Control method and control device of a blast furnace

Abstract

A control method for a blast furnace according to the present invention comprises: a temperature distribution estimation step for estimating the temperature distribution of the bottom of the blast furnace by performing heat transfer analysis using a numerical model of the blast furnace; a determination step for determining the risk of generating a molten iron flow failure 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 temperature value of the bottom of the blast furnace; and a control step for controlling the operating conditions of the blast furnace so as not to generate a molten iron flow failure area based on the determination result in the determination step.

Description

Technology Field

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

[0002] In the ironmaking method using a blast furnace, high-temperature gas is blown in from a blast tuyere at the bottom of the blast furnace to raise the temperature of raw materials such as iron ore or coke and react them, thereby producing pig iron. The produced pig iron is then melted together with slag and accumulates in the bottom of the blast furnace as a liquid phase, and is periodically discharged out of the furnace through a taphole. Generally, in addition to molten iron and molten slag, a coke-filled layer exists at the bottom of the blast furnace, and the molten material flows through the pores of the coke-filled layer. However, due to factors such as the coke-filled layer or 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 solidification layer region (hereinafter referred to as the molten iron flow poor region) with poor liquid permeability of the molten material may be formed. When such areas of poor molten iron flow form, the amount of tapped iron sludge decreases. This leads to a reduction in crude steel production or causes blast furnace troubles resulting from increased molten iron sludge, ultimately resulting in lower profitability. Therefore, technology is required to rapidly detect areas of poor molten iron flow and promptly implement operational actions to improve the permeability of the molten material.

[0003] Against this backdrop, Patent Document 1 describes a method for estimating the thickness of the solidified layer of contents attached to the inner surface of the refractory material present at the bottom of the blast furnace by heat analysis using the measurement results of a thermocouple installed at the bottom of the blast furnace. Additionally, Patent Document 2 proposes a method for estimating the formation and disappearance of the 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. Furthermore, Patent Document 3 proposes a method for diagnosing the inert state of the bottom of the blast furnace from the measured temperature of a thermocouple embedded in the center of the base plate at the bottom of the blast furnace and in the lower part near each tapping hole of the bottom side wall. Prior art literature

[0004] Japanese Published Patent Application No. Hei 10-273708, Japanese Patent No. 6947343, Japanese Published Patent Application No. 2005-272873 The problem to be solved

[0005] However, according to the method described in Patent Document 1, while it is possible to estimate the degree of erosion of the refractory material or the thickness of the solidification layer attached to the refractory material, it is not possible to detect the low-permeability layer generated by the powder of the coke-filled layer. Furthermore, since the detectable solidification layer is limited to that attached to the refractory material, it is not possible to estimate the inert state of the furnace core (a state in which the permeability or permeability of the molten material is reduced). Meanwhile, the amount of heat supplied to the molten iron is determined by unknown variables such as the combustibility of the coke or pulverized coal and the temperature of the furnace core coke, and it also changes moment by moment due to heat generation caused by the furnace wall or powder. For this reason, it is difficult to detect the solidification layer with high precision using an estimation method based solely on the thermal energy balance, such as the method described in Patent Document 2. In addition, the method described in Patent Document 3 utilizes the temperature measured at the bottom of the blast furnace as is, but the temperature at the bottom of the blast furnace varies significantly depending not only on the inert state inside the blast furnace but also on the strength of the cooling capacity and the ambient temperature of the blast furnace. For this reason, it is difficult to diagnose the inert state at the bottom of the blast furnace with high precision according to the method described in Patent Document 3.

[0006] The present invention is made to solve the above problem, and its objective is to provide a blast furnace control method and control device capable of suppressing the formation of a molten iron flow failure area by accurately determining the risk of a molten iron flow failure area being formed at the bottom of the blast furnace. means of solving the problem

[0007] A control method for a blast furnace according to the present invention comprises: a temperature distribution estimation step for estimating a temperature distribution at the bottom of a blast furnace by performing heat transfer analysis using a numerical model of the blast furnace; a determination step for determining a risk of generating a molten iron flow failure 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 temperature value at the bottom of the blast furnace; and a control step for controlling the operating conditions of the blast furnace so as not to generate the molten iron flow failure area based on the determination result in the determination step.

[0008] The above temperature distribution estimation step may include a step for estimating the temperature distribution of the bottom of the blast furnace by considering heat transfer from the outside air surrounding the blast furnace and heat transfer from the cooling water flowing through the piping of the blast furnace.

[0009] A control device for a blast furnace according to the present invention comprises: a temperature distribution estimation means for estimating a temperature distribution at the bottom of a blast furnace by performing heat transfer analysis using a numerical model of the blast furnace; a determination means for determining a risk of generating a molten iron flow failure 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 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 molten iron flow failure area is not generated based on the determination result of the determination means. Effects of the invention

[0010] According to the control method and control device of the blast furnace of the present invention, the risk of a molten iron flow failure area being created at the bottom of the blast furnace can be determined with high precision, thereby suppressing the creation of a molten iron flow failure area. Brief explanation of the drawing

[0011] FIG. 1 is a block diagram showing the configuration of a blast furnace control device, which is an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of a blast furnace control process, which is an embodiment of the present invention. Figure 3 is a diagram showing an example of the configuration of a numerical model of a blast furnace. Figure 4 is a diagram illustrating a method for estimating a molten metal flow failure area using a heat transfer failure index. Figure 5 is a diagram showing the change in the heat transfer coefficient in the embodiment. Figure 6 is a diagram showing the calculation result of the transmission failure index in the embodiment. Figure 7 is a diagram showing the trend of the output amount in an embodiment. Specific details for implementing the invention

[0012] (Form for carrying out the invention)

[0013] Hereinafter, a blast furnace control device, which is an embodiment of the present invention, will be described with reference to the drawings.

[0014] 〔composition〕

[0015] First, with reference to FIG. 1, the configuration of a blast furnace control device, which is an embodiment of the present invention, will be described.

[0016] 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 the blast furnace (2) by executing a computer program by a computational processing device such as a CPU within the information processing device. In addition, in this embodiment, a plurality of thermocouples (2a) are installed on the side wall bricks or furnace bottom bricks of the blast furnace (2), including the perimeter of the tapping hole, and each thermocouple (2a) inputs an electrical signal indicating the temperature of the blast furnace (2) at the installation location to the blast furnace control device (1).

[0017] A blast furnace control device (1) having such a configuration suppresses the formation of a molten iron flow failure area at the bottom of the blast furnace (2) by executing the blast furnace control process described below. Below, with reference to FIG. 2, the operation of the blast furnace control device (1) when executing the blast furnace control process will be described.

[0018] [Blast Furnace Control Processing]

[0019] FIG. 2 is a flowchart showing the flow of a blast furnace control process, which is an embodiment of the present invention. The flowchart shown in FIG. 2 is initiated at the timing when the operation of the blast furnace (2) is started, and the blast furnace control process proceeds to the processing of step S1.

[0020] In the processing 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 known technology. In this embodiment, the numerical model of the blast furnace (2) models the area below the twee of the blast furnace (2), including the solidification layer of pig iron remaining in the furnace, the coke filling layer, the molten iron material present in the voids of the coke filling layer, the furnace shell structure of the furnace body, and the refractory material, as shown in FIGS. 3(a) to (c). Additionally, a mesh structure for numerical calculation is generated within the area of ​​the numerical model of the blast furnace (2). Furthermore, the material of the blast furnace (2) is set to have a temperature dependency in order to perform the heat transfer analysis described later with high precision. Accordingly, the processing of Step S1 is completed, and the furnace control processing proceeds to the processing of Step S2.

[0021] In the processing of step S2, the blast furnace control device (1) sets the boundary conditions for heat transfer within the numerical model of the blast furnace (2) based on information, etc., that is pre-set by the operator, in accordance with the specifications of the blast furnace (2) and the current operating state. Here, the boundary conditions for heat transfer include the cooling capacity of the blast furnace (2) and the heat transfer received from the molten iron material inside the blast furnace (2). Specific examples of the cooling capacity of the blast furnace (2) include heat transfer from the outside air to the surface of the iron shell of the blast furnace wall, heat transfer from the cooling water flowing through the pipes of the cooling stave, and heat transfer from the cooling water flowing through the pipes of the furnace refractory material. Meanwhile, specific examples of the heat transfer received from the molten iron material inside the blast furnace (2) include heat transfer from the flow of molten iron material inside the blast furnace (2) due to tapping, and contact heat transfer due to the dripping of molten iron material heated by the twee. Accordingly, the processing of Step S2 is completed, and the furnace control processing proceeds to the processing of Step S3.

