Base Metals '13 Conference Diary

The 7th biennial Base Metals conference was held from September 2nd-3rd at the Ingwenyama Conference and Sports Resort, in White River, Mpumulanga, South Africa. Organised by the SAIMM, this conference series is intended to bring together workers in the minerals industry from the area covered by the Southern African IMM, but in reality it is very much a South African conference. Of the 130 delegates attending, only 10 in total represented the DRC, Botswana and Zambia, and there were 12 delegates representing non-African countries.

Barbara and I, as MEI media sponsors,  accounted for 50% of the UK contingent. This was our second Base Metals conference; two years ago we attended the meeting in Phalaborwa, but since then the commodities market has suffered, and the South African mining industry has been severely depressed, gold and PGMs in particular, but also base metals, the only mining commodities showing significant positive growth being coal and iron ore. So this year's event was very much different from that at Phalaborwa. Initially a 3-day conference, it was later reduced to two, and only 23 papers were presented over the two days. There was a very healthy number of exhibitors two years ago, but this year only 5 companies exhibited, in the same room as the conference presentations.

Sunday September 1st

The late afternoon registration and cocktail reception was well attended, and it  was good to see MEI Conferences sponsors Outotec well represented, with two each from Sweden and Finland and one from UK.

The Outotec team

Monday September 2nd

After the opening of the conference by SAIMM President-elect Prof. Jim Porter, the morning session got underway with a keynote address by Lee John of DRA Mineral Projects, who spoke of the challenges and design considerations in developing remote projects in Africa. His basic message was to keep things as simple as possible and this brought to mind recent discussions on the blog regarding the need to learn from the methods used in the dim and distant past. Over a century ago mineral processing plants were built on hillsides to make as much use as possible of natural gravity flow, an almost forgotten method of design now that expensive centrifugal pumps can transport slurries through the plant, and it was interesting to hear that Lee often refers to early 20th century designs, which can sometimes provide insights into building modern plants in difficult remote locations. Wherever possible simple cheap gravity concentration should be used initially, more expensive flotation and hydrometallurgy stages being added as the plant evolves. Expensive instrumentation should also be used sparingly, semi-skilled operators often providing adequate levels of manual control.

A very short coffee break followed two papers on the geology of the Zambian Copperbelt, after which there was a session on process improvements and optimisation, including a paper from Xstrata on the advantages of IsaMills in African base metal operations. Originally developed to allow the exploitation of the very fine grained ore deposits at Mt. Isa and McArthur River in Australia, there are now over 120 of these mills in operation around the world, particularly for regrinding copper and lead-zinc concentrates.

This was followed by a paper from Outotec describing their Solution Cooling Tower, designed to operate in harsh conditions, such as in gypsum removal before solvent extraction, uncontrolled gypsum precipitation having been one of the major SX challenges.

Over an excellent lunch it was good to catch up with Flotation '13 sponsors Axis House and their reagents development partners IOP Products.

Outotec were also involved with the afternoon session, with papers on the development of permanent cathode technology and environmental improvements for Peirce-Smith convertors. The afternoon session also contained a paper by Hatch on water saving options for sulphuric acid plants, and Weir Minerals described a new froth pump for improved flotation concentrate handling.

Prior to the conference dinner Barbara and I took a walk around the resort's spacious grounds and lakes, containing an abundance of bird-life.

The conference dinner rounded off a good first day.  A very relaxing informal (i.e. no speeches) event, with good food and excellent company.

Tuesday September 3rd

G. Cockburn of Nkomati Nickel JV began the day by setting the scene for tomorrow's optional mine visit by describing the challenges and successes at Nkomati.

Nickel and cobalt laterites were featured in the morning session.  Laterite ores typically contain less than 2% nickel and limonitic laterites contain large amounts of iron-rich minerals. Limonites, in contrast to magnesium-rich saprolites, are not ideally suited to pyrometallurgical smelting, and are mostly treated by hydrometallurgical routes. The ammonia-based Caron process has been used in several operations, but it is energy and reagent intensive and achieves nickel recoveries of only around 80%. High pressure acid leaching (HPAL) is also used on a commercial scale, the autoclave conditions facilitating rejection of iron as an oxide-based residue.

