Underground Coal Mines

Underground Coal Mines - Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of facilities that are subject to quarterly or more frequent sampling of mine ventilation systems by the Mine Safety and Health Administration (MSHA) would report emissions from underground coal mines. Owners or operators would collect emission data; calculate GHG emissions; and follow the specified procedures for quality assurance, missing data,

recordkeeping, and reporting.

Owners or operators of underground coal mines also would be required to report emissions under 40 CFR part 98, subpart KK (Suppliers of Coal).

How Is This Source Category Defined?

Under the proposal, this source category consists of underground coal mines that are active or under development, including all underground coal mines that have operational pre-mining degasification systems. It includes both mines under development and mines categorized by MSHA as active (where coal is currently being produced or has been produced within the previous 90 days).

This source category consists of the following emission points:

• Each ventilation well or shaft.

• Each degasification system well or shaft, including degasification systems deployed before,

during, or after mining operations.

Abandoned (closed) mines, surface coal mines, and post-coal mining activities are not included in this source category.

What GHGs Would Be Reported?

The proposal calls for underground coal mines to report:

• Methane (CH4) emissions from each ventilation well or shafts, and CH4 liberated from each degasification system deployed before, during, or after mining operations.

• Carbon dioxide (CO2) emissions from coal mine gas CH4 destruction where the gas is not a fuel input for energy generation or use.

In addition, each facility would report GHG emissions for other source categories for which calculation methods are provided in the rule. For example, facilities would report CO2, nitrous oxide (N2O), and CH4 emissions from each stationary combustion unit on site by following the requirements of 40 CFR part 98, subpart C (General Stationary Fuel Combustion Sources). Please refer to the relevant information sheet for a summary of the proposal for calculating and reporting emissions from any other source categories at the facility.

How Would GHG Emissions Be Calculated?

Under the proposal, total annual CH4 emissions would be estimated as the sum of quarterly CH4 that is liberated from ventilation wells and shafts and degasification systems, less the quantity of CH4 that is collected and destroyed.

• For ventilation wells and shafts, liberated CH4 would be determined by quarterly measurements of flow rate and CH4 concentration.

• For degasification systems, liberated CH4 would be determined by continuously measuring flow rate and CH4 concentration.

• CH4 destroyed would be determined by measuring flow rate and CH4 concentration of gas collected for destruction and applying a destruction efficiency (the lesser of 98 percent or the manufacturer’s specified destruction efficiency).

CO2 emissions from CH4 destruction would be estimated by applying a factor to the estimate of CH4 destroyed.

What Information Would Be Reported?

In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for underground coal mine owners or operators to report the following information annually:

• Volumetric flow rate, CH4 concentration, and any CH4 destruction for each ventilation system and degasification system.

• For each degasification system, dates in the reporting period where active ventilation of mining operations is taking place or when continuous monitoring equipment is not properly functioning.

• Quarterly CH4 liberated and CH4 emitted (net) from each ventilation well or shaft, and from each degasification system.

• Quarterly CO2 emissions from onsite destruction of coal mine gas CH4, where the gas is not a fuel input for energy generation or use.

Underground Coal Mines

Underground Coal Mines - Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of facilities that are subject to quarterly or more frequent sampling of mine ventilation systems by the Mine Safety and Health Administration (MSHA) would report emissions from underground coal mines. Owners or operators would collect emission data; calculate GHG emissions; and follow the specified procedures for quality assurance, missing data,

recordkeeping, and reporting.

Owners or operators of underground coal mines also would be required to report emissions under 40 CFR part 98, subpart KK (Suppliers of Coal).

How Is This Source Category Defined?

Under the proposal, this source category consists of underground coal mines that are active or under development, including all underground coal mines that have operational pre-mining degasification systems. It includes both mines under development and mines categorized by MSHA as active (where coal is currently being produced or has been produced within the previous 90 days).

This source category consists of the following emission points:

• Each ventilation well or shaft.

• Each degasification system well or shaft, including degasification systems deployed before,

during, or after mining operations.

Abandoned (closed) mines, surface coal mines, and post-coal mining activities are not included in this source category.

What GHGs Would Be Reported?

The proposal calls for underground coal mines to report:

• Methane (CH4) emissions from each ventilation well or shafts, and CH4 liberated from each degasification system deployed before, during, or after mining operations.

