New Design Basis for the Design of High Pressure Polyethylene Reactor Bay Using an Explosion Risk Analysis and Non Linear Finite Analysis

High pressure technology used for the production of Low Density Polyethylene (LDPE) requires a particularly high degree of safety to protect both reactor and surroundings from an accidental event. For this reason, historically, such tubular reactors have been enclosed in roofless bunkers designed on empirical data. Recent improvement in production capacities, scientific knowledge and calculation tools now allows historic designs of these concrete structures to be challenged. The study we have conducted has offered a better understanding of the mechanisms involved in case of an accidental release of ethylene (ventilation and atmospheric dispersion conditions, gas detection efficiency) and subsequent explosion inside the reactor bay (maximum overpressure, impulsion duration, etc…). The methodology, using a combination of an explosion risk analysis (with help of 3D CFD tool) and a non linear finite element analysis (NLFEA) calculation tool has made it possible to define a clear and new basis of design for the enclosure walls to explosion overpressure loads. This in turn also offers new possibilities for an optimisation of the concrete wall thickness and design.