JP2002293679A - Low-fluorine phosphatic fertilizer and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphatic fertilizer which is little in a fluorine content and fluorine elution rate. SOLUTION: This low-fluorine phosphatic fertilizer is decreased in the fluorine content to <=0.2 wt.% and the fluorine elution rate to <=25 mg/l, more preferably to <=8 mg/l by a first process step of preparing a sulfuric acid decomposing slurry by using raw material (phosphoric acid-lime raw material) essentially consisting of phosphoric acid-lime obtained from phosphoric acid subjected to defluorination treatment and adding sulfuric acid to this raw material and a second process step of adding the phosphoric acid-lime raw material and basic material to the slurry to neutralize the slurry and fixing the fluorine liberated into the slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an environment containing a fast-acting water-soluble phosphoric acid component and a slow-acting soluble phosphatic acid component, and having a low fluorine content and a small amount of eluted fluorine. The present invention relates to a fast-acting phosphate fertilizer that does not cause contamination and a method for producing the fertilizer.

[0002]

2. Description of the Related Art Conventionally used phosphate fertilizers include those obtained by a wet method, such as lime superphosphate and heavy superphosphate.
Melted phosphorus fertilizer, calcined phosphorus fertilizer, and the like are known as dry methods. The wet method is basically based on the use of phosphate rock as a raw material and adding sulfuric acid, phosphoric acid, or a mixed acid of sulfuric acid and phosphoric acid to produce monocalcium phosphate. A superphosphate containing lime and gypsum is obtained together with monolime, and those using phosphoric acid or a mixed acid of phosphoric acid and sulfuric acid can obtain heavy superphosphate having a high grade of monocalcium phosphate. Other wet-processed phosphate fertilizers include those manufactured from ingot manure and lime superphosphate or lime heavy superphosphate and a phosphoric acid solution, or a mixed solution of magnesium in ferronickel slag with phosphoric acid and sulfuric acid. Heat-decomposed, manufactured by changing magnesium to magnesium phosphate,
Known are those 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, phosphate fertilizers produced by the wet method are used to convert phosphate rock (fluorapatite) into mineral acid.
(Sulfuric acid, hydrochloric acid) is used as the raw material, and the fluorine contained in the raw material of phosphoric acid is directly contained in the fertilizer. The content is 0.7-2.5 wt%, and the elution amount of fluorine is more than 25 mg / l. Therefore, when fertilizing phosphate fertilizers manufactured by the conventional wet method in paddy fields and fields, there is a concern that fluorine will gradually accumulate in the soil and cause soil contamination, or plants will absorb fluorine and cause various obstacles. There is.
Further, there is a problem that fluorine eluted from fertilizer causes river and groundwater pollution.

[0004] The present invention has solved the above-mentioned problems in the conventional phosphate fertilizer, and it has been proposed to eliminate the contamination of fluorine as much as possible and immobilize fluorine contained in a phosphate fertilizer produced by a wet method. The purpose of the present invention is to provide a phosphate fertilizer that significantly reduces the amount of fluorine eluted compared to the conventional wet-type phosphate fertilizer and is excellent in environmental protection without causing soil contamination and excessive ingestion by fluorine and a method for producing the same. is there.

[0005]

According to the present invention, there is provided a phosphate fertilizer having the following constitution. (1) A low-fluorine phosphate fertilizer having a phosphoric acid content of 20 to 50 wt% and a fluorine elution amount of 25 mg / l or less. (2) The phosphate fertilizer according to (1) above, wherein the total fluorine content is 0.5 wt% or less and the fluorine elution amount is 8 mg / l or less. (3) The phosphoric acid component contains quosoluble phosphoric acid and water-soluble phosphoric acid.
The phosphoric acid fertilizer according to the above (1) or (2), wherein the proportion of water-soluble phosphoric acid is at least 60% by weight, but not less than 60% by weight. (4) It contains a magnesia component together with a phosphoric acid component, and the content of the magnesia component is 3 to 10% by weight in terms of magnesium oxide.
The above (1) to above, in which 97 wt% or more of the magnesia component is soluble gauze.
The phosphate fertilizer according to any of (3).

