Slag mass estimation method, slag mass estimation device, refining system, auxiliary raw material addition method, molten iron refining method, and molten steel manufacturing method

Abstract

To provide a slag mass estimation method, a slag mass estimation device and a refining system which are capable of estimating the mass of slag remaining in a furnace, and a method for adding an auxiliary raw material, a method for refining molten iron and a method for producing molten steel which are capable of efficiently producing molten steel based on the estimation result of the slag mass.SOLUTION: Disclosed is a slag mass estimation method comprising: an information acquisition step for acquiring information for specifying the relationship between the physical properties of slag 2 and the sedation behavior; a physical property determination step for determining the physical properties of the slag 2 from the operating conditions of the treatment of hot metal 3; a density estimation step for estimating the sedation behavior of the slag 2 based on the information acquired in the information acquisition step and the physical properties of the slag 2 and estimating a density of the slag 2 remaining after the slag 2 has been discharged; a volume estimation step for estimating a volume of the slag 2 remaining by measuring a height of the slag 2 in the furnace 1 and a volume of the furnace body; and a mass estimation step for estimating the mass of the slag 2 remaining in the furnace 1 based on the density and the volume of the slag 2.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a method, an apparatus, and a refining system for estimating the bulk density of foamed slag that occurs during settling of foamed slag containing CO gas after blowing treatment such as desiliconization or dephosphorization in a converter, in order to estimate the settling behavior of the foamed slag during refining. The present disclosure also relates to a method for adding auxiliary materials, a method for refining molten pig iron, and a method for producing molten steel, all of which use the method for estimating the bulk density of slag. [Background technology]

[0002] In recent years, advances have been made in molten iron pretreatment technology, and various methods for pretreatment of molten iron using converter-type refining furnaces have been developed. For example, Patent Document 1 discloses a method for desiliconization, dephosphorization, and decarburization using a converter, in which the next charge of molten iron is charged into the converter without discharging the decarburization slag from the previous charge, and when the silicon (Si) content of the molten iron drops to 0.2% or less, some of the slag is discharged from the furnace, followed by dephosphorization and decarburization.

[0003] As mentioned above, in the refining process of removing slag, increasing the slag volume by foaming the slag is important for ensuring the amount of slag that can be removed. Here, slag foaming occurs when carbon monoxide (CO) generated by the reaction between carbon (C) in the molten iron and iron oxide (FeO) in the slag is trapped in the slag.

[0004] When refining is performed after the slag removal process, the amount of auxiliary materials to be added is determined based on the mass of slag remaining in the furnace. If a discrepancy occurs between the calculated mass of slag remaining in the furnace and the actual mass of slag, excessive amounts of auxiliary materials are added, resulting in increased costs or heat loss. Conversely, if too few auxiliary materials are added, components such as phosphorus are removed. Therefore, in order to minimize costs, it is necessary to accurately estimate the mass of slag remaining in the furnace after the slag removal process.

[0005] Conventionally, the estimation of the mass of slag remaining in the furnace has been performed by an operator visually checking the status of slag discharge. However, the volume of the slag changes from moment to moment due to the occurrence of slag settling during slag discharge. Therefore, it is very difficult for an operator to estimate the mass of slag remaining in the furnace. In particular, in actual operation, variations in settling behavior are likely to occur due to differences in slag composition, temperature, blowing conditions, etc. This variation in settling behavior makes it even more difficult to accurately estimate the mass of slag remaining in the furnace.

[0006] To solve this problem, methods have been proposed for estimating the mass of slag remaining in a furnace from measurement data. For example, Patent Document 2 discloses a method for estimating the mass of slag remaining in a furnace from the final tilting angle of a converter. Furthermore, Patent Document 3 proposes a method for estimating the density of slag after slag removal and the mass of slag remaining in a furnace by continuously measuring the height of the slag before slag removal. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-323420 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-308773 [Patent Document 3] International Publication No. 2020 / 129887 Summary of the Invention [Problem to be solved by the invention]

[0008] In the process of discharging slag from a converter, predicting the mass of the slag after discharging is very important for determining the amount of lime to be added as an auxiliary raw material in the next process. Conventionally, methods have been proposed, such as a method for estimating the mass of the slag remaining in the converter from the final tilting angle of the converter, as shown in Patent Document 2, and a method for estimating the density of the slag after discharging and the mass of the slag remaining in the converter from the history of the slag height before discharging, as shown in Patent Document 3.

[0009] However, the method of Patent Document 2 assumes that the bulk density of the slag is constant, making it impossible to estimate the mass of the slag during settling. Furthermore, the method of Patent Document 3 takes into account the effects of settling behavior, but requires continuous measurement of the slag height for a certain period of time for each charge. This can lead to a decrease in productivity due to the time lost in measuring the slag height.

[0010] As described above, variations in settling behavior occur under actual operating conditions. This variation in settling behavior makes it difficult to estimate the bulk density of the slag after slag removal and the mass of the slag remaining in the furnace. It is necessary to easily predict the effects of slag settling behavior based on operating conditions and improve the accuracy of estimating the mass of the slag remaining in the furnace. Furthermore, improving the accuracy of estimating the mass of the slag remaining in the furnace is necessary to reduce the amount of lime added in the next process, reduce heat loss, and prevent component loss.

