废木料焚烧炉燃烧过程的数值模拟

Simulation of wood chips combustion process in biomass furnace

采用数值模拟方法研究了废木料焚烧炉的流动与燃烧状况,以预见不同条件下废木料燃烧与污染物的排放。应用RNGk ε双方程模型联合几率分布函数(pdf)的组分输运方程,结合颗粒轨道模型对废木料焚烧炉进行数值模拟,计算结果揭示了各种燃烧条件下,燃烧室内的速度场和温度场分布及CO等浓度分布。仅供一次风的情况下,二燃室出口温度高,CO燃烬效果较差;在合适的二次风供给的情况下,总的过量空气系数较小,对燃烧效果改善明显。

Numerical simulations of wood chips combustion process and emission were performed in order to predict the process of combustion and emission under different conditions using Navier-stokes equations, species transport equations, energy conservation equation, RNG k-ε turbulent closure and the joint PDF equations, as well as Lagrangian-Eulerian two-way coupling and discrete transfer radiation model for discrete phase particles. The numerical simulation of the composition of CO, CO_2 and O_2 , velocity and temperature field can provide the basis to improve the efficiency of gasification and combustion of wood chips, and the efficiency of co-firing of municipal solid waste and wood chips. When the primary air is only supplied, the temperature at the exit of secondary combustion chamber is higher and the CO concentration in exhaust gas is higher, too. However, the rate of burnout is improved evidently with staged air-supply and smaller excess air coefficient.