Study On The Performance In A Fluidized Bed With The FCC Catalysts And Vertical Sieve Trays

A study on cold model experiment of the behavior of gas-solid fluidization and mass transferring was carried out in a self-developed vertical sieve tray fluidized bed, using FCC catalysts and room air as fluidizing medium. The experiment investigated the flow state of both gas and solid in the S type, square type and opposite taper vertical sieve tray fluidized bed. The influence of the gas velocity in tray hole, the circulation volume of solid and the structure of the bubble caps on pressure drop of the bed was studied. Elevated quantity was measured by the self-developed elevated quantity collector. And the impact of the gas velocity in tray hole, the circulation volume of solid, the structure of the bubble caps on elevated quantity was fully investigated. During the system of moist catalyst-room air, the influence of the gas velocity in tray hole, the circulation volume of solid and the structure of the bubble caps on mass transfer efficiency was studied by the humidity changes of the catalyst passed through the sieve.The results show that the vertical sieve tray as inner-loop for a fluidized-bed is feasible. The fluidizing medium is fluidized fast within the vertical sieve tray fluidized bed, where there is no bubble, little back-mixing and the fluidization between the gas-solid two-phase is well-distributed and in good condition. The pressure drop of vertical sieve tray fluidized bed is low. The impact trends of the gas velocity in tray hole and the structure of the bubble caps on pressure drop of the bed in three vertical sieve trays are similar. However, the pressure drop of square vertical sieve tray is always higher than that of S type, and the pressure drop of S type is little different from opposite taper. Pressure drop of the bed mainly rise with the increase of the gas velocity in tray hole, the height of the bottom clearance, and decrease with the rise of the opening ratio of the cap and the pore size of tray hole, but pressure drop no longer change when the opening ratio reach3.0. The pressure drop of the bed and mass transfer efficiency are affected by the elevated quantity of bubble caps in the vertical sieve tray. The elevated quantity of the caps rise with the increase of the gas velocity in tray hole, the height of the bottom clearance, the pore size of tray hole and the circulation volume of solid, and decrease with the rise of the opening ratio of the cap. The mass transfer efficiency of vertical sieve tray fluidized bed is higher11.5%than that of the fluidized bed without any inner-loop, and the mass transfer efficiency of the S type is higher than that of square type which is higher than that of opposite taper. The mass transfer efficiency increase with the rise of the pore size of tray hole, the height of the bottom clearance, and fluidization air volume; while decrease with the opening ratio of the cap. The strength of the elevated quantity and the pressure drop are no longer change when the value ratio of the height of the bottom clearance and the opening ratio of the cap is0.55. The influence of the height of the cap and mesh size on the performance of vertical sieve tray fluidized bed is negligible.