Selection of viable ug technology

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SELECTION OF U NDERGROUND COAL MINING TECHNOLOGY FOR DEEP SEATED COAL DEPOSITS, VIZ; CONTINUOUS MINER, LONGWALL, OPERATIONAL & TECHNICAL PARAMETERS CONSIDERED FOR SELECTION OF CONTINUOUS MINER

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Selection of viable ug technology

  1. 1. SELECTION OF VIABLE TECHNOLOGY FOR UG COALMINES U. Siva Sankar email: uss_7@yahoo.com Back ground• The underground production in SCCL has come to the plateau at 12-13 Mt and any increase in quantum jump with present method of working and technology is looking bleak.• Added to the above Depth range is increasing – 350 to 600 m. Geological disturbances, Stress regime Gradient - 1 in 3 to 1in4 1
  2. 2. Back ground• Most important is the present cost of production with SDL and LHD is in the range of around Rs 2000 per Tonne, against the company average sales realization of around Rs 1423/ Tonne.• The recent wage hike has totally dashed hopes of viability with SDL and LHD technology. COST OF PRODUCTION FOR 2009-10 IN Rs. • LONGWALL - 1029.65 • BLASTING GALLERY - 1416.53 • CONTINUOUS MINER - 1543.04 • SDL - 1790.03 • LHD - 2068.45 • HS - 3128.40 • RH - 6723.61• The major contribution of cost of production in existing Bord & Pillar with HS/LHD/SDL is Wage component. – HS -74% – LHD-60% – SDL-62% 2
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  4. 4. OBJECTIVE• To design a suitable and viable “Method and Technology” for the available deposits keeping in view – Depth – Gradient – Geological disturbances – Low quality seams in upper horizons ISSUES• Depth – Present B&P / Rhombus shaped pillars at more than 350 m depth would not stand.• Requirement – long term stability (FoS-2)• Gradient –1 in 2.5 to 1in 4, there is limitation with working of technologies like SDL,LHD, and CM etc.• Requirement - Negotiate /suitable cross gradient or cutting the floor/ roof stone.• Geology – faults: Due to presence of faults Longwall technology is becoming non viable in present coal blocks.• Requirement- Viable LW technology (low cost) with shorter panels of length 500 -600 mtrs• Low quality seams in upper horizons-(IRR)• Requirement- ,stowing for lower seams, coal washeries 4
  5. 5. Technology selection MatrixTechnology Depth (m) Gradient CPT Geological disturbances Upto 300-600 Upto1 in Steeper 300 4/5 than 1 in 4Longwall J J J J J XSDL / LHD J x J x x JCM J J J x or J J JBM J J J x or J J J x or J indicates both options may work when floor cutting is possible INFERENCE • From the above, SDL / LHD deployment is not viable for deep and steeply inclined deposits. • The alternative Technologies – Longwall – The Low cost Longwalls, viable with even 500m to 600m length panels – continuous miner / miner bolter- The technology should be able to cut stone roof/floor to overcome cross gradient problem. • Alternative method: – As an alternative to the present Bord&Pillar / Rhombus type of development, Block development with long headings and liquidating with Fenders for stability during development and safety during depillaring. 5
  6. 6. Recommendations• Keeping in view of above parameters we can set out low cost Longwalls where, 600 to 1000m panels can be formed In other cases, where cut out distance permits and frequent movement with out damaging the floor is possible a continuous miner otherwise bolter miner is a suitable option.Operational and Technical Parameters Continuous Miner / Bolter miner Technical Parameters • Depth • Gradient • Cross Gradient • Floor Pressure or Ground Pressure • Cut out Distance • Number of Entries • Lead – Pillar Size • Angle between entries and crosscuts • Orientation of angled crosscuts 6
  7. 7. Depth• At present, the depth of working underground mines in SCCL is limited to 300m to 400m.• Most of the Extractable Reserves are lying at a depth range of 300 to 600m• Technology for faster extraction of coal seams is to be deployed to counter the problems of Ground control, Ventilation with increasing depths in order to ensure Safety and also to meet future energy requirements.• If depth exceeds 400 m, Pillar stability is major hindrance for safety in Bord & Pillar method.• To over come this, Instead of pillar formation, Block development with long headings and liquidating the same with Fenders. GradientThe limiting Gradient of Continuous Miner & Shuttle cars is 1 in 6(91/20) & 1 in 8 (70) Respectively Gradient of Coal seams vary from 1in 2.7 to 1in 8.Maximum workable seam gradient is 1 in 4 with apparent dip limited to1 in 6 due to limiting acute angle of Rhombus pillar Cross GradientWhile working on apparent dip, if floor is not competent, wheels ofshuttle cars / LHDs move on different individual horizons. This leads todamage of suspensions and breakdown of equipment.Joy Mining is offering individual suspension shuttle cars in new versionson optional basis.To overcome this, stone floor is to be cut on the rise side of the galleryto make it level. Stone cutting will lead to coal degradation during development.The limiting Cross Gradient of Continuous Miner & Shuttle cars is 1 in11.5 (50) 7
