Flotation of autogenously milled material

Abstract

A base metal mine is planning extensive modifications to its concentrator plant. It is proposed to enlarge the existing crushing/milling circuit with autogenous mills and to replace the conventional flotation cells with column cells. The ore was piloted in the AARL Pilot Plant and proved to be amenable to fully autogenous single stage milling. Successful column piloting was conducted at the mine on ball milled material. Laboratory rod milled material also showed a good flotation response. However flotation on fully (FAG) and semi-autogenous (SAG) milled material gave poor flotation responses. Deportment by size studies indicated that this was caused by a higher percentage of ultra fine sulphides and talc in the FAG/SAG products compared to rod milled material. The rougher/scavenger residence times had to be extended by almost 60 per cent to overcome the retarded flotation rate of FAG material. After the initial failure of column flotation to produce acceptable recoveries and grades on 80% - 74 μm FAG material, the column cell operating parameters were manipulated to produce flotation results comparable with conventional pilot plant flotation. The main variables changed were feed dilution water, wash water and gas to solid ratio.