Control method and control device for blast furnace

Abstract

The blast furnace control method of the present invention is as follows: heat transfer analysis is performed by using a numerical model of the blast furnace including the solidified layer of pig iron remaining at the bottom of the furnace and the iron sheet of the furnace body, thereby estimating the temperature distribution inside the blast furnace; stress analysis is performed by using the numerical model of the blast furnace and the estimated temperature distribution, thereby estimating the stress distribution inside the blast furnace; based on the estimated stress distribution, the allowable range of the furnace wall temperature is determined in a way that the thermal stress applied to the iron sheet of the furnace body is within an allowable range; and the cooling capacity of the blast furnace wall is controlled in a way that the furnace wall temperature is within the determined allowable range.

Description

Technical Field

[0001] This invention relates to a control method and control device for blast furnaces. Background Technology

[0002] When a blast furnace is shut down for an extended period due to production adjustments or large-scale maintenance, the pig iron remaining in the area below the taphole solidifies. Therefore, when the blast furnace restarts, the solidified pig iron expands due to heating, and during the period until the pig iron melts, the furnace lining is pushed out by the expansion of the pig iron, applying stress to the furnace lining. Furthermore, if the stress applied to the furnace lining exceeds the allowable value, the furnace lining may sometimes break. Based on this background, Patent Document 1 proposes a method where, during a long-term shutdown of the blast furnace, shrinkable mortar is filled into the gaps formed by the cooling and contraction of the solidified pig iron to prevent coke and other substances from entering the gaps, thus preventing the furnace lining from being pushed out by the expansion of the pig iron during restart. Patent Document 2 proposes a method where, during a long-term shutdown of the blast furnace, equipment is moved into the blast furnace to mechanically scrape out the residue inside.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 1-159308 Patent Document 2: Japanese Patent Application Publication No. 9-287010 Summary of the Invention

[0004] The problem that the invention aims to solve However, when loading shrinkable mortar, equipment, or other materials into the furnace as described in Patent Documents 1 and 2, the furnace temperature needs to be lowered to a suitable temperature for the materials. Therefore, when the blast furnace shutdown period is uncertain, it can be difficult to restart the blast furnace based on its condition. Furthermore, if holes are formed to accommodate the equipment, they need to be sealed by welding or other methods during restart, but this process may introduce defects and cause air leakage.

[0005] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method and control device for controlling a blast furnace that can suppress the stress on the furnace body sheet applied to the blast furnace to a value above the allowable value without charging the blast furnace with a counteracting agent.

[0006] Methods for solving problems The blast furnace control method of the present invention includes: a temperature distribution estimation step, which performs heat transfer analysis by using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the bottom of the furnace and the furnace body sheet, thereby estimating the temperature distribution within the blast furnace; a stress distribution estimation step, which performs stress analysis by using the numerical model of the blast furnace and the temperature distribution estimated in the aforementioned temperature distribution estimation step, thereby estimating the stress distribution within the aforementioned blast furnace; a determination step, which determines an allowable range of the furnace wall temperature of the aforementioned blast furnace based on the stress distribution estimated in the aforementioned stress distribution estimation step, in a manner that makes the thermal stress applied to the furnace body sheet within an allowable range; and a control step, which controls the cooling capacity of the furnace wall of the aforementioned blast furnace in a manner that makes the furnace wall temperature within the allowable range determined in the aforementioned determination step.

[0007] The aforementioned control steps can be implemented when the aforementioned blast furnace is restarted.

[0008] The aforementioned temperature distribution estimation step may include performing the aforementioned heat transfer analysis by taking into account the heat transfer between the furnace wall and the external gas and the heat transfer between the cooling water flowing in the piping within the furnace wall and the furnace wall.

[0009] The blast furnace control device of the present invention comprises: a temperature distribution estimation unit, which performs heat transfer analysis using a numerical model of the blast furnace including a solidified layer of pig iron remaining at the bottom of the furnace and the furnace body sheet, thereby estimating the temperature distribution within the blast furnace; a stress distribution estimation unit, which performs stress analysis using the numerical model of the blast furnace and the temperature distribution estimated by the temperature distribution estimation unit, thereby estimating the stress distribution within the blast furnace; a determination unit, which determines an allowable range of the furnace wall temperature based on the stress distribution estimated by the stress distribution estimation unit, such that the thermal stress applied to the furnace body sheet is within an allowable range; and a control unit, which controls the cooling capacity of the furnace wall to ensure that the furnace wall temperature is within the allowable range determined by the determination unit.

