Patent GB-834005-A (GB)
Title: Electrolysis apparatus
IPC: C25B1/36
Filed: 1956-05-22
Abstract: 834,005. Mercury-cathode electrolytic cells. ORONZIO DE NORA IMPIANTI ELETTROCHIMICI. May 22, 1956 [May 23, 1955], No. 15821/56. Class 41. An electrolytic cell has at least one vertical metal cathode support 25, Fig. 9, separated from a parallel anode 14 by a diaphragm 17, fluid-tight walls enclosing the anode 14 and support 25, either or both the anode and cathode compartments being totally enclosed, a supply line 27 delivering a downward flow of mercury amalgam over the support 25, a line 19 through which amalgam is discharged from the cell, and an electrolyte, e.g. brine, inlet and a common outlet or separate outlets for the discharge of brine and product gases. The term " vertical " here embraces all supports between 30 and 90 degrees to the horizontal. The apparatus comprises alternate insulating anode frames 10, Fig. 9, e.g. of hard rubber, and spacers 20, Fig. 6, defining cathode compartments, assembled as a filter press between end-plates 3, 4. The anodes 14 are graphite rods, preferably packed in magnetite or graphite lumps 35, the diahragms comprise asbestos 17a supported by a chlorine-resistant plastic mesh 17b secured to the frames 10, and the cathodes 25 comprise any perforated metallic material, preferably a rolled steel wire screen, which is secured to a connector 30 and passes through a slot 27a in the amalgam supply line 27, a plastic sheath 28 ensuring correct distribution of amalgam to the cathode 25, and a cover 32 sealing the top of the cathode compartments. The frames 10 and spacers 20 have co-operating holes to provide passages 21 for fresh brine and 22 for spent brine and gas. The fresh brine enters each anode compartment through holes in the frame 10 leading to a distributer 13, Fig. 2, spent brine leaving by the diagonally opposite corner of the compartment to pass via the apertures 22 to an outlet 41. Alternatively, the fresh brine may be delivered to the cathode compartment and, after passing through the diaphragms 17, leave the anode compartment as described above. The spacers 20, Fig. 6, slope down to a central slot 23 which forms a conduit leading amalgam to the outlet 19. The discharged amalgam is circulated by a pump to re-enter the cell via the line 27, a part of the discharged amalgam being first passed through a conventional denuder for extraction of sodium. The proportions of amalgam so treated is controlled by valves to control the degree of dilution of the returned amalgam which should contain 0.002 to 0.2% sodium by weight, and preferably 0.01%. Two modifications in which the cell is not of the filter press type are described. In the first, the anodes are embedded at their lower ends in a conducting base, e.g. of lead, the cathodes, diaphragms, and amalgam supply being similar to those previously described, but no frames or spacers are employed and brine enters at the top of the cell and spent brine and amalgam leave at the bottom, a mastic covering on the base of the cell between the anodes being formed in parallel troughs to lead amalgam to the outlet. In the second modification, two rows of anodes, each enclosed in a diaphragm, are separated by a vertical perforated metal, e.g. metal, e.g. wire screen, cathode, the electrodes being supported from the top in a closed casing. The amalgam supply is similar to that described above, amalgam leaving through the base of the cell which has a brine inlet at the bottom and a brine outlet and a chlorine outlet at its top. In a third modification, Fig. 19, frames 10 and 81 are employed, diaphragms and anodes being as described originally, amalgam being delivered via ducts formed by co-operating holes 82 in the frames to cathode supports which are vertical metal pipes 84 down the outside of which amalgam flows. Brine is delivered to the anode compartments through ducts 87, leaves by ducts 88, and chlorine escapes at 89. The pipes 84 may be closely spaced whereby the amalgam forms a continuous sheet on their outer surfaces.