaboration with USSR, ran into acute spares problem due to turmoil in USSR. Later determined efforts by our people made the development of indigenous spares possible. Longwall faces at Kottadih worked well with single lift extraction of 4.5m but third panel of Kottadih collapsed due to dynamic weighting and underrated supports causing three fatalities. The longwall powered supports from Dhemomain and Churcha projects were shifted to Jhanjra. The unfavorable Geo-mining condition has been the main hindrance in the success of longwall technology. This is evident from the fact that a number of longwall faces, which were planned for the working longwall, have been withdrawn. Moonidih project, Pooteki-balihari project, Balgoth project of BCCL had to be changed from Longwall and similarly longwall planned in Kaju area of CCL had to abandoned due to presence of dykes/faults etc. Barring the collapses, first at Churcha and then at Kottadih, the faces at Jhanjra, GDK-10A, JK-5 and VK-7 mines in SCCL gave consistently good results. LONGWALL TECHNOLOGY IN INDIA - THE PRESENT AND THE FUTURE For depths beyond 300m, Long wall is likely to be the main method for bulk production, and probably continuous miners will be used wherever conditions permit. Unfortunately no serious efforts has been made in respect of R&D for liquidating standing pillars which account for huge locked up reserves to the tune of about 3000 million tonnes. Maintaining these workings itself involves high cost in addition to losses due to deterioration, fires and safety problems. Present method of extraction of these reserves particularly in multi-seam workings by stowing is a slow process and the availability of sand is not assured in many coal-mining areas. There is an urgent need for planning liquidation of these reserves by mechanized methods. It is possible to use Longwall at many such places but the same needs determined effort and major policy decisions. There is a need to look objectively in order to avoid earlier mistakes from recurring. With the likely reduction of contribution from Open cast and the more or less stagnant production from Underground mining by Conventional methods, it is time that an impetus is given to boost Long wall Technology to able to meet the future energy needs of the country. Though the first fully mechanized Long wall face was commissioned in India in 1978 in Moonidih Colliery and more long wall sets came up in CIL and SCCL, Long wall mining has not really taken off in India, barring a few exceptions of moderately 5
  6. 6. successful faces (in range of 2500 to 3000 t/day). Even the one’s which have comparatively performed better have not proved economically viable beyond second/third year of operation due to variety of reasons. In retrospect it appears that the Longwall technology in India has neither been accepted nor rejected. In all the forums and discussions at various levels it is accepted that longwall technology needs to be pushed forward vigorously. There is a consensus also that time is running out and unless immediate steps are taken coal industry may be facing a serious problem because the gestation period in underground projects is quite long. Something more than seminars, discussions, forming committees need to be done. In the present public sector scenario longwall is difficult to work economically as is the case with most of the underground mining, yet there is no alternative to longwall on long term, if coal is to be produced from underground. On the positive side, coal companies have now gained sufficient experiences right from senior executive level to front line workforce to be able to plan, execute and work longwall faces. What are required are policy decisions and logistics. It is obvious that with the high cost of imported equipment and irregular supply of critical spares, without large blocks of coal identified for longwall, hesitation to make investment in view of its limited economic success has resulted in slow pace of longwall. The reasons for failure are not due to any deficiency in the technology but due to comparison of the economics with the opencast providing short-term cheap alternative. Yet the fact remains that beyond 300mts depth, Longwall method of mining will remain predominant method of work and it is better that solution are sought now. LONGWALL TECHNOLOGY- REASONS FOR SLOW PROGRESS  Large expansion in open cast mining in the past two decades provided cheaper and safe method for bulk coal production and as a result long wall had to take back seat.  Clear strategies were not pursued for its sustenance as there was mixed results from long wall in the early years of its introduction.  Longwalls were introduced mostly in the blocks left over by working bord and pillar method. Clean and extensive blocks have not been identified. Even the smaller blocks, which were identified, were of inferior grade coal.  Lack of proper planning in regard to longer length of panels and face lengths.  Inadequate geological information & too many geological surprises resulting in shorter panels.  Selection of inadequate capacity Powered roof supports. 6
