Modeling of Slurry Phase Olefin Polymerizations in a Semibatch Well-Mixed Stirred Tank: Effect of Mass Transfer

A multiscale model of slurry-phase olefin polymerization is developed by extending the multigrain model to account for the existence of gas-liquid mass transfer resistance in an isothermal semibatch reactor. The comprehensive model integrates the reaction kinetic model, single particle model, and overall mass conservation balance together, which is implemented on the platform of OpenFOAM. Meanwhile, a set of methods is provided to evaluate the interdependence of mass transfer resistance and polymerization reactions. The model prediction is validated with the literature data. The influences of operating conditions on the polymerization rate and polymer properties are also discussed. The results show that due to the lower monomer concentration and higher mass transfer resistance under high temperature and low pressure conditions, the gas-liquid mass transfer and intraparticle diffusion controlled period persist longer, leading to poor polymer quality. In addition, the number-average molecular weight increases with increasing pressure, while it decreases with increasing temperature.