Abstract: A method for continuous manufacture of higher-strength, lower-salt, aqueous sodium hypochlorite bleach from lower-strength aqueous sodium hypochlorite bleach that has some sodium hydroxide and that is essentially free of sodium chloride (salt) crystals, aqueous sodium hydroxide solution having a concentration by weight within a range from about 45% to about 51%, chlorine in gas and/or liquid phase that may or may not include inerts, and a recycle solution. Slurry is withdrawn from the tank at a level below where the lower-strength bleach, the sodium hydroxide solution, the chlorine, and the recycle solution begin to mix with slurry already in the tank. A first portion of the slurry is withdrawn and used as the recycle solution. A second portion of the slurry is withdrawn and processed to separate substantially all salt crystals from residual liquid that is recovered as the higher-strength lower-salt, aqueous sodium hypochlorite bleach.

Abstract: A method for continuous manufacture of higher-strength, lower-salt, aqueous sodium hypochlorite bleach from lower-strength aqueous sodium hypochlorite bleach that has some sodium hydroxide and that is essentially free of sodium chloride (salt) crystals, aqueous sodium hydroxide solution having a concentration by weight within a range from about 45% to about 51%, chlorine in gas and/or liquid phase that may or may not include inerts, and a recycle solution. Slurry is withdrawn from the tank at a level below where the lower-strength bleach, the sodium hydroxide solution, the chlorine, and the recycle solution begin to mix with slurry already in the tank. A first portion of the slurry is withdrawn and used as the recycle solution. A second portion of the slurry is withdrawn and processed to separate substantially all salt crystals from residual liquid that is recovered as the higher-strength lower-salt, aqueous sodium hypochlorite bleach.

Abstract: A process and apparatus for the manufacture of high-strength, low-salt sodium hypochlorite. An aqueous solution that comprises certain weight percentages of sodium hypochlorite and sodium hydroxide and that is essentially free of sodium chloride (salt) crystals, an aqueous solution that comprises a certain weight percentage of sodium hydroxide, and chlorine in gas and/or liquid phase that may or may not include inerts are reacted in a tank. This creates a solution having a precipitation zone where salt crystals are precipitating out of solution and falling downward to form a slurry, some of which is withdrawn, then cooled, and then re-introduced into the precipitation zone. Above the precipitation zone is a crystal-free mother liquor zone consisting essentially of crystal-free mother liquor containing a weight percentage of sodium hypochlorite greater than that of than the lower strength aqueous sodium hypochlorite bleach being reacted.