| Scope and method of study. Adsorption models are needed to provide information for the design of gas separation and purification processes as well as other applications. The goal of this study was to develop, analyze, and evaluate models for both pure and multicomponent adsorption. A generalized form of two-dimensional equations of state (2-D EOS) for describing an adsorbed phase was presented. Various specific 2-D EOS models, as well as other adsorption models such as the Langmuir and ideal adsorbed solution (IAS) theory, were analyzed, evaluated, and compared with experimental data. Methods for correlating binary data for 2-D EOS, including using interaction parameters and correction coefficient models, were developed and evaluated.; The adsorption of pure methane, nitrogen, and carbon dioxide as well as methane-nitrogen, methane-carbon dioxide, and nitrogen-carbon dioxide mixtures on coal at typical coalbed conditions was also modeled. This work addressed adsorption effects in the enhanced recovery of coalbed methane by the injection of nitrogen and/or carbon dioxide.; Findings and conclusions. Fugacity coefficient equations were derived from the proposed 2-D EOS to establish rigorous equilibrium relations between an adsorbed phase and a gas phase. The 2-D EOS models are capable of predicting nonideal behaviors and they provide the best overall prediction results among adsorption models available. The Langmuir and IAS models were proved to be unable to predict nonideal behaviors such as azeotropes and asymmetric x-y (adsorbate vs. gas mole fractions) behavior. The proposed spreading-pressure-dependent correction coefficient model for 2-D EOS exhibits attractive performance, especially in high pressure adsorption. The adsorption data of gases on coal were best described by the 2-D EOS models. |
