Blast furnace control method and control device

Abstract

A blast furnace control method according to the present invention involves: estimating a temperature distribution in a blast furnace by executing heat transfer analysis using a numerical model of a blast furnace including a solidified layer of pig iron remaining on a furnace bottom and a furnace body iron shell,; estimating a stress distribution in the blast furnace by executing stress analysis using the numerical model of the blast furnace and the estimated temperature distribution; determining an allowable range of the furnace wall temperature of the blast furnace such that the thermal stress applied to the furnace body iron shell is within an allowable range on the basis of the estimated stress distribution; and controlling the cooling capacity of the furnace wall of the blast furnace such that the furnace wall temperature of the blast furnace is within the determined allowable range.

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] When a blast furnace is shut down for an extended period of time to adjust its production volume or for large-scale repairs, pig iron remaining in the region below the taphole solidifies. Therefore, when the blast furnace is restarted, the solidified pig iron expands due to heating. Until the pig iron melts, the expansion of the pig iron spreads the furnace shell, applying stress to the furnace shell. If the stress applied to the furnace shell exceeds an allowable value, the furnace shell may be damaged. In light of this, Patent Document 1 proposes a method for preventing coke and other materials from entering the gaps and spreading the furnace shell due to the expansion of the pig iron when the blast furnace is restarted. Patent Document 2 also proposes a method for mechanically scraping out residual materials from the furnace by bringing equipment into the blast furnace during a long-term shutdown.

[0003] JP-A-1-159308 JP-A-9-287010

[0004] However, when charging countermeasures such as compressible mortar or equipment into the furnace as in the methods described in Patent Document 1 and Patent Document 2, it is necessary to lower the temperature inside the furnace to a temperature suitable for the countermeasures. Therefore, if the shutdown period of the blast furnace is fluid, it may be difficult to restart the blast furnace in accordance with the status of the blast furnace. Furthermore, if a hole is formed in the blast furnace to carry in the equipment, the hole must be closed by welding or the like when the blast furnace is restarted, but defects may occur in the processed part, which may cause air leakage.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a blast furnace control method and control device that can prevent stress applied to the furnace shell of a blast furnace from exceeding an allowable value when the blast furnace is restarted, without charging a countermeasure material into the blast furnace.

[0006] The blast furnace control method according to the present invention includes: a temperature distribution estimation step of estimating a temperature distribution within the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the hearth and a furnace body shell; a stress distribution estimation step of estimating a stress distribution within the blast furnace by performing a stress analysis using the numerical model of the blast furnace and the temperature distribution estimated in the temperature distribution estimation step; a determination step of determining an allowable range of a furnace wall temperature of the blast furnace based on the stress distribution estimated in the stress distribution estimation step so that the thermal stress applied to the furnace body shell falls within an allowable range; and a control step of controlling the cooling capacity of the furnace wall of the blast furnace so that the furnace wall temperature of the blast furnace falls within the allowable range determined in the determination step.

[0007] The control step may be performed when the blast furnace is restarted.

[0008] The temperature distribution estimation step may include a step of performing the heat transfer analysis in consideration of heat transfer between the furnace wall of the blast furnace and the outside air and heat transfer between the furnace wall and cooling water circulating in piping within the furnace wall.

[0009] The blast furnace control device of the present invention comprises: a temperature distribution estimation means for estimating the temperature distribution within the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the hearth and a furnace body shell; a stress distribution estimation means for estimating the stress distribution within the blast furnace by performing a stress analysis using the numerical model of the blast furnace and the temperature distribution estimated by the temperature distribution estimation means; a determination means for determining an allowable range of the furnace wall temperature of the blast furnace based on the stress distribution estimated by the stress distribution estimation means so that the thermal stress applied to the furnace body shell falls within an allowable range; and a control means for controlling the cooling capacity of the furnace wall of the blast furnace so that the furnace wall temperature of the blast furnace falls within the allowable range determined by the determination means.

[0010] According to the blast furnace control method and control device of the present invention, it is possible to prevent the stress applied to the furnace body shell of the blast furnace from exceeding the allowable value when the blast furnace is restarted, without charging a countermeasure material into the blast furnace.

[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 blast furnace control processing 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 showing furnace wall cooling conditions in an example. FIG. 5 is a diagram showing the estimated results of the shell temperature in an example. FIG. 6 is a diagram showing the shell stress and allowable value estimated from the shell temperature shown in FIG. 5. FIG. 7 is a diagram showing the actual measured values ​​of the shell temperature in an example. FIG. 8 is a diagram showing the actual measured values ​​of the shell stress 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.

[0015] The blast furnace control device 1 having such a configuration executes the blast furnace control process described below, thereby preventing the thermal stress applied to the furnace body shell of the blast furnace 2 from exceeding the allowable value when the blast furnace 2 is restarted, without charging a countermeasure material into the blast furnace 2. Hereinafter, the operation of the blast furnace control device 1 when executing the blast furnace control process will be described with reference to FIG.

