Effect of modified dry water on kinetic and recovery of hydration separation coal mine gas

The low carbon development of coal industry is the key to achieve the "dual carbon" goal, and the reduction of carbon emission intensity is its inevitable requirement. It is necessary to explore the method of rapid and efficient separation and recovery of coal bed methane in the context of carbon peak. In this study, dry water was modified with gellan gum, carbon nanotubes, and copper powder based on hydratre technology.The multiple cycles of hydrate formation were carried out in the static system at a condition of 3.0 MPa and 275.2 K using dry water as the experimental fluid phase. The authors examined the effects ofunmodified dry water, gellan gum-dry water, carbon nanotube-dry water, and copper powder-dry water on the separation kinetics and CH₄ recovery effect of 25% CH₄/67% N₂/8% O₂ mixture, and compared the performance stability of dry water with different modified materials for repeated applications. The results indicated that the separation effect of materials is best in gellan gum-dry water.Compared to the unmodified dry water system, the gellan gum-modified dry water system was significantly increased by a factor of 9.36, the initial growth rate of hydrate was improved by 87.45%, and the average CH₄ recovery was maximized to 56.4%.The graphite nanofluid containing 9% GDW is preferred among the four GDW systems mass concentrations (3%, 6%, 9%, and 12%) tested in this study. The preferred results showed that the 9% gellan gum-dry water had a better kinetic stability and recovery effect. However, the carbon nanotube-dry water and copper powder-dry water showed a slight inhibitory effect on the CBM hydrate formation. When partial dissociation occurs during multiple cycles of hydrate formation, there exists an optimal ratio of free water and undissociated dry water to achieve optimal kinetics. The high CH₄ recovery rate, enhanced repeated kinetics, and low-energy consumption of the GDW system demonstrated a new prospect for the separation of low-concentration CBM gas by hydrate method.