CN1146426A

CN1146426A - Production method for fodder grade calcium phosphate

Info

Publication number: CN1146426A
Application number: CN 96116482
Authority: CN
Inventors: 王大为; 陈葵; 李家权; 廖延武; 邹晓东; 廖洪军; 周晓葵; 范先国
Original assignee: LONGMANG MINERAL MATERIAL FODDER GROUP CO Ltd MIANZHU COUNTY SICHUAN PROV; East China University of Science and Technology
Current assignee: Longmang Group Co., Ltd., Sichuan Prov
Priority date: 1996-08-23
Filing date: 1996-08-23
Publication date: 1997-04-02
Anticipated expiration: 2016-08-23
Also published as: CN1042820C

Abstract

The characteristic lies in that the producing method uses calcium hydrogen phosphate as raw material which is passed through the solid phase direct conversion reaction with the refined concentrated phosphoric acid and the product is made up through crushing, drying, and sieving. Said method features simple and easy implementing method, low cost, and good quality of product.

Description

Production method of feed-grade monocalcium phosphate

The invention relates to a production method of feed-grade calcium phosphate.

Monocalcium phosphate, which is a feed additive, is naturally attracted by people because it is easily absorbed by aquatic animals.

At present, feed-grade monocalcium phosphate [ Ca (H)]₂PO₄)₂·H₂O]In terms of production, a direct neutralization method of hot-process phosphoric acid or wet-process concentrated phosphoric acid and lime powder is generally adopted at home and abroad, and although the method is simple and easy to implement, the method is greatly influenced by the price of raw material phosphoric acid, so that the cost is higher and higher, and the popularization and application of the product in the feed industry are limited to a great extent. In addition, although the production of feed-grade monocalcium phosphate by wet-process phosphoric acid is a desirable method, the quality index of harmful impurity elements in the product in the production process is difficult to meet the requirement, and concentration and crystallization are inevitably carried out, so that the energy consumption is high, and thus no report for directly producing feed-grade monocalcium phosphate by wet-process phosphoric acid exists so far.

Based on the current situation of producing monocalcium phosphate at home and abroad, the industry department in China hopes related scientific and technological workers to provide a novel method for preparing feed-grade monocalcium phosphate, which has cheap and easily-obtained raw materials and simple and feasible production and is suitable for the situation in China.

The present invention aims at overcoming the demerits of available technology, and provides one simple and feasible production process of feed level monocalcium phosphate.

The idea of the invention is that:

the inventor has found that pure calcium hydrogen phosphate (referred to as dicalcium phosphate in industry) can be economically produced by using wet-process phosphoric acid for a long time, and the product purification and separation are greatly facilitated due to the water insolubility of the calcium hydrogen phosphate. The inventors therefore envisage using pure dibasic calcium phosphate as starting material, or CaCO directly₂The ore is used as raw material, pure calcium hydrogen phosphate (prior art) produced by wet-process phosphoric acid is used as raw material, and the raw material and refined concentrated phosphoric acid are undergone the process of solid-phase direct conversion reaction to prepare feed-grade monocalcium phosphate [ Ca (H)₂PO₄)₂·H₂O]The method of (1).

In light of the above concepts, the disclosure and specific production methods relating to the present invention are described as follows:

the refined concentrated phosphoric acid and calcium hydrophosphate are uniformly mixed according to the chemical reaction formula proportion, and the feed-grade monocalcium phosphate is prepared by stockpiling and solid-phase conversion, crushing and drying.

The specific embodiment is as follows:

1. mixing and solid phase transformation

Firstly, adding calcium hydrophosphate with the particle size of less than or equal to 0.5mm (namely passing through a sieve mesh of 40 meshes) into a horizontal double-helical ribbon solid mixer, adding refined concentrated phosphoric acid into the mixer in a spraying mode through a pump and a spray head according to the proportion while stirring, continuing stirring for 3-5 minutes after the feeding is finished so as to ensure that calcium hydrophosphate particles and the concentrated phosphoric acid are uniformly contacted and mixed, discharging, turning and curing for 48-72 hours, and ensuring that the solid phase conversion reaction between the phosphoric acid and the calcium hydrophosphate is complete. The chemical reaction formula is as follows:

wherein n is 1.0 to 2.3 (corresponding to a concentration of the refined concentrated phosphoric acid of 85 to 70%)

During the curing of the compost, the completeness of the solid phase conversion reaction can be determined by measuring the pH value of a 5% aqueous solution of the semifinished product, and when the pH value is more than or equal to 3.0, the completion of the solid phase conversion reaction is indicated.

When the adopted calcium hydrogen phosphate is dried in advance to remove about 80 percent of crystal water, and meanwhile, when refined concentrated phosphoric acid with the concentration of 85 percent is adopted as the raw material, the free moisture in the semi-finished product after the solid phase conversion is not more than 4 percent, and at the moment, the product is not required to be dried again in the post-processing treatment and only needs to be crushed and sieved.

