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Albion process progress

Publishing Date
08 Nov 2002 12:00am GMT
Mining Journal: 08 Nov 2002
Journal Team
Last week, MIM Holdings Ltd announced that, as part of its plans to improve the profitability of its zinc business, it is conducting a feasibility study into the production of zinc metal at its McArthur River mine in Australia’s Northern Territory.The feasibility study is investigating the application of MIM’s Albion process.The process first involves the ultrafine grinding of an ore or concentrate (to 80% passing a mesh-size of less than 20 microns) using MIM’s proprietary ISAmill technology.The resulting slurry then undergoes autothermal oxidation (the oxidation of the sulphide minerals generates sufficient heat for the process to be self-sustaining) in open agitated tanks.According to Hydrometallurgical Research Ltd, part of MIM’s metallurgical development group, oxygen or air can be added to the leaching tanks (which are similar in design to those used in carbon-in-pulp operations).The company says that retention times in the leaching vessel are generally less than 24 hours and, depending on the sulphides involved, 85-98% of the sulphur is oxidised and 85-98% of metals recovered.The leached slurry is neutralised to precipitate impurities, ideally to produce a goethite residue.Harmful impurities such as arsenic are fixed in the neutralised solids as ferric arsenate.The neutralised slurry is subsequently thickened, and vacuum filters are used to produce a filter cake.The filter cake is then converted back into a slurry and sent for cyanidation for gold and silver recovery.The filtrate undergoes conventional solventextraction and electrowinning to recover metals such as copper, zinc and nickel.Hydromet says that base-metal recoveries for the Albion process are typically in excess of 95%, and those for gold and silver are 90-95%.MIM believes that the process offers a number of competitive advantages over other approaches.These include lower capital costs, improved environmental impact (no SO2 production), and the process is more robust than bioleaching.It also consumes less energy and requires fewer units for operation and a simpler plant layout.MIM expects to complete its pilotplant studies by the end of this year.The company reports that the pilotplant programme has been designed to evaluate feed options, including using a final concentrate (>45% Zn) or a rougher/cleaner concentrate (25-35% zinc), the latter offering increased metal recovery and lower concentrator costs.The plant is processing 400 kg/d of concentrate yielding 120 kg/d of zinc metal.The company expects to complete the full feasibility study for the project by the end of 2003, and anticipates that the use of the Albion process could result in total zinc costs of US$0.20/lb and a capital cost of less than US$1,000/t/y.The process may also be used at Mt Isa to process tailings and transitional ores.Dr David Winborne, MIM Holdings Ltd, 22 Corunna St, Albion, Queensland, 4010, Australia.Tel: +61 (0)7 3833 8009.E-mail: www.hydrometresearch
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