Molten iron temperature control method, blast furnace operation method, molten iron production method, molten iron temperature control device, and molten iron temperature control system

Abstract

This molten iron temperature control method is provided with: ventilation abnormality determination steps (S1 to S7) for determining an abnormality in the furnace ventilation of a blast furnace; an unfired pulverized coal generation determination step for determining the generation of unfired pulverized coal remaining after the pulverized coal blown in from the tuyere is not burned; and an action necessity determination step for determining the necessity of an action relating to molten iron temperature control on the basis of the determination results of the ventilation abnormality determination step and the unfired pulverized coal generation determination step.

Description

Technical Field

[0001] The present disclosure relates to a molten iron temperature control method, a blast furnace operation method, a molten iron production method, a molten iron temperature control device, and a molten iron temperature control system. Background Art

[0002] In the blast furnace process, molten iron temperature, air permeability, and ironmaking speed are the main controlled variables. Maintaining a constant temperature for the molten iron produced in the blast furnace is crucial. Furthermore, ensuring adequate air permeability within the blast furnace is crucial to ensure a steady flow of raw materials such as ore and coke, which are loaded from the top. Furthermore, the goal is to produce molten iron at the specified production rate (ironmaking speed) required by the steelmaking process, the next step in the blast furnace.

[0003] Controlling the molten iron temperature is crucial for efficient and stable blast furnace operation. A significant drop in molten iron temperature can lead to a furnace cooling accident, where the molten iron or slag in the lower furnace solidifies, potentially causing operational downtime. Furthermore, high molten iron temperature results in excessive use of pulverized coal or coke as fuel, leading to an increase in the ratio of reducing materials. In this case, the gases expand as the temperature rises within the furnace, deteriorating air permeability.

[0004] In recent blast furnace operations, there has been a strong demand for reducing the variation in molten iron temperature with the goal of reducing the ratio of reducing materials in order to reduce CO 2 .

[0005] Molten iron temperature is controlled by, for example, manipulating the coke ratio, air moisture content, air temperature, and pulverized coal flow rate. Blast furnaces are processes with large heat capacities, so changes in manipulated variables can result in a time delay of, for example, 2 to 8 hours before the molten iron temperature changes. Therefore, future predictions of the molten iron temperature, taking into account the time delay before the effects of actions are realized, and control based on these predictions are necessary.

[0006] Against this backdrop, methods for controlling molten iron temperature using physical models have been proposed. For example, Patent Document 1 describes a method that adjusts gas reduction balance parameters or furnace top coke ratio parameters in a physical model, calculates a predicted molten iron temperature using the physical model assuming the current operating conditions are maintained, and controls the molten iron temperature based on the calculated predicted value.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-24935

[0008] However, the physical model described in Patent Document 1 does not account for pulverized coal phenomena, such as coke pulverization and the accumulation of unburned pulverized coal, in order to shorten calculation time. Specifically, the physical model described in Patent Document 1 assumes complete combustion of pulverized coal, making it difficult to reflect the behavior of unburned pulverized coal. In recent blast furnace operations, efforts to reduce hot metal costs have focused on replacing coke with pulverized coal, leading to unburned pulverized coal and its accumulation. Consequently, unburned pulverized coal can lead to errors in the estimated molten iron temperature and ironmaking rate.

[0009] When unburned coal dust is produced, the combustion of coke is promoted, thereby increasing the rate of descent of the raw materials in the blast furnace, delaying the reduction of the ore by the gas, and increasing the direct reduction, which is an endothermic reaction. As a result, the temperature of the molten iron temporarily drops. Then, if the unburned coal dust is burned in the vortex zone, the rate of descent of the raw materials decreases, and the temperature of the molten iron recovers. However, if unburned coal dust accumulates, the unburned coal dust is used for direct reduction and disappears, and the temperature of the molten iron continues to drop. In addition, if unburned coal dust accumulates in the furnace, the permeability deteriorates. That is, it is believed that the accumulation of unburned coal dust can be determined based on the changes in the permeability index in the furnace and the inference error of process variables such as the ironmaking speed and the amount of dissolved carbon loss. In addition, as long as the accumulation of unburned coal dust can be determined with high precision, it is possible to detect a future decrease in the temperature of the molten iron. Summary of the Invention

[0010] The purpose of the present disclosure, which was completed in view of this situation, is to provide a molten iron temperature control method, a blast furnace operation method, a molten iron manufacturing method, a molten iron temperature control device, and a molten iron temperature control system that can detect a future drop in molten iron temperature that is difficult to predict through physical models and prompt actions to increase the molten iron temperature.

[0011] (1) A method for controlling the temperature of molten iron according to an embodiment of the present disclosure includes:

[0012] The ventilation abnormality determination step is to determine abnormality of ventilation in the blast furnace;

[0013] an unburned pulverized coal generation determination step, determining the generation of unburned pulverized coal remaining due to the pulverized coal blown in from the air inlet not being burned; and

[0014] The action necessity determination step determines the necessity of an action related to the molten iron temperature control based on the determination results of the ventilation abnormality determination step and the unburned coal generation determination step.

