GB735195A - Method and apparatus for carrying out electrochemical processes - Google Patents

Abstract

735,195. Electrolytic cells with diaphragms. DEUTSCHE GOLDUND SILBER-SCHEIDEANSTALT VORM. ROESSLER. Dec. 2, 1952 [Dec. 22, 1951; Dec. 31, 1951], No. 30590/52. Class 41. In carrying out an electrochemical process with the use of a tubular diaphragm surrounding a linear electrode extending along its axis of symmetry, the volume in cc. of the diaphragmchamber excluding the volume of the electrode within the chamber bears to the area in square cm. of the diaphragm a ratio not greater than 1 : 4, preferably from 1 : 6 to 1 : 12. The construction may be used in the production of chlorates, per chlorates, perphosphates, the electrolytic oxidation of organic compounds, or cathodic processes, such as the production of hydrosulphites or hydrazobenzene, but is particularly described in the manufacture of high concentration persulphuric acid, the anode being surrounded by the diaphragm and a current density of at least 500 amps. per litre of anolyte present in the diaphragm chamber being employed. As shown in Fig. 1, a linear anode 1 extends along the axis of a tubular diaphragm 2, the cathode 3 of lead being provided with a lead spiral cooling jacket 4. The anode liquid is supplied by a constanthead supply pipe 6 to the lower opening of the diaphragm, the liquid being carried up by the evolved anode gases. Valve 15 regulates the inflow of anolyte while an overflow 17 regulates the level of the electrolyte. Hydrogen from the cathode collects under a polyvinyl chloride or porcelain bell 8 and passes away through outlet 12 while anolyte and anode gas pass to an outlet trough 10, the anolyte passing through an outlet pipe 11 and the gas through an outlet pipe 13. The current-distributing bar 14 connected to the anode 1 is hollow and a cooling liquid flows therethrough to cool the upper end of the anode. According to a modification (Fig. 2, not shown) a number of cells as shown in Fig. 1 are connected in series the anolyte removed from the top of the first anode chamber being fed to the bottom of the next anode chamber in series by connecting supply pipes. According to a further modification (Figs. 3 and 4, not shown), a plurality of cells are provided in which the tubular diaphragms are grouped in units, the electrolyte flowing in parallel through the diaphragms of a unit, but in series through unit after unit. The electrodes may be a wire rod or a helix having a diameter small in relation to its length. A suitable insoluble anode for working the process described consists of a wire of silver, copper, or aluminium coated with a layer of tantalum and preferably also with an overlayer or winding of platinum. Such an electrode may be U-shaped, both ends being out of the electrolyte, thus avoiding the copper &c. of the core exposed at the cut surface of the wire being in contact with the electrolyte. In this form of electrode one limb of the U may be wound round the other.