JP2019151528A - Method of producing phosphate fertilizer raw material - Google Patents

Abstract

To provide a method of producing a phosphate fertilizer raw material having high fertilization effects and facilitating control of production conditions when producing the phosphate fertilizer raw material by dephosphorylating high phosphorus molten iron.SOLUTION: A method of a producing phosphate fertilizer raw material of this invention includes: adding, in a converter or a ladle, as a phosphorus removing agent, 5-25 kg/molten iron in total in terms of MgO of materials in which the total of magnesium oxide, magnesium carbonate, magnesium hydroxide, or a combination thereof is contained 90 mass% or more of the total mass of the phosphorus removing agent to molten iron whose C concentration is 3.0-5.0 mass%, whose Si concentration is 0.01-0.40 mass%, whose Mn concentration is 0.01-1.40 mass%, and whose P concentration is 0.8-4.0 mass%; and blowing or adding oxygen of 7 kg/molten iron ton or more (added MgO amount kg/molten ton+11)kg/molten ton or less in a form of oxygen gas or iron oxide within a molten iron temperature range of 1300-1450°C.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a phosphate fertilizer raw material having a high fertilizer effect.

  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.

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

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. In addition, suppose that a phosphorus containing mineral phase refers to the phase which phosphorus concentrated in each mineral phase in a fertilizer.

Patent Documents 5 to 7 include Ca ₃ (PO ₄ ) ₂ —Ca ₂ SiO ₄ solid solution phase, 5CaO · SiO ₂ · P ₂ O ₅ phase, or 7CaO · 2SiO ₂ · P ₂ O which is a phosphorus-containing mineral phase. _{Among the five} phases (hereinafter referred to as “solid solution phase”), the Ca ₃ (PO ₄ ) ₂ phase (hereinafter referred to as “C ₃ P phase”) and the glass phase, the phase having the highest fertilizer effect as phosphate fertilizer is the solid solution phase. And the composition conditions of the slag from which the solid solution phase crystallizes and the production method thereof are disclosed.

Japanese Patent No. 5105322 JP-A-11-158526 JP 2009-132544 A Japanese Patent No. 5594183 Japanese Patent Laying-Open No. 2015-189591 Japanese Patent Laid-Open No. 2006-74940 Japanese Patent Laid-Open No. 2006-88757

  In the methods described in Patent Documents 5 to 7, when producing phosphate fertilizer using steelmaking slag as raw material, hot metal having a high phosphorus concentration is produced by reducing the steelmaking slag once with an electric furnace or rotary kiln (hereinafter referred to as high P). Dephosphorization slag having a higher phosphoric acid concentration than steelmaking slag is manufactured by dephosphorizing the high P hot metal in a pan or the like. In addition, the composition of the dephosphorization slag is adjusted to a specific range by further controlling the dephosphorization conditions, and the cooling rate when solidifying the dephosphorization slag in the molten state is controlled to intentionally form the solid solution phase in the slag. The phosphoric acid fertilizer with high fertilizer effect is produced.

For example, in the methods described in Patent Documents 6 and 7, the basicity α indicating the slag composition as a weight 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)% by mass, iron oxide is controlled in the range of 5% by mass to 25% by mass in terms of Fe, and the cooling rate when solidifying from a molten state is 10 ° C./min or more. By doing so, the solid solution phase is crystallized to produce a fertilizer with high fertilizer effect.

However, on the other hand, when the high P hot metal is dephosphorized, the basicity α is smaller than 1.5, the basicity α is larger than 3.0, or the basicity α is 1.5 or more and 3.0 or less. However, if the P ₂ O ₅ concentration is more than (−4α ² + 23α-4) or the cooling rate is less than 10 ° C./min, there is a problem that the fertilizer effect falls off rapidly. This is because when the P ₂ O ₅ concentration in the slag exceeds (−4α ² + 23α-4), or the cooling rate is less than 10 ° C./min, the phosphorus-containing mineral phase in the dephosphorized slag is not a solid solution, but a fertilizer effect Β-Ca ₃ (PO ₄ ) ₂ , which is a low-phosphorus-containing mineral phase, crystallizes, and as a result, the fertilizer effect drops sharply. Therefore, in order to maintain the quality of slag with high fertilizer effect and produce phosphate fertilizer with good reproducibility regardless of the P concentration in hot metal, the slag composition and cooling rate are appropriately controlled during dephosphorization of high P hot metal. There is a problem that the control of conditions is severe.

  Therefore, in view of the above situation, the present invention provides a method for producing a phosphate fertilizer raw material having a high fertilizer effect, in which the control of production conditions is further relaxed when producing a phosphate fertilizer raw material by dephosphorizing high P hot metal. The purpose is to do.

In order to achieve the above object, the present inventor conducted a dephosphorization test on high P hot metal, and as a result,
(1) It is possible to crystallize Mg ₃ (PO ₄ ) ₂ in a dephosphorization slag by using a dephosphorization agent mainly composed of MgO in the dephosphorization of high P hot metal.
(2) It has been found that the phosphorus-containing mineral phase in the dephosphorization slag does not depend on the cooling rate if the conditions of the dephosphorization agent and the oxygen source are controlled.

