Integrated process for the production of alkali and alkaline earth metal chlorates and chlorine dioxide
AssigneeHuron Tech Corp
InventorJohn R. Jackson
Life of this patent
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Abstract
An integrated process for the production of alkali or alkaline earth metal chlorates and chlorine dioxide in which the chromium compound impurities in the alkali or alkaline earth metal chlorate aqueous solution produced by an electrochemical cell are removed and recycled to the electrochemical cell; a substantially chromium compound free alkali or alkaline earth metal chlorate is converted to chlorine dioxide and by-products; and the by-products are converted to substantially chlorine-free carbon dioxide, which is vented, and a dilute solution of an alkali or alkaline earth metal chlorate, which is recycled to the electrochemical cell.
Claims20
A process for producing chlorine dioxide comprising the steps of:
- (A) charging an electrochemical cell having an anode and a cathode with an input solution containing chromate values and an alkali metal chloride or an alkaline earth metal chloride dissolved in water;
- (B) electrolyzing the input solution in the cell to produce an output solution containing the chromate values and an alkali metal chlorate or an alkaline earth metal chlorate;
- (C) removing the chromate values from the output solution to obtain a treated solution that is substantially free of chromate values containing about 10 parts per million or less of total chromium ions by reacting the output solution at an elevated temperature and a neutral or an acid pH with a reducing agent selected from the group consisting of hydroxylamine, an addition compound thereof, and a salt thereof;
- (D) recycling the chromate values removed by inclusion in the input solution of step (A);
- (E) passing the treated solution of step (C) to a chlorine dioxide generator and producing chlorine dioxide and by-products from the treated solution;
- (F) converting the by-products to a substantially chlorine-free carbon dioxide and a reusable solution of an alkali metal chlorate or an alkaline earth metal chlorate, and
- (G) venting the carbon dioxide and recycling the reusable solution by inclusion in the input solution of step (A).
The process of claim 16 wherein the reaction in the third reaction zone of claim 35 is conducted at a pH of about 5 to about 8.5.
A process for producing chlorine dioxide comprising the steps of:
- (A) charging an electrolytic cell having an anode and a cathode with an input solution containing chromate values and sodium chloride dissolved in water;
- (B) electrolyzing the input solution in the cell to produce an output solution containing the chromate values and sodium chlorate;
- (C) removing the chromate values from the output solution to obtain a treated solution which is substantially free of chromate values containing about 10 parts per million or less of total chromium ions by reacting the output solution with hydroxylamine sulfate at a pH of about 5.0 to about 5.5 and at a temperature of about 70.degree. C. to about 95.degree. C.;
- (D) recycling the chromate values removed by inclusion in the input solution of step (A);
- (E) passing the treated solution of step (C) to a chlorine dioxide generator and producing chlorine dioxide and by-products from the treated solution;
- (F) converting the by-products to substantially chlorine-free carbon dioxide and a reusable solution of sodium chlorate in water;
- (G) venting the carbon dioxide and recycling the reusable solution of sodium chlorate by inclusion in the input solution of step (A)
- wherein the by-products of step (F) are converted to carbon dioxide and the reusable solution of sodium chlorate in water by reacting the by-products successively with sodium hydroxide dissolved in water and with chlorine gas followed by reaction with chlorine at a temperature of about 60.degree. C. to about 105.degree. C. and a pH of about 5 to about 7 and
- wherein the chromate values charged to the electrolytic cell in step (A) are present in a compound containing chromium in the divalent, trivalent, or hexavalent state.
Dependencies are inferred from the claim text.