Method for selecting scrap filling layers, apparatus for selecting scrap filling layers, and method for operating furnace

Abstract

To provide a method and device for selecting scrap filling layers that can indicate how to fill storage containers with scrap of various shapes and sizes in order to improve heat transfer to the scrap.SOLUTION: A method for selecting scrap filling layers according to the present invention comprises: a creation step of creating electronic data for multiple scrap filling layers with different scrap loading methods into a storage container; a fluid calculation step of calculating the gas flow velocity between scraps for each scrap filling layer using the electronic data; a temperature calculation step of calculating the temperature of the gas that has passed through the scrap packing layer for each scrap packing layer using the flow rate of the gas calculated in the fluid calculation step; and a selection step of selecting a scrap filling layer with good heat transfer to the scrap from among the multiple scrap filling layers based on the gas temperature calculated in the temperature calculation step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for selecting a packed scrap bed, an apparatus for selecting a packed scrap bed, and a method for operating a furnace. [Background technology]

[0002] An electric furnace is a facility that heats and melts scrap using heat (hereinafter referred to as arc heat) of several thousand to several tens of thousands of degrees Celsius generated by an arc between electrodes. To increase the efficiency of an electric furnace, it is necessary to efficiently apply arc heat to the scrap. However, generating an arc requires an insulating layer, such as air, through which electricity does not easily flow. Therefore, when arc heat is generated, not only the scrap but also surrounding gases, such as air, are heated and discharged as exhaust gas outside the electric furnace, resulting in heat loss. In light of this, Patent Document 1 proposes a method for reducing heat loss due to exhaust gas. Specifically, the method described in Patent Document 1 involves connecting a rotary furnace for preheating small scrap pieces to a hood covering the top of the electric furnace, connecting a shaft furnace for preheating large scrap pieces to the rotary furnace, and preheating the small scrap pieces and large scrap pieces with exhaust gas generated by the electric furnace. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-49217 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not disclose or suggest how scrap of various shapes and sizes should be loaded into a shaft furnace to improve heat transfer when scrap of various shapes and sizes is mixed. Scrap comes from a variety of products, so it comes in a variety of shapes and sizes. For example, scrap extracted from automobiles is often thin plate-shaped, while scrap extracted from construction materials used for rebar and piping is often cylindrical. Sizes also vary widely, for example, because the size of the material used for automobile doors differs from the size of the material used for the body. Therefore, in order to reduce heat loss due to exhaust gas from electric furnaces, a method is needed to show operators how scrap of various shapes and sizes should be loaded into a containment vessel to improve heat transfer.

[0005] The present invention has been made to solve the above-mentioned problems, and its object is to provide a method and apparatus for selecting a scrap packed bed that can present how scrap of various shapes and sizes should be packed into a containment vessel to improve heat transfer to the scrap. Another object of the present invention is to provide a method for operating a furnace that can reduce heat loss due to exhaust gas and thereby reduce the energy consumption of the furnace. [Means for solving the problem]

[0006] [1] The method for selecting a scrap packed bed according to the present invention includes a creating step of creating electronic data of a plurality of scrap packed beds having different methods of charging scrap into a storage vessel; a fluid calculation step of calculating the flow rate of gas flowing between the scrap for each scrap packed bed using the electronic data; a temperature calculation step of calculating the temperature of gas passing through the scrap packed bed for each scrap packed bed using the gas flow rate calculated in the fluid calculation step; and a selection step of selecting a scrap packed bed that has good heat transfer to the scrap from among the plurality of scrap packed beds based on the gas temperature calculated in the temperature calculation step.

[0007] [2] In the method for selecting a scrap packed bed according to the present invention, in the method for selecting a scrap packed bed described in [1], the multiple scrap packed beds include a mixed scrap packed bed in which two or more types of scrap are randomly charged, and a stacked scrap packed bed in which two or more types of scrap are stacked in order.

[0008] [3] The method for selecting a scrap packed bed according to the present invention is the method for selecting a scrap packed bed according to [2], wherein the stacked scrap packed bed includes a plurality of layers of the same type of scrap.

[0009] [4] The method for selecting a scrap packed bed according to the present invention is a method for selecting a scrap packed bed according to any one of [1] to [3], and includes a step of outputting information about the scrap packed bed selected in the selection step.

