燃煤电厂湿法脱硫前逃逸氨迁移转化和脱除特性

Migration,transformation and removal characteristics of escapted ammonia before wet desulfurization in coal-fired power plants

采用固定污染源烟气采样法、靛酚蓝分光光度法和离子色谱法采集和分析3台超低排放燃煤机组在脱硝出口、空预器出口、除尘器出口烟气中各形态氨组成和排放浓度,结合机组运行工况和烟气处理系统特点,研究逃逸氨在空预器和除尘器内迁移转化和脱除特性.结果表明:各机组在高低负荷运行工况下脱硝出口逃逸氨均为气态氨,且分布不均明显,局部位置氨排放浓度高于2.5mg/m^(3).气态氨随烟气进入空预器,开始向颗粒态氨转化,空预器出口颗粒态氨排放量可占氨总排放量的47.21%~68.85%.空预器内烟气的温降和流速影响颗粒态氨生成量.除尘器可脱除大部分逃逸氨,脱除效果主要来自于对颗粒态氨的脱除.机组装备不同除尘系统对颗粒态氨的脱除性能各有差异.经过除尘器脱除作用后,除尘器出口烟气中逃逸氨以气态氨形式为主,排放浓度在0.15~0.60mg/m^(3)之间.

The ammonia composition and emission concentration in the flue gas at denitration outlet,air preheater outlet and dust remover outlet of three ultra-low emission coal-fired units were collected and analyzed by flue gas sampling method of stationary source,indophenol blue spectrophotometry and ion chromatography.Considering the characteristics of units operating conditions and flue gas treatment system,the migration,transtration and removal characteristics of escaped ammonia in air preheater and dust collector were studied.The results showed that the escaped ammonia at denitration outlet of all units was gaseous ammonia under high and low load operating conditions,and the distribution was uneven,with the ammonia emission concentration at typical locations higher than 2.5mg/m^(3).Gaseous ammonia begined to transform into filtrable ammonia when it flowed through the air preheater along with the flue gas.The filtrable ammonia emitted at the outlet of the air preheater could account for 47.21%~68.85%of the total ammonia.The temperature drop and flow velocity of flue gas in air preheater affected the generation of filtrable ammonia.The dust collector could remove most of the escaped ammonia,and the removal effect mainly came from the removal of filtrable ammonia.The removal performance of filtrable ammonia varied with dust collector systems.The escaped ammonia in the flue gas of dust remover outlet was mainly in the form of gaseous ammonia,and the concentration was between 0.15 and 0.60mg/m^(3).