JP5569174B2 - Method for recovering iron and phosphorus from steelmaking slag, blast furnace slag fine powder or blast furnace slag cement, and phosphoric acid resource raw material - Google Patents

Description

  The present invention relates to a method for recovering iron and phosphorus contained in a steelmaking slag from a steelmaking slag containing phosphorus such as dephosphorization slag produced by a preliminary dephosphorization treatment of hot metal, and recovery of iron and phosphorus. The present invention relates to blast furnace slag fine powder or blast furnace slag cement obtained by recycling steelmaking slag, and further to a recovered phosphoric acid resource raw material.

Due to the iron ore component, hot metal (also referred to as “blast furnace hot metal”) melted in the blast furnace contains phosphorus (P). Since phosphorus is a harmful component for steel materials, conventionally, phosphorus removal treatment has been performed in the steel making process in order to improve the material properties of steel products. In this dephosphorization process, phosphorus in hot metal or molten steel is generally oxidized by oxygen gas or iron oxide, and then oxidized phosphorus (P ₂ O ₅ ) in slag containing CaO as a main component. It has been removed by being fixed to. When phosphorus in hot metal or molten steel is oxidized with oxygen gas, iron is also oxidized, and even when iron oxide is not added, iron is also contained in the form of iron oxide in the slag.

  Steelmaking slag containing phosphorus, which is generated by hot metal preliminary dephosphorization treatment or decarburization refining in a converter, has been conventionally discharged out of the steelmaking process as civil engineering materials. Phosphorus and iron in the slag are not recovered. The preliminary dephosphorization treatment is a treatment for removing phosphorus in the hot metal in advance before decarburizing and refining the hot metal in a converter.

  In recent years, from the viewpoint of environmental measures and resource saving, reducing the amount of steelmaking slag generated, including the recycling of steelmaking slag. For example, slag generated in converter decarburization refining of hot metal that has been subjected to preliminary dephosphorization treatment (slag generated in converter decarburization refining is referred to as “converter slag”) is used as an iron source and a CaO source for a slagging agent. Recycling to a blast furnace through an iron ore sintering process, recycling as a CaO source in a hot metal pretreatment process, and the like are performed.

  Pre-dephosphorized hot metal (also referred to as “dephosphorized hot metal”), especially converter slag generated in converter decarburization refining of dephosphorized hot metal preliminarily dephosphorized to the phosphorus concentration level of steel products, There is almost no inclusion, and there is no need to worry about the increase (pickup) of phosphorus concentration in hot metal resulting from recycling this slag to the blast furnace. However, the slag generated during preliminary dephosphorization, hot metal that has not been preliminarily dephosphorized (also referred to as “normal hot metal”), or the phosphorus concentration after dephosphorization even if predephosphorized, In the slag containing phosphorus, such as the converter slag generated by decarburization and refining of dephosphorized hot metal not reduced to the level, phosphorus recycled in the form of oxides in the blast furnace is reduced in the blast furnace. As a result, the phosphorus content of the hot metal is increased, resulting in a vicious circle in which the load of dephosphorization from the hot metal is increased.

  Accordingly, various proposals have been made for recycling phosphorus-containing steelmaking slag, particularly for recycling to processes involving refining and refining in order to prevent phosphorus from being picked up by hot metal. Of course, also in the case of recycling to an oxidation step such as preliminary dephosphorization, the function as a dephosphorizing agent is impaired and the amount recycled is limited.

  For example, in Patent Document 1, when smelting stainless steel is produced by a combination of a smelting reduction smelting process of chromium ore and a converter decarburization smelting process of chromium-containing hot metal melted by the smelting reduction smelting process. The carbon material is added to the dephosphorization slag generated by the dephosphorization treatment of the chromium-containing hot metal and heated, and the dephosphorization slag is vaporized and dephosphorized, and the dephosphorized slag after the vaporization and dephosphorization treatment is subjected to the smelting reduction smelting A technique for recycling to a process is disclosed.

In Patent Document 2, molten blast furnace slag and molten converter slag are mixed, and at least one of carbon, silicon, and magnesium is added to the mixed slag, and oxygen gas is blown into the mixed slag. in, and phosphorus vapor by reducing phosphorus oxide in the mixed slag, and sulfur in the mixed slag (S) and SO _2, these were volatilized phosphorus and sulfur less slag and without, the slag blast furnace or A technique for recycling to a converter is disclosed.

  Patent Document 3 discloses that dephosphorization slag produced by dephosphorization of hot metal or molten steel using a fouling agent mainly composed of an alkali metal carbonate is treated with water and carbon dioxide gas to obtain alkali metal phosphorus. A technique is disclosed in which an extract containing an acid salt is obtained, a calcium compound is added to the extract, and phosphorus is precipitated as calcium phosphate and separated and recovered.

  Further, Patent Document 4 discloses that a refining slag containing phosphorus and molten iron are supplied into a container containing a charcoal material and an oxidizing gas to burn the charcoal material, thereby melting the refining slag and refining. Phosphorus in the slag is reduced and extracted into the molten iron bath, and the low phosphorus slag after the phosphorus extraction is recovered as a slag for refining, and these steps are repeated once or twice or more. A technique for increasing the phosphorus concentration and then oxidatively dephosphorizing the molten iron bath thus increased in phosphorus concentration to obtain a slag containing a high concentration of phosphorus is disclosed.

  Patent Document 5 discloses that slag containing phosphorus generated by dephosphorization treatment or decarburization refining of hot metal is pulverized, and the pulverized slag is sprayed on a hot metal bath together with a carbon source and a medium solvent. The oxygen gas is supplied, phosphorus in the slag is reduced and extracted into the hot metal, and the slag in which phosphorus is reduced is recycled to the sintering process, and the reduction and extraction process of phosphorus from the slag is repeatedly performed in the hot metal. Is disclosed, in which oxygen is concentrated, then oxygen gas is blown into the molten iron containing phosphorus to decarburize and refine, slag having a high phosphorus concentration is recovered, and the recovered slag is used as, for example, a phosphate fertilizer. Yes.

Furthermore, in Patent Document 6, slag containing phosphorus generated by dephosphorization of hot metal is introduced into a hot metal bath, and carbon material and an oxygen source are supplied to reduce and extract the phosphorus in the slag into the hot metal bath. Then, hot metal containing 0.5 to 3% by mass of phosphorus is produced, and this hot metal is decarburized and refined to recover slag having a P ₂ O ₅ concentration of 10 to 30% by mass. The technique utilized as a phosphate fertilizer is disclosed.

