Precipitation of Sulfur Dioxide from Gaseous Feed by Oxidative Chemisorption

Several sorption processes based on precipitation of sulfur dioxide by absorption with chemical reaction have been investigated. The target of this study was the evaluation of process boundaries and boundaries of application for the following processes: •Absorption of sulfur dioxide with caustic soda.•Catalytically supported oxidation of sulfur dioxide in the liquid phase.•Absorption of sulfur dioxide with dichromate.•Absorption of sulfur dioxide with sulfate acidic hydrogen peroxide. The processes were investigated in a lab‐scale falling‐film absorption column. Mass transfer area of the film was 0.22 m2. In absorption of sulfur dioxide with aqueous solution of dichromate below pH values of 2.5, the rate of reaction of dichromate with sulfur dioxide is very fast. As a consequence, absorption of sulfur dioxide is mainly controlled by mass transfer in the gaseous phase. Absorption of sulfur dioxide with caustic additives from an oxygen‐containing gaseous phase is followed by oxidation in the liquid phase. Oxidation is accelerated by heavy metal catalysis. The role of iron(II) and manganese(II) in oxidation of sulfur dioxide has been investigated. Parallel to the oxidation of sulfur dioxide, the catalyst iron(II) is subject of irreversible deactivation by oxidation. Manganese(II) accelerates oxidation. Hydrogen peroxide, sometimes suggested for application in technical scale absorption of sulfur dioxide, causes instantaneous formation of sulfuric acid in the aqueous bulk phase. As long as the concentration of sulfuric acid can be kept below 20% by weight, absorption of sulfur dioxide is again controlled by the gas phase mass transfer resistance.