In addition, the present inventors further examined the dephosphorization treatment conditions in detail by a dephosphorization test.
(3) When the P concentration in the hot metal is 0.8 mass% or more, even magnesium oxide, which is generally said to have no dephosphorization effect, will be a sufficient dephosphorizer, and the oxygen content can be controlled appropriately. The phosphoric acid concentration in the slag is 10% by mass or more,
(4) When the concentration of P in the hot metal is high, the concentration of phosphoric acid in the slag is increased, and even with MgO—Fe ₂ O ₃ type flux having a high liquidus temperature and solidus temperature, P _{2 having} a low melting point. It was found that O ₅ itself has a hatching promoting effect and promotes dephosphorization.

The present invention based on the above findings is as follows.
(1) In the converter or ladle, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, the Mn concentration is 0.01 to 1.40 mass%, P With respect to the hot metal having a concentration of 0.8 to 4.0% by mass, the total amount of magnesium oxide, magnesium carbonate, magnesium hydroxide or a combination thereof as a dephosphorizing agent is 90% by mass in the total mass of the dephosphorizing agent. In addition, 5-25 kg / molten ton of hot metal is added in terms of MgO, and the molten metal temperature is 1300 to 1450 ° C., and oxygen in the form of oxygen gas or iron oxide is 7 kg / molten ton or more. blowing (MgO intensity kg / molten pig iron ton + 11) kg / molten pig iron ton or less or dephosphorization and by adding, as required, followed by _{cooling, CaO, MgO, SiO 2,} P 2 O 5, iron oxide (Fe conversion), l contains ₂ O ₃ and more than 70 wt% of MnO in total, MgO is 10 mass% or more, with P ₂ O ₅ is 10 mass% or more, the amount of iron oxide t. Fe is 40 mass% or less, CaO / MgO mass ratio is 0.3 or less, and MgO / P ₂ O ₅ mass ratio is 0.6 or more, and Mg ₃ (PO ₄ ) ₂ is crystallized as a phosphorus-containing mineral phase. A method for producing a phosphate fertilizer raw material, characterized in that the phosphate fertilizer raw material being taken out is obtained.
(2) The method for producing a phosphate fertilizer raw material according to (1) above, wherein the hot metal is hot metal produced by adding and reducing a carbonaceous material in an electric furnace using steelmaking slag as a raw material.

  According to the present invention, it is possible to produce a phosphate fertilizer raw material with a high fertilizer effect by dephosphorylation of high P hot metal.

It is a figure which shows an example of the process of manufacturing a phosphate fertilizer raw material in a steelmaking process. It is a figure which shows the relationship between hot metal concentration of P and phosphoric acid concentration in slag. It is a figure which shows the relationship between MgO addition amount and oxygen supply amount. Oxygen supply amount and phosphoric acid concentration in slag and t. It is a figure which shows the relationship with Fe density | concentration. MgO addition amount and phosphoric acid concentration in slag and t. It is a figure which shows the relationship with Fe density | concentration. It is a figure which shows the relationship between the addition amount of MgO in case hot metal P density | concentration is 0.8 mass%, and the phosphoric acid density | concentration in slag. After a high P hot metal dephosphorization, MgO in the slag, a diagram illustrating a P ₂ O ₅ concentration relationship. It is a diagram showing the relationship between the slag CaO / MgO ratio and _{Mg 3 (PO 4) 2,} Ca 3 (PO 4) 2 amount. It is a diagram showing the relationship between the slag MgO / P ₂ O ₅ ratio and Mg ₃ (PO _{4) 2} amount.

In the converter or ladle of the present invention, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, and the Mn concentration is 0.01 to 1.40. The total amount of magnesium oxide, magnesium carbonate, magnesium hydroxide, or a combination thereof as a dephosphorizing agent is in the total mass of the dephosphorizing agent with respect to hot metal having a mass% and a P concentration of 0.8 to 4.0 mass%. In addition, a total of 5 to 25 kg / molten ton of hot metal in terms of MgO is added, and the molten metal temperature is 1300 to 1450 ° C. and oxygen in the form of oxygen gas or iron oxide is 7 kg / molten iron. by more ton (MgO amount kg / molten pig iron ton + 11) dephosphorylated by blowing or added kg / molten pig iron ton or less, and then _{cooled, CaO, MgO, SiO 2,} P 2 O 5, iron oxide (F Equivalent), containing Al ₂ O ₃ and more than 70 wt% of MnO in total, MgO is 10 mass% or more, with P ₂ O ₅ is 10 mass% or more, the amount of iron oxide t. 40 wt% or less Fe, CaO and the ratio of the concentration of the MgO (CaO / MgO weight ratio) is 0.3 or less, and MgO and P ₂ concentration ratio between _{O 5 (MgO / P 2 O} 5 mass ratio ) Is 0.6 or more, and a phosphate fertilizer raw material in which Mg ₃ (PO ₄ ) ₂ is crystallized as a phosphorus-containing mineral phase is produced.

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

  First, the whole outline | summary including the pre-process of the manufacturing process which concerns on this invention about 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 using an electric furnace, and pulverized coal, an Al ₂ O ₃ source, an SiO ₂ source are added as a reducing agent and a modifying agent, and phosphorus is removed. A high P hot metal 42 containing a large amount of 0.8 to 4.0% by mass is produced.

Then, after the Cr removal treatment S12 is performed on the high P hot metal 42 as necessary, the slag generated in the reduction reforming treatment S11 and the slag after the treatment are possible when the Cr removal treatment S12 is performed. Remove as much as possible. After that, the MgO source, magnesium oxide, magnesium carbonate, magnesium hydroxide, dolomite, and brick waste were added as a raw material to adjust the composition, and oxygen-blowing dephosphorization treatment S13 was applied to produce 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. At this time, the composition of the added flux and the oxygen supply amount are controlled so that Mg ₃ (PO ₄ ) ₂ crystallizes in the phosphoric acid-containing slag 50. This dephosphorization treatment S13 can be performed in a hot metal ladle or an electric furnace.

