In the first presented papar, a brief history of percolation leaching and the current technology involved with successful heap leaching is given. A general orientation of nomenclature, design criteria and commercial applications of percolation leaching is provided.
A discussion of why so many heap leach operations have failed which includes a discussion on the failure to fully evaluate or scale up metallurgical testwork for full scale leaching, and a lack of methodology or design in the construction of the heap leach, is given. The fundamentals and rules of thumb in scale up of laboratory testwork results, plant design and heap leach construction are discussed. The very important interrelationship of pH control, percolation and lixivant consumption is discussed in some detail giving enlightenment as to why many heap leaches give unexplained poor recoveries.
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The second presented paper gives the thus far unpublished results of a pilot-scale heap leaching test of a Greek low-grade nickel oxide ore, aiming at verifying, at a large scale, the amenability of Greek laterites to heap leaching by the HELLAS (Heap Leaching LAteriteS) process, developed at the National Technical University of Athens for the first time worldwide and patented by some of the authors as early as in 1991. The test was conducted at the site of Aghios Ioannis mine of G.M.M.S.A. LARCO in 2006–2008 and was financed and supervised by the Institute of Geology and Mineral Exploration (I.G.M.E).
The ore sample, 800 t, was from the “Triada” deposit of LARCO, in Euboea, and contained 0.73% nickel, 0.06% cobalt, 35.6% iron and 15% silicon. The ore was ground to 18 mm and the leaching agent was 2N (100 g/L) sulphuric acid solution. The nickel and cobalt recoveries obtained at the time of termination but not completion of the test, after four leaching cycles and 114 days of irrigation, were 60 and 36%, respectively. The corresponding nickel and cobalt concentrations in the produced leach liquor were 3.4 and 0.17 g/L, respectively. The value of the ratio Fe/Ni in the leach liquor was 10/1, much lower than the value 45/1 in the ore, thus showing the selectivity of the leaching of nickel over iron in the Greek ores by the above method. The consumption of sulphuric acid was 66 kg H2SO4/kg Ni recovered. The preliminary feasibility study, that followed the test, confirmed the economic viability of the integrated HELLAS process for the low-grade nickel oxide ores of Greece.
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Υδρομεταλλουργία: το μέλλον της Μεταλλουργίας;
Το μέλλον της ΛΑΡΚΟ