  8. 8. Continuous miner development Cutting into Floor and Roof Roof cutting forrectangular roadways Floor cutting for rectangular roadways 8
  9. 9. Gradient & Cross Gradient 9
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  12. 12. Technical Parameters - Ground Pressure Ground pressure parameter is considered 1. For with standing partition between two contiguous seams, 2. For with standing of floor coal when working on cross gradient subjects to frequent movement of machinery. The compressive strength of the coal can be taken as a least value of 2.8 MPa (406 Psi) ( I seam of KTK – 5 Incline, NIRM Report) and maximum of 22.5 MPa. Tensile strength of the coal can be taken as minimum 0.28 MPa and 2.25 Mpa as maximum for our coal seams. Where Parting thickness between working sections is less than 1/5th of the Gallery width, failure is usually in tension. The ground pressure of Continuous Miner varies from 0.11 MPa (16 Psi) to 0.22 MPa (32 Psi) Shuttle car ground pressure varies from 0.834 MPa (121 Psi) to 1.09 MPa (158 Psi) 12
  13. 13. SPECIFICATIONS OF MINER BOLTER(MB), CONTINUOUS MINER(CM)CM or MB MC ACM10/ MB250 MB430* MB 670 MB 750 350 MC 250 MB450 MC255*Cutting 1.17 – 1.80 - 1.37 – 1.80 – 3.0 – 3.80 –height 3.1 3.60 2.70 3.0* & 4.5 4.50(m) 2.10 – 3.70Cutting 3.50 2.70 4.70 4.72 4.20/6.0 6.60/7.20Width (m)Weight 60 39/44* 75 62.30 97 115(Tonnes)Ground 0.158 0.11* / - -- 0.17 0.22 0.22Pressure 0.12(MPa) SPECIFICATIONS OF SHUTTLE CARS Shuttle 1 2 3 4 5 6 car Capacity 8 11 14 14 16 20 (Tonnes) Weight 18.1 20.48 22.70 25 27.20 29.50 (Tonnes) Ground 0.85 0.97 0.94 1.0 0.96 1.09 Pressure (MPa) 1,2,3 : Low to Medium height Seams, others : Medium to high seams 13
  14. 14. Technical Parameters - Cut out Distance or Length of a cutThe maximum unsupported span of the gallery whichcan be cut with Cutting machine safely with out anyfailure of immediate roof, which may or may not besupported laterIt plays vital role in the selection of Continuous mineror Bolter miner for particular geo mining condition Mine CMRI RMR Cut out Distance (m) GDK 11A 48 12 Incline (Caving) VK7 Incline 62 15 (Non- Caving)Beniawski RMR & Bartons Q – System Approach VK-7 GDK-11 14
  15. 15. Basic Geometry of Room & Pillar Workings Twin Entry Development Layout for Longwall 15
  16. 16. Sequence of cutting in Development 2 Left 0m 15-25m Continuous Miner 1 Left Main 1 Right 2 Right “Load-Haul- Twin Boom Dumper” (LHD) Roofbolter Shuttle Machine Cars Feeder Breaker Electrical Equipment (Load Center) Entry Mechanized Room & Pillar Layout 16
  17. 17. Number of Entries When the number of entries are less, there are only a few available working faces results in delays because cyclical mining (including continuous mining). When there are many working faces available, an activity can be shifted to another location without any interruption. More entries facilitates machines to maneuver easily and quickly and shuttle cars will have different routes for loaded and empty cars, thereby reducing travel times. The more the entries, less is the air resistance. However, with too many entries, section ventilation may be difficult and prone to leakages. One disadvantage of many entries is that it slows down development and therefore, pillaring. Hence, cash flow may be small for a long time. Generally 5 entries Panels are being preferred due to Less shifting of feeder breaker optimized Lead , Production. (since any less number of entries causes congestion with bridge conveyors) LeadProduction & productivity increases with reducing leadand Vice versa. Lead mainly depends up on pillar size, so pillar sizeshould be optimized considering Ground control as wellas techno-economic analysis. It impacts the haulage cycle times (shuttle or ram car)since when one car is in an entry, others have to waituntil the entry is cleared.For larger pillars, such idle waiting times can be long. 17
  18. 18. Angle between entries and crosscutsThe angle between crosscuts and entries depends on themachinery.Bridge conveyors and ram cars, require oblique angles,while shuttle cars require perpendicular angles.In case of FCT, spillage is high when the direction of flowtakes a sharp turn Therefore, oblique angles are to be planned wherever theconveyor flow direction is expected to change. Fig. Spillage at Transfer Points Orientation of angled crosscuts Angled crosscuts should be aligned with Major Horizontal stress direction for ensuring the stability of Trunk road ways or panel galleries. 18
