Effect Of Low Concentration Salts On Hydrate Formation

Natural gas hydrate is a non-stoichiometric cage complex formed by natural gas and water at low temperature and high pressure.It has the characteristics of high calorific value,large reserves and wide distribution.It is not only a potential energy source for natural gas in the future,but also has important value in desalination,cold storage and natural gas transportation.Because of the long induction time,slow growth rate,and severe formation conditions of hydrate formation process,the promotion of hydrate technology has been limited.Therefore,in recent years,scientific research on the direction of hydrate has focused on finding processes that can promote the formation of hydrate.At present,the most commonly used method is to add surfactants to the natural gas hydrate formation system.Compared with the promotion effect of surfactants,most salts such as NaCl are generally considered to be a thermodynamic inhibitor.In the early practical science Research is often used to inhibit the formation of hydrates,so there are relatively few studies on the effects of salt and surfactant complexes on the formation of hydrates.In order to more fully understand the effect of the salt and surfactant compound system on the formation of natural gas hydrates,this article selected the most soluble salts(NaCl,MgCl₂,MgSO₄and K₂SO₄)and the most common Representative three types of surfactants(SDS,APG,DTAC)were formulated.Under the environment of 275.15 K and 6 MPa,the effects of different types of salts and different types of surfactants on the formation of hydrates were studied.Finally,the solution ratio with the best promoting effect was selected,and its influence on hydrate formation in different porous media environments was studied.The experimental results show that the optimal salt concentration for hydrate growth is about 30 m M,and it will have an inhibitory effect when the salt concentration exceeds 50 m M;the combination of SDS and APG with low concentrations of salt will significantly promote methane hydrate The formation of DTAC and low-concentration salt solutions basically does not generate hydrates;the volume change of the porous medium does not affect its promotion effect,and the particle size change of the porous medium has a greater impact on the hydrate formation.The results show that low concentrations of salts,surfactants and porous media all promote the formation of hydrates.Salts can be thermodynamic inhibitors or kinetic accelerators;compared with the promotion effect of SDS and APG on hydrate formation,the promotion effect of DTAC on hydrate formation is not obvious;conducive to the formation of hydrates,the more obvious the effect on the promotion of hydrates.