JP2016088757A - Phosphate fertilizer raw material and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphate fertilizer raw material having high fertilizer effect while containing iron oxide and a manufacturing method therefor.SOLUTION: There are provided a phosphate fertilizer raw material containing CaO, SiO, POand iron oxide (in terms of Fe) of total 60% or more, having a basicity α represented by mass concentration ratio of CaO and SiOof 1.5 to 3.0 inclusive and containing POof 8 mass% to (-4α+23α-4) mass% inclusive and iron oxide in terms of Fe of 5 mass% to 25 mass% inclusive, the phosphate fertilizer raw material having a total of existing concentrations of one or more of Ca(PO)-CaSiOsolid solution, 5CaO SiOPOand 7CaO 2SiOPOof 28 mass% or more. A molten slag having the above composition at 1250 to 1400°C is cooled at 10°C/min or more till 600°C.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a phosphate fertilizer raw material and a method for producing the same.

  Since Japan has a large amount of precipitation, minerals flow out of the soil and the soil is easily acidified. Therefore, basic phosphate fertilizers that increase not only the phosphate concentration in soil but also soil pH are widely used as phosphate fertilizers used when growing plants. At present, as a basic phosphate fertilizer, dissolved phosphorus fertilizer containing a large amount of alkali is used.

  As shown in Non-Patent Document 1, in the past, Thomaslin fertilizer manufactured as a by-product in the Thomas steelmaking method, which is one of steelmaking methods, has been used as a basic phosphate fertilizer. However, because of the decline of the Thomas steelmaking method, Thomaslin fertilizer is not used at present.

  Currently, the hot metal discharged from the blast furnace contains about 0.1% phosphorus as an impurity. Phosphorus is oxidized and removed by adding flux and blowing oxygen in the steelmaking process and discharged as steelmaking slag. ing.

As shown in Patent Document 1, the steelmaking slag has a phosphoric acid concentration of about 1 to 4% by mass, which is not a sufficient concentration as a phosphate fertilizer, but the steelmaking slag is oxidized from the CaO content derived from the flux and the hot metal. Since the removed SiO _{2 component} is contained in a large amount, it is used as a silicate phosphate fertilizer.

  However, in Japan, which still depends on imports for the total amount of phosphate ore that is a raw material for phosphate fertilizer, the phosphoric acid content in steelmaking slag is considered as a useful phosphate fertilizer resource. As shown in Fig. 2, attempts have been made to produce phosphoric acid fertilizer from steelmaking slag by concentrating the phosphoric acid content in steelmaking slag to produce high phosphoric acid slag.

  By the way, in order to enhance the fertilizer effect when using the phosphate fertilizer as a fertilizer, it is necessary to control not only the phosphoric acid concentration but also the crystal state and mineral phase of phosphorus. For example, the above-mentioned melted phosphorus fertilizer is a fertilizer manufactured by melting and mixing phosphate ore and magnesium oxide and quenching with a jet water stream, and the phosphorus-containing mineral phase is made amorphous, that is, glass. , Enhance the fertilizer effect.

  The phosphorus-containing mineral phase in the present invention refers to a phase in which phosphorus is concentrated in each mineral phase in the fertilizer.

As shown in Non-Patent Document 1, Thomas phosphorus fertilizer is mainly composed of CaO, P ₂ O ₅ and SiO ₂ , so that the phosphorus-containing mineral phase is Ca ₃ (PO ₄ ) ₂ —Ca ₂ SiO _4. It is a solid solution phase, 5CaO · SiO ₂ · P ₂ O ₅ phase, or 7CaO · 2SiO ₂ · P ₂ O ₅ phase (hereinafter sometimes referred to as "solid solution phase"). The solid solution phase is a mineral phase with a high fertilizer effect.

In Patent Document 3, by controlling the composition, the mineral phase of phosphorus in the phosphate fertilizer is intentionally described as a Ca ₃ (PO ₄ ) ₂ phase (hereinafter sometimes referred to as “C ₃ P phase”). To increase the effect of fertilizer by forming

Thus, the fertilizer effect in high phosphate slag is high phosphorus-containing mineral phase is a glass phase, solid solution phase, and is believed to be a C ₃ P phase.

Japanese Patent No. 5105322 JP-A-11-158526 JP 2009-132544 A JP 2011-208277 A

Japan Soil Fertilizer Journal, Vol. 13, p93

  In Japan, where phosphorus ore, the raw material for phosphate fertilizer, is imported from overseas, phosphorus in hot metal is a very attractive resource. When producing phosphate fertilizer using phosphoric acid in hot metal or phosphoric acid in steelmaking slag, it is inevitable that iron oxide is mixed into the phosphate fertilizer. Therefore, it is desired to develop a phosphate fertilizer with high fertilizer effect.

  However, a phosphate fertilizer raw material containing iron oxide, a phosphate fertilizer raw material having a high fertilizer effect using steelmaking slag as a raw material, and a manufacturing method thereof have not been developed.

  For example, in solution phosphorus fertilizer, it is vitrified as described above to enhance the fertilizer effect, but crystallization occurs when iron oxide is mixed, and the fertilizer effect at that time is unknown.

In addition, Thomaslin fertilizer is in a composition region where the basicity represented by the weight ratio of CaO and SiO ₂ is very high as 5 or more, and when the steelmaking slag whose basicity is generally less than 5 is used as a raw material, The solid solution does not always precipitate, and the fertilizer effect is unknown.

  Patent Document 1 discloses that the slag recovered in the hot metal pretreatment process is used as a silicate phosphate fertilizer. However, since there is no step of intentionally concentrating the phosphoric acid concentration, phosphorus in the slag is disclosed. The acid concentration is as low as 5% or less, and the fertilizer effect as a phosphate fertilizer is low.

  Depending on the technique disclosed in Patent Document 2, it is possible to produce high-phosphate slag, but the cooling rate is not clearly specified, and the phosphate-containing mineral phase is not intentionally controlled. The fertilizer effect is unknown.

Depending disclosed in Patent Document 3 technologies, it is possible to produce a high phosphate slag, 3CaO · P ₂ O ₅ phase phosphorus-containing mineral phase (C ₃ P phase) and / or 4CaO · P ₂ fertilizer effect is not high because of the O ₅ phase. The reason will be described later.

The technique disclosed in Patent Document 4 also has a low fertilizer effect because the phosphorus-containing mineral phase in the phosphate fertilizer is controlled and mainly the C ₃ P phase. The reason will be described later.

  Therefore, in view of the above situation, the present invention aims to provide a phosphate fertilizer raw material containing iron oxide, or a phosphate fertilizer raw material when phosphorus in hot metal is used as a starting material, and a method for producing the same. And

  In order to achieve the above-mentioned object, the present inventor has studied the phosphate fertilizer raw material having a high fertilizer effect in terms of the component composition and production conditions. As a result, the phosphorus-containing mineral phase is arranged in terms of the fertilizer effect. I found out. And by controlling the component composition and cooling conditions, the precipitation of the mineral phase with a high fertilizer effect is promoted, the precipitation of the mineral phase with a low fertilizer effect is suppressed, and the fertilizer effect is high even if iron oxide is contained. A method for stably producing phosphate fertilizer was found.

  In the present invention, soluble phosphoric acid is used as an index for evaluating the fertilizer effect of phosphate fertilizer without using general soluble phosphate. Soluble phosphoric acid and soluble phosphoric acid are phosphoric acid in fertilizer, phosphoric acid dissolved in 2% aqueous citric acid solution, or phosphoric acid dissolved in 2% ammonium citrate solution, which is more neutral. It refers to the acid content.

  This is because the pH of soil in which plants grow well is weakly acidic to neutral, so it is evaluated with soluble phosphoric acid that dissolves in a solution close to neutrality rather than soluble phosphoric acid that dissolves in an acidic solution of about pH 2. This is based on the idea that this is more appropriate. Recently, it has been known that soluble phosphate corresponds to the growth of plants.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

[1] CaO, SiO ₂ , P ₂ O ₅ , and iron oxide (Fe conversion) are contained in a total of 60% by mass or more, and the basicity α expressed by the mass concentration ratio of CaO and SiO ₂ is 1.5 or more. A phosphate fertilizer raw material containing 3.0 mass% or less, 8 mass% or more (-4α ² + 23α-4) mass% or less of P ₂ O ₅ and 5 mass% or more and 25 mass% or less of iron oxide in terms of Fe. In the phosphate fertilizer raw material, one or two of Ca ₃ (PO ₄ ) ₂ -Ca ₂ SiO ₄ solid solution, 5CaO · SiO ₂ · P ₂ O ₅ , and 7CaO · 2SiO ₂ · P ₂ O ₅ The phosphate fertilizer raw material characterized in that the total concentration is 28% by mass or more.

