US4402923A
Expired / Lapsed
US
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Process for making phosphoric acid
Assignee: Davy McKee Corp
•
Filing: 1981-09-02
•
Granted: 1983-09-06
•
Expires: 2001-09-02
Abstract
Abstract A phosphate rock slurry, which may be used in the production of wet process phosphoric acid, is provided by wet grinding the rock with partially neutralized, acid water. In one aspect, wet process phosphoric acid is made by advantageously recycling mineral acid waste water effluent of the process. All or a portion of the effluent can be at least partially neutralized with neutralizing agent, e.g., by contact with the base-forming constituents of phosphate rock or extraneous neutralizing agent, e.g., preferably ammonia, to provide a mixture which is wet ground to produce a processable slurry. In one particularly preferred aspect, all of the acid water is at least partially neutralized with phosphate rock and a portion of this acid water is advantageously further neutralized with an extraneous neutralizing agent. The slurry is provided by such neutralization at a pH compatible with the milling, e.g., grinding, media utilized. The use of acid water permits the use of mixtures having high solids content in the mill and thus also reduces the amount of water required to wet grind the mixture. The wet ground processable phosphate rock slurry is advantageously used in the production of phosphoric acid and recycle mineral acid waste water effluent from the process is used in wet grinding phosphate rock and as part of the overall water balance control of the process.
Inventors
- 👤 Warren H. Lang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 22:22
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/01; C01B25/16; C01B25/18; C01B25/22; C01B25/222; C01B25/223
Claims Analysis
Total Claims: 67
Claim 1
Independent Claim
153 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with mineral acid waste water to at least partially neutralize said acid waste water; (ii) feeding the at least partially neutralized mineral acid waste water to a grinder; (iii) grinding a mixture including phosphate rock and the at least partially neutralized mineral acid waste water in the grinder to form a slurry of ground rock; (iv) reacting ground rock of said slurry with sulfuric acid and wash water effluent of step (vi) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that is passed to step (iv).
Claim 2
Independent Claim
153 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with mineral acid waste water to at least partially neutralize said acid waste water; (ii) feeding the at least partially neutralized mineral acid waste water to a grinder; (iii) grinding a mixture including phosphate rock and the at least partially neutralized mineral acid waste water in the grinder to form a slurry of ground rock; (iv) reacting ground rock of said slurry with sulfuric acid and wash water effluent of step (vi) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that is passed to step (iv).
Claim 3
Dependent Claim
31 words
The method of claim 1 wherein a basic material in addition to said phosphate rock is used to neutralize the said waste water to a pH of at least about 4.0.
Claim 4
Dependent Claim
12 words
The method of claim 2 wherein the said basic material comprises lime.
Claim 5
Dependent Claim
12 words
The method of claim 2, wherein the said basic material comprises ammonia.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein the said slurry of ground rock contains about 60 to 80% by weight solids.
Claim 7
Dependent Claim
31 words
The method of claim 1 wherein said acid waste water has a pH of about 0.3 to 3.5 and a P 2 O 5 content of about 0.01 to 3 percent.
Claim 8
Dependent Claim
33 words
The method of claim 1 wherein the -log 10 (H 3 O + ) of the said acid waste water is increased by about 10 to 30% in the contacting of step (i).
Claim 9
Independent Claim
177 words
A method for manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) grinding a mixture of phosphate rock containing base-forming constituents and at least partially neutralized waste water from step (iii), to form a slurry of ground rock; (ii) separating solids of said slurry of ground rock into coarser and finer portions; (iii) contacting the coarser ground rock portion with mineral acid waste water from a storage facility to at least partially neutralize said waste water; (iv) recycling said coarser ground rock portion and said at least partially neutralized waste water to said grinding step (i); (v) contacting said finer ground rock portion with sulfuric acid and wash water effluent of step (vii) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) subjecting said product slurry to separation whereby crystalline hydrated calcium sulfate is separated from phosphoric acid product; (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent; (viii) recycling said wash water effluent of step (vii) to step (v).
