Intensification of flotation separation process of residual carbon from coal gasification fine slag using ultrafine carbon particles conditioning

Coal gasification fine slag (CGFS) is a high-ash product with high content of residual carbon. Flotation is a common method to separate residual carbon from CGFS. However, conventional flotation is difficult to effectively remove residual carbon due to the intimate interlock between carbon and ash components in CGFS and the developed pore structure of residual carbon. In this work, a separation method was proposed using ultrafine carbon particles during conditioning to achieve the intensification of ash-carbon flotation separation from CGFS. The flotation results showed that employing ultrafine carbon particles conditioning pulp effectively increase the removal rate of unburned carbon by nearly 20%. To investigate the mechanism of the effect of variable contents of ultrafine carbon particles on the decarburization performance of CGFS, the mercury intrusion porosimeter and a self-made laboratory attachment process observation system were used, indicating that the proposed method reduced the cumulative pore volume of CGFS from 1.27 to 1.09, a 15% decrease. During the conditioning process, the ultrafine carbon particles could follow the fluid flow into the residual carbon pores, which prevented the flotation reagent entering the pores. Thus, this avoids waste of flotation reagents and improves flotation performance.