JP6040064B2 - Manufacturing method of mineral phosphophosphate fertilizer - Google Patents

Description

  The present invention relates to a method for producing a mineral phosphophosphate fertilizer and a mineral phosphophosphate fertilizer produced by the production method.

Phosphorus is a nutrient that is essential for the growth of crops and is often applied as a phosphate fertilizer. Most of phosphate fertilizers are produced from phosphate ore, but in recent years, phosphate ore depletion has led to a worldwide rise in phosphate fertilizers. For this reason, attempts have been made to use phosphoric acid contained in steelmaking slag, which is a byproduct of steel, as a fertilizer (Patent Documents 1 and 2).
In addition, “mineral phosphoric acid fertilizer” is defined as one of ordinary fertilizers based on the Fertilizer Control Law, and its standard is also established.

On the other hand, in Japanese farmland, fertilization of iron and manganese becomes ineffective due to soil alkalinization by continuous use of lime materials, or mineral shortage occurs due to unused organic resources such as compost and harvest residues. Mineral nutrient deficiencies have occurred.
In order to cope with mineral nutrient deficiency, siliceous fertilizers using steel slag as a raw material have been proposed, manufactured and sold (Patent Document 3).

Japanese Patent No. 5105322 JP-A-2-277709 Japanese Patent No. 4091745

The mineral phosphoric acid fertilizer may contain a fertilizer component having a soluble phosphoric acid content of 3.0 mass% or more, an alkali content of 20.0 mass% or more, and a soluble silicic acid content of 10.0 mass% or more. It is prescribed.
However, it is difficult to stably achieve a quality in which soluble phosphoric acid is 3.0% by mass or more while using steelmaking slag as a raw material, and it can be used as a “mineral phosphophosphate fertilizer” regulated by the Fertilizer Control Law. The current situation has not yet been reached.

For example, in Patent Document 1, the basicity is as low as 1.4 or less, the soluble lime is as low as 30% by mass or less, and the alumina concentration is as high as 4.5% by mass or more as shown in Examples. The phosphoric acid absorption capacity of the dephosphorized slag used as a raw material was not sufficient, so that the amount of phosphoric acid in the raw material slag was low. Furthermore, as shown in Patent Document 1, since slag having an iron content (total iron content) concentration of 13% by mass at most as an index of an oxidizing atmosphere during dephosphorization reaction is used as a raw material, slag originally has. The dephosphorization ability was not fully utilized. Thus, with the technique of Patent Document 1, it was not possible to stably secure 3.0% by mass or more of the soluble phosphoric acid defined by “Mineral Phosphate Fertilizer” of the Fertilizer Control Law.
Moreover, in patent document 2, it is essential to blow an inert gas together with the faux stone mixed with fluorite (CaF ₂ ) as a melting point depressant of slag, and there is a problem that fluorine remains in the fertilizer. .
In the “silicic acid fertilizer” disclosed in Patent Document 3, since the fertilizer is focused on securing soluble silicic acid, the soluble phosphoric acid concentration is 1 to 4 mass%. Therefore, in order to guarantee phosphoric acid, it was necessary to mix soluble phosphoric acid as a mixture without expensiveness.

  The present invention has been made in order to cope with the above-mentioned problems. A production method capable of stably producing the quality of “mineral phosphate fertilizer” defined by the Fertilizer Control Law without variation and a “mineralization” obtained by this production method. The purpose is to provide "phosphate fertilizer".

In the method for producing the mineral phosphophosphate fertilizer of the present invention, the soluble phosphoric acid contained in the entire mineral silicate fertilizer is 3.0% by mass or more, the alkali content is 20.0% by mass or more, and the soluble silicic acid is 10%. A method for producing a mineral phosphoric acid fertilizer, in which a mineral phosphoric acid fertilizer containing a fertilizer component of 0.0 mass% or more is produced from slag as a raw material,
The above slag has a basicity of 1.5 to 3.0, a soluble silicic acid concentration of 15 to 35 mass%, a soluble lime content of 30 to 45 mass%, and an aluminum oxide content of 4.5 mass% or less. A slag produced as a by-product in the hot metal pretreatment process, a pulverizing process for pulverizing the slag, and a magnetic beneficiation process for reducing the iron concentration in the entire mineral phosphate fertilizer to 17% by mass or less by magnetically selecting the slag. It is characterized by providing.
In addition, a granulation step of granulating the slag is provided after at least one of the pulverization step and the magnetic beneficiation step.
Moreover, blast furnace slag is mixed during the granulation step or before the granulation step.

