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Heap bio-leaching pilot

Responsible partner: Terrafame

Location of pilot: Sotkamo, Finland

TRL: 8

One of the larger pilots in the project is located at the Sotkamo mine in Finland. Today, Sotkamo is an important producer of Zn, Cu and Ni-Co products. Sotkamo is operated by Terrafame, represented in NEMO by its owner company Finnish Minerals group. Within NEMO, the Sotkamo mine acts as one of the case studies. In the present day Sotkamo process, metals are reclaimed through a bio heap leaching process in which a pregnant leach solution is produced. Sulphide precipitation is used to consecutively precipitate CuS, ZnS and (Ni-Co)S products. The bio heap leaching is operated in two steps, distinguishing the primary heap leaching, after which the solid leaching residue is reclaimed and fed to the secondary heap leaching. Within NEMO, focus is on the secondary heap leaching process.

To study and improve the secondary heap leaching process, a bio heap leaching pilot was set-up and brought into operation (see picture below) For the purpose of the pilot test, a pilot heap has been constructed with similar operational  parameters as the current secondary heap leaching operation at the mine (e.g. aeration, irrigation). The pilot is fed with the solid leaching residue from the primary heap leaching operations. The aim of the pilot is to test a new microbe population and enhanced operational conditions developed by the NEMO partners BRGM, Exeter University and the Sotkamo team. With the optimisation of the secondary heap leaching, the NEMO partners aim to improve the leaching of metals (Cu, Co, Ni, Zn), while a mineral fraction is left behind with low residual sulphide content, which remains in place as a final waste product of the process.

Picture: bio-heap leaching pilot constructed at the Sotkamo mine (Finland).

The pilot composes 900 tonnes of primary heap leaching residues. The pilot consists of two identically constructed heaps where the first heap is operated with new parameters and new microbial culture whereas the other acts as a reference heap operated with the same parameters as used in the current secondary leaching process. The first test heap was inoculated with the microbe culture for three times to ensure adequate microbial population. The pilot heap was constructed during the summer of 2020, started operation in august 2020 and will run for 2 years.

Contact: Ville.Heikkinen@terrafame.fi