[0015] (2) As an embodiment of the present disclosure, based on (1),

[0016] The ventilation abnormality determining step determines that there is an abnormality in the furnace permeability when the standard deviation of the shaft pressure at positions at equal vertical distances from the blast furnace roof exceeds a first threshold value in a plurality of layers at different distances.

[0017] (3) As one embodiment of the present disclosure, based on (1) or (2),

[0018] The unburned coal generation determination step determines that the unburned coal has been generated when the rate of change of the error between the calculated value obtained from the physical model and the actual value in at least one of the ironmaking speed and the dissolved carbon loss is equal to or greater than a second threshold.

[0019] (4) As one embodiment of the present disclosure, based on any one of (1) to (3),

[0020] When the abnormality in the ventilation determining step is determined to be present and the unburned pulverized coal is determined to be generated in the unburned pulverized coal generation determining step, the action necessity determining step prompts the action for increasing the molten iron temperature.

[0021] (5) A method for operating a blast furnace according to one embodiment of the present disclosure includes:

[0022] The step of controlling the blast furnace is performed based on the necessity of the above-mentioned action determined by the molten iron temperature control method according to any one of (1) to (4).

[0023] (6) A method for producing molten iron according to one embodiment of the present disclosure includes:

[0024] The step of controlling the blast furnace to produce molten iron according to the blast furnace operating method of (5).

[0025] (7) A molten iron temperature control device according to one embodiment of the present disclosure includes:

[0026] A ventilation abnormality determination unit determines abnormalities in ventilation in the blast furnace;

[0027] an unburned pulverized coal generation determination unit for determining the generation of unburned pulverized coal remaining due to the pulverized coal blown in from the tuyere not being burned; and

[0028] The action necessity determination unit determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination unit and the unburned coal generation determination unit.

[0029] (8) As an embodiment of the present disclosure, based on (7),

[0030] The ventilation abnormality determination unit determines that there is an abnormality in the furnace ventilation when the standard deviation of the shaft pressure at positions at equal vertical distances from the blast furnace roof exceeds a first threshold value in a plurality of layers at different distances.

[0031] (9) As one embodiment of the present disclosure, based on (7) or (8),

[0032] The unburned coal generation determination unit determines that the unburned coal has been generated when the rate of change in the error between the calculated value obtained from the physical model and the actual value in at least one of the ironmaking speed and the dissolved carbon loss is equal to or greater than a second threshold value.

[0033] (10) As one embodiment of the present disclosure, based on any one of (7) to (9),

[0034] The action necessity determination unit prompts the action for increasing the molten iron temperature when the ventilation abnormality determination unit determines that the furnace ventilation is abnormal and the unburned pulverized coal generation determination unit determines that the unburned pulverized coal is generated.

[0035] (11) A molten iron temperature control system according to one embodiment of the present disclosure includes a molten iron temperature control device and a terminal device, wherein:

[0036] A ventilation abnormality determination unit determines abnormality in ventilation in the blast furnace;

[0037] An unburned pulverized coal generation determination unit determines the generation of unburned pulverized coal remaining after the pulverized coal blown in from the air inlet is not burned;

[0038] an action necessity determination unit that determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination unit and the unburned coal generation determination unit;

[0039] an output unit that outputs a result of abnormality determination of ventilation in the furnace determined by the ventilation abnormality determination unit, a result of generation of unburned pulverized coal determined by the unburned pulverized coal generation determination unit, and an action for controlling the molten iron temperature outputted by the determination result of the action necessity determination unit; and

[0040] The display unit receives the output result from the output unit and displays the determination result of the ventilation abnormality determination unit, the determination result of the unburned coal powder generation determination unit, and the action for molten iron temperature control output by the action necessity determination unit.

[0041] According to the present disclosure, a molten iron temperature control method, a blast furnace operation method, a molten iron manufacturing method, a molten iron temperature control device, and a molten iron temperature control system can be provided, which can detect a future drop in molten iron temperature that is difficult to predict through a physical model and prompt actions to increase the molten iron temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a block diagram showing a configuration example of a molten iron temperature control device according to one embodiment of the present disclosure.

[0043] Figure 2 This is a flowchart illustrating the processing of the ventilation abnormality determination unit.

[0044] Figure 3 This is a flowchart illustrating the processing of the unburned coal powder generation determination unit.

[0045] Figure 4 This is a flowchart illustrating the processing of the action necessity determination unit.

[0046] Figure 5 This is a diagram showing time-series changes in the difference between the shaft pressure value and the average value at each height position when it is assumed that unburned pulverized coal is generated.

[0047] Figure 6 Is to express Figure 5 This graph shows the time series changes in the standard deviation of the shaft pressure value at each height position and the difference between the actual value and the calculated value of the ironmaking speed over time.

[0048] Figure 7 Is to express Figure 5 A graph showing the time series changes in the standard deviation of the furnace shell pressure value, the difference in ironmaking speed, and the difference in dissolved carbon loss at different times.