[0022] In the processing of step S3, the blast furnace control device (1) estimates the temperature distribution within the modeled blast furnace (2) by performing a heat transfer analysis for each calculation area (a rectangular area formed by generating a mesh structure) within the numerical model of the blast furnace (2) by calculating the following formula (1). In addition, in formula (1), C prepresents the specific heat of the area to be calculated (J / (kg·K)), ρ represents the density of the area to be calculated (kg / ㎥), T represents the temperature (K), t represents time (s), λ represents the thermal conductivity of the area to be calculated (W / (m·K)), Q represents the amount of heat transfer for the area to be calculated (J), and ΔV represents the unit volume (㎥) of the area to be calculated. Additionally, although the temperature distribution within the area of ​​the modeled blast furnace (2) can be estimated by calculating Equation (1), since the blast furnace (2) in operation is not necessarily in an equilibrium state, it is preferable to calculate Equation (1) as an unsteady state. Accordingly, the processing of Step S3 is completed, and the blast furnace control processing proceeds to the processing of Step S4.

[0023]

[0024] In the processing of Step S4, the blast furnace control device (1) calculates a heat transfer failure index ΔT (°C) for each thermocouple (2a) using the temperature distribution of the blast furnace (2) estimated in the processing of Step S3 and the temperature of the blast furnace (2) measured by each thermocouple (2a), as shown in the following formula (2). In addition, in formula (2), T obs is the temperature measurement of the thermocouple (2a), T calThe value represents the temperature estimate by the numerical model at a location close to the installation position of the thermocouple (2a). The temperature estimate by the numerical model is obtained by assuming a state in which no brick erosion is observed at all at the bottom of the blast furnace, and there are no layers that hinder heat transfer by molten iron flow, such as a low-permeability layer or a solidification layer. For this reason, the temperature estimate is unique for the set boundary conditions of heat transfer, but the measurement value of the thermocouple (2a) changes due to the formation or disappearance of brick erosion or layers that hinder heat transfer. For this reason, the risk of the formation of a molten iron flow failure area at the bottom of the blast furnace can be determined from the value of the heat transfer failure index ΔT. Specifically, when the risk of the formation of a molten iron flow failure area at the bottom of the blast furnace is low, the measurement value of the thermocouple (2a) increases, and thus the value of the heat transfer failure index ΔT increases. Meanwhile, when the risk of a molten iron flow failure area at the bottom of the blast furnace is high, the measurement value of the thermocouple (2a) decreases, so the value of the heat transfer failure index ΔT becomes smaller. Therefore, as shown in FIG. 4, the area where the molten iron flow failure area is created can be estimated from the value of the heat transfer failure index ΔT. Accordingly, the processing of step S4 is completed, and the blast furnace control processing proceeds to the processing of step S5.

[0025]

[0026] In the processing of step S5, the blast furnace control device (1) determines the risk of a molten iron flow failure area being created at the installation location of each thermocouple (2a) based on the heat transfer failure index ΔT calculated in the processing of step S4. Specifically, the blast furnace control device (1) determines that if the value of the heat transfer failure index ΔT is less than or equal to a predetermined threshold value (e.g., 10°C) set according to the operating conditions of the blast furnace (2), there is a high probability that a molten iron flow failure area is created at the installation location of the thermocouple (2a). In addition, the threshold value may be set for all heat transfer failure indices ΔT obtained from the measurement values ​​of the thermocouple (2a), or it may be set for the heat transfer failure index ΔT obtained from the average value of the measurement values ​​of the thermocouple (2a) set around the tap hole. And, if there is a region with a high risk of generating a region with poor molten iron flow, the blast furnace control device (1) controls the operating conditions of the blast furnace (2), such as the coke ratio, so that the region with poor molten iron flow is not generated. Accordingly, the processing of step S5 is completed, and the series of blast furnace control processes is terminated.

[0027] As is clear from the above description, in a blast furnace control process which is an embodiment of the present invention, first, a 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 molten iron flow failure area at the bottom of the blast furnace based on the difference between the estimated temperature distribution and the actual measured temperature of the bottom of the blast furnace, and controls the operating conditions of the blast furnace so that a molten iron flow failure area is not created based on the determination result. Accordingly, the risk of a molten iron flow failure area being created at the bottom of the blast furnace can be determined with high precision, thereby suppressing the creation of a molten iron flow failure area.

