Grants and Contracts Details
Description
The 300 MW Gilbert Circulating Fluidized Bed Combustor (CFBC) operating at East
Kentucky Power Cooperatives Spurlock Power Plant in Maysville, Kentucky, is currently
the cleanest in the State. It is also one of the most economical. The CFBC burns coal in
the presence of a bed of slaked limestone, which effectively absorbs sulfur dioxide (S02)
to form anhydrite (CaS04)' It low temperature operation produces much less thermal
NOx than pulverized coal combustion (PCC). By its nature CFBC is also fuel flexible,
and can burn very high ash and sulfur fuels cleanly and efficiently. This technology does
have a drawback however. Because it uses a higher CaiS ratio than a scrubbed PCC
system, it consumes more limestone produces more solid waste and C02 than
conventional coal plants.
The development of added value construction products from the Gilbert CFBC spent bed
materials is proposed. These products will replace Portland cement; an energy and C02
intensive product and thus help to mitigate carbon emissions.
CFBC produces two kind of spent bed materials, coarse bottom ash (BA) and a much
finer fly ash (FA). Both of these products are very high in calcium. The Gilbert BA
averages 55% CaO and the fly ash 30% CaO. Conventional fly ash from eastern U.S.
coal typically has much less than 5% CaO. Some of the calcium in the CFBC ash is
present as anhydrite, but about half of it is present as un-slaked lime. When properly
conditioned these materials are capable of acting as hydraulic cements, forming both
calcium aluminosulfate minerals, most importantly ettringite, as well as calcium-aluminasilica
gels, like that formed from Portland cement. Mortars with strengths ash high as
3,700 psi have been formulated at the CAER laboratory.
The research will focus on the creation of two classes of products. A medium strength
(2,000 psi to 3,000 psi) material made by pre-hydrating and milling the Gilbert spent bed
materials and stabilizing them with conventional fly ash. The second product is formed
by heating the spent bed material with other materials to form belite/sulfoaluminate
clinker, which, when ground and activated with conventional scrubber sludge, is the base
for sulfoaluminate cement (SAC). This material is of high value. It is very rapid and
very hard setting and capable of forming very high strength concrete (i.e. 10,000 psi to
12,000 psi). It's performance is as good as, or for some applications better than, that of
Portland cement. China currently produces about one million ton per year SAC cement.
Research will focus on formulations for both classes of materials that optimize stability.
Issues to be addressed include pre-hydration and strength optimization, dimensional
stability (e.g. shrinkage and expansion) and durability (e.g. freeze-thaw, chlorination and
carbonation resistance).
Status | Finished |
---|---|
Effective start/end date | 7/1/06 → 6/30/08 |
Funding
- KY Office of Energy Policy: $250,466.00
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