HOT METAL TEMPERATURE CONTROL METHOD, HOT METAL TEMPERATURE CONTROL DEVICE, HOT METAL TEMPERATURE CONTROL SYSTEM, AND TERMINAL DEVICE

Abstract

A HMT control method includes calculation steps (S11 to S19) of calculating a pulverized coal ratio manipulation amount by HMT control, calculating a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control, and prioritizing the HMT control or the pulverized coal ratio tracking control as an optimal action based on the magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio, a determination step of determining a rationale for calculation of the optimal action and adding a text statement to a rationale statement indicating the rationale, and a presentation step of presenting operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

Description

TECHNICAL FIELD

The present disclosure relates to a hot metal temperature (HMT) control method, a hot metal temperature control device, an HMT control system, and a terminal device.

BACKGROUND

The labor force is expected to decrease due to the declining birthrate and aging population, and the steel industry is also expected to see a decrease in skilled operators with knowledge and experience. Therefore, there is a demand for highly efficient and stable operation through process automation.

In the process in a blast furnace, raw materials such as coke and iron ore are charged into the upper part of the furnace, hot blast and pulverized coal are blown in through the tuyere at the lower part of the furnace to melt and reduce the iron ore, and molten iron is obtained from the taphole. In recent years, blast furnace operation has aimed for a low reducing agent ratio and low coke ratio in order to reduce CO₂ and hot metal costs. On the other hand, as high-quality raw materials are becoming scarce, fluctuations in raw material quality are expected to become greater. Therefore, control of the blast furnace process is expected to become even more difficult.

In order to realize highly efficient and stable blast furnace operation, it is important to control the hot metal temperature (HMT). If the hot metal temperature becomes extremely low, the temperature of the by-product slag drops and the slag viscosity increases, making it difficult to discharge from the furnace. Furthermore, the occurrence of a chilled blast furnace accident, in which the hot metal or slag in the lower part of the furnace solidifies due to insufficient heat, can lead to operational stoppage. If the target temperature is set higher to avoid a drop in the hot metal temperature, more fuel will be consumed, leading to an increase in the reducing agent ratio. By suppressing the variation in the hot metal temperature, it becomes possible to lower the target value while still satisfying the lower limit constraint of the hot metal temperature, which leads to a reduction in the reducing agent ratio.

The hot metal temperature is controlled by, for example, manipulating the coke ratio, blast moisture, blast temperature, pulverized coal ratio (PCR), and pulverized coal injection (PCI) flow rate. When an operational variable is changed, there is a time delay of about 2 to 8 hours before the hot metal temperature changes, since the blast furnace is a process with a large heat capacity. Therefore, it is necessary to predict the hot metal temperature taking into account the time delay until the effect of the action appears, and to control the hot metal temperature based on the prediction.

In view of this background, various methods of controlling the hot metal temperature have been proposed. For example, Patent Literature (PTL) 1 discloses a method of executing a dual-layer structure control loop of a first control (HMT control) and a second control (PCR tracking control) to calculate a target value of the pulverized coal ratio. In the first control, a target value of the pulverized coal ratio is calculated so that the hot metal temperature falls within a preset target range. In the second control, a pulverized coal injection flow rate manipulation amount is calculated to compensate for (reduce) the deviation between the target value of the pulverized coal ratio and the current actual value of the pulverized coal ratio.

CITATION LIST

Patent Literature

• • PTL 1: JP 7107444 B2

SUMMARY

Technical Problem

The method described in PTL 1 enables control of the hot metal temperature in a manner that is less susceptible to the change in burden descent. However, if the hot metal temperature deviates from the target value and there is a large discrepancy between the target value of the pulverized coal ratio and the current actual value of the pulverized coal ratio, excessive control action may be taken. Here, an excessive control action refers to the additional execution of a manipulation that is not essential. Although the method described in PTL 1 requires only the manipulation of the PCI flow rate (second control) to compensate for the deviation in the pulverized coal ratio, manipulation of the pulverized coal ratio (manipulation based on the first control) may be further performed. Furthermore, although PTL 1 achieves automatic control, automatic control generally does not indicate the reason for action. For example, by presenting the rationale for the calculation of the manipulation amount of the operational variable, the operator can be convinced.

In light of the above circumstances, the present disclosure aims to provide an HMT control method, a hot metal temperature control device, an HMT control system, and a terminal device that are capable of suppressing excessive control actions and of indicating optimal actions and the rationale for calculation.

Solution to Problem

(1) A hot metal temperature control method according to an embodiment of the present disclosure includes:

• • a calculation step of calculating a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculating a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritizing the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;
  • a determination step of determining a rationale for calculation of the optimal action and adding a text statement to a rationale statement indicating the rationale; and a presentation step of presenting operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

(2) As an embodiment of the present disclosure, in (1),

• • in the calculation step, in a case in which an absolute value of the pulverized coal injection flow rate manipulation amount is larger than an operation range of pulverized coal injection flow rate that is changeable each time, the pulverized coal ratio tracking control is prioritized and the pulverized coal ratio manipulation amount calculated by the hot metal temperature control is not taken into account in the target value of the pulverized coal ratio.

(3) As an embodiment of the present disclosure, in (1) or (2),

• • in the calculation step, in a case in which a predicted hot metal temperature calculated taking into account the pulverized coal injection flow rate manipulation amount falls outside a target range of the hot metal temperature, the hot metal temperature control is prioritized and the pulverized coal ratio manipulation amount calculated by the hot metal temperature control is taken into account in the target value of the pulverized coal ratio.

(4) As an embodiment of the present disclosure, in any one of (1) to (3),

• • the determination step includes adding a plurality of text statements to the rationale statement, and
  • the plurality of text statements includes a plurality of change contents arranged in order of a most recent change from a current time or a largest amount of change.

(5) As an embodiment of the present disclosure, in any one of (1) to (4),

• • the operation information is an operation amount presentation screen including a text statement expressing an intention of the optimal action, a rationale for calculating the optimal action, an accept button, and a reject button,
  • the accept button is used when an operator approves the optimal action displayed on the operation amount presentation screen, and
  • the reject button is used when the operator rejects the optimal action displayed on the operation amount presentation screen.

(6) As an embodiment of the present disclosure, in (5),

• • the presentation step includes, as a control mode, a semi-automatic mode in which the optimal action is executed with approval of the operator, and an automatic mode in which the optimal action is executed without the approval of the operator,
  • the operation information is an operation amount presentation screen further including a timer in a case in which the control mode is the automatic mode, and
  • the timer displays a length of time from when display regarding the optimal action is updated until a predetermined time, and the optimal action is executed in a case in which the reject button is not selected before the predetermined time is reached.