JP 2004-143492 A JP-A-55-97408 JP-A-56-22613 JP 7-316621 A JP 61-147807 A JP-A-11-158526

  However, the above prior art has the following problems.

  That is, in Patent Document 1, the dephosphorization slag can be recycled after the phosphorus is removed by vaporization and dephosphorization, but the vaporized and dephosphorized phosphorus is not recovered and is effective from the viewpoint of securing phosphorus resources. It is not a recycling method.

  In Patent Document 2, the converter slag containing phosphorus is mixed with the blast furnace slag in almost the same amount as the converter slag. However, in recent years, the blast furnace slag is not a waste material but has utility value as a civil engineering / building material. It is positioned as a high resource, and it is economically disadvantageous to use such blast furnace slag for dilution of converter slag.

  Patent Document 3 is a wet process. In the case of a wet process, not only chemicals necessary for the process are expensive, but also a large-scale processing facility is required, and both the equipment cost and the operation cost are expensive.

In Patent Document 4, when phosphorus extraction from slag is repeatedly performed, the phosphorus concentration in the hot metal gradually increases. Therefore, it takes time for the phosphorus extraction process (reduction process), and the recovery timing of low phosphorus slag after phosphorus extraction And confusion such that the timing of recycling the slag to the hot metal dephosphorization process does not coincide. In addition, since the transfer of molten iron and molten slag is carried out between containers in the steelmaking process, the iron yield is reduced, and high phosphorus hot metal and slag are attached to the container, and component defects due to phosphorus pickup are likely to occur. There is a problem. Furthermore, the reductive reaction of refined slag containing phosphorus uses only a carbon source, which is disadvantageous from the viewpoint of reducing energy consumption, particularly reducing the amount of CO ₂ generated. Furthermore, when a converter is used as a reaction vessel, the transfer of slag from the converter occurs in addition to the normal process, and the productivity of converters that originally perform hot metal dephosphorization or decarburization refining. Is greatly reduced.

In Patent Document 5 and Patent Document 6, phosphorus in the molten iron is recovered into slag by decarburizing and refining hot metal having a high phosphorus concentration in which phosphorus in the slag is concentrated. Phosphorus load is high, leading to an increase in refining time and amount of refining agent used. Further, the reduction reaction of slag containing phosphorus uses only a carbon source, which is disadvantageous from the viewpoint of reducing energy, particularly reducing the amount of CO ₂ generated. In Patent Document 6, slag reduction (phosphorus reduction extraction) → removal → phosphorus concentration is performed in the same furnace. The accompanying phosphorus component defect etc. are caused.

  The present invention has been made in view of the above circumstances, and its object is to recycle phosphorus and iron from the steelmaking slag at low cost in recycling steelmaking slag containing phosphorus such as dephosphorization slag and converter slag. Provided a method of recovering iron and phosphorus from steelmaking slag that can be efficiently recovered and effectively use the recovered phosphorus and iron as resources, and recycled steelmaking slag from which iron and phosphorus were recovered A blast furnace slag fine powder or blast furnace slag cement obtained at the time, and a high-quality phosphoric acid resource raw material recovered from steelmaking slag.

  A method for recovering iron and phosphorus from steelmaking slag according to the first invention for solving the above-mentioned problem is a steelmaking slag containing phosphorus generated in a steelmaking refining process, in which metallic iron is separated after solidification From the steelmaking slag, the slag is reduced using a reducing agent containing at least one of carbon, silicon, and aluminum, and the iron oxide and the phosphorous oxide in the steelmaking slag are used as molten phosphorus-containing molten iron. The first step of reduction / recovery, the second step of recycling the steelmaking slag from which iron oxide and phosphorous oxide have been reduced / recovered as a CaO source in the ironmaking step or the steelmaking step, and the reduction treatment were recovered. Phosphorus-containing molten iron is dephosphorized using a CaO-based flux that does not contain fluorine until the phosphorus concentration in the phosphorus-containing molten iron is 0.1% by mass or less. A third step of concentrating phosphorus and a phosphorus-containing molten iron having a phosphorus concentration of 0.1% by mass or less subjected to the dephosphorization treatment are mixed with a blast furnace hot metal discharged from a blast furnace as an iron source. And 4 steps.

  In the method for recovering iron and phosphorus from steelmaking slag according to the second invention, in the first invention, the slag generated in the decarburization refining of the hot metal in the converter is subjected to the reduction treatment in the first step. It is characterized by.

  The method for recovering iron and phosphorus from steelmaking slag according to the third invention is the method for recovering iron and phosphorus from the steelmaking slag according to the first invention, the slag generated in the decarburization refining of the hot metal in the converter, and the slag generated in the preliminary dephosphorization treatment of the hot metal. The mixture is subjected to the reduction treatment in the first step.

  In the method for recovering iron and phosphorus from steelmaking slag according to the fourth invention, in any one of the first to third inventions, the phosphorus-containing molten iron is a hot metal containing 3% by mass or more of carbon. Features.

  A method for recovering iron and phosphorus from steelmaking slag according to a fifth invention is characterized in that, in any of the first to fourth inventions, the reduction treatment of the first step is performed in the presence of blast furnace hot metal. To do.

  A method for recovering iron and phosphorus from steelmaking slag according to a sixth aspect of the present invention is the method for recovering iron and phosphorus according to any one of the first to fifth aspects, wherein the CaO-based flux enriched with phosphorus in the third step is used as a phosphorus resource. It is characterized by being.

  A method for recovering iron and phosphorus from steelmaking slag according to a seventh aspect of the present invention is the method of recovering and recovering iron oxide and phosphorus oxide according to any one of the first to sixth aspects of the invention by the reduction treatment of the first step. The metal iron mixed in the slag is separated from the steelmaking slag, and the steelmaking slag from which the metal iron is separated is recycled as a CaO source in the ironmaking process or the steelmaking process.

The method for recovering iron and phosphorus from steelmaking slag according to the eighth invention is the method of recovering iron and phosphorus according to any one of the first to seventh inventions, wherein the steelmaking slag reduced by the reduction treatment in the first step is adjusted for basicity. It is a steelmaking slag mixed with a SiO ₂ -containing material.

