Ono–Kondo lattice model for high-pressure adsorption: Pure gases

Abstract

Theoretical models for adsorption behavior are needed to develop optimal strategies for enhanced coalbed methane (CBM) recovery operations. Although several frameworks are available for describing this adsorption phenomenon, the Ono–Kondo (OK) lattice model offers several practical advantages in modeling supercritical, high-pressure adsorption systems. In this study, we evaluated the Ono–Kondo (OK) lattice model for correlating high-pressure, supercritical adsorption encountered in CBM recovery and CO 2 sequestration. Specifically, the parameters of the OK model were optimized to obtain reliable representation of pure-gas adsorption on carbon adsorbents. The results were used to develop generalized model parameters, expressed in terms of gas properties and adsorbent characterization which include the temperature dependence of the OK model parameters. The results indicate that the OK monolayer model appears effective in modeling pure-gas adsorption on carbon matrices. The model can represent the adsorption isotherms on activated carbons and coals with about 3.6% average absolute deviation (AAD), which is within the expected experimental uncertainties of the data. The generalized model can predict the adsorption isotherms on activated carbon with about 7%AAD. Moreover, generalized model parameters determined from isotherms of a single gas can be used to predict the adsorption isotherms of other gases. The generalized model also appears effective for pure-gas adsorption on wet coals when the moisture content in the coal is above the equilibrium value. However, at water contents below the saturation value, the model parameters are dependent on the water saturation.