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

There had been several processes for recovering exhaust gas heat at the boiler cold-end, thereby increasing the efficiency of a thermal power plant. However, the existing processes encounter a great challenge on the heat exchanger, wherein the acid corrosion, fouling and abrasion of heating surfaces are inevitable because it is working in very low temperature flue gas. In this paper, a novel hot air recirculation (HAR) process is advanced to avoid these tricky problems. To demonstrate the thermo- and techno-economic performance of the HAR, an in-service 600 MW brown-coal-fired power unit was used as a reference unit for analyses. Meanwhile, the performance of the conventional bypass flue (CBF) process was also calculated for comparison. The results show that, when recovering the boiler exhaust heat from 148 °C to 90 °C, the net coal savings, initial capital cost and payoff period of the HAR are 7.31 g/(kW·h), 2.522 million USD and 1.08 years, whereas the corresponding results of the CBF are 6.79 g/(kW·h), 6.074 million USD and 3.24 years. Overall, the HAR can benefit the power plant from a safe and reliable operation, a greater net coal savings and a better techno-economic performance, exhibiting an obvious superiority in the similar processes.