Kinetics and spatial distribution of tetrahydrofuran/methane hydrate formation in an unstirred reactor: Application in natural gas storage

Abstract

The use of solidified natural gas technology for storing natural gas (NG) has significant advantages because it finds an optimal balance between economic feasibility and safety. In this study, the effects of the gas–water volume ratio on tetrahydrofuran (THF)/methane (CH4) hydrate formation were explored via visualization in the presence of stoichiometric tetrahydrofuran (THF, 5.56 mol%). The space utilization rate of the reactor and the spatial distribution of hydrates in the reactor were carefully investigated using isochoric and isobaric gas injection methods. The results showed that the ideal gas–water volume ratio was 1.0 (250 mL of the solution) at 283.2 K and 3.0 MPa. Three occurrences of THF/CH4 hydrates in the reactor were discovered in isochoric multistage gas injection mode. Amorphous THF/CH4 hydrates completely filling the reactor were captured with single gas injection. A hollow hydrate column containing a 2-layer wall and massive free water was captured when gas was injected into the reactor twice. After three gas injections, the key features of hydrate columns with 3-layer walls and no free water inside them were unveiled. In isobaric gas injection mode, a layered distribution of the hydrate column was observed. This phenomenon attributed to the methane gas in the white layer was higher. Moreover, the space utilization rate of the reactor significantly improved and reached 89% in this gas injection mode. Searching the growth pattern of hydrates in reactors could be performed to obtain the optimum reactor configuration and result in an overall cost reduction for solidified natural gas (SNG) technology.