Moisture diffusivity during microwave drying of wastewater sewage sludge

摘要

Microwave drying of wastewater sewage sludge was investigated in this study. The power level ranged from 360 W to 600 W and the initial mass of the samples varied from 30 g to 50 g. The drying kinetic of sludge showed three distinct phases; a short adaptation period, a long constant drying rate period then a falling drying rate period. The dimensional measurements indicated that depending on the applied drying conditions the initial volume shrank up to 40%. Mathematical modeling of microwave drying of wastewater sewage sludge was performed using Fick's law. Analytical solution of diffusion model was achieved by incorporating shrinkage and finite dimensions of the sample. Diffusion coefficient was defined as a function of the applied drying conditions (power level, initial thickness and mass of the sample). In this study, it was proved that neglecting shrinkage or considering infinite shape brings to an over estimation of the diffusion coefficient.