Cooling device for end-box of mercury cathode chlor-alkali cells

Abstract

The invention describes heat exchange devices for dry-type inlet end-boxes of mercury cathode chlor-alkali electrolysis cells. The devices increase the heat exchange between recycled mercury and feed brine with the purpose of reducing the temperature of mercury to a substantial extent The devices consist of a first element directed to subdivide the mercury flow into a fine and a stable dispersion of rivulets and droplets and of a second element capable of increasing the brine level to allow the prolonged contact thereof with mercury. The decrease of mercury temperature below the critical value of 90-95 ° C. determines an advantageous duration improvement of the end-box internal lining.

1 . A dry operated inlet end-box for a mercury cathode chlor-alkali cell comprising a brine feed conduit, a slit for the admission of recycled mercury and at least one internal device for W heat exchange between said brine feed and said recycled mercury.  
   
   
       2 . The end-box of  claim 1  further comprising a bafle for the formation of a mobile film of mercury of predetermined thickness.  
   
   
       3 . The end-box of  claim 1  or wherein said at least one internal device comprises a first element for the dispersion of said recycled mercury.  
   
   
       4 . The end-box of  claim 3  wherein said at least one internal device comprises a second element for raising the level of said brine feed.  
   
   
       5 . The end-box of  claim 1  wherein said thermal exchange internal device is formed by elements made of or lined with a material chemically resistant in the operating conditions of a chlor-alkali cell, optionally selected from the group comprising titanium and alloys thereof, perfluorinated plastic materials, polycyclopentadiene, polyvinylidenfluoride, and polychlorotrifluoroethylene.  
   
   
       6 . The end-box of  claim 3  wherein said first element for the dispersion of mercury consists of a horizontal cylindrical distributor provided with perforations along the lower generatrix.  
   
   
       7 . The end-box of  claim 4  wherein said first element for the dispersion of mercury consists of a horizontal tray provided with lifted edge.  
   
   
       8 . The end-box of  claim 7  wherein said lifted edge provided with at least one multiplicity of upper openings.  
   
   
       9 . The end-box of  claim 8  wherein said upper openings have a passage section of triangular shape.  
   
   
       10 . The end-box of  claim 8  wherein said edge is provided with a double multiplicity of respectively upper and lower openings, optionally having a triangular passage section.  
   
   
       11 . The end-box of method of  claim 3  wherein said first element for the dispersion of mercury is connected to a wall of said end-box and said slit is sealed.  
   
   
       12 . The end-box of method of  claim 3  wherein said first element for the dispersion of mercury is connected to a coaxial pipe internal to the brine feed conduit and said slit is sealed.  
   
   
       13 . The end-box of method of  claim 3  wherein said first element for the dispersion of mercury is connected to a pipe coupled to said slit.  
   
   
       14 . The end-box of method of  claim 4  wherein said second element for raising the brine level is a case provided with an overflow.  
   
   
       15 . The end-box of  claim 14  wherein said case is provided with a damper of the falling brine which pours out above said overflow.  
   
   
       16 . The end-box of method of  claim 4  wherein said second element for raising the level is connected to the brine feed conduit.  
   
   
       17 . The end-box of method of  claim 4  wherein said first element for the dispersion of mercury is inserted inside said second element for raising the level.  
   
   
       18 . The end-box of  claim 17  wherein said first element for the dispersion of mercury is placed below the brine level in said second element.  
   
   
       19 . The end-box of method of  claim 14  wherein the said case for raising the level is provided with one or more ducts for the discharge of mercury containing a level of mercury in the interior.  
   
   
       20 . The end-box of  claim 19  wherein said one or more ducts are made of or lined with electrically non conductive and chemically inert material.  
   
   
       21 . The end-box of  claim 1  made of metallic material provided with an eboite or rubber coating, or of non metallic material.  
   
   
       22 . The end-box of  claim 1  wherein said internal device for the heat exchange is electrically insulated from the chlor-alkali cell.  
   
   
       23 . Mercury cathode chlor-alkali electrolysis cell comprising the inlet end-box of  claim 1 .  
   
   
       24 . Process of electrolysis of brine for the production of chlorine and caustic soda or potash, comprising using a cell of  claim 23 .  
   
   
       25 . The process of  claim 24  wherein the thermal longitudinal distribution in the cell is uniform.  
   
   
       26 . (canceled)