  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.

  In the present invention, in the dephosphorization treatment S13, a predetermined amount of a dephosphorizing agent is added to the high P hot metal having the above-described composition, and oxygen is supplied in a temperature range of 1300 to 1450 ° C. under predetermined conditions. By doing so, the phosphoric acid containing slag 50 of the composition mentioned above is manufactured.

  Furthermore, the phosphoric acid-containing slag 50 is cooled by the cooling process S14, and the phosphoric acid fertilizer raw material 60 that has been improved in effectiveness as a phosphate fertilizer by pulverizing the cooled phosphoric acid-containing slag 50 in the pulverizing process S15 as necessary. Manufacturing. In addition, since cooling conditions are not specifically limited, rapid cooling or slow cooling may be used.

In the following, in the de-P treatment S13, (1) the reason for limiting the components of the high P hot metal as the raw material, (2) the reason for using magnesium oxide, magnesium carbonate, magnesium hydroxide as the dephosphorizing agent, (3) oxygen The reason for limiting the supply amount, (4) the reason for limiting the addition amount in terms of MgO, and (5) the reason for limiting the hot metal temperature will be described. In addition, in order to promote crystallization of Mg ₃ (PO ₄ ) ₂ from the phosphorus-containing mineral phase of the phosphoric acid-containing slag, (6) the reason for limiting the total component composition in the phosphoric acid-containing slag, (7) MgO , P ₂ O ₅ and t. The reason for limiting the Fe concentration, (8) the reason for limiting the concentration ratio between CaO and MgO, and (9) the reason for limiting the concentration ratio between MgO and P ₂ O ₅ will be described.

[(1) Components of high P hot metal]
The composition of the phosphoric acid-containing slag is greatly influenced by the composition of the high P hot metal. Therefore, dephosphorization is performed with MgO, and the composition of the high P hot metal is limited in order to enhance the composition effect of the phosphoric acid-containing slag. There is a need.

Phosphoric acid-containing slag is affected by the composition of the high P hot metal that has been subjected to the dephosphorization treatment. In the present invention, “C concentration is 3.0 to 5.0 mass%, Si concentration is 0.01 to 0.40 mass%, Mn concentration is 0.01 to 1.40 mass%, and P concentration is 0.8. The hot metal of ˜4.0% by mass ”is examined, and among them, the component range suitable for the present invention is the subject of the present invention. In the present invention, since the high P hot metal is dephosphorized to produce phosphoric acid-containing slag, the target hot metal component needs to be available.
The slag produced according to the invention contains CaO, MgO, SiO ₂ , P ₂ O ₅ , iron oxide (Fe equivalent), Al ₂ O ₃ and MnO in total of 70% by mass or more, and MgO of 10% by mass or more. , P ₂ O ₅ is 10 mass% or more, and the amount of iron oxide is t. Fe is 40% by mass or less, CaO / MgO mass ratio is 0.3 or less, and MgO / P ₂ O ₅ mass ratio is 0.6 or more. It will be described later that this slag is excellent as a phosphate fertilizer raw material.

This examination was first conducted by experimenting with the above-mentioned hot metal using a high-frequency induction furnace.
First, 15 kg of hot metal is accommodated in a high-frequency induction furnace, and the hot metal temperature is within a range of 1300 to 1450 ° C., which is a general processing temperature during dephosphorization, from the viewpoint of suppressing the C concentration in the hot metal and general refractory erosion damage. After adjusting, oxygen and a dephosphorizing agent were added from above. Considering the hatching of the dephosphorizing agent, the oxygen supply amount was changed according to the amount of the dephosphorizing agent introduced. No bottom blowing gas was used.

  The C concentration in the high P hot metal is in the range of 3.0 to 5.0 mass%. When the C concentration is low, the liquidus temperature becomes high. In addition, since the de-C reaction proceeds simultaneously with the de-P reaction, the concentration of 3.0% by mass or more is necessary in order that the hot metal always becomes a liquid phase in the range of 1300 to 1450 ° C. which is the treatment temperature during the dephosphorization process. is required. On the other hand, the upper limit of the C concentration is about 5.0% by mass close to saturation.

The Si concentration in the high P hot metal is 0.40 mass% or less. All of the Si in the hot metal is oxidized to SiO ₂ during the de-P treatment and is mixed into the slag. If the amount of SiO ₂ in the slag is high, the de-P effect is reduced, so the Si concentration must be limited to 0.40% by mass or less. Moreover, since Si is inevitably contained in the hot metal, the Si concentration is substantially 0.01% by mass or more.

Mn in the high P hot metal is contained in an amount of 0.01% by mass or more accompanying the production of hot metal having a target P concentration of 0.8 to 4.0% by mass. Although Mn in the hot metal is also oxidized during the de-P treatment, the added phosphorus reacts with Fe in the hot metal to have the same effect as iron oxide produced in the slag. If the Mn concentration of the hot metal is high, a large amount of MnO will be contained in the slag. As with the slag having a high FeO concentration, the amount of slag will increase, resulting in a decrease in the P ₂ O ₅ concentration. It leads to the problem that the weight as a phosphate fertilizer will increase. Therefore, when manufacturing the slag having the composition according to the present invention by dephosphorizing the hot metal having a target P concentration of 0.8 to 4.0% by mass, the maximum allowable Mn concentration is 1.40% by mass. %. The upper limit of the Mn concentration can be controlled by adjusting the raw material for producing hot metal having a P concentration of 0.8 to 4.0% by mass.

