US4235854A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for purifying wet process phosphoric acid
Assignee: White Springs Agricultural Chemicals Inc
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Filing: 1977-08-25
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Granted: 1980-11-25
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Expires: 1997-08-25
Abstract
Abstract A method for removing impurities from wet process produced phosphoric acid and recovering phosphate values retained by the impurities is disclosed. The wet process produced phosphoric acid is filtered through a diatomite filter cake in a porous medium at a temperature from about 57° C. to about 77° C. During filtering an impurity-containing upper portion of the filter cake is removed exposing a fresh surface of the filter cake. An aqueous slurry is formed with the removed portion of filter cake. The slurry is filtered to recover a filtrate containing a major portion of the phosphate values retained by the removed portion of the filter cake.
Inventors
- 👤 Hudson C. Smith
- 👤 Wesley W. Atwood
- 👤 John S. Myrick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 01:40
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/18; C01B25/234; C01B25/235
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
150 words
A method for removing impurities from wet-process produced phosphoric acid and recovering values retained by the impurities comprising the steps of: forming a filter cake comprising diatomite on a surface of a porous medium; maintaining wet-process produced phosphoric acid containing particulate impurities at a temperature of from about 57° C. to about 77° C; filtering such phosphoric acid through the formed filter cake for removing particulate impurities from such phosphoric acid whereby such removed particulate impurities and phosphate values are retained by the filter cake; simultaneously with filtering such phosphoric acid, continuously removing an impurity-containing upper portion of the filter cake to expose to the wet-process phosphoric acid a fresh surface of the filter cake; forming an aqueous slurry of said removed portion of said filter cake; and filtering said slurry to recover a filtrate containing a major portion of the phosphate values retained by the filter cake for reprocessing.
Claim 2
Independent Claim
150 words
A method for removing impurities from wet-process produced phosphoric acid and recovering values retained by the impurities comprising the steps of: forming a filter cake comprising diatomite on a surface of a porous medium; maintaining wet-process produced phosphoric acid containing particulate impurities at a temperature of from about 57° C. to about 77° C; filtering such phosphoric acid through the formed filter cake for removing particulate impurities from such phosphoric acid whereby such removed particulate impurities and phosphate values are retained by the filter cake; simultaneously with filtering such phosphoric acid, continuously removing an impurity-containing upper portion of the filter cake to expose to the wet-process phosphoric acid a fresh surface of the filter cake; forming an aqueous slurry of said removed portion of said filter cake; and filtering said slurry to recover a filtrate containing a major portion of the phosphate values retained by the filter cake for reprocessing.
Claim 3
Dependent Claim
60 words
The method of claim 1 wherein said filter cake is formed over the outer surface of a porous cylinder and said cylinder is rotated during filtration so that a portion of said outer surface is intermittently contacted by said acid for the filtration thereof followed by contact with blade means for removing said impurity-containing outer portion of said filter cake.
Claim 4
Dependent Claim
18 words
The method of claim 2 wherein said cylinder is rotated at the rate of 1 revolution per minute.
Claim 5
Dependent Claim
16 words
The method of claim 2 wherein said blade means is advanced about 0.005 inches per revolution.
Claim 6
Dependent Claim
23 words
The method as defined in claim 1 wherein said acid is maintained at a temperature between about 70° C. and about 71° C.
Claim 7
Dependent Claim
20 words
The method of claim 1 wherein the wet-process phosphoric acid contains about 50% by weight P 2 O 5 .
Claim 8
Dependent Claim
236 words
In the wet process for producing phosphoric acid by the acidulation of phosphorus-bearing rock with sulfuric acid thereby to precipitate calcium sulfate and to release crude phosphoric acid containing sludge forming impurities and thereafter concentrating said crude impurity-containing phosphoric acid to a phosphate content of about 50% F 2 O 5 by weight, the improvement comprising the steps of: heating said concentrated acid to a temperature of between 57° C. and about 77° C.; forming a filter element consisting of a diatomite filter cake coat overlying the surface of a porous support member; intermittently contacting at least a portion of said filter element with said acid while maintaining reduced pressure on a side of said filter element opposite said filter cake thereby filtering said acid to remove at least a portion of the sludge forming impurities from said acid, cake, said filter cake impurities being retained in an outer portion of said filter cake retaining phosphate values; collecting said acid after filtration; removing said impurity-containing portion of said filter cake after contact thereof by said acid, thereby to present fresh filter surface for subsequent acid contact; collecting said removed outer portion of said diatomite coat; forming a water slurry of said collected removed outer portion; filtering said slurry, thereby yielding a filtrate containing a major portion of the phosphate values retained by the filter cake; and returning the filtrate to a phosphoric acid plant for reprocessing.