[0028] Examples

[0029] In this embodiment, the technology was applied to a large blast furnace with four tapping holes and a capacity of approximately 5,000 m³. First, a numerical model of the blast furnace was constructed from the size, shape, and material of the target blast furnace. Next, the specific heat, thermal conductivity, and density for each material were input to create the numerical model of the blast furnace. Next, boundary conditions for heat transfer were set. In the target blast furnace, a pipe through which cooling water flows is laid in the bottom of the furnace. To simulate this, the heat transfer coefficient of the bottom of the furnace was set to 30.6 W / m²·K, and the cooling water temperature was set to 50°C. Meanwhile, regarding the heat transfer received from the molten iron material inside the blast furnace, considering the heat transfer received from the molten iron flow at the bottom of the furnace generated by tapping, it was assumed that molten iron at 1,500°C flows in the area under the twee, and the heat transfer coefficient was calculated and assigned from the actual value of the tapping amount and the cross-sectional area of ​​the hearth. The heat transfer coefficient actually applied is shown in FIG. 5. Accordingly, heat transfer caused by the flow of molten iron due to the tapping of molten iron heated to 1500°C in the tweeter can be reproduced. Next, a heat transfer analysis for 48 days was performed. In addition, in this embodiment, a threshold value was set for the heat transfer failure index ΔT, and the blast furnace was operated so that the heat transfer failure index ΔT satisfied the condition shown in the following equation (3).

[0030]

[0031] After the calculation was completed, the heat transfer failure index ΔT was calculated by focusing on the thermocouples near the locations of the four installed tap holes and using their actual temperature measurements and the calculated temperature values ​​at the output point closest to each thermocouple. The results of the calculation are shown in Fig. 6. As shown in Fig. 6, the heat transfer failure index ΔT for all tap holes decreased rapidly from the 27th day of operation to the 30th day. This was caused by a rapid decrease in heat transfer due to the suspension of airflow during that period. Meanwhile, a decrease in the heat transfer failure index ΔT was confirmed overall from the 40th day of operation to the 48th day, and the decrease in the tap hole (1) was particularly steep. In fact, on the 48th day of operation, a tapping failure occurred in the tap hole (1), and it is possible that a molten iron flow failure area, such as a low-permeability layer or a solidification layer, was created near the tap hole (1) inside the blast furnace. Based on this, in order to satisfy the conditions shown in Equation (3), the coke ratio was increased after the 48th day to eliminate heat transfer failure at the bottom of the blast furnace. The trend of the amount of iron tapped at that time is shown in FIG. 7. As shown in FIG. 7, it was confirmed that core inertness could be avoided because the amount of iron tapped increased again with the increase in the coke ratio. From the above, it was confirmed that the formation of a molten iron flow failure area could be suppressed by controlling the operating conditions of the blast furnace (2), such as the coke ratio, based on the heat transfer failure index ΔT.

[0032] Although embodiments applying the invention made by the inventors have been described above, the present invention is not limited by the description and drawings that constitute part of the disclosure of the present invention according to the present embodiments. For example, in the case of a blast furnace in which the combustion state of each twee differs significantly and the heating conditions of the core or molten iron differ in the circumferential direction, the estimated combustion properties for each twee may be input into a numerical model, and the difference in combustion properties for each twee may be reflected in the heating conditions of the heat transfer analysis. As such, other embodiments, examples, and operational techniques made by those skilled in the art based on the present embodiments are all included within the scope of the present invention.

[0033] Industrial applicability

[0034] According to the present invention, a method for controlling a blast furnace and a control device capable of suppressing the formation of a molten iron flow failure area by accurately determining the risk of a molten iron flow failure area being formed at the bottom of the blast furnace can be provided. Explanation of the symbols

[0035] 1 : Blast furnace control device 2 : Therefore 2a : Thermocouple

Claims

Claim 1 A method for controlling a blast furnace, comprising: a temperature distribution estimation step for estimating the temperature distribution of the bottom of the blast furnace by performing heat transfer analysis using a numerical model of the blast furnace; a determination step for determining the risk of generating a molten iron flow failure area in the bottom of the blast furnace based on the difference between the temperature distribution estimated in the temperature distribution estimation step and the actual temperature of the bottom of the blast furnace; and a control step for controlling the operating conditions of the blast furnace so as not to generate the molten iron flow failure area based on the determination result in the determination step. Claim 2 A method for controlling a blast furnace according to claim 1, wherein the temperature distribution estimation step includes a step of estimating the temperature distribution of the bottom of the blast furnace by considering heat transfer from the outside air surrounding the blast furnace and heat transfer from the cooling water flowing through the piping of the blast furnace. Claim 3 A control device for a blast furnace, comprising: a temperature distribution estimation means for estimating the temperature distribution of the bottom of a blast furnace by performing heat transfer analysis using a numerical model of the blast furnace; a determination means for determining the risk of generating a molten iron flow failure area in the bottom of the blast furnace based on the difference between the temperature distribution estimated by the temperature distribution estimation means and the actual temperature of the bottom of the blast furnace; and a control means for controlling the operating conditions of the blast furnace so that the molten iron flow failure area is not generated based on the determination result of the determination means.

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