Geology Reference
In-Depth Information
TABLE 7.1 The Advantages and Disadvantages of Agglomeration Technologies
Agglomeration
Method
Advantages
Disadvantages
Other
Comments
Mixer
agglomeration
Simplest
technique;
Cheapest;
Simple binders
(such as water)
can be used
Weakest product;
Converts dust to
crumb-size product
Possible
application to
condition coals
for nearby use
Disk and drum
pelletizers
Simple concept;
Next cheapest;
Can make pellets
Relatively weak
product
Can make
pellets 5 to 80
mm in diameter
Roll press
Uniform
product size
Relatively
expensive; Needs
good binders
Extrusion
May not need a
binder
Relatively
expensive;
Strength is
problematic
Brick-shaped
product is
typical
SOURCE: Whitehead, 1997.
nature of the coal, required product characteristics (ease of handling and
strength), coal cost and product value, and binder availability and cost (Couch,
1998).
Another alternative is to create a slurry fuel from fine coal waste. In 1973,
the oil embargo prompted the development of coal-water slurry technology,
which consists of a pulverized, fluidized coal feed that can be transported by
pipeline and used as a fuel for utility boilers or gasifiers. The high-ash
(noncombustible material) fine waste produced by coal cleaning could be
treated similarly. Initially, slurries containing 60 percent solids (high-solids)
were tested, but more recently, slurries containing 50 percent solids (low-solids)
have been tested. Low-solids slurries require particles smaller than 100 mesh
(150 micrometer).
Several utilities have demonstrated coal-water slurry utilization in
conventional boilers, including Penelec (later GPU Genco), Tennessee Valley
Authority, and Southern Illinois Power Cooperative (J.Morrison and B.Miller,
Pennsylvania State University, personal communication, 2001). Coal-fired
boilers at Seward Station in western Pennsylvania use a slurry consisting of
material obtained directly from cleaning plant fines and from
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