JP2013163828A - Method for producing molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing molten steel with which, when the molten steel is produced from molten pig iron, the blending ratio of cold-iron source of iron scrap, etc., can be increased by adding powdery material, used as a refining agent in dephosphorizing treatment and decarburizing refining under heating or melting condition, to a furnace.SOLUTION: Powdery material 13 of oxidized iron, lime-based flux, etc., is sprayed toward a molten pig iron surface with oxygen gas as the conveying gas while forming flame under the tip of a top-blowing lance 3, and also molten pig iron 14 in a converter is dephosphorized by spraying the oxygen gas toward the molten pig iron surface. Successively, the obtained molten pig iron after dephosphorizing treatment is charged into another converter or the same converter, and while forming the flame under the tip of the top-blowing lance by using a top-blowing lance having the same constitution as the above top-blowing lance, the powdery material of the lime-based flux, manganese ore, etc., is sprayed toward the molten pig iron surface with the oxygen gas as the conveying gas, and also the molten pig iron is carburized and refined by spraying the oxygen gas toward the molten pig iron surface, and thus the molten steel is produced from the molten pig iron.

Description

  In the present invention, the hot metal discharged from the blast furnace is charged into the converter, the hot metal is subjected to dephosphorization treatment as a preliminary treatment, and then the hot metal is discharged from the converter and then another converter or the same converter. In particular, the present invention relates to a method of producing molten steel from hot metal by decarburizing and refining the molten iron in this converter. Specifically, when producing molten steel from molten iron using a converter, dephosphorization treatment and degassing are performed. The present invention relates to a method for producing molten steel that can increase the blending ratio of a cold iron source such as iron scrap by adding powder used as a refining agent in a carbon refining to a furnace in a heated or molten state.

In recent years, from the viewpoint of environmental protection, reducing CO ₂ emissions has become an important issue in the steelmaking process. In the steelmaking process, the ratio of cold iron sources such as iron scrap is increased as the iron source to be used. Attempts have been made to reduce the blending ratio. This is because in the manufacture of hot metal in a blast furnace, a large amount of energy is required to reduce and melt the iron ore, while the cold iron source only requires heat of melting. This is because when the cold iron source is used, the amount of energy used for reducing heat of the iron ore can be reduced, and the amount of CO ₂ generated can be greatly reduced.

  However, in the molten steel manufacturing process using a combination of blast furnace and converter, the melting heat source of the cold iron source is the sensible heat of the hot metal and the combustion heat due to the oxidation of carbon and silicon in the hot metal, and the melting amount of the cold iron source Therefore, various means have been proposed to increase the blending ratio of the cold iron source in the steelmaking refining process.

  For example, in Patent Document 1, when performing dephosphorization treatment (also referred to as “preliminary dephosphorization treatment”) as a hot metal pretreatment, a carbon source is added to the generated slag during the dephosphorization treatment, and oxygen is added to the slag. There has been proposed a method in which a carbon source is burned by blowing a source and the combustion heat is applied to the hot metal.

  Patent Document 2 discloses a method in which carbonaceous materials such as coal, coke, pitch, and heavy oil are blown together with oxygen into a molten iron bath for gasification, and at the same time, iron scrap is melted and refined. A gasifying agent blowing nozzle outside the nozzle, and an oxidation for secondary combustion of the in-furnace generated gas whose nozzle central axis is inclined 20 to 60 ° outward with respect to the lance axis There has been proposed a method of melting and refining iron scrap while performing gasification of a carbonaceous substance and simultaneously performing secondary combustion of the gas generated in the furnace using an upper blowing lance having an agent blowing nozzle.

In Patent Document 3, 0.05 to 0 per ton of hot metal from the bottom of the top-bottom converter is performed in order to efficiently perform dephosphorization with a small amount of slag and reduce the temperature drop of the hot metal in the dephosphorization process. .. While blowing a stirring gas of 60 Nm ³ / min, the hot metal in the furnace contains CaO powder and Al ₂ O ₃ powder of more than 20% by mass and less than 50% by mass with respect to this CaO powder from the top blowing lance A method has been proposed in which the mixed powder is sprayed with oxygen gas of 0.5 to 2.0 Nm ³ / min per ton of hot metal as a carrier gas.

  In Patent Document 4, when decarburizing and refining hot metal in a converter, the main hole for oxygen gas ejection and the supply flow path for oxygen gas ejected from the main hole are independent, and fuel gas, oxygen gas, and refining are performed. And using a top lance with a five-pipe structure having a flux supply sub-hole capable of simultaneously ejecting the flux for use, the oxygen gas jets ejected from the main holes are kept separated from each other, and the oxygen gas jets There has been proposed a converter refining method in which a flame is formed independently at the tip of a sub-hole, and a refining flux is allowed to pass through the flame to promote hatching of the refining flux.

  In Patent Document 5, when hot metal is dephosphorized by supplying an oxygen source, hot metal having a silicon content of 0.2% by mass or less is used, and a CaO-based powder medium solvent, oxygen gas, Using a top blow lance with a quadruple pipe structure that supplies fuel such as propane gas from the hole, a flame is formed at the tip of the top blow lance, and a powdery powder mainly composed of CaO heated, heated or melted by this flame. There has been proposed a method of dephosphorizing a dephosphorization medium solvent by spraying it on the hot metal together with oxygen gas.

Further, Patent Document 6 discloses that a powdery dephosphorization medium solvent mainly composed of CaO, SiO ₂ and iron oxide contains oxygen from a central hole arranged at the axial center of an upper blowing lance of a five-pipe structure. At the same time that the gas is blown onto the hot metal as a carrier gas, one or more of hydrocarbon-based gas fuel or liquid fuel is supplied from the first peripheral hole arranged around the central hole to form a flame, A method of heating and melting the dephosphorization medium solvent by the flame and dephosphorizing the hot metal by blowing a refining oxygen-containing gas to the hot metal from the second peripheral hole arranged outside the first peripheral hole. Has been proposed.

JP-A-9-20913 JP 60-67610 A JP 2000-345226 A Japanese Patent Laid-Open No. 11-80825 JP 2005-336586 A JP 2007-92158 A

  However, the above prior art has the following problems.

  That is, in Patent Document 1, the hot metal temperature is increased by adding the carbon source to the generated slag, but the sulfur contained in the carbon source is mixed into the hot metal and the sulfur concentration in the steel is increased. . Moreover, since it is necessary to ensure the combustion time of a carbon source, there exists a problem that refining time becomes long, productivity falls, and manufacturing cost rises.

