Radial behavior in riser and downer during the FCC process

In this paper, the radial behavior of riser and downer during the FCC process is studied on the basis of simulation results from a two-dimensional dispersion model. Although radial uniformity is observed in both reactors, the radial distribution of products is more uniform in the downer than in the riser. At the same feed conversion, about 5.5 wt.% higher gasoline yield is predicted in the downer due to the less axial backmixing and flatter radial distribution of gas–solids velocity and solids concentration. The simulation results also show that the radial gas dispersion plays an important role in determining the radial distribution of products. The profiles of gasoline in both riser and downer are calculated, and the simulation results of different models compared, showing that the consideration of radial non-uniformity is necessary.