Flotation specificity of coal gasification fine slag based on release analysis

Coal gasification fine slag is a solid waste of difficult-to-separate nature. In this study, the residual carbon was enriched from fine slag by conventional flotation. The optimal flotation results in the concentrates yield of 59.01%, the concentrates ash content of 37.64%, and the flotation perfect index of 41.12%, respectively. Under the identical conditions, step release flotation exhibits abnormal results, i.e., the lowest ash content is concentrates 3 (C3) corresponding to 29.21%. The particle distribution analysis of concentrates 1 (C1) to concentrates 5 (C5) and tailings (T) shows that particles of the highest carbon content transfer to C3, while dominated by ash are enriched in T. Additionally, the particle structure characteristics (with SEM, BET surface area, BJH pore volume/average pore width, FHH fractal characteristics) demonstrate that the particles differ in pore's volume, average width, and interior smoothness. This concludes that it is the larger pore volume, the wider average pore width, and the smoother pore interior that contributes to the greater amount of diesel adsorption and therefore easier release of carbon-content particles in flotation. Such regularities of particle transfer in flotation and release mechanism manifest the flotation specificities of gasification fine slag, which may provide a scientific reference for effectively enriching residual carbon in coal gasification fine slag.