大型燃煤锅炉SNCR/SCR混合脱硝数值模拟及工程验证

Numerical simulation and engineering confirmation of hybird SNCR / SCR process in commercial coal-fired boiler

为了提高选择性非催化还原/选择性催化还原(SNCR/SCR)混合脱硝中的还原剂在锅炉尾部烟道内的分布均匀性,基于FLUENT平台,对300 MW燃煤机组SNCR/SCR混合脱硝系统进行了数值模拟,重点分析转向室补氨喷射位置、混合器结构对烟气中氨氮组分混合的影响,计算结果与试验测量数据吻合很好.结果表明:SNCR反应后,转向室出口还原剂分布极不均匀;转向室侧墙补氨喷枪越靠近转向角位置,越有利于提升烟道内还原剂的平均分布;SCR反应器入口烟道设置新型复合X型混合器,进一步强化NH3与烟气的均匀混合,反应器首层催化剂入口截面还原剂浓度分布偏差从22%降低至7.4%;将优化的补氨喷射位置与混合器结构应用于现场锅炉,SNCR和SCR脱硝效率分别达到了35%和78.4%,SNCR/SCR联合脱硝效率达85.96%,脱硝效果良好.

To improve the uniform distribution of the reducing agent in the tail flue of the hybrid selective non-catalytic reducing and selective catalytic reducing（ SNCR / SCR） process,numerical simulation was performed for the hybrid SNCR / SCR process in a 300 MW pulverized-coal boiler by using the FLUENT software. The influence of ammonia supplementary position and mixture structure on the distribution of ammonia nitrogen in flue gas was emphatically analyzed. The calculation results agree well with the experimental data. the results reveal that after the SNCR reaction,the concentrations of the reducing agent distribute quite unevenly at the outlet of the reversing chamber.However,with the ammonia supplementary position approaching the reversing angle,the uniform distribution of the reducing agent is improved. Additionally,the distribution can be further optimized by arranging the newhybrid X-mixer device at the inlet of the SCR system. The standard deviation factor for the concentration of the reducing agent in the inlet section of the first layer catalyst of the reactor decreases from 22% to 7. 4%. With the combination of the optimized ammonia supplementary position and the newhybrid X-mixer device applied to the industrial boiler,the DeNO_x efficiencies of SNCR and SCR process can achieve 35% and 78. 4%,respectively,and the total combined De-NOxefficiency of the SNCR / SCR is up to 85. 96%,showing a satisfactory denitration performance.