EFFECT OF PROCESS VARIABLES ON MICROWAVE, CONVECTIVE,MICROWAVE-CONVECTIVE AND SUN DRYING OF PLASTER OF PARIS

摘要

Batch-type experimental dryer with an online weighing mechanism was developed for determining the drying behavior of casted and tempered plaster of paris. Drying rates of plaster slabs were experimentally determined by microwave, convective, combined microwave–convective and natural open air sun drying systems at three levels of microwave output power (180, 360 and 540 W), drying air temperature (40, 50 and 60°C), different combinations of microwave power and temperature (180W/60°C, 360/50°C and 540/40°C) and sample geometries (cylindrical, rectangle and square faced cuboids) for studying the drying kinetics with respect to varied initial moisture content and thicknesses of plaster. The type of dryer, microwave output power and sample thickness had a strong effect, whereas sample geometry and temperature did not have much impact on the drying rate. Microwave drying was investigated as potential method for drying.