[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 an instruction to restart the blast furnace 2 after shutdown is issued, 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 calculating the thermal stress applied to the furnace body shell 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, 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 the furnace body shell and hearth residues such as a solidified layer of pig iron remaining at the hearth, and a mesh structure for numerical calculation is generated within the region. Note that the material of the blast furnace 2 is set to have temperature dependency in order to accurately perform the heat transfer analysis and stress analysis described below. Furthermore, the boundary conditions for the heat transfer analysis are set so that changes in the amount of heat transfer received from the tuyere can be reproduced in accordance with the tuyere opening schedule at the time of restarting operation. 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 the cooling conditions of the furnace wall in the numerical model of the blast furnace 2 based on information preset by the operator, etc. The cooling conditions of the furnace wall significantly affect the calculated value of the thermal stress applied to the furnace shell, and therefore need to be accurately set in accordance with the structure and operating conditions of the blast furnace 2. In this embodiment, for example, in a blast furnace in which the surface of the furnace shell is exposed to the outside air and cooling stave piping through which cooling water flows is provided inside the cooling piping, the blast furnace control device 1 takes into account the heat transfer between the furnace wall and the outside air and between the furnace shell and the cooling water, and changes the respective heat transfer coefficients according to the operating conditions. Note that it is advisable to take into account the heat transfer from the hearth cooling piping with respect to the hearth bottom, and the heat transfer of the molten pig iron from the portion corresponding to the lower part of the open tuyere with respect to the contact surface between the molten pig iron and the solidified layer. This completes the processing of step S2, and the blast furnace control processing proceeds to the 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 ｐis 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.

[0020]

[0021] Then, the blast furnace control device 1 executes stress analysis to estimate the thermal stress distribution in the region of the blast furnace 2 modeled using the estimated temperature distribution. Specifically, the blast furnace control device 1 applies a temperature change ΔT to the structure (region to be calculated) based on the estimated temperature distribution, and estimates the thermal strain (thermal stress) in each calculation region using Hooke's law shown in the following formula (2). In formula (2), ε ｉ is the strain in the i-direction of the structure (-), ε is Young's modulus (kPa), σ ｉ is the stress in the i direction of the structure (kPa), v is the Poisson's ratio (-), σ ｊ is the stress in the j direction (kPa), σ ｋ where is the stress in the k direction (kPa), α is the thermal expansion coefficient (1 / K), and ΔT is the temperature change (K). In the heat transfer analysis and stress analysis, it is necessary to reproduce the temperature rise caused by restarting a blast furnace that has been in a low temperature state due to shutdown, but when restarting, the temperature distribution and stress distribution will be in a non-equilibrium state. For this reason, it is desirable to perform the heat transfer analysis and stress analysis 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.

[0022]

[0023] In step S4, the blast furnace control device 1 determines whether the thermal stress in each calculation domain is within the allowable range based on the thermal stress distribution estimated in step S3. If the thermal stress in each calculation domain is within the allowable range (step S4: Yes), the blast furnace control device 1 advances the blast furnace control process to step S5. On the other hand, if the thermal stress in each calculation domain is not within the allowable range (step S4: No), the blast furnace control device 1 returns the blast furnace control process to step S2. That is, the blast furnace control device 1 repeatedly resets the furnace wall cooling conditions, such as the amount and temperature of cooling water, and performs heat transfer analysis and stress analysis until the thermal stress in each calculation domain falls within the allowable range. For example, if the thermal stress is greater than the allowable range, the blast furnace control device 1 determines that the furnace wall temperature is higher than the allowable range and resets the furnace wall cooling conditions to increase the amount of cooling water and / or decrease the cooling water temperature in order to enhance cooling capacity. On the other hand, if the thermal stress is smaller than the allowable range, the blast furnace control device 1 determines that the furnace wall temperature is lower than the allowable range and resets the furnace wall cooling conditions so that the amount of cooling water is reduced and / or the temperature of the cooling water is increased in order to weaken the cooling capacity.

[0024] In the processing of step S5, the blast furnace control device 1 determines the upper and lower limit values ​​of the furnace wall temperature as the allowable range of the furnace wall temperature in accordance with the temperature distribution within the region of the blast furnace 2 estimated in the processing of step S3. This completes the processing of step S5, and the blast furnace control processing proceeds to the processing of step S6.

[0025] In the processing of step S6, the blast furnace control device 1 controls the operation of the blast furnace 2 so that the start-up operation of the blast furnace 2 is performed within the allowable range of the furnace wall temperature determined in the processing of step S5. Specifically, the blast furnace control device 1 controls the cooling capacity (amount and / or temperature of cooling water) of the furnace wall of the blast furnace 2 so that the furnace wall temperature of the blast furnace 2 falls within the allowable range determined. This completes the processing of step S6, and the series of blast furnace control processing ends.

