Geology Reference
In-Depth Information
7
Alternatives for Future Coal Waste Disposal
Coal system activities range from mining, to processing, to utilization, to
disposal, and involve resources, transportation, and the environment
(
Figure 1.2
). Redesigning systems like this to eliminate or reduce substantially
waste streams is the first priority of industrial ecology (
Sidebar 7.1
). In the coal
system, this can be accomplished by identifying the appropriate point in the
process for reducing or removing noncombustible material. Currently, waste is
created during the mining and processing stages and disposed of either in coarse
refuse piles or fine waste slurry impoundments. Consideration of the entire coal
system concept leads to the identification of alternatives to impoundment
disposal of fine coal waste by reducing the amount of waste generated, utilizing
waste, or disposing of waste elsewhere. These options attempt to minimize the
waste stream, transfer it to another part of the coal system, or redirect it,
respectively.
Fine coal waste from the preparation plant can be reduced or eliminated
during both the mining and the preparation phases. For example, selective
mining reduces the amount of noncombustible material. However, many of the
coal seams currently mined are of sufficiently low quality that they would not
be mined if this were required. Options for preparation plant waste elimination
are more numerous during coal preparation. Cleaning requirements are usually
imposed on the mine operator, whose coal cleaning and waste disposal may be
constrained by site and environmental considerations. One option is to transfer
cleaning responsibilities to the power plants (the majority of end-users).
Another is to add fine coal waste to the cleaned coarse coal product. Dewatering
the slurry product solidifies (to a degree) and reduces the volume of the waste.
Since 90 percent of the coal mined in the United States is used in power
plants (Freme, 2000), significant benefits can be achieved if advances in power
plant technologies are integrated into the coal system components. Emerging
power plant technologies, developed around fluidized-bed combustion with
appropriate flue gas desulfurization technology, allow
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