Master curves for mass transfer in bidisperse adsorbents for pressure-swing and volume-swing frequency response methods



A general model has been developed for pressure-swing and volume-swing frequency response methods with analytical solutions derived to analyze various mass transfer resistances in biporous adsorbents. The model can consider a combination of distributed mass transfer resistances acting independently or in series including macropore diffusion, micropore diffusion, and a surface barrier resistance at the entrance of micropores. Heat effects are included for nonisothermal systems. Temperature variations are shown to be less for pressure-swing compared with volume-swing systems. The general model is developed in such a way that information extracted from it is independent of whether a system is batch volume swing or flow-through pressure swing. Simulation results demonstrate that mass transfer mechanisms can be easily discriminated by the master curves. Isothermal models exhibit one-step curves, whereas nonisothermal effects are represented by two-step curves. Examples are given to demonstrate the use of the master curves to describe experimental data. © 2010 American Institute of Chemical Engineers AIChE J, 2011