Experimental Determination of CO2 Solubility in Liquid CH4/N2 Mixtures at Cryogenic Temperatures

Coalbed methane (CBM) is an atypical natural gas that may contain a large amount of nitrogen in addition to methane. When liquefying such CH4/N-2 mixtures, knowledge of solid solubility is very important and, in particular, CO2 solubility data are essential for determining the CO2 purification index. Although experimental data for CO2 solubility in pure methane are available for various conditions, such experimental data for CH4/N-2 mixtures are rare. In this paper, a solid liquid equilibrium experimental apparatus using a static-analytic method is described. Data for CO2 solubility in pure liquid methane were obtained and their accuracy was verified by comparison with published values. Solubility of CO2 in CH4/N-2 mixtures with nitrogen molar fractions of 10, 30, 50, and 70% were then measured at cryogenic temperatures between -190 and -150 degrees C.