Process for the removal of sulfur oxide from waste gas

Abstract

A process, in which sulfur dioxide gas contained in waste gas is removed therefrom and collected as gypsum. In said process, the waste gas is subjected to a flow of detergent solution of basic aluminium sulfate so that the sulfur dioxide is absorbed into the solution. This solution, now containing the sulfur dioxide, is thereafter subjected to oxidation, resulting in a decrease in the basicity thereof. The solution is then neutralized by calcium carbonate or calcium hydroxide, whereby gypsum is precipitated in the solution and collected therefrom and whereby the crude content of the solution is recovered so that it may be used again as a detergent for the waste gas.

What is claimed is: 
     
       1. A process for removing sulfur oxide from waste gas which comprises a. subjecting the waste gas to a countercurrent flow of an absorbent solution of 0.05 to 1 mol/liter of basic aluminum sulfate, said solution having a basicity of 0 to 60%, and containing .Iadd.about .Iaddend.20 g/l of a manganese salt to absorb the sulfur oxide into the solution and oxidize the absorbed sulfur oxide by means of the manganese salt; and   b. blowing air through the absorbent solution from step a) to oxidize sulfite ion in the solution to sulfate ion;   c. neutralizing the solution from step a) by adding calcium carbonate or calcium hydroxide whereby gypsum is precipitated; and   d. separating the gypsum and reusing the solution as the absorbent solution in step a).   
     
     
       2. The process as claimed in claim 1, in which the precipitated crystalline gypsum is collected by filtration. .Iadd. 3. A process for removing sulfur oxide from waste gas which comprises .Iadd. a. subjecting the waste gas to a countercurrent flow of an absorbent solution of 0.05 to 1 mol/liter of basic aluminum sulfate, said solution having a basicity of 0 to 60%, and containing an amount of a manganese salt sufficient to absorb the sulfur oxide into the solution and oxidize the absorbed sulfur oxide by means of the manganese salt; and .Iadd.   b. blowing air through the absorbent solution from step a) to oxidize sulfite ion in the solution to sulfate ion; .Iadd.   c. neutralizing the solution from step a) by adding calcium carbonate or calcium hydroxide whereby gypsum is precipitated; and .Iadd.   d. separating the gypsum and reusing the solution as the absorbent solution in step a)..Iaddend.