[0011] An object of the present disclosure is to provide a slag mass estimation method, a slag mass estimation device, and a refining system that can estimate the mass of slag remaining in a furnace, as well as a method for adding auxiliary materials that can efficiently produce molten steel based on the estimated slag mass, a method for refining molten pig iron, and a method for producing molten steel. [Means for solving the problem]

[0012] A slag mass estimation method according to an embodiment of the present disclosure includes: A slag mass estimation method for estimating a mass of slag remaining in a furnace after slag removal from a furnace for treating molten iron, comprising: an information acquisition step of acquiring information that identifies a relationship between the physical properties of the slag and the settling behavior of the slag; a physical property determination step of determining the physical properties of the slag based on the operating conditions of the treatment of the molten iron in the furnace; a density estimation step of predicting the settling behavior of the slag based on the information acquired in the information acquisition step and the physical properties of the slag determined in the physical property determination step, and estimating the density of the slag remaining in the furnace after the slag is discharged; a volume estimation step of estimating the volume of the slag remaining in the furnace by measuring the height of the slag in the furnace and the volume of the furnace body; a mass estimation step of estimating the mass of the slag remaining in the furnace based on the density of the slag estimated in the density estimation step and the volume of the slag estimated in the volume estimation step; Includes:

[0013] A method for adding an auxiliary material according to one embodiment of the present disclosure includes a step of adding an auxiliary material to a furnace based on the mass of slag remaining in the furnace, which is estimated by performing the slag mass estimation method.

[0014] A method for refining molten iron according to one embodiment of the present disclosure includes a step of performing blowing in a furnace to which auxiliary materials have been added by carrying out the above-described method for adding auxiliary materials.

[0015] A method for producing molten steel according to an embodiment of the present disclosure includes a step of pouring molten iron, which has been treated by carrying out the above-described method for refining molten iron, from a furnace.

[0016] A slag mass estimation device according to an embodiment of the present disclosure includes a processor that executes the above-described slag mass estimation method.

[0017] A refining system according to one embodiment of the present disclosure includes the above-described slag mass estimation device and a refining device for treating molten iron. [Effects of the Invention]

[0018] According to the present disclosure, there are provided a slag mass estimation method, a slag mass estimation device, and a refining system that can estimate the mass of slag remaining in a furnace, as well as a method for adding auxiliary materials, a method for refining molten pig iron, and a method for producing molten steel that can efficiently produce molten steel based on the estimated slag mass. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a block diagram illustrating an example configuration of a refining system according to the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view showing an example of a process for foaming slag in a refining furnace. [Figure 3] FIG. 1 is a cross-sectional view showing an example of a process for removing slag from a refining furnace. [Figure 4] FIG. 1 is a cross-sectional view showing an example of the change in foam height of slag over time. [Figure 5] 1 is a graph showing an example of a change in foam height of slag over time. [Figure 6] 1 is a graph showing an example of a change in slag density over time. [Figure 7] 1 is a flowchart illustrating an example of a procedure of an information processing method according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of a refining system 100 (see FIG. 1, etc.), an estimation device 50 (see FIG. 1, etc.), and an estimation method according to the present disclosure will be described with reference to the drawings. Each drawing is a schematic and may differ from the actual product. Furthermore, the following embodiments exemplify devices or methods for embodying the technical ideas of the present disclosure, and are not intended to limit the configuration to those described below. In other words, the technical ideas of the present disclosure can be modified in various ways within the technical scope described in the claims.

[0021] According to the refining system 100, estimation device 50, and estimation method of the present disclosure, the relationship between the physical properties of slag and the settling behavior of slag is investigated in advance through preliminary experiments, etc. By predicting the settling behavior during operation based on the relationship between the physical properties of slag and the settling behavior of slag, the bulk density of slag and the mass of slag remaining in the furnace can be estimated with high accuracy.

[0022] (Configuration example of refining system 100) As shown in FIG. 1, a refining system 100 according to one embodiment includes an estimation device 50 and a refining device 40.

[0023] <Refining Device 40> As illustrated in FIG. 2, the refining apparatus 40 includes a refining furnace 1 and a top-blowing lance 42. In this embodiment, the refining furnace 1 is of a converter type. The refining furnace 1 is not limited to a converter type and may be of various other types. The refining furnace 1 is also simply referred to as a furnace. The refining apparatus 40 according to this embodiment is configured to perform desiliconization treatment on the molten pig iron 3 contained in the refining furnace 1. The refining apparatus 40 is not limited to desiliconization treatment, and may be configured to perform various other treatments such as dephosphorization treatment.

[0024] In a refining apparatus 40, a desiliconization treatment is performed on the molten pig iron 3 in a refining furnace 1. In the desiliconization treatment, an oxygen-containing gas is supplied to the molten pig iron 3 from a top-blowing lance 42. The oxygen-containing gas supplied from the top-blowing lance 42 reacts with silicon (Si) in the molten pig iron 3 to produce slag 2. The slag 2 is also called desiliconization slag. Because the density of the slag 2 is lower than the density of the molten pig iron 3, the slag 2 floats above the molten pig iron 3.

[0025] The oxygen-containing gas supplied from the top lance 42 reacts with the carbon in the molten pig iron 3 to generate carbon monoxide (CO) gas. The slag 2 becomes foamy due to the inclusion of CO gas bubbles. The apparent volume of the slag 2 increases by several times or more due to the inclusion of CO gas bubbles. This state is also called a foaming state.

