Firstly, the experimental measurements of CH4, CO2 and their binary gas adsorption isotherms to investigate the adsorption behavior and use for prediction of adsorption equilibrium were conducted at 301 K at pressures up to 10 MPa. Secondly, a calculation formula of adsorbed amount of total gas was derived from relation between adsorbed amount and feed gas composition at standard state on condition of unknown equilibrium gas concentration during adsorption. Thirdly, the extended Langmuir, ideal adsorbed solution (IAS) theory in conjunction with Langmuir were used to predict the experimental data of binary gas adsorption based on an iterative algorithm. Finally, the prediction accuracy for experimental data of total and adsorbed amount of component gas and free gas compositions were analyzed.
Experimental data indicate adsorbed amounts of the total gas and single-component CO2 increase, but adsorbed amounts of CH4 increase at low equilibrium pressure and decrease at high pressure with increase of CO2 concentration in feed gas. Model predictions based on single-component isotherms and the calculation formula show that the quantitative formula obtained can be used to predict adsorption equilibrium of CH4/CO2 binary gas under feed gas conditions. The binary gas prediction data are quite variable and depend upon the feed gas composition. The IAS–Langmuir provides, on average, a better fit to total gas adsorption but is variable for the single-component adsorption with the feed gas composition. The predictions of total and component gas adsorption and equilibrium gas compositions illustrate similar trends with their experimental data.