Numerical calculation method for iron ore sintering process, calculation device, numerical calculation program, and production method for sintered ore

Abstract

According to the present invention, a numerical calculation method for an iron ore sintering process is for a sintering process for sintering a powdered substance that contains iron ore in a sintering machine to produce a sintered ore and includes a step for creating a calculation mesh for an area of the sintering machine that is formed by a starting material and a sinter cake and a step for calculating the state inside the sintering machine by calculating chemical reaction amounts, reaction heats, heat transmission amounts between gas molecules and solids, physical property values for substances, and temperature changes for the insides of cells and heat transfer amounts and gas molecule transfer amounts in the machine length direction and a layer thickness direction between cells.

Description

Numerical calculation method for iron ore sintering process, calculation device, numerical calculation program, and method for producing sintered ore

[0001] The present disclosure relates to a numerical calculation method for an iron ore sintering process, a calculation device, a numerical calculation program, and a method for producing sintered ore.

[0002] Sintered ore, which is one of the raw materials for the blast furnace ironmaking process, is produced by adding several percent of moisture to the main raw material, iron ore, auxiliary raw materials containing CaO such as limestone, auxiliary raw materials containing SiO ２ such as silica, return ore, and solid fuel, mixing and granulating them to form pseudo-granules, and then sintering them with the combustion heat of the solid fuel. After filling the pseudo-particles after granulation into a circulating pallet, ignition is carried out on the surface layer of the raw material filling layer, and air is sucked from below, so that the solid fuel in the filling layer burns from the top to the bottom, and the raw material is sintered to produce a sinter cake. After crushing the sinter cake with a crusher, it is sieved to collect lumpy products of 5 mm or more and used as sintered ore for blast furnaces.

[0003] In the sintering process, various in-layer conditions such as temperature and air permeability affect the productivity of the process and the quality of sintered ore. For example, when the porosity in the layer is low and the air permeability is poor, the gas flow rate passing through the layer decreases. When the gas flow rate in the layer decreases, the ignition and combustion of the solid fuel in the unburned area are delayed, the sintering speed decreases, and the productivity deteriorates. Also, when the temperature in the layer is low, the melting reaction of the raw material becomes insufficient, leading to a decrease in the lump ratio after crusher crushing and a decrease in the cold strength of the sintered ore. Since the in-layer conditions affect the productivity of the process and the quality of the finished product, etc., the estimation of the in-layer conditions by numerical simulation is expected to be a useful tool for determining operating conditions and controlling the quality of sintered ore, and various simulation models have been developed so far.

[0004] As models for calculating the in-layer conditions in the sintering layer and methods for their utilization, the following have been reported so far.

[0005] Patent Document 1 calculates the gas composition within the gas boundary film of coke particles, using the sintered layer temperature and combustion gas composition, which are calculated based on a combustion model that takes into account the balance of each substance and heat in the sintered layer, as input values, and the gas composition within the gas boundary film is CO and O ２ NO is produced by combustion based on the ratio of x An evaluation method has been proposed to assess the quantity of [something].

[0006] Patent Document 2 states that by using a physical model that considers chemical reactions and heat transfer phenomena, observable variables in the sintering process can be calculated, and unknown parameters in the physical model can be corrected based on the degree of deviation between the calculated values ​​and actual values, thereby enabling highly accurate estimation of the state of the sintering process. Furthermore, by accurately estimating temperature changes within the layers, it is possible to provide operational guidance aimed at improving yield regarding the proportion of coke in the raw materials and the pallet speed.

[0007] Non-patent document 1 proposes a simulation model that applies a coke combustion rate equation that takes into account the diffusion of oxygen within pseudoparticles. It is said that by calculating the combustion rate of coke contained in the fine powder that constitutes the pseudoparticles, taking into account the diffusion of oxygen within the fine powder layer, it is possible to obtain calculation results for the in-layer temperature distribution that are closer to the actual phenomenon.

[0008] Non-patent document 2 reports the development of a three-dimensional model capable of predicting sintered ore quality. It is stated that by using a three-dimensional model that takes into account various reactions, heat transfer, mass transfer, etc., within the sintered layer, it is possible to calculate the temperature, porosity, liquidus fraction, and mineral structure within the layer and predict the quality of the sintered ore.

[0009] Non-patent document 3 reports a numerical simulation analysis of the effects of injecting gaseous fuel on the sintered layer. The simulation model, which performs calculations to satisfy the conservation of mass, momentum, and energy, incorporates the combustion reaction of gaseous fuel to analyze the effects of injecting gaseous fuel into the sintered layer.

[0010] Non-patent document 4 reports a simulation model that takes into account various reactions occurring within the layer, as well as the pressure drop and wind speed within the layer. The temperature within the layer is calculated by calculating the temperature at minute time intervals using transient heat conduction equations for the heat balance of solids and gases in the sintered layer, and then evolving the model over time. By calculating the pressure drop and wind speed within the layer at each time step, wind speed and pressure close to experimental values ​​are obtained.