[0026] As illustrated in Fig. 3, the refining apparatus 40 can discharge at least a portion of the slag 2 from the refining furnace 1 by controlling the tilting angle of the refining furnace 1 without causing the molten iron 3 to flow out of the refining furnace 1. The process of discharging the slag 2 is also called slag removal processing.

[0027] The refining apparatus 40 may further include an input device that inputs auxiliary materials into the refining furnace 1. The auxiliary materials may include, for example, lime. The input device may be configured to control the type or amount of the auxiliary materials input into the refining furnace 1.

[0028] The refining apparatus 40 may include a process computer that controls the flow rate of gas supplied from the top-blowing lance 42, the type or amount of additives introduced into the refining furnace 1, the tilting angle of the refining furnace 1, etc. The process computer may include, for example, a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The process computer may include, for example, a storage device such as a semiconductor memory or an electromagnetic recording medium. The process computer may include a communication interface for communicating with other devices such as the estimation device 50.

[0029] <Estimation device 50> The estimation device 50 estimates the mass of the slag 2 remaining in the refining furnace 1 after the slag 2 is discharged from the refining furnace 1. The estimation device 50 is also referred to as a slag mass estimation device. The estimation device 50 includes a processor 52, a memory unit 54, and an interface 56.

[0030] The processor 52 may include, for example, a CPU or a GPU in order to control and manage various functions of the estimation device 50. The processor 52 may implement the functions of the estimation device 50 by reading and executing a program stored in the storage unit 54.

[0031] The memory unit 54 stores various types of information or data used by the estimation device 50. The memory unit 54 may store, for example, a program executed by the processor 52, or data or processing results used in processing executed by the processor 52. The memory unit 54 may function as a work memory for the processor 52. The memory unit 54 may be configured to include, for example, a semiconductor memory, but is not limited to this. The memory unit 54 may be configured as, for example, an internal memory of the processor 52, or may be configured as an electromagnetic recording medium such as a hard disk drive (HDD) accessible from the processor 52. The memory unit 54 may be configured as a non-transitory readable medium. The memory unit 54 may be configured integrally with the processor 52 or may be configured separately from the processor 52.

[0032] The interface 56 may include a communication interface for communicating with other devices, such as the refining apparatus 40, via a wired or wireless connection. The communication interface may be configured to communicate with other devices via a network. The interface 56 may include an input / output port for inputting and outputting data to and from other devices. The interface 56 transmits and receives necessary data and signals to and from a process computer or a higher-level system. The interface 56 may communicate based on a wired communication standard or a wireless communication standard. For example, the wireless communication standard may include cellular phone communication standards such as 3G, 4G, and 5G. Furthermore, for example, the wireless communication standard may include IEEE 802.11, Bluetooth (registered trademark), and the like. The interface 56 may support one or more of these communication standards. The interface 56 is not limited to these examples and may communicate with other devices or input and output data based on various standards.

[0033] The interface 56 may be configured to output information acquired from the processor 52. The interface 56 may notify the user of information by outputting visual information such as text, graphics, or images, directly or via an external device. The interface 56 may include a display device or may be connected to a display device via a wired or wireless connection. The display device may include various displays such as a liquid crystal display. The interface 56 may notify the user of information by outputting auditory information such as sound, directly or via an external device. The interface 56 may include an audio output device such as a speaker or may be connected to an audio output device via a wired or wireless connection. The interface 56 may include a vibration device. The interface 56 may notify the user of information by outputting not only visual information, auditory information, or tactile information, but also information that the user can perceive with other senses, directly or via an external device.

[0034] The interface 56 may include an input device that accepts input from a user. The input device may include, for example, a keyboard or physical keys, a touch panel or touch sensor, or a pointing device such as a mouse. The input device is not limited to these examples and may include various other devices.

[0035] (Example of operation of refining system 100) Below, an example of operation in the refining system 100 of this embodiment is described, in which the estimation device 50 estimates the mass of slag 2 remaining in the refining furnace 1 after the refining device 40 discharges the slag 2 from the refining furnace 1.

[0036] <Basic procedure example for estimating the mass of slug 2> In the information acquisition step (A), the processor 52 of the estimation device 50 acquires information that identifies the relationship between the physical properties of the slag 2 and the settling behavior of the slag 2. The physical properties of the slag 2 may include, for example, the viscosity, solid fraction, or surface tension of the slag 2. The physical properties of the slag 2 may include the rate of CO gas generation that occurs along with the slag 2. The settling behavior of the slag 2 is the behavior in which the volume of the slag 2 decreases as the CO gas contained in the slag 2 is released when the slag 2 enters a foaming state. The settling behavior of the slag 2 may be identified by the relationship between the elapsed time and the volume of the slag 2 as the volume of the slag 2 decreases.

[0037] As shown in FIG. 4, the settling behavior of the slag 2 may be expressed as a change over time in the height of the slag 2 from the hearth 11 of the refining furnace 1, which has become foamed in the refining furnace 1. The height of the slag 2 to the molten metal surface 21 after blowing is represented by H1. The height of the slag 2 decreases over time. The height of the slag 2 to the molten metal surface 22 after a predetermined time has elapsed is represented by H2.

[0038] The settling behavior of slag 2 may be expressed as the relationship between the elapsed time since the end of blowing and the height of slag 2, as shown in the graph of FIG. 5, for example. In the graph of FIG. 5, the horizontal axis represents the elapsed time since the end of blowing. The vertical axis represents the height of slag 2 that has become foamed. The height of slag 2 that has become foamed is also referred to as the foam height of slag 2. The points plotted with circles (○) on the graph of FIG. 5 represent the measured values ​​of the foam height of slag 2 over time. The solid line on the graph of FIG. 5 represents a function, such as an exponential function, that approximates the measured values ​​of the foam height of slag 2.