[0010] [5] The scrap packed bed selection device of the present invention comprises: a creation means for creating electronic data of a plurality of scrap packed beds having different methods of charging scrap into a storage vessel; a fluid calculation means for calculating the flow rate of gas flowing between the scrap for each scrap packed bed using the electronic data; a temperature calculation means for calculating the temperature of gas passing through the scrap packed bed for each scrap packed bed using the gas flow rate calculated by the fluid calculation means; and a selection means for selecting a scrap packed bed that has the best heat transfer to the scrap from among the plurality of scrap packed beds based on the gas temperature calculated by the temperature calculation means.

[0011] [6] The method for operating a furnace according to the present invention includes a step of charging scrap into a furnace so that the scrap is in a packed state similar to that of a scrap packed bed selected by the method for selecting a scrap packed bed according to any one of [1] to [4]. [Effects of the Invention]

[0012] The scrap packed bed selection method and device of the present invention can suggest how scrap of various shapes and sizes should be packed into a containment vessel to improve heat transfer to the scrap. Furthermore, the furnace operation method of the present invention can reduce heat loss due to exhaust gases and thereby reduce furnace energy consumption. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an electric furnace according to one embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of a processing device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the flow of the selection process according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating an example of mixed scrap packed layer data. [Figure 5] FIG. 5 is a diagram showing an example of stacked scrap packing layer data. [Figure 6] FIG. 6 is a diagram showing an example of stacked scrap packing layer data. [Figure 7] FIG. 7 is a diagram illustrating an example of boundary conditions for fluid calculation. [Figure 8] FIG. 8 is a diagram illustrating the shape of the storage container in the first embodiment. [Figure 9] FIG. 9 is a diagram showing the shape of the scrap in Example 1. [Figure 10] FIG. 10 is a diagram showing scrap packed bed data in Example 1. [Figure 11] FIG. 11 is a diagram illustrating boundary conditions for fluid calculation and temperature calculation in the first embodiment. [Figure 12] FIG. 12 is a diagram showing the calculation results of the measured exhaust gas temperature in the first embodiment. [Figure 13] FIG. 13 is a diagram showing the shape of the scrap in Example 2. [Figure 14] FIG. 14 is a diagram showing scrap packed bed data in Example 2. [Figure 15] FIG. 15 is a diagram showing the calculation results of the measured exhaust gas temperature in the second embodiment. [Figure 16] FIG. 16 is a diagram showing the shape of scrap in Example 3. [Figure 17] FIG. 17 is a diagram showing scrap packed bed data in Example 3. [Figure 18] FIG. 18 is a diagram showing the calculation results of the measured exhaust gas temperature in the third embodiment. [Figure 19] FIG. 19 is a diagram showing the shape of the scrap in Example 4. [Figure 20] FIG. 20 is a diagram showing scrap packed bed data in Example 4. [Figure 21] FIG. 21 is a diagram showing the calculation results of the measured exhaust gas temperature in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a method for selecting a packed scrap bed and a method for operating a furnace according to one embodiment of the present invention will be described with reference to the drawings.

[0015] [Configuration of electric furnace] First, the configuration of an electric furnace to which a method for selecting a scrap packed bed and a method for operating a furnace according to one embodiment of the present invention is applied will be described with reference to Figure 1. Note that while this embodiment applies the present invention to an electric furnace, the application of the present invention is not limited to electric furnaces and can be applied to any furnace equipped with a heat source for burning objects.

[0016] FIG. 1 is a schematic diagram showing the configuration of an electric furnace according to one embodiment of the present invention. As shown in FIG. 1, the electric furnace 1 according to one embodiment of the present invention is a preheating-type electric furnace that preheats scrap S, an iron source, using high-temperature exhaust gas G generated in the electric furnace 1. In this embodiment, the electric furnace 1 includes a preheating section 2 that preheats a packed bed of scrap S using the exhaust gas G, and a melting section 4 that melts the scrap S using the heat of an arc generated by graphite electrodes 3 to produce molten iron MI. The preheating section 2 and the melting section 4 are connected to each other. In the preheating section 2, the scrap S in the packed bed of scrap preheated by the high-temperature exhaust gas G generated in the melting section 4 is charged into the melting section 4 by its own weight or mechanical operation and melted.

[0017] [Configuration of processing device] Next, with reference to FIG. 2, the configuration of a processing device that executes a method for selecting a scrap packed bed according to one embodiment of the present invention will be described.

[0018] Fig. 2 is a block diagram showing the configuration of a processing device according to one embodiment of the present invention. As shown in Fig. 2, processing device 10 according to one embodiment of the present invention is configured as an information processing device such as a computer. An input device 21 and an output device 22 are connected to processing device 10. Input device 21 is configured as a known input device such as a keyboard or a mouse pointer, and inputs various information such as setting values to processing device 10. Output device 22 is configured as a known output device such as a display device, a printer, or an audio output device, and outputs various information in accordance with control signals from processing device 10.

[0019] The processing device 10 includes a containment vessel creation unit 11, a scrap shape creation unit 12, a scrap packed layer creation unit 13, a fluid calculation unit 14, a temperature calculation unit 15, and a scrap charging method selection unit 16. The functions of each of these units are realized by an arithmetic processing unit such as a CPU in the information processing device executing a computer program stored in the storage unit. The functions of each of these units will be described later. The storage unit may be a storage medium fixed to the computer or the like, or a storage medium removable from the computer or the like. Examples of storage media fixed to the computer or the like include an EPROM (Erasable Programmable ROM) and a hard disk drive (HDD, Hard Disk Drive).

[0020] Examples of recording media that can be removed from a computer or the like include USB (Universal Serial Bus) memory, flexible disks, magneto-optical disks, CD-ROMs (Compact Disc - Read Only Memory), CD-RWs (Compact Disc - Rewritable), DVDs (Digital Versatile Discs), BDs (Blu-ray (registered trademark) Discs), DATs (Digital Audio Tapes), 8mm tapes, and memory cards. Solid-state drives (SSDs) can be used as both removable and fixed storage media for computers or the like. Computer programs may be stored on a computer connected to a telecommunications line such as the Internet and provided by downloading the programs via the telecommunications line. Computer programs may also be provided or distributed via a telecommunications line such as the Internet.

[0021] The processing device 10 having such a configuration executes the selection process described below to present to the operator how scrap S of various shapes and sizes should be loaded into the preheating section 2 to effectively heat the scrap S. Hereinafter, with reference to FIG. 3, the operation of the processing device 10 when executing the selection process will be described.

[0022] [Selection process] 3 is a flowchart showing the flow of the selection process according to one embodiment of the present invention. The flowchart shown in FIG. 3 starts when an execution command for the selection process is input to the processing device 10, and the selection process proceeds to step S1.

[0023] In the processing of step S1, the containment vessel creation unit 11 uses a shape creation tool such as three-dimensional CAD (Computer Aided Design) software to create and store electronic data of the containment vessel, which shows the structure of a shaft-shaped containment vessel that mimics the shape of the preheating section 2 into which the scrap S will be loaded. It is desirable to store the electronic data of the containment vessel as an intermediate file that can be used with many shape creation tools, such as STL (Standard Triangulated Language), STEP (Standard for the Exchange of Product Model Data), and IGE (Initial Graphics Exchange Specification). This completes the processing of step S1, and the selection process proceeds to step S2.

[0024] In step S2, the scrap shape creation unit 12 uses a shape creation tool such as 3D CAD software to create object data for multiple scraps S of different shapes and sizes. Strictly speaking, no scrap S used in the electric arc furnace 1 has the same shape. However, in this process, object data for scraps S is created to represent scraps with similar shapes. Specific shapes of scrap S include flat, rectangular, cylindrical, spherical, ellipsoidal, round bar, square bar, wire rod, cantilever, and wire. Object data may be created for all of these shapes, or only for representative shapes commonly used in operations. Since sizes vary, scraps to be used may be surveyed and object data of an average size may be created, or object data for multiple sizes may be created. Similar to the electronic data for the containment vessel, it is desirable to save the object data as an intermediate file that can be used with various shape creation tools such as STL, STEP, and IGES. This completes step S2, and the selection process proceeds to step S3.

[0025] In the process of step S3, the scrap packed bed creation unit 13 creates data on the scrap packed bed in the containment vessel using the electronic data of the containment vessel created in the process of step S1 and the object data of the scrap S created in the process of step S2. The Discrete Element Method (DEM) can be used as a method for filling the scrap S into the containment vessel. DEM is a method for calculating the movement, collision, and friction between objects using dynamic equations such as Newton's equations, but other methods can also be used as long as they can solve the dynamic equations and take into account the movement, collision, and friction between objects. Below, a method for filling the containment vessel with scrap will be described, assuming the use of DEM.

