Mathematical modeling of membrane system for hydrocarbon gas (C1 – C3) recovery in polyethylene plant

Abstract

This study proffers a solution to the issue of hydrocarbon loss in petrochemical plants. Three sections were identified as locations where the loss occurred during the polyethylene production operations within the Indorama polyethylene plant facility. This study focused on developing a hollow-fiber membrane system designed to enhance the recovery of methane, ethylene, and propylene within polyethylene production plants. The membrane model was developed and analyzed for use in the Indorama polyethylene plant to predict the recovery of hydrocarbon gas at designated points of loss. Comprehensive modeling showed that the system was described by eleven coupled ordinary differential equations accounting for mass, energy, and momentum. The model equations were discretized into a set of algebraic equations using the orthogonal collocation method, and the solution to these equations was obtained using the Newton-Raphson method. The results showed a remarkable recovery of methane (~86%), ethylene (~80%), and propylene (~91%) on the shell side while capturing about 82% of carbon dioxide on the fiber side. These results were achieved using the spirobisindane-based ladder polymer (PIM-1) membrane material under 90 bar and 2 bar pressure on the shell and fiber side, respectively, with a membrane area of 6900 m². These findings were instrumental in assessing the effectiveness of the PIM-1 for recovering these hydrocarbon gases.