Continuous process for scrubbing sulfur dioxide from a gas stream

Claim 2

A process as defined in claim 1 wherein the alkaline reagent utilized in the absorbent is ammonium hydroxide.

Claim 3

A process as defined in claim 1 wherein the alkaline reagent utilized in the absorbent is an alkali metal hydroxide or carbonate.

Claim 4

A process as defined in claim 4 wherein said alkali metal is sodium.

Claim 5

A process as defined in claim 4 wherein said alkali metal is potassium.

Claim 6

A process as defined in claim 1 wherein said alkaline reagent utilized in the absorbent stream is an alkaline earth metal hydroxide or carbonate.

Claim 7

A process as defined in claim 1 wherein the thiosulfate production conditions utilized in step (b) include a temperature of about 20* to about 150* C. and a pressure sufficient to maintain the effluent stream from step (a) in the liquid phase.

Claim 8

A process as defined in claim 1 wherein the reduction conditions utilized in step (c) include a temperature of about 100* to about 350* C. and a pressure sufficient to maintain the effluent stream from step (b) in the liquid phase.

Claim 9

A process as defined in claim 1 wherein the amount of carbon monoxide charged to step (c) is sufficient to provide a mole ratio of carbon monoxide to thiosulfate of at least 4:1.

Claim 10

A process as defined in claim 1 wherein the reducing agent utilized in step (b) is hydrogen sulfide.

Claim 11

A process as defined in claim 11 wherein at least a portion of the hydrogen sulfide utilized in step (b) is obtained by passing to step (b) a portion of the hydrogen sulfide stripped in step (d).

Claim 12

A process as defined in claim 1 wherein the reducing agent utilized in step (b) is finely divided sulfur which is used in an amount at least sufficient to provide a mole ratio of sulfur to sulfite of 1:1.

Claim 13

A process as defined in claim 1 wherein the reducing agent utilized in step (b) is a polysulfide compound which is used in an amount at least sufficient to provide a mole ratio of polysulfide to sulfite of 1:6.

Claim 14

A process as defined in claim 1 wherein the reducing agent utilized in step (b) is a water-soluble sulfide compound which is used in an amount at least sufficient to provide a mole ratio of sulfide to sulfite of 1:2.

Claim 15

A process as defined in claim 1 wherein step (c) is performed in the presence of the catalyst comprising activated carbon.

Claim 16

A process as defined in claim 1 wherein step (c) is performed in the presence of a catalyst comprising a metallic component selected from the group consisting of the transition metals of groups VI AND VIII of the Periodic Table combined with a porous carrier materIal.

Claim 17

A process as defined in claim 17 wherein the catalyst is cobalt sulfide combined with activated carbon or alumina.

Claim 18

A process for treating an input gas stream containing SO2 in order to continuously remove SO2 therefrom, said process comprising the steps of: a. contacting the input gas stream with an aqueous absorbent containing ammonium carbonate or bicarbonate at scrubbing conditions selected to form a treated gas stream containing a reduced amount of SO2 and an effluent water stream containing ammonium sulfite or bisulfite; b. contacting at least a portion of the effluent water stream from step (a) with a reducing agent, selected from the group consisting of finely divided sulfur, a polysulfide compound, a water-soluble sulfide compound and mixtures thereof, at thiosulfate production conditions selected to result in an effluent stream containing ammonium thiosulfate; c. reacting the effluent stream from step (b) with carbon monoxide at reduction conditions selected to produce an aqueous effluent stream containing ammonium sulfide or hydrosulfide; d. stripping hydrogen sulfide from the aqueous effluent stream from step (c) with a carbon dioxide-containing stripping gas to form a regenerated aqueous absorbent stream containing ammonium bicarbonate or carbonate and an overhead gaseous stream containing hydrogen sulfide; and thereafter, e. passing at least a portion of the resulting regenerated absorbent stream back to step (a).

Claim 19

A process as defined in claim 19 wherein the reducing agent utilized in step (b) is hydrogen sulfide.

Claim 20

A process as defined in claim 20 wherein at least a portion of the hydrogen sulfide reactant utilized in step (b) is obtained by passing a portion of the overhead stream produced in step (d) to step (b).