Patent GB-394316-A (GB)
Title: Improvements in or relating to the extraction of copper from its ores
IPC: C22B15/00
Filed: 1931-12-07
Abstract: A cyclic process for obtaining pure copper or compounds thereof consists in treating a copper ore with sulphuric acid, precipitating cuprous iodide from the copper sulphate solution so obtained by means of iodine or hydriodic acid in the presence of sulphur dioxide with coincident regeneration and formation of sulphuric acid, and regenerating iodine or hydriodic acid from the precipitate, the sulphuric acid and iodine or hydriodic acid being re-employed in the process.  Conversion of the cuprous iodide may be effected by several methods.  In examples: (1) The copper sulphate solution is treated with sulphur dioxide obtained by roasting sulphur or sulphide ores, and then passed to closed chambers or the first of a series of towers filled with quartz, wherein it is treated with iodine vapour and further sulphur dioxide.  From a deposit at the bottom, the suspension is pumped to the top of the first tower and also to a corresponding deposit at the bottom of the second tower to the top of which it is pumped, and so on.  Small quantities of iodine in the gases from the towers are absorbed by passing them through a chamber through which is byepassed copper sulphate solution saturated with sulphur dioxide.  Sulphur dioxide which is used in 10 per cent excess over that theoretically required is separated from the gases by passing them over dicalcium phosphate.  The mixture of monocalcium phosphate and calcium bisulphite formed is heated to 100 DEG  C., reforming dicalcium phosphate and liberating sulphur dioxide.  The suspension of cuprous iodide is filtered, the acid filtrate containing also ferric sulphate returned to the leaching, and the dried cakes oxidized at 600 DEG  C. with air to which superheated steam may be added.  Iodine evolved passes to the first tower, and the copper oxide <PICT:0394316/III/1> <PICT:0394316/III/2> <PICT:0394316/III/3> may be reduced to the metal.  When hydriodic acid is employed, the iodine vapour evolved by roasting the cuprous iodide is reacted in towers with sulphur dioxide for reformation of the acid.  (2) The cuprous iodide produced as in example (1) is decomposed by oxidized copper with formation of iodine and cuprous oxide.  This is effected in a furnace, Figs. 4 and 4a, which comprises an oscillatable chamber divided by a wall of magnesite bricks into two compartments A, B, communicating only at the bottom by holes T.  The furnace is inclined, and copper is melted in chamber B and oxidized by air from jets T<1>.  By oscillating the furnace, the cupric oxide is transferred to chamber A, wherein it reacts with cuprous iodide fed thereinto by screw S.  The gases evolved pass to condensers C, wherein volatilized cuprous iodide is deposited, the iodine vapours passing to the precipitation towers. Cuprous oxide withdrawn from chamber A is reduced with wood.  (3) The cuprous iodide is dissolved in, for example, ammonia or alkali-cyanide or hyposulphite solution and electrolyzed for the production of copper and iodine.  (4) The cuprous iodide is suspended in water and a metal more electronegative than copper, for example, granulated zinc, is added.  Copper is deposited and the zinc iodide, say, is roasted, iodine being liberated for re-use, with coincident formation of zinc oxide.  (5) The dried cuprous iodide is mixed with sulphur and fed through a hopper into the top of a vertical shaft furnace maintained at 450 DEG  C.  A stirring device is provided.  Copper sulphide is discharged at the bottom by a worm and the vapours are led to condensers wherein sulphur is deposited.  Iodine vapours pass on to the towers.  (6) The cuprous iodide is mixed with concentrated sulphuric acid in tanks 18, 19, 20 and reacted therewith below 300 DEG  C. in siliceous iron oil-jacketed closed vessels 1, 2, 3, Fig. 6.  Hot air or other oxidizing gas such as nitrous gases or ozonized air is supplied to each through line 21.  Iodine escaping is collected in condensers 4, 5.  Anhydrous copper sulphate formed and the sulphuric acid are pumped by compressed air from line 22 to receivers 15, 16, 17 and thence to settling tanks 9-12.  The anhydrous copper sulphate may be converted to metallic copper and sulphuric acid by adding water or 30 DEG  B<\>e sulphuric acid and heating with sulphur dioxide at 180 DEG  C. and at 160 lbs. sq. in. This reaction may be effected in the vessels 1, 2, 3, sulphur dioxide being supplied through line 23.  (7) Cuprous iodide, precipitated by hydriodic acid in the presence of sulphur dioxide, is treated with sulphuretted hydrogen forming cuprous sulphide, which may be roasted and reduced to copper, and hydriodic acid for re-use.  Sulphuretted hydrogen may be obtained by reacting iron sulphide with sulphuric acid, or by heating a mixture of sulphur and petroleum at 200 DEG C., or by the reaction of sulphur dioxide on gaseous hydrocarbons. (8) The cuprous iodide suspension at 70 DEG  C. is run into concentrated alkali (sodium) carbonate or hydroxide solution at 70 DEG  C., cuprous oxide being precipitated.  Iodine is precipitated from the alkali iodide solution by chlorine.  After removing traces of iodine by hot air, the alkali chloride solution is electrolyzed to regenerate chlorine and alkali hydroxide.  (9) The cuprous iodide is heated at 350-400 DEG  C. with alkali (sodium) hydroxides or carbonates.  Alkali iodide is recovered from the cuprous iodide by leaching and evaporating the solution to dryness.  It is then mixed with manganese dioxide and heated in an oxidizing atmosphere.  Iodine is evolved, alkali manganate being also formed.  The latter is treated for regeneration of alkali hydroxide and manganese dioxide. (10) The cuprous iodide is dissolved in ammonia solution.  Ammonium iodide solution separated from the cuprous oxide is decomposed with alkali hydroxide. Alkali iodide is decomposed with chlorine and the alkali chloride electrolyzed.  If the ore contains nickel, this may be extracted from the solution obtained after precipitation of the cuprous iodide.  Reference has been directed by the Comptroller to Specification 215,439, [Class 1 (iii), Oxides &c., Metallic].ALSO:In a process for extracting copper from its ores, the metal is obtained in the following manners: (1) Cuprous iodide is suspended in water in the presence of a metal more electronegative than copper, for example, granulated zinc.  (2) Anhydrous copper sulphate is heated in the presence of water or 30 DEG  B<\>ae sulphuric acid with sulphur dioxide at 180 DEG  C. and under a pressure of 160 lbs. per sq. in. Metallic copper and sulphuric acid are produced. The reaction may be effected in siliceous iron oil-jacketed vessels.  Reference has been directed by the Comptroller to Specification 215,439, [Class 1 (iii), Oxides &c., Metallic].