[0039] The processor 52 may acquire data on the change in foam height over time in an actual refining furnace 1 as information specifying the relationship between the physical properties of the slag 2 and the settling behavior of the slag 2. However, it is difficult to measure the change in foam height over time in an actual refining furnace 1. Therefore, the processor 52 may acquire data acquired by conducting a preliminary experiment that reproduces the internal state of the refining furnace 1 immediately after blowing, for example, as information specifying the relationship between the physical properties of the slag 2 and the settling behavior of the slag 2. The preliminary experiment may be conducted using an aqueous solution that simulates the physical properties of the slag 2 in order to investigate the influence of the physical properties of the slag 2, such as the viscosity or solid fraction, on the settling behavior of the slag 2.

[0040] In a preliminary experiment, gas is sprayed onto an aqueous solution simulating the physical properties of slag 2. The change over time in the volume of the aqueous solution, which is foamed by the gas spray and enters a foaming state, is measured. The height of the aqueous solution in the foaming state may be measured as the volume of the aqueous solution in the foaming state. The height of the aqueous solution in the foaming state is also referred to as the foam height of the aqueous solution. The measurement results of the change over time in the foam height of the aqueous solution represent the change over time in the foam height of slag 2 when slag 2, whose physical properties are simulated by the aqueous solution, enters a foaming state in a refining furnace 1.

[0041] The physical properties of slag 2 are identified by a combination of various parameter values ​​that identify the physical properties. A preliminary experiment may be conducted using aqueous solutions that simulate each of multiple combinations of parameter values ​​that identify the physical properties of slag 2. That is, a preliminary experiment may be conducted using aqueous solutions that simulate each of slag 2 exhibiting different physical properties. Through the preliminary experiment, data on the change in foam height over time for slag 2 exhibiting different physical properties is obtained as measured values ​​of the change in foam height over time for aqueous solutions that simulate each of slag 2 exhibiting different physical properties. Processor 52 may acquire information that associates combinations of parameter values ​​that identify the physical properties of slag 2 with measured values ​​of the change in foam height over time for aqueous solutions that simulate the physical properties of slag 2, as information that identifies the relationship between the physical properties of slag 2 and the settling behavior of slag 2.

[0042] Information associating a combination of parameter values ​​specifying the physical properties of the slag 2 with measured values ​​of the change in foam height over time of an aqueous solution simulating the physical properties of the slag 2 may be prepared in advance as a database. The database may be stored in the memory unit 54 of the estimation device 50 or in an external storage device. The processor 52 may acquire information specifying the association between the physical properties of the slag 2 and the settling behavior of the slag 2 from the database.

[0043] In the physical property determination step (B), the processor 52 determines the physical properties of the slag 2 based on the operating conditions when the molten iron 3 is treated in the refining furnace 1. The operating conditions may include the amount of impurities such as silicon (Si) contained in the molten iron 3, the amount of lime added as an auxiliary material to the molten iron 3, or the estimated temperature of the slag 2. The operating conditions may include, for example, the amount of the molten iron 3 in the refining furnace 1, the carryover amount of slag 2 (the amount of slag 2 remaining after the slag 2 is deslag-depleted), an estimated value of the foaming height of the slag 2, or an estimated amount of iron oxide (FeO). The processor 52 may derive physical properties of the slag 2 that affect the settling behavior of the slag 2, such as the viscosity, solid fraction, or surface tension of the slag 2, based on a thermodynamic database or the like.

[0044] In the density estimation step (C), the processor 52 predicts the settling behavior of the slag 2 based on the information acquired in the information acquisition step (A) and the physical properties of the slag 2 determined in the physical property determination step (B), and estimates the density of the slag 2 remaining in the refining furnace 1 after the slag 2 is discharged.

[0045] Specifically, the processor 52 extracts measurement data of the change in foam height over time of an aqueous solution simulating the physical properties of slag 2 from the information acquired in the information acquisition process (A) that identifies the relationship between the physical properties of slag 2 and the settling behavior of slag 2, and acquires this as predicted data of the settling behavior of slag 2.

[0046] The processor 52 also estimates the bulk density of the slag 2 when the slag discharge is completed based on the predicted data of the settling behavior of the slag 2. The bulk density of the slag 2 increases over time as the CO gas contained in the foamed slag 2 escapes over time, reducing the foam height of the slag 2. The bulk density of the slag 2 increases over time, as shown in the graph of FIG. 6, for example. In the graph of FIG. 6, the horizontal axis represents the elapsed time after the end of blowing. The vertical axis represents the bulk density of the slag 2 at each time. The elapsed time from the end of blowing to the end of the slag discharge of the slag 2 is represented by TO. The processor 52 estimates the bulk density of the slag 2 when the elapsed time is TO in the graph of FIG. 6 as the bulk density of the slag 2 when the slag discharge is completed.

[0047] In the volume estimation step (D), the processor 52 estimates the volume of the slag 2 remaining in the refining furnace 1 by measuring the height of the slag 2 in the refining furnace 1 and the volume of the furnace body of the refining furnace 1. The processor 52 may obtain a measurement value of the height of the slag 2 when the refining furnace 1, which was tilted to discharge the slag 2, is returned to its original position. The processor 52 may estimate the volume of the slag 2 remaining in the refining furnace 1 based on the measurement value of the height of the slag 2 and the volume of the furnace body of the refining furnace 1.

