EP4667590A1

EP4667590A1 - Molten iron temperature control method, blast furnace operation method, molten iron production method, molten iron temperature control device, and molten iron temperature control system

Info

Publication number: EP4667590A1
Application number: EP24766997.1A
Authority: EP
Inventors: Ryosuke Masuda; Yoshinari Hashimoto; Hiroyuki SHIMAMOTO
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-03-07
Filing date: 2024-02-28
Publication date: 2025-12-24
Also published as: JPWO2024185626A1; KR20250141775A; JP7522999B1; CN120826481A

Abstract

A hot-metal temperature-control method includes a permeability-abnormality determination step (S1 to S7) of determining an abnormality in furnace permeability of a blast furnace, an unburned-coal occurrence determination step of determining the occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned, and an action-necessity determination step of determining whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination step and the unburned-coal occurrence determination step.

Description

TECHNICAL FIELD

The present disclosure relates to a hot-metal temperature-control method, a blast-furnace operating method, a hot metal production method, a hot-metal temperature-control device, and a hot-metal temperature-control system.

BACKGROUND

In the blast furnace process, the hot-metal temperature, permeability, and production rate are the main control variables. It is important to keep the temperature of the hot metal produced in a blast furnace constant. In addition, in a blast furnace, in order to steadily lower the burden (raw material) such as ore and coke charged from the furnace top, it is necessary to ensure good permeability inside the furnace. Furthermore, it is necessary to produce hot metal according to a predetermined production rate (pig iron production rate) required by the steel-making process, which is the next process in the blast furnace.
In order to achieve highly efficient and stable blast furnace operation, control of the hot-metal temperature is particularly important. If the hot-metal temperature drops significantly, it may cause a chilled blast furnace accident in which the hot metal or slag in the hearth (lower part of furnace) solidifies, resulting in operational stoppage. Moreover, a high hot-metal temperature indicates over-injection of pulverized coal or coke, which is fuel, leading to an increase in the reducing agent ratio. In this case, the gas expands as the gas temperature in the furnace rises, and the permeability also deteriorates.
In recent years, blast furnace operation has aimed to reduce the reducing agent ratio in order to reduce CO₂ emissions, and there is a strong demand to reduce the variation in hot-metal temperature.
The hot metal temperature is controlled by, for example, manipulating the coke ratio, blast moisture, blast temperature, and pulverized coal injection (PCI) flow rate. When a control variable is changed, there is a time delay of about 2 to 8 hours, for example, before the hot metal temperature changes, since the blast furnace is a process with a large thermal capacity. Therefore, it is necessary to predict the future 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 light of this background, a method for controlling the hot-metal temperature using a transient model has been proposed. For example, Patent Literature (PTL) 1 describes a method in which a gas-reduction equilibrium parameter or a parameter of the coke ratio at the furnace top in a transient model is adjusted, a predicted value of the hot-metal temperature is calculated in the transient model under the assumption that the current manipulation amount is maintained, and the hot-metal temperature is controlled based on the calculated predicted value.

CITATION LIST

Patent Literature

PTL 1: JP 2018-24935 A

SUMMARY

(Technical Problem)

However, in the transient model described in PTL 1, in order to reduce calculation time, phenomena related to powder, such as coke fines (powdering) and accumulation of unburned pulverized coal, are not taken into consideration. In other words, the transient model described in PTL 1 assumes complete combustion of pulverized coal, and it is difficult to reflect the behavior of unburned pulverized coal. In recent years, blast furnace operation has been moving toward replacing coke with pulverized coal for hot-metal cost reduction, but this pulverized coal tends to accumulate unburned. Therefore, unburned pulverized coal can cause errors in estimating the hot-metal temperature or the production rate.
When unburned pulverized coal occurs, the combustion of coke is promoted, which increases the burden descent speed inside the blast furnace, slows the reduction of the ore by gas, and increases direct reduction, which is an endothermic reaction. This causes a temporary drop in the hot-metal temperature. Subsequently, when the unburned pulverized coal burns in the raceway, the burden descent speed decreases and the hot-metal temperature recovers. However, if unburned pulverized coal accumulates, the unburned pulverized coal will be used for direct reduction and disappear, causing the hot-metal temperature to continue to decrease. Furthermore, if unburned pulverized coal accumulates inside the furnace, the permeability decreases. In other words, it is considered that the accumulation of unburned pulverized coal can be determined based on the change in the permeability index inside the furnace and the estimation errors of process variables such as the production rate and the solution-loss carbon amount. Furthermore, if the accumulation of unburned pulverized coal can be determined accurately, it will be possible to detect a future decrease in the hot-metal temperature.
In consideration of the above circumstances, it is an aim of the present disclosure to provide a hot-metal temperature-control method, a blast-furnace operating method, a hot metal production method, a hot-metal temperature-control device, and a hot-metal temperature-control system that are capable of detecting a future hot-metal temperature drop, which is difficult to predict using a transient model, and proposing actions to increase the hot-metal temperature.

