JP2003002772A - Low-fluorine phosphoric acid fertilizer and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphoric acid fertilizer with less elution of sulfuric acid radical and fluorine. SOLUTION: The environment preservation type phosphoric acid fertilizer is a phosphoric acid fertilizer of quick-acting and slow-acting consisting essentially of water-soluble phosphoric acid and citric acid-soluble phosphoric acid and is characterized by that fluorine content is <=0.2 wt.%, elution quantity of fluorine is <=25 mg/l, preferably <=10 mg/l by a first process in which a raw material consisting essentially of monocalcium phosphate (monocalcium phosphate raw material) obtained from defluorination-treated phosphoric acid is hydrolyzed to phosphoric acid slurry and by a second process in which free fluorine in the slurry is immobilized while pelletizing slurry after adding the monocalcium phosphate raw material and a basic material thereto.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fast-acting water-soluble phosphoric acid component and a slow-acting soluble copper-soluble phosphoric acid component, which is substantially free of sulfate radicals, and has a fluorine content and an elution fluorine content. The present invention relates to a fast-release phosphate fertilizer which is small in amount and therefore does not cause environmental pollution due to accumulation of sulfate radicals and fluorine, and a method for producing the same.

[0002]

2. Description of the Related Art Phosphate fertilizers that have been conventionally used are those obtained by a wet method such as lime superphosphate and lime hyperphosphate.
As a dry method, fused phosphorus fertilizer and calcined phosphorus fertilizer are known. The wet method is based on the use of phosphate rock as a raw material and the addition of sulfuric acid, phosphoric acid, or a mixed acid of sulfuric acid and phosphoric acid to produce monocalcium phosphate. Calcium superphosphate containing gypsum is obtained together with lime, and those using phosphoric acid or a mixed acid of phosphoric acid and sulfuric acid can obtain lime superphosphate having high grade of lime monolime. Phosphate fertilizers by other wet methods include those made from fertilizer and lime superphosphate or lime hyperphosphate and a phosphoric acid solution, and magnesium in ferronickel slag in a mixed solution of phosphoric acid and sulfuric acid. Heat decomposed, manufactured by changing magnesium to magnesium phosphate,
It is known that one produced by reacting a mixture containing an alkaline earth metal compound and soluble silicic acid with a phosphoric acid solution or a mixed solution of phosphoric acid and sulfuric acid.

[0003]

Among these, the phosphate fertilizer by the wet method is one in which phosphate ore (fluorapatite) is used as a mineral acid.
Phosphoric acid obtained by decomposing with (sulfuric acid, hydrochloric acid) is used as the raw material, and since the fluorine contained in the phosphoric acid raw material is contained in the fertilizer as it is, the fluorine content in the phosphate fertilizer is high and The content is 0.7 to 2.5 wt% and the amount of fluorine elution is more than 25 mg / l. Therefore, when fertilizers produced by the conventional wet method are applied to paddy fields or upland, there is a concern that fluorine will gradually accumulate in the soil and cause soil pollution, or that plants will absorb fluorine and cause various disorders. There is. Further, there is a problem that fluorine eluted from fertilizer causes pollution of rivers and groundwater.

The present invention solves the above-mentioned problems in conventional phosphate fertilizers, and in a phosphate fertilizer produced by a wet method, the contamination of fluorine is eliminated as much as possible and a slight amount of residual fluorine is eliminated. Provided is a phosphate fertilizer that is immobilized and significantly suppresses the elution amount of fluorine compared to conventional phosphate fertilizers by the wet method, and does not cause soil pollution by fluorine or excessive intake and is excellent in environmental protection and a manufacturing method thereof. It is a thing.

[0005]

According to the present invention, there is provided a phosphate fertilizer having the following constitution. (1) A fast-release phosphoric acid fertilizer containing Cu-soluble phosphoric acid and water-soluble phosphoric acid as main components, which is a raw material containing phosphorus-monocalcium phosphate as a main component obtained from defluorinated phosphoric acid. Acid-lime raw material) to hydrolyze the phosphoric acid slurry into a first step, and add the above-mentioned phosphate-lime raw material and basic material to this slurry and fix the fluorine released in the slurry while granulating The second step of converting the fluorine content to 0.2 w
A low-fluorine phosphate fertilizer characterized by having t% or less and a fluorine elution amount of 25 mg / l or less. (2) The phosphate fertilizer according to (1) above, which has a total fluorine content of 0.15 wt% or less and a fluorine elution amount of 10 mg / l or less. (3) The content of the phosphoric acid component is 30 to 45%, and the soluble phosphoric acid in the phosphoric acid component is 97% or more and the water-soluble phosphoric acid is 60% or less (1) or (2) Phosphate fertilizer. (4) A magnesia component is contained together with a phosphoric acid component, and the content of the magnesia component is 4 to 7 wt% in terms of magnesium oxide.
Phosphate fertilizer of (1), (2) or (3). (5) Ku-soluble magnesia component is 2 to 5 in terms of magnesium oxide
The phosphate fertilizer according to any of (1) to (4) above, which is wt%.

