Study On The Fluidization Process In The Feedstock Zone Of The FCC Riser

In the existing circulating fluidized bed device of the laboratory,a study on cold model experiment of the behavior of gas-solid two-phase fluidization in the riser feed injection zone was carried out,making FCC catalysts and room air as the fluidizing medium,The impacts of the jet gas velocity,the pre-lift gas velocity,particle circulating rate,angle of nozzle jet,nozzle number on particle concentration distribution and particle flow behavior were investigated.The radial particle concentration was measured by the self-developed solid concentration probe.The results showed that the fluidization condition of the two symmetrical nozzle feed was better than a single nozzle feed,and the optimal jet angle was 30?.Pressure gradient AP/AZ gradually reduced with the increase of axial position,and pre-lift gas or jet gas was greater,AP/?Z was instead smaller.Nozzle feedstock injection had remarkable effect on the flow of gas-solid two-phase flow in the riser feed injection zone,the distance from the nozzle axial location was closer,the effects were large.When injecting angle was 0°,particle concentration distribution was the opposite ring-nuclear distribution of dense center and low side wall,while the distribution was high middle as good as center and low side wall when injecting angle was 30°.With the increase of axial position,the effects were weakened gradually,and particle concentration distribution also was transformed into the distribution form of strong low center and high side wall by degrees.Pre-lift gas had a greater influence on the particle concentration distribution of riser center than side wall,with pre-lift gas velocity(Ur)increasing,the solid holdup reduced,radial distribution was more uniform.When the superficial gas velocity was same,the solid holdup of every cross section was increased with particle circulation rate(Gs)increasing.Finally,on the base of the gas-solid two phase flow model,combined with catalytic cracking lumped kinetic model,the effects of gas-solid two phase flow,mass transfer,heat transfer,reaction etc.were taken into account comprehensively and systematically,the gas-solid two-phase flow reaction model of FCC riser reactor was developed,as well as the boundary conditions of the model equation and the model numerical solution were given.