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Slide 2:

Coal is mined by two main methods : Underground or 'deep' mining Surface or 'open-cut' mining The choice of method is largely determined by the geology of the coal deposit, in particular the depth of the seam below the surface. The majority of the world's coal reserves are recoverable by underground mining. Currently, almost two-thirds of hard coal production worldwide comes from underground mines, but in certain important coal producing countries, such as the USA and Australia, this proportion is significantly lower.

Underground Mining:

There are two main methods of extracting coal by underground mining: room-and-pillar (or, bord -and-pillar) and longwall mining. Room-and-pillar minin g involves cutting a network of 'rooms' or panels into the coal seam and leaving behind 'pillars' of coal to support the roof of the mine. Initially, recoveries are reduced (to 50-60 per cent) because of the coal left in the pillars - however, this coal can sometimes be recovered at a later stage of mine life. Longwall mining involves the use of mechanised shearers to cut and remove the coal at the face, which can vary in length from 100-250 m. Self-advancing, hydraulic-powered supports temporarily hold up the roof whilst the coal is extracted. The roof over the area behind the face, from which the coal has been removed, is then allowed to collapse. Over 75 per cent of the coal in the deposit can be extracted using this method. Underground Mining

Open-Cut (Surface) Mining:

Surface mining, economic only when the coal seam is relatively close to the surface, recovers a higher proportion of the coal deposit than underground methods. The equipment used includes: draglines, which remove the overburden (the term given to the strata between the coal seams and the surface); power shovels; large trucks, which transport overburden and coal; bucket wheel excavators; and high capacity conveyors. Open-Cut (Surface) Mining

Slide 5:

Surface mining equipment has increased dramatically in size over recent years. However, in some countries, the high capital cost of importing this equipment can favour the selection of underground mining.

What determines the type of mining?:

What determines the type of mining? Underground v.s . Surface Mining v.s . Solution Depth of below surface Size of the ore body Shape of the ore body Grade Type of Ore

When do you use Surface Mining?:

When do you use Surface Mining? Large tonnage High rates of production Overburden (including rock) is thin


Surface mining has several advantages over shaft mining : 1. An increase in worker productivity in tons per man-day by at least three fold . 2. A resource recovery of approximately 90% versus 60% or less for underground mining (room and pillar). 3. A reduction in initial site preparation costs. 4. Less than one-half the injuries per work-hour and avoidance of high death rate from respiratory diseases. 5. Less vulnerability to labor strikes, due to lower manpower requirements. ADVANTAGES

Mining Techniques:

There are four basic techniques used in surface mining as per American standard: 1. Contour mining 2. Area mining 3. Open pit mining 4. Auger mining 5. High Wall Mining Mining Techniques

Contour Mining:

Contour strip mining of coal is commonly used in mountainous or hilly terrain where the coal is removed from the outcrop along the face of a hill. The two basic types of removal are cross ridge removal for mountaintop operations and box cut mining on hillsides . The intent of these methods is to cut the coal out and allow reclamation of the land in a manner which does not later produce adverse environmental impacts. Contour Mining

Contour Strip Mining:

Contour Strip Mining

Slide 12:

Spoil banks Bench Undisturbed land Overburden Pit Coal seam Coal seam Overburden Highwall

Mountain Top Removal:

The mountaintop (cross ridge removal) method employs a series of cuts in the top of a mountain with gradual removal of the coal. This produces a flat area on the top of a mountain which can be used for agriculture or dwelling. In box cut mining , the overburden is excavated and placed on the downside slope, after which the coal is removed . One disadvantage of this technique is that the overburden placed on the downside slope can fall down the side of the hill. An alternative to the box cut method is to haul the overburden to a mined-out area. The coal is extracted after the overburden is physically removed from the area. This method reduces the spoil bank problem and makes it easier to return land back to its original contour. Mountain Top Removal

Mountain Top Mining:

Mountain Top Mining

Area Mining:

Area mining is commonly used in flat terrain where there is minimum change in contour and seams dip gently. The spoil pile of overburden is normally placed on land that has already been mined and the coal is loaded by a back hoe, front-end loader , or shovel into the truck. Following the extraction of coal, another frontend loader and bulldozer are often used to regrade the spoil pile as the first stage in reclamation. Area Mining

Slide 16:

Schematic flow diagram for area surface mining of coal.

Open Pit Mining:

Open pit coal mining has been popular in Europe, but is used on a more limited basis in the United States for lignite extraction in the northern Great Plains and for Wyoming subbituminous coal. The method is a type of area stripping which allows almost complete removal of coal from very thick seams, using a mining approach reminiscent of rock quarrying. Multiple benches are employed to reach greater depths than normally achieved in area stripping. Open pit mining does not allow for refilling of the coal voidage and because of the thick seams, a permanent depression is left . Open pit mining has been practiced extensively in Germany for the mining of lignite. Open Pit Mining

Open Pit Mining:

Open Pit Mining

?Dinky Toy?:

?Dinky Toy?