  Here, the soluble silicic acid refers to silicic acid that is leached when a substance containing silicic acid is shaken in a 0.5N hydrochloric acid solution at 30 ° C. for 1 hour. ) Is called soluble lime. The soluble phosphoric acid is a phosphoric acid that dissolves a substance containing phosphoric acid in a 2% by mass citric acid solution (pH 2). Soluble silicic acid, soluble lime and soluble phosphoric acid are analyzed by the fertilizer analysis method (Agricultural Environment Technology Research Institute, Ministry of Agriculture, Forestry and Fisheries). Moreover, the said alkali content says the quantity which added the quantity of the soluble lime measured by the same method as the said soluble lime x1.3914 to the quantity of soluble lime.

  The mineral phosphoric acid fertilizer of this invention is manufactured by the said manufacturing method.

  The method for producing the mineral phosphophosphate fertilizer according to the present invention has a sufficient iron content concentration by using steelmaking slag having sufficient basicity and soluble lime and reducing the alumina concentration to a predetermined concentration or less, and crushing and magnetically orienting the slag. 17 mass% or less and soluble phosphoric acid can be 3.0 mass% or more, and the quality of “mineral phosphoric acid fertilizer” defined by the Fertilizer Control Law can be manufactured stably and without variation.

It is a manufacturing-process figure of a sandy mineral phosphophosphate fertilizer. It is a manufacturing-process figure of a granular mineral phosphophosphate fertilizer.

In the method of manufacturing the slag phosphate fertilizer of the present invention, the basicity of by-product from steel plants (CaO / SiO ₂₎ is 1.5 to 3.0, the soluble silicate concentration of 15 to 35 wt%, the soluble lime A steelmaking slag containing 30 to 45% by mass and aluminum oxide of 4.5% by mass or less is used as a raw material. This steelmaking slag is by-produced in the hot metal pretreatment process at the steelworks.

In order to increase the phosphate absorption capacity in the steelmaking slag in the hot metal pretreatment dephosphorization process at the ironworks, it is essential that the basicity is 1.5 or more. Steelmaking slag that has undergone the dephosphorization process, that is, slag that sufficiently absorbs the phosphoric acid intended by the present invention usually contains 10 to 50% by mass of iron. This iron content is the iron content generated or remaining in the slag by adding gaseous oxygen and / or solid oxygen such as iron oxide as an oxidant in the ironworks hot metal pretreatment dephosphorization process. It exists in the iron oxide state such as iron, FeO, Fe ₂ O ₃ and magnetite.

  Aluminum oxide reduces the dephosphorization ability of slag, reduces phosphate absorption into slag, and inhibits elution of soluble silicic acid and soluble phosphoric acid after becoming fertilizer, so 4.5 mass % Or less, preferably 3.0% by mass or less.

  As described above, in order to promote the dephosphorylation reaction, it is necessary to maintain the basicity at 1.5 or more. Further, the iron content is required to be at least 10% by mass in order to keep the degree of oxidation high, but from the viewpoint of securing a high iron yield in the iron making process, it is economically appropriate to keep it at 50% by mass or less. is there. However, in the actual hot metal preliminary treatment dephosphorization step, in addition to iron oxide, the content of the granular iron physically wound up by nitrogen gas or oxygen gas blown into the hot metal for the purpose of promoting the reaction, or CO gas generated by the reaction, etc. Is present in the slag, it is difficult to strictly control the iron concentration. For this reason, as described above, the iron concentration in the raw material slag varies.

About soluble silicic acid, if it is 15 mass% or less, the effect as a silicic acid fertilizer is not enough, and even if it exceeds 35 mass%, the effect as a silicic acid fertilizer will be saturated.
If the soluble lime is less than 30% by mass, the soil neutralization ability required for vegetables and the like is reduced, and if it exceeds 45% by mass, the concentration of soluble silicic acid is reduced.

