(231g) Design and  Optimization of Multiphase FCC Regenerator Hydrodynamics Coupled with Reaction Kinetics

Fluidized catalytic cracking(FCC), profoundly referred as “gasoline machine”. Transforms relatively dense hydrocarbons to monetary worth gasoline with a elevated octane rating & other dominant petrochemical feed stock. FCC regenerator is utilized in the retrieval of solid FCC catalyst reactivity, & furthermore enhances significantly catalyst temperature to impart thermal energy to endothermic catalytic cracking reactions in FCC riser. It is of paramount importance in determining FCC process economics. In FCC regenerator, there coexists multiphase flow regimes, a heavier dense typically employed in the fast fluidization regime characterized by high circulation rates prompt to the non-uniform dispersal of particle velocity and solid holdup, a intermediate regime characterized by cluster formation of the catalyst which is the phenomena of catalyst segregation and backmixing, & an upper dilute transport regime, scattered flow region having reactor cyclone systems, which handles gas-solid separation. The challenge is to maximize catalyst regeneration by thorough dispatch of spent catalyst and air in FCC regenerator & mitigate thermal/mechanical degradation of catalyst. To distinguish the hydrodynamic effects on selectivity and conversion, including attaining perception into the performance of FCC regenerator. The laws of thermodynamics, phase & chemical reaction equilibrium(coke burn-off from the FCC catalyst particles in regenerator both homogenous & hetrogenous reactions) will be coupled with the hydrodynamics. These three-dimensional multiphase numerical flow simulations assimilating chemistry modeling and multi-species transport along with
incorporating radiative heat transfer will help in dictating operating framework of FCC regenerator. FCC regenerator design, optimization & scale-up is still predominantly empirical, owing to slender comprehension of intrinsic multiphase flow in regenerator. Impact of dominant closure models such as viscous/turbulence stress models, boundary conditions, drag models, and chemical reaction kinetic models on forecasting conversion needs to be sternly scrutinized. The multiphase Euler - Euler approach, with kinetic theory of granular flow is employed for CFD study of FCC regenerator. It includes drag model & restitution coefficient for the gas - solid interaction drag force & to define the solid - solid collision forces respectively. A chemical reaction model is utilized which includes coke combustion kinetic equations with apt kinetic constants to simulate the gas phase & interphase reactions in the regenerator. FCC regenerator multiphase simulations predict the phase pressure drop, effect of gas velocity on residence time distribution. Turbulence characteristics namely, ensemble averaged velocity statistics, dissipation of turbulent momentum by fluid velocity fluctuations which helps in analyzing heat and mass transfer properties in turbulent suspensions & turbulence amplification/attenuation due to fluid-solid interaction. It further explores the combustion characteristics such as gas species i.e, mass fraction, the particle temperature, solid-holdup. The simulation results also provide detailed quantitative mapping of the regenerator behavior including afterburning, & predict clustering behavior of the FCC catalysts which results in temperature hotspots accompanying
with higher vapor compositions, which causes irreversible attenuation of FCC catalyst reactivity.