[0010] Invention Effects According to the blast furnace control method and control device of the present invention, the stress on the furnace body sheet applied to the blast furnace during the next operation of the blast furnace can be suppressed to a value above the allowable value without the introduction of countermeasures into the blast furnace. Attached Figure Description

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[0019] Hereinafter, a blast furnace control device according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] 〔constitute〕 First, refer to Figure 1 The configuration of a blast furnace control device, which is one embodiment of the present invention, will be described.

[0021] Figure 1 This is a block diagram illustrating the configuration of a blast furnace control device as one embodiment of the present invention. Figure 1 As shown, the blast furnace control device 1, as one embodiment of the present invention, is composed of 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 through a processing unit such as a CPU within the information processing device.

[0022] The blast furnace control device 1, with this configuration, suppresses the thermal stress on the furnace body sheet of the blast furnace 2 to an allowable value or higher by performing the blast furnace control process as described below, without charging the blast furnace 2 with any countermeasures. Hereinafter, refer to... Figure 2 The operation of blast furnace control device 1 during blast furnace control processing is explained.

[0023] [Blast Furnace Control and Processing] Figure 2 This is a flowchart illustrating the process of blast furnace control processing as one embodiment of the present invention. Figure 2 The flowchart shown indicates the start time for restarting blast furnace 2 after it has been shut down, and the blast furnace control process then proceeds to step S1.

[0024] In 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 sheet. The numerical model of the blast furnace 2 is created by numerically modeling the size, shape, and material of the blast furnace 2, and can be generated using existing technology from CAD data of the blast furnace 2. In this embodiment, as... Figure 3 As shown in (a) to (c), the numerical model of blast furnace 2 is modeled by representing the region below the tuyeres of blast furnace 2, including the solidified layer of pig iron remaining at the furnace bottom and the furnace body sheet. A mesh structure for numerical calculation is generated within this region. It should be noted that, to ensure accurate implementation of the heat transfer and stress analyses described later, the material of blast furnace 2 is set to be temperature-dependent. Furthermore, the boundary conditions used for heat transfer analysis are set to reproduce the changes in heat transfer received from the tuyeres in accordance with the tuyeres opening plan during subsequent operation. Thus, step S1 is completed, and the blast furnace control process proceeds to step S2.

[0025] In step S2, the blast furnace control device 1 sets the cooling conditions of the furnace wall within the numerical model of the blast furnace 2 based on information preset by the operator. The cooling conditions of the furnace wall significantly affect the calculated value of the thermal stress applied to the furnace sheet, therefore, they need to be correctly set in conjunction with the structure and operating conditions of the blast furnace 2. In this embodiment, for example, for a blast furnace where the surface of the furnace sheet is exposed to external gas and has cooling water flowing through cooling pipes inside, the blast furnace control device 1 considers the heat transfer between the furnace wall and the external gas and cooling water, and changes the respective heat transfer coefficients according to the operating conditions. It should be noted that, regarding the furnace bottom, heat transfer from the furnace bottom cooling pipes should be considered, and regarding the contact surface between the molten iron and the solidified layer, heat transfer from the portion of the molten iron corresponding to the lower part of the tuyeres should be considered. Thus, step S2 is completed, and the blast furnace control process proceeds to step S3.

[0026] In step S3, the blast furnace control device 1 performs a heat transfer analysis based on the mathematical formula (1) shown below for each computational region (a rectangular region formed by generating a mesh structure) within the numerical model of the blast furnace 2, thereby estimating the temperature distribution within the modeled blast furnace 2 region. It should be noted that in mathematical formula (1), C... p ρ represents the specific heat of the calculated region (J / (kg·K)) and ρ represents the density of the calculated region (kg / m³).3 T represents temperature (K), t represents time (s), λ represents the thermal conductivity of the computational region (W / (m·K)), Q represents the heat transfer relative to the computational region (J), and ΔV represents the unit volume of the computational region (m³). 3 ).