(7) A hot metal temperature control device according to an embodiment of the present disclosure includes:

• • a calculation unit configured to calculate a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculate a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritize the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;
  • a determination unit configured to determine a rationale for calculation of the optimal action and add a text statement to a rationale statement indicating the rationale; and
  • a presentation unit configured to present operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

(8) As an embodiment of the present disclosure, in (7),

• • in a case in which an absolute value of the pulverized coal injection flow rate manipulation amount is larger than an operation range of pulverized coal injection flow rate that is changeable each time, the calculation unit is configured to prioritize the pulverized coal ratio tracking control and not to take the pulverized coal ratio manipulation amount calculated by the hot metal temperature control into account in the target value of the pulverized coal ratio.

(9) As an embodiment of the present disclosure, in (7) or (8),

• • in a case in which a predicted hot metal temperature calculated taking into account the pulverized coal injection flow rate manipulation amount falls outside a target range of the hot metal temperature, the calculation unit is configured to prioritize the hot metal temperature control and to take the pulverized coal ratio manipulation amount calculated by the hot metal temperature control into account in the target value of the pulverized coal ratio.

(10) As an embodiment of the present disclosure, in any one of (7) to (9),

• • the determination unit is configured to add a plurality of text statements to the rationale statement, and
  • the plurality of text statements includes a plurality of change contents arranged in order of a most recent change from a current time or a largest amount of change.

(11) As an embodiment of the present disclosure, in any one of (7) to (10),

• • the operation information is an operation amount presentation screen including a text statement expressing an intention of the optimal action, a rationale for calculating the optimal action, an accept button, and a reject button,
  • the accept button is used when an operator approves the optimal action displayed on the operation amount presentation screen, and
  • the reject button is used when the operator rejects the optimal action displayed on the operation amount presentation screen.

(12) As an embodiment of the present disclosure, in (11),

• • the presentation unit includes, as a control mode, a semi-automatic mode in which the optimal action is executed with approval of the operator, and an automatic mode in which the optimal action is executed without the approval of the operator,
  • the operation information is an operation amount presentation screen further including a timer in a case in which the control mode is the automatic mode, and
  • the timer displays a length of time from when display regarding the optimal action is updated until a predetermined time, and the optimal action is executed in a case in which the reject button is not selected before the predetermined time is reached.

(13) A hot metal temperature control system according to an embodiment of the present disclosure is

• • a hot metal temperature control system including:
  • a hot metal temperature control device and a terminal device,
  • a calculation unit configured to calculate a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculate a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritize the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;
  • a determination unit configured to determine a rationale for calculation of the optimal action and add a text statement to a rationale statement indicating the rationale;
  • an output interface configured to output operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action;
  • a communication unit configured to transmit and receive the operation information;
  • an acquisition unit configured to acquire the optimal action and the operation information related to the optimal action including the rationale statement;
  • a display unit configured to display the acquired optimal action and the operation information so as to include the rationale statement; and
  • an interface unit configured to receive an instruction for the displayed operation information and output a set value for an operational variable in response to the instruction or based on elapse of a predetermined time.

(14) A terminal device according to an embodiment of the present disclosure is

• • a terminal device configuring a hot metal temperature control system together with a hot metal temperature control device that outputs operation information, for controlling hot metal temperature, including at least one of a pulverized coal ratio manipulation amount and a pulverized coal injection flow rate manipulation amount calculated as an optimal action based on a magnitude of discrepancy between a target value of a pulverized coal ratio and an actual value of the pulverized coal ratio, and including a rationale statement indicating a rationale for calculation of the optimal action, the terminal device including:
  • an acquisition unit configured to acquire the optimal action and the operation information related to the optimal action including the rationale statement;
  • a display unit configured to display the acquired optimal action and the operation information so as to include the rationale statement; and
  • an interface unit configured to receive an instruction for the displayed operation information and output a set value for an operational variable in response to the instruction or based on elapse of a predetermined time.

(15) As an embodiment of the present disclosure, in (14),

• • the operation information includes a plurality of operational conditions and is displayed together with an order of priority.

Advantageous Effect

According to the present disclosure, an HMT control method, a hot metal temperature control device, an HMT control system, and a terminal device that are capable of suppressing excessive control actions and of indicating optimal actions and the rationale for calculation can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram illustrating a configuration example of a hot metal temperature control device according to an embodiment of the present disclosure;

FIG. 2 is a flowchart illustrating processing by a calculation unit;

FIG. 3 is a flowchart illustrating processing by a determination unit;

FIG. 4 is a flowchart illustrating processing by a presentation unit;

FIG. 5 is a diagram illustrating an example of an operation amount presentation screen when the control mode is automatic mode;

FIG. 6 is a diagram illustrating an example of an operation amount presentation screen when the control mode is semi-automatic mode;

FIG. 7 is a diagram illustrating an example of another operation amount presentation screen when the control mode is automatic mode;

FIG. 8 is a diagram illustrating an example of changes in the target values of hot metal temperature and pulverized coal ratio, and the set value of the PCI flow rate, for the past 8 hours and the next 10 hours, with the current time being set to 0;

FIG. 9 is a diagram illustrating another example of changes in the target values of hot metal temperature and pulverized coal ratio, and the set value of the PCI flow rate, for the past 8 hours and the next 10 hours, with the current time being set to 0;

FIG. 10 is a diagram illustrating an example of changes in hot metal temperature, coke ratio, pulverized coal ratio manipulation amount, pulverized coal ratio, pulverized coal injection flow rate manipulation amount, PCI flow rate, blast volume, and production rate over 60 hours;

FIG. 11 is a diagram illustrating an example of changes in hot metal temperature, coke ratio, pulverized coal ratio, PCI flow rate, blast volume, production rate, and low-grade raw material input ratio over 60 hours; and

FIG. 12 is a block diagram illustrating a configuration example of an HMT control system including a hot metal temperature control device.

DETAILED DESCRIPTION

Hereinafter, an HMT control method, a hot metal temperature control device, an HMT control system, and a terminal device according to an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, identical or equivalent parts are marked with the same symbol. In the description of the present embodiment, a description of identical or equivalent parts will be omitted or simplified as appropriate.

[Configuration of Hot Metal Temperature Control Device]

FIG. 1 is a block diagram illustrating a configuration example of a hot metal temperature control device 1 according to an embodiment of the present disclosure. As illustrated in FIG. 1, a hot metal temperature control device 1 according to the present embodiment can be configured by an information processing device such as a computer. Specifically, an internal calculation processing device such as a CPU (Central Processing Unit) executes a program, causing the computer or the like to function as the hot metal temperature control device 1.

