Heating and Water Desorption Characteristics of Silica Gels under Microwave Irradiation

Abstract

For development of a highly efficient desiccant air conditioning system, we have proposed to apply microwave heating as regeneration energy source of adsorbents. In this study, we focused on heating and water desorption characteristics for some silica gels under microwave irradiation. Microwave heating was performed for three particulate silica gels (RD, B, ID type). Moreover, water desorption experiments were also conducted for silica gel RD with various initial amounts of adsorbed water, microwave powers, and humid nitrogen flow velocities. As a result, a big difference in achieving temperature with microwave irradiation was observed between silica gels even under dry condition, meaning that each silica gel had a different microwave absorptivity. Among them, silica gel RD indicated the best microwave absorptivity and achieved the highest bed temperature, initial desorption rate, and desorption ratio by microwave irradiation. For silica gel RD, an amount of desorbed water in an equilibrium state was observed to be approximately proportional to initial amount of adsorbed water in every microwave power. It was also found that water desorption was promoted as increasing microwave power.