JP2012007189A - Method for recovering iron and phosphorus from steelmaking slag, blast furnace slag fine powder or blast furnace slag cement, and phosphate resource raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preliminarily recover phosphorus from phosphorus-containing steelmaking slag at low cost and effectively utilize the recovered phosphorus as resources when the slag is recycled to a pig iron making process and a steelmaking process.SOLUTION: A method for recovering iron and phosphorus from steelmaking slag includes: a first step of subjecting phosphorous-containing steelmaking slag, from which metal iron is separated, to reduction treatment and recovering high-phosphorus and high Mn pig iron containing 0.5 mass% or more of phosphorus; a second step of recycling the slag obtained through the reduction treatment to a pig iron making process or a steelmaking process; a third step of subjecting the high-phosphorus and high Mn pig iron to demanganization treatment; a fourth step of discharging the slag produced in the demanganization treatment; a fifth step of subjecting molten iron in a treatment chamber after the slag is discharged to dephosphorization treatment; a sixth step of recycling the molten iron to the steelmaking step, wherein phosphorus concentration in the molten iron is reduced to 0.10 mass% or less through the dephosphorization treatment in the fifth step; and a seventh step of recovering the slag produced in the dephosphorization treatment in the fifth step to use as phosphate resource raw materials.

Description

  The present invention recovers iron and phosphorus from phosphorus-containing steelmaking slag such as dephosphorization slag of hot metal generated in the steelmaking refining process and converter decarburization refining slag, and steelmaking slag from which iron and phosphorus have been recovered is steelmaking. A method for recovering iron and phosphorus from steelmaking slag and recycling steelmaking slag from which iron and phosphorus have been recovered in order to recycle the recovered iron and phosphorus as resources, and to recycle the recovered steel and slag. The present invention relates to a blast furnace slag fine powder or a blast furnace slag cement to be obtained, and a recovered phosphate 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 to P ₂ O ₅ by an oxygen source such as oxygen gas or iron oxide, and then the generated P ₂ O ₅ is converted to CaO. It is removed by being fixed in the slag as the main component. When phosphorus in hot metal or molten steel is oxidized with oxygen gas, iron is also oxidized, and even when iron oxide is not used as an oxygen source, iron is also contained in the form of iron oxide in the slag. The hot metal preliminary dephosphorization process is a process for removing phosphorus in the hot metal in advance before decarburizing and refining the hot metal in a converter.

By the way, due to the problem of depletion of phosphate ore and the inclusion of phosphate ore in China, the United States, etc., phosphorus resources have soared, and phosphorus in steelmaking slag generated in the steel refining process has been reviewed as a valuable phosphorus resource. Yes. However, since the phosphorus concentration in the hot metal discharged from the blast furnace is about 0.1% by mass, P in steelmaking slag produced by conventional general hot metal preliminary dephosphorization treatment and converter decarburization refining is used. ₂ O ₅ concentration is about 5% by mass at most, and there is almost no utilization place as a phosphoric acid resource, and these steelmaking slags are conventionally discharged out of the steel manufacturing process as earthwork materials such as roadbed materials. Thus, phosphorus and iron in the slag were not recovered.

  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 hot metal phosphorous concentration caused by 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 molten iron is increased, resulting in a vicious circle in which the load of dephosphorization from the molten iron is increased.

  Therefore, with regard to recycling of steelmaking slag containing phosphorus, especially for recycling to processes involving reductive refining, a method of removing phosphorus from steelmaking slag or in steelmaking slag in order to prevent picking up phosphorus concentration in hot metal Various proposals such as a method for recovering phosphorus have been made. In the case of recycling to oxidative refining such as preliminary dephosphorization treatment, the function as a dephosphorizing agent is impaired because it already contains phosphorus, 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.

  Patent Document 2 discloses a technique in which carbon is added to molten or semi-molten smelted slag containing phosphorus, oxygen is blown up under reduced pressure, and phosphorus in the slag is vaporized and removed. Yes.

In Patent Document 3, a molten blast furnace slag and a 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 mixture slag. the phosphorus oxide in the mixed slag is reduced and phosphorus vapor, and the sulfur in the mixed slag and SO _2, these are evaporated as a small slug of phosphorus and sulfur, recycling the slag to a blast furnace or converter technology Is disclosed.

  Patent Document 4 discloses a technique for regenerating dephosphorization slag by adding carbonaceous material to dephosphorization slag, heating to 1450 ° C. or more and less than 1700 ° C. to remove and recover phosphorus in the slag to the hot metal side. Yes.

  Patent Document 5 discloses an alkali metal phosphate obtained by treating dephosphorization slag produced by dephosphorization of hot metal or molten steel with water and carbon dioxide gas, using a slagging agent containing alkali metal carbonate as a main component. A technique is disclosed in which an extract containing selenium is obtained, a calcium compound is added to the extract, and phosphorus is precipitated as calcium phosphate and separated and recovered.

  Patent Document 6 discloses that a refining slag containing phosphorous and molten iron are supplied into a container containing a carbonaceous material and an oxidizing gas to burn the carbonaceous material, melting the refining slag, The phosphorus in the molten iron bath is reduced and extracted, and the low phosphorus slag after the phosphorus extraction is recovered as a slag for refining, and these steps are repeated once or twice to obtain the concentration of phosphorus in the molten iron bath. Next, a technique for obtaining a slag containing a high concentration of phosphorus by oxidizing and dephosphorizing the molten iron bath thus increased in phosphorus concentration is disclosed.

  Patent Document 7 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, and at the same time oxygenated toward the hot metal bath. The gas is supplied, phosphorus in the slag is reduced and extracted into the hot metal, the slag in which phosphorus is reduced is recycled to the sintering process, and the process of reducing and extracting phosphorus from the slag is repeatedly performed. Next, a technique is disclosed in which oxygen gas is blown into a hot metal enriched with phosphorus and decarburized and refined to recover slag having a high phosphorus concentration, and the recovered slag is used as, for example, a phosphate fertilizer.

Further, in Patent Document 8, slag containing phosphorus generated by dephosphorization of hot metal is introduced into a hot metal bath, and a carbon material and an oxygen source are supplied to reduce and extract phosphorus in the slag into the hot metal bath. Then, the hot metal containing 0.5 to 3% by mass of phosphorus is smelted, the hot metal is decarburized and refined to recover slag having a P ₂ O ₅ concentration of 10 to 30% by mass, and the recovered slag is converted to phosphoric acid. A technique for use as a fertilizer is disclosed.

JP 2004-143492 A JP 9-316519 A JP-A-55-97408 JP 2002-69526 A 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. Similarly, in Patent Document 2, phosphorus cannot be recovered as a resource, and pressure reduction is necessary, resulting in high equipment costs.

  In Patent Document 3, 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 4 discloses the process up to the step of recovering phosphorus in the slag to the hot metal side, but does not mention how to treat the phosphorus recovered and concentrated in the hot metal thereafter.

