Top blowing lance for converter, method of adding a secondary raw material, and method of refining molten iron

Abstract

The present invention provides a technology capable of increasing a heat allowance and increasing the amount of cold iron source used in the refining treatment of molten iron. The present invention is a top-blown lance for a converter, which is configured in such a manner that a burner having a jet hole for jetting fuel and combustion-supporting gas is provided at the tip of one lance for top blowing of an oxidizing gas into molten iron accommodated in a converter-type vessel or at the tip of another lance provided separately from the one lance, and a powdered auxiliary raw material or an auxiliary raw material processed into a powder is blown from the one lance or the other lance into the molten iron so as to pass through a flame formed by the burner, a prescribed heating time can be ensured, and a prescribed powder fuel ratio can be ensured. The present invention is a method for adding an auxiliary raw material using the top-blown lance and a refining method for molten iron.

Description

Technical Field

[0001] This invention relates to top-blown lances for converters, methods for adding auxiliary raw materials, and methods for refining molten iron. More specifically, it relates to techniques for increasing heat margin and increasing the amount of cold iron source used in the refining process of molten iron contained in a converter-type vessel. Background Technology

[0002] Previously, a steelmaking method was developed that involved dephosphorizing the molten pig iron during the molten pig iron stage (hereinafter referred to as pre-dephosphorization treatment) to reduce the phosphorus concentration in the molten pig iron to a certain extent, followed by decarburization blowing in the converter. In this pre-dephosphorization treatment, oxygen sources such as gaseous oxygen and solid oxygen were added to the molten pig iron along with lime-based solvents. Therefore, the oxygen sources reacted not only with the phosphorus in the molten pig iron but also with carbon and silicon, thereby increasing the temperature of the molten pig iron.

[0003] In recent years, from the perspective of preventing global warming, the steel industry has been reducing its consumption of fossil fuels to decrease CO2 emissions. In the ironmaking industry, carbon is used to reduce iron ore to produce molten pig iron. In producing this molten pig iron, approximately 500 kg of carbon source is required per ton of molten pig iron to reduce the iron ore. On the other hand, when using scrap iron or other chilled iron sources as raw materials in a converter to produce molten steel, the carbon source required for iron ore reduction is no longer needed. In this case, even considering the energy required to melt the chilled iron source, replacing 1 ton of molten pig iron with 1 ton of chilled iron results in a reduction of approximately 1.5 tons of CO2 emissions. That is, in converter steelmaking methods using molten iron, increasing the proportion of chilled iron reduces CO2 emissions. Here, molten iron refers to both molten pig iron and molten chilled iron.

[0004] To increase the amount of chills used, the heat required to melt the chills needs to be supplied. As mentioned above, the heat of reaction of carbon and silicon, which are impurity elements in molten pig iron, is usually used to compensate for the heat of melting of the chills. However, with the increase in the proportion of chills, the heat from the carbon and silicon components in the molten pig iron alone is insufficient.

[0005] For example, Patent Document 1 proposes a technology that supplies heating agents such as ferrosilicon, graphite, and coke into the furnace, while simultaneously supplying oxygen, to perform heat compensation for melting the cold iron source.

[0006] Furthermore, in the aforementioned pre-dephosphorization treatment, the final temperature is approximately 1300°C, which is lower than the melting point of the scrap iron used as a chill source. Therefore, during pre-dephosphorization blowing, carbon contained in the molten pig iron carburizes into the surface layer of the scrap iron, thereby lowering the melting point of the carburized portion and allowing the scrap iron to melt. Therefore, to promote the melting of the scrap iron, it is important to promote the migration of carbon contained in the molten pig iron.

[0007] For example, Patent Document 2 proposes a scheme to promote the stirring of molten iron in the converter by supplying bottom-blown gas, thereby promoting the melting of the cold iron source.