2. Pulverizing, and drying

The semi-finished product after the solid phase conversion reaction (curing of the stockpile) is difficult to avoid caking due to high reaction heat, high water content and the like, so the semi-finished product is crushed firstly and then dried, and the arrangement is favorable for improving the finished product yield of a drying device. The coarse grains which are not screened by the 40-mesh sieve can be returned to the grinder to be ground again, and then the finished product is prepared by a drying device.

The refined phosphoric acid can be one of hot industrial phosphoric acid with the concentration of 85 percent by weight, mud phosphoric acid with the concentration of 70 percent by weight, or wet concentrated phosphoric acid with the concentration of 80 percent by weight;

the calcium hydrophosphate raw material comprises the following main components in percentage by weight:

P₂O₅more than or equal to 40 percent, less than or equal to 0.18 percent of F and more than or equal to 22 percent of Ca; feed grade dibasic calcium phosphate is commonly used.

The ratio of the refined concentrated phosphoric acid to the calcium hydrophosphate (converted into P according to a chemical reaction formula)₂O₅The molar ratio of (a) to (b) is 0.8 to 1: 1, and an equimolar reaction is preferred. It is often converted into weight ratio in practice for convenient operation.

The semi-finished product obtained by solid phase conversion reaction (which is customarily called stack-turning curing in industry) is obtained through the processes of crushing, drying and screening to obtain the finished product.

Wherein: the drying mode can be selected at will, but the invention recommends adopting air flow drying, and the drying temperature is 70-90 ℃;

when screening, more than 98% of the product is ensured to pass through a 40-mesh sieve (the fineness requirement of the product).

When the calcium hydrophosphate is adopted for drying and about 80 wt% of crystal water is removed, the drying is preferably carried out by adopting air flow drying, and the drying temperature is 140-160 ℃.

The present invention will be further illustrated with reference to the following drawings and examples, which are not intended to limit the scope of the present invention.

FIG. 1-one of the process embodiments of the invention.

FIG. 2-the second process embodiment of the invention.

Wherein:

1-Mixer

2-solid phase reaction curing pool

3-disintegrator

4-drying apparatus

5-sifter

Placing refined concentrated phosphoric acid and calcium hydrophosphate in a mixer 1 according to the weight ratio or molar ratio of a reaction equation, fully stirring and uniformly mixing, then discharging the mixture into a curing pool 2, curing for 48-72 hours, when the pH value of a 5% aqueous solution of a semi-finished product is measured to be greater than 3.0, finishing a solid phase conversion reaction (curing), conveying the cured semi-finished product into a pulverizer 3 for pulverizing, then feeding into a drying device for drying and dehydrating until the water content of the product is less than or equal to 4%, passing through a sieving device 5, obtaining the product of the invention after passing through a 40-mesh sieve, and returning the material which does not pass through the 40-mesh sieve to the pulverizer 3 for re-pulverizing and drying.

FIG. 2 is substantially similar to the process scheme of FIG. 1, except that FIG. 2 is a line of calcium hydrogen phosphate (CaHPO) to be fed₄·2H₂O) raw materials are firstly dehydrated by a drier 4 to remove about 80 percent of crystal water, then the weight and refined concentrated phosphoric acid (85 percent by weight) are weighed according to the molar ratio of the reaction equation and are fully stirred and uniformly mixed in a mixer 1, and the rest processes of solid phase reaction (curing of stockpile), crushing, sieving and the like are all as shown in figure 1. Because the calcium hydrogen phosphate adopted in the process shown in figure 2 is dried and dehydrated, the water content in the cured product can be ensured to be less than or equal to 4 percent, and the drying is not needed in the subsequent process. It is apparent that the plant capacity of the process of figure 2 is greater than the process plant capacity of figure 1. Therefore, the plant should prioritize the process route of fig. 2 in the layout of the production apparatus. However, the process of FIG. 1 is still one of the preferred embodiments for producing feed grade monocalcium phosphate when the source of concentrated phosphoric acid (85% wt) is difficult to refine and a slurry of 70% wt is conveniently obtained.

Example 1

50 kg of calcium hydrogen phosphate (containing P)₂O₅41.3％、F 0.14％、H₂O0.3%, fineness 98.8% passing through a 40 mesh sieve) and 30 kg (85% wt) of thermal phosphoric acid, placing the mixture in a mixer, stirring and mixing for 5 minutes, discharging the mixture into a curing pool, turning and curing the mixture for 56 hours, determining the pH of a semi-finished product to be 3.0 and the free moisture to be 9.3%, crushing the semi-finished product, and drying the semi-finished product at 80 ℃ in an air flow manner to obtain 72kg of a finished product, wherein the mass composition of the semi-finished product is as follows:

P₂O₅(Total): 54.1%, P₂O₅(Water)/P₂O₅92.3% of total, 16.85% of Ca, 0.1% of F, and H₂O is 1.3 percent, and the fineness is 98.5 percent, and the mixture passes through a 40-mesh sieve.

