Modelling Transient Leaks of Multi-Component Fluids Including Time-Varying Phase Composition

A fast time-varying discharge model with safety system capabilities has been extended to handle the accidental release of multi-component mixtures. Previously the model could only handle pure components or “pseudo-component” mixtures, but the new multi-component model carries out vapour-liquid equilibrium (VLE) calculations. This allows accurate predictions of the phase envelope between a mixture’s bubble point and dew point. In this region liquid and vapour compositions inside the vessel vary over time, as will the composition of material leaking into the atmosphere. The theory of the model is presented, and a case study illustrates the importance of rigorous multi-component modelling to get an accurate source-term description of releases of hazardous mixtures.