[0026] In DEM, when a force such as gravity is applied to an object, the object moves according to dynamics equations, and if it is determined that the objects are within contact distance, collisions and friction are calculated. If the file format of the electronic data for the containment vessel is stl, stl stores shape data in the form of triangular elements glued together on the object surface, so when using DEM, collisions and friction are determined for each triangular element and calculations are performed. Similarly, if the file format of the object data for scrap S is stl, collisions and friction are determined for each triangular element and calculations are performed when using DEM. Alternatively, the shape of scrap S can be approximated to a sphere, and if an object is within the radius of the approximated sphere, collisions and friction are determined and calculations are performed.

[0027] In this process, two or more shapes of scrap S are input. The shape of the scrap S to be input is selected based on the shape of the scrap S actually used from the shape data of scrap S created in step S2. When using DEM, a DEM calculation domain is set and a containment vessel is placed within the DEM calculation domain. A scrap inlet boundary region is then set above the containment vessel, through which the input scrap S is lowered. The size of the scrap inlet boundary region is set so that the input scrap S from the scrap inlet boundary region can be lowered and contained within the containment vessel. However, it is also possible to create shape data for a bucket that charges scrap S into the preheating section 2 in an actual machine, load the bucket shape data into DEM, and set the size of the scrap input boundary region by reproducing the operation of the actual machine. Then, by changing the settings for the input method of scrap S into the scrap inlet boundary region, multiple types of scrap packed bed data can be created.

[0028] Examples of data on the packed layer of multiple types of scrap include mixed scrap packed layer data in which scrap of different shapes and sizes is randomly mixed, and stacked scrap packed layer data in which scrap of different shapes and sizes is stacked in order. The scrap packed layer data is created according to the expected operating conditions, but at a minimum, the mixed scrap packed layer data and stacked scrap packed layer data described above are created. Figure 4 shows mixed scrap packed layer data in which two types of scrap SA and SB are randomly mixed, and Figure 5 shows stacked scrap packed layer data in which two types of scrap SA and SB are stacked in order.

[0029] The stacked scrap packed bed data will have two layers if there are two types of scrap S, and three layers if there are three types of scrap S. Furthermore, if three or more types of scrap S are used, it is not necessary to use shape data for all types of scrap S; two or more types may be used. The stacked scrap packed bed data may have multiple layers of the same type of scrap. Figure 6 shows an example of multiple layers of two types of scrap. Furthermore, when creating the scrap packed bed, the amount of scrap S to be charged is adjusted so that the difference in weight between the scrap packed beds is within 10%, so that the heat transfer to the scrap S can be compared between the scrap packed beds. This completes the processing of step S3, and the selection process proceeds to step S4.

[0030] In step S4, the fluid calculation unit 14 uses the scrap packed bed data created in step S3 to calculate the flow velocity of gas flowing between the scrap S packed in the containment vessel. Specifically, the fluid calculation unit 14 first creates a calculation structured grid within the containment vessel so that computational grid points are located in the gas region where at least fluids such as exhaust gas G flow. Next, the fluid calculation unit 14 calculates the signed distance at the position of the scrap S in the scrap packed bed data and determines whether each computational grid point is located within the gas region based on the calculated signed distance. The signed distance indicates the distance from the nearest scrap surface position (the position of a perpendicular line drawn from the computational grid point to the scrap surface) to the target computational grid point. If the computational grid point is located within the scrap S, a negative sign is assigned, and if it is located within the gas region, a positive sign is assigned. However, as long as it can be determined whether the computational grid point is located within the scrap S or the gas region, it does not matter whether the signed distance is positive or negative.

[0031] The fluid calculation unit 14 then applies a fluid simulation method, such as the lattice Boltzmann method, to the computational grid points determined to be within the gas region to calculate the gas flow velocity at those computational grid points. Any fluid calculation method can be used as long as it can calculate the gas flow velocity at the computational grid points. Figure 7 shows an example of boundary conditions set in the fluid calculation. As shown in Figure 7, in this example, the gas inlet boundary condition used to calculate the gas flow velocity is set below the scrap packed bed, at a location close to the assumed actual plant. The gas inlet boundary condition is set to a gas flow velocity or flow rate based on the operating conditions of the actual plant. For example, the gas flow velocity in the gas inlet boundary condition is set to approximately 0.1 to 10 m / s. In addition, wall boundary conditions are set around the containment vessel and at locations corresponding to the scrap S. The gas outlet boundary condition should preferably be a pressure boundary condition. Specifically, the pressure value set at the gas outlet boundary is not important, but it is generally set to 0.