[0049] Figure 8 Is to express Figure 7 This is a graph showing time-series changes in input and output variables of a physical model when it is assumed that unburned pulverized coal is generated.

[0050] Figure 9 This is a block diagram showing a configuration example of a molten iron temperature control system including a molten iron temperature control device. DETAILED DESCRIPTION

[0051] Hereinafter, a molten iron temperature control method, a blast furnace operating method, a molten iron manufacturing method, a molten iron temperature control device, and a molten iron temperature control system according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0052] [Structure of molten iron temperature control device]

[0053] First, refer to Figure 1 The structure of a molten iron temperature control device as one embodiment of the present disclosure will be described.

[0054] Figure 1 1 is a block diagram showing the structure of a molten iron temperature control device 1 according to one embodiment of the present disclosure. Figure 1 As shown, the molten iron temperature control device 1, as one embodiment of the present disclosure, is comprised of an information processing device such as a computer. When the molten iron temperature control device 1 is a computer, a CPU (Central Processing Unit) or other processing unit executes programs, thereby functioning as a ventilation abnormality determination unit 11, an unburned coal dust generation determination unit 12, and an action necessity determination unit 13. The functions of each unit will be described later.

[0055] The operation database 2 is connected to the molten iron temperature control device 1 in a data-readable manner. The operation database 2 sequentially stores and stores the measurement data required for operation and the operation factors required for molten iron temperature control, and this information is read and used as needed. In this embodiment, the operation database 2 stores operation factors such as the furnace top coke ratio, air flow rate, oxygen enrichment, air temperature, air moisture content, and coal powder flow rate. In addition, the operation database 2 stores the calculated values ​​of the process variables output by the physical model. Whenever the molten iron temperature control device 1 calculates, the calculated values ​​of the process variables output by the physical model are sequentially stored in the operation database 2. In addition, the operation database 2 stores the actual values ​​of the process variables calculated based on the volume fraction of CO and CO2 in the discharged furnace top gas. In addition, the operation database 2 stores historical data of the pressure values ​​obtained from the furnace body pressure gauge. Here, as process variables, molten iron temperature, ironmaking speed, dissolved carbon loss, gas utilization rate, etc. can be cited.

[0056] The physical model used in this disclosure is the same as the method described in Reference 1 (Michiharu Hanedano et al., "Study of Ignition Operation Based on a Non-steady-state Model of a Blast Furnace," Iron & Steel, vol. 68, p. 2369). Specifically, the physical model consists of a system of partial differential equations that account for multiple physical phenomena, including iron ore reduction, heat exchange between iron ore and coke, and iron ore melting. This model is capable of calculating variables (output variables) representing the state within the blast furnace under non-steady conditions.

[0057] The molten iron temperature control device 1 having such a configuration executes each process of the molten iron temperature control method by the ventilation abnormality determination unit 11, the unburned pulverized coal generation determination unit 12, and the action necessity determination unit 13, and outputs an appropriate action for molten iron temperature control.

[0058] [Operation of the Abnormal Ventilation Determination Unit]

[0059] The shaft pressure is the pressure of the shaft portion of the blast furnace. The shaft pressure exhibits synchronous behavior (e.g., rising or falling at the same time) at all measuring points during normal operation. However, if the permeability in the furnace deteriorates, the pressure distribution in the furnace becomes disordered, and thus the shaft pressure exhibits asynchronous changes at some measuring points. In particular, the gas flow in the furnace is not uniform in the circumferential direction, and thus the shaft pressure at a specific azimuth angle in the circumferential direction changes. Here, the azimuth angles are, for example, east (E), south (S), west (W), and north (N), and are used to distinguish the circumferential regions in the cylindrical furnace and to indicate their positions. In the present embodiment, the ventilation abnormality determination unit 11 calculates the standard deviation of the shaft pressure at each measuring point that is at an equal distance from the furnace top, that is, at each height position. Then, the ventilation abnormality determination unit 11 determines ventilation abnormality based on whether the nearest standard deviation at multiple height positions exceeds a threshold value.

[0060] Reference Figure 2 The following describes the operation of the ventilation abnormality determination unit 11. As described above, the ventilation abnormality determination unit 11 determines abnormality in the ventilation properties within the blast furnace.

[0061] Figure 2 This is a flowchart showing the flow of ventilation abnormality determination as one embodiment of the present disclosure. Figure 2 The illustrated processing corresponds to a ventilation abnormality determination step. Figure 2 The flowchart shown starts when an instruction to execute ventilation abnormality determination is input to the molten iron temperature control device 1. The ventilation abnormality determination proceeds to the processing of step S1.

[0062] In the process of step S1, the ventilation abnormality determination unit 11 obtains the shaft pressure data from the operation database 2. The data acquisition cycle is preferably 1 minute to 30 minutes. Thus, the process of step S1 is completed, and the ventilation abnormality determination proceeds to the process of step S2.

