Retrospective Consideration of Decomposition Events in the High-Pressure Polymerization Process

Zusatztext

The drastic process conditions of the high-pressure polymerization of ethene are decisive for the occurrence of decomposition reactions, which can spontaneously occur as a highly exothermic and pressure-forming reaction. This poses various safety related challenges and questions for reactors or product separators. This work includes further generalization of the process description including the relief of gases under high-pressure conditions and the decomposition reaction of ethene based on the numerical models with mass and energy balance. Decomposition products are investigated both experimentally and theoretically by equilibrium calculations depending on the respective type of decomposition event. The relief of various technical and other gas mixtures relevant in the high-pressure process is investigated experimentally and with aid of a relief model utilizing real gas equation of states, whereby a focus is given to the accurate description for venting the decomposition products. The investigation of pressure relief extended to the exhaust line of the relief system. The improved description of the pyrolysis gas venting helps to characterize the influence of the induced flow on the decomposition reaction in the coupled process by ventilated decompositions. Transient state variables obtained via the retro analytical method are used to calculate heat input into reactor components, which can alter the reactor material and raise questions about integrity. This is done by a CFD simulation to describe the heat transfer and the radial temperature distribution in the steel material. A separate topic highlights the negative influence of decomposition products, more precisely soot oils, on the process stability of the high-pressure polymerization.

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