What is HIGHWALL MiningMining Coal from a visible, horizontal or inclined coal seam, making rectangular, parallel, unsupported entries, with unmanned cutter head and coal transport system, which is remotely controlled from a mining unit positioned outside the drive, in front of highwall.
When to Highwall Mining• When economic strip limits are reached.• When strip limits are reached by surface conditions.• Extend operational life of mine• Transition from surface mining to underground mining• Specific Highwall Mining situations Contour Mining Open Cast Mining Trench Mining Augered seams
Advantage of Highwall MiningCOST : Highwall mining is clearly cheaper, due to the lowerestablishment and development costs. No in-seam support ortransport systems are required, the cost of ventilation measuresis negligible and the capital cost is a fraction of that of alongwall.FLEXIBILTY : Highwall mining can economically access smallerblocks of coal and is more readily able to avoid geologicalstructures or other impediments to production. The mobility ofthe highwall mining equipment makes it easy to move around apit, from pit to pit or from mine to mine.
Advantage of Highwall MiningAPPLICABILITY : Because it operates by remote control, highwallmining equipment can work in thin seams without having to cutstone to make height for people to move around, or it canselectively extract a high-quality segment of a seam. Theequipment can operate on steeper dips than miners and shuttlecars, and can mine multiple seams without subsidence.SAFETY : Remotely controlled operations, so all personnelremain outside the entries & therefore not exposed tounderground hazards such as roof falls, gas, dust, irrespirableatmospheres, flooding, vehicle movements in confinedspaces, etc. With the use of ventilation or inert gas, highwallmining can continue in gassy seam conditions that would stop orimpede underground mining.
Production & ProductivityPRODUCTION : Modern highwall mining equipment operate inseam heights of 0.76 meter to 3.05 meter in one pass and seamdips of up to 12 degrees. Coal production per machine rangesfrom 0.5 million tons per year for low seams to 1.5 million tonsper year for high seams, in a continuous operation.PRODUCTIVITY : Highwall mining requires fewer personnel canproduce 1.5 million tonne pa, compared to around 90 people (3shifts) to get the same output from an underground mine.When factoring the lower capital and labour costs of highwallmining, the cost per tonne is much less than undergroundmining.
Requirement for Highwall Mining Competent coal. Competent immediate overburden. If overburden is not competent, coal may be left as roof. Coal seams dipping from -12 to + 5 degrees. Relative flat seams, no faults Coal seams thicker than 80cm.
Web and Barrier Pillars Web pillars ensure support of OB Barrier pillars prevent cascading collapse Barrier pillar typically every 10 to 20 drives Calculation method to be approved by local Mine Safety Authorities. WEB PILLAR BARRIER PILLAR
Cycle of Operation• Seam is penetrated by a Continuous Miner propelled by a Hydraulic Pushbeam Transfer Mechanism (PTM).• Cycle includes pushing forward, raising and lowering of the Cutter head boom to cut entire length of coal.• Pushbeams of 6 m is placed between the cutter head and power head as depth of penetration increases.• Using Video imaging and gamma detector, the Cutter head moves inside the seam and cuts only coal.• All functioning is controlled from a touch screen panel located in operators cabin.
Safety Consideration• Highwall Hazard- Resulting from crushing of Pillar or Failures associated with insitu structures.- Avoided by developing 2 Zones i.e. General Safety Zone and Vertical Drop Zone.
Safety Consideration• Roof Span Collapse Hazard- Successful and Safe Operation can be Achieved with Rapid Entry and Retraction. Otherwise HM Could Readily be Buried in Rock.• Explosion Hazards- To Minimize the Explosion FLP enclosure of Machinery and Instrumentation Entering the Highwall Drives. Methane Monitoring Equipments Installed.
Key Features Penetration upto 300 meters Dip +5 to -12 degrees Production up to 120,000 t / month Up to 75% seam recovery Operates with a 4 / 5 man crew per shift Personnel safety Low establish cost Lower production cost than underground No external contamination or product dilution.
DIMENSIONSLength base : 16.6 mWidth base : 8.3 mWeight miner : 225 tLength of push Beam : 6 mWeight of push beam : 5150 kg50 push beams per minerMax. Push Force:in: 136 t : out: 276 t
Cutter Head Low Seam Cutter Module Seam height : 75 cm to 1.50 m Width : 2.90 mHigh Seam Cutter ModuleSeam height : 1.20 m to 3.05 mWidth : 3.50 m
Push BeamPush beams are 6 m long , rectangular , reinforced steel boxstructures joined together to form a string, which connects thehighwall mining system to the cutter assembly.The push beam string is the backbone of the machine; pushingand pulling the cutter module in and out of the highwall withretract forces up to 363 tonnes (400 tons) at 345 bars. The push beams also transport mined coal and support the hosechain that supplies control and power to the cutter.Moving coal inside the push beam (via a pair of screw conveyors)protects the coal from contamination and the movingmechanical parts from rock debris, resulting in higheravailability.
Reel & Chain Power chain for cutter module o Electrical cables o Hydraulic lines o Cooling water lines o Methane sensor cable o Control cables Hoses / cabling protected by steel plating Auto unwinds/winds in trough on push beams > 300 m
Anchoring System Stabilizes the Highwall Miner Two Machine mounted drills Two high strength 2.5 m pins
Controls Operated from the cabin Fully graphical touch screen interface Automated mining mode Automatic seam following: o Cutter motor current o Gamma Ray Sensor (Optional) All machine diagnostics Accurate heading: o Precise alignment o FOG (fiber optic gyro) guided steering (Optional)
Generator By the grid via a transformer 1500 kW Generator Set 80 kW auxiliary set Build in a sound attenuated 20 ft container Mounted on tracks Tropical / Arctic version
Tracks• 4 Hydraulically powered tracks articulate 90 degrees for straight and cross travel• Circle mode for accurate heading• Each track 1 meter vertical movement for adjusting seam dip and floor contour• Turning of each track is achieved automatically
Mobility For quick relocation over long distances, the highwall mining system can be taken apart in modules. Rapid disassembly and reassembly is facilitated by convenient hydraulic and electrical connectors All modules are sized for transport using regular public roads Tracks for positioning in the mine, relative short distances. Longer distances on heavy weight special transport low loader.
Safety Features Elevated cab with cameras Above-ground operation Small-crew size for its operation Remote operation Anchoring system Continuous monitoring of the methane by DGMS approved methane Sensors Intrinsically safe & fail safe in design Methane sensor device interlocked with PLC control system
Protection Against Methane Continuous monitoring of the methane by DGMS approved methane Sensors Intrinsically safe & fail safe in design Methane sensor device interlocked with PLC control system Power to UG will be “ON” only if: The Methane sensor is “ON” & Working properly Methane level is below 1.25% When Methane level: =0.8% - Operator get audio-visual alarm >1.25% - U/G part of the machine will be powered “OFF
Optional Features of HM Push beam holding device for operation in seams dipping in access of 8 degrees Water pump on cutter module for operation in seams with ingress of big volumes of water. Inert gas system for operation in gaseous seams. Arctic and Tropical execution of the miner / genet. Second air-conditioned cabin for personnel working on push beam launch platform. Stacker belt for stockpiling mined coal.
Concluding…Highwall Mining as a coal mining method :- increases your mine-able reserves,- mine coal cost effectively,- with maximum safety- with minimum risk,that otherwise would be unrecovered.BECAUSE RESOURCES ARE LIMITED