[0011] Japanese Patent Publication No. 5447192, Japanese Unexamined Patent Publication No. 2024-50752, Iron and Steel, 101 (2015), 19. Iron and Steel, 92 (2006), 769. ISIJ Int., 51 (2011), 913. Iron and Steel, 70 (1984), 1567.

[0012] Conventionally, simulation programs that take into account various phenomena within the sintered layer have been proposed, as shown in Non-Patent Documents 1 and 2. Furthermore, as shown in Patent Documents 1 and 2 and Non-Patent Document 3, simulation programs that take into account NO, which is subject to environmental regulations, have been proposed. ｘ Simulations of conditions within a sintered layer have been used for purposes such as predicting the amount of material produced, improving yield through operational guidance, and analyzing the effects of introducing flammable gases into the layer. However, conventional simulations still have unconsidered factors, and there is still room for improvement in the calculation methods for conditions within the layer. One of the unconsidered factors is the transfer of heat and mass in the direction of the sintering machine's length.

[0013] Furthermore, the sintering process involves drawing gas from below and advancing the combustion section from the upper layer to the lower layer. Therefore, the movement of heat and gas molecules within the layer is predominantly in the thickness direction. However, within the sintered layer, temperature and pressure gradients occur not only in the thickness direction but also in the machine length direction. Consequently, within the sintered layer, heat and gas molecule movement occurs in accordance with the temperature and pressure gradients not only in the thickness direction but also in the machine length direction. In particular, in processes such as those described in Non-Patent Document 3, where flammable gas is drawn into the layer from above, the location within the layer where the injected gas is transported and combusted is a crucial factor, and a simulation program capable of analyzing the two-dimensional movement of gas molecules within the layer is necessary.

[0014] However, most conventional simulation programs, as described in Non-Patent Documents 1 and 4, were one-dimensional models that defined space only in the thickness direction. This is because, as mentioned above, heat and gas molecule transfer within a sintered layer is predominantly in the thickness direction, and therefore, little development has been done on simulation programs that focus on heat and mass transfer in the machine length direction. Non-Patent Document 2 reports the development of a three-dimensional simulation program, but it does not show a calculation method for determining heat and mass transfer in the machine length direction. In particular, there is no description of how to determine the pressure distribution within the layer and the two-dimensional gas velocity distribution that satisfy the boundary conditions around the sintering machine. Therefore, there was a need to develop a simulation program that could perform two-dimensional gas transfer analysis taking into account heat and mass transfer in both the thickness direction and the machine length direction.

[0015] The purpose of this disclosure is to provide a method for calculating the state within a sintered layer, taking into account heat and gas mass transfer in two directions: the thickness direction and the machine length direction. The method disclosed also enables two-dimensional analysis of gas transfer amounts.

[0016] [1] A numerical calculation method for an iron ore sintering process, comprising the steps of: creating a computational mesh in a region on the sintering machine composed of raw materials and sinter cake, in a sintering process in which powdered material containing iron ore is sintered in a sintering machine; and calculating the state inside the sintering machine by calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule transfer between cells in the machine length direction and layer thickness direction.

[0017] [2] The numerical calculation method for the iron ore sintering process described in [1] above, characterized in that, in calculating the amount of gas molecule movement between each cell in the machine length direction and the layer thickness direction, convergence calculations are performed such that all of the following are satisfied: Ergun's equation relating to the pressure difference and gas flow velocity in the layer thickness direction, Ergun's equation relating to the pressure difference and gas flow velocity in the machine length direction, and the continuity equation.

[0018] [3] A numerical calculation method for an iron ore sintering process according to [1] or [2] above, characterized in that, in calculating the amount of gas molecule movement between each cell in the machine length direction and the layer thickness direction, the steps of: calculating the amount of gas molecule movement between each cell in the layer thickness direction using the continuity equation; calculating the pressure inside each cell using Ergun's equation relating to the amount of gas molecule movement in the layer thickness direction, the pressure difference in the layer thickness direction, and the gas flow velocity; and repeatedly performing convergence calculations of the amount of gas molecule movement between each cell and the pressure inside each cell using Ergun's equation relating to the pressure inside each cell, the pressure difference in the machine length direction, and the gas flow velocity, the pressure at the outer edge of the sintered layer matches the atmospheric pressure around the sintering machine and the pressure inside the wind box.

[0019] [4] A numerical calculation device for an iron ore sintering process, comprising a control unit, which calculates the state inside the sintering machine by creating a computational mesh in a region on the sintering machine composed of raw materials and sinter cake, and calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule movement between cells in the machine length direction and layer thickness direction.

[0020] [5] A numerical calculation program for an iron ore sintering process, which involves causing a computer to perform the following actions in a sintering process in which powdered material containing iron ore is sintered in a sintering machine to produce sintered ore: creating a computational mesh in the region composed of raw materials and sinter cake on the sintering machine; and calculating the state inside the sintering machine by calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule transfer between cells in the machine length direction and layer thickness direction.

