Production of chlorine dioxide

Claim 2

The process of claim 1 wherein said sulphate ion-containing acidic material in said first reaction medium is sulphuric acid.

Claim 3

A continuous process for the production of chlorine dioxide which comprises continuously feeding sodium chlorate and sodium chloride to a first reaction vessel containing a first aqueous reaction medium having an acidity from 6 to 12 N and comprising sodium chlorate, sodium chloride and sulphuric acid, continuously feeding sulphuric acid to said first reaction vessel, continuously generating chlorine dioxide and chlorine from said first reaction medium, continuously evaporting sufficient water from said first reaction medium to precipitate continuously sodium acid sulphate from said first reaction medium in said first vessel, continuously recovering from said first vessel a gaseous mixture comprising chlorine dioxide, chlorine and evaporated water, continuously recovering said precipitated sodium acid sulphate from said first vessel, feeding at least part of said recovered sodium acid sulphate to a second reaction vessel, said second reaction vessel containing a second aqueous reaction medium comprising sodium chlorate and sodium chloride, said second reaction medium having an acidity of from 2 to 4.8 N, at least a major proportion of said latter acidity being provided by said fed sodium acid sulphate, continuously feeding sodium chlorate and sodium chloride to said second vessel, continuously generating chlorine dioxide and chlorine from said second reaction medium, continuously evaporating sufficient water from said second reaction medium to precipitate continuously anhydrous sodium sulphate from said second reaction medium in said second vessel, continuously removing from said second vessel a gaseous mixture comprising chlorine dioxide, chlorine and evaporated water, and continuously recovering said precipitated anhydrous sodium sulphate from said second vessel.

Claim 4

The process of claim 4 wherein said first reaction medium and said second reaction medium are maintained at a boiling temperature and said first and second vessels are maintained under reduced pressure.

Claim 5

The process of claim 4 wherein an aqueous solution containing sodium chlorate and sodium chloride is fed to said second reaction vessel.

Claim 6

The process of claim 4 wherein an aqueous solution of sodium chlorate and an aqueous solution of sodium chloride are fed separately to said first vessel.

Claim 7

The process of claim 4 wherein an aqueous solution of sodium chlorate and an aqueous solution of sodium chloride are fed separately to said second vessel.

Claim 8

The process of claim 4 wherein dry sodium chlorate and dry sodium chloride are fed to said first reaction vessel.

Claim 9

A process for the production of chlorine dioxide which comprises generating chlorine dioxide and chlorine from a first aqueous reaction medium contained in a first reaction zone, said first aqueous reaction medium comprising sodium chlorate, a chloride selected from sodium chloride, hydrogen chloride and mixtures thereof, and a sulphate ion-containing acidic material, evaporating sufficient water from said first reaction medium and providing an acidity in said first reaction medium to precipitate a sodium acid sulphate from said first reaction zone, recovering said sodium acid sulphate from said first reaction zone, forming a second aqueous reaction medium having an acidity less than 4.8 N in a second reaction zone by feeding said recovered sodium acid sulphate to an aqueous solution containing sodium chlorate and a chloride selected from sodium chloride, hydrogen chloride and mixtures thereof, generating chlorine dioxide and chlorine from said second reaction medium in said second zone, evaporating sufficient water from said second reaction medium to precipitate anhydrous sodium sulphate in said second zone and recovering chlorine dioxide and chlorine generated in said first and second reaction zones.