Abstract A process for the removal of SO2 from a gas stream containing SO2 and O2 wherein the use of a conventional scrubbing solution containing an alkaline reagent results in the formation of undesired, intractable sulfate byproducts, is improved by adding to the scrubbing zone a reducing agent selected from the group consisting of finely divided sulfur, a polysulfide compound, a water-soluble sulfide compound and mixtures thereof, and by thereafter operating the scrubbing zone under thiosulfateproduction conditions, thereby suppressing the production of undesired sulfate byproducts. Principal utility of this improved process is associated with a process for scrubbing SO2 from a flue or stack gas stream. Key feature of this improved process involves the selective conversion of the absorbed SO2 to the corresponding thiosulfate compound within the scrubbing zone, thereby minimizing the opportunity for the oxygen contained in the gas stream to oxidize the sulfite salt to the undesired sulfate byproducts.
An improved process as defined in claim 1 wherein the alkaline reagent is ammonium carbonate.
Claim 2
Dependent Claim
15 words
An improved process as defined in claim 1 wherein the alkaline reagent is ammonium hydroxide.
Claim 3
Dependent Claim
15 words
An improved process as defined in claim 1 wherein the alkaline reagent is sodium hydroxide.
Claim 4
Dependent Claim
15 words
An improved process as defined in claim 1 wherein the alkaline reagent is sodium carbonate.
Claim 5
Dependent Claim
35 words
An improved process as defined in claim 1 wherein the thiosulfate-production conditions include a temperature of about 5* to about 150* C. and a pressure sufficient to maintain the scrubbing solution in the liquid phase.
Claim 6
Dependent Claim
37 words
An improved process as defined in claim 1 wherein the reducing agent is finely divided sulfur which is used in amounts sufficient to at least provide a mole ratio of sulfur to the absorbed SO2 of 1:1.
Claim 7
Dependent Claim
19 words
An improved process as defined in claim 7 wherein a wetting agent is also added to the contacting zone.
Claim 8
Dependent Claim
17 words
An improved process as defined in claim 8 wherein the wetting agent is a quaternary ammonium salt.
Claim 9
Dependent Claim
37 words
An improved process as defined in claim 1 wherein the reducing agent is a polysulfide compound which is used in an amount sufficient to at least provide a molE ratio of polysulfide to absorbed SO2 of 1:6.
Claim 10
Dependent Claim
38 words
An improved process as defined in claim 1 wherein the reducing agent is a water-soluble sulfide compound which is used in an amount at least sufficient to provide a mole ratio of sulfide to absorbed SO2 of 1:2.
Claim 11
Dependent Claim
15 words
An improved process as defined in claim 11 wherein the reducing agent is hydrogen sulfide.
Claim 12
Dependent Claim
15 words
An improved process as defined in claim 11 wherein the reducing agent is ammonium hydrosulfide.