Patent ID: 7931795
Filing Date: 2011-04-26
Classification: C25B

Abstract:
1. A process for electrolytically producing chlorine gas, sodium hydroxide, and sodium hypochlorite, comprising: a. contacting solid sodium chloride and softened water in a brine module to form a saturated aqueous solution of sodium chloride (saturated brine); said brine module comprising: at least one briner tank, in which solid sodium chloride having a low total hardness content and softened water can be contacted to form a saturated aqueous solution of sodium chloride (saturated brine); and an outlet for saturated brine which is in fluid communication with the briner tank; b. feeding the saturated brine to a brine softener module to form softened brine, wherein the brine is continuously circulated through at least one chelating ion exchange resin bed located in the brine softener module; c. feeding the softened brine to a plurality of anolyte compartments in an electrolyzer module, each electrolyzer module comprising: an anolyte tank, a conductivity sensor, a chlorine head tank, an NaOH head tank, an NaOH receiver tank, and a plurality of electrolyzers, wherein: d. feeding an aqueous solution of NaOH to the catholyte compartments of the electrolyzers; e. applying a current to the electrolyzers sufficient to produce a chlorine gas/brine mixture in the anolyte compartments and a hydrogen gas/NaOH solution mixture in the catholyte compartments; f. drawing off the chlorine gas from the chlorine gas/brine mixture to form a chlorine gas stream and a depleted brine stream; g. drawing off the hydrogen gas from the hydrogen gas/NaOH solution with air to form a hydrogen/air stream and a concentrated NaOH solution stream; and, h. contacting the chlorine gas stream or portion thereof from step f with an NaOH solution in a sodium hypochlorite conversion module to directly form a 2-15% trade NaOCl solution; wherein from 1-100% of the chlorine gas generated in step f is contacted with the NaOH solution in step h to form the trade NaOCl solution; said sodium hypochlorite conversion module comprising: