Quantifying the Effects of Spatial Inhomogeneity in an Autoclave LDPE Reactor Using CFD

ABSTRACT Fluid simulations are cost‐effective and zero‐waste alternatives for research and development of polymer reactors. However, many polymer‐specific simulation software packages assume a homogeneous reactant mixture, overly simplifying the physics. Computational Fluid Dynamics (CFD) simulations provide more insight into this process but are difficult to utilize with detailed chemistry mechanisms. This work seeks to verify the implementation of free radical polymerization chemistry into a plant‐scale CFD reactor model for Low‐Density Polyethylene (LDPE) to investigate spatial gradients and their impact on the system. The process resulted in the most accurate CFD polymer reactor simulation to date, known to the authors, and sets a precedent for the verification and validation of other reactor models. It was found that the axial flow profiles formed distinct regions within the reactor wherein there were unmixed polymer properties. Significantly more variability was also found in the upstream‐most reactor zone compared to a downstream zone, exemplified by a coefficient of variation of 447% in the former and 0.372% in the latter for the polydispersity index on a central plane of the reactor. Additionally, noticeable differences in properties were found between the inside and outside of the mixing shaft, which were only fractions of a percent different.