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Ceramic exchanger beats the heat.

The U.S. Department of Energy is funding the development of a ceramic heat exchanger that will make possible the mating of a conventional coal combustor with a gas turbine engine. The exchanger is being built as part of a program for the development and testing of an externally fired combined-cycle (EFCC) design that would allow electric utilities in the United States to use coal to produce electricity. The cycle would be capable of heat rates of 7500 to 8000 Btu/kWh at a total power generation cost lower than other fossil fuel alternatives currently available,

Gases produced by coal combustion are not used to directly drive gas turbine engines, as they are laden with impurities such as sulfur and carbon dioxide. The exchanger, which is being designed by Hague International (South Portland, Maine), transfers the heat produced in the coal combustor to a stream of clean high-pressure air that spins the turbine.

Ceramics are used in the exchanger to withstand the approximately 3500 [degrees] F produced by coal combustors. The exchanger transfers enough heat to bring the turbine air-stream temperature up to about 2300 [degrees] F

Hague is also developing a system to prevent fly-ash particles in the coal gas stream from sticking to exchanger tubes. For larger particles, an inertial impact separator will be used, said Hague International president Paul LaHaye. Finer particles could be separated by electrically charging the particles before the gases enter the exchanger. An electric field then would shunt them away.

The exchanger will be put through its paces in a test facility being built near South Portland. The test site is funded with $2.2 million from the DOE, with an additional $2 million coming from Hague and a group of industrial sponsors including Foster Wheeler, du Pont, Stone & Webster, Pyropower, Consolidated Edison, Florida Power, and the Empire State Electric Energy Research Corp.

The exchanger is part of the broader EFCC effort, which is being led by Hague and Stone & Webster. The EFCC concept, which can be adapted to existing steam-cycle power plants, was described in papers presented at the 1989 ASME Third International Symposium on Turbo-machinery, Combined-cycle Technologies, and Cogeneration and the 1990 52d Annual Meeting of the American Power Conference.

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Title Annotation:Tech News; ceramic heat exchanger
Publication:Mechanical Engineering-CIME
Date:Apr 1, 1991
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