As described above, the iron content in the slag is kept high from the viewpoint of the dephosphorization reaction, so that the degree of oxidation of the slag can be secured, the dephosphorization reaction is promoted, and the phosphoric acid concentration in the slag can be increased. However, from the viewpoint of soluble phosphoric acid that is actually absorbed into crops, it is desirable to reduce the iron content in the slag as much as possible. This is because, after fertilizer application, phosphoric acid binds with CaO or CaO-SiO ₂ composite oxide and is not easily soluble in phosphoric acid, but is stably bound with CaO composite oxide containing iron and iron oxide. Therefore, it becomes difficult to release the crop so that it can be absorbed.
Therefore, in the present invention, the basicity sufficiently containing iron described above is 1.5 to 3.0, the concentration of soluble silicic acid is 15 to 35% by mass, the soluble lime is 30 to 45% by mass, and the aluminum oxide is Steelmaking slag of 4.5% by mass or less is used as a raw material, and this raw material is pulverized and prepared so that the iron concentration is 17% by mass or less, preferably 15% by mass or less by magnetic separation (magnetic separation). A preferable lower limit of the iron concentration is 5% by mass. This makes it possible to increase the concentration ratio of soluble phosphoric acid in the slag to 3% by mass or more. In particular, the concentration of soluble phosphoric acid can be increased by removing components such as metallic iron and magnetite in the iron concentration.

The manufacturing method of the mineral silicic acid fertilizer of this invention is demonstrated with FIG. 1 and FIG.
FIG. 1 is a production process diagram of sandy slag phosphate fertilizer.
The steelmaking slag 1 carried in from the steelworks is pulverized in the pulverization step 2. In the pulverization step, the fertilizer effect can be expected as the maximum particle size of the mineral phosphate fertilizer is smaller, but it is necessary to select a particle size that takes into account dust and scattering during spraying. As in the mineral phosphophosphate fertilizer standard, the particle diameter is set to pass through a sieve having a mesh size of 4 mm. Moreover, you may perform the dispersion | distribution process by an oil component, organic substance, etc.

The magnetic separation process 3 is a process of removing metallic iron by a magnetic separator so that the iron content in the mineral phosphoric acid fertilizer is 17% by mass or less.
In the pulverization process 2 and the magnetic separation process 3, the pulverization-magnetic separation may be repeated a plurality of times depending on conditions such as the particle size of the raw material slag, the iron concentration, and the size of the granular iron. As for the particle size after pulverization, it is possible to select a size that allows efficient magnetic separation as long as the product particle size can be maintained.

The slag phosphate fertilizer that has undergone the magnetic separation process 3 is sized by the sizing process 4. In the sizing step 4, the total water content is preferably adjusted to 5% by mass or less. Adhesion between particles is reduced, pulverization is facilitated, and free calcium oxide and the like can be stabilized.
In the sizing step 4, the product is sieved so as to have a particle diameter passing through a product vibration sieve having a mesh size of 4 mm.

  The sieved slag phosphate fertilizer is dried to a predetermined moisture value in the drying step 5. The total water content is preferably 5% by mass or less. In the drying step 5, it is preferable to continuously stabilize free calcium oxide or the like simultaneously with the drying for adjusting the water content, particularly by using a kiln dryer or the like.

  In the product adjustment step 6, the screened mineral phosphophosphate fertilizer is subjected to final adjustment such as mixing of auxiliary materials and mixing with other fertilizer components to produce sandy silicate phosphate fertilizer 7.

FIG. 2 is a production process diagram of granular mineral phosphoric acid fertilizer.
In FIG. 2, the steps described in FIG. 1 can be adopted as the steps up to magnetic separation process 3 and the product adjustment process 6. A drying / pulverization process 8, a mixing process 9, a granulation process 10, and a granulated product drying process 11 for granulation after the magnetic separation process 3 are provided.
The drying / pulverization step 8 is a step of finely pulverizing after drying and moisture adjustment. In the drying and moisture adjustment step, the total moisture content is adjusted to 5% by mass or less. By adjusting the total amount of water within this range, the particles can be less adhered to each other and pulverized easily, and contributes to the stabilization of free calcium oxide and the like. In particular, by using a kiln dryer or the like, it is preferable to continuously stabilize free calcium oxide or the like simultaneously with drying for adjusting the water content.
The fine pulverization is performed using a ball mill or the like. The steelmaking slag 1 is temporarily stored in a slag bunker and further pulverized by a ball mill. The ball mill is mainly used in a dry type and can be further finely pulverized than a dry self-pulverizing mill.

