燃煤烟气常规污染物净化设施协同控制汞的研究

Research on Mercury Collaborative Control by Conventional Pollutants Purification Facilities of Coal-fired Power Plants

采用Ontario Hydro方法对国内20个典型燃煤电厂选择性催化还原脱硝(selective catalytic reduction denitrification,SCR)系统、除尘系统(静电除尘器electrostatic precipitator,ESP)、布袋除尘器(fabric filter,FF)、湿法烟气脱硫系统(wet flue gas desulfurization,WFGD)前后烟气汞的形态和浓度进行测试,研究电厂常规污染物控制设施对烟气汞的形态转化及协同控制作用。结果表明,SCR对烟气中总汞的减排效果不明显,但促进了Hg0向Hg2+的转变;SCR催化氧化Hg0与煤中的氯含量成正相关性,NH3对SCR催化氧化Hg0具有抑制作用。ESP/FF对烟气中汞的影响主要体现在对Hgp的协同脱除上,FF的脱汞效率高于ESP的脱汞效率,循环流化床锅炉配置ESP的脱汞效果高于煤粉炉配置ESP的脱汞效果。WFGD对汞的脱除依赖于烟气中Hg2+的比例,随着液气比(L/G)、pH的增加,WFGD脱汞效率逐渐增加。SCR促进了ESP、WFGD的脱汞效果,对于配置SCR+ESP+WFGD的燃煤电厂,对烟气汞的排放具有很好的协同控制能力。

OH method had been applied to determine the mercury speciation and concentration in flue gas emitted from twenty typical coal-fired power plants, which was equipped with conventional pollution control devices, including selective catalytic reduction denitrification （SCR）, precipitator （ESP/FF）, and wet flue gas desulfurization （WFGD）. The effect of the conventional pollution control devices on mercury emission was investigated. The results show that SCR has little effect on mercury emission reduction while SCR catalyst promotes the oxidation of Hg^0 to Hg^2＋ and mercury emission. The oxidation has significant impacts on of Hg^0 by SCR catalyst is greatly affected by chlorine content in coal and NH3 is detrimental to SCR catalytic oxidation of Hg^0. ESP/FF affects mercury emission by removal of Hg^p. The mercury removal efficiency of FF is higher than that of ESP, and mercury removal efficiency of circulating fluidized bed boiler is higher than that of pulverized coal boiler. The mercury removal efficiency of WFGD depends on the concentration of Hg^2＋, and with liquid gas ratio and pH increasing, mercury removal efficiency increases. SCR promotes the mercury removal by ESP and WFGD. The coal-fired power plants, equipped with SCR, ESP and WFGD, could well control mercury emission from flue gas.