摘要
在双流体模型以及团聚修正曳力模型的基础上,采用停留时间分布(RTD)模型,对工业催化裂化装置汽提器内气体和催化剂的停留时间进行了模拟计算,得到了人字型挡板、盘环型挡板和两段环流汽提器内气固两相的RTD特征。三种结构汽提器中气体的RTD曲线都呈现很不平滑的多峰分布,而催化剂颗粒的RTD曲线则呈现平滑的单峰分布,气体及催化剂颗粒的RTD曲线都出现了拖尾现象。模拟结果表明,三种汽提器内气体及颗粒的流动明显偏离平推流,催化剂的返混程度比气体强。与人字型挡板相比,盘环型挡板改善了汽提器内气固接触效果,从而提高汽提效率;与人字型挡板和盘环型挡板相比,两段环流汽提器不但改善了气固接触效果,还延长了催化剂颗粒的停留时间,并且降低催化剂的返混程度,模拟结果解释了工业两段环流汽提器汽提效率最高的原因。
Based on the two-fluid model and modified Gidaspow drag model,the residence time distributions（RTD） of gas and solid in three industrial fluid catalytic cracking（FCC） strippers equipped separately with V-type,disk-donut and annular baffles were simulated by RTD model.In three FCC strippers,the RTDs of gas are greatly different from RTDs of particles.The RTD curves of gas in three strippers with different structures exhibit rough curves with multi-peak distributions,while those of solid show smooth curves with single-peak distribution.All the RTD curves of gas and solid have long tails,which indicate the existence of back mixing phenomena.The simulation results indicate that the flow patterns of gas and solid in three strippers deviate from the plug flow,and the back mixing extent of the solid is stronger than that of gas.The contact of gas and solid in the disk-donut stripper is better than that in the V-baffled stripper,which leads to a higher stripping efficiency.Comparing with V-baffled and disk-donut strippers,the annular stripper not only improves the gas-solid contact,but also prolongs the residence time of the catalyst and decreases the catalyst back mixing.The simulation results explain the reason of why the annular stripper has the highest stripping efficiency in industrial application.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2010年第5期770-775,共6页
Journal of Chemical Engineering of Chinese Universities
基金
国家自然科学基金资助项目(20490202)
国家杰出青年基金项目(20725620)
关键词
流化催化裂化
汽提器
停留时间分布
汽提效率
计算流体力学
fluid catalytic cracking
stripper
residence time distribution
stripping efficiency
computational fluid dynamics
