Exxon Chemical's Coal-Fired Combined Cycle Power Technology

Abstract

Exxon Chemical's Central Engineering Division has recently developed and patented CAT-PAC for Industrial Cogeneration and Utility Power Plants. It involves the marriage of a conventional direct pulverized coal-fired boiler radiant section with a convection section adapted from our furnace experience. In particular, it is an open-cycle, hot air turbine arrangement with indirect heating of the air in the boiler convection section. The turbine exhaust is then used as pre-heated combustion air for the boiler. The air coil heats the 150 psig air from the standard gas turbine axial compressor to approximately, 1750°F. Today, CAT-PAC would require about 10% less fuel (or 1000 Btu/kwh) than the best coal-fired Utility Plant for the same net power output, at a comparable investment. With improved air heater metallurgy, and/or trim firing of a premium fuel (up to 2000° F permissible gas turbine temperature), CAT-PAC savings would double to 20%. Today, in an industrial coal-fired cogeneration plant, CAT-PAC can produce up to 75% more power for a given steam load, while maintaining the highest cogeneration efficiencies. With improved metallurgy, and/or trim firing, the additional power would approach 100%.