CN116443830A - Preparation and application technology of impurity remover for producing monoammonium phosphate ammoniated slurry system by wet-process phosphoric acid - Google Patents
Preparation and application technology of impurity remover for producing monoammonium phosphate ammoniated slurry system by wet-process phosphoric acid Download PDFInfo
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- CN116443830A CN116443830A CN202310268377.4A CN202310268377A CN116443830A CN 116443830 A CN116443830 A CN 116443830A CN 202310268377 A CN202310268377 A CN 202310268377A CN 116443830 A CN116443830 A CN 116443830A
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- phosphoric acid
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- ammonium fluoride
- acid
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 118
- 239000002002 slurry Substances 0.000 title claims abstract description 94
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims abstract description 59
- 239000012535 impurity Substances 0.000 title claims abstract description 52
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 title claims abstract description 33
- 235000019837 monoammonium phosphate Nutrition 0.000 title claims abstract description 33
- 239000006012 monoammonium phosphate Substances 0.000 title claims description 22
- 238000002360 preparation method Methods 0.000 title abstract description 10
- 238000005516 engineering process Methods 0.000 title description 2
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 claims abstract description 65
- 239000002253 acid Substances 0.000 claims abstract description 46
- 238000006243 chemical reaction Methods 0.000 claims abstract description 46
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000000706 filtrate Substances 0.000 claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 claims abstract description 16
- 239000012065 filter cake Substances 0.000 claims abstract description 14
- 238000004176 ammonification Methods 0.000 claims description 27
- 238000002156 mixing Methods 0.000 claims description 25
- 238000001914 filtration Methods 0.000 claims description 17
- 238000006386 neutralization reaction Methods 0.000 claims description 15
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 229910019142 PO4 Inorganic materials 0.000 claims description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 4
- 239000010452 phosphate Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 3
- 239000007790 solid phase Substances 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 34
- 239000000047 product Substances 0.000 abstract description 25
- 238000002425 crystallisation Methods 0.000 abstract description 18
- 230000008025 crystallization Effects 0.000 abstract description 18
- 229910052782 aluminium Inorganic materials 0.000 abstract description 17
- 239000011777 magnesium Substances 0.000 abstract description 16
- 239000002244 precipitate Substances 0.000 abstract description 14
- 229910052742 iron Inorganic materials 0.000 abstract description 13
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 8
- 229910052749 magnesium Inorganic materials 0.000 abstract description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract description 7
- 239000003795 chemical substances by application Substances 0.000 abstract description 6
- 239000006227 byproduct Substances 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 4
- 230000000903 blocking effect Effects 0.000 abstract description 2
- 229910021529 ammonia Inorganic materials 0.000 description 8
- 230000008901 benefit Effects 0.000 description 5
- 239000012452 mother liquor Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 239000000741 silica gel Substances 0.000 description 4
- 229910002027 silica gel Inorganic materials 0.000 description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229910017958 MgNH Inorganic materials 0.000 description 2
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002686 phosphate fertilizer Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 239000005955 Ferric phosphate Substances 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229940032958 ferric phosphate Drugs 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 1
- 150000002680 magnesium Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/16—Halides of ammonium
- C01C1/162—Ammonium fluoride
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention provides a method for producing crystalline ammonium dihydrogen phosphate from wet-process phosphoric acid ammoniated slurry, and relates to the technical field of ammonium dihydrogen phosphate preparation. The invention prepares the impurity removing agent ammonium fluoride of the ammoniated slurry by utilizing the reaction of byproduct fluosilicic acid and liquid ammonia, the method is reliable, the material is convenient, the manufacturing cost is lower, and the impurity removing agent ammonium fluoride and the impurities of iron, aluminum and magnesium in the ammoniated slurry generate (Fe, al) Mg (NH) 4 ) 2 (HPO 4 ) 2 F 2 The complex precipitates, and the complex precipitates are filtered and then are discarded along with a filter cake, so that the filtrate is purer, the impurity removing effect is obvious, the impurity discarding rate is improved, the system scaling blocking rate is slowed down, and the device operation rate is improved; increasing yield; the crystallization condition is improved, and the product purity is improved.
