Production process

The process flow in Talvivaara consists of four main steps: mining, crushing, bioheapleaching and metals recovery. The mining method selected for use at Talvivaara is open pit mining planned to be at a scale of approximately 24 million tonnes per annum. Crushing is done in four stages, followed by agglomeration with PLS solution in order to consolidate the fines with coarser ore particles.

After the agglomeration, the ore is conveyed and stacked eight meters high on the primary heap pad for one and one-half years of bioheapleaching. The heap pad is equipped with piping, laid on the bottom of the pad, through which low-pressure fans supply air to the stacked ore. From the top, the heap is irrigated with leach solution, which is recycled through the heap until its metal content is sufficient for metals recovery.

After one and one-half years of leaching on the primary pad, the leached ore will be reclaimed, conveyed and re-stacked onto the secondary heap pad, where it will be leached further in order to recover metals from those parts of the primary heaps, where leach solution has had poor contact. Such areas include, for example, the slopes and possible precipitates formed inside the heap. After secondary leaching, the barren ore will remain permanently on the secondary heaps.

In metals recovery, nickel, copper, zinc and cobalt are precipitated from the pregnant leach solution and filtered to produce saleable metal products. After the metals are removed, the solution is further purified and returned to irrigate the heaps.