用计算流体力学方法对人字型挡板、盘环型挡板和两段环流3种工业重油催化裂化(Resid Fluid Catalytic Cracking,RFCC)汽提段内的气固两相流动进行了模拟研究,考察了汽提段内的颗粒体积分数分布情况；结合模拟示踪技术得到了催化剂出口处颗粒的停留时间分布( RTD),通过对RTD曲线进行分析,得到了表征汽提段内颗粒混合特性的参数,平均停留时间(tm)、无因次方差(σθ2)、Peclet准数(Pe),以及死区、活塞流区和全混流区的体积分数.模拟结果表明,环流汽提段外环区和内环区间存在密度差,是催化剂环流流动的推动力.人字形挡板汽提段内的tm最小,σθ2最大,Pe值最小,同时死区体积达到了汽提段体积的40％,而活塞流区体积仅占15.8％,说明其中颗粒的返混非常剧烈,汽提效率最低.相对于盘环型挡板汽提段,两段环流汽提段内颗粒的σθ2较大,Pe较小,颗粒的整体返混程度高于盘环型挡板汽提段.但从死区模型的分析看,活塞流流动的增强有利于促进气同间的传质死区体积增大则是由于环流流动的增强所导致的,这些都有利于提高汽提效率.两段环流汽提段内活塞流区体积为26.8％,死区体积占32.3％,都大于盘环型挡板汽提段,使环流汽提段的汽提效率更高.%Flow behaviors in the V-baffled, Disk-donut and two-stage annular industrial resid fluid catalytic cracking (RFCC) strippers were investigated by using computational fluid dynamics (CFD) method. The volume fraction distribution and the residence time distributions (RTD) of catalysts were obtained at the outlet in the way of coupling the tracer technology. The parameters indicating mixing characteristics, i.e., mean residence time tm, dimensionless variance σθ2, and Peclet number were analyzed, and the fractions of dead, plug and well-mixed volumes were obtained. The results show that the density difference between the outer and inner loop in the annular stripper is the driving force for catalysts' annular flow. The V-baffled stripper possesses the smallest tm and Pe, and the biggest σθ2. Meanwhile, the dead volume fraction in the V-baffled stripper is about 40% while the plug volume fraction is only 15.8%. All above demonstrate the serious back-mixing and low stripping efficiency in the V-baffled stripper. Compared to the disk-donut stripper, the two-stage annular stripper exhibits bigger σθ2 and smaller Pe, standing for stronger overall back-mixing. In terms of the dead volume model, however, the plug and the dead volumes are respectively 26.8% and 32.3% in the two-stage annular stripper, higher than that in the disk-donut stripper and causing a higher stripping efficiency.
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