Development of a multi-compartment dynamic model for the prediction of particle size distribution and particle segregation in a catalytic olefin polymerization FBR

Abstract

Abstract In the present study a comprehensive multi-scale, multi-compartment model is developed for the prediction of morphological (i.e., particle size distribution (PSD), particle segregation) and molecular (i.e., molecular weight distribution (MWD)) distributed polymer properties in a catalytic olefin polymerization FBR. The multi-scale description of the FBR utilizes models at four different levels, namely, a kinetic model, a single particle model, a population balance model and a multi-compartment reactor-mixing model. At the molecular level, a two-site Ziegler-Natta catalytic copolymerization model is employed to describe the copolymerization of ethylene with propylene. To calculate the particle growth and the spatial monomer and temperature profiles in a particle, the random pore polymeric flow model (RPPFM) is utilized. The RPPFM is solved together with a dynamic discretized particle population balance model, to predict the PSD. Moreover, overall dynamic mass and energy balances in the reactor level are derived, in order to calculate the monomer(s) concentration and temperature profiles along the reactor height. The effects of various fluidized bed operating conditions (e.g., fluidization gas velocity, temperature, catalyst feed rate) on the morphological and molecular distributed polymer properties and reactor operability are analyzed.