[0021] [6] A method for producing sintered ore, comprising calculating the state inside a sintering machine using the numerical calculation method for the iron ore sintering process described in any one of the above items [1] to [3], and sintering a powdered substance containing iron ore in a sintering machine to produce sintered ore.

[0022] According to this disclosure, it is possible to calculate the state within the sintered layer, taking into account heat and gas mass transfer in two directions: the thickness direction of the sintered layer and the length direction of the machine.

[0023] This figure shows an example of a numerical calculation system for an iron ore sintering process according to one embodiment of the present disclosure. This figure schematically represents the structure of a sintering machine equipped with the numerical calculation system according to the present disclosure. This is a schematic diagram of the calculation target area according to the present disclosure. This is an enlarged view of a part of the calculation target area according to the present disclosure. This is a calculation flowchart for gas molecule movement and pressure according to the present disclosure. This is a calculation flowchart for gas molecule movement in the layer thickness direction according to the present disclosure. This is a calculation flowchart for pressure inside each cell according to the present disclosure. This is a calculation flowchart for gas molecule movement in the machine length direction according to the present disclosure. This is a flowchart for calculating the in-layer state according to the present disclosure. This figure shows the temperature of each cell in the calculation target area according to one embodiment of the present disclosure. This figure shows the relationship between temperature and time at a specific layer thickness position according to one embodiment of the present disclosure as a graph. This figure shows the wind velocity in the layer thickness direction of each cell in the calculation target area according to one embodiment of the present disclosure. This figure shows the wind velocity in the machine length direction of each cell in the calculation target area according to one embodiment of the present disclosure. This figure shows the pressure of each cell in the calculation target area according to one embodiment of the present disclosure. This figure shows the relationship between wind velocity in the layer thickness direction and machine length position at a specific layer thickness position according to one embodiment of the present disclosure as a graph. This figure shows a graph illustrating the relationship between the wind speed in the direction of the machine length and the machine length position at a specific layer thickness position according to one embodiment of this disclosure. This figure shows a graph illustrating the relationship between the pressure at a specific layer thickness position and the machine length position according to one embodiment of this disclosure.

[0024] The embodiments for carrying out the present invention will be described in detail below. The embodiments described below are merely examples of the present invention and do not limit the configuration of the present invention.

[0025] Figure 1 shows an example of a numerical calculation system for an iron ore sintering process according to one embodiment of the present disclosure. The numerical calculation system 1 comprises a calculation device 10 and a sintering machine 20.

[0026] The computing device 10 is a general-purpose computer such as a workstation or personal computer. Alternatively, the computing device 10 may be a dedicated computer configured to function as the computing device 10 of the numerical calculation system 1.

[0027] The computing device 10 comprises a control unit 11, an input unit 12, an output unit 13, and a storage unit 14.

[0028] The control unit 11 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0029] The control unit 11 reads programs, data, etc., stored in the storage unit 14 and executes various functions.

[0030] The input unit 12 includes one or more input interfaces that detect user input and acquire input information based on user operations. The input unit 12 includes, for example, physical keys, capacitive keys, a touchscreen integrated with the display of the output unit 13, or a microphone that accepts voice input.

[0031] The output unit 13 includes one or more output interfaces that output information and notify the user. The output unit 13 includes, for example, a display that outputs information as an image, a speaker that outputs information as sound, etc. The display included in the output unit 13 may be, for example, an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube) display, etc.

[0032] The storage unit 14 is, for example, a flash memory, a hard disk, or an optical memory. Part of the storage unit 14 may be located outside the computing device 10. In this case, part of the storage unit 14 may be a hard disk, memory card, or the like, connected to the computing device 10 via any interface.

[0033] The memory unit 14 stores programs for the control unit 11 to execute various functions, data used by those programs, and so on.

[0034] Figure 2 is a schematic diagram of the structure of the sintering machine 20. The sintering machine 20 sintersects the sintering raw material and produces agglomerated sintered ore. The sintering raw material may be, for example, a mixture containing powdered iron ore and limestone.

[0035] The sintering machine 20 comprises a raw material charging section 21, an ignition furnace 22, a waste material discharge section 23, and a wind box 24.

[0036] The raw material charging section 21 charges the sintering raw material into the sintering machine 20. After being charged into the sintering machine 20, the sintering raw material may be in the form of multiple layers.

[0037] The ignition furnace 22 ignites the sintering raw material, which has been charged into the sintering machine 20 via the raw material charging section 21. The ignited sintering raw material is transported to the ore discharge section 23 by pallets or the like. During the transport process to the ore discharge section 24, the sintering raw material is ignited in the ignition furnace 22, and combustion proceeds to produce sintered ore. The sintered ore produced during the sintering process is discharged from the ore discharge section 23. Multiple window boxes 24 provided in the sintering machine 20 draw in gas.

