Adsorption and desorption through packed and fuidized clay‑based composite desiccant beds: a comparison study

Abstract

The present study considers the composite desiccant employing horse dung, sawdust with clay and later impregnating CaCl2 into the host material. The microscopic and spectroscopic experimental methods such as scanning electron microscope (SEM) and X-ray difraction (XRD) were used to characterize the composite desiccants. The specifc heat (Cp) quantifcation reveals higher values for clay-additives composite desiccants with lower pore volume and larger grain sizes, whereas lower values for clay composite desiccants with higher pore volume and smaller grain sizes. Adsorption–desorption experiments for moisture removal and addition are conducted in a vertical column in static and fuidized states. The desiccant beds are subjected to an initially set value of process air velocity, relative humidity, temperature and mass of bed. Moisture removal capacity, moisture addition capacity and mass transfer coefcient are the parameter indices adopted to measure the heat and mass transfer characteristics of vertical packed and fuidized bed comprising clay-additives-CaCl2 composite desiccants. Comparing packed and fuidized beds, a higher surface area of bed in fuidization improves dehumidifcation performance and results in higher desorption rates. Experimental results confrmed that clay and clay-additives-based desiccants have desired adsorption–desorption characteristics of a suitable desiccant. The interesting advantage of fabricated clay and clayadditives-based composite adsorbents is that the air exits the desiccant bed at a lower temperature, saving cooling energy requirements of sorption-based systems.