[0008] In addition, patent documents 3 and 4 disclose a smelting reduction method in which a secondary raw material feeding nozzle is provided separately from the top-blown nozzle for supplying oxidizing gas, which is set on the axis of the iron bath type smelting reduction furnace. In this nozzle, a burner containing a powder nozzle for spraying granular ore or metal oxide, a gas fuel nozzle, and an oxygen nozzle are arranged in a concentric circle. The ore or metal oxide is loaded into the iron bath type smelting reduction furnace in such a way that it passes through the flame generated by the burner.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2011-38142

[0012] Patent Document 2: Japanese Patent Application Publication No. 63-169318

[0013] Patent Document 3: Japanese Patent Application Publication No. 2007-138207

[0014] Patent Document 4: Japanese Patent Application Publication No. 2008-179876

[0015] Non-patent literature

[0016] Non-patent literature 1: Science chronology

[0017] Non-Patent Document 2: Japan Society of Mechanical Engineers Heat Transfer Engineering Data, 4th Revised Edition, 1986

[0018] Non-Patent Literature 3: Japan Society for Metals, Metallurgy, 2000 Summary of the Invention

[0019] The problem that the invention aims to solve

[0020] However, the aforementioned existing technology has the following problems.

[0021] In the method described in Patent Document 1, the oxygen required for the oxidation and combustion of the carbon and silicon in the supplied heating agent is used for thermal compensation, resulting in prolonged processing time and reduced productivity in the converter. Furthermore, the combustion of silicon produces SiO2, leading to an increase in slag ejection.

[0022] The technology described in Patent Document 2 can expect a melting-promoting effect and thus improve productivity by increasing the stirring force of molten pig iron. However, it is not a technology that supplies the heat required to melt the chilled iron source, so it cannot increase the amount of chilled iron source used.

[0023] In the technologies of patent documents 3 and 4, the heat transfer pattern when the by-product passes through the burner flame is not considered. Since only the powder / fuel ratio is specified, it cannot be said that it is possible to properly operate operating factors such as the lance height, which are considered to contribute to heat exchange efficiency, to optimize the heat margin, for example, the heat exchange of the burner.

[0024] The present invention was made in view of the following circumstances, and its object is to provide a technique for refining molten iron contained in a converter-type vessel that can increase heat margin and increase the amount of chilled iron source used.

[0025] Methods for solving problems

[0026] The top-blown lance of the converter of the present invention, which advantageously solves the above-mentioned problems, is characterized in that it is configured such that a burner having injection holes for spraying fuel and combustion-supporting gas is provided at the front end of a lance that top-blown oxidizing gas into the molten iron contained in the converter-type vessel or at the front end of another lance provided separately from the lance. Powdered byproducts or byproducts processed into powder form blown into the molten iron from the lance or the other lance pass through the flame formed by the burner, thereby ensuring a specified heating time and a specified powder-to-fuel ratio.

[0027] It should be noted that the following solutions for the top-blown spray gun of the converter of the present invention are considered to be more preferred solutions:

[0028] (1) The distance l from the tip of the spray gun with the above-mentioned burner to the liquid surface h (m) and the ejection velocity u of the powder constituting the above-mentioned powdered by-product or the powdered by-product processed into powder. p (m / s) is determined in a manner that satisfies the following mathematical formula 1, and the above fuel supply flow rate Q 燃料 (Nm 3 ( / minute) and the supply amount V of the above-mentioned by-products per unit time. p (kg / min) is determined in a manner that satisfies the following mathematical formula 2, (in the mathematical formula, t0 represents the heating time (s) determined from the particle size of the powdered by-product or processed by-product into powder, H 燃烧 This represents the heat generated through fuel combustion (MJ / Nm³). 3 C0 represents a constant (kg / MJ).

[0029] (2) The heating time t0 required for the above-mentioned powdered by-product or the above-mentioned processed by-product is determined by the particle size d of the above-mentioned powdered by-product or the above-mentioned processed by-product. p The adiabatic flame temperature of the aforementioned fuel, the flow rate of the combustion gases of the aforementioned fuel, and the ejection velocity u of the aforementioned powder. p Decide;

[0030] (3) The constant C0 in mathematical formula 2 is determined by the type of fuel gas used.

[0031] [Mathematical Expression 1]

[0032]

[0033] [Mathematical Expression 2]

[0034]

[0035] Furthermore, the method for adding auxiliary raw materials according to the present invention, which advantageously solves the above-mentioned problems, is a method for adding auxiliary raw materials when refining molten iron by supplying oxidizing gas to molten iron contained in a converter-type vessel. The method is characterized by using the top-blown lance of the converter as described in any one of technical solutions 1 to 4, blowing the powdered auxiliary raw material or the auxiliary raw material processed into powder form as part of the auxiliary raw material into the molten iron in a manner that passes through the flame formed by the burner, heating the powdered auxiliary raw material or the auxiliary raw material processed into powder form for a predetermined heating time or more, and spraying it with a predetermined powder fuel ratio.

