关键词: 湿法脱硫, 石膏雨, 净烟气加热, 混合式烟气再热技术, 烟气再热器（GGH）, 热二次风, 煤耗

Abstract: A large number of raindrops, so-called gypsum rain are found frequently around the smoke stack of large thermal power plants with no GGH installedin the wet FGD system in China. , which seriously affects the environment and the living of people around the plant. It is mainly attributed to the lowe temperature and high humidity of the cleaned flue. Therefore, heating the cleaned flue gas by hot secondary air from boiler island, i. e. admixing and heating the cleaned flue gas(AHG) is designed and applied to eliminate the gypsum rain. Based on the practice in a cogeneration power plant in Fushun, the principle, implementing measure and main designed parameters of AHG are introduced. The technical and economic analysis is carried out with the test data, such as boiler efficiency, auxiliary power consumption and net coal consumption. Taking a 300-MW unit for example, the economics and the safety are compared among AHG, medium GGH and rotation GGH. Significant economic and social benefits are observed from the practice in which the gypsum rain is eliminated by AGH with low investment and annual cost, no corrosion or blocking compared with GGH.

Key words: wet flue gas desulfurization, gypsum rain, heating of cleaned flue gas, fundamentals on admixing and heating of cleaned flue gas, gas-gas heater, hot secondary air, coal consumption