大型CFB锅炉的SNCR-SCR耦合脱硝技术应用  

Application and Discussion of SNCR-SCR Coupling Denitrification Tchnology in Large CFB Boiler

作　　者：胡刚 刘伟 HU Gang;LIU Wei(Shaanxi Energy Linbei Power Generation Co.,Ltd.,Baoji 721500,China)

机构地区：[1]陕西能源麟北发电有限公司,陕西宝鸡721500

出　　处：《电力学报》2022年第4期336-342,共7页Journal of Electric Power

摘　　要：基于低温燃烧方式的优势特点,CFB锅炉普遍采用SNCR(选择性非催化还原)烟气脱硝技术。在基本负荷(50%~100%BMCR)下,锅炉燃烧工况稳定,旋风分离器入口烟气温度适当(800℃~950℃),SNCR脱硝能力可满足NO超低排放要求,若CFB锅炉机组参与电网深度调峰(30%~50%BMCR)期间,锅炉燃烧工况减弱,旋风分离器入口烟气温度低(650℃~750℃),采用单一的SNCR脱硝技术会导致脱硝效率明显下降,无法满足新的火电厂大气污染物NO排放标准。以某电厂2×350 MW超临界循环流化床锅炉为例,对低于50%额定负荷工况下,SNCR反应窗口温度失调而导致的脱硝尿素耗量大、效率低、氨逃逸率高、空预器堵塞、尾部烟道及设备腐蚀等问题进行分析,提出了大型CFB锅炉SNCR-SCR耦合脱硝技术应用改造方案。利用机组检修窗口期,在锅炉后端空间安装一层SCR低温(280℃~420℃)催化剂。改造后,机组在30%~100%负荷下,脱硝效率可达到75%以上,尿素消耗量最高可下降近50%。运行实践证明,SNCR-SCR耦合脱硝技术具有脱硝效率高、投资及运行费用低,可以分步实施优化改造等特点,对大型CFB锅炉烟气脱硝技术改造方案的选择具有借鉴价值。Based on the advantages of low temperature combustion,SNCR(selective non-catalytic reduction)is widely used in flue gas denitrification technology of CFB boilers.Under the basic load of CFB boiler(50%~100%BMCR),the boiler combustion condition is stable,the flue gas temperature of cyclone separator inlet is appropriate(800℃~950℃),and the SNCR denitrification capacity can meet the requirements of NO_(x) ultralow emission.If the CFB boiler unit is involved in the depth peak regulation of the power grid(30%~50%BM-CR),the boiler combustion condition is weak,the flue gas temperature at the inlet of the cyclone separator is low(650℃~750℃),and the denitrification efficiency of the single SNCR denitrification technology decreases significantly.It cannot meet the NO_(x) emission standard of the new thermal power plant.A 2×350 MW supercritical circulating fluidized bed boiler unit in a power plant is taken as the example,and typical problems such as large consumption of denitrification urea,low efficiency,high ammonia escape rate,air preheater blockage,tail flue and equipment corrosion caused by the temperature imbalance of SNCR reaction window under the condition that the two units are lower than 50%rated load are analyzed.During the unit grade maintenance window,a layer of SCR low-temperature(280℃~420℃)catalyst was installed in the rear end space of the boiler.After the transformation,the denitrification efficiency of the unit can reach more than 75%under 30%~100%load,and the maximum urea consumption can be reduced by nearly 50%.The operation practice proved that,SNCR-SCR coupled denitrification technology has the characteristics of high denitrification efficiency,low investment and operation cost,and can be implemented step by step to optimize the transformation.It has reference value for the selection of flue gas denitrification transformation technology of large CFB boiler units.

关 键 词：CFB锅炉 SNCR-SCR NO_(x) 氨逃逸 

分 类 号：TK229.66[动力工程及工程热物理—动力机械及工程]