Separation of CH4 - CO2 gas mixture by gas hydrate crystallisation: A parametric study

Abstract

In the present study a comprehensive experimental study of the CO2 gas hydrate recovery from the CH4 (81.70 mol.%) - CO2 (18.30 mol.%) experimental gas mixture was realised. The effect of the mode, temperature, pressure, and promoter on the CO2 gas hydrate recovery efficiency was investigated. The parametric study will optimise the technology of gas hydrate crystallisation to CO2 remove from natural gas. The gas mixture process separation factor and gas hydrate recovery were studied in SDS (0.30 wt%) aqueous solutions with and without THF (3.80 wt%). The separation simulation was performed for the two modes: pressure-dropping and constant pressure in the temperature range 272.15–283.15 К at the driving forces 1.00 and 2.00 MPa 8 h after the start of the gas hydrate formation. The different temperature dependence is shown for the CH4 and CO2 gas hydrate recovery in depending on the aqueous solution. The CO2 gas hydrate recovery maximum, equal to 63.92% (without THF) and 57.19% (with THF), is observed at the constant pressure separation at 272.15 K and 2.00 MPa. However, THF addition makes it possible to decrease the gas hydrate dissociation pressure of the experimental gas mixture in 7.87 times at 272.15 K. Thus, the choice of the aqueous solution was determined by the aim for the gas hydrate separation – high gas hydrate recovery (without THF) or low process pressure (with THF).