CN116835544A - Production method and device for producing multi-grade calcium feed by concentrated acid method - Google Patents
Production method and device for producing multi-grade calcium feed by concentrated acid method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000011575 calcium Substances 0.000 title claims abstract description 44
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title claims abstract description 39
- 229910052791 calcium Inorganic materials 0.000 title claims abstract description 39
- 239000002253 acid Substances 0.000 title claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 238000006243 chemical reaction Methods 0.000 claims abstract description 116
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 86
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 68
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000002002 slurry Substances 0.000 claims abstract description 58
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 43
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 34
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 34
- 238000005406 washing Methods 0.000 claims abstract description 32
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 29
- 238000002156 mixing Methods 0.000 claims abstract description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000001506 calcium phosphate Substances 0.000 claims abstract description 18
- 238000002360 preparation method Methods 0.000 claims abstract description 18
- 230000008569 process Effects 0.000 claims abstract description 18
- 239000007788 liquid Substances 0.000 claims abstract description 15
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 8
- 229910000389 calcium phosphate Inorganic materials 0.000 claims abstract description 7
- 235000011010 calcium phosphates Nutrition 0.000 claims abstract description 6
- 238000007664 blowing Methods 0.000 claims abstract description 4
- 238000001816 cooling Methods 0.000 claims abstract description 3
- 239000000463 material Substances 0.000 claims description 33
- 239000007787 solid Substances 0.000 claims description 9
- 238000012216 screening Methods 0.000 claims description 6
- ZQBZAOZWBKABNC-UHFFFAOYSA-N [P].[Ca] Chemical compound [P].[Ca] ZQBZAOZWBKABNC-UHFFFAOYSA-N 0.000 claims description 4
- 230000005587 bubbling Effects 0.000 claims description 4
- NKWPZUCBCARRDP-UHFFFAOYSA-L calcium bicarbonate Chemical compound [Ca+2].OC([O-])=O.OC([O-])=O NKWPZUCBCARRDP-UHFFFAOYSA-L 0.000 abstract description 17
- 229910000020 calcium bicarbonate Inorganic materials 0.000 abstract description 17
- 239000000839 emulsion Substances 0.000 abstract description 16
- 238000005469 granulation Methods 0.000 abstract description 5
- 230000003179 granulation Effects 0.000 abstract description 5
- 238000007873 sieving Methods 0.000 abstract description 5
- 239000007789 gas Substances 0.000 description 35
- 229960005069 calcium Drugs 0.000 description 28
- 239000000047 product Substances 0.000 description 24
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 10
- 229910052698 phosphorus Inorganic materials 0.000 description 10
- 239000011574 phosphorus Substances 0.000 description 10
- 239000012066 reaction slurry Substances 0.000 description 9
- 235000019739 Dicalciumphosphate Nutrition 0.000 description 7
- FUFJGUQYACFECW-UHFFFAOYSA-L calcium hydrogenphosphate Chemical compound [Ca+2].OP([O-])([O-])=O FUFJGUQYACFECW-UHFFFAOYSA-L 0.000 description 7
- 229910000390 dicalcium phosphate Inorganic materials 0.000 description 7
- 229940038472 dicalcium phosphate Drugs 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- YYRMJZQKEFZXMX-UHFFFAOYSA-L calcium bis(dihydrogenphosphate) Chemical compound [Ca+2].OP(O)([O-])=O.OP(O)([O-])=O YYRMJZQKEFZXMX-UHFFFAOYSA-L 0.000 description 5
- 235000019691 monocalcium phosphate Nutrition 0.000 description 5
- CDDBPMZDDVHXFN-ONEGZZNKSA-N 2-[(e)-3-(1,3-benzodioxol-5-yl)prop-2-enyl]-1-hydroxypiperidine Chemical compound ON1CCCCC1C\C=C\C1=CC=C(OCO2)C2=C1 CDDBPMZDDVHXFN-ONEGZZNKSA-N 0.000 description 4
- 229960001714 calcium phosphate Drugs 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- -1 hydrogen ions Chemical class 0.000 description 4
- 229910000150 monocalcium phosphate Inorganic materials 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000010992 reflux Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 235000016709 nutrition Nutrition 0.000 description 2
- 230000035764 nutrition Effects 0.000 description 2
- 239000002367 phosphate rock Substances 0.000 description 2
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 2
- 235000019731 tricalcium phosphate Nutrition 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 235000019728 animal nutrition Nutrition 0.000 description 1
- 229940062672 calcium dihydrogen phosphate Drugs 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 244000144977 poultry Species 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 229910000391 tricalcium phosphate Inorganic materials 0.000 description 1
- 229940078499 tricalcium phosphate Drugs 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
- C01B25/32—Phosphates of magnesium, calcium, strontium, or barium
- C01B25/325—Preparation by double decomposition
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
-
- 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
- C01P2006/82—Compositional purity water content
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The application discloses a production method and a device for producing multi-grade calcium feed by a concentrated acid method, and relates to the technical field of preparation of feed-grade calcium phosphate. Sending the carbon dioxide tail gas into a washing tower, and washing by using process water to obtain washing liquid and washed carbon dioxide; the washing liquid is sent into a slurry mixing tank, calcium carbonate is added for slurry mixing, and the washed carbon dioxide is sent into the slurry mixing tank; feeding the slurry reacted in the slurry preparation tank into a reaction tank, adding phosphoric acid into the reaction tank, and blowing carbon dioxide-containing gas out of the slurry preparation tank into the reaction tank; feeding the slurry reacted in the reaction tank into a reactor for continuous reaction, and feeding the slurry into a granulator through a spiral feeder when the slurry is in a semi-dry state; and (3) granulating, drying, sieving, crushing and cooling to obtain the multi-grade feed calcium phosphate salt. The calcium carbonate emulsion containing the calcium bicarbonate is prepared by utilizing the carbon dioxide tail gas, carbon dioxide is introduced into a reaction tank to improve the reaction efficiency of phosphoric acid and calcium carbonate, and the calcium feeding production efficiency is improved by adopting a non-return granulation process.
Description
Technical Field
The application relates to the technical field of feed-grade calcium phosphate preparation, in particular to a production method and a device for producing multi-grain-grade calcium feed by a concentrated acid method.
Background
The feed-grade calcium phosphate (for short, calcium feeding) is an excellent phosphorus and calcium nutrition supplement in the feed of poultry and livestock because of containing main mineral nutrition sources required by animal nutrition. The main varieties of the feed calcium phosphate are as follows: monocalcium phosphate (MCP), dicalcium phosphate (DCP), dicalcium phosphate (MDCP), tricalcium phosphate (TCP or DFP). The calcium feeding product in China mainly comprises DCP, MCP, MDCP. The feed calcium phosphate salt is the second bulk phosphorus chemical product in addition to the phosphate fertilizer. The process for producing the feed calcium mainly comprises a dilute acid method and a concentrated acid method. The dilute acid method has lower requirements on the quality of phosphorite and phosphoric acid, but only DCP can be produced; the concentrated acid method has high requirements on quality of phosphorite and phosphoric acid, but has short flow, and can produce various phosphates such as DCP, MCP, MDCP and the like. Compared with DCP, the MDCP has higher water-soluble phosphorus, higher absorptivity and lower additive amount, has the characteristic of more environmental protection when in use, has wider application range and higher market value. However, the traditional concentrated acid method has the problems of high free acid content (3% -5%), high residual calcium carbonate content (3% -6%), easy caking, easy moisture absorption and reduced phosphorus content of the product caused by insufficient reaction of phosphoric acid and calcium carbonate. The problems of large material returning quantity and lower production efficiency exist in the production of granular calcium feed.
