Method for operating a converter and method for producing molten steel

Abstract

This invention proposes an operating method for converters that reduces the consumption of by-products. In this method, when oxygen is supplied to the molten iron in a converter-type refining furnace for desiliconization, dephosphorization, and decarburization refining, during slag discharge from the furnace mouth, one or more of the following parameters are measured to estimate the slag discharge quantity and the physical properties of the slag. In this method, during a refining process sequentially performing part or all of desiliconization and dephosphorization, an intermediate slag discharge process where part or all of the generated slag is discharged from the furnace mouth, and the remaining refining processes, during the intermediate slag discharge process, one or more of the following parameters are measured to estimate the slag discharge quantity and the physical properties of the slag, and the residual slag quantity, or the residual slag quantity and slag composition. Based on the estimation results, the amount of by-products input in the refining processes of other refining processes is determined.

Description

Technical Field

[0001] This invention relates to a method for operating a converter that supplies oxygen to molten iron in a converter-type refining furnace to produce molten steel, and to a method for operating a converter and producing molten steel that reduces the consumption of by-products such as lime. Background Technology

[0002] In recent years, the development of pretreatment methods for molten iron (desiliconization, dephosphorization, and desulfurization) has been promoted, and the concentrations of phosphorus and sulfur in the molten iron charged into the converter have been reduced to levels where further removal is no longer necessary. Therefore, steel refining processes that primarily involve decarburization in the converter are becoming increasingly sophisticated. Desiliconization and dephosphorization are reactions that use oxygen from the oxygen source (oxygen, iron oxide) supplied to the molten iron to oxidize and remove silicon or phosphorus. Desulfurization is a reaction in which desulfurizing materials such as CaO react with sulfur in the molten iron, thereby removing sulfur into the slag.

[0003] In particular, the dephosphorization process, as shown in equation (A) below, is carried out by using CaO-containing substances added as dephosphorization refining agents to fix phosphorus oxides (P2O5) generated by the oxidation of phosphorus in molten iron by oxygen in an oxygen source (FeO).

[0004] 2[P]+5(FeO)+3(CaO)=(3CaO·P2O5)+5[Fe](A)

[0005] In formula (A), [P] and [Fe] represent the components in the molten iron, while (FeO), (CaO), and (3CaO·P2O5) represent the components in the slag. The reaction is as follows: phosphorus in the molten iron is oxidized by FeO in the slag. The P2O5 generated by this oxidation reaction reacts with CaO and is absorbed into the slag formed by the slagging of CaO-containing substances.

[0006] In other words, from the perspective of the equilibrium of the dephosphorization reaction, in order for the generated phosphorus oxides (P2O5) to be absorbed by the slag, the basicity of the slag (=(mass%CaO) / (mass%SiO2)) needs to be above a specified value. Generally speaking, in order to promote the dephosphorization reaction, the basicity of the slag needs to be controlled within the range of 1.5 to 3.0.

[0007] However, molten iron tapped from a blast furnace contains approximately 0.2% to 0.4% silicon by mass. Thermodynamically, silicon in the molten iron is preferentially oxidized compared to phosphorus when oxygen is supplied. Therefore, if the silicon concentration in the molten iron before dephosphorization is high, the amount of SiO2 produced during dephosphorization increases. In this case, to ensure the slag basicity is within the specified range, not only does the amount of CaO-containing substances used increase, but the amount of slag produced also increases, leading to higher manufacturing costs.

[0008] Therefore, the following technology has been proposed (for example, see Patent Document 1): using a converter to desiliconize molten iron that has not undergone desiliconization treatment, and then proceeding with dephosphorization treatment after the desiliconization treatment, refining is temporarily stopped after the desiliconization treatment, and the slag generated during the desiliconization treatment, which is mainly composed of SiO2, is discharged from the converter (hereinafter referred to as "intermediate slag discharge"). This technology achieves the following effects: reducing the amount of slag in the furnace and reducing the amount of CaO-containing substances used in the dephosphorization treatment to ensure the basicity of the slag.

[0009] In addition, Patent Document 2 discloses the following method: when the Si concentration in the molten iron exceeds 0.2% by mass, intermediate slag discharge is performed, and the slag generated in the above-mentioned dephosphorization process is put into the furnace for desiliconization treatment. After adjusting the slag basicity to the range of 0.5 to 1.8, desiliconization treatment is performed. In this way, the yield of molten steel is increased while the CaO source is reduced.

[0010] Patent document 3 proposes the following technology: using a weighing machine to determine the amount of slag discharged in the intermediate slag discharge, thereby ensuring that the amount of CaO-containing substances added in the next process is appropriate.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 10-152714

[0014] Patent Document 2: Japanese Patent Application Publication No. 2011-137196

[0015] Patent Document 3: Japanese Patent Application Publication No. 2010-126790

[0016] Non-patent literature

[0017] Non-patent literature 1: Slag Atlas 2nd edition: Verlag Stahleisen GmbH, (1995) Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] However, the above-mentioned prior art has the following problems.

[0020] As mentioned above, controlling the basicity of the slag to a specified value is effective for efficient dephosphorization. Therefore, as disclosed in Patent Documents 1 and 2, when desiliconization, intermediate slag discharge, and dephosphorization are performed continuously in a converter, in order to reduce the amount of CaO-containing substances used in the dephosphorization process and ensure that the basicity of the slag in the dephosphorization process is at a specified value, it is necessary to control the silicon concentration in the molten iron at the end of the desiliconization process to a specific range, and it is necessary to estimate the amount of slag discharged from the system during the intermediate slag discharge process. However, the amount of slag discharged in Patent Documents 1 and 2 is not clear.