[0032] The fluid properties of the gas may be those of ordinary air, or may be those that take into account the temperature used in the actual equipment. If a special gas is used in the actual equipment, the properties of that gas may also be used. The fluid calculation is performed until the gas flow rate reaches a steady state. The fluid calculation unit 14 performs fluid calculations for each scrap packed bed data created. For example, if there are two types of scrap packed bed data, the fluid calculation unit 14 performs fluid calculations using each scrap packed bed data. However, the boundary conditions and fluid property setting values are set to be the same for each scrap packed bed data. This completes the processing of step S4, and the selection process proceeds to step S5.

[0033] In the processing of step S5, the temperature calculation unit 15 calculates the temperatures of the scrap S and the gas for each scrap packed bed data set using a mathematical formula obtained by discretizing the thermal advection-diffusion equation using the gas flow velocity calculated in the processing of step S4 using the finite volume method. At this time, the boundary conditions and temperature property setting values are the same for each scrap packed bed data set. As long as the temperatures of the scrap S and the gas can be calculated based on the gas flow velocity calculated in the processing of step S4, there are no limitations on the temperature calculation method. The temperature calculation of the scrap S and the gas is performed in an unsteady state until a set time. The set time is set to a time before the time when the temperatures in the calculation domain all become the same, specifically, approximately 1 to 12,000 seconds.

[0034] If the same computational grid as that used in the processing of step S4 is used as the computational grid for the temperature calculation, there is no need to convert the gas flow rate information for each computational grid, thereby reducing the calculation time. The ambient temperature at that time is used as the initial temperature of the computational domain, and is often set to about 10 to 80°C. The inlet temperature boundary condition is set at the same position as the gas inlet boundary condition shown in Figure 7, and a temperature higher than the initial temperature is set based on operational data. In many cases, it is set to about 500 to 2000°C. One of the following conditions is set for the wall boundary shown in Figure 7: isothermal boundary condition, adiabatic boundary condition, heat transfer boundary condition, and radiation heat transfer boundary condition. The heat transfer boundary condition sets the ambient temperature and the heat transfer coefficient. In many cases, the ambient temperature is set to 10 to 80°C, and the heat transfer coefficient is set to 5 to 1000 W / m 2When using the radiative heat transfer boundary condition, the ambient temperature for setting the area and view factor is often set to 10 to 80°C, and the emissivity is set to 0.5 to 1.

[0035] The area and shape factor vary greatly depending on the shape, so they are set through experiments to suit the installation environment. The heat exchange between the gas and the scrap S is calculated using the heat transfer coefficient. The heat transfer coefficient can be a fixed value, or it can be set using an empirical or theoretical formula with the gas flow rate as a variable. When a fixed value is used, the heat transfer coefficient should be 5 to 500 W / m 2 It is desirable to set it within the range of K. As the temperature property, the temperature property of general air may be set, or the temperature property of air with temperature as a variable may be set. The temperature property of iron is set for the scrap S. If the scrap S is other than iron, the metal type of the scrap S is investigated and the temperature property of that metal is set. This completes the processing of step S5, and the selection processing proceeds to the processing of step S6.

[0036] In step S6, the scrap charging method selection unit 16 selects the scrap packed bed data that is determined to provide the best heat transfer to the scrap S under the specified conditions, based on the gas temperatures of the scrap packed bed data calculated in step S5. Specifically, in the gas temperature calculation, a temperature higher than the initial temperature is set as the inlet temperature boundary condition. Therefore, the scrap packed bed data that provides the best heat transfer to the scrap S has the lowest gas temperature after passing through the scrap packed bed. In other words, the term "good heat transfer to the scrap S" indicates that when gas at a predetermined temperature is applied from the gas inlet boundary to the scrap S in the scrap packed bed, heat transfer from the gas to the scrap S is facilitated. As a result, the gas temperature is lower at the gas outlet boundary than at the gas inlet boundary. It is considered that the lower the gas temperature (or the exhaust gas temperature, described later) at the gas outlet boundary is compared to the gas temperature at the gas inlet boundary, the more heat is transferred to the scrap S. Therefore, the scrap charging method selection unit 16 acquires the gas temperature at a gas temperature measurement point (see FIG. 7) set at a position where the gas temperature after passing through the scrap packed bed can be measured as the measured exhaust gas temperature. In the present invention, this measured exhaust gas temperature may be treated as the gas temperature at the gas outlet boundary. The gas temperature measurement points may be set on a plane rather than at a point, and the gas temperatures on that plane may be averaged or other statistically processed to obtain the measured exhaust gas temperature. The positions of the gas temperature measurement points and the statistical processing method are the same for each scrap packed bed data.

