Natural Gas Hydrate Formation Using Saline/Seawater for Gas Storage Application

Abstract

Solidified natural gas (SNG) technology is regarded as the safest, cost-effective, and environmentally benign mode of natural gas storage suited for long-term and large-scale applications. Key challenges barricading the commercial exploitation of this technology include the formation kinetics and storage stability. In this study, we investigate the macroscopic kinetics of mixed natural gas hydrate formation using a C1 (93%)–C2 (5%)–C3 (2%) gas mixture along with a tetrahydrofuran promoter in the presence of saline water and seawater. The main objective is to examine the effect of the presence of salt (NaCl) in influencing the natural gas hydrate formation kinetics. Experiments were performed to study the effect of the pressure (driving force) on the mixed natural gas hydrate formation kinetics with the presence of 3 wt % NaCl (saline water) and actual seawater (2.72 wt % salinity) in an unstirred reactor configuration. The presence of salt (3 wt % NaCl) significantly retards the mixed natural gas hydrate formation kinetics, resulting in a slower rate of hydrate formation, reduced gas uptake (15.6% drop), and delay in the time taken for completion of hydrate formation (about 3.8 times longer). The plausibility of the improvement in kinetics of mixed natural gas hydrate formation with saline water in the presence of leucine and tryptophan amino acids (kinetic promoters) was also examined in this study. Leucine amino acid has shown the potential to improve the kinetics of mixed natural gas hydrate formation in saline water.