The Asia Miner

JUL-SEP 2019

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

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Page 12 of 59

the asia miner • volume 16 • issue 3 11 LEADING DEVELOPMENTS A new EU project explores innovaঞve technologies and concepts for recovering ultrafine parঞcles of raw materials. Criঞcal raw materials such as copper, cobalt, and rare earths are of strategic importance to the European economy. However, the ore grain size of many of these metals remaining in deposits are too small to be separated using the standard process of flotaঞon. In the FineFuture project, coordinated by Helmholtz- Zentrum Dresden-Rossendorf (HZDR), a consorঞum of 16 partners from industry and science seeks to explore fine parঞcle flotaঞon phenomena and to develop new technological soluঞons for this process. The three-year project has received over €6.2 million in funding from the EU. Europe currently accounts for just three per cent of global mine producঞon – compared to 40 per cent in the year 1900. But there are now signs of a turnaround. The reasons for this development are rising prices and the growing global demand for strategically important, technologically interesঞng metals. Deposits previously considered uneconomic to mine are now increasingly becoming the focus of the mining industry. These sought- a[er, yet low concentrated ores are finely dispersed in the rock, meaning that tremendous technological effort is required to recover them. "The issue of raw materials can only be addressed at the European level," emphasized Professor Kersঞn Eckert from the Insঞtute of Fluid Dynamics at HZDR, which is coordinaঞng the whole project. "With the consorঞum's combined experঞse, we have the chance to make substanঞal improvements in the yield and recovery rate." The FineFuture project involves cooperaঞon between partners from a total of eleven countries, with an aim to combine progressive facility design and process innovaঞons to achieve a 30 per cent higher recovery rate in the future. In addiঞon, more efficient techniques involving fewer process steps should reduce water and energy consumpঞon and minimise the discharge of chemicals to the environment. WHAT IS FLOTATION? "In the metals and minerals industry, froth flotaঞon is the most important way of recovering valuable raw materials from ores," explained Dr Marঞn Rudolph from the Helmholtz Insঞtute Freiberg for Resource Technology (HIF), which belongs to the HZDR. "However, recovery of parঞcles below 20 micrometers in size – which is less than half the thickness of a human hair – is beyond the capabiliঞes of current flotaঞon technologies." Froth flotaঞon exploits the differences in the surface properঞes of mineral parঞcles. If gas bubbles are added to a liquid with finely ground parঞcles, the bubbles adhere to parঞcles with a hydrophobic, that is water-repellent, surface. These parঞcles, with air bubbles aached, then rise to the surface and form a froth layer, which can be skimmed off. Reagents tailored to the relevant recoverable material ensure that the 'right' parঞcles find their way into the froth. Other auxiliary substances cause non-target parঞcles to sediment to the boom or stabilise the valuable froth. Factors such as the quanঞty of gas added, the bubble size, the degree of turbulence in the flow, the reagents used, and adhesion energies determine the yield. Many fundamental quesঞons have yet to be answered before mineral parঞcles in the range of 0.1 to 20 micrometers can be separated on an industrial scale in the future. Such a technology would also be of major importance for recycling or for recovering raw materials from old heaps. COMPUTER MODELLING OF FINE PARTICLES IN PULP AND FROTH Research undertaken by the nine academic project partners mainly focuses on developing a beer understanding of the mechanisms and microprocesses involved in fine parঞcle flotaঞon. Two of the nine work packages concentrate on the physico- chemical and hydrodynamic aspects of processing. These include the binding mechanisms and frothing characterisঞcs of the valuable parঞcles, and turbulent flows in the flotaঞon tank. The laer influence the collision frequency of parঞcles and bubbles. Adhesion is only possible when air bubbles come into contact with hydrophobised mineral parঞcles. No less than three groups at the HZDR are working to improve the yield of fine parঞcle flotaঞon – not only Kersঞn Eckert's team, but also colleagues from the Department of Computaঞonal Fluid Dynamics and a research group led by Marঞn Rudolph. Using model experiments, newly developed measurement methods and computer simulaঞons, they invesঞgate flow condiঞons in the flotaঞon bath, which cannot be seen from the outside, and how parঞcles, fluids and gas bubbles interact. A BENEFIT FOR THE ENVIRONMENT The partners hope that their research results will enable them to derive approaches, such as innovaঞve hydrodynamic concepts, that can be used to increase the probability of bubbles colliding with fine parঞcles. This is where the know- Froth flotaon pilot plant: Dr. Marn Rudolph (Helmholtz Instute Freiberg for Resource Technology) is a specialist in ore processing. Source ©HZDR/Robert Möckel A foam bath for ores

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