Modelling of breakthrough curve in water adsorption on silica gel and zeolite 4A

This paper presents the development of a computational model to simulate the adsorption of water in a fixed bed, comparing the performance of zeolite 4A and silica gel type ‘A’. A variation of the Langmuir isotherm for zeolite 4A and Tóth isotherm for the silica gel were used; Linear Driving Force (LDF) model was used for adsorption rate with an overall coefficient temperature dependent. The model is composed of five partial differential equations associated with mole fraction of water, temperature, pressure, superficial velocity and water loading. Method of lines (MOL) was used with the function ODE15S of Matlab® to solve the system. As response variables the characteristic time interval of the breakthrough curve, asymmetry, maximum temperature and pressure drop, through a two-level factorial scheme were evaluated. Adsorbent was the most influential variable on the response variables. Zeolite has the highest rate of adsorption due to the shape of the adsorption isotherm, but has a lower water retention loading and increased resistance to mass transfer.