High moisture content and complex composition restrict the direct application of livestock manure, therefore efficient drying constitutes an essential pre-treatment step. Conventional drying suffers from long duration, high energy consumption and uneven heating, while the internal mass-transfer resistance of high-moisture porous materials impedes moisture migration. In this study, using swine manure (moisture content 75.16 wt.%) as the raw materials, microwave drying was applied to the dehydration for biomass-to-fuel production. The effects of microwave power (400 W, 500 W, 600 W, 700 W, 800 W) and load mass (10 g, 15 g, 20 g, 25 g) on heating performance, drying results and specific energy consumption were investigated. The results showed that with microwave power increased form 400 W to 800 W, the heating rate was improved from 0.245 ^oC/s to 0.406 ^oC/s and the drying time decreased from 18.8 min to 6.7 min and the higher heating value (HHV) was elevated from 3500 kJ/kg to the range of 10000 - 11500 kJ/kg. When the load mass increased from 10 g to 25 g, the heating rate was reduced from 0.923 ^oC/s to 0.181 ^oC/s and drying time increased from 5.4 min to 10.8 min. The specific energy consumption ranged from 58.7 kJ/g to 31.3 kJ/g and it declined originally and then increased when the microwave power or loading mass increased. The lowest specific energy consumption was obtained at 700 W and 15 g, achieving the best balance between drying efficiency and energy consumption. These findings clarify the application advantages of microwave drying for swine-manure dehydration, reveal the underlying mechanism of microwave-assisted moisture removal, and provide theoretical support and technical guidance for energy-efficient biomass pre-treatment as well as for the scale-up of microwave drying technology in the treatment of manure-derived solid wastes.
 

Microwave drying,Swine manure,Biomass fuel,Dehydration rate