Patent GB-220720-A (GB)
Title: Improvements in or relating to leaching systems, particularly for copper
IPC: B01D11/02
Filed: 1923-05-24
Abstract: 220,720. Perkins, W. G., Taplin, T. J. and Metals Production, Ltd. May 24, 1923. Solids, treating with liquids.-In the extraction of metals such as copper by successive leaching operations with ammoniacal liquors, particularly where the ores have received a preliminary treatment to render the metal content more soluble, as described in Specifications 185,242 and 190,246, and in which the ammonia content of the liquor may be diminished progressively as the copper &c. content of the ore is reduced, so that less ammonia is retained in the fully treated material, a rich ore charge is treated with a strong liquor to remove the bulk of the copper in one operation, the liquor being for this purpose circulated from the ore to an aerating apparatus and a storage tank and back to the same charge of ore, and the liquor may return to the ore via another ore charge which is therefore in series with the first. When the bulk of the copper has thus been extracted from an ore charge so as to make a solutipn containing, say, 5 per cent of copper, it may be aerated and passed through a fresh ore charge so as to bring the content of copper up to about 6 per cent. The operation may be continuous or intermittent, that is to say, liquor from ore at one stage of exhaustion may pass successively to ore at a less stage of exhaustion and so on through the whole series, or the liquor, after passing over the more exhausted ore charges in succession, may be all collected in a storage tank in which its strength and ammonia content are adjusted and from which it is drawn off as required for repeated circulation through a rich ore charge to remove the bulk of the copper in one operation. If desired the ore may be wetted with water before leaching, to prevent temporary supersaturation of the liquor and consequent precipitation of metal compounds in the pores of the ore residue. When the liquor is distilled to recover the ammonia and precipitate the copper, the distillation mav be carried so far as to remove about 80 per cent of the ammonia, then a part of the liquor may be used for leaching as weak liquor, the remainder being further distilled to recover the rest of the ammonia. To reduce the quantity of ammonia left in the final distillation residues an alkali or alkaline earth or an alkali or alkaline earth carbonate may be added, the former being preferably used after the leaching is completed, while the carbonates may be added at any stage. The apparatus described comprises ore-treating tanks 1 - - 10 with supply tanks 110 - - 119 between them, the pipe connections for all the tanks being the same. The tank 5, for instance, receives liquor from the supply tank 114 through a pipe 32 having branches 33, 34 for supplying liquor to the top or bottom of the ore as desired. Outlet pipes 35, 36 from the bottom and top respectively lead to a centrifugal pump 37 which delivers the liquor to an aerator 39 from which the liquor passes to the supply tank 115 while the air passes to a fan 41 which delivers it to the suction side of the next aerator to conserve its ammonia content, the air from all the aerators being finally collected and passed to a wash tower. The aerator may be of the kind shown in Figs. 2 and 3. A centrifugal impeller 16 is mounted upon a shaft 15 in a casing having a square lower part 14 and a tapered part 13, the shaft being provided with a liquid seal 27, 28, 29, 30 at the top and the casing having a liquidsealed cover 25. The impeller works in a circular casing 18 having a part cut away at 20, and if desired a hole 21 having a cover 22. A projection 19 prevents rotation of the casing. Liquor is drawn in by an inlet 17 and air by a pipe 40, the aerated liquor leaving by a pipe 31. The apparatus shown in Fig. 4 comprises ore-treating tanks 51 - - 58, store tanks 59 - - 62, and further store tanks 102. 103 for liquor ready to be distilled. Each of the tanks 59 - - 62 is connected at the top with mains 73 - - 76 and at the bottom with mains 77 - - 79. and each of the store tanks 59 - - 62 is connected with mains 82. 83, 86, 87 and with mains 107, 109, 120 with the various cross-connections shown. Each ore-tank has at the bottom an outlet 63 for liquor leading to an air-lift 64 into which air is injected under pressure through a nozzle. The top of the airlift is connected by a pipe 65 to the top of the leaching-tank so that the liquor can be re-circulated through the ore if desired. Water is supplied by the main 107 and ammonia from a vessel 108 through a main 109. An aerator 98 is provided in addition to the numerous air lifts and may be of any suitable form providing for the liquor descending in a shower or percolating downwards against an ascending current of air, which mav be collected from the various airlifts.