| As the proportion of natural gas in China’s energy consumption continues to increase,research into its storage technology has become critical.Hydrate based gas storage technology has become a research focus due to its advantages such as high gas storage density and easy storage and release.Water-in-oil emulsion is a new hydration enhanced material in recent years,which has good hydrate based gas storage potential.However,there are too few reports on the hydrate based gas storage performance of emulsions,and the understanding of its gas storage performance is not perfect.In this paper,the hydration properties of water-in-decane emulsions were systematically studied in both static and stirred reaction systems;Based on this,a dry water-in-oil material was prepared.Finally,the hydration kinetic and enhanced mechanism of water-in-oil materials’each reaction system were analyzed.In this paper,it was determined that the emulsion obtained by water-oil volume ratio of55/45 and compound emulsifier Span80/Tween80 of 5 wt%was most suitable for hydrate based gas storage through the study of the properties and static hydration reaction of the emulsions.At temperature of 274.15 K,initial methane pressure of 9 MPa,and gas-water volume ratio in the reactor of 10:1,the gas storage capacity of the emulsion could reach120.25 V/V,which meaned that the emulsion could be used as a hydrate based gas storage material,but the disadvantage was slow hydration rate.In order to further improve the hydration rate,mechanical stirring was used as a promotion method.In stirred reaction systems,the optimal emulsion hydration and gas storage conditions were selected:temperature of 274.15K,gas-water volume ratio in the reactor of 10:1,methane initial pressure of 6 MPa,stirring rate of 700 rpm,and emulsifier dosage of 5 wt%.In this condition,the gas storage capacity was 141.42 V/V.Further cyclic gas storage experiment proved that the emulsion had good recyclability.The gas storage capacity in the four hydration processes were stable above 130 V/V,and the maximum instantaneous gas storage rate increased from 5.84 V/（V?min）in the first hydration process to8.30 V/（V?min）in the fourth hydration process.The fast gas storage stage in four hydration processes took 40 to 50 minutes,and the gas storage capacity was stable above 107 V/V,accounting for 77.05%to 82.23%of the total gas storage capacity..Dry water-in-oil material with water-to-oil volume ratio of 95/5 also was prepared in this work in order to reduce the thickness of the oil layer and eliminate the interference of the emulsifier molecules.When it wraps water droplet of same particle size,the thickness of oil film is only 1/10 of the water-to-oil ratio of 55/45 emulsion.And the gas-liquid contact area in reaction system increased to 10,000 times that of static emulsion.Its gas storage capacity reached 156.90 V/V and the maximum instantaneous gas storage rate was 12.61 V/（V?min）in a static reaction system of 274.15 K and 7 MPa.Adding aluminum foil as a thermally conductive material could increase its gas storage capacity and maximum instantaneous gas storage rate to 176.80 V/V and 15.47 V/（V?min）,respectively.The cyclic gas storage performance of DW/O decreased slower than DW with the number of cycles.The experimental data of each water-in-oil material’s reaction system and the calculated value of the modified KJMA crystallization kinetic model had a good fit,and the rate constants respectively are 0.0516 min-1,0.0818 min-1,0.109 min-1,and 0.136 min-1.The research in this work develops new gas storage materials for hydrate based gas storage technology,and provide a reference for the application of derivative technologies based on the absorption-hydration process of the water-in-oil structure. |
PDF Full Text Request