Drying Characteristic of Porous Ceramic Microspheres in a Microwave Heated Fluidised Bed

Abstract

This paper presents drying characteristics of both water and nitrate salt solution (simulated waste) impregnated ceramic microspheres in a pilot-scale (10 kg), batch fluidised bed drier heated with microwave energy, under isothermal bed conditions. For comparison, some constant microwave power experiments with water saturated microspheres were also conducted. The effects of bed temperature, fluidising gas flow rates and initial moisture content on drying kinetics were examined. For a given initial moisture and gas flow rate, the total microwave energy consumption for both isothermal bed and constant power level experiments was found to be approximately the same. The decline in drying rates in the presence of nitrate salts was attributed to a decrease in the effective diffusivity resulting from changes in structural properties of salt solution impregnated powders. The use of fluidised bed coupled with microwave heating produced controlled drying of 10 kg batches of simulated waste loaded ceramic powders without any significant agglomeration or coating.