Alternatives for Future Coal Waste Disposal - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 134

have been in operation since the mid-1990s (Rousaki and Couch, 2000).
The site in Indiana has a two-stage, entrained-flow gasifier that takes
bituminous coal slurry feed. An entrained-flow gasifier in Florida uses slurry
with approximately 10 percent ash. The Pinon Pine plant in Nevada uses high-
quality coal from Utah in its fluidized-bed gasifier. A new plant with a moving
bed gasifier is planned in Kentucky and will use high-sulfur, bituminous coal
and municipal solid waste feed (Rousaki and Couch, 2000).
Gasification has significant environmental benefits, because it creates less
of the traditional waste products, such as particulates and wastewater. In
addition, 99 percent of the sulfur can be removed, and NO x can be reduced by
90 percent and CO 2 by 35 percent (Arey, 1997; Rousaki and Couch, 2000).
Most of the ash produced in gasification is recirculated through the system and
converted to the preferable and lower volume bottom ash or slag (lyengar and
Ramakrishnan, 1992). Sulfur and other trace elements can be removed from the
gas stream. Waste such as elemental sulfur and vitrified slag are marketable
products. In addition, less water is used in integrated gasification combined
cycle plants than in traditional coal-fired plants (Arey, 1997).
Although gasification is a proven technology, costs are still prohibitive for
implementation even using clean coal. However, the environmental benefits of
improved emissions and potential uses for waste products appear to be
significant. Research is still underway for potential markets for waste slag
(Barbara Arnold, PrepTech, Inc., personal communication, 2001).
As part of the Vision 21 program, DOE recently selected two projects for
the demonstration of gasification facilities capable of utilizing coal water slurry
as the gasifier feed to produce a combination of electric power, heat, fuel, and
chemicals. In another Vision 21 project, gasification of a biomass and coal
slurries blend is being demonstrated (J.Morrison and B.Miller, Pennsylvania
State University, personal communication, 2001).
The committee concludes that the combustion of fine coal waste in
advanced combustion technologies, such as fluidized-bed combustion and
gasification, is an alternative that also shows considerable long-term promise.
Atmospheric fluidized-bed units are already in use for combustion of fine coal
waste slurries from both preparation plants and old slurry impoundments, but
they have not gained wide usage. The available fluidized-bed combustion units
generally produce more expensive electricity than conventional boilers, but they
have advantages in reducing air pollutants (SO 2 , NO x , CO 2 ), and their relatively
small size for location near coal mines makes them worthy of the utility
industry's consideration. Pressurized fluidized-bed technologies offer gains in
efficiency over atmospheric technologies but have not been utilized in full-scale
applications