Uneven Distribution of Particle Flow in the Riser of Rfcc: Effect of the Number of Feed Injector

Two typical troubles associated with reactors in commercial Residue Fluidized Catalytic Cracking (RFCC) process are uneven distribution of particle flow in the riser and formation of carbonaceous deposits in the secondary reactor cyclone. The uneven distribution of particle flow means each outlet of the riser has a different particle mass flow rate and the formation of carbonaceous deposits cause serious catalyst carryover into the fractionators. These two problems are found by the number and location of the completely blocked cyclone with deposits in the commercial RFCC process. This study analyzes particle-fluid flow patterns in the riser using computational particle fluid dynamics (CPFD) method to troubleshoot the real industrial problem. The CPFD method, which has been developed to complement the Eulerian–Eulerian and the Eulerian–Lagrangian methods, applies the Navier–Stokes equation for fluid phase and multi-phase-particle-in-cell (MP-PIC) model for particle phase. Particle flow distribution is different each of outlets from 15.5% to 18.7% in the 1-injector case in which solid loading ratio of each of cyclones is different affecting the cyclone separation efficiency and the formation of carbonaceous deposits. Through this analysis, the uneven distribution of particle flow is diagnosed, and the standard deviations of particle flow distributions were investigated for the cases of 1, 2, 4, 6, and 8 injectors and evaluated to be 1.12, 0.58, 0.36, 0.24, and 0.39, respectively. From the results, the effect of the number of feed injectors was investigated and the 6-injector case is found to have a largely even particle flow distribution.