(Solution to Problem)

(1) A hot-metal temperature-control method according to an embodiment of the present disclosure includes:
- a permeability-abnormality determination step of determining an abnormality in furnace permeability of a blast furnace;
- an unburned-coal occurrence determination step of determining occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned; and
- an action-necessity determination step of determining whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination step and the unburned-coal occurrence determination step.
(2) As an embodiment of the present disclosure, in (1),
the permeability-abnormality determination step includes determining that the abnormality exists in the furnace permeability in a case in which a standard deviation of shaft pressure existing at positions having a distance equal in a vertical direction from a blast furnace top exceeds a first threshold at a plurality of stages for which the distance differs.
(3) As an embodiment of the present disclosure, in (1) or (2),
the unburned-coal occurrence determination step includes determining that the unburned pulverized coal has occurred in a case in which an error-change rate between a calculated value obtained from a transient model and an actual value is a second threshold or more for at least one of a production rate and a solution-loss carbon amount.
(4) As an embodiment of the present disclosure, in any one of (1) to (3),
the action-necessity determination step includes presenting the action for raising a hot-metal temperature in a case in which the abnormality in the furnace permeability is determined to exist in the permeability-abnormality determination step and the unburned pulverized coal is determined to have occurred in the unburned-coal occurrence determination step.
(5) A blast-furnace operating method according to an embodiment of the present disclosure includes
controlling the blast furnace according to whether the action is determined to be necessary by the hot-metal temperature-control method of any one of (1) to (4).
(6) A hot metal production method according to an embodiment of the present disclosure includes
controlling the blast furnace according to the blast-furnace operating method of (5) to produce hot metal.
(7) A hot-metal temperature-control device according to an embodiment of the present disclosure includes:
- a permeability-abnormality determination unit configured to determine an abnormality in furnace permeability of a blast furnace;
- an unburned-coal occurrence determination unit configured to determine occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned; and
- an action-necessity determination unit configured to determine whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination unit and the unburned-coal occurrence determination unit.
(8) As an embodiment of the present disclosure, in (7),
the permeability-abnormality determination unit is configured to determine that the abnormality exists in the furnace permeability in a case in which a standard deviation of shaft pressure existing at positions having a distance equal in a vertical direction from a blast furnace top exceeds a first threshold at a plurality of stages for which the distance differs.
(9) As an embodiment of the present disclosure, in (7) or (8),
the unburned-coal occurrence determination unit is configured to determine that the unburned pulverized coal has occurred in a case in which an error-change rate between a calculated value obtained from a transient model and an actual value is a second threshold or more for at least one of a production rate and a solution-loss carbon amount.
(10) As an embodiment of the present disclosure, in any one of (7) to (9),
the action-necessity determination unit is configured to present the action for raising a hot-metal temperature in a case in which the permeability-abnormality determination unit determines that the abnormality in the furnace permeability exists and the unburned-coal occurrence determination unit determines that the unburned pulverized coal has occurred.
(11) A hot-metal temperature-control system according to an embodiment of the present disclosure is
a hot-metal temperature-control system comprising:
- a hot-metal temperature-control device and a terminal device;
- a permeability-abnormality determination unit configured to determine an abnormality in furnace permeability of a blast furnace;
- an unburned-coal occurrence determination unit configured to determine occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned;
- an action-necessity determination unit configured to determine whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination unit and the unburned-coal occurrence determination unit;
- an output unit configured to output a determination result of the abnormality in the furnace permeability determined by the permeability-abnormality determination unit, a determination result of the occurrence of unburned pulverized coal determined by the unburned-coal occurrence determination unit, and a hot-metal temperature-control action outputted by a determination result of the action-necessity determination unit; and
- a display unit configured to acquire an output result from the output unit and display the determination result of the permeability-abnormality determination unit, the determination result of the unburned-coal occurrence determination unit, and the hot-metal temperature-control action output by the action-necessity determination unit.

(Advantageous Effect)

According to the present disclosure, it is possible to provide a hot-metal temperature-control method, a blast-furnace operating method, a molten metal manufacturing method, a hot-metal temperature-control device, and a hot-metal temperature-control system that are capable of detecting a future hot-metal temperature drop, which is difficult to predict using a transient model, and presenting actions to increase the hot-metal temperature.