The mixing step 9 is a step of mixing, as the mixture 9a, a binder, a blast furnace slag, or a mixture of a binder and a blast furnace slag with the finely pulverized steelmaking slag.
As the binder, for example, one or more selected from phosphoric acid, clay, bentonite, polyvinyl alcohol, carboxymethyl cellulose, polyacrylic acid, molasses, lignin, lignin sulfonic acid metal salt, magnesium sulfate, starch and the like alone or It can be used by mixing. In consideration of granulation properties in a dish type granulator preferably used in the granulation step, molasses, lignin or lignin sulfonic acid metal salt is preferred.
As the blast furnace slag, granulated slag and / or slowly cooled slag discharged during pig iron smelting in the blast furnace can be used. By mixing blast furnace slag, granulation and soil disintegration after fertilizer application can be enhanced. However, in view of securing the soluble phosphoric acid concentration which is the original purpose, the concentration of the blast furnace slag to be mixed is 10% by mass or less in view of the fact that the soluble phosphoric acid concentration level is lower than other components such as soluble silicic acid. It is preferable that Moreover, it is preferable that a binder (solid content conversion) shall be 7 mass% or less.
By using a mixture of binder and blast furnace slag, the amount of binder can be minimized.

  The granulation step 10 is a step of granulating the steelmaking slag of the mixing step 9. As the fertilizer granulator, a drum type, a stirring type, and a dish type are used. In the present invention, a dish type granulator that easily ensures the shape quality of product grains is preferable.

  The granulated product drying step 11 is a step of drying the granulated product to a predetermined moisture value. A preferable moisture content is 5 mass% or less with respect to the whole mineral silicate fertilizer.

In the product adjustment step 6, the screened mineral silicate phosphate fertilizer is subjected to final adjustment to produce granular silicate phosphate fertilizer 7 '. In the product adjustment step 6, mixing of auxiliary raw materials such as mixing of potassium and humic acid, mixing with other fertilizer components, and the like can be performed.
The particle diameter of the granular mineral phosphophosphate fertilizer 7 ′ is 1.5 to 6 mm, preferably 1.7 to 5.5 mm.

  The mineral phosphoric acid fertilizer 7 and 7 'manufactured in FIG. 1 or FIG. 2 described above increases the phosphate absorption capacity of the dephosphorized slag by setting the basicity during the dephosphorization process to a range of 1.5 to 3.0. The steelmaking slag having a soluble silicic acid concentration of 15 to 35% by mass, soluble lime of 30 to 45% by mass and aluminum oxide of 4.5% by mass or less obtained by dephosphorization is pulverized. Subsequently, magnetic separation is carried out to reduce the iron concentration to 17% by mass or less, so that 3.0% by mass or more of soluble phosphoric acid is stably obtained. At the same time, soluble lime, which is an alkali component, is obtained in an amount of 30% by mass or more, and the concentration of soluble silicic acid is 15% by mass or more. It is possible to enjoy the effect.

Examples 1-30 and Comparative Examples 1-10
Three types of steelmaking slags with basicities of 1.74, 2.02 and 2.36 obtained by charging hot metal into a converter-type refining furnace and dephosphorizing it in the steelmaking process at the steelworks Used as slag. The composition of the raw material slag is shown in Table 1. In Table 1, T.W. CaO is the total CaO concentration, T.I. SiO ₂ is the total silicic acid concentration and the basicity is T.P. CaO / T. SiO ₂ . T. Fe represents the total iron content concentration. Each component was analyzed by the fertilizer analysis method (Ministry of Agriculture, Forestry and Fisheries, Agricultural Environment Technology Laboratory Method).

Using the raw material slag, a sand-like slag phosphate fertilizer was manufactured in the manufacturing process of FIG. 1, and a granular slag phosphate fertilizer was manufactured in the manufacturing process of FIG. Table 2 shows the composition of the obtained mineral phosphophosphate fertilizer, the presence or absence of the compounding agent, and the product shape. In addition, in the mineral phosphoric acid fertilizers of Examples 1 to 30, the iron concentration was 10 levels in the range of 17% by mass or less, and the soluble phosphoric acid in each case was analyzed, and 3% by mass or more of the soluble phosphoric acid was found. The resulting ratio was evaluated as stability. The results are shown in Table 2 as the achievement status. In Table 2, the achievement rate refers to the rate at which products satisfying the specifications of mineral phosphophosphate fertilizer are produced by a plurality of production times (levels) for the same steelmaking slag as a raw material.
In addition, Table 2 shows examples in which the iron concentration exceeds 17% by mass as Comparative Examples 1 to 10 even when magnetic separation is performed. In Table 2, the meaning of each simplified composition is the same as in Table 1.