  The method for recovering iron and phosphorus from the steelmaking slag according to the ninth invention is the method of recovering iron and phosphorus from any one of the first to eighth inventions, wherein the recycling destination of the steelmaking slag in the second step is an iron ore sintering step or It is a hot metal production process in a blast furnace.

  The method for recovering iron and phosphorus from steelmaking slag according to the tenth aspect of the invention is the method for recovering iron and phosphorus from any one of the first to eighth aspects, wherein the recycling destination of the steelmaking slag in the second step is a hot metal dephosphorization step or a It is a hot metal decarburization refining process in a furnace.

  The blast furnace slag fine powder or the blast furnace slag cement according to the eleventh aspect of the invention is a blast furnace slag fine powder or a blast furnace slag cement according to any one of the first to eighth aspects. Using the blast furnace slag discharged from the blast furnace when the recycling destination is the iron ore sintering process or the hot metal production process in the blast furnace, and the slag is recycled to the iron ore sintering process or the hot metal production process in the blast furnace It is manufactured.

  The phosphoric acid resource raw material according to the twelfth invention is enriched with phosphorus in the third step in the method for recovering iron and phosphorus from steelmaking slag according to any one of the first to tenth inventions, It is characterized by comprising a CaO-based flux separated and recovered from phosphorus-containing molten iron.

  According to the present invention, it contains phosphorus such as dephosphorization slag generated by the preliminary dephosphorization treatment of hot metal, and converter slag generated by converter decarburization refining using dephosphorization hot metal that is not sufficiently molten or dephosphorized. In recycling steelmaking slag, first, the metallic iron mixed in the steelmaking slag is separated and removed, and then the iron oxide and phosphorous oxide in the steelmaking slag from which the metallic iron has been removed are reduced and recovered as phosphorus-containing molten iron. The steelmaking slag from which iron oxide and phosphorous oxide have been removed is recycled as a CaO source in the steelmaking process or the steelmaking process, and the phosphorus-containing molten iron is dephosphorized to a phosphorus concentration of 0.1% by mass or less to be a blast furnace On the other hand, the phosphorus in the molten iron containing phosphorus is concentrated to a level sufficient to be recovered as a phosphorus resource in the CaO-based flux by the dephosphorization process. Effective use of iron and phosphorus contained in steelmaking slag as resources without increasing the phosphorus concentration of hot metal or impairing its function as a dephosphorizing agent in recycling use in the steel process Is realized.

In particular, the steelmaking slag is reformed into a blast furnace slag by recycling the steelmaking slag after the reduction treatment to an iron ore sintering process or a hot metal production process in a blast furnace. By using this blast furnace slag in the form of fine powder as an admixture for cement, the effect that CaO originally present in the steelmaking slag, like the cement, contributes to the development of the strength of the concrete is obtained. It is done. Conventionally, the CaO content of the cement raw material used is calcined calcium carbonate (CaCO ₃ ). In this case, calcining energy is required and CO ₂ is generated, but blast furnace slag fine powder is used as cement. When mixed into a blast furnace slag cement, the firing energy and the amount of CO ₂ generated can be reduced according to the mixing ratio of blast furnace slag fine powder / ordinary Portland cement.

It is a figure which shows the schematic of the dephosphorization processing equipment used by this invention. It is a figure which shows the behavior of phosphorus during the dephosphorization process of high phosphorus hot metal.

  Hereinafter, the present invention will be described in detail.

The present inventors have found that the dephosphorization slag generated during the preliminary dephosphorization of hot metal, and the phosphorus concentration after dephosphorization is higher than the phosphorus concentration level of the product even if the hot metal or the preliminary dephosphorization is performed. Steelmaking slag containing phosphorus (also referred to as “phosphorus-containing steelmaking slag”) such as converter slag generated during converter decarburization and refining using phosphorous iron is used as a dephosphorizing agent (CaO for fixing P ₂ O ₅ ). ) And as a CaO source for ironmaking agents, the phosphorus contained in the steelmaking slag is reduced in the blast furnace reducing atmosphere and transferred to hot metal, and the phosphorus concentration in the hot metal is reduced. Because of the rise, it was studied to eliminate the influence of phosphorus contained in the steelmaking slag on the hot metal discharged from the blast furnace.

  The converter slag generated during decarburization and refining of hot metal that has been pre-dephosphorized to the phosphorus concentration level of the product in advance has not been picked up by the phosphorus concentration in the hot metal, but has been subjected to the iron ore sintering process and the blast furnace. Recycled as a slagging agent. Therefore, if phosphorus is removed from the phosphorus-containing steelmaking slag, it can be recycled into a blast furnace. Therefore, removal of phosphorus from the steel slag containing phosphorus was examined.

In phosphorus-containing steelmaking slag, phosphorus is contained as an oxide of P ₂ O ₅ , and generally steelmaking slag is mainly composed of CaO and SiO ₂ , and phosphorus is calcium (Ca) and silicon ( Since the affinity for oxygen is weak compared to Si), P ₂ O ₅ in phosphorus-containing steelmaking slag can be easily reduced if phosphorus-containing steelmaking slag is reduced with carbon, silicon, aluminum, or the like. I understood. In this case, the phosphorus-containing steelmaking slag, iron in the form of FeO and Fe ₂ O ₃ (hereinafter, collectively referred to as "Fe _x O") are contained in the oxides, these iron oxide oxygen Therefore, when phosphorus-containing steelmaking slag is reduced with carbon, silicon, aluminum, etc., Fe _x O in the steelmaking slag is reduced at the same time.

By the way, the phosphorus-containing steelmaking slag contains about 5 to 10% by mass of metallic iron (molten metal or molten steel) by mixing in the refining reaction or in the waste. This metallic iron is separable from slag, and since it is in a metallic state, there is no need to reduce P ₂ O ₅ , Fe _x O, etc. in the slag. By removing, the energy required for high-temperature treatment of phosphorus-containing steel slag per unit mass can be reduced. Therefore, in the present invention, before reducing the phosphorus-containing steelmaking slag, metallic iron is separated and removed from the phosphorus-containing steelmaking slag in advance.

