Effective benefication of Finnish platinum deposits as the goal

Photo: Rodeo/ Ossi Lehtonen

Platinum and palladium required in industry are mainly produced from sulphide rich ores, but other types of ores production methods are being developed to cater for the increased demand. In cooperation with the University of Oulu, GTK is currently implementing a research project on the beneficiation of platinum group minerals from sulphide poor ores.

At present, platinum group metals are produced mostly from sulphide ores containing nickel and copper with platinum as the main product or an economically important by-product. The major producing countries are South Africa and Russia. South Africa generates 80% of the platinum in the world, and Russia and South Africa combined produce in practice all the palladium in the world.

The demand of the platinum group metals – platinum and palladium in particular – has clearly increased in the past decades. These metals are used in the automotive industry and chemical industry in catalysers, and also the electronics industry. The other metals of the platinum group are rhodium, iridium and ruthenium.

Due to higher demand and increased prices, platinum metal deposits are studied to a greater extent. The largest deposits after Russia and South Africa are found in Finland, Canada and Zimbabwe. In addition to the easily floatable sulphide ores, the interest towards utilising the platinum group metals in ores with low sulphide content is increasing. Such ores are plentiful all around the world but the beneficiation process is more difficult and requires more production technology development.

A little over 12% of the known global platinum metal deposits are in Finland. There are both sulphide rich ore deposits and ores with low sulphide content. Platinum metals are not currently produced in Finland but several of the deposits are being extensively studied.

Ores with low sulphide content is a challenge

– Platinum group metal ores with low sulphide content have been studied in South Africa, and they are also utilised
there but not to the same extent as sulphide ores. There is hardly any tradition of the beneficiation of ores with low sulphide content in other parts of the world, says Chief Scientist Saija Luukkanen of the GTK Mineral Processing Laboratory in Outokumpu. Luukkanen is the Project Manager for the research project of GTK and the University of Oulu.

GTK started its first preliminary studies on platinum metal ores with low sulphide content in 2004, in cooperation
with the Oulu University Department of Geosciences. The objective of the current two-year project is to promote the longterm objective of developing sustainable and economical methods for the utilisation of ores with low sulphide content. Representatives of the mining industry and equipment manufacturers are also involved in the project. The main financier of the project with a budget of over a million euro is the Finnish Funding Agency for Technology and Innovation (TEKES).

The research project has been divided into six sub-projects. The mineralogy sub-project promotes the understanding of the beneficiation process as a whole. Platinum mineralogy is studied by analysing ore samples and beneficiation products from each process stage. Samples from Finnish deposits owned by two mining companies are studied.

The second sub-project studies the pre-processing and activation of ore samples. Typically, pre-processing of ore consists of crushing, grinding and treating the ore with substances that activate the ore’s mineral surfaces.

– Clean mineral surfaces can be achieved by using ultrasound or microwaves, for example. These methods have been studied and tested with several ores globally. The research is not completed, however, and these special applications are not extensively utilised by the industry as ore pre-treatment methods, Luukkanen says.

– Studies on the activation of mineral surfaces include studies on the impact of added carbon dioxide. CO₂ causes chemical reactions in the slurry, and this has been observed to improve the enrichment results in some cases. Reports on such results with other minerals have been obtained elsewhere, and our results suggest the same. The method is apparently not as yet in use in industrial-scale enrichment, Luukkanen says.

Fine-grained materials increase energy consumption

The process chemistry sub-project studies in more detail what occurs at the chemical level, especially during flotation.

– The phenomena occurring during flotation are surface chemical and electrochemical. We are seeking to improve our understanding of these phenomena. We need to study the impact mechanisms of added CO2 in more detail, for example, Luukkanen says.

When the reaction mechanisms are better known, it will be possible to achieve favourable flotation conditions to ensure better attachment of the flotation chemicals onto the mineral surfaces. In the studies, the flotation chemicals used are different combinations of commercially available products.

The mineral processing sub-project seeks an optimal beneficiation process on a case-by-case basis, starting at the labor-atory scale. The best combinations of methods are tested using the mini-pilot system of the GTK Mineral Processing Laboratory and later on tested at pilot scale.

The flotation technology sub-project studies the transfer from laboratory-scale flotation to the pilot stage and further to full-scale industrial processes. The issues studied include optimal bubble creation with feed air and the energy required for mixing.

– If the slurry contains plenty of fine-grained materials after crushing and grinding, much more energy needs to be used when mixing the sludge during flotation. Flotation of highly fine-grained materials is also a problem, Luukkanen mentions.

– There are many similarities with the ores in South Africa and ores in Finland, but also many differences. In South Africa, they apply both new and old methods to solve problems.

The final sub-project of the research project is modelling and simulation of the entire process. When the entire process is better understood, it is also possible to better adjust the industrial process.

The research project will be concluded at the turn of the year but development may be continued in a new project.

PROMISING DISCOVERIES FROM ALL AROUND THE WORLD

For process design, Outokumpu can offer a pilot-scale test plant with the capacity of handling one tonne of material per hour. The size of a normal sample batch is 300–400 tonnes. The plant can be customised for each client by combining the different equipment alternatives available. Photo: GTK

From time to time, there is a fleet of trucks on the move at Outokumpu when several hundreds of tonnes of ore come from some part of the globe to the GTK Mineral Processing Laboratory for analysis. The GTK laboratory is one of a kind in Europe, and there are only a handful of competitors globally. The customers are offered services ranging from mineralogical analyses to process design.

Most of the samples coming to the laboratory originate in Finland and the other Nordic countries, but GTK has also analysed batches from Africa, Asia, North America and Australia.

– Large mining companies have their own R&D units, and some of them also sell their services to third parties. The companies usually specialise in a specific metal and not many clients want to buy research services from their competitors, says the GTK Mineral Processing Laboratory Manager, Kauko Ingerttilä.

– There is major global demand for our services, he continues.

Lately, the Mineral Processing Laboratory has focused on the process development of new ore deposits for clients. Most of the projects have been on nickel, gold, platinum, iron and phosphate deposits.

Geological Survey of Finland
Mineral Processing Laboratory
Tutkijankatu 1
FI-83500 Outokumpu Finland
Phone +358 20 550 11

TEXT Harriet Öster