[0038] Next, we will explain the processes executed by the control unit 11 of the computing device 10.

[0039] (Method for Creating Computational Mesh) The control unit 11 of the computing device 10 sets a computational target area that includes the raw material layer and the sinter cake on the sintering machine strand. After setting the computational target area, the control unit 11 of the computing device 10 divides the computational target area into meshes so as to divide it in the machine length direction and the layer thickness direction, and calculates the state of the entire computational area by calculating the state within each individual mesh. Although it is arbitrary how many divisions are made in the machine length and layer thickness by the meshes, as an example, the layer thickness is divided into 50 parts and the machine length is divided into 30 parts.

[0040] (Method for Calculating Gas Transfer Amount between Cells and Pressure inside Cells) The control unit 11 of the computing device 10 calculates the gas molecular transfer amounts in two directions, namely the sintering layer thickness direction and the sintering machine length direction, and the pressure inside each cell. Here, the calculation of the gas molecular transfer amount and the pressure is performed so that all three of the following continuous equations (1), and Ergun's equations (2) and (3), which are relational expressions of the pressure difference and the gas flow velocity in the layer thickness direction and the machine length direction, are satisfied. Note that the definitions of the respective variables in the above equations (1) to (3) are as follows. U ｘ : Gas molecular transfer amount in the layer thickness direction between each cell (mol / sec) U ｙ : Gas molecular transfer amount in the machine length direction between each cell (mol / sec) m: Gas molecular generation amount inside each cell (mol / sec) Δp ｘ : Pressure gradient in the layer thickness direction (cmH ２ O / cm) Δp ｙ : Pressure gradient in the machine length direction (cmH ２ O / cm) u ｘ : Gas flow velocity in the layer thickness direction (cm / sec) u ｙ : Gas flow velocity in the machine length direction (cm / sec) g: Acceleration due to gravity (cm / sec ２ ) μ: Viscosity coefficient of gas (poise ) ε: Void fraction (-) D: Pseudo particle diameter (cm) ρ: Specific gravity of gas (g / cm ３ )

[0041] The control unit 11 of the computing device 10 iterates the steps of calculating the gas molecular transfer amount in the layer thickness direction by the continuous equation, calculating the pressure inside each cell by Ergun's equation, and calculating the gas molecular transfer amount in the machine length direction from Ergun's equation, thereby calculating the pressure and the gas molecular transfer amount that satisfy all three equations

[0042] The calculation methods for gas molecule transfer and pressure will be explained below using Figures 3A to 4D. Figure 3A is a schematic diagram of the calculation area. Figure 3B is an enlarged view of the shaded area in Figure 3A. Figure 4A is a calculation flowchart for gas molecule transfer and pressure. Figure 4B is a calculation flowchart for gas molecule transfer in the layer thickness direction. Figure 4C is a calculation flowchart for pressure inside each cell. Figure 4D is a calculation flowchart for gas molecule transfer in the machine length direction. In the following explanation, i is the cell number in the layer thickness direction, and j is the cell number in the machine length direction. ｍａｘ is the number of cell divisions in the layer thickness direction, and j ｍａｘ This is the number of cell divisions in the direction of the aircraft's length. ｘ (i, j) is the amount of gas molecule transfer in the layer thickness direction between each cell, U ｙ (i,j) is the amount of gas molecule movement in the direction of the machine length, and P(i,j) is the pressure in each cell. n is the number of calculation iterations, and n ｍａｘ This is its maximum value.

[0043] The control unit 11 of the computing device 10 determines the amount of gas molecule transfer U in the layer thickness direction between each cell. ｘ Calculate (i, j). The method for calculating the amount of gas molecule movement in the layer thickness direction is as follows.

[0044] From equation (1) above, the relationship shown in equation (4) below holds for the amount of gas molecules transferred in each cell. In the above formula (4), m(i,j) represents the combustion reaction, CaCO₃ ３ This is the amount of gas molecules generated inside the cell (i,j) due to thermal dissociation, etc., and is determined in the step of calculating various chemical reactions described later.

[0045] Also, U ｘ (i, j) is the amount of gas molecule movement on a molar basis, and the gas flow velocity u ｘ (i, j) is calculated by the following formula (5). In equation (5) above, R is the gas constant and T(i,j) is the gas temperature inside the cell.

[0046] According to the above formula (4), U ｘ (1, j) and U ｙ Given (i, j), i = 1, i = iｍａｘ Amount of gas molecule migration in the layer thickness direction U ｘ and gas flow velocity u ｘ This can be calculated. Here, at the first iteration of the calculation, n=0, U ｙ (i, j) may be assumed to be 0, and P(i, j) may be assumed to be equal to the ambient pressure around the sintering machine. The control unit 11 of the calculation device 10 sets i = i ｍａｘ Amount of gas molecule migration in the layer thickness direction U ｘ The amount of gas molecule migration in the layer thickness direction U is calculated one line at a time until the calculation is complete. ｘ Calculate.

