US 4,393,036 AGranted

Production of mixed sulfuric and hydrochloric acid feed and chlorine dioxide generation therewith

AssigneeERCO Industries Limited

InventorMaurice C. J. Fredette

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Abstract

A mixture of hydrochloric acid and sulphuric acid for use as a feed to a chlorine dioxide generator to provide reactant chemicals therefor is formed by the reaction of chlorine, sulphur dioxide and water. The reaction is effected in the presence of excess chlorine to avoid the presence of dissolved sulphur dioxide in the acid mixture. The proportion of the excess of the chlorine also can be used to control the strength of the acid mixture which can be made without dissolved sulphur dioxide.

Claims9

Dependent claims

A process for the production of chlorine dioxide, which comprises:

reacting sodium chlorate with chloride ions and hydrogen ions in an aqueous acid reaction medium having a total acid normality of about 2 to about 4.8 normal to form chlorine dioxide and chlorine, said chloride ions being provided by hydrochloric acid alone or by hydrochloric acid and sodium chloride and said hydrogen ions being provided by sulphuric acid and said hydrochloric acid,
maintaining said reaction medium at its boiling point at a temperature below that above which substantial decomposition of chlorine dioxide occurs while applying a subatmospheric pressure to a first reaction zone containing said reaction medium to form steam in a volume ratio of steam to chlorine dioxide of about 4:1 to about 10:1,
depositing anhydrous neutral sodium sulphate from the reaction medium and removing the same from said first reaction zone,
removing a gaseous mixture of chlorine dioxide, chlorine and steam from said first reaction zone and forming an aqueous solution of said chlorine dioxide therefrom, said aqueous solution of chlorine dioxide also containing part of said chlorine,
forwarding the chlorine not dissolved in said chlorine dioxide solution at substantially atmospheric pressure and in admixture with air to a second reaction zone to which sulphur dioxide and water, along with additional chlorine, if necessary, are fed for reaction between said chlorine, sulphur dioxide and water in the presence of excess chlorine to form an aqueous mixture of hydrochloric acid and sulphuric acid,
venting unreacted chlorine and said air from said second reaction zone, controlling the partial pressure of said unreacted chlorine vented from said second reaction zone to a value in the range of about 150 to about 550 mm Hg to provide sufficient of said excess chlorine in said second reaction zone to form said aqueous mixture of hydrochloric acid and sulphuric acid having a total acid normality of about 6 to about 14 normal and from which dissolved sulphur dioxide is absent, and
forwarding said aqueous mixture of hydrochloric acid and sulphuric acid to said reaction medium and forwarding such additional quantities of hydrogen ions, chloride ions and sulphate ions to said reaction medium as are required by the stoichiometry of the reactions occurring in the reaction medium.

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A process for the production of hydrochloric acid and sulphuric acid, which comprises:

separately feeding chlorine, sulphur dioxide and water to a reaction zone;
intimately contacting said chlorine, sulphur dioxide and water in the presence of air and excess chlorine and water and reacting the same in accordance with the equation:
SO.sub.2 +Cl.sub.2 +2H.sub.2 O.fwdarw.2HCl+H.sub.2 SO.sub.4
to form an aqueous mixture of hydrochloric acid and sulphuric acid,
venting unreacted chlorine and said air from said reaction zone, controlling the partial pressure of said unreacted chlorine vented from said reaction zone to a value in the range of about 150 to about 550 mm Hg to provide sufficient of said excess chlorine in said reaction zone to form said aqueous mixture of hydrochloric acid and sulphuric acid having a total acid normality of about 6 to about 14 normal and from which dissolved sulphur dioxide is absent, and
removing the sulphur dioxide-free aqueous mixture of hydrochloric acid and sulphuric acid from the reaction zone.

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Dependencies are inferred from the claim text.

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Abstract

A process for the production of chlorine dioxide, which comprises:

reacting sodium chlorate with chloride ions and hydrogen ions in an aqueous acid reaction medium having a total acid normality of about 2 to about 4.8 normal to form chlorine dioxide and chlorine, said chloride ions being provided by hydrochloric acid alone or by hydrochloric acid and sodium chloride and said hydrogen ions being provided by sulphuric acid and said hydrochloric acid,
maintaining said reaction medium at its boiling point at a temperature below that above which substantial decomposition of chlorine dioxide occurs while applying a subatmospheric pressure to a first reaction zone containing said reaction medium to form steam in a volume ratio of steam to chlorine dioxide of about 4:1 to about 10:1,
depositing anhydrous neutral sodium sulphate from the reaction medium and removing the same from said first reaction zone,
removing a gaseous mixture of chlorine dioxide, chlorine and steam from said first reaction zone and forming an aqueous solution of said chlorine dioxide therefrom, said aqueous solution of chlorine dioxide also containing part of said chlorine,
forwarding the chlorine not dissolved in said chlorine dioxide solution at substantially atmospheric pressure and in admixture with air to a second reaction zone to which sulphur dioxide and water, along with additional chlorine, if necessary, are fed for reaction between said chlorine, sulphur dioxide and water in the presence of excess chlorine to form an aqueous mixture of hydrochloric acid and sulphuric acid,
venting unreacted chlorine and said air from said second reaction zone, controlling the partial pressure of said unreacted chlorine vented from said second reaction zone to a value in the range of about 150 to about 550 mm Hg to provide sufficient of said excess chlorine in said second reaction zone to form said aqueous mixture of hydrochloric acid and sulphuric acid having a total acid normality of about 6 to about 14 normal and from which dissolved sulphur dioxide is absent, and
forwarding said aqueous mixture of hydrochloric acid and sulphuric acid to said reaction medium and forwarding such additional quantities of hydrogen ions, chloride ions and sulphate ions to said reaction medium as are required by the stoichiometry of the reactions occurring in the reaction medium.

4 more elements