  Further, Patent Document 5 is a wet process, and 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.

According to Patent Document 6, 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 timing for recovering the low phosphorus slag after the 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 7 and Patent Document 8, phosphorus in the molten iron is recovered into slag by decarburizing and refining hot metal having a high phosphorus concentration obtained by concentrating phosphorus in slag, and degassing in the decarburizing and refining process. 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. Further, Patent Document 8 performs slag reduction (phosphorus reduction extraction) → removal → phosphorus concentration in the same furnace, which reduces the productivity of the converter, decreases the hot metal temperature, phosphorus contamination due to high phosphorus slag adhesion, and The accompanying phosphorus component defect etc. are caused.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to recycle a steelmaking slag containing phosphorus, such as dephosphorization slag and converter slag, into a steelmaking process and a steelmaking process. In order to prevent the influence of phosphorus contained on the hot metal and molten steel, phosphorus and iron can be recovered from the steelmaking slag in advance at low cost and efficiently, and the recovered phosphorus and iron can be effectively used as resources, respectively. Provided a method for recovering iron and phosphorus from steelmaking slag, and also provided high quality recovered from steelmaking slag, blast furnace slag fine powder or blast furnace slag cement obtained when recycling steelmaking slag from which iron and phosphorus have been recovered It is to provide a phosphoric acid resource raw material.

The method for recovering iron and phosphorus from steelmaking slag according to the first invention for solving the above-mentioned problems is a method for recovering slag generated during decarburization of hot metal in a converter and slag generated during preliminary dephosphorization of hot metal. Steelmaking slag containing at least any one of the above phosphorus and solidified after the solidified iron is reduced using a reducing agent containing one or more of carbon, silicon, and aluminum A first step of recovering a high-phosphorus high manganese pig iron containing 0.5% by mass or more of phosphorus and 0.5% by mass or more of manganese, and a phosphorus content by the reduction treatment in the first step; After the second step of recycling the lowered slag as a CaO source in the iron making process or the steel making process, and after processing the high phosphorus high manganese pig iron recovered in the first step without using a fluorine compound as a solvent Basicity of slag (mass% CaO / mass% SiO ₂₎ is supplied to CaO source and an oxygen source to be 0.5 to 1.0, the hot metal in the manganese concentration after treatment was 0.4 mass% A third step of demanganese treatment until the following, a fourth step of discharging the slag produced by the demanganese treatment of the third step from the treatment vessel used in the demanganese treatment, and the fourth step 40% by volume or more of the total oxygen source in terms of oxygen gas required for the dephosphorization reaction with respect to the hot metal in the processing container after the slag produced during the demanganese process is discharged from the processing container Oxygen gas is supplied to the hot metal from the top blowing lance, and 40% by mass or more of the CaO source required for the dephosphorization reaction is supplied to the hot metal together with oxygen gas through the upper blowing lance. And a fifth step of dephosphorization until the phosphorus concentration in the hot metal after the treatment becomes 0.10% by mass or less, and degassing until the phosphorus concentration in the hot metal becomes 0.10% by mass or less by the fifth step. A sixth step of recycling the hot metal treated with phosphorus to the steelmaking process; and a seventh step of recovering the slag generated by the dephosphorization treatment of the fifth step to use as a phosphoric acid resource raw material. And

In the method for recovering iron and phosphorus from the steelmaking slag according to the second invention, in the first invention, the steelmaking slag before the reduction treatment in the first step has a basicity (mass% CaO / mass% SiO ₂ ). Is 1.6 to 3.0.

  In the method for recovering iron and phosphorus from steelmaking slag according to the third invention, in the first or second invention, the high phosphorus high manganese pig iron recovered in the first step contains 3 mass% or more of carbon. It is characterized by that.

  The method for recovering iron and phosphorus from steelmaking slag according to the fourth invention is the method of recovering iron and phosphorus from any one of the first to third inventions, after the slag discharged from the processing container by the fourth step is recovered, Recycled as a source of manganese for decarburization and refining of hot metal.

The method for recovering iron and phosphorus from steelmaking slag according to the fifth invention is the method for recovering iron and phosphorus in any one of the first to fourth inventions, wherein the slag recovered in the seventh step is phosphoric acid concentration (P ₂ O ₅ concentration). Is 15% by mass or more and the manganese oxide concentration is 8% by mass or less.

  The method for recovering iron and phosphorus from steelmaking slag according to the sixth invention is the method of recovering iron and phosphorus from any one of the first to fifth inventions, from the slag whose phosphorus content has been reduced by the reduction treatment in the first step. The metallic iron mixed in is separated, and the slag from which the metallic iron is separated is recycled as a CaO source in the iron making process or the steel making process.

The method for recovering iron and phosphorus from steelmaking slag according to the seventh aspect of the present invention is the method for recovering iron and phosphorus according to any one of the first to sixth aspects, 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 steelmaking slag according to the eighth invention is the method of recovering iron and phosphorus from the high phosphorus high manganese pig iron recovered in the first step and the blast furnace in any of the first to seventh inventions. After the hot metal is mixed with the hot metal, the phosphorus concentration of the hot metal is adjusted to 0.5 to 2.0 mass% and the manganese concentration is adjusted to 2.0 mass% or less, and then the third step to the seventh step. It is characterized by performing the process.

  The method for recovering iron and phosphorus from 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 slag in the second process is an iron ore sintering process or a blast furnace It is a hot metal manufacturing process in

  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 in any one of the first to eighth aspects, wherein the slag recycling destination in the second step is the preliminary removal of hot metal in the steelmaking refining step. It is characterized by decarburization and refining of hot metal in a phosphorus treatment or converter.

  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 recovered in the seventh step in the method for recovering iron and phosphorus from the steelmaking slag according to any one of the first to tenth inventions. Features.

  According to the present invention, a steelmaking slag containing phosphorus of at least one of dephosphorization slag generated during preliminary dephosphorization of hot metal and converter slag generated in decarburization refining of hot metal in a converter. In recycling to the steelmaking process or the steelmaking process, first, the metallic iron mixed in the steelmaking slag is separated and removed, and then the iron oxide, phosphorous oxide and manganese oxide in the steelmaking slag from which the metallic iron has been removed, Steelmaking slag that has been reduced and recovered as high-phosphorus high-manganese pig iron and whose phosphorus content has been reduced is recycled as a CaO source in the ironmaking process or steelmaking process. Is reduced until the phosphorus concentration becomes 0.10% by mass or less, and the molten iron after the dephosphorization treatment is supplied to the steelmaking process as an iron source to remove high phosphorus and high manganese pig iron. The slag produced during the process can be used effectively as a phosphorus resource because the phosphorous oxide is concentrated to a level sufficient to be recovered as a phosphorus resource, increasing the phosphorus concentration of the hot metal or impairing the function as a dephosphorizing agent, etc. Recycling of phosphorus-containing steelmaking slag to the ironmaking process or steelmaking process has been realized without causing any harmful effects, and at the same time, iron, manganese and phosphorus contained in steelmaking slag can be effectively used as resources. 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 the schematic of the dephosphorization processing equipment used in the dephosphorization test of high phosphorus high manganese pig iron.

