CO2 enclathration in a semi-continuous quiescent hydrate-forming reactor operated with pure CO2 and water soluble additives.

CO2 capture by gas hydrates is now considered as a promising alternative to classical separation processes, especially in applications when the inlet gas is available at high pressure and CO2 is to be reinjected in a geological formation. In a continuous process, forming the gas hydrates under quiescent (or unstirred) conditions would be very interesting for many reasons, including economical and safety aspects, even though the technical challenge is then to achieve high water conversion and high hydrate formation rates. The laboratory experiments presented here show that this challenge can be met by using a low concentration of appropriate water-soluble additives. These experiments extend to semicontinuous (or semi-batch) conditions a previous series of experiments conducted in a closed vessel using as additives a combination of a small quantity – in or below the percent range – of a surfactant (sodium dodecyl sulfate) and an organic compound (tetrahydrofuran). An almost complete conversion of water into hydrates is reached in a reasonable amount of time despite the quiescent conditions used. Enhanced capture kinetics and possible actions mechanisms of this combination of two additives are analyzed and discussed on the basis of experimental equilibrium curves, visual observations, kinetics data, hydrate formation rate and final water conversion