Blast furnace control method and control device

Abstract

The blast furnace control method of the present invention includes a temperature distribution estimation step of estimating the temperature distribution at the bottom of the blast furnace by performing heat transfer analysis using a numerical model of the blast furnace, a determination step of determining the risk of generation of a poor molten iron flow area at the bottom of the blast furnace based on the difference between the temperature distribution estimated in the temperature distribution estimation step and the actual measured temperature value at the bottom of the blast furnace, and a control step of controlling the operating conditions of the blast furnace so that a poor molten iron flow area is not generated based on the determination result in the determination step.

Description

[Technical Field]

[0001] The present invention relates to a method and a control device for a blast furnace. [Background technology]

[0002] In steelmaking using a blast furnace, hot gas is blown into the furnace through a blast tuyer at the bottom, heating and reacting raw materials such as iron ore and coke to produce pig iron. The resulting pig iron, along with slag, melts and accumulates as a liquid at the bottom of the blast furnace and is periodically discharged from the furnace through a taphole. Generally, a coke-packed layer is present at the bottom of the blast furnace in addition to the molten pig iron and molten slag, and the molten material flows through the voids in the coke-packed layer. However, due to factors such as the coke-packed layer and pulverized coal fines, a decrease in coke particle size, and insufficient furnace heat, a low-permeability layer or solidified layer with poor permeability of the molten material (hereinafter referred to as a "poor molten pig iron flow zone") can form. The formation of such a poor molten pig iron flow zone reduces the amount of pig iron and slag tapped, which can lead to reduced crude steel production and blast furnace trouble due to increased molten pig iron and slag production, resulting in reduced profits. Therefore, a technology is needed to quickly detect areas of poor molten iron flow and quickly implement operational actions to improve the permeability of the molten metal.

[0003] In light of this background, Patent Document 1 describes a method for estimating the thickness of the refractory present at the bottom of a blast furnace and the solidified material layer adhering to its inner surface by heat transfer analysis using the results of measurements from thermocouples installed at the bottom of the blast furnace. Patent Document 2 also proposes a method for estimating the formation and disappearance of a solidified layer from the amount of heat supplied to the molten iron at the bottom of the blast furnace and the amount of heat of the molten iron being tapped. Patent Document 3 also proposes a method for diagnosing the inert state of the bottom of a blast furnace from the temperatures measured by thermocouples embedded in the center of the bottom plate of the blast furnace and in the lower part of the hearth side wall near each tap hole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-273708 [Patent Document 2] Patent No. 6947343 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-272873 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while the method described in Patent Document 1 can estimate the degree of refractory erosion and the thickness of the solidified layer attached to the refractory, it cannot detect a low-permeability layer formed due to the coke powder in the packed bed. Furthermore, because the detectable solidified layer is limited to that attached to the refractory, it cannot estimate the inert state of the deadman (a state in which the gas permeability and permeability of the molten material are reduced). Meanwhile, the amount of heat supplied to the molten pig iron is determined by unknown variables such as the combustibility of the coke and pulverized coal and the temperature of the deadman coke, and it also changes from moment to moment due to heat removal by the furnace wall and the fine phase. For this reason, it is difficult to accurately detect the solidified layer using an estimation method based solely on the thermal energy balance, such as the method described in Patent Document 2. Furthermore, the method described in Patent Document 3 directly uses the temperature measured at the bottom plate of the blast furnace. However, the temperature at the bottom of the blast furnace varies significantly not only depending on the inert state inside the blast furnace but also on the strength of the cooling capacity and the ambient temperature outside the blast furnace. For this reason, it is difficult to accurately diagnose the inert state of the bottom of the blast furnace using the method described in Patent Document 3.

[0006] The present invention has been made to solve the above-mentioned problems, and its object is to provide a blast furnace control method and control device that can accurately determine the risk of a poor molten iron flow area being generated at the bottom of the blast furnace and prevent the generation of the poor molten iron flow area. [Means for solving the problem]

[0007] The blast furnace control method of the present invention includes a temperature distribution estimation step of estimating the temperature distribution at the bottom of the blast furnace by performing heat transfer analysis using a numerical model of the blast furnace, a determination step of determining the risk of generation of a poor molten iron flow area at the bottom of the blast furnace based on the difference between the temperature distribution estimated in the temperature distribution estimation step and the actual measured temperature value at the bottom of the blast furnace, and a control step of controlling the operating conditions of the blast furnace so that the poor molten iron flow area is not generated based on the determination result in the determination step.

[0008] The temperature distribution estimation step may include a step of estimating the temperature distribution at the bottom of the blast furnace in consideration of heat transfer from the outside air around the blast furnace and heat transfer from cooling water circulating in the piping of the blast furnace.