[0036] Furthermore, the refining method for molten iron of the present invention, which advantageously solves the above-mentioned problems, is a method for refining molten iron by adding auxiliary raw materials to molten iron contained in a converter-type vessel while supplying oxidizing gas. The method is characterized by using the top-blown lance of the converter as described in any one of technical solutions 1 to 4 to blow powdered auxiliary raw materials or processed into powdered auxiliary raw materials into the molten iron in a manner that passes through a flame formed by the burner. The powdered auxiliary raw materials or processed into powdered auxiliary raw materials are heated for a predetermined heating time or more, and the injection is performed at a predetermined powder-fuel ratio.

[0037] Invention Effects

[0038] According to the present invention, a burner having injection holes for ejecting fuel and combustion-supporting gases is provided at the front end of a top-blown oxidizing gas lance or at the front end of another lance separately from the top-blown lance. Powdered byproducts or byproducts processed into powder form are blown into the molten iron in a manner that allows them to pass through a flame formed by the burner. The byproducts are heated for a predetermined heating time or longer, and are injected at a predetermined powder-to-fuel ratio. Thus, the powdered byproducts are sufficiently heated by the burner flame, becoming a heat transfer medium and effectively transferring heat to the molten iron in the converter. As a result, heat exchange efficiency is improved, the amount of carbon and silicon sources added as heating agents can be reduced, processing time can be shortened, and slag production can be suppressed. Furthermore, since the powder supplied as a fluxing agent is heated, it also has the effect of shortening the slag melting time and improving metallurgical efficiency. Attached Figure Description

[0039] Figure 1 A longitudinal sectional view showing the general outline of the converter used in an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of a burner according to one embodiment of the present invention. Figure 2 (a) shows a longitudinal sectional view of the front end of the spray gun. Figure 2 (b) shows a bottom view taken from below the nozzle.

[0041] Figure 3 This is a graph showing the relationship between the powder fuel ratio V / QH and the heat exchange efficiency when the burner described in the above embodiment is used to heat and supply powder.

[0042] Figure 4 To represent the distance l from the tip of the spray gun to the liquid surface when heating and supplying powder using the burner described in the above embodiment. h For powder particle size d p A graph showing the effect of heat exchange efficiency.

[0043] Figure 5 To indicate the particle size d of each powder when heating and supplying powder using the burner described in the above embodiment. p A graph showing the time-varying changes in particle temperature and combustion gas temperature.

[0044] Figure 6 To express the appropriate range of the present invention as the ratio of powder fuel to powder (V / QH) and the residence time of the powder in the flame (l) h / u p A diagram showing the relationships between them. Detailed Implementation

[0045] The embodiments of the present invention will now be described in detail. It should be noted that the accompanying drawings are illustrative and may sometimes differ from actual embodiments. Furthermore, the following embodiments illustrate apparatus and methods for embodying the technical concept of the present invention, and do not specifically limit the configuration to the following configuration. That is, the technical concept of the present invention can be modified in various ways within the scope of the claims.

[0046] Figure 1 This is a schematic longitudinal sectional view of a converter-type vessel 1 with a bottom blowing function used in a hot iron refining method according to one embodiment of the present invention. Figure 2 This is a schematic diagram showing the front end of the spray gun of a burner with powder supply function. Figure 2 (a) represents a longitudinal sectional view. Figure 2 (b) is the A-A' sectional view.

[0047] For example, firstly, scrap iron, which serves as a source of chilled iron, is loaded into converter-type vessel 1 using a chip guide chute (not shown). Then, molten pig iron is loaded into converter-type vessel 1 using a loading pot (not shown).

