Nickel Processing '12 Conference Diary

Processing of Nickel Ores and Concentrates '12, the 3rd in the series, was held at the Vineyard Hotel, Cape Town, from November 14-15, 2012.

Sponsored by Nalco Africa, the conference was attended by 35 delegates from eight countries. These are the smallest of MEI's conferences, but they always attract high quality audiences and papers.

Conference delegates

I hope that my brief overview will be supplemented by comments from the delegates.

Wednesday November 14th
Todays sessions focused on the processing of nickel laterites. Although future supplies of nickel depend on laterite ores, their processing is inherently energy intensive and expensive as, unlike sulphide ores, they cannot be significantly upgraded, meaning the entire ore needs to be treated in the process. Innovative technologies are being developed that are attempting to address the current processing issues, including some that are in their early stages of development.

With Anne Oxley and Nic Barcza

The conference got off to a great start with an excellent keynote lecture by Anne Oxley of Alyssum Ventures, UK and Nic Barcza (South Africa) on the integration of hydro and pyro processes in the processing of nickel laterites.

Hydrometallurgical process routes are seen to be the future for treatment of the lower grade nickel laterites ores. Hydrometallurgical projects of recent years have focused on HPAL and have been largely unsuccessful economically, with huge capital cost overruns. The simplest and least capital intensive of the possible alternatives to HPAL is atmospheric heap leaching. Development work is also underway by several companies into atmospheric tank leaching which is also a potentially viable alternative. The natural product for a leaching process is a high grade nickel intermediate either from a direct precipitation process (containing approx. 36% Ni) or via Ion Exchange (>50% Ni).

There are many existing pyrometallurgical facilities which could easily be adapted to take this nickel intermediate giving them significant potential benefits especially as raw ore grades diminish. The nickel production from these plants could also be increased and for new plants large capital and operating cost savings achieved. There are also potential environmental benefits with much less energy consumed and lower greenhouse gases emitted per tonne of nickel produced. In the future an integrated hydrometallurgical plant with attached existing smelter or a more advanced pyrometallurgical smelting process (e.g. a DC Arc Furnace) could well be the way forward for new projects.

Following the keynote were seven papers on laterite processing, from Canada, Australia, South Africa and UK. These included a paper on the direct reduction of nickel and iron from laterite ore using the Carbonyl Process, which was invented over 100 years ago. The Canadian company CVMR Corp. has developed the process of direct extraction of nickel and iron from laterite ores in the form of metal carbonyls and production of pure metals. The technology has been applied to several types of Limonite and Saprolite ores containing additional metal values such as Copper, Cobalt, PGE and REE.

Chris Pickles of Queen's University Canada presented two papers on the selective sulphidisation of laterite ores, and there were papers on leaching of laterites as well as an intesting paperfrom the University of Queensland on the recovery of nickel and cobalt from laterite leach tailings through resin-in-pulp scavenging and selective ammoniacal elution.


Thursday November 15th
Nickel sulphide processing was the main them of today's papers, starting with three presentations from South Africa on the flotation of nickel sulphides.

The use of solvent extraction (SX) in the separation of base metals continues to dominate the field of metallurgy and commercial plants based on this process account for more than 50% of base metal production. Current industrial extractants, however, are based on oxygen donors such as the LIX and Cynex reagents, and a question of selectivity has not been addressed in full, considering that hard ions have a greater affinity for these extractants.

A paper from Rhodes University, South Africa proposed the use of nitrogen donor extractants as reagents for the separation of base metals through exploiting the stability and stereochemical preferences of metal ion-extractant species formed in a solvent extraction system. They presented a rationale for using amines as extractants of base metals.

Nicole Chapman of Curtin University, Australia presented papers at Precious Metals '12 and Process Mineralogy '12 which preceded this conference, and today gave another paper showing how an understanding of ore mineralogy and elemental deportment is critical in selecting the optimal processing route for the extraction of valuable metals from ore. However, common ore characterization techniques such as XRD and QEMSCAN may be costly and time-consuming. Diagnostic leaching is a potential cheaper and simpler alternative. The nickel laterite industry does not currently routinely employ diagnostic leaching and an investigation was therefore conducted to determine a viable leach protocol for these ore types.

James Vaughan of the University of Queensland discussed how the production of a mixed nickel-cobalt hydroxide precipitate (MHP) is becoming more prevalent as laterite ores become more dominant in the industry. One recently developed method is an oxidative acid leach which selectively dissolves nickel from the MHP leaving an oxidised residue containing significant Co, Mn, and entrained Ni along with relatively small amounts of Al, Ca, Cu, Cr, Fe, Mg, Zn. This residue has been leached under controlled reducing conditions for the optimum extraction of Ni and Co.

Farewell drinks in the Vineyard gardens

Over the two days, 17 papers were presented, and all of these are available on CD from MEI.