Scale Effects in the Artificial Reproduction of Natural Gas Hydrates in Lab Vessels

Natural gas hydrates (NGHs), as the largest hydrocarbon resource on Earth, offer a promising reservoir of sustainable fuels, particularly due to the potential of the CO2-CH4 replacement process. Most of the literature on the study of NGHs comes from laboratory experimental campaigns using reactors for the artificial reproduction of the conditions in which NGHs form in nature. In order to develop production technologies at the field scale and also compare experimental results obtained in different setups, it is crucial to assess the effects that a particular geometry or size has on the results, from both thermodynamic and kinetic points of view. In this perspective, the paper compares the hydrate formation process carried out in two different reactors with similar cylindrical geometry, one with a volume of 1 L and the other with a volume of 60 L. The analysis covers, for two different values of hydrate saturation (10% and 20%), the thermal aspects, in order to understand how hydrates form and grow inside the reactor, the quantity of hydrate formed and gas uptake, and the kinetic aspects. At 10%, the formation front behaves differently between the two reactors, while at higher saturation, hydrates similarly form in the upper section of the reactor and subsequently advance to the lower section. With regard to gas uptake, it is higher in the small reactor, resulting in a higher utilization of the gas phase for hydrate formation. Also, the kinetics differs with size, especially at higher saturations. The pressure reduction rate is generally higher in the 1 L reactor.