Computational Fluid Dynamics Modeling and Control of Phthalic Anhydride Synthesis in a Fixed-Bed Catalytic Reactor

Abstract

This work focuses on computational fluid dynamics (CFD) modeling and control of a phthalic anhydride (PA) synthesis in a fixed-bed catalytic reactor. Specifically, a CFD model of a two-dimensional in space fixed-bed catalytic reactor is first developed in ANSYS Fluent with appropriate geometry characteristics and catalyst packing. Subsequently, to regulate the product yield of phthalic anhydride in the reactor outlet and avoid the formation of a hot-spot inside the reactor due to the exothermicity of the PA synthesis reaction, model predictive control is utilized to optimize the outer jacket temperature (manipulated variable) via a data-driven model of the reactor constructed using CFD model data. To implement MPC in real-time within the dynamic CFD simulation of the fixed-bed catalytic reactor, a user-defined function (UDF) of ANSYS Fluent is employed to invoke an MPC solver outside of the CFD modeling environment to obtain the optimized manipulated inputs. The CFD simulation results demonstrate that under MPC, the outlet concentration of phthalic anhydride can be driven to its set-point while the temperature of inner reactor fluid remains below the maximum allowable temperature.