Experimental Study On The Kinetics Of Methane Hydrate Formation For Natural Gas Solid-state Storage And Transportation

With the worsening of the world energy situation, natural gas is becoming aprimary energy resource in the world and can not be ignored. The exploration andutilization of natural gas resource plays an important role in environmental protectionand sustainable development of the national economy. Thus, natural gas resource hasreceived wide attention around the world. However, because natural gas consumersincluding urban centres and industry enterprise are far from the gas production sites, asa result, continuous and efficient delivery of natural gas to users is particularlyimportant and the natural gas storage and transportation technology should be improvedconstantly.The hydrate-based storage and transportation technology for natural gas storagehas significant advantages on economic cost, storage capacity, safety, andenvironmental protection. However, the reaction rate and the storage capacity of gashydrates have not achieved the standards required in the industrial applications. Toincrease the reaction rate and the storage capacity of gas hydrate for natural gas storageis a key problem to be solved at present. This paper introduced surfactants, porousmedia and thermodynamics accelerator into the reaction system, and investigated theeffects of surfactant (sodium dodecyl sulfate, SDS), thermodynamics accelerator(cyclopentane) and porous media (silica sand) on the kinetics of methane hydrateformation. The main conclusions are obtained as follows:①SDS is an ideal surfactant for methane hydrate formation. The induction time iseffectively reduced and the gas storage capacity of methane hydrate is greatly increasedin the presence of SDS. It is found that the concentration of500ppm SDS is the optimalconcentration among all the SDS concentrations tested.②The gas storage capacity of methane hydrate formed in the fixed bed of silicasand saturated by SDS solution is slightly higher than that obtained in the stirred reactorunder the same experimental conditions. Therefore, the fixed bed of silica sandsaturated by SDS solutions has a better prospect than the stirred reactor due to its costsaving in the mechanical agitation investment.③The kinetics of methane hydrate formation in the systems of CP/H2O andCP/SDS/H2O have been studied. The results showed that although the addition ofcyclopentane can greatly reduce the hydrate equilibrium conditions and save the mechanical agitation energy, but low gas storage capacity will affect the overalleconomic benefits. Thus, CP is not an ideal thermodynamic accelerator for theformation of methane hydrate.④When the surfactant SDS is introduced into the cyclopentane system, theinduction time of methane hydrate crystallization is significantly reduced. However,with the increase of undercooling, the rapid growth of methane hydrate will result in itsaggregation at the gas-liquid interface and therefore hinder the further growth ofmethane hydrates at the gas-liquid interface under static conditions. Compared to astatic reactor, the gas consumption, the reaction rate, and the gas storage capacity aresignificantly increased in a stirred reactor.