小型CFB锅炉烟气脱硝改造两步法应用及探讨

Small CFB Boiler Flue Gas Denitration Modified Two-Step Application and Discussion

由于循环流化床(CFB)锅炉特有的结构和燃烧方式,其氮氧化物排放低于其它炉型,有清洁炉型之称,但随着烟气污染物排放标准的进一步提高,其氮氧化物的排放已不能满足新的排放需要。选择性非催化还原法(SNCR)工艺+低氮燃烧(LNB)脱硝技术具有投资费用少、运行成本低、锅炉改造范围小等优势,而CFB锅炉具有烟气在炉内停留时间长、便于还原剂在炉内混合等特点,该脱硝改造两步法在小型循环流化床锅炉脱硝改造中被广泛应用。本文以75t/h循环流化床锅炉为模型,并采用环保性较高的尿素作为脱硝还原剂,通过低氮燃烧(LNB)+SNCR工艺两步法脱硝技术改造方式,进一步提高脱硝效率,并对锅炉进行针对性的改进以提高其出力,最终使烟气中NO_x排放达到新的国家标准要求。主要从实施背景、技术路线、疑难问题解决及改造后的效果分析、存在问题等进行分析探讨。

Because of the circulating fluidized bed （CFB） boiler＇s own specific structure and combustion way, the nitrogen oxide emission is lower than other type furnace, which is regarded as clean furnace type. However, with the increase of flue gas pollutants emission standards, the nitrogen oxide emissions cannot meet the needs of the new emissions. Since selective non-catalytic reduction（SNCR） ＋ low nitro- gen combustion （LNB） denitration technology has the advantages of low investment and operation cost, small boiler retrofit, and the CFB boiler is easy for flue gas to stay in furnace for a long time and easy for reducing agent to be mixed in the oven etc, the denitration modified two-step in small circulating fluidized bed boiler denitration transformation is widely used. Taking 75t/h circulating fluidized bed boiler as a model, this paper describes using the environmental protection high urea as the denitration reducing agent by the low nitrogen combustion （LNB） ＋ SNCR process two-step denitration technology, and improving the denitration efficiency and the boiler＇s output by targeted improvements, which eventually make the NOx in flue gas emissions to meet the new national standard requirements. This paper is mainly from the implementation background, technical route, difficult problem solving, and the effect after transforming analysis, and existing problems to analyze and discuss.