Abstract
Hydrate-based gas separation (HBGS) has good potential in the separation of helium from helium-rich natural gas. HBGS should be carried out under a pressure higher than the thermodynamic equilibrium hydrate formation pressure (P(eq)) to ensure the formation of hydrate so that the accurate prediction of P(eq) is the basis of the determination of HBGS pressure. In this work, the P(eq) of the helium-rich natural gases with different helium contents (1 mol%, 10 mol%, and 50 mol%) in gas and different tetrahydrofuran (THF) contents (5 wt%, 10 wt%, and 19 wt%) in liquid at different temperatures were experimentally investigated through the isothermal pressure search method. A new thermodynamic model was proposed to predict the P(eq) of helium-rich natural gas. This model can quantitatively describe the effects of THF and helium on P(eq), and it predicts the P(eq) of the helium-rich natural gases in this work accurately. The average relative deviation of the model is less than 3%. This model can guide the determination of the operating condition of the HBGS of helium-rich natural gas.