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Patent
The LIXS2 heap-leaching process, US Patent Office 6,569,391 B1, was patented in March 2003; industrial scale test have been developed jointly by METEX/ INGESOL Ltda.
The proprietary sulphide copper ores heap leaching technology of METES/ INGESOL Ltda makes it possible to put copper from sulphide or mixed ores in solution, from which it can be directly recovered by electro winning; other patents of INGESOL Ltda. allow copper concentrate leaching and ROM (run-of-mine) copper ore leaching.
The process uses water, sulphuric acid and sodium nitrate; sodium nitrate increases the sulphides dissolution rates to commercial application levels.
All copper sulphides are dissolved by the LIXS2 process; all copper sulphides species dissolve at different speeds due to the intrinsic reaction rates dependence from the chemical bonds between Cu, Fe, and S.
This acid oxidizing process which allows leaching of sulfides at reasonable cost, faster than bacterial leaching (2.54 times greater than bacteria leaching based on column leaching tests with 100 kg. of ore) and in an environmentally compatible manner, as estimated from prior testing to date and from chemical reaction parameters.
The market size for sulphide ores leaching in Chile is large. Currently Chile produces only about 25% of its copper from oxide copper ores leaching, equivalent to approximately 1,200,000 tons per year.
The remainder 3,600,000 tons are produced as ores, concentrates (of which only 60 % is processed in Chile), blister copper and mainly as standard copper cathode obtained from the dissolution/electro winning of fire refined smelter copper anodes.
Highlights of the LIXS2 Heap-Leaching Project
The LIXS2 process represents a breakthrough in copper leaching technology that targets mixed ores at low capital and environmental cost. It will generate high returns from innovative thinking and application of technology:
It will produce a high value-added copper metal product, copper powder, which commands a significant price premium over LME copper metal.
It will produce copper in solution directly from crushed mixed or sulfide copper ores by heap-leaching, without prior beneficiation. This is simpler than many competing technologies.
Copper powder is obtained directly by electro winning of copper in solution, which is a more environmentally friendly process than cementation or smelting, and more efficient.
Because of its chemical nature, the new process is intrinsically more efficient and stable than existing bacterial heap-leaching processes, which are organic by nature, and more susceptible to environmental factors.
Chemical processes such as LIXS2 are also faster than bacterial leaching, and therefore ore dissolution rates are faster (4 to 8 months compared to 18 months as per industrial data), reducing working capital requirements, reducing copper inventories and risk of leach failure.
The copper cathode and copper metal powder production by EMEW electro winning equipment has been industrially proven and is commercially available.
Copper metal powder is currently in high demand for high-technology products (car brake-pads, sintered metal castings, special alloys, etc.), and this is expected to continue, especially with the massive demand being generated by China, and to a lesser extent India.
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