[0037] The scrap charging method selection unit 16 then sets the scrap packed bed data with the lowest measured exhaust gas temperature as the optimal scrap packed bed, and outputs information about the charging method of the scrap S in that scrap packed bed (such as the layer thickness, amount, and ratio of scrap S for each scrap S charging timing (skip)) to the output device 22, thereby proposing a charging method for the scrap S in the actual furnace. For example, if the measured exhaust gas temperature of the mixed scrap packed bed is the lowest, the scrap charging method selection unit 16 proposes the mixed charging method as the optimal charging method. The timing of the proposal may be at the start of processing or during processing. By outputting the proposed charging method to the output device 22 and having the operator operating the electric furnace 1 select that charging method, a charging method for the scrap S that effectively heats the scrap S being charged can be selected, thereby reducing heat loss during operation and improving operational efficiency. Furthermore, since the scrap S is better heated, the time required for raising the temperature by the arc heat required to melt the scrap S is reduced, shortening the time required to melt the scrap S and further improving the efficiency of the operation of the electric furnace 1. This completes the processing of step S6, and the series of selection processes ends.

[0038] In the above explanation, an example is given of selecting the scrap packed bed with the "best" heat transfer to the scrap S, but one or more scrap packed beds with the best heat transfer to the scrap S may be selected based on predetermined conditions. For example, a scrap packed bed may be selected in which the difference between the gas temperature at the gas inlet boundary and the gas temperature (or exhaust gas temperature) at the gas outlet boundary is equal to or greater than a predetermined temperature. In this case, if multiple scrap packed beds are selected, one scrap packed bed may be finally selected based on further conditions or at the discretion of the operator.

[0039] As is clear from the above description, in the selection process according to one embodiment of the present invention, the scrap packed bed creation unit 13 creates multiple scrap packed bed data sets for different methods of charging the scrap S into the containment vessel, and the fluid calculation unit 14 calculates the flow velocity of the gas flowing between the scrap S for each scrap packed bed data set. The temperature calculation unit 15 then uses the calculated gas flow velocity to calculate the temperature of the gas passing through the scrap packed bed for each scrap packed bed data set. The scrap charging method selection unit 16 then selects, from the multiple scrap packed bed data sets, scrap packed bed data sets that provide the best heat transfer to the scrap based on the calculated gas temperature. This makes it possible to present how scrap of various shapes and sizes should be charged into the containment vessel to provide the best heat transfer to the scrap.

[0040] [Example 1] In this example, first, using the 3D CAD software SpaceClaim2021R1, electronic data for a 100 x 100 x 250 rectangular parallelepiped containment vessel as shown in Figure 8 was created and saved as an STL file. The top of the containment vessel is open, and the bottom is sealed. Next, using the 3D CAD software SpaceClaim2021R1, object data for two types of scrap—flat scrap and ellipsoidal scrap—as shown in Figures 9(a) and (b) were created and saved as STL files. Next, the containment vessel and scrap data were loaded into the particle simulator Rocky DEM 4.3.1, and three types of scrap packed bed data were created as shown in Figures 10(a) to 10(c). For each scrap packed bed data, the amount of scrap S charged was adjusted to have the same weight, and the scrap S was assumed to be iron, with a density of 7800 kg / m. 3 The weight of the packed bed of mixed scrap shown in Fig. 10(a) was 5.59 kg, the weight of the packed bed of stacked scrap (two layers) shown in Fig. 10(b) was 5.59 kg, and the weight of the packed bed of stacked scrap (four layers) shown in Fig. 10(c) was 5.52 kg.