[0048] In the mass estimation step (E), the processor 52 estimates the mass of the slag 2 remaining in the refining furnace 1 based on the density of the slag 2 estimated in the density estimation step (C) and the volume of the slag 2 remaining in the refining furnace 1 after slag removal estimated in the volume estimation step (D).

[0049] <<Flowchart example>> The processor 52 of the estimation device 50 may execute a slag mass estimation method including the steps of the flowchart illustrated in Fig. 7. The slag mass estimation method may be realized as a slag mass estimation program executed by the processor 52. The slag mass estimation program may be stored in a non-transitory computer-readable medium.

[0050] In an information acquisition step (A), the processor 52 acquires the results of a preliminary experiment as information identifying the relationship between the physical properties of the slag 2 and the settling behavior of the slag 2 (step S1). In a physical property determination step (B), the processor 52 derives the physical properties of the slag 2 whose mass is to be estimated (step S2). In a density estimation step (C), the processor 52 estimates the bulk density of the slag 2 after the slag 2 has been discharged from the refining furnace 1 (step S3). In a volume estimation step (D), the processor 52 estimates the volume of the slag 2 remaining in the refining furnace 1 after the slag 2 has been discharged (step S4). In a mass estimation step (E), the processor 52 estimates the mass of the slag 2 remaining in the refining furnace 1 (step S5). After executing the procedure of step S5, the processor 52 ends the execution of the procedure of the flowchart of FIG. 7.

[0051] <<Summary>> By executing the above-described example of the basic procedure, the estimation device 50 can estimate the mass of the slag 2 remaining in the refining furnace 1 after the slag 2 has been removed, without measuring the state of the slag 2 from immediately after blowing until the completion of the slag removal. Being able to estimate the mass of the slag 2 without measuring the state of the slag 2 avoids interrupting the process for measurement. As a result, work efficiency is improved.

[0052] In the refining system 100, the refining device 40 can determine the amount of auxiliary materials to be added in the next stage of refining processing based on the estimated mass of the slag 2 remaining in the refining furnace 1. By estimating the mass of the slag 2 remaining in the refining furnace 1 with high accuracy, the amount of auxiliary materials required in the next stage of processing can be estimated with high accuracy. By estimating the amount of auxiliary materials with high accuracy, the auxiliary materials do not become surplus in the refining furnace 1. In other words, the amount of auxiliary materials charged is kept appropriate. As a result, the amount of auxiliary materials charged is reduced. Furthermore, by estimating the amount of auxiliary materials with high accuracy, heat loss in the refining process is reduced. Furthermore, by estimating the amount of auxiliary materials with high accuracy, the composition of the refined molten pig iron 3 is less likely to deviate from the target. In other words, the quality of the molten pig iron 3 produced is improved.

[0053] <Example of information acquisition process> The information acquisition step (A) may include a data acquisition step (F), a mathematical formulation step (G), and a stability derivation step (H). In the data acquisition step (F), the processor 52 acquires data on the settling behavior of the slag 2, obtained by an experiment that reproduces the settling phenomenon under operation, taking into account similarity conditions of dimensionless numbers related to the physical properties of the slag 2, as information specifying the relationship between the physical properties of the slag 2 and the settling behavior of the slag 2. In the mathematical formulation step (G), the processor 52 mathematically formulates the data on the settling behavior of the slag 2 acquired in the data acquisition step (F) by function approximation. In the stability derivation step (H), the processor 52 derives the forming stability from the approximate function obtained in the mathematical formulation step (G).

[0054] Regarding the data acquisition step (F), there are no limitations on the specific method for investigating in advance the relationship between the physical properties of slag 2 and the settling behavior of slag 2. For example, the relationship between the physical properties of slag 2 and the settling behavior of slag 2 may be investigated by conducting a cold model experiment that simulates the settling behavior of slag 2 using an aqueous solution.

[0055] In order to reproduce the influence of slag properties in the cold model experiment, the Morton number Mo, which is a dimensionless number related to the stability of bubbles and is expressed by the following equation (1), or the solid fraction Φ, which is a dimensionless number that represents the influence of particle precipitation in slag 2 and is expressed by the following equation (2), is used. s The physical properties of the aqueous solution are adjusted so that at least one of them matches the physical properties of the slag 2.

[0056]

number

number

[0057] In equation (1), μ is the viscosity of the liquid [Pa·s]. g is the gravitational acceleration [m / s 2 ]. ρ is the liquid density [kg / m 3It is σ. σ is the surface tension of the liquid [N / m]. In Equation (2), V s is the solid volume [m 3 contained in the solid-liquid coexistence body. V l is the liquid volume [m 3 contained in the solid-liquid coexistence body.

[0058] The aqueous solution adjusted based on the above Equation (1) or (2) is foamed by gas blowing. The calming phenomenon is reproduced in the foamed aqueous solution after the gas generation is stopped. The time change of the foam height of the aqueous solution at this time is recorded. In this experiment, experiments may be conducted for a plurality of combinations of the values of the parameters specifying the physical properties of the slag 2 assumed in the actual machine and the value of the gas velocity blown onto the hot metal 3. By conducting experiments for a plurality of combinations, data on the calming behavior of the slag 2 under various operating conditions are acquired.