  Hereinafter, the present invention will be described in detail.

The present inventors have made a steelmaking slag containing phosphorus such as dephosphorization slag generated during preliminary dephosphorization of hot metal and converter slag generated in decarburization refining of hot metal in a converter (“phosphorus-containing steelmaking slag”). In addition, when phosphorus is reused in a steelmaking process or a steelmaking process as a dephosphorizing agent (CaO for fixing P ₂ O ₅ ) or a CaO source as a fossilizing agent, phosphorus contained in the steelmaking slag is a blast furnace In this reducing atmosphere, it is reduced and transferred to hot metal, and the phosphorus concentration in the hot metal rises. First, to eliminate the effect of phosphorus contained in this steelmaking slag on the hot metal discharged from the blast furnace It was investigated. That is, a method for removing phosphorus from steelmaking slag before recycling 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 contains iron as an oxide in the form of FeO or Fe ₂ O ₃ (hereinafter collectively referred to as “Fe _x O”). Therefore, when phosphorus-containing steelmaking slag is reduced with carbon, silicon, aluminum, etc., Fe _x O in the steelmaking slag is also reduced. Further, the steelmaking slag contains manganese in the form of oxides in the form of MnO or Mn ₂ O ₃ (hereinafter collectively referred to as “Mn _X O”). Manganese oxides also have an affinity for oxygen with iron or phosphorus. Therefore, Mn _X O in the steelmaking slag is also 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 and manganese have high solubility in iron, and phosphorus and manganese produced by the reduction are rapidly dissolved in iron produced by the reduction. Here, the present invention aims to remove phosphorus from phosphorus-containing steelmaking slag to improve it into a steelmaking slag having a low phosphorus content. In order to quickly separate phosphorus produced by reduction from 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. When the steelmaking slag is brought into 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. Therefore, the carbon concentration of the produced molten iron is set to 3% by mass or more. 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 a hot metal containing a high concentration of phosphorus and manganese by carburization (this hot metal is called “high phosphorus high manganese hot metal to distinguish it from blast furnace hot metal, Will be called).

Further investigations revealed that in the steelmaking slag reduction treatment, the basicity of the steelmaking slag before the reduction treatment (mass% CaO / mass% SiO ₂ ) also affects the reduction reaction of phosphorus and manganese. General converter slag has a basicity of about 3.0 to 5.0, and preliminary dephosphorization slag has a basicity of 3.0 or less. When the basicity of the steelmaking slag to be subjected to the reduction treatment is higher than 3.0, since the melting point of the slag is high, a reduction treatment temperature of 1550 ° C. or higher is necessary, and further, separation of iron and slag after reduction is performed. Also becomes difficult. Since the reduction treatment at a high temperature increases the load on the furnace body, therefore, in the case of steelmaking slag having a basicity higher than 3.0, the basicity of the steelmaking slag used for the reduction treatment is 3.0 on average. It is preferable to mix the converter slag and the preliminary dephosphorization slag so as to be the following. On the other hand, it was confirmed that the lower the basicity of the steelmaking slag, the lower the reduction treatment temperature, but when the basicity of the steelmaking slag is low, when this steelmaking slag is recycled to the steelmaking process or the steelmaking process, Since the value as a CaO source becomes low, the basicity of the steelmaking slag used for the reduction treatment is preferably 1.6 or more on average. As a means for reducing the basicity of the steelmaking slag, it is also possible to mix a SiO ₂ -containing substance such as silica, silica sand, glass wool, or silicon sludge into the steelmaking slag. In addition, by performing the reduction treatment in the state where the phosphorus-containing steelmaking slag coexists with the blast furnace hot metal, the reduction of phosphorus, iron, and manganese in the phosphorus-containing steelmaking slag becomes easy.

  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. However, the steelmaking slag after the reduction treatment contains fine metallic iron, that is, high phosphorus and high manganese. Since pig iron 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. In addition, although said reduction | restoration process investigation experiment was performed with the rotary kiln type | mold processing container, what kind of thing may be used as a processing container, if the steelmaking slag can be heated and reduced. In addition to the rotary kiln, for example, an arc heating type electric furnace, a converter having a heating device with a burner or oxygen, a pot-type processing container, an induction heating furnace, an RHF type processing container, and the like can be given.

  By the way, generally, the mass ratio (mass% P / mass% Fe) of phosphorus and iron in the phosphorus-containing steelmaking slag is 0.005 to 0.075, while the mass ratio of manganese and iron (mass). % Mn / mass% Fe) is about 0.005 to 0.15. Therefore, in the molten iron after reduction, that is, high phosphorus and high manganese hot metal, phosphorus is 0.5 to 7.5 mass% and manganese is 0.00. About 5 to 15% by mass is contained. On the other hand, the phosphorus content of the blast furnace hot metal discharged from the blast furnace is currently about 0.1% by mass. Accordingly, when high phosphorus-high manganese hot metal having a phosphorus concentration of about 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 use of hot metal is limited, and in some cases, it may not be used as an iron source for iron making.

  Therefore, by adding iron alloy, the blast furnace hot metal was added with iron concentration of 4.0% by mass, manganese concentration of 4.0% by mass (level A), phosphorus concentration of 3.0% by mass and manganese concentration of 3.0% by mass. % (Level B), phosphorus concentration is 2.0 mass%, manganese concentration is 2.0 mass% (level C), phosphorus concentration is 0.5 mass% and manganese concentration is 0.5 mass% (level D). The blast furnace hot metal adjusted to 4 levels was used as an alternative to the high phosphorus high manganese hot metal, and the dephosphorization test was conducted using the dephosphorization equipment currently used for preliminary dephosphorization of the blast furnace hot metal. did.

