Studies on characteristics and flotation of a hard-to-float high-ash fine coal

High-efficiency separation of hard-to-float high-ash fine coals has been a research hotspot in some countries, especially in China. Separation of hard-to-float high-ash fine coals by froth flotation, although considered to be the most effective, remains some challenges to be overcome. In this paper, the mineralogical/petrologic, physical and chemical characteristics of the of a hard-to-float high-ash fine coal collected in Kailuan mining area were studied. The floatability and liberation characteristics of this coal sample and potential separation processes were investigated experimentally. According to the coal characteristics, four separation processes were put forward and evaluated. Experimental results indicated that classified floatation couldn’t effectively improve the fine coal quality, while the processes of fine grinding-recleaning to roughing cleaning coal and selective agglomeration-floatation were suitable for the Kailuan coal. Compared with the original coal flotation process, the processes of fine grinding-recleaning to roughing cleaning coal increased the cumulative yield from 50.87% up to 55.53% while reduced the product ash content from 11.76% down to 10.74%. In the processes of selective agglomeration-floatation, the lowest ash of clean coal is 10.69%, with 58.72% yield, 7.85% higher in yield and 1.07% lower in ash content. The ash contents of the products from the two processes are lower than 11%, which meets the clean coal requirement.