Authors: Zhijun Yang a,b, Yongmin Zhang a, Adefarati Oloruntoba a, and Junrong Yue c
a State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, PR Chin
b Dalian Research Institute of Petroleum and Petrochemicals, SINOPEC, Dalian 116045, PR China
c State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Science, Beijing 100190, PR China
Source: This paper was published in 2021, Volume 412 of Chemical Engineering Journal.
Abstract: Improving distribution uniformity of spent catalyst and adding horizontal baffles are two effective measures to improve the regeneration performance of a fluid catalytic cracking (FCC) unit. In this study, an industrial coaxial compact FCC regenerator is simulated using a Eulerian- Lagrangian multi-phase particle in cell (MP-PIC) method. By using the energy-minimization multi-scale (EMMS) drag model based on turbulent flow regime, the MP-PIC simulation predicts the typical solids fraction profile which is in good agreement with industrial data. The Crosser grid (a typical horizontal baffle) is successfully constructed with the help of “virtual baffles” in simulation. The simulation results show that, after adding Crosser grid (a new horizontal fluidized bed baffle by our group), the bed height increases slightly, the lateral maldistribution index of solids decreases and the descending flux of spent catalysts decreases significantly. The distribution uniformity of spent catalyst distribution along the bed cross section is more uniform when spent catalyst particles are distributed more uniformly. The presence of gas cushion beneath the Crosser grid allows it to act as a pseudo gas distributor, eliminating gas channeling and decreasing zones of low fluidization quality. The rising bubbles are absorbed by the gas cushion and new small bubbles are generated above the Crosser grid, thereby strengthening the gas–solid contact. The guiding vanes of Crosser grid accelerate the lateral movement of particles. The Crosser grid also proves its stronger suppression on the axial back-mixing of solids.