Phase Equilibrium Data and Storage Capacity of the Ethane Gas Hydrate in the Presence of 1,4-Dioxane and Polyvinylpyrrolidone

Gas hydrate has always been the focus of researchers due to its high storage capacity and low space occupation. It is obvious that investigating kinetic factors such as suitable mixing and nucleation and thermodynamic factors such as temperature and pressure have a significant role in hydrate formation. The present work has been done to obtain the equilibrium points of ethane gas hydrate in the presence of 1,4-dioxane and polyvinylpyrrolidone additives at initial pressures of 12.6, 15.8, 18.1, 21.7, and 24.2 bar and a temperature range of 272.8 to 294 K. The measured equilibrium data with the addition of 0.2, 0.5, 1.0, and 4.5 mass percentages of 1,4-dioxane and 0.02, 0.05, 0.10, and 0.15 mass percentages of PVP aqueous solutions are obtained based on the isochoric pressure search method. The equilibrium results acquired from this experiment for pure water and ethane are compared with those of the extant literature, and it is determined that the experimental methodology and apparatus performance are adequate and the measured points demonstrate good accuracy. The equilibrium points of ethane gas hydrate have not been investigated in the presence of PVP, which is usually known as a polymeric surfactant, and 1,4-dioxane in the already available literature. The results show that 1,4-dioxane acts as a thermodynamic hydrate inhibitor at all concentrations, and the inhibition rate is higher at high concentrations. In addition, PVP has been used as a kinetic hydrate inhibitor. On the other hand, the gas storage capacity and induction time for ethane gas hydrate in the presence of PVP polymer with a molecular weight of 25000-30000 have been calculated. Three-phase (H-L-V) equilibrium data for ethane gas hydrate with addition of the mentioned additives can provide useful information in the fields of storage, separation, and transmission.