The present invention also relates to a method for producing a phosphate fertilizer having the following constitution. (6) A first step of hydrolyzing a raw material containing phosphoric acid monolime obtained from defluorinated phosphoric acid as a main component (phosphoric acid monolime raw material) to form a phosphoric acid slurry; By adding a lime raw material and a basic material and fixing the fluorine released in the slurry while granulating, a water-soluble phosphoric acid is converted to a soluble phosphoric acid to increase the soluble ratio. A method for producing a phosphate fertilizer, which comprises granulating while neutralizing the acidity of the slurry and converting fluorine released in the slurry into calcium fluoride. (7) In the first step, the water ratio to the raw material of monocalcium phosphate is 1.5 or less, the pH of the hydrolysis slurry is 2.4 or less,
The production method according to (6) above, wherein the slurry temperature is adjusted to 90 ° C. or lower. (8) In the first step, the water ratio to the monocalcium phosphate raw material is adjusted to 0.5 to 1.0, the pH of the hydrolysis slurry is adjusted to 2.3 or less, and the slurry temperature is adjusted to 80 ° C. or less. Production method. (9) In the second step, the total addition amount of the monocalcium phosphate raw material and the basic material is 55 to 85 parts by weight with respect to 100 parts by weight of the phosphoric acid slurry, (6), (7) or (8) Manufacturing method. (10) The production method according to any one of (6) to (9) above, which uses a calcined phosphorus fertilizer and / or a magnesia material as the basic material.

As described above, the phosphate fertilizer of the present invention uses, for example, a raw material whose main component is monolime phosphate obtained from defluorinated phosphoric acid, and this raw material is hydrolyzed to form a phosphoric acid slurry. And a second step of converting the fluorine liberated in the slurry to calcium fluoride and immobilizing it while granulating by adding the above-mentioned monocalcium phosphate raw material and basic material to this slurry and The fluorine content and the fluorine elution amount are drastically reduced by the concrete. Specifically, the fluorine content is 0.2 wt% or less and the fluorine elution amount is 25 mg / l.
Below, the fluorine content is preferably 0.15 wt% or less and the fluorine elution amount is 10 mg / l or less, and more preferably the fluorine elution amount is significantly reduced to 5 mg / l or less.

Since the phosphate fertilizer of the present invention does not use sulfuric acid when decomposing monocalcium phosphate, but hydrolyzes by adding water to form a phosphoric acid slurry, it does not substantially contain sulfate radicals.
Moreover, the fluorine content is small, and the elution amount of fluorine is greatly reduced. Therefore, accumulation of sulfate radicals and fluorine in the soil can be suppressed, and environmental pollution due to these can be prevented. Furthermore, since the above-mentioned phosphate fertilizer of the present invention is a fast-release phosphate fertilizer containing both components of the slow-acting ingredient, soluble phosphoric acid and the fast-acting ingredient, water-soluble phosphoric acid, it can be used for a long period of time. The fertilizing effect continues. Further, when a magnesia material is added as a basic material during granulation, it can be used as a phosphate fertilizer having a magnesia component.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to embodiments. Phosphate fertilizer of the present invention is a fast-release phosphate fertilizer mainly composed of Cu-soluble phosphoric acid and water-soluble phosphoric acid, the main component of which is monolime phosphate obtained from defluorinated phosphoric acid. And a first step of hydrolyzing a raw material (monocalcium phosphate raw material) into a phosphoric acid slurry, and adding the above-mentioned monocalcium phosphate raw material and a basic material to the slurry to granulate the slurry. The second step of fixing the liberated fluorine is characterized in that the fluorine content is 0.2 wt% or less and the fluorine elution amount is 25 mg / l or less.

