Modelling of slurry reactors. A fundamental approach

Abstract

Multiphase reactors in the form of bubble columns and stirred tank reactors are being used in large numbers throughout the petrochemical and biochemical industry today, and steadily for more complicated reaction systems. It has become increasingly more important to develop good, and theoretically sound models for scaling up and design of the reactors. The most common models used today rely heavily upon empirical information obtainable only from pilot size experiments and this makes “a priori” design from small scale data difficult. The model presented is based on a “first principles” approach where the parameters are fundamental in nature and as far as possible, obtainable from general fluid dynamics literature. It is a dynamic two phase model incorporating a k-ε turbulence model, compressible gas phase and axisymmetry. The equations are discretisized using a finite volume technique with an upwind or hybrid differencing scheme and solved using a variation of the SIMPLE (Semi Implicit Method for Pressure Linked Equations) method. The results from simulations of a two-phase bubble column are compared with measured radial distributions of gas hold-up, liquid velocity and turbulent kinetic energy using air and desalinated water as media. As chemical reaction, the production of methanol from synthesis gas is implemented. Simulation results using a pseudohomogenous 3-phase slurry model are compared with data from literature.