The P concentration in the high P molten iron is 0.8 to 4.0% by mass. The reason for limiting the P concentration to this range was confirmed by the following experiment.
First, as the dephosphorizing agent, magnesium oxide is used, and the C concentration in the molten iron is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.4 mass%, and the Mn concentration is 0.01 to 1. .40 mass%, and P concentration of 0.2, 0.8, 1.0, and 3.0 mass%, respectively, MgO was added at 15 kg / molten ton and oxygen was 20 kg. / Molten iron was added. FIG. 2 shows the relationship between the phosphoric acid concentration in the slag and the P concentration in the molten iron when a dephosphorization experiment was conducted at that time.

As shown in FIG. 2, the de-P reaction did not proceed at all when the P concentration in the hot metal before the treatment was 0.2% by mass. On the other hand, when the P concentration in the hot metal before the treatment was 0.8% by mass or more, the dephosphorization reaction proceeded easily, and the P ₂ O ₅ concentration in the slag was also 10% by mass or more. In blast furnace hot metal having a general P concentration of about 0.1% by mass, MgO is considered to have little effect on dephosphorization, but in this experiment, there is a dephosphorization effect on high P hot metal. confirmed.

There are two reasons for this. The first reason is that, since the P concentration in the hot metal simply becomes higher than that in the blast furnace hot metal, P becomes easier to react, and dephosphorization proceeds even with MgO, which is weaker than CaO. Secondly, since the melting point of P ₂ O ₅ alone is low, if the phosphoric acid concentration in the slag is high, even the MgO—FeO _x type flux that has a high liquidus temperature and is not easily hatched has been hatched. .

  In the example shown in FIG. 2, 15 kg / molten ton of MgO was added at once. However, when 25 kg / molten ton of MgO was added later in the experiment shown in FIG. 6, the P concentration was 0.8 mass%. It was confirmed to be the lower limit. From the above results, the P concentration in the hot metal is 0.8% by mass or more. In order to obtain a large amount of slag having a high phosphoric acid concentration, it is preferable that the P concentration in the hot metal before the treatment is high, and it is preferably 1% by mass or more. In addition, the upper limit of the P concentration in the hot metal is 4.0% by mass as an available range.

[(2) Reason for using magnesium oxide, magnesium carbonate, magnesium hydroxide as a dephosphorizing agent]
2 and FIG. 6 shown later, if the P concentration in the hot metal is 0.8 mass% or more, the P ₂ O ₅ concentration in the slag produced when MgO is added and dephosphorized becomes 10 mass%. I found out that However, as will be described later with reference to FIGS. 8 and 9, in order to contain a large amount of Mg ₃ (PO ₄ ) ₂ useful in the phosphoric acid-containing slag as a phosphate fertilizer raw material, it is added as a dephosphorizing agent. It is necessary to use MgO with a purity as high as possible.
Therefore, the dephosphorizing agent used is magnesium oxide, magnesium hydroxide, magnesium carbonate, or a combination thereof. And in the whole dephosphorization agent, the sum total of magnesium oxide, magnesium hydroxide, magnesium carbonate, or these combinations needs to be 90 mass% or more. In order to produce Mg ₃ (PO ₄ ) ₂ as a phosphorus-containing mineral phase by dephosphorylation of high P hot metal, MgO is required as a flux, and magnesium hydroxide and magnesium carbonate are heated at a high temperature of 1200 to 1400 ° C. Because MgO is used, the magnesium oxide, magnesium hydroxide, and magnesium carbonate fluxes all become MgO at a high temperature and work effectively as a dephosphorizing agent.

[(3) Reason for limiting oxygen supply]
It is necessary to appropriately control the oxygen supply amount according to the MgO addition amount. Since the P concentration in the high P molten iron is high, the amount of slag generated is largely determined by the amount of dephosphorization agent and oxygen added. However, at this time, if the amount of oxygen is too small regardless of the amount of MgO added, the reaction stops mainly when Si in the hot metal is oxidized, and sufficient dephosphorization reaction does not proceed. On the other hand, when there is too much oxygen amount with respect to MgO addition amount, dephosphorization reaction will be saturated and excess oxygen will be used for the production | generation of FeO and MnO, and decarburization. Therefore, there is an appropriate oxygen supply amount.

Here, the result of having investigated the composition of the phosphoric acid containing slag produced | generated according to the relationship between the basic unit of MgO and an oxygen basic unit is shown in FIG. In this investigation, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, the Mn concentration is 0.01 to 1.40 mass%, and the P concentration is 0.8 to Accommodates 15 kg of 4.0% by mass of hot metal in a high-frequency induction furnace, adds 5 to 25 kg of magnesium oxide / ton as a dephosphorizing agent, and iron oxide as an oxygen source in a temperature range of 1300 to 1450 ° C. 5-40 kg / molten ton was added. In FIG. 3, the P ₂ O ₅ concentration is 10% by mass or more and t. When the Fe concentration is 40% by mass or less, “◯”, when the P ₂ O ₅ concentration is less than 10% by mass, “X”, the P ₂ O ₅ concentration is 10% by mass or more, and t. A Fe concentration exceeding 40% by mass is indicated by “▲”.