An operation database 2 is connected to the hot metal temperature control device 1 in a data readable form. In the present embodiment, the operation database 2 stores operational factors, calculated values of process variables, actual values of process variables, and historical data of the temperature or pressure measured in the furnace body, furnace top, or furnace bottom. The operational factors include, for example, the coke ratio at furnace top, the blast volume, the enriched oxygen amount, the blast temperature, the blast moisture, the pulverized coal ratio, and the PCI flow rate. The calculated values of the process variables are gas utilization, solution loss carbon, hot metal temperature, and production rate, which are output by a transient model. The actual values of the process variables are, for example, calculated based on the volume fraction of CO or CO₂ in the discharged top gas. Examples of the process variables include the production rate, hot metal temperature, solution loss carbon, and gas utilization. Measured data required for operation and operational factors required for HMT control are sequentially saved and stored in the operation database 2, and this information is read out and used as required. In addition, the calculated values of the process variables output by the transient model are sequentially saved in the operation database 2 each time a calculation is performed by the hot metal temperature control device 1.

The transient model used in the present disclosure is the same as the model of the method described in the reference (Michiharu Hatano et al.: “Investigation of Furnace Start-Up Operation through the Blast Furnace Transient Model”, Tetsu-to-Hagane, vol. 68, p. 2369). In other words, the transient model is composed of a system of partial differential equations that take into account multiple physical phenomena such as the reduction of iron ore, heat exchange between iron ore and coke, and fusion of iron ore, and is a transient model that can calculate variables (output variables) representing the blast furnace condition in a non-steady state.

The hot metal temperature control device 1 according to the present embodiment includes a calculation unit 11, a determination unit 12, and a presentation unit 13. The hot metal temperature control device 1 can control the hot metal temperature by the calculation unit 11, the determination unit 12, and the presentation unit 13 executing the processes described below. Furthermore, the hot metal temperature control device 1 may include a memory device, in which case the memory device may store the transient model. When executing the processes described below, the hot metal temperature control device 1 may read out a transient model from the memory device and use the transient model for calculations.

[Operation of the Calculation Unit]

The operation of the calculation unit 11 will be described with reference to FIG. 2. At least a part of the processing illustrated in FIG. 2 corresponds to the calculation step executed by the calculation unit 11.

FIG. 2 is a flowchart illustrating the flow of processing by the calculation unit 11. The flowchart illustrated in FIG. 2 starts when an execution command is input to the calculation unit 11, and proceeds to the processing in step S11.

In the processing in step S11, the calculation unit 11 calculates a pulverized coal ratio manipulation amount ΔPCR₀ so that the hot metal temperature predicted by the transient model falls within a preset target range. In the present embodiment, the calculation method in step S11 is similar to the HMT control method described in PTL 1 above. In other words, ΔPCR₀ and ΔPCI₀, which is described below, are calculated by controlling the hot metal temperature.

In calculating the pulverized coal ratio manipulation amount (ΔPCR), which is the manipulation amount of the pulverized coal ratio (PCR), a so-called velocity-type method is used in which an amount of change is added to or subtracted from the manipulation amount. Therefore, the adjusted pulverized coal ratio is set by adding ΔPCR to the current target value of the pulverized coal ratio (PCR_ref(0)).

Next, using the current production rate Prod(0) and a relaxation coefficient α₀ (0<α₀≤1), the pulverized coal injection flow rate manipulation amount ΔPCI₀ corresponding to the pulverized coal ratio manipulation amount ΔPCR₀ is calculated by Expression (1). The pulverized coal injection flow rate manipulation amount (APCI) is the manipulation amount of the PCI flow rate. The subscript 0 indicates correspondence to ΔPCR₀. As for the PCI flow rate, a pulverized coal injection flow rate manipulation amount ΔPCI₀ is calculated as an increase or decrease from the current PCI value. The processing by the calculation unit 11 proceeds to step S12.

$\begin{array}{cc}\left[\mathrm{Math}.1\right]& \\ \Delta {\mathrm{PCI}}_0={\alpha }_0·\Delta {\mathrm{PCR}}_0·\mathrm{Prod}\left(0\right)& \left(1\right)\end{array}$

In the processing in step S12, the calculation unit 11 calculates the pulverized coal injection flow rate manipulation amount to compensate for the deviation between the target value of the pulverized coal ratio and the current value (the current actual value of the pulverized coal ratio). In the present embodiment, the calculation method in step S12 is similar to the method of PCR tracking control described in PTL 1 above. That is, the following ΔPCR₁ is calculated by PCR tracking control. First, the current PCI flow rate is set as PCI(0), the target value of the pulverized coal ratio is set as PCR_ref(0), and the deviation δPCR between the target value and the actual value of the pulverized coal ratio is calculated by Expression (2).

$\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ \delta \mathrm{PCR}=\frac{\mathrm{PCI}\left(0\right)}{\mathrm{Prod}\left(0\right)}-{\mathrm{PCR}}_{\mathrm{ref}}\left(0\right)& \left(2\right)\end{array}$

Next, using a relaxation coefficient α₁ (0<α₁≤1), the pulverized coal injection flow rate manipulation amount ΔPCI₁ for compensating for the deviation δPCR between the target value and the actual value of the pulverized coal ratio is calculated by Expression (3). The processing by the calculation unit 11 proceeds to step S13.

$\begin{array}{cc}\left[\mathrm{Math}.3\right]& \\ \Delta {\mathrm{PCI}}_1=-{\alpha }_1·\delta \mathrm{PCR}·\mathrm{Prod}\left(0\right)& \left(3\right)\end{array}$

In the processing in step S13, the calculation unit 11 judges whether the absolute value |ΔPCI₁| of the pulverized coal injection flow rate manipulation amount for compensating for the deviation δPCR between the target value and the actual value of the pulverized coal ratio is larger than an operation range A of PCI flow rate that is changeable each time. If |ΔPCI₁| is larger than the operation range A, it means that there is a large discrepancy between the actual value of the pulverized coal ratio and the current target value of the pulverized coal ratio. Here, in the method described in PTL 1 above, if the hot metal temperature deviates from the target value and there is a large discrepancy between the target value of the pulverized coal ratio and the current actual value of the pulverized coal ratio, excessive control action may be taken. In the present embodiment, when this discrepancy is large, the optimal action is, in principle, not to take into account the increase or decrease in the pulverized coal ratio manipulation amount based on the HMT control, i.e., not to add to the target value of the pulverized coal ratio, but to manipulate only the PCI flow rate with the sole purpose of following the target value of the pulverized coal ratio at that time. When this discrepancy is large, excessive control action can be suppressed by not taking into account (reflecting) the pulverized coal ratio manipulation amount calculated by the HMT control in the target value of the pulverized coal ratio. That is, in the present embodiment, when the discrepancy is large, priority is given to the PCR tracking control in principle, and only the PCI flow rate is manipulated to compensate for the deviation of the pulverized coal ratio, thereby preventing a decrease in accuracy of the HMT control due to excessive manipulation of the pulverized coal ratio. When |ΔPCI₁| is greater than the operation range A (Yes in step S13), the calculation unit 11 proceeds to the processing in step S14. When |ΔPCI₁| is equal to or less than the operation range A (No in step S13), the calculation unit 11 proceeds to the processing in step S19.

