GB2032897A - Ammoniating Phosphoric Acid - Google Patents
Ammoniating Phosphoric Acid Download PDFInfo
- Publication number
- GB2032897A GB2032897A GB7932123A GB7932123A GB2032897A GB 2032897 A GB2032897 A GB 2032897A GB 7932123 A GB7932123 A GB 7932123A GB 7932123 A GB7932123 A GB 7932123A GB 2032897 A GB2032897 A GB 2032897A
- Authority
- GB
- United Kingdom
- Prior art keywords
- reaction mixture
- steam
- ammonium phosphate
- phosphoric acid
- reaction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 15
- 239000011541 reaction mixture Substances 0.000 claims abstract description 37
- 239000006260 foam Substances 0.000 claims abstract description 17
- 239000004254 Ammonium phosphate Substances 0.000 claims abstract description 15
- 235000019289 ammonium phosphates Nutrition 0.000 claims abstract description 15
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims abstract description 13
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims abstract description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000005187 foaming Methods 0.000 claims abstract description 10
- 239000007921 spray Substances 0.000 claims abstract description 7
- 239000007787 solid Substances 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 abstract description 2
- 230000008020 evaporation Effects 0.000 abstract description 2
- 235000011007 phosphoric acid Nutrition 0.000 description 11
- 239000000047 product Substances 0.000 description 9
- 239000012530 fluid Substances 0.000 description 5
- 239000011435 rock Substances 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000011800 void material Substances 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- ZRIUUUJAJJNDSS-UHFFFAOYSA-N ammonium phosphates Chemical class [NH4+].[NH4+].[NH4+].[O-]P([O-])([O-])=O ZRIUUUJAJJNDSS-UHFFFAOYSA-N 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 150000003016 phosphoric acids Chemical class 0.000 description 2
- 239000012265 solid product Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 238000013019 agitation Methods 0.000 description 1
- 239000002518 antifoaming agent Substances 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000004088 foaming agent Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/28—Ammonium phosphates
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Fertilizers (AREA)
Abstract
In reacting ammonia with phosphoric acid in a reaction vessel to form a reaction mixture comprising ammonium phosphate, the reaction mixture is allowed to foam whereby there is formed a foaming reaction mixture comprising steam and ammonium phosphate; and steam and ammonium phosphate are discharged from the reaction vessel through a common outlet. Preferably the ammoniation is carried out under pressure and the foam reaction mixture is discharged via a spray nozzle into a zone of lower pressure where water is evolved spontaneously, e.g. by flash evaporation as the product is sprayed, to give a solid particulate product.
Description
SPECIFICATION
Phosphatic Fertilizer
The present invention relates to a process, notably a process for preparing ammonium phosphates.
In our British Patent No. 1,081,296 we have described and claimed a process for preparing solid ammonium phosphates which comprises reacting phosphoric acid, for example wet process phosphoric acid containing less than 60% P205 by weight, with ammonia gas under superatmospheric pressure to give a fluid ammonium phosphate solution at its boiling point containing 4% to 15% by weight of water, and subsequently expelling the resulting fluid ammonium phosphate solution into a zone at ambient pressures thereby reducing its water content and giving a solid product. Such a process is conventionally carried out in a stirred reactor with a steam outlet and a separate product outlet.The steam from the process is a valuable energy source and the reaction vessel is designed so as to facilitate separation of the steam from the reaction mixture, e.g. by providing a large steam disengagement zone above the reaction mixture. Furthermore, it has been considered essential to avoid the use of certain phosphoric acids which could form foams due to impurities therein since the formation of a foam phase in the reaction vessel would have hindered efficient disengagement of the steam from the reaction mixture.
Surprisingly, we have now found that the reaction mixture during the ammoniation of wet process phosphoric acid can with advantage exist as a foam of reaction mixture and steam and not as two distinct phases. Such a foam readily lends itselt to discharge through a single outlet.
Discharging the reaction mixture together with the steam would have been expected (on the hitherto held belief that they existed as two separate and distinct phases) to have been impractical and difficult to control. Furthermore, since the steam is evolved at a larger volume rate than the fluid reaction product, it would have been expected that the material discharging through a common outlet would have been in the form of bursts of steam with intermittent batches of fluid. Such a discharge would have been expected to lead to erratic variations of pressure within the reaction vessel and uneven discharge of the product.