[0063] In step S2, the ventilation abnormality determination unit 11 determines whether the shaft pressure values ​​acquired in step S1 contain abnormal values ​​due to measurement errors or data transmission anomalies. For example, if the shaft pressure value is lower than the furnace top pressure or higher than the blast pressure, the ventilation abnormality determination unit 11 may determine that the shaft pressure value is an abnormal value. If it is determined that the shaft pressure data contains abnormal values, the ventilation abnormality determination unit 11 removes the observations indicating abnormal values ​​(step S6). The ventilation abnormality determination process then proceeds to step S3. If it is determined that the shaft pressure data does not contain abnormal values, the ventilation abnormality determination process proceeds directly to step S3.

[0064] In the processing of step S3, for the furnace body pressure data without abnormal values ​​or with abnormal values ​​removed, the ventilation abnormality determination unit 11 takes the measurement points at equal distances from the furnace top as a group (set) and calculates the standard deviation of the measurement point group. Assume that there are N measurement points for the furnace body pressure in the height direction and M measurement points in the circumferential direction. The N measurement points in the height direction correspond to the respective measurement points in the N layers of regions obtained by dividing the blast furnace according to the distance in the vertical direction from the blast furnace top. In the circumferential direction of one layer of region, there are M measurement points for the furnace body pressure, and the above-mentioned M measurement points exist at positions at equal distances from the blast furnace top in the vertical direction. When a certain height position is set as i, a certain circumferential azimuth is set as j, and the furnace body pressure at a certain time t is set as p i，j，t In the case of time t, the average value a(p i，t ) is calculated using formula (1).

[0065] [Formula 1]

[0066]

[0067] And, using the average value a(p i，t ) Calculate the standard deviation σ using formula (2) i，t .

[0068] [Formula 2]

[0069]

[0070] Then, the median value σ of the standard deviation of the most recent T1 is calculated for each height position. i , find the standard deviation array σ shown in formula (3). Here, each height position refers to each area of ​​the N layers of the blast furnace divided by the vertical distance from the blast furnace top. As an example, T1 is 15 minutes. For the furnace pressure data of the last 15 minutes, find the standard deviation σ of a height position i，t , based on multiple standard deviations σ over a 15-minute period i，t Calculate the median value σ i Calculate the central value σ at each height position i , and the array σ is obtained as its collection.

[0071] [Formula 3]

[0072]

[0073] If T1 is extremely small, a temporary change in shaft pressure due to noise could lead to a false positive for ventilation anomaly. If T1 is too large, the timing of ventilation anomaly determination is delayed, making it difficult to initiate appropriate action. Therefore, T1 is preferably set within the range of 10 to 60 minutes. This completes step S3, and ventilation anomaly determination proceeds to step S4.

[0074] In step S4, the ventilation abnormality determination unit 11 counts the number of height positions (layers) at which the standard deviation array σ obtained in step S3 exceeds a threshold value α (a first threshold value). If the counted value k is 2 or greater, step S4 is completed, the ventilation abnormality is determined to be "abnormal" (step S5), and the series of processes ends. If the counted value k is 1 or less, step S4 is completed, the ventilation abnormality is determined to be "normal" (step S7), and the series of processes ends. By incorporating a determination based on the number of layers, it is possible to avoid misjudging the magnitude of temporary deviations caused by noise, etc., occurring in a single layer as an "abnormal" ventilation condition. Here, threshold α is determined based on the volume of the blast furnace and the location at which the shaft pressure is measured. If the unit of shaft pressure is kPa, threshold α can be determined, for example, within a range of 2 to 10 kPa. In step S4, the process branches based on whether the counted value k is 2 or greater or less than 2 (or less than 1), but the number (reference value) used in the branching determination is not limited to 2. For example, when the size of the blast furnace is large or the number of measurement points is large, the reference value may be set to a number larger than 2 in order to further enhance the effect of preventing erroneous determination.

[0075] Here, the ventilation abnormality determination unit 11 may use a calculated value different from the standard deviation. As another example, the ventilation abnormality determination unit 11 may also calculate the difference between the maximum and minimum values ​​at a height position for the most recent shaft pressure data during T1, instead of the standard deviation, and calculate the median value based on this difference during T1.

[0076] [Operation of the Unburned Coal Generation Determination Unit]

[0077] Next, refer to Figure 3 The operation of the unburned coal generation determination unit 12 will be described. The unburned coal generation determination unit 12 determines the generation of unburned coal remaining after the pulverized coal injected from the blast furnace has not been burned. Hereinafter, the generation of unburned coal refers to a state in which unburned coal is generated and accumulated to the extent that the molten iron temperature continues to drop.

[0078] Figure 3 This is a flowchart showing the flow of determining the generation of unburned pulverized coal according to one embodiment of the present disclosure. Figure 3 The illustrated process corresponds to the unburned pulverized coal generation determination step. Figure 3The flowchart shown starts when an execution command for determining the generation of unburned pulverized coal is input to the molten iron temperature control device 1. The determination of the generation of unburned pulverized coal proceeds to the processing of step S10.

