CH-18-010 -- Improving the Energy Efficiency of a Midsize Power Plant by Increased Recovery and Reuse of Waste Heat PDF

An older, midsized coal-fired power plant was studied toimprove overall plant efficiency. The power plant consists of acirculating fluidized bed (CFB) boiler and three turbines thatproduce up to 120 MW of electricity. Lake water provides coolingto the cycle through the condenser. The study examinedincreasing the heat recovery from the exhaust gases to increasethe overall efficiency. Flue gas from the CFB is regularly near160°C (320°F), allowing for a large amount of potential heatrecovery. One realistic scenario was a 66.7°C (120°F) reductionof flue gas temperature, being partially condensed in aseparate coated heat exchanger. If the recovered energy iscompletely used, the cycle efficiency would increase by 0.83%.The study examines possible uses for the heat, such as sellingit to an industry if one was nearby, drying incoming coal,preheating air, or running an organic Rankine cycle (ORC).Selling the energy to an industry, if one was nearby, was thebest economic option because there was a fairly low initialcost, and much of the heat could be used with the appropriateindustry./p>