(691f) Extension of Fluidized Catalytic Cracking Regenerator Modeling to Improve Emissions Performance

Fluidized Catalytic Cracking (FCC) units have been used by refiners for over 70 years to upgrade low valued feed stocks into much higher valued LPG olefins and motor fuels. The FCC regenerator processes the spent catalyst returning from the reactor, cleaning coke off the catalyst via combustion, while providing process heat.

Computational Fluid Dynamics (CFD) models of FCC regenerators have been introduced in recent years, with primary focus on erosion and afterburn reduction. This presentation considers recent regenerator modeling work, both published and unpublished, and shows how available information can be used to extrapolate to refinery operation decision making beyond the direct CFD model scope.

Computational modeling was performed using Barracuda Virtual Reactor^® software employing the Computational Particle Fluid Dynamics (CPFD^®) numerical approach. Both generalized and localized regenerator afterburn are discussed. The connection between localized afterburn and maldistribution of the spent catalyst entering the regenerator is shown as impacted by overall catalyst fluidization patterns. An example of how the CFD modeling enabled informed decision-making for potential modification of regenerator internals, with extrapolation to impact of maldistribution and mixing on emissions, is presented. Finally the case of a US gulf coast refiner is used to highlight how modeling enabled a reduction in excess O2 and combustion promotor use while positively impacting CO and NOx flue gas emissions following a 2016 refinery shut down.