Patent GB-1056488-A (GB)
Title: Improvements in or relating to ore extraction
IPC: C01G1/06
Filed: 1963-06-11
Abstract: A mixture of mineral salts, for example an ore, may be leached by forming a slurry of the ore in a finely divided state, saturating the slurry with gaseous hydrogen chloride, maintaining the slurry saturated with the gas for a <PICT:1056488/C1/1> time sufficient to digest the solids available to hydrochloric acid, and passing the digested slurry to separation plant for separating the different metal chlorides formed during digestion. The gaseous hydrogen chloride and a stream of slurry may be passed continuously in countercurrent through a digester so that the gas and slurry come into intimate contact with one another to saturate the slurry with the gas and so digest it.  The withdrawn slurry may be passed to a tank where it is continuously agitated for several minutes prior to being transferred to a second digester where it again flows in countercurrent to gaseous hydrogen chloride, the slurry being withdrawn from the second digester to a second tank where it is continuously agitated for several minutes prior to passing to the separation plant.  As illustrated in Fig. 3, slurry is formed at 100 and passes into the upper end of digester 101 at the lower end 102 of which gaseous hydrogen chloride is admitted.  After less than a minute the slurry passes via outlet 105 to tank 106 provided with stirrer 107 driven by electric motor 108.  After several minutes the slurry passes via outlet 110 to the upper end of second digester 111 at the lower end 112 of which gaseous hydrogen chloride is admitted. After less than a minute the slurry passes via outlet 113 to second tank 114 provided with stirrer 115. After several minutes the slurry passes via outlet 116 to separation plant, Figs. 1 and 2 (not shown). Unabsorbed gaseous hydrogen chloride passes from the top of the digesters via 103 to absorption equipment 104.  The or each digester, which preferably is an upright tower loosely packed with a material inert to the products of leaching and to gaseous hydrogen chloride, is preferably held at a temperature between 90 and 110 DEG  C. and may be artificially cooled, for example by an external water jacket. The gaseous hydrogen chloride may be admitted hot, optionally mixed with steam, to the or each digester and may have been obtained at least in part from thermal decomposition of chlorides, for example aluminium chloride, separated from the digested slurry. The slurry may be aqueous or non-aqueous. When it is non-aqueous it may include an alcohol, for example methanol, or an ether, for example di-isopropyl ether; when the slurry is aqueous only one digester may be used, the gaseous hydrogen chloride flowing upwardly through a pool of slurry in the bottom of the digester and upwardly in countercurrent to slurry passing downwardly over loosely packed inert material in the digester and the digested slurry being withdrawn from the pool after it has been in the digester for less than one hour. The slurry may be formed with ore in a raw untreated state, when the particle size is preferably not greater than 0.015 inch, and having a high titanium content.  The ore may be bauxite, when the particle size is preferably less than 0.005 inch.  Products obtained from the separation plant may include the chlorides of aluminium, iron, titanium, gallium, manganese and calcium, from which alumina and titanium, iron and gallium oxides may be formed.  If present in the starting material copper, cobalt and nickel may also be extracted. Residual material comprises a siliceous mud which may be of sufficiently high silica content to be formed into refractory bricks.