[0048] After molten pig iron is charged, oxygen is blown onto the molten iron 3 from a top-blown oxidizing gas lance 2. Inert gases such as argon and N2 are supplied as stirring gases from a tuyer 4 located at the bottom of the furnace to stir the molten iron 3. Then, auxiliary materials such as heating agents and slag-forming materials are added to dephosphorize the molten iron 3 in the converter-type vessel 1. At this time, powdered auxiliary materials such as lime powder or processed powdered auxiliary materials (hereinafter, both are collectively referred to as "powdered auxiliary materials") are supplied using carrier gas from a powder supply pipe located on the top-blown oxidizing gas lance 2 or from a powder supply pipe located on another lance 5 separately from the lance 2. Here, a burner with injection holes for spraying fuel and combustion-supporting gases is also provided at the front end of the lance 2 or at the front end of another lance 5 separately from the lance 2. Then, during at least a portion of the dephosphorization process, the powdered auxiliary materials supplied from the powder supply pipe are blown in such a way that they pass through the flame formed by the burner. Figure 2The schematic diagram shows the front end of the spray gun 5, which is separate from the spray gun 2 and has a burner at its front end. A powder supply pipe 11 with injection holes is positioned at the center, surrounded by a fuel supply pipe 12 with injection holes and a combustion-supporting gas supply pipe 13. An outer casing with a cooling water passage 14 is provided on its outer side. Fuel gas 16 and combustion-supporting gas 17 are supplied from the injection holes located on the outer periphery of the powder supply pipe 11, forming a burner flame. The powdered byproduct material (powder 15) is then heated in this burner flame. As a result, since the powdered byproduct material becomes the heat transfer medium, the heat transfer efficiency to the molten iron can be improved. Consequently, the amount of heating agents such as carbon sources and silicon sources can be reduced, and the prolongation of dephosphorization processing time can be suppressed. To effectively transfer heat to the powder, it is important to ensure the residence time of the powder 15 in the burner flame. In addition to pure oxygen, a mixture of oxygen and CO2, or inert gases, can also be used as the oxidizing gas. As combustion-supporting gases, air, oxygen-enriched air, and oxidizing gases can be used. As fuels, fuel gases such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas), liquid fuels such as heavy oil, and solid fuels such as coke powder can be used. However, from the perspective of reducing CO2 production, fuels with lower carbon sources are preferred.

[0049] The inventors conducted burner heating tests on lime powder using a converter-type vessel, making various changes to the carrier gas flow rate and lance height. The results showed that high heat exchange efficiency could be achieved by setting the residence time of the powder within the burner flame to approximately 0.05 s to approximately 0.1 s. Reducing the powder flow rate is effective in ensuring the residence time within the flame. However, a constant flow rate of carrier gas must be supplied for transport within the piping. Under actual operating conditions, the powder flow rate is in the range of 30 m / s to 60 m / s. Therefore, to ensure the aforementioned residence time within the flame, it is preferable to set the powder outlet (the front end of the burner lance) at a height of approximately 2 m to approximately 4 m above the molten iron surface (lance height). This will be explained in detail below.

[0050] That is, with Figure 1 The apparatus consists of a burner lance 5 supplying CaO powder with an average particle size of 50 μm as a powdered byproduct to a 330-ton converter-type vessel 1 at a rate of 500 kg / min. In this case, the effect on heat exchange efficiency when the powdered fuel ratio (V / QH) is changed by altering the flow rate of fuel gas 16 will be shown. Figure 3Here, as shown in equation (2) of mathematical formula 3 below, the powder-to-fuel ratio (V / QH) is the value obtained by dividing the supply amount of powdered auxiliary raw materials per unit time by the product of the fuel supply flow rate and the heat generated by fuel combustion. In addition, the heat exchange efficiency (%) is expressed as the percentage of the heat exchange (MJ) calculated from the change in molten iron temperature relative to the heat input (MJ) generated by the combustion of fuel gas, and the same applies below. The heat exchange efficiency is improved by increasing the powder-to-fuel ratio. It can be seen that by using the heat generated by the combustion of the burner to provide heat input to the powder, the heated powder penetrates into the molten iron, thereby improving the heat exchange efficiency. This shows that in order to obtain such an improved heat exchange efficiency, it is necessary to maintain an appropriate amount of gas and powder in the burner flame. When the powder is too small relative to the flame gas, the proportion that is ejected outside the furnace as sensible heat of the gas increases, thus showing a decrease in heat exchange efficiency. Secondly, as for the influence of the type of gas, such as Figure 3 This indicates that, when using LPG, the heat exchange efficiency remains constant when the powdered fuel ratio is 0.3 kg / MJ or higher. Furthermore, when using LNG, the heat exchange efficiency remains constant when the powdered fuel ratio is 0.45 kg / MJ or higher. Therefore, the powdered fuel ratio needs to be controlled according to the type of fuel gas used. That is, the following equation (2) needs to be satisfied. In equation (2), V / QH represents the powdered fuel ratio (kg / MJ), V p Q represents the supply rate of powdered by-products per unit time (kg / min). 燃料 Indicates the fuel supply flow rate (Nm³). 3 / minute), H 燃烧 This represents the heat generated through fuel combustion (MJ / Nm³). 3 C0 represents a constant (kg / MJ) determined by the type of fuel gas used. It should be noted that the upper limit of the powder-to-fuel ratio is determined by the condition that the temperature of the heated powder is below the temperature of molten iron.