  First, the P concentration in the hot metal had no significant effect in the investigated range. If the P concentration is 0.8% by mass or more under the conditions of Si concentration of 0.01 to 0.40% by mass and Mn concentration of 0.01 to 1.40% by mass, depending on the amount of MgO and the amount of oxygen It can be said that there is no effect on the composition of slag produced.

Next, when the oxygen supply amount was 5 kg / molten iron ton, the P ₂ O ₅ concentration was less than 10% by mass regardless of the amount of MgO added. In this way, when the amount of oxygen supplied is small, oxygen is mainly consumed for reaction with Si in the hot metal and also reacts with C, Fe, and Mn, so that the concentration of P ₂ O _{5 in the} slag becomes 10% by mass or more. It doesn't come up.

For example, when the MgO addition amount is 15 kg / molten ton, the P ₂ O ₅ concentration according to the oxygen supply amount and t. It can be seen from FIG. 4, which shows the change with Fe concentration. If the added amount of MgO is 15 kg / molten ton, it can be said that the amount is sufficient for the reaction with P ₂ O ₅ produced by oxygen, but if the supply amount of oxygen is 5 kg / molten ton, the concentration of P ₂ O ₅ is 4 mass. Only about% was produced. When the oxygen supply amount was 10 kg / molten ton, the P ₂ O ₅ concentration was about 25% by mass. Therefore, in order for the P ₂ O ₅ concentration to be 10% by mass or more, the oxygen supply amount was approximately 7 kg. / It can be said that more than hot metal ton was necessary.

In FIG. 4, the P ₂ O ₅ concentration increased until the oxygen supply amount reached 15 kg / molten metal ton, but when the oxygen supply amount exceeded that, it decreased instead. The concentration of Fe increased. t. Fe is not an essential component in the phosphate fertilizer raw material, but increases its weight and further lowers the P ₂ O ₅ concentration relatively, so it is 40% by mass or less. The MnO concentration in the slag is t. Since the MnO concentration is high when the Fe concentration is high, the control of the MnO concentration is t. This can be represented by controlling the Fe concentration.

Further, when the oxygen supply amount is 20 kg / molten ton, the added amount of MgO is the P ₂ O ₅ concentration in the generated slag and t. The effect on the Fe concentration is shown in FIG. In FIG. 5, the amount of MgO added was 5 kg / molten ton and the P ₂ O ₅ concentration was 9% by mass. Fe exceeds 50% by mass, t. It has been diluted with Fe. Therefore, as shown in FIG. 3, it can be seen that it is appropriate to set the MgO addition amount to 5 kg / molten ton or more to obtain P ₂ O ₅ : 10% or more, but unless the oxygen supply amount is appropriately restricted, t. It can be said that the Fe concentration becomes too high, and the target that the P ₂ O ₅ concentration is 10% by mass or more cannot be achieved. Here, as the amount of MgO added is increased, the P ₂ O ₅ concentration increases. However, when the amount of MgO added is about 20 kg / molten ton or more, the increase in P ₂ O ₅ concentration stops. This is because the amount of slag produced increased with the increase in the amount of MgO added, so that the reaction between P and iron oxide in the hot metal and the reaction between P ₂ O ₅ and MgO produced by the reaction are difficult to proceed. It is thought that it was influenced. Therefore, it is understood that there is an appropriate range in the relationship between the added amount of MgO and the oxygen supply amount.

As a result of the above experiment, from the empirical formula, as shown in FIG. 3, the amount of oxygen to be supplied is 7 kg / molten ton or more (MgO addition amount kg / molten ton + 11) kg / molten ton or less. Within this range, P ₂ O ₅ concentration of 10 mass% or more and t. A phosphoric acid-containing slag having an Fe concentration of 40% by mass or less can be produced.

[(4) Reason for limiting the addition amount in terms of MgO]
The addition amount of MgO as a dephosphorizing agent needs to be 5 to 25 kg / molten ton. Here, as described above, the dephosphorizing agent is one in which the total of magnesium oxide, magnesium hydroxide, magnesium carbonate, or a combination thereof is 90% by mass or more in the total mass of the dephosphorizing agent, The total added amount of MgO contained in these (added amount in terms of MgO) is defined as the added amount of MgO. Further, the amount of slag generated as described above is determined by the amount of MgO added and the amount of oxygen. Therefore, when there is too little addition amount of MgO, since the phosphoric acid containing slag to produce | generate will decrease, economic rationality will not become.

On the other hand, if the amount of MgO added is too large, the amount of slag generated is too large and overflows from the furnace, so there is an upper limit. Further, as shown in FIG. 2, when the P concentration in the hot metal before the treatment is low, the P ₂ O ₅ concentration in the slag is lower than when the P concentration in the hot metal is high. Therefore, when the P concentration in the hot metal is low and the slag amount is further increased, the phosphoric acid concentration in the slag is relatively low. Therefore, it is necessary to appropriately control the amount of MgO to be added.

FIG. 6 is a diagram showing the relationship between the amount of MgO added and the phosphoric acid concentration after dephosphorization when using hot metal having a P concentration of 0.8% by mass in the hot metal. The oxygen supply amount was in the range of 7 kg / molten ton or more (MgO addition amount kg / molten ton + 11) kg / molten ton or less. As shown in FIG. 6, when the added amount of MgO is 30 kg / molten ton, the P ₂ O ₅ concentration in the slag decreased to less than 10% by mass. In this case, the MgO addition amount needs to be 25 kg / molten ton or less.

