JP2019172548A - High phosphorus-containing slag, manufacturing method of slag-based fertilizer, and phosphate fertilizer - Google Patents

Abstract

To provide a manufacturing method for providing high phosphorus-containing slag easy to use as a phosphorus resource, from steel slag.SOLUTION: A high phosphorus-containing slag is manufactured through: a first process for reduction treating steel slag containing phosphorous generated in a steel-making refining process, and reducing iron oxide in the steel slag to recover the same as a phosphorous-containing molten iron; a second process for dephosphorylation treating the phosphorus-containing molten iron obtained in the first process to recover resulting high phosphorus slag; a third process for heating the high phosphorus slag obtained in the second process at a temperature of 1500°C or higher to separate it into two liquid phases, and recovering ultra high phosphorus slag in an upper layer; and a fourth process for using the ultra high phosphorus slag obtained in the third process as it is, or conducting at least one of methods of a magnetic separation, a floatation separation, and a gravity separation to obtain a slag having phosphoric acid of 30 mass% or more, and an iron component of less than 10 mass% (in terms of Fe).SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a high phosphorus content slag and a method for producing a slag fertilizer.
The present invention also relates to a phosphoric acid fertilizer comprising a slag fertilizer obtained by a method for producing a slag fertilizer or using the slag fertilizer as a main raw material.

There are many uses for phosphorus, including agriculture, food, electronic parts, medicine, and the automobile industry. However, phosphorus ore, the raw material for phosphorus, depends on imports in Japan.
For this reason, efforts are actively made to recover phosphorus from industrial byproducts such as steelmaking slag containing phosphorus.

  That is, since the hot metal produced in the blast furnace contains about 0.1% by mass of phosphoric acid, among the steelmaking slag generated in the hot metal refining process, the converter slag and hot metal pretreatment slag are 1 to 5% by mass of phosphoric acid is contained.

  Under such circumstances, phosphoric acid in steelmaking slag has been reviewed as a potential phosphoric acid-containing substance. However, as mentioned above, the phosphoric acid concentration in the hot metal is about 0.1% by mass, and the phosphoric acid concentration in steelmaking slag is at most about 5% by mass, and the phosphoric acid concentration is too low. The actual situation is that there is almost no utilization place.

The following proposals have been made as methods for concentrating and separating phosphorus contained in steelmaking slag and converting it into fertilizer.
For example, in Patent Document 1, steelmaking slag containing phosphorus is reduced using a reducing agent such as carbon, silicon, and aluminum, and iron oxide and phosphorus oxide in the steelmaking slag are used as phosphorus-containing molten iron. There has been proposed a technique for reducing and recovering, dephosphorizing the phosphorus-containing molten iron, and recovering slag containing a high concentration of phosphoric acid produced by the dephosphorization treatment as a phosphoric acid resource. And T. of dephosphorization slag. If the sum of the Fe concentration and the MnO concentration is less than 20% by mass, the slag containing phosphoric acid is increased in slag soluble phosphoric acid concentration, which is superior to a plant growth test as a phosphate fertilizer.

Patent Document 2 describes a method for producing high phosphorus slag.
In the technique described in Patent Document 2, hot metal having a phosphorus concentration of 0.15% by mass or less is dephosphorized, and the obtained phosphorus-containing slag is put into a hot metal bath to supply a carbon material and iron oxide and / or oxygen. Then, the phosphorus in the slag is reduced and extracted into the hot metal bath to produce a hot metal having a phosphorus concentration of 0.5 to 3% by mass, and after the slag produced in the first step is discharged, The flux is added so that the slag basicity after treatment becomes 2 to 8, and the concentration of carbon contained in the hot metal is reduced to 1% by mass or less by adding an iron oxide source and / or blowing oxygen gas. In the second step, a method of obtaining a high phosphorus slag having a phosphoric acid concentration of 10 to 35% by mass after the treatment has been proposed. The slag obtained by this method contains a high concentration of phosphoric acid and can be used directly as a fertilizer.

According to the technique described in Patent Document 2, there is room for improving the elution characteristics of phosphoric acid by reducing the concentration of iron in the slag. When using steelmaking slag as a fertilizer, in order to increase the solubility and solubility of phosphoric acid, it is necessary to increase the phosphoric acid concentration in addition to controlling the crystalline state and mineral phase of phosphorus. Further, it is known that the solubility of phosphoric acid is lowered by containing Al ₂ O ₃ or Fe ₂ O ₃ . However, since the above components are inevitably contained in the slag, it is desirable to increase the phosphoric acid concentration in the slag and reduce the Al ₂ O ₃ and Fe ₂ O ₃ concentrations.

