Techno‐economic comparison of boiler cold‐end flue gas heat recovery processes for efficient hard‐coal‐fired power generation

An important method to increase the efficiency of thermal power plants is to recover the exhaust gas heat at the boiler cold‐end with the stepwise integration of a steam turbine heat regenerative system. To this end, there are currently three typical heat recovery processes, that is, a low‐temperature economizer (LTE), segmented air heating (SAH) and bypass flue (BPF). To provide useful guidance to thermal power plants for optimal and efficient processes, the thermal economy and techno‐economic performance of the three aforementioned processes were calculated and compared using an in‐service 600‐MW hard‐coal‐fired ultra‐supercritical power unit as a reference. The results demonstrate that with the use of the LTE, SAH and BPF, respectively, to recover the exhaust heat, reducing the exhaust temperature from 122 °C to 90 °C, the net standard coal consumption rate of the 600‐MW unit can be reduced by 1.51, 1.71 and 2.81 g/(kW h). The initial costs of the three heat recovery projects are 1.69, 2.91 and 2.53 million USD. If the 600‐MW unit runs 5500 h per year at the rated load, the three processes can increase the earnings of the unit by 0.49, 0.52 and 0.94 million USD from coal savings annually, meaning that their dynamic payback periods are 4.42, 8.66 and 3.29 years, respectively. The results indicate that for a hard‐coal‐fired power unit, the coal savings achieved by exhaust heat recovery are notable. Among the three processes, SAH shows the worst techno‐economic performance because it induces a significant increase in initial costs while obtaining a limited increase in thermal economy, while BPF exhibits the best techno‐economic performance owing to the significant increase in thermal economy. Copyright © 2016 John Wiley & Sons, Ltd.