A COMPREHENSIVE MODEL FOR THE PREDICTION OF PARTICLE-SIZE DISTRIBUTION IN CATALYZED OLEFIN POLYMERIZATION FLUIDIZED-BED REACTORS

A generalized steady-state population balance model is developed to in vestigate the particle-size distribution developments in gas-phase flu idized-bed olefin polymerization reactors. The model rigorously accoun ts for the combined effects of particle growth, attrition, elutriation and agglomeration for both uniform-size and size distributed catalyst feed. Model predictions are found to be in agreement with recent expe rimental results on particle elutriation and agglomeration in polyethy lene fluidized beds. Simulation results show that the rate of particle agglomeration exhibits an exponential increase with the bed temperatu re. Furthermore, particle elutriation is influenced by the agglomerati on process which largely reduces the number of small-size particles. I t is also shown that due to the large polymerization rates exhibited i n gas-phase olefin polymerization processes and to the near-well-mixed bed behaviour, the feed catalyst size distribution strongly affects t he particle-size distribution in the bed. The population balance model developed in this paper proves to be a unique tool for simulating the effects of different process parameters on the polymer size distribut ion in gasphase fluidized-bed olefin polymerization reactors. (C) 1998 Elsevier Science Ltd. All rights reserved.