• Carbon dioxide (CO2) emissions from coal mine gas CH4 destruction where the gas is not a fuel input for energy generation or use.

In addition, each facility would report GHG emissions for other source categories for which calculation methods are provided in the rule. For example, facilities would report CO2, nitrous oxide (N2O), and CH4 emissions from each stationary combustion unit on site by following the requirements of 40 CFR part 98, subpart C (General Stationary Fuel Combustion Sources). Please refer to the relevant information sheet for a summary of the proposal for calculating and reporting emissions from any other source categories at the facility.

How Would GHG Emissions Be Calculated?

Under the proposal, total annual CH4 emissions would be estimated as the sum of quarterly CH4 that is liberated from ventilation wells and shafts and degasification systems, less the quantity of CH4 that is collected and destroyed.

• For ventilation wells and shafts, liberated CH4 would be determined by quarterly measurements of flow rate and CH4 concentration.

• For degasification systems, liberated CH4 would be determined by continuously measuring flow rate and CH4 concentration.

• CH4 destroyed would be determined by measuring flow rate and CH4 concentration of gas collected for destruction and applying a destruction efficiency (the lesser of 98 percent or the manufacturer’s specified destruction efficiency).

CO2 emissions from CH4 destruction would be estimated by applying a factor to the estimate of CH4 destroyed.

What Information Would Be Reported?

In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for underground coal mine owners or operators to report the following information annually:

• Volumetric flow rate, CH4 concentration, and any CH4 destruction for each ventilation system and degasification system.

• For each degasification system, dates in the reporting period where active ventilation of mining operations is taking place or when continuous monitoring equipment is not properly functioning.

• Quarterly CH4 liberated and CH4 emitted (net) from each ventilation well or shaft, and from each degasification system.

• Quarterly CO2 emissions from onsite destruction of coal mine gas CH4, where the gas is not a fuel input for energy generation or use.

Underground Coal Mines

Underground Coal Mines - Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of facilities that are subject to quarterly or more frequent sampling of mine ventilation systems by the Mine Safety and Health Administration (MSHA) would report emissions from underground coal mines. Owners or operators would collect emission data; calculate GHG emissions; and follow the specified procedures for quality assurance, missing data,

recordkeeping, and reporting.

Owners or operators of underground coal mines also would be required to report emissions under 40 CFR part 98, subpart KK (Suppliers of Coal).

How Is This Source Category Defined?

Under the proposal, this source category consists of underground coal mines that are active or under development, including all underground coal mines that have operational pre-mining degasification systems. It includes both mines under development and mines categorized by MSHA as active (where coal is currently being produced or has been produced within the previous 90 days).

This source category consists of the following emission points:

• Each ventilation well or shaft.

• Each degasification system well or shaft, including degasification systems deployed before,

during, or after mining operations.

Abandoned (closed) mines, surface coal mines, and post-coal mining activities are not included in this source category.

What GHGs Would Be Reported?

The proposal calls for underground coal mines to report:

• Methane (CH4) emissions from each ventilation well or shafts, and CH4 liberated from each degasification system deployed before, during, or after mining operations.

• Carbon dioxide (CO2) emissions from coal mine gas CH4 destruction where the gas is not a fuel input for energy generation or use.

In addition, each facility would report GHG emissions for other source categories for which calculation methods are provided in the rule. For example, facilities would report CO2, nitrous oxide (N2O), and CH4 emissions from each stationary combustion unit on site by following the requirements of 40 CFR part 98, subpart C (General Stationary Fuel Combustion Sources). Please refer to the relevant information sheet for a summary of the proposal for calculating and reporting emissions from any other source categories at the facility.

How Would GHG Emissions Be Calculated?

Under the proposal, total annual CH4 emissions would be estimated as the sum of quarterly CH4 that is liberated from ventilation wells and shafts and degasification systems, less the quantity of CH4 that is collected and destroyed.

• For ventilation wells and shafts, liberated CH4 would be determined by quarterly measurements of flow rate and CH4 concentration.

• For degasification systems, liberated CH4 would be determined by continuously measuring flow rate and CH4 concentration.

