Study on CO2 Hydrate Formation Kinetics in Saline Water in the Presence of Low Concentrations of CH4

Abstract

Gas-hydrate formation has numerous potential applications in the fields of water desalination, capturing greenhouse gases, and energy storage. Hydrogen bonds between water and guest gas are essential for hydrates to form, and their presence in any system is greatly influenced by the presence of either electrolytes or inhibitors in the liquid or impurities in the gas phase. This study considers CH4 as a gaseous impurity in the gas stream employed to form hydrates. In developing gas-hydrate formation processes to serve multiple purposes, CO2 hydrate formation experiments were conducted in the presence of another hydrate-forming gas, CH4, at low concentrations in saline water. These experiments were conducted in both batch and stirred tank reactors in the presence of sodium dodecyl sulfate (SDS) as a kinetic additive at 3.5 MPa and 274.15 K, under isobaric and isothermal conditions. Gas loading was taken as the detection criterion for hydrate formation. It was observed that overall gas loading was hindered by more than 70% with the addition of salts after 2 days. The addition of CH4 to the gas stream led to a further reduction of approximately 30% of gas loading in the batch reactor under quiescent conditions. However, the addition of 100 ppm of SDS improved the gas loading by recovering 34% of the loss observed in volumetric gas loading through the addition of salts and CH4. The introduction of stirring improved the gas loading, and 64% of the loss was recovered through the addition of salts and CH4 after 34 h. The investigation was continued further by substituting CH4 with N2, whereupon accelerated hydrate formation was observed.