WO2025150235A1 - Blast furnace control method and control device - Google Patents

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

The present invention relates to a method and device for controlling a blast furnace.

In the steelmaking process using a blast furnace, hot gas is blown in from the blast tuyeres at the bottom of the blast furnace to heat and react raw materials such as iron ore and coke, producing pig iron. The pig iron produced melts together with slag and accumulates as a liquid phase at the bottom of the blast furnace, and is periodically discharged outside the furnace through a tap hole. Generally, in addition to molten iron and molten slag, a coke-packed layer is present at the bottom of the blast furnace, and the molten material flows between the gaps in the coke-packed layer. However, due to factors such as the coke-packed layer and powder derived from pulverized coal generated at the bottom of the blast furnace, a decrease in coke particle size, and insufficient furnace heat, a low-permeability layer or solidified layer area with poor permeability of the molten material (hereinafter referred to as a molten iron flow poor area) may be formed. When such a molten iron flow poor area is formed, the amount of molten iron and slag tapped decreases, which causes blast furnace troubles due to a decrease in crude steel production and an increase in the amount of molten iron and slag, leading to reduced profits. For this reason, 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.

In light of this background, Patent Document 1 describes a method for estimating the thickness of the refractory material present at the bottom of a blast furnace and the solidified layer of contents adhering to its inner surface through heat transfer analysis using the measurement results of a thermocouple 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 inactive state of the bottom of a blast furnace from the measured temperatures of thermocouples embedded in the center of the bottom plate of the blast furnace and in the lower part near each tapping hole in the hearth side wall.

Japanese Patent Application Publication No. 10-273708 Patent No. 6947343 JP 2005-272873 A

However, according to the method described in Patent Document 1, although it is possible to estimate the degree of erosion of the refractory and the thickness of the solidified layer attached to the refractory, it is not possible to detect the low-permeability layer generated due to the powder of the coke packed bed. In addition, since the solidified layer that can be detected is limited to that attached to the refractory, it is not possible to estimate the inactive state of the furnace core (a state in which the air permeability and liquid permeability of the molten material are reduced). On the other hand, the amount of heat supplied to the molten pig iron is determined by unknown quantities such as the combustibility of the coke and pulverized coal and the temperature of the furnace core coke, and also changes from moment to moment due to heat extraction by the furnace wall and the powder phase. For this reason, it is difficult to accurately detect the solidified layer with an estimation method based only on the thermal energy balance such as the method described in Patent Document 2. In addition, the method described in Patent Document 3 uses the temperature measured at the bottom plate of the blast furnace as it is, but the temperature of the bottom of the blast furnace varies greatly not only depending on the inactive state inside the blast furnace but also on the strength or weakness of the cooling capacity and the outside air temperature of the blast furnace. For this reason, it is difficult to accurately diagnose the inactive state of the bottom of the blast furnace with the method described in Patent Document 3.

The present invention has been made to solve the above problems, and its purpose is to provide a blast furnace control method and control device that can accurately determine the risk of a poor molten iron flow area forming at the bottom of the blast furnace and prevent the formation of a poor molten iron flow area.

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 a heat transfer analysis using a numerical model of the blast furnace, a determination step of determining the risk of the 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.

The temperature distribution estimation step may include a step of estimating the temperature distribution at the bottom of the blast furnace, taking into account heat transfer from the outside air around the blast furnace and heat transfer from the cooling water flowing through the piping of the blast furnace.

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 a 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.

The blast furnace control method and control device of the present invention can accurately determine the risk of a poor molten iron flow area occurring at the bottom of the blast furnace, and can prevent the poor molten iron flow area from occurring.

FIG. 1 is a block diagram showing the configuration of a blast furnace control device according to an embodiment of the present invention. FIG. 2 is a flowchart showing a flow of a blast furnace control process according to an 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 region using a heat transfer poor index. FIG. 5 is a diagram showing the change in heat transfer coefficient in the examples. FIG. 6 is a diagram showing the calculation results of the poor transmission index in the examples. FIG. 7 is a diagram showing the progress of the amount of pig iron produced in the examples.

Below, we will explain one embodiment of the blast furnace control device with reference to the drawings.

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

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 with an information processing device such as a computer. The blast furnace control device 1 controls the operating state of the blast furnace 2 by executing a computer program with an arithmetic processing device such as a CPU in the information processing device. In this embodiment, multiple thermocouples 2a are installed on the sidewall bricks and hearth bricks of the blast furnace 2, including around the tapping hole, 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.