Surprisingly, the foam reaction mixture can be readily discharged through a single outlet with simple controls and can be sprayed satisfactorily to give a dry product. The steam in the foam reduces the risk of premature solidification of the foam due to cooling before spraying. The steam also aids spraying of the product and may inhibit solids build-up on the spray nozzle.
The ability to discharge the steam with the fluid reaction mixture has the advantage that there is no longer need to provide a steam disengagement zone (saving in capital cost of the plant) and also enables one to use a wider range of phosphoric acids that had hitherto been considered possible. Also, there is no need to incorporate foam breakers or similar devices into the reaction vessel nor to incoporate anti-foaming agents into the reaction mixture.
Accordingly the present invention provides a process which comprises reacting ammonia with phosphoric acid in a reaction vessel to form a reaction mixture comprising ammonium phosphate characterised in that the reaction mixture is allowed to foam whereby there is formed a foaming reaction mixture comprising steam and ammonium phosphate; and in that steam and ammonium phosphate are discharged from the reaction vessel through a common outlet. Preferably the ammoniation is carried out under pressure and the foam reaction mixture is discharged via a spray nozzle into a zone of lower pressure where water is evolved spontaneously, e.g. by flash evaporation as the product is sprayed, to give a solid particulate product.
The term "foam" is used herein and in the claims to denote that, due to the presence of steam therein, the density of the overall reaction mixture is less than 70%, preferably 25 to 50%, of the density of a similar reaction mixture containing no steam therein.
Within reason, the reaction mixture can be more highly foamed than indicated. However, increasing the level of foaming reduces the through-put of the reaction vessel and may result in a commercially unacceptable reduction in plant capacity.
The ammoniation of the phosphoric acid is preferably carried out by passing gaseous ammonia into wet process phosphoric acid in an agitated reactor. The agitation can be achieved mechanically and/or spontaneously due to formation of bubbles in the liquid phase of the reaction mixture. As indicated above, the reaction is preferably carried out under pressure, e.g. at from 0.5 to 5 kg/cm2 gauge. Thus, for example the ammoniation is carried out in the manner described in our British Patent No. 1,081,296 or variations thereof, e.g. BP 1,191,497.
The phosphoric acid for present use will typically be a wet process phosphoric acid. Since it is desired to form a foaming reaction mixture, it is not necessary to use only those acids which have been treated to reduce the foaming tendancies thereof as hitherto. Thus, suitable acids for present use include those obtained from rocks from the North African and USA deposits, e.g. Morocco, Algeria, Senegal, Tunisia, Sahara or
Florida. If desired a foaming agent can be incorporated into the acid (during or after its manufacture) to aid foam formation during ammoniation.
The outlet from the reaction mixture takes any appropriate form. However, we have found that the use of a stand pipe type outlet offers advantages in that the outlet also acts as a weir to maintain the level of reaction mixture in the vessel at a desired height. Preferably, the stand pipe has a V notch type weir. The outlet is also provided with means for retaining the desired pressure within the reactor. This means is, for example, a control valve on the reactor discharge activated by the reactor pressure. Alternatively, where the reaction mixture is to be sprayed into a zone of lower pressure, e.g. into a void tower or onto particles in a granulator, an adjustable orifice in the spray nozzle can be used to provide the necessary back pressure to maintain the desired pressure in the reaction vessel. In a further alternative, steam may be injected upstream of the spray nozzle.Due to the fact that the mixture being discharged from the reactor contains more steam than with a conventional process, the mass flow of air in the zone of lower pressure may be reversed. Thus, for example the bir flow in a void tower may be down the tower rather than up. It may therefore be necessary to put any cyclones or other effluent treatment at the base of the tower.
The invention will now be illustrated by the following Examples in which all parts and percentages are by weight unless specified otherwise.
