Determination of the velocity profile by rheological models for modelling of polymerisation of MMA in a tubular reactor

Abstract

ABSTRACT In this work, theoretical and experimental studies of a tubular reactor where methyl methacrylate was polymerised were presented. This study focused on the rheological characterisation of the mixture in the various reactor lengths. Three different rheological models for the viscosity of the mixture (i.e. Power-law, Bingham-plastic, Herschel–Bulkley) were studied and the axial velocity distribution of these three models was determined. Unlike the Power-law and Bingham-plastic models, the Herschel–Bulkley model does not have the velocity distribution equation in the literature. Therefore, this equation was derived (This calculation was described in the appendix). The reactor was modelled based on these velocity profiles. Results from this study indicate that models with more adjustable parameters provide the best viscosity prediction for the mixture. Furthermore, the behaviour of the mixture in the reactor inlet is quasi-Newtonian fluid and as the conversion develops, the mixture has a shear-thinning behaviour. In addition, the velocity profile begins from the parabolic profile and as the conversion develops, it approaches the plug mode. Finally, by comparing the conversion rate between these three models with experiments, it is concluded that Herschel–Bulkley’s modelling is the most reliable.