[0051] [Mathematical Expression 3]

[0052]

[0053] by Figure 1 The apparatus consists of a burner lance 5 supplying CaO as a powdered byproduct at a rate of 700 kg / min to a 330-ton converter-type vessel 1. In this case, the average particle size d of the powder is... p (μm) and the distance from the tip of the spray gun to the liquid surface (l) h The effect on heat exchange efficiency is shown in Figure 4In this study, LPG was used as the fuel gas, and the powder-to-fuel ratio (V / QH) was set to 0.5 kg / MJ. When the average particle size of the CaO powder increased, a decrease in heat exchange efficiency was observed. For the same particle size, a higher spray gun height resulted in higher heat exchange efficiency. It should be noted that the powder ejection velocity was in the range of 30 m / s to 60 m / s.

[0054] As a reason, it is believed that the degree to which the powder is heated during its passage through the burner flame will have an impact. Therefore, referring to Non-Patent Literature 1-3, the temperature shift of the powder passing through the flame is estimated by the following method. It should be noted that the specific heat capacity C of the powder is... p,P The effective concentration is set to 1004 J / (kg·K), and the particle density ρ is set to 3340 kg / m³. 3 , the particle emissivity ε p The thermal conductivity λ of the gas is set to 0.9 and 0.03 W / (m·K). The fuel gas is set to LPG, and the powder supply rate / fuel flow rate (V / Q) is set to 100 kg / Nm³. 3 The combustion reaction is based on chemical reactions (a) to (e) shown in chemical formulas 1 to 5 below. The equilibrium constant K for each reaction is... i The partial pressure P of the gas associated with reaction (i) can be used to determine the reaction. G (G is the chemical formula of the gas type) Calculate. Here, the subscript i indicates the chemical reaction formulas (a) to (e) shown in the chemical formulas 1 to 5 below. The total pressure P in the combustion flame is the sum of the partial pressures of each gas type, as shown in formula (3) in mathematical formula 4 below, which totals 1 atm.

[0055] [Chemical Formula 1]

[0056]

[0057] [Chemical Formula 2]

[0058]

[0059] [Chemical Formula 3]

[0060]

[0061] [Chemical Formula 4]

[0062]

[0063] [Chemical Formula 5]

[0064]

[0065] [Mathematical Expression 4]

[0066]

[0067] Equation (4) is the formula for calculating the equilibrium flame temperature. This is to show the change in particle enthalpy (H) from the reference temperature to the equilibrium flame temperature. 0 -H 0 298 ) P The enthalpy change of the gas from the reference temperature to the equilibrium flame temperature (H) 0 -H 0 298 ) g The difference between the enthalpy change (-ΔH) and the enthalpy change of the gaseous reactions (a) to (e) satisfying equation (3) 0 298 The equilibrium flame temperature is estimated through trial and error in the same manner.

[0068] Equation (5) is a formula that estimates the temperature change of a particle as the sum of the heat input generated by heat transfer and the heat input generated by radiation.

[0069] Equation (6) is the formula for calculating the heat flux of heat transfer.

[0070] Equation (7) is the formula for calculating the heat flux of radiation.

[0071] Equation (8) is a formula that uses the flame as a thermal fluid to represent the dimensionless number relationship related to forced convection, where Nu represents the Nusselt number and Re represents the heat transfer number. P represents the Reynolds number, and Pr represents the Prandtl number.

[0072] Where m is the mass of the powder (kg), C p,P A is the specific heat capacity of the powder (J / (kg·K)). S,P The surface area of ​​the particle (m 2 ), T g and T P These represent the gas temperature and particle temperature (K), respectively, q P and q R These represent the convective heat transfer term and the radiative heat transfer term, respectively, where λ is the gas thermal conductivity (W / (m·K)), d is the particle size in terms of representative length, and ε... P Let be the emissivity of the particle (-), and σ be the Stefan-Boltzmann coefficient. The powder temperature T is calculated using the fourth Runge-Kutta method. P .