Claim 10
Independent Claim
177 words
A method for manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) grinding a mixture of phosphate rock containing base-forming constituents and at least partially neutralized waste water from step (iii), to form a slurry of ground rock; (ii) separating solids of said slurry of ground rock into coarser and finer portions; (iii) contacting the coarser ground rock portion with mineral acid waste water from a storage facility to at least partially neutralize said waste water; (iv) recycling said coarser ground rock portion and said at least partially neutralized waste water to said grinding step (i); (v) contacting said finer ground rock portion with sulfuric acid and wash water effluent of step (vii) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) subjecting said product slurry to separation whereby crystalline hydrated calcium sulfate is separated from phosphoric acid product; (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent; (viii) recycling said wash water effluent of step (vii) to step (v).
Claim 11
Dependent Claim
28 words
The method of claim 8 wherein said finer ground rock portion of said slurry of ground rock of step (v) has about 60 to 80% by weight solids.
Claim 12
Dependent Claim
33 words
The method of claim 8 wherein the feed rate of coarse ground rock slurry of step (iv) to said grinding is about 10% to 350% of the feed rate of said phosphate rock.
Claim 13
Dependent Claim
31 words
The method of claim 8 wherein said acid waste water has a pH of about 0.03 to 3.5 and a P 2 O 5 content of about 0.01 to 3 percent.
Claim 14
Dependent Claim
33 words
The method of claim 8 wherein the -log 10 (H 3 O + ) of the said acid waste water is increased by about 10 to 30% in the contacting of step (v).
Claim 15
Dependent Claim
31 words
The method of claim 8 wherein a basic material in addition to said ground rock is used to neutralize the said waste water to a pH of at least about 4.0.
Claim 16
Dependent Claim
12 words
The method of claim 13 wherein the said basic material comprises lime.
Claim 17
Dependent Claim
12 words
The method of claim 13 wherein the said basic material comprises ammonia.
Claim 18
Dependent Claim
19 words
The method of claim 15 wherein the resulting phosphoric acid product contains about 0.05 to 0.4 weight percent ammonia.
Claim 19
Independent Claim
179 words
A method of manufacturing wet process phosphoric acid containing about 0.05 to about 1 weight percent ammonia from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with mineral acid waste water from a storage facility to partially neutralize said acid waste water; (ii) further neutralizing the partially neutralized acid waste water with ammonia to a pH of at least about 4.0; (iii) feeding the further neutralized mineral acid waste water to a grinder; (iv) grinding a mixture including phosphate rock and the further neutralized mineral acid waste water in the grinder to form a slurry of ground rock; (v) reacting ground rock of said slurry with sulfuric acid and wash water effluent of step (vii) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that it passed to step (v).
Claim 20
Independent Claim
179 words
A method of manufacturing wet process phosphoric acid containing about 0.05 to about 1 weight percent ammonia from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with mineral acid waste water from a storage facility to partially neutralize said acid waste water; (ii) further neutralizing the partially neutralized acid waste water with ammonia to a pH of at least about 4.0; (iii) feeding the further neutralized mineral acid waste water to a grinder; (iv) grinding a mixture including phosphate rock and the further neutralized mineral acid waste water in the grinder to form a slurry of ground rock; (v) reacting ground rock of said slurry with sulfuric acid and wash water effluent of step (vii) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that it passed to step (v).
Claim 21
Dependent Claim
26 words
The method of claim 17 wherein the ammonia used to neutralize the said waste water to a pH of at least about 4.0 is anhydrous ammonia.
Claim 22
Independent Claim
169 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting mineral acid waste water from a storage facility with phosphate rock containing base-forming constituents for a sufficient duration to at least partially neutralize said acid waste water; (ii) feeding the at least partially neutralized acid waste water and the phosphate rock along with fresh water to a grinder; (iii) grinding a mixture of the at least partially neutralized acid waste water, the fresh water and the phosphate rock to form a slurry of ground rock; (iv) reacting the ground rock of said slurry with sulfuric acid and wash water effluent of step (vi) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that is passed to step (iv).
Claim 23
Independent Claim
169 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting mineral acid waste water from a storage facility with phosphate rock containing base-forming constituents for a sufficient duration to at least partially neutralize said acid waste water; (ii) feeding the at least partially neutralized acid waste water and the phosphate rock along with fresh water to a grinder; (iii) grinding a mixture of the at least partially neutralized acid waste water, the fresh water and the phosphate rock to form a slurry of ground rock; (iv) reacting the ground rock of said slurry with sulfuric acid and wash water effluent of step (vi) to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent that is passed to step (iv).
Claim 24
Dependent Claim
16 words
The method of claim 17 wherein the phosphoric acid product is used to produce diammonium phosphate.
Claim 25
Independent Claim
171 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with a first portion of mineral acid waste water to at least partially neutralize said acid waste water; (ii) feeding the phosphate rock and the at least partially neutralized first portion of mineral acid waste water to a grinder; (iii) grinding a mixture including the phosphate rock and said first portion of mineral acid waste water in the grinder to form a slurry of ground rock; (iv) reacting ground rock of said slurry with sulfuric acid, wash water effluent of step (vi) and a second portion of mineral acid waste water to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain wash water effluent that is passed to step (iv).
Claim 26
Independent Claim
171 words
A method of manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) contacting phosphate rock containing base-forming constituents with a first portion of mineral acid waste water to at least partially neutralize said acid waste water; (ii) feeding the phosphate rock and the at least partially neutralized first portion of mineral acid waste water to a grinder; (iii) grinding a mixture including the phosphate rock and said first portion of mineral acid waste water in the grinder to form a slurry of ground rock; (iv) reacting ground rock of said slurry with sulfuric acid, wash water effluent of step (vi) and a second portion of mineral acid waste water to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (v) separating crystalline hydrated calcium sulfate and phosphoric acid from the product slurry to provide phosphoric acid and crystalline hydrated calcium sulfate; and (vi) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain wash water effluent that is passed to step (iv).
Claim 27
Dependent Claim
31 words
The method of claim 21 wherein a basic material in addition to said phosphate rock is used to neutralize the said waste water to a pH of at least about 4.0.
Claim 28
Dependent Claim
12 words
The method of claim 22 wherein the said basic material comprises lime.
Claim 29
Dependent Claim
12 words
The method of claim 22, wherein the said basic material comprises ammonia.
Claim 30
Dependent Claim
21 words
The method of claim 21 wherein the said slurry of ground rock in step (iv) contains about 60 to 80% solids.
Claim 31
Dependent Claim
31 words
The method of claim 21 wherein said acid waste water has a pH of about 0.3 to 3.5 and a P 2 O 5 content of about 0.01 to 3 percent.
Claim 32
Dependent Claim
33 words
The method of claim 21 wherein the -log 10 (H 3 O + ) of the said acid waste water is increased by about 10 to 30% in the contacting of step (i).
Claim 33
Dependent Claim
24 words
The method of claim 21 wherein the contacting time for step (i) is sufficient to allow the evolution of gases formed during said contacting.
Claim 34
Independent Claim
193 words
A method for manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) grinding a mixture of phosphate rock containing base-forming constituents and an at least partially neutralized first portion of waste water from step (iii), to form a slurry of ground rock; (ii) separating solids of said slurry of ground rock into coarser and finer portions; (ii) contacting said coarser ground rock portion with said first portion of mineral acid waste water to at least partially neutralize said first portion of waste water; (iv) recycling said coarser ground rock portion and said at least partially neutralized waste water to said grinding step (i); (v) contacting said finer ground rock portion with sulfuric acid and wash water effluent of step (vii), and a second portion of mineral acid waste water to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) subjecting said product slurry to separation whereby crystalline hydrated calcium sulfate is separated from phosphoric acid product; (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent; (viii) recycling said wash water effluent of step (vii) to step (v).
Claim 35
Independent Claim
193 words
A method for manufacturing wet process phosphoric acid from phosphate rock comprising the steps of (i) grinding a mixture of phosphate rock containing base-forming constituents and an at least partially neutralized first portion of waste water from step (iii), to form a slurry of ground rock; (ii) separating solids of said slurry of ground rock into coarser and finer portions; (ii) contacting said coarser ground rock portion with said first portion of mineral acid waste water to at least partially neutralize said first portion of waste water; (iv) recycling said coarser ground rock portion and said at least partially neutralized waste water to said grinding step (i); (v) contacting said finer ground rock portion with sulfuric acid and wash water effluent of step (vii), and a second portion of mineral acid waste water to yield a product slurry of crystalline hydrated calcium sulfate and phosphoric acid; (vi) subjecting said product slurry to separation whereby crystalline hydrated calcium sulfate is separated from phosphoric acid product; (vii) washing the crystalline hydrated calcium sulfate with an aqueous medium to obtain a wash water effluent; (viii) recycling said wash water effluent of step (vii) to step (v).
Claim 36
Dependent Claim
24 words
The method of claim 29 wherein said fines portion of said slurry of ground rock of step (v) has about 60 to 80% solids.
Claim 37
Dependent Claim
26 words
The method of claim 30 wherein said finer ground rock portion of said slurry of ground rock of step (v) has about 60 to 80% solids.
Claim 38
Dependent Claim
31 words
The method of claim 29 wherein said acid waste water has a pH of about 0.03 to 3.5 and a P 2 O 5 content of about 0.01 to 3 percent.
Claim 39
Dependent Claim
33 words
The method of claim 29 wherein the -log 10 (H 3 O + ) of the said acid waste water is increased by about 10 to 30% in the contacting of step (iii).
Claim 40
Dependent Claim
24 words
The method of claim 29, wherein the contacting time for step (iii) is sufficient to allow the evolution of gases formed during said contacting.
Claim 41
Dependent Claim
31 words
The method of claim 29 wherein a basic material in addition to said ground rock is used to neutralize the said waste water to a pH of at least about 4.0.
Claim 42
Dependent Claim
12 words
The method of claim 35 wherein the said basic material comprises lime.
Claim 43
Dependent Claim
12 words
The method of claim 35 wherein the said basic material comprises ammonia.
Claim 44
Dependent Claim
19 words
The method of claim 37 wherein the resulting phosphoric acid product contains about 0.05 to 0.4 weight percent ammonia.
Claim 45
Dependent Claim
30 words
The method of claim 11 wherein the acid waste water has a pH of about 1.4 to 1.9 and a P 2 O 5 content of 1 to 2 percent.
Claim 46
Dependent Claim
19 words
The method of claim 13 wherein the waste water is neutralized to a pH of at least about 4.6.
Claim 47
Dependent Claim
18 words
The method of claim 16 wherein the phosphoric acid product contains about 0.05 to 0.4 weight percent ammonia.
Claim 48
Dependent Claim
17 words
The method of claim 17 wherein the phosphoric acid contains about 0.1 to 1 weight percent ammonia.
Claim 49
Dependent Claim
19 words
The method of claim 18 wherein the waste water is neutralized to a pH of at least about 4.6.
Claim 50
Dependent Claim
19 words
The method of claim 19 wherein the waste water is neutralized to a pH of at least about 4.6.
Claim 51
Independent Claim
98 words
A method for wet grinding phosphate rock with a phosphate rock-compatible, mineral acid water in corrosion-susceptible milling media to produce a processable phosphate rock slurry comprising preliminarily at least partially neutralizing the mineral acid water by contacting the mineral acid water with phosphate rock containing base-forming constituents to increase the pH of the acid water and render it less corrosive on the milling media, and milling phosphate rock with the at least partially neutralized acid water in the milling media to increase the surface area of rock and produce a processable slurry of finer particles of phosphate rock.
