Measurements and calculations of the equilibrium adsorption amounts of CO2\u2013N2, CO\u2013N2, and CO2\u2013CO mixed gases on 13X zeolite

Abstract

Pressure swing adsorption (PSA) is one practical process for CO2 separation from the exhaust gases in various industries, such as blast furnace gas in steel works. For optimum design of the PSA process, precise estimation of the adsorption equilibrium of mixed gases is desired. The ideal adsorbed solution (IAS) model is a reliable model for this estimation. However, the IAS model requires convergent calculations, which significantly increase the calculation load, especially in dynamic PSA simulations. An analytical formula such as the extended Langmuir (EX-LM) equation is more useful for calculation of the equilibrium adsorption amounts of mixed gases. A drawback of this equation, however, is the uncertainty of the thermodynamic consistency and consequently the accuracy of the calculation results. In order to clarify the necessary conditions for application of the EX-LM equation as an approximation of the IAS model with Langmuir equation (IAS-LM model), both the analytical features and the estimation accuracy of these different methods were evaluated. To evaluate the accuracy of the equations, the equilibrium adsorption amount of mixed gases consisting of CO2, N2, and CO, which are the major gas components of blast furnace gas in steel works, on 13X zeolite were measured experimentally. The results confirmed that the accuracy of the EX-LM equation varies depending on the gas pressure and also the affinities of the adsorbates. Under higher gas pressure conditions, more reliable calculation results were obtained by the IAS-LM model.