Reactive CFD Simulation of Fixed Coke Formation in an Industrial RFCC Riser Reactor

Abstract Severe fixed Coke in the industrial residue fluid catalytic cracking (RFCC) riser reactor often results in the reduction of product yield and unplanned unit shutdown. It is difficult to simultaneously depict physical and chemical formation of fixed coke near wall due to no approach and coking model. In this paper, the complex gas-solid-liquid three phase flow, mixing and cracking reaction are in agreement with the industrial data by 3D reactive simulation with multiphase Eulerian granular model coupling with the vaporization empirical correlation and the energy-minimization multi-scale (EMMS) drag and mass transfer models. A new coking index is developed to predict the formation possibility of fixed coke based on the 3D accurate simulation. The variations of coking profiles at different diameter of oil droplet are investigated. The results indicate that the fixed coke formation can be well depicted by the coking index. The predicted of fixed coke in the feed injection zone is same with the actual positions in industrial unit, which mainly located near the walls of the 0.5∼3.0m height above the feed nozzles and the circumferential between adjacent nozzles. The feed oil droplet size can improve the formation possibility of fixed coke.