Alternatives for Future Coal Waste Disposal - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 131

SIDEBAR 7.3 ATMOSPHERIC FLUIDIZED-BED COMBUSTORS
Firing atmospheric fluidized-bed combustors with fine coal waste from
preparation plants has been demonstrated in a number of countries—
Australia, Canada, Japan, South Africa, China, and India (Couch, 1998).
Waste slurry from impoundment cleanup can also be fired (Couch, 1998).
This use of fine coal waste can reduce traditional coal processing steps
(and costs) for mined coal, because the boilers will operate at an overall
lower energy content than conventional boilers (Couch, 1998; C.Norris,
Geo-Hydro, Inc., personal communication, 2001). Fluidized-bed plants are
generally smaller than conventional power plants, and the boilers can be
built in a factory and shipped to the site. Operating them close to the mine
can result in savings in coal transportation costs. Limestone, however, as
part of the fluidized bed, must be transported to the site to remove SO 2
SIDEBAR 7.4 ATMOSPHERIC CIRCULATING FLUIDIZED-
BED BOILERS
Alstom Power and the Warkworth Mine in New South Wales,
Australia, have demonstrated the firing of an atmospheric circulating
fluidized-bed power plant with fine coal waste (J.Durant, Alstom Power,
personal communication, 2001). The 140-megawatt Redbank Power
Project in New South Wales uses two fluidized-bed boilers fired with 100
percent waste coal, both from an impoundment and from the mine's
preparation plant. The coal waste is fed from a preparation plant using
Jameson cell technology followed by centrifugation to reduce the moisture
content to approximately 30 percent. The ash content of the fine coal
waste is around 15 percent, and the particle size of 58 to 79 percent of the
feed is smaller than 200 mesh (75 micrometer). A conveying system
transports the fuel from the preparation plant to the power plant site
(Goldbach and Tanca, 2001). SO 2 emissions have been estimated at 412
pounds per hour and NO x at 397 pounds per hour of burning coal waste
(J.Durant, Alstom Power, personal communication, 2001). Alstom has
similar projects underway in Pennsylvania and Illinois, although these
projects will use fuel of a larger particle size and lower moisture content
(J.Durant, Alstom Power, personal communication, 2001).