JP5594183B2 - Method for recovering iron and phosphorus from steelmaking slag and raw material for phosphate fertilizer - Google Patents

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 for recycling to the process or steelmaking process and effectively using the recovered iron and phosphorus as resources, and for phosphate fertilizer recovered from steelmaking slag by this recovery method Regarding raw materials.

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 a CaO source and iron source for the ironmaking 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.

  Further, Patent Document 5 discloses that dephosphorization slag produced by dephosphorization of hot metal or molten steel using a fouling agent containing alkali metal carbonate as a main component 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 to be separated and recovered.

JP 2004-143492 A JP 9-316519 A JP-A-55-97408 JP 2002-69526 A JP-A-56-22613

  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, which is phosphorus-containing slag, is mixed with the same amount of blast furnace slag as the converter slag, but in recent years, the blast furnace slag is not a waste but a utility value as a civil engineering / building material. It is economically disadvantageous to use such blast furnace slag for diluting 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.

  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. From the steelmaking slag, the phosphorus and iron can be recovered from the steelmaking slag in advance at a low cost, and the recovered phosphorus and iron can be effectively used as resources, respectively, in order to prevent the contained phosphorus from affecting the molten iron and molten steel. It is to provide a method for recovering iron and phosphorus, and to provide a raw material for phosphate fertilizer recovered from steelmaking slag by this recovery method.

The gist of the present invention for solving the above problems is as follows.
(1) Steelmaking slag containing phosphorus of at least any one of slag generated in decarburization and refining of hot metal in a converter and preliminary dephosphorization of hot metal is made of carbon, silicon, 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 containing one or more of them; A second step of recycling slag having a reduced phosphorus content by the reduction treatment in the first step as a CaO source in the iron making step or the steel making step, and the high phosphorus high manganese pig iron recovered in the first step Without using a fluorine compound as a solvent, supplying a CaO source and an oxygen source so that the basicity (mass% CaO / mass% SiO ₂ ) of the treated slag is 0.5 or more and 1.0 or less. After processing A third step of demanganese treatment until the manganese concentration in the hot metal is 0.4 mass% or less, and the slag produced by the demanganese treatment in the third step is discharged from the treatment vessel used in the demanganese treatment. In the fourth step and the fourth step, the total amount of oxygen gas equivalent required for the dephosphorization reaction with respect to the molten iron in the treatment vessel after the slag produced during the demanganese treatment is discharged from the treatment vessel. 40% by volume or more of oxygen gas in the oxygen source is supplied by blowing from the top blowing lance to the hot metal, and 40% by weight or more of the CaO source required for the dephosphorization reaction is supplied through the top blowing lance. A fifth step in which the hot metal is sprayed and supplied together with the oxygen gas, and the phosphorus concentration in the hot metal after the treatment is reduced to 0.10% by mass or less, and the phosphorus concentration in the hot metal by the fifth step is reduced to 0. 1 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 And a method for recovering iron and phosphorus from steelmaking slag.
(2) The basicity (mass% CaO / mass% SiO ₂ ) of the steelmaking slag before the reduction treatment in the first step is 1.6 to 3.0, as described in (1) above To recover iron and phosphorus from steelmaking slag.
(3) The iron and phosphorus from the steelmaking slag according to (1) or (2) above, wherein the high phosphorus high manganese pig iron recovered in the first step contains 3% by mass or more of carbon. Recovery method.
(4) The slag discharged from the processing vessel is recovered by the fourth step, and the recovered slag is recycled as a manganese source in the hot metal converter decarburization refining. The method for recovering iron and phosphorus from steelmaking slag according to any one of (3) above.
(5) The slag recovered in the seventh step has a phosphoric acid (P ₂ O ₅ ) concentration of 15% by mass or more and a manganese oxide concentration of 10% by mass or less. The method for recovering iron and phosphorus from the steelmaking slag according to any one of (4).
(6) The slag recovered in the seventh step has a phosphoric acid (P ₂ O ₅ ) concentration of 15% by mass or more and a manganese oxide concentration of 8% by mass or less. The method for recovering iron and phosphorus from the steelmaking slag according to any one of (4).
(7) The main phosphorus-containing compound in the slag recovered in the seventh step is Ca ₃ (PO ₄ ) ₂ , and the Ca ₃ (PO ₄ ) ₂ does not dissolve MnO and FeO. The method for recovering iron and phosphorus from steelmaking slag according to any one of (1) to (6) above,
(8) Any one of (1) to (7) above, 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. A method for recovering iron and phosphorus from steelmaking slag as described in 1.
(9) The above (1) to ((1), wherein the recycling destination of the slag in the second step is hot metal preliminary dephosphorization treatment in a steelmaking refining step or hot metal decarburization refining in a converter. The method for recovering iron and phosphorus from the steelmaking slag according to any one of 7).
(10) The phosphorus concentration of the hot metal 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 is 0.5 to 2.0 mass%, the manganese concentration Is adjusted to 2.0% by mass or less, and thereafter, from the third step to the seventh step is performed, as described in any one of (1) to (9) above A method for recovering iron and phosphorus from steelmaking slag.
(11) A phosphate fertilizer raw material comprising the slag recovered in the seventh step in the method for recovering iron and phosphorus from the steelmaking slag according to any one of (1) to (4) above, The phosphoric acid (P ₂ O ₅ ) concentration in the phosphate fertilizer raw material is 15% by mass or more, the manganese oxide concentration is 10% by mass or less, and the main phosphorus-containing compound in the phosphate fertilizer raw material is Ca ₃ ( A raw material for phosphate fertilizer, characterized in that it is PO ₄ ) ₂ .