  [2] The phosphate fertilizer raw material according to [1], wherein the phosphate fertilizer raw material is a steelmaking slag produced by dephosphorizing hot metal produced in a blast furnace.

[3] The method for producing a phosphate fertilizer raw material according to [1] or [2], wherein CaO, SiO ₂ , P ₂ O ₅ , and iron oxide (Fe conversion) are 60% by mass or more in total. And the basicity α expressed by the mass concentration ratio of CaO and SiO ₂ is 1.5 or more and 3.0 or less, and P ₂ O ₅ is 8 mass% or more (−4α ² + 23α-4) mass%, A molten slag of 1200 to 1450 ° C. containing iron oxide in an amount of 5% by mass or more and 25% by mass or less in terms of Fe was divided by the time until the temperature reached 600 ° C. until the temperature reached 600 ° C. A method for producing a phosphate fertilizer raw material, which is controlled by numerical values and controlled to be 10 ° C./min or higher.

  [4] The molten slag of 1200 to 1450 ° C. is controlled to be 30 ° C./min or more by a numerical value obtained by dividing the temperature drop until reaching 600 ° C. by the time to reach 600 ° C. And the method for producing a phosphate fertilizer raw material according to [3] above.

  [5] The above-mentioned [3] or [4], wherein the molten slag is a steelmaking slag produced by dephosphorizing high phosphorus hot metal containing 0.5 to 4% by mass of phosphorus. Manufacturing method of phosphate fertilizer raw material.

  ADVANTAGE OF THE INVENTION According to this invention, although it contains iron oxide, a phosphoric acid fertilizer raw material with a high phosphoric acid concentration and a high fertilizer effect and its manufacturing method can be provided.

It is a figure which shows an example of the process of manufacturing phosphoric acid containing slag in a steelmaking process. It is a figure which shows the relationship between a soluble phosphoric acid ratio (soluble phosphoric acid concentration / total phosphoric acid concentration) and crystallinity. It is a figure which shows the relationship between phosphoric acid concentration and basicity, and a phosphorus containing mineral phase. Crystallinity and t. It is a figure which shows the relationship of Fe density | concentration. The concentration of the solid solution phase and t. Relationship between Fe concentration, C ₃ P phase existing concentration and t. It is a figure which shows the relationship of Fe density | concentration. Is a diagram showing the relationship between existence concentration and the cooling rate of the solid solution phase or C ₃ P phase.

The phosphate fertilizer raw material of the present invention (hereinafter sometimes referred to as “the present fertilizer raw material”) contains CaO, SiO ₂ , P ₂ O ₅ , and iron oxide (in terms of Fe) in total of 60% by mass or more. The basicity α expressed as a mass concentration ratio of CaO and SiO ₂ is 1.5 or more and 3.0 or less, P ₂ O ₅ is 8 mass% or more (−4α ² + 23α-4) mass%, iron oxide Is a phosphate fertilizer raw material containing 5 mass% or more and 25 mass% or less in terms of Fe, and the Ca ₃ (PO ₄ ) ₂ —Ca ₂ SiO ₄ solid solution, 5CaO · SiO ₂ · P _{2 in the} phosphate fertilizer raw material The total of the concentration of one or more of O ₅ and 7CaO.2SiO ₂ .P ₂ O ₅ is 28% by mass or more.

The method for producing a phosphate fertilizer raw material according to the present invention (hereinafter sometimes referred to as “the present invention production method”) is a method for producing the fertilizer raw material according to the present invention, and includes CaO, SiO ₂ , P ₂ O ₅ , iron oxide ( Fe content) is 60% by mass or more in total, the basicity α expressed by the mass concentration ratio of CaO and SiO ₂ is 1.5 or more and 3.0 or less, and P ₂ O ₅ is 8% by mass or more (− 4α ² + 23α-4) Less than mass%, iron oxide is contained in an amount of 5% by mass to 25% by mass in terms of Fe, and the amount of temperature drop until reaching 600 ° C. is 1000 to 1450 ° C. It is characterized by cooling by controlling it to be 10 ° C./min or more by a numerical value divided by the time to reach ° C.

  First, the manufacturing method of the phosphoric acid containing slag which can be used as a raw material (phosphate fertilizer raw material) of the phosphate fertilizer for plant growth is demonstrated. FIG. 1 shows an example of a process for producing phosphoric acid-containing slag in the steel making process.

