Effect of pressure on methane hydrate formation in graphite nanofluids in non-stirred system

Abstract

Given the increasing demand for clean natural gas energy, solidified natural gas (SNG) is regarded as a potential natural gas storage technology owing to its numerous advantages. In this work, the effects of the concentration of graphite nanoparticles (GNs) on the rate of hydrate formation, gas consumption, induction time, and morphology of methane hydrates under different pressures were studied. The results showed that under lower pressure, the low concentration of GNs increased the gas consumption of hydrates, but the hydrate formation rate decreased by 50% and the induction time increased. The addition of high concentration GNs decreased the hydrate formation rate significantly, there was no obvious induction period, and the final gas consumption changed little. At the same time, only a small amount of hydrate was formed, accompanied by a considerable volume of foam. Under higher pressure, the addition of GNs promoted the formation of hydrates, increased the rate of hydrate formation. Among them, the 0.3 wt% concentration of GNs showed the best promotion effect, and the final gas consumption was higher than that of other metal and oxide nanofluids. Therefore, under the proper pressure, using cheap GNs as promoters can not only effectively promote hydrate formation, but also save costs.