基于半干法脱硫的300 MW CFB锅炉的SO3排放特性研究

某300 MW循环流化床(CFB)锅炉采用炉内喷钙、SNCR、预电除尘器和烟气循环流化床半干法脱硫的烟气净化路线,满足最新的超低排放要求。以该300 MW CFB锅炉为对象,分别对不同工况下不同烟道位置的SO_3浓度进行监测分析。结果表明:原始SO_3浓度随锅炉负荷升高而降低,负荷升高促进了预电除尘器对SO_3的捕集,但不利于半干法脱硫装置对SO_3的脱除;炉内脱硫减少了原始SO_3的形成,但提高了飞灰的比电阻,降低了预电除尘器的SO_3脱除效率; SO_3的形成和脱除基本不受煤种的影响,不同工况下半干法脱硫装置对SO_3的脱除率达到了95%以上,与预电除尘器相结合,可脱除锅炉燃烧产生的95%～97%SO_3;采用烟气循环流化床半干法脱硫的技术路线,最终SO_3排放浓度低于1. 2 mg/m3,完全消除了"蓝烟"现象。

Research on SO3 Emission Characteristics of a 300 MW CFB Boiler based on Semi-Dry Flue Gas Desulfurization

A 300 MW CFB boiler achieved ultra-low emission with the combination of in-furnace desulfurization,SNCR,pre-ESP,and circulating fluidized bed flue gas desulfurization (CFB-FGD).SO3 concentration at different sampling points under different operation conditions were detected and analyzed.Results revealed that,the original SO3 content declined with the increase of boiler load,which improved the capture of SO3 in pre-ESP,but decreased SO3 removal efficiency of CFB-FGD.In-furnace desulfurization inhibited the formation of SO3,but increased fly ash resistivity,and thus resulted in lower SO3removal efficiency of pre-ESP.The formation and the removal of SO3 were almost unaffected by coal type.Under all conditions,SO3 removal efficiency of CFB-FGD was higher than 95%.With the combination of pre-ESP and CFB FGD,95%~97% of the original SO3 could be removed,and the final emission rate was under 1.2 mg/m3,which meant stack blue plume was completely eliminated.