  7. 7.  Longwall had to co-exist with the conventional mining in most of the mines, which caused management problems.  There were deficiencies in the spares management. Most of the spares had to be imported and the supplies were not reaching in time.  Coal companies were sensitive to the failures of a few long wall faces and were not prepared to risk huge investments.  Development of Longwall panels could not keep pace with the extraction of Longwall panels. Reasons for slow progress are delay in dip development & roadway development which affected the performance.  Mindset among the persons handling Longwalls regarding achievable capacity per Longwall face.  Indigenization of spares require improvement in quality particularly Metallurgy, fluid couplings and seals.  Inadequate training to technicians and operational persons for maintenance & operation in the face. In spite of Long wall not having achieved any great success yet the cost of production in Long wall taken alone, safety and productivity are in favour of Long wall than any other underground method. The accident statistics reveal that the fatality rate for million tonnes of coal produced by Longwall is comparable to that of opencast. LONGWALL IN SCCL- FUTURE 1. As per SCCL experience in Longwall technology, most of the faces were produced coal to the satisfactory levels during the initial two to three years only, after that the production levels reduced because of improper planning for development of new panels, non availability of spares in time. 2. Indigenous development of powered roof support is being taken up by APHMEL in collaboration with SCCL. All the cyclic tests except for overload test were completed successfully. Problem is with non availability of required steel in India for structural fabrication. 3. On successful completion of support at APHMEL, they can be utilized initially for a production of 1 million tonnes per face or for extraction of pillars by Longwall. 4. After a thorough study of all the worked Longwall panels of SCCL, a conclusion has made that during the initial periods high production is achieved due to the 7
  8. 8. technical assistance provided by the countries which are in collaboration with the project and the equipment was also in good condition. Basing on this and to achieve world standard production levels (about 2MT/year), SCCL plans to introduce the new Longwalls on Risk gain sharing concept for a period of 7 years. Hence most of future Longwall projects with virgin blocks are proposed to be offered on sharing of risk/gain basis. 5. The bidder is required to conduct all the geological studies required for implementation of Longwall with world standards. 6. The successful bidder has to bring the Longwall equipment on cost basis and install in the faces provided by SCCL and produce the coal at the targeted levels i.e. 2MT per annum per face. 7. Total maintenance of the equipment and technical assistance are to be provided by the bidder and to guide the operation. 8. SCCL, initially wants to implement the Longwall technology in the following 4 blocks on sharing Risk gain. a. Adriyala Shaft Project b. Jallarama Shaft Project c. Kakatiya Longwall Project (KTK-8&8A) d. Peddampeta Shaft Project 9. The Bhoopalpalli coalfields (KTK-8 & 8A Blocks) of SCCL are steeply inclined where it is proposed to introduce Longwall technology as here is no other safe method of extraction is possible. 10.In this connection a Vendor meet was organized by SCCL with various manufacturing, scientific and coal producing company’s present world over to design tender conditions. 11.The contract envisages that, the successful bidder shall produce 2MT of coal per annum per face and the period of contract is for 7 years. 12.SCCL is planning to extract the standing pillars by ‘Oblique longwall method’ in one of its mines and after the success of the same will implement in few other mines. CONCLUSION 8
  9. 9. 1. Decision-making persons are not conversant with Longwall is one of the factors for poor performance of Longwall in the past. 2. Improper Maintenance, indegenisation of Spares with inadequate expertise are one of the reasons for low production. 3. Adequate Support Calculations and implementation of Rapid face advance are essential for the LW success. 4. Indigenization of total Longwall equipment will definitely add to the introduction of more number of Longwall faces in India. 5. Foreign participation is required for extraction of thin seams and steeply inclined seams. This may be adopted as joint venture participation with country having such expertise. 6. Indian experience in Longwall is to be improved from this new concept (Risk gain sharing concept) by inviting foreign collaboration in new projects so as to make other projects to compete with world production levels. 7. Abnormal delay in preparation of Longwall panels to match with extraction rate due to non availability of roadway development equipment with proper bolting arrangement. 8. It is high time to provide infrastructure required to manufacture Longwall package from both the world reputed manufactures with assured market of three packages to each on compatibility basis for bringing down he cost of Longwall package or to provide custom duty exemption so as to make it economically viable. 9. Concerted efforts are required by the DGMS, policy makers, Coal companies and manufacturers to translate the ideas into concrete action and reap the benefits of Longwall Technology in the years to come. ACKNOWLEDGEMENT The views expressed are those of the authors and should not be attributed to Singareni Collieries. Nor do any of the conclusions represent the official policy of Singareni Collieries or it’s Directors or the country they represent. REFERENCES 1. Anwar Ahmed, EE (E&M), CMTM, March 2003, a Technical paper on “Challenges before coal industry & strategies ahead (Balrampur Longwall Experience)”. 2. Mukunda Reddy, CGM, SCCL, Indo-polish working group, a Technical paper on “Technological options for future coal mining – A review”. 3. “Compendium on Experiences of Longwall Technology”, SCCL, June 2002. 4. CL.Hanjura, D.Suresh, L.Sudhakar, SCCL, MMF, December 2002., a Technical paper on “Longwall technology – the need for promotion”. 9
  10. 10. 10