Research on the gas storage properties of ice and water conversion into methane hydrates in silica gel with various pore sizes

Hydrates can effectively store cooling energy and gases, showing great potential in the field of gas storage, separation and transportation. Three kinds of silica gel were used to strengthen the formation of methane hydrate. The structural and morphological characteristics of ice crystals, as well as the decomposition process of hydrates, were investigated utilizing a Powder X-ray Diffractometer, a stereoscopic microscope, a Differential Scanning Calorimeter, and a cryo-Scanning Electron Microscope. The results showed that the freezing point is transferred to 262.4 K in the pores of silica gel. Hexagonal ice and cubic ice are formed in the pores and on the surface, and ice film is formed on the surface. In the temperature of 253.1–268.1 K and the initial pressure of 4.0–6.0 MPa, the temperature increase or the pressure reduction enhance the methane dissolution and the initial methane hydrate formation rate. In the pore size of 9.31 nm–40.3 nm, with the increase of pore size, the lower the hydrate formation pressure, and the higher the gas consumption and consumption rate. Within the range of 40.3 nm–77.14 nm for pore size and 42.6 m2/g to 188.1 m2/g for specific surface area, the influence of these parameters on gas consumption and the rate of consumption during hydrate formation is minimal. The optimal conditions for methane hydrate formation are identified as 268.1 K, 4.0 MPa, utilizing silica gel type III. The gas storage ratio reached 50.09 V/V, and the final pressure was 2.5 MPa, which is advantageous for the application of hydrate-based gas storage and the utilization of cooling energy.