As is apparent from Table 2, at all levels of basicity 1.74 (Examples 1-10), 2.02 (Examples 11-20), and 2.36 (Examples 21-30), It was confirmed that the soluble phosphoric acid concentration in each Example was stably 3% by mass or more.
At the same time, it was found that the alkali content was 20% by mass or more and the soluble silicic acid was 20% by mass or more, satisfying the conditions of “mineral silicate fertilizer” of the fertilizer control method. As a result, 3 mass% or more of soluble phosphoric acid can be assured, and the amount of phosphoric acid that is generally replenished with expensive chemical fertilizers can be reduced, resulting in a significant cost reduction.

  In Comparative Examples 1 to 10, when the iron concentration exceeds 17% by mass even after magnetic separation, the rate at which 3% by mass or more of soluble phosphoric acid is obtained is 70%, and Examples 1 to 30 are achieved. It was found that the stability was inferior compared to. That is, since 3% by mass or more of soluble phosphoric acid, which is a condition of “mineral phosphoric acid fertilizer” stipulated in the Fertilizer Control Law, cannot be guaranteed, it cannot be a standard product of “mineral phosphoric acid fertilizer”.

Comparative Examples 11-20
As Comparative Examples 11 to 15, five types of steelmaking slag having a basicity of 1.0 to 1.4 were pulverized or granulated to produce a mineral phosphoric acid fertilizer.
Moreover, as Comparative Examples 16-20, five types of steelmaking slag having a basicity of 1.6-3.0 were pulverized or granulated to produce a mineral phosphoric acid fertilizer. The results are shown in Table 3. In Table 3, the meaning of each simplified composition is the same as in Table 1.

  The slags of Comparative Examples 11 to 20 have a basicity of 1.5 to 3.0, soluble lime of 30 to 45 mass%, aluminum oxide of 4.5 mass% or less, and iron concentration of 17 mass% or less. Therefore, the soluble phosphoric acid concentration of the fertilizer product could not be stably increased to 3% by mass or more.

  The production method of the mineral phosphophosphate fertilizer of the present invention can stably produce a soluble phosphoric acid concentration of 3.0% by mass or more stipulated by the Fertilizer Control Law with little variation in quality. It can be used to improve agricultural productivity in Japan.

DESCRIPTION OF SYMBOLS 1 Steelmaking slag 2 Grinding process 3 Magnetic separation process 4 Granulation process 5 Drying process 6 Product adjustment process 7, 7 'Mineral phosphoric acid fertilizer 8 Drying and fine grinding process 9 Mixing process 10 Granulation process 11 Granulated product drying process

Claims (3)

Mineral slag containing fertilizer components containing 3.0 mass% or more of soluble phosphoric acid, 20.0 mass% or more of the alkali content, and 10.0 mass% or more of the soluble silicic acid contained in the entire mineral silicate fertilizer. A method for producing a mineral phosphate fertilizer in which phosphate fertilizer is produced from slag as a raw material,
The slag contains 1.5 to 3.0 basicity, 15 to 35 mass% soluble silicic acid, 30 to 45 mass% soluble lime, and 4.5 mass% or less aluminum oxide. Slag by-produced in the pretreatment process,
Crushing step of crushing the slag;
A method for producing a mineral phosphophosphate fertilizer, comprising: a magnetic beneficiation step in which the slag is subjected to magnetic beneficiation so that the concentration of iron contained in the entire slag phosphate fertilizer is 17% by mass or less.   The method for producing a mineral phosphophosphate fertilizer according to claim 1, further comprising a granulation step of granulating the slag after at least one of the pulverization step and the magnetic separation process.   3. A method for producing a mineral phosphoric acid fertilizer according to claim 2, wherein blast furnace slag is mixed during the granulation step or before the granulation step.

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