By the way, from Non-Patent Document 1 and Non-Patent Document 2, in basic research mainly aimed at improving hot metal dephosphorization reaction, CaO—FeO—P ₂ O ₅ —MgO and CaO—FeO—P ₂ O _{5 in the} presence of hot metal. It is known that when a synthetic slag composed of —SiO ₂ is melted, it exhibits a two-liquid phase state. A composition region in which this property is confirmed is indicated by A in FIG. This two-liquid phase state consists of a phase having a high P ₂ O ₅ content and a low iron oxide content (high phosphorus phase) and a phase having a low P ₂ O ₅ content and a high iron oxide content (high iron phase). Become.

However, the actual dephosphorization slag (P ₂ O ₅ concentration (B in FIG. 1)) has a composition different from the composition region indicated by A in FIG. 1, and practically utilizes the two-liquid phase separation state. The recovery of phosphorous was considered difficult. Furthermore, even in actual slag, which is a complicated system containing MgO, SiO ₂ , and Al ₂ O ₃ , even if the composition is similar to that of Non-Patent Document 1 and Non-Patent Document 2, phosphorus resource recovery using two liquid phases A method has not been developed.

  Moreover, in patent document 3, the crystallization of the mineral phase with a high fertilizer effect is accelerated | stimulated by controlling the phosphate fertilizer component composition and cooling conditions which contain iron oxide, a high phosphoric acid concentration, and a high fertilizer effect, It has proposed a method for stably producing a phosphate fertilizer having a high fertilizer effect even if it contains iron oxide by suppressing crystallization of a mineral phase having a low fertilizer effect.

  Patent Document 3 states that the crystalline state and the mineral phase of phosphorus are controlled, and even if iron is contained, elution characteristics can be improved if phosphoric acid is contained as an amorphous material. This is an example in which the fertilizer characteristics of phosphoric acid are improved by means different from the present invention.

Japanese Patent No. 5935770 JP 2017-53017 A JP 3017-31013 A

ISIJ int. 44, 476-481, 2004 Arch. Eisenhuttenwes. No. 19 1948, pages 111-117 National Agriculture, Forestry and Fisheries Consumption Safety Technology Center, “Fertilizer Testing Method (2017)”

The conventional phosphorus concentration method has a problem that it has a high content of iron and Al ₂ O ₃ and is difficult to use as a phosphorus resource such as a phosphate ore substitute or phosphate fertilizer.
The present invention utilizes steelmaking slag containing phosphorus such as preliminary dephosphorization slag of hot metal generated in the steelmaking refining process and converter decarburization refining slag, recovering phosphorus from the steelmaking slag, and recovering high phosphorus slag from which phosphorus has been recovered. The first object is to obtain a high phosphorus content slag by performing a two-liquid phase separation process.
In addition, a second object of the present invention is to obtain a steelmaking slag fertilizer having a higher sol-soluble fertilizer component and a higher fertilizer effect by using the high phosphorus content slag as a phosphate fertilizer.

That is, the gist configuration of the present invention is as follows.
1. A method for producing high phosphorus content slag,
(1) The steelmaking slag containing phosphorus generated in the steelmaking refining process is reduced using a reducing agent containing at least one selected from carbon, aluminum and silicon, and iron oxide in the steelmaking slag is removed. A first step of reducing and recovering as phosphorus-containing molten iron;
(2) a second step of dephosphorizing the phosphorus-containing molten iron obtained in the first step and recovering the obtained high phosphorus slag;
(3) A third step of heating the high phosphorus slag obtained in the second step to a temperature of 1500 ° C. or higher to perform two-liquid phase separation and recovering the super-high phosphorus slag in the upper layer;
(4) The ultra-high phosphorus slag obtained in the third step is used as it is or by performing at least one method of magnetic separation, flotation and specific gravity separation, and phosphoric acid 30% by mass or more, iron content And a fourth step of obtaining a slag containing less than 10% by mass (in terms of Fe).