The blast furnace control device 1 having such a configuration executes the blast furnace control process described below to prevent the formation of a poor molten iron flow area at the bottom of the blast furnace 2. Below, the operation of the blast furnace control device 1 when executing the blast furnace control process will be described with reference to FIG. 2.

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

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 of 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, the numerical model of the blast furnace 2 is a model of the region below the tuyere of the blast furnace 2, including the solidified layer of pig iron remaining at the hearth, the coke packed layer, the hearth residue such as molten pig iron slag present in the gaps in the coke packed layer, and the iron shell structure and refractories of the furnace body, as shown in Figures 3(a) to (c). In addition, a mesh structure for numerical calculation 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 perform the heat transfer analysis described later with high accuracy. This completes the process of step S1, and the blast furnace control process proceeds to the process of step S2.

In the process of step S2, the blast furnace control device 1 sets the boundary conditions of 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 previously set by the operator. Here, the boundary conditions of heat transfer include the cooling capacity of the blast furnace 2 and the 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 surface of the steel shell of the blast furnace wall, heat transfer from the cooling water flowing in the cooling stave piping, and heat transfer from the cooling water flowing in 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 from the dripping of molten metal and slag heated in the tuyere. This completes the process of step S2, and the blast furnace control process proceeds to the process of step S3.

In the process of step S3, the blast furnace control device 1 estimates the temperature distribution in the region of the modeled blast furnace 2 by performing a heat transfer analysis to calculate the following mathematical formula (1) for each calculation region (rectangular region formed by generating a mesh structure) in the numerical model of the blast furnace 2. In addition, in the mathematical formula (1), C _p is the specific heat (J/(kg·K)) of the calculation target region, ρ is the density (kg/m ³ ) of the calculation target region, T is the temperature (K), t is the time (s), λ is the thermal conductivity (W/(m·K)) of the calculation target region, Q is the amount of heat transfer (J) for the calculation target region, and ΔV is the unit volume (m ³ ) of the calculation target region. In addition, although the temperature distribution in the region of the modeled blast furnace 2 can be estimated by calculating the mathematical formula (1), since the blast furnace 2 in operation is not necessarily in an equilibrium state, it is preferable to calculate the mathematical formula (1) as a non-steady state. As a result, the process of step S3 is completed, and the blast furnace control process proceeds to the process of step S4.

In the process of step S4, the blast furnace control device 1 calculates a heat transfer poor 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. In the formula (2), T _obs indicates the temperature measurement value of the thermocouple 2a, and T _cal indicates the temperature estimated by the numerical model at a position close to the installation position of the thermocouple 2a. The temperature estimated by the numerical model is obtained assuming a state in which no brick erosion is observed at the bottom of the blast furnace and no layer that inhibits heat transfer by the molten iron and slag flow, such as a low permeability layer or a solidified layer, is present. For this reason, the temperature estimated value is unique for the set boundary conditions of heat transfer, but the measured value of the thermocouple 2a changes due to brick erosion and the formation and disappearance of a layer that inhibits heat transfer. For this reason, the risk of formation of a molten iron flow poor area at the bottom of the blast furnace can be determined from the value of the heat transfer poor index ΔT. Specifically, when the risk of generation of a poor molten iron flow region at the bottom of the blast furnace is low, the measurement value of the thermocouple 2a increases, and the value of the poor heat transfer index ΔT increases. On the other hand, when the risk of generation of a poor molten iron flow region at the bottom of the blast furnace is high, the measurement value of the thermocouple 2a decreases, and the value of the poor heat transfer index ΔT decreases. Therefore, as shown in Fig. 4, the region where the poor molten iron flow region is generated 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.

In the process of step S5, the blast furnace control device 1 judges the risk of the generation of a molten iron flow poor area at the installation position of each thermocouple 2a based on the heat transfer poor index ΔT calculated in the process of step S4. Specifically, when the value of the heat transfer poor index ΔT is equal to or less than a predetermined threshold value (e.g., 10°C) set according to the operating status of the blast furnace 2, the blast furnace control device 1 judges that there is a high possibility that a molten iron flow poor area has been generated at the installation position of the thermocouple 2a. The threshold value may be set for all heat transfer poor indexes ΔT obtained from the measured values of the thermocouples 2a, or may be set for the heat transfer poor index ΔT obtained from the average value of the measured values of the thermocouples 2a set around the tap hole. Then, when there is an area with a high risk of the generation of a molten iron flow poor area, the blast furnace control device 1 controls the operating conditions of the blast furnace 2, such as the coke ratio, so that a molten iron flow poor area is not generated. This completes the process of step S5, and the series of blast furnace control processes ends.