  In Patent Document 2, iron scrap is melted while the secondary combustion heat is applied to the iron bath. However, the efficiency of the secondary combustion heat to the iron bath is low, and a lot of secondary combustion heat is applied. If the secondary combustion rate is increased as much as possible, the heat damage of the refractory of the smelting furnace body becomes severe, causing a problem that the life of the furnace is shortened.

In Patent Document 3, although the melting point of CaO is lowered by the addition of Al ₂ O ₃ and the hatching of CaO is promoted, the refractory material of the furnace body is worn as the concentration of Al ₂ O ₃ in the slag increases. On the contrary, there is a concern that the cost will be high. In addition, when the Al ₂ O ₃ concentration in the slag is around 50% by mass, there is also a problem that the dephosphorization rate decreases.

  Patent Documents 4 to 6 describe a dephosphorization process performed as a pretreatment on hot metal, which is an effective technique for increasing the hot metal temperature by causing the combustion heat of fuel to reach the hot metal via a medium solvent or the like. However, there is no description on how to decarburize and refine the hot metal after dephosphorization. In other words, if the heat capacity of the hot metal is increased by dephosphorization treatment, the blending ratio of the cold iron source will increase accordingly, but the ratio of the cold iron source will be increased by performing an operation to increase the heat capacity of the hot metal in the converter decarburization and refining. Is even higher. References 4 to 6 do not describe this point.

  In addition, when supplying the powder used as the refining agent from the center hole of the top blowing lance, if an inert gas is used as the carrier gas, iron oxide is generated in the region of the hot metal surface irradiated with the powder. Although it is difficult and the problem that the dephosphorization reaction of hot metal is not promoted occurs, Patent Documents 4 to 6 use oxygen gas as a carrier gas, and this problem is prevented beforehand. Also, in the decarburization refining in the converter, if nitrogen gas, which is one of the inert gases, is used as the carrier gas, nitrogen pick-up to the molten steel occurs and adversely affects the quality. When using an inert gas, it is necessary to use expensive Ar gas.

  The present invention has been made in view of the above circumstances. The object of the present invention is to charge the molten iron discharged from the blast furnace into the converter and subject the molten iron to dephosphorization as a preliminary treatment. After hot metal is discharged from the converter, it is charged into another converter or the same converter, and decarburization and refining is performed on the hot metal in this converter. A method for producing molten steel that is excellent in heat receiving efficiency and productivity, and can increase the blending ratio of cold iron sources such as iron scrap, by adding the powder used as a refining agent in the furnace in a heated or molten state. Is to provide.

The gist of the present invention for solving the above problems is as follows.
[1] A central hole for spraying powder used as a refining agent together with a carrier gas to the hot metal bath surface in the converter, a fuel injection hole for injecting fuel, and a refining oxygen gas to the hot metal bath surface in the converter Using an upper blowing lance having a peripheral hole to be blown separately,
While injecting fuel from the fuel injection hole to form a flame below the tip of the top lance, one or more powders of iron oxide, lime-based solvent, and carbon-containing material are discharged from the center hole with oxygen gas. While spraying toward the hot metal bath surface as a transport gas, oxygen gas is sprayed from the surrounding holes toward the hot metal bath surface to dephosphorize the hot metal in the converter,
Next, the obtained hot metal after dephosphorization is discharged from the converter into a hot metal holding container, and this hot metal is charged into another converter or the converter, and the upper blow lance has the same configuration. Using a blow lance,
While injecting fuel from the fuel injection hole to form a flame below the tip of the top blowing lance, oxygen gas is applied to one or more powders of lime based solvent, manganese ore, and carbon-containing substance from the center hole. While spraying toward the hot metal bath surface as a transport gas, oxygen gas is sprayed from the surrounding holes toward the hot metal bath surface to decarburize and refine the hot metal in the converter,
Thus, a method for producing molten steel, comprising producing molten steel from molten iron.
[2] The upper blowing lance supplies a powder supply passage for supplying powder together with a carrier gas, a fuel supply passage for supplying fuel, and a refining oxygen gas from the center side in the cross-sectional structure. The method for producing molten steel according to the above [1], which has a five-pipe structure having a refining oxygen gas supply flow path and two flow paths for cooling water supply and drainage.
[3] The top blowing lance has a powder supply channel for supplying powder together with a carrier gas, a fuel supply channel for supplying fuel, and a fuel for burning the fuel from the center side in the cross-sectional structure. A six-pipe having a combustion oxygen gas supply flow path for supplying combustion oxygen gas, a refining oxygen gas supply flow path for supplying refining oxygen gas, and two flow paths for cooling water supply and drainage The method for producing molten steel according to the above [1], which has a structure.

According to the present invention, in the dephosphorization treatment in the converter performed as a pretreatment for the hot metal, and the decarburization refining in the converter of the hot metal subjected to the dephosphorization treatment, the powder used as a refining agent is increased. Heat is generated by the flame formed below the tip of the blowing lance, and the heat of the flame is applied to the hot metal via the powder, so the temperature of the hot metal rises, iron scrap in the dephosphorization treatment of the hot metal and decarburization refining, etc. This makes it possible to increase the blending ratio of the cold iron source, thereby realizing a significant reduction in CO ₂ emission compared to the conventional case.

It is a schematic sectional drawing which shows an example of the converter equipment provided with the upper blowing lance of the 5-pipe structure used when implementing the dephosphorization process and decarburization refining of hot metal in the 1st example of this invention. It is a general | schematic expanded longitudinal cross-sectional view of the upper blowing lance shown in FIG. It is a schematic sectional drawing which shows an example of the converter equipment provided with the upper blowing lance of the 6-pipe structure used when implementing the dephosphorization process and decarburization refining of hot metal in the 2nd example of this invention. It is a general | schematic expanded longitudinal cross-sectional view of the upper blowing lance shown in FIG.

  Hereinafter, the present invention will be described in detail. First, the background to the present invention will be described.

The present invention reduces the amount of CO ₂ emissions when a hot metal produced in a blast furnace is subjected to dephosphorization treatment as a preliminary treatment, and the dephosphorized hot metal is decarburized and refined in a converter to produce molten steel. In addition, the purpose is to increase the blending ratio of cold iron sources such as iron scrap, and the converter has a large freeboard, and the melting of the cold iron source is promoted by vigorously stirring the molten iron. The dephosphorization process to be performed was premised on using a converter similarly to decarburization refining.

  In hot metal dephosphorization, a technique for increasing the temperature of hot metal by heating a lime-based medium solvent such as quick lime with a burner flame using an upper blowing lance having a burner function is performed in Patent Document 4 and the like. Also in the present invention, the powder used as a refining agent is heated and melted using an upper blowing lance having a burner function. Therefore, when the powder is heated using an upper blowing lance having a burner function, and the heat of the flame is applied to the hot metal via the heated powder, the heat is efficiently applied to the powder blowing the heat of the burner flame. It was tested using two types of top blowing lances, a five-pipe structure and a six-pipe structure.

  The five-pipe top blow lance used has a Laval nozzle type central hole, an annular annular nozzle around the central hole, and a plurality of Laval nozzle type peripheral holes around the annular nozzle. And an upper blowing lance having two flow paths for supplying and discharging cooling water. The six-tube structure top blowing lance used is a Laval nozzle type central hole, an annular first annular nozzle around the central hole, and an annular circumference around the first annular nozzle. The second annular nozzle and a plurality of Laval nozzle type peripheral holes on the outer periphery of the second annular nozzle, and an upper blowing lance having two flow paths for cooling water supply and drainage .

  These top blowing lances were installed at the top of a vertical tubular furnace having an inner diameter of 1.0 m and a height of 3.0 m, and a flame was formed below the tip of the top blowing lance as a powder. Is blown with a mixture of quick lime and iron oxide (80% by weight quick lime-20% by weight iron oxide) of 100-300 μm from the top blowing lance, and the temperature of the powder in the powder blowing is measured with a radiation thermometer, The heating condition of the powder was investigated. The test was conducted under the following four test conditions.

  Test condition 1: Using a top lance with a five-pipe structure, propane gas is blown as fuel from the center hole, oxygen gas for propane gas combustion is blown from an annular nozzle, and oxygen gas for refining is transported from the surrounding hole The powder was blown together with oxygen for refining as a gas.

  Test condition 2: Using an upper blowing lance with a six-pipe structure, the above powder is blown from the center hole using nitrogen gas as a carrier gas, propane gas is blown from the first annular nozzle as fuel, and the second circle Oxygen gas for propane gas combustion was blown from the annular nozzle, and refining oxygen gas was blown from the surrounding holes.

  Test condition 3: Using an upper blowing lance of a six-pipe structure, the above powder was blown from the center hole using Ar gas as a carrier gas, propane gas was blown from the first annular nozzle as fuel, and the second circle Oxygen gas for propane gas combustion was blown from the annular nozzle, and refining oxygen gas was blown from the surrounding holes.

  Test condition 4: Using an upper blowing lance with a five-pipe structure, the above powder is blown from the center hole using oxygen gas as the carrier gas, propane gas is blown from the annular nozzle as fuel, and oxygen gas for refining from the surrounding hole Infused.

  In test conditions 1 to 4, the total supply amount of oxygen gas was adjusted to be the same. Table 1 shows the test conditions and the measurement results of the powder temperature.

  Under test condition 4, the powder ejected from the center hole using oxygen gas as the carrier gas and the flame formed by the combustion of fuel formed around the center hole are close to each other, and the combustion heat of the burner is efficiently applied to the powder. Heat transfer, powder is supplied from the peripheral hole, and the powder injection part and the burner part are separated from each other, and test condition 2 and test condition in which the powder is conveyed from the central hole by an inert gas. Compared to 3, it was found that the temperature of the powder was higher. Further, it has been found that even if oxygen gas for fuel combustion is not blown independently, the fuel is burned without any problem by the oxygen gas supplied as the carrier gas from the vicinity of the fuel injection hole. Moreover, the difference between the nitrogen gas and the Ar gas in the powder conveying gas from the central hole was small. The reason why the powder temperature is lower in the test conditions 2 and 3 than in the test condition 4 is that the amount of heat supplied to the powder is relatively reduced by heating the inert gas for conveyance. This may be due to the fact that the inert gas for transportation hinders the transfer of flame heat to the powder.

  From these results, in order to efficiently heat the combustion heat of the burner flame to the powder used as a refining agent, whether it is dephosphorization treatment as a pretreatment or decarburization refining, the top blowing lance It was found that it was effective to form a flame by spraying the powder used as a refining agent from the center hole of the metal to the hot metal bath surface using oxygen gas as the carrier gas and supplying fuel from the periphery of the center hole. It was. In this case, oxygen gas for refining used for dephosphorization and decarburization refining is separately supplied from the outer peripheral side of the flame. As the top blow lance of this configuration, a top blow lance having a five-pipe structure is suitable, but a combustion oxygen gas injection hole for separately supplying oxygen gas for burning fuel is further provided close to the fuel injection hole. An upper blowing lance having a six-pipe structure on the outer peripheral side is also a suitable upper blowing lance for carrying out the present invention.

  The present invention has been made based on the above test results, and the method for producing molten steel according to the present invention comprises a center hole for blowing powder used as a refining agent to a hot metal bath surface in a converter together with a conveying gas, Using an upper blowing lance having a fuel injection hole for injecting fuel and a peripheral hole for blowing refining oxygen gas to the hot metal bath surface in the converter, fuel is injected from the fuel injection hole and below the tip of the upper blowing lance While forming a flame on the center hole, one or more powders of iron oxide, lime based solvent, and carbon-containing material are blown toward the hot metal bath surface using oxygen gas as a carrier gas and surrounding holes. Then, oxygen gas is blown toward the hot metal bath surface to dephosphorize the hot metal in the converter, and then the hot metal obtained after dephosphorization is discharged from the converter into the hot metal holding container, Charge to another converter or the converter, and Using a top lance with the same structure as the blow lance, fuel is injected from the fuel injection hole to form a flame below the tip of the top blow lance, and from the center hole, lime-based solvent, manganese ore, carbon content One or more types of powders are blown toward the hot metal bath surface using oxygen gas as the carrier gas, and oxygen gas is sprayed from the surrounding holes toward the hot metal bath surface to decarburize the hot metal in the converter. Refining, thus producing molten steel from hot metal.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. First, a first embodiment using an upper blowing lance with a five-pipe structure will be described.

  FIG. 1 is a schematic cross-sectional view showing an example of a converter facility equipped with a top blow lance of a five-pipe structure used when performing dephosphorization treatment and decarburization refining of hot metal in the first embodiment of the present invention. FIG. 2 is a schematic enlarged longitudinal sectional view of the upper blowing lance shown in FIG. In the present invention, decarburization and refining of the hot metal that has been subjected to the dephosphorization treatment is also performed using the converter equipment having the configuration shown in FIG.

  As shown in FIG. 1, the converter equipment 1 used for hot metal dephosphorization treatment and decarburization refining in the present invention has an outer shell composed of an iron shell 4, and a refractory 5 is enforced inside the iron shell 4. A furnace body 2 and an upper blowing lance 3 inserted in the furnace body 2 and movable in the vertical direction are provided. An upper portion of the furnace body 2 is provided with a hot water outlet 14 for pouring hot metal 14 after dephosphorization treatment or molten steel (not shown) after decarburization refining, and at the bottom of the furnace body 2. Are provided with a plurality of bottom blowing tuyere 7 for blowing the gas 16 for stirring. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8.

  The top blowing lance 3 carries oxygen gas (industrial pure oxygen gas) with powder 13 made of one or more of iron oxide, lime-based solvent, manganese ore, and carbon-containing material used as a refining agent. A powder supply pipe 9 for supplying oxygen gas as a working gas, a fuel supply pipe 10 for supplying fuel such as propane gas, liquefied natural gas, coke oven gas, petroleum, heavy oil, and oxygen gas for refining A refining oxygen gas supply pipe 11 for supplying (industrial pure oxygen gas), a cooling water supply pipe and a drain pipe for supplying / discharging cooling water for cooling the top blowing lance 3 (not shown) ) And are connected.

  The other end of the powder supply pipe 9 is connected to a dispenser 12 containing the powder 13, and the dispenser 12 is connected to a powder supply gas supply pipe 9A. The oxygen gas supplied to the dispenser 12 functions as a conveying gas for the powder 13 accommodated in the dispenser 12, and the powder 13 accommodated in the dispenser 12 passes through the powder supply pipe 9 and blows upward. 3 and can be sprayed toward the hot metal 14 from the tip of the upper blowing lance 3.

  As shown in FIG. 2, the upper blow lance 3 is composed of a cylindrical lance body 17 and a copper cast lance tip 18 connected to the lower end of the lance body 17 by welding or the like. 17 is comprised of five types of concentric steel pipes, that is, a quintuple pipe, that is, an innermost pipe 22, an inner pipe 23, an intermediate pipe 24, an outer pipe 25, and an outermost pipe 26. The powder supply pipe 9 communicates with the innermost pipe 22, the fuel supply pipe 10 communicates with the inner pipe 23, the refining oxygen gas supply pipe 11 communicates with the middle pipe 24, and the cooling water supply pipe and the drain pipe are respectively provided. It communicates with either the outer tube 25 or the outermost tube 26. That is, the powder 13 passes through the inner tube 22 together with oxygen gas (= carrier gas), the fuel such as propane gas passes through the gap between the inner tube 22 and the inner tube 23, and the oxidizing gas for refining The gap between the inner pipe 23 and the middle pipe 24 and the gap between the middle pipe 24 and the outer pipe 25 and the gap between the outer pipe 25 and the outermost pipe 26 serve as a cooling water supply channel or drainage channel. Yes. One of the gap between the middle pipe 24 and the outer pipe 25 and the gap between the outer pipe 25 and the outermost pipe 26 is a water supply flow path, and the other is a drainage flow path. The cooling water is configured to reverse at the position of the lance tip 18.

  The inside of the innermost tube 22 communicates with a center hole 19 disposed substantially at the axial center of the lance tip 18, and a gap between the innermost tube 22 and the inner tube 23 is an annular nozzle around the center hole 19. Alternatively, it communicates with the fuel injection holes 20 that are opened as a plurality of concentric nozzle holes, and the gap between the inner tube 23 and the intermediate tube 24 communicates with a plurality of peripheral holes 21 provided on the outer periphery of the fuel injection hole 20. ing. The center hole 19 is a nozzle for spraying the powder 13 together with oxygen gas (= carrier gas), the fuel injection hole 20 is a nozzle for injecting fuel, and the peripheral hole 21 is for spraying refining oxygen gas. Nozzle.

  That is, the inside of the innermost tube 22 is a powder supply channel, the gap between the innermost tube 22 and the inner tube 23 is a fuel supply channel, and the gap between the inner tube 23 and the inner tube 24 is a refining oxygen gas supply. It is a flow path. In FIG. 2, the center hole 19 and the peripheral hole 21 take the shape of a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. Nozzle may be used. The fuel injection hole 20 is a straight nozzle that opens in an annular slit shape, or a straight nozzle that has a circular cross section.

  In the upper blowing lance 3, the fuel is injected from the fuel injection hole 20 and only the oxygen gas is injected from the center hole 19, so that the flame is formed below the tip of the upper blowing lance 3 without blowing the powder 13. Can be formed.

  In order to increase the blending ratio of the cold iron source using the converter equipment 1 having this configuration, the hot metal 14 is first dephosphorized as shown below, and then the dephosphorized hot metal 14 is subjected to the dephosphorization process. Decarburization refining is performed to produce molten steel from the molten iron 14. Hereinafter, the dephosphorization process will be described in order.

In performing dephosphorization treatment on the hot metal 14, first, a cold iron source is charged into the furnace body 2. The cold iron source used is iron scrap such as slabs and steel plate crops and city scraps generated at steelworks, bullion recovered from slag by magnetic sorting, and cold iron, reduced iron, etc. can do. The blending ratio of the cold iron source is preferably 5% by mass or more based on the total iron source to be charged (mixing ratio of the cold iron source (mass%) = cold iron source blending amount × 100 / (molten iron blending amount). + Cold iron source blending amount)). This is because when the blending ratio of the cold iron source is less than 5% by mass, not only the effect of improving the productivity is small but also the effect of reducing the amount of CO ₂ generation is small. The upper limit of the blending ratio of the cold iron source does not need to be particularly determined, and the hot metal temperature after the dephosphorization treatment can be added up to an upper limit that can maintain the target range. Before and after the completion of charging of the cold iron source, blowing of the stirring gas 16 from the bottom blowing tuyere 7 is started.