  Steelmaking slag including phosphorus-containing steelmaking slag is discharged into a slag yard and the like, and after being discharged, cooled and cooled in the atmosphere, solidified, and then dug up and collected by a heavy machine such as a bulldozer. Generally, slag that has been dug up by heavy machinery is crushed because of its various sizes and difficulty in transport. In the present invention, metallic iron is separated and removed by the phosphorus-containing steelmaking slag at this crushed stage. Further, when separating and removing metallic iron, the phosphorus-containing steelmaking slag may be further finely crushed as necessary. Magnetic iron separation, specific gravity separation, particle size separation, wind power separation, etc. can be used as a method for separating and removing metallic iron. Even if these separation means are used, all of the metallic iron in the steelmaking slag is not separated and removed, and some metallic iron such as fine metallic iron buried in the slag grains remains. In the present invention, steelmaking slag that has been treated at least once by the above separating means even if a certain amount of metallic iron remains is defined as “steeling slag from which metallic iron is separated”.

  In the reduction treatment, phosphorus has high solubility in iron, and phosphorus produced by reduction dissolves rapidly in iron produced by reduction. Here, the present invention aims to remove phosphorus from the phosphorus-containing steelmaking slag to improve the steelmaking slag having a low phosphorus content, and to quickly separate the phosphorus produced by the reduction from the steelmaking slag, It has been found that it is desirable to reduce at a high temperature so that the iron produced by the reduction is in a molten state. That is, if the iron produced | generated by reduction | restoration is a molten state, the melted iron will be easy to isolate | separate from slag, and isolation | separation from the steelmaking slag of the iron produced | generated by reduction | restoration will be accelerated | stimulated. Moreover, the generated phosphorus is dissolved in the molten iron, so that the separation of phosphorus from the steelmaking slag is also accelerated. It has also been found that when steelmaking slag is in a molten state, separation from iron containing phosphorus is further promoted.

  In this case, the lower the melting point of the molten iron produced, the more the separation of the molten iron and slag is promoted. Therefore, it is preferable to dissolve the carbon in the produced molten iron and produce molten iron as the molten iron. I understand. Specifically, when the carbon concentration of the molten iron becomes 3% by mass or more, the liquidus temperature of the molten iron, that is, the molten iron becomes 1300 ° C. or less. It is preferable to do. In order to dissolve carbon in the produced molten iron, carbon is used as a reducing agent, or when silicon or aluminum is used as a reducing agent, the molten iron produced by coexisting carbon with steelmaking slag. Is carburized and becomes a hot metal containing phosphorus in a high concentration (this hot metal is called "high phosphorus hot metal" to distinguish it from blast furnace hot metal, and the solidified material is called "high phosphorus iron").

  Moreover, by separately charging blast furnace hot metal in advance and performing reduction treatment in a state where the blast furnace hot metal coexists with phosphorus-containing steelmaking slag, all of the above conditions are satisfied and the separation of phosphorus from the steelmaking slag is promoted. I also understood that. That is, it has been found that it is preferable to perform a reduction treatment of phosphorus-containing steelmaking slag by separately charging a blast furnace hot metal in advance if the conditions allow hot metal to be procured.

  The steelmaking slag after the reduction treatment may be recycled as it is to the ironmaking process and the steelmaking process as a source of CaO for the dephosphorizing agent and ironmaking agent, but the steelmaking slag after the reduction treatment contains fine metallic iron, that is, high-phosphorous pig iron. Since it remains, it is preferable to separate and remove metallic iron from the steelmaking slag after the reduction treatment from the viewpoint of enhancing the recovery of iron and phosphorus and preventing recycling of phosphorus. Separation / removal method of metallic iron from steelmaking slag after reduction treatment should be performed using magnetic separation, specific gravity separation, particle size separation, wind separation, etc. after crushing steelmaking slag after reduction treatment as necessary Can do. Phosphorus is concentrated in the recovered metallic iron. By separating and removing metallic iron from the steelmaking slag after the reduction treatment, the phosphorus content of the steelmaking slag after the reduction treatment is reduced.

  The steelmaking slag after the reduction treatment has a significantly lower phosphorus content than the phosphorus-containing steelmaking slag before the treatment, and without dephosphorizing agent or ironmaking agent without increasing the phosphorus concentration of hot metal. As a CaO source, it can be recycled in the iron making process and steel making process.

  By the way, generally, since the mass ratio (mass% P / mass% Fe) of phosphorus and iron in the phosphorus-containing steelmaking slag is 0.005 to 0.075, the molten iron after reduction (high phosphorus hot metal) Contains about 0.5 to 7.5% by mass of phosphorus. On the other hand, the phosphorus content of the blast furnace molten iron discharged from the blast furnace is currently about 0.1% by mass. Therefore, when high phosphorus hot metal having a phosphorus concentration of 0.5 to 7.5% by mass cannot be dephosphorized to the level of blast furnace hot metal having a phosphorus concentration of about 0.1% by mass, the operation of the high phosphorus hot metal is limited. In some cases, it may not be used as an iron source.

  Therefore, the phosphorus concentration is 4.0 mass% (level 1), 2.0 mass% (level 2), 1.1 mass using the dephosphorization equipment currently used for the preliminary dephosphorization treatment of the blast furnace hot metal. Blast furnace hot metal adjusted to 4 levels of% (level 3) and 0.5 mass% (level 4) was used as a substitute for high phosphorus hot metal, and a dephosphorization test was conducted. The phosphorus concentration of the blast furnace hot metal was adjusted using an iron-phosphorus alloy.

  In FIG. 1, the schematic of the used dephosphorization processing equipment is shown. In FIG. 1, a hot metal ladle 4 containing a high phosphorus hot metal 2 having a adjusted phosphorus concentration is loaded on a carriage 5 and carried into a dephosphorization processing facility 1. The dephosphorization processing equipment 1 is provided with an upper blowing lance 6 and an injection lance 7 that can move up and down in the hot metal ladle 4. From the upper blowing lance 6, an iron oxide such as oxygen gas or iron ore is provided. Is sprayed onto the high phosphorus hot metal 2, and CaO-based flux or iron oxide is blown into the high phosphorus hot metal 2 from the injection lance 7. The dephosphorization processing equipment 1 is further provided with raw material supply equipment such as a hopper and a chute for adding CaO-based flux and iron oxide to the inside of the hot metal ladle 4 but is omitted in FIG. Yes.

