Enhanced clathrate hydrate phase change with open-cell copper foam for efficient methane storage

Abstract

Rapid phase change of hydrate with high gas storage capacity is very important for the application of natural gas hydrates technology. Three discs of open-cell copper foam (CF) with different pore densities (or pores per inch, PPI) herein were immersed in sodium dodecyl sulfate (SDS) solution for enhancing methane storage in solid hydrate. The promotion effects of CF on the methane hydrate formation in the metal-embedded systems were investigated via an unstirred tank reactor. The results demonstrated that the surface of CF skeleton is covered with abundant micro holes and micro grooves, which can provide many metal nuclei for gas–water crystallization. The nest-like metal skeleton acts as crisscross “highway” for the crystallization heat transfer. Methane hydrate was quickly formed in the SDS/CF systems, but CF with the pore densities of 5 and 30 PPI was not favorable for conversion of more water to hydrate. Compared with these two composite systems, the SDS solution with the 15 PPI CF were able to store more methane at a faster formation rate. A theoretical model based highly porous two-phase systems was used to predict the effective thermal conductivity (ETC) of the metal foam filled with hydrate. It was found that the ETC of the hydrate/CF composite was significantly enhanced by employing CF matrix, and the low pore density CF had a more positive impact on improving the ETC of the composite. Further comparative experiments conducted at various pressures indicated that the solutions with 15 PPI CF exhibited higher methane storage capacities and larger hydration rates than the simple SDS solution, especially at the low pressure.