HIGHWALL MINER

Presented By :- Pulkit Paliwal

Introduction to Continuous Miner

Machine produces constant flow and used in Room and Pillar method.

Today driverless and remote controlled are used.

Consist of large rotating Drum comprising Steel and Tungsten Carbide Teeth, scraps the coal from seam/face. (Rooms 6.1 to 9.1 m in Length).

Extracted Coal is Transported Via Conveyor System.

Can produces 5 Tons of Coal in minute (Max.).

Mounted on Rubber Tyres and Crawler Track.

Introduction to Highwall Miner

Effective and Efficient means of coal recovery.

New technology, which can extend the life of opencast mine without disturbing the Surface Dwellings, maintaining economy and productivity.

Highwall Face has series of unsupported drives.

The Pillar Remaining Between Adjacent Drives are Capable Of Supporting the Overlying Structure.

In India, 60% Energy requirements are met by Coal itself and this accounts for 500MT Coal/Year and 80% is met by opencast mining.

Introduction to Highwall Miner

Existing pits are reaching beyond which economic mining is not possible, So there is a great need of Highwall Miner.

Method comprises extraction of coal from a series of parallel entries driven in the coal seam from the Highwall Mining face.

Entries are unmanned, unsupported, and unventilated.

CIMFR adopting Highwall Miner in SCCL at Ramagundum Opencast Mine and Tata Steel is adopting for Quarry SEB and AB In West Borkaro.

Interchangeable Cutter Head Module.

Programmable Logic Controller.

Pushbeams.

Reel and Chain.

Tracks.

Anchoring System.

Right Angle Conveyor.

Generator.

Design, Key features & Components

Highwall MinerA Terex™ Highwall Miner

Installation Complete unit can be assembled in 2 days and

dismantle in 3 days. Machine equipped with Bench Anchoring System. 2 Machine mounted drills are located in front of the

Highwall Miner. Capable of drilling 2.5m holes in the pit floor. 2 High strength rods of Dia. 15cm is then inserted

in the pit floor. During mining and retract cycle anchoring system

supports and stabilizes the Highwall miner.

Methods of Working 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 6.1m is placed between the cutter head and power head as depth of penetration increases. Maximum penetration upto 300m.

Using Video imaging and gamma detector, the Cutter head moves inside the seam and cuts only coal.

Unwanted material and other debris is left inside, which supports the strata.

Methods of Working Unwanted material and other debris is left inside, which

supports the strata.

All functioning is controlled from a touch screen panel located in operators cabin.

Coal is transported via conveyor system and washed by the unit itself before discharging onto stockpile.

Recovery is much better than any other operation.

Can be used in closed mines, But large capital is required for its purchase and operation.

Power from Generator of 2000hp, 1500 KW, 995 Volt, Enclosed in super silent container of 6.1m.

Highwall Miner Working (Video)

Considerations in its Application

GROUND CONTROL:

Roof Strength: Very good roof and strong to bear the load of overlying strata.

Web Pillars: Mostly thickness of 70% of the seam height is projected.

Barrier Pillars: Each pillar after 10 to 20 drives is left and load assumed on pillar is taken as Load of the overlying strata above pillar plus on each side half the load of overlying strata above the drives to the Next Barrier Pillar.

Dip: Seam dipping from 2-15 degrees. Almost impossible to apply the system into steeper dipping coal seams.

Considerations in its Application

RECOVERY RATES:

Less recovery as coal is left to maintain the Highwall Stability.

Low seam under low overburden have recovery rate around 70%, while high seam under low overburden have recovery rate around 15%.

FAULTS:

Mining through faults always avoided, and safe distance at least the width of barrier web pillar should be kept from faults.

UNDERGROUND MINES:

Highwall through abandoned Underground areas must be avoided.

Considerations in its Application

PRODUCTION RATES:

Production rates in favorable conditions and well maintained locations with avg. penetration of 70 to 95% lead to annual production of 0.5 to 1.5 Million Tons of Coal. But changes from site to site and also affected by local circumstances.

SEAM UNDULATIONS:

Strong seam undulations are more difficult to follow by cutter head.

INTEGRATION IN MINE PLANNING:

Highwall Mining system saves cost of making benches from spoil. Miner should be planned to proceed with least interruption.

Safety in Highwall Mining Although, all operating personnel are surface located in the pit, Coal

cutting occurs in an Underground Environment, But still there are few hazards:

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 in Highwall Mining Roof Span Collapse Hazard

- Continuous in Operation and System Results in Unsupported Opening, So Successful and Safe Operation can be Achieved with Rapid Entry and Retraction. Otherwise CHM Could Readily be Buried in Rock.

Explosion Hazards

- Operations Occurs in Underground Environment, So Methane Explosion can Occur. To Minimize the Explosion Flame Proof Enclosure of Machinery and Instrumentation Entering the Highwall Drives. Methane Monitoring Equipments Installed in Operators Cabin.

Ground Control of Highwall Mining

While designing layout, Engineer must specify- Web Pillar Width- No. of Web Pillar between Barrier Pillars.- Barrier Pillar Width. Coal Pillar Strength

SP = SI [0.64 + 0.54 W / H], Where:

SP = Web or Barrier Pillar Strength

SI = Insitu Coal Strength

W = Web or Barrier Pillar Width

H = Mining Height Coal Pillar Stress

SWP= SV (WWP + WE) / WWP, Where:

SV = Insitu Vertical Stress

WWP = Web Pillar Width

WE = Highwall Miner Hole Width.

Ground Control of Highwall Mining

Finally, the Stability Factor For Web Pillars against Strength Failure is Simply:

 

SFWP = Web Pillar Strength(SP) / Web Pillar Stress (SWP).

Typical Highwall Miner Holes and Web Pillars.

Note: Barrier Pillar or “Skip Hole” indicated by arrow.

Site of Massive Web Pillar Collapse resulting in Highwall Slope Failure.Note: Photograph is taken from adjacent spoil pile. Highwall is about 150 feet high. A 110 ton Coal Haulage truck is buried in Rockfall Debris.

Advantages

Cost Flexibility Applicability Safety Coal Recovery Productivity Environmental Impacts

Limitations

Method is not suitable in steeper gradient.

Penetration depth has got its limit depending upon the dip of the seam.

Requires skilled and qualified personnel. Added to that it is not an end of the

mining rather underground mining can extent farther from the highwall.

Highwall Mining in India & Conclusion

It is logical to prioritize Highwall Mining in sites with the following parameters:

Strong roof  Straight seams Dip angle < 6 degrees Seam Height < 3.5 metres Coal of high value or superior grades Where open cast pits have to be closed

 

Highwall Mining in India & Conclusion

Recently, a high level delegation of coal companies visited USA and also the manufacturers of the Highwall mining machines. Two companies of Coal India Limited and the Singareni Collieries have shown their inclination towards Highwall mining and are set to introduce this technology in selected mines.

Experts believe that there will be lot of scope for introduction of this technology in Indian mines in coming years and there could be additional production of 10 to 15 million tones per annum with these new machines. 

Thank You