[0041] Next, the same computational grid was created for each scrap packed bed data, and fluid calculations were performed with the same boundary conditions and fluid properties. The computational grid was divided into 128 on the x-axis, 396 on the y-axis, and 128 on the z-axis. The boundary conditions are as shown in Figure 11. The fluid properties were set assuming air as the gas. Specifically, the density was set to 1.17 kg / m 3 , viscosity 1.822e -5 The gas velocity was set to Pa·s. The lattice Boltzmann method was used as the calculation method, and calculations were performed until the gas velocity reached a steady state. Next, the same calculation grid was created for each scrap data packed bed, and the same boundary conditions and temperature properties were given to perform temperature calculations. The calculation grid used was the same as that used when performing the fluid calculations. The boundary conditions are as shown in Figure 11. The temperature properties were set assuming air for the gas and iron for the scrap S. Specifically, the gas density was set to 1.17 kg / m 3 , thermal conductivity 0.00257W / mK, specific heat 1000J / kg-K, density of scrap 7800kg / m 3 The thermal conductivity was set to 45 W / mK, and the specific heat was set to 461 J / kg-K. The heat transfer coefficient was used for the heat exchange between the gas and the scrap S, and the heat transfer coefficient was set to 100 W / m 2 -K was set. Temperature calculations were performed in an unsteady state using a formula discretized by the finite volume method for the heat advection-diffusion equation. The initial temperatures of the gas and scrap S were set to 27°C, and the calculation was completed 100 seconds after the start of the calculation.

[0042] The scrap packed bed data with the best heat transfer was then determined based on the measured exhaust gas temperature at the exhaust gas temperature measurement point calculated for each scrap packed bed data, and the scrap S charging method was selected. As shown in Figure 11, the exhaust gas temperature measurement point was set on a plane perpendicular to the gas inflow direction of the gas inlet boundary condition, 150 mm from the edge of the scrap packed bed on the inlet gas boundary condition side, after the gas had passed through the scrap packed bed. Because measurements were taken on a plane, multiple gas temperatures were included at the gas temperature measurement point, but these were arithmetically averaged to determine the measured exhaust gas temperature. For each scrap packed bed temperature calculation result, exhaust gas temperatures were calculated by measuring the exhaust gas temperature at the same position. Figure 12 shows a comparison of the measured exhaust gas temperatures for each scrap packed bed. As shown in Figure 12, the stacked scrap packed bed (4 layers) had the lowest measured exhaust gas temperature, and this was the scrap S charging method with the best heat transfer to the scrap S when charging the scrap shown in Figures 9(a) and (b). Therefore, the method of stacking in four layers was output to a monitor, etc., and proposed as a scrap charging method for the actual machine.

[0043] Example 2 In this example, the dimensions of the ellipsoidal scrap in Example 1 were increased by 1.5 times, and heat transfer to the scrap in each packed bed was confirmed. As shown in Figures 13(a) and 13(b), the dimensions of the flat scrap were the same as in Example 1, and for the ellipsoidal scrap, both the semi-major and semi-minor radii were increased by 1.5 times. Three types of scrap packed bed data were then created, as shown in Figures 14(a) to 14(c). The weight of the mixed scrap packed bed shown in Figure 14(a) was 5.59 kg, the weight of the stacked scrap packed bed (two layers) shown in Figure 14(b) was 5.6 kg, and the weight of the stacked scrap packed bed (four layers) shown in Figure 14(c) was 5.62 kg. The conditions for fluid flow calculations and temperature calculations were the same as in Example 1. In the scrap charging method selection process, the measured gas temperature was calculated using the arithmetic mean of the same surface as in Example 1. The measured exhaust gas temperatures for each scrap packed bed data are shown in Figure 15. As shown in Fig. 15, in this example, it was confirmed that the stacked scrap packed bed (two layers) provides good heat transfer to the scrap in the packed bed. For this reason, a charging method for scrap S that results in a similar packed state of scrap S in the stacked scrap packed bed (two layers) was output to a monitor or the like, and proposed as a scrap charging method for an actual machine.

[0044] Example 3 In this example, as shown in Figures 16(a) and 16(b), instead of the ellipsoidal scrap used in Example 1, pipe-shaped scrap with internally interconnected pores was used. Three types of scrap packed bed data were generated, as shown in Figures 17(a) to 17(c). The weight of the mixed scrap packed bed shown in Figure 17(a) was 5.66 kg, the weight of the stacked scrap packed bed (two layers) shown in Figure 17(b) was 5.66 kg, and the weight of the stacked scrap packed bed (four layers) shown in Figure 17(c) was 5.59 kg. The conditions for fluid flow calculation and temperature calculation were the same as in Example 1. In the scrap charging method selection process, the measured flue gas temperature was calculated using the arithmetic mean of the surfaces, as in Example 1. The measured flue gas for each scrap packed bed data is shown in Figure 18. As shown in Figure 18, in this example, the stacked scrap packed bed (two layers) had the poorest heat transfer to the scrap in the packed bed, and the stacked scrap packed bed (four layers) had the best heat transfer to the scrap in the packed bed. For this reason, a method of charging scrap S that would result in the same filling state of scrap S as in the stacked scrap filling layer (4 layers) was output to a monitor, etc., and proposed.

