Recovery of Flake Graphite from KR Desulfurization Slag

In the desulfurization process of molten iron, the supersaturated carbon dissolved in molten iron precipitates in the form of graphite. In this paper, according to the characteristics of graphite contained in molten iron desulfurization slag, the flotation method was firstly used to recover the graphite with kerosene used as collector and No.2 oil used as foaming agent, and then the ball milling and magnetic separation process was used to physically remove the impurities of the recovered graphite, and finally the hydrochloric acid and hydrofluoric acid were used for chemically purification. With the result, high purity flake graphite was prepared. The results show that the graphite recovery firstly increases and then decreases with the increase of flotation agent dosage. When the total dosage of kerosene and No.2 oil is 1200 g/t and w (kerosene: No.2 oil) = 4:1, the recovery is more than 97%. The ball milling treatment separated the impurities from the graphite surface, while the magnetic separation reduced iron content in graphite. After three times of the ball milling and magnetic separation treatment, the fixed carbon content in graphite increases from 58% to more than 88%. Under the optimum conditions, the ash content of graphite can be reduced to 0.03% by mixed acid treatment, reaching the standard of high purity graphite. SEM analysis also showed no significant difference in shape between the recovered flake graphite and the natural flake graphite.