GB948287A - Improvements in or relating to electrolytic cells for the manufacture of alkali metal chlorate - Google Patents

Abstract

948,287. Electrolytically producing alkali metal chlorate. KREBS & CO. A.G. Nov. 13,1961 [Nov. 12, 1960], No. 40455/61. Heading C7B. Aqueous alkali metal chloride solution is electrolysed to produce alkali metal chlorate by passing the electrolyte between electrodes at an average velocity of at least 10 cms. per second and using a current density of at least 5 amps. per 100 sq. cms. The electrolyte leaving the electrodes is cooled and then recirculated. Fig. 1 shows a cell comprising an iron tank, anodes 14, metal or graphite perforate and imperforate cathodes 6 and 6a, an electrolyte supply 5 and cooling pipes 15. The upper part 9 of the tank has a corrosion resistant lining and is provided with a lid 11. The cathodes extend the full length of the tank and are secured, e.g. by welding, to the tank walls and are spaced from the anodes by not more than 10 mms. Cathode connecting clamps 8, Fig. 2, are provided on the tank walls. In operation, the evolution of gases at the electrodes causes the electrolyte to circulate as indicated in Fig. 1 past the cooling pipes 15. Fig. 4 shows a modification where circulation is aided by a pump 18. A sheet iron funnel 16 and a perforated plate 20 are also incorporated. The pump may circulate the electrolyte as shown or in the opposite direction. As an' alternative, the pump may be arranged above the electrodes. Fig. 7 shows an embodiment where electrolyte circulation is aided by bubbling additional gas through a pipe 22. Reference is made to an electrolyte storage tank for a group of electrolytic cells, the tank containing cooling means and the electrolyte from all the cells circulating through the tank. Sodium dichromate may be added to the electrolyte to form a membrane on the cathode surfaces which helps to suppress undesired cathodic reduction of alkali metal hypochlorite formed in the cell.