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 permeability-abnormality determination unit;
FIG. 3 is a flowchart illustrating processing by an unburned-coal occurrence determination unit;
FIG. 4 is a flowchart illustrating processing by an action-necessity determination unit;
FIG. 5 is a diagram illustrating the time-series change in the difference of the shaft pressure value from the average value at each height position when unburned pulverized coal is considered to have occurred;
FIG. 6 is a diagram illustrating the time-series change related to the standard deviation of shaft pressure values at each height position and the difference between the actual value and calculated value of the production rate, for the same time period as in FIG. 5;
FIG. 7 is a diagram illustrating the time-series change related to the standard deviation of shaft pressure values, the difference in production rate, and the difference in solution-loss carbon amount at times different from those in FIG. 5;
FIG. 8 is a diagram illustrating the time-series change in input variables and output variables of a transient model in a case in which unburned pulverized coal is considered to have occurred during the same time period as in FIG. 7;
FIG. 9 is a block diagram illustrating a configuration example of an hot-metal temperature-control system including a hot-metal temperature-control device.

DETAILED DESCRIPTION

Hereinafter, a hot-metal temperature-control method, a blast-furnace operating method, a hot metal production method, a hot-metal temperature-control device, and a hot-metal temperature-control system according to an embodiment of the present disclosure will be described with reference to the drawings.

[Configuration of hot-metal temperature-control device]

First, with reference to FIG. 1, a configuration of a hot-metal temperature-control device according to an embodiment of the present disclosure will be described.
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, the hot-metal temperature-control device 1 according to an embodiment of the present disclosure can be configured by an information processing device such as a computer. When the hot-metal temperature-control device 1 is a computer, an arithmetic processing device such as a CPU (Central Processing Unit) executes a program to function as a permeability-abnormality determination unit 11, an unburned-coal occurrence determination unit 12, and an action-necessity determination unit 13. The functions of each unit will be described later.
An operation database 2 is connected to the hot-metal temperature-control device 1 in a data readable form. Measured data required for operation and operating factors required for hot-metal temperature-control are sequentially saved and stored in the operation database 2, and this information is read out and used as required. In the present embodiment, the operation database 2 stores operating factors such as the coke ratio at furnace top, blast volume, enriched oxygen amount, blast temperature, blast moisture, and PCI flow rate. Furthermore, the operation database 2 stores calculated values of process variables output by the transient model. 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. Furthermore, the operation database 2 stores actual values of process variables calculated based on the volume fractions of CO and CO₂ in the discharged furnace top gas. The operation database 2 also stores historical data of pressure values obtained from a shaft-pressure gauge. Examples of the process variables include the hot-metal temperature, production rate, solution-loss carbon amount, and gas utilization ratio.
The transient model used in the present disclosure is the same as the model of the method described in Reference 1 (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 can calculate variables (output variables) representing the condition inside the blast furnace in a non-steady state.
The hot-metal temperature-control device 1 having such a configuration executes each process of the hot-metal temperature-control method using the permeability-abnormality determination unit 11, the unburned-coal occurrence determination unit 12, and the action-necessity determination unit 13, and outputs an appropriate action for hot-metal temperature-control.

[Operation of the permeability-abnormality determination unit]