  19. 19. Operational Parameters• Floor Condition• Watery condition• Cables handling & Equipment Rerouting• Damage of Cables & Tyres• Bolter & Miner Compatibility• Side spalling• Floor Heaving• Fire problem• Ventilation• Quality• Roadway Maintenance• Extraction of Developed Pillars Floor condition & watery Condition The floor coal gets crushed due to frequent movement of Machinery and lead to formation of ditches, which in further leads to heightening of galleries. The Minimum required compressive strength of floor coal is 15 Mpa for movement of machinery.. With presence of water used for dust suppression (≈30 GPM) or seepage water causes slushy conditions results in skidding of shuttle cars even on stone floors. To overcome the above problems 1. Routing cars in different routes & placement of feeder breaker to facilitate unloading in three directions 2. Dinting floor on dip side to collect and divert water 19
  20. 20. Cables Handling & Equipment Rerouting• In case of electrically operated machinery, cables handling is cumbersome at the time of operation & equipment rerouting• Continuous miner cable to be handled manually & cables need to be lifted at junctions through which shuttle cars travel. Damage of Cables & Tyres• cumbersome cable handling and slushy floor conditions leading to damage of cables & tyres of shuttle cars• Foam filled tyres instead of air filled and also chains engulf to tyres to prevent the damage of tyres Bolter & Miner Compatibility• With Quadra bolter the distance between two side booms is fixed and it is not possible to use all the booms simultaneously for bolting, if the spacing between bolts is to be varied.• Bottom row of side bolting could not be done with the dual boom bolter (above 1.5 m from floor)• Mismatch of Bolter & miner leading to idling of Miner during development and also during widening of developed pillars Ventilation• For development, 1200 cu.m /min air quantity is required to facilitate comfortable working conditions.• Automatic methane monitoring system is incorporated in CM to cut off power incase of exceeding limits. 20
  21. 21. QUALITY • To overcome the gradient problem, Floor stone/coal to be made level by cutting stone in thin seams. • For cutting stone floor, Design requirement for cutting drum is different and only sandvik is offering to cut the stone up to 35 Mpa compressive strength. • This will results in to coal contamination, varies from 6% to 16% depends on seam gradient. Ground Control Problem • The success of any extraction method is depends on Cavability. • Induced blasting to be adopted where caving is not regular • Jumbo drill to be included in the CM/BM package for Induced Blasting wherever required. As a final point• Continuous miner/ Miner Bolter feasibility depends on the Geo mining parameters.• Its success depends on suitable mechanized environment at the mine.• Facilities like man riding, Good ventilation system, spares management, availability- utilization and overall maintenance adds to achieve improved performance. 21
  22. 22. ADVANTAGES OF CM/ BM• The Continuous Miner/BM can extract the coal to full seam thickness of 4.5m to 5.0m in a single lift.• Strata control problems can be minimized by avoiding blasting operations as the depth is increasing 350m and more.• It gives higher production rates.• Remote operation leads to safety.• Risk of spontaneous heating can be reduced due to faster rate of extraction.• Moderate Capital cost when compared to Longwall. Continuous miner Vs Bolter miner CM BMFloor degradation Cutting is done by Cutting is done by tractive force Hydraulic Sumping Frequent plying to facilitate bolting More floor damage Better floor conditionCut out distance Limits the applicability Eliminates the and performance problem of cut out Where cut out distance distance is more, it gives high productionStrata Immediate supporting Simultaneous cuttingmanagement is not possible and supporting possible 22
  23. 23. SOLUTION• Quality Geo-tech Information. As depths are increasing huge investments on technology, energy activity like supports , ventilation etc becomes expensive. – For a viable design quality geological information is required.• Technology suggested: – Longwall – Low cost Longwalls to work shorter panels and still viable. – Bolter miner: Bolter miner instead of continuous miner in view of cutout distance. 23

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