  FIG. 1 shows a schematic diagram of a dephosphorization treatment facility used in a dephosphorization test. In FIG. 1, reference numeral 1 denotes a dephosphorization treatment equipment, 2 a hot metal, 3 a CaO-based dephosphorizing agent or iron oxide or a mixture of CaO-based dephosphorizing agent and iron oxide, 4 a CaO-based dephosphorizing agent, 5 Is a hot metal ladle, 6 is a cart, 7 is an upper lance, 8 is an injection lance, 9 is a storage tank, 10 is a storage tank, 11 is a hopper, 12 is a raw material transfer device, 13 is a chute, 14 is a generated slag, A hot metal ladle 5 containing hot metal 2 in which the concentrations of phosphorus and manganese are adjusted is loaded on a carriage 6 and carried into the dephosphorization processing facility 1. The dephosphorization processing equipment 1 is provided with an upper blowing lance 7 and an injection lance 8 that can move up and down in the hot metal ladle 5, from which oxygen gas and oxygen gas are conveyed. The powdered CaO-based dephosphorizing agent 4 is sprayed onto the hot metal 2 from the tip of the top blowing lance 7, and the injection lance 8 uses a CaO-based dephosphorizing agent or iron oxide as a carrier gas such as nitrogen gas or air. Etc. are blown into the hot metal 2 (injection). Furthermore, a raw material supply facility comprising a hopper 11, a raw material transfer device 12, and a chute 13 is installed, and using this raw material supply facility, a CaO-based dephosphorizing agent or iron oxide contained in the hopper 11 or The mixture of CaO type | system | group dephosphorizing agent and iron oxide is comprised so that it can be added on the inside of the hot metal ladle 5 and added.

  Using this dephosphorization processing equipment, oxygen gas is blown from the top blowing lance to 200 tons of hot metal in the hot metal ladle, and at the same time, a powdered CaO-based dephosphorizing agent is blown as a CaO source. Powdered CaO-based dephosphorizing agent was blown in using nitrogen gas as a carrier gas to perform dephosphorization treatment of the blast furnace hot metal in which the phosphorus concentration and manganese concentration were adjusted. In addition, as a CaO type | system | group dephosphorizing agent, only quick lime (CaO pure part: about 95 mass%) is used, and fluorine compounds, such as a fluorite, are not mixed. Moreover, the hot metal temperature after a process was adjusted in the range of 1270-1400 degreeC. The main results in the experiment are shown in Table 1.

  As shown in Table 1, the phosphorus concentration in the hot metal after the treatment is dephosphorized to 0.10% by mass or less by controlling the oxygen basic unit and the CaO-based dephosphorizing unit basic unit introduced at any level. I understood that. With this phosphorus concentration, it can be used as an iron source for steel making, no different from blast furnace hot metal.

On the other hand, paying attention to the slag composition after the dephosphorization treatment, it was confirmed that the P ₂ O ₅ concentration in the slag was high at any level and was concentrated to 19 to 26% by mass. However, since demanganese reaction also occurs simultaneously with the dephosphorization treatment, the Mn _x O concentration in the slag was also concentrated to a relatively high level of 14 to 16% by mass. When the slag is recovered and used as a phosphorus resource, the Mn _X O concentration is high, so the P ₂ O ₅ concentration is relatively lowered, and the added value is undesirably lowered. That is, when slag is utilized as a phosphorus resource, the Mn _x O concentration in the slag is preferably low. On the other hand, 70% by mass or more of phosphoric acid contained in the slag after dephosphorization treatment is citric acid-soluble phosphoric acid (phosphorus acid that can be absorbed by the plant taking out acid from the roots). It turns out that it is available.

The present inventors have continuously studied a method for obtaining a high P ₂ O ₅ low Mn _X O slag in order to utilize the recovered slag as a phosphorus resource. Since P ₂ O _{5 in} slag is inherently unstable, it can be present in the slag in the form of 3CaO · P ₂ O ₅ by adding a CaO source (CaO-based dephosphorizing agent). On the other hand, Mn _X O can exist in the slag as Mn _X O without adding a CaO source. Therefore, the present inventors first supplied an oxygen source in advance without adding a CaO source or adding a small amount of CaO source to adjust the basicity of the slag to the high phosphorus high manganese hot metal. After demanganese treatment, slag with a high Mn _x O concentration produced by demanganese treatment is discharged, and then a CaO source (CaO-based dephosphorizing agent) and an oxygen source are further supplied to the molten iron to remove phosphorus. In order to concentrate P ₂ O ₅ in the slag, a high P ₂ O _{5 and} low Mn _X O slag could be obtained. went.

The experiment was carried out in the same manner as the above-described dephosphorization test using the dephosphorization processing equipment shown in FIG. That is, during demanganese treatment, oxygen gas was blown into the hot metal from the top blowing lance, and quick lime was blown from the injection lance as a CaO source for adjusting the basicity of the slag, using nitrogen gas as the carrier gas. In addition, quick addition of quicklime from the chute was also used. However, when the basicity (mass% CaO / mass% SiO ₂ ) of the generated slag is increased during the demanganese treatment, a dephosphorization reaction occurs. Therefore, in order to suppress the dephosphorization reaction, The amount of quicklime added was adjusted so that the basicity was 1.0 or less. The hot metal temperature at the end of the demanganese treatment was adjusted in the range of 1300 to 1500 ° C. In this demanganese treatment, only quick lime is used as the CaO source of the solvent, and no fluorine compound such as fluorite is mixed in the CaO source.

  After completion of the demanganese treatment, the produced slag was discharged from the hot metal ladle, and then the hot metal was dephosphorized.

  In the dephosphorization treatment, powdered CaO-based dephosphorizing agent, which is an oxygen gas and a CaO source, is sprayed onto the hot metal from the top blowing lance ("projection" means that powder such as CaO-based dephosphorizing agent is sprayed onto the hot metal from the top blowing lance. In addition, a powdery CaO-based dephosphorizing agent was blown from the injection lance using nitrogen gas as a carrier gas. Moreover, the CaO type | system | group dephosphorizing agent from a chute | shoot and the addition addition of iron oxide were also used together. The hot metal temperature at the end of the dephosphorization treatment was adjusted to 1270 to 1400 ° C. In this dephosphorization treatment, only quick lime is used as the CaO-based dephosphorizing agent, and no fluorine compound such as fluorite is mixed with the CaO-based dephosphorizing agent.

  The results of the demanganese treatment in this experiment are shown in Table 2, and the results of the subsequent dephosphorization treatment are shown in Table 3. Experiments were carried out from levels 1 to 12.

At level 1, an experiment was conducted with a small addition amount of CaO source (quick lime) aiming at cost reduction during demanganese treatment, and the basicity of slag after demanganese treatment was 0.4. However, at level 1, the basicity of slag during demanganese treatment was low, the viscosity of slag was high, and slag was ejected during demanganese treatment. When slag is ejected, there are concerns about deterioration of iron yield and failure of the transport carriage, so in subsequent levels 2 and 3, the amount of quicklime was increased to increase basicity. At levels 2 and 3, the basicity of slag after demanganese treatment was 0.50 and 0.60, respectively, and under these conditions, no large slag jetting occurred and demanganese treatment could be performed. . Further, in the subsequent dephosphorization treatment, the phosphorus concentration in the hot metal can be reduced to 0.10% by mass or less, the P ₂ O ₅ concentration of the slag after the dephosphorization treatment is high, and the Mn _X O concentration can be lowered. It was.

