The Structure Optimization Of Multi Stage Circulation Stripper

Stripper is an important part of fluid catalytic cracking(FCC)plant,affecting the smooth and efficient operation of entire device greatly.MSCS(Multi stage circulation stripper)is designed based on the characteristic of the stripping process and has been successfully used in factories.Subject to experimental conditions and measurement methods,few reports about commercial-scale MSCS stripper can be found in literature.In this paper,two-fluid model is used for simulation of a commercial-scale MSCS stripper to investigate the flow field and fluid dynamics behavior and attempt to optimize the structure of the stripper.Simulation results show some disadvantages of the old stripper,for example,steam short circuit between two neighboring annular baffle or conical baffle occurs,and steam passing through the holes is distributed unreasonably,moreover,the bias current of steam and solid exists in the zone with draft tube.Keeping the percentage of holes area on baffle unchanged,a new baffle structure that can distribute the steam through holes reasonably is proposed by rearranging the hole on the baffle.When the new baffle is used,the phenomenon of bias current is weakened,and solid concentration profile become more even in the baffle zone.After using the new structure baffle,flow field and hydrodynamic behavior of baffle zone influenced by circulating flow rate of catalyst and superficial gas velocity is investigated.The result indicates that changing the circulating flow rate of catalyst has little influence on distribution and hydrodynamic behavior of solid and steam.Superficial gas velocity affects flow field and hydrodynamic behavior greatly.When the superficial gas velocity increases,the distribution of steam becomes ununiform,characterized by solid holdup in the region under baffle rising first and then falling,while solid holdup of other position decreasing all the time.Compared with the original baffle structure,there is a good contact between solid and steam on the baffle when the new structure baffle is used and the stripping efficiency has a certain degree of improvement.