Strip Mining of Coal:

Strip Mining of Coal Kansas Geological Survey

Strip Mining:

Strip Mining

Auger Mining:

Augering is used for less than 1% of U.S. coal mining6 and is attractive when the economic overburden limit is reached in contour strip mining but the tonnage accessible is not large enough to justify an underground mine. An auger drills into the exposed coal seam at the high wall and removes the coal by backing the cuttings along the spiral of the auger. The bits are usually 96 inches in diameter Auger Mining

Slide 23:

and may penetrate 300 feet into the vein, recovering 40% to 60% of the coal in place. It has been proposed that augering could be used in conjunction with strip mining to reduce reclamation and mining costs; a trench would be formed by dragline and augering would be used within the trench. However, the resource recovery would suffer somewhat compared to strip mining.

Approximate Costs of an Area Stripping Operation (Basis: western coal, 2 x 106 tons/year, 15 ft. seam thickness, 100 ft. overburden thickness, 1980 costs):

Costs $106 Capital Costs Dragline (I ) 11.2 Loaders, dozers, trucks, and graders 4.8 Other equipment 0.9 Total direct 16.9 Indirect, engineering, overhead, Contingency, fee, construction 5.2 Total 22.1 Operating Costs Labor and supervision, including welfare 6.4 Operating supplies, power, and water 5.0 Payroll overhead 1.3 Total 12.7 Approximate Costs of an Area Stripping Operation ( Basis: western coal, 2 x 106 tons/year, 15 ft. seam thickness, 100 ft. overburden thickness, 1980 costs)

Approximate Costs for Underground Eastern Bituminous Mine (Basis: 6 ft. seam, 500 ft. depth, 106 tons/year, 1980 costS)13:

Costs $ 106 Capital Costs Continuous miners, loading machines, cars 6.8 Conveyors, haulage system 3.8 Auxiliary equipment (power, vehicles, track, safety) 2.9 Total direct 13.5 Estimated development cost (site preparation ) 16.5 Indirect capital 3.0 Gross estimate 33.0 Operating Costs Labor and supervision, including welfare 8.6 Operating supplies, power, and water 7.1 Payroll Overhead 2.6 Total 18.3 Approximate Costs for Underground Eastern Bituminous Mine (Basis: 6 ft. seam, 500 ft. depth, 106 tons/year, 1980 costS )13

At a Glance...:

27% of primary energy needs worldwide were met by coal in 2007. (25% in 1973.) 42% of global electricity was generated from coal in 2007. (38% in 1973). Poland, South Africa, Australia and China all rely on coal to produce over three-quarters of their electricity, India over 60%, and the USA and Germany more than half. Almost 70% of global steel production depends on coal feedstock, with around 814 Mt of coking coal being being consumed globally in 2008. Further quantities of coal provided much of the electricity used to power electric arc furnaces to produce the balance of global steel production. Global hard coal production has more than doubled in the past 30 years or so - from 2,800 Mt in 1980 to 5,845 Mt  in 2008. At a Glance ...

Slide 27:

Major hard coal producers include China 2,761 Mt, USA 1,007 Mt, India 489 Mt, Australia 325 Mt, Russia 247 Mt, Indonesia 246,and South Africa 236 Mt. (2008) Brown coal/lignite production totalled 951 Mt in 2008, with Germany (175 Mt), Russia (76 Mt), Turkey (73 Mt), Australia (72 Mt), USA (69 Mt), Greece (66 Mt) and Poland (60 Mt) being the leading producers and consumers.

Slide 28:

Underground Mining

When do we mine underground?:

When do we mine underground? The ore deposit is deep Ore body is steep Grade is high enough to cover costs

Some types of underground mining:

Some types of underground mining Room and Pillar Cut and Fill Long wall (coal) Shrinkage Stoping Block Caving

Room and Pillar:

Room and Pillar

Cut and Fill:

Cut and Fill

Long Wall:

Long Wall

Shrinkage Stoping:

Shrinkage Stoping

Block Caving:

Block Caving

Solution Mining:

Solution Mining

Potential Environmental Problems:

Potential Environmental Problems A. Mining operation itself Disposal of a large amount of rock and waste Noise Dust Beneficiation Smelting and refining









Continuous MINER:

Continuous MINER

Long wall Mining:

Long wall Mining





Bucket Wheel ExcAVATOR:

Bucket Wheel ExcAVATOR





Dozer Scraper Mining:

Dozer Scraper Mining