Using this dephosphorization processing equipment 1, oxygen gas is blown from the top blowing lance 6 to the 200-ton high phosphorus hot metal 2 in the hot metal ladle, and at the same time, nitrogen gas is used as a carrier gas from the injection lance 7. A high-phosphorus molten iron 2 was dephosphorized by blowing a CaO-based flux. The blown CaO-based flux melts to form dephosphorization slag 3. In this case, phosphorus in the high phosphorus hot metal is oxidized by oxygen gas to become P ₂ O ₅ and is taken into the hatched CaO-based flux, and dephosphorization of the high phosphorus hot metal 2 proceeds. Table 1 shows the experimental conditions. In addition, quick lime is used as a CaO type | system | group flux, and does not contain fluorine sources, such as a fluorite. In addition, when a predetermined amount of CaO is added to the hot metal, it may be used together with the injection lance 7 and sprayed onto the hot metal bath surface together with oxygen gas from the top blowing lance 6.

  FIG. 2 shows the behavior of phosphorus in the high phosphorus hot metal in the dephosphorization treatment performed in the experiment. As shown in FIG. 2, it was found that the dephosphorization reaction rate was higher as the phosphorus concentration in the hot metal before the start of the dephosphorization treatment was higher. Further, even with a dephosphorization treatment method generally performed on blast furnace hot metal, dephosphorization treatment up to about 0.1% by mass of phosphorus equivalent to blast furnace hot metal is performed on high phosphorus hot metal 2. I found it possible. And, it was confirmed that the high phosphorus hot metal 2 after the dephosphorization treatment can be used by mixing with the blast furnace hot metal as an iron source without any difference from the blast furnace hot metal.

Table 2 shows the composition of the dephosphorization slag produced by this dephosphorization treatment. In order to effectively use this dephosphorization slag as a phosphorus resource, it is preferable to set it to a level equivalent to 3CaO · P ₂ O ₅ (mass ratio of CaO and P ₂ O ₅ = 54: 46) which is the composition of phosphate ore. Therefore, the dephosphorization slag was aimed to contain at least 20% by weight of P ₂ O ₅ .

As shown in Table 2, the dephosphorization slag produced contains 20% by mass of P ₂ O ₅ even if the phosphorus concentration in the hot metal before the dephosphorization treatment is level 4 of 0.5% by mass. further, P ₂ O ₅ concentration levels 1 and level 2, dephosphorization slag is higher than CaO concentration, it was found that further P ₂ O ₅ than the composition of 3CaO · P ₂ O ₅ is concentrated. That is, it was found that the dephosphorized slag produced can be sufficiently utilized as a phosphorus resource. As an example, 70% by mass or more of phosphoric acid contained in the slag enriched with phosphoric acid after dephosphorization treatment is citric acid-soluble phosphoric acid (soluble phosphoric acid: phosphoric acid that can be absorbed by the plant taking out acid from the root). Therefore, it was confirmed that it can be used as a phosphate fertilizer.

  In addition, it is known that the CaO-based flux used for the preliminary dephosphorization treatment of the blast furnace hot metal promotes the dephosphorization reaction by promoting the hatching of CaO by adding about 5% by mass of a fluorine source such as fluorite. However, when the generated dephosphorized slag is used as, for example, a phosphorus fertilizer, fluorine is eluted from the phosphorous fertilizer (dephosphorized slag), and the fluorine elution value becomes a problem with respect to the soil environmental standards. In the present invention, no fluorine source is used. Fluorine fixes phosphoric acid in the slag and produces a fluorine compound (fluorinated apatite) with a low proportion of soluble phosphoric acid. Therefore, when fluorine-containing slag is used as a fertilizer raw material, A sufficient concentration cannot be ensured. From this point of view, it is not preferable to use a fluorine compound.

  The present invention has been made based on the above test results, and the method for recovering iron and phosphorus from the steelmaking slag according to the present invention is a steelmaking slag containing phosphorus generated in the steelmaking refining process and solidified. Steelmaking slag from which metallic iron has been separated is reduced using a reducing agent containing one or more of carbon, silicon, and aluminum, and the iron oxide and phosphorous oxide in the steelmaking slag are melted in the phosphorous state. A first step of reducing and recovering from the steelmaking slag as contained molten iron, and a second step of recycling the steelmaking slag from which iron oxide and phosphorous oxide have been reduced and recovered as a CaO source in the ironmaking step or the steelmaking step, and The phosphorus-containing molten iron recovered by the reduction treatment is dephosphorized using a CaO-based flux not containing fluorine until the phosphorus concentration in the phosphorus-containing molten iron becomes 0.1 mass% or less. The third step of concentrating phosphorus in the CaO-based flux and the phosphorus-containing molten iron having a phosphorus concentration of 0.1% by mass or less subjected to the dephosphorization treatment were discharged from the blast furnace as an iron source. And a fourth step of mixing with the blast furnace hot metal.

  According to the present invention configured as described above, phosphorus such as dephosphorization slag generated by the preliminary dephosphorization treatment of hot metal, converter slag generated by converter decarburization refining using normal hot metal or dephosphorization hot metal with insufficient dephosphorization, etc. In the recycling of steelmaking slag containing steel, first, the metallic iron mixed in the steelmaking slag is separated and removed, and then the iron oxide and phosphorous oxide in the steelmaking slag from which the metallic iron has been removed are reduced to phosphorus-containing molten iron. The recovered steelmaking slag from which iron oxide and phosphorous oxide have been removed is recycled as a CaO source in the iron making process or the steelmaking process, and the phosphorus-containing molten iron is dephosphorized to a phosphorus concentration of 0.1% by mass or less. On the other hand, the phosphorus in the molten iron containing phosphorus is concentrated to a CaO-based flux enough to be recovered as a phosphorus resource by the dephosphorization process, so that the phosphorus concentration in the hot metal is increased. Without causing problems such as it is implemented to effectively utilize the iron contained in the steelmaking slag and phosphorus as a resource, respectively.

  Note that the converter slag generated during the decarburization refining of the hot metal, which has been preliminarily dephosphorized to the phosphorus concentration level of the product, also contains phosphorus, not zero. Therefore, it is possible to apply the present invention to this converter slag, but the slag has a low phosphorus content, and even if recycled to a blast furnace as it is, the influence of phosphorus can be ignored. By applying the invention, the cost is increased. Therefore, the steel-making slag containing phosphorus, which is the subject of the present invention, is higher than the concentration that increases the phosphorus concentration of hot metal or molten steel when the steel-making slag is recycled to a blast furnace or the like, and causes an increase in cost for normal operations. This steelmaking slag contains phosphorus.

