GB796778A - Process for producing chloride dioxide - Google Patents

Abstract

<PICT:0796778/III/1> Chlorine dioxide is obtained by contacting an aqueous acid solution containing a trivalent chromium compound and a chlorate dissolved therein with a hot inert gas, preferably steam, in amount sufficient to heat the solution with consequent formation of chlorine dioxide, and to strip the chlorine dioxide from the solution. In the preferred embodiment the reacting solution is contained and prepared in vessel 1, and consists of an alkali metal chlorate and chromic sulphate in an acid aqueous medium, the acid concentration being preferably between 2 and 4 mols./litre. The preferred acid is sulphuric acid. To prevent reaction it is desirable to prepare and keep this solution below 40 DEG C. It is preferred to have between 20 and 120 per cent excess chromic compound present, and particularly 50 to 100 per cent excess. This solution passes downwardly through a gas-liquid contact column 3 in countercurrent to hot steam which enters at 7, heating the solution usually to between 80 DEG and 100 DEG C., and stripping out the chlorine dioxide as it is formed. The vapours pass into scrubber 25 where they are condensed by contact with water to form a solution of chlorine dioxide, which is stored in tank 31. To avoid explosions it is preferred to use a large excess of steam or other inert gas, for example at least 5 and preferably 9 or more volumes per volume of chlorine dioxide. The solution passes from the bottom of column 3 into chamber 18, where it is treated with sulphur dioxide to regenerate the chromic sulphate, and is then recycled to vessel 1. Sodium sulphate may be removed by crystallization before the regeneration. Specifications 581,931 and 796,779 are referred to.