GB711954A - Improvements relating to the refining of metals by distillation - Google Patents

Abstract

711,954. Distillingmetals. BROKEN HILL ASSOCIATED SMELTERS PROPRIETARY, Ltd. July 24, 1950 [Aug. 5, 1949], No. 18457/50. Class 82 (1) In a method of separating and recovering a relatively volatile constituent from a molten metal complex, the molten metal is passed progressively downwards in a substantially vertically extended evaporating zone within an enclosed space maintained at a low pressure and within which is a substantially vertically extended condensing zone, the latter being such that the volatile constituent is condensed first'as a solid until the temperature of the surface is such that condensation is in the liquid state the liquid volatile constituent being discharged separately from the treated molten metal. As shown, applied to the separation of zinc from lead containing it, the molten metal is introduced by a pipe 23 into an enclosed vessel 10 mounted on three levelling screws 22 resting on brickwork 21. The molten metal flows over a weir formed by a control ring 14 spaced from the upper rim of an evaporating vessel comprised by a downwardly convergent tube 13. The zinc is evaporated from the film of molten metal flowing down the tube 13 and condenses on a downwardly directed, water-cooled condenser 12 situated centrally of the evaporation zone. the zinc condensing first as a solid and then, when equilibrium conditions have been reached, as a liquid which falls on to a baffle.plate 31 and finally is discharged to a barometric column of zinc in a pipe 28. The lead, free from most of the zinc is discharged to a barometric column of lead in a pipe 26. The enclosed space is maintained at a low pressure by a vacuum pump having its suction pipe passing through the condenser, a scraper 41 being provided to remove any zinc condensing inside the pipe. In a modification, Fig. 5 (not shown), the suction of the vacuum pump is at the bottom of the vessel. The inner surface of the evaporation tube may be provided with a helical channel, Fig. 7 (not shown). In a further modification, Fig. 6 (not shown) the zinc is dissolved in softened lead bullion which requires an addition of zinc for a succeeding desilvering operation.