  As a method of recycling steelmaking slag from which iron oxide and phosphorous oxide have been removed by reduction treatment, as described above, it is used as a CaO source (slagging agent) in the iron ore sintering step, and then in a blast furnace. In addition to the method used as the charging raw material in the hot metal production process, as a method directly used as a iron making agent in the hot metal production process in the blast furnace, or as a CaO-based flux as a dephosphorizing agent in the preliminary dephosphorization treatment of the blast furnace hot metal Preferred examples include the method used, the method used as a slagging agent in the decarburizing and refining process of hot metal in a converter, and the method used as a CaO-based desulfurizing agent in the desulfurization treatment of blast furnace hot metal. It is done. Even if it is a process other than this, as long as it is the iron making process and steelmaking process in an ironworks, if it is a process using quicklime, it can be used as a substitute for quicklime.

  Furthermore, an example of a steel-making slag containing phosphorus that is suitable for practicing the present invention is as follows. Converter slag alone generated by converter decarburization and refining using dephosphorized hot metal that is not sufficiently molten or dephosphorized. A mixture of the converter slag and the dephosphorization slag generated by the preliminary dephosphorization treatment of the hot metal is preferable.

This is because the converter slag has a high basicity (mass% CaO / mass% SiO ₂ ) (usually about 3 to 5) and is advantageous as a CaO source in the iron ore sintering process in the second step. However, since converter slag has a high basicity and is inferior in hatchability during the sintering process, dephosphorization slag may be mixed with the converter slag in order to increase hatchability. The dephosphorization slag has a basicity of about 1.5 to 2.5, and the hatchability is improved by the contained SiO ₂ . In other words, when a mixture of converter slag and dephosphorization slag is used, the sintering process can be performed smoothly without using a fluorine source, and phosphorus-containing molten iron phosphorus can be used. Since the concentration is increased, the phosphorus concentration of the CaO-based flux recovered in the third step after the dephosphorization treatment is increased, and the utilization as a phosphorus resource is promoted. However, the use of dephosphorized slag alone is not preferable because the basicity is low and the CaO source is insufficient in the sintering process.

In addition, when a mixture of converter slag and dephosphorization slag is used as the steelmaking slag to be subjected to the reduction process in the first step, hatching of the steelmaking slag reduced by SiO ₂ contained in the dephosphorization slag. In addition, the effect of promoting the separation of the phosphorus-containing molten iron obtained by reduction and the steelmaking slag during the reduction treatment is also exhibited. As means for reducing the basicity of the converter slag, it is possible to mix SiO ₂ -containing materials such as silica, silica sand, glass wool, and silicon sludge into the steelmaking slag instead of dephosphorization slag.

The phosphorus-containing steelmaking slag, since manganese may be contained in the oxide form of MnO and Mn ₂ O _3, affinity of these manganese oxides oxygen is equivalent to iron and phosphorus, steelmaking By reducing the slag with carbon, silicon, aluminum, etc., the manganese oxide in the steelmaking slag is also reduced at the same time and shifts to a high phosphorus hot metal. When this high phosphorus hot metal is dephosphorized, manganese is contained in the dephosphorization slag produced by oxidizing manganese in the high phosphorus hot metal. When dephosphorization slag is used as a phosphorus resource, if the P ₂ O ₅ concentration is relatively lowered by the manganese oxide contained in the slag, the added value as a phosphorus resource may decrease. For this purpose, it is preferable to take measures such as treating phosphorus-containing steelmaking slag with low manganese oxide, or pre-oxidizing and removing manganese before dephosphorization of the high phosphorus hot metal.

  The total amount of converter slag generated may be used for the reduction treatment in the first step of the present invention, but the use of converter slag in the hot metal preliminary dephosphorization treatment is also effective from the viewpoint of resource saving. Therefore, a part of the generated converter slag may be used as a CaO source in the hot metal preliminary dephosphorization process, and the remaining part of the converter slag may be used for the reduction process in the first process.

  The blast furnace hot metal discharged from the blast furnace is received by a topped car, the blast furnace hot metal accommodated 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 and the blast furnace in the hot metal ladle. The molten iron is subjected to mechanical stirring desulfurization treatment, the blast furnace hot metal after this desulfurization treatment is charged into the converter, decarburized and refined in the converter, and thus the molten steel is melted from the blast furnace molten iron. The present invention was applied in the steelmaking process. Table 3 shows examples of chemical components of the blast furnace hot metal and molten steel from the blast furnace tapping to the end of converter decarburization refining.

As shown in Table 3, the blast furnace hot metal after desiliconization and dephosphorization contains 0.05% by mass of phosphorus, which is higher than the phosphorus concentration level (0.025% by mass or less) of the product, The converter slag generated by the converter decarburization refining using this blast furnace hot metal contains about 1.5% by mass of phosphorus (about 3.4% by mass with P ₂ O ₅ ). When this steelmaking slag is reused as a CaO source in the sintering process, enrichment of phosphorus in the blast furnace hot metal occurs. Therefore, a test (Invention Example 1) for applying the present invention to this converter slag was conducted.

  The converter slag was magnetically separated 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 previously separated and removed. 250 ton converter slag from which metallic iron has been separated and removed in advance, 50 ton blast furnace hot metal, and coke as a reducing agent are charged into a three-phase AC type arc furnace to generate an arc to convert the converter slag. The coke was heated to reduce the converter slag. Blast furnace hot metal promotes the reduction of steelmaking slag by heating the steelmaking slag in the presence of molten metal in the furnace in advance, and at the same time, rapidly takes in the phosphorus-containing iron produced by the reduction of the steelmaking slag, It was inserted for the purpose of promoting separation from steelmaking slag. The temperature of the blast furnace hot metal was 1300 ° C. About 100 tons of high phosphorus hot metal including the previously charged blast furnace hot metal was obtained by the reduction treatment for 30 minutes. Table 4 shows the conditions for the reduction treatment, and Table 5 shows the composition of the steelmaking slag before and after the reduction treatment.

In addition, the present invention is applied to a mixture of dephosphorization slag generated by the preliminary dephosphorization of hot metal and from which the metallic iron is separated and removed in advance by the magnetic separator (mixing ratio = 1: 1). The test (Invention Example 2) was also carried out. The composition of the converter slag is the same as that of the converter slag used in Example 1 of the present invention (see Table 5). The composition of the dephosphorization slag is CaO: 22 mass%, SiO ₂ : 18 mass%, P: They were 2.4% by mass, FexO: 28% by mass, MgO: 5.2% by mass, and MnO: 4.1% by mass.