[0079] During step S10, the unburned coal generation determination unit 12 obtains historical data (physical model calculation results) of the calculated values ​​of process variables output by the physical model from the operation database 2. Process variables used in the unburned coal generation determination include, for example, the ironmaking rate and the amount of dissolved carbon loss. Step S10 is then completed, and the unburned coal generation determination proceeds to step S11. The reduced material ratio or the gas utilization rate can be used as process variables for the unburned coal generation determination. While the physical model assumes that all injected coal reacts, a portion of the injected coal actually does not react when unburned coal is generated, causing the reduced material ratio to deviate from the calculated value. Furthermore, while the physical model assumes that all injected coal converts to CO, a portion of the injected coal actually does not react when unburned coal is generated, resulting in a decrease in CO generation and a deviation in the gas utilization rate from the calculated value. Therefore, similar to the ironmaking rate and the amount of dissolved carbon loss, the accumulation of unburned coal can be determined based on estimation errors in the reduced material ratio or the gas utilization rate.

[0080] In the process of step S11, the unburned coal powder generation determination unit 12 obtains historical data (operation performance data) of actual values ​​of process variables from the operation database 2. Thus, the process of step S11 is completed, and the unburned coal powder generation determination proceeds to the process of step S12.

[0081] In the process of step S12, the unburned coal powder generation determination unit 12 calculates the change rate of the estimated error of the process variable at the most recent time T2 using the historical data of the calculated value of the process variable obtained in step S10 and the historical data of the actual value of the process variable obtained in step S11. In this embodiment, the actual value y of the process variable y at time t is calculated using formula (4). act (t) and the calculated value y cal The error y of (t) err (t) was modeled.

[0082] [Formula 4]

[0083] yerr(t)=A·t+B (-T2≤t≤0) (4)

[0084] Based on the acquired historical data, A of formula (4) is calculated by the least square method. A is the rate of change of the inferred error. B is the offset. Here, if T2 is made extremely small, the rate of change of the inferred error will change significantly in the actual value of the process variable due to the influence of noise caused by abnormal measurement of the composition of the furnace top gas. In addition, if T2 is too large, the contribution of the past normal time becomes large and it is difficult to capture the recent rapid change in the inferred error. Therefore, considering the time it takes for the raw materials loaded at the furnace top to descend to the tuyere, T2 is preferably determined within the range of 3 to 12 hours. Here, T2 can be different depending on the type of process variable. Thus, the processing of step S12 is completed, and the determination of the generation of unburned coal powder enters the processing of step S13.

[0085] In step S13, the unburned coal generation determination unit 12 compares the rate of change in the error between the calculated value obtained from the physical model and the actual value of the process variable (error change rate A), calculated in step S12, with a threshold value β (a second threshold value). Threshold value β varies depending on the type of process variable. If the absolute value of the error change rate A is less than threshold value β, step S13 is completed, and the unburned coal generation determination unit 12 determines that no unburned coal has been generated (step S15), terminating the series of steps. Alternatively, if the absolute value of the error change rate A is greater than threshold value β, step S13 is completed, and the unburned coal generation determination unit 12 determines that unburned coal has been generated (step S14), terminating the series of steps.

[0086] [Actions of the Action Necessity Judgment Unit]

[0087] Next, refer to Figure 4 The operation of the action necessity determination unit 13 will be described. The action necessity determination unit 13 determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination unit 11 and the unburned coal generation determination unit 12.

[0088] Figure 4 This is a flowchart showing the flow of action necessity determination related to molten iron temperature control according to the present embodiment. Figure 4 The illustrated processing corresponds to the action necessity determination step. Figure 4 The flowchart shown starts when an instruction to execute the action necessity determination is input to the molten iron temperature control device 1. The action necessity determination proceeds to the processing of step S20.

[0089] In step S20, the action necessity determination unit 13 determines whether ventilation is normal or abnormal based on the determination result of the ventilation abnormality determination unit 11. If ventilation is "abnormal," step S20 is completed, and the action necessity determination process proceeds to step S21. If ventilation is "normal," step S20 is completed, and the action necessity determination process proceeds to step S22.

[0090] In step S21, the action necessity determination unit 13 determines whether unburned pulverized coal has been generated based on the determination result of the unburned pulverized coal generation determination unit 12. If unburned pulverized coal has been generated, step S21 is completed, and the action necessity determination process proceeds to step S23. If unburned pulverized coal has not been generated, step S21 is completed, and the action necessity determination process proceeds to step S22.

[0091] In the process of step S22, the action necessity determination unit 13 infers the state in the furnace where there is no accumulation of unburned pulverized coal (the pulverized coal is completely burned), and prompts the action of molten iron temperature control. That is, in the process of step S22, the action necessity determination unit 13 prompts the action of molten iron temperature control based on the calculated value of the molten iron temperature using the existing physical model. The action prompt in this case can use the method described in reference 2 (Y. Hashimoto et al., ISIJ International, Vol. 59 (2019), p. 1573-1581), for example. Thus, the process of step S22 is completed, and a series of action necessity determinations are ended.

