超低排放下燃煤电厂氨排放特征

Characteristics of Ammonia Emission in Flue Gas from Ultra-Low Emission Coal-Fired Power Plants

燃煤电厂采用SCR(选择性催化还原)脱硝过程消耗大量的氨,同时存在氨逃逸和氨排放问题.为了掌握超低排放燃煤机组的氨排放程度、脱硝氨逃逸情况以及各环保设施对氨的协同脱除能力,为燃煤电厂氨减排政策制定和氨减排技术研发提供支持.在京津冀大气污染传输通道城市中选取11个城市中的14台机组,采用例如DL T 260—2012《燃煤电厂烟含脱硝装置性能验收试验规范》的标准方法用稀硫酸吸收烟气中的氨再结合分光光度测试方法,对环保设施多个位置的烟气中氨进行浓度测试.结果表明:①氨排放浓度介于0.05~3.27 mg/m^3之间,平均约0.95 mg/m^3,通过烟气排入大气中氨的浓度不高;②测试的14台机组中有7台机组(约50%)脱硝氨逃逸值高于设计值(2.28 mg/m^3),说明脱硝氨逃逸超过设计值呈普遍现象,个别电厂脱硝氨逃逸严重,氨逃逸亟待解决;③环保设施对逃逸氨具有较好的协同脱除能力,平均脱除率约为64.86%.建议对于SCR脱硝氨逃逸严重的机组,对SCR出口烟道截面氮氧化物(NO x)实施网格式测试,在此基础上实施精细化精准喷氨、优化流场、提高SCR脱硝运行水平(或采用专业化运维),从源头上减少氨耗量,降低系统能耗和氨排放.

Selective catalytic reduction(SCR)denitration process in coal-fired power plants consumes massive amount of ammonia,also generates subsequent problems including ammonia emission and ammonia slip.In-depth study of ammonia emission,such as ammonia slip level and ammonia removal efficiency in the existing ultra-low emission systems of coal-fired power plants can facilitate the formulation of ammonia emission reduction policies and development of ammonia emission reduction technologies.In this study,14 coal-fired power plants in 11 cities in the air pollution transmission channel of the Beijing-Tianjin-Hebei Region were selected to test the ammonia concentrations at multiple locations of environmental protection facilities.According to the standard test methods such as DL T 260-2012,ammonia in the flue gas was absorbed by dilute sulfuric acid,and the ammonium concentrations in the solution were determined by spectrophotometry.The results showed that the ammonia emission concentration was low in the chimney,ranging from 0.05 to 3.27 mg/m^3,with an average of 0.95 mg/m^3.However,the NH 3-slip concentration of 50%units(7 of the 14 units tested)was higher than the design concentration of 2.28 mg/m^3,indicating that a common phenomenon that the NH 3-slip concentration of denitration exceeded the design concentration.In some units,serious ammonia slip became a crucial problem.In addition,dry dedusting,wet desulfurization and wet electrostatic precipitator had good ammonia removal ability,with an average removal rate of about 64.86%.For serious NH 3-slip units,it was suggested to carry out network measures of NO x concentration at the outlet of SCR then conduct refined ammonia spraying and flow field optimization of flue gas to improve SCR denitration operation level(or employ professional operation and maintenance services).These measures can reduce ammonia consumption,reduce system energy consumption and reduce ammonia emissions.