US3911093A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recovery of SO{HD 2 {B from waste gas emissions
Assignee: D&M CONSOLIDATED PARTNERSHIP
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Filing: 1972-10-05
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Granted: 1975-10-07
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Expires: 1992-10-05
Abstract
Abstract A process for recovering sulfur values from gas emissions by absorbing SO2 in an aqueous solution comprising a mixture of Na2HPO4 and NaH2PO4 at a pH between about 2.5 and about 5 at an absorption temperature between about 85* and about 200* F., treating the phosphate solution containing absorbed SO2 with H2S to produce sulfur, separating the sulfur from the phosphate solution and recycling the phosphate solution to the absorber. Provision is made to remove sulfate, which builds up in phosphate absorbent, by crystallizing sulfate from a purge stream. The process is particularly useful in the field of pollution abatement for recovering SO2 from the off-gas obtained from a Claus-type reactor system.
Inventors
- 👤 Fawzy G Sherif
- 👤 John S Hayford
- 👤 Julian E Blanch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 03:43
CPC Classifications
C; C01; C01B; C01B17/00; C01B17/02; C01B17/04; C01B17/05; B; B01; B01D; B01D53/00; B01D53/14; B01D53/1418; B01D53/1456; B01D53/1481; B01D53/1493; Y; Y02; Y02A; Y02A50/00; Y02A50/20
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
124 words
A METHOD FOR RECOVERING SULFATE FROM SO2 CONTAINING GASES WHICH COMPRISES (A) ABSORBING IN AN ABSORBENT COMPRISING AN AQUEOUS SOLUTION CONTAINING AN ALKALI METAL PHOSPHATE AT A PH BETWEEN ABOUT 4.5 AND ABOUT 2.5 AT A TEMPERATURE BETWEEN ABOUT ROOM TEMPERATURE AND ABOUT 200*F. IN AN ABSORPTION ZONE, (B) PASSING THE SO2 CONTAINING ABSORBENT FROM SAID ABSORPTION ZONE, INTO REACTION ZONE, (C) INTRODUCING GASEOUS H2S INTO SAID SO2 CONTAINING ABSORBENT IN SAID REACTION ZONE IN AN AMOUNT IN EXCESS OF THAT REQUIRED TO REACT THE SO2 IN SAID SO2 CONTAINING OBSORBENT TO SULFUR WHEREIN SAID ABSORBENT IS MAINTAINED AT A PH BETWEEN ABOUT 2.5 AND ABOUT 5.5 TO PRODUCE SULFUR, (D) SEPARATING SULFUR FROM THE ABSORBENT AND RECYCLING THE ABSORBENT TO SAID ABSORPTION ZONE.
Claim 2
Independent Claim
124 words
A METHOD FOR RECOVERING SULFATE FROM SO2 CONTAINING GASES WHICH COMPRISES (A) ABSORBING IN AN ABSORBENT COMPRISING AN AQUEOUS SOLUTION CONTAINING AN ALKALI METAL PHOSPHATE AT A PH BETWEEN ABOUT 4.5 AND ABOUT 2.5 AT A TEMPERATURE BETWEEN ABOUT ROOM TEMPERATURE AND ABOUT 200*F. IN AN ABSORPTION ZONE, (B) PASSING THE SO2 CONTAINING ABSORBENT FROM SAID ABSORPTION ZONE, INTO REACTION ZONE, (C) INTRODUCING GASEOUS H2S INTO SAID SO2 CONTAINING ABSORBENT IN SAID REACTION ZONE IN AN AMOUNT IN EXCESS OF THAT REQUIRED TO REACT THE SO2 IN SAID SO2 CONTAINING OBSORBENT TO SULFUR WHEREIN SAID ABSORBENT IS MAINTAINED AT A PH BETWEEN ABOUT 2.5 AND ABOUT 5.5 TO PRODUCE SULFUR, (D) SEPARATING SULFUR FROM THE ABSORBENT AND RECYCLING THE ABSORBENT TO SAID ABSORPTION ZONE.
Claim 3
Dependent Claim
23 words
The method of claim 1 in which the pH in said absorption and reaction zones is maintained between about 2.8 and about 4.5.
Claim 4
Dependent Claim
24 words
The method of claim 1 in which said absorbent containing alkali metal phosphate has an alkali metal phosphate ratio between about 2.5:1 and 1:1.
Claim 5
Dependent Claim
23 words
The method of claim 1 in which said alkali metal phosphate has an alkali metal:phosphate ratio of between about 1.2:1 to about 2:1.
Claim 6
Dependent Claim
13 words
The method of claim 1 in which said alkali metal phosphate comprises Na2HPO4.
Claim 7
Dependent Claim
18 words
The method of claim 1 in which said alkali metal phosphate comprises a mixture of Na2HPO4 and NaH2PO4.
Claim 8
Dependent Claim
25 words
The method of claim 1 in which the phosphate concentration of the solution in said absorption zone is between about 2 and about 0.5 molar.
Claim 9
Dependent Claim
21 words
The method of claim 1 in which the temperature in said reaction zone is between about 90* and about 200* F.
Claim 10
Dependent Claim
59 words
The method of claim 1 in which said H2S is fed to said reaction zone at rate to maintain a ratio relative to SO2 between about stoichiometric and about 500% excess over the amount stoichiometrically necessary to react with the SO2 in the absorbent to form sulfur and excess gaseous H2S is separated and withdrawn from said reaction zone.
Claim 11
Dependent Claim
36 words
The method of claim 1 in which a portion of the absorbent separated from sulfur in step (d) is treated for sulfate salt removal in a sulfate removal zone and thereafter recycled to said absorption zone.
Claim 12
Dependent Claim
23 words
The method of claim 10 in which said absorbent is cooled to selectively crystallize sulfate salt from said absorbent which is then recycled.
Claim 13
Dependent Claim
35 words
The method of claim 1 in which the SO2 containing gas fed to said absorption zone contains between about 0.1 and about 15% SO2 and is substantially free of H2S, COS, CS2 and sulfur vapor.
Claim 14
Dependent Claim
24 words
The method of claim 1 in which the SO2 containing gas fed to said absorption zone is incinerated off gas from a Claus-type reactor.
Claim 15
Dependent Claim
27 words
The process of claim 1 wherein the absorbent contains between about 0.5 to about 1.25 molar phosphate and an alkali metal:phosphate ratio between 1:1 and about 2.5:1.
References Cited (Backward Citations)
US1995545A
Cited
US2534063A
Cited
US2729543A
Cited
US2747962A
Cited
US2816820A
Cited
US3257176A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-06 | 1979-04-07 | 1979-10-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-06 | 1983-04-07 | 1983-10-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-06 | 1987-04-07 | 1987-10-07 | $7700.00 | Window Closed / Lapsed |