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JULY 2014 • E&MJ; 87 www.e-mj.com P R O C E S S I N G S O LU T I O N S • Nickel and cobalt recoveries are high. • The lixiviant is regenerated and recycled. • Secondary neutralization is not needed to remove residual iron. • Solid/liquid separation properties are superior to sulphuric acid processes. • There are opportunities to recover saleable byproducts. Drawbacks? Nitric acid solutions, said Taylor, are corrosive—but less so than chloride solutions, allowing use of stan- dard 304 and 316 stainless steel ves- sels. The handling of acid vapors involves personnel safety issues, and depending on the water balance, environmental problems can arise from the release of nitrate-containing solutions. Moving Toward Commercialization Currently, two nitric-based processes are actively moving ahead: a tank-leach method developed by Direct Nickel Ltd. (DNi) with research assistance from Australia's CSIRO; and a heap-leach approach developed by GME Resources, a Perth, Australia-based nickel explo- ration company, which, through its sub- sidiary NiWest Ltd., owns a large nickel laterite deposit at Murrin Murrin in Western Australia. Full-scale testing of the DNi process began in March 2013 at a 1-ton-per-day (t/d) pilot plant at CSIRO facilities in Western Australia. During the pilot plant testing stage, Russell Debney, managing director and CEO of Direct Nickel, said the process setup and operating costs were less than half of those of existing processes, and the DNi process was more efficient in extracting the nickel from the laterite ores. It was also believed to be the first process capable of treating all types of laterite ores. Finding a way to separate the solution containing nickel, cobalt, iron and magnesium metals from the waste products was a key step in the process development. Earlier this year, Direct Nickel released the results of the 2013 pilot plant demonstration program, deeming it successful and a major milestone along the road to commercial development. In fact, Direct Nickel has partnered with Indonesia's largest nickel miner, PT Antam (Persero) Tbk to develop a com- mercial-scale DNi plant. Concurrently with the release of the pilot plant results, Direct Nickel said it had begun a feasibility study focused on building the first process plant at PT Antam's Buli operation (which provided the pilot plant feed) in Halmahera, Indonesia, adjacent to Antam's new fer- ronickel smelter, currently under construc- tion. The company said the plant would likely be capable of producing 10,000 to 20,000 mt/y of nickel in concentrate. Direct Nickel cited a number of advantages claimed by the DNi process, including: • An "elegant" process chemistry in which reagents are regenerated and recycled within the process; • An ability to treat limonite and sapro- lite ores and blends without loss in nickel recovery; • Low process intensity; i.e., no need for high temperatures or high pressure; • Ability to use off-the-shelf materials and equipment, with familiar design and scale-up methodology; • Low volume, benign tailings that can be disposed as landfill; and • Valuable byproduct recovery (MgO and hematite). Refining the Process Also earlier this year, GME Resources announced that its patent applications for acid regeneration and ore pelletization— processes that will be used in the pro- posed heap leach flow sheet for its NiWest nickel laterite project—had been granted. The announcement followed the release of results in December 2013 for a scoping study of the heap leaching and direct solvent extraction/electrowin- ning process to be used at the NiWest project. GME said the study confirmed the technical and potential economic viability for a project at NiWest that would produce 14,000 mt/y of nickel cathode and 540 mt/y of cobalt over a minimum 20-year mine life. GME Managing Director Jamie Sullivan said the unique characteristics of the NiWest ore and high quality of techni- cal work completed to date provided con- fidence in the development potential of the NiWest Project, adding, "The relative- ly simple heap-leach processing route identified in the scoping study has been considered and trialed at several other nickel laterite projects including at the adjacent Murrin Murrin nickel refinery, which has recently commercialized a heap leaching program on similar ore types." The company said the patented acid regeneration process was expected to enable reuse of a significant proportion of the acid applied in the heap leach stage. Test work indicated that up to 30% of the consumed acid could be regenerated. The pelletization process is designed to stabilize the ore and begin the leach- ing cycle prior to the pellets being stacked on the heap. GME said large-scale metallurgical test work would be conducted in 2014 to further refine these processes and, in particular, to increase the percentage of acid that can be regenerated. Tentative site layout plan for a laterite ore heap leach plant at GME Resources' NiWest property in Western Australia. (Photo courtesy of GME Resources) EMJ_pg86-87_EMJ_pg86-87 7/1/14 2:38 PM Page 87