N₂ in liquid phase/dense phase CO₂ dissolved in the process of test and the molecular dynamics research

Carbon emissions from coal mining and use are one of the causes of global warming, to reduce CO₂ emissions and achieve the dual carbon goal, it is necessary to promote the development of carbon capture, utilization, and storage (CCUS) technology. The research on the properties of CO₂ is fundamental to CCUS technology, and dense phase CO₂ is involved in both the capture and storage stages of carbon dioxide. However, there is still a gap in the current research on the properties of dense phase CO₂. Therefore, to further explore the dissolving ability of dense phase CO₂, N₂ is carried out in laboratory to dissolve in the liquid phase, dense phase CO₂ test, obtained the N₂. The research results show that the solubility of N₂ in CO₂ is positively correlated with pressure in various single phase states between 5 and 9 MPa at 287.15 K. Generally, the N₂ content in liquid CO₂ fluctuates around 14%, while in dense CO₂ it fluctuates around 20%. The transition from general liquid to dense phase results in a sudden increase in N₂ content from 13.38% to 18.45%, and the results of molecular dynamics simulation indicate that the diffusion coefficient, radial distribution function, and interaction energy between CO₂ molecules and N₂ molecules are the direct reasons for the stronger solubility of dense phase CO₂. The changes in bond angle and coordination number of CO₂ molecules are only affected by the pressure changes in the receptor system, and are not directly affected by the CO₂ phase change, which is an indirect reason for the stronger solubility of dense phase CO₂. The bond length of CO₂ molecules does not change significantly with the pressure and CO₂ phase change in the system, so it is not the reason for the stronger solubility of dense phase CO₂.