Modelling of heat and mass transfer during the polymerisation of olefins on heterogeneous Ziegler catalysts

The modelling of heat and mass transfer during the gas and slurry phase pol ymerisation of olefins is examined. It is demonstrated that it might not be necessary in many cases to calculate concentration gradients in the growin g catalyst/polymer complex, and that the currently used representation of h eat transfer from small, highly active particles using standard chemical en gineering correlations might not be accurate. Close examination of the morphology of catalyst particles shows that it is unlikely that the particles should be treated as a pseudo-homogeneous mediu m, and in fact the critical length scale for mass transfer is not the parti cle radius, but is much smaller, Furthermore, computational fluid dynamic s imulations of single and interacting particles shows that convection is not the dominant heat transfer mechanism during the critical stages of the rea ction. (C) 1999 Elsevier Science B.V. All rights reserved.