[(5) Reason for limiting the processing temperature]
When manufacturing a phosphoric acid containing slag, it is necessary to perform a dephosphorization process at 1300-1450 degreeC.

  In the present invention, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, the Mn concentration is 0.01 to 1.40 mass%, and the P concentration is 0.8 to 4%. In order to dephosphorize 0.0% by mass of hot metal, the hot metal temperature during dephosphorization is required to be 1300 ° C. or higher in order to avoid solidification of a part of the hot metal. Furthermore, when the hot metal temperature is less than 1300 ° C., the slag may not be completely melted, and in that case, the fertilizer effect as a phosphate fertilizer does not appear. On the other hand, when the hot metal temperature exceeds 1450 ° C., dephosphorization does not proceed easily from the dephosphorization reaction equilibrium, the phosphoric acid concentration in the slag decreases, heating costs increase, and the refractory of the processing vessel wears out. Also gets fierce. For the above reasons, the dephosphorization treatment is performed in the hot metal temperature range of 1300 to 1450 ° C.

As described above, the dephosphorization slag of high P hot metal is affected by the composition of the high P hot metal subjected to the dephosphorization treatment. In the present invention, “C concentration is 3.0 to 5.0 mass%, Si concentration is 0.01 to 0.40 mass%, Mn concentration is 0.01 to 1.40 mass%, and P concentration is 0.8. -4.0 mass% "hot metal.
For such hot metal, a dephosphorizing agent containing 90% by mass or more of magnesium oxide or the like is added in a total amount of 5 to 25 kg / ton ton in terms of MgO, and the temperature of the hot metal is 1300 to 1450 ° C., oxygen gas By blowing or adding oxygen in the form of iron oxide 7 kg / molten ton or more and MgO addition amount / molten ton + 11) kg / molten ton or less, CaO, MgO, SiO ₂ , P ₂ O ₅ , iron oxide (Fe Conversion), Al ₂ O ₃ and MnO in total 70 mass% or more, MgO 10 mass% or more, P ₂ O ₅ 10 mass% or more, and the amount of iron oxide is t. A phosphoric acid-containing slag is produced that is 40 mass% or less in Fe, the CaO / MgO mass ratio is 0.3 or less, and the MgO / P ₂ O ₅ mass ratio is 0.6 or more.
Below, it demonstrates that this slag is suitable as a phosphate fertilizer raw material.

[(6) Reason for limiting the total composition of slag components]
The total of each component of CaO, MgO, SiO ₂ , P ₂ O ₅ , iron oxide (Fe conversion), Al ₂ O ₃ and MnO is dephosphorized by the slag when the hot metal to be processed is produced. In some cases, there is a possibility that a part of the slag may remain, but the main component of the slag is CaO, SiO ₂ , Al ₂ O ₃ , so the total of each component is 70% by mass or more. Is normal. However, as the dephosphorizing agent, a magnesium oxide, magnesium carbonate, magnesium hydroxide or a combination thereof containing 90% by mass or more of the total mass of the dephosphorizing agent is used, and extra components are brought in. You must be careful not to. If the total amount of each component is less than 70% by mass, components other than the above components and phosphoric acid form a compound, and the target phosphorus-containing mineral phase cannot be crystallized. % Or more. Preferably it is 80 mass% or more.

[(7) MgO, P ₂ O ₅ and t. Reasons for limiting Fe concentration]
In the phosphate fertilizer raw material, the higher the concentration of P ₂ O ₅ is better. However, there is an appropriate P ₂ O ₅ concentration range due to the property of dephosphorization of high P hot metal. Therefore, in the present invention, the lower limit of the P ₂ O ₅ concentration is defined as 10% by mass. In FIG. 7, C concentration is 3.0-5.0 mass%, Si concentration is 0.01-0.40 mass%, Mn concentration is 0.01-1.40 mass%, and P concentration is 0.8- The total amount of magnesium oxide, magnesium carbonate, magnesium hydroxide or a combination thereof as a dephosphorizing agent containing 4.0% by mass of high P molten iron is 90% by mass or more in the total mass of the dephosphorizing agent. The relationship between the MgO concentration in the slag and the P ₂ O ₅ concentration when dephosphorized at 1400 ° C. using a sample is shown. When the concentration of MgO in the slag was increased, the concentration of P ₂ O ₅ was increased. When P ₂ O ₅ was 10% by mass or more, MgO was 10% by mass or more. From the above results, it is understood that the phosphoric acid-containing slag obtained by the above-described production method has a P ₂ O ₅ concentration of 10% by mass or more and an MgO concentration of 10% by mass or more.

In addition, t. Regarding the Fe concentration, as described above, t. Fe is not an essential component in the phosphate fertilizer raw material, but increases its weight and further lowers the P ₂ O ₅ concentration relatively. As shown in FIG. 3, this requirement is achieved by limiting the amount of oxygen supplied according to the amount of MgO added. Specifically, the oxygen supply unit (kg / molten ton) may be MgO addition unit (kg / molten ton) +11 (kg / molten ton).

