Dynamics of particle growth and overheating in gas-phase polymerization reactors

The particle overheating is an important problem in the industrial catalyti c gas-phase olefin polymerization reactors. It has been first investigated with a pseudo-stationary model of a single polymer particle by Hutchinson a nd Ray (J. Appl. Poly. Sci. 34 (1987) 657). A systematic study of overheati ng of polymer particle with models based on Fick's and dusty gas model (DGM ) transport described below is conducted by tools of continuation (steady-s tate) analysis and by dynamic simulations. The consideration of convective flow of species in particle pores driven by pressure gradient due to the ch ange in the number of moles in the course of the polymerization reaction ma kes the polymer particle in the reaction environment containing only monome r more susceptible to overheating. It is found that an intraparticle mass t ransport resistance has an important effect on particle overheating. The pr ediction and discussion of a time-scale of particle overheating under indus trial process conditions is coupled with the discussion of the dynamics of particle growth and dynamic changes of catalyst activity. (C) 2001 Elsevier Science Ltd. All rights reserved.