Numerical Simulations of Polymer Devolatilization in a Steam Contactor: Correlating Particle Distribution With Volatile Content Removal

Abstract

The current study focuses on a polymer devolatilization process in a device called a contactor, which 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 the turbulent steam flow as a continuous phase and 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 comprehensive analysis of the same is conducted through a series of 69 different CFD 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 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.