Measurement of Diffusivity and Thermal Parameters of Gas Adsorption with a Volumetric Method

Abstract

A volumetric method was developed to measure diffusivity, gas–solid heat transfer coefficient, thermal conductivity of an adsorbent, and dynamic heat of adsorption simultaneously for pure gas adsorption. Dynamic pressures in the two vessels and dynamic temperatures along the radial direction of the spherical adsorption vessel were measured, and the mathematical model was constructed for the adsorption process. The adsorption isotherms at temperatures from 6 to 60 °C and pressures up to 10 bar are correlated with Toth equation. The parameters were determined by the method of least-squares. Mass transport of N2 or O2 in the macropores of zeolite 5A is considered as the combination of the viscous flow and Knudson diffusion. Temperature difference between the gas and adsorbent in the adsorption vessel exists during the early about 15 s of the adsorption process and disappears afterward. The dynamic heat of adsorption changes more rapidly with the adsorption coverage than the isosteric heat. In simulating the dynamic process, the dynamic heat rather than the isosteric heat should be used in the mathematical model.