  At level 4, the oxygen gas ratio in the dephosphorization process was as low as 36% by volume, and the phosphorus concentration in the hot metal after the dephosphorization process was as high as 0.15% by mass. Since the hot metal has a high phosphorus concentration, when this hot metal is used in the steel making process, the manufacturing cost increases. Here, the oxygen gas ratio means that the oxygen source (oxygen gas, iron oxide) required for the dephosphorization reaction is converted to oxygen gas, and the amount of oxygen gas supplied from the top blowing lance for all oxygen sources converted to oxygen gas Ratio (percentage).

At level 4, various reasons for the high phosphorus concentration in the hot metal were investigated. As a result, the high temperature of Fe _X O in the vicinity (collision position on the hot metal bath surface of the oxygen gas from the top lance) top-blown fire point by the oxygen gas supplied from the lance is formed, blowing top and the Fe _X O lance High dephosphorization efficiency is obtained by reaction with the powdered CaO-based dephosphorization agent supplied from No. 4, but it was found that the amount of oxygen gas supplied from the top blowing lance was insufficient at level 4 and the dephosphorization reaction was lowered. It was. In other words, it was found that in order to promote an efficient dephosphorization reaction, it is necessary to raise the ratio of the oxygen gas supplied from the top blowing lance to some extent.

  Based on this result, at level 5, dephosphorization treatment was carried out with an oxygen gas ratio of 40% by volume. As a result, the phosphorus concentration in the hot metal after the dephosphorization treatment could be reduced to 0.10% by mass or less. From this result, it was confirmed that the oxygen gas ratio in the dephosphorization treatment should be 40% by volume or more.

  At level 6, the projection ratio of the CaO-based dephosphorizing agent from the top blowing lance in the dephosphorization process was as low as 33% by mass, and the phosphorus concentration in the hot metal after the dephosphorization process was as high as 0.16% by mass. Here, the projection ratio of the CaO-based dephosphorizing agent is the ratio (percentage) of the added amount of the CaO-based dephosphorizing agent supplied from the top blowing lance to the total added amount of the CaO-based dephosphorizing agent required for the dephosphorization reaction. It is. As described above, the hot metal having a phosphorus concentration of 0.16% by mass has a higher phosphorus concentration than the blast furnace hot metal, and when this hot metal is used in the steelmaking process, the production cost is increased. Can not be used as. Accordingly, in order to improve the dephosphorization reaction, it is considered necessary to increase the supply of powdered CaO-based dephosphorizing agent from the top blowing lance, and in the subsequent level 7, the CaO-based dephosphorizing agent from the top blowing lance The projection ratio was set to 40% by mass.

  As a result, at level 7, the phosphorus concentration in the hot metal after the treatment could be reduced to 0.10% by mass or less. From this result, it was confirmed that the projection ratio of the CaO-based dephosphorizing agent from the top blowing lance needs to be 40% by mass or more. In level 7, the basicity of the slag produced during the demanganese treatment was set to 1.00, but the dephosphorization reaction during the demanganese treatment was suppressed, and the basicity of the produced slag during the demanganese treatment was reduced. It was confirmed that the dephosphorization reaction during the demanganese treatment was suppressed by adjusting to 1.0 or less.

At level 8, the manganese concentration in the hot metal after the demanganese treatment was 0.50% by mass. When this hot metal was dephosphorized, the phosphorus concentration in the hot metal after the treatment was lowered to 0.096 mass%, but the Mn _x O concentration of the slag formed was as high as 10.6 mass%. The Mn _x O concentration of the slag after dephosphorization treatment obtained at level 3 described above was 8.0% by mass, and in any case there was no problem with the characteristics as a fertilizer. However, from the viewpoint of increasing the manganese recovery rate and increasing the phosphorus concentration in the slag, the manganese concentration in the hot metal after demanganese treatment at level 3 was 0.4% by mass. It was confirmed that the slag produced during the dephosphorization treatment can be used as a raw material for phosphoric acid fertilizer having a high phosphoric acid concentration when the manganese concentration of the steel is 0.4 mass% or less.

Level 9 is a test in which the phosphorus concentration and manganese concentration in hot metal before demanganese treatment are adjusted to 2% by mass, and level 10 is a test in which the phosphorus concentration and manganese concentration in hot metal before demanganese treatment is adjusted to 3% by mass, respectively. It is. In both levels 9 and 10, the phosphorus concentration in the hot metal after the dephosphorization treatment was 0.10% by mass or less, and the slag after the dephosphorization treatment was also high P ₂ O _{5 and} low Mn _X O. However, at level 10, in particular, the oxygen unit and the CaO-based dephosphorization unit to be supplied are very large, and there are still problems that the processing time is long and the processing cost is high. From this result, the phosphorus concentration and manganese concentration of the hot metal before demanganese treatment are desirably 2.0 mass% or less. In order to adjust the phosphorus concentration and manganese concentration of the hot metal before the demanganese treatment to 2.0% by mass or less, the high phosphorus high manganese pig iron obtained by the reduction treatment may be mixed with the blast furnace hot metal.

At level 11, the phosphorus concentration and manganese concentration in hot metal before demanganese treatment were 0.5% by mass, respectively, and at level 12, the phosphorus concentration and manganese concentration in hot metal before demanganese treatment were each 0.3% by mass. Went. The P ₂ O ₅ concentration of the slag obtained after the dephosphorization treatment was 15.3% by mass at level 11 and 13.2% by mass at level 12. As a result of the fertilizer test, although there was no problem in the fertilizer characteristics, the level 11 was more effective than the level 12 as the fertilizer characteristics. Accordingly, the P ₂ O ₅ concentration of the slag after the dephosphorization treatment is preferably 15% by mass or more, and for that purpose, the phosphorus concentration in the hot metal before the demanganese treatment needs to be 0.5% by mass or more. It is.

  Incidentally, the CaO-based dephosphorization agent used for the preliminary dephosphorization treatment of the blast furnace hot metal, by adding about 5% by mass of a fluorine compound such as fluorite, promotes the hatching of CaO and promotes the dephosphorization reaction. However, when the dephosphorized slag to be produced is used as, for example, a fertilizer, fluorine is eluted from the phosphorus fertilizer, and the fluorine elution value becomes a problem with respect to soil environmental standards. Accordingly, in the present invention, dephosphorization is performed using a CaO-based dephosphorizing agent that does not contain a fluorine compound. 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, the concentration of soluble phosphoric acid is reduced. It cannot be secured sufficiently. Also from this viewpoint, the use of a fluorine compound is not preferable. In the above test, a hot metal ladle-shaped treatment vessel was used as the treatment vessel. However, an upper blow lance that can supply oxygen gas and powdered CaO-based dephosphorizing agent, and an injection lance or bottom for stirring the hot metal with gas. Any processing container having a blow plug may be used. Other than the hot metal ladle, for example, a converter type refining furnace or a kneading car can be used.