  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, iron oxide, phosphorous oxide, manganese oxide in the steelmaking slag is reduced and recovered as high phosphorus high manganese pig iron, and the steelmaking slag with reduced phosphorus content is Recycled as a source of CaO in the ironmaking process or steelmaking process, the recovered high phosphorus high manganese pig iron is dephosphorized until the phosphorus concentration becomes 0.10% by mass or less after the manganese concentration is reduced by demanganese treatment. The hot metal after the dephosphorization process is supplied to the steelmaking process as an iron source, and the slag produced during the dephosphorization process of the high phosphorous high manganese pig iron is sufficient to be recovered as a phosphorus resource. Since the oxides are concentrated and can be effectively used as a phosphorus resource, the steelmaking slag containing phosphorus is produced without causing any adverse effects such as increasing the phosphorus concentration of hot metal or impairing the function as a dephosphorizing agent. Alternatively, recycling to the steelmaking process is realized, and at the same time, effective use of iron, manganese and phosphorus contained in the steelmaking slag as resources is realized.

It is the schematic of the dephosphorization processing equipment used in the dephosphorization test of high phosphorus high manganese pig iron. It is a figure which shows the result of having identified the compound composition of the slag obtained after the dephosphorization process of the level 14 by X-ray diffraction. It is a figure which shows the result of having identified the compound composition of the slag obtained after the dephosphorization process of the level 15 by X-ray diffraction.

  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.

  Phosphorus and manganese have a high solubility in iron, and phosphorus and manganese produced by reduction rapidly dissolve in iron produced by 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, and therefore the carbon concentration of the generated molten iron is ensured by 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 carburized to become a hot metal containing phosphorus and manganese in a high concentration (referred to as “high phosphorus high manganese hot metal” to distinguish this hot metal from blast furnace hot metal).

Also, by further study, in the reduction process of steelmaking slag basicity of the steel slag before reduction treatment (mass% CaO / mass% SiO ₂₎ have also been found to affect the reduction reaction of phosphorus and manganese. The basicity of general converter slag is about 3.0 to 5.0, and the basicity of preliminary dephosphorization slag is usually about 1.2 to 2.5, and at most 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. It turned out to be 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 found that the lower the basicity of the steelmaking slag, the lower the reduction treatment temperature. However, when the basicity of the steelmaking slag is low, the value as a CaO source when recycled to the steelmaking process or the steelmaking process. Therefore, the basicity of the steelmaking slag used for the reduction treatment is preferably 1.6 or more on average.

  Steelmaking slag after reduction treatment has a reduced phosphorus content, and does not cause an increase in the phosphorus concentration of hot metal, and can be recycled in the ironmaking process and steelmaking process as a CaO source for dephosphorizing agents and ironmaking agents. Is possible. 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, so that the molten iron after the reduction (high phosphorus and high manganese hot metal) contains 0.5 to 7.5 mass% of phosphorus and 0.8% of manganese. 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 recovering the slag and utilizing it as a phosphorous resource, the Mn _x O concentration is high, so the P ₂ O ₅ concentration is relatively lowered and the added value is lowered. For example, this slag is used as a phosphate fertilizer The fertilizer test revealed that the growth of crops was inhibited due to the high Mn _X O concentration.

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 the slag is inherently unstable, the addition of a CaO source (CaO-based dephosphorizing agent) in the form of 3CaO · P ₂ O ₅ (Ca ₃ (PO ₄ ) ₂ ) Can exist. 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 and the iron oxide addition from a chute | shoot were 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 level 1 to level 13.

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).