  As shown in FIG. 1, in the steelmaking process, hot metal produced in a blast furnace, usually containing 0.08 to 0.15% by mass of phosphorus, is transferred to a converter, and slag is placed on the hot metal. After forming, oxygen source is blown, and hot metal dephosphorization treatment S01 is performed by reaction of hot metal and slag.

  The converter dephosphorization slag 41 generated by the dephosphorization process S01 is discharged from the converter, and then slag is formed again on the molten iron in the converter, and an oxygen source is blown to perform a decarburization process S02. After subjecting the molten steel obtained in the decarburization treatment S02 to secondary refining S03, a steel slab is produced in continuous casting S04.

  After the dephosphorization treatment S01, the converter dephosphorization slag 41 discharged from the converter contains a large amount of iron together with phosphoric acid obtained by oxidizing phosphorus in the hot metal. Therefore, in order to recover valuable elements such as iron and phosphorus from the converter dephosphorization slag 41, the converter dephosphorization slag 41 is subjected to reduction / reforming treatment S11.

In the reduction / reformation treatment S11, the converter dephosphorization slag 41 is melted, pulverized coal, an Al ₂ O ₃ source, and an SiO ₂ source are added as a reducing agent and a modifying agent, and phosphorus is added in an amount of 0.5-4. The high P hot metal 42 containing as much as mass% is manufactured.

Then, after applying a Cr removal treatment S12 to the high P hot metal 42 as necessary, a flux using quick lime, SiO ₂ or the like as a raw material is added, and a phosphorus removal treatment S13 in which oxygen is blown is applied to obtain phosphorus for plant growth. The phosphoric acid containing slag 50 which can be used as a raw material (acid fertilizer raw material) of acid fertilizer is manufactured.

  Note that the hot metal 51 dephosphorized to a phosphorus content concentration of 0.1 to 0.3 mass% by the dephosphorization treatment S13 is supplied to the converter together with the hot metal generated in the blast furnace.

  When manufacturing the phosphoric acid containing slag 50, it is necessary to control the component composition and the cooling rate to increase the amount of soluble phosphoric acid in the phosphoric acid containing slag.

In the fertilizer raw material of the present invention, the total of CaO, SiO ₂ , P ₂ O ₅ and iron oxide (in terms of Fe) is 60% by mass or more, and the basicity α expressed by the mass concentration ratio of CaO and SiO ₂ is 1. 5 to 3.0, P ₂ O ₅ is 8% by mass or more (−4α ² + 23α-4)% by mass, iron oxide is 5% by mass to 25% by mass in terms of Fe, and Ca _{3 (PO 4) 2 -Ca 2 SiO} 4 solid _{solution, 5CaO · SiO 2 · P 2} O 5 _{and,, 7CaO · 2SiO 2 · P} 2 O 5 ( hereinafter, collectively three mineral phases may be referred to as "solid solution phase" The total of the concentration of one kind or two kinds or more) is 28% by mass or more.

Further, when performing the dephosphorization treatment S13 (see FIG. 1), the basicity α of the molten slag in the processing container at the end of the dephosphorization treatment S13 is 1.5 to 3.0, and P ₂ O _The dephosphorization conditions are adjusted so that ₅ is 8% by mass or more (-4α ² + 23α-4)% by mass and iron oxide is 5% by mass or more and 25% by mass or less in terms of Fe.

  Then, the amount of temperature drop until the molten slag adjusted as described above reaches 600 ° C. from 1200 to 1450 ° C., which is the temperature at the end of the treatment, is the time until it reaches 600 ° C. Cooling by dividing the numerical value (hereinafter sometimes referred to as “cooling rate to 600 ° C.”) to be 10 ° C./min or higher, preferably 30 ° C./min or higher. To do.

Hereinafter, the reason for accelerating the precipitation of the solid solution phase from the phosphorus-containing mineral phase of the phosphoric acid-containing slag and suppressing the precipitation of the C ₃ P phase, the reason for limiting the component composition, the basicity, the P ₂ O ₅ concentration, the iron oxide concentration The reason why the basicity, the phosphoric acid concentration, and the cooling rate are limited when the phosphoric acid-containing slag is produced by performing the dephosphorization process will be described.

First, the reason for promoting the precipitation of the solid solution phase and suppressing the precipitation of the C ₃ P phase will be described.

