Modeling and analysis of a gas sweeping process for polycarbonate polymerization

This article deals with (1) the development of a mathematical model for the finishing polycarbonate polymerization process with a horizontal, rotating disk-type reactor with countercurrent gas sweeping and (2) the performance analysis of the reactor system with the model. We propose a model describing a reactor system consisting of two phases in which the byproduct (phenol) is removed from the polymer melt phase to the countercurrently flowing vapor phase to facilitate the forward reaction and, therefore, produce a high molecular weight polymer compatible with the products of commercial grades. The vapor phase is represented by the tanks-in-series model, whereas the polymer melt phase is regarded as a plug flow reactor. The major concerns here are the influences of the reactor operating conditions, including the catalyst concentration, reaction temperature, mass-transfer rate, melt-phase residence time, and vapor-phase velocity, on the polymer molecular weight, the melt-phase concentrations of various components, and the molar fraction of phenol in the vapor phase. To corroborate the validity of the proposed model and investigate the complex phenomena of the process, we have conducted a series of simulation studies with various operating policies, and we compare the performance of the process with the performances of the cocurrent process and the vacuum process. According to the results of this study, this new type of reactor system shows satisfactory performance and is sometimes even better than the conventional high-vacuum process.