Experimental study of leakage diffusion in supercritical/dense phase CO2 pipelines

The risk of leakage of supercritical/dense-phase CO2 pipelines during transportation is unavoidable, and CO2 diffusion and low-temperature effects may cause harm to the surrounding environment and personnel. In order to reveal the variation rules of pressure, temperature and flow rate at the leakage port, as well as the distribution characteristics of CO2 concentration and temperature in the diffusion zone, this study conducted several sets of large-scale CO2 pipeline leakage experiments, which took into account the effects of different pressures, temperatures, and leakage port conditions. The lowest temperature at the leakage port was measured to reach −72.6 °C by an independently designed method of near-leakage port parameter measurement, and the flow integral calculation verified the generation of dry ice particles. For far-field diffusion, the concentration and temperature drop in the diffusion zone increased significantly with increasing pressure and leak port in the pipe, and decreased with increasing temperature in the pipeline. The diffusion distances for different concentration thresholds (1 %, 4 %, 10 %) are quantitatively analyzed and the hazard distance is classified according to 4 % (Immediately Dangerous to Life or Health, IDLH). The low temperature distribution pattern is discussed and the diffusion distance of 10 °C is analyzed, and the lowest temperature in the diffusion zone can be as large as −37.5 °C. Through the concentration and temperature distribution at different heights to reflect the characteristics of CO2 heavy gas diffusion. The experimental data can provide a reference for engineering pipeline operation, and at the same time provide a validation benchmark for numerical simulation studies.