For many years now ultrafine grinding – grinding of mineral products to 20µm or less – has been employed to assist or improve mineral recovery, mainly in platinum and gold plants. The technology has matured and is now marketed by several companies including FLSmidth who acquired the Knelson-Deswik (now the FLSmidth VXP) mills with the buyout of Knelson Concentrators.
Ultrafine grinding (UFG) is used in the precious metal industries to liberate and expose extremely finely disseminated gold and platinum minerals and make them amenable to flotation or leaching. Definitely UFG has its place, but it is not the universal panacea for refractory ores that it was once thought to be.
Ultrafine grinding not only liberates minerals, but also creates vast numbers of extremely small particles with enormous total surface area. Increased surface area will generally lead to increased reagent usage, and in the gold industry it will often result in increased oxygen demand and depressed leach kinetics.
Weighing up the pros and cons of UFG can really only be done with metallurgical testwork, and fortunately Peacocke & Simpson has a bench-scale 2-litre VXP mill and a Mastersizer for particle size measurement. With kinetic leach and flotation tests on ultrafine product, we are able to determine the metallurgical benefits and implications of UFG. Testwork conducted over a range of particle sizes allows us to quantify recovery and kinetic changes, and reagent and oxygen demand, as well as revealing any untoward or unusual behaviour.
All being well and benefits proven, it would then be necessary to employ a larger VXP mill to determine scale-up and power factors, which can be done at an FLSmith Technology Centre.
Peacocke and Simpson is one of very few minerals testing laboratories in Africa – and in the world for that matter – that can test the metallurgical effects and – to a limited extent – the cost/benefit trade-offs of ultrafine grinding. In these tight times it may well be worth your while to let us help you maximise your margins.
For more information about ultrafine grinding, or the products available to employ it, please feel free to contact us.