[0009] The blast furnace control device of the present invention comprises a temperature distribution estimation means for estimating the temperature distribution at the bottom of the blast furnace by performing heat transfer analysis using a numerical model of the blast furnace, a determination means for determining the risk of the formation of a poor molten iron flow area at the bottom of the blast furnace based on the difference between the temperature distribution estimated by the temperature distribution estimation means and the actual measured temperature value at the bottom of the blast furnace, and a control means for controlling the operating conditions of the blast furnace so that the poor molten iron flow area is not formed based on the determination result of the determination means. [Effects of the Invention]

[0010] According to the blast furnace control method and control device of the present invention, the risk of a poor molten iron flow region occurring at the bottom of the blast furnace can be accurately determined, and the occurrence of a poor molten iron flow region can be suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of a blast furnace control device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the flow of a blast furnace control process according to one embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of the configuration of a numerical model of a blast furnace. [Figure 4]FIG. 4 is a diagram for explaining a method for estimating a poor molten iron flow region using a poor heat transfer index. [Figure 5] FIG. 5 is a diagram showing the change in heat transfer coefficient in the examples. [Figure 6] FIG. 6 is a diagram showing the calculation results of the poor transmission index in the examples. [Figure 7] FIG. 7 is a diagram showing the transition of the amount of pig iron produced in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a blast furnace control device according to one embodiment of the present invention will be described with reference to the drawings.

[0013] 〔composition〕 First, with reference to FIG. 1, the configuration of a blast furnace control device according to one embodiment of the present invention will be described.

[0014] Fig. 1 is a block diagram showing the configuration of a blast furnace control device according to one embodiment of the present invention. As shown in Fig. 1, the blast furnace control device 1 according to one embodiment of the present invention is configured by an information processing device such as a computer. The blast furnace control device 1 controls the operating state of a blast furnace 2 by having an arithmetic processing device such as a CPU in the information processing device execute a computer program. In this embodiment, a plurality of thermocouples 2a are installed on the sidewall bricks and hearth bricks of the blast furnace 2, including those around the taphole, and each thermocouple 2a inputs an electric signal indicating the temperature of the blast furnace 2 at the installation position to the blast furnace control device 1.

[0015] The blast furnace control device 1 having such a configuration executes the blast furnace control process described below to prevent the generation of a poor molten metal flow region at the bottom of the blast furnace 2. Hereinafter, with reference to Fig. 2, the operation of the blast furnace control device 1 when executing the blast furnace control process will be described.

[0016] [Blast furnace control processing] 2 is a flowchart showing the flow of the blast furnace control process according to one embodiment of the present invention. The flowchart shown in FIG. 2 starts when the operation of the blast furnace 2 starts, and the blast furnace control process proceeds to step S1.

[0017] In the process of step S1, the blast furnace control device 1 constructs a numerical model of the blast furnace 2 for numerically calculating the temperature distribution in the blast furnace 2. The numerical model of the blast furnace 2 is a numerical model of the size, shape, and material of the blast furnace 2, and can be generated from CAD data of the blast furnace 2 using publicly known technology. In this embodiment, as shown in FIGS. 3(a) to 3(c), the numerical model of the blast furnace 2 is a model of the region below the tuyere of the blast furnace 2, including hearth residues such as a solidified layer of pig iron remaining at the hearth, a coke packed layer, and molten pig iron slag present in voids in the coke packed layer, as well as the steel shell structure and refractories of the furnace body. In addition, a mesh structure for numerical calculations is generated within the numerical model of the blast furnace 2. In addition, the material of the blast furnace 2 is set to have temperature dependency in order to accurately perform the heat transfer analysis described below. This completes the process of step S1, and the blast furnace control process proceeds to the process of step S2.

[0018] In the processing of step S2, the blast furnace control device 1 sets boundary conditions for heat transfer in the numerical model of the blast furnace 2 according to the specifications and current operating state of the blast furnace 2, based on information preset by the operator, etc. Here, the boundary conditions for heat transfer include the cooling capacity of the blast furnace 2 and heat transfer from the molten metal and slag in the blast furnace 2. Specific examples of the cooling capacity of the blast furnace 2 include heat transfer from the outside air on the steel shell surface of the blast furnace wall, heat transfer from cooling water flowing through the cooling stave piping, and heat transfer from cooling water flowing through the hearth refractory piping. On the other hand, specific examples of heat transfer from the molten metal and slag in the blast furnace 2 include heat transfer from the flow of molten metal and slag in the blast furnace 2 due to tapping, and contact heat transfer due to the dripping of molten metal and slag heated in the tuyere. This completes the processing of step S2, and the blast furnace control processing proceeds to processing of step S3.

