US4684512A
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Phosphate recovery from wet phosphoric acid purification process
Assignee: Stauffer Chemical Co
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Filing: 1986-08-25
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Granted: 1987-08-04
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Expires: 2006-08-25
Abstract
Abstract The invention is a process for recovering phosphorus value from magnesium pyrophosphate containing filter media in the wet superphosphoric acid purification process. The invention comprises treating the filter cake with a salt to remove the adhering phosphoric acid without solubilizing magnesium acid pyrophosphate. The filter cake, after phosphoric acid removal, can be utilized as commercial or technical grade magnesium acid pyrophosphate.
Inventors
- 👤 John M. Stewart
- 👤 Teddy R. Clark
- 👤 Thomas E. Edging
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:00
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/24; C01B25/26; C01B25/28; C01B25/30; C01B25/38; C01B25/42
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
53 words
A process for recovering phosphorus values adhering to the magnesium acid pyrophosphate crystals from wet process superphosphoric acid filtration media comprising suspending the filter media in a sufficient amount of an alkali metal or ammonium salt solution to solubilize free phosphoric acid contained therein and recovering the free acid from the filter cake.
Claim 2
Dependent Claim
53 words
A process for recovering phosphorus values adhering to the magnesium acid pyrophosphate crystals from wet process superphosphoric acid filtration media comprising suspending the filter media in a sufficient amount of an alkali metal or ammonium salt solution to solubilize free phosphoric acid contained therein and recovering the free acid from the filter cake.
Claim 3
Dependent Claim
21 words
The process of claim 1 wherein the alkali metal salt is chosen from the group consisting of carbonates, bicarbonates or hydroxides.
Claim 4
Dependent Claim
13 words
The process of claim 2 wherein the alkali metal salt is sodium hydroxide.
Claim 5
Dependent Claim
16 words
The process of claim 2 wherein the alkali metal salt is sodium carbonate or its hydrates.
Claim 6
Dependent Claim
12 words
The process of claim 1 wherein the ammonium salt is ammonium hydroxide.
Claim 7
Dependent Claim
19 words
The process of claim 1 wherein the magnesium acid pYrophosphate crystals, after removal of the acid phosphate, are recovered.
Claim 8
Dependent Claim
28 words
The process of claim 1 wherein the salt solution is used in an amount of from 1.5 to 4.0 times the equivalent amount of the superphosphoric acid present.
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) | 1990-08-03 | 1991-02-02 | 1991-08-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-03 | 1995-02-02 | 1995-08-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-03 | 1999-02-02 | 1999-08-04 | $7700.00 | Window Closed / Lapsed |