Disclosure of Invention
The application aims to provide a production method and a device for producing multi-grade calcium feed by a concentrated acid method, which solve the problem of low production efficiency caused by the non-ideal product quality and large return quantity of the existing concentrated acid method.
In order to solve the technical problems, the application adopts the following technical scheme: the production method for producing the multi-grade calcium feed by the concentrated acid method is characterized by comprising the following steps of:
s1, delivering carbon dioxide tail gas generated in calcium feeding by a concentrated acid method into a washing tower, and washing by process water to obtain washing liquid and washed carbon dioxide;
s2, delivering the washing liquid into a slurry mixing tank, adding calcium carbonate for slurry mixing, and delivering the washed carbon dioxide into the slurry mixing tank;
s3, feeding the slurry reacted in the slurry preparation tank into a reaction tank, adding phosphoric acid into the reaction tank, blowing carbon dioxide-containing gas out of the slurry preparation tank into the reaction tank, and staying the slurry in the reaction tank for 1-2 min;
s4, allowing the slurry reacted in the reaction tank to enter a reactor for continuous reaction for 10-30 min, and feeding the slurry into a granulator through a spiral feeder when the slurry is in a semi-dry state;
s5, granulating, drying, screening, crushing and cooling to obtain the multi-grade feed calcium phosphate finished product.
Further technical proposal is that P in the phosphoric acid 2 O 5 The content is more than or equal to 50 percent.
The further technical proposal is that the solid content of the slurry after reaction in the slurry preparation tank is more than or equal to 65 percent, the reaction temperature in the reaction tank is 80 to 90 ℃, and the calcium-phosphorus ratio of the slurry after reaction in the reaction tank is 0.65 to 0.80.
The further technical proposal is that the bubbling amount of the bubbling carbon dioxide-containing gas is controlled in the step S3, so that the height of the materials in the reaction tank is not more than 85 percent of the total height of the reaction tank.
The further technical proposal is that the gas-liquid volume flow ratio in the washing tower in the step S1 is 3-1:1.
The further technical proposal is that the purity of the calcium carbonate in the step S2 is more than or equal to 98 percent, and the grain diameter is less than or equal to 75 mu m.
The production device used by the production method comprises a washing tower, a slurry distribution tank, a reaction tank, a reactor, a spiral feeder, a granulator, a dryer and a screening device which are connected in sequence, wherein a tail gas outlet of the reaction tank is connected with a gas inlet of the washing tower, a gas outlet of the washing tower is connected with the slurry distribution tank, and a gas outlet of the slurry distribution tank is connected with the reaction tank.
Reaction mechanism:
the basic process of the concentrated acid method is that purified phosphoric acid meeting the technological requirements and calcium carbonate are adopted to react in a mixing reaction tank, and then are granulated, dried, screened, crushed and packaged to obtain a qualified product. The main reactions are shown in the formulas (1) and (2),
CaCO 3 +2H 3 PO 4 ＝Ca(H 2 PO 4 ) 2 ·H 2 O+CO 2 ↑ (1)
CaCO 3 +H 3 PO 4 +H 2 O＝CaHPO 4 ·2H 2 O+CO 2 ↑ (2)
the concentrated acid method for preparing the feed calcium is characterized in that the liquid-solid ratio is low, the product coated calcium carbonate is easy to form, the incomplete reaction of the calcium carbonate and phosphoric acid (high free acid and high residual calcium carbonate) is caused, meanwhile, the liquid-solid ratio is low, the reaction is severe in the initial stage of the reaction, a large amount of fine crystal grains are produced to coat free water, and a part of free water is needed (formula (2)) when calcium hydrophosphate is generated, so that the flowability of the system is poor in a short time, the diffusion rate of hydrogen ions in the system is rapidly reduced, the reaction rate is reduced, the material conversion rate is reduced, and the product free acid and residual calcium carbonate are higher.