[0006] The present invention also relates to a method for producing a phosphate fertilizer having the following constitution. (5) Low fluorine, comprising a step of decomposing monobasic lime phosphate with sulfuric acid to form a slurry to elute fluorine, and a step of adding a basic material to the slurry to neutralize and fix fluorine. Manufacturing method of phosphate fertilizer. (6) The method of the above (5), wherein a monocalcium phosphate raw material mainly containing monocalcium phosphate obtained from defluorinated phosphoric acid is used. (7) In the fluorine immobilization step, a monocalcium phosphate material is added together with a basic material to adjust the amount of the phosphoric acid component.
The production method according to (5) or (6). (8) pH of sulfuric acid decomposition slurry in slurrying process
(5), (6) or (7), wherein the pH is adjusted to 2.0 or less and the pH at the time of adding and reacting a basic material to the sulfuric acid decomposition slurry in the fluorine fixing step is adjusted to 3.0 or more. (9) The method according to the above (8), wherein the pH in the slurrying step is 1.5 or less and the pH in the fluorine fixing step is 4.5 to 5.5. (10) The method according to any one of the above (1) to (9), wherein monocalcium phosphate is used as a main component and a Ca / P molar ratio is from 0.55 to 0.75. (11) The method according to any one of the above (5) to (10), wherein one or more of calcined phosphorus fertilizer, fused phosphorus fertilizer, serpentine, ferronickel slag, and lightly burned magnesia are used as the basic material.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on embodiments. The phosphate fertilizer of the present invention is a low-fluorine phosphate fertilizer having a phosphoric acid content of 20 to 50 wt% and an elution amount of fluorine of 25 mg / l or less, and preferably has a total fluorine content of 0.5 wt% and a fluorine content of 0.5 wt%. It is a low fluorine phosphate fertilizer having an elution amount of 8 mg / l or less, more preferably a fluorine elution amount of 5 mg / l or less. The “Environmental Standards for Soil Contamination” (August 23, 1991, Notification of the Environment Agency No. 46) specifies that the concentration of fluorine in a diluted test solution of collected soil should be 0.8 mg / l or less. .
The phosphate fertilizer of the present invention has a fluorine elution amount of 25 mg / l or less, preferably 8 mg / l or less, more preferably 5 mg / l or less. It is suitable for reducing the concentration of fluorine remaining in the soil after being eluted from the soil below the standard. The phosphoric acid fertilizer of the present invention is, for example, a sulfuric acid decomposition of monocalcium phosphate raw material, a slurrying step of eluting fluorine into a slurry, and adding a basic material to the slurry, neutralizing and fixing fluorine. The amount of fluorine eluted is reduced through the process.

[0008] The phosphate fertilizer of the present invention preferably contains, in addition to suppressing the elution amount of fluorine, both a slow-acting component, soluble phosphate and a fast-acting component, water-soluble phosphoric acid. It is a fast-releasing phosphate fertilizer. Specifically, for example, a phosphoric acid fertilizer having a proportion of quorous phosphoric acid of 97 wt% or more and a proportion of water-soluble phosphoric acid of 60 wt% or less in a phosphoric acid content of 20 to 50 wt%. If the phosphoric acid content is less than 20% by weight, the effect of phosphoric acid is poor, and it is not suitable as a phosphate fertilizer. On the other hand, since the phosphoric acid component is mainly contained as phosphate lime, the phosphoric acid content excluding the calcium content is generally about 50% by weight or less. When the ratio of the quosoluble phosphoric acid to the water-soluble phosphoric acid in the phosphoric acid component is within the above range, a good quick-releasing fertilizing effect can be obtained for the phosphoric acid component.

Further, in the present invention, by using a gypsum raw material as a basic material at the time of fixing fluorine,
It is possible to obtain a phosphate fertilizer containing a magnesia component. Preferably, the content of the magnesia component is 3 in terms of magnesium oxide.
-10 wt%, and 97 wt% or more of this formic acid component can provide a phosphate-soluble fertilizer of soluble gauze.