[0073] [Mathematical Expression 5]

[0074]

[0075] [Mathematical Expression 6]

[0076]

[0077] [Mathematical Expression 7]

[0078]

[0079] [Mathematical Expression 8]

[0080] q R =ε P ·σ(T g 4 -T P 4 (7)

[0081] [Mathematical Expression 9]

[0082] Nu = 2 + 0.6·Re P 1 / 2 Pr 1 / 3 (8)

[0083] Particle size d p The combustion gas temperature T, estimated by the above formula, when the powder passes through a flame. g Changes with particle temperature T P The impact of changing relationships is shown in Figure 5 In the middle. By Figure 5 It can be seen that in order to increase the temperature T of the powder inside the flame P Gas temperature T on the flame side g The time required for them to become equal depends on the particle size d. p However, there are significant differences. The heating time t0 required for the powdered by-product can be set, for example, to the gas temperature T. g With particle temperature T P The difference is less than 10°C in time. Specifically, to control heat exchange efficiency, it is important to control the powder ejection velocity u. p Spray gun height l h The following equation (1) holds true between them.

[0084] [Mathematical Expression 10]

[0085]

[0086] The burner lance 5 of the top-blown lance constituting the converter in this embodiment is configured such that, in order to fully heat the powdered auxiliary material using the burner flame, the lance height l can be adjusted, for example. h So that the residence time of the powder in the flame (l h / u p The heating time t0 is greater than or equal to the time required for heating. The heating time t0 can be estimated using the above formula, based on the particle size d of the powdered by-product. p The adiabatic flame temperature of the fuel, the flow rate of the combustion gases, and the ejection velocity of the powder, u.p To calculate. It should be noted that the spray gun height l h Due to equipment limitations, the tip of the spray gun cannot protrude outside the furnace opening. Regarding the powder ejection velocity u... p From the perspective of stable gas delivery of powder using carrier gas, an appropriate range is determined. In addition, the nozzle diameter of the burner nozzle 5 is designed in a way that the powder fuel ratio (V / QH) can satisfy the above equation (2).

[0087] exist Figure 6 The figure shows the appropriate range based on equations (1) and (2). Figure 6 The horizontal axis represents the powder fuel ratio V / QH (kg / MJ), and the vertical axis represents the residence time of the powder in the flame. h / u p (s). The shaded area represents the region at the powder particle size d. p =50μm, the fuel gas is LPG, and the powder particle size d p =150μm, the appropriate range when the fuel gas is LNG.

[0088] Example

[0089] Use with Figure 1 The converter-type vessel 1 shown is a 300-ton bottom-blown converter (oxygen top-blown, argon bottom-blown) of the same type used for decarburization and refining of molten iron. The oxygen blowing top-blowing lance 2 is a lance with five Laval nozzle-type nozzles at the front end. The nozzles are arranged at equal intervals on the same circumference relative to the axis of the top-blowing lance 2, with the nozzle spray angle set at 15°. It should be noted that the throat diameter dt of the nozzle is 73.6 mm, and the outlet diameter de is 78.0 mm.

[0090] First, scrap iron is loaded into the converter. Then, 300 tons of molten pig iron, which has undergone pre-treatment for desulfurization and dephosphorization, is loaded into the converter. The chemical composition and temperature of the molten pig iron are shown in Table 1.

[0091] [Table 1]

[0092]

[0093] Next, while argon gas, used as a stirring gas, is blown into the molten iron 3 from the bottom tuyeres 4, oxygen gas, used as an oxidizing gas, is sprayed onto the surface of the molten iron 3 from the top lance 2, thus initiating the decarburization refining of the molten iron 3. The amount of scrap iron charged is adjusted so that the temperature of the molten steel after decarburization refining reaches 1650°C.

[0094] Then, in the decarbonization refining process, quicklime, acting as a CaO-based medium solvent, is introduced from the burner lance 5 of the by-product feedstock to carry out decarbonization refining until the carbon concentration in the molten iron reaches 0.05% by mass. The amount of quicklime added is adjusted so that the alkalinity of the slag generated in the furnace ((mass% CaO) / (mass% SiO2)) is 2.5. LNG is used as the fuel gas, and the flow rate of oxygen for fuel combustion is controlled to achieve an air-fuel ratio of 1.2. The powder supply rate u is controlled as shown in Table 2. p Flow rate of fuel gas Q 燃料 The height l of the burner nozzle 5 for feeding auxiliary raw materials h .