As a result of various investigations on the reason for the high phosphorus concentration in the hot metal at level 4, the high temperature Fe near the fire point (the collision position of the oxygen gas from the upper blowing lance on the hot metal bath surface) by the oxygen gas supplied from the upper blowing lance. _{It was found that X} O is formed, and this Fe _X O reacts with the powdery CaO-based dephosphorizing agent supplied from the top blowing lance to obtain high dephosphorization efficiency. That is, in order to promote an efficient dephosphorization reaction, it was necessary to raise the ratio of oxygen gas supplied from the top blowing lance to some extent, and it was found that at level 4, the oxygen gas ratio was too low.

  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 11.6 mass%. When this slag was subjected to a fertilizer test, growth inhibition of the crops was observed. The Mn _x O concentration in the slag after dephosphorization treatment obtained at level 3 described above was 8.0% by mass, and in this case, no growth inhibition of the crop was observed. Since the manganese concentration in the hot metal after demanganese treatment at level 3 was 0.4% by mass, if the manganese concentration after demanganese treatment was 0.4% by mass or less, slag produced during dephosphorization treatment It was confirmed that can be used as a raw material for phosphate fertilizer.

Furthermore, the upper limit of the Mn _x O concentration in the slag when using slag as a raw material for phosphate fertilizer was examined. At level 9, as a result of dephosphorizing the hot metal after the demanganese treatment, the Mn _x O concentration of the slag to be produced was 10.0% by mass. When this slag was subjected to a fertilizer test, leaf yellowing occurred slightly, but the effect as a phosphate fertilizer was not different between level 3 and level 9. If the Mn _X O concentration in the phosphate fertilizer is high, there is a possibility that a growth disorder appears in the crop when applied to the crop. This is because phosphoric acid is the main fertilizer component, so the amount of phosphate fertilizer applied is large, and the amount of manganese applied increases simultaneously with phosphoric acid.

From the results of fertilizer tests of slag of different levels 3, 8 and 9 with different Mn _X O concentrations in the slag, at the level 3 where the Mn _X O concentration is 8.0% by mass, crop growth failure does not occur, At level 9, which is effective as a phosphate fertilizer and the Mn _X O concentration is 10.0% by mass, although slight leaf yellowing occurred, there was no growth hindrance, while the Mn _X O concentration was 11.6% by mass. At level 8, which is%, crop growth failure occurred.

From these results, if the Mn _x O concentration of the slag after the dephosphorization treatment is 10% by mass or less, this slag can be used as a raw material for phosphate fertilizer, and further, the Mn _x O of the slag after the dephosphorization treatment It was confirmed that a concentration of 8% by mass or less was more preferable as a phosphate fertilizer.

Level 10 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 11 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 10 and 11, the phosphorus concentration in the hot metal after dephosphorization was 0.10% by mass or less, and the slag after dephosphorization was also high P ₂ O _{5 and} low Mn _X O. However, particularly at level 11, the oxygen unit to be supplied and the CaO-based dephosphorizing agent unit 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 12, the phosphorus concentration and manganese concentration in the hot metal before demanganese treatment were 0.5% by mass, respectively, and at level 13, 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 12 and 13.2% by mass at level 13. As a result of the fertilizer test, a fertilizer effect was recognized at level 12, but level 13 was not very effective. 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 produced is used, for example, as a raw material for phosphate fertilizer, fluorine is eluted from the raw material for phosphate fertilizer, and the fluorine elution value is a problem with respect to soil environmental standards. It becomes. Accordingly, in the present invention, dephosphorization is performed using a CaO-based dephosphorizing agent that does not contain a fluorine compound. 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 2,3,5,7,10,11,12 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 the hot metal is performed in a converter type processing vessel, and the components are generally adjusted in the secondary refining such as RH and LF after the 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 testing, the high Mn _x O slag was no different from the manganese ore used in the past, 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.

  Furthermore, in order to investigate the influence of the demanganese treatment performed before the dephosphorization treatment on the fertilizer effect when the slag after the dephosphorization treatment is used as a raw material for the phosphoric acid fertilizer, the present inventors have set a level of 14 And level 15 tests were performed. At level 14, the dephosphorization process was performed after the demanganese process. In Level 15, the manganese concentration of the hot metal was adjusted to 0.1% by mass which does not require the demanganese treatment, and only the dephosphorization treatment was performed without performing the demanganese treatment. The conditions and results of the level 14 demanganese treatment are shown in Table 4, and the conditions and results of the levels 14 and 15 dephosphorization treatment are shown in Table 5.

