In order to construct large-scale CO2 transportation pipelines and improve the application range of CCUS technology, it is very important to explore the disaster of supercritical CO2 leakage and diffusion in high-pressure pipelines. In this paper the industrial scale CO2 pipeline (length 257m, inner diameter 233mm) is taken as the research object, and the numerical model of supercritical CO2 leakage and diffusion in high-pressure pipeline is built by using computational fluid dynamics simulation technology to simulate actual leakage. In this model, the influence of the far-field flow of dry ice generated during the jet process is added to the release rate and the release temperature during the diffusion process. The reliability and accuracy of the model are verified by the experimental results of 100mm leakage diameter. The diffusion characteristics of CO2 molar fraction and temperature under different leakage diameters are obtained by analyzing the leakage simulation results of high-pressure supercritical CO2 pipeline and the dangerous areas are divided. The results show that the axial CO2 molar fraction mainly goes initial stage, rising stage and descending stage. In the radial direction, a transition period of reversed growth occurs after the initial stage and then goes through the descending stage. Gravity and wind have little influence on vertical and radial flow. Temperature mainly goes through two stages: temperature drop section and temperature rise section. The temperature danger zone is mainly concentrated near the source of leakage, and its range is smaller than that of CO2 molar fraction danger zone. Temperature indirectly affects the molar fraction distribution of CO2 mainly by affecting the density of CO2. Temperature tends to promote the expansion of the dangerous area and lasts for a long time so its danger cannot be ignored. When the release rate and release temperature are available, it has a certain reference value for the prediction of CO2 leakage and diffusion hazards.

Authors: YU Jian-liang;LIU Chang-yuan;YAN Xing-qing;CAO Qi;LIU Shao-rong;