[0092] During step S23, the action necessity determination unit 13 suggests an action to increase the molten iron temperature. This is because, if unburned pulverized coal accumulates, it is consumed by direct reduction and eliminated, causing the molten iron temperature to continue to drop. Examples of actions to increase the molten iron temperature include reducing the moisture content of the supply air, increasing the pulverized coal ratio, increasing the supply air temperature, or increasing the coke ratio. The amount of change in the action can be fixed values ​​predetermined for each of the supply air moisture content, pulverized coal ratio, supply air temperature, and coke ratio. This completes step S23, concluding the series of action necessity determinations.

[0093] Here, the action necessity determination may be performed before the step S20 by performing the processing of step S21. That is, the order of step S20 and step S21 may be reversed.

[0094] The molten iron temperature control method executed by the above-mentioned molten iron temperature control device 1 can be part of the blast furnace operating method. For example, the blast furnace operating method may include the step of controlling the blast furnace based on the necessity of the action determined by the molten iron temperature control method. This blast furnace operating method can appropriately execute an action in the direction of increasing the molten iron temperature. In addition, the above-mentioned molten iron temperature control method or blast furnace operating method can be part of the molten iron manufacturing method. For example, the molten iron manufacturing method may include the step of controlling the blast furnace based on the blast furnace operating method to manufacture molten iron. The necessity and content of the determined action can be automatically reflected in the operation or manufacturing, for example, by using the communication function between the molten iron temperature control device 1 and a computer that manages the operation of the blast furnace or the production of molten iron. In addition, the necessity and content of the determined action can be prompted to the operator who manages the operation or manufacturing, for example, by displaying it on a display, and can also be used as a guide for the operator's action decision.

[0095] In addition, if Figure 9 As shown, a molten iron temperature control system can be constructed. The molten iron temperature control system is composed of a molten iron temperature control device 1 and a terminal device 3. In addition, the molten iron temperature control system can further include an operation database 2. The structure of the molten iron temperature control device 1 and the operation database 2 is the same as Figure 1 That is, the ventilation abnormality determination unit 11, the unburned coal powder generation determination unit 12, the action necessity determination unit 13 and the operation database 2 are the same as those described above. However, Figure 9 In the example, the molten iron temperature control device 1 further includes an output unit 14 that outputs the suggested action, etc., to the terminal device 3. For example, if the molten iron temperature control device 1 is a computer, the processing unit executes a program and thus also functions as the output unit 14. The terminal device 3 is, for example, a device used by an operator. The terminal device 3 can be a mobile terminal such as a smartphone or tablet.

[0096] The output unit 14 outputs the abnormality determination result of the ventilation abnormality determination unit 11, the unburned coal generation determination result determined by the unburned coal generation determination unit 12, and the action for molten iron temperature control outputted by the action necessity determination unit 13. For example, the output unit 14 may output the presence of ventilation abnormality and its basis (the height position indicating the abnormality of the shaft pressure and the standard deviation value determined as abnormal) outputted by the ventilation abnormality determination unit 11 to the terminal device 3. Furthermore, for example, the output unit 14 may output the determination result of the presence of unburned coal generation and its basis (the process variable and error change rate used in the determination) to the terminal device 3. Here, the process variable is, for example, the ironmaking speed, the amount of dissolved carbon loss, etc. Furthermore, for example, the output unit 14 may output the determination result of the action necessity determination unit 13 and the manipulated variable for molten iron temperature control to the terminal device 3. The terminal device 3 may include a display unit 30 that receives the output result from the output unit 14 and displays the output result. The display unit 30 displays the determination results of the ventilation abnormality determination unit 11, the determination results of the unburned coal generation determination unit 12, and the molten iron temperature control action output by the action necessity determination unit 13. The display unit 30 may be a liquid crystal display (LCD), etc. The display on the display unit 30 may be displayed on a general-purpose browser.

[0097] The molten iron temperature control device 1, the operation database 2 and the terminal device 3 are configured to be able to communicate with each other via a network such as a LAN (Local Area Network). Figure 9 The structure is an example. The molten iron temperature control device 1 and the terminal device 3 may not include Figure 9 In addition, the molten iron temperature control device 1 and the terminal device 3 may have Figure 9 In addition, the components included in the molten iron temperature control device 1 and the terminal device 3 are not limited to Figure 9 For example, the action necessity determination unit 13 and the display unit 30 may be located in the same device. Alternatively, the ventilation abnormality determination unit 11, the unburned coal generation determination unit 12, and the display unit 30 may be located in the terminal device 3, while the action necessity determination unit 13 and the output unit 14 may be located in the molten iron temperature control device 1. Furthermore, data can be transmitted and received between the various components through inter-process communication or communication over a network.

