630MW燃煤超低排放机组SCR对汞的协同作用研究

Study on Mercury Synergistic Effect by SCR Catalyst of a 630 MW Coal-fired Ultra-low Emission Power Unit

对国内某630MW超低排放燃煤电厂选择性催化还原(SCR)烟气脱硝系统前后烟气汞的形态和质量浓度进行测试,研究了燃煤烟气气氛中氯、氨和SO3等在SCR表面的竞争机制及其对汞的协同作用。结果表明:SCR前后燃煤烟气总汞质量浓度和HgP质量浓度变化不大,SCR催化剂可促进汞氧化,对汞的排放特性产生了很大影响;烟气中氯的质量浓度对于SCR催化氧化Hg^0有较大影响,高氯煤燃烧后产生的高氯烟气流经SCR对Hg^0的氧化效果更好;NH_3对SCR催化剂催化氧化烟气中的Hg^0具有抑制作用;SO_3对SCR氧化Hg^0有促进作用;超低改造中增加催化剂层数对于Hg^0的氧化效果更好。

The mercury speciation and concentration in flue gas before and after selective catalytic reduction（SCR）system of a 630 MW coal-fired utility boiler were measured,while the reaction mechanism and effect of chlorine,ammonia and sulfur trioxide in flue gas on the mercury oxidation by SCR catalyst were studied.Results show that SCR has little effect on the mass concentration of total and particulate mercury.SCR catalyst promotes the oxidation of elemental mercury and has significant impacts on mercury emission characteristics.The oxidation of elemental mercury by SCR catalyst is greatly affected by the chlorine content in coal,and high chlorine-containing atmosphere obtained by burning high chlorine coal benefits the Hg^0 oxidation in the SCR system.NH3 is detrimental and SO3 is promotive to the SCR catalytic oxidation of elemental mercury.Increasing the number of catalyst layers is beneficial to the SCR catalytic oxidation of elemental mercury.