  The slag raw material having the composition shown in Table 1 is produced by the dephosphorization treatment S13. The slag generated by the dephosphorization treatment S13 is cooled by controlling the cooling rate from 1200 to 1450 ° C. to 600 ° C., which is the slag temperature at the end of the treatment, to 10 ° C./min or more. After the temperature reached room temperature of about 25 ° C., the phosphorus-containing mineral phase in the sample was confirmed by XRD, SEM or the like.

In some slag samples, a glass phase was confirmed in addition to the crystalline phase. The glass phase was confirmed to contain phosphorus. On the other hand, the crystal phase could be classified into three mineral phases: phosphate phase, silicate phase, and FeO phase. There were two types of phosphate phases: C ₃ P phase and solid solution phase.

  The results are summarized in Table 1.

It was found that the mineral phase in which phosphorus, which is an important part as a phosphate fertilizer, is present (hereinafter sometimes referred to as “phosphorus-containing mineral phase”) is a glass phase, a C ₃ P phase, and a solid solution phase. ○ in Table 1 indicates that it is a major mineral phase, and Δ means a minor mineral phase or a minor mineral phase. Never C3P phase and solid solution phase is a crystal phase is precipitated at the same time, also, C ₃ P phase, or, when the solid solution phase is precipitated, there is a case where the glass phase is precipitated at the same time.

  In order to investigate the relationship between the phosphorus-containing mineral phase of the produced slag and the fertilizer effect, the crystallinity and soluble phosphoric acid ratio of the slag samples shown in Table 1 were measured. The results are shown in FIG.

  The soluble phosphate rate is the ratio of the soluble phosphate concentration to the total phosphate concentration in the phosphate fertilizer feedstock. When using phosphate fertilizer, the amount of phosphate fertilizer is adjusted according to the phosphate concentration of the phosphate fertilizer and added to the soil so that the amount of phosphate is constant, so the fertilizer effect is not the soluble phosphate concentration The soluble phosphate rate was evaluated.

From FIG. 2, it can be seen that when the C ₃ P phase precipitates (see “x” in the figure), the soluble phosphoric acid ratio decreases as the crystallinity increases. When a solid solution is precipitated (see “◯” in the figure), the degree of crystallinity is almost 100%, and the soluble phosphoric acid ratio may be higher than when a C ₃ P phase and a glass phase are present. I understand.

From these results, (a) the soluble phosphoric acid ratio of the C ₃ P phase, the glass phase, and the solid solution phase has an order, and (b) the soluble phosphoric acid in the order of C ₃ P phase << glass phase <solid solution phase. It was found that (c) the solid solution phase was the phase having the highest soluble phosphoric acid ratio, and the C ₃ P phase was the phase having the lowest soluble phosphoric acid ratio.

From this, it is understood that in order to increase the fertilizer effect in slag, that is, the concentration of soluble phosphoric acid, it is necessary to suppress the precipitation of the C ₃ P phase as much as possible and to actively precipitate the solid solution phase. .

In fact, as described later, Hiroshima vegetables are grown using high phosphate slag in which 28.2% by mass of the solid solution phase is precipitated and high phosphate slag that does not contain the solid solution phase and includes only the C ₃ P phase. The growth was confirmed. The results are shown in Table 2.

As shown in Table 2, when high-phosphate slag with a solid solution phase precipitated was used (sample No. 4), the growth of Hiroshima vegetable was good, but the solid solution phase was not included and only the C ₃ P phase was included. When high phosphate slag was used (sample No. 9), it was confirmed that the growth of Hiroshima vegetable was poor.

That is, the present inventors can produce dephosphorization slag (phosphate fertilizer raw material) with a high soluble phosphoric acid concentration by suppressing the precipitation of the C ₃ P phase and promoting the precipitation of the solid solution phase in the phosphorus-containing mineral phase. It was confirmed.

The phosphate fertilizer raw material contains CaO, SiO ₂ , P ₂ O ₅ and iron oxide as main components, and the total of each component is 60% by mass or more. If the total of each component is less than 60% by mass, components other than the above components and phosphoric acid form a compound, and generation of a phosphoric acid-containing mineral phase cannot be controlled. 60 mass% or more. Preferably it is 70 mass% or more.

  However, the concentration of iron oxide is expressed as the Fe concentration in the sample, and hereinafter referred to as “t.Fe concentration”.