Claim 9
Dependent Claim
236 words
In the wet process for producing phosphoric acid by the acidulation of phosphorus-bearing rock with sulfuric acid thereby to precipitate calcium sulfate and to release crude phosphoric acid containing sludge forming impurities and thereafter concentrating said crude impurity-containing phosphoric acid to a phosphate content of about 50% F 2 O 5 by weight, the improvement comprising the steps of: heating said concentrated acid to a temperature of between 57° C. and about 77° C.; forming a filter element consisting of a diatomite filter cake coat overlying the surface of a porous support member; intermittently contacting at least a portion of said filter element with said acid while maintaining reduced pressure on a side of said filter element opposite said filter cake thereby filtering said acid to remove at least a portion of the sludge forming impurities from said acid, cake, said filter cake impurities being retained in an outer portion of said filter cake retaining phosphate values; collecting said acid after filtration; removing said impurity-containing portion of said filter cake after contact thereof by said acid, thereby to present fresh filter surface for subsequent acid contact; collecting said removed outer portion of said diatomite coat; forming a water slurry of said collected removed outer portion; filtering said slurry, thereby yielding a filtrate containing a major portion of the phosphate values retained by the filter cake; and returning the filtrate to a phosphoric acid plant for reprocessing.
Claim 10
Dependent Claim
23 words
The process as defined in claim 7 wherein said acid is heated to a temperature between about 70° C. and about 71° C.
Claim 11
Dependent Claim
60 words
The process as defined in claim 7 wherein said diatomite coat is formed over the outer surface of a porous cylinder and said cylinder is rotated so that a portion of said coated outer surface is contacted by said acid for the filtration thereof followed by contact with blade means for removing said impurity-containing outer portion of said diatomite coat.
Claim 12
Dependent Claim
20 words
The process as defined in claim 7 wherein said cylinder is rotated at the rate of one revolution per minute.
Claim 13
Dependent Claim
18 words
The process as defined in claim 7 wherein said blade means is advanced about 0.005 inches per revolution.
Claim 14
Independent Claim
91 words
A method for removing impurities from wet-process produced phosphoric acid and recovering values retained by the impurities comprising the steps of: maintaining wet-process produced phosphoric acid containing particulate impurities at a temperature of from about 57° C. to about 77° C.; filtering such phosphoric acid for removing particulate impurities from such phosphoric acid, said removed particulate impurities retaining phosphate values; forming an aqueous slurry of removed particulate impurities; and filtering said slurry to recover a filtrate containing a major portion of the phosphate values retained by the particulate impurities for reprocessing.
Claim 15
Independent Claim
91 words
A method for removing impurities from wet-process produced phosphoric acid and recovering values retained by the impurities comprising the steps of: maintaining wet-process produced phosphoric acid containing particulate impurities at a temperature of from about 57° C. to about 77° C.; filtering such phosphoric acid for removing particulate impurities from such phosphoric acid, said removed particulate impurities retaining phosphate values; forming an aqueous slurry of removed particulate impurities; and filtering said slurry to recover a filtrate containing a major portion of the phosphate values retained by the particulate impurities for reprocessing.
Claim 16
Dependent Claim
22 words
The method as defined in claim 12 wherein said acid is maintained at temperature between about 70° C. and about 71° C.
References Cited (Backward Citations)
CA915389A
Cited
US2123785A
Cited
US2308716A
Cited
US2415797A
Cited
US2917367A
Cited
US3505013A
Cited
US3338675A
Cited
US3328123A
Cited
US3494736A
Cited
US3554694A
Cited
US3642439A
Cited
US4048289A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-11-25 | 1984-05-26 | 1984-11-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-11-25 | 1988-05-26 | 1988-11-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-11-25 | 1992-05-26 | 1992-11-25 | $7700.00 | Window Closed / Lapsed |