(463d) Developing a Polymerization Reactor Reduced Order Model

Chemical reactors are vital in numerous industrial operations; yet, experimental investigations of these processes are costly and time-consuming. Chemical simulation packages limit insight into localized phenomena due to their use of continuous stirred tank reactors (CSTR), which assume perfect mixing. Computational fluid dynamics (CFD) simulations are beneficial, because they capture spatiotemporal gradients of velocity, temperature, species concentrations, and more. However, due to the additional computational load of kinetics implementation into already rigorous meshes, CFD simulations of chemical reactions can be prohibitively time consuming. A flow field may reach quasi-steady state (QSS) quickly, but convergence of kinetic solutions may take longer. This work aims to develop a reduced order model (ROM) of a verified/validated free radical polymerization reaction in CFD to decrease solver runtime without sacrificing accuracy. We take advantage of the time-scale disparity between fluid convection and diffusion-limited statistics calculations. Specifically, it focuses on a CSTR ROM to later be incorporated into a full-scale reactor model. In ROM simulations, presumably irrelevant (low timescale) temporal changes in localized flow and turbulence phenomena are ignored. However, the model remains valid; everything needed to calculate polymer properties is still intact. Tests vary combinations of disabled features/equations including flow, turbulence, energy, and more. Time step size and species’ diffusivities are also altered. Accuracy, run rate, and number of time steps to reach a converged solution are tracked for each case. Accuracy is determined by percent error in polydispersity index (PDI) from the verified base case, which has everything enabled. The most accurate ROM case, with flow, mesh motion, and turbulence disabled, has a run rate 1.4x the base and is accurate within 0.09% of the target PDI value. This demonstrates the feasibility of CFD ROMs in simulating chemical reactors. Substantial savings in time and resources for reactor-scale simulations can be reached using this method.