[0047] The control unit 11 of the calculation device 10 calculates the pressure P(i,j) in each cell. The method for calculating the pressure in each cell is as follows:

[0048] From equation (2) above, the following relationship (6) holds between the pressure and gas flow velocity in each cell. In equation (6) above, Δx is the length of one cell in the layer thickness direction. According to equation (6) above, i=1 to i=i ｍａｘ The pressure P(i,j) in the cell can be calculated. The control unit 11 of the calculation device 10 calculates the pressure P(i ｍａｘ Calculate the pressure P(i,j) in each cell, row by row, until you find the value of j.

[0049] Here, P(i ｍａｘ ,j) is U ｘ The larger (1, j), the higher it becomes. Therefore, the control unit 11 of the computing device 10 will keep U until the condition of equation (7) below is satisfied. ｘ (1, j) in a small amount ΔU ｘ Increase it by only that much and repeat the above calculation. By performing this process, the pressure conditions inside the window box and on the sintering machine are satisfied. ｘ (i, j) and P(i, j) can be determined. In equation (7) above, ΔP(j) is the pressure difference between the surface of the sintered layer and the wind box.

[0050] The calculations shown in Figures 4B and 4C above are performed from j=1 to j=j ｍａｘ By performing this, the control unit 11 of the computing device 10 determines P(i,j) and U that satisfy the pressure conditions inside the window box and on the sintering machine. ｘ(i, j) can be calculated across the entire computational domain.

[0051] Here, similar to equation (6), the gas flow velocity u in the direction of the machine length ｙ The following relationship (8) holds between (i, j) and pressure P(i, j). In equation (8) above, Δy is the length of one cell in the aircraft's longitudinal direction.

[0052] Equation (8) above is the gas flow velocity u in the direction of the machine length. ｙ This is a quadratic equation in which P(i, j) and P(i, j+1) are given, and u ｙ This can be easily calculated. As shown in Figures 4B and 4C, P(i,j) has been calculated for all cells constituting the calculation target area, so as shown in Figure 4D, the control unit 11 of the calculation device 10 calculates the gas flow velocity u in the machine length direction for all cells using equation (8). ｙ It is possible to calculate u using equation (8). ｙ When calculating the flow velocity in the machine direction at the point adjacent to the ore discharge section (i, jmax), the ambient pressure around the sintering machine is applied instead of P(i, j+1) in equation (8).

[0053] Similar to equation (5), the amount of gas molecule transfer U based on the amount of substance in the longitudinal direction of the machine. ｙ (i, j) and gas flow velocity u y The relationship shown in equation (9) below holds for (i, j). Therefore, the control unit 11 of the calculation device 10 calculates U for all cells. ｙ (i, j) can be calculated. In the calculation for n=1, U was obtained in this way. ｙ Using (i, j), the calculations in Figures 4B, 4C, and 4D are performed again, and U ｙ Obtain the recalculated value of (i, j). Perform a similar calculation on U ｘ (i, j), U ｙ The nth and n+1th calculation results for (i,j) and P(i,j) are equal, or n = n ｍａｘ Repeat until U ｘ , U ｙ , P, u ｘ u ｙ The convergence calculation result is obtained for n. ｍａｘ U ｘ(i, j), U ｙ The calculations for (i,j) and P(i,j) should be set to converge sufficiently; one example is 200 iterations.

[0054] U obtained by this convergence calculation ｘ , U ｙ , P, u ｘ u ｙ This satisfies equations (1), (2), and (3) throughout the entire calculation area, thereby achieving the calculation of gas molecule migration in the layer thickness direction and machine length direction that is the target of this disclosure.

[0055] (Method for calculating inter-cell heat transfer) The control unit 11 of the calculation device 10 calculates the amount of heat transferred between each cell. In this disclosure, two factors are considered for inter-cell heat transfer: the amount of heat transferred by conduction of the solid and the amount of sensible heat possessed by the gas moving between cells. For the amount of heat transfer by conduction of the solid, the amount of heat transferred in the thickness direction Q when moving from cell (i, j) to cell (i+1, j) is calculated. ｘ (i, j) is represented by the following equation (10). Also, Q is the amount of heat transfer in the machine length direction when moving from cell (i, j) to cell (i, j+1). ｙ (i, j) is expressed by the following equation (11). In equations (10) and (11) above, λ is the thermal conductivity of the solid in the cell, and Ts(i,j) is the temperature of the solid in the cell. By using equations (10) and (11) above, the control unit 11 of the calculation device 10 can calculate the amount of heat conduction of the solid in the layer thickness direction and the machine length direction.

