Fluid dynamic numerical simulation of a gas phase polymerization reactor

This article presents preliminary fluid dynamic simulation results of ethylene polymerization dense fluidized bed using the twophase flow numerical code ESTET-ASTRID developed by Electricité de France for CFB boilers and based on the two-fluid modelling approach. The continuous phase consists of gas and the dispersed phase consists of catalyst particles. The particle fluctuating motion is modelled using two-separate transport equations, on the particle kinetic energy and the fluid-particle covariance, developed in the frame of kinetic theory of granular medium accounting for particle-particle and fluid-particle interactions. Time-dependent 2D and 3D simulations have been performed for industrial and pilot reactor operating conditions. The numerical predictions are in good qualitative agreement with the observed behaviour in terms of bed height, pressure drop and mean flow organization, such as the down falling of the PE particle layer along the walls. Moreover, these simulations help to provide information about instantaneous and time-averaged solid concentration and velocity fields. Characteristic mechanisms and influence of model closure assumptions on flow predictions are also investigated. Finally, such numerical simulations look very powerful, when validated on exhaustive data collection, to improve design and performance of industrial facilities and to provide insight into the complex physical mechanisms involved.