[0010] The phosphate fertilizer of the present invention can be obtained, for example, by the following production method. [Raw material of monocalcium phosphate] The phosphate fertilizer of the present invention is produced using a raw material containing monocalcium phosphate as a main component (referred to as a raw material of monocalcium phosphate). Usually, phosphoric acid is phosphate ore [Ca ₅ F
(PO ₄ ) ₃ ] is decomposed by sulfuric acid or phosphoric sulfuric acid (mixed acid of sulfuric acid and phosphoric acid) .This phosphoric acid solution contains hydrogen fluoride derived from fluorine contained in phosphate rock, Part of hydrogen fluoride contains silicic hydrofluoric acid (H ₂ SiF ₆ ) formed by reacting with silicic acid in phosphate rock.

The present invention preferably uses a monocalcium phosphate raw material produced from defluorinated phosphoric acid. Specifically, for example, those obtained by subjecting the total fluorine content to 0.5 wt% or less, preferably 0.2 wt% or less, are preferred.
By using a raw material having a small amount of total fluorine, the burden of fixing fluorine is reduced. Hydrogen fluoride contained in the raw material can be removed by heating and volatilizing. In addition, silicic hydrofluoric acid (H ₂ SiF ₆ ) can be removed by adding an alkali metal salt (Na, K), turning it into silicic hydrofluoric acid (Na ₂ SiF ₆ , K ₂ SiF ₆ ), and causing precipitation. it can. If the amount of silicic acid is small, the effect of removing fluorine is reduced, so that silicic acid may be added together with alkali ions.

By adding calcium carbonate to the defluorinated phosphoric acid, monocalcium phosphate is obtained as shown in the following formula (1). Usually, this is the monocalcium phosphate of lime contains a small amount of phosphate dibasic lime-produced [CaHPO ₄ · 2H ₂ O]. The monocalcium phosphate material used in the present invention may include a part of such dicalcium phosphate. CaCO ₃ + 2H ₃ PO ₄ → Ca (H ₂ PO ₄ ) ₂・ H ₂ O ＋ CO ₂ … (1)

The monocalcium phosphate material preferably has a Ca / P molar ratio of 0.55 or more and 0.75 or less. Ca / P
If the molar ratio is less than 0.55, the content of P ₂ O ₅ is high, but the monocalcium phosphate is too sticky to handle. On the other hand, if the Ca / P molar ratio exceeds 0.75, the content of P ₂ O ₅ decreases, which is not preferable for producing a phosphate fertilizer having a high P ₂ O ₅ content.

[First Step: Sulfuric Acid Decomposition Slurry] Sulfuric acid is added to the above raw material of monocalcium phosphate to decompose it to form a slurry to elute fluorine contained in the raw material. As shown in the following formula (2), monocalcium phosphate is decomposed into calcium ions and phosphate ions by sulfuric acid, and at the same time, gypsum is produced as a by-product. Fluorine compounds contained in monocalcium phosphate decompose under this acidity and elute in the slurry. 2Ca (H ₂ PO ₄ ) ₂・ H ₂ O ＋ H ₂ SO ₄ → Ca ²⁺ ＋ 4HPO ₄ ^2- ＋ CaSO ₄・ 2H ₂ O ↓ …… (2)

According to the present invention, water-soluble fluorine and water-insoluble fluorine contained in a monocalcium phosphate material are eluted into a slurry by decomposing the monocalcium phosphate material with sulfuric acid.
The eluted fluorine is fixed in the next step. In this sulfuric acid decomposition step, the elution amount of fluorine depends on the pH of the slurry. For example, almost all of water-soluble fluorine elutes at pH 2.0 or less, and part of non-water-soluble fluorine elutes at pH 1.5 or less. . At around pH 1.0, 90w of total fluorine
More than t% elute. Therefore, in order to elute at least the entire amount of water-soluble fluorine, it is preferable to carry out a decomposition reaction so that the pH of the slurry becomes 2.0 or less, and further, elute as little water-insoluble fluorine as possible and fix it in the next step. Preferably, the decomposition reaction is performed so that the pH of the slurry is 1.5 or less. The concentration and the amount of sulfuric acid to be added to the monocalcium phosphate material may be determined so that the pH of the slurry is in a target range. For example, monocalcium phosphate raw material 1
Sulfuric acid having a concentration of 98 wt% with respect to 00 parts by weight may be used in an amount of 10 to 20 parts by weight.

