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US4325927A
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Purified monoammonium phosphate process
Assignee: Freeport Mcmoran Resource Partners Ltd
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Filing: 1980-12-10
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Granted: 1982-04-20
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Expires: 2000-12-10
Abstract
Abstract A method of producing purified monoammonium phosphate from wet process phosphoric acid and ammonia is provided. The ammoniation takes place in two stages, the acid being ammoniated in the first stage to a pH between about 1.5 and 2.5. This mixture is allowed to age after which the mixture is ammoniated to a pH between about 4 and 5. An impurity-containing precipitate is formed in the first and second stages of ammoniation that is easily filterable from the monoammonium phosphate solution derived from the second ammoniation stage.
Inventors
- 👤 Charles W. Weston
- 👤 John W. Wen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 17:06
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/26; C01B25/28
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
151 words
A process for the production of purified monoammonium phosphate from wet process phosphoric acid comprising: (a) ammoniating to a pH between about 1.5 and 2.5 for a period of about 10 minutes or more wet process phosphoric acid having a concentration between about 25% and 35% by weight P 2 O 5 and a fluorine content of less than about 2.0% by weight, said ammoniation taking place at a temperature between 75° C. and 105° C. to form a mixture containing a crystalline impurity precipitate; (b) allowing said mixture to age for a period of about 10 minutes or more after step (a) is completed; (c) further ammoniating said mixture from step (b) to a pH between about 4 and 5 to form a monoammonium phosphate solution and to precipitate additional impurities; and (d) removing said precipitated impurities from said monoammonium phosphate solution resulting in a purified solution of monoammonium phosphate.
Claim 2
Dependent Claim
151 words
A process for the production of purified monoammonium phosphate from wet process phosphoric acid comprising: (a) ammoniating to a pH between about 1.5 and 2.5 for a period of about 10 minutes or more wet process phosphoric acid having a concentration between about 25% and 35% by weight P 2 O 5 and a fluorine content of less than about 2.0% by weight, said ammoniation taking place at a temperature between 75° C. and 105° C. to form a mixture containing a crystalline impurity precipitate; (b) allowing said mixture to age for a period of about 10 minutes or more after step (a) is completed; (c) further ammoniating said mixture from step (b) to a pH between about 4 and 5 to form a monoammonium phosphate solution and to precipitate additional impurities; and (d) removing said precipitated impurities from said monoammonium phosphate solution resulting in a purified solution of monoammonium phosphate.
Claim 3
Dependent Claim
26 words
The process as recited in claim 1 further comprising forming monoammonium phosphate crystals in said purified monoammonium phosphate solution obtained from step (d) in claim 1.
Claim 4
Dependent Claim
23 words
The process as recited in claim 2 further comprising removing said monoammonium phosphate crystals from said purified solution resulting in a mother liquor.
Claim 5
Dependent Claim
22 words
The process as recited in claim 3 wherein said monoammonium phosphate crystals are formed by cooling and/or evaporating said purified ammoniated solution.
Claim 6
Dependent Claim
18 words
The process as recited in claim 3 wherein said mother liquor is recycled to the first ammoniation stage.
Claim 7
Dependent Claim
24 words
The process as recited in claim 2 further comprising removal in crystalline form of substantially all of said monoammonium phosphate from said purified solution.
Claim 8
Dependent Claim
40 words
The process as recited in claim 1 wherein said phosphoric acid contains iron and aluminum in an atomic ratio of fluorine to iron and aluminum between about 1.0 and 2.0, and contains less than about 1.0% SiO 2 by weight.
Claim 9
Dependent Claim
73 words
The process as recited in claim 7 wherein said phosphoric acid contains fluorine, iron and aluminum in an atomic ratio of fluorine to iron and aluminum between about 1.25 and 1.35, and has a weight ratio of iron oxides to aluminum oxides of greater than about 1.0 and at least 0.5% by weight each of iron oxides and aluminum oxides and said acid contains between 0.1% and 0.75% by weight SiO 2 .
Claim 10
Dependent Claim
47 words
The process as recited in claim 1 wherein the concentration of said phosphoric acid is initially from about 48% to about 56% P 2 O 5 and is diluted with water prior to ammoniation to a concentration between about 25% and 28% P 2 O 5 .
Claim 11
Dependent Claim
36 words
The method as recited in claim 1, 9, 7 or 8 wherein said wet process phosphoric acid is derived from Florida phosphate rock and is ammoniated in said first stage to a pH of about 2.3.
Claim 12
Dependent Claim
25 words
The process as recited in claim 1 wherein said first stage ammoniation takes place for a period of between about 10 minutes and 45 minutes.
Claim 13
Dependent Claim
26 words
The method as recited in claim 1 wherein said first stage ammoniation takes place at a temperature of from about 85° C. to about 95° C.
Claim 14
Dependent Claim
120 words
In a process for the production of purified monoammonium phosphate from wet process phosphoric acid wherein the phosphoric acid is ammoniated to form monoammonium phosphate, the steps comprising ammoniating wet process phosphoric acid having a concentration of between about 25% and 35% by weight P 2 O 5 to a pH between about 1.5 and 2.5 to form a crystalline precipitate, said ammoniation taking place at a temperature between about 75° C. and 105° C. for a period of about 10 minutes or more and thereafter aging the ammoniated phosphoric acid for about 10 minutes or more after the ammoniation to a pH between about 1.5 and 2.5 is completed and prior to further ammoniation to form said monoammonium phosphate.