In order to solve the problems of high free acid and high residual calcium carbonate of the product caused by low conversion rate and low reaction rate due to low diffusion of wrapping and hydrogen ions, the application adopts the following method:
1. and (3) washing the tail gas generated in the concentrated acid method to absorb phosphoric acid carried in the tail gas, reducing the temperature of the tail gas and increasing the concentration of carbon dioxide in the tail gas.
2. Adding the tail gas containing carbon dioxide into a calcium carbonate emulsion prepared by washing liquid and calcium carbonate, and carrying out a formula (3) reaction on the carbon dioxide and the calcium carbonate emulsion to obtain a calcium carbonate emulsion containing calcium bicarbonate with better solubility, namely
CaCO 3 +CO 2 +H 2 O＝Ca(HCO 3 ) 2 (3)
3. The calcium carbonate emulsion containing the better soluble calcium bicarbonate enters a reaction tank, and then phosphoric acid is added to generate
Ca(HCO 3 ) 2 +2H 3 PO 4 ＝Ca(H 2 PO 4 ) 2 ·H 2 O+H 2 O+2CO 2 ↑ (4)
Ca(HCO 3 ) 2 +H 3 PO 4 ＝CaHPO 4 ·2H 2 O+2CO 2 ↑ (5)
4. During the second reaction step, unreacted carbon dioxide is bubbled into the third calcium carbonate emulsion and phosphoric acid reaction to increase the fluidity of the system.
The reaction tail gas has relatively high temperature, mainly carbon dioxide gas, and carries water vapor and a small amount of phosphoric acid. After the tail gas is washed by the process water, the temperature is reduced, wherein water vapor and phosphoric acid enter the process water, the tail gas becomes low-temperature high-concentration carbon dioxide gas, and the low-temperature high-concentration carbon dioxide gas is favorable for the reaction of carbon dioxide and calcium carbonate to generate calcium bicarbonate.
The calcium carbonate emulsion containing calcium bicarbonate is compared with the pure calcium carbonate emulsion, and when reacting with phosphoric acid in a reaction tank, the calcium bicarbonate solution and the phosphoric acid are mixed at molecular level, and the mixture is uniform, and the reaction is rapid and complete; when calcium bicarbonate reacts with phosphoric acid, no extra free water is needed, and part of water is released when calcium dihydrogen phosphate is generated, so that the fluidity of the system and the diffusion rate of hydrogen ions are increased; meanwhile, compared with the reaction of calcium carbonate and phosphoric acid, the reaction of calcium bicarbonate and phosphoric acid releases more carbon dioxide, which is also beneficial to increasing the fluidity of the system, leading the reactants to be mixed more uniformly, reducing the package and leading the reaction to be more complete; the test shows that the fluidity of the calcium carbonate and phosphoric acid reaction system is in direct proportion to the liquid-solid ratio, the higher the liquid-solid ratio is, the better the fluidity is, the higher the temperature is, the better the fluidity is, the larger the foam amount is, and the better the fluidity is. And (3) blowing the carbon dioxide which does not participate in the reaction in the slurry preparation tank to the reaction tank to increase the foam quantity, so that the fluidity of the system can be increased, and the reaction of calcium carbonate and phosphoric acid is promoted.
Meanwhile, experiments show that as reactions (1), (2), (4) and (5) proceed, the reaction materials gradually lose plasticity and become semi-dry materials, and the semi-dry materials can directly enter a granulator for granulation through a screw feeder. The granulating process has no material returning process, and the granulating and production efficiency is obviously improved. After granulation, the calcium feed products with multiple particle sizes can be obtained after drying, sieving and crushing, and at least 3 calcium feed products with different particle sizes can be obtained.
