多喷嘴对置式气化炉内气固两相流动与炉壁的颗粒捕捉特性

摘要

3D numerical simulation was conducted to investigate the gas-solid two phase flows and particle capture characteristics of the wall in an opposed multi-burner gasifier. The Realizable k-εmodel was used to calculate the complex turbulent gas flow, Euler-Lagrange model was used to simulate turbulent gas-solid flows in the gasifier, while stochastic trajectory model was adopted to trace particles trajectories. The simulation results agree with the experimental data of cold model reasonably well, the flow field conforms to the phenomenon of the hot model experimental results, and the average diameter of the particles the gasifier wall captured is consistent with the experimental data of hot model. The results show that the average diameter of particles captured by the wall of gasifier wall presents certain regularity. There are two positions (2.8 m above and 0.2 m below the burner plane) where the average diameter of the particles has local maximums. Above the burner plane, the captured particle diameters decrease as the density of the particles increases. The particle deposition covers the entire lining of gasifier, and with the effect of impacting stream the deposition rate reaches the greatest at positions of 1.8 m above and 1.9 m below the burner plane respectively. Shortening the straight segments above the burner plane affects the flow field in the furnace, the impacting stream restricted by the dome becomes shorten and widen, and makes the average diameter of particles the dome captured and the deposition rate increase.%对多喷嘴对置式气化炉内复杂的气固两相流动与炉壁的颗粒捕捉特性进行三维数值模拟。应用Euler-Lagrange模型模拟气固两相流动，采用Realizable k-ε湍流模型计算炉内气相湍流流场，颗粒轨迹跟踪采用随机轨道模型。模拟结果与冷模测试数据吻合，且流场与热模实验现象一致，壁面捕捉颗粒平均粒径与热态水煤浆气化实验数据吻合。工业规模模拟结果表明，壁面捕捉的颗粒平均粒径呈现一定的规律性，存在两个极大值位置，分别在喷嘴平面下方0.2 m及上方2.8 m处，在喷嘴平面上方，壁面捕捉颗粒粒径随颗粒密度的增大而减小；颗粒沉积能基本覆盖整个炉膛内壁，颗粒在撞击流股作用下在喷嘴平面上方1.8 m及下方1.9 m处沉积量最大；缩短喷嘴上方直段高度将影响炉内流场，拱顶对撞击流股产生一定的限制作用，使其变短变宽，并且使拱顶捕捉颗粒粒径增加，颗粒沉积速率增加。