Integrated chlorine dioxide producing system

Abstract

Chlorine dioxide and chlorine are produced by reduction of sodium chlorate with chloride ions in an aqueous acid medium having a total acid normality of 2 to 4.8 normal. The reaction medium is maintained at its boiling point under a subatmospheric pressure to provide steam dilution of the chlorine dioxide and chlorine and anhydrous neutral sodium sulphate is deposited therefrom. Chlorine dioxide is recovered as an aqueous solution containing some dissolved chlorine while the bulk of the chlorine is recovered in gaseous form. Part of the recovered chlorine is reacted with sulphur dioxide and water, preferably in heat exchange relationship with the reaction medium to impart heat of reaction thereto, to form hydrochloric acid and sulphuric acid for feed to the reaction medium in sufficient quantity to provide no more than the quantity of sulphate ions required at the prevailing efficiency of the chlorine dioxide-producing reaction to form neutral sodium sulphate from sodium ions introduced to the reaction medium with the sodium chlorate. The remainder of the hydrogen ion and chloride ion feed requirements of the reaction medium are provided either by hydrogen chloride or hydrochloric acid, preferably formed by reaction of chlorine, including recovered chlorine, and hydrogen, or by a mixture of 2 moles of sodium chloride and one mole of sulphuric acid.