Experimental study on leakage characteristics of large-scale CO2 pipelines containing CH4 and CO impurities

The presence of impurities will change the thermophysical properties of CO2, which will affect the leakage characteristics of CO2 transport pipelines. The difficulty of experimental work and limitations of scale have constrained the application value of existing research for actual pipelines, and experimental work under impurity-containing conditions is even more limited. Therefore, based on a large-scale CO2 pipeline experimental platform, we conducted large-scale CO2 pipeline leakage experiments containing CH4 and CO impurities for the first time in this work, and investigated the influence mechanism of impurities on the pipeline leakage process. The research reveals that under the impurity conditions studied, CH4 reduced the initial pressure wave velocity by 4.43 % compared to pure CO2, while CO exhibited a more pronounced reduction of 18.05 %. The maximum elevation of the first pressure plateau increased by 36.33 % and 50.88 %, respectively. CO exhibited stronger suppression of the temperature drop rate and elevation of the minimum temperature compared to CH4 impurities. Additionally, both CH4 and CO impurities mitigated the phase transition non-equilibrium during the instantaneous pipeline leakage. The experimental scale approached industrial pipeline conditions, which could provide reliable actual applicability data support and reference for numerical simulation studies on impurity-containing pipeline.