MODELLING AND ADVANCED CONTROL FOR POLYETHYLENE PRODUCTION

A modified model for the gas-phase polymerization of polyethylene in fluidized-bed catalyst reactors (FBR) using Ziegler-Natta catalyst is presented in this study. This mathematical model accounts for mass and heat transfer between the bubbles and the clouds without chemical reaction, between the clouds and the emulsion without chemical reaction, and between emulsion and solid with chemical reaction that occurs at the surface of the catalyst particles. The model also, accounts for the effect of catalyst particles type for the rate of adsorption,desorption and catalyst surface reaction on the site of reaction. In this work, the concentration and temperature profiles in the bubble, cloud and emulsion phases are calculated. The effect of important reactor parameters such as superficial gas velocity, catalyst injection rate, catalyst particle growth and minimum fluidization velocity on the dynamic behavior of the FBR is investigated.