High efficiency production of chlorine dioxide by solvay process

Claim 1

In a process of producing chlorine dioxide by reducing sodium chlorate with methanol in an aqueous reaction medium containing sulphuric acid in the substantial absence of added chloride ions, the improvement comprises: maintaining a single-chambered generator-evaporator-crystallizer apparatus containing said aqueous reaction medium under a subatmospheric pressure, maintaining said reaction medium at its boiling point at a temperature below that above which substantial decomposition of chlorine dioxide occurs to evaporate water from the reaction medium and provide a gaseous mixture containing steam and chlorine dioxide, removing said gaseous mixture from said single-chambered apparatus, recovering an aqueous solution of chlorine dioxide from said removed mixture, maintaining substantially steady state conditions in said reaction medium by continuously feeding said sodium chlorate, methanol and sulphuric acid into said reaction medium to make up chemicals consumed in said reducing step and to maintain a total acid normality in said reaction medium in excess of about 9 normal, maintaining the liquid level in said single-chambered apparatus substantially constant by balancing water fed to the single-chambered apparatus with water removed therefrom, continuously depositing sodium bisulphate or sesquisulphate from said reaction medium after the reaction medium becomes saturated thereby after the initial start up of the process, and removing said deposited sodium bisulphate or sesquisulphate from said single-chambered apparatus.