  In the above arc furnace, 250 tons of a mixture of converter slag and dephosphorization slag, 50 tons of blast furnace hot metal, and coke as a reducing agent are charged, an arc is generated to heat the mixed slag and coke, Reduction treatment of mixed slag was performed. Blast furnace hot metal promotes the reduction of mixed slag by heating the molten slag in the presence of molten metal in the furnace in advance, and at the same time, rapidly takes in the phosphorus-containing iron produced by the reduction of the mixed slag, It is inserted for the purpose of promoting separation from the mixed slag.

  The furnace slag melted earlier than in the first invention example, and a high phosphorus hot metal of about 100 tons was obtained by the reduction treatment for 25 minutes together with the blast furnace hot metal charged in advance. The conditions for the reduction treatment are the same as in Table 4 described above. Table 5 described above shows the composition of the mixed slag before and after the reduction treatment.

  In both Invention Example 1 and Invention Example 2, the obtained high phosphorus hot metal was discharged from the arc furnace to the hot metal ladle, and then about 200 tons of slag remaining in the furnace was discharged into the slag pot. In the present invention example 1, the chemical components of the obtained high phosphorus hot metal were: carbon: 4.3% by mass, silicon: 0.01% by mass, manganese: 2.2% by mass, phosphorus: 3.0% by mass, sulfur : 0.05% by mass, and in Example 2 of the present invention, carbon: 4.3% by mass, silicon: 0.01% by mass, manganese: 3.1% by mass, phosphorus: 4.5% by mass, sulfur: 0.00%. It was 05 mass%. Invention Example 2 had a higher phosphorus concentration, but the others were equivalent.

  P / Fe of the phosphorus-containing steelmaking slag is 0.5 to 7.5% by mass in terms of P concentration, but in this example, it is diluted to a concentration of about ½ using blast furnace hot metal. In this case, the P concentration is 0.25 to 3.75% by mass, and the phosphorus concentration is within this range, which is consistent with the past results. The high phosphorus hot metal was dephosphorized using the dephosphorization equipment shown in FIG. Table 6 shows the dephosphorization treatment conditions performed on the high phosphorus hot metal in Invention Example 1 and Invention Example 2.

By this dephosphorization treatment, the phosphorus concentration of the high phosphorus hot metal was reduced to 0.1% by mass in both inventive examples 1 and 2. Table 7 shows the chemical composition of the high phosphorus hot metal before and after the dephosphorization treatment. Further, by this dephosphorization treatment of the high phosphorus hot metal, both of the inventive examples 1 and 2 were CaO: 62 mass%, SiO ₂ : 2.2 mass%, P: 28 mass%, Fe _x O: 2. A dephosphorized slag of 8% by mass, MgO: 4% by mass, and MnO: 0.8% by mass was obtained. This dephosphorization slag could be used as a phosphorus fertilizer.

  The high phosphorus hot metal after the dephosphorization treatment was mixed with the blast furnace hot metal, and the mixed hot metal was subjected to desiliconization / dephosphorization treatment, and then charged into the converter through a desulfurization treatment step. In the converter, ordinary refining was performed to produce molten steel of a predetermined component.

  On the other hand, the converter slag after the reduction treatment is cooled, and then used as a CaO source for the iron making agent in the iron ore sintering step, and the manufactured sintered ore is charged into the blast furnace as the iron source, Blast furnace hot metal was produced. The phosphorus concentration of the blast furnace hot metal melted was about 0.1% by mass, and there was no problem at all. In addition, as a result of manufacturing blast furnace slag fine powder and blast furnace slag cement using blast furnace slag discharged from the blast furnace when recycling the slag after reduction treatment, the quality standard of JIS A 6206 “Blast furnace slag fine powder for concrete” Satisfied, JIS R 5211 “Blast Furnace Cement” properties such as strength were similar to the conventional ones and there were no problems, and it was possible to save energy in cement production as before.

  On the other hand, when the converter slag generated in the steelmaking process is recycled as it is as a CaO source of sintered ore, the phosphorus concentration in the hot metal discharged from the blast furnace becomes high, and in the preliminary dephosphorization treatment of the hot metal The basic unit of the dephosphorizing agent (oxygen source and CaO-based flux) and the amount of dephosphorizing slag generated increased 1.5 times, and the productivity was reduced by 20%.

  In the present invention, about 90% by mass of iron contained in the converter slag is recovered, and this is a higher recovery rate than when the converter slag is directly recycled as a CaO source of sintered ore. there were.

  The converter slag and dephosphorization slag generated in the iron making-steel making process shown in Example 1 are subjected to a reduction treatment, whether or not metallic iron is removed from the steelmaking slag before the reduction treatment, and the steelmaking after the reduction treatment. The effect of the removal of metallic iron from the slag on the recovery rate of high phosphorus pig iron in the reduction process was investigated.

  Magnetic separation of the steelmaking slag before the reduction treatment and magnetic separation of the steelmaking slag after the reduction treatment were both performed using a magnetic separator having a magnetic force of 3000 G and a slag treatment capacity of 50 to 150 t / Hr. Metallic iron recovered from the steelmaking slag after reduction by magnetic separation was calculated as high-phosphorous pig iron. The reduction treatment was performed by using a rotary kiln equipped with a heating burner and heating the steelmaking slag and coke charged into the rotary kiln with a burner. The operating temperature of the rotary kiln was adjusted to 1450 to 1550 ° C., and a high phosphorus molten iron in a molten state was obtained by reduction treatment. Table 8 shows test conditions and test results of a total of five tests (test numbers 1 to 5).

Test No. 1 is a converter slag that does not separate metallic iron (basicity (mass% CaO / mass% SiO ₂ ) = 3.0) and preliminary dephosphorized slag that does not separate metallic iron (basicity = 1). .5) Reduction test of the mixture, test number 2 is the converter slag subjected to magnetic separation (basicity = 3.0) and preliminary dephosphorization slag subjected to magnetic separation (basicity = 1.5) Test No. 3, which was a reduction treatment of the mixture of No. 3, was a mixture of converter slag (basicity = 3.0) subjected to magnetic separation and preliminary dephosphorization slag (basicity = 1.5) subjected to magnetic separation. Test in which reduction treatment was performed, and the slag after reduction was further magnetically separated to recover high-phosphorous pig iron. Test No. 4 was conducted on a converter slag (basicity = 3.0) subjected to magnetic separation as a SiO ₂ -containing substance. glass wool (SiO ₂ = 100 mass%) and mixed to adjust the basicity 2.25 Stuff reduction treatment, the slag was further magnetically separated to recover a high phosphorus pig iron test after reduction, Test No. 5, SiO ₂ contained in the converter slag subjected to magnetic separation (basicity = 3.0) Silicon sludge (Si = 15% by mass, SiO ₂ = 85% by mass) as a substance was mixed and the basicity was adjusted to 2.25. Then, the reduced slag was further magnetically separated to obtain high phosphorus. This is a test that collected pig iron.