In the processing in step S14, the calculation unit 11 calculates a predicted hot metal temperature taking into account the pulverized coal injection flow rate manipulation amount ΔPCI₁. A step response S_PCI(k|t₀) of the hot metal temperature k hours later for a unit change response of the PCI flow rate at the current time to and a free response y_free(t₀+k) of the hot metal temperature assuming that the current input variables are maintained in the future are calculated using a transient model. A predicted hot metal temperature y_pre(t₀+k) taking into account the pulverized coal injection flow rate manipulation amount ΔPCI₁ for compensating for the deviation δPCR between the target value and the actual value of the pulverized coal ratio is calculated by the following Expression (4). The calculation unit 11 proceeds to the processing in step S15.

$\begin{array}{cc}\left[\mathrm{Math}.4\right]& \\ y_{\mathrm{pre}}\left(t_0+k\right)=S_{\mathrm{PCI}}\left(k❘t_0\right)·\Delta {\mathrm{PCI}}_1+y_{\mathrm{free}}\left(t_0+k\right)& \left(4\right)\end{array}$

In the processing in step S15, the calculation unit 11 determines whether the predicted hot metal temperature y_pre(t₀+k) is within the target range of the hot metal temperature. When performing the processing of step S15, there is a large discrepancy between the target value and the actual value of the pulverized coal ratio. If priority is given to the PCR tracking control, however, there is a risk that the hot metal temperature will remain lower or higher than the target (i.e., will fall outside the target range of the hot metal temperature). In this case, the pulverized coal ratio can also be manipulated while giving priority to the HMT control. When the predicted hot metal temperature y_pre(t₀+k) is within the target range of the hot metal temperature (Yes in step S15), the calculation unit 11 proceeds to the processing in step S16. When the predicted hot metal temperature y_pre(t₀+k) is not within the target range of the hot metal temperature (No in step S15), the calculation unit 11 proceeds to the processing in step S18. The calculation unit 11 prioritizes the HMT control or the PCR tracking control as the optimal action based on the magnitude of the discrepancy between the target value and the actual value of the pulverized coal ratio.

In the processing in step S16, the calculation unit 11 sets a “PCR tracking control priority flag”. The calculation unit 11 proceeds to the processing in step S17.

In the processing in step S17, the calculation unit 11 does not take ΔPCI₀ into account in the pulverized coal ratio manipulation amount ΔPCR to be ultimately presented, but rather sets the pulverized coal injection flow rate manipulation amount ΔPCI to be ultimately presented as ΔPCI₁ and terminates the series of processes.

In the processing in step S18, the calculation unit 11 sets an “HMT control priority flag”. The calculation unit 11 proceeds to the processing in step S19.

In the processing of step S19, the calculation unit 11 sets the pulverized coal ratio manipulation amount ΔPCR to be ultimately presented to ΔPCR₀, sets the pulverized coal injection flow rate manipulation amount ΔPCI to be ultimately presented to the sum of ΔPCI₀ and ΔPCI₁ (the value obtained by adding ΔPCI₁ to ΔPCI₀), and terminates the series of processes.

[Operation of the Determination Unit]

The operation of the determination unit 12 will be described with reference to FIG. 3. At least a part of the processing illustrated in FIG. 3 corresponds to the determination step executed by the determination unit 12. The determination unit 12 determines the rationale for the calculation of the optimal action, and adds a text statement to a rationale statement indicating the rationale. Specific examples of added statements will be described later.

FIG. 3 is a flowchart illustrating the flow of processing by the determination unit 12. The flowchart illustrated in FIG. 3 starts when an execution command is input to the determination unit 12, and proceeds to the determination in step S21.

In the processing in step S21, the determination unit 12 determines whether the PCR tracking control priority flag is set in the calculation unit 11. If the PCR tracking control priority flag is set, the determination unit 12 proceeds to the processing in step S22. If the PCR tracking control priority flag is not set, the determination unit 12 proceeds to the processing in step S23.

In the processing in step S22, the determination unit 12 adds “priority on PCR tracking control” to the rationale statement. The rationale statement indicates the reason for a manipulation (action) in the operation and is the content displayed in the “presentation rationale 32 for optimal action” described later. The rationale statement may be stored in a memory device included in the hot metal temperature control device 1. As a result, the determination unit 12 proceeds to the processing in step S25.

In the processing in step S23, the determination unit 12 determines whether the HMT control priority flag is set in the calculation unit 11. If the HMT control priority flag is set, the determination unit 12 proceeds to the processing in step S24. If the HMT priority flag is not set, the determination unit 12 proceeds to the processing in step S25.

In the processing in step S24, the determination unit 12 adds “priority on HMT” to the rationale statement. As a result, the determination unit 12 proceeds to the processing in step S25.

In the processing in step S25, the determination unit 12 determines whether the action on the pulverized coal ratio or the PCI flow rate is in violation of an operation constraint to skip action.

For example, an excessive pulverized coal ratio may lead to deterioration of permeability. Therefore, there may be an operation constraint in the form of an upper limit of the pulverized coal ratio. If the current target value of the pulverized coal ratio exceeds the upper limit, the determination unit 12 adds “upper limit of PCR” to the rationale statement. If, for example, the reducing agent ratio is extremely small, this may lead to a rapid drop in the hot metal temperature and a deterioration of permeability. Therefore, there may be an operation constraint in the form of a lower limit of the reducing agent ratio. If the current reducing agent ratio falls below the lower limit, the determination unit 12 adds “lower limit of reducing agent ratio” to the rationale statement. A low temperature of furnace top gas, for example, may lead to soot at the furnace top or condensation of moisture in blast furnace gas, which may cause damage to the blast furnace equipment. Therefore, there may be an operation constraint in the form of a lower limit of the temperature of furnace top gas. If the current temperature of furnace top gas falls below the lower limit, the determination unit 12 adds “lower limit of top gas temperature” to the rationale statement. If, for example, the theoretical flame temperature at the tuyere tip is too low, the pulverized coal may not burn at the tuyere. On the other hand, if the theoretical flame temperature is too high, the tuyere may be damaged. Therefore, there may be operation constraints in the form of upper and lower limits of the theoretical flame temperature. If the current theoretical flame temperature is not within the range of the upper and lower limits, the determination unit 12 adds “upper limit of theoretical flame temperature” or “lower limit of theoretical flame temperature” to the rationale statement.