[0021] Furthermore, the technology disclosed in Patent Document 3 involves more splashing of molten material onto the trolley, and requires extensive maintenance to obtain accurate weighing values. Additionally, since a sedative is sometimes added to the slag pot to quickly settle the slag after discharge, accurate values ​​are sometimes impossible to measure.

[0022] This invention was made in view of the above circumstances, and its object is to provide a converter operation method and a method for producing molten steel. The converter operation method is a method of refining molten iron to produce molten steel using a converter-type refining furnace. In this method, the amount of slag discharged and the properties of the slag can be estimated with high precision, thereby reducing the consumption of by-products used in the refining process. Specifically, this invention provides a converter operation method and a method for producing molten steel in which, during the refining process of molten iron through a refining process, an intermediate slag discharge process, and other refining processes, the amount of slag discharged and the properties of the slag discharged in the intermediate slag discharge process can be estimated simply and with high precision, thereby reducing the consumption of by-products used in subsequent refining processes.

[0023] Methods for solving problems

[0024] The inventors conducted in-depth research on these problems and found that the amount of slag discharged and the physical properties of the slag could be estimated based on the shape of the slag discharge flow, the slag discharge velocity, and the surface shape of the slag in the converter-type refining furnace during slag discharge. Based on this insight, the present invention was completed.

[0025] The first converter operation method of the present invention, which effectively solves the above problems, is a converter operation method for supplying oxygen to molten iron in a converter-type refining furnace to perform desiliconization refining, dephosphorization refining, and decarburization refining of molten iron. The method is characterized in that, when slag is discharged from the furnace mouth, one or more of the following are measured: slag discharge flow shape, slag discharge flow rate, and slag surface shape; and one or both of the following are estimated: slag discharge amount and physical properties of the slag discharge material.

[0026] The second converter operation method of the present invention, which effectively solves the above problems, is as follows: When desiliconizing, dephosphorizing, and decarburizing molten iron in a converter-type refining furnace, the following method is used: First, a refining step involving partial desiliconization of the molten iron is selected, combined with other refining steps involving dephosphorization or decarburization of the molten iron, based on the remaining portion of the desiliconization refining. Second, a refining step involving either desiliconization or dephosphorization of the molten iron, or both, is combined with dephosphorization refining of the molten iron. The method of operating the converter is characterized in that, in the above-mentioned intermediate slag discharge process, between one refining process and other refining processes, an intermediate slag discharge process is performed to discharge the slag produced in one refining process from the furnace opening. The intermediate slag discharge process is characterized in that, between one and two of the slag discharge flow shape, slag discharge flow velocity and slag surface shape, one or two of the slag discharge amount and slag material properties are estimated, and the amount of slag remaining in the above-mentioned converter-type refining furnace, or the amount of slag remaining in the above-mentioned converter-type refining furnace and slag composition, is estimated. Based on the estimation result, the amount of by-product input in any of the above-mentioned other refining processes is determined.

[0027] It should be noted that the converter operation method of the present invention is the operation method of the first or second converter described above, wherein the following are considered to be more preferred solutions:

[0028] (a) The determination of the above-mentioned slag flow shape, slag flow velocity and slag surface shape is to determine any one or more of the following: the horizontal arrival distance of the slag flow at a certain distance below the furnace mouth, the slag surface height of the furnace mouth reference in the above-mentioned converter-type refining furnace, the slag surface flow velocity at the furnace mouth position and the slag thickness at the furnace mouth position.

[0029] (b) The kinematic viscosity of the slag is approximated in advance by using a polynomial to approximate the relationship between the horizontal reach of the slag discharge flow at a certain distance below the furnace mouth and the slag surface height at the furnace mouth reference in the converter-type refining furnace, or the relationship between the slag surface height at the furnace mouth reference in the converter-type refining furnace and the slag thickness at the furnace mouth position. Then, slag discharge is carried out, and the kinematic viscosity of the slag is estimated from the measurement results of the slag discharge flow shape and the slag surface shape during slag discharge.

[0030] (c) The horizontal arrival distance L (m) of the slag discharge flow from a certain distance below the furnace opening and the slag thickness h at the furnace opening position. e(m) The slag discharge volume W(t) of the mass reference is estimated using the following mathematical formulas 1 to 3 (where W is the slag discharge volume (t) of the mass reference, t is the slag discharge time (s), ΔW / Δt is the slag discharge velocity of the mass reference (t / s), and w(h) is the width (m) of the slag discharge flow at height h). e ρ is the surface width (m) of the slag flow at the furnace opening, and ρ is the slag density (t / m³). 3 ), where v(h) is the slag velocity (m / s) at height h, v e The surface velocity of the slag at the furnace opening (m / s), h e Let be the slag thickness at the furnace opening (m), a and b be constants, H be the distance the slag flow falls (m), L be the horizontal distance the slag flow reaches at distance H (m), and g be the acceleration due to gravity (9.8 m / s²). 2 )).

[0031]

[0032]

[0033]

[0034] The steel manufacturing method of the present invention, which effectively solves the above problems, is characterized by using any of the above-mentioned converter operation methods to supply oxygen to the molten iron in the converter-type refining furnace, performing desiliconization refining, dephosphorization refining and decarburization refining of the molten iron, and performing slag discharge treatment or intermediate slag discharge treatment.

