燃煤烟气超低排放全流程协同削减三氧化硫效果分析

Analysis on Coordinated Reduction of SO_3 in Whole Process of Ultra-low Emission in Coal-Fired Flue Gas

烟气三氧化硫(SO_3)是形成雾霾的前驱体之一,研究火电厂烟气污染物控制流程中SO_3的形态、浓度、排放水平以及影响因素很有必要。对容量300~1 000 MW的燃煤机组超低排放设施进行实测,并对1 000 MW机组开展了全流程测试,同时与常规污染物控制流程进行比较,表明超低排放设施对SO_3具有更好的控制效果,SO_3综合脱除效率可达到90%。对烟气流程各设备脱除SO_3机理与减排效果进行分析,结果表明:(1)SCR脱硝装置具有将SO_2催化氧化成SO_3的作用。(2)空气预热器烟温降低过程间接消耗SO_3,低低温电除尘器、湿法脱硫吸收塔与湿式电除尘器对SO_3有削减作用,各设备对SO_3的削减份额分别占SO_3总量的30%、40%、15%、5%。(3)空气预热器、电除尘器运行温度对SO_3脱除率有较大影响。(4)高效脱硫协同除尘一体化吸收塔具有更好的脱除SO_3效果。

It is necessary to study the formation,concentration,emission level and influencing factors of the sulfur trioxide in the control process of flue gas pollutants in thermal power plants because the sulfur trioxide in the flue gas is one of the precursors of smog.Based on the onsite measurements of ultra-low emission facilities of300~1000MW coal-fired units and the whole process test of a1000MW unit,the comparison with the conventional pollutant control process shows that the ultra-low emission facilities have a better control effect on SO3with SO3comprehensive removal efficiency reaching90%.The SO3removal mechanism and effect of each equipment in flue gas flow process were also analyzed.The results show that:(1)SCR denitrification device has a catalytic oxidation effect on SO2converted to SO3.(2)The air preheater consumes SO3indirectly during the process of the flue gas temperature drop.The low-low temperature electrostatic precipitator,the wet desulfurization absorber and the wet electrostatic precipitator all contribute to the SO3reduction,accounting for30%,40%,15%and5%of total reduction respectively.(3)The air preheater,electrostatic precipitator operating temperature has great impacts on SO3removal rate.(4)The high-efficiency desulfurization synergistic dust removing integrated absorption tower has a better effect of SO3removal.