US4485078A
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Process for producing wet process phosphoric acid from phosphate rocks containing fluochlorapatite and related minerals
Assignee: Freeport Mcmoran Resource Partners Ltd
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Filing: 1983-03-08
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Granted: 1984-11-27
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Expires: 2003-03-08
Abstract
Abstract Phosphoric acid is produced by the wet process from phosphate rock containing fluochlorapatite. The rock is ground in a crusher (10) to a size such that from about 50% to about 90% by weight will be passed by a -200 mesh U.S.S. sieve before being passed into a digestor (14) where it is mixed with sulfuric acid and recycled phosphoric acid to form a slurry. A suitable reductant such as sulphur dioxide is added to the slurry to maintain the oxidation-reduction potential in the range from about +150 mv to about +750 mv. The gypsum by-products are then removed from the slurry at filter (16) and a portion of the acid is recycled to digestor (14). The remaining acid is either concentrated and further processed to make fertilizers or is further processed via path (20) to remove aluminum and/or iron impurities. Select amounts of fluoride and sodium containing compounds are added to the acid in a stirred reactor (30) to cause precipitation of aluminum, principally as Na 2 AlF 5 . After about 15 to about 60 minutes of stirring at a temperature below about 70° C., the precipitate is removed at filter (32) where the acid is either processed to make fertilizer or subjected to additional processing to remove iron contaminants. Iron contaminants are removed from the filter acid or from aluminum removed acid from filter (32) by adding sufficient ammonia to the acid in a stirring reactor (40) to cause precipitation of iron principally as NH 4 Fe 2 H 8 (PO 4 ) 5 .AH 2 O, to reduce the level of iron to desired levels. After aging in the reactor from about 2 to about 24 hours at a temperature below the boiling point of the acid, the precipitate is removed at filter (42) and the resulting iron reduced acid is concentrated and subjected to conventional processing for making fertilizers.
Inventors
- 👤 Charles W. Weston
- 👤 John W. Wen
- 👤 Frederick S. Mandel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:12
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/18; C01B25/22; C01B25/222; C01B25/223; C01B25/225; C01B25/234; C01B25/237; C01B25/238
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
110 words
A process for producing phosphoric acid from phosphate rock containing fluochlorapatite, comprising the steps of: (a) crushing the phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) adding a reductant to the digestor slurry formed in step (b) to maintain the oxidation-reduction potential of said slurry in the range from about +150 mv to about +750 mv; and (d) filtering the resulting slurry of step (c) to remove gypsum by-products therefrom to obtain a phosphoric acid.
Claim 2
Dependent Claim
110 words
A process for producing phosphoric acid from phosphate rock containing fluochlorapatite, comprising the steps of: (a) crushing the phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) adding a reductant to the digestor slurry formed in step (b) to maintain the oxidation-reduction potential of said slurry in the range from about +150 mv to about +750 mv; and (d) filtering the resulting slurry of step (c) to remove gypsum by-products therefrom to obtain a phosphoric acid.
Claim 3
Dependent Claim
48 words
The process of claim 1 further comprising the steps of: (e) recycling a portion of the acid obtained in step (d); and (f) concentrating the unrecycled portion of said acid obtained in step (d) to a level of about 40% to about 54% P 2 O 5 .
Claim 4
Dependent Claim
31 words
The process of claim 1 wherein sufficient quantity of reductant is added in step (c) to maintain the oxidation-reduction potential of said slurry from about +250 mv to about +500 mv.
Claim 5
Dependent Claim
122 words
A process for producing phosphoric acid from phosphate rock containing fluochlorapatite, comprising the steps of: (a) crushing the fluochlorapatite containing phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) filtering the resulting slurry of step (b) to remove gypsum by-products therefrom to obtain a phosphoric acid; and (d) adding sufficient reductant to a portion of the phosphoric acid obtained in step (c) to be recycled to the digestor to maintain the oxidation-reduction potential of the slurry formed in step (b) from about +150 mv to about +750 mv.
Claim 6
Dependent Claim
122 words
A process for producing phosphoric acid from phosphate rock containing fluochlorapatite, comprising the steps of: (a) crushing the fluochlorapatite containing phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) filtering the resulting slurry of step (b) to remove gypsum by-products therefrom to obtain a phosphoric acid; and (d) adding sufficient reductant to a portion of the phosphoric acid obtained in step (c) to be recycled to the digestor to maintain the oxidation-reduction potential of the slurry formed in step (b) from about +150 mv to about +750 mv.
Claim 7
Dependent Claim
36 words
The process of claim 4 further comprising the step of: (e) concentrating the unrecycled portion of the phosphoric acid in step (d) to a level of about 40% to about 54% P 2 O 5 .
Claim 8
Dependent Claim
32 words
The process of claim 4 wherein a sufficient quantity of reductant is added in step (d) to maintain the oxidation-reduction potential of said slurry from about +250 mv to about +500 mv.
Claim 9
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is metallic iron.
Claim 10
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is metallic aluminum.
Claim 11
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is metallic zinc.
Claim 12
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is sodium sulfite.
Claim 13
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is ammonium bisulfite.
Claim 14
Dependent Claim
13 words
The process of claim 1 or 4 wherein the reductant is sulfur dioxide.
Claim 15
Dependent Claim
32 words
The process of claim 1 or 4 wherein sufficient active silica is added to the slurry to maintain the F/SiO 2 weight ratio of said slurry from about 1.9 to about 2.3.
Claim 16
Dependent Claim
27 words
The process of claim 1 or 4 wherein the temperature of said slurry is maintained below about 78° C. prior to filtering of the gypsum by-products therefrom.
Claim 17
Dependent Claim
32 words
The process of claim 14 wherein the temperature of said slurry is maintained in a range from about 70° C. to about 85° C. prior to filtering of the gypsum by-products therefrom.
Claim 18
Dependent Claim
67 words
The process of claim 1 or 4 further comprising the steps of: (g) treating the phosphoric acid obtained in step (d) to remove excess aluminum by adding sufficient soluble sodium and fluoride containing compounds to said phosphoric acid to precipitate aluminum from said solution as a crystalline salt; and (h) removing said aluminum precipitate from the solution of step (g) to obtain an aluminum removed phosphoric acid.
Claim 19
Dependent Claim
103 words
The process of claim 16 wherein the amount of fluoride (X) added in step (g) is determined by the relation: X=1.86 (Al 2 O 3 )+1.90 (SiO 2 )-(F) and the amount of sodium containing material (Y) is determined by the relation: Y=0.90 (Al 2 O 3 )+0.76 (SiO 2 )-(Na), where Al 2 O 3 is the amount of alumina in the phosphoric acid, SiO 2 is the amount of soluble silica in the phosphoric acid, F is the total amount of fluoride already present in the phosphoric acid and Na is the total amount of sodium present in the phosphoric acid.
Claim 20
Dependent Claim
24 words
The process of claim 16 wherein the fluoride containing compound added in step (g) is hydrofluoric acid, ammonium fluoride, ammonium bifluoride or calcium fluoride.
Claim 21
Dependent Claim
24 words
The process of claim 16 wherein the sodium containing compound added in step (g) is sodium chloride, sodium sulfate, sodium carbonate or sodium hydroxide.
Claim 22
Dependent Claim
22 words
The process of claim 16 wherein the sodium and fluoride containing compounds added in step (g) are sodium fluoride or sodium bifluoride.
Claim 23
Dependent Claim
28 words
The process of claim 16 wherein the reaction in step (g) is carried out in a stirred reactor for a period from about 15 to about 60 minutes.
Claim 24
Dependent Claim
21 words
The process of claim 16 wherein the reaction in step (g) is carried out at a temperature below about 70° C.
Claim 25
Dependent Claim
28 words
The process of claim 22 wherein the reaction in step (g) is carried out at a temperature in the range from about 30° C. to about 50° C.
Claim 26
Dependent Claim
60 words
The process of claim 1 or 4 further comprising the steps of: (i) treating the filtered phosphoric acid obtained in step (d) to remove excess iron by adding a sufficient quantity of ammonia to precipitate iron as an insoluble crystalline salt; and (j) removing the iron precipitate from the solution in step (i) to obtain an iron reduced phosphoric acid.
Claim 27
Dependent Claim
62 words
The process of claim 24 wherein the amount of ammonia added in step (i) is determined by the relation ##EQU3## where A is the amount of ammonia required, I i is the initial amount of iron present (as Fe), I f is the final amount of residual iron desired (as Fe), and W is the total weight of acid to be treated.
Claim 28
Dependent Claim
26 words
The process of claim 24 wherein step (i) is carried out in a stirred reactor for a period of from about 2 to about 24 hours.
Claim 29
Dependent Claim
18 words
The process of claim 26 wherein the process is carried out from about 3 to about 20 hours.
Claim 30
Dependent Claim
52 words
The process of claim 24 wherein step (i) is carried out at a temperature in the range from about 50° C. to about 110° C. and prior to removing the precipitate in step (j), the mixture is cooled to a temperature in the range from about 30° C. to about 50° C.
Claim 31
Dependent Claim
25 words
The process of claim 24 wherein step (i) is carried out at a temperature in the range from about 70° C. to about 95° C.
Claim 32
Dependent Claim
352 words
A process for producing phosphoric acid from phosphate rock containing from about 0.2% to about 2.4% chloride as fluochlorapatite, from about 0.4% to about 9.5% Fe 2 O 3 as hematite and geothite, from about 0.2% to about 3.0% Al 2 O 3 as crandellite, from about 0.1% to about 0.35% MnO 2 as pyrolusite, and from about 0.4% to about 3.0% TiO 2 as ilmenite, comprising the steps of: (a) crushing the phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) adding a reductant to the slurry formed in step (b) to maintain the oxidation-reduction potential in the range from about +150 mv to about +750 mv, wherein said reductant is metallic iron, aluminum or zinc, sodium sulfite, ammonium bisufite or sulphur dioxide; (d) adding sufficient active silica to the digestor slurry obtained in step (b) to maintain the F/SiO 2 weight ratio of said slurry between 1.9 and 2.3; (e) filtering the resulting slurry of step (d) to remove gypsum by-products therefrom to obtain a phosphoric acid; (f) treating the phosphoric acid obtained in step (e) to remove excess aluminum by adding sufficient soluble sodium and fluoride containing compounds to said phosphoric acid to precipitate aluminum as a crystalline salt, when the aluminum content of the acid obtained in step (e) is unacceptably high; (g) removing the aluminum precipitate from the solution of step (f) to obtain an aluminum removed phosphoric acid; (h) treating the phosphoric acid obtained in step (e) to remove excess iron by adding sufficient ammonia to the filtered acid to precipitate iron as a crystalline salt, when the level of iron in the acid obtained in step (e) is unacceptably high; (i) removing the iron precipitate from the solution of step (h) to obtain an iron reduced phosphoric acid; and (j) concentrating the acid obtained in steps (e)-(i) to a value of about 40% to about 54% P 2 O 5 .
Claim 33
Dependent Claim
352 words
A process for producing phosphoric acid from phosphate rock containing from about 0.2% to about 2.4% chloride as fluochlorapatite, from about 0.4% to about 9.5% Fe 2 O 3 as hematite and geothite, from about 0.2% to about 3.0% Al 2 O 3 as crandellite, from about 0.1% to about 0.35% MnO 2 as pyrolusite, and from about 0.4% to about 3.0% TiO 2 as ilmenite, comprising the steps of: (a) crushing the phosphate rock to a size such that from about 50% to about 90% by weight thereof will pass a -200 mesh U.S.S. sieve; (b) mixing the rock crushed in step (a) with sulfuric acid and recycled phosphoric acid to form a slurry; (c) adding a reductant to the slurry formed in step (b) to maintain the oxidation-reduction potential in the range from about +150 mv to about +750 mv, wherein said reductant is metallic iron, aluminum or zinc, sodium sulfite, ammonium bisufite or sulphur dioxide; (d) adding sufficient active silica to the digestor slurry obtained in step (b) to maintain the F/SiO 2 weight ratio of said slurry between 1.9 and 2.3; (e) filtering the resulting slurry of step (d) to remove gypsum by-products therefrom to obtain a phosphoric acid; (f) treating the phosphoric acid obtained in step (e) to remove excess aluminum by adding sufficient soluble sodium and fluoride containing compounds to said phosphoric acid to precipitate aluminum as a crystalline salt, when the aluminum content of the acid obtained in step (e) is unacceptably high; (g) removing the aluminum precipitate from the solution of step (f) to obtain an aluminum removed phosphoric acid; (h) treating the phosphoric acid obtained in step (e) to remove excess iron by adding sufficient ammonia to the filtered acid to precipitate iron as a crystalline salt, when the level of iron in the acid obtained in step (e) is unacceptably high; (i) removing the iron precipitate from the solution of step (h) to obtain an iron reduced phosphoric acid; and (j) concentrating the acid obtained in steps (e)-(i) to a value of about 40% to about 54% P 2 O 5 .
Claim 34
Dependent Claim
41 words
The process of claim 30 wherein the fluoride containing compound in step (f) is hydrofluoric acid, ammonium fluoride, ammonium bifluoride or calcium fluoride and the sodium containing compound in step (f) is sodium chloride, sodium sulfate, sodium carbonate or sodium hydroxide.
Claim 35
Dependent Claim
22 words
The process of claim 30 wherein the sodium and fluoride containing compounds used in step (f) are sodium fluoride or sodium bifluoride.
Claim 36
Dependent Claim
103 words
The process of claim 30 wherein the amount of fluoride added in step (f) is determined by the relation: X=1.86 (Al 2 O 3 )+1.90 (SiO 2 )-(F) and the amount of sodium added in step (f) is determined by the relation: Y=0.90 (Al 2 O 3 )+0.76 (SiO 2 )-(Na), where Al 2 O 3 is the amount of alumina in the phosphoric acid, SiO 2 is the amount of soluble silica in the phosphoric acid, F is the total amount of fluoride already present in the phosphoric acid and Na is the total amount of sodium present in the phosphoric acid.
Claim 37
Dependent Claim
62 words
The process of claim 30 wherein the amount of ammonia added in step (h) is determined by the relation: ##EQU4## where A is the amount of ammonia required, I i is the initial amount of iron present (as Fe), I f is the final amount of residual iron desired (as Fe) and W is the total weight of acid to be treated.
Claim 38
Dependent Claim
50 words
The process of claim 30 wherein steps (b)-(c) are carried out at a temperature below 78° C., step (f) is carried out at a temperature below about 70° C., and step (h) is carried out at a temperature in the range of from about 50° C. to about 110° C.
Claim 39
Dependent Claim
89 words
The process of claim 35 wherein steps (b)-(e) are carried out at temperatures in the range from about 70° C. to about 85° C., step (f) is carried out at temperatures in the range from about 30° C. to about 50° C., step (h) is carried out at temperatures in the range from about 70° C. to about 95° C. and the mixture obtained in step (h) is allowed to cool to a temperature of from about 30° C. to about 50° C. prior to carrying out step (i).
Claim 40
Dependent Claim
32 words
The process of claim 30 wherein sufficient reductant is added in step (c) to maintain the oxidation-reduction potential of the slurry in the range from about +250 mv to about +500 mv.
Claim 41
Dependent Claim
26 words
The process of claim 30 wherein the crushed rock of step (c) is pretreated prior to step (b) to reduce the ilmenite content below about 2.5%.
Claim 42
Dependent Claim
208 words
A process for reducing the aluminum content of phosphoric acid having a P 2 O 5 concentration from about 17% to about 54%, wherein the ratio of Al 2 O 5 to MgO is at least 5 to 1, comprising the steps of: (a) adding sufficient sodium and fluoride containing compounds to the phosphoric acid to precipitate aluminum as a crystalline salt principally in the form of Na 2 AlF 5 , wherein the amount of fluoride added is determined by the relation X=1.86 (Al 2 O 3 )+1.90 (SiO 2 )-(F) and the amount of sodium containing material (Y) is determined by the relation Y=0.90 (Al 2 O 3 )+0.76 (SiO 2 )-(Na) where Al 2 O 3 is the amount of alumina in the phosphoric acid, SiO 2 is the amount of soluble silica in the phosphoric acid, F is the total amount of fluoride already present in the phosphoric acid and Na is the total amount of sodium present in the phosphoric acid; (b) stirring the mixture obtained in step (a) from about 15 to about 60 minutes at a temperature less than about 70° C.; and (c) filtering the aluminum precipitate from the mixture of step (b) to obtain an aluminum removed phosphoric acid.
Claim 43
Dependent Claim
208 words
A process for reducing the aluminum content of phosphoric acid having a P 2 O 5 concentration from about 17% to about 54%, wherein the ratio of Al 2 O 5 to MgO is at least 5 to 1, comprising the steps of: (a) adding sufficient sodium and fluoride containing compounds to the phosphoric acid to precipitate aluminum as a crystalline salt principally in the form of Na 2 AlF 5 , wherein the amount of fluoride added is determined by the relation X=1.86 (Al 2 O 3 )+1.90 (SiO 2 )-(F) and the amount of sodium containing material (Y) is determined by the relation Y=0.90 (Al 2 O 3 )+0.76 (SiO 2 )-(Na) where Al 2 O 3 is the amount of alumina in the phosphoric acid, SiO 2 is the amount of soluble silica in the phosphoric acid, F is the total amount of fluoride already present in the phosphoric acid and Na is the total amount of sodium present in the phosphoric acid; (b) stirring the mixture obtained in step (a) from about 15 to about 60 minutes at a temperature less than about 70° C.; and (c) filtering the aluminum precipitate from the mixture of step (b) to obtain an aluminum removed phosphoric acid.
Claim 44
Dependent Claim
34 words
The process of claim 39 further comprising the step of: (d) concentrating the acid obtained in step (c) by evaporation to a level of about 40% to about 54% P 2 O 5 .
Claim 45
Dependent Claim
25 words
The process of claim 39 wherein step (b) is carried out at a temperature in the range from about 30° C. to about 50° C.
Claim 46
Dependent Claim
24 words
The process of claim 39 wherein the sodium containing compound added in step (a) is sodium chloride, sodium sulfate, sodium carbonate or sodium hydroxide.
Claim 47
Dependent Claim
20 words
The process of claim 39 wherein the fluoride containing compound is hydrofluoric acid, ammonium fluoride, ammonium bifluoride or calcium fluoride.
Claim 48
Dependent Claim
21 words
The process of claim 39 wherein the sodium and fluoride containing compounds in step (a) are sodium fluoride or sodium bifluoride.
Claim 49
Dependent Claim
157 words
A process for reducing the iron content of phosphoric acid to a desired level, comprising the steps of: (a) adding sufficient ammonia to the phosphoric acid to precipitate iron as a crystalline salt, principally in the form of NH 4 Fe 2 H 8 (PO 4 ) 5 .4H 2 O, where the amount of ammonia to be added is determined by the relation: ##EQU5## where A is the amount of ammonia required, I i is the initial amount of iron present (as Fe), I f is the final amount of residual iron desired (as Fe) and W is the total weight of the acid to be treated; (b) aging the mixture obtained in step (a) from about 2 to about 24 hours at a temperature from about 25° C. to about the boiling point of said acid; and (c) filtering the iron precipitate from the mixture of step (b) to obtain an iron reduced phosphoric acid.
Claim 50
Dependent Claim
157 words
A process for reducing the iron content of phosphoric acid to a desired level, comprising the steps of: (a) adding sufficient ammonia to the phosphoric acid to precipitate iron as a crystalline salt, principally in the form of NH 4 Fe 2 H 8 (PO 4 ) 5 .4H 2 O, where the amount of ammonia to be added is determined by the relation: ##EQU5## where A is the amount of ammonia required, I i is the initial amount of iron present (as Fe), I f is the final amount of residual iron desired (as Fe) and W is the total weight of the acid to be treated; (b) aging the mixture obtained in step (a) from about 2 to about 24 hours at a temperature from about 25° C. to about the boiling point of said acid; and (c) filtering the iron precipitate from the mixture of step (b) to obtain an iron reduced phosphoric acid.
Claim 51
Dependent Claim
29 words
The process of claim 45 further comprising the step of: (d) concentrating phosphoric acid obtained in step (c) by evaporation to a level of about 40% to about 54%.
Claim 52
Dependent Claim
21 words
The process of claim 45 wherein step (b) is carried out for a period of about 3 to about 20 hours.
Claim 53
Dependent Claim
24 words
The process of claim 45 wherein step (b) is carried out at temperatures in the range from about 50° C. to about 110° C.
Claim 54
Dependent Claim
24 words
The process of claim 45 wherein step (b) is carried out at temperatures in the range from about 70° C. to about 95° C.
Claim 55
Dependent Claim
29 words
The process of claim 45 wherein the mixture of step (b) is allowed to cool to a temperature in the range from about 30° C. to about 50° C.
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