If the above operation constraints are violated, the determination unit 12 proceeds to the processing in step S26. If no operation constraints are violated, the determination unit 12 proceeds to the processing in step S27.

In the processing in step S26, the determination unit 12 adds “upper limit of PCR”, “lower limit of reducing agent ratio”, “lower limit of top gas temperature”, “upper limit of theoretical flame temperature”, or “lower limit of theoretical flame temperature”, for example, to the rationale statement as described above. As a result, the determination unit 12 proceeds to the processing in step S27.

In the processing in step S27, the determination unit 12 determines, based on the transition of the operational variables related to HMT control or the transition of indicators highly correlated with the hot metal temperature, whether there has been a change in the operational variables or the indicators. Examples of the operational variables include the coke ratio, pulverized coal ratio, blast temperature, and blast humidity. Examples of indicators highly correlated with the hot metal temperature include the embedded tuyere temperature, the silicon content in molten iron, the sulfur content, the theoretical flame temperature, and solution loss carbon. The determination unit 12 can determine whether there has been a change by calculating the difference from the value at the current time and determining whether the absolute value of the difference exceeds a threshold. The determination unit 12 may also determine the change in the indicators using a machine learning model that receives as input a graph of the transition. When a plurality of items has changed, the determination unit 12 may arrange a corresponding plurality of text statements in order of proximity to the current time or in order of the largest amount of change. If there is a change in an operational variable or indicator, the determination unit 12 proceeds to the processing in step S28. If there is no change in the operational variables or the indicators, the determination unit 12 terminates the series of processes.

In the processing in step S28, the determination unit 12 adds, for example, the operational variable or indicator that has changed, the time when the change occurred (for example, how many hours before the current time) and the direction of the change (for example, increase or decrease), and the like in correspondence with each other to the rationale statement. The determination unit 12 thereby terminates the series of processes. In this way, the determination unit 12 adds a text statement to the rationale statement indicating the grounds for the calculation of the aforementioned optimal action.

Here, as described above, the rationale statement may include a plurality of operation constraints and change contents. However, to avoid information overload, the number of operation constraints and change contents included in the rationale statement is preferably one to four.

[Operation of the Presentation Unit]

The operation of the presentation unit 13 will be described with reference to FIG. 4. The presentation unit 13 presents operation information to the operator. At least a part of the processing illustrated in FIG. 4 corresponds to the presentation step executed by the presentation unit 13.

FIG. 4 is a flowchart illustrating the flow of processing by the presentation unit 13. The flowchart illustrated in FIG. 4 starts when an execution command is input to the presentation unit 13, and proceeds to the processing in step S31.

In the processing in step S31, the presentation unit 13 determines whether the absolute value of the manipulation amount of the optimal action obtained by the calculation unit 11 exceeds the minimum configurable unit, thereby determining whether execution is necessary. For example, when the target value of the pulverized coal ratio is changed in increments of at least 2 kg/t, even if the calculation unit 11 calculates the pulverized coal ratio manipulation amount to be +1 kg/t, it is determined that no action is necessary. By the processing of step S31, excessively frequent presentation can be avoided. In addition, avoiding excessively frequent presentation helps prevent hunting of the hot metal temperature. If it is determined in step S31 that an action is required, the processing by the presentation unit 13 proceeds to step S32. If it is determined in step S31 that no action is required, the presentation unit 13 terminates the series of processes.

In the processing in step S32, the presentation unit 13 determines whether τ₁ minutes have elapsed since the last action was executed. τ₁ is non-zero, but is not limited to any particular value. If τ₁ minutes have elapsed since the last action was executed, the processing by the presentation unit 13 proceeds to step S33. If τ1 minutes have not elapsed since the last action was executed, the presentation unit 13 ends the series of processing. Since use of a blast furnace is a process with a long time constant, it takes time for the effects of actions to appear. Therefore, performing a similar action too soon after a recent manipulation may result in an overreaction. The processing in step S32 is important in order to prevent excessive control actions. Here, τ₁ is preferably selected from among a plurality of values. τ₁ is preferably set to different values in a normal state and in a case in which an emergency operation is required, such as when the blast volume, the enriched oxygen amount, or the coke ratio has recently been significantly changed.

In the processing in step S33, the presentation unit 13 determines whether the difference between the set value of the operational variable (for example, the blast volume, the enriched oxygen amount, or the coke ratio) used in the processing in step S32 and the set value of the operational variable currently set is within a threshold. If the difference is within a threshold, the processing by the presentation unit 13 proceeds to step S34. If the difference is greater than the threshold, the presentation unit 13 terminates the series of processes. If an operator significantly changes a set value during the series of processes for some reason, such as equipment trouble or furnace condition deterioration, the manipulation amount obtained by the processing of the calculation unit 11 is not a recommended action, and executing the action may cause the controllability of the hot metal temperature to deteriorate. The processing in step S33 makes it possible to prevent the hot metal temperature control device 1 from going out of control due to external disturbances.

In the processing in step S34, the presentation unit 13 determines the control mode that has been set. In the present embodiment, the presentation unit 13 has two control modes. That is, the presentation unit 13 can use a semi-automatic mode in which the optimal action is executed with approval of the operator, or an automatic mode in which the optimal action is executed without the approval of the operator. If the control mode is the automatic mode, the processing by the presentation unit 13 proceeds to step S35. If the control mode is the semi-automatic mode, the processing by the presentation unit 13 proceeds to step S36.

In the processing in step S35, information based on the optimal action illustrated in FIG. 5 is displayed as a pop-up on the operation terminal of the operator, and an alarm is issued. When the control mode is the automatic mode, a timer 36 until an action is executed is provided on the screen. The moment the popup is displayed, that is, when the display regarding the optimal action is updated, the timer 36 is set to τ₂ seconds and a countdown begins. If the operator presses the reject button 35 before the timer 36 reaches 0 seconds, the pop-up disappears and the presentation unit 13 terminates the series of processes. If the operator does not press (select) the reject button 35 before the timer 36 reaches 0 seconds, or if the operator presses (selects) an accept button 34, the processing by the presentation unit 13 proceeds to step S37. That is, if the operator does not reject the request within τ₂ seconds, the optimal action is executed. To make the user aware of the automatic execution of the action, an alarm may be issued at a timing τ₃ that satisfies 0≤τ₃≤τ₂. τ₂ and τ₃ are non-zero but are not limited to any particular values. Here, “0 seconds” is an example of the predetermined time, and other values may be used. The timer 36 is not limited to a countdown timer but may be any timer that displays the time remaining until a predetermined time is reached.

