Page 266 - Advances In Productive, Safe, and Responsible Coal Mining

Sustainable coal waste disposal 13

practices

,† †
Joseph C. Hirschi* , Y. Paul Chugh †
*Smart Solutions, Komatsu Mining Corporation, Mt. Vernon, IL, United States, Mining and
Mineral Resources Engineering, Southern Illinois University, Carbondale, IL, United States

13.1 Introduction and background information

13.1.1 Coal waste defined
Coal is a sedimentary rock that occurs in seams bounded by layers of rock. The gen-
eration of waste is unavoidable during coal extraction and beneficiation. Mine waste
or “spoils” are materials that are moved from its in situ location during the mining
process but are not processed to obtain the final product. Dealing with mine waste
is a major part of surface mining methods, where all of the rock above the coal seam
(overburden and sometimes interburden) must be removed to expose the coal seam.
This is done in a systematic fashion of digging pits with most of the overburden waste
being cast from above the coal to be extracted into an adjacent pit from which the coal
has already been extracted. Minimizing the handling of overburden waste is one of the
keys to economic success in surface coal mining. Various techniques, such as cast
blasting, are used to achieve this objective.
If underground mining methods are used, the amount of out-of-seam material han-
dled is much less than in surface mining, and minimizing that amount has multiple
economic benefits as discussed in Chapter 11. When large amounts of out-of-seam
material have to be removed for underground infrastructure such as ventilation over-
casts and undercasts and conveyor belt transfer points, it can be “gobbed” or left
underground in untraveled mine openings. However, most of the out-of-seam material
extracted in underground mines is mixed with the coal and constitutes part of the run-
of-mine (ROM) or “raw coal” product.
Because modern mechanized mining equipment does not distinguish between the
coal seam and layers of rock that encapsulate it and because complete or full extrac-
tion of a mineable coal seam is generally the objective of any coal-mining operation,
there will always be some level of out-of-seam dilution in the ROM product. In most
cases, out-of-seam material extracted with the coal must be separated from the coal
before shipment to satisfy customer quality requirements. This is accomplished with
coal preparation plants that generate a “clean coal” product and a waste material
referred to as “coal refuse.” Coal preparation plants utilize various mineral processing
technologies that, with few exceptions, are slurry-based and involve the use of sub-
stantial quantities of water [1]. The efficiency of these processing systems depends
on the size of material being treated. Hence, raw coal must be classified into different
Advances in Productive, Safe, and Responsible Coal Mining. https://doi.org/10.1016/B978-0-08-101288-8.00012-2
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