Patent US3787304A successfully refreshed from Google Patents.
US3787304A
Expired / Lapsed
US
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Production of hf from fluorine by-products
Assignee: Honeywell International Inc
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Filing: 1972-01-31
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Granted: 1974-01-22
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Expires: 1992-01-31
Abstract
Abstract Fluorine values are recovered from fluosilicic acid aqueous streams by electrodialytic water-splitting of fluoride salt to hydrofluoric acid and hydroxide base and further optionally concentration of the hydrofluoric acid via membrane electrodialysis, to produce anhydrous HF.
Inventors
- 👤 F Chlanda
- 👤 Jen Liu Kang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:45
CPC Classifications
C; C01; C01B; C01B7/00; C01B7/19; C01B7/191
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
28 words
The method of claim 1 wherein said aqueous hydrofluoric acid is concentrated by electrodialysis above the concentration of the azeotrope and thereafter recovering anhydrous hydrofluoric acid by distillation.
Claim 2
Dependent Claim
68 words
A process for converting fluosilicic acid in an aqueous stream to aqueous hydrofluoric acid which comprises reacting said stream with potassium hydroxide from an electrodialytic water-splitter to produce potassium fluosilicate, liberating potassium fluoride from the potassium fluosilicate by reaction with potassium hydroxide from an electrodialytic water-splitting to produce potassium fluoride, and further treating said potassium fluoride in an electrodialytic water-splitter to produce aqueous hydrofluoric acid and potassium hydroxide.
Claim 3
Dependent Claim
96 words
A process for recovering fluorine values from waste gases formed into an aqueous effluent, said gases resulting from the treatment of phosphate rock with a strong acid and containing silicon tetrafluoride and hydrogen fluoride, the steps comprising precipitating potassium fluosilicate, reacting said potassium fluosilicate with potassium hydroxide from an electrodialytic water-splitter to produce aqueous potassium fluoride, separating said aqueous potassium fluoride from the precipitated silica, electrodialytically water-splitting said potassium fluoride to produce hydrofluoric acid, concentrating the hydrofluoric acid by electrodialysis to a concentration of at least 38 percent, and recovering the anhydrous hydrogen fluoride by distillation.
Claim 4
Dependent Claim
107 words
A process for recovering fluorine values from waste gases introduced into an aqueous effluent, said gases resulting from the treatment of phosphate rock with a strong acid and containing silicon tetrafluoride and hydrogen fluoride, the steps comprising precipitating a fluosilicate salt with a hydroxide base, reacting said fluosilicate salt with a hydroxide base, said base being produced in an electrodialytic water-splitter to produce an aqueous fluoride salt, separating said aqueous fluoride salt from the precipitated silica, electrodialytically water-splitting said fluoride salt to produce hydrofluoric acid, and concentrating the hydrofluoric acid by electrodialysis to a concentration of greater than 38 percent and recovering substantially anhydrous fluoride by distillation.
References Cited (Backward Citations)
US2829095A
Cited
US3450609A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-21 | 1977-07-23 | 1978-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-21 | 1981-07-23 | 1982-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-21 | 1985-07-23 | 1986-01-22 | $7700.00 | Window Closed / Lapsed |