Alternatives for Future Coal Waste Disposal - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 127

recovered fine waste from impoundments (J.J.Battista, Cofiring Alternatives,
personal communication, 2001). Masudi and Samudrala (1996) assessed a blend
of 15 percent coal waste fines and 85 percent clean coal in utility boilers. Slurry
fuel produced from the blend contained 46.9 percent moisture and 19.8 percent
ash. After dewatering and wet milling, the final ash content of the fuel was 10.5
percent.
Although benefits of using coal slurry include reducing nitrogen oxide
(NO x ) emissions by as much as 30 percent (J.J.Battista, Cofiring Alternatives,
personal communication, 2001), the costs of processing and transporting are
significant. Conventional utility boilers are usually far from the coal preparation
plant, and pulverized coal-fired boilers may impose stringent quality demands
on the characteristics of the slurry for direct burning. The coal slurry produced
at a preparation plant may not meet the requirements of the power plant.
Nevertheless, there is a potential for creating a market to acquire and process
slurries from diverse sources to supply custom slurry to diverse customers.
The committee concludes that technologies for utilization of fine coal
waste for electricity generation in conventional coal-fired power plants are
available. These technologies offer near-term opportunities for the reduction of
fine coal waste disposed of in impoundments. The technologies produce coal
that is more expensive than cleaned coal, as a result of capital and operating
costs of additional equipment, and, in the case of coal water slurry, the
additional cost of transportation. However, the avoided costs of slurry
impoundments must be included in the cost comparison. A definitive cost
analysis, which is necessary for any cost comparison of technologies, was not
performed in this study.
Alternative Combustion and Gasification Technologies
While pulverized coal-fired combustion is the dominant technology for
generating electricity from coal, other technologies have long been recognized
as advantageous for operating efficiency and reduced air pollution. Fluidized-
bed combustion and gasification have been commercially available for at least
10 years and show promise for recovering the heat content of fine coal waste
while avoiding some of the operational problems that limit use of coal fines in
conventional pulverized coal-fired boilers. Because of the potential for cleaner,
more efficient fossil fuels through the use of these technologies, the U.S.
Department of Energy (DOE) included these two technologies in the Vision 21
program for fossil fuel options of the future. The National Academy of Sciences
reviewed this