Electrodialytic water splitter and process for removal of SO.sub. 2 from gases containing same and for recovery of SO.sub.2 and NaOH

摘要

An electrodialytic water splitting process for recovering SO. sub.2 - containing gases for converting the spent materials used in alkaline sodium scrubbing of SO.sub.2 -containing gases into NaOH. The alkaline sodium scrubbing materials such as Na.sub.2 CO.sub.3, NaHCO.sub. 3 or mixtures thereof are used in the form of an aqueous slurry or aqueous solution to scrub SO.sub.2 from gases containing same to form a reaction mixture comprising Na.sub.2 SO.sub.3, Na.sub.2 SO.sub.4, and possibly NaHSO.sub.3, and a gas depleted in SO.sub.2. The reaction mixture is contacted with an aqueous hydrogen ion solution comprising Na. sub.2 SO. sub.4 and H.sub.2 SO.sub.4 formed in an acid compartment of a two- or three-compartment electrodialytic water splitter to form a solution comprising aqueous SO.sub.2 values and aqueous Na.sub.2 SO.sub.4. Contact of the reaction mixture with the aqueous hydrogen ion solution may be performed externally, of the water splitter or internally, in an acid compartment of the water splitter. Gaseous SO.sub.2 can then be recovered from the aqueous SO.sub.2 values. A liquid comprising water and at least a portion of the aqueous sodium values in the aqueous Na.sub.2 SO.sub.4 is transfered to a base compartment of the electrodialytic water splitter to produce a liquid comprising aqueous NaOH. The aqueous solution comprising NaOH can then be recovered from the base compartment.