Description
Technical Field
The invention relates to the technical field of ammonium dihydrogen phosphate preparation, in particular to a method for producing crystalline ammonium dihydrogen phosphate from wet-process phosphoric acid ammoniated slurry.
Background
Crystalline monoammonium phosphate (also known as monoammonium phosphate) has found wide application in the agricultural field. At present, the crystallization type monoammonium phosphate mainly adopts the following production process: the concentration of desulphurised and dearsenated from the phosphoric acid plant was 45% (P 2 O 5 % by weight), the pretreated phosphoric acid (also called wet phosphoric acid) and part of ammonium dihydrogen phosphate crystallization mother liquor and process condensate water are mixed and prepared into 18-25% of prepared acid, the diluted prepared acid enters a first-stage ammonification reactor to carry out first-stage ammonification reaction with ammonia, the ammonia acid ratio value (the ratio of the volume flow of the acid to the mass flow of the ammonia) is set, the pH value of the reaction is controlled to be 2.5-3.0, slurry formed by the first-stage ammonification reaction enters a second-stage ammonification reactor to carry out further neutralization reaction with the ammonia, and ammoniated slurry with the end point pH value of 4.0-4.3 is generated, wherein the main component in the ammoniated slurry is ammonium dihydrogen phosphate solution, and phosphate impurity sediment, sulfate and the like. The ammoniated slurry is filtered by a vertical filter press and a plate frame filter, a filter cake is formed after a precipitate generated by the reaction is filtered, filtrate formed by the filtration becomes ammonium dihydrogen phosphate solution, the filtrate enters a crystallization system after evaporation and concentration, the concentrated slurry is evaporated and cooled in a crystallizer for crystallization, the crystal slurry is taken out from the bottom of the crystallizer for centrifugal separation, the separated crystal is fluidized and dried to form a product, and part of the centrifugal mother liquor is returned to an acid tank or is sent to other phosphate fertilizer devices for recycling, wherein the technological process is shown in figure 1.
The wet-process phosphoric acid contains some impurities (main components and impurity contents are shown in table 1) such as iron, aluminum, magnesium, sulfur and the like, and if the main impurities are not removed in a large amount in the ammonification reaction process, the main impurities are carried out of the system along with a filter cake, and then the filtrate is carried into monoammonium phosphate solution and remains in the system to generate complex complexes, and when the complex complexes reach a certain concentration, flocculent or gelatinous precipitates are often separated out, so that the purity of the product is influenced, the concentration equipment is scaled, and the yield and the operating rate of the device are influenced; moreover, the rising of the impurities can cause the crystallization mother liquor to become sticky, so that the crystallization habit is arranged in disorder, the crystallization effect is affected, the centrifugal separation of the product is difficult, and the yield and quality are affected.
At present, there are two main types of impurity removal techniques used at home and abroad:
one is to carry out deep purification on wet phosphoric acid, generally adopting organic solvent extraction to obtain purer wet phosphoric acid, and then producing monoammonium phosphate by using the purified phosphoric acid to obtain purer monoammonium phosphate which is often used for producing battery grade monoammonium phosphate products, and has higher production cost and more complex production flow.
The other is that after the ammoniated slurry is filtered, the filtrate is used for removing Fe, mg and Al metal ions in the filtrate by an ion exchange method, and the method is immature in process and is difficult to apply in industrial production.
