Techno-economic evaluation of the novel hot air recirculation process for exhaust heat recovery from a 600 MW hard-coal-fired boiler

To increase the efficiency of thermal power plants, we have recently proposed and analyzed a novel exhaust heat recovery process called hot air recirculation (HAR), applied to a brown-coal-fired power unit as a test case. However, the performance of HAR, applied to a hard coal-fired power unit, is not clearly understood yet. In this study, the HAR process was redesigned to match the actual supply air and flue gas layout of a hard-coal-fired boiler. The thermo- and techno-economic performances of HAR, as well as the conventional bypass flue (CBF) process, applied to a 600 MW hard-coal-fired power unit, were analyzed in detail. The results indicate that, when the boiler exhaust heat is recovered from 122 to 90 degrees C, the net coal savings, initial capital cost, and payoff period of HAR are 3.49 g/(kW.h), $1.473 million, and 1.34 years, respectively, whereas those of CBF are 2.98 g/(kW.h), $2.528 million, and 3.04 years, respectively. Therefore, it is established that HAR can benefit a hard-coal-fired power plant with a greater saving on coal consumption and a more economical project investment, in addition to providing a safe and reliable operation, as compared to similar processes. (C) 2020 Elsevier Ltd. All rights reserved.