[0026] 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 in the blast furnace 2 by performing a heat transfer analysis using a numerical model of the blast furnace 2, including the solidified layer of pig iron remaining at the hearth and the furnace shell. Next, the blast furnace control device 1 estimates the stress distribution in the blast furnace 2 by performing a stress analysis using the numerical model of the blast furnace 2 and the estimated temperature distribution. Next, the blast furnace control device 1 determines an allowable range for the furnace wall temperature of the blast furnace 2 based on the estimated stress distribution so that the thermal stress applied to the furnace shell falls within the allowable range. Then, the blast furnace control device 1 controls the cooling capacity of the furnace wall of the blast furnace 2 so that the furnace wall temperature of the blast furnace 2 falls within the determined allowable range. This makes it possible to prevent the stress applied to the furnace shell of the blast furnace from exceeding the allowable value when the blast furnace 2 is restarted, without charging a countermeasure material into the blast furnace 2.

[0027] In this example, approximately 5000 m ３ The blast furnace control method according to the present invention was applied to the start-up of a large blast furnace of this size after a long shutdown. Regarding the operation method of the blast furnace during start-up, the policy was to open one to three tuyere holes per day to raise the temperature of the hearth residue from the first day of start-up to the 20th day. Therefore, in this example, when constructing a numerical model of the blast furnace, the size, shape, and material of the blast furnace were set, and then the heat transfer that the upper surface of the hearth residue receives from the tuyere was set for the period from the first day of start-up to the 20th day. Next, the cooling conditions of the furnace wall will be explained. The steel shell surface of the blast furnace is exposed to the outside air, and inside it are cooling stave piping with cooling water piping installed. In other words, the furnace wall receives heat transfer from the outside air on the steel shell surface and the cooling water in the cooling stave piping. Therefore, in this example, as shown in FIG. 4 , the cooling conditions of the furnace wall were set to an ambient temperature of 30 (°C), a heat transfer coefficient of 100 (W / m ２ ・K).

[0028] Heat transfer and stress analyses were performed by defining heat transfer from the furnace wall under the above-described furnace wall cooling conditions. Figure 5 shows the estimated shell temperatures from the first day of startup to the 50th day, and Figure 6 shows the allowable values ​​for the horizontal shell stress estimated from the shell temperatures shown in Figure 5. As shown in Figure 6, the thermal stress on the furnace shell was below the allowable values. Therefore, the cooling conditions at startup were determined based on the estimated shell temperature to achieve a cooling capacity that would keep the shell temperature between 35 and 50°C. Figures 7 and 8 show the measured shell temperatures and shell stresses during startup operations with a cooling capacity equivalent to the determined cooling conditions. As shown in Figure 7, when operation was performed to meet the determined cooling conditions, the shell temperature was maintained at approximately 45°C. Furthermore, as shown in Figure 8, the measured shell stress was always below the allowable value, enabling the blast furnace to be started up without damaging the shell.

[0029] The above describes an embodiment of the invention developed by the inventors. However, 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, to improve the accuracy of heat transfer analysis and stress analysis, the temperature and stress of the steel shell of a blast furnace that has been decided to be shut down for a long period of time may be measured, and the thermal properties, structural mechanical properties, or various heat transfer coefficients of the numerical model in that region may be adjusted so that the measured values ​​match the calculated values. Furthermore, the furnace wall temperature of the blast furnace may be adjusted to be within an allowable range not only when the furnace is restarted but also during normal blast furnace operation. This prevents safety issues caused by high steel shell temperatures. Thus, 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.

[0030] According to the present invention, it is possible to provide a blast furnace control method and control device that can prevent stress applied to the furnace body shell of a blast furnace from exceeding an allowable value when the blast furnace is restarted, without charging a countermeasure material into the blast furnace.

[0031] 1 Blast furnace control device 2 Blast furnace

Claims

1. A method for controlling a blast furnace, comprising: a temperature distribution estimation step of estimating a temperature distribution within the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the hearth and a furnace body skin; a stress distribution estimation step of estimating a stress distribution within the blast furnace by performing a stress analysis using the numerical model of the blast furnace and the temperature distribution estimated in the temperature distribution estimation step; a determination step of determining an allowable range of a furnace wall temperature of the blast furnace based on the stress distribution estimated in the stress distribution estimation step so that the thermal stress applied to the furnace body skin is within an allowable range; and a control step of controlling the cooling capacity of the furnace wall of the blast furnace so that the furnace wall temperature of the blast furnace is within the allowable range determined in the determination step.

2. The method of claim 1, wherein said control step is performed when said blast furnace is restarted.

3. A method for controlling a blast furnace as described in claim 1 or 2, wherein the temperature distribution estimation step includes a step of performing the heat transfer analysis taking into account heat transfer between a furnace wall of the blast furnace and the outside air and heat transfer between the furnace wall and cooling water circulating in piping within the furnace wall.

4. A blast furnace control device comprising: a temperature distribution estimation means for estimating a temperature distribution within the blast furnace by performing a heat transfer analysis using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the hearth and a furnace body skin; a stress distribution estimation means for estimating a stress distribution within the blast furnace by performing a stress analysis using the numerical model of the blast furnace and the temperature distribution estimated by the temperature distribution estimation means; a determination means for determining an allowable range of the blast furnace wall temperature based on the stress distribution estimated by the stress distribution estimation means so that the thermal stress applied to the furnace body skin is within the allowable range; and a control means for controlling the cooling capacity of the blast furnace wall so that the blast furnace wall temperature is within the allowable range determined by the determination means.

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