Further, the present inventors have met the requirements of the present invention to recover a high Mn _X O slag obtained in levels 2,3,5,7,9,10,11 after removal manganese treatment, the high Mn _X Recycling of O slag for hot metal decarburization refining in the converter in the steelmaking refining process was studied.

The decarburization and refining of hot metal is performed in a converter-type processing vessel, and the components are generally adjusted in secondary refining such as RH and LF after decarburization and refining. Manganese adjustment of molten steel is performed using Fe-Mn alloy iron and electrolytic Mn in secondary refining, but these are expensive, and technology to add and reduce manganese ore in a converter to reduce melting costs It has been known. The present inventors examined whether high Mn _x O slag could be used as an alternative to this manganese ore, and as a result of conducting tests, the high Mn _x O slag was not inferior to the conventionally used manganese ore, It was found that it can be recycled in a converter as a manganese source. By using high Mn _x O slag, which is cheaper than manganese ore, the smelting cost can be further reduced.

Manganese is an essential nutrient element of higher plants, and since healthy growth is inhibited by deficiency of manganese, it is also effective to use high Mn _X O slag produced by demanganese treatment as manganese fertilizer. Similarly, functions as Mn _X O also manganese fertilizer high P ₂ O ₅ low Mn _X O in the slag generated by dephosphorization of high phosphorus and high manganese hot metal after removing the manganese treatment. However, depending on the type of plant, sometimes impairing the growth and manganese is too large (e.g., yellowing phenomena of the leaves of the tobacco (chlorosis)), Mn _X O high P ₂ O ₅ low Mn _X O in slag It is preferable to adjust to an appropriate amount.

The present invention has been made on the basis of the above test results, and the method for recovering iron and phosphorus from steelmaking slag according to the present invention is a preliminary removal of slag and hot metal generated during decarburization and refining of hot metal in a converter. Steelmaking slag containing at least any one of the slags generated in the phosphorous treatment, in which the metal iron is separated after solidification, containing one or more of carbon, silicon, and aluminum A first step of recovering a high-phosphorus high manganese pig iron containing 0.5% by mass or more of phosphorus and 0.5% by mass or more of manganese by performing a reduction treatment using a reducing agent to The second step of recycling slag whose phosphorus content has been reduced by the reduction treatment as a CaO source in the iron making process or the steel making process, and the high phosphorus high manganese pig iron recovered in the first step as a solvent The supplies CaO source and an oxygen source as slag basicity after treatment (mass% CaO / mass% SiO ₂₎ is 0.5 to 1.0 without using, after processing the hot metal in the manganese A third step of demanganese treatment until the concentration is 0.4% by mass or less, and a fourth step of discharging the slag produced by the demanganese treatment of the third step from the treatment vessel used in the demanganese treatment. The total oxygen source in terms of oxygen gas required for the dephosphorization reaction with respect to the molten iron in the processing container after the slag produced during the demanganese processing is discharged from the processing container by the process and the fourth process. 40% by volume or more of oxygen gas is supplied by blowing from the top blowing lance to the molten iron, and 40% by weight or more of the CaO source required for the dephosphorization reaction is supplied as oxygen gas through the top blowing lance. In addition, a fifth step of spraying and supplying the hot metal to the hot metal and dephosphorizing the hot metal after the treatment until the phosphorus concentration in the hot metal becomes 0.10% by mass or less, and the phosphorus concentration in the hot metal by the fifth step is 0.10. A sixth step of recycling the hot metal, which has been dephosphorized until it becomes less than or equal to mass%, to the steelmaking process; and a seventh step of recovering the slag produced by the dephosphorization process of the fifth step and using it as a phosphoric acid resource raw material It is characterized by having.

  As a method for recycling steelmaking slag in which the content of iron oxide, phosphorous oxide, and manganese oxide is reduced by the reduction treatment in the first step, as described in the “Background Art” section, In addition to the method used as a CaO source (slagging agent) in the sintering process and then used as a charging raw material in the hot metal manufacturing process in the blast furnace, it is directly used as a CaO-based iron making agent in the hot metal manufacturing process in the blast furnace. A method of using, a method of using as a CaO-based dephosphorizing agent in a preliminary dephosphorization treatment of blast furnace hot metal, a method of using as a iron making agent in a decarburizing and refining process of hot metal in a converter, and further, a blast furnace hot metal A suitable example is a method of using it as a CaO-based desulfurization agent in the desulfurization treatment. Even if it is a process other than this, as long as it is the process which uses the quicklime of the iron making process and steelmaking process in an ironworks, it can be used as a substitute for quicklime.

  Although the total amount of converter slag generated may be used for the reduction treatment in the first step of the present invention, it is effective from the viewpoint of resource saving to use converter slag in the preliminary dephosphorization treatment of hot metal. Therefore, a part of the generated converter slag is used as a CaO source (CaO-based dephosphorizing agent) in the hot metal preliminary dephosphorization process, and the remainder of the converter slag is used for the reduction process in the first step. It is preferable to provide.

  As described above, according to the present invention having the above-described configuration, at least one of dephosphorization slag generated during hot metal preliminary dephosphorization processing and converter slag generated during decarburization refining of hot metal in a converter. In recycling steelmaking slag containing seed phosphorus to the steelmaking process or steelmaking process, first, the metallic iron mixed in the steelmaking slag is separated and removed, and then the iron oxide in the steelmaking slag from which the metallic iron has been removed , Phosphorus oxide, Manganese oxide is reduced and recovered as high phosphorus high manganese pig iron, Steelmaking slag with low phosphorus content is recycled as CaO source in ironmaking process or steelmaking process, while recovered high phosphorus high manganese The pig iron is dephosphorized until the phosphorus concentration becomes 0.10% by mass or less after the manganese concentration is lowered by the demanganese treatment, and the molten iron after the dephosphorization treatment is used as an iron source for the steelmaking process. In addition, the slag produced during the dephosphorization treatment of high phosphorus and high manganese pig iron can be effectively used as a phosphorus resource because the phosphorous oxide is concentrated to a level sufficient to be recovered as a phosphorus resource. Recycling of phosphorus-containing steelmaking slag to a steelmaking process or a steelmaking process is realized without causing adverse effects such as impairing the function as a dephosphorizing agent, and at the same time, iron, manganese and Effective utilization of phosphorus as a resource is realized.

  In addition, the converter slag generated during the decarburization refining of the hot metal that has been subjected to the preliminary dephosphorization treatment up to the phosphorus concentration level of the steel product in advance also contains phosphorus instead of 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, there is a risk of increasing the cost. Therefore, the “steel-making slag containing phosphorus” targeted in the present invention means that when the steel-making slag is recycled to a blast furnace or the like, the hot metal or the phosphorous concentration of the molten steel increases, resulting in an increase in cost relative to normal operations. It is a steelmaking slag containing phosphorus at a concentration or higher.