In the processing in step S36, information based on the optimal action illustrated in FIG. 6 is displayed as a pop-up on the operation terminal of the operator, and an alarm is issued. When the control mode is the semi-automatic mode, the timer 36 until the action is executed is not provided on the screen. Execution of the action requires operator approval. If the operator presses an accept button 44, the processing by the presentation unit 13 proceeds to step S37. If the operator presses a reject button 45, the pop-up disappears and the presentation unit 13 terminates the series of processes. To prevent the operator from letting the pop-up remain displayed, an alarm may be issued every time τ₄ minutes have elapsed from the moment the popup display is displayed without either the accept button 44 or the reject button 45 being pressed. 4 is non-zero but is not limited to any particular value.

In the processing in step S37, the pop-up that was displayed in step S35 or step S36 disappears, and the set value of the operational variable is overwritten (updated) by the value calculated in accordance with the optimal action. This completes the processing in step S37, and the presentation unit 13 terminates the series of processes. The overwritten (updated) set values of the operational variables are output to, for example, a computer that controls the operation equipment 4 (see FIG. 12) and are reflected in the operation equipment 4.

[Operation Amount Presentation Screen]

FIG. 5 is a diagram illustrating an operation amount presentation screen when the control mode of the hot metal temperature control device 1 is the automatic mode.

The operation amount presentation screen displays a text statement 31 expressing the intention of the optimal action (for example, increasing the hot metal temperature, decreasing the hot metal temperature, or controlling the pulverized coal ratio), and a presentation rationale 32 for the optimal action determined by the determination unit 12. Furthermore, the operation amount presentation screen displays an optimal manipulation amount 33, an accept button 34, a reject button 35, and a timer 36. The optimal manipulation amount 33 indicates at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

FIG. 6 is a diagram illustrating an operation amount presentation screen when the control mode of the hot metal temperature control device 1 is the semi-automatic mode.

The operation amount presentation screen displays a text statement 41 expressing the direction of the optimal action (for example, increasing the hot metal temperature, decreasing the hot metal temperature, or controlling the pulverized coal ratio), and a presentation rationale 42 for the optimal action determined by the determination unit 12. Furthermore, the operation amount presentation screen displays an optimal manipulation amount 43, an accept button 44, and a reject button 45. The optimal manipulation amount 43 indicates at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

FIG. 7 is a diagram illustrating another operation amount presentation screen when the control mode of the hot metal temperature control device 1 is the automatic mode. In FIG. 7, the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action are presented, and two cases are presented in which another manipulation amount (blast moisture in the example of FIG. 7) calculated by HMT control based on a transient model is used as another action. In the example in FIG. 7, the operation information includes a plurality of operational conditions and is displayed together with the order of priority (1 to 3 in FIG. 7). Here, there may be a manipulation amount that cannot be implemented due to operation constraints. Therefore, a plurality of recommended actions is preferably presented to the operator to allow the operator to select an operation, as in the example in FIG. 7. In addition, in order to prevent button pressing errors, a specification may be adopted in which an “Execute” button is pressed after pressing the “Accept” or “Reject” button.

Example 1

In the present example, a case in which the HMT control priority flag is set by the processing of the calculation unit 11 is illustrated in FIG. 8. FIG. 8 is a diagram illustrating changes in the target values of the hot metal temperature (HMT) and the pulverized coal ratio (PCR), and the set value of the PCI flow rate (PCI), for the past 8 hours and the next 10 hours, with the current time being set to 0. The dashed lines for the hot metal temperature indicate the upper and lower limits of the target value. The thick solid line for the past eight hours is the actual value. The thin solid line is a calculated value from a transient model including future predictions. The dotted line indicates the predicted value of the hot metal temperature if the calculated action is implemented. The triangular plot of the pulverized coal ratio represents the actual value of the pulverized coal ratio at the current time. Moreover, the arrows in the pulverized coal ratio and PCI flow rate indicate the actions calculated in the calculation unit 11. In the present example, while there is a large discrepancy between the target value and the actual value of the pulverized coal ratio, if priority is given to PCR tracking control, the rise in hot metal temperature cannot be suppressed. Therefore, actions for pulverized coal ratio and PCI flow rate were presented, with priority given to HMT control.

Example 2

In the present example, a case in which the PCR tracking control priority flag is set by the processing of the calculation unit 11 is illustrated in FIG. 9. FIG. 9 is a diagram illustrating changes in the target values of the hot metal temperature and the pulverized coal ratio, and the set value of the PCI flow rate, for the past 8 hours and the next 10 hours, with the current time being set to 0, at times different from those illustrated in FIG. 8. In the present example, while there is a large discrepancy between the target value and the actual value of the pulverized coal ratio, the prediction was that the hot metal temperature would not change significantly. Therefore, only the action for the PCI flow rate was presented, with priority given to the PCR tracking control.

Example 3

In the present example, the semi-automatic mode was used as the control mode in the hot metal temperature control device 1, and operation was carried out by manipulating the pulverized coal ratio and the PCI flow rate. τ₁ is 40 minutes.

FIG. 10 is a diagram illustrating an example of changes in hot metal temperature, coke ratio, pulverized coal ratio manipulation amount, pulverized coal ratio, pulverized coal injection flow rate manipulation amount, PCI flow rate, blast volume, and production rate over 60 hours.

In FIG. 10, the solid lines indicate actual values for the hot metal temperature and pulverized coal ratio. The dashed lines indicate the target values. The circles in FIG. 10 for the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount are actual values. The triangles indicate the optimal actions calculated by the hot metal temperature control device 1. The operator accepted all of the optimal actions presented by the hot metal temperature control device 1. Therefore, for the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount in FIG. 10, the optimal actions and the actual manipulations (performance) all match. As illustrated in the pulverized coal ratio and PCI flow rate in FIG. 10, by appropriately adjusting the PCI flow rate, the actual value of the pulverized coal ratio tracked the target value. Furthermore, the coke ratio in FIG. 10 gradually decreased due to manual operation by the operator, but as indicated by the pulverized coal ratio in FIG. 10, the hot metal temperature control device 1 increased the target value of the pulverized coal ratio, thereby offsetting the effect of the decrease in the coke ratio on the hot metal temperature. In other words, the hot metal temperature was controlled to be close to the target value.