[0056] Regarding the sensible heat of the gas moving between cells, the heat quantity q in the thickness direction moving from cell (i, j) to cell (i-1, j) is... ｘ (i, j) is expressed by the following equation (12). Also, the amount of heat q moving in the machine length direction from cell (i, j) to cell (i, j+1) is... ｙ (i, j) is expressed by the following equation (13). In equations (12) and (13) above, C is the specific heat on a molar basis of the gas molecules in cell (i, j). U obtained by calculating the inter-cell gas transfer rate and intra-cell pressure ｘ , U ｙBy applying this to equations (12) and (13), the control unit 11 of the calculation device 10 can calculate the amount of gas sensible heat transfer in the layer thickness direction and the machine length direction.

[0057] (Method for calculating the amount of heat transfer between gas and solid) The control unit 11 of the calculation device 10 calculates the amount of heat transfer that occurs between the gas phase and the solid in each cell. The amount of heat H transferred from the gas to the solid is expressed by the following formula (14). In (14) above, h is the heat transfer coefficient between the solid and the gas, and may be calculated using the Lanz-Marshall equation.

[0058] Next, we will explain how the numerical calculation system 1 calculates numerical values ​​in the process of sintering iron ore. Figure 5 is a flowchart showing the method for calculating the in-layer state according to this disclosure.

[0059] In the method for calculating the in-layer state of this disclosure, t=0 is the start time of the calculation, and a predetermined time t ｍａｘ The state within the sintered layer after a certain period of time is calculated. In calculating the state of the region to be calculated, the state of all cells is calculated at small time intervals Δt, and then the state is calculated at a predetermined time t. ｍａｘ The state of the entire computational domain is calculated. Here, Δt can be set arbitrarily as long as the calculation result does not diverge, for example it is 2 seconds. ｍａｘ It is preferable to set a time that is sufficiently longer than the time required for the sintering process, for example, 3000 seconds.

[0060] In step S101, the control unit 11 of the calculation device 10 acquires various calculation conditions for calculating the in-layer state of the sintering raw material. When acquiring the calculation conditions, for example, values ​​obtained from operational performance data in actual operations or arbitrarily set values ​​may be used as calculation conditions.

[0061] The calculation conditions include: sintering machine strand length, raw material layer thickness, pressure inside the windbox, ambient pressure around the sintering machine, position of the ignition furnace on the sintering machine strand, temperature inside the ignition furnace, pallet speed, charging density of sintering raw materials, pseudo particle size, porosity of the raw material layer, blending ratio of solid fuel in the sintering raw materials, blending ratio of limestone in the sintering raw materials, and Fe in the sintering raw materials. ２ O ３This includes the blending ratio and the water content of the sintering raw materials.

[0062] In this disclosure, the region consisting of the raw material layer and sinter cake on the sintering machine strand, as shown in the shaded area of ​​Figure 2, is the subject of the calculation. Furthermore, in the calculation of the intralayer state, two-dimensional heat mass transfer in the layer thickness direction and the machine length direction is calculated. Therefore, the calculation conditions include the layer thickness and the sintering machine strand length as the size of the region to be calculated.

[0063] In this disclosure, the gas transfer rate and pressure within the layer, which is the calculation target region, are calculated using the surrounding pressure as a boundary condition. Therefore, the pressure of the atmosphere surrounding the calculation target region, i.e., inside the wind box and around the sintering machine, is included in the calculation conditions.

[0064] Furthermore, in calculating the gas transfer rate and pressure within the layer, Ergun's equation and the continuity equation are solved simultaneously. Here, the porosity and particle size introduced in Ergun's equation are included in the calculation conditions.

[0065] Generally, in a sintering machine, the surface layer of the sintering material is ignited in the ignition furnace, and combustion proceeds from the upper layer to the lower layer by downward suction. In this disclosure, the heating of the solid directly below the ignition furnace and the ignition of the solid fuel are calculated by calculating the heat exchange between the high-temperature gas drawn into the layer from the ignition furnace and the solid within the layer. Here, the heat exchange between the high-temperature gas in the ignition furnace and the solid directly below it occurs during the period that the material remains in the ignition furnace, and the longer the ignition furnace length and the slower the pallet speed, the longer the ignition time. Also, the higher the gas temperature in the ignition furnace, the greater the amount of heat received by the solid directly below the ignition furnace, and the higher the temperature of the solid. Since the length of the ignition furnace, the temperature inside the ignition furnace, and the pallet speed are necessary to calculate the temperature below the ignition furnace, the calculation conditions include the position of the ignition furnace on the strand and the pallet speed.

[0066] In this disclosure, the amount of chemical reaction and the heat of reaction are calculated for each cell delimited by the computational mesh shown in Figure 2. Reactions occurring within the layer during the sintering process include evaporation and condensation of water, thermal dissociation of limestone, combustion of solid fuel, and Fe ２ O ３ and melting of CaO, Fe ２ O３ - This includes the solidification of molten CaO. To calculate the reaction amounts and heat of reaction of these chemical reactions, the mixing ratio of solid fuel, water content, limestone mixing ratio, and Fe ２ O ３ The mixing ratio and the mass of the raw materials in the raw material layer, i.e., the charging density, are required. Therefore, the calculation conditions include the charging density of the sintering raw materials, the solid fuel mixing ratio, the water content, the limestone mixing ratio, and Fe ２ O ３ The blending ratio is included.

