电场增强CO₂溶解封存机理研究

Study on Mechanism of Enhancing CO₂ Dissolved Sequestration by Electric Field

摘要: CO₂地质封存是现阶段最具前景的负碳技术，是我国实现双碳目标的兜底保障。其中咸水层封存被认为是未来最具潜力的地质封存技术。CO₂在水中的溶解是咸水层封存的重要机理，如何提高CO₂在地层水中的溶解度对咸水层封存效果至关重要。文章基于分子动力学模拟提出了提高CO₂在地下水中溶解度的新方法。通过研究H₂O和CO₂分子在地层疏水固体壁面附近的赋存规律，以及一定温度压力条件下电场的非热效应对于CO₂-H₂O系统溶解度的影响，发现固液界面处CO₂分子的分布受外电场方向以及场强的调节：CO₂分子在与界面平行的电场下聚集于界面，在与界面垂直的电场下离开界面并溶解到水溶液中；在与界面垂直的电场基础上，施加场强越高，CO₂分子越趋向于离开界面并溶解于水溶液中。当电场方向与界面垂直时，至多可以增强CO₂溶解度297.26%。本研究揭示了一种调节水溶液中CO₂积累和溶解的新机制，在提高CO₂地质封存效果方面具有巨大的应用潜力。

Abstract: CO₂ geological storage is the most promising negative carbon technology at present, and it is the backstop for China to achieve the goal of the carbon peaking and carbon neutrality goals. Saline aquifer sequestration is considered to have the most potential for CO₂ geological storage technology in the future. The dissolution of CO₂ in water is an important mechanism for saline aquifer sequestration. How to improve the solubility of CO₂ is very important for the storage effect. In this paper, based on molecular dynamics simulation method, the distribution of CO₂ and H₂O molecules near the hydrophobic solid wall of formation is studied to find a way to improve the solubility of CO₂ in the underground water. The influence of non-thermal effect of electric field on the solubility of CO₂-H₂O system under certain temperature and pressure is studied. The results show that the distribution of molecules at the solid-liquid interface is regulated by the direction and intensity of the external electric field: CO₂ molecules gather at the interface under the electric field parallel to the interface, and leave the interface under the electric field perpendicular to the interface and dissolve into the aqueous solution. Based on the electric field perpendicular to the interface, the higher the field intensity is applied, the more CO₂ molecules tend to leave the interface and dissolve in the aqueous solution. When the electric field direction is perpendicular to the interface, the solubility of CO₂ can be enhanced by 297.26% at most. This study reveals a new mechanism to regulate the accumulation and dissolution of CO₂ in aqueous solutions, which has great application potential in improving the effect of CO₂ geological storage.