The shaft pressure is the pressure in the shaft zone of the blast furnace. During normal operation, shaft pressure exhibits synchronous behavior (for example, rising or falling at the same time) at all measurement points. However, when the permeability inside the furnace deteriorates, the pressure distribution inside the furnace becomes disturbed. Consequently, the shaft pressure exhibits asynchronous changes at some measurement points. In particular, the gas flow inside the furnace becomes non-uniform in the circumferential direction, causing the shaft pressure to vary in a particular circumferential direction. Here, the directions are, for example, east (E), south (S), west (W) and north (N), and are used to divide the circumferential area inside the cylindrical furnace and to indicate the position. In the present embodiment, the permeability-abnormality determination unit 11 calculates the standard deviation of the shaft pressure for each measurement point at an equal distance from the furnace top, i.e., for each height position. The permeability-abnormality determination unit 11 then determines a permeability abnormality depending on whether the most recent standard deviation at a plurality of height positions exceeds a threshold.
The operation of the permeability-abnormality determination unit 11 will be described with reference to FIG. 2. As described above, the permeability-abnormality determination unit 11 determines an abnormality in furnace permeability of a blast furnace.
FIG. 2 is a flowchart illustrating the flow of permeability-abnormality determination according to an embodiment of the present disclosure. The processing illustrated in FIG. 2 corresponds to the permeability-abnormality determination step. The flowchart in FIG. 2 starts when an execution command for the permeability-abnormality determination is input to the hot-metal temperature-control device 1. The permeability-abnormality determination proceeds to the processing in step S1.
In the processing in step S1, the permeability-abnormality determination unit 11 acquires shaft pressure data from the operation database 2. The data acquisition cycle is preferably 1 to 30 minutes. This completes the processing in step S1, and the permeability-abnormality determination proceeds to the processing in step S2.
In the processing in step S2, the permeability-abnormality determination unit 11 determines whether the shaft pressure values acquired in the processing in step S1 include an abnormal value due to measurement failure, a data transmission error, or the like. For example, the permeability-abnormality determination unit 11 may determine that the shaft pressure value is an abnormal value when the shaft pressure value is lower than the furnace-top pressure or higher than the blast pressure. When it is determined that the shaft pressure data includes an abnormal value, the permeability-abnormality determination unit 11 removes the observed value indicating the abnormal value (step S6). The permeability-abnormality determination then proceeds to the processing in step S3. If it is determined that the shaft pressure data does not include an abnormal value, the air flow abnormality determination proceeds directly to the processing in step S3.
In the processing in step S3, the permeability-abnormality determination unit 11 calculates the standard deviation in a measurement point group for shaft pressure data that has no abnormal values or has had abnormal values removed, with measurement points that are the same distance from the furnace top being treated as one group. Assume that there are N shaft pressure measurement points in the height direction and M shaft pressure measurement points in the circumferential direction. The N measurement points in the height direction correspond to the measurement points in areas of N stages obtained by dividing the blast furnace by the distance in the vertical direction from the blast furnace top. There are M shaft pressure measurement points in the circumferential direction of the area of one stage, and these M measurement points are located at positions having a distance equal in the vertical direction from the blast furnace top. If the shaft pressure at a certain height position i, a certain circumferential direction j, and a certain time t is p_i,j,t, the average value a(p_i,t) of the shaft pressure at the height position i at time t can be calculated by Expression (1).
[Math. 1] $a (p_{i, t}) = \frac{\sum_{j = 1}^{M} p_{i, j, t}}{M}$
Furthermore, the standard deviation σ_i,t is calculated by Expression (2) using the average value a(p_i,t).
[Math. 2] $σ_{i, t} = \sqrt{\frac{\sum_{j = 1}^{M} {(p_{i, j, t} - a (p_{i, t}))}^{2}}{M}}$
Furthermore, the median σ_i of the standard deviation of the most recent T₁ is calculated for each height position, and an array σ of standard deviations illustrated in Expression (3) is obtained. Here, for each height position means per area of N stages into which the blast furnace is divided based on the vertical distance from the blast furnace top. As an example, T₁ is 15 minutes, the standard deviation σ_i,t at one height position is obtained for the shaft pressure data for the most recent 15 minutes, and the median σ_i is calculated from a plurality of standard deviations σ_i,t over the 15 minutes. The median σ_i is calculated for each height position, and the array σ is obtained as a set of these values.
[Math. 3] $σ = (\begin{matrix} σ_{1} \\ σ_{2} \\ σ_{3} \\ ⋮ \\ σ_{N} \end{matrix})$
Here, if T₁ is extremely small, there is a possibility that a temporary change in shaft pressure due to noise will be misjudged as a permeability abnormality. Moreover, if T₁ is too large, the timing for determining that there is a permeability abnormality is delayed, making it difficult to present an appropriate action. Therefore, T₁ is preferably determined in the range of 10 minutes to 60 minutes. This completes the processing in step S3, and the permeability-abnormality determination proceeds to the processing in step S4.
In the processing in step S4, the permeability-abnormality determination unit 11 counts the height positions (step numbers) exceeding a threshold α (first threshold) for the array σ of standard deviations obtained in the processing in step S3. If the counted value k is 2 or more, the processing in step S4 is completed, a permeability-abnormality determination of "abnormal" is made (step S5), and the series of processes is terminated. If the counted value k is 1 or less, the processing in step S4 is completed, a permeability-abnormality determination of "normal" is made (step S7), and the series of processes is terminated. By adding the determination based on the number of stages, it is possible to avoid misjudging the magnitude of a temporary deviation caused by noise or the like occurring in one stage as an "abnormality" in the permeability. Here, the threshold α is determined depending on the volume of the blast furnace and the measurement position of the shaft pressure. When the unit of shaft pressure is kPa, the threshold α may be determined to be a value in the range of 2 to 10 [kPa], for example. In step S4, the process is branched depending on whether the counted value k is 2 or more, or less than 2 (1 or less). However, the number (reference value) used to determine branching 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 greater than 2 in order to further increase the effect of avoiding misjudgment.
Here, the permeability-abnormality determination unit 11 may use a calculated value different from the standard deviation. As another example, the permeability-abnormality determination unit 11 may calculate the difference between the maximum and minimum values at one height position for the shaft pressure data of the most recent T₁ instead of the standard deviation, and calculate the median from the difference between the maximum and minimum values of T₁.

