IsaMill Ultrafine Grinding for a Sulphide Leach Process

Fine grinding mills have improved in design and efficiency in recent years, allowing major opportunities for treatment of materials where liberation to grind sizes below fifteen microns are required. The successful development of the IsaMill, a horizontal stirred mill, has produced equipment capable of grinding the larger tonnages which exist in mineral processing operations, to product sizes below ten microns. Initially developed for use with base metal flotation circuits, significant test work conducted in 1998 shows that major economic gains can be achieved by producing finely ground material for leaching. IsaMill development and operation is reviewed. Results from test work to produce a feed stock for both straight cyanidation and sulphide leaching are discussed, with emphasis on energy consumption, product size and leachability. A number of options for ultrafine grinding and leaching are also discussed.