In view of the dominant quantity of iron in typical limonite ores (40-50%) it has long been desired to develop a commercial scale process that is capable of recovering iron as a saleable by-product, and a presentation by Anglo American Technical Solutions discussed the development of the iron-focused laterite (ARFe) process, which not only derives additional revenue from the iron contained in the laterite, but dramatically reduces the total solid residue from the process and facilitates regeneration of the primary reagents.

Mintek has been involved in extensive testwork since the early 1990s in the recovery of nickel and cobalt from leach liquors saturated in calcium, using synergistic solvent extraction systems. This has led to the development of the Nicksyn reagent.  A paper by du Preez and Kotze of Mintek showed how the versatic 10 Acid/Nicksyn synergistic system has been evaluated for the recovery of nickel and cobalt from synthetic lateritic sulphate leach liquor, the recommendation being that Nicsyn, now commercially available, is a very attractive option and should be included in the evaluation for all HPAL projects.

Cobalt is typically associated with copper and nickel ores and is often recovered as an intermediate hydroxide or carbonate product, which is sold to cobalt refineries to produce quality cobalt metal. Another paper from Mintek described a new alternative process for cobalt recovery by direct electrowinning. Although cobalt produced by direct electrowinning would not be LME grade its revenue is projected to be significantly higher than that of the mixed hydroxide product route, and this is the major economic driver of the flowheet proposed.

Changes to the process flowsheet at the Anglo American Platinum Rustenburg Base Metal Refinery circuit resulted in increased deportment of zinc to the nickel and cobalt-containing process stream, and a presentation from Rustenburg showed how ion exchange has proved to be an appropriate technology to remove these trace amounts of zinc and ensure continued consistent quality of the nickel cathode.

The processing of nickel/cobalt/zinc ores often leads to the presence of unwanted cations such as manganese and iron in solution. Many technologies exist for the removal of these impurities, a notable one over recent years being oxidative precipitation using a gas mixture of sulphur dioxide and air. Priscillia Muzadi of Mintek described how this process has been improved and the practical considerations for the implementation of the technology on an industrial scale.

The morning session concluded with a presentation by CM Solutions on the analysis of the effects of changes in operating conditions on the agitated leaching of copper. The hydrometallurgical processing of copper is a complex process due to factors such as recycles and complex chemistry. Consequently it is extremely difficult to predict with confidence the effect of changes in operating parameters on the circuit.  The aim of the work was to investigate the effects of such changes on the economic performance of the circuit.

Three papers were presented in the final afternoon session of the conference. Workers from the Tshwane University of Technology discussed atmospheric pressure leaching for the recovery of copper and nickel from low-grade sources, and University of Stellenbosch researchers the recovery of nickel and cobalt from a sulphate bioleach solution using ion-exchange with Dow M4195.

Ion exchange is an effective technology for the removal of various impurities from cobalt advance electrolytes. Although primarily used for nickel removal in the past, more recently it has been considered for the removal of copper, zinc and cadmium as well. As discussed in the final paper, by Mintek and TENOVA Bateman authors, Mintek is currently evaluating ion exchange fibres for a number of ion-exchange applications, including the removal of copper from cobalt advance electrolytes. Fibrous ion exchangers have major advantages compared to granular resins in that they have significantly higher reaction rates, and wash water volumes can be limited.

Although the number of papers presented this year has suffered due to the mining recession, the quality of the papers was generally of a very high standard, and many will be of great practical significance, particularly to hydrometallurgists, so it is likely that the Proceedings Volume will prove to be a very valuable source of reference. This can be obtained direct from the SAIMM (ISBN 978-1-920410-50-6).

This has been a very worthwhile and well organised event, and I congratulate the organisers, particularly Raymond Van der Berg and Cameron Nagel, who were always in attendance. I look forward to the next Base Metals conference, which will be held in Zambia in 2015. Hopefully by then the mining industry will have recovered from its present slump.