[0035] Invention Effects

[0036] According to the present invention, in the operation method of a converter for refining molten iron to produce steel by supplying an oxygen source to molten iron in a converter-type refining furnace, the amount of slag discharged and the properties of the slag can be estimated with high precision, thereby reducing the consumption of by-products used in the refining process. Particularly in the refining process of molten iron through a sequential refining process, an intermediate slag discharge process, and other refining processes, the amount of slag discharged and the properties of the slag discharged in the intermediate slag discharge process can be estimated easily and with high precision, thereby reducing the consumption of by-products used in subsequent refining processes. Furthermore, by using this converter operation method to produce molten steel, the consumption of by-products can be reduced and molten steel can be produced more efficiently. Attached Figure Description

[0037] Figure 1 This is an explanatory diagram schematically showing a general outline of an apparatus configuration suitable for carrying out the present invention, having a converter-type refining furnace.

[0038] Figure 2 This is a schematic cross-sectional view showing the shape of the above-mentioned converter-type refining furnace when tilted and slag is discharged.

[0039] Figure 3 It is Figure 2 A schematic cross-sectional view of part A after enlargement.

[0040] Figure 4 This shows the slag surface h0 and the slag thickness h at the furnace mouth position in the water model experiment. e A diagram showing the relationships between them.

[0041] Figure 5 This shows the surface velocity v at the furnace opening location in the water model experiment. e A graph showing the relationship between the estimated and measured values.

[0042] Figure 6 This is a graph showing the relationship between the estimated and measured values ​​of the slag discharge rate ΔW / Δt for the mass baseline in the water model experiment.

[0043] Figure 7 This is a graph showing the effect of kinematic viscosity ν on the relationship between the slag surface h0 and the horizontal arrival distance L of the slag discharge flow in the water model experiment.

[0044] Figure 8 This shows the kinematic viscosity ν of the slag surface h0 and the slag thickness h at the furnace mouth position in the water model experiment. e A diagram illustrating the impact of the relationship.

[0045] Figure 9 This is a graph showing the effect of kinematic viscosity ν on the relationship between slag surface h0 and the slag discharge rate Q of the volume reference in the water model experiment.

[0046] Figure 10 This is a graph showing the influence of the kinematic viscosity ν on the slag surface height h0 relative to the furnace mouth and the horizontal arrival distance L of the slag discharge flow. Detailed Implementation

[0047] The embodiments of the present invention will now be described in detail. It should be noted that the accompanying drawings are schematic and may differ from reality. Furthermore, the following embodiments are intended to illustrate apparatus and methods for embodying the technical concept of the present invention, and are not intended to limit the construction to these specific details. That is, the technical concept of the present invention can be modified in various ways within the scope of the claims.

[0048] <Experiment 1>

[0049] Before conducting actual machine experiments, the inventors used a water model approximately 1 / 10 the size of the actual machine to simulate slag, continuously draining the water and repeatedly measuring the results. Figure 3 The projects shown are studied. Figure 4The figure shows the slag surface height h0 at the furnace mouth reference and the slag thickness h at the furnace mouth location in the water model experiment. e The relationship. Here, as... Figure 3 As shown in the enlarged schematic diagram, the slag surface height h0 of the furnace mouth reference refers to the approximate horizontal liquid level height at a position that is a certain distance away from the furnace mouth 14 inside the converter-type refining furnace 2, with the lowest position of the furnace mouth 14 where the slag discharge flow 13 begins to fall as the reference. Figure 5 The same applies to surface flow velocity v. e (m / s) shows the velocity v of the slag discharge flow determined from the horizontal arrival distance L of the slag discharge flow 13. e (calc) and the surface velocity v obtained from dynamic images of the water surface through image analysis. e The relationship between (obs). Here, v e (calc) is a value derived from the following equation (3). In equation (3), H is the distance the slag flow falls (m), L is the horizontal distance the slag flow reaches at the distance H from the fall point (m), and g is the acceleration due to gravity (9.8 m / s²). 2 In this experiment, 0.1m was used as the distance H from which the slag flowed down.

[0050]

[0051] Depend on Figure 5 It can be clearly stated that the surface velocity v is estimated from the horizontal arrival distance L of the slag discharge flow (water) 13. e (calc) and the measured surface velocity v e (obs) are very consistent. Therefore, by measuring the horizontal arrival distance L of the slag flow at a certain slag flow drop distance H, the surface velocity v at the furnace mouth can be estimated. e .

[0052] Furthermore, in the same experiment, dynamic images were captured from the front of the furnace opening to measure the surface width w of the slag discharge flow (water) at the furnace opening location. e The slag discharge rate ΔW / Δt (g / s) of the mass standard was estimated using equation (2) shown below, and compared with the actual value obtained from the weight change of the slag pot 20. The result is as follows: Figure 6 In equation (2), w(h) is the horizontal width (m) of the slag discharge flow 13 at a height h at the furnace opening 14, and ρ is the density of the liquid (t / m³). 3 v(h) is the slag discharge velocity (m / s) at height h of position 14 at the furnace opening. e The surface velocity (m / s) of the slag discharge flow at the furnace mouth, h e Let be the slag thickness (m) at the furnace opening, and a and b be constants. It should be noted that w represents the surface width of the slag discharge (water) at the furnace opening. eAlternatively, the slag thickness h at the furnace opening 14 can be determined by the pre-calculated profile, the inclination angle of the converter-type refining furnace 2, and the slag thickness h at the furnace opening 14 position. e To calculate.

