GB1013004A - Improvements in or relating to the production of alkali metals - Google Patents

Abstract

<PICT:1013004/C6-C7/1> An alkali metal vapour such as of Na or K is produced by electrolysing a fused alkali metal salt, e.g. NaCl or KCl, in the presence of a molten lead cathode which both flow through a horizontal electrolytic chamber, the fused salt on top of the molten lead, below the anode or anodes of an electrolytic cell, to form a molten alkali metal-lead alloy generally containing 10-50% of alkali metal, withdrawing the molten alloy from the electrolytic chamber and passing it into a vaporizer, e.g. where it is either heated or subjected to a partial vacuum, to evaporate the alkali metal from the alloy. As shown, an elongated electrolytic cell body 12 contains the molten lead cathode 16 supplied through conduit 80 and fused salt supplied through conduit 82 with anodes 50 supported by stems 52 in the electrolytic chamber 17 from a graphite cover 30; interior channels are provided in the anodes and cover e.g. for withdrawing chlorine. The cell body 12 may be heated by means of molten lead circulating through longitudinal conduits 20 communicating (means not shown) with molten lead 46 in the circumferential channel 34 which is fitted with a corresponding flange 42 for hydraulically sealing the chamber 17. The cover is electrically insulated from the cell body by an insulating sheet 61, the interior of the chamber 17 being insulated by refractory lining 60. The end compartment 89 of the chamber contains a cylindrical sleeve 94 having apertures 95 through which the alloy formed is discharged to pass through the nose 96 of the sleeve 94 to a vaporizer 120 preferably fitted with a cyclone separator 121. After a proportion of the alkali metal has vaporized away through conduit 122 from the cathode stream in the vaporizer, the remaining alloy is returned via a fuser 130 back to the cell. For producing potassium vapour, CaCl2 may be added to KCl to lower the melting-point of the electrolyte e.g. to 720 DEG C., so that the alloy need be heated to only 760 DEG C. in the vaporizer. Specifications 986,223, 1,007,778 and 1,011,819 are referred to.