Dynamic Modeling and Optimization of Flash Separators for Highly-Viscous Polymerization Processes

Abstract

In the present study, a multi-phase, multi-zone mathematical model is developed to describe the dynamic operation of industrial high-pressure separators (HPSs) for highlyviscous polymer systems. The proposed multi-phase, multi-zone description of the highpressure separator takes into account the complex gas carry-under and liquid droplets carryover phenomena. Moreover, the model takes into account the mass transfer rate from the liquid droplets to the gas phase as well as the bubble formation in the liquid zone. Extensive numerical simulations are carried out to determine the optimal operating conditions (i.e., temperature, pressure, feed composition and mass flowrate, etc.) on the dynamic performance and the separation efficiency of the HPS for highly-viscous fluids. It is shown that the proposed model is capable of simulating the dynamic operation of industrial-scale HPSs over a wide range of operating conditions (i.e., pressures 200-260 bar and temperatures 220-260 0 C) and copolymers of different copolymer composition and viscoelastic properties (i.e., melt index in the range of 2-50 g/10min). Finally, it is shown that industrial HPSs do not operate near the thermodynamic equilibrium conditions. Therefore, their non-ideal behaviour should be taken into account when simulating their dynamic operation. Subsequently, model-based optimization and control studies are carried out to optimize the dynamic operation and performance of an industrial HPS.