US3650692A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of sulfur dioxide from waste gases
Assignee: Chemical Construction Corp
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Filing: 1969-12-09
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Granted: 1972-03-21
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Expires: 1989-12-09
Abstract
Abstract Waste gases containing sulfur dioxide and entrained solids such as fly ash are scrubbed with an aqueous magnesium oxide-sulfite slurry, which dissolves sulfur dioxide to form further magnesium sulfite and also scrubs entrained solids from the gas stream into the aqueous slurry. Magnesium oxide is regenerated by calcining a portion of the slurry or the solids component of a slurry portion, which generates a dust-laden off-gas rich in sulfur dioxide. Buildup of entrained solids such as fly ash in the system is effectively prevented by scrubbing the dust-laden offgas with an aqueous solution, to which a portion of the solids component of the slurry or regenerated magnesium oxide may be added. The scrubbing step solubilizes magnesium compounds as magnesium bisulfite, due to high sulfur dioxide concentration, and the resulting aqueous magnesium bisulfite solution is filtered to remove residual solids such as fly ash. Magnesium oxide is added to the residual liquid phase to precipitate solid magnesium sulfite, which is filtered from the final residual liquid phase. A portion of this final liquid phase may be discarded to prevent buildup of alkali sulfates or the like, and the balance of the final liquid phase is recycled to the off-gas scrubbing step. The precipitated solid magnesium sulfite is recycled to the calcining step.
Inventors
- 👤 John F Villiers-Fisher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 00:27
CPC Classifications
C; C01; C01F; C01F5/00; C01F5/42; B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/48; B01D53/50; B01D53/501; C01B; C01B17/00; C01B17/48; C01B17/50; C01B17/60
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
32 words
The process of claim 1, in which said waste gas stream is a flue gas derived from the combustion of a sulfur-containing fuel, and said entrained solid particles consist of fly ash.
Claim 2
Dependent Claim
82 words
The process of claim 1, in which an additional portioN of the circulating magnesium oxide-sulfite slurry is drawn off, and the solids component of said additional slurry portion is added to said aqueous solution, whereby the magnesium compounds contained in said additional portion are converted to magnesium bisulfite during the scrubbing of said dust-laden gas stream, and the inert solids within said additional portion and derived from said waste gas stream are separated from said resulting aqueous solution containing dissolved magnesium bisulfite.
Claim 3
Dependent Claim
85 words
The process of claim 1, in which said regenerated solid magnesium oxide contains inert solid particles derived from said waste gas stream, and a portion of said regenerated solid magnesium oxide is added to said aqueous solution, whereby the magnesium oxide contained in said portion is converted to magnesium bisulfite during the scrubbing of said dust-laden gas stream and the inert solid particles contained in said portion and derived from said waste gas stream are separated from said resulting aqueous solution containing dissolved magnesium bisulfite.
Claim 4
Dependent Claim
25 words
The process of claim 1, in which at least a portion of said aqueous scrubbing solution of step (a) consists of said residual aqueous solution.
Claim 5
Dependent Claim
46 words
The process of claim 1, in which water is added to said regenerated solid magnesium oxide to form an aqueous slurry, and said aqueous slurry of magnesium oxide is added to said circulating aqueous magnesium oxide-sulfite slurry to provide additional magnesium oxide in said circulating slurry.
Claim 6
Dependent Claim
36 words
The process of claim 1, in which said magnesium oxide added to the solids-free resulting aqueous solution to solid convert dissolved magnesium bisulfite to magnesium sulfite consists of a portion of said regenerated solid magnesium oxide.
Claim 7
Dependent Claim
323 words
A process for the removal of sulfur dioxide and entrained solid particles from a waste gas stream which comprises: a. scrubbing a waste gas stream containing sulfur dioxide and entrained solid particles with an aqueous slurry containing solid magnesium oxide and magnesium sulfite, whereby sulfur dioxide is dissolved in said aqueous slurry to form further magnesium sulfite and solid particles are scrubbed from said waste gas stream into said slurry, b. separating the resulting aqueous slurry from the scrubbed waste gas stream, c. dividing said resulting aqueous slurry into a first portion and a second portion, d. adding makeup magnesium oxide to the first portion of said resulting aqueous slurry, e. recycling the combined aqueous slurry formed by step (d) to step (a), f. calcining at least a portion of the solids component of the second portion of said resulting aqueous slurry, said solids component containing magnesium oxide, magnesium sulfite and solid particles derived from said waste gas stream, whereby a gas stream containing sulfur dioxide and dust is formed and a regenerated solids stream containing magnesium oxide is produced, said dust principally consisting of magnesium oxide, magnesium sulfite and inert solid particles derived from said waste gas stream, g. contacting the dust-laden gas stream containing sulfur dioxide formed by step (f) with an aqueous scrubbing solution, whereby sulfur dioxide is dissolved in said aqueous solution, magnesium-containing components of said dust are converted to magnesium bisulfite and thereby dissolved in said aqueous solution, and inert solid particles are entrained in said aqueous solution, h. separating the solids component consisting of inert solid particles from the aqueous solution formed by step (g), i. adding magnesium oxide to the residual solids-free aqueous solution formed by step (h), whereby dissolved magnesium bisulfite is converted to solid magnesium sulfite, j. separating the solid magnesium sulfite formed by step (i) from the residual liquid phase, and k. recycling the separated solid magnesium sulfite to calcining in step (f).
Claim 8
Dependent Claim
32 words
The process of claim 8, in which said waste gas stream is a flue gas derived from the combustion of a sulfur-containing fuel, and said entrained solid particles consist of fly ash.
Claim 9
Dependent Claim
115 words
The process of claim 8, in which said second portion of said resulting aqueous scrubbing slurry is divided into a major portion and a minor portion, the major portion is processed according to step (f), and the solids component of said minor portion is added to said aqueous solution during step (g), whereby the magnesium compounds contained in the solids component of said minor portion are converted to magnesium bisulfite during the contacting of said dust-laden gas stream with said aqueous solution according to step (g), and the inert solids within the solids component of said minor portion and derived from said waste gas stream are separated from said aqueous solution according to step (h).
Claim 10
Dependent Claim
102 words
The process of claim 8, in which said regenerated solids stream containing magnesium oxide produced by step (f) also contains inert solid particles derived from said waste gas stream, and a portion of said regenerated solids stream is added to said aqueous scrubbing solution during step (g), whereby the magnesium oxide contained in said portion is converted to magnesium bisulfite during the contacting of said dust-laden gas stream with said aqueous scrubbing solution during step (g), and the inert solid particles contained in said portion and derived from said waste gas stream are separated from said aqueous solution according to step (h).
Claim 11
Dependent Claim
29 words
The process of claim 8, in which at least a portion of said aqueous scrubbing solution of step (g) consists of said residual liquid phase separated in step (j).
Claim 12
Dependent Claim
45 words
The process of claim 8, in which water is added to said regenerated solids stream containing magnesium oxide to form an aqueous slurry, and said aqueous slurry of magnesium oxide is added to said first portion of said resulting aqueous slurry according to step (d).
Claim 13
Dependent Claim
44 words
The process of claim 8, in which said magnesium oxide added to the residual solids-free aqueous solution according to step (i) to convert magnesium bisulfite to magnesium sulfite consists of a portion of the regenerated solids stream containing magnesium oxide formed by step (f).
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-21 | 1975-09-20 | 1976-03-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-21 | 1979-09-20 | 1980-03-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-21 | 1983-09-20 | 1984-03-21 | $7700.00 | Window Closed / Lapsed |