小型循环流化床锅炉的选择性非催化还原脱硝工艺改造

Retrofit of Selective Non-catalytic Reduction Denitrification Process of Small-scale Circulating Fluid Bed Boiler

为应对日益严峻的环境问题,进一步降低NOx排放浓度,对一台15 t/h循环流化床锅炉进行选择性非催化还原(SNCR)脱硝工艺改造。首先对旋风分离器内的流场进行了模拟,模拟结果表明,烟气在旋风分离器内的速度分布呈现出较好的对称性,能够为SNCR脱硝过程提供良好的混合及反应条件。在此基础上,根据锅炉结构特征和实际运行情况,为锅炉设计并安装脱硝系统。经过调试,SNCR脱硝系统运行稳定,经济性良好。锅炉高温烟道和尾部烟道内烟气中的NO_x浓度分别降低了54.9%和44.9%,NOx排放浓度和氨逃逸量均远低于相关标准的限值。

In order to deal with the increasing environmental problems and further reduce NOxemissions,a 15 t/h circulating fluid bed boiler was retrofitted by selective noncatalytic reduction（ SNCR） denitrification technology. Firstly the flow field in the cyclone separator was simulated,and the results show that the velocity distribution of flue gas exhibits a pretty symmetry,which can provide a good mixing and reaction condition for the SNCR denitrification process. Based on that,the SNCR denitrification system is designed and installed for the boiler in accordance with its structural characteristics and practical operation. After debugging,the denitrification system runs stably and economically,and NO_x concentrations at high temperature gas duct and tail duct decreased by 54. 9% and 44. 9% respectively. The concentration of NO_x emission and the amount of escaped ammonia are far below the limits of relevant standards.