In the sulfuric acid decomposition step, the reaction temperature is 3
The temperature is preferably from 0 ° C to 90 ° C. Since the decomposition of monocalcium phosphate is an exothermic reaction, the generated slurry generally has a temperature of room temperature or higher, but may be heated so as to be in the above temperature range.
If the temperature is higher than 90 ° C., the decomposition reaction proceeds excessively, and the slurry becomes extremely low in viscosity, and it becomes difficult to granulate in the next step. Therefore, it is preferable to control the temperature to 90 ° C. or lower.

[Second Step: Immobilization of Fluorine] A basic material is added to the sulfuric acid decomposition slurry to neutralize the slurry, and fluorine eluted in the slurry is fixed. As the basic material, an alkaline earth metal compound which reacts with fluorine to form a hardly soluble fluorine compound is suitable, for example, calcined phosphorus fertilizer [2CaNaPO ₄ .Ca ₃ (PO ₄ ) ₂ ], or clay Raw materials can be used. Serpentine (3MgO ・ 2SiO ₂・
2H ₂ O), ferronickel slag (2MgO · SiO ₂ ), lightly burned magnesium (MgO), and fused phosphorus fertilizer are suitable.

The acidity of the slurry is neutralized by adding the above basic material to the sulfuric acid decomposition slurry, and the fluorine ions released in the slurry react with calcium ions and magnesium ions by the neutralization reaction. Generates and hardens hardly soluble calcium fluoride and magnesium fluoride. The reaction for immobilizing fluorine is affected by the pH when a basic material is added to the slurry to cause a reaction. Specifically, for example, the pH is preferably 3.0 or more to suppress the amount of eluted fluorine to 20 mg / l or less, and the pH is preferably 4.5 or more to suppress the amount of eluted fluorine to 5 mg / l or less. However, when the pH is higher than 6, phosphoric acid is dissolved. Therefore, to maintain the content of water-soluble phosphoric acid at a constant level, pH 6 or less is appropriate, and pH 5.5 or less is preferable. From the above, the pH in the slurrying step of sulfuric acid monocalcium phosphate raw material by decomposition with sulfuric acid is suitably from 3.0 to 6.0, and preferably from pH 4.5 to 5.5. Incidentally, the pH at the time of this reaction is the pH of the phosphate fertilizer.

Further, by adding the alkaline earth metal compound to the sulfuric acid decomposition slurry, phosphate ions (HPO ₄ ²⁻ ) in the slurry react with the Ca component and the Mg component of the alkaline earth metal compound, and Phosphate ions are converted into quosoluble phosphate compounds [CaHPO ₄ , MgHPO ₄ ], and the proportion of quosoluble phosphate components increases. Specifically, it is possible to obtain a phosphate fertilizer having 97% by weight or more of water-soluble phosphoric acid and 60% by weight or less of water-soluble phosphoric acid in the phosphoric acid component.

Further, by using formic acid raw materials such as serpentine, ferronickel slag, light-burned magnesium, and fused phosphorus fertilizer as a part of the basic material, and adjusting the amount of addition, 3 to 3 in terms of magnesium oxide. It is possible to obtain a phosphate fertilizer containing 10 wt% of a magnesia component. In this case, 97 wt% or more of the forsterite component can be made soluble in hardener.

The amount of the basic material added to the sulfuric acid decomposition slurry may be determined so that the pH after the addition falls within the above range. For example, when 50 to 70 parts by weight of the basic material is added to 100 parts by weight of the slurry, the pH after mixing is generally 3.5 to 5.5, depending on the pH of the slurry. The released fluorine can be fixed effectively.

Further, the phosphoric acid content is increased by adding a raw material of monocalcium phosphate together with a basic material to the sulfuric acid decomposition slurry. The phosphoric acid concentration of the sulfuric acid decomposition slurry is generally about 25 to 30 wt%, and the phosphoric acid content is reduced to 45 wt% to 50 wt.
Increase to about wt%. The amount of the monocalcium phosphate raw material may be determined according to the target phosphoric acid content.

