GB766877A - Improved method and apparatus for the continuous vacuum distillation of metals - Google Patents

Abstract

766,877. Refining metals by distillation. BROKEN HILL ASSOCIATED SMELTERS PROPRIETARY, Ltd. July 15, 1954 [July 16, 1953], No. 19783/53. Class 82(1) A metal containing a volatile constituent is refined by passing the molten metal in an attenuated condition (exposed surface is large relative to its volume) into and through an evaporating zone within an evacuated space whereby the volatile constituent is evaporated, passing a second molten metal at a lower temperature into and through the evacuated space, condensing the evaporated constituent and dissolving the condensate in the second molten metal. Preferably the path of the second metal is substantially parallel to the evaporating zone. In the form shown in Fig. 1 for separating zinc from de-silverized lead bullion, the latter is supplied to a vacuum chamber 10 at a temperature of 600-700‹C. by a pipe 14 into a relatively deep annular well 13 and passes up smalldiameter feed pipes 17 into an annular trough 16 from which it overflows on to the inner surface of a convergent spreading tube 12 provided with a flexible joint 12<SP>1</SP>. It then collects in a channel 19 from which it is discharged at a temperature of about 600‹C. by a pipe 20 maintained with a barometric leg. The evaporated zinc condenses in the solid condition on an open-ended tube 22 which is kept at a temperature of 420‹C. by an encircling cooling coil 25 until the deposit 26 is close to the tube 12 when the zinc condenses in the liquid condition, as described in Specification 711,954. Alternatively, the deposit 26 could be pre-formed. Liquid zinc falls into a pool 27 of softened lead bullion at a. temperature above 415‹C. and supplied through a passage 33 surrounding a vacuum pipe 30 which is surmounted by a water-cooled cover 31, the bullion overflowing a lip 35 to form a curtain 36. The pool 27 overflows into a channel 29 from which it is discharged by a pipe 37 also maintained with a barometric leg. In the form shown in Fig. 4, softened bullion is supplied to a vacuum chamber 40 by pipes 43, 42 leading to a well 45 which overflows into a pool 46 which overflows into a basin 49 having a discharge pipe 50 with a barometric leg, the wall 44 of the well 45 being of such height as to leave a free space in the pipe 42 for the removal of gases by a vacuum take-off pipe 47. De-silverized lead bullion is supplied by a pipe 57 and passes over a lip 59 into a recess 58 in a downwardly-concave disc 53 which is rotated by a spindle 51. The bullion then drops on to a ledge 53<SP>1</SP> and is projected outwardly over the lower surface of the disc 53 into a channel 54 full of re-zinced bullion. The channel 54 discharges into a pipe 55 connected to a pipe 56 with a barometric leg. The evaporated zinc condenses on the surface of the pool 46. According to the Provisional Specification a conical tube below the disc 53 projects into the pool 46, and the invention is not limited in its application to the refining of metals.