Further, the phosphoric acid fertilizer of the present invention preferably has a phosphoric acid component content of 30 to 45 wt%, a solubilization ratio of the phosphoric acid component of 97% or more, and a water solubility ratio of 60%.
% Or less, total fluorine content 0.15 wt% or less, and fluorine elution amount 10 mg / l or less. In addition, more preferably, the elution amount of fluorine is 5 mg / l or less. Further, the phosphate fertilizer of the present invention can include a magnesia component together with the phosphoric acid component (ku-soluble phosphoric acid and water-soluble phosphoric acid). The suitable amount of the magnesia component is 4 to 7 wt% in terms of magnesium oxide. Furthermore, the phosphate fertilizer of the present invention includes one having a solubilized magnesia component of 2 to 5 wt% in terms of magnesium oxide.

The phosphate fertilizer of the present invention can be obtained, for example, by the following production method. [Monophosphate Phosphate Raw Material] As the phosphoric acid raw material of the present invention, one having as its main component monocalcium phosphate obtained from defluorinated phosphoric acid (this is referred to as monocalcium phosphate raw material) is used as a raw material. Phosphate ore [Ca ₅ F (PO ₄ ) ₃ ] with sulfuric acid or sulfuric acid
The phosphoric acid solution obtained by decomposing with (mixed acid of sulfuric acid and phosphoric acid) contains hydrogen fluoride (HF) together with gypsum [CaSO ₄ .2H ₂ O] as shown in the following formula. Silica hydrofluoric acid (H ₂ SiF ₆ ) formed by reacting part of hydrogen with silicic acid in phosphate rock
Contains. Ca ₅ F (PO ₄ ) ₃ ＋ 5H ₂ SO ₄ ＋ 10H ₂ O → 3H ₃ PO ₄ ＋5 (CaSO ₄・ 2H ₂ O) ↓ ＋ HF… (1) Ca ₅ F (PO ₄ ) ₃ ＋ 7H ₃ PO ₄ ＋ 5H ₂ O → 5 [Ca (H ₂ PO ₄ ) ₂・ H ₂ O] ＋ HF… (2) Ca (H ₂ PO ₄ ) ₂・ H ₂ O + H ₂ SO ₄ ＋ H ₂ O → CaSO ₄・ 2H ₂ O ↓ ＋ 2H ₃ PO ₄ … (3)

In the present invention, the defluorinated phosphoric acid is the phosphoric acid solution from which fluorine has been removed.
Hydrogen fluoride volatilizes by heating. Silica hydrofluoric acid (H ₂ SiF ₆ ) can be removed by adding an alkali metal salt (Na, K) and converting the silica hydrofluoric acid salt (Na ₂ SiF ₆ , K ₂ SiF ₆ ) into a precipitate. it can. If the silicic acid content is low, the effect of removing fluorine is reduced, so the silicic acid content may be added together with the alkali ions.

In the case of decomposing phosphate rock with sulfuric acid or sulfur dioxide, it is necessary to use an excessive amount of sulfuric acid or sulfur phosphate with respect to the phosphate rock, so the obtained phosphoric acid solution contains excess sulfate radical. Remains. The above defluorinated phosphoric acid is one in which fluorine is removed and this sulfate radical is removed. Sulfuric acid roots in the phosphoric acid solution can be removed by adding calcium salts such as slaked lime and converting into gypsum to cause precipitation. When removing fluorine and sulfate, it is advisable to first add caustic soda or the like to precipitate the silica hydrofluoride, and then add slaked lime or quick lime to precipitate gypsum.

By adding calcium carbonate to the defluorinated phosphoric acid, monocalcium phosphate is obtained as shown in the following formula. Usually, this monocalcium phosphate contains a small amount of by-produced dicalcium phosphate [CaHPO ₄ .2H ₂ O]. The monocalcium phosphate raw material used in the present invention may partially contain such dicalcium phosphate. CaCO ₃ + 2H ₃ PO ₄ → Ca (H ₂ PO ₄ ) ₂ · H ₂ O + CO ₂ … (4)

This monocalcium phosphate raw material preferably has a Ca / P molar ratio of 0.55 to 0.75, and the total fluorine content is 0.01 to the total phosphoric acid content by weight. The following are preferable. When the Ca / P molar ratio is less than 0.55, the content of P ₂ O ₅ is high, but the adhesiveness of monocalcium phosphate is too strong, making it difficult to handle. In addition, this molar ratio is
75 over the P ₂ O ₅ content is not preferred for the production of high phosphate fertilizer of P ₂ O ₅ content becomes lower. Further, if the total fluorine content is higher than this, the fluorine content in the phosphate fertilizer becomes high, which is not preferable.