The phosphate fertilizer of the present invention may contain iron. As an iron raw material, iron ore, mill scale, bengara and the like discharged from an ironworks or the like can be used. In addition, the phosphate fertilizer of the present invention contains gel silica, and the phosphoric acid component is wrapped by the gel silica, thereby suppressing the reaction between the water-soluble phosphate component and iron and preventing the fertilizer from solidifying. can do.

By subjecting the phosphate fertilizer of the present invention to granulation together with the above-mentioned fluorine fixation, a granular phosphate fertilizer can be obtained. Specifically, for example, the sulfuric acid decomposition slurry obtained in the first step, the monobasic lime phosphate material and the basic material are continuously introduced into the granulating means and granulated while reacting, thereby fixing and fixing fluorine. Improve the quality of soluble phosphoric acid components. The granulation means is not limited. A continuous dish granulator or the like can be appropriately used. In addition, the conventional granulation is for the purpose of simply adjusting the powder into granules, and therefore, the granulation time is about 3 to 4 minutes. However, in the present invention, in order to sufficiently fix the fluorine,
It is preferable to carry out the granulation time about 1.3 to 2 times longer (about 5 to 15 minutes) than before.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples.

[Production of monocalcium phosphate] 200 kg / h of concentrated phosphoric acid (P ₂ O ₅ : 53.4 wt%, F: 0.50 wt%) obtained by a wet method was used, and this was used for diatomaceous earth (silica content: 90 wt%). 0.996 kg / h, 3.5 kg / h of caustic soda (50 wt% concentration) were continuously supplied to the reaction vessel, and the resulting solid (Na ₂ SiF ₆ etc.) was separated from the phosphoric acid solution by pressure filtration and clarified. Phosphoric acid was obtained. The phosphoric acid solution had a phosphoric acid concentration of 53% by weight and a fluorine content of 0.17%.
It was 5% by weight. 215 kg / h of this phosphoric acid solution and 106.5 kg / h of calcium carbonate powder (600 mesh, concentration 98 wt%) are continuously supplied to the reaction vessel, and the reaction product is continuously taken out and dried, and the phosphoric acid solution is dried. 235 kg / h of lime were obtained. The components of this monocalcium phosphate are P ₂ O ₅ : 48.36 wt%, CaO: 2
4.98 wt%, MgO: 0.46 wt%, total fluorine content: 0.4
It is 16% by weight (amount of water-soluble fluorine: 0.03% by weight).

[Sulfuric acid decomposition step] To 450 kg / h of monocalcium phosphate produced as described above, 333 kg / h of a sulfuric acid solution having a concentration shown in Table 1 was added, and the mixture was kept for 1 hour to form a slurry.
Reaction temperature, slurry pH, amount and rate of sulfuric acid added,
Table 1 shows the concentration of phosphoric acid, the amount of calcium, the amount of eluted fluorine and the elution rate of fluorine contained in the supernatant. The solid portion of the slurry is the formed gypsum and the undecomposed monocalcium phosphate material.

As shown in Table 1, the pH of the slurry was 1.
When the pH is 9 to 2.0, the fluorine elution rate is 26 to 29 wt%.
0 wt% or more. Since the amount of water-soluble fluorine of monocalcium phosphate used in this example is 18.8 wt% based on the total amount of fluorine, those having a fluorine elution rate higher than this value are water-soluble fluorine and water-insoluble. Fluorine is eluted. Therefore, in this example, all of the water-soluble fluorine was eluted and the water-insoluble fluorine was further eluted, and the fluorine elution rate was high. As described above, most of the total fluorine amount is eluted and is immobilized in the next step, so that the amount of eluted fluorine can be significantly reduced.

[0029]

[Table 1]

[Granulation / Fixation of Fluorine] To 783 kg of the phosphoric acid slurry, the amounts of monocalcium phosphate, calcined phosphorus fertilizer, and lightly burned magnesia shown in Table 3 were added (total amount: 468 to 47).
5 kg) was continuously supplied to a granulator and granulated while reacting to obtain a granular phosphate fertilizer on which fluorine was fixed. The phosphate content of this phosphate fertilizer (TP ₂ O ₅ , CP ₂ O ₅ , WP
₂ O ₅ ), amount of magnesia (T-MgO, C-MgO), water content, total fluorine content, eluted fluorine content, pH, etc. along with the amount of raw materials used.
It was shown to. The amount of eluted fluorine was determined by using a ground sample passed through a 0.5 mm sieve, as described in “Environmental Standards for Soil Contamination” (Heisei 3
On August 23, 2003, by the Environment Agency Notification No. 46). The pH was measured according to the official fertilizer method.

