Abstract:

A post-riser system in RFCC unit has a significant influence on product yield and distribution, as well as long term operation of the unit. Quick separators are the core equipment of the system. The fundamental research, development and commercialization of quick separators of post-riser system in China were reviewed. The influence of key geometric configuration and size on the two-phase flow field, separation efficiency and pressure drop were also analyzed and discussed. In order to reduce the contact time of catalyst and oil gas and to discharge oil gas as soon as quickly, a rough cut cyclone was coupled with a pre-stripper. Internals were mounted in the system, which were also called FSC and CSC system, to diminish the fluctuating processing vortex core and to reduce the influence of pre-stripping steam. Then a post-riser system called VQS was proposed, which included a vortex quick separator and an isolated shell. The study was conducted to optimize the geometric configuration of the separator, and the one with long and downward spiral arms was found to have excellent performance. Furthermore, the simulation results showed that severe short cut flow occurred in the vicinity of the exit of arms, leading to significant drop of separation efficiency. Then, a new system called SVQS was proposed by adding an annular cover and a tube into the system. As a result, the separation efficiency considerably increased about 30% for 18 μm talc, meanwhile the separation pressure drop raised only 400 Pa. In order to reduce the separation time, a quick separator was proposed and optimized. The separation time was reduced to less than 1 s, and separation efficiency was closed to 75% for 44 μm talc, which was slightly lower than separation efficiency of cyclone.

Key words: fluidization, multiphase flow, separation, RFCC, post-riser system

摘要：

催化裂化后反应系统对装置的产品收率、分布和长周期运转具有重要的意义，提升管出口快分是后反应系统的核心装备。对近年来我国催化裂化后反应系统快分的基础研究、开发和工业化进行了回顾，对关键几何结构和尺寸对不同类型快分内两相流场、分离效率和压降的影响进行了总结和分析。为减少油剂接触时间并尽快引出油气，将提升管出口粗旋和一个预汽提器耦合起来并形成了FSC和CSC系统。系统内设置了多个内构件以消除旋进涡核的摆动效应并减弱底部预汽提蒸汽对旋分流场的影响。针对内提升管进而提出了包含旋流头和封闭罩的VQS系统。优化结果表明，带有向下旋转的长臂的旋流头具有更加优越的性能。此外，数值模拟结果显示在臂出口存在严重的短路流现象，导致分离效率显著下降。为解决这一问题，增设了一个环形盖板和隔流筒，从而形成了SVQS系统。结果表明，对平均粒径18 μm的滑石粉SVQS系统的分离效率提高了约30%，与此同时压降仅增加不到400 Pa。为了进一步缩短油剂在分离器内的分离时间，提出了一种新型SRTS快分，该快分能够将分离时间缩短到1 s以内，与此同时分离效率仅略低于旋风分离器。

关键词: 流态化, 多相流, 分离, 催化裂化, 后反应系统