催化裂化装置四旋分离系统内气相流场的数值研究

NUMERICAL SIMULATION OF GAS-PHASE FLOW FIELD IN FOURTH STAGE SEPARATION SYSTEM IN FCCU

采用雷诺应力模型(RSM)对两种催化裂化装置四旋分离系统内气相流动的三维流场进行数值模拟,分析了两种第四级旋风分离系统(简称四旋)内气相流场的特点。结果表明:在传统式结构中,储料罐内部分区域气流向上运动,不利于颗粒沉降,料腿内产生气流反窜现象,四旋内存在偏流,影响颗粒输送,结构设计不合理是导致颗粒堵塞的主要原因;改进式结构中,储料罐内气相速度很小,有利于颗粒沉降,料腿中周期性的二次涡影响颗粒的气力输送,可能对壁面产生磨损,四旋分离空间内流场稳定,有利于颗粒分离,改进式结构可以有效避免颗粒堵塞现象的发生。两种结构内部气相流场的对比为合理设计四旋分离系统结构提供了参考依据。

Based on the Reynolds Stress Model, the three-dimensional gas-phase flow fields of two kinds of the fourth stage separation systems in FCCU were simulated. The characteristics of gas flow fields in the two systems were especially analyzed. The results show that in the material storage tank of the traditional structure, the gas flows upward at some areas, which is not conducive to particle sedi- mentation. Reverse flow exists in the dipleg. Bias flow happens in the cyclone separator, by which par- ticle transportation is affected. The unreasonable structure design is the main reason for particle plug- ging. However, in the improved one, the air flow is relatively slow, favorable to particle sedimentation. In the dipleg, the pneumatic transportation is influenced by the periodic secondary vortex that can wear the wall. The flow field in the cyclone separator is stable enough for particle separation. Particle plugging can be avoided effectively in the improved structure. The comparison of the gas flow field in the two structures provides valuable guidance for designing efficient fourth stage separation system.