  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 hot metal is desulfurized by a mechanical stirring desulfurization device, the blast furnace hot metal after this desulfurization treatment is charged into the converter, and decarburization refining is performed in the converter, thus producing molten steel from the blast furnace hot metal. The present invention was applied in the steelmaking process. Table 4 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 4, the blast furnace hot metal after desiliconization and dephosphorization contains 0.050% by mass of phosphorus, which is higher than the phosphorus concentration level (0.015% by mass or less) of steel products. The converter slag generated by converter decarburization refining using this blast furnace hot metal contains about 0.8% by mass of phosphorus (about 1.8% by mass with P ₂ O ₅ ). When this converter slag is used as a CaO source in the iron ore sintering step, enrichment of phosphorus in the blast furnace hot metal occurs. Further, the preliminary dephosphorization slag generated in the preliminary dephosphorization treatment has a higher phosphorus concentration than the converter slag, and when the preliminary dephosphorization slag is recycled to the iron ore sintering step, the phosphorus concentration of the blast furnace hot metal similarly increases. Then, the test which applies this invention to this converter slag and preliminary dephosphorization slag was implemented.

[Test 1]
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. The 200-ton converter slag from which the metallic iron had been separated and removed in advance and coke as a reducing agent were charged into a rotary kiln equipped with a heating burner, and the converter slag and coke were heated by the burner for conversion. Reduction treatment of furnace slag was carried out. The amount of input coke was 100 kg / t-slag, and the operating temperature of the rotary kiln was adjusted to 1450 to 1550 ° C.

  The high-phosphorus high-manganese pig iron recovered after the reduction treatment was 43 tons, and its components were C = 4.0% by mass, P = 3.4% by mass, and Mn = 6.5% by mass. On the other hand, 150 tons of slag was recovered after the reduction treatment. Table 5 shows the slag composition before the reduction treatment and after the reduction treatment.

  The slag after the reduction treatment was used as a CaO source for the iron making agent in the iron ore sintering step, and the produced sintered ore was charged into a blast furnace as an iron source to produce a blast furnace hot metal. The phosphorus concentration of the molten blast furnace hot metal was about 0.1% by mass, and there was no increase in phosphorus concentration due to recycling of steelmaking slag. In addition, as a result of manufacturing blast furnace slag cement using blast furnace slag discharged from the blast furnace when recycling the slag after the reduction treatment, the quality of the blast furnace slag cement is the same as before, there is no problem, the same as before In addition, energy saving in cement production was possible.

[Test 2]
100 ton converter slag from which metallic iron was previously removed by the magnetic separator used in Test 1, 100 ton preliminary dephosphorization slag from which metallic iron was previously removed, and coke as a reducing agent were heated by a burner. The converter slag, the preliminary dephosphorization slag, and the coke were heated by a burner to reduce the slag. The amount of input coke was 100 kg / t-slag, and the operation temperature of the rotary kiln was adjusted to 1300 to 1450 ° C.

  The high-phosphorus high-manganese pig iron recovered after the reduction treatment was 49 tons, and its components were C = 4.0% by mass, P = 4.0% by mass, and Mn = 7.6% by mass. On the other hand, 145 tons of slag was recovered after the reduction treatment. Table 6 shows slag compositions before and after the reduction treatment.

  Similarly to Test 1, slag after the reduction treatment was used as a CaO source for a slagging agent in the iron ore sintering step to produce a blast furnace hot metal. The phosphorus concentration of the molten blast furnace hot metal was about 0.1% by mass, and there was no problem. 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.

  In contrast to Test 1 and Test 2, when the converter slag generated in the steelmaking process is recycled as it is as a CaO source of sintered ore, the concentration of phosphorus in the hot metal discharged from the blast furnace increases, In the steelmaking process, the CaO-based iron making agent and the oxygen source basic unit increased, the amount of generated slag increased 1.5 times, and the productivity decreased by 20%.

Each high phosphorus high manganese pig iron obtained in Test 1 and Test 2 was mixed with 150 ton each of blast furnace hot metal in a hot metal ladle. Adjusting so that the basicity (mass% CaO / mass% SiO ₂ ) of the slag after demanganese treatment is 0.5 or more and 1.0 or less with respect to the molten iron after mixing, a CaO source (quick lime) and an oxygen source Was supplied to perform demanganese treatment. After the manganese removal treatment, the high Mn _X O slag produced by the manganese removal treatment was discharged from the hot metal ladle, and then the hot metal in the hot metal ladle was subjected to a dephosphorization treatment. In the dephosphorization process, 40% by volume or more of the oxygen source in terms of oxygen gas required for the dephosphorization reaction is supplied by blowing from the top blowing lance to the hot metal, and the CaO required for the dephosphorization reaction. 40% by mass or more (in terms of pure CaO) of the source (CaO-based dephosphorizing agent) was supplied to the hot metal along with oxygen gas through an upper blowing lance. Table 7 shows changes in the hot metal components, and Table 8 shows slag compositions obtained after the demanganese treatment and the dephosphorization treatment.

The phosphorus concentration in the hot metal after the dephosphorization treatment was 0.10% by mass or less, and this hot metal could be used in the steel making process without any problem thereafter. In addition, high Mn _X O slag obtained after demanganese treatment was used as an alternative to manganese ore in the decarburization of hot metal in the converter, and the manganese concentration in the molten steel after decarburization and refining could be increased at a low cost. . Furthermore, the slag after the dephosphorization treatment can also be made high P ₂ O ₅ low Mn _X O, and the recovered slag after the dephosphorization treatment can be used as a raw material for phosphoric acid fertilizer.

  The reduction treatment is performed on the converter slag and the preliminary dephosphorization slag generated in the steelmaking-steel making process shown in Example 1, whether or not metallic iron is removed from the steelmaking slag before the reduction treatment, and after the reduction treatment. The effect of the removal of metallic iron from steelmaking slag on the recovery rate of high phosphorus and high manganese 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 phosphorus high manganese pig iron. In addition, the reduction treatment was performed by using a rotary kiln equipped with a heating burner and heating steelmaking slag and coke charged in the rotary kiln with a burner, as in Example 1. The operating temperature of the rotary kiln was adjusted to 1450 to 1550 ° C. Table 9 shows the 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. A test in which reduction treatment and slag after reduction were further magnetically separated to recover high phosphorus and high manganese pig iron, Test No. 4 is a converter slag (basicity = 3.0) subjected to magnetic separation containing SiO ₂ glass wool (SiO ₂ = 100 mass%) and mixed to basicity as substance 2.2 A test in which the slag after the reduction was subjected to reduction treatment, and the slag after reduction was further magnetically separated to recover high-phosphorus high manganese pig iron, Test No. 5 was a converter slag (basicity = 3.0) subjected to magnetic separation. ) Is mixed with silicon sludge (Si = 15 mass%, SiO ₂ = 85 mass%) as a SiO ₂ -containing substance and the basicity is adjusted to 2.25, and the slag after reduction is further magnetized. It is the test which isolate | separated and collect | recovered high phosphorus high manganese pig iron.

