Safety assessment of decomposition and pressure relief scenarios in high-pressure LDPE process

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Pressure relief systems are crucial for safeguarding pressure vessels and equipment from excess pressure. In emergencies, they must vent enough mass to lower pressure to safe levels, making relief device sizing methods vital. This study investigates decomposition and pressure relief phenomena using fast measurement techniques with lab-scale autoclaves capable of 500 MPa. High-sensitive piezoelectronic sensors and custom double typ-S-thermocouples are employed to measure flame front propagation and pressure relief trajectories. A one-phase flow nozzle model calculates maximal mass flux at supercritical conditions and characterizes the pressure and temperature behavior of an isentropic relief system, incorporating factors like geometry, friction, and heat transfer through a discharge coefficient. The kinetics and thermodynamics of vinyl acetate and ethylene decomposition are modeled using combustion principles, including laminar burning velocity and adiabatic flame temperature. A compartmental model of burned and unburned volumes predicts time-dependent flame front propagation and mass conversion, accounting for turbulence effects. Chromatographic and spectroscopic methods provide essential data for structural modeling. By combining experimental and numerical techniques, various scenarios of decomposition and pressure relief phenomena can be visualized under different operating conditions.