GB984378A - Improvements in or relating to sodium hypochlorite production - Google Patents

Abstract

<PICT:0984378/C1/1> High strength sodium hypochlorite liquor containing more than 10% by weight of chlorine, a sodium chlorate concentration of less than 0.1% by weight and a free caustic content of not less than 0.1%, and preferably between 0.2 and 0.8%, by weight is continuously produced by the continuous absorption in an aqueous caustic soda solution of gaseous chlorine at the rate of between 0.01 and 0.5, and preferably between 0.05 and 0.2 pounds of chlorine per cubic foot of solution per minute at a temperature above 22 DEG C. and preferably between 25 DEG and 30 DEG C. The chlorine is supplied as a gaseous mixture containing between 25% and 99.9% by volume of molecular chlorine with inert diluent gas or gases, suitable mixtures being an air and chlorine mixture with molecular chlorine content between 50% and 75% by volume, compressed cell gas with molecular chlorine content of about 97% by volume resulting from the electrolysis of brine, and the uncondensed residue from the condensation of chlorine gas produced in electrolytic cells. In Fig. 3, a reactor 1 is fed with chlorine gas mixture through line 2 and sparge assembly 3 and with caustic liquor through line 4. An emergency overflow line 5 connects the reactor with an empty vessel 6. Residual inert gases are vented through line 7. A detector 8 automatically records the redex potential of the mixture and controls the feed rate of either chlorine or caustic liquor by operation of either valve 9 or valve 10, the feed rate of the other component being controlled manually. Hypochlorite liquor is removed through line 11, passed to a cooler 12 and recirculated to the reactor for cooling purposes after a minor portion has been bled off via line 13 to storage, the rate of withdrawal being controlled automatically to maintain a constant level in vessel 1.