基于CFD的焚烧炉二次风优化布置数值模拟研究

Numerical investigation on the optimized arrangement of secondary air in incinerator based on CFD

为研究二次风布置形式和前后墙风速对焚烧炉内流场、温度场及污染物生成浓度的影响规律,针对某200t/d城市生活垃圾焚烧炉进行了CFD数值模拟研究,采用FLIC与FLUENT软件分别模拟了垃圾床层燃烧及炉膛气相燃烧过程,借助二次开发平台开发了自定义程序,完成了FLIC与FLUENT数据耦合。仿真结果表明,当二次风口采用交错布置时,前墙风速(21.657m/s)应小于后墙风速(40.220m/s),烟气主流位于炉膛出口中央,二次风根部产生的涡流较小,烟道内气流分布更为均匀,烟气充盈度更佳。当二次风口采用对冲布置时,前墙风速应等于后墙风速(风速为33.413m/s),高温烟气才能位于烟道中部。通过对比污染物生成浓度,发现在采用前后墙各12个二次风口并且互相交错布置时,当前墙风速(21.657m/s)小于后墙风速(40.220m/s),所产生的CO浓度最小,数值为41.64mg/Nm^(3),上述发现可为焚烧炉设计时合理地选择技术参数、改善燃烧效率、降低能耗提供理论支撑。

To study the influence of secondary air layout and front and rear wall wind speed on the flow field,temperature field,and pollutant generation concentration inside incinerator,CFD numerical simulation was conducted to investigate a 200t/d municipal solid waste incinerator.software FLIC and FLUENT were used respectively to simulate the combustion process of dense waste bed and the gaseous phase combustion inside furnace chamber.A customized program was developed using the secondary development platform to achieve the coupling of FLIC and FLUENT data.The simulation results indicate that,in the scenario that secondary air is arranged in staggered manner,front wall wind speed(21.657m/s)should be slower than rear wall wind speed(40.220m/s)to keep the main flue gas flow located in the center of furnace and reduce the vortex generated at the root of secondary air,which leads to a more uniform airflow distribution and a higher filling degree of flue gas in furnace.While secondary air is arranged in a countering manner,front wall wind speed is roughly equal to back wall air wind(33.413m/s)so that high-temperature flue gas is kept in the middle of furnace.Furthermore,a minimum CO concentration(41.64mg/m^(3))was found in the scenario of staggered arrangement of secondary air,the front wall wind speed(21.657m/s)is slower than the rear wall wind speed(40.220m/s),The secondary air arrangement manner introduced in this paper is favourable to reduce energy consumption and improve combustion efficiency,which provides reasonable technical parameters for design of incinerator.