Hydrate-Based CH4 Storage at Moderate Temperatures: Can Metal Packings Enhance Hydrate Kinetics under Saline Conditions?

The present study focuses on hydrate-based CH₄ storage and transportation at moderate temperatures using thermodynamic promoters such as tetrahydrofuran (THF). This work successfully demonstrates that hydrate-based storage at a moderate temperature (288.15 K) can be successfully achieved in a scaled-up 25 L reactor using metal packing-based porous media under mild saline conditions. Kinetic promoters such as amino acids and surfactants can enhance mixed CH₄–THF hydrate growth. However, chemical additives increase the operating cost of the reactor during scale-up due to reusability issues and expensive manufacturing processes. The present study utilizes the inherent characteristics of the THF–water system and capillary action during hydrate growth for scale-up by using highly porous metal packings (porosity of 0.98). The commonly available water sources for use in the hydrate formation process are generally saline. Therefore, experiments were conducted at 0.01, 0.1, 1, and 3.5 wt % NaCl concentrations to investigate whether metal packings can be effective in saline solutions. The experiments are conducted by using a temperature-controlled 25 L reactor with gas injected at an initial pressure of 75 bar. The metal packings increase the water-to-hydrate conversion and hydrate formation rate at low salinity (≤1 wt % NaCl). However, the packings reduce the hydrate kinetics at 3.5 wt % NaCl, even compared to a nonpacked-bed arrangement. There is lower hydrate growth along the reactor walls for 3.5 wt % NaCl concentration compared to 0.01 wt % concentration. Extreme saline conditions inhibit capillary action. The study has also successfully demonstrated hydrate kinetics using chemical affinity modeling.