Compared with the prior art, the application has the beneficial effects that: preparing calcium carbonate emulsion containing calcium bicarbonate by utilizing phosphoric acid as a phosphorus source and utilizing carbon dioxide tail gas generated in a calcium feeding production process by a concentrated acid method as a calcium source for calcium feeding by the concentrated acid method, and introducing redundant carbon dioxide in a slurry preparation process into a reaction tank to increase the mixing efficiency of a reaction system and the diffusion efficiency of hydrogen ions so as to improve the reaction efficiency of phosphoric acid and calcium carbonate, thereby improving the conversion rate of phosphoric acid and calcium carbonate materials; the later stage of the reaction system gradually loses fluidity, and the production efficiency of calcium feeding is increased by adopting a non-return granulation process; and after granulation, drying, screening and crushing to obtain the finished product of the feed calcium phosphate salt with multiple particle sizes and good product consistency.
Drawings
FIG. 1 is a process flow diagram of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The production device comprises a washing tower, a slurry preparation tank, a reaction tank, a reactor, a spiral feeder, a granulator, a dryer and a screening device which are sequentially connected, wherein a tail gas outlet of the reaction tank is connected with a gas inlet of the washing tower, a gas outlet of the washing tower is connected with the slurry preparation tank, a gas outlet of the slurry preparation tank is connected with the reaction tank, and the reactor is a tank reactor with a stirring device.
Example 1
Phosphoric acid (P) 2 O 5 50.02%) and a calcium carbonate emulsion (CaCO) containing calcium bicarbonate 3 65.00 percent of the content of the calcium and the phosphorus are added into a reaction tank, the reaction temperature is 80 ℃, the calcium and the phosphorus ratio of the materials at the outlet of the reaction tank is controlled to be 0.65, and the reflux CO is controlled at the same time 2 The height of the materials in the reaction tank is not more than 85% of the total height of the reaction tank so as to prevent the reaction materials from overflowing the reaction tank. The tail gas of the reaction tank enters a washing tower, the tail gas is countercurrent washed at normal temperature by using process water, and the gas-liquid volumetric flow ratio is 3:1. the washed process water is taken as washing liquid to enter a slurry mixing tank, calcium carbonate (the purity is 98.45 percent, the grain diameter is less than or equal to 75 microns) is added, and then the washed carbon dioxide-containing gas is introduced into the slurry mixing tank, the solid content in the slurry mixing tank is controlled to be 65 percent, so that calcium carbonate emulsion containing calcium bicarbonate is obtained, and the calcium carbonate emulsion is sent into a reaction tank. Unreacted carbon dioxide gas is blown into the reaction tank to increase the fluidity of the reaction materials, and the reaction slurry stays in the reaction tank for 1min.
After the fluidity of the reaction slurry is weakened, the reaction slurry in the reaction tank is sent into a tank reactor with stirring paddles to continue to react for 10min, and the slurry gradually loses plasticity to become a semi-dry material. The semi-dry material enters the granulator under the conveying of the screw feeder. The material was continuously reacted in a granulator at a rate of 300rpm, granulated, and left for 5 minutes, and fed into a forced air dryer. After drying, the temperature of the outlet material is 80 ℃, and the water content of the finished product is 4%.
The multi-grain calcium feed with the grain diameter of 0.5-0.15 mm, 2-0.5 mm and less than or equal to 0.15mm (the product with the grain diameter of more than 2mm is crushed by a crusher) can be produced by sieving. Through testing, the main indexes of the three products are shown in table 1, and the consistency of the three products of the multi-grain calcium feeding is good from table 1.
