Particle Size and Type Effects of Quartz Sand and Calcite on Methane Hydrate Formation Kinetics in Amino Acid−β-Cyclodextrin Systems

Abstract

Aiming at the insufficient kinetic promotion of methane hydrate in binary amino acid−β-cyclodextrin liquid systems and their deviation from the real geological environment of submarine sediments, this paper constructs a ternary green promotion system consisting of amino acid, β-cyclodextrin, and porous media, and investigates the effects of two typical submarine minerals (quartz sand and calcite) with three particle size fractions on methane hydrate formation kinetics. The results show that methane uptake and gas storage density continuously rise with the decreasing particle size of quartz sand; the system with 0.18–0.42 mm quartz sand achieves a 13.5% higher methane uptake than the binary system. The time required for 90% methane conversion (T90) presents a nonmonotonic trend of first decreasing, then increasing as particle size reduces, which verifies the critical pore size effect. Under identical conditions, quartz sand outperforms calcite in hydrate promotion due to its larger specific surface area and higher surface roughness. The unique quartz sand displacement phenomenon is only observed in the methionine + β-cyclodextrin +0.42–0.85 mm quartz sand system, driven by the coupling of capillary force and volumetric expansion thrust of hydrates. Subcooling degree is adopted to quantify the thermodynamic driving force; both cooling and pressurization can strengthen hydrate formation driving force. Comprehensive analysis of energy consumption and equipment cost identifies 275.15 K and 7 MPa as the optimal operating condition. The ternary system achieves synergistic promotion of three components, offering an eco-friendly and efficient strategy for solid-state natural gas storage and transportation.