燃煤烟气中SO_3迁移转化特性及其控制的研究现状及展望

Research status and prospects of migration, transformation and control of SO_3 from coal-fired flue gas

SO_3排放导致的烟羽浊度增大、蓝烟/黄烟现象及其排入大气环境后转化为二次气溶胶等问题,已引起广泛关注。燃煤电厂SO_3的排放主要由煤燃烧以及SCR烟气脱硝中SO2氧化形成,随着选择性催化还原(SCR)脱硝设施的推广应用及高硫煤使用量的增多,控制燃煤SO_3排放已迫在眉睫。本文分析综述了燃煤烟气SO_3在SCR脱硝过程、低低温电除尘、湿法烟气脱硫以及湿式电除尘中的生成、迁移转化及脱除特性。同时介绍了两类控制燃煤烟气系统中SO_3的技术,一是利用现有污染物控制设备的协同作用;二是喷射碱性吸收剂吸收SO_3,综合比较了各类碱性吸收剂以及不同喷射位置,提出一种将喷碱性吸收剂与脱硫废水烟道蒸发技术相结合的控制方法。最后指出探究烟气系统中SO_3迁移转化特性以及碱性吸附剂脱除SO_3的反应机理及其影响因素是未来燃煤烟气SO_3控制技术研究的发展方向。

The increased plume turbidity,the phenomenon of blue/yellow smoke and the conversion into secondary aerosol after its entry into the atmosphere caused by SO3 emission have aroused increasing attention.The emission of SO3 in coal-fired power plant mainly consists of coal combustion and SO2 oxidation in selective catalytic reduction(SCR).With the increasing application of SCR and the use of high sulfur coal,the control of SO3 emission from coal-fired is imminent.This paper reviewed the migration,transformation and removal of SO3 in SCR,low-low temperature electrostatic precipitator,wet flue gas desulfurization and wet electrostatic precipitator.At the same time,this paper expounds two kinds of SO3 control technologies in flue gas of coal-fired power plant,one is to take advantage of the synergistic effects of existing pollutant control devices,and the other is to absorb SO3 through the injection of alkaline absorbent.The different types of alkaline absorbent and the injection position were compared.A control method combining alkaline absorbent spray with desulfurization wastewater evaporation treatment in flue gas duct was put forward.It is pointed out that exploring the characteristics of SO3 migration and transformation in flue gas system,as well as the reaction mechanism of alkaline adsorbent for removing SO3 and its influencing factors are the developing directions on the research of SO3 control technology in coal-fired flue gas.