关键词: 褐煤, 火力发电厂, 烟道气, 余热利用, 技术经济性分析

Abstract: It is an important way to increase the efficiency of a thermal power plant by recovering the waste exhaust gas heat at boiler cold-end with a stepwise integration with the heat regenerative system of steam turbines. In this paper,an in-service 600MW lignite-fired supercritical power unit was used as a reference unit to calculate and compare the thermal economy and techno-economic performances of three kinds of typical heat recovery processes at boiler cold-ends:low-temperature economizer,segmented air heating and bypass flue. The results showed that,with the recovery of boiler exhaust heat from 148℃ to 90℃,the three above-mentioned processes can make the net standard coal consumption rate reduced by 4.43g/(kW·h),5.84g/(kW·h) and 6.48g/(kW·h),respectively. Meanwhile,25.62 million CNY,23.48 million CNY and 22.61 million CNY are needed as the initial costs of the three heat recovery projects. If the 600MW unit runs 5500 hours per year with the rated load,the three processes can annually increase the earning of the unit by 9.94 million CNY,13.50 million CNY and 15.14 million CNY from coal savings,meaning that their dynamic payback periods are 3.12 years,2.00 years and 1.71 years,respectively. Those results indicate that the efficiency of a lignite-fired power unit can be significantly increased via an exhaust heat recovery process. Among the three processes,the bypass flue process shows the best thermal economy and techno-economic performance,therefore,it is recommended for preferential applications.

Key words: lignite, thermal power plant, flue gas, waste heat recovery, techno-economic analysis