US4252777A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recovery of aluminum and other metal values from fly ash
Assignee: United States Department of Energy
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Filing: 1979-11-01
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Granted: 1981-02-24
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Expires: 1999-11-01
Abstract
Abstract The invention described herein relates to a method for improving the acid leachability of aluminum and other metal values found in fly ash which comprises sintering the fly ash, prior to acid leaching, with a calcium sulfate-containing composition at a temperature at which the calcium sulfate is retained in said composition during sintering and for a time sufficient to quantitatively convert the aluminum in said fly ash into an acid-leachable form.
Inventors
- 👤 William J. McDowell
- 👤 Forest G. Seeley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 13:18
CPC Classifications
C; C01; C01F; C01F7/00; C01F7/02; C01F7/20; C01F7/26; C01F7/68; C01F7/74; C01F7/741; C22; C22B; C22B21/00; C22B21/0007
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
65 words
A method for improving the acid leachability of aluminum and other metal values found in fly ash which comprises sintering the fly ash, prior to acid leaching, with a calcium sulfate-containing composition at a temperature at which the calcium sulfate is retained in said composition during sintering and for a time sufficient to quantitatively convert the aluminum in said fly ash into an acid-leachable form.
Claim 2
Independent Claim
65 words
A method for improving the acid leachability of aluminum and other metal values found in fly ash which comprises sintering the fly ash, prior to acid leaching, with a calcium sulfate-containing composition at a temperature at which the calcium sulfate is retained in said composition during sintering and for a time sufficient to quantitatively convert the aluminum in said fly ash into an acid-leachable form.
Claim 3
Dependent Claim
17 words
The method according to claim 1 in which the sintering temperature is in the range 800°-1300° C.
Claim 4
Dependent Claim
45 words
The method according to claim 1 in which the calcium sulfate-containing composition is selected from the group consisting of calcium sulfate, mixtures of calcium sulfate with magnesium sulfate or calcium carbonate or the sludge resulting from treating SO 2 -containing effluents with lime or limestone.
Claim 5
Dependent Claim
18 words
The method according to claim 1 in which the acid leachant is sulfuric acid and aqueous solutions thereof.
Claim 6
Dependent Claim
18 words
The method according to claim 1 in which the acid leachant is nitric acid or aqueous solutions thereof.
Claim 7
Dependent Claim
18 words
The method according to claim 1 in which the acid leachant is hydrochloric acid or aqueous mixtures thereof.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-24 | 1984-08-25 | 1985-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-24 | 1988-08-25 | 1989-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-24 | 1992-08-25 | 1993-02-24 | $7700.00 | Window Closed / Lapsed |