An Approach to Carbon Dioxide Particle Distribution in Accidental Releases

The main problem in calculating the consequences of a carbon dioxide dispersion following an accidental release is the formation of solid CO2 during the expansion to ambient pressure. The dispersion models more frequently used in the framework of quantitative risk analysis, cannot describe the carbon dioxide behaviour, in particular with respect to the calculation of the rainout fraction. Moreover, only scarce data is available for two phase CO2 releases. In the present study, a specific approach was developed to calculate the particle size distribution following the release of pressurized liquid (or supercritical) CO2. The approach combines several submodels accounting for the different mechanisms of jet break-up and specifically addresses the possible formation of solid particles. The model was validated using experimental data available for CO2 and for the release of other pressurised, superheated liquids. The model developed can find further applications in rain-out calculations for two-phase releases of conventional substances.