  After charging the cold iron source into the furnace body 2, the hot metal 14 is charged into the furnace body 2. The hot metal 14 used can be processed with any composition, and may be subjected to desulfurization or desiliconization before the dephosphorization. Incidentally, the main chemical components of the hot metal 14 before the dephosphorization treatment are: carbon: 3.8 to 5.0 mass%, silicon: 0.3 mass% or less, phosphorus: 0.08 to 0.2 mass%, sulfur : About 0.05% by mass or less. However, if the amount of slag 15 generated in the furnace body during the dephosphorization process increases, the dephosphorization efficiency decreases. As described above, the amount of slag generated in the furnace body is reduced to increase the dephosphorization efficiency. Therefore, it is preferable to previously reduce the silicon concentration in the hot metal to 0.20 mass% or less, desirably 0.10 mass% or less by desiliconization treatment. Moreover, if the hot metal temperature is in the range of 1200 to 1450 ° C., dephosphorization can be performed without any problem.

  Next, oxygen gas is supplied to the dispenser 12, and the powder 13 made of one or more of iron oxide, lime-based solvent, and carbon-containing material is poured into the hot metal 14 together with oxygen gas from the center hole 19 of the top blowing lance 3. Spray toward the bath surface. Before and after the powder 13 is sprayed, fuel is injected from the fuel injection hole 20 of the upper blowing lance 3. The fuel supplied from the fuel injection hole 20 and the oxygen gas for conveying the powder 13 injected from the center hole 19 are close to each other in all directions in the radial direction of the upper blowing lance, and thus interfere with each other. Because the ambient temperature is high, even when there is no ignition device, combustion occurs when the fuel concentration reaches the combustion limit range, and a flame is formed below the upper blowing lance 3. The powder 13 is heated or heated / melted by receiving the heat of the flame to be formed, and sprayed onto the bath surface of the hot metal 14 in a heated or molten state. Thereby, the heat | fever of the powder 13 arrives at the hot metal 14, the temperature of the hot metal 14 rises, and melt | dissolution of the added cold iron source is accelerated | stimulated.

  At that time, oxygen gas for refining is blown toward the bath surface of the hot metal 14 from the peripheral hole 21 of the upper blowing lance 3.

The dephosphorization reaction of the hot metal 14 is a process in which phosphorus in the hot metal reacts with oxygen gas or iron oxide to form phosphor oxide (P ₂ O ₅ ), and this phosphor oxide is formed by the incubation of the lime-based solvent. It progresses by being absorbed by 15. In addition, the rate of dephosphorization increases as the hatching of the lime-based medium solvent is promoted. Therefore, as the powder 13, it is preferable to use a lime-based medium solvent such as quick lime (CaO), limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), dolomite (CaO—MgO). A mixture of quicklime with fluorite (CaF ₂ ) or alumina (Al ₂ O ₃ ) as a hatching accelerator can also be used as the lime-based solvent. It is also possible to use converter slag produced in the decarburization refining process of molten iron 14 (CaO-SiO ₂ slag) as all or part of the lime-based medium solvent.

  When a lime-based solvent is used as the powder 13, not only the flame heat is applied to the molten iron 14, but also the lime-based solvent sprayed on the molten metal bath immediately hatches to form a slag 15. In addition, the supplied oxygen gas for refining reacts with phosphorus in the hot metal to form a phosphorus oxide. Combined with the strong stirring of the hot metal 14 and the slag 15 by the stirring gas 16, the formed phosphorous oxide is quickly absorbed into the hatched slag 15, and the dephosphorization reaction of the hot metal 14 proceeds promptly. When the lime-based medium solvent is not used as the powder 13, the lime-based medium solvent is separately put on top from the furnace hopper.

  When iron oxide such as iron ore, iron ore sintered ore, or mill scale is used as the powder 13, not only does the heat of the flame reach the hot metal 14, but the iron oxide functions as an oxygen source. The dephosphorization reaction proceeds with the phosphorus in the hot metal. Further, the iron oxide reacts with the lime-based medium solvent to form a FeO-CaO compound on the surface of the lime-based medium solvent, which promotes the hatching of the lime-based medium solvent and promotes the dephosphorization reaction. When iron oxide containing combustible materials such as blast furnace dust and converter dust is used, the combustible materials are burned by the flame, and in addition to the above, the combustion heat of the combustible materials is used to heat the hot metal 14. Contribute.

  When a carbon-containing material such as waste plastic, coke, or graphite is used as the powder 13, the carbon-containing material is burned by a flame, and the combustion heat of the carbon-containing material is in addition to the combustion heat of the fuel. Contributes to heating. When the powder 13 is a mixture of iron oxide, a lime-based medium solvent, and a carbon-containing substance, the respective effects can be obtained in parallel.

  Further, the powder 13 is heated or heated / melted, and the heat is transmitted to the hot metal 14, and further, the combustion heat of the flame at the tip of the upper blowing lance existing above the hot metal 14 is transmitted to the hot metal 14. For this reason, in combination with the vigorous stirring of the hot metal 14, dissolution of the cold iron source in the hot metal is promoted. That is, the melting of the charged cold iron source is completed during the dephosphorization process.

  Thereafter, when the phosphorus concentration in the hot metal 14 becomes the target value or less, all the supply from the top blowing lance 3 to the hot metal 14 is stopped and the dephosphorization process is completed. After the dephosphorization process, the furnace body 2 is tilted, and the hot metal 14 subjected to the dephosphorization process is discharged into a hot metal holding container such as a ladle or a converter charging pot through the hot water outlet 6. After the hot metal 14 is discharged, the furnace body 2 is tilted, and the slag 15 in the furnace body is also discharged into the slag container.

  After that, the hot metal 14 discharged from the hot metal holding container is used in another converter equipment (not shown) equipped with an upper blowing lance 3 shown in FIG. 2 or in the above dephosphorization process. The furnace body 1 is charged into the furnace body 2 and the hot metal 14 is decarburized and refined. Also in the case of decarburization refining, a flame is formed at the tip of the top blowing lance 3, the powder 13 used as a refining agent is heated and melted in this flame, and the heat of the flame is passed through the powder 13 in the furnace body. The hot metal 14 is heated. However, in the case of decarburization refining, as the powder 13, one or more of lime-based solvent, manganese ore, and carbon-containing substance are used.

Also in the case of decarburization refining, the furnace body 2 is charged in advance with a cold iron source similar to the cold iron source used in the dephosphorization process before the molten iron 14 is charged. The heat source for melting the cold iron source in this decarburization refining process depends on the sensible heat of the hot metal 14, the carbon concentration in the hot metal and the amount of heat received from the flame. If the source blending ratio is set high, the cold iron source blending ratio must be set low in the decarburization refining process using the hot metal 14. Accordingly, the mixing ratio of the cold iron source in the decarburizing and refining process is such that the total value of the mixing ratio in the dephosphorizing process and the mixing ratio in the decarburizing and refining process is 8% by mass or more. It is preferable to set according to the blending ratio. This is because if the total blending ratio of the cold iron source is less than 8% by mass, not only the productivity improvement effect is small but also the CO ₂ generation amount reduction effect is small.