[0053]

[0054] Depend on Figure 6 The results show that the slag discharge rate ΔW / Δt, estimated based on the shape of the slag discharge flow, is in excellent agreement with the actual values. The slag discharge rate ΔW / Δt can be estimated by measuring the shape of the slag discharge flow. Furthermore, it is evident that by integrating the slag discharge rate with the slag discharge time as the integration domain, the slag discharge volume for a series of slag discharge processes can be estimated.

[0055] <Experiment 2>

[0056] The inventors further conducted experiments using a water model approximately 1 / 10 the size of the one used in Experiment 1, employing water, ethanol-water solutions, and various liquid paraffins with different physical properties, particularly kinematic viscosity, to simulate slag, and repeatedly measured the results in the same manner as in Experiment 1. Figure 3 The projects shown were studied. Figures 7-9 In the diagram, A represents water, B represents a 30% ethanol-water solution, and C through E represent liquid paraffins with different kinematic viscosities (ν). The kinematic viscosities at 28℃ are as follows: Water A: 0.84 mm⁻¹ 2 / s, 30% ethanol-water solution B: 2.73mm 2 / s, Liquid paraffin C: 14.2mm 2 / s, D: 22.7mm 2 / s, E: 31.6mm 2 / s.

[0057] Figure 7 This illustrates the effect of the kinematic viscosity ν of the liquid on the slag surface height h0 (based on the furnace opening 14) and the horizontal arrival distance L of the slag discharge flow 13 in a water model experiment. The horizontal arrival distance L of the slag discharge flow 13 was measured with a drop distance H of 0.1 m. Figure 7 The results clearly show that if the kinematic viscosity ν of the discharged slag (liquid) changes, the relationship between the horizontal arrival distance L of the discharged slag flow 13 and the slag surface height h0 relative to the furnace mouth 14 reference will also change.

[0058] Figure 8 The kinematic viscosity ν of the liquid in the water model experiment is shown, with the slag surface height h0 and slag thickness h at the furnace mouth reference given. e The impact of the relationship. Figure 8 The results clearly show that if the kinematic viscosity of the discharged slag (liquid) changes, the slag thickness h at the furnace mouth will increase. eThe relationship between the slag surface height h0 and the furnace mouth reference will also change.

[0059] Figure 9 This illustrates the influence of the kinematic viscosity ν of the liquid on the relationship between the slag surface height h0 (at the furnace mouth) and the slag discharge velocity Q (at the volumetric reference) in a water model experiment. Figure 9 The results clearly show that if the kinematic viscosity ν of the discharged slag (liquid) changes, the relationship between the volume-based slag discharge rate Q and the slag surface height h0 at the furnace mouth will also change.

[0060] according to Figures 7-9 The result is that as long as the slag surface height h0 at the furnace mouth reference and the slag thickness h at the furnace mouth position can be measured, e By determining the kinematic viscosity ν and discharge velocity of the slag based on any two of the horizontal distance L reached by the slag discharge flow, the kinematic viscosity ν and discharge velocity of the slag can be estimated. Furthermore, the relationship between the slag viscosity μ (=ρ·ν) and the slag basicity (CaO / SiO2) has long been known; the slag basicity can be estimated from the estimated slag viscosity and temperature. For example, by calculating the amount of SiO2 in the slag from the Si balance during desilication treatment, the amount of CaO in the slag can be estimated from the estimated slag basicity.

[0061] <Actual Equipment>

[0062] First, based on Figure 1 and 2 To illustrate the preferred configuration of the converter equipment used in implementing the present invention.

[0063] The preferred apparatus 1 for implementing the present invention includes: a converter-type refining furnace 2, a top-blown lance 3, a control computer 8, a top-blown lance height control device 9 configured to operate independently using control signals sent from the control computer 8, a top-blown lance 3 height control device 9, a top-blown lance oxidizing gas flow control device 10 for adjusting the flow rate of the oxidizing gas ejected from the top-blown lance 3, and a bottom-blown gas flow control device 11 for adjusting the flow rate of the stirring gas blown in from the bottom-blown vent 5.

[0064] The control computer 8 is configured to send control signals that allow the spray gun height control device 9, which adjusts the height of the top-blowing spray gun 3, the oxidizing gas flow control device 10, which adjusts the flow rate of the oxidizing gas ejected from the top-blowing spray gun 3, and the bottom-blowing gas flow control device 11, which adjusts the flow rate of the stirring gas blown in from the bottom-blowing air outlet 5, to operate independently or simultaneously.

[0065] In the converter operation method of this embodiment, using the aforementioned equipment 1 with a converter-type refining furnace 2, oxidizing gas is injected from the top-blown lance 3, or further oxidizing gas or inactive gas is injected from the bottom-blown tuyeres 5, thereby performing desiliconization refining, dephosphorization refining, and decarburization refining of the molten iron 6. It should be noted that the molten iron 6 contains 0.02% by mass or more of Si. A lance nozzle 4 is provided at the front end of the top-blown lance 3, and during refining, an oxidizing gas jet 12 is sprayed toward the surface of the molten iron 6.