• CH4 destroyed would be determined by measuring flow rate and CH4 concentration of gas collected for destruction and applying a destruction efficiency (the lesser of 98 percent or the manufacturer’s specified destruction efficiency).

CO2 emissions from CH4 destruction would be estimated by applying a factor to the estimate of CH4 destroyed.

What Information Would Be Reported?

In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for underground coal mine owners or operators to report the following information annually:

• Volumetric flow rate, CH4 concentration, and any CH4 destruction for each ventilation system and degasification system.

• For each degasification system, dates in the reporting period where active ventilation of mining operations is taking place or when continuous monitoring equipment is not properly functioning.

• Quarterly CH4 liberated and CH4 emitted (net) from each ventilation well or shaft, and from each degasification system.

• Quarterly CO2 emissions from onsite destruction of coal mine gas CH4, where the gas is not a fuel input for energy generation or use.

Underground Coal Mines

Underground Coal Mines - Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of facilities that are subject to quarterly or more frequent sampling of mine ventilation systems by the Mine Safety and Health Administration (MSHA) would report emissions from underground coal mines. Owners or operators would collect emission data; calculate GHG emissions; and follow the specified procedures for quality assurance, missing data,

recordkeeping, and reporting.

Owners or operators of underground coal mines also would be required to report emissions under 40 CFR part 98, subpart KK (Suppliers of Coal).

How Is This Source Category Defined?

Under the proposal, this source category consists of underground coal mines that are active or under development, including all underground coal mines that have operational pre-mining degasification systems. It includes both mines under development and mines categorized by MSHA as active (where coal is currently being produced or has been produced within the previous 90 days).

This source category consists of the following emission points:

• Each ventilation well or shaft.

• Each degasification system well or shaft, including degasification systems deployed before,

during, or after mining operations.

Abandoned (closed) mines, surface coal mines, and post-coal mining activities are not included in this source category.

What GHGs Would Be Reported?

The proposal calls for underground coal mines to report:

• Methane (CH4) emissions from each ventilation well or shafts, and CH4 liberated from each degasification system deployed before, during, or after mining operations.

• Carbon dioxide (CO2) emissions from coal mine gas CH4 destruction where the gas is not a fuel input for energy generation or use.

In addition, each facility would report GHG emissions for other source categories for which calculation methods are provided in the rule. For example, facilities would report CO2, nitrous oxide (N2O), and CH4 emissions from each stationary combustion unit on site by following the requirements of 40 CFR part 98, subpart C (General Stationary Fuel Combustion Sources). Please refer to the relevant information sheet for a summary of the proposal for calculating and reporting emissions from any other source categories at the facility.

How Would GHG Emissions Be Calculated?

Under the proposal, total annual CH4 emissions would be estimated as the sum of quarterly CH4 that is liberated from ventilation wells and shafts and degasification systems, less the quantity of CH4 that is collected and destroyed.

• For ventilation wells and shafts, liberated CH4 would be determined by quarterly measurements of flow rate and CH4 concentration.

• For degasification systems, liberated CH4 would be determined by continuously measuring flow rate and CH4 concentration.

• CH4 destroyed would be determined by measuring flow rate and CH4 concentration of gas collected for destruction and applying a destruction efficiency (the lesser of 98 percent or the manufacturer’s specified destruction efficiency).

CO2 emissions from CH4 destruction would be estimated by applying a factor to the estimate of CH4 destroyed.

What Information Would Be Reported?

In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for underground coal mine owners or operators to report the following information annually:

• Volumetric flow rate, CH4 concentration, and any CH4 destruction for each ventilation system and degasification system.

• For each degasification system, dates in the reporting period where active ventilation of mining operations is taking place or when continuous monitoring equipment is not properly functioning.

• Quarterly CH4 liberated and CH4 emitted (net) from each ventilation well or shaft, and from each degasification system.

• Quarterly CO2 emissions from onsite destruction of coal mine gas CH4, where the gas is not a fuel input for energy generation or use.

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining

Underground mining is used when the coal seam lies deep in the earth. In an underground mine only some of the coal is removed. The coal that remains helps support the mine roof.

Underground mines look like a system of tunnels. The tunnels are used for traveling throughout the mine, moving coal from place to place and allowing air to circulate in the mine.

This is a diagram of an underground room and pillar mine.