  As shown in Tables 4 and 5, level 14 is that the phosphorus concentration in the hot metal before demanganese treatment is 1.0 mass% and the manganese concentration is 2.0 mass%, and after demanganese treatment, dephosphorization treatment is performed. Carried out. In the level 15 performed as a comparison, the phosphorus concentration in the hot metal before the treatment was set to 1.0 mass% and the manganese concentration was set to 0.1 mass%. Only the dephosphorization treatment was performed without performing the demanganese treatment.

The P ₂ O ₅ concentration in the slag obtained after these dephosphorization treatments was 29.7% by mass at level 14 and 30.0% by mass at level 15, and was almost equivalent. The collected fertilizer components of these slags were investigated, and komatsuna cultivation tests were conducted using these slags as phosphate fertilizers. Furthermore, the compound composition of these slags was identified by X-ray diffraction. These results are shown in Table 6.

The concentration of 2% citric acid (pH 2) soluble P ₂ O ₅ (referred to as “soluble phosphonic acid”), which is a fertilizer component in slag, is 28.7% by mass at level 14 and 15.1% by mass at level 15. The ratio of soluble phosphoric acid to the phosphoric acid content (phosphoric acid solubility) was 97% at level 14 and 50% at level 15. That is, although the P ₂ O ₅ concentration in the slag was the same, the level 14 where the demanganese treatment was performed was higher in both the soluble phosphate concentration and the phosphate dissolution rate than the level 15.

  Moreover, even in the cultivation test result of Komatsuna, the weight of the pot applied with the slag of level 14 was heavier than the pot applied with the slag of level 15, and the slag having higher phosphate fertilizer effect than the level 15 was obtained at the level 14. It was confirmed.

As a result of identifying the main compound composition constituting the slag by X-ray diffraction in order to clarify the factor that the phosphate solubility at level 14 was excellent and the phosphate fertilizer effect was high, as shown in FIG. The main phosphorus-containing compound is Ca ₃ (PO ₄ ) _2. On the other hand, at level 15, the main phosphorus-containing compound has MnO and FeO dissolved in Ca ₃ (PO ₄ ) ₂ as shown in FIG. Ca ₁₉ Mn ₂ (PO ₄ ) ₁₄ and Ca ₉ Fe (PO ₄ ) ₇ . At level 14, Ca ₁₉ Mn ₂ (PO ₄ ) ₁₄ and Ca ₉ Fe (PO ₄ ) ₇ were hardly identified. In the case where the main phosphorus-containing compounds are Ca ₁₉ Mn ₂ (PO ₄ ) ₁₄ and Ca ₉ Fe (PO ₄ ) ₇ , the phosphate solubility is reduced. 2 shows the X-ray diffraction result of the level 14 slag, and FIG. 3 shows the X-ray diffraction result of the level 15 slag.

Thus, by performing the demanganese treatment before the dephosphorization treatment, MnO and FeO are not dissolved in Ca ₃ (PO ₄ ) ₂ and at least 50 of the slag phosphorus-containing compound produced by the dephosphorization treatment. It has been found that slag having a higher effect as a phosphate fertilizer can be obtained when the mass% or more becomes Ca ₃ (PO ₄ ) ₂ .

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. A steelmaking slag containing at least any one of the slags generated in the phosphorus treatment is reduced using a reducing agent containing one or more of carbon, silicon, and aluminum, and phosphorus is reduced to 0. A first step of recovering high-phosphorus high manganese pig iron containing not less than 5% by mass and not less than 0.5% by mass of manganese, and a step of making a slag having a reduced phosphorus content by the reduction treatment in the first step Or the 2nd process recycled as a CaO source in a steelmaking process, and the basicity (mass%) of the slag after processing the high phosphorus high manganese pig iron collect | recovered by the said 1st process, without using a fluorine compound as a solvent. aO-/ wt% SiO ₂₎ is supplied to CaO source and an oxygen source to be 0.5 to 1.0, removing manganese process until the hot metal in the manganese concentration after processing is 0.4 wt% or less And the fourth step of discharging the slag produced by the demanganese treatment in the third step from the treatment vessel used in the demanganese treatment, and the fourth step, during the demanganese treatment. From the top lance, 40% by volume or more of oxygen gas in the total oxygen source in terms of oxygen gas required for the dephosphorization reaction is applied to the hot metal in the processing container after the generated slag is discharged from the processing container. The hot metal is sprayed and supplied, and 40% by mass or more of the CaO source necessary for the dephosphorization reaction is supplied by spraying the hot metal together with oxygen gas through the upper blowing lance, and the phosphorus concentration in the hot metal after the treatment A fifth step of dephosphorizing until 0.10% by mass or less, and recycling the hot metal dephosphorized by the fifth step until the phosphorus concentration in the hot metal becomes 0.10% by mass or less are recycled to the steelmaking process. And 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.

