Dewatering of fine coal slurries by selective heating with microwaves

Comparative experimental studies on the dewatering of a fine coal slurry sample containing ≈52% moisture by microwave heating vis-à-vis thermal heating are reported. For thermal heating, thermogravimetric analysis (TGA) using different masses and different heating rates were employed. Similar experiments were carried out for dewatering by microwave heating using a conventional oven operating at 2.45 GHz and 800 W power. These quantitative experiments show that microwave heating is an order of magnitude more efficient than thermal heating, although about 10% of the residual moisture, perhaps trapped in the capillaries of the coal particles, is not removed even by microwave heating. Based on these results, a bench scale dewatering unit was designed and tested in which coal slurry in kg quantities was fed on a conveyor belt. The efficiency of this unit for dewatering fine coal slurries was estimated to be over 80% of the theoretical limit. A cost estimate of about $3/ton for the power consumed for 10% reduction of moisture is made.