Example 2

50 kg of dicalcium phosphate (also known as dicalcium phosphate in the industry, the composition of which is the same as that in example 1) and 36 kg (concentration of which is 70 wt%) of muddy phosphoric acid (prepared from leftovers of the yellow phosphorus production process) are taken and produced in the same way as in example 1, 74 kg of finished products can be obtained, and the quality composition of the finished products is as follows:

P₂O₅(Total): 53.1%, P₂O₅(Water)/P₂O₅91% of (total), 16.8% of Ca, 0.12% of F, H₂O is 3.2 percent, and the fineness of the product is 98 percent and passes through a 40-mesh sieve.

Example 3

80 kg of calcium hydrogen phosphate (the composition is the same as in example 1) are dehydrated by air flow at 150 ℃ to obtain the composition P₂O₅66 kg of 50.2 percent of dehydrated calcium hydrophosphate, 48 kg (with the concentration of 85 percent by weight) of thermal phosphoric acid is added into a mixer to be stirred and mixed evenly for 5 minutes, and then the mixture is discharged into a curing pool to be turned over and cured for 72 hours.

Then crushing and screening to obtain 112 kg of finished products, wherein the mass composition is as follows:

P₂O₅(Total): 55.2%, P₂O₅(Water)/P₂O₅94.8% of total, 16.9% of Ca, 0.11% of F, and H₂O is 1.2 percent, and the fineness of the product is 99.3 percent and the product passes through a 40-mesh sieve.

Thus, according to the concept of the invention, feed-grade monocalcium phosphate products can be produced simply and conveniently.

Incidentally, since the national standard for feed-grade monocalcium phosphate is not available at present, the enterprise will advise experts for this purpose to set the unified national standard for feed-grade monocalcium phosphate as follows:

P₂O₅(Total) ≥53.1％；

P₂O₅(Water)/P₂O₅(total) is more than or equal to 90 percent;

Ca ≤17％；

F ≤0.15％；

H₂O ≤4％；

PH ≥3.0；

the fineness is more than or equal to 98 percent and the mixture passes through a 40-mesh sieve pore;

the appearance was white crystalline powder with good fluidity.

The product of the invention has the above standards, and completely meets the quality requirements of the industry departments on feed-grade monocalcium phosphate.

In a word, the method has wide market development prospect.

Claims

1. A production method of feed-grade monocalcium phosphate is characterized by comprising the following steps:

the refined concentrated phosphoric acid and calcium hydrophosphate are used as raw materials and are uniformly mixed according to the proportion of a reaction formula, then the mixture is placed in a curing tank for solid phase conversion reaction, and then the product of the invention is prepared by the processes of crushing, drying and screening.

2. The method of claim 1, wherein the purified concentrated phosphoric acid is one of hot process industrial phosphoric acid having a concentration of 85 wt%, sludge phosphoric acid having a concentration of 70 wt%, or wet concentrated phosphoric acid having a concentration of more than 80 wt%.

3. The method as set forth in claim 1, characterized in that said calcium hydrogen phosphate raw material comprises the following main components in percentage by weight:

P₂O₅≥40％，F≤0.18％，Ca≥22％

4. the method according to claim 1, wherein the ratio of concentrated refined phosphoric acid to calcium hydrogen phosphate is 0.8 to 1: 1 (in terms of P)₂O₅The latter molar ratio).

5. The method of claim 1, wherein the mixing is carried out in a horizontal twin-ribbon blender, solid calcium hydrogen phosphate is added to the blender, then the phosphoric acid is added in a spraying manner under stirring, and the stirring and mixing are continued for 3-5 minutes after the addition is completed, so as to obtain the uniformly mixed material.

6. The method according to claim 1, wherein the solid phase conversion reaction is performed by placing the uniformly mixed materials in a curing tank for 48-72 hr of turning curing.

7. The method according to claim 1, wherein the drying is carried out by air-flow drying at a temperature of 70 to 90 ℃.

8. A process for preparing feed-class monocalcium phosphate includes such steps as drying calcium hydrogen phosphate to remove about 80% of crystal water, mixing with refined phosphoric acid (85 wt.%), stirring, solid-phase reaction in ageing pool for 48-72 hr, pulverizing and sieving.

9. The method of claim 8, wherein the drying and dehydration of calcium hydrogen phosphate is carried out by air drying at 140-160 ℃.

10. The method as claimed in claims 1 and 8, characterized in that the obtained feed-grade monocalcium phosphate all reach the following technical specifications:

P₂O₅(total) is more than or equal to 53 percent;

P₂O₅(Water)/P₂O₅(total) is more than or equal to 90 percent;

Ca ≤17％；

F ≤0.15％；H₂o is less than or equal to 4 percent; the PH value is more than or equal to 3.0; the fineness is more than or equal to 98 percent and the mixture passes through a 40-mesh sieve pore; the appearance was white crystalline powder with good fluidity.