Green Mining | PROSU – Process Scale-up for Sulphide Poor PGE Ores
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PROSU – Process Scale-up for Sulphide Poor PGE Ores

Name: Process scale-up for sulphide-poor PGE ores, Further development of the sustainable beneficiation process

Acronym: PROSU, BePGE II

Duration: 1.6.2010-31.12.2013

Total costs: 1 805 000 €/Tekes support 1 047 000 €

Leading research organization partner: Geological Survey of Finland

Contact persons: tero.korhonen(at), jari.ruuska(at), riitta.keiski(at), kari.heiskanen(at), marja.oja(at)


Research organization partners: Oulun yliopisto, Aalto yliopisto

Company partners: FQM Kevitsa Mining, Gold Fields Arctic Platinum Oy, Nordic Mines, Outotec, Nortec Minerals Oy

International partners: Luleå University of Technology, University of Cape Town, Bergakademi Freiberg, CSIRO, Australia

Number of reviewed publications, incl. submitted manuscripts: 3

Number of other publications and reports: 9

Number of thesis: Master 2

Need and motivation of the project:
Platinum-group elements (PGEs) possess a range of unique physical and chemical properties that render them indispensable to modern technology and industry. As the need of PGEs is increasing, concerns have been raised about the long-term ability to supply them to meet likely future demands. The majority of current primary PGE production is derived from sulphide ores. However, there are several sulphide-poor deposits and sulphide-bearing deposits around the world in which PGMs do not occur as inclusions in base metal sulphide grains. While the beneficiation of sulphide-poor deposits has not been common so far, there is clearly a need to develop selective, economical and sustainable methods to concentrate PGMs from sulphide-poor PGE ores. The research projects PROSU and BEGPE II were a continuation for the research project Bepge ‘Advanced and sustainable beneficiation of platinum-group minerals (PGM) in sulphide-poor platinum (PGE) deposits’. In Bepge, very promising results for the beneficiation of sulphide-poor PGE ores were obtained both in bench scale laboratory tests and in minipilot test campaigns.

Main set targets:
The main targets of the research project PROSU and BEGPE II were to optimize an ecological and cost-effective beneficiation process for PGE ores with low sulphur content and scale-up the optimized process for industrial marketing. Prosu and BEGPE II consisted of several subprojects where the mineralogy of the ores and process concentrates as well as process technology, flotation conditions and the effect of grinding environment were studied. To examine the effect of grinding environment on flotation, various grinding atmospheres (air vs. carbon dioxide) and grinding media (mild steel vs. stainless steel) were used. In the pilot run various flowsheets with or without flash flotation and classification for tailings and flotation mixing mechanisms (OK vs. Outotec FloatForce) were tested. In addition, the effect of carbon dioxide and soda ash were investigated and Outotec Chena, the online electrochemical potential analyzer was used to monitor several mineral electrode potentials in the pulp.


Key results


Large differences in pulp potential observed after grinding correlated with the quality of the rougher concentrate. Anyhow the differences in recoveries, observed in rougher concentrates, levelled off during the flotation. Also the pulp potentials of various tests approached each other towards the end of flotation. The regrinding of flotation tailings followed by flotation improved especially the recoveries of platinum and palladium probably due to higher liberation degrees. The copper, gold and sulphur had the fastest kinetics. Palladium, platinum and nickel show slower kinetics. The similar kind of observations were done in the pilot run. In addition it was confirmed that Chena on-line potential analyzer shows the major changes in process conditions.  FloatForce flotation mechanisms seemed to have a little bit more mass pull into concentrates compared with OK mechanisms.



In general pre-treatments seems to have positive effect for both flotation kinetic and recovery. Highly reducing grinding environment created with CO2 was found to have positive effect on flotation behavior and yield of the low-S PGE minerals. According to modeling and simulations highest grades and recoveries for nickel, copper, gold and PGE can be achieved in the following conditions: mild iron mill for grinding, air as flotation gas and low 5-6 pH.


Commercialization measures and/or potential

Most of the processing conditions suggested in this work could be applied and tested in the industrial scale.


List of publications

Miettunen, H. & Kaukonen, R. & Corin, K. & Ojala, S. & Keiski, R.L. 2012. Effect of reducing grinding conditions on the flotation behaviour of low-S content PGE ores. Minerals Engineering. Vol. 36–38. Pp 195–203.

Ruuska, J. & Yliniemi L. 2011. Simulation model for flotation of sulphide-poor platinum group minerals (In Finnish), Automaatio XIX-seminar, Helsinki, Pp. 1-6.

Ruuska, J., Lamberg, P., Leiviskä K., 2012. Flotation model based on floatability component approach – PGE minerals case, IFAC Workshop on Automation in the Mining, Mineral and Metal Industries, Gifu, Japan, 10.-12.9.2012, Pp. 1-6.


List of other publications and reports

Korhonen, T., Taskinen, A., Mörsky, P., 2014. Process Scale up for Sulphide Poor PGE Ores Technical Report (PROSU): Final report.

Taskinen, A., Grinding environment in the processing of sulphide-poor PGE ores. Final thesis, Aalto University, OTAFOCUS 2012-2013.

Miettunen, H., Kaukonen, R., Corin, K., Ojala, S., Keiski, R., 2011. Effect of reducing grinding conditions on the flotation behaviour of low-S content PGE containing ores, Flotation ’11 Conference, Cape Town, South Africa, November 14-17, 2011, Proceedings CD. (Oral presentation; Full paper submitted to the Special Issue of Mineral Engineering)

Miettunen, H., 2011. Effect of reducing grinding conditions on the flotation behaviour of low-S content PGE containing ores. Student Flotation Day 18.11.2011, Cape Town University. (Poster)

Riihimäki, M., Ruuska, J., Ämmälä, A., Miettunen, H., Kaukonen, R., Saavalainen, P., Turpeinen, E., Keiski, R., 2012. Further development of the sustainable beneficiation process for sulfide poor PGE ores -BePGE II. SUSMP’12 International Conference on Sustainable Mineral Processing, University of Oulu, 10-13.12.2012, Oulu, Finland. (Poster)

Turpeinen, E., Riihimäki, M., Miettunen, H., Keiski, R., 2012. Microflotation of synthetized NiTe2. SUSMP’12. (Poster)

Keiski, R. 2012. Sustainable Mineral Processing Research at the University of Oulu. SUSMP’12. (Oral presentation)

Korhonen, T., Taskinen, A., Mörsky, P., Maksimainen, T., Luukkanen, S., 2013. Process Scale-up for Sulphide Poor PGE Ores. Fennoscandian Exploration and Mining conference Levi 29-31.10.2013. (Tekes Green Mining Poster Exhibition).

Korhonen, T., Taskinen, A., Mörsky, P., Maksimainen, T., Luukkanen, S., 2013. Process Scale-up for Sulphide Poor PGE Ores. Flotation ‘2013 conference, Cape Town, South Africa 18-21.11.2013. (Poster Exhibition).


Master thesis

Karvonen, S., 2011.  Comparison of flotation response of different ore types of Kevitsa (University of Oulu).

Kumar, H., 2011. Utilization of Carbon Dioxide in Beneficiation of PGE Minerals (University of Oulu).