Process for production of chlorine dioxide

1 . A process for the production of chlorine dioxide, said process comprising the steps of continuously:

(a) feeding to a reactor an acid, alkali metal chlorate and a reducing agent;

(b) reacting the alkali metal chlorate with the acid and the reducing agent to form a product stream comprising chlorine dioxide and alkali metal salt of the acid;

(c) bringing the product stream from the reactor to an eductor and mixing it with motive fluid fed to the eductor and thereby forming a diluted product stream;

(d) bringing the diluted product stream to a gas-liquid separator where gas is separated from liquid therein,

(e) withdrawing a gaseous product stream comprising chlorine dioxide and inert gas from said gas-liquid separator; and

(f) withdrawing a liquid phase from the gas-liquid separator;

wherein from about 20 to about 80% of the chlorine dioxide in the diluted product stream brought to the gas liquid separator is withdrawn in the gaseous product stream.

2 . A process as claimed in claim 1 , wherein from about 30 to about 70% of the chlorine dioxide in the diluted product stream brought to the gas liquid separator is withdrawn in the gaseous product stream.

3 . A process as claimed in claim 1 further comprising a step of recovering at least a portion of the liquid phase withdrawn from the gas-liquid separator as a chlorine dioxide containing liquid product.

4 . A process as claimed in claim 1 further comprising a step of recirculating at least a portion of the liquid phase withdrawn from the gas-liquid separator and feeding it to the eductor as motive fluid.

5 . A process as claimed in claim 1 , wherein a portion of the liquid phase withdrawn from the gas-liquid separator is recovered as a chlorine dioxide containing liquid product while another portion is recirculated and fed to the eductor as motive fluid.

6 . A process as claimed in any one of claims 1 - 5 , wherein make-up water is added to the process.

7 . A process as claimed in claim 1 , wherein inert gas is added to the diluted product stream.

8 . A process as claimed in claim 1 , wherein the acid is sulphuric acid.

9 . A process as claimed in claim 1 , wherein the reducing agent is hydrogen peroxide.

10 . A process as claimed in claim 1 , wherein the reactor is a through-flow vessel or a pipe.

11 . A process as claimed i in claim 1 , wherein the acid, the alkali metal chlorate and the reducing agent are fed close to one end of the reactor while the product stream is withdrawn at the other end of the reactor.

12 . A process as claimed in claim 1 , wherein the gas-liquid separator is a stripper column.

13 . A process as claimed in claim 1 , wherein the gas-liquid separator is a cyclone separator.

14 . A process as claimed in claim 1 , wherein the gas-liquid separator is a vented tank provided with a blower for introducing inert gas at the bottom thereof.

15 . A process for the production of chlorine dioxide, said process comprising the steps of continuously:

(a) feeding to a reactor an acid, alkali metal chlorate and a reducing agent;

(b) reacting the alkali metal chlorate with the acid and the reducing agent to form a product stream comprising chlorine dioxide and alkali metal salt of the acid;

(c) bringing the product stream from the reactor to an eductor and mixing it with motive fluid fed to the eductor and thereby forming a diluted product stream;

(d) bringing the diluted product stream to a gas-liquid separator where inert gas is added;

(e) separating gas from said diluted product stream in the gas-liquid separator to an such an extent that from about 20 to about 70% of the chlorine dioxide in the diluted product stream is withdrawn as a gaseous product stream;

(f) withdrawing a liquid phase from the gas-liquid separator; and,

(g) recovering at least a portion of the liquid phase withdrawn from the gas-liquid separator as a chlorine dioxide containing liquid product.

16 . A process as claimed in claim 15 , wherein the gas-liquid separator is a stripper column.

17 . A process for the production of chlorine dioxide, said process comprising the steps of continuously:

(a) feeding to a reactor an acid, alkali metal chlorate and a reducing agent;

(b) reacting the alkali metal chlorate with the acid and the reducing agent to form a product stream comprising chlorine dioxide and alkali metal salt of the acid;

(c) bringing the product stream from the reactor to an eductor and mixing it with motive fluid fed to the eductor and thereby forming a diluted product stream;

(d) bringing the diluted product stream to a gas-liquid separator where inert gas is added;

(e) separating gas from said diluted product stream in the gas-liquid separator to an such an extent that from about 20 to about 70% of the chlorine dioxide in the diluted product stream is withdrawn as a gaseous product stream;

(f) withdrawing a liquid phase from the gas-liquid separator; and,

(g) recirculating at least a portion of the liquid phase withdrawn from the gas-liquid separator and feeding it to the eductor as motive fluid.

18 . A process as claimed in claim 17 , wherein the gas-liquid separator is a stripper column.

19 . Production unit for the production of chlorine dioxide, said unit comprising:

(a) a reactor provided with one or more feed inlets for acid, reducing agent and alkali metal chlorate;

(b) an eductor connected to the reactor provided with an inlet for motive fluid, means for mixing a product stream from the reactor with motive fluid to obtain a diluted product stream and an outlet for said diluted product stream;

(c) a gas-liquid separator connected to the outlet of the eductor, said gas-liquid separator being designed for bringing from about 20 to about 80% of the chlorine dioxide from the diluted product stream into a gas phase; and,

(d) means for withdrawing a gaseous product stream from the gas-liquid separator.