Research on grinding and flotation decarbonization of coal gasification fine slag

Coal gasification fine slag (CGFS), a solid waste byproduct of the coal gasification process, is predominantly treated through landfilling or stacking, with limited large-scale industrial applications. Given the high ash content, high porosity, and numerous continuous components of CGFS, this study focuses on a dry powder CGFS sourced from northern China. By analyzing the material composition, particle size distribution, surface morphology, and internal structure, a secondary-flotation decarbonization method based on pre-grinding was innovatively developed and the optimal dosage of reagents was determined. Experimental results indicate that fine grinding exposes the residual carbon surface of CGFS, significantly enhancing its floatability. With a grinding time of 3.5 min, the consumption of collector (Oil #3, a lightweight alkyl compound) in roughing flotation was 14 kg/t, while foaming agent (MIBC, methyl isobutyl carbinol) consumption was 3 kg/t. In scavenging flotation, Oil #3 consumption was 14 kg/t, and MIBC consumption was 1.5 kg/t. The concentrate yield was 3.20 %, with an ash content of 26.91 %. The tailings mineral content reached 37.67 %, with an ash content of 91.77 % and a loss on ignition (LOI) of 8.23 %. The tailings products met the requirements of Class III fly ash.