小型循环流化床锅炉NOx超低排放改造试验

Ultra-low NOx emission retrofitting test for small-scale CFB boilers

小型循环流化床锅炉NOx超低排放改造已经成为当前进一步推动工业源超低排放改造的重要对象。本文针对某台75 t/h循环流化床锅炉展开脱硝系统运行情况诊断、升级改造,并对脱硝系统实现超低排放的性能进行测试。结果表明:该锅炉测试过程中NOx原始生成质量浓度约210~270 mg/m^3,脱硝系统升级改造后,无炉内脱硫工况下,尿素喷射量增大至89 L/h(质量分数40%,下同)时,NOx排放质量浓度下降至28.7 mg/m^3,炉内脱硫工况下,尿素喷射量增大至95.2 L/h时,NOx排放质量浓度下降至48.10 mg/m^3;原选择性非催化还原(SNCR)脱硝系统效率较低,仅为22.29%~64.46%,改造后的SNCR脱硝系统在无炉内脱硫工况下脱硝效率达到了约90%,炉内脱硫工况下脱硝效率最高近77.5%;SNCR脱硝系统提效改造技术路线对小型循环流化床锅炉NOx超低排放改造效果较好,但应尽量减少炉内脱硫工艺的影响。本研究对全国小型循环流化床锅炉NOx超低排放改造具有重要的借鉴意义。

Ultra-low NOx emission retrofitting for small scale circulating fluidized bed(CFB)boilers has become the important project for further promoting the ultra-low emission retrofitting for industrial sources currently.In this study,the denitration system of a 75 t/h CFB boiler was diagnosed and upgraded.Moreover,the performance of the denitration system to achieve ultra-low emissions was tested.The results show that,during the whole test,the original mass concentration of NOx generated in the boiler was 210~270 mg/m^3.After the retrofitting,the NOx emission mass concentration decreased to 28.7 mg/m^3 while the injection amount of urea solution increased to 89 L/h(mass fraction 40%)without in-furnace desulfurization.The NOx emission mass concentration decreased to 48.10 mg/m^3 while the injection amount of urea solution increased to 95.2 L/h with in-furnace desulfurization.The denitration efficiency of the original selective non-catalytic reduction(SNCR)denitration system was only 22.29%~64.46%,which was relatively low,and after the retrofitting,it reached about 90%without in-furnace desulfurization,and 77.5%with in-furnace desulfurization.The technical route for efficiency improvement of the SNCR denitration system was suitable for ultra-low NOx emission of small CFB boilers,but the effect of in-furnace desulfurization should be minimized.This study will provide an important reference for ultra-low NOx emission retrofitting of nationalwide small-scale CFB boilers.