2. A method for producing phosphate fertilizer by concentrating phosphorus and removing iron from steelmaking slag containing phosphorus generated in a steelmaking refining process,
(1) The steelmaking slag is reduced using a reducing agent containing at least one selected from carbon, aluminum, and silicon, and iron oxide in the steelmaking slag is reduced and recovered as phosphorus-containing molten iron. The first step,
(2) a second step of dephosphorizing the phosphorus-containing molten iron obtained in the first step and recovering the obtained high phosphorus slag;
(3) A third step of heating the high phosphorus slag obtained in the second step to a temperature of 1500 ° C. or higher to perform two-liquid phase separation and recovering the super-high phosphorus slag in the upper layer;
(4) The ultra-high phosphorus slag obtained in the third step is used as it is or by performing at least one method of magnetic separation, flotation and specific gravity separation, and phosphoric acid 30% by mass or more, iron content And a fourth step of obtaining a slag containing less than 10% by mass (in terms of Fe).

3. The manufacturing method of the slag type fertilizer of said 2 whose slag soluble phosphoric acid concentration of the said steelmaking slag type fertilizer is 20 mass% or more.

4). A phosphate fertilizer comprising the slag fertilizer described in 2 or 3 above, or comprising the slag fertilizer as a main raw material and having a polycrystalline crystal structure.

According to the present invention, phosphorus is recovered from steelmaking slag containing phosphorus such as preliminary dephosphorization slag of hot metal generated in the steelmaking refining process and converter decarburization refining slag, and high phosphorus content slag that is easy to utilize as a phosphorus resource is obtained. Obtainable.
Moreover, according to this invention, the slag type fertilizer with a higher fertilizer effect can be obtained from the high phosphorus content slag obtained as mentioned above.

It is a ternary phase diagram of CaO—FeO _n —P ₂ O ₅ at 1600 ° C. In the figure, black squares indicate phosphorus-enriched slag (high phosphorus slag), white squares indicate examples of the present invention, and white triangles indicate comparative examples.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In the present invention, steelmaking slag containing phosphorus such as dephosphorization slag generated during hot metal preliminary dephosphorization treatment or converter slag generated in decarburization refining in a converter is used as a starting material.
Next, iron oxide and phosphorus oxide in the steelmaking slag are reduced with at least one selected from carbon, aluminum, and silicon in a rotary kiln, and a phosphorus-containing melt having a phosphorus concentration of 0.5% by mass or more. Collect iron. Here, as a processing container used in the reduction treatment step, a rotary kiln, an arc furnace, a ladle holding a hot metal as a heat source and seed water, a topped car, and the like can be used. The amount of reducing agent to be charged is preferably about 30 to 120 kg when using carbon, 45 to 180 kg when using aluminum, and about 35 to 145 kg when using silicon, per ton of molten slag.
When hot metal is used as a heat source and seed hot water, a part of the carbon in the hot metal also acts as a reducing agent. However, excessive charging of the reducing agent not only increases the cost, but the excess aluminum and silicon that are not subjected to reduction are dissolved in the phosphorus-containing molten iron and are added to Al ₂ O ₃ in the high phosphorus slag described later. And SiO _{2, which} is not desirable because it lowers the concentration of P ₂ O ₅ and inhibits the two-liquid phase.

Subsequently, the phosphorus-containing molten iron obtained is dephosphorized using lime, and phosphoric acid is concentrated in the CaO-containing flux so that the P ₂ O ₅ concentration is 7% by mass or more to obtain a high phosphorus slag. In addition, in order to control not only the P ₂ O ₅ concentration in the high phosphorus slag but also the SiO ₂ concentration and the manganese oxide concentration, desiliconization treatment and demanganese treatment may be performed before the dephosphorization treatment.
Here, there is no restriction | limiting in particular as a supply method of a lime source, Supply to hot metal can be performed by arbitrary methods, such as injection into hot metal with an immersion lance, and a top loading. The injection into the hot metal by the immersion lance may be performed together with the solid oxygen source. Further, in order to increase the dephosphorization efficiency, a lime source can be projected (sprayed) onto the bath surface from above the hot metal bath surface using a carrier gas. As this carrier gas, nitrogen, inert gas, or gaseous oxygen can be used.

The high phosphorus slag obtained as described above is transferred to a slag pan, an electric furnace or the like, heated from the periphery, upper or lower part of the container, and heated to a temperature at which the slag temperature becomes 1500 ° C. or more, Separate into phases.
The resulting two-liquid phase has a specific gravity difference, and the upper layer is P ₂ O ₅ > 25 mass%, the sum of iron oxide (FeO + Fe ₂ O ₃ : FeO conversion) and metallic iron (M.Fe: FeO conversion) ≦ 15 It becomes a high phosphorus phase of mass%. On the other hand, the lower layer becomes a high iron phase of P ₂ O ₅ <20% by mass, the sum of iron oxide (FeO + Fe ₂ O ₃ : FeO equivalent) and metallic iron (M.Fe: FeO equivalent)> 15% by mass. Here, the upper layer of the two liquid phase is an ultra-high phosphorus slag.

Here, the reason why the reheating temperature is limited will be described.
In general, the dephosphorization treatment is preferably performed at a low temperature, and is performed at about 1300 to 1450 ° C. However, in this temperature range, almost no liquid phase is generated in the slag. The concentrated slag does not separate into two liquid phases, and a high phosphorus and low iron phase cannot be obtained. By heating phosphorus-enriched slag, that is, high phosphorus slag, to 1500 ° C. or higher, the liquid phase ratio of slag becomes 70% by mass or higher and can be separated into two liquid phases. The heating temperature is preferably 1680 ° C. or less from the viewpoint of the heating cost of the slag and the melting loss of the container.
The heating time is preferably 10 minutes or longer in order to sufficiently melt the phosphorus-enriched slag. The upper limit of the heating and holding time is not particularly limited, but about 120 minutes is sufficient.

In the present invention, two-liquid phase separation is confirmed within the range shown in FIG. 1A. However, when the concentration of P ₂ O ₅ in the phosphorus-concentrated slag is 7% by mass or less, when recovering as a slag separated into multi-phases containing two liquid phases, it becomes a multi-phase containing two liquid phases with a satisfactory phosphorus concentration. The amount of separated slag cannot be obtained.
Therefore, the P ₂ O ₅ concentration in the phosphorus-enriched slag is 7% by mass or more. Preferably it is 10 mass% or more, More preferably, it is 15 mass% or more.

Further, the phosphoric concentration slag, SiO ₂ is mixed. If the SiO ₂ concentration of 10 mass% or more, without separating the liquid phase is biphasic, or high phosphorus phase can not be obtained, since the iron oxide concentration in the high phosphorus phase increases, SiO ₂ concentration of 10 mass %. A more desirable SiO ₂ concentration is 5% by mass or less. It may be 0% by mass.

Further, in the present invention, MgO together with manganese oxide, MgO <16% by mass, and 15% by mass <iron oxide (FeO + Fe ₂ O ₃ : FeO equivalent) and metallic iron (M.Fe: FeO equivalent) and manganese oxide (MnO + MnO ₂ : MnO equivalent) can be contained in a range that satisfies the sum <80% by mass.
Here, if the MgO concentration is 16% by mass or more, the substitution ratio of MgO to the C ₃ P phase, which is the main phase after cooling the high phosphorus phase, is not preferable. In general, phosphate ore is mainly used as a phosphoric acid raw material, but when the phosphate ore is decomposed with sulfuric acid, a large amount of impurity magnesium ammonium phosphate (MAP) is produced in the presence of MgO. Therefore, in order to prevent the occurrence of such MAP, MgO is preferably less than 10% by mass.
Further, when the sum of the iron oxide concentration and the manganese oxide concentration is 15% by mass or less, it is not preferable because the two-liquid phase separation does not occur and an almost uniform phase is obtained. This is not preferable because the amount of the collected product with respect to the reheating cost is reduced. The sum of iron oxide, metallic iron and manganese oxide is preferably 25% by mass or more and 55% by mass or less. More preferably, it is the range of 40 mass% or more and 55 mass% or less.

Having described the preferred composition of the phosphorus concentration slag according to the present invention, it is to the slag, Besides Al ₂ O ₃ is contained degree 5 wt% or less.

  As a method for recovering the ultra-high phosphorus slag described above, there is a method in which the lower low-slag slag is extracted from the lower outlet in a molten state and the ultra-high phosphorus slag remaining in the container is recovered. Further, after the hot water is poured into the tilted slag field, the upper and lower layers may be broken or cut in a solid state to recover the upper layer.

  After melt mixing, the mixed slag is taken out of the container and cooled and solidified. Cooling and solidification may be performed when taking out from the container, or may be carried out when taking out from another container containing the extracted mixed slag.

