Macroscopic kinetic investigations on mixed natural gas hydrate formation for gas storage application

Abstract

Solidified natural gas (SNG) technology via clathrate hydrates is a promising technology for the long-term and large-scale storage of natural gas, owing to multifaceted benefits offered, including environmentally benign, compact, and safest mode of gas storage in comparison to conventional methods. In this study, we investigate the macroscopic kinetics of natural gas hydrate formation using a C1 (93%)−C2 (5%)−C3 (2%) gas mixture. The main objective is to examine the effect of the presence of low concentrations of higher hydrocarbons (ethane and propane) in influencing the natural gas hydrate formation kinetics along with the additional presence of a thermodynamic promoter, tetrahydrofuran. Experiments were performed to study the effect of pressure (driving force) on the mixed natural gas hydrate formation kinetics in an unstirred reactor configuration. Plausibility of the improvement in kinetics of mixed natural gas hydrate formation in the presence of an amino acid (kinetic promoter) was also attempted. Concentration of 300 ppm of tryptophan was found to be effective in enhancing the mixed natural hydrate formation kinetics at experimental conditions of 283.2 K and 5.0 MPa, albeit a minor drop in gas uptake. Results from this study will be helpful in advancing the SNG technology toward commercial implementation.