  When the hot metal 14 is charged into the furnace body 2, the top blowing lance 3 is inserted into the furnace body 2, and Ar gas or the like is blown into the hot metal 14 as the stirring gas 16 from the bottom blowing tuyere 7. From the center hole 19, the powder 13 is injected using oxygen gas as a carrier gas, and from the fuel injection hole 20, gas fuel such as propane gas, natural gas, coke oven gas, or hydrocarbons such as heavy oil and kerosene. The liquid fuel is supplied, and oxygen gas for decarburization refining is blown from the peripheral hole 21 of the upper blowing lance 3 onto the hot metal bath surface.

A flame is formed at the tip of the upper blowing lance 3, and the powder 13 is heated or heated / melted by receiving the heat of the formed flame, and sprayed onto the bath surface of the hot metal 14 in the heated or molten state. Thereby, the heat | fever of the powder 13 arrives at the hot metal 14, the temperature of the hot metal 14 rises, and melt | dissolution of the added cold iron source is accelerated | stimulated. Further, the decarburization reaction (2C + O ₂ → 2CO) proceeds by the oxygen gas supplied from the peripheral hole 21.

  As the powder 13 supplied from the central hole 19 of the top blowing lance 3, the above-mentioned lime-based solvent such as quick lime (quick lime, dolomite, etc.), manganese ore, or carbon-containing substances such as coke, graphite and waste plastics are used. use. Moreover, it is not necessary to supply all of these auxiliary materials from the top blowing lance 3, and some of these may be added from the furnace hopper. Furthermore, the supply from the top blowing lance 3 and the addition of the upper part may be used in combination.

  When a lime-based solvent is used as the powder 13, not only does the heat of the flame reach the hot metal 14, but the lime-based solvent sprayed on the hot metal bath immediately hatches to cover the bath surface. 15 is formed to prevent spitting (scattering of metal) or to promote dephosphorization reaction. When manganese ore is used as the powder 13, not only does the heat of the flame reach the hot metal 14, but the manganese ore is reduced by the carbon in the hot metal and functions as a manganese source for adjusting the molten steel components. When a carbon-containing material such as waste plastic, coke, or graphite is used as the powder 13, the carbon-containing material is burned by a flame, and the combustion heat of the carbon-containing material is in addition to the combustion heat of the fuel. Contributes to heating.

  If the oxygen gas supplied from the peripheral hole 21 of the top blowing lance 3 reacts with the carbon in the hot metal and the decarburization reaction proceeds to reduce the carbon concentration to the target value, Stop all supply to the iron bath and finish decarburization refining. Thus, the hot metal discharged from the blast furnace is decarburized and refined to produce molten steel. The added cold iron source dissolves during the decarburization process. The produced molten steel is poured out into a ladle and, if necessary, subjected to secondary refining with an RH vacuum degasser or the like, and then cast into a slab with a continuous casting machine.

The top blowing lance 3 used in the present invention is configured such that the addition amount and addition timing of the powder 13 can be arbitrarily adjusted. That is, powder 13 such as lime-based medium solvent is supplied from the center hole 19 as a heat transfer medium for burner combustion heat. However, if the addition amount of lime-based medium solvent is increased in preference to heat transfer of combustion heat, lime-based medium solvent is increased. The system solvent becomes excessive, leading to a significant increase in the amount of slag generated in the furnace body. In addition, the decarbonation efficiency during decarburization refining increases from the initial stage of refining to 100% in the middle stage of refining, and decreases again as the carbon concentration in the molten iron at the end of the refining period decreases. That is, since FeO is generated by the oxygen gas to be added to the decarburization refining the initial, the addition of lime medium solvent at that time, CaO-Fe _t O melt is formed, slag formation of lime medium solvent -It becomes possible to promote melting (here, Fe _t O is a general term for iron oxides such as FeO and Fe ₂ O ₃ ). In that case, it is not necessary to supply the lime-based medium solvent after the middle stage of the decarburizing and refining when the decarbonization efficiency is 100%, and the decarburization and refining is more stable if the supply of the lime-based medium solvent is stopped instead. .

  Next, a second embodiment using an upper blowing lance with a six-pipe structure will be described. The only difference between the first embodiment and the second embodiment is the difference between the upper blow lance used in the five-pipe structure and the six-pipe structure, which overlaps the description of the first embodiment. However, the converter equipment used in the second embodiment will be described in detail.

  FIG. 3 is a schematic cross-sectional view showing an example of a converter facility equipped with an upper blowing lance of a six-pipe structure used when performing dephosphorization treatment and decarburization refining of hot metal in the second embodiment of the present invention. FIG. 4 is a schematic enlarged longitudinal sectional view of the upper blowing lance shown in FIG. In the present invention, similarly to the first embodiment, decarburization and refining of the hot metal that has been subjected to the dephosphorization treatment is also performed using the converter equipment having the configuration shown in FIG. In FIG. 3, reference numeral 46 denotes a slag.

  As shown in FIG. 3, the converter 31 used for hot metal dephosphorization and decarburization refining in the present invention is composed of an iron shell 34 as an outer shell, and a refractory 35 is enforced inside the iron shell 34. A furnace body 32 and an upper blowing lance 33 which is inserted into the furnace body 32 and is movable in the vertical direction. An upper portion of the furnace main body 32 is provided with a hot water outlet 45 for discharging hot metal 45 after dephosphorization processing or molten steel (not shown) after decarburization refining, and at the bottom of the furnace main body 32. Are provided with a plurality of bottom blowing tuyere 37 for blowing the stirring gas 47. The bottom blowing tuyere 37 is connected to a gas introduction pipe 38.

  The upper blow lance 33 conveys oxygen gas (industrial pure oxygen gas) with a powder 44 made of one or more of iron oxide, lime-based solvent, manganese ore, and carbon-containing material used as a refining agent. A powder supply pipe 39 for supplying oxygen gas as a working gas, a fuel supply pipe 40 for supplying fuel such as propane gas, liquefied natural gas, coke oven gas, petroleum, heavy oil, etc., and burning the supplied fuel Combustion oxidizing gas supply pipe 41 for supplying oxidizing gas such as oxygen gas and air for refining, and refining oxygen gas supplying pipe for supplying refining oxygen gas (industrial pure oxygen gas) 42 is connected to a cooling water supply pipe and a drain pipe (not shown) for supplying and discharging cooling water for cooling the upper blowing lance 33.

