循环流化床锅炉SNCR+SCR联合脱硝流场优化研究

Flow field optimization study of SNCR + SCR combined denitrification on CFB boiler

采用CFD软件对某75 t/h燃煤型循环流化床锅炉SNCR+SCR联合脱硝的速度场、浓度场、温度场进行了数值模拟,比较了SCR部分优化前后的速度分布、浓度分布,并重点研究了SNCR部分还原剂喷入点的位置、喷射速度、喷雾粒径、喷雾锥角对SNCR脱硝的影响。结果表明:对该脱硝装置中的SCR部分进行优化时,可以仅对速度场进行优化而忽略对还原剂浓度场的优化;对于SNCR部分,还原剂喷入点设在进口段内侧优于外侧;增大喷射速度、增大雾化粒径均能增强还原剂与烟气的混合,有利于SNCR脱硝反应,而增大喷雾锥角对还原剂浓度分布的影响并不明显。

The velocity field,concentration field and temperature field of SNCR ＋ SCR combined denitrification on a 75 t/h coal-fired CFB boiler were numerically simulated by CFD software. The velocity and concentration distribution were compared before and after optimization,and the effect of the location,injection speed,spray size and spray cone angle of reductant on SNCR denitrification efficiency at SCR part were studied. The results show that when we optimize the SCR part of this denitrification device,only the velocity field needs to be optimized,and the optimization on the concentration field could be ignored. For the SNCR part,the reductant injection point located at the inside of inlet section,increasing the spray velocity and increasing the atomized particle size can enhance the mixing of reductant and flue gas,which is beneficial to the SNCR denitrification reaction.The effect of increasing the spray cone angle on the concentration distribution of reductant is not obvious.