GB605983A - Manufacture of alkali chlorites - Google Patents

Abstract

In the manufacture of an alkali chlorite, a mixture of chlorine and chlorine-dioxide, produced by the action of hydrochloric acid on an alkali and/or alkaline earth chlorate and entrained by air, is caused to undergo particle physical purification of the chlorine dioxide by being mixed with a concentrated solution of an alkali or alkaline earth chloride and/or chlorate, whereby most of the chlorine dioxide and a little chlorine are absorbed, which mixture is then desorbed, e.g. by a current of air, and further purified by being passed through a solution or milk of lime or another alkaline earth base after which the chlorine dioxide is absorbed by an alkali hydroxide and/or carbonate, the products, e.g. sodium chlorite and sodium chlorate thus obtained being separated by crystallisation and, if desired, by evaporation. The chlorates, for the production of which the unabsorbed gases from the partial physical purification may be used, fused in the production of the chlorine dioxide may be previously freed from all or a part of alkali or alkaline earth chlorides. The solution after desorption may be used for absorbing further quantities of the gases, while the gaseous mixture from the desorption tower may be brought into contact with a solution or milk of an alkaline earth hydroxide to produce a gaseous mixture containing only air and chlorine, dioxide and a solution of alkaline earth chloride and chlorate which may be returned to the chlorine dioxide generator, as may be the alkali chlorate separated from the chlorite in the final stage while the mother liquors may be returned to the final absorption.