[0027] [Mathematical Expression 1] Then, the blast furnace control unit 1 uses the estimated temperature distribution to perform an estimated stress analysis of the thermal stress distribution within the modeled blast furnace 2 region. Specifically, based on the estimated temperature distribution, the blast furnace control unit 1 assigns a temperature change ΔT to the structure (the calculation area) and uses Hooke's law, as shown in the following mathematical formula (2), to estimate the thermal strain (thermal stress) in each calculation area. It should be noted that in mathematical formula (2), ε i The strain in the i-direction of the structure is represented by (-), ε represents Young's modulus (kPa), and σ represents the strain in the i-direction of the structure. i The stress (kPa) in the i-direction of the structure is represented by v, which represents Poisson's ratio (-). σ j The stress (kPa) and σ in the j-direction are represented by... k Let α represent the stress in the k-direction (kPa), α represent the coefficient of thermal expansion (1 / K), and ΔT represent the temperature change (K). In the heat transfer and stress analyses, it is necessary to reproduce the blast furnace's temperature rise after restarting following a shutdown at a low temperature. However, during restart, the temperature and stress distributions become non-equilibrium. Therefore, it is desirable to perform the heat transfer and stress analyses under unstable conditions. Thus, step S3 is completed, and the blast furnace control process proceeds to step S4.

[0028] [Mathematical Expression 2] In step S4, the blast furnace control device 1 determines whether the thermal stress in each calculation region is within the allowable range based on the thermal stress distribution estimated in step S3. If the result is that the thermal stress in each calculation region is within the allowable range (step S4: Yes), the blast furnace control device 1 proceeds to step S5. Conversely, if the thermal stress in each calculation region is not within the allowable range (step S4: No), the blast furnace control device 1 returns to step S2. That is, the blast furnace control device 1 repeatedly performs the process of resetting the cooling conditions of the furnace wall, such as the cooling water volume and temperature, and conducting heat transfer and stress analyses until the thermal stress in each calculation region converges within the allowable range. For example, if the thermal stress exceeds the allowable range, the blast furnace control device 1 determines that the furnace wall temperature is higher than the allowable range and, in order to enhance cooling capacity, resets the furnace wall cooling conditions by increasing the cooling water volume and / or decreasing the cooling water temperature. On the other hand, if the thermal stress is less than the allowable range, the blast furnace control device 1 determines that the furnace wall temperature is less than the allowable range. In order to reduce the cooling capacity, the cooling conditions of the furnace wall are reset by reducing the amount of cooling water and / or increasing the temperature of the cooling water.

[0029] In step S5, the blast furnace control device 1 determines the upper and lower limits of the furnace wall temperature as the allowable range of the furnace wall temperature based on the temperature distribution within the blast furnace 2 region estimated in step S3. Thus, step S5 is completed, and the blast furnace control process proceeds to step S6.

[0030] In step S6, the blast furnace control device 1 controls the operation of blast furnace 2 to start up the blast furnace 2 within the allowable range of the furnace wall temperature determined in step S5. Specifically, the blast furnace control device 1 controls the cooling capacity (volume and / or temperature of cooling water) of the furnace wall of blast furnace 2 to keep the furnace wall temperature within the determined allowable range. Thus, step S6 is completed, and the series of blast furnace control processes ends.

[0031] As explained above, in the blast furnace control process of one embodiment of the present invention, firstly, the blast furnace control device 1 performs heat transfer analysis using a numerical model of the blast furnace 2, which includes the solidified layer of pig iron remaining at the furnace bottom and the furnace body scale, thereby estimating the temperature distribution within the blast furnace 2. Next, the blast furnace control device 1 performs stress analysis using the numerical model of the blast furnace 2 and the estimated temperature distribution, thereby estimating the stress distribution within the blast furnace 2. Next, based on the estimated stress distribution, the blast furnace control device 1 determines the permissible range of the furnace wall temperature of the blast furnace 2 in a manner that ensures the thermal stress applied to the furnace body scale is within an acceptable range. Then, the blast furnace control device 1 controls the cooling capacity of the furnace wall of the blast furnace 2 in a manner that ensures the furnace wall temperature of the blast furnace 2 is within the determined permissible range. Thus, it is possible to suppress the stress on the furnace body scale applied to the blast furnace to a value above the permissible value without introducing any countermeasures into the blast furnace 2 during its re-operation.

[0032] Example In this embodiment, approximately 5000m 3 The blast furnace control method of this invention is applied to the startup operation of large blast furnaces after long-term shutdown. In describing the blast furnace operation method during startup, the policy is to open the tuyeres at a rate of 1 to 3 openings per day from the first day of startup to the 20th day, thereby heating the bottom residue. Therefore, in this embodiment, when constructing the numerical model of the blast furnace, after setting the size, shape, and material of the blast furnace, the heat transfer received by the upper surface of the bottom residue from the tuyeres during the period from the first day of startup to the 20th day is set. Next, the cooling conditions of the furnace wall will be described. The blast furnace sheet surface is in contact with the external gas, and there are cooling wall pipes with cooling water pipes distributed throughout its inner side. That is, the furnace wall receives heat transfer from the external gas on the sheet surface and the cooling water in the cooling wall pipes. Therefore, in this embodiment, as... Figure 4 As shown, the cooling conditions for the furnace wall are set as follows: atmosphere temperature 30°C and heat transfer coefficient 100 W / m². 2 ·K).

