Separation and Purification of Methane from coal-Bed Methane via the Hydrate Technology

The separation of methane from coal-bed methane (CBM) via hydrate process using tetrahydrofuran (THF) + sodium dodecyl sulfate (SDS) as additives was investigated in this work. The effect of additives, the concentration of the additives and hydrate memory effect on the hydrate-based separation process were examined at various concentrations of THF + SDS solutions. The results indicate that THF + SDS solutions decrease the formation pressure of methane remarkably and show that the methane concentration in CBM can be enhanced effectively with the system of THF (1.0 mol%) + SDS (500 ppm) in the moderate condition. The concentration of CH₄ can be increased by about 20% for the two feed gases (20% and 50% CH₄/N₂). It indicates the CBM with low methane can be improved to the one which can be used directly by several steps of the hydrate-based separation technology.