Claim 52
Independent Claim
98 words
A method for wet grinding phosphate rock with a phosphate rock-compatible, mineral acid water in corrosion-susceptible milling media to produce a processable phosphate rock slurry comprising preliminarily at least partially neutralizing the mineral acid water by contacting the mineral acid water with phosphate rock containing base-forming constituents to increase the pH of the acid water and render it less corrosive on the milling media, and milling phosphate rock with the at least partially neutralized acid water in the milling media to increase the surface area of rock and produce a processable slurry of finer particles of phosphate rock.
Claim 53
Dependent Claim
32 words
The method of claim 45 wherein the mineral acid water is a mineral acid waste water produced in the manufacture of wet process phosphoric acid, and the milling media is grinding media.
Claim 54
Dependent Claim
30 words
The method of claim 46 wherein the phosphate rock includes substantial amounts of phosphate rock particles which have been increased in surface area to increase the pH of the mixture.
Claim 55
Dependent Claim
35 words
The method of claim 47 wherein the processable slurry is separated into a coarse fraction and a fine fraction, and the coarse fraction provides the phosphate rock particles which have been increased in surface area.
Claim 56
Dependent Claim
19 words
The method of claim 46 including further neutralizing the mineral acid water with ammonia, caustic or lime prior milling.
Claim 57
Dependent Claim
12 words
The method of claim 49 wherein the further neutralizing agent includes ammonia.
Claim 58
Dependent Claim
17 words
The method of claim 48 including further neutralizing the mineral acid water with ammonia, caustic or lime.
Claim 59
Dependent Claim
12 words
The method of claim 51 wherein the further neutralizing agent includes ammonia.
Claim 60
Dependent Claim
83 words
A method of claim 46 wherein phosphate rock containing base-forming constituents is contacted with a first portion of mineral acid waste water to at least partially neutralize said acid waste water; the partially neutralized mixture of phosphate rock and said first portion of mineral acid waste water is ground to form a slurry of ground rock; and the ground rock slurry is reacted with sulfuric acid and water from a second portion of mineral acid waste water to produce a phosphoric acid product.
Claim 61
Dependent Claim
17 words
The method of claim 53 including further neutralizing the mineral acid water with ammonia, caustic or lime.
Claim 62
Dependent Claim
20 words
The method of claim 54 wherein the acid water is partially neutralized to a pH of at least about 4.
Claim 63
Dependent Claim
11 words
The method of claim 54 wherein the neutralizing agent includes ammonia.
Claim 64
Dependent Claim
18 words
The method of claim 54 wherein the said slurry of ground rock contains about 60 to 80% solids.
Claim 65
Dependent Claim
31 words
The method of claim 54 wherein said acid waste water has a pH of about 0.3 to 3.5 and a P 2 O 5 content of about 0.01 to 3 percent.
Claim 66
Dependent Claim
46 words
The method of claim 53 wherein the phosphate rock slurry from the grinding media is combined with water from a second portion of acid water to form a resulting slurry and ground rock and said resulting slurry is reacted with sulfuric acid to produce phosphoric acid.
Claim 67
Dependent Claim
80 words
The method of claim 59 wherein the solids of said resulting slurry of ground rock is separated into coarser and finer portions; the coarser ground rock portion is contacted with the first portion of mineral acid waste water to at least partially neutralize said waste water; the coarser ground rock portion and said at least partially neutralized waste water are recycled to the grinding step; and the finer ground rock portion is contacted with sulfuric acid to produce phosphoric acid.
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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) | 1986-09-05 | 1987-03-07 | 1987-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-09-05 | 1991-03-07 | 1991-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-09-05 | 1995-03-07 | 1995-09-06 | $7700.00 | Window Closed / Lapsed |