Patent GB-735372-A (GB)
Title: Improvements in or relating to a new or improved electrolytic cell of the diaphragm type
IPC: C25C7/00
Filed: 1953-01-22
Abstract: 735,372. Electrolytic cells; titanium production. TITAN CO., Inc. Jan. 22, 1953 [Jan. 31, 1952], No. 1927/53. Class 41. An electrolytic cell for the production of a refractory metal such as titanium by solubilization and reduction of a halide of the metal in a fused salt bath, comprises in combination with the bath; an anode; at least two cathodes; and porous electrically non-conductive diaphragms in the bath arranged both to segregate one of the cathodes, the solubilization cathode, from the remaining cathode or cathodes and the anode from each of the cathodes, the diaphragms being arranged relative to each other and to the salt bath such that a high concentration differential of reduced metal halides is maintained in the bath between the electrolyte in contact with the cathodes. As shown in Fig. 1, an electrolic cell for the production of titanium comprises a graphite anode 26 surrounded by a diaphragm 44, a hollow solubilization nickel cathode 20 surrounded by a diaphragm 43, and a solid nickel deposition cathode 32. The diaphragms 43 and 44 are made of fuzed porous aluminium and are so arranged that the region 73 surrounding the deposition cathode is twenty-three times the volume of the region 72 surrounding the solubilization cathode, thus providing the required concentration differential, the level of the electrolyte in region 72 being maintained higher than that in the region 73 so that titanium dichloride and trichloride formed in the region 72 from vaporous titanium tetrachloride supplied through the hollow cathode 20 hydrostatically diffuses through the diaphragm 43. The cell 10 is filled with a molten halide electrolyte, is made of an alloy of nickel, chromium and iron with an internal lining 14 of silica, and is heated in a gas furnace 45. The cell is hermetically sealed by a hollow cover 11 and the space above the electrolyte is filled with an inert gas such as argon fed through a pipe 41 and leaving through a pipe 42. Cooling liquid circulates through the hollow cover by means of pipes 18 and 19. The chlorine evolved at the anode is guided by an impervious tubular gas barrier 30 to an exhaust port 31. The deposition cathode 32 is supported by a copper rod 33 which extends upwardly through a jacketed stack 12. The stack is provided adjacent its lower end with a valved air-lock 37. After metal has accumulated on the cathode, the latter is drawn up above the air-lock 37 which is then closed, the deposited metal being allowed to cool in an inert atmosphere provided in the upper part of the stack. The anode may be made hollow so that additional salts may be added to the anode chamber without removal of the cover 11. According to a modification, the cell is triangular with the electrodes disposed in the corners. Diaphragms in the form of rectangular plates supported by their vertical edges in grooves in the side walls of the cell and seated at their lower ends on the bottom of the cell cut off the apices carrying the anode and solubilization cathode from the rest of the cell. A pair of heating electrodes projecting through the side walls of the cell provide the heat in this modification.