[0059] Regarding the mathematical formula process (G) and the stability derivation process (H), the function used to mathematize the calming behavior of the slag 2 (the time change of the foam height of the slag 2 when the slag 2 is calmed) is not limited. For example, an equation shown as the following Equation (3) may be used as an approximation function.

[0060]

Number

[0061] In Equation (3), v(t) is the generated gas velocity [m / s] at the time t seconds after setting the current time to 0 seconds (-∞ < t < 0). τ is the time constant [s -1 representing the forming stability. h ∞ is the height of the slag 2 when the slag 2 is completely calmed (the liquid phase height of the slag 2). Here, the generated gas velocity v(t) is known by being specified under the experimental conditions. The time change of the forming height h is measured in advance. Based on v(t) and the time change of h, the time constant τ representing the forming stability is derived.

[0062] <Operation example of the physical property determination process> The physical property determination step (B) may include an operating condition extraction step (I) and a slag physical property estimation step (J). In the operating condition extraction step (I), the processor 52 extracts the operating conditions of the refining furnace 1 from data of a process computer that controls the operation of the refining furnace 1. In the slag physical property estimation step (J), the processor 52 estimates the physical properties of the slag 2 using a thermodynamic database and the operating conditions of the refining furnace 1 extracted in the operating condition extraction step (I).

[0063] In the operating condition extraction step (I), operating conditions necessary for deriving the physical properties of slag 2 are extracted. For example, the amount of molten pig iron 3, the amount of slag 2 carried over (the amount of slag 2 remaining after slag removal), the amount of auxiliary raw materials charged, or the estimated temperature of slag 2, which are necessary for deriving the viscosity, solid fraction, and surface tension of slag 2, may be extracted. In addition, the estimated foam height or the estimated amount of iron oxide (FeO) immediately after the end of blowing, which are necessary for deriving the gas generation rate, may be extracted.

[0064] In the slag property estimation step (J), the viscosity or solid fraction of the slag 2 may be obtained from a thermodynamic database such as FactSage. The surface tension may be calculated based on Butler's model. The CO gas generation rate v(t) may be expressed, for example, as the following equation (4):

[0065]

number

[0066] In equation (4), V CO is the CO gas generation rate [m / s] just before the end of blowing. T0 is the elapsed time [s] from the end of blowing. τ CO is the decay coefficient of the CO gas generation rate after the end of blowing [s -1 ].

[0067] CO gas generation rate during operation V CO and the decay coefficient τ of CO gas generation rate after the end of blowing COIt is difficult to measure or calculate these values ​​in real time. Therefore, these values ​​may be analytically derived from past operational data. The analytically derived values ​​may then be linked to the CO gas generation rate v(t) and the estimated amount of iron oxide (FeO) by assuming a correlation.

[0068] First, the foaming height h(T0) at the CO gas generation rate v(t) assumed in equation (4) and the gas phase ratio Φ(T0), which represents the gas phase ratio contained in the foamed slag 2, are expressed by the following equations (5) and (6).

[0069]

number

number

[0070] That is, the foaming height h(t0) and gas phase ratio Φ(T0) when T0 seconds have elapsed since the end of blowing depend on the CO gas generation rate V CO , the time constant τ representing the foaming stability, and the decay coefficient τ of the CO gas generation rate after the end of blowing CO Among the variables included in equations (5) and (6), V CO is estimated based on the foam height immediately after blowing (T0 = 0 seconds). τ is known in the stability derivation step (H). Therefore, the unknown variables are Φ(T0) and τ CO The gas phase ratio Φ(T0) is estimated by the following equation (7):

[0071]

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[0072] In equation (7), ρ air is the density of air [kg / m 3 ]. ρ slag is the density of the pure solid-liquid slag [kg / m 3Here, the bulk density ρ(T0) of slag 2 when T0 seconds have elapsed since the end of blowing is estimated based on operational records. For example, the bulk density of slag 2 at the start of slag discharge is calculated by dividing the mass of slag 2 estimated from the amount of auxiliary raw materials charged by the volume of slag 2 estimated based on the tilting angle of the refining furnace 1.

[0073] Finally, the damping coefficient τ CO By carrying out this series of operations on multiple charges, the estimated amount of iron oxide (FeO) and the CO gas generation rate V CO and the damping coefficient τ CO On-line, the CO gas generation rate V corresponding to the estimated amount of iron oxide (FeO) can be calculated. CO and the damping coefficient τ CO A method of estimating the CO gas generation rate by subtracting

[0074] <Example of density estimation process> The density estimation step (C) may include a dimensionless number calculation step (K), a settling behavior allocation step (L), and a bulk density determination step (M). In the dimensionless number calculation step (K), the processor 52 calculates dimensionless numbers related to the physical properties of the slag 2 estimated in the slag physical property estimation step (J). In the settling behavior allocation step (L), the processor 52 allocates a settling behavior corresponding to the operating conditions of the refining furnace 1 based on the foaming stability derived in the stability derivation step (H) and the dimensionless number calculated in the dimensionless number calculation step (K). In the bulk density determination step (M), the processor 52 determines the bulk density of the slag 2 based on the elapsed time since the end of blowing in the refining furnace 1 and the settling behavior allocated in the settling behavior allocation step (L).

[0075] Regarding the dimensionless number calculation process (K), by substituting the physical property values ​​of slag 2 calculated in the slag physical property estimation process (J) into the above-mentioned formulas (1) and (2), Morton's number Mo and solid fraction Φ s is derived.

[0076] Regarding the settling behavior allocation process (L), Morton's number Mo and solid fraction Φ derived in the dimensionless number calculation process (K) s A time constant τ representing the forming stability corresponding to the above is assigned.

[0077] In the bulk density determination step (M), the gas phase fraction Φ(T0) of the slag 2 remaining in the refining furnace 1 after the end of slag removal (when T0 seconds have elapsed since the end of blowing) is calculated using the above-mentioned formula (6). Then, the bulk density of the slag 2 remaining in the refining furnace 1 is estimated using the following formula (8).

[0078]

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[0079] <Example of volume estimation process> The volume estimation step (D) may include a slag height measurement step (N) and a slag volume estimation step (O). In the slag height measurement step (N), the height from the hearth 11 to the melt surface 21 or 22 of the slag 2 (see FIG. 4) after the slag removal is completed is measured by, for example, a method using microwaves. In the slag volume estimation step (O), the volume V of the slag 2 remaining in the refining furnace 1 after the slag removal is completed is calculated using the following equation (9): slag is calculated.

[0080]

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[0081] In equation (9), S(h) is the cross-sectional area [m 2 ]. V metal is the volume of the injected hot metal [m 3 ].

[0082] <Example of mass estimation process> Regarding the mass estimation process (E), the slag density ρ (T0) remaining in the refining furnace 1 after the completion of slag removal calculated in the bulk density determination process (M) and the volume V of slag 2 calculated in the slag volume estimation process (O) slag Based on this, the slag mass M remaining in the refining furnace 1 is calculated using the following equation (10): slag is estimated.

[0083]

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[0084] (Example) Examples carried out by the inventors of the present disclosure are described below. In the examples, the mass of the slag 2 remaining in the refining furnace 1 is estimated from the bulk density and volume of the slag 2 after the completion of slag removal (300 seconds after the end of blowing) in the refining process of a charge (molten pig iron 3 containing impurities to be refined) specified by the following parameters: Basicity C / S: 1.8 Estimated amount of iron oxide (FeO) in slag 2: 30% Estimated slag temperature: 1400℃

[0085] To reproduce the physical properties of slag 2 under the above-mentioned operating conditions at room temperature, the inventors prepared an aqueous solution by adding glycerol and glass beads to pure water. The prepared solution was foamed by blowing gas into it, and the sedation phenomenon was reproduced by stopping the gas generation. The data obtained by measuring the change in the foam height of the aqueous solution over time are represented by the dots plotted with circles (○) in the graph in Figure 5. The curve approximating the plotted dots corresponds to the graph of Equation (3) above. Based on this approximation curve, the time constant τ was calculated to be 130 seconds.

[0086] CO gas generation rate V when the estimated amount of iron oxide (FeO) contained in slag 2 is 40% CO and the decay coefficient τ of CO gas generation rate after the end of blowing COThe value of has been estimated in advance based on the results of another charge. By substituting these values ​​and the time constant τ, which represents the foaming stability, into the above equation (5), the time history of the height of slug 2, h(T0), was obtained.

[0087] The time history of the height of slag 2, h(T0), and the above-mentioned equations (6) and (8) were used to obtain the time history of the bulk density of slag 2, ρ(T0), as shown in the graph in Figure 6. Then, by substituting the elapsed time of 300 seconds from the end of blowing to the end of slag removal into T0, the bulk density ρ(T0) of slag 2 after the end of slag removal was calculated to be 246 kg / m 3 It was estimated that.

[0088] The bulk density ρ(T0) of the slag 2 after the slag removal was estimated as described above, and the volume V of the slag 2 remaining in the refining furnace 1 after the slag removal was estimated by the microwave method. slag =20m 3 By substituting this into the above equation (10), the mass M of the slag 2 remaining in the refining furnace 1 is obtained. slag The value was calculated to be 4.9 tonnes.

[0089] Here, as a comparative example, the bulk density ρ(T0) of the slag 2 after the completion of slag removal is compared with the bulk density of the slag 2 immediately after the completion of blowing (ρ=100 kg / m 3 ) was assumed to be equal to the mass of slag 2 remaining in the refining furnace 1. The estimated value of the residual slag mass in the comparative example was 2.0 tons. On the other hand, the value of the mass of slag 2 remaining in the refining furnace 1 derived from the weighing value of the slag rolling cart to which slag 2 was discharged was 6.0 tons. In other words, the estimated value of the residual slag mass in this example is closer to the actual residual slag mass than the estimated value of the residual slag mass in the comparative example. From the above, it can be seen that the accuracy of estimating the mass of slag 2 remaining in the refining furnace 1 is improved by implementing the slag mass estimation method taking into account the settling behavior.

[0090] As described above, according to the slag mass estimation method of the present disclosure, the mass of the slag 2 remaining in the refining furnace 1 after the completion of slag removal can be estimated with high accuracy and in a simple manner.

[0091] (Other embodiments) By executing the above-described slag mass estimation method, the mass of the slag 2 remaining in the refining furnace 1 is estimated. The process computer of the refining apparatus 40 may control the amount of auxiliary material to be charged into the refining furnace 1 based on the estimated remaining slag mass. The process computer of the refining system 100 or the refining apparatus 40 may execute an auxiliary material addition method including a step of adding an auxiliary material to the refining furnace 1 based on the mass of the slag 2 remaining in the refining furnace 1.

[0092] The process computer of the refining apparatus 40 may perform blowing in the refining furnace 1 to which the auxiliary material has been added by executing the above-described method for adding the auxiliary material. The process computer of the refining system 100 or the refining apparatus 40 may perform a refining method including a step of performing blowing in the refining furnace 1 to which the auxiliary material has been added by executing the above-described method for adding the auxiliary material.

[0093] The process computer of the refining apparatus 40 may produce molten steel by pouring the molten pig iron 3 treated by executing the above-described refining method from the refining furnace 1. The process computer of the refining system 100 or the refining apparatus 40 may execute a method for producing molten steel, which includes a step of pouring the molten pig iron 3 refined by executing the above-described refining method.

[0094] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present disclosure. For example, the functions included in each component or step can be rearranged so as not to cause logical inconsistencies, and multiple components or steps can be combined or divided into one. The embodiments of the present disclosure can also be realized as a program executed by a processor included in an apparatus or a storage medium on which a program is recorded. It should be understood that these are also included within the scope of the present disclosure. [Explanation of symbols]

[0095] 100 Refining System 40 Refining equipment (1: refining furnace, 11: hearth, 2: slag, 21: slag surface immediately after blowing, 22: slag surface after a predetermined time has elapsed, 3: molten iron, 42: top blowing lance) 50 Estimation device (52: processor, 54: memory unit, 56: interface)

Claims

1. A slag mass estimation method for estimating a mass of slag remaining in a furnace after slag removal from a furnace for treating molten iron, comprising: an information acquisition step of acquiring information that identifies a relationship between the physical properties of the slag and the settling behavior of the slag; a physical property determination step of determining the physical properties of the slag based on the operating conditions of the treatment of the molten iron in the furnace; a density estimation step of predicting the settling behavior of the slag based on the information acquired in the information acquisition step and the physical properties of the slag determined in the physical property determination step, and estimating the density of the slag remaining in the furnace after the slag is discharged; a volume estimation step of measuring the height of the slag in the furnace after the slag has been removed and estimating the volume of the slag remaining in the furnace using the cross-sectional area of ​​the furnace body for each height of the furnace body; A slag mass estimation method including a mass estimation step of estimating the mass of the slag remaining in the furnace based on the density of the slag estimated in the density estimation step and the volume of the slag estimated in the volume estimation step.

2. A slag mass estimation method as described in claim 1, wherein in the volume estimation process, the height of the slag in the furnace after the slag has been discharged is measured only once.

3. A slag mass estimation method for estimating the mass of slag remaining in a furnace after slag removal from a furnace for treating molten iron, comprising: an information acquisition step of acquiring information that identifies a relationship between the physical properties of the slag and the settling behavior of the slag; a physical property determination step of determining the physical properties of the slag based on the operating conditions of the treatment of the molten iron in the furnace; a density estimation step of predicting the settling behavior of the slag based on the information acquired in the information acquisition step and the physical properties of the slag determined in the physical property determination step, and estimating the density of the slag remaining in the furnace after the slag is discharged; a volume estimation step of estimating the volume of the slag remaining in the furnace by measuring the height of the slag in the furnace and the volume of the furnace body; a mass estimation step of estimating the mass of the slag remaining in the furnace based on the density of the slag estimated in the density estimation step and the volume of the slag estimated in the volume estimation step; The information acquisition step includes a data acquisition step of acquiring data on the settling behavior of the slag, the data being obtained by an experiment that reproduces the settling phenomenon under operation, taking into account similarity conditions of dimensionless numbers related to the physical properties of the slag, as information specifying the relationship between the physical properties of the slag and the settling behavior of the slag; The density estimation step includes a mathematical formulation step of formulating data on the settling behavior of the slag acquired in the data acquisition step by function approximation, and a stability derivation step of deriving forming stability from the approximate function obtained in the mathematical formulation step. Slag mass estimation method.

4. The slag mass estimation method according to claim 3, wherein the physical property determination step includes an operating condition extraction step of extracting operating conditions of the furnace from data of a process computer that controls the operation of the furnace, and a slag physical property estimation step of estimating the physical properties of the slag using a thermodynamic database and the operating conditions of the furnace extracted in the operating condition extraction step.

5. 5. The slag mass estimation method according to claim 4, wherein the density estimation step includes a dimensionless number calculation step of calculating dimensionless numbers related to the physical properties of the slag estimated in the slag physical property estimation step, a settling behavior allocation step of allocating a settling behavior corresponding to the operating conditions of the furnace based on the foaming stability derived in the stability derivation step and the dimensionless number calculated in the dimensionless number calculation step, and a bulk density determination step of determining a bulk density of the slag based on the elapsed time since the end of blowing in the furnace and the settling behavior allocated in the settling behavior allocation step.

6. A method for adding auxiliary materials to a furnace, the method comprising: adding an auxiliary material to the furnace based on the mass of slag remaining in the furnace, the mass of slag being estimated by executing the slag mass estimation method according to any one of claims 1 to 5.

7. A method for refining molten iron, comprising the step of carrying out blowing in a furnace to which auxiliary materials have been added by carrying out the method for adding auxiliary materials according to claim 6.

8. A method for producing molten steel, comprising the step of pouring from a furnace molten iron that has been treated by carrying out the method for refining molten iron according to claim 7.

9. A slag mass estimation device comprising a processor that executes the slag mass estimation method according to any one of claims 1 to 5.

10. A refining system comprising the slag mass estimation device according to claim 9 and a refining device that processes molten iron.

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