[0031]

[Table 2]

As shown in Table 2, the phosphate fertilizer of the present example
In each case, the total fluorine content is on the order of 0.13 wt%, which is significantly low. Fertilizers having a pH of 3.7 to 3.8 have a fluorine elution amount of 16.9 to 18 mg / l, but have a pH of 4.9 to 5.9.
In the fertilizer adjusted to 0, the elution amount of fluorine was suppressed to 5 mg / l or less. Each fertilizer has a phosphoric acid content of 43wt%
The content of the soluble phosphoric acid is 41% or more (the solubilization rate is 97% or more), and the content of the water-soluble phosphoric acid is 16.55 to 25.19 wt% (the water solubility is 35.0%). 9-5
7.7%).

[0033]

Since the phosphate fertilizer of the present invention uses a defluorinated monocalcium phosphate material, the total amount of fluorine contained in the phosphate fertilizer is much larger than that of the conventional phosphate fertilizer produced by a wet method. Few. Moreover, almost all of the fluorine contained in the raw material is eluted once in the slurrying step, and the eluted fluorine is fixed in the next granulation step,
The amount of fluorine eluted from the phosphate fertilizer has been significantly reduced. Therefore, it is an environment-conserving low-fluorine phosphate fertilizer that can suppress the accumulation of fluorine in soil when fertilized in paddy fields and fields, and can prevent environmental pollution.

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Claims (11)

[Claims] 1. A phosphoric acid content of 20 to 50% by weight,
A low-fluorine phosphate fertilizer having a fluorine elution amount of 25 mg / l or less. 2. The phosphate fertilizer according to claim 1, wherein the total fluorine content is 0.5 wt% or less, and the fluorine elution amount is 8 mg / l or less. 3. A phosphoric acid component containing quosoluble phosphoric acid and water-soluble phosphoric acid, wherein the proportion of quosoluble phosphoric acid in the phosphoric acid component is 97% by weight or more and the ratio of water-soluble phosphoric acid is 60% by weight or less. 3. A phosphate fertilizer according to claim 1 or 2. 4. A composition containing a magnesia component together with a phosphoric acid component, wherein the content of the magnesia component is 3 to 10% by weight in terms of magnesium oxide.
The phosphate fertilizer according to any one of claims 1 to 3, wherein 97% by weight or more of the magnesia component is soluble magnesia. 5. A process comprising: decomposing monobasic lime phosphate with sulfuric acid to form a slurry to elute fluorine; and adding a basic material to the slurry to neutralize and fix fluorine. Manufacturing method of low fluorine phosphate fertilizer. 6. The method according to claim 5, wherein a monocalcium phosphate raw material mainly containing monocalcium phosphate obtained from defluorinated phosphoric acid is used. 7. The method according to claim 5, wherein in the fluorine fixing step, the amount of the phosphoric acid component is adjusted by adding a monocalcium phosphate material together with the basic material. 8. The pH of the sulfuric acid decomposition slurry is set to 2.0 or less in the slurrying step, and the pH of the sulfuric acid decomposition slurry is adjusted to 3.0 or more in the fluorine fixing step by adding a basic material to the slurry. The manufacturing method of 5, 6 or 7. 9. The production method according to claim 8, wherein the pH in the slurrying step is 1.5 or less, and the pH in the fluorine fixing step is 4.5 to 5.5. 10. A composition mainly composed of monocalcium phosphate and Ca / P
The method according to any one of claims 5 to 9, wherein a monocalcium phosphate material having a molar ratio of 0.55 to 0.75 is used. 11. The method according to claim 5, wherein one or more of calcined phosphorus fertilizer, fused phosphorus fertilizer, serpentine, ferronickel slag, and lightly burned magnesia are used as the basic material.