[0066] For example, after a refining process involving desiliconization, the process is transferred to an intermediate slag removal process. The converter-type refining furnace 2 is tilted, and slag 7 is removed without discharging molten iron 6 outside the furnace (hereinafter referred to as slag removal). Figure 2 At this time, the converter-type refining furnace 2 is tilted, and multiple measuring cameras 19 for photographing the area near the furnace opening 14 of the converter-type refining furnace 2 during slag discharge are set up so as to be able to photograph the front and side of the furnace opening 14 and the falling position of the slag discharge flow 13.

[0067] During the slag removal process, at a time when the tilt angle of the converter-type refining furnace 2 has been fixed for a specified period of time, the slag surface 7 at the furnace opening 14 is inspected. Based on the tilt angle of the furnace body at that time and the outline of the furnace opening 14 under the same tilt angle as previously photographed, the slag thickness h at the furnace opening position is estimated. e The time for fixing the tilt angle can be selected from the range of 1 to 60 seconds, preferably from the range of 5 to 20 seconds. Alternatively, it can be estimated from the slag surface height h0 of the furnace mouth reference in the converter-type refining furnace 2. In addition, the horizontal arrival distance L of the slag flow 13 at the drop height H of the slag flow 13 is measured, and the surface velocity v of the slag at the furnace mouth position is estimated using the above formula (3). e The drop height H depends on the equipment configuration and can range from approximately 5m to approximately 15m. It should be noted that the high-temperature slag 7 is cooled by contact with the atmosphere, resulting in uneven temperature distribution on the surface (e.g., changes in brightness and color). Therefore, the movement of this uneven temperature distribution can be observed using a camera to determine the surface velocity of the slag discharge flow 13.

[0068] The slag thickness h at the measured or estimated furnace mouth location e (m), the surface width w of the slag discharge flow at the furnace opening e (m) and slag surface velocity v e (m / s), the slag discharge amount W(t) of the quality standard is calculated by the following equation (1) and equation (2) above. Here, constants a and b are determined in advance in a way that minimizes the deviation between the estimated value of the slag discharge amount W and the actual value measured by the weighing sensor, etc. In equation (1), t is the processing time (s) of the slag discharge process.

[0069]

[0070] Based on the slag discharge rate W estimated using the above method and the total slag amount calculated from material balance, the amount of slag remaining in converter-type refining furnace 2 is estimated. Then, the input amounts of by-products for other refining processes, such as dephosphorization refining, are determined, and dephosphorization refining is carried out. Thus, dephosphorization refining can be performed efficiently without the input of excessive CaO sources.

[0071] Furthermore, the slag surface height h0 of the slag discharge flow 13, which falls at a distance H from the slag discharge flow 13, reaches a distance L and is based on the furnace mouth reference in the converter-type refining furnace 2, is determined by a pre-made approximate curve (e.g., Figure 10 (See figure), to estimate the kinematic viscosity ν of the slag. After a separate desilication refining process, using the measured or estimated slag temperature, the slag basicity, slag composition, and especially the CaO concentration in the slag, corresponding to the estimated kinematic viscosity of the slag, are estimated. Here, Figure 10 The approximate curve shown is approximated using the following equation (4). In equation (4), α and β are constants that depend on the kinematic viscosity ν of the slag. It should be noted that as long as the kinematic viscosity ν can be specified, the relationship between any two or more of the following can be established and used: the horizontal arrival distance of the slag flow at a certain distance below the furnace mouth, the slag surface height at the furnace mouth reference in the converter-type refining furnace, the slag surface velocity at the furnace mouth position, and the slag thickness at the furnace mouth position. For example, the kinematic viscosity ν of the slag can be calculated for the slag surface height h0 at the furnace mouth reference in the converter-type refining furnace and the slag thickness h at the furnace mouth position. e The impact of the relationship.

[0072]

[0073] Based on the obtained slag properties, especially the estimated values ​​of CaO concentration and the amount of slag remaining in converter-type refining furnace 2, the input amount of by-products for other refining processes, such as dephosphorization refining, is determined, and dephosphorization refining is carried out. This allows for further, more precise reduction of the CaO source.

[0074] The above example uses top-and-bottom blowing refining as an example, but it can also be applied to top-blown refining and oxygen-bottom blowing refining. Furthermore, the slag removal process is not limited to after desiliconization refining; it can also be applied during desiliconization refining, after dephosphorization refining and before decarburization refining, and after decarburization refining. For example, by accurately controlling the amount of residual slag after dephosphorization refining, high-precision blowing calculations can be performed during decarburization refining. When the residual slag after decarburization refining is used as the precursor slag for subsequent desiliconization and dephosphorization refining processes, it can also help reduce the amount of solidification materials required.

[0075] As another embodiment of the present invention, the method for manufacturing molten steel is as follows: using the converter operation method of the above embodiment, an oxygen source is supplied to the molten iron in the converter-type refining furnace to perform desiliconization refining, dephosphorization refining, and decarburization refining of the molten iron, and slag removal treatment or intermediate slag removal treatment is performed. The quantity, properties, and composition of the slag during slag removal treatment and intermediate slag removal treatment can be estimated to improve the precision of each refining process, and it also helps to reduce by-products, enabling efficient production of molten steel.

[0076] (Example 1)

[0077] As processing No.1, using with Figure 1 and 2 The converter-type refining furnace 2 shown is a top-and-bottom blown converter (oxygen top blowing, argon bottom blowing) of the same type, with a capacity of 300 tons, used for desiliconization refining, dephosphorization refining, and decarburization refining of molten iron 6. First, after iron scrap is loaded into the converter-type refining furnace 2, 300 tons of molten iron at a temperature of 1200-1280℃ are loaded into the converter.