[0045] Example 4 In this example, the size of the pipe-shaped scrap in Example 3 was increased by 1.5 times, as shown in Figures 19(a) and 19(b). Three types of scrap packed bed data were created, as shown in Figures 20(a) to 20(c). The weight of the mixed scrap packed bed shown in Figure 20(a) was 5.6 kg, the weight of the stacked scrap packed bed (2 layers) shown in Figure 20(b) was 5.58 kg, and the weight of the stacked scrap packed bed (4 layers) shown in Figure 20(c) was 5.59 kg. The fluid calculation step, fluid calculation, and temperature calculation conditions were the same as in Example 1. In the scrap charging method selection process, the measured flue gas temperature was calculated using the arithmetic mean of the surfaces, as in Example 1. The measured flue gas for each scrap packed bed data is shown in Figure 21. As shown in Figure 21, in this example, the stacked scrap packed bed (4 layers) had the poorest heat transfer to the scrap in the packed bed, and the mixed scrap packed bed had the best heat transfer to the scrap in the packed bed. Therefore, a charging method for scrap S that would be similar to the packed state of scrap S in the mixed scrap packed bed was output to a monitor, etc., and proposed.

[0046] (Example of use: furnace operation method) The furnace operation method according to the present invention utilizes the scrap packed bed selection method according to the embodiment. Specifically, after the processing of step S6, scrap S is charged into the furnace so that the packed state of scrap S is similar to that of the selected scrap packed bed with the best heat. In this case, the "furnace" also includes the preheating section 2. By utilizing the scrap packed bed selection method according to the embodiment, it is possible to reduce heat loss due to exhaust gas and thereby reduce the energy consumption of the furnace.

[0047] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Explanation of symbols]

[0048] 1 electric furnace 2 Preheating section 3. Graphite electrodes 4 Melting part 10 Processing equipment 11. Containment Vessel Fabrication Department 12 Scrap shape creation section 13 Scrap packing layer creation section 14 Fluid calculation section 15 Temperature calculation section 16 Scrap charging method selection section 21 Input Devices 22 Output Devices G, G1 exhaust gas MI molten iron S, SA, SB scrap

Claims

1. a creating step of creating electronic data of a plurality of scrap packed beds having different methods of charging scrap into a containment vessel; a fluid calculation step of calculating a flow rate of gas flowing between the scrap for each packed layer of scrap using the electronic data; a temperature calculation step of calculating a temperature of the gas having passed through each scrap packed bed using the flow velocity of the gas calculated in the fluid calculation step; a selection step of selecting a scrap packed bed that has good heat transfer to the scrap from among a plurality of scrap packed beds based on the gas temperature calculated in the temperature calculation step; A method for selecting a scrap packing layer, comprising:

2. 2. The method for selecting a scrap packed bed according to claim 1, wherein the plurality of scrap packed beds include a mixed scrap packed bed in which two or more types of scrap are randomly charged, and a stacked scrap packed bed in which two or more types of scrap are stacked in order.

3. 3. The method for selecting a scrap packing layer according to claim 2, wherein the stacked scrap packing layer includes multiple layers of the same type of scrap.

4. 2. The method for selecting a scrap packing layer according to claim 1, further comprising the step of outputting information about the scrap packing layer selected in said selecting step.

5. a generating means for generating electronic data of a plurality of scrap packed beds having different methods of charging scrap into a containment vessel; a fluid calculation means for calculating a flow rate of gas flowing between the scrap for each packed layer of scrap using the electronic data; a temperature calculation means for calculating the temperature of the gas passing through each scrap packed bed using the gas flow velocity calculated by the fluid calculation means; a selection means for selecting, from among a plurality of scrap packed beds, a scrap packed bed that has good heat transfer to the scrap based on the gas temperature calculated by the temperature calculation means; A scrap packed bed selection device comprising:

6. A method for operating a furnace, comprising the step of charging scrap into the furnace so as to achieve a packed state similar to that of a scrap packed bed preselected by the method for selecting a scrap packed bed according to any one of claims 1 to 4.

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