[Operation of unburned-coal occurrence determination unit]

Next, the operation of the unburned-coal occurrence determination unit 12 will be described with reference to FIG. 3. The unburned-coal occurrence determination unit 12 determines the occurrence of unburned pulverized coal due to pulverized coal that is injected from the tuyere of the blast furnace and remains unburned. In the following description, unburned-coal occurrence refers to a state in which unburned pulverized coal occurs and accumulates to such an extent that the decrease in the hot-metal temperature continues.
FIG. 3 is a flowchart illustrating the flow of unburned-coal occurrence determination according to one embodiment of the present disclosure. The process illustrated in FIG. 3 corresponds to the unburned-coal occurrence determination step. The flowchart in FIG. 3 starts when an execution command for the unburned-coal occurrence determination is input to the hot-metal temperature-control device 1. The unburned-coal occurrence determination proceeds to the processing in step S10.
In the processing in step S10, the unburned-coal occurrence determination unit 12 acquires, from the operation database 2, historical data of the calculated values of the process variables output by the transient model (transient model calculation results). Process variables used in the unburned-coal occurrence determination include, for example, production rate, solution-loss carbon amount, and the like. This completes the processing in step S10, and the unburned-coal occurrence determination proceeds to the processing in step S11. Here, the reducing agent ratio or the gas utilization ratio may be used as the process variable used in the unburned-coal occurrence determination. In the transient model, it is assumed that all of the injected pulverized coal reacts, but in reality, when unburned pulverized coal occurs, part of the pulverized coal does not react, causing the reducing agent ratio to deviate from the calculated value. In addition, the transient model assumes that all of the injected pulverized coal is converted into CO. However, in reality, when unburned pulverized coal occurs, some of the pulverized coal does not react, resulting in a decrease in the amount of CO generated, and causing the gas utilization ratio to deviate from the calculated value. Therefore, it is possible to determine the accumulation of unburned pulverized coal from the estimation error of the reducing agent ratio or gas utilization ratio, as with the production rate and the solution-loss carbon amount.
In the processing in step S11, the unburned-coal occurrence determination unit 12 acquires historical data (operating data) of the actual values of the process variables from the operation database 2. This completes the processing in step S11, and the unburned-coal occurrence determination proceeds to the processing in step S12.
In the processing in step S12, the unburned-coal occurrence determination unit 12 calculates the error-change rate of the process variables for the most recent T₂ using historical data of the calculated values of the process variables obtained in step S10 and historical data of the actual values of the process variables obtained in step S11. In the present embodiment, the error y_err(t) between the actual value y_act(t) and the calculated value y_cal(t) of the process variable y at time t is modeled by Expression (4).
[Math. 4] $y_{err} (t) = A \cdot t + B (- T_{2} \leq t \leq 0)$
Based on the acquired historical data, A in Expression (4) is calculated by least-squares fitting. A is the error-change rate. B is the offset. Here, if T₂ is made extremely small, the error-change rate in the actual values of the process variables changes significantly due to the influence of noise caused by abnormal measurements of the components of the furnace top gas. Moreover, if T₂ is too large, the contribution of past normal times becomes large, making it difficult to capture a rapid change in the most recent estimation error. Therefore, taking into consideration the time it takes for the burden (raw material) charged at the furnace top to descend to the tuyere, it is preferable that T₂ be determined in the range of 3 to 12 hours. Here, T₂ may vary depending on the type of process variable. This completes the processing in step S12, and the unburned-coal occurrence determination proceeds to the processing in step S13.
In the processing in step S13, the unburned-coal occurrence determination unit 12 compares the error-change rate (error-change rate A) between the calculated value obtained from the transient model for the process variable and the actual value, as calculated in step S12, with a threshold β (second threshold). The threshold β varies depending on the type of process variable. If the absolute value of the error-change rate A is smaller than the threshold β, the processing in step S13 is completed, the unburned-coal occurrence determination unit 12 determines that no unburned pulverized coal has occurred (step S15), and the series of processes is terminated. If the absolute value of the error-change rate A is equal to or greater than the threshold β, the processing in step S13 is completed, the unburned-coal occurrence determination unit 12 determines that unburned pulverized coal has occurred (step S14), and the series of processes is terminated.

[Operation of action-necessity determination unit]