[(8) Reason for limiting the concentration ratio of CaO and MgO]
The ratio of mass concentration of CaO and MgO (hereinafter referred to as CaO / MgO mass ratio) needs to be 0.3 or less. This is because CaO and MgO are more likely to form a compound with phosphoric acid in the slag. When the CaO / MgO ratio exceeds 0.3, depending on the P ₂ O ₅ concentration, β-Ca ₃ (PO ₄ ) ₂ crystallizes as a phosphorus-containing mineral phase, and Mg ₃ (PO _4), which is the target phosphorus-containing mineral phase. This is because the crystallization of the _two phases cannot be controlled. Preferably, it is 0.1 or less. Also in this condition, the slag at the time of producing the high P hot metal to be treated is sufficiently eliminated before dephosphorizing the high P hot metal, and the dephosphorizing agent used is magnesium oxide, By using magnesium hydroxide, magnesium carbonate, or a combination thereof of 90% by mass or more, the amount of CaO mixed in the phosphoric acid-containing slag can be suppressed, and this is achieved without difficulty.

In FIG. 8, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, the Mn concentration is 0.01 to 1.40 mass%, and the P concentration is 0.8 to The CaO / MgO ratio, Ca ₃ (PO ₄ ) ₂ and Mg ₃ (PO ₄ ) of slag obtained when 4.0 mass% high P hot metal was dephosphorized using a flux containing MgO and CaO. The abundance ratio with ₂ . When the CaO / MgO ratio is 0.3 or less, there is no Ca ₃ (PO ₄ ) ₂ in the slag, and Mg of 20% by mass or more serving as a guideline that can fully enjoy the effects of the present invention. It can be seen that ₃ (PO ₄ ) ₂ exists. On the other hand, it can be seen that β-Ca ₃ (PO ₄ ) ₂ crystallizes out when the CaO / MgO ratio exceeds 0.3. For this reason, a CaO / MgO ratio shall be 0.3 or less. Preferably, it is 0.1 or less.

[(9) Reason for limiting the concentration ratio between MgO and P ₂ O ₅ ]
The ratio of mass concentration of MgO and P ₂ O ₅ (hereinafter, MgO / P ₂ O ₅ mass ratio) is 0.6 or more. C concentration is 3.0 to 5.0 mass%, Si concentration is 0.01 to 0.40 mass%, Mn concentration is 0.01 to 1.40 mass%, and P concentration is 0.8 to 4.0 mass%. % Of the high P hot metal, the total amount of magnesium oxide, magnesium hydroxide, magnesium carbonate or a combination thereof is 90% by mass or more as a dephosphorizing agent. Add a total of 5 to 25 kg / molten ton of magnesium, etc. in terms of MgO, and at a molten metal temperature of 1300 to 1450 ° C., oxygen in the form of oxygen gas or iron oxide is 7 kg / molten ton or more (MgO addition amount kg / Blow or add hot metal ton +11) kg / mol of hot metal ton or less. As a result, as shown in FIG. 9, the lower limit of the MgO / P ₂ O ₅ mass ratio is about 0.6. The smaller the index of MgO / P ₂ O ₅ ratio, the higher the dephosphorization efficiency with MgO (the higher the ratio of fixing P ₂ O _{5 with} MgO). Under the condition where the CaO / MgO mass ratio is limited to 0.3 or less, P ₂ O ₅ is considered to have a higher ratio of reacting with MgO, but the MgO / P ₂ O ₅ mass ratio is up to about 0.6, It was found that MgO was bound to P ₂ O ₅ in the present invention.

On the other hand, when the P concentration in the hot metal is low, the treatment temperature is high, or the dephosphorization treatment is performed under conditions unfavorable for dephosphorization, the MgO / P ₂ O ₅ mass ratio increases. The condition that Mg ₃ (PO ₄ ) ₂ is about 20% by mass or more in the slag serves as a guideline for fully enjoying the effects of the present invention, so the MgO / P ₂ O ₅ mass ratio is 1.6. The following is preferable.

The phosphoric acid containing slag of the composition mentioned above is obtained by the above manufacturing method. Then, Mg ₃ (PO _{4) 2} as a phosphorus-containing mineral phase by cooling the phosphoric acid-containing slag is crystallized, phosphate fertilizer material having the same composition as the phosphate-containing slag as described above is obtained.

Next, in order to obtain the phosphate fertilizer effect more efficiently, the phosphate fertilizer raw material is preferably pulverized to 150 μm or less. When a particle having a particle size exceeding 150 μm is included, a specific particle having a large particle size has a small specific surface area, and the solubility due to P ₂ O ₅ is reduced as a whole. After pulverizing the phosphoric acid-containing slag, it is preferable to screen with a standard sieve of 150 μm.

Since more than in the manufacturing method of the phosphate fertilizer material of the present invention as compared to the solid solution phase of Patent Document 5-7 are relaxed in the range of P ₂ O _5, it will not be further constrained on the cooling conditions The degree of freedom in manufacturing conditions can be increased.

  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 P hot metal obtained from the converter dephosphorization slag was dephosphorized and manufactured phosphoric acid containing slag, manufacture of phosphoric acid containing slag Is not limited to this description.

For example, you may manufacture by adding Fe-P to the hot metal produced | generated with the blast furnace, manufacturing high P hot metal, and dephosphorizing it. Alternatively, phosphoric acid-containing slag may be produced by mixing quick lime, SiO ₂ , P ₂ O ₅ , iron oxide or the like so as to fall within the above composition range and then melting.

  Examples of the present invention will be described. 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.

  First, as a pre-process, the steelmaking slag discharged from the converter in the steelmaking process is poured into a slag supply container in a molten state (solid phase ratio of 25% or less), temporarily stored, and then the slag supply container is set to 10 By tilting once a minute, about 8 tons of hot steelmaking slag was allowed to flow into the electric furnace once. And while supplying electric power to the electric furnace, coke powder was supplied into the electric furnace from the auxiliary material supply pipe. Further, fly ash: 378 kg / t-slag and bauxite powder: 47 kg / t-slag as slag modifiers were continuously supplied from the auxiliary material supply pipe to the molten slag layer. And the reduction process was performed by controlling the temperature in the electric furnace.