Example 1
Moroccan wet process phosphoric acid (50%
P205) was reacted with liquid ammonia in a stirred reactor operated at a temperature of 160--1700C and at a pressure of 2.1 bar achieved by appropriate sizing of the nozzle through which the product was discharged and/or by injecting further steam into the reaction vessel or the spray nozzle. The product was discharged at a pH of 4.0 into a void tower operating at ambient temperature and pressure to give a particulate solid product. The product was discharged from the reaction vessel through a single stand pipe outlet. Satisfactory operation was achieved at production rates of between 3 and 12 tons per hour, even though the reaction mixture was in the form of a foam having a density approximately 50% of that of an all liquid reaction mixture, as determined by level sensors in the reaction vessel.
Example 2
A batch process was carried out in a thermosyphon reaction vessel under the same conditions as in Example 1 using acids derived from Florida rock and from Yousoufia rock. The foaming reaction mixtures were sprayed into a void tower as in Example 1 via a stand-pipe outlet from the reaction vessel. In the case of Florida rock the density of the foaming reaction mixture was 40% of that of an all liquid reaction mixture and in the case of Yousoufia rock the density of the foam fluctuated between 10 and 30% of that of an all liquid reaction mixture.
Claims (9)
1. A process for ammoniating phosphoric acid which comprises reacting ammonia with phosphoric acid in a reaction vessel to form a reaction mixture comprising ammonium phosphate characterised in that the reaction mixture is allowed to foam whereby there is formed a foaming reaction mixture comprising steam and ammonium phosphate; and in that steam and ammonium phosphate are discharged from the reaction vessel through a common outlet.
2. A process as claimed in claim 1 characterised in that the foaming reaction mixture has a density 25 to 50% of the density a similar mixture containing no steam.
3. A process as claimed in claim 1 characterised in that the phosphoric acid is a wet process phosphoric acid which has not been treated so as to reduce the foaming tendancies thereof.
4. A process as claimed in claim 1 characterised in that the reaction is carried out under pressure and the reaction mixture is discharged into a zone at lower pressure whereby water is evolved spontaneously from the reaction mixture to give a solid particulate product.
5. A process as claimed in claim 1 characterised in that the common outlet is provided by a stand pipe in the reaction vessel.
6. A process as claimed in claim 5 characterised in that the stand pipe discharges the steam and ammonium phosphate via a spray nozzle.
7. A process as claimed in claim 1 substantially as hereinbefore described.
8. A process substantially as hereinbefore described in the Examples.
9. Ammonium phosphate whenever produced by a process as claimed in any one of the preceding claims.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7932123A GB2032897B (en) | 1978-10-07 | 1979-09-17 | Ammoniating phosphoric acid |
| ES484761A ES484761A0 (en) | 1978-10-07 | 1979-10-05 | PROCEDURE FOR AMMONIATING PHOSPHORIC ACID |
| IT26295/79A IT1125448B (en) | 1978-10-07 | 1979-10-05 | PROCEDURE FOR PREPARING AMMONIUM PHOSPHATES AND PHOSPHATES SO OBTAINED |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7839732 | 1978-10-07 | ||
| GB7932123A GB2032897B (en) | 1978-10-07 | 1979-09-17 | Ammoniating phosphoric acid |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2032897A true GB2032897A (en) | 1980-05-14 |
| GB2032897B GB2032897B (en) | 1982-08-11 |
Family
ID=26269116
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7932123A Expired GB2032897B (en) | 1978-10-07 | 1979-09-17 | Ammoniating phosphoric acid |
Country Status (3)
| Country | Link |
|---|---|
| ES (1) | ES484761A0 (en) |
| GB (1) | GB2032897B (en) |
| IT (1) | IT1125448B (en) |
-
1979
- 1979-09-17 GB GB7932123A patent/GB2032897B/en not_active Expired
- 1979-10-05 ES ES484761A patent/ES484761A0/en active Granted
- 1979-10-05 IT IT26295/79A patent/IT1125448B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| ES8102055A1 (en) | 1980-12-16 |
| ES484761A0 (en) | 1980-12-16 |
| IT1125448B (en) | 1986-05-14 |
| GB2032897B (en) | 1982-08-11 |
| IT7926295A0 (en) | 1979-10-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |