Investigation of the hydrate formation process in fine sediments by a binary CO2/N2 gas mixture

Abstract

Abstract To obtain the fundamental data of CO2/N2 gas mixture hydrate formation kinetics and CO2 separation and sequestration mechanisms, the gas hydrate formation process by a binary CO2/N2 gas mixture (50:50) in fine sediments(150–250 μm) was investigated in a semibatch vessel at variable temperatures(273, 275, and 277 K)and pressures (5.8–7.8 MPa). During the gas hydrate reaction process, the changes in the gaseous phase composition were determined by gas chromatography. The results indicate that the gas hydrate formation process of the binary CO2/N2 gas mixture in fine sediments can be reduced to two stages. Firstly, the dissolved gas containing a large amount of CO2 formed gas hydrates, and then gaseous N2 participated in the gas hydrate formation. In the second stage, all the dissolved gas was consumed. Thus, both gaseous CO2 and N2 diffused into sediment. The first stage in different experiments lasted for 5–15 h, and > 60% of the gas was consumed in this period. The gas consumption rate was greater in the first stage than in the second stage. After the completion of gas hydrate formation, the CO2 content in the gas hydrate was more than that in the gas phase. This indicates that CO2 formed hydrate easily than N2 in the binary mixture. Higher operating pressures and lower temperatures increased the gas consumption rate of the binary gas mixture in gas hydrate formation.