The present inventors examined the conditions under which the solid solution phase is most stably precipitated. In FIG. The Fe concentration was fixed to 10% by mass, the MnO concentration was fixed to 5% by mass, the MgO concentration was fixed to 5% by mass, the Al ₂ O ₃ concentration was fixed to 3% by mass, and the molten slag was removed after the dephosphorization treatment S13 (see FIG. 1). The relationship between the phosphoric acid concentration and the basicity and the phosphorus-containing mineral phase when the cooling rate from 1200 to 1450 ° C. to 600 ° C., which is the temperature, is controlled to be 10 ° C./min or higher is shown.

That is, FIG. 3 shows the basicity dependency and the P ₂ O ₅ concentration dependency of the phosphorus-containing mineral phase. ○ indicates a case where a solid solution phase is precipitated, and × indicates a case where a C ₃ P phase is precipitated. When the basicity α (= CaO / SiO ₂ ) is 1.5 or more and 3.0 or less, a solid solution phase is precipitated. Therefore, in order to enhance the fertilizer effect, the basicity α needs to be 1.5 or more and 3.0 or less.

Basicity α is 1.5 or less, or, if greater than 3.0, the fertilizer effect decreases in precipitation C ₃ P phase. Therefore, at the time of dephosphorization treatment, the amount of flux such as quick lime and SiO _{2 to be} added is adjusted so that the basicity α of the slag is 1.5 or more and 3.0 or less. When the abundance ratio of the solid solution phase in the slag having a basicity α of 1.5 or more and 3.0 or less with respect to the total slag mass is measured by SEM, the phosphoric acid concentration is 8 mass% or more and the solid solution phase is 28 mass% or more. Was confirmed.

On the other hand, the reason why the upper limit of the phosphoric acid concentration is limited by a secondary expression of basicity α will be described. As shown in FIG. 3, even when the basicity α is in the range of 1.5 to 3.0, the C ₃ P phase starts to precipitate when the phosphoric acid concentration increases more than a certain level. Since it was experimentally confirmed that the phosphate concentration at which the C ₃ P phase begins to precipitate increases with a quadratic curve when the basicity α increases, the phosphoric acid concentration that increases with a quadratic curve (−4α ² + 23α-4).

That is, when the basicity is kept constant and the phosphoric acid concentration is increased from 0% by mass, a solid solution phase is precipitated from the condition of 8% by mass, and the phosphoric acid concentration becomes (−4α ² + 23α-4). In the region of mass% or less, the phosphorus-containing mineral phase is a solid solution phase, but when it exceeds (−4α ² + 23α-4) mass%, the phosphorus-containing mineral phase becomes a C ₃ P phase.

Therefore, if the phosphorus-containing mineral phase of the phosphate fertilizer raw material is a C ₃ P phase, the fertilizer effect is reduced, so the phosphoric acid concentration is 8 mass% or more (−4α ² + 23α-4) mass% or less. Therefore, it is necessary to adjust the amount of flux added to the slag during the dephosphorization treatment so that the phosphoric acid concentration is 8 mass% or more (−4α ² + 23α-4) mass% or less.

When the phosphoric acid concentration is less than 8% by mass, the phosphoric acid concentration is low, and it is not a solid solution phase but a C ₃ P phase. As a result, the amount of phosphoric acid fertilizer used becomes large, and the commercial value as a fertilizer decreases.

  t. Fe concentration shall be 5 mass% or more and 25 mass%. Among the samples shown in Table 1, the degree of crystallinity and t. In a sample having a basicity α of 1.5 or more and 3.0 or less and a phosphoric acid concentration of 12% by mass or more and 20% by mass or less. The relationship of Fe concentration is shown in FIG.

  t. When the Fe concentration was less than 5.0% by mass, a glass phase was present in the slag. When the Fe concentration was 5% by mass or more, the crystallinity was 100% and a crystal phase was present. Iron oxide is considered to exist as FeO and is a basic oxide and a component that promotes crystallization of slag. Therefore, it can be understood that 5% by mass or more of iron oxide is necessary to precipitate the solid solution phase which is a crystalline phase.

FIG. 5 shows the concentration of the solid solution phase in the sample and t. Relationship between Fe concentration, C ₃ P phase existing concentration and t. The relationship of Fe concentration is shown. t. When the Fe concentration is in the range of 5% by mass or more and 25% by mass or less, a solid solution phase is precipitated, and t. When the Fe concentration exceeded 25% by mass, a C ₃ P phase was precipitated.