As shown in the above formula (2), when phosphate rock is decomposed with sulfuric acid, monocalcium phosphate is partially generated. The monocalcium phosphate contained in the phosphoric acid solution obtained by this sulfuric acid decomposition. It is not appropriate to use the sulfuric acid decomposition solution of phosphate rock directly as a raw material, because the concentration of is very low, and a large amount of gypsum is produced as a by-product, and it takes time to remove fluorine.

[First Step: Slurrying Step] The above-mentioned monolime phosphate raw material is dissolved in water to form a phosphoric acid slurry, and the water-soluble fluorine compound is eluted. As shown in the following formula (5), the raw material of monocalcium phosphate reacts with water and hydrolyzes to generate dicalcium phosphate and phosphoric acid. At this time, the pH of the slurry is 2.4.
The following is preferred, and a pH of 2.3 or less is more preferred. Under this acidic condition, the elution of the water-soluble fluorine compound contained in the monocalcium phosphate raw material is promoted. Since this phosphoric acid slurry was not obtained by decomposing the monocalcium phosphate raw material with sulfuric acid, gypsum did not form as a by-product and it was a slurry containing substantially no sulfate radicals. Ca (H ₂ PO ₄ ) ₂ · H ₂ O + xH ₂ O → CaHPO ₄ ↓ + H ₃ PO ₄ + (x + 1) H ₂ O… (5)

The above hydrolysis reaction is greatly affected by the mixing ratio of the monolime phosphate raw material and water and the temperature of the phosphoric acid slurry. As for the mixing ratio of the monocalcium phosphate raw material and water, 200 parts by weight or less of water (water ratio of 2.0 or less) is suitable for 100 parts by weight of the monocalcium phosphate raw material, and 150 parts by weight or less of water (water ratio). 1.5 or less) is preferable, and 50 to 100 parts by weight of water (water ratio 0.5 to 1.0) is more preferable. If the amount of water is less than 50 parts by weight, the amount of hydrolysis will decrease and the amount of undecomposition will increase. Moreover, since the water content is low, the viscosity of the phosphoric acid slurry becomes high, making granulation difficult. On the other hand, if the amount of water is more than 200 parts by weight, the concentration of phosphoric acid generated by the decomposition of monocalcium phosphate is low, and thus the hydrolysis is difficult to proceed, and thus the elution rate of the water-soluble fluorine compound decreases. . Incidentally, as shown in Table 1 of the example, in the range of the water ratio of the slurry is higher than 1.0 and lower than or equal to 1.5 and higher than pH 2.3 and lower than or equal to pH 2.4, the elution rate of fluorine is 6 or less.
It is 0 to 80%, and the elution rate of fluorine is 80% or more in the range of the water ratio of the slurry of 0.5 to 1.0 and the pH of 2.3 or less.

In the slurry forming step, the temperature of the slurry is suitably 90 ° C. or lower, preferably 80 ° C. or lower. When the temperature of the slurry exceeds 90 ° C., hydrolysis becomes significant, and the production amounts of dicalcium phosphate and phosphoric acid greatly increase. For this reason, the neutralization reaction becomes insufficient in the subsequent granulation step, and the stability of immobilization of fluorine becomes insufficient. The hydrolysis reaction that produces this phosphoric acid slurry is an exothermic reaction, and since the temperature of the slurry is approximately 30 ° C., hydrolysis may be continued in this state.

[Second Step: Granulation / Fluorine Immobilization Step] A monolime phosphate raw material and a basic material are added to the above phosphoric acid slurry to increase the phosphoric acid concentration and increase the proportion of cousable phosphoric acid. Granulation is performed while neutralizing the slurry and fixing the liberated fluorine in the slurry. Alkaline earth metal compounds are suitable as the basic material. For example, calcined phosphorus fertilizer [2CaNaPO ₄ .Ca ₃ (PO ₄ ) ₂ ] or a raw material of magnesia can be used. Serpentine (3MgO ・ 2SiO ₂・ 2H ₂ O), ferronickel slag (2MgO ・ SiO ₂ ), light burned magnesium (Mg)
O) and soluble phosphorus fertilizer are suitable.

By adding the above alkaline earth metal compound to the phosphoric acid slurry, the phosphate ion (HPO ₄ ²⁻ ) in the phosphoric acid slurry reacts with the calcium content and magnesium content of the alkaline earth metal compound, Water-soluble phosphate ion (HPO ₄ ^2- ) is a soluble phosphate compound (CaHPO ₄ ,
MgHPO ₄ ], and the proportion of the fusible phosphoric acid component increases. In addition, the acidity of the slurry is neutralized. Accompanying this neutralization reaction, the fluorine ions liberated in the slurry react with calcium ions, making it difficult to dissolve calcium fluoride.
(CaF ₂ ) is generated and immobilized. By this immobilization of fluorine, the elution amount of fluorine is 25 mg / l or less, preferably 10 mg
/ l or less, more preferably 5 mg / l or less.