  About 30 tons of hot metal AK as shown in Table 1 below was obtained by the reduction treatment as described above. As for hot metal H, for the purpose of investigating the influence on the dephosphorization treatment according to the present invention, the hot metal H was manufactured after the reduction treatment was completed at a stage where the P concentration in the hot metal was still low.

Next, the hot metal A to K manufactured in the previous step is accommodated in the hot metal pan, and after removing the slag generated in the previous step until the hot metal surface appears and cannot be removed, the hot metal temperature is 1350 ° C to 1450 ° C. In the temperature range, seawater magnesia (MgO: 95% by mass, CaO: 1.3% by mass, SiO ₂ : 2.7% by mass) is added in a total amount of 5 to 30 kg / molten ton in terms of MgO, and oxygen is added to iron oxide or Phosphoric acid fertilizer raw material was manufactured by adding 5-27 kg / molten ton in the form of gaseous oxygen and then cooling. The results are shown in Table 2.

In Examples _{1~7, CaO, MgO, SiO 2} , P 2 O 5, iron oxide (Fe conversion), Al ₂ O ₃ and containing a total of 70 mass% or more MnO, MgO is 10 mass% or more, P ₂ O ₅ is 10 mass% or more and the amount of iron oxide is t. A slag having Fe of 40% by mass or less, a CaO / MgO ratio of 0.3 or less, and an MgO / P ₂ O ₅ mass ratio of 0.6 or more could be produced. Furthermore, when the phosphorus-containing mineral phase was investigated after cooling, it was confirmed that Mg ₃ (PO ₄ ) ₂ was crystallized in an abundance ratio of 20% by mass or more in the slag. In addition, when the soluble phosphoric acid density | concentration was also evaluated about these Examples 1-7, it was all high and the thing of the fertilizer effect was high.

  Here, soluble phosphoric acid refers to the phosphoric acid content dissolved in the ammonium citrate solution, and is one index of fertilizer effect. As a result of the examination so far, it has been found that soluble phosphate has a very good correlation with plant growth, so the soluble phosphate concentration was used as an index for judging the fertilizer effect.

On the other hand, in Comparative Example 1, since the P concentration of the hot metal was less than 0.8% by mass, the P ₂ O ₅ concentration was less than 10% by mass.
In Comparative Example 2, since the MgO addition amount was excessively increased to 30 kg / molten metal ton, the P ₂ O ₅ concentration was relatively less than 10% by mass.
In Comparative Example 3, since the oxygen supply amount was less than 7 kg / molten metal ton, dephosphorization did not progress so much, and the P ₂ O ₅ concentration was less than 10% by mass.
In Comparative Example 4, the oxygen supply amount was 27 kg / molten metal ton, which was larger than 26 kg / molten metal ton, which was (MgO addition amount kg / molten metal ton + 11) kg / molten metal ton. Therefore, t. Fe concentration exceeded 40 mass%.

Further, in Comparative Examples 1-4, was investigated phosphorus-containing mineral phase after cooling, Comparative Examples 1 to 3 had low P ₂ O ₅ concentration. In Comparative Example 4, the soluble phosphoric acid concentration was similar to that of the Examples, but t. Which is relatively unnecessary as a phosphate fertilizer. Since a large amount of Fe is contained, the weight is large, and it cannot be used as a phosphate fertilizer product.

  ADVANTAGE OF THE INVENTION According to this invention, P concentration and MgO density | concentration are high, and the phosphate fertilizer raw material with a high fertilizer effect can be provided as a phosphate fertilizer. Therefore, the present invention has high applicability in the steel industry and the plant breeding industry.

Claims (2)

In the converter or ladle, the C concentration is 3.0 to 5.0 mass%, the Si concentration is 0.01 to 0.40 mass%, the Mn concentration is 0.01 to 1.40 mass%, and the P concentration is 0. The total amount of magnesium oxide, magnesium carbonate, magnesium hydroxide, or a combination thereof is 90% by mass or more in the total mass of the dephosphorizing agent with respect to the hot metal of 0.8 to 4.0% by mass. In total, add 5-25 kg / molten ton of MgO in terms of MgO, and in the temperature range of 1300 to 1450 ° C, the amount of oxygen in the form of oxygen gas or iron oxide is 7 kg / molten ton or more (MgO addition) Kg / molten ton + 11) Dephosphorization by blowing or adding kg / molten ton or less, and then cooling to obtain CaO, MgO, SiO ₂ , P ₂ O ₅ , iron oxide (Fe conversion), Al ₂ O ₃ and MnO are contained in a total of 70% by mass or more, MgO is 10% by mass or more, P ₂ O ₅ is 10% by mass or more, and the amount of iron oxide is t. Fe is 40 mass% or less, CaO / MgO mass ratio is 0.3 or less, and MgO / P ₂ O ₅ mass ratio is 0.6 or more, and Mg ₃ (PO ₄ ) ₂ is crystallized as a phosphorus-containing mineral phase. A method for producing a phosphate fertilizer raw material, characterized in that the phosphate fertilizer raw material being taken out is obtained.   The method for producing a phosphate fertilizer raw material according to claim 1, wherein the hot metal is a hot metal produced by adding and reducing a carbonaceous material in an electric furnace using steelmaking slag as a raw material.