[0019] In the process of step S3, the blast furnace control device 1 executes a heat transfer analysis to calculate the following mathematical formula (1) for each calculation domain (rectangular domain formed by generating a mesh structure) in the numerical model of the blast furnace 2, thereby estimating the temperature distribution in the modeled domain of the blast furnace 2. Note that in the mathematical formula (1), C p is the specific heat of the calculation area (J / (kg K)), and ρ is the density of the calculation area (kg / m 3 ), T is temperature (K), t is time (s), λ is the thermal conductivity of the calculation target area (W / (m K)), Q is the amount of heat transferred to the calculation target area (J), and ΔV is the unit volume of the calculation target area (m 3 ) is shown. Furthermore, by calculating the formula (1), the temperature distribution within the region of the modeled blast furnace 2 can be estimated. However, since the blast furnace 2 during operation is not necessarily in an equilibrium state, it is preferable to calculate the formula (1) in a non-steady state. This completes the processing of step S3, and the blast furnace control processing proceeds to the processing of step S4.

[0020]

number

[0021] In the process of step S4, the blast furnace control device 1 calculates the heat transfer failure index ΔT (°C) shown in the following formula (2) for each thermocouple 2a using the temperature distribution of the blast furnace 2 estimated in the process of step S3 and the temperature of the blast furnace 2 measured by each thermocouple 2a. Note that in formula (2), T obs is the temperature measurement of thermocouple 2a, T calindicates the temperature estimated by the numerical model at a location near the location of thermocouple 2a. The temperature estimated by the numerical model is obtained assuming no brick erosion at the bottom of the blast furnace and no layers that would impede heat transfer due to the molten iron / slag flow, such as low-permeability layers or solidified layers. Therefore, the temperature estimate is unique for the specified heat transfer boundary conditions, but the measurement value of thermocouple 2a changes due to brick erosion and the formation and disappearance of layers that impede heat transfer. Therefore, the value of the poor heat transfer index ΔT can be used to determine the risk of the formation of a poor molten iron flow area at the bottom of the blast furnace. Specifically, if the risk of the formation of a poor molten iron flow area at the bottom of the blast furnace is low, the measurement value of thermocouple 2a will increase, resulting in a large value of the poor heat transfer index ΔT. On the other hand, if the risk of the formation of a poor molten iron flow area at the bottom of the blast furnace is high, the measurement value of thermocouple 2a will decrease, resulting in a small value of the poor heat transfer index ΔT. Therefore, as shown in Figure 4, the area where a poor molten iron flow area is formed can be estimated from the value of the poor heat transfer index ΔT. This completes the process of step S4, and the blast furnace control process proceeds to the process of step S5.

[0022]

number

[0023] In the process of step S5, the blast furnace control device 1 determines the risk of the formation of a poor molten iron flow region at the installation position of each thermocouple 2a based on the poor heat transfer index ΔT calculated in the process of step S4. Specifically, if the value of the poor heat transfer index ΔT is equal to or less than a predetermined threshold (e.g., 10°C) set according to the operating status of the blast furnace 2, the blast furnace control device 1 determines that there is a high possibility that a poor molten iron flow region has formed at the installation position of the thermocouple 2a. Note that the threshold may be set for all poor heat transfer indexes ΔT calculated from the measurements of the thermocouples 2a, or may be set for the poor heat transfer index ΔT calculated from the average of the measurements of the thermocouples 2a set around the taphole. Then, if there is a region with a high risk of the formation of a poor molten iron flow region, the blast furnace control device 1 controls the operating conditions of the blast furnace 2, such as the coke rate, so as to prevent the formation of a poor molten iron flow region. This completes the process of step S5, and the series of blast furnace control processes ends.

[0024] As is clear from the above description, in the blast furnace control process according to one embodiment of the present invention, first, the blast furnace control device 1 estimates the temperature distribution at the bottom of the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace 2. Then, the blast furnace control device 1 determines the risk of a poor molten iron flow region at the bottom of the blast furnace based on the difference between the estimated temperature distribution and the actual measured temperature at the bottom of the blast furnace, and controls the operating conditions of the blast furnace based on the determination result so as to prevent the formation of a poor molten iron flow region. This makes it possible to accurately determine the risk of a poor molten iron flow region at the bottom of the blast furnace and prevent the formation of a poor molten iron flow region. [Example]

[0025] In this example, approximately 5000 m 3 This technology was applied to a large blast furnace with four tap holes in a single class. First, a numerical model of the blast furnace was constructed based on the size, shape, and materials of the target blast furnace. Next, the specific heat, thermal conductivity, and density of each material were input to create a numerical model of the blast furnace. Next, the boundary conditions for heat transfer were set. In the target blast furnace, pipes for circulating cooling water are laid out on the hearth base. To simulate this, the heat transfer coefficient of the hearth base was set to 30.6 W / m 2 The temperature was set to 100°C, and the cooling water temperature was set to 50°C. Regarding heat transfer from the molten iron and slag in the blast furnace, heat transfer from the molten iron flow at the hearth caused by tapping was considered. We assumed that molten iron at 1500°C flows in the area below the tuyere, and calculated the heat transfer coefficient from the actual tapping rate and the cross-sectional area of the hearth. Figure 5 shows the actual heat transfer coefficient. This allows us to reproduce the heat transfer caused by the molten iron and slag flow caused by tapping of the molten iron heated to 1500°C in the tuyere. Next, a heat transfer analysis was performed over a 48-day period. In this example, a threshold value was set for the heat transfer defect index ΔT, and the blast furnace was operated so that the heat transfer defect index ΔT satisfied the condition shown in Equation (3) below.

[0026]

number

[0027] After the calculations were completed, the heat transfer index ΔT was calculated by focusing on the four thermocouples located closest to the tapholes. The measured temperatures and the calculated temperatures at the output points closest to each thermocouple were used to calculate the heat transfer index ΔT. The results are shown in Figure 6. As shown in Figure 6, the heat transfer index ΔT for all tapholes dropped sharply from the 27th to 30th day of operation. This was due to a sudden decrease in heat transfer caused by the blast furnace being shut down during this period. Meanwhile, a general decrease in the heat transfer index ΔT was also observed from the 40th to 48th day of operation, with the steepest decrease at taphole 1. In fact, tapping failure occurred at taphole 1 on the 48th day of operation, which may have been due to poor molten iron flow areas, such as a low permeability layer or solidification layer, occurring near taphole 1 within the blast furnace. Based on this, in order to satisfy the condition shown in Equation (3), the coke rate was increased from the 48th day onward to resolve the heat transfer problem at the bottom of the blast furnace. The change in productivity over time is shown in Figure 7. As shown in Figure 7, productivity increased again as the coke rate increased, confirming that deadman inactivation had been avoided. From the above, it was confirmed that the formation of poor molten iron flow areas can be suppressed by controlling the operating conditions of blast furnace 2, such as the coke rate, based on the poor heat transfer index ΔT.

[0028] Although the present invention has been described above as an embodiment applying the invention made by the present inventors, the present invention is not limited to the description and drawings that form part of the disclosure of the present invention according to this embodiment. For example, in a blast furnace in which the combustion state varies greatly from one tuyere to another and the temperature rise conditions of the deadman and molten iron vary circumferentially, the combustibility estimated for each tuyere may be input into a numerical model, and the difference in combustibility for each tuyere may be reflected in the temperature rise conditions for heat transfer analysis. In this way, all other embodiments, examples, operational techniques, etc. made by those skilled in the art based on this embodiment are included in the scope of the present invention. [Industrial Applicability]

[0029] According to the present invention, it is possible to provide a blast furnace control method and control device that can accurately determine the risk of a poor molten iron flow area being generated at the bottom of the blast furnace and prevent the generation of a poor molten iron flow area. [Explanation of symbols]

[0030] 1 Blast furnace control device 2 blast furnace 2a thermocouple

Claims

1. a temperature distribution estimation step of estimating a temperature distribution at the bottom of the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace; a determination step of calculating a difference value between the temperature distribution estimated in the temperature distribution estimation step and an actual measurement value of the temperature of the blast furnace bottom, and determining that there is a high risk of a poor molten iron flow region occurring at the blast furnace bottom when the difference value is equal to or less than a predetermined threshold value; a control step of controlling the operating conditions of the blast furnace based on the determination result in the determination step so that the poor molten iron flow region is not generated; A method for controlling a blast furnace, including:

2. 2. The blast furnace control method according to claim 1, wherein the temperature distribution estimation step includes a step of estimating the temperature distribution at the bottom of the blast furnace in consideration of heat transfer from outside air around the blast furnace and heat transfer from cooling water circulating in piping of the blast furnace.

3. a temperature distribution estimation means for estimating a temperature distribution at the bottom of the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace; a determination means for calculating a difference between the temperature distribution estimated by the temperature distribution estimation means and an actual measurement value of the temperature at the bottom of the blast furnace, and determining that there is a high risk of a poor molten iron flow region at the bottom of the blast furnace when the difference is equal to or less than a predetermined threshold value; a control means for controlling the operating conditions of the blast furnace based on the determination result of the determination means so that the poor molten iron flow region is not generated; A blast furnace control device comprising:

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