Table 1 technical index of multi-grade calcium feed
| Particle size (mm) | Total phosphorus (%) | Free acid (%) | Residual calcium carbonate (%) |
| 0.5～0.15 | 21.31 | 0.89 | 0.88 |
| 2～0.5 | 21.29 | 0.90 | 0.88 |
| ≤0.15 | 21.33 | 0.91 | 0.89 |
Example 2
Phosphoric acid (P) 2 O 5 51.30 percent of calcium bicarbonate and calcium carbonate emulsion (67 percent of CaCO 3) containing calcium bicarbonate are added into a reaction tank, the reaction temperature is 90 ℃, the calcium-phosphorus ratio of the materials at the outlet of the reaction tank is controlled to be 0.80, and the reflux CO is controlled at the same time 2 The height of the materials in the reaction tank is not more than 85% of the total height of the reaction tank so as to prevent the reaction materials from overflowing the reaction tank. The tail gas of the reaction tank enters a washing tower, the tail gas is countercurrent washed at normal temperature by using process water, and the gas-liquid flow ratio is 1:1. the process water after washing is taken as washing liquid to enterAdding calcium carbonate (purity is 98.45%, particle size is less than or equal to 75 μm) into a slurry mixing tank, introducing the washed carbon dioxide-containing gas into the slurry mixing tank, controlling the solid content in the slurry mixing tank to 70%, obtaining calcium carbonate emulsion containing calcium bicarbonate, and sending into a reaction tank. Unreacted carbon dioxide gas is blown into the reaction tank to increase the fluidity of the reaction materials, and the reaction slurry stays in the reaction tank for 2min.
After the fluidity of the reaction slurry is weakened, the reaction slurry in the reaction tank is sent into a tank reactor with stirring paddles to continue to react, and after 20 minutes of reaction, the slurry gradually loses plasticity to become a semi-dry material. The semi-dry material enters the granulator under the conveying of the spiral discharging machine. The material was continuously reacted in a granulator at a rate of 300rpm, granulated, and left for 5 minutes, and fed into a forced air dryer. After drying, the temperature of the outlet material is 85 ℃, and the water content of the finished product is 3.6%.
The multi-grain calcium feed with the grain diameter of 0.5-0.15 mm, 2-0.5 mm and less than or equal to 0.15mm (the product with the grain diameter of more than 2mm is crushed by a crusher) can be produced by sieving. The main indexes of the three products are shown in Table 2.
Table 2 technical index of multi-grade calcium feed
| Particle size (mm) | Total phosphorus (%) | Free acid (%) | Residual calcium carbonate (%) |
| 0.5～0.15 | 21.10 | 0.92 | 0.90 |
| 2～0.5 | 21.13 | 0.91 | 0.92 |
| ≤0.15 | 21.12 | 0.93 | 0.95 |
Example 3
Phosphoric acid (P) 2 O 5 52.23 percent of calcium bicarbonate and calcium carbonate emulsion (CaCO 3 content 65 percent) containing calcium bicarbonate are added into a reaction tank, the reaction temperature is 90 ℃, the calcium-phosphorus ratio of the materials at the outlet of the reaction tank is controlled to be 0.75, and the reflux CO is controlled at the same time 2 The height of the materials in the reaction tank is not more than 85% of the total height of the reaction tank so as to prevent the reaction materials from overflowing the reaction tank. The tail gas of the reaction tank enters a washing tower, the tail gas is countercurrent washed at normal temperature by using process water, and the gas-liquid flow ratio is 2:1. the washed process water is taken as washing liquid to enter a slurry mixing tank, calcium carbonate (the purity is more than or equal to 98 percent, the grain diameter is less than or equal to 75 mu m) is added, the washed carbon dioxide-containing gas is introduced into the slurry mixing tank, the solid content in the slurry mixing tank is controlled to be 65 percent, and the calcium carbonate emulsion containing the calcium bicarbonate is obtained and is sent into a reaction tank. Unreacted carbon dioxide gas is blown into the reaction tank to increase the fluidity of the reaction materials, and the reaction slurry stays in the reaction tank for 3min.
After the fluidity of the reaction slurry is weakened, the reaction slurry in the reaction tank is sent into a tank reactor with stirring paddles to continue to react, and the slurry gradually loses plasticity after 30 minutes of reaction, so that a semi-dry material is formed. The semi-dry material enters the granulator under the conveying of the spiral discharging machine. The material was continuously reacted in a granulator at a rate of 300rpm, granulated, and left for 5 minutes, and fed into a forced air dryer. After drying, the temperature of the outlet material is 85 ℃, and the water content of the finished product is 3.5%.
The multi-grain calcium feed with the grain diameter of 0.5-0.15 mm, 1.2-0.5 mm, 1.2-2.5 mm and less than or equal to 0.15mm (obtained by crushing products with the grain diameter of more than 2mm by a crusher) can be produced by sieving. Through testing, main indexes of the four products are shown in table 3, and the consistency of the four products of the multi-grain calcium feeding is good from table 3.
Table 3 Multi-grade calcium feeding technical index
| Particle size (mm) | Total phosphorus (%) | Free acid (%) | Residual calcium carbonate (%) |
| 0.5～0.15 | 21.13 | 0.94 | 0.89 |
| 1.2～0.5 | 21.12 | 0.92 | 0.90 |
| 1.2～2.5 | 21.14 | 0.91 | 0.91 |
| ≤0.15 | 21.11 | 0.89 | 0.92 |
While the application has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope of the disclosure. More specifically, various modifications and improvements may be made to the component parts or arrangements within the scope of the disclosure, drawings and claims. In addition to variations and modifications in the component parts or arrangements, other uses will be apparent to those skilled in the art.
Claims (7)
1. The production method for producing the multi-grade calcium feed by the concentrated acid method is characterized by comprising the following steps of:
s1, delivering carbon dioxide tail gas generated in calcium feeding by a concentrated acid method into a washing tower, and washing by process water to obtain washing liquid and washed carbon dioxide;
s2, delivering the washing liquid into a slurry mixing tank, adding calcium carbonate for slurry mixing, and delivering the washed carbon dioxide into the slurry mixing tank;
s3, feeding the slurry reacted in the slurry preparation tank into a reaction tank, adding phosphoric acid into the reaction tank, blowing carbon dioxide-containing gas out of the slurry preparation tank into the reaction tank, and staying the slurry in the reaction tank for 1-2 min;
s4, allowing the slurry reacted in the reaction tank to enter a reactor for continuous reaction for 10-30 min, and feeding the slurry into a granulator through a spiral feeder when the slurry is in a semi-dry state;
s5, granulating, drying, screening, crushing and cooling to obtain the multi-grade feed calcium phosphate finished product.
2. The method for producing multi-grade calcium feed by the concentrated acid method according to claim 1, which is characterized in that: p in the phosphoric acid 2 O 5 The content is more than or equal to 50 percent.
3. The method for producing multi-grade calcium feed by the concentrated acid method according to claim 1, which is characterized in that: the solid content of the slurry after reaction in the slurry preparation tank is more than or equal to 65%, the reaction temperature in the reaction tank is 80-90 ℃, and the calcium-phosphorus ratio of the slurry after reaction in the reaction tank is 0.65-0.80.
4. The method for producing multi-grade calcium feed by the concentrated acid method according to claim 1, which is characterized in that: and in the step S3, the bubbling amount of the bubbling carbon dioxide-containing gas is controlled so that the height of the materials in the reaction tank is not more than 85% of the total height of the reaction tank.
5. The method for producing multi-grade calcium feed by the concentrated acid method according to claim 1, which is characterized in that: the gas-liquid flow ratio in the washing tower in the step S1 is 3-1:1.
6. The method for producing multi-grade calcium feed by the concentrated acid method according to claim 1, which is characterized in that: in the step S2, the purity of the calcium carbonate is more than or equal to 98 percent, and the grain diameter is less than or equal to 75 mu m.
7. The production method for producing multi-grade calcium feed by a concentrated acid method according to any one of claims 1 to 6, which is characterized by comprising the following steps: the production device used in the production method comprises a washing tower, a slurry preparation tank, a reaction tank, a reactor, a spiral feeder, a granulator, a dryer and a screening device which are connected in sequence, wherein a tail gas outlet of the reaction tank is connected with a gas inlet of the washing tower, a gas outlet of the washing tower is connected with the slurry preparation tank, and a gas outlet of the slurry preparation tank is connected with the reaction tank.
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