Next, the operation of the action-necessity determination unit 13 will be described with reference to FIG. 4. The action-necessity determination unit 13 determines whether action is necessary regarding hot-metal temperature-control based on the determination results of the permeability-abnormality determination unit 11 and the unburned-coal occurrence determination unit 12.
FIG. 4 is a flowchart illustrating the flow of action-necessity determination regarding hot-metal temperature-control in the present embodiment. The processing illustrated in FIG. 4 corresponds to the action-necessity determination step. The flowchart illustrated in FIG. 4 starts when an execution command for an action-necessity determination is input to the hot-metal temperature-control device 1. The action-necessity determination proceeds to the processing in step S20.
In the processing in step S20, the action-necessity determination unit 13 determines whether the permeability is normal or abnormal based on the determination result of the permeability-abnormality determination unit 11. If the permeability is "abnormal", the processing in step S20 is completed, and the action-necessity determination proceeds to the processing in step S21. If the permeability is "normal", the processing in step S20 is completed, and the action-necessity determination proceeds to the processing in step S22.
In the processing in step S21, the action-necessity determination unit 13 determines whether unburned pulverized coal has occurred based on the determination result of the unburned-coal occurrence determination unit 12. In the case of "present" for unburned pulverized coal, the processing in step S21 is completed, and the action-necessity determination proceeds to the processing in step S23. In the case of "absent" for unburned pulverized coal, the processing in step S21 is completed, and the action-necessity determination proceeds to the processing in step S22.
In the processing in step S22, the action-necessity determination unit 13 estimates the condition inside the furnace where there is no accumulation of unburned pulverized coal (the pulverized coal is completely combusted) and presents a hot-metal temperature-control action. That is, in the processing in step S22, the action-necessity determination unit 13 presents a hot-metal temperature-control action based on the calculated value of the hot-metal temperature using a conventional transient model. In this case, the action can be presented using, for example, the method described in Reference 2 (Y. Hashimoto et al., ISIJ International, Vol. 59 (2019), pp. 1573-1581). This completes the processing in step S22 and terminates the series of the action-necessity determination.
In the processing in step S23, the action-necessity determination unit 13 presents an action to increase the hot-metal temperature. This is because if unburned pulverized coal accumulates, the unburned pulverized coal will be used for direct reduction and disappear, causing the hot-metal temperature to continue to decrease. Actions to increase the hot-metal temperature include reducing the blast moisture, increasing the pulverized coal ratio, increasing the blast temperature, or increasing the coke ratio. The change amounts in the action may be preset fixed values for each of the blast moisture, the pulverized coal ratio, the blast temperature, and the coke ratio. This completes the processing in step S23 and terminates the series of the action-necessity determination.
Here, the action-necessity determination may be performed by executing the processing in step S21 prior to step S20. In other words, the order of steps S20 and S21 may be reversed.
The hot-metal temperature-control method executed by the hot-metal temperature-control device 1 can be part of a blast-furnace operating method. For example, a blast-furnace operating method may include a step of controlling the blast furnace according to whether an action is determined to be necessary by the hot-metal temperature-control method. This blast-furnace operating method makes it possible to appropriately take action to increase the hot-metal temperature. The hot-metal temperature-control method or blast-furnace operating method may be part of a hot metal production method. For example, a hot metal production method may include a step of controlling a blast furnace according to a blast-furnace operating method to produce hot metal. The determined necessity and content of an action may be automatically reflected in operation or production by, for example, using a communication function between the hot-metal temperature-control device 1 and a computer that manages the operation of the blast furnace or the production of hot metal. In addition, the determined necessity and content of an action may be presented to an operator managing operation or production by display, for example, for use as guidance for the operator in deciding on an action.
The hot-metal temperature-control system may be configured as illustrated in FIG. 9. The hot-metal temperature-control system includes the hot-metal temperature-control device 1 and a terminal device 3. The hot-metal temperature-control system may further include the operation database 2. The configurations of the hot-metal temperature-control device 1 and the operation database 2 are the same as those in FIG. 1. That is, the permeability-abnormality determination unit 11, the unburned-coal occurrence determination unit 12, the action-necessity determination unit 13, and the operation database 2 are as described above. However, in the example of FIG. 9, the hot-metal temperature-control device 1 further includes an output unit 14 that outputs actions to be presented and the like to the terminal device 3. For example, when the hot-metal temperature-control device 1 is a computer, the arithmetic processing device executes a program to function as the output unit 14 as well. 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 output unit 14 outputs a determination result of the abnormality in the furnace permeability determined by the permeability-abnormality determination unit 11, a determination result of the occurrence of unburned pulverized coal determined by the unburned-coal occurrence determination unit 12, and a hot-metal temperature-control action outputted by a determination result of the action-necessity determination unit 13. For example, the output unit 14 may output to the terminal device 3 the existence of and reason for a permeability abnormality (the height position indicating an abnormality in the shaft pressure, and the standard deviation at which the abnormality is determined), as output by the permeability-abnormality determination unit 11. For example, the output unit 14 may output to the terminal device 3 the determination result of and reason for unburned-coal occurrence (the process variable used in the determination and the error-change rate). Here, the process variables are the production rate, the solution-loss carbon amount, and the like. Furthermore, for example, the output unit 14 may output the determination result of the action-necessity determination unit 13 and the manipulation amount of the hot-metal 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 permeability-abnormality determination unit 11, the determination results of the unburned-coal occurrence determination unit 12, and the hot-metal temperature-control action output by the action-necessity determination unit 13. The display unit 30 may be a liquid crystal display or the like. Here, the display on the display unit 30 may be a display on a general-purpose browser.
The hot-metal 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). Here, the configuration in FIG. 9 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. 9. The hot-metal temperature-control device 1 and the terminal device 3 may also include components other than those illustrated in FIG. 9. 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. 9. For example, the action-necessity determination unit 13 and the display unit 30 may be included in the same device. In addition, for example, the permeability-abnormality determination unit 11, the unburned-coal occurrence determination unit 12, and the display unit 30 may be located in the terminal device 3, and the action-necessity determination unit 13 and the output unit 14 may be located in the hot-metal temperature-control device 1. Furthermore, data may be transmitted and received between each component via inter-process communication or communication using a network.

