Industrial high pressure ethylene polymerization initiated by peroxide mixtures: A reduced mathematical model for parameter adjustment

Abstract

We present a method for the adjustment of parameters in the mathematical modeling of industrial tubular reactors for high pressure polymerization of ethylene. We propose a reduced mathematical model for these reactors that aids in the task of model parameter update commonly done periodically in industrial plants. This reduced model was built from a detailed model for multiple peroxide and oxygen initiator systems we had developed before. Some of the assumptions in that rigorous model were reviewed in order to minimize computational effort. Good and faster predictions were obtained by assuming different constant jacket temperatures and pressures at each zone. Pressure pulse equations had to be included in the model. A simplification of the adjustment procedure is also proposed here. It consists in using only the reactions considered crucial for the description of this polymerization. The peroxide initiator and solvent mixtures were treated as fictitious unique initiator and solvent respectively. A procedure was established for the quick estimation of the kinetic parameters that represent initiator and solvent mixtures of different compositions. This resulted in a model that can be adjusted rapidly to predict the behavior of a specific industrial reactor. The reduced model was validated using experimental runs initiated by oxygen either alone or together with peroxide mixtures.

Optimal operation of ethylene polymerization reactors for tailored molecular weight distribution

“…The same modifier mixture, and therefore the same single fictitious modifier, that is employed for the main reactor feed is considered for possible lateral feeds. However, peroxide mixtures for the first and second lateral feeds are different in composition, 15 and hence they are represented in this model by two different fictitious peroxides (I 1 for the first lateral feed and I 2 for the second one). The set of kinetic constants obtained in Asteasuain et al 15 is used here.…”

“…However, peroxide mixtures for the first and second lateral feeds are different in composition, 15 and hence they are represented in this model by two different fictitious peroxides (I 1 for the first lateral feed and I 2 for the second one). The set of kinetic constants obtained in Asteasuain et al 15 is used here. The main model equations are listed in the Appendix.…”

“…Oxygen initiation 15 against several data sets from an industrial tubular reactor. The same modifier mixture, and therefore the same single fictitious modifier, that is employed for the main reactor feed is considered for possible lateral feeds.…”

High‐Pressure Polymerization of Ethylene in Tubular Reactors: A Rigorous Dynamic Model Able to Predict the Full Molecular Weight Distribution

“…This work is focused on the analysis of the tubular reactor unit. The mathematical model of the polymerization reactor is based on a previous, comprehensive steady‐state model developed by the authors,9, 22 which is extended by incorporating the process dynamics. The model assumes plug flow and supercritical reaction mixture.…”

“…None of them attempted to model the complete MWD of the polymer. In previous works, we have developed a rigorous steady state model of a LDPE tubular reactor 9, 22. This model was validated against experimental data from an actual industrial reactor.…”