Page 175 - Advances In Productive, Safe, and Responsible Coal Mining

Out-of-seam dilution: Economic 9

impacts and control strategies

,† †
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

9.1 Introduction and background

9.1.1 Out-of-seam dilution defined
Out-of-seam dilution (OSD) results when strata above and/or below the coal seam are
intentionally or unintentionally included in the run-of-mine (ROM) product. Some
coal seams contain rock partings, the mining of which generates in-seam dilution.
With few exceptions, parting and coal seam thicknesses rule out selective mining that
does not extract in-seam dilution, so it is generally considered a natural part of ROM
product. Extraction of OSD, however, can be avoided if sufficient care is taken in the
mining process.
The industry’s understandable focus on improving productivity [1] has led to more
powerful machinery that advances at faster rates often without concern for increasing
levels of OSD being extracted. The three most common reasons given for not paying
attention to OSD are as follows: (a) The more powerful machinery is larger and needs
a certain height to operate in, which is more than the coal seam height; (b) the imme-
diate roof strata are often weak and need to be removed to prevent them from falling
and causing injury; and (c) all of the ROM product will be processed in the preparation
plant, which is fully capable of rejecting OSD. While these are the reasons given by
mine operators for extracting out-of-seam material, they do not match what is actually
observed in mines; for example, mining height often exceeds required equipment
height by as much as 1.0ft (0.3m) or as much as 10in. (0.25m) of dilution being
removed from the floor.
There are legitimate reasons for extracting out-of-seam material, such as grad-
ing belt entries for proper belt alignment and cutting overcasts and undercasts to
provide ventilation; however, these necessary excavations can often be managed
such that dilution material is placed underground and not sent out of the mine with
the regular product. Thus, while each mining operation has unique conditions that
justify producing some OSD, in most cases, there are tremendous opportunities to
significantly improve mine profitability through moderately conservative reduc-
tions in OSD.

Advances in Productive, Safe, and Responsible Coal Mining. https://doi.org/10.1016/B978-0-08-101288-8.00006-7
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