  From this result, in order to precipitate the solid solution phase, the amount of oxygen blown during the dephosphorization treatment is adjusted, and t. It can be seen that the Fe concentration needs to be 5 mass% or more and 25 mass% or less.

  When manufacturing a phosphate fertilizer raw material, it is necessary to control and cool the 1200 to 1450 degreeC molten slag adjusted to the said composition so that the cooling rate to 600 degreeC may be 10 degreeC / min or more.

  If the temperature of the molten slag is less than 1200 ° C., the slag may not be completely melted, and in that case, the fertilizer effect as a phosphate fertilizer does not appear. Setting the temperature of the molten slag to a temperature exceeding 1450 ° C. makes it difficult for dephosphorization to proceed from the dephosphorization reaction equilibrium, resulting in a decrease in the phosphoric acid concentration in the slag, increasing the heating cost, and the processing container. The refractory material wears too much, so it is inappropriate.

Molten slag basicity, phosphoric acid concentration, t. Even if the Fe concentration is within the above range, the precipitation of the C ₃ P phase cannot always be suppressed. In order to suppress the precipitation of the C ₃ P phase, the cooling rate for cooling the molten slag is also an important factor.

The inventors of the present invention have a basicity α: 1.6, Al ₂ O ₃ : 3% by mass, MgO: 9% by mass, P ₂ O ₅ : 18% by mass, t. Fe concentration: 6 mass% of molten slag sample is controlled so that the cooling rate to 600 ° C. is 1 ° C./min, 5 ° C./min, 10 ° C./min, 30 ° C./min, and 50 ° C./min. The sample was cooled and the concentration of phosphorus-containing mineral phase in the sample was examined.

  The reason for controlling the cooling rate between the temperature after the dephosphorization process to 600 ° C. so as to be equal to or higher than the predetermined cooling rate until reaching 600 ° C. is that the phosphorus-containing mineral phase in the slag However, it is determined in the temperature range, and the mineral phase does not change in the temperature range below 600 ° C. The survey results are shown in FIG.

As shown in FIG. 6, when the cooling rate is 1 ° C./min and 5 ° C./min, only the C ₃ P phase is precipitated, and at 10 ° C./min, 30 ° C./min and 50 ° C./min, only the solid solution phase is precipitated. Precipitated.

  From this result, in order to increase the existing concentration of the solid solution phase to 28% by mass or more, the above-mentioned numerical value until reaching 600 ° C. is used by using water cooling or a method of pouring molten slag into a steel plate and quenching. It turns out that it is necessary to control and cool so that it may become 10 degrees C / min or more. Preferably it is 30 degrees C / min or more.

  As mentioned above, although the manufacturing method and phosphoric acid containing slag of phosphoric acid containing slag were demonstrated, this invention is not limited to the said description, In the range which does not deviate from the technical idea of invention, it can change suitably.

  In addition, in the process of manufacturing the phosphoric acid containing slag shown in FIG. 1, although it demonstrated that the high phosphorus hot metal obtained from the converter dephosphorization slag was dephosphorized and manufactured phosphoric acid containing slag, manufacturing phosphoric acid containing slag was manufactured. Is not limited to this description.

For example, the hot metal produced in the blast furnace may be manufactured by dephosphorization. In addition, quick lime, SiO ₂ , P ₂ O ₅ , iron oxide and the like are mixed as starting materials so as to enter the above composition range, and then melted and cooled at the cooling rate to produce a phosphate fertilizer raw material. Also good.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on these one example conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
Dephosphorization treatment S13 (refer to FIG. 1), the composition of the slag after the treatment contains CaO, SiO ₂ , P ₂ O ₅ , and iron oxide (Fe conversion) in a total of 60% by mass or more, The basicity α expressed by the mass concentration ratio of SiO ₂ is 1.5 or more and 3.0 or less, P ₂ O ₅ is 8 mass% or more (−4α ² + 23α-4) mass%, and iron oxide is converted to Fe. The temperature was adjusted to 5 mass% or more and 25 mass% or less, and the temperature after the treatment was controlled to 1250 to 1400 ° C.

  The slag generated at that time is mainly cooled to 600 ° C. so as to be a cooling rate of 10 ° C./min with the above numerical value, and the abundance ratio of the solid solution phase of the slag, the soluble phosphoric acid ratio, and The crystallinity was investigated. The results are shown in Table 3.

