# The Experimental and Modeling Study on the Effect of Ethane in Helium-Rich Natural Gas on the Thermodynamic Equilibrium of Hydrate Formation in the Presence of Tetrahydrofuran

## TL;DR

This study investigates how ethane in helium-rich natural gas affects hydrate formation during helium extraction, using experiments and a new model to predict optimal conditions.

## Contribution

A new thermodynamic model is proposed to accurately predict hydrate formation pressure in helium-rich natural gas with varying ethane and THF contents.

## Key findings

- Ethane and THF compete in affecting hydrate formation pressure (Peq) in helium-rich natural gas.
- The proposed model predicts Peq with an average relative deviation of less than 3%.
- The study provides guidance for optimizing helium extraction using hydrate-based gas separation.

## 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.