The coal that is mined is put on conveyor belts. The conveyor belts take the coal to the surface.

It is very dark underground.

A conveyor belt takes coal out of the mine. The pillars are covered with a white powdered limestone to prevent spontaneous combustion.

There are three types of underground mines: slope, drift, and shaft.
When the coal seam is close to the surface but too deep to use surface mining, a slope mine can be built. In a slope mine a tunnel slants down from the surface to the coal seam.

In a slope mine, the miners and materials ride in special cars to get to the coal seam.

A drift mine is built when the coal seam lies in the side of a hill or mountain. Drift mines may also be built in a surface mine that has become too deep. There are many drift mines in the eastern United States.

The most common type of mine in Illinois is the shaft mine. These mines may be 125 to 1,000 feet deep. A large hole, or shaft, is drilled down into the ground until it reaches the coal seam.

The shaft can be 30 feet in diameter.

Men and materials ride an elevator down to the coal seam at a shaft mine.

Two Types of Underground Mining
In Illinois, two types of underground mining are used: room and pillar mining and longwall mining. Room and pillar mining leaves pillars, or blocks, of coal in the mine to support the roof. In longwall mining the roof is allowed to collapse in a planned sequence. More coal is mined during longwall mining.

Continuous miner
machines are used to cut the coal in room and pillar mining.

This continuous miner is operated by remote control.

Continuous miners
have a large rotating drum that moves up and down. Strong bits on the drum cut the coal. As the coal falls, large arms under the drum gather the coal onto a conveyor chain. The conveyor chain carries the coal to the back of the machine. The coal is unloaded at the back of the machine onto ram cars. The ram cars haul the coal to a conveyor belt.

Left to right: ram car and continuous miner Below: rotating drum with bits that cut the coal.

Longwall mining removes more coal than room and pillar mining.
Large panels of coal are extracted. The panels are 750 to 1,000 feet wide. The continuous miner cuts tunnels 18 to 20 feet wide.

The longwall panel shows how much coal the longwall mining machine cuts.

The longwall machine has large shields that support the roof and protect the miners during mining.

The shields are shown in yellow in the pictures.

The shearer is shown in orange. It shears the coal away. The conveyor belt is shown in gray.

A rotating drum, called a shearer, cuts the coal. The coal drops onto a conveyor belt. As more of the coal is cut, the machine moves forward. The roof behind the machine falls in a planned order.

The shields are shown in yellow in the pictures.

In 2000, there were 12 underground mines in Illinois.
The 3,131 employed miners produced 29,700,000 tons of coal.

Corn and soybeans grow above this underground coal mine.

Underground Mining

Underground mining is used when the coal seam lies deep in the earth. In an underground mine only some of the coal is removed. The coal that remains helps support the mine roof.

Underground mines look like a system of tunnels. The tunnels are used for traveling throughout the mine, moving coal from place to place and allowing air to circulate in the mine.

This is a diagram of an underground room and pillar mine.

The coal that is mined is put on conveyor belts. The conveyor belts take the coal to the surface.

It is very dark underground.

A conveyor belt takes coal out of the mine. The pillars are covered with a white powdered limestone to prevent spontaneous combustion.

There are three types of underground mines: slope, drift, and shaft.
When the coal seam is close to the surface but too deep to use surface mining, a slope mine can be built. In a slope mine a tunnel slants down from the surface to the coal seam.

In a slope mine, the miners and materials ride in special cars to get to the coal seam.

A drift mine is built when the coal seam lies in the side of a hill or mountain. Drift mines may also be built in a surface mine that has become too deep. There are many drift mines in the eastern United States.

The most common type of mine in Illinois is the shaft mine. These mines may be 125 to 1,000 feet deep. A large hole, or shaft, is drilled down into the ground until it reaches the coal seam.

The shaft can be 30 feet in diameter.

Men and materials ride an elevator down to the coal seam at a shaft mine.

Two Types of Underground Mining
In Illinois, two types of underground mining are used: room and pillar mining and longwall mining. Room and pillar mining leaves pillars, or blocks, of coal in the mine to support the roof. In longwall mining the roof is allowed to collapse in a planned sequence. More coal is mined during longwall mining.

Continuous miner
machines are used to cut the coal in room and pillar mining.

