Patent GB-176819-A (GB)
Title: Improvements in and relating to the method of and apparatus for reduction of ores
IPC: C22B4/00
Filed: 1920-09-13
Abstract: 176,819. Alexander, A. E., (Cobb Electro Reduction Corporation of Canada). Sept. 13, 1920. Dry processes of extracting metals.-Complex ores are smelted in a bath of high-resistance materials through which a main direct current of electricity is passed, a secondary direct current automatically controlled, being passed in different directions through the fused mass as the main circuit varies. The furnace 1 is provided with a charging-element 5, a discharging-opening 6, and slag opening 7. A cathode 8, preferably in the form of a cylinder with its upper end flush with the floor, is fitted at the bottom of the furnace and is provided with a conductor 9 embedded in the masonry and with its part which pierces the outer wall arranged above the level of the molten contents of the retort. Two anodes 10, preferably of carbon, pass through the arch 4 and are adjustable relatively to the cathode. Leads 12, 11 connect the anodes and cathode to supply mains. Other electrodes 13, 14 passing through the sides of the chamber 1 are connected bv leads 15, 16 to contacts on a reversing-switch 17, the other contacts of which are connected by conductors 24, 25 through switches 27, 28 to the mains. The switch 17 is provided with a fourarm member 21 carrying bridge-pieces and mounted on a shaft 20 adapted to be rotated by a motor 26 the current to which is controlled by fluctuations in the main circuit. The reversing- switch may be entirely cut out and current passed in one direction only between the electrodes 13, 14 by operating the interconnected switches 27, 28. The switch 17 is operated by a relay 29 comprising a pair of oppositely disposed magnets 31, 31<1> having different circuits. The circuit of the magnet 31<1> is normally closed but that of the magnet 31 is completed by a switch 30 operated when the current in a shunt circuit in one of the power mains reaches a predetermined value. When the magnet 31 is excited the armature 32 of the relay is attracted to this magnet against the pull of the magnet 31<1>. The movement of the armature completes a circuit from a lead 36 to one or other contact 37, 38 connected to terminals 39, 40 on a motor control switch, Fig. 7. The terminals 39, 40 are provided with contacts 43, 44 adapted to be engaged by a spring contact 48 carried by a disc 47 which is rotated through pinion gear from the reversing switch spindle 20. The upper end of the contact 48 engages a conducting-plate 49 connected to the terminal 51, whence a lead passes to the motor 26. In operation, when the armature is pulled towards the magnet 31<1> the contact 37 is engaged, the motor circuit is completed, and the motor revolves, rotating the reversing - switch and also the disc 47. When the reversing - switch has moved through 90‹ the disc 47 has carried the contact 48 away from the contact 43 and into engagement with the contact 44 thus breaking the motor circuit. If the magnet 31 should be excited the motor circuit is completed through the contact 38 and the reversing switch operated once more. In starting the furnace for example in the smelting of tin the floor and exposed surface of the cathode are covered with a flux, such as 40 per cent of fluorspar, 40 per cent of coke, and 20 per cent of old slag all finely ground. The electrodes 10 are lowered into the flux and as the flux is fused finely divided slag is added until the chamber is threefourths full of the fused mass. Ore preferably mixed with old slag is then added and the balancing current brought into operation. Some of the impurities will be vaporized and pass out of the retort and the remaining metals will be stratified in the order of their electropositiveness round the cathode. When the metal is in condition to he drawn, the molten metal is run off into a suitable receptacle. The slag from a crust on the surface and the various impurities adhere to this crust which may be removed bv inserting a hook therein before it hardens and afterwards lifting the crust by a tackle. The balancing-current may be reversed by hand by rotating the disc carrying the terminals 39, 40 through 180‹.