Method for recovering performance of electrolyzer for use in production of polysulfide and method for stopping holding electrolyzer

Abstract

In an electrolyzer comprising an anode compartment provided with porous anodes, a cathode compartment, and a membrane providing a partition between the anode compartment and the cathode compartment, wherein a solution containing sulfide ions is introduced into the anode compartment, and an aqueous solution containing caustic soda is introduced into the cathode compartment, thereby producing a polysulfide containing polysulfide sulfur through electrolytic oxidation, wherein the anode compartment of the electrolyzer is cleaned with the use, of an aqueous solution containing at least either one of an inorganic acid, a chelating agent, and a scale-cleaning agent, thereby recovering performance of the electrolyzer. Further, when the contents of the anode compartment are replaced with an alkaline aqueous solution containing not more than 0.1 mass % of sulfide ions and not more than 0.1 mass % of carbonate ions upon stopping the electrolytic oxidation, thereby maintaining the performance of the electrolyzer.

1 . A method for recovering performance of an electrolyzer, the electrolyzer comprising an anode compartment provided with porous anodes, a cathode compartment, and a membrane providing a partition between the anode compartment and the cathode compartment, wherein a solution containing sulfide ions is introduced into the anode compartment, and an aqueous solution containing caustic soda is introduced into the cathode compartment, thereby producing a polysulfide containing polysulfide sulfur through electrolytic oxidation, said method comprising the step of cleaning the anode compartment of the electrolyzer with the use of an aqueous solution containing at least either one of an inorganic acid, a chelating agent, and a scale-cleaning agent. 
   
   
       2 . The method of  claim 1 , wherein the aqueous solution for use in cleaning the anode compartment contains hydrochloric acid having concentration 0.3 to 1.0 mass %. 
   
   
       3 . The method of  claim 1 , wherein the aqueous solution for use in cleaning the anode compartment contains sulfamic acid having concentration in a range of 0.2 to 1.0 mass %. 
   
   
       4 . The method of  claim 1 , wherein the aqueous solution for use in cleaning the anode compartment contains the chelating agent having concentration in a range of 0.5 to 4 mass %. 
   
   
       5 . The method of  claim 1 , wherein the aqueous solution for use in cleaning the anode compartment contains the scale-cleaning agent having concentration in a range of 0.005 to 0.1 mass %. 
   
   
       6 . The method of  claim 1 , wherein the aqueous solution for use in cleaning the anode compartment contains anticorrosive having concentration in a range of 0.05 to 3.0 mass %. 
   
   
       7 . The method of  claim 1 , wherein the contents of the anode compartment are replaced with an alkaline aqueous solution containing not more than 0.1 mass % of sulfide ions and not more than 0.1 mass % of carbonate ions upon stopping the electrolytic oxidation, subsequently the anode compartment is cleaned with the use of an aqueous solution containing at least either one of the inorganic acid, the chelating agent, and the scale-cleaning agent. 
   
   
       8 . A method for producing polysulfide, comprising the steps of introducing a solution containing sulfide ions into an anode compartment of an electrolyzer, the electrolyzer comprising the anode compartment provided with porous anodes, a cathode compartment, and a membrane providing a partition between the anode compartment and the cathode compartment, and introducing an aqueous solution containing caustic soda into the cathode compartment of the electrolyzer, thereby producing a polysulfide containing polysulfide sulfur through electrolytic oxidation, said method further comprising the step of resuming electrolysis after cleaning the anode compartment of the electrolyzer with the use of an aqueous solution containing at least either one of an inorganic acid, a chelating agent, and a scale-cleaning agent, conducted after stopping the electrolytic oxidation. 
   
   
       9 . The method of  claim 8 , wherein the contents of the anode compartment are replaced with an alkaline aqueous solution containing not more than 0.1 mass % of sulfide ions and not more than 0.1 mass % of carbonate ions upon stopping the electrolytic oxidation, thereby stopping-holding electrolysis. 
   
   
       10 . A method for stopping-holding an electrolyzer, the electrolyzer comprising an anode compartment provided with porous anodes, a cathode compartment, and a membrane providing a partition between the anode compartment and the cathode compartment, wherein a solution containing sulfide ions is introduced into the anode compartment, and an aqueous solution containing caustic soda is introduced into the cathode compartment, thereby producing a polysulfide containing polysulfide sulfur through electrolytic oxidation, wherein the contents of the anode compartment are replaced with an alkaline aqueous solution containing not more than 0.1 mass % of sulfide ions and not more than 0.1 mass % of carbonate ions upon stopping the electrolytic oxidation, thereby stopping-holding electrolysis. 
   
   
       11 . The method of  claim 10 , wherein the alkaline aqueous solution for use in replacement of the solution in the anode compartment contains caustic soda having concentration in the range of 6 to 10 mass %. 
   
   
       12 . The method of  claim 10 , wherein alkaline aqueous solution for use in replacement of the solution in the anode compartment contains an aqueous solution including caustic soda produced in the cathode compartment. 
   
   
       13 . A method for producing polysulfide, comprising the steps of introducing a solution containing sulfide ions into an anode compartment of an electrolyzer, the electrolyzer comprising the anode compartment provided with porous anodes, a cathode compartment, and a membrane providing a partition between the anode compartment and the cathode compartment, and introducing an aqueous solution containing caustic soda into the cathode compartment of the electrolyzer, thereby producing a polysulfide containing polysulfide sulfur through electrolytic oxidation, said method further comprising the step of resuming electrolysis after stopping-holding electrolytic oxidation by replacing the contents of the anode compartment with an alkaline aqueous solution containing not more than 0.1 mass % of sulfide ions, and not more than 0.1 mass % of carbonate ions upon stopping the electrolytic oxidation.