Investigation of using graphite nanofluids to promote methane hydrate formation: Application to solidified natural gas storage

Solidified natural gas storage using gas hydrates is a promising technology for non-explosive, high capacity, and environmentally-friendly natural gas storage at mild storage conditions. Improvement in the kinetics of gas hydrate formation is essential for the further development of this novel technology. In this work, the use of graphite nanofluids for enhancing the CH4 hydrate formation was investigated. The experiments were conducted in a stirred tank reactor at 277.15 K and 6.0 MPa. The behavior of the CH4 hydrate nucleation and growth in graphite nanofluids was observed using a microscopy apparatus. The results indicate that compared to liquid water, the gas storage capacity obtained in graphite nanofluids increased by 3%, the induction time for the CH4 hydrate formation decreased by 89%, and the total time for hydrate formation decreased by 67%. Among the three graphite nanoparticles concentrations (0.2, 0.5, and 1.0 wt%) tested in this work, the concentration of 0.5 wt% was optimal for the enhancement of CH4 hydrate formation. The gas storage capacity obtained in the 0.5 wt% graphite nanofluids was higher than that obtained in other nanofluids such as the Fe3O4 and ZnO nanofluids. Thus, the use of graphite nanofluids is an effective approach to enhance hydrate formation for solidified natural gas storage, but the gas storage capacity should be further increased in future work. (C) 2020 Elsevier Ltd. All rights reserved.