Phase equilibria of hydrates from ternary mixtures of methane plus ethane plus propane and methane plus propane plus carbon dioxide

Hydrate-liquid-vapour (HLV) equilibrium of aqueous clathrates formed from gas mixtures can be complex compared to hydrates formed with single guests. Typically, pressure and temperature are controlled to obtain these data, but for multicomponent systems, it is necessary to control/report more intensive variables, namely, composition. Metastability, manifested as impractically long experimental times, has been reported to be a challenge with some multicomponent systems. We present HLV equilibrium conditions of two ternary gas mixtures: methane + ethane + propane (90:7:3 molar ratio) and methane + propane + carbon dioxide (55:5:40 molar ratio). Conditions varied in the temperature range of 275-285 K and the pressure range of 1.24-4.75 MPa. Experimental standard uncertainties were on average 0.10 K and 0.005 MPa for methane + ethane + propane and 0.19 K and 0.005 MPa for methane + propane + carbon dioxide. Our technique allowed us to bypass the limitations reported in the literature and provided fast, reproducible HLV equilibria for gas-dominated systems.

Automated summary

The HLV equilibrium conditions of two ternary gas mixtures were investigated in this study, and it was found that the long experimental times pose a challenge for multicomponent systems. The technique used in this research bypasses these limitations and provides fast and reproducible HLV equilibrium data for gas-dominated systems.