[0078] Next, argon gas is blown into the molten iron through the bottom tuyer 5 for stirring, while oxygen is blown into the molten iron bath surface through the top lance 3 to begin the desiliconization refining of the molten iron. It should be noted that the amount of scrap iron is adjusted to ensure that the temperature of the molten iron after dephosphorization refining is 1360℃.

[0079] In the desiliconization refining process, the basicity of the slag is set within the range of 0.8 to 1.0. After about 5 minutes, intermediate slag discharge is carried out. Then, while controlling the basicity of the slag within the range of 1.0 to 1.5, dephosphorization refining continues.

[0080] In the intermediate slag removal process, the slag thickness h at the furnace mouth is measured every 1 second. e The horizontal arrival distance L of the slag discharge flow at the drop height H is measured. The drop height H is approximately 10m. Regarding h... e And L, take the moving average of the past 5 seconds as the actual value at that moment. Then, use the above equations (1) to (3) to estimate the slag discharge amount W of the quality benchmark. It should be noted that the constants a and b on the right side of equation (2) are determined by using the weighing actual value of the intermediate slag discharge amount W over the past 10 ch to minimize the error between the estimated value and the actual value.

[0081] The amount of slag carried over to the next process, dephosphorization blowing, is estimated by subtracting the slag discharge amount W (quality basis) from the slag amount before intermediate slag discharge (quality basis). It should be noted that the slag amount before intermediate slag discharge (quality basis) is determined by summing the total amount of by-products added in the desiliconization refining process, the SiO2 generation estimated from Si in the molten iron, and the FeO generation estimated from waste gas analysis values.

[0082] (Example 2)

[0083] As for Process No. 2, the same equipment as in Example 1 was used, and under the same conditions, desiliconization refining, intermediate slag discharge, dephosphorization refining, and decarburization refining were carried out.

[0084] In the intermediate slag removal process, the slag thickness h at the furnace mouth is measured every 1 second. e The horizontal arrival distance L of the slag discharge flow at the drop height H was measured. The drop height H was set to approximately 10 m. Regarding h... e And L, take the moving average of the past 5 seconds as the actual value at that moment. Then, use the above equations (1) to (3) to estimate the slag discharge amount W of the quality benchmark. It should be noted that the constants a and b on the right side of equation (2) are determined by using the weighing actual value of the intermediate slag discharge amount W over the past 10 ch to minimize the error between the estimated value and the actual value.

[0085] In this embodiment, the slag discharge volume W, obtained as a quality benchmark, is monitored in real time while the tilt angle of the converter-type refining furnace is adjusted for intermediate slag discharge. The amount of slag introduced into the dephosphorization refining process (quality benchmark) is estimated by subtracting this amount from the slag volume before intermediate slag discharge, thereby determining the amount of CaO added in the dephosphorization refining process. It should be noted that the slag volume before intermediate slag discharge (quality benchmark) is determined by summing the total amount of by-products added in the desiliconization refining process, the SiO2 generation estimated from the molten iron Si, and the FeO generation estimated from the waste gas analysis values.

[0086] (Example 3)

[0087] As for Process No. 3, the same equipment as in Example 1 was used, and under the same conditions, desiliconization refining, intermediate slag discharge, dephosphorization refining and decarburization refining were carried out.

[0088] In the intermediate slag removal process, the slag thickness h at the furnace mouth is measured every 1 second. e The horizontal arrival distance L of the slag discharge flow at the drop height H is measured. The drop height H is approximately 10m. Regarding h... e And L, take the moving average of the past 5 seconds as the actual value at that moment. Then, use the above equations (1) to (3) to estimate the slag discharge amount W of the quality benchmark. It should be noted that the constants a and b on the right side of equation (2) are determined by using the weighing actual value of the intermediate slag discharge amount W over the past 10 ch to minimize the error between the estimated value and the actual value.

[0089] In this embodiment, the amount of slag carried into the dephosphorization refining process is estimated by subtracting the slag discharge amount W (mass reference) obtained from the slag amount (mass reference) before intermediate slag discharge. Furthermore, the influence of the kinematic viscosity of the slag on the horizontal arrival distance L of the slag discharge flow at the drop height H and the slag surface height h0 (furnace reference) within the converter-type refining furnace 2 is approximated using equation (4) above. The kinematic viscosity ν of the slag is determined using known literature, such as non-patent literature 1, based on slag composition analysis values ​​and temperature measurements.

[0090] In this ch, α and β in equation (4) are determined based on the slag flow shape measured when the tilt angle is fixed at 10s or more, in a way that makes the actual values ​​consistent with the estimated values. The obtained values ​​of α and β are compared with past slag discharge records to estimate the kinematic viscosity of the slag.

[0091] The amount of CaO dissolved and the composition of the slag are estimated based on the FeO generated from the exhaust gas analysis value, the SiO2 generated from the change in Si concentration in molten iron, the MnO generated from the change in Mn concentration in molten iron, the MgO and Al2O3 amounts estimated from the by-products fed into the desiliconization refining process, and the estimated kinematic viscosity ν of the slag.

[0092] Based on the estimated composition of the slag and the estimated amount of slag introduced into the dephosphorization refining process (mass benchmark), the amount of CaO added in the dephosphorization refining process is determined. It should be noted that the amount of slag before intermediate slag discharge (mass benchmark) is determined by summing the total amount of by-products added in the desiliconization refining process, the estimated SiO2 and MnO formation based on changes in the molten iron composition, and the estimated FeO formation based on waste gas analysis values.