  The other end of the powder supply pipe 39 is connected to a dispenser 43 containing the powder 44, and the dispenser 43 is connected to a powder supply gas supply pipe 39A. Oxygen gas supplied to the dispenser 43 through it functions as a gas for conveying the powder 44 accommodated in the dispenser 43, and the powder 44 contained in the dispenser 43 passes through the powder supply pipe 39 and is blown upward. 33 is supplied from the tip of the upper blowing lance 33 toward the hot metal 45.

  As shown in FIG. 4, the upper blow lance 33 is composed of a cylindrical lance body 48 and a lance tip 49 made of a copper casting connected to the lower end of the lance body 48 by welding or the like. Reference numeral 48 denotes an innermost tube 54, a partition tube 55, an inner tube 56, an intermediate tube 57, an outer tube 58, and six types of concentric steel tubes, that is, a six-fold tube. The powder supply pipe 39 communicates with the innermost pipe 54, the fuel supply pipe 40 communicates with the partition pipe 55, the combustion oxidizing gas supply pipe 41 communicates with the inner pipe 56, and the refining oxygen gas supply pipe 42 The cooling water supply pipe and the drain pipe communicate with either the outer pipe 58 or the outermost pipe 59, respectively. That is, the powder 44 passes through the inside of the innermost pipe 54 together with oxygen gas (= carrier gas), the fuel such as propane gas passes between the innermost pipe 54 and the partition pipe 55, and the oxidizing gas for combustion becomes The refining oxidizing gas passes through the gap between the inner pipe 56 and the inner pipe 57, the gap between the inner pipe 57 and the outer pipe 58, and the outer pipe 58 and the outermost pipe. A gap with 59 serves as a cooling water supply channel or a drain channel. One of the gap between the middle pipe 57 and the outer pipe 58 and the gap between the outer pipe 58 and the outermost pipe 59 is a water supply flow path, and the other is a drainage flow path. The cooling water is configured to reverse at the position of the lance tip 49.

  The innermost tube 54 communicates with a center hole 50 disposed substantially at the axial center of the lance tip 49, and a gap between the innermost tube 54 and the partition tube 55 is an annular nozzle around the center hole 50. Alternatively, the gap between the partition pipe 55 and the inner pipe 56 communicates with the fuel injection holes 51 that are opened as a plurality of concentric nozzle holes, and an annular nozzle or a plurality of concentric circles are formed around the fuel injection holes 51. The combustion oxidizing gas injection hole 52 opened as a nozzle hole communicates, and the gap between the inner tube 56 and the intermediate tube 57 communicates with a plurality of peripheral holes 53 provided on the outer periphery of the combustion oxidizing gas injection hole 52. doing. The center hole 50 is a nozzle for spraying the powder 44 together with oxygen gas (= carrier gas), the fuel injection hole 51 is a nozzle for injecting fuel, and the combustion oxidizing gas injection hole 52 is for burning fuel. The nozzle for injecting the oxidizing gas and the peripheral hole 53 are nozzles for blowing the refining oxygen gas.

  That is, the inside of the innermost pipe 54 is a powder supply flow path, the gap between the innermost pipe 54 and the partition pipe 55 is a fuel supply flow path, and the gap between the partition pipe 55 and the inner pipe 56 is a supply of combustion oxygen gas. A flow path is formed, and a gap between the inner pipe 56 and the middle pipe 57 is a refining oxygen gas supply flow path. In FIG. 4, the center hole 50 and the peripheral hole 53 have the shape of a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. Nozzle may be used. The fuel injection holes 51 and the combustion oxidizing gas injection holes 52 are straight type nozzles that open in an annular slit shape, or straight shape nozzles that have a circular cross section.

  In the upper blow lance 33, whether or not oxygen gas is supplied from the center hole 50 by injecting fuel from the fuel injection hole 51 and simultaneously injecting oxidizing gas from the oxidizing gas injection hole 52 for combustion. Regardless, a flame can be formed below the tip of the upper blowing lance 33. That is, in the case of forming a flame below the tip of the top blowing lance 33, it is essential to inject fuel from the fuel injection hole 51 and simultaneously inject oxidizing gas from the combustion oxidizing gas injection hole 52. And As a matter of course, the oxygen gas injected from the center hole 50 also functions as a combustion gas for the fuel injected from the fuel injection hole 51.

  Using the converter equipment 31 configured as described above, the molten iron 45 is first subjected to dephosphorization treatment, then decarburized and refined, and molten steel is produced from the molten iron discharged from the blast furnace. This dephosphorization treatment and decarburization refining are performed in the same manner as in the first embodiment, and the description thereof is omitted.

As described above, according to the present invention, as a refining agent, in the dephosphorization treatment in the converter performed as a preliminary treatment to the hot metal, and the decarburization refining in the converter of the hot metal subjected to the dephosphorization treatment, The powder to be used is heated by a flame formed below the tip of the top blowing lance, and the heat of the flame is applied to the hot metal via the powder. It becomes possible to increase the blending ratio of cold iron sources such as iron scrap in coal refining, thereby realizing a significant reduction in CO ₂ emissions compared to the prior art.

  For the hot metal discharged from the blast furnace (also referred to as “blast furnace hot metal”) using the converter facility 1 shown in FIG. The present invention was applied to perform dephosphorization treatment and decarburization refining, and a test operation for producing molten steel from hot metal was performed for 50 heats. As the powder blown from the top blowing lance 3, a mixture of quick lime and iron oxide having a particle size of 100 to 300 μm (80% by mass quick lime−20% by mass iron oxide) is used for both dephosphorization and decarburization refining. Propane gas was used as the fuel, and Ar gas was used as the bottom blowing agitation gas. For comparison, the following three comparative examples were performed.

  Comparative Example 1: Using the top blow lance 3 of the five-pipe structure shown in FIG. 2, propane gas was blown as fuel from the center hole 19, and oxygen gas for propane gas combustion was blown from the surrounding fuel injection holes 20. Dephosphorization treatment and decarburization refining were performed by blowing powder (80 mass% quicklime-20 mass% iron oxide) together with the oxygen gas for refining using oxygen gas for refining from the surrounding hole 21 as a carrier gas.