  The soluble phosphoric acid ratio was evaluated by evaluating the soluble phosphoric acid ratio of 0.6 or more as ◎, and less than 0.5 as x.

In the slag samples of Examples 1 to 9 having a cooling rate of 10 ° C./min, the basicity is 1.5 or more and 3.0 or less, and the phosphoric acid concentration is 8 mass% or more (−4α ² + 23α-4) mass% or less. T. The Fe concentration is 5% by mass or more and 25% by mass or less, and the abundance ratio of the solid solution phase with respect to the total slag mass is 28% by mass or more.

In the slag samples of Comparative Examples 1 to 8, since the basicity α was as low as less than 1.5 and the phosphoric acid concentration exceeded (−4α ² + 23α-4) mass%, in Comparative Example 9, the basicity was α is as low as less than 1.5, t. Since the Fe concentration was as high as more than 25% by mass, in Comparative Example 10, the basicity was higher than 3.0, so the solid solution phase did not precipitate.

In Comparative Example 11, the phosphoric acid concentration was lower than 8% by mass, and in Comparative Example 12, since it was higher than (−4α ² + 23α-4), the solid solution phase did not precipitate. In Comparative Example 13, t. The Fe concentration is lower than 5%, resulting in a glass phase. In Comparative Examples 14 and 15, t. Since the Fe concentration was higher than 25%, no solid solution phase precipitated.

  In the slag sample of Comparative Example 13, the cooling rate was less than 10 ° C./min, so no solid solution was precipitated.

  When Examples 6 and 10 having the same composition and different cooling rates are compared with Comparative Example 16, when the cooling rate up to 600 ° C. is set to 10 ° C./min or more, the solid solution phase is 28% by mass or more. It was confirmed that the concentration of the solid solution phase was higher in the example where the cooling rate to 600 ° C. was increased to 30 ° C./min.

  As described above, according to the present invention, it is possible to provide a phosphate fertilizer raw material that contains iron oxide but has a high phosphate concentration and a high fertilizer effect, and a method for producing the same. Therefore, the present invention has high applicability in the steel industry and the plant breeding industry.

Claims (5)

CaO, SiO ₂ , P ₂ O ₅ and iron oxide (Fe conversion) are contained in a total of 60% by mass or more, and the basicity α expressed by the mass concentration ratio of CaO and SiO ₂ is 1.5 or more and 3.0. A phosphate fertilizer raw material containing 8% by mass or more (-4α ² + 23α-4)% by mass or less of P ₂ O ₅ and 5% by mass or more and 25% by mass or less of iron oxide in terms of Fe, Presence of one or more of Ca ₃ (PO ₄ ) ₂ -Ca ₂ SiO ₄ solid solution, 5CaO · SiO ₂ · P ₂ O ₅ and 7CaO · 2SiO ₂ · P ₂ O ₅ in phosphate fertilizer raw material A phosphate fertilizer raw material characterized in that the total concentration is 28% by mass or more.   The phosphate fertilizer raw material according to claim 1, wherein the phosphate fertilizer raw material is a steelmaking slag produced by dephosphorizing hot metal produced in a blast furnace. A method of manufacturing a phosphate fertilizer material of claim 1 or _{2, CaO, SiO 2, P} 2 O 5, and contain more than 60 wt% iron oxide (Fe conversion) in total, CaO and SiO _The basicity α expressed by a mass concentration ratio of ₂ is 1.5 or more and 3.0 or less, P ₂ O ₅ is 8 mass% or more (−4α ² + 23α-4) mass% or less, and iron oxide is converted into Fe. A numerical value obtained by dividing a molten slag of 1250 to 1400 ° C. containing 5% by mass or more and 25% by mass or less by a time until reaching 600 ° C. until reaching 600 ° C. A method for producing a phosphate fertilizer raw material, which is controlled and cooled so as to be at least min.   Cooling by controlling the molten slag of 1250 to 1400 ° C. to be 30 ° C./min or higher by dividing the amount of temperature drop until reaching 600 ° C. by the time to reach 600 ° C. The manufacturing method of the phosphate fertilizer raw material of Claim 3 characterized by the above-mentioned.   5. The phosphate fertilizer raw material according to claim 3, wherein the molten slag is a steelmaking slag produced by dephosphorizing high P hot metal containing 0.5 to 4 mass% of phosphorus. Production method.

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