[0033] Under the aforementioned furnace wall cooling conditions, heat transfer from the furnace wall is defined, and heat transfer analysis and stress analysis are performed. Figure 5 This shows the estimated sheet metal temperature from day 1 of startup to day 50. Figure 6 It is shown by Figure 5 The diagram shows the horizontal stress and allowable values ​​of the sheet metal, estimated from the sheet metal temperature. (See figure.) Figure 6As shown, the thermal stress applied to the furnace sheet is below the allowable value. Therefore, the cooling conditions during startup are determined based on an estimated sheet temperature, with a cooling capacity that brings the sheet temperature to converge at 35–50°C. The measured values ​​of sheet temperature and sheet stress during startup, implemented with a cooling capacity equivalent to the determined cooling conditions, are shown below. Figure 7 , 8 .like Figure 7 As shown, when operating in a manner that meets the determined cooling conditions, the sheet metal temperature is maintained at approximately 45°C. Additionally, as... Figure 8 As shown, the measured value of the sheet stress was always lower than the allowable value, thus enabling the blast furnace to start up without damaging the sheet.

[0034] The embodiments of the invention implemented by the inventors of this application have been described above, but the present invention is not limited to the description and drawings that constitute a part of the disclosure of the present invention based on this embodiment. For example, in order to improve the accuracy of heat transfer analysis and stress analysis, the temperature and stress of the iron sheet of a blast furnace that has been shut down for a long time can be measured, and the thermal properties, structural mechanical properties, or various heat transfer coefficients of the numerical model in that region can be adjusted in a way that makes the measured values ​​consistent with the calculated values. In addition, the furnace wall temperature can be adjusted to an acceptable range not only when restarting the furnace but also during normal blast furnace operation. As a result, safety problems caused by the iron sheet becoming too hot can be suppressed. In this way, other embodiments, examples, and applications implemented by those skilled in the art based on this embodiment are all included within the scope of the present invention.

[0035] Industrial availability According to the present invention, a method and control device are provided for controlling a blast furnace that can suppress the stress on the furnace body sheet applied during blast furnace restart to a value above the allowable value without introducing a counteracting agent into the blast furnace.

[0036] Explanation of reference numerals in the attached figures 1. Blast Furnace Control Device 2 Blast Furnace

Claims

1. Blast furnace control methods, including: The temperature distribution estimation step involves performing heat transfer analysis using a numerical model of the blast furnace, which includes the solidified layer of pig iron remaining at the bottom of the furnace and the iron sheet of the furnace body, thereby estimating the temperature distribution inside the blast furnace. The stress distribution estimation step involves performing stress analysis using the numerical model of the blast furnace and the temperature distribution estimated in the temperature distribution estimation step, thereby estimating the stress distribution within the blast furnace. The determination step involves determining the permissible range of the blast furnace wall temperature based on the stress distribution estimated in the stress distribution estimation step, in a manner that ensures the thermal stress applied to the furnace sheet is within acceptable limits. and The control step controls the cooling capacity of the blast furnace wall in a manner that brings the furnace wall temperature within the allowable range determined in the determining step.

2. The blast furnace control method as described in claim 1, wherein, The control steps are implemented when the blast furnace is restarted.

3. The blast furnace control method as described in claim 1 or 2, wherein, The temperature distribution estimation step includes performing the heat transfer analysis by taking into account the heat transfer between the furnace wall and the external gas and the heat transfer between the cooling water flowing in the piping within the furnace wall and the furnace wall.

4. The control device for the blast furnace, which includes: The temperature distribution estimation unit performs heat transfer analysis using a numerical model of a blast furnace that includes a solidified layer of pig iron remaining at the bottom of the furnace and the iron sheet of the furnace body, thereby estimating the temperature distribution inside the blast furnace. The stress distribution estimation unit performs stress analysis by using the numerical model of the blast furnace and the temperature distribution estimated by the temperature distribution estimation unit, thereby estimating the stress distribution inside the blast furnace. The determining unit determines the permissible range of the furnace wall temperature based on the stress distribution estimated by the stress distribution estimation unit, in a manner that makes the thermal stress applied to the furnace sheet within the permissible range. and The control unit controls the cooling capacity of the blast furnace wall in a manner that keeps the furnace wall temperature within an allowable range determined by the determining unit.

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