GB688502A - Improvements in or relating to the generation of chlorine dioxide - Google Patents

Abstract

<PICT:0688502/III/1> In a process for continuous or intermittent generation of chlorine dioxide by the action of sulphur dioxide on an aqueous solution of an alkali metal chlorate acidified with a strong acid other than a halogen acid, the concentration of the alkali metal chlorate in the solution is maintained at or below 0.6 mols/litre, preferably 0.1-0.5 mol/litre, by continuous or intermittent addition of alkali metal chlorate and strong acid. The acid concentration should be 1-5.5 mols/litre. Aqueous sodium chlorate and aqueous sulphuric acid are continuously or intermittently introduced through pipes 11, 13 respectively into generator 10, which has a water cooling jacket to maintain the temperature at say 25-35 DEG C. Sulphur dioxide and air or other inert diluent gas are passed into generator 10 through diffuser plate 33 from pipe 30 and gas containing chlorine dioxide at a partial pressure of less than 300 mm. of mercury is withdrawn at 35. Concentric vertical tube 34 is provided above diffuser plate 33 to obtain circulation within generator 10. Liquor may be removed by 38, 39 to maintain a constant volume in generator 10 and the liquor may be either evaporated and cooled to recover sodium bisulphate, or neutralized with caustic soda or soda ash to obtain sodium sulphate, which is recovered by filtering or centrifuging. Some of the liquor may be recycled through 40. Specifications 577,054 and 649,562 are referred to.