急冷废热锅炉进口分配器内分布管椭圆度对气体流动与分布的影响

摘要

For improving the performance of the four-inlet bathtub-type transfer line exchanger (TLE) used in a 10000 t yearly capacity cracking furnace, the characteristics of flow field in the entrance of TLE was investigated with CFD method. The effects of ellipse eccentricity of the cross-section of the distributor tubes on the low velocity region, residence time, vorticity, rate of turbulent dissipation and gas maldistribution were investigated. The results indicate that higher ellipse eccentricity reduces the low velocity region, residence time, vorticity, rate of turbulent dissipation in the entrance of the TLE, but increases the maldistribution. A dimensionless performance index taking account of vorticity, turbulent dissipation rate and gas maldistribution was employed to compare and evaluate the overall performance in different ellipse eccentricity of distributor tube. The result shows that the optimal ellipse eccentricity of gas distributor tubes is between 1. 12 and 1. 2.%针对10万吨／年大型乙烯裂解炉用四进口“浴缸式”急冷废热锅炉现存问题,采用稳态与瞬态CFD数值计算方法研究了急冷废热锅炉进口分配器内的流动状况.比较了圆形截面和椭圆形截面分布管对流动的影响,分析了不同分布管截面椭圆度时废热锅炉换热管内的气体分配不均匀性及分配器内的低速区、停留时间、涡量和湍流耗散率.采用综合考虑涡量、湍流耗散率和气体分配不均匀性的量纲1化综合性能指标比较各结构的综合性能,结果表明当分布管椭圆度e在1.12～1.2之间时气体流动状况较佳.