NICKEL PROCESSING (UNITED STATES PATENT 5211745)We claim: 1. A method of processing intermediate nickel bearing products, said method comprising subjecting intermediate nickel bearing products selected from the group consisting of nickel sulphide concentrate and nickel iron oxide calcine to an acid leach in order to dissolve substantially all acid soluble magnesium bearing minerals contained therein to provide an upgraded nickel bearing residue and a leach solution. 2. A method according to claim 1 wherein the acid leach utilises sulphuric acid, hydrochloric acid or sulphurous acid. 3. A method according to claim 1 wherein the leach solution contains at least minor levels of dissolved nickel and valuable base metals, the method including the additional step of processing the leach solution to recover substantially all of the dissolved nickel and valuable base metals. 4. A method according to claim 3 wherein the step of processing the leach solution comprises oxidation of contained iron together with selective precipitation of the valuable base metals via pH adjustment with lime or other suitable bases to raise the pH to the region of 5 to 6 to at least precipitate the dissolved iron. 5. A method according to claim 1 wherein the dissolution of valuable base metals and minor levels of nickel during the acid leach are minimised by the use of comparatively lower acid strengths and/or minimum excess acid conditions. 6. A method according to claim 1 wherein the intermediate nickel bearing products are nickel sulphide concentrates and wherein the method subjects the nickel sulphide concentrates to an acid leach, the upgraded nickel concentrate residue providing a concentrate having a higher nickel concentration and a lower magnesia concentration than the initial concentrate. 7. A method according to claim 1 wherein the intermediate nickel bearing products are nickel iron oxide calcine and wherein the method subjects nickel iron oxide calcine to an acid leach, the upgraded calcine residue providing a calcine having a higher nickel concentration and a lower MgO/SiO2 concentration than the feed nickel iron oxide calcine. 8. A method according to claim 1 wherein the intermediate nickel bearing products are from nickel ore bodies from dunite rock types which have been subjected to hydrothermal carbonate alteration. 9. A method according to claim 1 wherein the acid of the acid leach is sulphuric acid having a concentration in the range of 2.5 to 30% by weight. 10. A method according to claim 1 wherein the temperature of the acid leach is from about ambient temperature to a temperature below boiling, at ambient pressure. 11. A method according to claim 10 wherein the temperature of the acid leach is about 75 deg C. 12. A method of processing nickel sulphide concentrates, said method comprising extracting rock from a nickel or body, subjecting the extracted rock to normal beneficiation processes, said beneficiation processes including crushing, grinding, flotation and thickening, to produce a nickel sulphide flotation concentrate, and subjecting the nickel sulphide flotation concentrate to an acid leach using sulphuric acid in order to dissolve substantially all acid soluble magnesium bearing minerals contained therein to provide an upgraded nickel concentrate residue and a leach solution. www.freepatentsonline.com/5211745.html
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