  As a method of cooling and solidifying, when cooling a melt or a supercooled liquid, for example, a high-pressure air is blown to the generated mixed slag to be scattered, and the mixture is cooled and granulated (wind crushing method) or mixed. A method of spraying high-pressure water on slag to disperse, cooling and granulating (hydrocracking method), a method of causing mixed slag generated on a thick steel plate to flow out, cooling by forced cooling with a thick steel plate and heat radiation to the air, Such a method can be adopted. In the case of slow cooling, a method of receiving slag in a soot pot and then discharging it to a slag treatment plant is conceivable.

  The slag thus obtained can be used as it is as an ultra-high phosphorus slag containing 30% by mass or more of phosphoric acid and less than 10% by mass of iron (in terms of Fe). By implementing at least one of these methods, the phosphorus concentration can be further increased.

In addition, when the shape after cooling and solidification is a lump, etc., after carrying out crushing (pulverization) treatment, at least one of magnetic ore flotation and specific gravity beneficiation is performed to obtain a granular ultra-high Rinse slag.
The pulverization is performed using a pulverizer so that the particle size after pulverization is 75 μm or less. The pulverizer may be a jet mill type in which slag is put on jet air and pulverized by causing the slag to collide with each other, and a slag is pulverized by putting a hard ball in the container and rotating the slag. A ball mill method may be used.

Next, the manufacturing method of slag type fertilizer is demonstrated.
Using phosphorus-containing steelmaking slag such as dephosphorized slag and converter slag as a starting material, this is reduced to phosphorus-containing molten iron, and this phosphorus-containing molten iron is dephosphorized to high phosphorus slag. Until it is heated to a temperature of 1500 ° C. or higher and separated into two liquid phases, the super-high phosphorus slag in the upper layer is recovered to make a slag containing 30% by mass or more of phosphoric acid and less than 10% by mass of iron (Fe conversion) The same as described above.
And the slag type fertilizer with a higher fertilizer effect can be obtained by utilizing the ultra-high phosphorus slag obtained in this way as a phosphorus fertilizer.

  By the way, the molten phosphorus fertilizer that has been used conventionally as a high-concentration soluble phosphonic acid source is vitreous, so it is difficult for water to penetrate inside. It changes variously. For example, fine powdered phosphorus fertilizer has an early onset of fertilization effect and a short duration, whereas coarse granular phosphorous fertilizer has a late onset of fertilizing effect and a long duration. Therefore, in order to obtain a stable fertilization effect onset time and duration, the composition of the particle size must be strictly determined whether a specific particle size range is used alone or in combination with a plurality of particle size ranges. There is a need to manage.

  The manufacturing method of the present invention does not require rapid solidification unlike the conventional manufacturing method of molten phosphorus fertilizer, so the high phosphorus content slag and steelmaking slag fertilizer manufactured by the manufacturing method of the present invention are not used. Both have a polycrystalline crystal structure. In the case of polycrystalline, moisture permeates into the inside through the grain boundary between crystals, so that the change in the onset time and duration of the fertilization effect accompanying the change in the particle size becomes more gradual than in the glassy material.

  The high phosphorus content slag manufactured by the manufacturing method of the present invention and the soluble phosphonic acid of the steelmaking slag fertilizer were measured by the method described in Non-Patent Document 3. However, in the method shown in Non-Patent Document 3, the sample is pulverized by a pulverizer until it passes through the sieve having a mesh size of 1 mm and then stirred for 1 hour in a citric acid solution. In order to investigate changes in the amount of soluble phosphoric acid dissolved, the sample size passes through a sieve with a mesh opening of 1 mm, and passes through a sieve with a mesh opening of 5.6 mm without passing through a sieve with a mesh opening of 2.8 mm. The particle size was measured for each of four types of particle size: a sample that did not pass through a sieve with an aperture of 5.6 mm without passing through a sieve with an aperture of 11.2 mm, and a sample that did not pass through a sieve with an aperture of 11.2 mm.

  As a result, the total solubility of those passing through a sieve with a mesh opening of 5.6 mm without passing through a sieve with a mesh opening of 2.8 mm, and passing through a sieve with a mesh opening of 11.2 mm without passing through a sieve with a mesh opening of 5.6 mm The amount of phosphoric acid eluted was the same as the amount of soluble phosphoric acid, though all passed through a 1 mm sieve. The elution amount of the soluble phosphoric acid that did not pass through the sieve with a mesh opening of 11.2 mm was less than half the amount of elution of the soluble phosphoric acid that passed through the sieve with a mesh opening of 1 mm, and was unstable. .

