Method for removal of SO.sub.2 from gases
First Claim
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1. Method for direct generation of SO2 and a liquor which is capable of absorbing SO2 from an aqueous SO2 -containing salt solution in which soluble sulfites and bisulfites are present which comprises:
- (a) dividing said solution into two streams A and B;
(b) subjecting said streams to electrodialytic water splitting in a two-compartment water splitter comprised of alternating cation and a bipolar module consisting of a combination of anion and cation membranes functioning as a bipolar membrane, wherein one of said streams is introduced into the water splitter compartments between the cation membranes and the anion membranes of the bipolar membrane combination;
(c) introducing the other stream, A, into the compartments of said splitter between the cation sides of said bipolar module and the cation membranes;
(d) passing a direct current through the water splitter thereby effecting the acidification of the stream A and the basicification of the stream B and the transfer of cations from stream A to stream B and producing an aqueous solution comprised of SO2 derived from stream A and a solution comprised of base capable of absorbing SO2 derived from stream B.
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Abstract
Removal of sulfur dioxide from an aqueous solution containing the same is effected by subjecting the solution to electrodialytic water splitting. In particular SO2 is removed from dilute gas streams by means of alkaline solution scrubbing, regeneration of the scrubbing solution and liberation of concentrated SO2 by means of a membrane water splitter. Waste sulfate produced in the process may be converted to sulfuric acid in a separate membrane water splitter or otherwise processed by conventional means.
43 Citations
20 Claims
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1. Method for direct generation of SO2 and a liquor which is capable of absorbing SO2 from an aqueous SO2 -containing salt solution in which soluble sulfites and bisulfites are present which comprises:
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(a) dividing said solution into two streams A and B; (b) subjecting said streams to electrodialytic water splitting in a two-compartment water splitter comprised of alternating cation and a bipolar module consisting of a combination of anion and cation membranes functioning as a bipolar membrane, wherein one of said streams is introduced into the water splitter compartments between the cation membranes and the anion membranes of the bipolar membrane combination; (c) introducing the other stream, A, into the compartments of said splitter between the cation sides of said bipolar module and the cation membranes; (d) passing a direct current through the water splitter thereby effecting the acidification of the stream A and the basicification of the stream B and the transfer of cations from stream A to stream B and producing an aqueous solution comprised of SO2 derived from stream A and a solution comprised of base capable of absorbing SO2 derived from stream B. - View Dependent Claims (8, 9, 10, 11, 12, 17)
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2. A method for removing SO2 from a gas which comprises:
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(a) absorbing SO2 from said gas by contact with a basic aqueous solution thereby forming an aqueous SO2 -containing salt solution in which soluble sulfites and bisulfites are present; (b) dividing said solution into two streams A and B; (c) subjecting said streams to electrodialytic water splitting in a two-compartment water splitter comprised of alternating cation and a bipolar module consisting of a combination of anion and cation membranes functioning as a bipolar membrane, wherein one of said streams is introduced into the water splitter compartments between the cation membranes and the anion membranes of the bipolar membrane combination; (d) introducing the other stream, A, into the compartments of said splitter between the cation sides of the bipolar module and the cation membranes; (e) passing a direct current through the water splitter thereby effecting the acidification of the stream A and the basicification of the stream B and the transfer of cations from stream A to stream B and producing an aqueous solution comprised of SO2 derived from stream A and a solution comprised of base capable of absorbing SO2 derived from stream B. - View Dependent Claims (3, 4, 5, 6, 7, 13, 14, 15, 16, 18, 20)
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19. A process for converting a soluble sulfate to insoluble CaSO4 and base by subjecting an aqueous solution of the soluble sulfate to treatment in a two-compartment water splitter containing combinations of cation and anion membranes functioning as a bipolar membrane and cation membranes, converting at least a portion of the soluble sulfate to the bisulfate, thereby also generating a base, thereafter treating the acidified stream with a calcium base to form insoluble CaSO4 and soluble sulfate and recycling said soluble sulfate to the water splitter.
Specification