330 MW燃煤机组逃逸氨迁移转化特性研究

The migration and conversion characteristics of ammonia slip in a 330 MW ultra-low emission coal-fired unit

为研究某330 MW超低排放燃煤机组的逃逸氨迁移转化特性,使用固定污染源废气采样法结合靛酚蓝分光光度法和离子色谱分析法对烟气中不同形态的逃逸氨进行了检测。结果表明,选择性催化还原脱硝出口的逃逸氨在烟气经过全流程净化设施的过程中,占逃逸氨95%以上的气态氨转化为主要成分为硫酸铵盐的颗粒态氨或水溶性NH_(4)^(+),且其中超过90%被烟气净化设施脱除,仅有6.1%~6.6%的选逸氨以气态氨和颗粒态氨的形式直接排入大气。烟气经过空气预热器烟温下降,90%以上的气态氨转化为颗粒态氯,3%左右的选逸氧以颗粒态氧的形态被空预器冷端受热面拦截。烟气经过静电除尘器,剩余气态氨中20.0%~42.9%也转化为颗粒态氨,同时85%以上的逃逸氨以颗粒态氨的形态被脱除。之后,烟气在石灰石-石膏湿法脱硫系统和湿式电除尘器共同净化下,WFGD入口气态氨的8.3%~16.7%和颗粒态氨的37.5%~44.4%迁移进入浆液成为水溶性NH:,然后通过脱硫废水和石膏排出一部分。总之,330MW燃煤机组的逃逸氨在迁移转化过程中,85%以上的逃逸氨进入了粉煤灰,不足10%的选逸氨进入了浆液、脱硫废水、石膏或直排大气。

An experimental research was conducted on the ammonia slip migratio n and con version characteristics in a 330MW ultra-low emission coal-fired unit with sampling methods of stationary source flue gas and analysis methods of indophenol blue spectrophotometry and ion chromatography for detection of ammonia slip of different types.The results showed that all the ammonia slip at the outlet of the selective catalytic reduction denitrification system(SCR)was gaseous.In the process of flue gas passing through all the air pollution control devices(APCDs),the gaseous ammonia accounting for over 95%of the ammonia slip con verted to particle ammonia con sisti ng mainly of ammonium sulfate or water soluble NH_(4)^(+),over 90%of which were removed by APCDs later.Finally,only 6.1%~6.6%of the ammonia slip in form of gaseous ammonia and particle ammonia directly discharged into the atmosphere.Specifically,after passing through the air heater(AH),the flue gas temperature decli ned sharply.More than 90%of the gaseous ammonia con verted to particle ammonia and about 3%of the ammonia slip was trapped by the cold end heated surface of AH in form of particle ammonia.When passing through the electrostatic precipitator(ESP),20.0%~42.9%of the left gaseous ammonia also con verted to particle ammonia and more than 85%of the ammonia slip as particle ammonia were removed.After the flue gas was sequentially purified by the limestone-gypsum wet flue gas desulfurization(WFGD)and the wet electrostatic precipitator(WESP)system,8.3%~16.7%of gaseous ammonia and 37.5%~44.4%of particle ammonia at the inlet of WFGD migrated into the slurry as water soluble NH_(4)^(+),part of which was discharged with gypsum and desulfurization waste water.In a word,less than 10%of the ammonia slip entered into slurry,desulfurization waste water and gypsum or directly emitted into atmosphere,while over 85%of ammonia slip migrated into fly ash in the process of migration and conversion in a 330MW ultra-low emission coal-fired unit.