某300MW燃煤锅炉选择性催化还原脱硝导流系统的分析

Analysis of the Selective Catalytic Reduction Denitrification and Diversion System for a 300 MW Coal-fired Boiler

为探究某300 MW燃煤锅炉选择性催化还原(Selective Catalytic Reduction,SCR)脱硝系统内烟道导流方案的可行性,利用FLUENT 6.3软件,对该导流方案下SCR系统的流场和氨浓度分布进行数值模拟研究.结果表明:烟道截面变化以及弯头偏转导致系统流场严重不均,且现有导流系统导流效果较差,AIG下游截面最大速度偏差达31.25 m/s,反应器入口速度也存在偏差,且尾部烟道内流场不均,会对下游设备产生影响;系统流场不均导致氨浓度不均,AIG下游截面氨的浓度偏差达60.0%,反应器入口截面氨的浓度偏差达38.4%,大的浓度偏差严重影响系统的脱硝效率,且反应器出口氨逃逸量达5.266 ppm,这会对大气造成二次污染.这些研究结果可为燃煤锅炉选择性催化还原脱硝导流系统的改进提供参考.

In order to explore the feasibility of the fluid diversion in the flue of the Selective Catalytic Reduction denitrification system for a 300 MW coal-fired boiler,utilizing the software FLUENT 6. 3,the flow field and the distribution of ammonia concentration of the Selective Catalytic Reduction system under the diversion schemes were analyzed by numerical simulation. The results show that the flow field of the system is severely nonuniform because of the variation of the flue’s sections and the deflection of the elbow,and the efficiency of the present diversion system is poor,the maximum velocity deviation is up to 31. 25 m / s in the downstream sections of AIG. The deviations exist among the inlet velocities of reactors,the flow field in the tail flue is nonuniform,which will affect the operation of the devices in the downstream. The nonuniform flow field of the system results in the nonuniform distribution of ammonia concentration.The deviation of ammonia concentration is up to 60. 0% in the downstream sections of AIG,and the deviation of ammonia concentration is up to 38. 4% in the inlet sections of reactors,which severely affects the denitrification efficiency. The quantity of ammonia escape is up to 5. 266 ppm in the outlet of reactors,which will cause secondary pollution to atmosphere. The investigation results have important reference for the improvement of the Selective Catalytic Reduction denitrification and diversion system for coal-fired boilers.