Study On Process And Performance Of Functional Carbon Materials Promoting Gas Storage Of Hydrate

Hydrate gas storage technology holds immense potential in the realm of clean energy.Enhancing its gas storage efficiency and energy storage density is crucial for the industrial development of this technology.In this paper,starting from the control factors of hydrate growth,functional carbon materials were used to improve the heat and mass transfer efficiency of hydration process,optimize the gas-liquid interface properties of hydrate generation to promote the rapid growth of hydrate.Coupled adsorption method and hydration method,and the generation of binary hydrate further improve the gas storage performance.Firstly,expanded graphite with low density and high surface area was used to enhance mass and heat transfer at the gas-liquid interface to promote the formation of methane hydrate.Under static conditions,a small amount of 0.08wt%expanded graphite can accelerate gas mass transfer,increase nucleation sites and heat transfer efficiency at the gas-liquid interface of hydrate reaction,and improved gas storage performance.Under mild conditions(273.2 K and 6 MPa),methane gas storage reached 190.4 cm3STP/gH2O,with an average gas storage rate of 8.75 cm3·g-1·min-1,which was 1.12-1.37 times and 1.67-30.17 times higher than that of other carbon materials such as graphite and carbon nanotubes,respectively.However,at the end of gas storage,the layered structure of expanded graphite was destroyed,resulting in the increase of its density and the loss of the function of promoting gas storage of hydrate.Subsequently,the hydrophobic graphene modified by fluoride was used to promote the hydration gas storage process,which improved the stability of the functional carbon material at the gas-liquid interface.The results indicated that the methane storage process achieved a gas storage capacity of 165.2 cm3STP/gH2O and an average gas uptake rate of 11.88 cm3·g-1·min-1 at 273.2 K and 6 MPa,while the carbon dioxide storage process reached a gas storage capacity of 112.5 cm3STP/gH2O at 274.2 K and 3.1 MPa.According to the analysis,the superhydrophobic fluorinated graphene facilitated hydrate growth from liquid phase to gas phase by establishing a growth platform at the hydration interface and enhanced gas-liquid mass transfer efficiency,thereby achieving optimal gas storage performance.Compared to expanded graphite,fluorinated graphene exhibited superior stability in hydrate systems.Even after ten cycles of gas storage,the methane storage capacity remained above 90%.This modification method for strengthening the gas-liquid interface provided a novel approach to enhancing gas storage performance in hydrates.Then,in order to improve methane gas storage,the adsorption-hydration coupling gas storage was studied.By optimizing the surface properties and structures of carbon materials,it has been discovered that fluorinated graphene with a hydrophobic nanostructure and superhydrophobic properties can achieve a uniform carbon-enclosed water structure after high-speed mixing with water,which had tiny water droplets while preserving the transport channel of gas.In the optimal water-carbon ratio(Rw=10)system,the hydrate can grow stably in the particle accumulation hole.At 273.2 K and 6.5 MPa,methane gas storage reached 229.4 cm3STP/gH2O,which realized the concept of wet gas storage by adsorption-hydration in wet carbon materials.Finally,to further enhance the energy density of the system,research was conducted on the formation process of methane-hydrogen binary hydrates by storing hydrogen gas in the free cage space of methane hydrates with high saturation.The methane-hydrogen binary hydrates were synthesized at 273 K and 17 MPa by using the method of forming the methane hydrate structure to provide a place for hydrogen storage and combining with the hydrate memory effect.By re-hydrating the decomposed memory water through multiple gas injection,the hydrogen storage capacity reached 0.77wt%and the highly saturated methane of 199 cm3STP/gH2O was also contained.This approach not only yielded binary hydrates with higher hydrogen storage capacity,but also enhanced the energy storage density of methane hydrates.