Numerical simulations of polymer devolatilization in a steam contactor: Correlating particle distribution with volatile content removal

Abstract The focus of the current study is on a polymer devolatilization process in a device called a contactor, that involves the use of superheated steam to eliminate volatile cyclohexane, through evaporation, from the polymer mixture, also known as cement. The primary objective is to analyze the cement particle distribution and how it relates to the cyclohexane content at the exit or the devolatilization efficiency. The study develops a computational fluid dynamics (CFD) model that solves for the turbulent steam flow as a continuous phase and the the flow of cement droplets as a discrete phase. Following validation of the CFD model by comparing cement particle size distribution at the exit of the contactor to experimental data, a detailed examination of the same is conducted through a series of 69 CFD different calculations to understand its influence on the evaporation of the volatile in the polymer mixture. Two metrics are developed here: a cluster distribution index (CDI) based on the actual particle pairwise distances and a new mass-CDI based on the the radial distribution of masses. It is demonstrated that by relating the CDI and mass-CDI to the reduction in the cyclohexane content in the contactor, these metrics can be utilized to achieve the desirable input conditions in this polymer processing operation. Through a detailed examination of the particle dynamics in a steam contactor under various conditions, this study assists the polymer manufacturing industry in optimizing the devolatilization process for better steam savings and improved product quality.