[0098] [Example 1]

[0099] Figure 5This is a graph showing the time series changes related to the difference between the furnace pressure value and the average value at each height position when it is considered that unburned coal powder has been generated. The up and down directions of the graph are consistent with the height of the blast furnace in the vertical direction. That is, the first height position is the position closest to the blast furnace top (high), and the seventh height position is the position farthest from the blast furnace top (low). In addition, the difference in line type indicates the difference in the azimuth angle of the measuring point in the circumferential direction. Figure 5 In the example, the shaft pressure values ​​in the lower two layers (the sixth and seventh height positions) change asynchronously, indicating a deterioration in the ventilation of the lower part of the furnace. Moreover, in the last 0.5 hours, the shaft pressure values ​​at specific azimuth angles in the lower four layers increase, further deteriorating the ventilation. Figure 5 For the vertical axis, the average value of the shaft pressure at all azimuths of each layer is calculated, and the difference from the average value is used to represent the shaft pressure value at each azimuth. For example, a negative value indicates a shaft pressure value lower than the average value.

[0100] Figure 6 Is to express Figure 5 The graph shows the time series changes of the standard deviation of the shaft pressure value at each height position and the difference between the actual value and the calculated value of the ironmaking speed. The difference in the line shape of the standard deviation of the shaft pressure indicates the difference in the height position of the measurement point. In this embodiment, the threshold value α is set to 4 [kPa]. In addition, Figure 6 In the graph of the ironmaking speed, the solid line represents the actual performance value y act (t) and the calculated value y cal The dotted line shows the result of linear regression assuming the relationship of formula (4).

[0101] For ventilation abnormality determination, T1 was set to 15 minutes. The standard deviation was calculated for each altitude position, and the number of altitude positions (floors) exceeding a threshold α was counted. If the standard deviation of three floors exceeded the threshold α, ventilation was determined to be "abnormal."

[0102] Regarding the determination of unburned coal generation, the error change rate A of the ironmaking speed is positive, indicating an increasing error. This means the actual ironmaking speed has exceeded the predicted (calculated) value in the physical model. T2 is set to 10 minutes. Furthermore, the threshold value β is set to 30. The absolute value of the error change rate A is compared with the threshold value β to determine the presence of unburned coal generation.

[0103] As described above, the molten iron temperature control device 1 can detect the risk of molten iron temperature drop, which is not reflected in the molten iron temperature prediction of the existing physical model. If it is determined that unburned coal is generated, the molten iron temperature control device 1 can prompt an action to increase the molten iron temperature (for example, reduce the moisture content of the air supply).

[0104] [Example 2]

[0105] Figure 7 Is to express Figure 5 A graph showing time-series changes in the standard deviation of the shaft pressure value at each height position, the difference between the actual and calculated values ​​of the ironmaking speed, and the difference between the actual and calculated values ​​of the dissolved carbon loss.

[0106] For ventilation abnormality determination in this embodiment, threshold α is set to 4 kPa. Furthermore, T1 is set to 15 minutes. The standard deviation is calculated for each altitude position, and the number of altitude positions (layers) exceeding threshold α is counted. If the standard deviation of two layers exceeds threshold α, ventilation is determined to be abnormal.

[0107] Regarding the determination of the generation of unburned coal powder in this embodiment, the error change rate A of the ironmaking speed and the amount of dissolved carbon loss is positive, and the error is expanding. It is believed that the rate of descent of the raw materials in the blast furnace increases, the reduction of the ore by gas is delayed, and the unburned coal powder is preferentially dissolved and lost. Regarding the estimated error of the ironmaking speed, T2 is set to 10 minutes. In addition, the threshold β is set to 30. In addition, regarding the estimated error of the amount of dissolved carbon loss, T2 is set to 8 minutes. In addition, the threshold β is set to 1. The absolute value of the error change rate A is compared with the threshold β. In the ironmaking speed and the amount of dissolved carbon loss, if the absolute value of the error change rate A is greater than the threshold β, it is determined that "unburned coal powder" is generated. Here, the determination of the generation of unburned coal powder can be made without using both the ironmaking speed and the amount of dissolved carbon loss, but only using one side (refer to Example 1). However, by using both, the accuracy of the determination can be further improved.

[0108] Figure 8 Is to express Figure 7 A diagram showing the time series changes of the input variables and output variables of the physical model over time. The input variables are the coke ratio (CR), oxygen enrichment flow rate (BVO), air flow rate (BV), air temperature (BT), air moisture content (BM), and pulverized coal flow rate (PCI). The output variable is the molten iron temperature (HMT). The solid line of the air moisture content represents the history of actions taken to control the molten iron temperature according to the method of this embodiment. The dotted line of the air moisture content represents the action output at time 0 hours based on the above-mentioned necessity of action. In the physical model, the increase in pulverized coal flow rate and the decrease in air moisture content from 3 hours ago are reflected, and it is predicted that the molten iron temperature will rise. In addition, it is determined that the ventilation is "abnormal" and "there is" unburned pulverized coal. Regardless of the molten iron temperature prediction of the physical model, the risk of a drop in molten iron temperature is detected, and an action in the direction of increasing the molten iron temperature (for example, reducing air moisture content) is suggested. For example, as a reduction in air moisture content, a fixed value (-3g / Nm as an example) can be used. 3) prompts the operating amount. As a result, the molten iron temperature drops slightly, but does not drop significantly below the target value, and the molten iron temperature is appropriately controlled.

