Particle size effect in microwave heating of granular materials

Heating and drying of granular Al 2O 3 and Fe 3O 4 particles by microwave energy (2.45 GHz, 500 W) are reported. The results show that drying of Al 2O 3 was influenced by both particle size and initial moisture content, whereas drying of Fe 3O 4 was independent of these two variables. However, heating was particle size dependent in both cases but the effect was opposite, viz., fine Al 2O 3 heated faster than coarse Al 2O 3, whereas coarse Fe 3O 4 heated faster than fine Fe 3O 4. Relevance of the results in practical applications is also discussed.