Method and device for producing an alkali metal hypochlorite solution

Abstract

The invention provides a method and a device for the production of an alkali metal hypochlorite solution, in particular a sodium hypochlorite solution, having at least one non-divided electrolytic cell ( 12 ), means ( 20, 22, 24, 26 ) for supplying a brine solution into the electrolytic cell ( 12 ) at a defined volumetric flow rate and a defined salt concentration, and having an a.c. voltage source ( 18 ) for the production of current across the electrolytic cell ( 12 ). The current intensity is adjusted to a fixed value so that the concentration of chlorate produced during electrolysis is limited to a maximum of 1.5 g/l, preferably to 0.6 g/l.

1 . A method of producing an alkali metal hypochlorite solution, wherein a brine is supplied into a non-divided electrolytic cell at a preset volumetric flow rate and a specific salt concentration and wherein said electrolytic cell is operated at a current intensity that is preset to a fixed value so that a concentration of chlorate produced during electrolysis is limited to a maximum of 1.5 g/l.  
   
   
       2 . The method as defined in  claim 1 , wherein said current intensity is preset to between 2 and 6 amperes.  
   
   
       3 . The method as defined in  claim 1 , wherein a constant salt concentration of said brine is obtained by mixing a saturated brine with water.  
   
   
       4 . The method as defined in  claim 1 , wherein a brine with a given salt concentration is used as brine solution, that is supplied into the electrolytic cell at a constant feed rate.  
   
   
       5 . The method as defined in  claim 1 , wherein a salt concentration of said brine supplied into the electrolytic cell is preset to a value of between 2 and 10 g/l.  
   
   
       6 . The method as defined in  claim 1 , wherein said brine is supplied into said electrolytic cell at a constant volumetric flow rate V that is determined by the formula V=w×A, depending on the effective electrode area A (in m 2 ), where V is the flow velocity, for which a value is selected between 4×10 −5  m/s and 12×10 −5  m/s.  
   
   
       7 . A device for producing an alkali metal hypochlorite solution, comprising at least one non-divided electrolytic cell, means for supplying a brine into said electrolytic cell at a defined volumetric flow rate and a defined salt concentration, and comprising a DC voltage source for the production of current across said electrolytic cell, said DC voltage source operating said electrolytic cell at a preset current intensity so that a concentration of chlorate produced during electrolysis is limited to a maximum of 1.5 g/l.  
   
   
       8 . The device as defined in  claim 7 , wherein said current intensity is preset to between 2 and 6 amperes.  
   
   
       9 . The device as defined in  claim 8 , wherein said DC voltage source is configured as a constant-current source.  
   
   
       10 . The device as defined in  claim 7 , wherein said means for supplying brine comprises a brine tank with saturated brine solution and a water tank with water, each of which are coupled with said electrolytic cell via a metering pump.  
   
   
       11 . The device as defined in  claim 7 , wherein said means for supplying brine comprise a brine tank with brine solution which is coupled with said electrolytic cell via a metering pump.  
   
   
       12 . The device as defined in  claim 7 , wherein a brine solution is supplied into said electrolytic cell at a constant salt concentration which is preset to a value of between 2 and 10 g/l.  
   
   
       13 . The device as defined in  claim 7 , wherein said means for supplying brine into said electrolytic cell is preset to deliver a constant volumetric flow rate V that is determined by the formula V=w×A, depending on an effective electrode area A (in m 2 ), where V is the flow velocity, for which a value is selected between 4×10 −5  m/s and 12×10 −5  m/s.  
   
   
       14 . The device as defined in  claim 7 , wherein said electrolytic cell comprises electrodes that are made from a material selected from the group formed by iron, mercury, stainless steel, titanium and platinum.  
   
   
       15 . The device as defined in  claim 14 , wherein the said electrolytic cell comprises electrodes that consist of uncoated titanium.  
   
   
       16 . A device for producing an alkali metal hypochlorite solution, comprising at least one non-divided electrolytic cell, means for supplying a brine into said electrolytic cell at a preset volumetric flow rate and a specific salt concentration, and comprising a DC voltage source for the production of current across the electrolytic cell which is preset to deliver a constant current intensity between 2 and 6 amperes so that the concentration of chlorate produced during electrolysis is limited to a maximum of 1.5 g/l, and wherein said means for supplying brine into said electrolytic cell is preset to deliver a constant salt concentration between 2 and 10 g/l.  
   
   
       17 . The device as defined in  claim 15 , wherein said brine is supplied into the electrolytic cell at a constant volumetric flow rate V that is determined by the formula V=w×A, depending on an effective electrode area A (in m 2 ), where V is the flow velocity, for which a value is selected between 4×10 −5  m/s and 12×10 −5  m/s.  
   
   
       18 . The device as defined in  claim 16 , wherein said current intensity of said electrolytic cell is set to a fixed value so that said concentration of chlorate produced during electrolysis is limited to a maximum of 0.6 g/l.  
   
   
       19 . A method of producing an alkali metal hypochlorite solution, wherein a brine is supplied into a non-divided electrolytic cell at a specific volumetric flow rate and a specific salt concentration and wherein said non-divided electrolytic cell is operated at a current intensity that is set to a fixed value between 2 and 6 amperes so that the concentration of chlorate produced during electrolysis is limited to a maximum of 1.5 g/l, and wherein said brine is supplied into said electrolytic cell with a constant salt concentration which is preset to a value of between 2 and 10 g/l.  
   
   
       20 . The method of  claim 19 , wherein said electrolytic cell is operated at a current intensity that is set to a fixed value between 2 and 6 amperes so that the concentration of chlorate produced during electrolysis is limited to a maximum of 0.6 g/l.