CFD simulation of an industrial FCC regenerator

Through a Computational Fluid Dynamics (CFD) simulation of the particle laden flow of the two stages of a Fluid Catalytic Cracking (FCC) High Temperature Regenerator (HTR), new designs for the particle distributor in the combustor stage and the arm disengagers in the regenerator stage that improved the HTR performance were proposed. The simulations involved 580 thousand cells for the combustor and 1.5 million cells for the regenerator and were conducted with the commercial CFD software package Fluent 15.0 using an Euler-Euler model and a phase-coupled SIMPLE algorithm. Athorough analysis of a 298-hole air distributor conducted prior to the combustor simulation, set the air flow boundary conditions of the 22 m high and 3.2 m diameter combustor. After the evaluation of several drag models available in the literature, the Modified model with cluster diameters of 400 m and 200 m for the dense and dilute phases, respectively, reproduced the theoretical characteristics of the turbulent bed that is typical of HTR combustors. The same drag model also reproduced the bubbling bed that is reported for the regenerator stage of HTRs. An analysis of the solid distribution showed that when solids enter the reactor through simple inlets located at opposite locations, the solid distribution is poor. However, when a two-arm, solid distributor that includes six lateral and a central inlet is implemented, the solid distribution improves, as the mal-distribution coefficient (Mf ) decreases from 0.31 to 0.22 in the most critical region of the dense phase. Improvements in the characteristics of the Residence Time Distribution (RTD) and the size of the bed are also evidence of the benefits that the new proposed combustor design gives to the HTR performance. For the regenerator stage of the HTR the CFD simulation revealed the existence of a high-velocity field surrounding the solid disengangers that transport the solid from the combustor. This high velocity contributed to a relatively high solid flow through the cyclones, 42%, when compared to the recommended range of 20% to 30%. By increasing the length of the disenganger shroud, the gas velocity decreased and the solid flow though cyclones was reduced to 34%. The two simulations illustrate the ability of CFD to improve the performance of complex industrial equipment

• Autores: Alzate Hernández, Juan David
• Fecha de publicación: 2016
• Institución: Universidad Nacional de Colombia
• Repositorio: Universidad Nacional de Colombia
• Idioma: spa
• OAI Identifier: oai:repositorio.unal.edu.co:unal/57858
• Acceso en línea: https://repositorio.unal.edu.co/handle/unal/57858; http://bdigital.unal.edu.co/54307/
• Palabra clave: 54 Química y ciencias afines / Chemistry; 66 Ingeniería química y Tecnologías relacionadas/ Chemical engineering; Fluid catalytic; Cracking regenerator
• Rights: openAccess
• License: Atribución-NoComercial 4.0 Internacional