It is shown that the problems of decomposition of the three phase sulfur emulsions that form dur ing hydrothermal oxidation of pyrrhotine and the choice of conditions of their stabilization represent one of the main problems of the theory and practice of the pressure oxidizing leaching (POL) of nickel-pyrrhotine concentrates (NPCs) carried out at high temperatures. The character and the degree of influence of a number of stabilizing factors (mixing intensity, consumption of commercial lignosulphonates (LSNs), amount of added gangue) on the particle size distribution of elemental sulfur during POL of NPCs, which have different contents of the main components, are studied. Mathematical statistics is used to derive regression equations and response surfaces to describe the dependence of the extraction of elemental sulfur into hard to float par ticle size classes (-10 µm, +150 µm) on the factors under study. It is found that the key factor that determines the particle size distribution of elemental sulfur is the consumption of LSN surfactants during high temper ature leaching of NPCs irrespective of the chemical-mineralogical composition. A pronounced synergetic effect of a positive influence of LSN and a rock containing addition is experimentally detected during leach ing of high sulfur NPC.

As a result of the innovative solutions found due to the joint efforts of Russian and Finnish researchers, the recovery of nonferrous and precious metals in Norilsk Nickel Harjavalta was significantly increased (%): the recovery of Ni was increased to 98.7; that of Cu, to 99.5; Pt, to 99.6; and Pd to 99.6. Simultaneously, a copper cake (one of the main commercial products) of an improved composition, namely, (%) 57-62 Cu, <3 Ni, 8-11 Fe, was produced. The arsenic content in the copper cake was decreased from 1.5-2 to 0.15-0.3%. The largest projects are as follows: stage-by stage implementation of a matte-free technology with simultaneous modification of the matte line for processing converter matte; the development of a jarosite technology of iron deposition from a nickel solution, which decreased the irreversible losses of nonferrous and precious metals with a waste iron cake as much as possible (the losses of nickel and cobalt were decreased by 11 times; those of copper, by 23 times; platinum, by 16%; palladium, by 10%; rhodium, by 9%; gold, by 12%); and the building and introduction of carbonate processing, which allowed the production of nickel cathodes to be increased. As a result of the measures taken to redistribute raw materials, the mattes of slag-cleaning furnaces, which contained 35-40% Fe, were moved to KGMK. This integration solution led to a significant synergy effect in Nornickel. One of the key factors of the economic efficiency of the matte-free technology was a decrease in the specific consumption of the main reagents (oxygen, air, sulfuric acid) and the energy resources used for the manufacture of nickel products. As a result, the transaction costs were decreased by ~3.5 mln dollars per year.

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Atmospheric purification of a nickel3cobalt solution to remove copper with a high-copper converter matte was studied. The structural and textural characteristics and the phase and chemical composition of the high-copper converter matte and of the solid residue remaining after atmospheric copper removal were examined. The mechanism of copper precipitation and leaching-out of elements belonging to the iron triad was determined, and the extents of the main chemical reactions were calculated.

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