Abstract: High strength, low salt solutions of alkali hypochlorite (e.g. sodium hypochlorite) can advantageously be produced in a system comprising a subsystem in which alkali hydroxide solution and chlorine are reacted to produce alkali hypochlorite and salt solids in a crystallizer, while drawing a vacuum in the crystallizer. In a system comprising a chlor-alkali plant, the alkali hydroxide solution and chlorine can be directly obtained (i.e. without concentrating) from the electrolyzer in the plant. A net energy savings in the system can be achieved and water consumption in the chlor-alkali plant can be substantially decreased by returning chlorinated condensate from the crystallizer to the recycle line in the chlor-alkali plant. Salt can be efficiently recovered by redissolving the salt solids produced in depleted brine and returning it directly to the electrolyzer. As a result, high strength, low salt hypochlorite can be produced without the need to evaporate caustic.

Abstract: High strength, low salt solutions of alkali hypochlorite (e.g. sodium hypochlorite) can advantageously be produced in a system comprising a subsystem in which alkali hydroxide solution and chlorine are reacted to produce alkali hypochlorite and salt solids in a crystallizer, while drawing a vacuum in the crystallizer. In a system comprising a chlor-alkali plant, the alkali hydroxide solution and chlorine can be directly obtained (i.e. without concentrating) from the electrolyzer in the plant. A net energy savings in the system can be achieved and water consumption in the chlor-alkali plant can be substantially decreased by returning chlorinated condensate from the crystallizer to the recycle line in the chlor-alkali plant. Salt can be efficiently recovered by redissolving the salt solids produced in depleted brine and returning it directly to the electrolyzer. As a result, high strength, low salt hypochlorite can be produced without the need to evaporate caustic.

Abstract: Fluoride ions can be removed from an aqueous stream to desirable levels (e.g. less than 1 ppm) using two precipitation reactions in series. In this method, calcium chloride and a phosphate salt are added to form a first precipitate and then a carbonate salt is added to form a second precipitate. However under certain circumstances, the conventional stoichiometries employed have been found to remove insufficient fluoride. Instead, sufficient fluoride can be removed by employing unconventional stoichiometries, specifically excessive calcium chloride or deficient carbonate salt.

Abstract: High strength, low salt solutions of alkali hypochlorite (e.g. sodium hypochlorite) can advantageously be produced in a system comprising a subsystem in which alkali hydroxide solution and chlorine are reacted to produce alkali hypochlorite and salt solids in a crystallizer, while drawing a vacuum in the crystallizer. In a system comprising a chlor-alkali plant, the alkali hydroxide solution and chlorine can be directly obtained (i.e. without concentrating) from the electrolyzer in the plant. A net energy savings in the system can be achieved and water consumption in the chlor-alkali plant can be substantially decreased by returning chlorinated condensate from the crystallizer to the recycle line in the chlor-alkali plant. Salt can be efficiently recovered by redissolving the salt solids produced in depleted brine and returning it directly to the electrolyzer. As a result, high strength, low salt hypochlorite can be produced without the need to evaporate caustic.