[0067] In step S102, the control unit 11 of the calculation device 10 sets the calculation target area, which consists of the raw material layer and sinter cake on the sintering machine strand. After setting the calculation target area, the control unit 11 of the calculation device 10 divides the calculation target area into meshes in the machine length direction and the layer thickness direction, and calculates the state of the entire calculation area by calculating the state within each mesh. The number of divisions of the machine length and layer thickness with meshes is arbitrary, but as an example, the layer thickness is divided into 50 divisions and the machine length into 30 divisions.

[0068] In step S103, the control unit 11 of the computing device 10 sets t to 0. Then, in step S104, the control unit 11 of the computing device 10 adds a small time interval Δt to t.

[0069] In step S105, the control unit 11 of the calculation device 10 calculates the amount of chemical reaction and the heat of reaction in each cell included in the calculation target area. Chemical reactions inside each cell include evaporation and condensation of water, thermal dissociation of limestone, combustion of solid fuel, and Fe ２ O ３ and melting of CaO, Fe ２ O ３ - This includes the solidification of the CaO melt. For each cell, the amount of reaction product and the heat of reaction are calculated within a small time interval Δt. For calculating the amount of reaction within a small time interval Δt, for example, the reaction rate equation shown in Non-Patent Document 1 may be applied.

[0070] In step S106, the control unit 11 of the calculation device 10 calculates the amount of gas molecule movement in two directions, the sintered layer thickness direction and the sintering machine length direction, and the pressure inside each cell.

[0071] In step S107, the control unit 11 of the computing device 10 calculates the amount of heat transfer between each cell.

[0072] In step S108, the control unit 11 of the computing device 10 calculates the amount of heat transfer that occurs between the gas phase and the solid in each cell.

[0073] In step S109, the control unit 11 of the computing device 10 calculates the physical property values of the solid and gas in the cell. The physical property values calculated here include the specific heat of the solid and gas.

[0074] In step S110, the control unit 11 of the computing device 10 calculates the temperature change amounts of the gas and solid in each cell from the heat transfer amount, reaction heat amount, and specific heat calculated so far. In this step calculation, the temperature change amount during a minute time is calculated from the unsteady heat conduction equation. For the calculation in this step, a calculation method similar to the methods shown in Non-Patent Documents 1 and 4 may be used.

[0075] In step S111, the control unit 11 of the computing device 10 checks whether the value of t is the same as t ｍａｘ When the value of t is the same as t ｍａｘ (step S112: Yes), the process proceeds to step S113. When the value of t is not the same as t ｍａｘ (step S112: No), the control unit 11 of the computing device 10 re-performs the process of step S104

[0076] In step S112, the control unit 11 of the computing device 10 outputs the calculation result to the output unit 13.

[0077] By performing the calculation as described above, it is possible to estimate the state in the sintered layer considering the heat and mass transfer in the layer thickness direction and the machine length direction. Also, at each time step, the amount of gas molecule transfer in two directions, the layer thickness direction and the machine length direction, and each cell pressure are calculated so as to satisfy both the Ergun's equation and the continuity equation, enabling two-dimensional gas transfer amount analysis.

[0078] Hereinafter, embodiments of the present invention will be described. Note that the embodiments of the present invention are not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

[0079] In this embodiment, a mesh is created by dividing it into 50 sections in the layer thickness direction and 30 sections in the machine length direction, and the state of each cell separated by the mesh is calculated. Figure 6 shows the temperature of each cell in the calculation target area. In Figure 6, the vertical axis represents the layer thickness, and the horizontal axis represents the position in the machine length direction. The horizontal axis also shows the elapsed time at each machine length position calculated from the pallet speed. A heat pattern typical of the sintering process, where the high-temperature region expands as you go to the lower layers, is calculated.

[0080] Figure 7 shows a plot of elapsed time on the horizontal axis and temperature on the vertical axis for the layer thickness positions (i), (ii), and (iiii) shown in Figure 6. (i), (ii), and (iiii) are located at 100 mm, 300 mm, and 500 mm from the surface, respectively, relative to a total layer thickness of 600 mm. The dashed lines in Figure 7 represent the temperature measurements at 100 mm, 300 mm, and 500 mm from the surface during firing tests in a sintering pot tester under the same layer thickness, composition, and suction pressure conditions as shown in Table 1. The calculation results agree well with the experimental results shown by the dashed lines, indicating that the temperature within the layer is appropriately calculated using this calculation method.