  As shown in Table 8, it was confirmed that by separating and removing the metallic iron in the slag before the reduction treatment, it was possible to recover more high-phosphorous iron with a small amount of reducing coke used. It was also confirmed that more high-phosphorous pig iron can be recovered by magnetically separating the slag after the reduction treatment.

  Moreover, the high-phosphorous iron obtained in Test No. 2 is mixed with 150 tons of blast furnace hot metal in a hot metal ladle, and CaO source (quick lime) and oxygen source are supplied to the hot metal after mixing to carry out dephosphorization treatment. did. And the slag obtained by the dephosphorization process was collect | recovered, and the fertilization effect as a phosphate fertilizer was done with respect to the collect | recovered slag. At that time, for the purpose of comparison, a fertilization effect test was also conducted on ordinary steelmaking slag.

Koeko test method using "Komatsuna" as used plant, as used soil to "surface erosion Andosols", was added 100mg-P ₂ O ₅ / pot fertilizer efficiency test target slag, evaluation of toxicity The three items of the germination rate, the plant height (height), and the weight of the living body (g / pot) showing the growth promotion effect were evaluated. Specifically, a substance adjusted so as to have the same P ₂ O ₅ concentration with a chemical was used as a reference material, and evaluation was performed by an average value of three items when the result of the reference material was 100.

  Table 9 shows the results of the fertilization test of three items of the components of the two types of slags subjected to the fertilization effect test, the concentration of soluble phosphoric acid, germination rate, plant height (height), and body weight (g / pot). In addition, the fertilization effect test result has shown that it is excellent as a phosphate fertilizer, so that a numerical value is high.

  As shown in Table 9, it was confirmed that the slag obtained by the present invention has a high concentration of soluble phosphoric acid and is excellent as a phosphate fertilizer.

DESCRIPTION OF SYMBOLS 1 Dephosphorization processing equipment 2 High phosphorus hot metal 3 Dephosphorization slag 4 Hot metal ladle 5 Bogie 6 Top blowing lance 7 Injection lance

Claims (12)

A steelmaking slag containing phosphorus generated in a steelmaking refining process, which has been solidified and then separated from metallic iron, is reduced using a reducing agent containing one or more of carbon, silicon, and aluminum. Te, iron oxide and phosphorus oxide of the steel slag, phosphorus concentration and higher Engineering you reducing and recovering from steelmaking slag as the phosphorus-containing molten iron in the molten state of more than 0.5 mass%, the pre-Symbol reduction treatment the recovered phosphorus-containing molten iron, with a CaO-based flux containing no fluorine, phosphorus concentration of the phosphorus-containing molten iron to dephosphorization until 0.1 wt% or less, phosphorus in CaO-based flux P and the ₂ O ₅ as engineering which Ru is concentrated 20 wt% or more, and having a method for recovering iron and phosphorus from steelmaking slag. The slag generated in the decarburization refining of molten iron in the converter, and wherein the subjecting prior Kikae source processing, iron and a method for recovering phosphorus from steel slag according to claim 1. And slag generated in decarburization refining of molten iron in the converter, a mixture of the slag generated in pre-dephosphorization of molten pig iron, and wherein the subjecting prior Kikae source processing, steel making according to claim 1 Recovery method of iron and phosphorus from slag.   The method for recovering iron and phosphorus from steelmaking slag according to any one of claims 1 to 3, wherein the phosphorus-containing molten iron is hot metal containing 3 mass% or more of carbon. And performing pre Kikae source in the presence of a blast furnace hot metal, iron and a method for recovering phosphorus from steelmaking slag according to any one of claims 1 to 4. The CaO-type flux phosphorus is concentrated in step of concentrating the phosphorous in CaO-based flux, which is characterized by utilizing as the phosphorus resources, the steel slag according to any one of claims 1 to 5 Recovery method of iron and phosphorus. Before the steelmaking slag iron oxide by Kikae based processing and phosphorus oxides are reduced and recovered to separate the metallic iron to be mixed into the slag, the separated steel slag of metallic iron in the ironmaking process or steelmaking The method for recovering iron and phosphorus from steelmaking slag according to any one of claims 1 to 6, wherein the iron and phosphorus are recycled as a CaO source. Steelmaking slag is reduced in the previous Kikae source process is characterized in that SiO ₂ containing material for basicity adjustment is mixed steel slag, in any one of claims 1 to 7 A method for recovering iron and phosphorus from the described steelmaking slag. 9. The steelmaking slag, in which iron oxide and phosphorous oxide are reduced and recovered by the reduction treatment, is recycled to an iron ore sintering process or a hot metal production process in a blast furnace. A method for recovering iron and phosphorus from steelmaking slag according to any one of the above. The steelmaking slag from which iron oxide and phosphorous oxide have been reduced and recovered by the reduction treatment is recycled to a hot metal dephosphorization step or a hot metal decarburization refining step in a converter. The method for recovering iron and phosphorus from the steelmaking slag according to any one of 8. The recycling destination of the steelmaking slag, in which the iron oxide and phosphorous oxide are reduced and recovered by the reduction treatment in the method for recovering iron and phosphorus from the steelmaking slag according to any one of claims 1 to 8, is an iron ore recycling destination. It is a hot metal production process in a sintering process or a blast furnace, and is manufactured using blast furnace slag discharged from the blast furnace when the slag is recycled to the iron ore sintering process or the hot metal production process in the blast furnace. Blast furnace slag fine powder or blast furnace slag cement, characterized by that. The phosphorus is concentrated in the step of concentrating phosphorus in the CaO-based flux in the method for recovering iron and phosphorus from the steelmaking slag according to any one of claims 1 to 10, and thereafter, the phosphorus-containing molten iron and A phosphoric acid resource raw material comprising a separated and recovered CaO-based flux.

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