Effect of pressure on the moisture adsorption of silica gel and zeolite 13X adsorbents

Abstract

The effect of pressure on the adsorption characteristics of spherical adsorbents of zeolite 13X and RD silica gel is numerically analyzed in this study. The numerical model considers simultaneous heat and mass transfer in a spherical desiccant particle, which accounts for diffusion of moisture into the particles by both Knudsen and surface diffusion. The calculations indicate a dramatic difference of the adsorption behaviors between silica gel and zeolite 13X at a higher pressure of 7.5 atm due to the capability of adsorption and the diffusive ability of adsorbate within the adsorbent. For a lower system pressure of 1 atm, the variation amid silica gel and zeolite 13X is opposite to that at P = 7.5 atm. This is because the amount of the adsorbate for silica gel at P = 1 atm is significantly reduced. At a higher system pressure of 7.5 atm, the initial water content casts a very small influence on the adsorption behaviors for silica gel. However, for a normal pressure of 1 atm, a detectable difference is encountered subject to initial water contents. On the other hand, the initial water content casts appreciable influence on the adsorption characteristics for zeolite 13X.