As a concrete example of production, a pulverized product of a monocalcium phosphate raw material and a basic material is added to the phosphoric acid slurry obtained in the first step, and the mixed slurry is introduced into a granulating means and reacted. Granulate to fix fluorine and improve the quality of the fusible phosphoric acid component. The granulating means is not limited. A continuous dish granulator or the like can be used as appropriate. The addition amount of monocalcium phosphate raw material and basic material to the phosphoric acid slurry is
It is suitable that the total addition amount of the monocalcium phosphate raw material and the basic material is 55 to 85 parts by weight with respect to 100 parts by weight of the phosphoric acid slurry. In this case, the solubilization rate of the phosphoric acid component is generally 97% or more and the water solubilization rate is 60% or less. At this time, the pH is about 4-5.

In the second step, the granulation time is preferably longer than that in the conventional manufacturing method. The conventional granulation has a granulation time of about 3 to 4 minutes because it is merely aimed at adjusting the shape of the granules. However, in the present invention, since the fluorine is sufficiently immobilized, the granulation time is longer than that of the conventional production method. It is preferable to carry out the granulation time about 1.3 to 2 times longer (about 5 to 15 minutes).

The phosphate fertilizer of the present invention may contain iron. As the raw material of the iron component, iron ore, mill scale, red iron oxide, etc. discharged from a steel mill can be used. Further, the gelled silica is contained in the phosphate fertilizer of the present invention, and the reaction between the water-soluble phosphate component and iron is suppressed by encapsulating the phosphate component by the gelled silica, and the fertilizer is solidified. Can be prevented.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition,% is wt%.

[Production of Monocalcium Phosphate] Concentrated phosphoric acid obtained by a wet method (P ₂ O ₅ : 53.4%, F: 0.50%, SO ₃ : 2.17%) 2
00kg / h is used, and this is diatomaceous earth (silica content 90%) 0.96kg /
h, caustic soda (50% concentration) 3.5 kg / h, quick lime (50% concentration)
The solid content (Na ₂ SiF ₆ , CaSO ₄ .2H ₂ O, etc.) produced was continuously supplied to a reaction vessel together with 6.08 kg / h, and separated from the phosphoric acid solution by pressure filtration to obtain clear phosphoric acid. . The components of this phosphoric acid solution are 52.9% phosphoric acid, 0.170% fluorine, and SO _3.
It was 0.61%. 215.5 kg / h of this phosphoric acid solution and 106.6 kg / h of calcium carbonate powder (600 mesh, concentration 98%) were continuously supplied to the reaction vessel, and the reaction product was continuously taken out and dried to obtain phosphoric acid 235.5 kg / h of lime was obtained. The components of this monocalcium phosphate are 48.40% total phosphoric acid and total CaO2.
4.83%, total MgO 0.46%, total fluorine 0.155
%, Water-soluble fluorine 0.028%, and total SO ₃ 0.56%.

[Production of Phosphoric Acid Slurry] Water was added to the above-mentioned monocalcium phosphate [main component Ca (H ₂ PO ₄ ) ₂ .H ₂ O] and hydrolyzed for 1 hour to obtain a phosphoric acid slurry. Table 1 shows the decomposition temperature, the amount of raw materials used, the amount of slurry components, the amount of filtrate components and pH, and the elution rate of water-soluble fluorine.

[Granulation] Calcium monocalcium phosphate 338 kg, calcined phosphorus fertilizer (TP ₂ O ₅ : 42.4%, T-CaO: 45.9%) 90 kg, serpentine (M
72 kg of gO: 39.5%, SiO ₂ : 35.1%) and 30 kg of light-burning magnesia (MgO: 92.2%) are mixed and pulverized to form a basic material 53.
0 kg / h was prepared. This basic material and the phosphoric acid slurry in the amounts shown in Table 2 are continuously supplied to a granulator, granulated while reacting, and dried to give 1000 kg / h of granular phosphate fertilizer.
Got Table 2 shows the total sulfate group content, total fluorine content, amount of eluted fluorine, water-solubilization rate with respect to the total amount of phosphoric acid of this phosphate fertilizer. The amount of eluted fluorine was measured by using a crushed sample that passed through a 0.5 mm sieve according to the Environmental Agency Notification No. 13, “Test method for metals contained in industrial waste”.

