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During the cement making process, large amounts of fine
material are given off and carried out by the flow of hot gas within a cement kiln.
This kiln dust isn't incorporated into the cement clinker formed within the
kiln, and instead becomes a waste byproduct.
In 1990, on average 9 tons of this cement kiln dust (CKD) was produced for every
100 tons of clinker.
(Kessler, 1995)
The potential exists to reuse CKD within the cement making industry as well as
in other fields due to its lime content and its cementitious properties.
Today's technology minimizes the generation of CKD and allows most, and sometimes all of the
cement kiln dust to be reused, minimizing air pollution and disposal problems.
In some facilities though, cement kiln dust is still an issue and some cement kilns don't reuse all of the dust they produce. The material is collected using pollution control systems like cyclones,
electrostatic
precipitators, or baghouses, and is then landfilled either on or off site. Some
facilities also have stockpiles of the cement kiln dust that was
produced before technology allowed for its reuse in cement production, as is the
case with the Dragon Cement facility in Thomaston, Maine.
Currently various projects take advantage of
reusing much of the kiln dust that is now produced, as well as some of the
stockpiled byproduct. The beneficial use of cement kiln dust is feasible because
the material isn't considered hazardous by the Environmental Protection Agency's
RCRA regulations. Although precautions have to be taken, and preliminary
analysis should be done on a case-by-case basis with cement kiln dust projects,
the material doesn't pose any major environmental risks. |
