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Languages : en
Pages : 13
Book Description
South African Patent : ZA857152 : Process for the Pressure Oxidation Acid Leaching of Non-ferrous Metal and Iron-containing Sulphidic Material
Author: European Patent : EP0175556 : Process for the Pressure Oxidation Leaching of Non-ferrous Metal Containing Sulphidic Material
Author: The Leaching of Sulphidic Mattes Containing Non-ferrous Metals and Iron
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This patent covers a process for leaching sulphidic mattes containing large percentages of iron together with non-ferrous metals substantially all of which are soluble in sulphuric acid, typically cobalt, copper, nickel and zinc. Fe:5% to 60%, S:15% to 40%. In acid non-oxidative leaching of such mattes the iron tends to dissolve at least as fast as the non-ferrous metals consuming large amounts of H2SO4 and causing a separation problem. If the leach is oxidative the Fe precipitates as haematite or goethite but the sulphur is oxidised to H2SO4 which then has to be neutralised prior to metals recovery. In this process the finely ground matte is leached with H2SO4 under oxygen partial pressure of 200 to 500 kPa at a temperature of 90 to 100 degrees C. The quantity of H2SO4 in the leach solution is adjusted such that a residual concentration of between 2 1/2 and 15 gpl will remain after all the soluble non-ferrous metals have been dissolved. At this stage the leach liquor will only contain 1 to 5 gpl of dissolved iron. Iron dissolves with the NFM's but continuously reprecipitates until virtually all the NFM's are dissolved and H2SO4 concentration too low to dissolve more iron and under correct conditions the iron is in the form of goethite which is filterable: Thus only a limited amount of acid is consumed and the surplus sulphur in the matte acid is converted to elemental S. The leach temperature must be kept below the mp of sulphur. The key to the invention is really the control of the amount of H2SO4 used for the leach to just more than the stochiometric amount required for the dissolution of the NFM's. The precious metals present in the leach remain undissolved.
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