The phosphoric acid fertilizers (Sample Nos. 1 to 12) of the present invention produced through the above steps all have a total fluorine content of 0.1.
It is 15% or less, and the amount of eluted fluorine is 25 mg / L or less. Moreover, the total SO ₃ content is 0.5% or less, and the amount of sulfate radicals is significantly small. The amount of eluted fluorine of Samples No. 7 to No. 9 is from 7 mg / l to 8.2 mg / l, which is slightly higher than that of No. 1 to No. 6, but much less than the conventional one. On the other hand, of these, Samples No. 1 to No. 6 have a significantly small amount of eluted fluorine of 5 mg / l or less. Samples No. 7 and No. 8 had a slightly high water ratio, so the amount of eluted fluorine in the product was 18 to 21 mg / l. Sample No. 9 had a slightly high slurry temperature, so the amount of eluted fluorine was 15 mg / l. However, in each case, the amount of eluted fluorine is smaller than that of conventional products.

[0030]

EFFECTS OF THE INVENTION The phosphate fertilizer of the present invention has a fluorine content lower than that of the phosphate fertilizer produced by the conventional wet method,
Moreover, since the water-soluble fluorine is fixed, the amount of eluted fluorine is greatly reduced. Furthermore, the content of sulfate radicals is significantly low. Therefore, when the fertilizer is applied to paddy fields and upland fields, it is an environmental conservation type fertilizer that can suppress the accumulation of fluorine and sulfate in the soil and prevent environmental pollution.

[0031]

[Table 1]

[0032]

[Table 2]

Claims (10)

[Claims] 1. A fast-release phosphoric acid fertilizer containing ku soluble phosphoric acid and water-soluble phosphoric acid as main components, which is a raw material whose main component is monolime phosphate obtained from defluorinated phosphoric acid. First step of hydrolyzing (phosphate-lime raw material) into a phosphoric acid slurry, and fluorine liberated in the slurry while granulating by adding the above-mentioned phosphate-lime raw material and basic material to the slurry A low-fluorine phosphate fertilizer characterized by having a fluorine content of 0.2 wt% or less and a fluorine elution amount of 25 mg / l or less by the second step of fixing the. 2. The phosphate fertilizer according to claim 1, which has a total fluorine content of 0.15 wt% or less and a fluorine elution amount of 10 mg / l or less. 3. The content of the phosphoric acid component is 30 to 45%, and the fusible phosphoric acid in the phosphoric acid component is 97% or more and the water-soluble phosphoric acid is 60% or less. Phosphate fertilizer. 4. The phosphate fertilizer according to claim 1, 2 or 3, which contains a magnesium oxide component together with a phosphoric acid component, and the content of the magnesium oxide component is 4 to 7 wt% in terms of magnesium oxide. 5. The phosphate fertilizer according to any one of claims 1 to 4, wherein the soluble magnesium-containing component is 2 to 5 wt% in terms of magnesium oxide. 6. A first step of hydrolyzing a raw material containing monolime phosphate as a main component obtained from defluorinated phosphoric acid (monolime phosphate raw material) to form a phosphoric acid slurry, By the second step of adding the monocalcium phosphate raw material and the basic material and fixing the liberated fluorine in the slurry while granulating, the water-soluble phosphoric acid is converted to the soluble phosphoric acid and the soluble ratio And a method for producing a phosphate fertilizer, which comprises granulating while neutralizing the acidity of the slurry and converting fluorine released in the slurry into calcium fluoride. 7. In the first step, the ratio of water to the raw material of monocalcium phosphate is 1.5 or less, and the pH of the hydrolysis slurry is 2.
4. The slurry temperature is adjusted to 4 or less and the slurry temperature to 90 ° C. or less.
Manufacturing method. 8. In the first step, the water ratio to the monocalcium phosphate raw material is adjusted to 0.5 to 1.0, the pH of the hydrolysis slurry is adjusted to 2.3 or less, and the slurry temperature is adjusted to 80 ° C. or less. Manufacturing method. 9. The second step, wherein the total addition amount of the monocalcium phosphate raw material and the basic material is 55 to 85 parts by weight with respect to 100 parts by weight of the phosphoric acid slurry.
Manufacturing method. 10. Baked phosphorus fertilizer and / or as a basic material
Or the manufacturing method in any one of Claims 6-9 which uses a magnesia raw material.