As a result, it was found that the elution rate of the soluble phosphoric acid does not change even if the particle diameter changes within the range as long as it passes through a sieve having an opening of 11.2 mm.
Thus, the slag fertilizer manufactured with the manufacturing method of this invention has the characteristic that the exact management of a particle size structure is unnecessary.

Examples of the present invention will be described below.
Example 1
The blast furnace hot metal discharged from the blast furnace is received by a topped car, the blast furnace hot metal contained in the topped car is subjected to desiliconization treatment and preliminary dephosphorization treatment, and then the blast furnace hot metal is transferred to the hot metal ladle, The hot metal was desulfurized by a mechanical stirring type desulfurization apparatus. The blast furnace hot metal after the desulfurization process was charged into the converter and decarburized and refined in the converter. The present invention was applied in a steelmaking-steelmaking process in which molten steel is produced from such blast furnace hot metal. That is, the converter slag produced | generated in said iron making-steel making process was used as a starting material.
In addition, the converter slag was magnetically separated in advance using a magnetic separator having a magnetic force of 3000 G and a slag treatment capacity of 50 to 150 t / Hr, and the metallic iron in the converter slag was separated and removed.

50 tons of steelmaking slag containing phosphorus produced in the steelmaking process and 4000 kg of coke (carbon) as a reducing agent are charged into a rotary kiln furnace equipped with a heating burner, and the steelmaking slag and coke are heated to 1000 ° C. or more by the burner. To reduce the steelmaking slag. The iron oxide in the steelmaking slag was reduced by coke to produce reduced iron. Moreover, phosphorus in steelmaking slag is also reduced, and the produced phosphorus reacts with reduced iron, that is, the produced phosphorus is taken into the reduced iron, and phosphorus-containing reduced iron containing phosphorus in a high concentration (phosphorus-containing molten iron). ) Produced. In the above reduction treatment, even if silicon or aluminum was used as a reducing agent instead of carbon, iron oxide and phosphorous oxide in steelmaking slag could be reduced without any problem, but silicon or aluminum was used. In this case, it is desirable that the amount of SiO ₂ or Al ₂ O ₃ in the slag rises in the subsequent dephosphorization treatment and the formation of two-liquid phase or soluble phosphoric acid is inhibited if it is used in an excessive amount more than necessary for the reduction. Absent.
The phosphorus-containing reduced iron obtained by the above reduction treatment contained 1.0 to 4.0% by mass of phosphorus. This phosphorus-containing reduced iron was poured into a blast furnace hot metal accommodated in a hot metal holding container and dissolved, and a phosphorus-containing hot metal having a phosphorus concentration adjusted to 0.5 to 3.0% by mass was produced.

  The phosphorus-containing hot metal is charged into a top-bottom-blown converter type reactor, and oxygen gas is sprayed from the top-blowing lance toward the phosphorus-containing hot metal. Dephosphorization treatment was performed by blowing 25 kg of powdered quicklime (CaO pure content: about 95% by mass) of 1 mm or less per ton of phosphorus-containing reduced iron. In addition, the solvent used was only powdered quicklime and does not mix a fluorine compound such as fluorite.

The high phosphorus slag obtained by the above dephosphorization treatment is transferred to a slag pan, an electric furnace, etc., heated from the periphery of the container, reheated to a temperature at which the slag temperature becomes 1550 ° C. or higher, and separated into two liquid phases. I let you. The resulting two-liquid phase has a specific gravity difference, the upper layer is P ₂ O ₅ > 25% by mass, the high phosphorus phase of iron oxide and metal iron (FeO equivalent) ≦ 15% by mass, and the lower layer is P ₂ O ₅ A low phosphorus layer of <25% by mass was obtained. Note that the samples SiO ₂ is contained more than 10 wt%, a two-liquid phase separation was not observed.

  The main results in the test are shown in Table 1. In Table 1, Level 1 and Level 2 are the chemical compositions of high phosphorus slag, respectively. Level 3 is the chemical composition of the slag that has been subjected to the two-liquid phase separation process for level 1, and level 4 is the chemical composition of the ultra-high phosphorus slag that has been subjected to the two-liquid phase separation process for level 2.

