Production of chlorine dioxide at high efficiency

Claim 1

In a method of producing chlorine dioxide from sodium chlorate, which comprises: (a) establishing in a reaction zone an aqueous reaction medium containing dissolved quantities of sodium chlorate, sodium chloride and hydrochloric acid, said aqueous reaction medium being substantially saturated with sodium chloride, (b) continuously feeding an aqueous solution of sodium chlorate to said aqueous reaction medium, (c) continuously feeding hydrochloric acid or hydrogen chloride to said aqueous reaction medium, (d) continuously maintaining said reaction medium at its boiling point at the absolute pressure thereon and continuously maintaining said reaction zone under a subatmospheric pressure sufficient to maintain said reaction medium at its boiling point, (e) continuously generating chlorine dioxide, chlorine and sodium chloride in said reaction medium, (f) continuously removing from said reaction zone a gaseous mixture of chlorine dioxide, chlorine and steam wherein the volume ratio of steam to chlorine dioxide is greater than that below which substantial decomposition of chlorine dioxide occurs, (g) continuously depositing said generated sodium chloride from said reaction medium in said reaction zone, (h) removing said deposited sodium chloride from said reaction zone, and (i) continuously maintaining the volume of liquid in said reaction zone substantially constant, the improvement which comprises: (j) continuously feeding said aqueous solution of sodium chlorate to said aqueous reaction medium in sufficient quantity to maintain a concentration of sodium chlorate in said reaction medium substantially saturating the same and to maintain said aqueous reaction medium at a mole ratio of chlorate ions to chloride ions of about 5.9:1 to about 2.1:1, (k) continuously maintaining the actual hydrogen ion concentration in said reaction medium in the range of about 0.05 to about 0.3 normal, and (l) continuously maintaining said boiling point of said reaction medium in the range of about 30° to about 85° C and continuously maintaining said subatmospheric pressure on said reaction zone in the range of about 20 to about 400 mm Hg, said improvement resulting in the production of chlorine dioxide from sodium chlorate at an efficiency equivalent to about 39 to about 50 Gram Atom Percent ClO 2 .