[0109] As described above, the molten iron temperature control method, blast furnace operating method, molten iron production method, molten iron temperature control device 1, and molten iron temperature control system according to this embodiment can detect a future drop in molten iron temperature that is difficult to predict using physical models and suggest actions to increase the molten iron temperature. Specifically, based on the deviation in the furnace shaft pressure value and the estimation errors in process variables such as the ironmaking rate and the amount of dissolved carbon loss, it is possible to identify abnormalities caused by the in-furnace behavior of unburned pulverized coal that are difficult to predict using physical models, and suggest appropriate actions to increase the molten iron temperature.

[0110] While the embodiments have been described above, the present disclosure is not limited to the descriptions and drawings that form part of the present disclosure based on these embodiments. In other words, other embodiments, examples, and application technologies accomplished by those skilled in the art based on these embodiments are all within the technical scope of the present disclosure.

[0111] Description of Reference Numerals

[0112] 1… molten iron temperature control device; 2… operation database; 3… terminal device; 11… ventilation abnormality determination unit; 12… unburned coal powder generation determination unit; 13… action necessity determination unit; 14… output unit; 30… display unit.

Claims

1. A method for controlling the temperature of molten iron, characterized in that: include: The ventilation abnormality determination step is to determine abnormality of ventilation in the blast furnace; an unburned pulverized coal generation determination step, determining the generation of unburned pulverized coal remaining due to the pulverized coal blown in from the air inlet not being burned; as well as The action necessity determination step determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination step and the unburned coal generation determination step.

2. The molten iron temperature control method according to claim 1, characterized in that: The ventilation abnormality determining step determines that there is an abnormality in the furnace permeability when the standard deviation of the shaft pressure at positions at equal vertical distances from the blast furnace roof exceeds a first threshold value in a plurality of layers at different distances.

3. The molten iron temperature control method according to claim 1 or 2, characterized in that: The unburned coal generation determination step determines that the unburned coal has been generated when the rate of change of the error between the calculated value obtained from the physical model and the actual value in at least one of the ironmaking speed and the dissolved carbon loss is equal to or greater than a second threshold.

4. The method for controlling the temperature of molten iron according to any one of claims 1 to 3, wherein: When it is determined in the ventilation abnormality determining step that the furnace ventilation is abnormal and in the unburned pulverized coal generation determining step that the unburned pulverized coal is generated, the action necessity determining step prompts the action for increasing the molten iron temperature.

5. A method for operating a blast furnace, characterized in that: include: A step of controlling the blast furnace based on the necessity of the action determined by the molten iron temperature control method according to any one of claims 1 to 4.

6. A method for producing molten iron, characterized in that: include: The blast furnace operating method according to claim 5 comprises the steps of controlling the blast furnace to produce molten iron.

7. A molten iron temperature control device, characterized in that: have: A ventilation abnormality determination unit determines abnormalities in ventilation in the blast furnace; An unburned pulverized coal generation determination unit determines the generation of unburned pulverized coal remaining after the pulverized coal blown in from the air inlet is not burned; as well as The action necessity determination unit determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination unit and the unburned coal generation determination unit.

8. The molten iron temperature control device according to claim 7, characterized in that: The ventilation abnormality determination unit determines that there is an abnormality in the furnace permeability when the standard deviation of the shaft pressure at positions at equal vertical distances from the blast furnace roof exceeds a first threshold value in a plurality of layers at different distances.

9. The molten iron temperature control device according to claim 7 or 8, characterized in that: The unburned coal generation determination unit determines that the unburned coal has been generated when the rate of change of the error between the calculated value obtained from the physical model and the actual value in at least one of the ironmaking speed and the dissolved carbon loss is equal to or greater than a second threshold value.

10. The molten iron temperature control device according to any one of claims 7 to 9, characterized in that: The action necessity determination unit prompts the action for increasing the molten iron temperature when the ventilation abnormality determination unit determines that the furnace ventilation abnormality exists and the unburned pulverized coal generation determination unit determines that the unburned pulverized coal has been generated.

11. A molten iron temperature control system comprising a molten iron temperature control device and a terminal device, characterized in that: have: A ventilation abnormality determination unit determines abnormalities in ventilation in the blast furnace; An unburned pulverized coal generation determination unit determines the generation of unburned pulverized coal remaining after the pulverized coal blown in from the air inlet is not burned; an action necessity determination unit that determines the necessity of an action related to molten iron temperature control based on the determination results of the ventilation abnormality determination unit and the unburned coal generation determination unit; an output unit for outputting a result of abnormality determination of ventilation in the furnace determined by the ventilation abnormality determination unit, a result of generation of unburned pulverized coal determined by the unburned pulverized coal generation determination unit, and an action for controlling the molten iron temperature outputted as a result of the determination by the action necessity determination unit; as well as The display unit receives the output result from the output unit and displays the determination result of the ventilation abnormality determination unit, the determination result of the unburned coal powder generation determination unit, and the action for molten iron temperature control output by the action necessity determination unit.

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