  As shown in Table 9, it was confirmed that by separating / removing metallic iron in the slag before the reduction treatment, more high-phosphorus high manganese pig iron can be recovered with a small amount of reducing coke used. It was also confirmed that more high-phosphorus high-manganese pig iron can be recovered by magnetically separating the slag after the reduction treatment.

In addition, the high-phosphorus high manganese pig iron obtained in Test No. 2 was mixed with 150 tons of blast furnace hot metal in a hot metal pan. First, the basicity (mass% CaO) of the slag after demanganese treatment with respect to the hot metal after mixing. / Mass% SiO ₂ ) was adjusted to be 0.5 or more and 1.0 or less, and a CaO source (quick lime) and an oxygen source were supplied to perform demanganese treatment. After this demanganese treatment, the high Mn _X O slag produced by the demanganese treatment was discharged from the hot metal ladle, and then the hot metal in the hot metal pan was dephosphorized. In the dephosphorization process, 40% by volume or more of the oxygen source in terms of oxygen gas required for the dephosphorization reaction is supplied by blowing from the top blowing lance to the hot metal, and the CaO required for the dephosphorization reaction. 40% by mass or more (in terms of pure CaO) of the source (CaO-based dephosphorizing agent) was supplied to the hot metal along with oxygen gas through an upper blowing lance.

  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 carried out for normal steelmaking slag and dephosphorization slag produced when dephosphorizing high-phosphorus high manganese pig iron without performing demanganese treatment.

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 10 shows the results of the three types of fertilization tests, which are the components of the three types of slag that were subjected to the fertilization test, the concentration of soluble phosphoric acid, and the 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 10, 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 Hot metal 3 CaO type | system | group dephosphorizing agent or iron oxide, or these mixtures 4 CaO type | system | group dephosphorizing agent 5 Hot metal ladle 6 Carriage 7 Top blowing lance 8 Injection lance 9 Storage tank 10 Storage tank 11 Hopper 12 Raw material conveyance apparatus 13 Shoot 14 Generated slag

Claims (12)

Steelmaking slag containing at least one of phosphorous from slag generated in decarburization and refining of hot metal in the converter and slag generated in preliminary dephosphorization treatment of hot metal, and after solidifying, metallic iron is separated. The steelmaking slag is reduced using a reducing agent containing one or more of carbon, silicon, and aluminum, and high phosphorus containing 0.5% by mass or more of phosphorus and 0.5% by mass or more of manganese. A first step of recovering high manganese pig iron;
A second step of recycling the slag having a reduced phosphorus content by the reduction treatment of the first step as a CaO source in the iron making step or the steel making step;
The basicity (mass% CaO / mass% SiO ₂ ) of the slag after the treatment of the high phosphorus high manganese pig iron recovered in the first step without using a fluorine compound as a solvent is 0.5 or more and 1.0 or less. A third step of supplying a CaO source and an oxygen source so that the manganese concentration in the molten iron after the treatment is 0.4 mass% or less,
A fourth step of discharging the slag produced by the demanganese treatment in the third step from the treatment vessel used in the demanganese treatment;
40 of the total oxygen source in terms of oxygen gas required for the dephosphorization reaction with respect to the hot metal in the processing container after the slag produced during the demanganese processing is discharged from the processing container by the fourth step. While supplying oxygen gas of volume% or more to the hot metal from the top blowing lance, 40% by mass or more of the CaO source required for the dephosphorization reaction is blown to the hot metal with oxygen gas through the top blowing lance. A fifth step of dephosphorizing until the phosphorus concentration in the hot metal after treatment is 0.10% by mass or less;
A sixth step of recycling the hot metal, which has been dephosphorized until the phosphorus concentration in the hot metal becomes 0.10% by mass or less in the fifth step, to the steelmaking process;
A seventh step of recovering the slag produced by the dephosphorization treatment of the fifth step and using it as a phosphoric acid resource raw material;
A method for recovering iron and phosphorus from steelmaking slag, comprising: 2. The steelmaking slag according to claim 1, wherein the steelmaking slag before the reduction treatment in the first step has a basicity (mass% CaO / mass% SiO ₂ ) of 1.6 to 3.0. For recovering iron and phosphorus from sewage.   The method for recovering iron and phosphorus from steelmaking slag according to claim 1 or 2, wherein the high phosphorus high manganese pig iron recovered in the first step contains 3 mass% or more of carbon.   The slag discharged from the processing vessel in the fourth step is recovered and then recycled as a manganese source in hot metal converter decarburization and refining. A method for recovering iron and phosphorus from steelmaking slag according to claim 1. The slag recovered in the seventh step has a phosphoric acid concentration (P ₂ O ₅ concentration) of 15% by mass or more and a manganese oxide concentration of 8% by mass or less. A method for recovering iron and phosphorus from the steelmaking slag according to any one of the above.   The metallic iron mixed in the slag is separated from the slag whose phosphorus content has been reduced by the reduction treatment in the first step, and the separated metallic iron is recycled as a CaO source in the ironmaking process or the steelmaking process. The method for recovering iron and phosphorus from a steelmaking slag according to any one of claims 1 to 5, wherein The steelmaking slag reduced by the reduction treatment in the first step is a steelmaking slag mixed with a SiO ₂ -containing material for adjusting the basicity. A method for recovering iron and phosphorus from steelmaking slag according to one.   After mixing and mixing the high phosphorus high manganese pig iron recovered in the first step and the hot metal discharged from the blast furnace, the phosphorus concentration in the hot metal is 0.5 to 2.0 mass%, and the manganese concentration is 2. The iron from the steelmaking slag according to any one of claims 1 to 7, wherein the iron is adjusted to 0% by mass or less and thereafter the third step to the seventh step are performed. And phosphorus recovery method.   The steelmaking slag according to any one of claims 1 to 8, wherein a recycling destination of the slag in the second step is an iron ore sintering step or a hot metal production step in a blast furnace. For recovering iron and phosphorus from sewage.   The slag recycling destination in the second step is either hot metal preliminary dephosphorization treatment in a steelmaking refining step or hot metal decarburization refining in a converter. A method for recovering iron and phosphorus from steelmaking slag according to one.   9. The method for recovering iron and phosphorus from steelmaking slag according to any one of claims 1 to 8, wherein the slag recycling destination in the second step is an iron ore sintering step or a hot metal production step in a blast furnace. Blast furnace slag fine powder, characterized in that it is produced 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 Or blast furnace slag cement.   A phosphate resource raw material recovered in the seventh step of the method for recovering iron and phosphorus from steelmaking slag according to any one of claims 1 to 10.

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