  Comparative Example 2: Using an upper blow lance 33 having a six-pipe structure shown in FIG. 4, powder (80% by mass quicklime-20% by mass iron oxide) was blown from the center hole 50 using nitrogen gas as a carrier gas, and fuel Propane gas is blown as fuel from the injection holes 51, oxygen gas for propane gas combustion is blown from the combustion oxidizing gas injection holes 52, and refining oxygen gas is blown from the peripheral holes 53 to perform dephosphorization and decarburization refining. It was.

  Comparative Example 3: Using an upper blowing lance 33 having a six-pipe structure shown in FIG. 4, powder (80% by mass quicklime-20% by mass iron oxide) was blown from the center hole 50 using Ar gas as a carrier gas, and fuel Propane gas is blown as fuel from the injection holes 51, oxygen gas for propane gas combustion is blown from the combustion oxidizing gas injection holes 52, and refining oxygen gas is blown from the peripheral holes 53 to perform dephosphorization and decarburization refining. It was.

  In Comparative Examples 1 to 3, 50 heats were respectively performed. Table 2 shows the hot metal temperature and hot metal components before treatment in the dephosphorization treatment and decarburization refining in the present invention example and Comparative Examples 1 to 3.

  Table 3 shows the refining conditions in the dephosphorization treatment and decarburization refining in the present invention example and Comparative Examples 1 to 3.

  Table 4 shows the amount of heat given in the dephosphorization treatment and decarburization refining by the combustion heat of the fuel in terms of calorie distribution. It shows that the higher the calorific value conversion, the higher the amount of heat of the flame that reaches the molten iron. Specifically, it is shown that the conversion ratio of the calorific value can be increased by 1.0%, and the mixing ratio of the cold iron source can be increased by 1.0% compared to the case where the powder is not heated. Yes. Compared to Comparative Example 1, it was found that the amount of heat received was significantly increased in Comparative Examples 2 and 3 and the inventive example. In addition, compared with Comparative Examples 2 and 3, the inventive example had a higher heat receiving amount. This is due to the difference in powder temperature, similar to the test results shown in Table 1. It has been confirmed that if the amount of fuel supplied is increased, the calorific value conversion increases.

  Table 4 shows the phosphorus concentrations in the hot metal and in the molten steel after the dephosphorization treatment and decarburization refining. In the examples of the present invention, in the hot metal dephosphorization treatment, oxygen gas was used as the powder conveying gas from the center hole, so that the phosphorus concentration in the hot metal after the dephosphorization treatment was low and stable. Also in decarburization refining, the effect of carrier gas on the phosphorus concentration in the molten steel after treatment was confirmed. Use of an inert gas as a powder carrier gas increases costs. In particular, the cost increase is significant for Ar gas. On the other hand, in the present invention example in which oxygen gas is used as the carrier gas, the oxygen gas serves as both the fuel combustion oxygen gas and the refining oxygen gas, so that the cost does not increase. In Table 4, hot metal and molten steel are collectively indicated as “molten iron”.

  According to the present invention, the powder for refining is supplied from the center hole, and the burner hole (fuel, combustion oxygen) is disposed around the powder so that the powder is efficiently heated by the flame formed by the burner. However, it can be supplied to the hot metal. Further, since the powder conveying gas from the center hole is oxygen gas, it has become possible to promote the dephosphorization reaction in the dephosphorization of hot metal and reduce the refining cost in the decarburization refining. As a result, it is possible to reduce production costs in dephosphorization and decarburization refining, achieving resource saving and energy saving, stabilizing the converter operation, and providing an industrially beneficial effect.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Furnace main body 3 Top blowing lance 4 Iron skin 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Powder supply pipe 10 Fuel supply pipe 11 Refinement oxygen gas supply pipe 12 Dispenser 13 Powder 14 Hot metal 15 Slag 16 Gas for stirring 17 Lance main body 18 Lance tip 19 Center hole 20 Fuel injection hole 21 Peripheral hole 31 Converter equipment 32 Reactor main body 33 Top blowing lance 34 Iron skin 35 Refractory 36 Hot water outlet 37 Bottom blowing tuyere 38 Gas introduction pipe 39 Powder supply pipe 40 Fuel supply pipe 41 Combustion oxidizing gas supply pipe 42 Refining oxygen gas supply pipe 43 Dispenser 44 Powder 45 Hot metal 46 Slag 47 Gas for stirring 48 Lance body 49 Lance tip 50 Center hole 51 Fuel injection holes 52 Combustion oxidizing gas injection holes 53 Peripheral holes

Claims (3)

A central hole that sprays powder used as a refining agent on the hot metal bath surface in the converter together with the carrier gas, a fuel injection hole that injects fuel, and a peripheral hole that sprays refining oxygen gas on the hot metal bath surface in the converter And using a top blowing lance having separately,
While injecting fuel from the fuel injection hole to form a flame below the tip of the top lance, one or more powders of iron oxide, lime-based solvent, and carbon-containing material are discharged from the center hole with oxygen gas. While spraying toward the hot metal bath surface as a transport gas, oxygen gas is sprayed from the surrounding holes toward the hot metal bath surface to dephosphorize the hot metal in the converter,
Next, the obtained hot metal after dephosphorization is discharged from the converter into a hot metal holding container, and this hot metal is charged into another converter or the converter, and the upper blow lance has the same configuration. Using a blow lance,
While injecting fuel from the fuel injection hole to form a flame below the tip of the top blowing lance, oxygen gas is applied to one or more powders of lime based solvent, manganese ore, and carbon-containing substance from the center hole. While spraying toward the hot metal bath surface as a transport gas, oxygen gas is sprayed from the surrounding holes toward the hot metal bath surface to decarburize and refine the hot metal in the converter,
Thus, a method for producing molten steel, comprising producing molten steel from molten iron.   The upper blow lance is configured to have a powder supply channel for supplying powder together with a carrier gas, a fuel supply channel for supplying fuel, and a refining oxygen for supplying refining oxygen gas from the center side in the cross-sectional structure. The method for producing molten steel according to claim 1, wherein the molten steel has a five-pipe structure having a gas supply channel and two channels for supplying and discharging cooling water.   The upper blow lance has a powder supply channel for supplying powder together with a carrier gas, a fuel supply channel for supplying fuel, and a combustion oxygen for burning the fuel from the center side in the cross-sectional structure. It has a six-pipe structure having a combustion oxygen gas supply flow path for supplying gas, a refining oxygen gas supply flow path for supplying refining oxygen gas, and two flow paths for cooling water supply and drainage. The manufacturing method of the molten steel of Claim 1 characterized by the above-mentioned.

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