Electrolytic cells and their use

Abstract

The present invention provides an electrolytic cell suitable for electrolysing certain inorganic compounds of alkali and alkaline earth (Group 1 and Group 2) metals in their molten state. The cell (100) comprises a vessel (102) for containing a molten electrolyte, an anode (10) and a cathode (70) both inside the vessel (102), and a source (20) of a magnetic field having a gradient with a positive component in a direction (– x) from the anode (10) to the cathode (70), such that the strength of the magnetic field increases from the anode (10) to the cathode (70). The rest of the electrolytic cell (100), apart from the source of the magnetic field, including at least both the vessel (102) and the anode (10), consists of material having a magnetic susceptibility with an absolute value of less than 10-2. Thus the rest of the electrolytic cell, which is made of diamagnetic and / or paramagnetic material(s), does not affect the magnetic field between the anode (10) and the cathode (70) to any appreciable extent in comparison to the same magnetic field in free space. The source of the magnetic field between the anode (10) and the cathode (70) may either be a permanent magnet (20) located outside the vessel (102) adjacent to the cathode (70), or it may be provided by permanently magnetizing the cathode (70) itself. In the latter case, the cathode comprises an electrically conducting "hard" ferromagnetic material with a high Curie temperature. In the former case, the cathode instead consists of an electrically conducting material also having a magnetic susceptibility with an absolute value of less than 10-2, so as not to affect the magnetic field from the permanent magnet (20) located outside the vessel (102). In either case, if such a cell (100) is used to electrolyse a halide of an alkali metal, a halide of an alkaline earth metal except beryllium or a hydroxide of an alkali metal in their molten state, the magnetic field between the anode (10) and the cathode (70) inhibits a back-reaction between the electrolysis products formed at the anode (10) and cathode (70), thereby improving the energy efficiency of the cell. A plurality of such cells (100) may also be arranged with just one permanent magnet (20) as the source of the magnetic field between the anode (10) and cathode (70) inside the respective vessels (102) of two adjacent electrolytic cells (100), thereby halving the total number of magnetized components which are used. [Fig. 4A]

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