[0081] Figures 8A to 8C show the calculated wind speed and pressure for each cell. Figures 8A to 8C show the wind speed in the layer thickness direction, the wind speed in the machine length direction, and the pressure for each cell, respectively. Because the calculation method described in this disclosure is adopted, as shown in Figure 8B, not only the wind speed in the layer thickness direction but also the wind speed in the machine length direction for each cell is calculated. Note that the wind speed in the machine length direction is considered positive in the pallet travel direction and negative in the opposite direction.

[0082] Figures 9A to 9C show plots of the calculated wind speed and pressure on the vertical axis, with the machine length position on the horizontal axis, for each layer thickness position shown in (i) to (iii) in Figures 8A to 8C. In Figure 9A, the wind speed in the layer thickness direction is plotted on the vertical axis. In Figure 9B, the wind speed in the machine length direction is plotted on the vertical axis. In Figure 9C, the pressure is plotted on the vertical axis. For all layer thickness positions (i) to (iii), a relatively large wind speed is generated in the direction of pallet movement near machine length position 0m. This indicates that gas is being drawn from the area in front of the ignition furnace toward the ignition furnace due to suction from the wind box. In addition, for each layer thickness position (i) to (iii), a wind speed in the opposite direction to the direction of pallet movement is generated at machine length positions of approximately 20m, 40m, and 70m. This indicates that, near the high-temperature section shown in Figure 5, the pressure is higher on the ore discharge side than on the ignition furnace side, resulting in a gas flow opposite to the pallet's direction of travel.

[0083] In order to actually measure the velocity distribution of gas flowing within a layer in the direction of the machine's length, it is extremely difficult, as it would require installing a flow meter inside the actual sintering machine layer. By applying the calculation method presented in this disclosure, it becomes possible to estimate the gas flow in the direction of the machine's length within the layer, which is difficult to measure in practice.

[0084] This disclosure is not limited to the embodiments described above. For example, multiple blocks described in the block diagram may be combined, or a single block may be divided. Instead of executing multiple steps described in the flowchart in chronological order as described, they may be executed in parallel or in a different order, depending on the processing capacity of the device performing each step, or as necessary. Other modifications are possible without departing from the spirit of this disclosure.

[0085] 1 Numerical calculation system 10 Calculation device 11 Control unit 12 Input unit 13 Output unit 14 Memory unit 20 Sintering machine 21 Raw material charging unit 22 Ignition furnace 23 Ore discharge unit 24 Window box

Claims

1. A numerical calculation method for an iron ore sintering process, comprising the steps of: creating a computational mesh in a region on the sintering machine composed of raw materials and sinter cake, in a sintering process in which a powdered material containing iron ore is sintered in a sintering machine to produce sintered ore; and calculating the state inside the sintering machine by calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule transfer between cells in the machine length direction and layer thickness direction.

2. A numerical calculation method for an iron ore sintering process according to claim 1, characterized in that, in calculating the amount of gas molecule movement between each cell in the machine length direction and the layer thickness direction, convergence calculations are performed such that all of the following are satisfied: Ergun's equation relating to the pressure difference and gas flow velocity in the layer thickness direction, Ergun's equation relating to the pressure difference and gas flow velocity in the machine length direction, and the continuity equation.

3. A numerical calculation method for an iron ore sintering process according to claim 1 or 2, characterized in that, in calculating the amount of gas molecule movement between each cell in the machine length direction and the layer thickness direction, the steps of: calculating the amount of gas molecule movement between each cell in the layer thickness direction using the continuity equation; calculating the pressure inside each cell using Ergun's equation relating to the amount of gas molecule movement in the layer thickness direction, the pressure difference in the layer thickness direction, and the gas flow velocity; and repeatedly performing convergence calculations of the amount of gas molecule movement between each cell and the pressure inside each cell so that the pressure at the outer edge of the sintered layer matches the atmospheric pressure around the sintering machine and the pressure inside the windbox.

4. A calculation device for an iron ore sintering process, comprising: a control unit that calculates the state inside the sintering machine by creating a computational mesh in a region on the sintering machine composed of raw materials and sinter cake, in a sintering process in which powdered material containing iron ore is sintered in a sintering machine to produce sintered ore; and calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule transfer between cells in the machine length direction and layer thickness direction.

5. A numerical calculation program for an iron ore sintering process, which causes a computer to perform the following actions in a sintering process in which powdered material containing iron ore is sintered in a sintering machine to produce sintered ore: create a computational mesh in the region composed of raw materials and sinter cake on the sintering machine; and calculate the state inside the sintering machine by calculating the amount of chemical reaction, reaction heat, amount of heat transfer between gas molecules and solids, physical properties of each substance, temperature changes, and the amount of heat transfer between cells in the machine length direction and layer thickness direction, as well as the amount of gas molecule transfer between cells in the machine length direction and layer thickness direction.

6. A method for producing sintered ore, comprising calculating the state inside a sintering machine using the numerical calculation method for an iron ore sintering process described in any one of claims 1 to 3, and sintering a powdered material containing iron ore in a sintering machine to produce sintered ore.

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