[0095]

[0096] As shown in Table 2, the heat exchange efficiency of the invention example is significantly improved compared to the comparative example. Furthermore, the slag formation was evaluated through a series of operations. Slag composition analysis was performed, comparing the CaO concentration (%f-CaO) of the unslagred slag. The results showed that in treatment conditions No. 1 to 7, (%f-CaO) was 0 to 0.5% by mass, while in treatment conditions No. 10 to 13, (%f-CaO) was 0.4 to 2.6% by mass. This indicates that the present invention is also effective in promoting CaO melting.

[0097] Industrial availability

[0098] The top-blown lance of the converter, the method for adding auxiliary raw materials, and the refining method for molten iron according to the present invention improve heat exchange efficiency, shorten processing time, suppress slag production, and achieve the effects of shortened slag melting time and improved metallurgical efficiency, thus proving industrially useful. Furthermore, it is not limited to converter types and is applicable to processes requiring a heat source, such as electric furnaces.

[0099] Symbol Explanation

[0100] 1. Converter-type container

[0101] 2. Top-blown spray gun for oxidizing gases

[0102] 3 Molten Iron

[0103] 4 Bottom air outlet

[0104] 5. Burner spray gun

[0105] 10. Front end of burner nozzle

[0106] 11 Powder supply pipe

[0107] 12 Fuel supply pipe

[0108] 13 Combustion-supporting gas supply pipe

[0109] 14 Cooling water passage

[0110] 15 Powder

[0111] 16 Fuel

[0112] 17. Combustion-supporting gases

[0113] 18. Cooling water.

Claims

1. A method for controlling the top-blown spray gun of a converter, characterized in that, A top-blown lance configured as follows: A burner with injection holes for injecting fuel and combustion-supporting gases is provided at the front end of one lance or another lance separately positioned to blow oxidizing gases onto molten iron contained in a converter-type vessel. Powdered byproducts or processed byproducts blown into the molten iron from the lance or other lance pass through the flame formed by the burner, ensuring a specified heating time and a specified powder-to-fuel ratio. The distance l from the tip of the nozzle with the burner to the liquid surface h (m) and the ejection velocity u of the powder constituting the powdered by-product or the powdered by-product processed into powder. p (m / s) is determined in a manner that satisfies the following mathematical formula 1, and the fuel supply flow rate Q 燃料 (Nm 3 / minute) and the supply amount V of the by-product per unit time. p (kg / min) is determined in a manner that satisfies the relationship described in the following mathematical formula 2. Where t0 represents the heating time (in seconds) determined from the particle size of the powdered by-product or by-product processed into powder. H 燃烧 This represents the heat generated through fuel combustion (MJ / Nm³). 3 ), C0 represents a constant (kg / MJ) determined by the type of fuel gas used. [Mathematical Expression 1] [Mathematical Expression 2] 。 2. The method for controlling the top-blown spray gun of a converter according to claim 1, characterized in that, The heating time t0 required for the powdered by-product or the by-product processed into powder is determined by the particle size d of the powdered by-product or the by-product processed into powder. p The adiabatic flame temperature of the fuel, the flow rate of the combustion gases of the fuel, and the ejection velocity u of the powder. p Decide.

3. A method for adding by-products, comprising adding by-products during the refining process of molten iron contained in a converter-type vessel by supplying an oxidizing gas, characterized in that, After the top-blown lance control method of the converter according to claim 1 or 2 satisfies the mathematical formula 1 and the mathematical formula 2, the powdered auxiliary raw material or the processed auxiliary raw material as part of the auxiliary raw material is blown into the molten iron in a manner that passes through the flame formed by the burner, the powdered auxiliary raw material or the processed auxiliary raw material is heated for a predetermined heating time or more, and is injected with a predetermined powder fuel ratio.

4. A method for refining molten iron, characterized in that, while adding by-products to molten iron contained in a converter-type vessel and simultaneously supplying an oxidizing gas, the molten iron is refined; After the top-blown lance control method of the converter according to claim 1 or 2 satisfies the mathematical formula 1 and the mathematical formula 2, the powdered auxiliary raw material or the processed auxiliary raw material as part of the auxiliary raw material is blown into the molten iron in a manner that passes through the flame formed by the burner, the powdered auxiliary raw material or the processed auxiliary raw material is heated for a predetermined heating time or more, and is injected with a predetermined powder fuel ratio.

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