GB1400053A - Diaphragm cells for electrolysis - Google Patents

Abstract

1400053 Diaphragm cells for electrolysis ORONZIO DE NORA IMPIANTI ELETTROCHIMICI SpA 18 Sept 1972 [22 Sept 1971 43202/72 Heading C7B An electrolysis cell comprises substantially horizontal cell units stacked one on top of the other and in bi-polar connection with each other. As shown in Fig. 1, an electrolytic cell, e.g. for electrolysis of brine is built up from frames A 1 - A 5 . Each frame (except for the top one) encloses the cathode compartment (comprising a cathode screen D 1 -D 4 and steel bottom plate C 1 -C 3 ) of one cell unit and the anode compartment (comprising an anode I) of the cell unit next below. Each anode is substantially planar, has voids therethrough (e.g. 30-60 % voids), is of valve metal (such as Ti, Ta, Zr, Mo, Nb or W) and has an electrically conductive electrocatalytic coating containing a platinum group metal or a platinum group metal oxide, e.g. one or more oxides of platinum group metals together with other protective oxides, such as oxides of Ti. Anode supports H may be Ti clad Cu. The cathode screens are covered with diaphragms (not shown) of asbestos fibre, paper or cloth. Details of the connection between the cathode of one cell unit and the anode of the next are illustrated in Figs. 1a and 1b (not shown). Frames A 1 -A 5 are of steel but the anode boxes have protective linings G of Ti, Ta, hard rubber or plastics material. There are insulating gaskets F 3 between frames. Brine is supplied through lines J, J 2 , and chlorine is removed at K, K 1 . Details of removal of H 2 and NaOH are illustrated in Figs. 3 and 4 (not shown). Fig. 9 shows a modification where frames 3, which enclose the cathode compartments are of steel and frames 4, which enclose the anode compartments, are of glass fibre reinforced polyester resin. Steel cathode screens 3a are covered by diaphragms 10 and are supported by steel ribs 3c on steel bottom plates 3d. The plates 3d are in contact with Ti or Ta back plates 6 from which anodes 5 are supported. Brine is supplied to the cell units via line 7 and balconies 8. See Fig. 9a (not shown) for details of brine supply and removal of Cl 2 , H 2 and NaOH. In operation pressure is applied to drive anolyte through the diaphragms. This is obtained either by throttling the discharge of Cl 2 or by sucking out the H 2 . Different ways of mounting anodes are illustrated in Figs. 10 and 15 (not shown). Anodes of mesh and of parallel bars are illustrated respectively in Figs 19 and 20 (not shown). The cell stacks are sloped 1 degree or 2 degrees from the horizontal to aid drainage. Fig. 10 (not shown) shows suction nozzles 3b which are used to facilitate deposition of diaphragm material and then closed by caps 3g.