Claim 15
Dependent Claim
120 words
In a process for the production of purified monoammonium phosphate from wet process phosphoric acid wherein the phosphoric acid is ammoniated to form monoammonium phosphate, the steps comprising ammoniating wet process phosphoric acid having a concentration of between about 25% and 35% by weight P 2 O 5 to a pH between about 1.5 and 2.5 to form a crystalline precipitate, said ammoniation taking place at a temperature between about 75° C. and 105° C. for a period of about 10 minutes or more and thereafter aging the ammoniated phosphoric acid for about 10 minutes or more after the ammoniation to a pH between about 1.5 and 2.5 is completed and prior to further ammoniation to form said monoammonium phosphate.
Claim 16
Dependent Claim
55 words
The process as recited in claim 13 wherein said phosphoric acid prior to ammoniation contains fluorine, iron and aluminum impurities in an atomic ratio of fluorine to iron and aluminum between about 1.0 and 2.0 and said acid contains less than about 1.0% by weight SiO 2 and less than about 2.0% by weight fluorine.
Claim 17
Dependent Claim
70 words
The process as recited in claim 14 wherein said phosphoric acid contains fluorine in an atomic ratio of fluorine to iron and aluminum between about 1.25 and 1.35 and has a weight ratio of iron oxides to aluminum oxides of greater than about 1.0 and at least 0.5% by weight of each iron oxides and aluminum oxides and an SiO 2 concentration of between about 0.1% and 0.75% by weight.
Claim 18
Dependent Claim
16 words
The process as recited in claim 13 wherein said aging takes place for about 30 minutes.
Claim 19
Dependent Claim
31 words
The process as recited in claim 13 wherein the concentration of said phosphoric acid prior to ammoniation is from about 25% to about 28% by weight P 2 O 5 .
Claim 20
Dependent Claim
22 words
The process as recited in claim 13 wherein said ammoniation takes place at a temperature between about 85° C. and 95° C.
Claim 21
Dependent Claim
72 words
The process as recited in claim 13, 16, 17, 14, 15 or 6 further comprising: (a) further ammoniating the phosphoric acid to a pH between about 4 and 5 to form an ammonium phosphate solution and precipitate additional impurities; (b) thereafter removing the precipitates from said ammonium phosphate solution resulting in a purified solution of monoammonium phosphate; and (c) crystallizing at least part of the monoammonium phosphate present in said purified solution.
Claim 22
Independent Claim
202 words
A method for the manufacture of purified monoammonium phosphate from wet process phosphoric acid comprising: (a) ammoniating phosphoric acid to a pH between about 1.5 and 2.5 at a temperature between about 75° C. and 105° C., said phosphoric acid having a concentration of between about 25% and 35% by weight P 2 O 5 , a fluorine content of less than about 2.0% by weight, an atomic ratio of fluorine to iron and aluminum between about 1.0 and 2.0, and between about 0.1% and 0.75% by weight SiO 2 , said ammoniation taking place over a period of about 10 minutes or more to produce a resulting mixture containing precipitated impurities; (b) allowing said resulting mixture to age for about 10 minutes or more after completion of ammoniation in step (a); (c) further ammoniating said resulting mixture from step (b) to a pH between about 4 and 5 at a temperature between about 75° C. and 105° C. over a period of between about 10 minutes and 30 minutes to precipitate additional impurities and form a monoammonium phosphate solution; and (d) removing said precipitated impurities from the monoammonium phosphate solution obtained in step (c) to produce a purified monoammonium phosphate solution.
Claim 23
Independent Claim
202 words
A method for the manufacture of purified monoammonium phosphate from wet process phosphoric acid comprising: (a) ammoniating phosphoric acid to a pH between about 1.5 and 2.5 at a temperature between about 75° C. and 105° C., said phosphoric acid having a concentration of between about 25% and 35% by weight P 2 O 5 , a fluorine content of less than about 2.0% by weight, an atomic ratio of fluorine to iron and aluminum between about 1.0 and 2.0, and between about 0.1% and 0.75% by weight SiO 2 , said ammoniation taking place over a period of about 10 minutes or more to produce a resulting mixture containing precipitated impurities; (b) allowing said resulting mixture to age for about 10 minutes or more after completion of ammoniation in step (a); (c) further ammoniating said resulting mixture from step (b) to a pH between about 4 and 5 at a temperature between about 75° C. and 105° C. over a period of between about 10 minutes and 30 minutes to precipitate additional impurities and form a monoammonium phosphate solution; and (d) removing said precipitated impurities from the monoammonium phosphate solution obtained in step (c) to produce a purified monoammonium phosphate solution.
Claim 24
Dependent Claim
25 words
The method as recited in claim 20 further comprising forming and separating monoammonium phosphate crystals from said purified monoammonium phosphate solution leaving a mother liquor.
Claim 25
Dependent Claim
23 words
The method as recited in claim 21 wherein said monoammonium phosphate crystals are formed by cooling and/or evaporating said purified monoammonium phosphate solution.
Claim 26
Dependent Claim
20 words
The method as recited in claim 21 or 22 wherein said monoammonium phosphate crystals are removed by filtration or centrifugation.
Claim 27
Dependent Claim
32 words
The method as recited in claim 21 or 22 further comprising removing essentially all of the monoammonium phosphate present in the mother liquor by evaporation of water present in the mother liquor.
Claim 28
Dependent Claim
24 words
The method as recited in claim 21 wherein said mother liquor is combined with wet process phosphoric acid to provide phosphoric acid for ammoniation.
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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) | 1985-04-19 | 1985-10-19 | 1986-04-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-04-19 | 1989-10-19 | 1990-04-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-04-19 | 1993-10-19 | 1994-04-20 | $7700.00 | Window Closed / Lapsed |