Blowdown of vessels containing two-phase hydrocarbons exposed to thermal radiation

摘要

This paper presents the depressurisation of a high pressure, two-phase, hydrocarbon containing vessel under the impingement of thermal radiation from an engulfing pool fire. The depressurisation process is simulated over a series of reducing pressure steps until the required pressure is reached. A mathematical model, and computer program is developed for this purpose. The model accounts for non-equilibrium effects between both liquid and vapour phases, single/two-phase orifice discharge, the transient temperature profiles generated in both the vapour and liquid wall sections, the induced wall thermal stresses, and the pressure and inventory variations with time. In the model, blowdown is assumed to start at the same time as the fire. The model is first validated by comparing it's predictions under zero external heat flux conditions with rigorous experimental data and with BLOWDOWN from which good agreement is obtained. It's predictions are then presented for depressurisation under a 90 kW/m~2 external heat flux. The total resident stresses within the vessel is also predicted to access the vessel integrity under fire impingement.