Adjustable anodes for diaphragm chlor-alkali electrolyzers

Abstract

It is described a newly designed anode suitable for bipolar type diaphragm chlor-alkali electrolyzers characterised by being made of two parallel opposed titanium sheets provided with openings and a catalytic coating for chlorine evolution, and with an elastically responding expansion device fixed to each surface of the two sheets, wherein the opening of the expansion device and thereby of the sheets fixed thereto is adjusted by a mobile pivot comprising two sections of different diameter and a spring. The spring is compressed when the anodes are assembled in the electrolyzer allowing the sliding of the pivot causing the two sheets to spread out. Hence, the distance between sheets and cathode-supported diaphragms is decreased or even suppressed depending on the regulation of the device effected before assembling and the operating electric voltage of the electrolyzer results substantially reduced. During the dismantling effected in the maintenance phase the spring spreads out causing the pivot to return to the rest position with consequent contraction of the sheets, so that the extraction of the anodes may easily occur with no risk of mechanical damaging.

1 . An expandable anode for diaphragm bipolar cells comprising two opposed main surfaces secured to a support structure and separated by a hollow space housing a reversible expansion device in its interior.  
     
     
         2 . The anode of  claim 1  wherein said opposed main surfaces are provided with openings and are coated with a film of catalytic material for chlorine evolution.  
     
     
         3 . The anode of  claim 1  wherein said reversible expansion device forces said opposed main surfaces in a spread out position when the anode is assembled in the diaphragm bipolar cell and in a restrained position when the anode is disassembled.  
     
     
         4 . The anode of  claim 3  wherein the extent of said expansion is present prior to the cell assemblage.  
     
     
         5 . The anode of  claim 1  wherein said reversible expansion device comprises a first elastic component fixed to said main surfaces connected to a second mobile component capable of reversible shifting said main surfaces provoking the expansion or contraction thereof respectively during the cell assembly or disassembly.  
     
     
         6 . The anode of  claim 5  wherein said mobile component is a pivot provided with spring and stopper.  
     
     
         7 . The anode of  claim 6  wherein said pivot comprises a first major diameter section capable of bringing said first elastic component to a restrained position, a second minor diameter section connected to said major diameter section by means of a conical junction capable of bringing said first elastic component from a position of maximum expansion to a position of intermediate expansion, a third electrically insulating tip section, said position of maximum expansion and said position of intermediate expansion determined by the distance between the apex of said third tip section and said spring.  
     
     
         8 . The anode of  claim 7  wherein said third tip section comprises a chemically inert polymeric material.  
     
     
         9 . The anode of  claim 7  wherein said distance between the apex of said third tip section and said spring is adjustable.  
     
     
         10 . The anode of  claim 9  wherein said distance between the apex of said third tip section and said spring is adjusted by rotating said third tip section in a condition of disassembled cell.  
     
     
         11 . The anode of  claim 5  wherein said first elastic component and said second mobile component are made of materials comprising titanium.  
     
     
         12 . The anode of  claim 1  wherein said reversible expansion device comprises a strip secured to said support structure, provided with an elastic section and with a wedge-shaped component determining said expansion of said main surfaces fixed to said strip at the opposed extremity to that secured to said support structure.  
     
     
         13 . The anode of  claim 12  wherein said elastic section comprises a serpentine.  
     
     
         14 . The anode of  claim 12  wherein said wedge-shaped component has an acute angle apex oriented toward said strip.  
     
     
         15 . The anode of  claim 14  wherein said wedge-shaped component is electrically insulated in at lest one planar section opposed to said acute angle apex.  
     
     
         16 . The anode of  claim 12  wherein said wedge-shaped component is obtained by folding and fixing to an additional sheet said strip, and wherein the expansion of said surfaces is adjustable by means of the regulation of said acute angle.  
     
     
         17 . The anode of  claim 12  wherein said strip and said wedge-shaped component are made of materials comprising titanium.  
     
     
         18 . A bipolar diaphragm cell comprising an anode of  claim 1 .  
     
     
         19 . A chlor-alkali electrolyzer comprising at least one cell of  claim 18 .  
     
     
         20  (cancelled)