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Notes from the Lab

GENERATING EFFICIENT ELECTRICITY

Burning coal in a fluidized bed combustor (FBC) at high pressure produces steam and hot gases that can run multiple electricity-generating units, producing a system with efficiencies well above those of traditional power plants. However, commercialization of pressurized FBCs has been slowed by the inability to predict how large plants will behave. Designs that produce high performance in a pilot plant often give unsatisfactory results when the full-scale bed is built-an expensive and time-consuming disappointment.

MIT Energy Laboratory researchers led by Leon Glicksman, professor of building technology and mechanical engineering, have now developed "scaling laws" for making physical models that simulate the behavior of full-scale beds but are a fraction of their size and run at room temperature and pressure. Working with industry, the MIT team has built small-scale models that accurately simulate the behavior of industrial FBCs of different sizes and designs.

The researchers are now examining how the design features and operating conditions of such scale models affect mixing, heat transfer, and other factors that contribute to performance. The insights produced will be equally valid for the large-scale beds being simulated. They have also found that analogous kinds of scale-model studies accurately predict the air-circulation behavior in large buildings. The work is funded by the DOE, the Electric Power Research Institute and the NSF.

(Source: Nancy Stauffer, MIT Energy Laboratory)

A version of this article appeared in MIT Tech Talk on November 20, 1996.

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