Patent GB-106050-A (GB)
Title: An Improved Method of and Apparatus for Recovering Zinc from Zinc-bearing Ore.
Inventor: JONES DAVID BENTON
IPC: C22B19/14
Filed: 1916-10-25
Abstract: 106,050. Jones, D. B. Oct. 25, 1916. Electrode furnaces; resistance furnaces. -In the distillation of zinc in a closed furnace for obtaining zinc or oxide, current is passed through a series of resistive zinc ore briquettes of such character as to be unchanged in form by distillation of the zinc. Such briquettes may be made. as described in Specification 104,564, [Class 82 (i), Metals, Extracting &c.], by heating and then moulding under high pressure a mixture of 50-60 per cent of zinc ore, ground and calcined, 30-40 per cent of a reducing agent such as coke, and 10-20 per cent of a binder such as hard pitch. Before use as above, they are heated to carbonize the binder, either in a separate furnace, in which they are protected by fine coke or by tightly closing the furnace, or in the electric furnace, by the heat retained from previous operations by the walls. Temperatures of 400-600‹ C, or preferably 650- 700‹ C, are suitable for this treatment. The briquettes are preferably cylindrical. As shown in Figs. 2a and 3, they may form six pairs of columns 23. Three pairs rest on three-phase graphite electrodes 25<a>, and the other three on a Y-shaped neutral electrode 25. Three graphite connecting blocks 25<1> each rest on adjacent pairs of columns, and may be weighted by additional briquettes. The bottom electrodes 25<a>, 25 are carried by a perforated tile 24 or grid which forms the top of a ccndenser B and fits in and against a centrallyapertured tile 5 at the base of the electric furnace A. The condenser, with the electrodes and briquettes, can be lowered clear of the furnace, being raised by an hydraulic cylinder. When the furnace is closed, connexion with the electrodes 25a is made by graphite bars 26 pressed in against them through the furnace walls by means of watercooled flanged boxes 38, Fig. 3, terminal plates 28 in contact therewith, and springs surrounding guides for the plates and boxes, which are insulated from the guides. Current is preferably supplied by a variable-pressure transformer, heating being gradual at first. By maintaining for some time a temperature of 950‹ C, at which no appreciable distillation occurs, a better concentration of zinc vapour is subsequently obtained. The furnace walls are double, with heat-insulating material between. A hole may be provided in the roof 4 for escape of vapour and gas during the preliminary heating; this hole is plugged during the distillation of zinc. The base 5 of the furnace is supported by double walls based on a platform 6, which rests on heat-insulating material 3<c> in a receptacle 9 supported by pillars 7. The condenser B comprises inner and outer cylindrical walls separated by powdered graphite, forming a heating-resistance between three vertical carbon strips, also situated between the walls and supplied with current by bars 27 pressed inwards by means similar to those acting on the bars 26 in the furnace. The temperature of the condenser varies from 650‹ C, near the top, to 500‹ C near the bottom. Within the condenser, and spaced from its walls, are four perforated vertical partitions 18 forming a cross in plan view. Ledges 19<a> on the partitions support loose quadrant-shaped plates 19 sloping downwards towards their inner corners, at which they are cut away to leave a passage for vapour. Exit pipes for liquid zinc and for gases are shown at 31, 32.