In level 3 where the two-liquid phase separation process was performed on level 1 containing 10% by mass or more of SiO ₂ , two-liquid phase separation was not confirmed.
On the other hand, in the level 4 where the two-liquid phase separation process was performed on the level ₂ , the P ₂ O ₅ concentration was 27.7% by mass and the T.P. An ultra-high phosphorus slag having an Fe concentration of 11.3% by mass could be obtained.
However, T. cerevisiae, which inhibits the solubility of phosphate. Fe concentration is high and there is room for further reduction.

(Example 2)
In this example, the effect of the ultra-high phosphorus slag separation method was verified.
As a target, the ultra-high phosphorus slag shown in Level 4 was used.
X-ray diffraction measurement confirmed that the level 4 ultra-high phosphorus slag had a C ₃ P phase and a (FeMg ₂ ) O ₄ phase.
Therefore, the ultra-high phosphorus slag was pulverized to 75 μm or less with a ball mill, and magnetic separation and specific gravity separation were performed.
Magnetic beneficiation was performed by a wet process in order to prevent aggregation of particles. The specific gravity separation was cyclone separation.
With respect to the final recovered material that has been subjected to the separation treatment of ultrahigh phosphorus slag as described above, the P ₂ O ₅ concentration and the T.O. Fe concentration was measured by chemical analysis.
The obtained results are shown in Table 2.

As shown in the table, the concentration of P ₂ O ₅ in the recovered product can be further increased by carrying out at least one separation method. The Fe concentration could be reduced to less than 10% by mass.

Next, fertilizer components were analyzed for level 1 and level 5.
The results are shown in Table 3.

As shown in the table, it can be seen that the solubility of phosphoric acid was improved before and after separation.
Thus, according to the manufacturing method of the phosphate fertilizer of the present invention, high P ₂ O ₅ concentration, iron oxide and base metal concentration is low, it is possible to obtain a high phosphate fertilizer with fertilizer effect.
Moreover, when the crystal structure of the phosphate fertilizer obtained by this invention was investigated, it was confirmed that all are polycrystalline.

  The conditions in the examples are one condition example adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to this one condition example. 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.

Claims (4)

A method for producing high phosphorus content slag,
(1) The steelmaking slag containing phosphorus generated in the steelmaking refining process is reduced using a reducing agent containing at least one selected from carbon, aluminum and silicon, and iron oxide in the steelmaking slag is removed. A first step of reducing and recovering as phosphorus-containing molten iron;
(2) a second step of dephosphorizing the phosphorus-containing molten iron obtained in the first step and recovering the obtained high phosphorus slag;
(3) A third step of heating the high phosphorus slag obtained in the second step to a temperature of 1500 ° C. or higher to perform two-liquid phase separation and recovering the super-high phosphorus slag in the upper layer;
(4) The ultra-high phosphorus slag obtained in the third step is used as it is or by performing at least one method of magnetic separation, flotation and specific gravity separation, and phosphoric acid 30% by mass or more, iron content And a fourth step of obtaining a slag containing less than 10% by mass (in terms of Fe). A method for producing phosphate fertilizer by concentrating phosphorus and removing iron from steelmaking slag containing phosphorus generated in a steelmaking refining process,
(1) The steelmaking slag is reduced using a reducing agent containing at least one selected from carbon, aluminum, and silicon, and iron oxide in the steelmaking slag is reduced and recovered as phosphorus-containing molten iron. The first step,
(2) a second step of dephosphorizing the phosphorus-containing molten iron obtained in the first step and recovering the obtained high phosphorus slag;
(3) A third step of heating the high phosphorus slag obtained in the second step to a temperature of 1500 ° C. or higher to perform two-liquid phase separation and recovering the super-high phosphorus slag in the upper layer;
(4) The ultra-high phosphorus slag obtained in the third step is used as it is or by performing at least one method of magnetic separation, flotation and specific gravity separation, and phosphoric acid 30% by mass or more, iron content And a fourth step of obtaining a slag containing less than 10% by mass (converted to Fe).   The method for producing a steelmaking slag fertilizer according to claim 2, wherein the slag-soluble phosphoric acid concentration of the steelmaking slag fertilizer is 20% by mass or more. A phosphate fertilizer comprising the slag fertilizer according to claim 2 or 3, wherein the slag fertilizer is a main raw material, and the crystal structure is polycrystalline.

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