[Example 1]

FIG. 5 is a diagram illustrating the time-series change in the difference of the shaft pressure value from the average value at each height position when unburned pulverized coal is considered to have occurred. The up and down direction of the diagram corresponds to the vertical height of the blast furnace. That is, the first height position is the closest (highest) position to the blast furnace top, and the seventh height position is the farthest (lowest) position from the blast furnace top. Also, different line types represent different circumferential directions of the measurement points. In the example of FIG. 5, the shaft pressure values change asynchronously especially in the bottom two stages (the sixth and seventh height positions), indicating a deterioration in permeability in the hearth (lower part of furnace). Furthermore, the shaft pressure value in a specific direction among the bottom four stages has increased in the last 0.5 hours, further worsening the permeability. Here, the vertical axis of FIG. 5 indicates the shaft pressure value in each direction as the difference from the average value of the shaft pressure in all directions at each stage. For example, a negative value indicates a shaft pressure value that is lower than the average value.
FIG. 6 is a diagram illustrating the time-series change of the standard deviation of shaft pressure values at each height position and the difference between the actual value and calculated value of the production rate, for the same time period as in FIG. 5. Different line types in the standard deviation of shaft pressure represent different height positions of the measurement points. In the present embodiment, the threshold α was set to 4 [kPa]. In addition, in the graph of the production rate in FIG. 6, the solid line represents the error between the actual value y_act(t) and the calculated value y_cal(t). The dashed line represents the result of linear regression assuming the relationship of Expression (4).
For the determination of a permeability abnormality, T₁ was set to 15 minutes. The standard deviation was calculated for each height position, and the height positions (number of stages) exceeding the threshold α were counted. When the standard deviation of three stages exceeded the threshold α, the permeability was determined to be "abnormal".
In addition, for the unburned-coal occurrence determination, the error-change rate A of the production rate is positive, and the error tends to increase. In other words, the actual production rate increased more than the prediction (calculated value) of the transient model. T₂ was set at 10 min. In addition, the threshold β was set to 30. The absolute value of the error-change rate A was compared with the threshold value β, and it was determined that unburned pulverized coal was "present".
As described above, the hot-metal temperature-control device 1 can detect the risk of a hot-metal temperature drop that is not indicated by the hot-metal temperature prediction using a conventional transient model. When it is determined that unburned pulverized coal is "present", the hot-metal temperature-control device 1 is able to suggest an action to increase the hot-metal temperature (for example, reducing the blast moisture).

[Example 2]

FIG. 7 is a diagram illustrating the time-series change related to the standard deviation of shaft pressure values at each height position, the difference between the actual values and calculated values of the production rate, and the difference between the actual values and calculated values of the solution-loss carbon amount at times different from those in FIG. 5.
In the present embodiment, the threshold α for determining a permeability abnormality was set to 4 [kPa]. Additionally, T₁ was set to 15 minutes. The standard deviation was calculated for each height position, and the height positions (number of stages) exceeding the threshold α were counted. When the standard deviation of two stages exceeded the threshold α, the permeability was determined to be "abnormal".
In the unburned-coal occurrence determination of the present Example, the error-change rates A for the production rate and the solution-loss carbon amount are both positive, and the errors tend to increase. It is believed that the rate at which the burden (raw material) descended inside the blast furnace increased, the reduction of the ore by gas was delayed, and the unburned pulverized coal was preferentially converted into solution loss. For the estimation error of the production rate, T₂ was set to 10 min. In addition, the threshold β was set to 30. For the estimation error of the solution-loss carbon amount, T₂ was set to 8 minutes. In addition, the threshold β was set to 1. The absolute value of the error-change rate A was compared with the threshold β, and since the absolute value of the error rate of change A for the production rate and the solution-loss carbon amount was equal to or greater than the threshold β, it was determined that unburned pulverized coal is "present". Here, the determination of unburned-coal occurrence may be made based on only one of the production rate and the solution-loss carbon amount, rather than on both (see Example 1). However, by using both, the accuracy of the determination can be further improved.
FIG. 8 is a diagram illustrating the time-series change in the input variables and output variables of the transient model during the same time period as in FIG. 7. The input variables are coke ratio (CR), enriched oxygen flow rate (BVO), blast volume (BV), blast temperature (BT), blast moisture (BM) and PCI flow rate (PCI). The output variable is the hot-metal temperature (HMT). The solid line for blast moisture represents the history of actions taken to control the hot-metal temperature according to the method of the present embodiment. The dashed line for the blast moisture represents the action output at time 0 based on the aforementioned action-necessity determination. The transient model predicted that the hot-metal temperature would increase, reflecting the increase in PCI flow rate and the decrease in blast moisture over the previous three hours. In addition, the permeability was determined to be "abnormal" and unburned pulverized coal to be "present". Regardless of the hot-metal temperature prediction of the transient model, a risk of a drop in the hot-metal temperature was detected, and an action to increase the hot-metal temperature (for example, reducing the blast moisture) was presented. For example, the manipulation amount may be presented as a fixed value (such as -3 g/Nm³) for reducing the blast humidity. As a result, the hot-metal temperature dropped slightly but did not fall significantly below the target value. The hot-metal temperature was thus appropriately controlled.
As described above, the hot-metal temperature-control method, blast-furnace operating method, molten metal manufacturing method, hot-metal temperature-control device 1, and hot-metal temperature-control system according to the present embodiment are capable of detecting a future hot-metal temperature drop, which is difficult to predict using a transient model, and presenting an action to increase the hot-metal temperature. In other words, abnormalities caused by the behavior of unburned pulverized coal inside the furnace, which are difficult to predict using transient models, can be identified from deviations in shaft pressure values and estimation errors in process variables such as the production rate and solution-loss carbon amount, and appropriate actions can be presented for raising the hot-metal temperature.
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. 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
11: Permeability-abnormality determination unit
12: Unburned-coal occurrence determination unit
13: Action-necessity determination unit
14: Output unit
30: Display unit