[0093] (Example 4)

[0094] As for Process No. 4, the same equipment as in Example 1 was used, and under the same conditions, desiliconization refining, intermediate slag discharge, dephosphorization refining and decarburization refining were carried out.

[0095] In the intermediate slag removal process, the slag thickness h at the furnace mouth is measured every 1 second. e The horizontal arrival distance L of the slag discharge flow at the drop height H is measured. The drop height H is approximately 10m. Regarding h... e And L, take the moving average of the past 5 seconds as the actual value at that moment. Then, use the above equations (1) to (3) to estimate the slag discharge amount W of the quality benchmark. It should be noted that the constants a and b on the right side of equation (2) are determined by using the weighing actual value of the intermediate slag discharge amount W over the past 10 ch to minimize the error between the estimated value and the actual value.

[0096] In this embodiment, while monitoring the slag discharge amount W of the obtained quality benchmark in real time, the tilt angle of the converter refining furnace is adjusted to perform intermediate slag discharge. By subtracting the slag amount (quality benchmark) before intermediate slag discharge, the amount of slag brought into the dephosphorization refining (quality benchmark) is estimated, thereby determining the amount of CaO added in the dephosphorization refining. In addition, the influence of the kinematic viscosity of the slag on the horizontal arrival distance L of the slag discharge flow at the drop height H and the slag surface height h0 of the furnace mouth benchmark in the converter refining furnace 2 is approximated in the above formula (4). Among them, the kinematic viscosity ν of the slag is calculated based on the slag composition analysis value and the temperature measurement results according to known literature.

[0097] In this ch, α and β in equation (4) are determined based on the slag flow shape measured when the tilt angle is fixed at 10s or more, in a way that makes the actual values ​​consistent with the estimated values. The obtained values ​​of α and β are compared with past slag discharge records to estimate the kinematic viscosity of the slag.

[0098] The amount of CaO dissolved and the composition of the slag are estimated based on the FeO generated from the exhaust gas analysis value, the SiO2 generated from the change in Si concentration in the molten iron, the MnO generated from the change in Mn concentration in the molten iron, the MgO and Al2O3 amounts estimated from the input by-products, and the estimated kinematic viscosity ν of the slag.

[0099] Based on the estimated composition of the slag and the estimated amount of slag introduced into the dephosphorization refining process (mass benchmark), the amount of CaO added in the dephosphorization refining process is determined. It should be noted that the amount of slag before intermediate slag discharge (mass benchmark) is determined by summing the total amount of by-products added in the desiliconization refining process, the estimated SiO2 and MnO formation based on changes in the molten iron composition, and the estimated FeO formation based on waste gas analysis values.

[0100] (Comparative Example)

[0101] As Process No. 5, the same equipment as in Example 1 was used, and desilication refining, intermediate slag discharge, dephosphorization refining, and decarburization refining were performed under the same conditions. Under these conditions, the shape of the slag flow was not measured during intermediate slag discharge. Furthermore, the amount of CaO added during dephosphorization refining was determined based on past operating records.

[0102] (Summarize)

[0103] Under the operating conditions of treatments No. 1–5, each treatment was carried out for 30 ch, and the average results are shown in Table 1. The results are shown in Table 2. The average slag discharge rate is the percentage of slag discharge at the mass baseline relative to the amount of slag before intermediate slag discharge (mass baseline). The reduction in lime units is expressed by comparison with treatment No. 5. The deviation of the final phosphorus concentration [P] (mass%) in the molten iron during dephosphorization refining is expressed as standard deviation 1σ.

[0104] [Table 1]

[0105]

[0106] [Table 2]

[0107]

[0108] Compared to the comparative examples, the invention examples were able to accurately estimate the intermediate slag discharge rate each time, thereby optimizing the lime input in dephosphorization refining, keeping the lime unit at a low level, and reducing the deviation of the endpoint [P]. Furthermore, in processes No. 2 and 4, by tilting the converter-type refining furnace while monitoring the intermediate slag discharge rate in real time, the slag discharge rate was improved compared to the past. It should be noted that the total refining time in the invention examples and the comparative examples is approximately the same.

[0109] Industrial availability

[0110] According to the present invention, by measuring the shape of the slag flow, the slag flow velocity, and the slag surface shape during slag discharge, the amount of slag discharged and the composition of the slag can be estimated, thereby reducing the amount of by-products added in the next process. Regardless of the type of refining furnace, it is suitable for applications requiring control over the amount and properties of the slag remaining after slag discharge.