This continuous miner is operated by remote control.

Continuous miners
have a large rotating drum that moves up and down. Strong bits on the drum cut the coal. As the coal falls, large arms under the drum gather the coal onto a conveyor chain. The conveyor chain carries the coal to the back of the machine. The coal is unloaded at the back of the machine onto ram cars. The ram cars haul the coal to a conveyor belt.

Left to right: ram car and continuous miner Below: rotating drum with bits that cut the coal.

Longwall mining removes more coal than room and pillar mining.
Large panels of coal are extracted. The panels are 750 to 1,000 feet wide. The continuous miner cuts tunnels 18 to 20 feet wide.

The longwall panel shows how much coal the longwall mining machine cuts.

The longwall machine has large shields that support the roof and protect the miners during mining.

The shields are shown in yellow in the pictures.

The shearer is shown in orange. It shears the coal away. The conveyor belt is shown in gray.

A rotating drum, called a shearer, cuts the coal. The coal drops onto a conveyor belt. As more of the coal is cut, the machine moves forward. The roof behind the machine falls in a planned order.

The shields are shown in yellow in the pictures.

In 2000, there were 12 underground mines in Illinois.
The 3,131 employed miners produced 29,700,000 tons of coal.

Corn and soybeans grow above this underground coal mine.

Underground Mining

Underground mining is used when the coal seam lies deep in the earth. In an underground mine only some of the coal is removed. The coal that remains helps support the mine roof.

Underground mines look like a system of tunnels. The tunnels are used for traveling throughout the mine, moving coal from place to place and allowing air to circulate in the mine.

This is a diagram of an underground room and pillar mine.

The coal that is mined is put on conveyor belts. The conveyor belts take the coal to the surface.

It is very dark underground.

A conveyor belt takes coal out of the mine. The pillars are covered with a white powdered limestone to prevent spontaneous combustion.

There are three types of underground mines: slope, drift, and shaft.
When the coal seam is close to the surface but too deep to use surface mining, a slope mine can be built. In a slope mine a tunnel slants down from the surface to the coal seam.

In a slope mine, the miners and materials ride in special cars to get to the coal seam.

A drift mine is built when the coal seam lies in the side of a hill or mountain. Drift mines may also be built in a surface mine that has become too deep. There are many drift mines in the eastern United States.

The most common type of mine in Illinois is the shaft mine. These mines may be 125 to 1,000 feet deep. A large hole, or shaft, is drilled down into the ground until it reaches the coal seam.

The shaft can be 30 feet in diameter.

Men and materials ride an elevator down to the coal seam at a shaft mine.

Two Types of Underground Mining
In Illinois, two types of underground mining are used: room and pillar mining and longwall mining. Room and pillar mining leaves pillars, or blocks, of coal in the mine to support the roof. In longwall mining the roof is allowed to collapse in a planned sequence. More coal is mined during longwall mining.

Continuous miner
machines are used to cut the coal in room and pillar mining.

This continuous miner is operated by remote control.

Continuous miners
have a large rotating drum that moves up and down. Strong bits on the drum cut the coal. As the coal falls, large arms under the drum gather the coal onto a conveyor chain. The conveyor chain carries the coal to the back of the machine. The coal is unloaded at the back of the machine onto ram cars. The ram cars haul the coal to a conveyor belt.

Left to right: ram car and continuous miner Below: rotating drum with bits that cut the coal.

Longwall mining removes more coal than room and pillar mining.
Large panels of coal are extracted. The panels are 750 to 1,000 feet wide. The continuous miner cuts tunnels 18 to 20 feet wide.

The longwall panel shows how much coal the longwall mining machine cuts.

The longwall machine has large shields that support the roof and protect the miners during mining.

The shields are shown in yellow in the pictures.

The shearer is shown in orange. It shears the coal away. The conveyor belt is shown in gray.

A rotating drum, called a shearer, cuts the coal. The coal drops onto a conveyor belt. As more of the coal is cut, the machine moves forward. The roof behind the machine falls in a planned order.

The shields are shown in yellow in the pictures.

In 2000, there were 12 underground mines in Illinois.
The 3,131 employed miners produced 29,700,000 tons of coal.

Corn and soybeans grow above this underground coal mine.