Example 4

In the present example, during a period different from that of Example 3, operation was performed by manipulating the pulverized coal ratio and the PCI flow rate using the automatic mode as the control mode in the hot metal temperature control device 1. τ₁ is 40 minutes.

FIG. 11 is a diagram illustrating an example of changes in hot metal temperature, coke ratio, pulverized coal ratio, PCI flow rate, blast volume, production rate, and low-grade raw material input ratio over 11 days.

The hot metal temperature in FIG. 11 indicates the difference from the target hot metal temperature value at time zero. In the graphs in FIG. 11, other than the hot metal temperature, the average value for the period is set to zero. As a result of automatic control of the pulverized coal ratio and PCI flow rate by the hot metal temperature control device 1 throughout the entire period illustrated in the drawing, the hot metal temperature fluctuated within the range of −25° C. to 35° C., and automatic control of the hot metal temperature was achieved. In addition, on the 9^th day, the blast volume was reduced due to deterioration of permeability, which resulted in a drop in the hot metal temperature. However, the hot metal temperature was controlled to be close to the target value by increasing the pulverized coal ratio. Furthermore, although yard sinter and yard coke were used throughout the entire period illustrated in the drawing, the fluctuations in the hot metal temperature were suppressed. In this way, it was confirmed that the hot metal temperature control device 1 has good controllability even under severe operating conditions such as blast reduction due to deterioration of permeability, or when low-grade raw materials are used.

(HMT Control System)

FIG. 12 is a block diagram illustrating a configuration example of an HMT control system including a hot metal temperature control device 1. The HMT control system includes the hot metal temperature control device 1 and a terminal device 3. The HMT control system may further include an operation database 2. In the HMT control system, the hot metal temperature control device 1 may include a calculation unit 11, a determination unit 12, and a presentation unit 13, and additionally a communication unit 14 that transmits and receives operation information. The communication unit 14 transmits the optimal action, operation information, and the like in particular to the terminal device 3. Also, in the HMT control system, the hot metal temperature control device 1 can present information via the terminal device 3 instead of directly presenting information. Therefore, the presentation unit 13 functions as an output interface that outputs the optimal action, operation information, and the like to the communication unit 14. The terminal device 3 is, for example, a device used by an operator. The terminal device 3 may be a mobile terminal such as a smartphone or a tablet. The operation equipment 4 is equipment used in blast furnace operation. The HMT control system is configured to be able to communicate with the operation equipment 4 via a network and outputs, to the operation equipment 4, the set values of the operational variables, updated in accordance with the optimal action, for example. In the HMT control system, the hot metal temperature control device 1 executes the aforementioned processing, and screens like those in FIGS. 5 to 7 are displayed on the terminal device 3. When, for example, an operator performs an operation (provides instructions), the set values of the operational variables are output to the operation equipment 4 in accordance with the instructions. The hot metal temperature control device 1 is also capable of receiving instructions regarding operation information from the operator via the communication unit 14.

(Terminal Device)

The terminal device 3 includes an acquisition unit 131, a display unit 132, and an interface unit 133. The acquisition unit 131 acquires an optimal action and operation information, related to the optimal action, including a rationale statement. The display unit 132 displays the acquired optimal action and operation information so as to include the rationale statement. For example, the display unit 132 may display operation information (see FIG. 7) including a rationale statement and a plurality of operational conditions, in which the operational conditions are displayed in order of priority. The interface unit 133 receives an instruction for the displayed operation information and outputs the set value for an operational variable in response to the instruction or based on the elapse of a predetermined time. Here, the set values for the operational variables may be output to the operation equipment 4 directly by the interface unit 133 or via the hot metal temperature control device 1.

The hot metal temperature control device 1, the operation database 2, the terminal device 3, and the operation equipment 4 are configured to be able to communicate with each other via a network such as a LAN (Local Area Network) or the Internet. Here, the configuration in FIG. 12 is just an example. The hot metal temperature control device 1 and the terminal device 3 do not need to include all of the components illustrated in FIG. 12. The hot metal temperature control device 1 and the terminal device 3 may also include components other than those illustrated in FIG. 12. Furthermore, the components included in each of the hot metal temperature control device 1 and the terminal device 3 are not limited to those illustrated in the example of FIG. 12. For example, the determination unit 12 and the display unit 132 may be included in the same device. In addition, for example, some of the components of the hot metal temperature control device 1 in FIG. 12 may be located on the terminal device 3 side. Some of the components provided in the terminal device 3 in FIG. 12 may, for example, be provided on the hot metal temperature control device 1 side. Therefore, the HMT control system that includes the hot metal temperature control device 1 and the terminal device 3 may be configured as a whole to include the calculation unit 11, the determination unit 12, the presentation unit 13 (output interface), the communication unit 14, the acquisition unit 131, the display unit 132, and the interface unit 133.

As described above, the HMT control method, hot metal temperature control device 1, HMT control system, and terminal device 3 according to the present embodiment are able to suppress excessive control actions and indicate optimal actions and the rationale for calculation through the above processes and configurations. In the present embodiment, even in automatic control (automatic mode), the rationale for calculation is presented to the operator, so that the operator can be convinced. In addition, the operation amount presentation screen having an accept button and a reject button is suitable for the operator to quickly indicate approval or rejection and is preferable as an interface unit for blast furnace operations, for example, in which decisions may need to be made every few minutes.

Although embodiments have been described above, the present disclosure is not limited by the description and drawings that form part of the present disclosure in relation to the embodiments. For example, changing the operational variable for HMT control leads to fluctuations in the tuyere tip gas temperature. From the perspective of maintaining equipment for tuyere refractory and the like and preventing deterioration of permeability due to unburnt pulverized coal, the tuyere tip gas temperature is preferably maintained within a predetermined range. Therefore, the way in which the tuyere tip gas temperature changes when the optimal action calculated by the hot metal temperature control device 1 is implemented may be visualized on the operation amount presentation screen. In other words, all other embodiments, examples, operational techniques, and the like that can be made by those skilled in the art based on the embodiments are all included in the technical scope of the present disclosure.