[0111] Symbol Explanation

[0112] 1. Equipment with a converter-type refining furnace

[0113] 2. Converter-type refining furnace

[0114] 3 Top-blowing spray gun

[0115] 4. Spray gun nozzle

[0116] 5 Bottom air outlet

[0117] 6 Molten Iron

[0118] 7. Slag

[0119] 8. Control computer

[0120] 9. Top-blowing spray gun height control device

[0121] 10 Oxidizing Gas Flow Control Device for Top-Blow Spray Gun

[0122] 11 Bottom-blown gas flow control device

[0123] 12 Oxidizing Gas Jet

[0124] 13 Slag Discharge Flow

[0125] 14. Furnace opening of converter-type container

[0126] 15. Movable fume hood

[0127] 16 Oxidizing gas supply pipe for top-blown spray gun

[0128] 17 Cooling water supply pipe for top-blowing spray gun

[0129] 18 Cooling water drain pipe for top-blown spray gun

[0130] 19. Measurement camera

[0131] 20 Slag Pot

Claims

1. A method for operating a converter, comprising supplying an oxygen source to the molten iron in a converter-type refining furnace to perform desiliconization refining, dephosphorization refining, and decarburization refining of the molten iron, characterized in that, When slag is discharged from the furnace opening, one or more of the following parameters are measured: slag flow shape, slag flow velocity, and slag surface shape. Then, one or both of the following parameters are estimated: slag discharge volume and physical properties of the slag material. The kinematic viscosity of the slag is approximated in advance by using a polynomial to approximate the relationship between the horizontal arrival distance of the slag flow at a certain distance below the furnace mouth and the slag surface height at the furnace mouth reference in the converter-type refining furnace, or the relationship between the slag surface height at the furnace mouth reference and the slag thickness at the furnace mouth position. Then, slag is discharged, and the kinematic viscosity of the slag is estimated from the measurement results of the slag flow shape and slag surface shape during slag discharge.

2. A method for operating a converter, wherein, For molten iron in a converter-type refining furnace, when supplying an oxygen source from a top-blown lance to the molten iron, or further blowing oxidizing or inactive gases from a bottom-blown tuyer to the molten iron for desiliconization, dephosphorization, and decarburization refining, the following refining methods are employed: a combination of one refining step involving a portion of the desiliconization refining and another refining step involving dephosphorization or decarburization, or a combination of either desiliconization or dephosphorization and another refining step involving either dephosphorization or decarburization; and a combination of either desiliconization or dephosphorization and a combination of either dephosphorization or decarburization and another refining step involving slag discharge from one refining step or another refining step between the refining steps. The converter operation method is characterized by the following: In the intermediate slag removal process, one or more of the following are measured: slag flow shape, slag flow velocity, and slag surface shape. One or both of the following are estimated: slag quantity and physical properties of the slag. The amount of slag remaining in the converter-type refining furnace, or the amount and composition of slag remaining in the converter-type refining furnace, are also estimated. Based on this estimation result, the amount of by-product input in any of the other refining processes is determined. The kinematic viscosity of the slag is approximated in advance by using a polynomial to approximate the relationship between the horizontal arrival distance of the slag flow at a certain distance below the furnace mouth and the slag surface height at the furnace mouth reference in the converter-type refining furnace, or the relationship between the slag surface height at the furnace mouth reference and the slag thickness at the furnace mouth position. Then, slag is discharged, and the kinematic viscosity of the slag is estimated from the measurement results of the slag flow shape and slag surface shape during slag discharge.

3. The converter operation method according to claim 1 or 2, characterized in that, In the determination of the slag flow shape, slag flow velocity and slag surface shape, one or more of the following are measured: the horizontal arrival distance of the slag flow at a certain distance below the furnace opening, the slag surface height at the furnace opening reference in the converter-type refining furnace, the slag surface velocity at the furnace opening position, and the slag thickness at the furnace opening position.

4. The converter operation method according to claim 1 or 2, characterized in that, The horizontal reach of the slag discharge flow from a certain distance below the furnace opening is L (m), and the slag thickness h at the furnace opening is also considered. e (m) The slag discharge amount W(t) based on the quality standard is estimated using the following mathematical formulas 1 to 3. Where W is the slag discharge volume (t) based on mass, t is the slag discharge time (s), ΔW / Δt is the slag discharge velocity based on mass (t / s), and w(h) is the width (m) of the slag discharge flow at height h. e ρ is the surface width (m) of the slag flow at the furnace opening, and ρ is the slag density (t / m³). 3 ), where v(h) is the slag velocity (m / s) at height h, v e The surface velocity of the slag at the furnace opening (m / s), h e Let be the slag thickness at the furnace opening (m), a and b be constants, H be the distance the slag flow falls (m), L be the horizontal distance the slag flow reaches at distance H (m), and g be the acceleration due to gravity (9.8 m / s²). 2 ).

5. The converter operation method according to claim 3, characterized in that, The horizontal reach of the slag discharge flow from a certain distance below the furnace opening is L (m), and the slag thickness h at the furnace opening is also considered. e (m) The slag discharge amount W(t) based on the quality standard is estimated using the following mathematical formulas 1 to 3. Where W is the slag discharge volume (t) based on mass, t is the slag discharge time (s), ΔW / Δt is the slag discharge velocity based on mass (t / s), and w(h) is the width (m) of the slag discharge flow at height h. e ρ is the surface width (m) of the slag flow at the furnace opening, and ρ is the slag density (t / m³). 3 ), where v(h) is the slag velocity (m / s) at height h, v e The surface velocity of the slag at the furnace opening (m / s), h e Let be the slag thickness at the furnace opening (m), a and b be constants, H be the distance the slag flow falls (m), L be the horizontal distance the slag flow reaches at distance H (m), and g be the acceleration due to gravity (9.8 m / s²). 2 ).

6. A method for manufacturing molten steel, characterized in that, Using the converter operation method according to any one of claims 1 to 5, an oxygen source is supplied to the molten iron in the converter-type refining furnace to carry out desiliconization refining, dephosphorization refining and decarburization refining of the molten iron, and slag discharge treatment or intermediate slag discharge treatment is carried out.

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