Blast furnace control method and control device

Abstract

A blast furnace control method according to the present invention includes: a temperature distribution estimation step for estimating the temperature distribution of a blast furnace bottom section by executing heat transfer analysis using a blast furnace numerical model; a determination step for determining the risk of generation of a molten iron flow failure region at the blast furnace bottom section on the basis of 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 section; and a control step for controlling blast furnace operation conditions on the basis of the determination result in the determination step so that a molten iron flow failure region is not generated.

Description

Blast furnace control method and control device

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

[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, in addition to molten pig iron and molten slag, a coke-packed layer is present at the bottom of the blast furnace, with the molten material flowing through the voids in the coke-packed layer. However, due to factors such as the coke-packed layer and pulverized coal fines, reduced coke particle size, and insufficient furnace heat, low-permeability or solidified layers with poor permeability of the molten material (hereinafter referred to as "poor molten iron flow zones"). The formation of such poor molten iron flow zones reduces the amount of molten iron and slag tapped, leading to reduced crude steel production and blast furnace troubles due to increased molten 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 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 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.

[0004] Japanese Patent Application Laid-Open No. 10-273708 Japanese Patent No. 6947343 Japanese Patent Application Laid-Open No. 2005-272873

[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 generated by the coke-packed layer powder. Furthermore, since 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 air 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 also changes from moment to moment due to heat removal by the furnace wall and the fine phase. Therefore, 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, but 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 or weakness of the cooling capacity and the ambient temperature outside the blast furnace. Therefore, 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.

[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.

[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.

[0011] FIG. 1 is a block diagram showing the configuration of a blast furnace control device according to one embodiment of the present invention. FIG. 2 is a flowchart showing the flow of a blast furnace control process according to one embodiment of the present invention. FIG. 3 is a diagram showing an example of the configuration of a numerical model of a blast furnace. FIG. 4 is a diagram for explaining a method for estimating a molten iron flow poor area using a heat transfer poor index. FIG. 5 is a diagram showing changes in heat transfer coefficient in an example. FIG. 6 is a diagram showing calculation results of the heat transfer poor index in an example. FIG. 7 is a diagram showing changes in iron production rate in an example.

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

[0013] [Configuration] 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 an arithmetic processing device such as a CPU in the information processing device executing 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 suppress the generation of a poor molten iron 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] Fig. 2 is a flowchart showing the flow of the blast furnace control processing 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 processing 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 numerically models 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 models the region below the tuyere of the blast furnace 2, including hearth residues such as the solidified layer of pig iron remaining at the hearth, the coke packed layer, and molten pig iron slag present in the voids in the coke packed layer, as well as the steel shell structure and refractories of the furnace body. Furthermore, a mesh structure for numerical calculations is generated within the numerical model of the blast furnace 2. Furthermore, 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, etc., previously set by the operator. 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 formula (1) for each calculation region (rectangular region formed by generating a mesh structure) in the numerical model of the blast furnace 2, thereby estimating the temperature distribution in the region of the modeled blast furnace 2. Note that in formula (1), C ｐ is the specific heat of the calculation area (J / (kg K)), 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), ΔV is the unit volume of the calculation target area (m ３ ) is shown. Furthermore, by calculating the formula (1), the temperature distribution in 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]

[0021] In the process of step S4, the blast furnace control device 1 calculates a 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. ｏｂｓ is the temperature measurement value of the thermocouple 2a, T ｃａｌ indicates the temperature estimated by the numerical model at a position close to the installation position of thermocouple 2a. The temperature estimated by the numerical model is obtained under the assumption that there is no brick erosion at the bottom of the blast furnace and that there are no layers, such as low-permeability layers or solidified layers, that inhibit heat transfer due to the molten iron and slag flow. Therefore, the temperature estimated value is unique for the set heat transfer boundary conditions, but the measurement value of thermocouple 2a changes due to brick erosion and the formation and disappearance of layers that inhibit heat transfer. Therefore, the risk of the formation of a poor molten iron flow area at the bottom of the blast furnace can be determined from the value of the poor heat transfer index ΔT. 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 increases, and the value of the poor heat transfer index ΔT becomes large. 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 decreases, and the value of the poor heat transfer index ΔT becomes small. 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]

[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 blast furnace control process ends.

[0024] As is clear from the above description, in the blast furnace control process according to one embodiment of the present invention, the blast furnace control device 1 first 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. The blast furnace control device 1 then 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.

[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 material 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 ２The 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 taken into consideration. The heat transfer coefficient was calculated from the actual value of the tapping rate and the cross-sectional area of ​​the hearth, assuming that molten iron at 1500°C flows in the area below the tuyere. The actual heat transfer coefficient is shown in Figure 5. This allows for the reproduction of heat transfer resulting from the molten iron and slag flow caused by tapping of molten iron heated to 1500°C in the tuyere. Next, a heat transfer analysis was performed for 48 days. 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]

[0027] After the calculations were completed, the heat transfer index ΔT was calculated by focusing on the four thermocouples located closest to the tapholes and using the measured temperatures and the calculated temperatures at the output points closest to each thermocouple. The calculation 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 days of operation. This was due to a sudden decrease in heat transfer caused by the blast stoppage during this period. Meanwhile, a general decrease in the heat transfer index ΔT was also observed from the 40th to 48th days of operation, with the steepest decrease at taphole 1. In fact, poor tapping 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 inside 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 onwards to resolve the poor heat transfer at the bottom of the blast furnace. The change in the amount of hot metal produced over that time is shown in Figure 7. As shown in Figure 7, the amount of hot metal produced increased again as the coke rate increased, confirming that deadman deactivation was avoided. From the above, it was confirmed that the generation of poor hot metal flow areas can be suppressed by controlling the operating conditions of the 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.

[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.

[0030] 1 Blast furnace control device 2 Blast furnace 2a Thermocouple

Claims

1. A method for controlling a blast furnace, comprising: 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 determining a generation risk of a hot metal flow failure region at the bottom of the blast furnace based on a difference value between the temperature distribution estimated in the temperature distribution estimation step and a measured value of the temperature at the bottom of the blast furnace; and a control step of controlling the operating conditions of the blast furnace so that the hot metal flow failure region is not generated based on the determination result in the determination step.

2. The method for controlling a blast furnace 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 the outside air around the blast furnace and heat transfer from the cooling water flowing through the pipes of the blast furnace.

3. A control device for a blast furnace, comprising: 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 determining a generation risk of a hot metal flow failure region at the bottom of the blast furnace based on a difference value between the temperature distribution estimated by the temperature distribution estimation means and a measured value of the temperature at the bottom of the blast furnace; and a control means for controlling the operating conditions of the blast furnace so that the hot metal flow failure region is not generated based on the determination result of the determination means.

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