MP-PIC simulation of the effects of spent catalyst distribution and horizontal baffle in an industrial FCC regenerator. Part I: Effects on hydrodynamics

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 412; p. 128634
• Main Authors: Yang, Zhijun, Zhang, Yongmin, Oloruntoba, Adefarati, Yue, Junrong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2021
• Subjects: FCC; Horizontal baffle; Hydrodynamics; MP-PIC simulation; Regenerator; Spent catalyst distribution; Horizontal baffle; Spent catalyst distribution; Hydrodynamics; Regenerator; FCC; MP-PIC simulation
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.128634

•MP-PIC simulations successfully employed in an industrial coaxial compact FCC regenerator.•Better understanding on the role of horizontal baffles in improving fluidization quality.•Better understanding of the effect of horizontal baffles on axial and lateral solids mixing. 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 mal-distribution 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.