GB1144866A - Continuous method and apparatus for producing magnesium metal from magnesium chloride - Google Patents

Abstract

1,144,866. Electrolysis of molten magnesium chloride. NATIONAL LEAD CO. June 2, 1967 [June 8, 1966], No.25667/67. Heading C7B. In a continuous process for electrolytically producing Mg from MgCl 2 , the MgCl 2 is melted in a melt cell 15, mixed with other molten chlorides in a charging cell 26 and fed to a series of electrolytic cells E 1 -E x from which the resultant Mg and electrolyte depleted in MgCl 2 are fed to a refining cell 31 where the Mg is separated from the electrolyte and the electrolyte then fed to the charging cell 26 where it is recharged with MgCl 2 and fed back to the electrolysis cells E 1 -E x . Chlorine gas evolved from the electrolysis cells passes through conduits C 1 -C x to a manifold 40. The electrolyte composition may consist of 5- 25% MgCl 2 , 5-55% LiCl, the balance being chloride salts of ore or more of Ca, K and Na. For example the electrolyte may be 50% LiCl, 5% NaCl, 10% KCl, 20% CaCI 2 and 15% MgCl 2 , percentages being by weight. Substantially anhydrous MgCl 2 blocks 10 are fed to the melt cell 15 as also are HClcontaining hot gases which remove surface moisture from the MgCl 2 . In the melt cell 15, oxide impurities are electrolytically decomposed at 2 volts D. C. using carbon electrodes 21, 22 to produce CO. The melt cell 15, charging cell 26 and refining cell 31 are all heated by passing A. C. therethrough and scum can be removed therefrom using a device 24. As shown in Fig. 2, an electrolytic cell E x comprises a steel tank 42 lined with brick 43. Pairs of steel cathodes 45, 46 and interposed graphite anodes 47 are supported by precast shapes 44 which rest on the main cell structure. Semiwalls 48, 49 separate the Cl 2 and Mg produced in the cell. The Cl 2 is removed through outlet ports 53 and the Mg together with some of the electrolyte is removed over a weir (57), Figs. 3 and 5 (not shown). During extended operation, the semi-walls 48, 49 break away along their lower edges. This may be compensated for by raising the level of the weir (57). The Mg and electrolyte is fed from the electrolysis cells to the refining cell 31, Fig. 1, where the Mg 37 remains on one side of a semiwall 36 whilst the electrolyte passes beneath it. A permanent flux cover 39 is maintained on the surface of the Mg 37. The electrolyte passes from the refining cell 31 to the charging cell 26 through a conduit 30. Fig. 4 (not shown) illustrates apparatus wherein a refining and charging cell are combined in a single unit (69).