Journal of the Southern African Institute of Mining and Metallurgy
On-line version ISSN 2411-9717
Print version ISSN 0038-223X
The Talvivaara deposits are located in Eastern Finland, within the Kainuu Schist Belt. These polymetallic sulphide deposits are of relatively low grade, but bioheapleaching enables economically profitable nickel extraction from the ore. Zinc, cobalt, and copper are also produced. Talvivaara's production process begins with large-scale open-pit mining and four crushing stages, followed by stacking of the ore in bioleaching heaps. The ore is first leached for 13-14 months on the primary leach pad, after which the leached ore is reclaimed, conveyed, and re-stacked on the secondary heap pad. After secondary leaching, the barren ore will remain on the secondary heaps permanently. In the metals recovery process, the metals are precipitated from the pregnant leaching solution. Construction of the process was begun in spring of 2007 and first metal sulphides were produced at the plant in October 2008. The development of the bioheapleaching process was begun in a 17 000 t on-site pilot heap operated during 2005-2008 and has continued in the industrial heap. At industrial scale, the development measures have focused on improving the permeability and aeration of the heap. Challenges with crushing and aerations systems at the beginning of industrial-scale leaching delayed the increase in metal recovery, but after the first two operational years the leaching results have improved significantly and the process is performing as targeted.
Keywords : bioheapleaching; polymetallic sulphides; nickel; process development; aeration; permeability..