Method for electrolytic production of hypobromite for use as a biocide

Abstract

An electrolytic cell is provided that can include: a first electrode plate including a first surface that can include a graphite material; a second electrode plate including a second surface that can include a graphite material opposing the first surface; an electrolytic reaction zone between the first surface and the second surface; and an inlet to and an outlet from the electrolytic reaction zone. The first electrode plate and the second electrode plate can include impregnated graphite. The first electrode plate and the second electrode plate can essentially form a chamber for the electrolytic reaction. Methods are provided for using the electrolytic cells, a sodium chloride solution, and a sodium bromide solution, for on-site electrolytic production of hypobromite solution for use as a biocide in water systems.

1 . A method of electrolytic production of hypobromite, the method comprising: 
 providing an electrolytic cell, the cell comprising: 
 a first electrode plate including a first surface;  
 a second electrode plate including a second surface opposing the first surface;  
 an electrolytic reaction zone between the first surface and the opposing second surface;  
 an inlet to the electrolytic reaction zone; and  
 an outlet from the electrolytic reaction zone;  
   providing an electrolytic solution stream comprising sodium bromide, sodium chloride, and at least one of an aqueous solution, an aqueous mixture, water, or a combination thereof;    providing power to the first electrode plate and the second electrode plate; and    pumping the electrolytic solution stream along a flow path from the inlet to the outlet and through the electrolytic reaction zone, wherein the electrolytic reaction zone is a closed-cell such that all fluid flowing through the electrolytic cell flows along a flow path through the inlet, through the electrolytic reaction zone, and through the outlet.    
     
     
         2 . The method of  claim 1 , further comprising setting a flow rate of the stream to obtain a conversion efficiency of bromide to hypobromite ion of about 95% or greater.  
     
     
         3 . The method of  claim 1 , wherein the sodium bromide includes a sodium bromide solution from about 35% by weight to about 45% by weight sodium bromide, and the sodium chloride includes a sodium chloride solution comprises from about 20% by weight to about 25% by weight sodium chloride.  
     
     
         4 . The method of  claim 1 , wherein the electrolytic solution is a mixture having a mixture ratio of the sodium bromide and the sodium chloride, to water from about 1:10 to 1:30.  
     
     
         5 . The method of  claim 1 , further comprising setting a flow rate of the electrolytic solution stream to control the electrolytic cell to produce from about 0.5 grams to about 1.5 grams of hypobromite measured as chlorine for each amp hour of power provided.  
     
     
         6 . The method of  claim 1 , wherein at least one of the first and second surfaces comprises graphite.  
     
     
         7 . The method of  claim 1 , wherein the electrolytic cell further comprises an insulating spacer disposed between the first surface and the opposing second surface.  
     
     
         8 . The method of  claim 1 , wherein the insulating spacer has a thickness of less than or equal to about 0.25 inches.  
     
     
         9 . The method of  claim 1 , wherein the inlet is a hole through one of the first electrode plate and the second electrode plate, and the outlet is a hole through the other of the first electrode plate and the second electrode plate.  
     
     
         10 . The method of  claim 1 , wherein the electrolytic reaction zone includes an electrolytic zone electrode surface area, and wherein providing the power provides a current from about 0.5 amps per square inch to about 1.5 amps per square inch of electrolytic cell surface.  
     
     
         11 . The method of  claim 1 , wherein the providing power provides from about 0.5 amp hours to about 1.5 amp hours of power per square inch of electrolytic zone surface area per each molar portion of sodium bromide, sodium chloride, and water, needed, to produce from about 1.0 gram to about 1.1 grams of hypobromite measured as chlorine.  
     
     
         12 . The method of  claim 1 , wherein a polarity of the current supplied by the power is reversed to the first electrode plate and second electrode plate at a cycle of from about one cycle per 1 minute to about 1 cycle per 1440 minutes.  
     
     
         13 . The method of  claim 1 , wherein pumping the electrolytic solution stream maintains a pressure of at least about 100 PSI in the electrolytic cell.  
     
     
         14 . The apparatus of  claim 1 , wherein the electrolytic solution stream includes a sodium bromide and sodium chloride solution that includes from about 17.3% by weight to about 27.3% by weight sodium bromide, from about 7.7% by weight to about 17.7% by weight sodium chloride, and the balance being water.