Graphite rejection in a lead concentrate using gravity concentration techniques

During the sequential flotation of the ore from Dariba-Rajpura mines of Hindustan Zinc Limited (India), graphite reports in considerable amounts into the lead concentrate. Graphite above a stipulated limit of 2.5% decreases the sinter strength to a great extent. Reports on flotation routes for graphite rejection from lead concentrate showed limited success. In the present study, attempts were made for exploiting the specific gravity differential between graphite and lead-bearing minerals using gravity techniques. Lead rougher concentrate collected from the operating plant was treated in a laboratory model multi-gravity separator and in a 75mm water-only cyclone. The metallurgical data obtained at different test conditions was analysed. The results indicated that lead concentrates with a graphite could be obtained using both the techniques. The concentrate grade and recovery values obtained in multi-gravity separator were better than water-only cyclone. However, considering the capacity of both the units. The possibility of a hybrid circuit with water-only cyclone as a pre-concentrator and multi-gravity separator for graphite rejection from water-only cyclone overflow product is discussed