Combined effects of additives and power levels on microwave drying performance of lignite thin layer.

The microwave drying performance of lignite thin layer in a bench-scale setup was highlighted in terms of three additives with 10% dosage. The dielectric loss for dried lignite, raw lignite, lignite/coal fly ash, lignite/Na2SO4, and lignite/Na2CO3at 2,450 MHz were 0.06, 0.13, 0.14, 0.15, and 0.18. In comparison with raw lignite, the average temperature rising of the thin layer at 385 W for lignite blending with sodium carbonate, sodium sulfate, and coal fly ash was about 10, 7, and 2°C. The apparent activation energies of both falling rate periods for lignite blending with three additives were less than that of raw lignite. Sodium carbonate among three additives could be preferable one, followed by sodium sulfate and coal fly ash. The energy efficiency increased with the addition of sodium carbonate, sodium sulfate, and coal fly ash. The required electricity energy for lignite/Na2CO3blend at 385 W was reduced by about one half compared with the raw lignite. [ABSTRACT FROM PUBLISHER]