Improving Pyrite Liberation and Grinding Efficiency in Fine Coal Comminution by Swelling Pretreatment

Abstract

Experimental studies with Kentucky bituminous coals have shown that ash content has a significant influence on the coal's grindability. For the Kentucky coals studied, the specific energy consumption in grinding the coal to 10 urn, at which 90 percent liberation of the mineral matter can be achieved, exceeds 400 kwh/ton for high ash-content (> 20%) coals, while less than 100 kwh/ton energy consumption is required for low ash (< 5%) coals. An innovative technique has been investigated to improve the liberation of mineral matter and, simultaneously reduce grinding energy consumption in fine coal grinding of the coals. By treating coal with a swelling chemical agent prior to grinding, the grindability of coals can be considerably improved. The Hardgrove Grindability tests show that the HGI values for a high-pyrite Kentucky No. 9 coal is increased by 50–150 percent after swelling pretreatment, depending on the treatment reagent and time. Batch stirred ball mill grinding results demonstrate that this new techn...