A review of experimental and modelling methods for accidental release behaviour of high-pressurised CO2 pipelines at atmospheric environment

The aim of this article is to review past progress on experimental and modelling developments for depressurisation, release and dispersion of CO2 from high-pressurised pipelines. For the experimental work, several data were analysed from big projects (COOLTRANS, CO2PipeHaz, CO2PIPETRANS and COSHER) to understand release behaviours of high-pressure CO2 and to validate models developed for assessment of safety distances of CO2 pipelines. For the modelling development, mathematical and numerical models were applied to predict the thermo- and fluid-dynamical behaviours of CO2 in a broken pipeline and in a near field, and the dispersing cloud of CO2 in a far field. It was found that homogeneous relaxation model has given better predictions of the CO2 depressurisation and release than homogeneous equilibrium model. It was also found that Peng-Robinson and three-phase accurate equations of state could accurately predict the thermodynamic behaviours of CO2 in the broken pipeline and in the near field respectively. The Lagrangian particle-tracking method was found to accurately predict the far-field CO2 concentration with the presence of complex terrain. No impacts of toxic impurities (H2S, SO2) on depressurisation, release and dispersion of CO2 mixture was experimentally investigated. Further modification and validation of the novel method proposed for the high-pressure CO2 release from buried pipelines are required to accurately predict the unbalanced flow and the behaviour of solid CO2 in and around the crater. Finally, further laboratory- and large-scale experimental data are required to investigate and support validation of models predicting the impact of the toxic impurities on the CO2-mixture release.