# US RE31,348 E · Hypochlorous acid process using sweep reactor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US RE31,348 E - Document ID: USRE31348E - Status: Granted - Kind: E - Application number: 06/297,386 - Filed: 1981-08-28 - Granted: 1983-08-16 - Earliest claimed: 1978-03-09 - Assignees: Olin Corporation - Inventors: John A. Wojtowicz; Andrew J. Klanica - Web page: https://patentgrep.com/patent/USRE31348E ## Abstract A process for preparing hypochlorous acid in a sweep reactor is described in which gaseous chlorine is passed rapidly across the surface of an agitated aqueous solution of [alkali metal] sodium hydroxide at a reduced temperature. The resulting gaseous product mixture of hypochlorous acid, chlorine monoxide, and unreacted chlorine is conveyed from the reactor to a suitable scrubber to produce an aqueous hypochlorous acid solution. The aqueous reaction product of the sweep reactor is a suspension of [alkali metal] sodium chloride in [alkali metal] sodium hypochlorite, which is withdrawn and filtered to separate the solid. The clarified aqueous solution of [alkali metal] sodium hypochlorite is reacted with the aqueous hypochlorous acid solution from the scrubber, chlorine and lime to form an aqueous slurry of calcium hypochlorite. This slurry may be granulated by the spray graining technique, for example, to produce strong rounded granules of calcium hypochlorite. ## Claims ### Claim 1 A process for preparing hypochlorous acid in a reactor which comprises rapidly passing gaseous chlorine in contact with the surface of an agitated solution of [an alkali metal] sodium hydroxide at a temperature below about 50.degree. C. a. whereby a gaseous phase containing unreacted chlorine, hypochlorous acid, and chlorine monoxide is formed, b. whereby a reaction product of suspended particles of [alkali metal] sodium chloride in an aqueous solution of [alkali metal] sodium hypochlorite is formed, and c. separating said gaseous phase as it forms. ### Claim 2 (depends on 1) The process of claim 1 wherein said chlorine is passed in contact with said surface at a rate sufficient to provide a residence time in said reactor ranging from about 0.01 to about 5 minutes. ### Claim 3 (depends on 1) The process of claim 1 wherein said chlorine in passed in contact with said surface at a rate sufficient to provide a residence time in said reactor ranging from about 0.1 to about 1 minute. ### Claim 4 (depends on 3) The process of claim 3 wherein the [alkali metal] sodium hydroxide concentration is in the range from about 40 to about 70 percent by weight. ### Claim 5 (depends on 4) The process of claim 4 wherein the conversion of said chlorine contacted with the surface of said [alkali metal] sodium hydroxide solution ranges from about 1 to about 75 percent per pass. ### Claim 6 (depends on 5) The process of claim 5 wherein the conversion of said chlorine contacted with the surface of said [alkali metal] sodium hydroxide solution ranges from about 1 to about 35 percent per pass. ### Claim at position 7 (depends on 6) [7. The process of claim 6 wherein said alkali metal hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof.] ### Claim at position 8 (depends on 5, 7, 9, 10, 12, 13, 15, 16) [8. The process of claim 7 wherein said alkali metal hydroxide is sodium hydroxide.] 9. The process of claim 5 wherein said temperature is in the range from about 5.degree. to about 20.degree. C. 10. The process of claim 9 wherein said vaporized hypochlorous acid and chlorine monoxide containing unreacted chlorine, after separating from said surface, is contacted with an aqueous medium to produce an aqueous solution of hypochlorous acid. The process of claim 10 wherein said unreacted chlorine is separated from said aqueous hypochlorous acid and recycled for reaction with additional [alkali metal] sodium hydroxide solution. The process of claim 9 wherein said [alkali metal] sodium hydroxide solution is reacted with sufficient chlorine to effect conversion of at least about 90 percent by weight of said [alkali metal] sodium hydroxide to form an aqueous solution of the corresponding [alkali metal] sodium hypochlorite containing suspended therein solid particles of the corresponding [alkali metal sodium chloride and separating said [alkali metal sodium chloride from said aqueous solution of [alkali metal] sodium hypochlorite. 13. The process of claim 12 wherein calcium hypochlorite is prepared by reacting said aqueous [alkali metal] sodium hypochlorite solution with said hypochlorous acid solution, lime and chlorine to produce an aqueous slurry of calcium hypochlorite, and dewatering said aqueous slurry to produce granular calcium hypochlorite particles. 14. The process of claim 13 wherein said dewatering is effected by spray drying said aqueous slurry of calcium hypochlorite. 15. The process of claim 13 wherein said dewatering is effected by spray graining said aqueous slurry of calcium hypochlorite. 16. The process of claim 15 wherein said aqueous slurry of calcium hypochlorite is adjusted to a water concentration within the range of from about 45 to about 90 percent by weight of water prior to spray graining. 17. The process of claim 16 wherein the concentration of said aqueous slurry of calcium hypochlorite is adjusted within the range of from about 50 to about 60 percent by weight of water prior to said spray graining.