Disclosure of Invention
The invention aims to provide a method for removing impurities in an ammonification slurry system for producing monoammonium phosphate by wet-process phosphoric acid, which can be used for efficiently removing iron, aluminum and magnesium impurities in the ammonification slurry, improving crystallization conditions, improving product purity, and is simple in flow, low in cost and suitable for industrial production.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for removing impurities in an ammonification slurry system for producing monoammonium phosphate by wet-process phosphoric acid, which comprises the following steps:
mixing fluosilicic acid solution with liquid ammonia for neutralization reaction to obtain ammonium fluoride slurry;
blending wet phosphoric acid to obtain blended acid;
mixing the blended acid with ammonia gas to perform a primary ammonification reaction to obtain primary ammonification slurry;
mixing the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas to perform a second-stage ammoniation reaction to obtain a second-stage ammoniated slurry;
filtering the two-stage ammoniated slurry to obtain a filter cake and filtrate;
for 1m 3 The volume usage of the first ammoniated slurry obtained by wet phosphoric acid is as follows: v=kx [ ρ ] 1 ×(C 1 /102+C 2 /160)]/C 3 /ρ 2 Formula 1;
in formula 1: v-fluorinationVolume of ammonium solution, m 3 ；
6.0 to 8.0K-factor;
ρ 1 density of phosphoric acid by wet process, kg/m 3 ；
C 1 -Al in wet phosphoric acid 2 O 3 Mass concentration;
C 2 fe in phosphoric acid by wet process 2 O 3 Mass concentration;
C 3 -mass concentration of ammonium fluoride in the ammonium fluoride slurry;
ρ 2 density of ammonium fluoride slurry, kg/m 3 ；
102—Al 2 O 3 A formula weight;
160—Fe 2 O 3 the formula weight.
Preferably, by H 2 SiF 6 The mass concentration of the fluosilicic acid solution is 15-18 percent.
Preferably, the fluosilicic acid solution is obtained by absorbing tail gas generated in the process of decomposing phosphate ore by sulfuric acid and concentrating phosphoric acid by water, and then filtering solid phase matters in the obtained absorption slurry by a membrane.
Preferably, the neutralization reaction temperature is 75-83 ℃.
Preferably, the end point pH of the neutralization reaction is 8.0 to 8.3.
Preferably, the pH value of the first-stage ammonification reaction is 2.5-3.0, and the reaction time is 60-70 minutes.
Preferably, the end pH value of the two-stage ammoniation reaction is 4.0-4.3.
Preferably, the main components and impurity contents of the wet phosphoric acid are shown in table 1:
TABLE 1 Main component and impurity content of Wet phosphoric acid
| Project | Mass percent is percent | Number of moles per unit volume (kmol/m) 3 ) |
| H 3 PO 4 Concentration (in P) 2 O 5 % meter | 44.5～45.5 | - |
| Solid content | 0.5～1.0 | - |
| F content | 1.2～1.4 | 1.01～1.19 |
| MgO | 1.66～1.8 | 0.63～0.70 |
| Fe 2 O 3 | 1.05～1.2 | 0.1～0.12 |
| Al 2 O 3 | 1.3～1.8 | 0.19～0.27 |
| As | 0.00365～0.004 | - |
| SO 4 2- | 0.6～1.0 | - |
。
Preferably, at P 2 O 5 The concentration of the blended acid is 18-25% by mass percent.
Preferably, after obtaining the filter cake and the filtrate, crystallizing the filtrate to obtain crystalline monoammonium phosphate.
The invention prepares the ammoniated slurry impurity remover ammonium fluoride by utilizing the reaction of fluosilicic acid solution and liquid ammonia, and silica gel (SiO) generated by the reaction of fluosilicic acid and liquid ammonia 2 ) Can be filtered together with the two-stage ammoniated slurry, and is carried out of the system along with a filter cake, and the impurity removing agent ammonium fluoride and iron, aluminum and magnesium impurities in the ammoniated slurry generate (Fe, al) Mg (NH) 4 ) 2 (HPO 4 ) 2 F 2 The complex precipitates, and the filtered complex precipitates are removed along with the filter cake, so that the filtrate is purer, the aim of removing impurities is fulfilled, the removal rate of the impurities is improved, the rate of system scaling blockage is slowed down, and the operation rate of the device is improved; increasing yield; the crystallization condition is improved, and the product purity is improved.
Furthermore, the fluosilicic acid solution is a byproduct of wet phosphoric acid, and has the advantage of convenient material acquisition.
Drawings
FIG. 1 is a flow chart of a prior art process for producing crystalline monoammonium phosphate;
FIG. 2 is a flow chart of a method for producing crystalline monoammonium phosphate from a wet-process phosphoric acid ammoniated slurry according to the invention.
