(54w) A CFD-Based Model for Investigating Thermal Runaway of MMA Suspension Polymerization in a Batch Reactor

Thermal runaway has been a major issue for the safety of polymer industry for decades. The gel effect that the dramatic viscosity increase hinders mixing and diffusion is recognized as a direct cause of thermal runaway. In this work, a three-dimensional computational fluid dynamics (CFD) model is developed to investigate thermal runaway process of suspension polymerization of methyl methacrylate (MMA) in a lab-scale batch reactor. Energy, momentum, and species transport equations are solved using a CFD software package. A mechanistic polymerization kinetic model is coupled with the CFD model, as a source term, using a user defined function (UDF) code. Gel effect is considered as a temperature-dependent factor of the kinetic model. Laminar flow regime is assumed as common practice for lab-scale suspension polymerization. Multiple reference frames (MRF) technique is employed to model the rotation behavior of the reactor impeller.

Considering the complexity of the proposed CFD model, the continuity, energy and momentum equations are first solved to guarantee numerical convergence. Subsequently the CFD model coupled with kinetic model and species transport equation is solved for conversion and temperature profiles. Experimental data from a Reaction Calorimeter (RC1e) with a similar reactor configuration in the literature are used to compare with simulation results. The temperature evolution and non-homogeneity inside the reactor during thermal runaway is unveiled by the CFD model. The model is then employed to predict the consequences of two common failure scenarios of batch reactors: (1) impeller failure, and (2) loss of cooling.