Claims

A hot-metal temperature-control method comprising:
a permeability-abnormality determination step of determining an abnormality in furnace permeability of a blast furnace;

an unburned-coal occurrence determination step of determining occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned; and

an action-necessity determination step of determining whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination step and the unburned-coal occurrence determination step.
The hot-metal temperature-control method according to claim 1, wherein the permeability-abnormality determination step includes determining that the abnormality exists in the furnace permeability in a case in which a standard deviation of shaft pressure existing at positions having a distance equal in a vertical direction from a blast furnace top exceeds a first threshold at a plurality of stages for which the distance differs.
The hot-metal temperature-control method according to claim 1 or 2, wherein the unburned-coal occurrence determination step includes determining that the unburned pulverized coal has occurred in a case in which an error-change rate between a calculated value obtained from a transient model and an actual value is a second threshold or more for at least one of a production rate and a solution-loss carbon amount.
The hot-metal temperature-control method according to any one of claims 1 to 3, wherein the action-necessity determination step includes presenting the action for raising a hot-metal temperature in a case in which the abnormality in the furnace permeability is determined to exist in the permeability-abnormality determination step and the unburned pulverized coal is determined to have occurred in the unburned-coal occurrence determination step.
A blast-furnace operating method comprising controlling the blast furnace according to whether the action is determined to be necessary by the hot-metal temperature-control method of any one of claims 1 to 4.
A hot metal production method comprising controlling the blast furnace according to the blast-furnace operating method according to claim 5 to produce hot metal.
A hot-metal temperature-control device comprising:
a permeability-abnormality determination unit configured to determine an abnormality in furnace permeability of a blast furnace;

an unburned-coal occurrence determination unit configured to determine occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned; and

an action-necessity determination unit configured to determine whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination unit and the unburned-coal occurrence determination unit.
The hot-metal temperature-control device according to claim 7, wherein the permeability-abnormality determination unit is configured to determine that the abnormality exists in the furnace permeability in a case in which a standard deviation of shaft pressure existing at positions having a distance equal in a vertical direction from a blast furnace top exceeds a first threshold at a plurality of stages for which the distance differs.
The hot-metal temperature-control device according to claim 7 or 8, wherein the unburned-coal occurrence determination unit is configured to determine that the unburned pulverized coal has occurred in a case in which an error-change rate between a calculated value obtained from a transient model and an actual value is a second threshold or more for at least one of a production rate and a solution-loss carbon amount.
The hot-metal temperature-control device according to any one of claims 7 to 9, wherein the action-necessity determination unit is configured to present the action for raising a hot-metal temperature in a case in which the permeability-abnormality determination unit determines that the abnormality in the furnace permeability exists and the unburned-coal occurrence determination unit determines that the unburned pulverized coal has occurred.
A hot-metal temperature-control system comprising:
a hot-metal temperature-control device and a terminal device;

a permeability-abnormality determination unit configured to determine an abnormality in furnace permeability of a blast furnace;

an unburned-coal occurrence determination unit configured to determine occurrence of unburned pulverized coal due to pulverized coal that is injected from a tuyere and remains unburned;

an action-necessity determination unit configured to determine whether action is necessary regarding hot-metal temperature-control based on a determination result of the permeability-abnormality determination unit and the unburned-coal occurrence determination unit;

an output unit configured to output a determination result of the abnormality in the furnace permeability determined by the permeability-abnormality determination unit, a determination result of the occurrence of unburned pulverized coal determined by the unburned-coal occurrence determination unit, and a hot-metal temperature-control action outputted by a determination result of the action-necessity determination unit; and

a display unit configured to acquire an output result from the output unit and display the determination result of the permeability-abnormality determination unit, the determination result of the unburned-coal occurrence determination unit, and the hot-metal temperature-control action output by the action-necessity determination unit.