  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 a steelmaking process or a steelmaking process, first, iron oxide, phosphorous oxide, and manganese oxide in the steelmaking slag are reduced and recovered as high phosphorus high manganese pig iron, Steelmaking slag with reduced phosphorus content is recycled as a CaO source in the steelmaking process or steelmaking process, while the recovered high phosphorus high manganese pig iron has a phosphorus concentration of 0.10 mass after decreasing the manganese concentration by demanganese treatment. The dephosphorization treatment is carried out until the amount becomes less than or equal to%, and the molten iron after the dephosphorization treatment is supplied as an iron source to the steelmaking process. Phosphorus oxide is concentrated to a level sufficient to be recovered and can be effectively used as a phosphorus resource, so it contains phosphorus without causing adverse effects such as increasing the phosphorus concentration of hot metal or impairing its function as a dephosphorizing agent. Recycling of the steelmaking slag that has been made into the steelmaking process or the steelmaking process is realized, and at the same time, iron, manganese, and phosphorus contained in the steelmaking slag are each effectively used as resources.

  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 7 shows examples of the 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 7, the blast furnace hot metal after desiliconization and dephosphorization contains 0.050% by mass of phosphorus, which is higher than the phosphorus concentration level of steel products (0.015% by mass or less). 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. Then, the test which applies this invention to this converter slag was implemented.

  200 tons of converter slag 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 a burner to reduce the converter slag. 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% 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. Table 8 shows slag compositions before 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.

  100 tons of converter slag, 100 tons of preliminary dephosphorization slag and coke as a reducing agent are charged into a rotary kiln equipped with a heating burner, and the converter slag, preliminary dephosphorization slag and coke are added by the burner. The slag was reduced by heating. 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 amount of high-phosphorus high manganese pig iron recovered after the reduction treatment was 49 tons, and the components were C = 4% 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. Table 9 shows the slag composition before and after the reduction treatment.

  In the same manner as in Example 1, the slag after the reduction treatment was used as a CaO source for the 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 contrast to Example 1 and Example 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 becomes high, and thereafter 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%.

The high phosphorus high manganese pig iron obtained in Example 1 and Example 2 was mixed with 150 tons 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 dephosphorization treatment was performed on the hot metal in the hot metal ladle. 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 10 shows changes in the hot metal components, and Table 11 shows slag compositions obtained after the demanganese treatment and the dephosphorization treatment.

The concentration of phosphorus in the hot metal after the dephosphorization treatment was 0.10% by mass or less, and this hot metal could be used in the steelmaking 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 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 (11)

Steelmaking slag containing at least any one of the slag generated in the decarburization and refining of hot metal in the converter and the slag generated in the preliminary dephosphorization treatment of hot metal is converted into one of carbon, silicon, and aluminum. A first step of reducing 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 containing at least a seed;
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: Wherein the basicity of the steel slag before reduction process in the first step (wt% CaO / mass% SiO ₂₎ is 1.6 to 3.0, from steelmaking slag according to claim 1 Recovery method of iron and phosphorus.   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% by mass or more of carbon.   The slag discharged from the processing vessel is recovered by the fourth step, and the recovered slag is recycled as a manganese source in hot metal converter decarburization refining. A method for recovering iron and phosphorus from steelmaking slag as set forth in any one of the above. The slag recovered in the seventh step has a phosphoric acid (P ₂ O ₅ ) concentration of 15% by mass or more and a manganese oxide concentration of 10% by mass or less. 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 (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 steelmaking slag according to claim 1. The main phosphorus-containing compound in the slag recovered in the seventh step is Ca ₃ (PO ₄ ) ₂ , and the Ca ₃ (PO ₄ ) ₂ does not dissolve MnO and FeO. A method for recovering iron and phosphorus from a steelmaking slag according to any one of claims 1 to 6.   The steelmaking slag according to any one of claims 1 to 7, 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 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 item 1.   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 a steelmaking slag according to any one of claims 1 to 9, 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. A raw material for phosphate fertilizer comprising the slag recovered in the seventh step in the method for recovering iron and phosphorus from the steelmaking slag according to any one of claims 1 to 4, wherein the raw material for phosphate fertilizer The phosphoric acid (P ₂ O ₅ ) concentration in the mixture is 15% by mass or more, the manganese oxide concentration is 10% by mass or less, and the main phosphorus-containing compound in the phosphate fertilizer raw material is Ca ₃ (PO ₄ ) ₂ . A raw material for phosphate fertilizer, characterized in that it exists.

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