REFERENCE SIGNS LIST

• • 1 Hot metal temperature control device
  • 2 Operation database
  • 3 Terminal device
  • 4 Operation equipment
  • 11 Calculation unit
  • 12 Determination unit
  • 13 Presentation unit (output unit)
  • 14 Communication unit
  • 31 Text statement expressing intention of optimal action
  • 32 Rationale for presenting optimal action
  • 33 Optimal manipulation amount
  • 34 Accept button
  • 35 Reject button
  • 36 Timer
  • 41 Text statement expressing intention of optimal action
  • 42 Presentation rationale for optimal action
  • 43 Optimal manipulation amount
  • 44 Accept button
  • 45 Reject button
  • 131 Acquisition unit
  • 132 Display unit
  • 133 Interface unit

Claims

1. A hot metal temperature control method comprising:

a calculation step of calculating a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculating a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritizing the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;

a determination step of determining a rationale for calculation of the optimal action and adding a text statement to a rationale statement indicating the rationale; and

a presentation step of presenting operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

2. The hot metal temperature control method according to claim 1, wherein in the calculation step, in a case in which an absolute value of the pulverized coal injection flow rate manipulation amount is larger than an operation range of pulverized coal injection flow rate that is changeable each time, the pulverized coal ratio tracking control is prioritized and the pulverized coal ratio manipulation amount calculated by the hot metal temperature control is not taken into account in the target value of the pulverized coal ratio.

3. The hot metal temperature control method according to claim 1, wherein in the calculation step, in a case in which a predicted hot metal temperature calculated taking into account the pulverized coal injection flow rate manipulation amount falls outside a target range of the hot metal temperature, the hot metal temperature control is prioritized and the pulverized coal ratio manipulation amount calculated by the hot metal temperature control is taken into account in the target value of the pulverized coal ratio.

4. The hot metal temperature control method according to claim 1, wherein

the determination step includes adding a plurality of text statements to the rationale statement, and

the plurality of text statements includes a plurality of change contents arranged in order of a most recent change from a current time or a largest amount of change.

5. The hot metal temperature control method according to claim 1, wherein

the operation information is an operation amount presentation screen including a text statement expressing an intention of the optimal action, a rationale for calculating the optimal action, an accept button, and a reject button,

the accept button is used when an operator approves the optimal action displayed on the operation amount presentation screen, and

the reject button is used when the operator rejects the optimal action displayed on the operation amount presentation screen.

6. The hot metal temperature control method according to claim 5, wherein

the presentation step includes, as a control mode, a semi-automatic mode in which the optimal action is executed with approval of the operator, and an automatic mode in which the optimal action is executed without the approval of the operator,

the operation information is an operation amount presentation screen further including a timer in a case in which the control mode is the automatic mode, and

the timer displays a length of time from when display regarding the optimal action is updated until a predetermined time, and the optimal action is executed in a case in which the reject button is not selected before the predetermined time elapses.

7. A hot metal temperature control device comprising:

a calculation unit configured to calculate a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculate a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritize the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;

a determination unit configured to determine a rationale for calculation of the optimal action and add a text statement to a rationale statement indicating the rationale; and

a presentation unit configured to present operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action.

8. The hot metal temperature control device according to claim 7, wherein in a case in which an absolute value of the pulverized coal injection flow rate manipulation amount is larger than an operation range of pulverized coal injection flow rate that is changeable each time, the calculation unit is configured to prioritize the pulverized coal ratio tracking control and not to take the pulverized coal ratio manipulation amount calculated by the hot metal temperature control into account in the target value of the pulverized coal ratio.

9. The hot metal temperature control device according to claim 7, wherein in a case in which a predicted hot metal temperature calculated taking into account the pulverized coal injection flow rate manipulation amount falls outside a target range of the hot metal temperature, the calculation unit is configured to prioritize the hot metal temperature control and to take the pulverized coal ratio manipulation amount calculated by the hot metal temperature control into account in the target value of the pulverized coal ratio.

10. The hot metal temperature control device according to claim 7, wherein

the determination unit is configured to add a plurality of text statements to the rationale statement, and

the plurality of text statements includes a plurality of change contents arranged in order of a most recent change from a current time or a largest amount of change.

11. The hot metal temperature control device according to claim 7, wherein

the operation information is an operation amount presentation screen including a text statement expressing an intention of the optimal action, a rationale for calculating the optimal action, an accept button, and a reject button,

the accept button is used when an operator approves the optimal action displayed on the operation amount presentation screen, and

the reject button is used when the operator rejects the optimal action displayed on the operation amount presentation screen.

12. The hot metal temperature control device according to claim 11, wherein

the presentation unit includes, as a control mode, a semi-automatic mode in which the optimal action is executed with approval of the operator, and an automatic mode in which the optimal action is executed without the approval of the operator,

the operation information is an operation amount presentation screen further including a timer in a case in which the control mode is the automatic mode, and

the timer displays a length of time from when display regarding the optimal action is updated until a predetermined time, and the optimal action is executed in a case in which the reject button is not selected before the predetermined time elapses.

13. A hot metal temperature control system comprising:

a hot metal temperature control device and a terminal device;

a calculation unit configured to calculate a pulverized coal ratio manipulation amount by hot metal temperature control so that a hot metal temperature predicted by a transient model capable of calculating a state inside a blast furnace falls within a preset target range, calculate a pulverized coal injection flow rate manipulation amount by pulverized coal ratio tracking control to compensate for a deviation between a target value of a pulverized coal ratio taking into account the pulverized coal ratio manipulation amount and a current actual value of the pulverized coal ratio, and prioritize the hot metal temperature control or the pulverized coal ratio tracking control as an optimal action based on a magnitude of discrepancy between the target value and the actual value of the pulverized coal ratio;

a determination unit configured to determine a rationale for calculation of the optimal action and add a text statement to a rationale statement indicating the rationale; and

an output interface configured to output operation information including the rationale statement and at least one of the pulverized coal ratio manipulation amount and the pulverized coal injection flow rate manipulation amount calculated as the optimal action;

a communication unit configured to transmit and receive the operation information;

an acquisition unit configured to acquire the optimal action and the operation information related to the optimal action including the rationale statement;

a display unit configured to display the acquired optimal action and the operation information so as to include the rationale statement; and

an interface unit configured to receive an instruction for the displayed operation information and output a set value for an operational variable in response to the instruction or based on elapse of a predetermined time.

14. A terminal device configuring a hot metal temperature control system together with a hot metal temperature control device that outputs operation information, for controlling hot metal temperature, including at least one of a pulverized coal ratio manipulation amount and a pulverized coal injection flow rate manipulation amount calculated as an optimal action based on a magnitude of discrepancy between a target value of a pulverized coal ratio and an actual value of the pulverized coal ratio, and including a rationale statement indicating a rationale for calculation of the optimal action, the terminal device comprising:

an acquisition unit configured to acquire the optimal action and the operation information related to the optimal action including the rationale statement;

a display unit configured to display the acquired optimal action and the operation information so as to include the rationale statement; and

an interface unit configured to receive an instruction for the displayed operation information and output a set value for an operational variable in response to the instruction or based on elapse of a predetermined time.

15. The terminal device according to claim 14, wherein the operation information includes a plurality of operational conditions and is displayed together with an order of priority.