Microwave Drying of Brown Coal Agglomerates

Abstract

Brown coal spheres and cylinders were heated with microwave power and their drying rate studied. The drying rate of identical samples in a conventional drying oven was also measured for comparison. The results have shown that microwave drying was one to two orders of magnitude faster than convective drying. In both methods of drying the constant rate drying period was absent. Convective drying followed a first order drying rate, which was also the case in microwave drying at low moisture content. With high moisture content microwave drying was characterized by a “liquid pumping” effect, the extent of which was sample size and power level dependent.