Simulation and Sensitivity Study of Industrial Low Density Polyethylene Tubular Reactor

Abstract

The development and application of process modelling technology for polymer industry is relatively increasing. Accurate simulation of the polymerisation process can help industrial community to maximise their polymer production with minimal energy and cost. In this study, industrial Low Density Polyethylene (LDPE) tubular reactor process has been simulated using Aspen Plus software. Aspen Polymer (Aspen Plus component) was used to model the free radical polymerisation part of the polymer. The reactor properties, reaction mechanisms and kinetic model for the polymerisation process was taken from several referred journals. Sanchez-Lacombe equation of state was used to describe the thermodynamic properties of the process. Based on a comparison with available literature data, the selected equation of state and reaction kinetic model had performed well in simulating tubular reactor temperature profile, polymer molecular weight and monomer conversion. Sensitivity study was also conducted to study the behaviour of controlled parameters in the tubular reactor process. In this study, the effect of initiators flow rate, oxygen flow rate, and Chain Transfer Agent (CTA) flow rate towards ethylene conversion and temperature profile were observed. From the sensitivity study, both initiators and oxygen flow rate had displayed considerable effect on the observed parameters. Among them, the second initiator flow rate displayed the most significant effect. CTA flow rate gave the minimal effect since its main purpose is to modify the polymer molecular properties. This demonstrates the important of proper regulation of second initiator flow rate in order to meet desired polymer conversion while maintaining the reactor temperature.