Abstract
Hydrate-based gas separation (HBGS) is a new method for extracting helium from helium-rich natural gas (HNG). The ethane in HNG affects the thermodynamic equilibrium hydrate formation pressure (Peq), and Peq is crucial to the application of HBGS for extracting helium. In this work, the Peq of the HNGs with different ethane contents (0.5 mol%, 1.0 mol%, and 10 mol%) and the solutions with different tetrahydrofuran (THF) contents (5 wt%, 10 wt%, and 19 mol%) at different temperatures were experimentally investigated through the isothermal pressure search method. Ethane and THF have a competitive effect on hydrate formation. A new thermodynamic model was proposed to predict the Peq of different HNG-THF solution systems. The effect of ethane on Peq can be quantitatively described, and the Peq of HNGs can be accurately predicted by the model in this work. The average relative deviation of the model for predicting Peq of HNGs in different THF aqueous solution systems is less than 3%. The results of this study can guide the operating conditions for the optimization of extracting helium from HNGs by the HBGS process.