Detailed Description
The invention provides a method for removing impurities in an ammonification slurry system for producing monoammonium phosphate by wet-process phosphoric acid, which comprises the following steps:
mixing fluosilicic acid solution with liquid ammonia for neutralization reaction to obtain ammonium fluoride slurry;
blending wet phosphoric acid to obtain blended acid;
mixing the blended acid with ammonia gas to perform a primary ammonification reaction to obtain primary ammonification slurry;
mixing the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas to perform a second-stage ammoniation reaction to obtain a second-stage ammoniated slurry;
filtering the two-stage ammoniated slurry to obtain a filter cake and filtrate;
for 1m 3 The volume usage of the first ammoniated slurry obtained by wet phosphoric acid is as follows: v=kx [ ρ ] 1 ×(C 1 /102+C 2 /160)]/C 3 /ρ 2 Formula 1;
in formula 1: v-ammonium fluoride solution volume, m 3 ；
6.0 to 8.0K-factor;
ρ 1 density of phosphoric acid by wet process, kg/m 3 ；
C 1 -Al in wet phosphoric acid 2 O 3 Mass concentration;
C 2 fe in phosphoric acid by wet process 2 O 3 Mass concentration;
C 3 -mass concentration of ammonium fluoride in the ammonium fluoride slurry;
ρ 2 density of ammonium fluoride slurry, kg/m 3 ；
102—Al 2 O 3 A formula weight;
160—Fe 2 O 3 the formula weight.
The invention mixes fluosilicic acid solution and liquid ammonia to perform neutralization reaction to obtain ammonium fluoride slurry.
In the present invention, H is 2 SiF 6 The mass concentration of the fluorosilicic acid solution is preferably 15 to 18%, more preferably 16 to 17%. In the present invention, the fluorosilicic acid solution is preferably obtained by filtering a solid phase substance in an absorption slurry obtained by absorbing tail gas generated in the process of decomposing phosphate ore with sulfuric acid and concentrating phosphoric acid with water. In the invention, F in the tail gas is SiF 4 In the form of a gel. The invention utilizes the byproduct fluorine generated by wet phosphoric acidThe silicic acid solution is used for preparing the ammonium fluoride, so that the materials are convenient to obtain and the price is low. Compared with the traditional preparation process of ammonium fluoride, namely sulfuric acid (H 2 SO 4 ) Decomposing fluorite (CaF) 2 ) Hydrogen Fluoride (HF) is generated and ammonia (NH) 3 ) Reaction with hydrogen fluoride to give ammonium fluoride (NH) 4 F) The solution is concentrated, crystallized and dried to obtain the finished product of ammonium fluoride, and the invention has lower cost and reduces the risk of ammonium fluoride production.
In the present invention, the temperature of the neutralization reaction is preferably 75 to 83 ℃, more preferably 75 to 80 ℃; the end pH of the neutralization reaction is preferably 8.0 to 8.3. According to the invention, the liquid ammonia is used for preparing the ammonium fluoride, and can better absorb the heat released by the reaction of the fluosilicic acid and the ammonia, so that the reaction temperature is controlled. The invention has no special requirement on the dosage of the liquid ammonia, and ensures that the final pH value is reached. In the invention, fluosilicic acid is strong acid, is extremely easy to generate rapid neutralization reaction with ammonia, and generates ammonium fluoride and silica gel (SiO) when the pH value reaches 8.0-8.3 2 ) The specific reaction equation is as follows:
H 2 SiF 6 +6NH 3 +2H 2 O＝6NH 4 F+SiO 2
the invention prepares wet phosphoric acid to obtain the prepared acid.
In the present invention, the main components and impurity contents of the wet process phosphoric acid are preferably shown in table 1:
TABLE 1 Main component and impurity content of Wet phosphoric acid
| Project | Mass percent is percent | Number of moles per unit volume (kmol/m) 3 ) |
| H 3 PO 4 Concentration (in P) 2 O 5 % meter | 44.5～45.5 | - |
| Solid content | 0.5～1.0 | - |
| F content | 1.2～1.4 | 1.01～1.19 |
| MgO | 1.66～1.8 | 0.63～0.70 |
| Fe 2 O 3 | 1.05～1.2 | 0.1～0.12 |
| Al 2 O 3 | 1.3～1.8 | 0.19～0.27 |
| As | 0.00365～0.004 | - |
| SO 4 2- | 0.6～1.0 | - |
In the present invention, the density of the wet process phosphoric acid is preferably 1520 to 1550kg/m 3 。
The invention has no special requirements on the blending process, and the blending process well known in the art can be adopted. Specifically, in the present invention, the blending preferably includes: mixing the wet phosphoric acid with part of ammonium dihydrogen phosphate crystallization mother liquor and condensed water. In the present invention, P is 2 O 5 The concentration of the blending acid is preferably 18-25% by mass.
After the blended acid is obtained, the blended acid is mixed with ammonia gas to perform a first-stage ammonification reaction, so that a first-stage ammonification slurry is obtained. In the present invention, the pH value of the one-stage ammoniation reaction is preferably 2.5 to 3.0, and the time is preferably 60 to 70 minutes. The pH value of the primary ammonification reaction is preferably controlled in the above range by the flow rate of the blended acid and the ammonia gas.
In the present invention, the purpose of the one-stage ammoniation reaction is to:
the method has the advantages that the ammonification reaction speed is slowed down by sectional ammonification, and the reaction is prevented from being too violent.
The coarse impurity particles are formed conveniently, filtering is facilitated, fine particles are prevented from penetrating and filtering, filtering speed is improved, and impurity discarding rate is improved.
The ammonification reaction temperature is controlled to be in an optimal state, and the service life of the filtering equipment is prolonged.
After the ammonium fluoride slurry and the first-stage ammoniated slurry are obtained, the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas are mixed for a second-stage ammoniation reaction to obtain the second-stage ammoniated slurry.
In the present invention, 1m is aimed at 3 The volume usage of the first ammoniated slurry obtained by wet phosphoric acid is as follows: v=kx [ ρ ] 1 ×(C 1 /102+C 2 /160)]/C 3 /ρ 2 Formula 1;
in formula 1: v-ammonium fluoride solution volume, m 3 ；
6.0 to 8.0K-factor;
ρ 1 density of phosphoric acid by wet process, kg/m 3 ；
C 1 -Al in wet phosphoric acid 2 O 3 Mass concentration;
C 2 fe in phosphoric acid by wet process 2 O 3 Mass concentration;
C 3 -mass concentration of ammonium fluoride in the ammonium fluoride slurry;
ρ 2 density of ammonium fluoride slurry, kg/m 3 ；
102—Al 2 O 3 A formula weight;
160—Fe 2 O 3 the formula weight.
In the present invention, the end pH of the two-stage ammoniation reaction is preferably 4.0 to 4.3.
F in wet phosphoric acid is mainly fluosilicic acid (H 2 SiF 6 ) Exists in a form; SO (SO) 4 2- Mainly by H 2 SO 4 In the form, the diluted formulated acid is contacted and mixed with ammonia to react as follows:
①H 3 PO 4 +NH 3 →NH 4 H 2 PO 4
②H 2 SO 4 +NH 3 +NH 4 H 2 PO 4 →NH 4 HSO 4 ·NH 4 H 2 PO 4
③H 2 SiF 6 +2NH 3 →(NH 4 ) 2 SiF 6
④(Fe,Al) 3 (H 2 O)H 8 (PO 4 ) 6 ·6H 2 O+NH 3 →(Fe,Al) 3 NH 4 H 8 (PO 4 ) 6 ·6H 2 O+H 2 O
⑤(Fe,Al) 3 (H 3 O)H 8 (PO 4 ) 6 ·6H 2 O+3Mg(H 2 PO 4 ) 2 +9NH 3 +H 2 SiF 6 →(Fe,Al)MgNH 4 (HPO 4 ) 2 F 2 +6NH 4 H 2 PO 4 +SiO 2 +5H 2 O
⑥NH 4 HSO 4 ·NH 4 H 2 PO 4 +NH 3 →(NH 4 ) 2 SO 4 +NH 4 H 2 PO 4
⑦6(Fe,Al) 3 MgNH 4 (HPO 4 ) 2 F 2 +(NH 4 ) 2 SiF 6 +4NH 3 +2H 2 O→6(Fe,Al)Mg(NH 4 ) 2 (HPO 4 ) 2 F 2 +SiO 2
⑧Mg(H 2 PO 4 ) 2 +NH 3 →MgHPO 4 +NH 4 H 2 PO 4
⑨(Fe,Al)NH 4 H 8 (PO 4 ) 6 ·6H 2 O+2NH 3 →3(Fe,Al)NH 4 (HPO 4 ) 2 ·0.5H 2 O+5.5H 2 O
the above reaction forms water-soluble compounds (reactions (1) to (3)) and citrate-soluble complexes (reactions (4) to (5)) at pH of about 2.5; when the pH value is raised to 4.35, iron, aluminum and magnesium complexes are formed (reactions (7) to (9)).
In the present invention, the precipitate obtained when wet-process phosphoric acid was aminated to different pH is shown in Table 2.
TABLE 2 Wet-process phosphoric acid ammoniation of precipitate to different pH values
As can be seen from Table 2, the complex precipitate of magnesium is formed only when the pH is not less than 3.5. Due to F in wet phosphoric acid - Limited and affected by the pH conditions of the ammoniation reaction, leading to F in wet-process phosphoric acid - The amount of the precipitated impurities cannot be satisfied. The invention provides enough F-and ensures that a magnesium composite precipitate, NH, is formed in a proper pH range by adding ammonium fluoride slurry during the two-stage ammoniation reaction 4 F has higher solubility and ionization degree in water solution, and can provide more F - Is beneficial to the abandoning and removing of impurity iron, aluminum and magnesium, and leads to the generation of (Fe, al) Mg (NH) 4 ) 2 (HPO 4 ) 2 F 2 The reaction balance of (2) moves rightwards, and the reaction is more completeThe impurity removing effect is better.
In addition, the generated ammonium fluoride slurry (comprising ammonium fluoride and silica gel) is added into the first-stage ammoniated slurry to perform a second-stage ammoniation reaction, the ammonium fluoride reacts with impurities of the slurry to generate precipitate, and the precipitate and the silica gel enter an ammoniated slurry filtering system to filter and remove the impurities, so that the utilization effect is achieved.
After the second-stage ammoniated slurry is obtained, the second-stage ammoniated slurry is filtered to obtain a filter cake and filtrate.
The invention has no special requirement on the filtration, and adopts a filtration mode well known in the field, specifically, the filtration is carried out by a vertical filter press and a plate-and-frame filter in sequence.
After the filtrate is obtained, the filtrate is preferably crystallized to obtain crystalline monoammonium phosphate.
The crystallization process is not particularly limited in the present invention, and crystallization processes well known in the art, such as evaporative cooling crystallization, may be employed. After the crystallization is finished, the crystal slurry is preferably subjected to centrifugal separation, and the separated crystals are fluidized and dried to form a product, and part of the centrifugal mother liquor is returned to an acid tank or is sent to other phosphate fertilizer devices for recycling.
FIG. 2 is a flow chart of a method for producing crystalline monoammonium phosphate from a wet-process phosphoric acid ammoniated slurry according to the invention. As shown in fig. 2, mixing fluosilicic acid solution with liquid ammonia to perform neutralization reaction to obtain ammonium fluoride slurry; blending wet phosphoric acid to obtain blended acid; mixing the blended acid with ammonia gas to perform a primary ammonification reaction to obtain primary ammonification slurry; mixing the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas to perform a second-stage ammoniation reaction to obtain a second-stage ammoniated slurry; filtering the two-stage ammoniated slurry to obtain a filter cake and filtrate; crystallizing the filtrate to obtain crystalline ammonium dihydrogen phosphate.
The method for producing crystalline monoammonium phosphate from the wet-process phosphoric acid ammoniated slurry according to the invention will be described in detail with reference to examples, but they should not be construed as limiting the scope of the invention.
Examples 1, 3, 5 and 6
Mixing fluosilicic acid solution with liquid ammonia for neutralization reaction to obtain ammonium fluoride slurry;
blending wet phosphoric acid to obtain blended acid;
mixing the blended acid with ammonia gas to perform a primary ammonification reaction to obtain primary ammonification slurry;
mixing the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas to perform a second-stage ammoniation reaction to obtain a second-stage ammoniated slurry;
filtering the two-stage ammoniated slurry to obtain a filter cake and filtrate;
crystallizing the filtrate to obtain crystalline ammonium dihydrogen phosphate.
Experiment No. 2, 4
The crystallization type monoammonium phosphate is prepared by adopting a traditional process method, and the specific difference between the crystallization type monoammonium phosphate and the embodiment is that ammonium fluoride slurry is not added during the two-stage ammonification reaction.
The density of wet process phosphoric acid used below was 1530kg/m 3 The composition is shown in table 3 below.
TABLE 3 composition of Wet phosphoric acid runs No. 1-6
| Project | Unit (B) | The components are% | Number of moles per unit volume (kmol/m) 3 ) |
| P 2 O 5 | ％ | 44.76 | - |
| Solid content | ％ | 0.74 | - |
| F content | ％ | 1.2 | 0.99 |
| MgO | ％ | 1.66 | 0.64 |
| Fe 2 O 3 | ％ | 1.14 | 0.138 |
| Al 2 O 3 | ％ | 1.34 | 0.20 |
| As | mg/kg | 36.5 | - |
| SO 4 2- | ％ | 0.66 | - |
。
Preparation of ammonium fluoride slurry:
the fluosilicic acid solution and liquid ammonia are mixed for neutralization reaction, and ammonium fluoride slurry is obtained, and specific preparation conditions and the quality of the ammonium fluoride slurry are shown in Table 4.
TABLE 4 preparation conditions and quality of ammonium fluoride slurry
As can be seen from the data in Table 4, the prepared ammonium fluoride slurry has stable ammonium fluoride content and stable index, and can meet the quality requirement of the impurity removal reaction of the ammoniated slurry.
Experiment nos. 1 to 6 first-stage ammoniation and second-stage ammoniation conditions:
table 5 comparison of impurity content of filtrate under the conditions of first-stage and second-stage ammoniation of experiment Nos. 1 to 6
Note that: the addition amount of the ammonium fluoride slurry is 0.0639-0.0853 m according to the formula 1 3 Per ton of product;
the minimum theoretical addition of the folded ammonium fluoride is as follows:
0.0639m 3 per ton of product X1072 kg/m 3 X 25.03% = 17.1 kg/ton product;
the maximum theoretical addition amount of the folded ammonium fluoride is as follows:
0.0853m 3 per ton of product X1072 kg/m 3 X 25.03% = 22.9 kg/ton product;
thus, the theoretical addition amount of ammonium fluoride is 17.1-22.9 kg/ton of product.
Impurity rejection rate calculation:
the impurity rejection rate was measured and calculated under the fixed process conditions in table 5, and the specific results are shown in table 6.
TABLE 6 impurity rejection rate measurement calculation table
As can be seen from Table 6, since the rejection of Fe and Al is sensitive to pH, the rejection rate is high, the rejection rate after adding ammonium fluoride is improved, the rejection rate of Mg is obviously improved by a proper addition amount of the impurity removing agent, the rejection rate of Mg is about 34% when no impurity is added, and the rejection rate is about 62% when 20 kg/ton of product (folded purity) is normally added.
And the product quality is improved:
an experiment of adding and removing impurities of ammonium fluoride in a production system is carried out in 2021 for 9 to 11 months according to the thickness of 0.3m 3 And comparing and verifying the two modes of adding 20 kg/ton of product after the purification and not adding, and examining the effect of ammonium fluoride addition on product quality improvement, wherein the specific conditions are shown in Table 7.
TABLE 7 comparison of the effects of ammonium fluoride addition on product quality improvement
As can be seen from Table 7, after ammonium fluoride is added normally, the main content of the product is improved by 0.8-0.9%, the impurity water insoluble substances are reduced by 0.22% on average, the Mg content in the product is reduced by 877Mg/kg on average, the product quality is obviously improved, and the product is obviously improved from the original use of satisfying facility agriculture to the present use of satisfying the production of ferric phosphate in a group.
The economic benefit analysis results are shown in Table 8:
table 8 table for calculating production cost of ammonium fluoride
And (3) calculating economic benefits:
the minimum price of the ammonium fluoride market is calculated according to 12500 yuan/ton, and the self-produced ammonium fluoride is different from the purchase price:
12500-1993.9 =10506 yuan/ton.
The consumption of ammonium fluoride is 12kg per ton of monoammonium phosphate, the annual output is 50000 tons, and the annual demand of ammonium fluoride is: 50000×12/1000=600 tons/year.
The expenditure is reduced every year: 600 x 10506= 630.3 ten thousand yuan.
As can be seen from the effect data of the above examples and comparative examples, the method for preparing the impurity removing agent ammonium fluoride of the ammoniated slurry by utilizing the reaction of byproduct fluosilicic acid and liquid ammonia is reliable, the material is convenient to obtain, the manufacturing cost is low, and the impurity removing agent ammonium fluoride and the impurities of iron, aluminum and magnesium in the ammoniated slurry generate (Fe, al) Mg (NH) 4 ) 2 (HPO 4 ) 2 F 2 The complex precipitates, and the complex precipitates are filtered and then are discarded along with a filter cake, so that the filtrate is purer, the impurity removing effect is obvious, the impurity discarding rate is improved, the system scaling blocking rate is slowed down, and the device operation rate is improved; increasing yield; the crystallization condition is improved, and the product purity is improved.
Compared with outsourcing addition, the preparation method saves production cost and has obvious economic benefit through ammonium fluoride preparation and use.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A process for removing impurities from an ammoniated slurry system for the production of monoammonium phosphate from wet-process phosphoric acid comprising the steps of:
mixing fluosilicic acid solution with liquid ammonia for neutralization reaction to obtain ammonium fluoride slurry;
blending wet phosphoric acid to obtain blended acid;
mixing the blended acid with ammonia gas to perform a primary ammonification reaction to obtain primary ammonification slurry;
mixing the ammonium fluoride slurry, the first-stage ammoniated slurry and ammonia gas to perform a second-stage ammoniation reaction to obtain a second-stage ammoniated slurry;
filtering the two-stage ammoniated slurry to obtain a filter cake and filtrate;
for 1m 3 The volume usage of the first ammoniated slurry obtained by wet phosphoric acid is as follows: v=kx [ ρ ] 1 ×(C 1 /102+C 2 /160)]/C 3 /ρ 2 Formula 1;
in formula 1: v-ammonium fluoride solution volume, m 3 ；
6.0 to 8.0K-factor;
ρ 1 density of phosphoric acid by wet process, kg/m 3 ；
C 1 -Al in wet phosphoric acid 2 O 3 Mass concentration;
C 2 fe in phosphoric acid by wet process 2 O 3 Mass concentration;
C 3 -mass concentration of ammonium fluoride in the ammonium fluoride slurry;
ρ 2 density of ammonium fluoride slurry, kg/m 3 ；
102—Al 2 O 3 A formula weight;
160—Fe 2 O 3 the formula weight.
2. The method of claim 1, wherein H is used as 2 SiF 6 The mass concentration of the fluosilicic acid solution is 15-18 percent.
3. The method according to claim 2, wherein the fluorosilicic acid solution is obtained by filtering a solid phase substance in an absorption slurry obtained by absorbing tail gas generated in the concentration process of sulfuric acid decomposed phosphate ore and phosphoric acid by water.
4. The method of claim 1, wherein the neutralization reaction temperature is 75-83 ℃.
5. The method according to claim 1 or 4, wherein the neutralization reaction has an end point pH of 8.0 to 8.3.
6. The method according to claim 1, wherein the pH value of the first ammoniation reaction is 2.5-3.0, and the reaction time is 60-70 minutes.
7. The method of claim 1, wherein the two-stage ammoniation reaction has an end point pH of 4.0 to 4.3.
8. A method according to claim 1 or 3, wherein the main components and impurity contents of the wet phosphoric acid are shown in table 1:
TABLE 1 Main component and impurity content of Wet phosphoric acid
。
9. The method of claim 1, wherein the impurity is removed by P 2 O 5 The concentration of the blended acid is 18-25% by mass percent.
10. The method of claim 1, further comprising crystallizing the filtrate after obtaining the filter cake and the filtrate to obtain crystalline ammonium dihydrogen phosphate.
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