As is clear from the above explanation, in the blast furnace control process which is 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 the generation of a poor molten iron flow area at the bottom of the blast furnace based on the difference between the estimated temperature distribution and the actual measured temperature value at the bottom of the blast furnace, and controls the operating conditions of the blast furnace so that a poor molten iron flow area is not generated based on the determination result. This makes it possible to accurately determine the risk of the generation of a poor molten iron flow area at the bottom of the blast furnace and suppress the generation of a poor molten iron flow area.

In this embodiment, this technology was applied to a large blast furnace with four tap holes of about 5000 ^m3 . 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 of heat transfer were set. In the target blast furnace, piping through which cooling water flows is laid out on the hearth base. In order to simulate this, the heat transfer coefficient of the hearth base was set to 30.6 W/ ^m2 ·K and the cooling water temperature was set to 50°C. On the other hand, regarding the heat transfer from the molten iron and slag in the blast furnace, the heat transfer from the molten iron flow at the hearth caused by tapping was taken into consideration, and it was assumed that molten iron at 1500°C flows in the area below the tuyere, and the heat transfer coefficient was calculated and given from the actual value of the amount of tapping and the cross-sectional area of the hearth. The heat transfer coefficient actually given is shown in FIG. 5. This makes it possible to reproduce the heat transfer caused by the flow of molten iron and slag due to the tapping of molten iron whose temperature is raised to 1500°C at the tuyere. Next, a heat transfer analysis for 48 days was performed. In this embodiment, a threshold value was set for the heat transfer poor index ΔT, and the blast furnace was operated so that the heat transfer poor index ΔT satisfied the condition shown in the following formula (3).

After the calculations were completed, the heat transfer poor index ΔT was calculated by focusing on the thermocouples installed near the four tap holes and using the measured temperature values and the calculated temperature values at the output points closest to each thermocouple. The calculation results are shown in Figure 6. As shown in Figure 6, the heat transfer poor index ΔT at all tap holes dropped sharply from the 27th to 30th day of operation. This was due to the sudden drop in heat transfer caused by the implementation of a blast stop during this period. On the other hand, a drop in the heat transfer poor index ΔT was confirmed overall from the 40th to 48th day of operation, and the drop at tap hole 1 was particularly steep. In fact, tapping poorly occurred at tap hole 1 on the 48th day of operation, and it is possible that areas of poor molten iron flow, such as low permeability layers and solidified layers, occurred near tap hole 1 inside the blast furnace. Based on this, in order to satisfy the conditions shown in formula (3), the coke rate was increased from the 48th day onwards to eliminate the poor heat transfer at the bottom of the blast furnace. The change in the amount of molten iron produced over that time is shown in Figure 7. As shown in Figure 7, the amount of molten iron produced increased again as the coke rate increased, confirming that the deadman deactivation was avoided. From the above, it was confirmed that the occurrence 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.

The above describes an embodiment in which the invention made by the present inventors is applied, but the present invention is not limited by 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 for each tuyere and the temperature rise conditions of the core and molten iron vary in the circumferential direction, 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 of the heat transfer analysis. In this way, all other embodiments, examples, and operational techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

The present invention provides a blast furnace control method and control device that can accurately determine the risk of a poor molten iron flow area forming at the bottom of the blast furnace and prevent the formation of a poor molten iron flow area.

1 Blast furnace control device 2 Blast furnace 2a Thermocouple

Claims (3)

A temperature distribution estimation step of estimating a temperature distribution at a 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 risk of generation of a poor molten iron flow 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 an actual measured value of the temperature at the bottom of the blast furnace;
a control step of controlling operation conditions of the blast furnace based on a result of the judgment in the judgment step so that the poor molten iron flow region is not generated;
A method for controlling a blast furnace, comprising: 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, taking into account heat transfer from the outside air around the blast furnace and heat transfer from the cooling water flowing through the piping of the blast furnace. A temperature distribution estimation means for estimating a temperature distribution at a 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 risk of generation of a poor molten iron flow region in the bottom of the blast furnace based on a difference value between the temperature distribution estimated by the temperature distribution estimation means and an actual measured value of the temperature in the bottom of the blast furnace;
a control means for controlling the operating conditions of the blast furnace based on the judgment result of the judgment means so that the poor molten iron flow region is not generated;
A blast furnace control device comprising: