Blast furnace operation method

Abstract

A blast furnace operation method according to one embodiment of the present disclosure includes a parameter estimation step of estimating blast parameters and a pulverized coal ratio in the second operation such that the pig iron output, molten iron temperature, and top gas temperature in the second operation are the same as those in the standard operation; a change information acquisition step of acquiring information on changes over time in one or both of the molten iron temperature and the pig iron output when the second operation is carried out based on the pig iron output parameters and the pulverized coal ratio estimated in the parameter estimation step with a predetermined delay time after switching from the standard operation to the first operation; a repeating step of performing the change information acquisition step multiple times with different predetermined times; and an optimal delay time acquisition step of determining, based on the information acquired in the repeating step, a predetermined time at which the change over time in the molten iron temperature or the pig iron output is minimized as an optimal delay time, and after switching from the standard operation to the first operation, the second operation based on the pig iron output parameters and the pulverized coal ratio estimated in the parameter estimation step is started with a delay of the optimal delay time.

Description

[Technical field]

[0001] The present disclosure relates to a method for operating a blast furnace. This application claims priority based on Japanese Patent Application No. 2024-027364, filed on February 27, 2024, the contents of which are incorporated herein by reference. [Background technology]

[0002] In blast furnace operation, sintered ore, pellets, lump ore, etc. (hereinafter collectively referred to as "iron raw materials") as iron sources, and coke as a reducing agent and fuel are charged alternately from the top of the furnace, and hot air is blown from tuyeres at the bottom of the furnace, while auxiliary fuel such as pulverized coal is blown in. The iron raw materials and coke (hereinafter collectively referred to as "charge materials") charged from the top of the furnace form layers of ore and coke that are alternately stacked, and as the charge materials are lowered, they gradually descend inside the blast furnace toward the bottom of the furnace, while being heated by the gas rising from the bottom of the furnace, and their temperature is raised. The iron raw materials descend while being heated and reduced in the blast furnace, melt and separate into pig iron and slag, which drip onto the hearth.

[0003] Up until now, blast furnace operation methods have been studied in which part of the iron raw material is replaced with reduced iron, with the aim of lowering the reducing agent ratio (RAR), improving the permeability of the ore layer, and improving the air and liquid permeability by raising the temperature of the deadman coke. Here, reduced iron includes scrap, pig iron, direct reduced iron (DRI), and hot briquetted iron (HBI). Piggy iron is cold pig iron that has been cast into a lump of about 10 to 30 kg for easier handling.

[0004] Patent Documents 1 to 3 show examples of blast furnace operation methods in which a part of the iron raw material is replaced with reduced iron. Patent Document 1 proposes a blast furnace operation method in which the amount of scrap charged from the furnace top to the periphery of the furnace interior is increased in order to maintain the reduction efficiency and high-temperature properties of the ore layer when the alumina content in sintered ore increases. Patent Document 2 proposes a blast furnace operation method in which the permeability of the furnace interior is maintained by replacing a part of the iron raw material with scrap when the reduction degradation index (RDI) of sintered ore or the drum strength (DI) of coke deteriorates below a reference value. Patent Document 3 proposes a blast furnace operation method in which the increase in pressure loss (deterioration of permeability) accompanying an increase in the amount of pulverized coal injection is measured, and the amount of reduced iron charged is increased according to the amount of increase. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3017009 [Patent Document 2] JP 2008-240028 A [Patent Document 3] Patent No. 3589016 [Non-patent literature]

[0006] [Non-Patent Document 1] :Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol.39(1999), No.1, p.15-22) [Non-Patent Document 2] Iron and Steel, Vol. 79 (1993) N618 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when a part of the iron raw material is replaced with reduced iron, operational parameters such as the amount of iron produced, the temperature of molten iron, and the temperature of the top gas change unsteadily. The greater the change in the amount of reduced iron charged, the greater the change in the above operational parameters. By appropriately adjusting the blast specifications (blast volume, oxygen enrichment amount) and pulverized coal ratio, it is possible to suppress changes in the pig iron production rate, molten iron temperature, top gas temperature, etc. However, depending on the values ​​of the blast specifications (blast volume, oxygen enrichment amount) and pulverized coal ratio, and the timing of changing these, the pig iron production rate and molten iron temperature may fluctuate significantly, which may cause unstable blast furnace operation.

[0008] In view of the above, an object of the present disclosure is to stably operate a blast furnace while suppressing fluctuations in the amount of iron tapped and the temperature of molten iron when increasing or decreasing the amount of reduced iron charged in reduced iron operation, which is an operation in which part of the iron raw material is charged in place of reduced iron. [Means for solving the problem]

[0009] The gist of the present disclosure is as follows. (1) A blast furnace operating method according to one embodiment of the present disclosure includes: defining an operation having the same blast specifications and a pulverized coal ratio as a standard operation and a different amount of reduced iron charged from the standard operation as a first operation; and defining an operation having the same amount of reduced iron charged from the first operation and a different blast specifications and a pulverized coal ratio from the first operation as a second operation, the method including: estimating blast specifications and a pulverized coal ratio in the second operation such that a pig iron output, a molten iron temperature, and a top gas temperature in the second operation are the same as those in the standard operation; and estimating the blast specifications and the pulverized coal ratio in the second operation with a delay of a predetermined time after switching from the standard operation to the first operation. the second operation based on the estimated blowing specifications and the pulverized coal ratio estimated in the specification estimation step is started after a delay of the optimal delay time. (2) In the method for operating a blast furnace described above in (1), preferably, an amount of reduced iron charged in the first operation is greater than that in the standard operation. (3) In the method of operating a blast furnace according to the above (1) or (2), preferably, in the second operation, the blending ratio of reduced iron contained in the iron raw material is 0.5 mass % or more and 50 mass % or less. (4) Preferably, in the blast furnace operation method described in any one of (1) to (3) above, in the change information acquisition step, information on changes over time of both the molten iron temperature and the tapping rate is acquired, and in the optimal delay time acquisition step, the predetermined time at which the change over time of either the molten iron temperature or the tapping rate, whichever is more sensitive to delay time, is minimized is determined as the optimal delay time. (5) Preferably, in the method for operating a blast furnace according to any one of the above (1) to (4), when an operation in which the blast specifications and the pulverized coal ratio are the same as those in the second operation and an amount of reduced iron charged is larger than those in the second operation is defined as a third operation, and an operation in which the amount of reduced iron charged is the same as those in the third operation and an amount of reduced iron charged is different from those in the third operation is defined as a fourth operation, the method further comprises a second parameter estimation step of estimating blast specifications and a pulverized coal ratio in the fourth operation such that a pig iron output, a molten iron temperature, and a top gas temperature in the fourth operation are the same as those in the second operation, and a pre-operational parameter estimation step of estimating blast specifications and a pulverized coal ratio in the fourth operation with a predetermined delay after switching from the second operation to the third operation, based on the blast specifications and the pulverized coal ratio estimated in the second parameter estimation step. The method further includes a second change information acquisition step of acquiring information regarding changes over time in one or both of the molten iron temperature and the tapping rate when the fourth operation is performed, a second repetition step of performing the second change information acquisition step multiple times by changing the predetermined time, and a second optimal delay time acquisition step of determining, based on the information acquired in the second repetition step, the predetermined time at which the change over time in the molten iron temperature or the tapping rate is minimized as a second optimal delay time, and after switching from the second operation to the third operation, the fourth operation is started based on the blowing parameters and pulverized coal ratio estimated in the second parameter estimation step with a delay of the second optimal delay time. (6) Preferably, in the method of operating a blast furnace according to any one of (1) to (5) above, when an operation having the same blast specifications and pulverized coal ratio as the second operation and a larger amount of reduced iron charged than the second operation is defined as a third operation, and an operation having the same amount of reduced iron charged as the third operation and a different blast specifications and pulverized coal ratio is defined as a fourth operation, the method further includes a second parameter estimation step of estimating blast specifications and pulverized coal ratio in the fourth operation such that the iron output, molten iron temperature, and top gas temperature in the fourth operation are the same as those in the second operation, and after switching from the second operation to the third operation, the fourth operation is started with a delay of the optimal delay time based on the blast specifications and pulverized coal ratio estimated in the second parameter estimation step. Effect of the Invention

[0010] According to the present disclosure, when the amount of reduced iron charged is increased or decreased in a reduced iron operation, the blast furnace can be stably operated while suppressing fluctuations in the amount of pig iron produced and the temperature of molten iron. This makes it possible to fully enjoy the effects of the reduced iron charging, such as improved reduction efficiency and permeability, and a reduced reducing agent ratio (RAR). [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a blast furnace. [Diagram 2] 1 is a flowchart showing a method for operating a blast furnace. [Diagram 3] 1 shows the results of obtaining information regarding the change over time in molten iron temperature and iron tapping rate (Example). [Figure 4A] 11 is a graph for explaining a method of determining an optimal delay time according to determination method 1. [Figure 4B] 11 is a graph for explaining a method of determining an optimal delay time according to determination method 1. [Figure 5A] 13 is a graph for explaining a method of determining an optimal delay time according to determination method 2. [Figure 5B] 13 is a graph for explaining a method of determining an optimal delay time according to determination method 2. [Figure 6A] This is a graph corresponding to determination method 1, with the horizontal axis representing "the timing of switching from the first operation to the second operation" and the vertical axis representing "the maximum difference from the reference value for the iron tapping rate." [Figure 6B] This is a graph corresponding to determination method 1, with the horizontal axis representing "the timing of switching from the first operation to the second operation" and the vertical axis representing "the maximum difference from the reference value for the iron tapping rate." [Figure 7A] 13 is a graph corresponding to determination method 1, with the horizontal axis representing "the timing of switching from the first operation to the second operation" and the vertical axis representing "the maximum value of the difference from the reference value of the molten iron temperature." [Figure 7B] 13 is a graph corresponding to determination method 1, with the horizontal axis representing "the timing of switching from the first operation to the second operation" and the vertical axis representing "the maximum value of the difference from the reference value of the molten iron temperature." [Figure 8A] This is a graph corresponding to determination method 2, with the horizontal axis indicating "the timing of switching from the first operation to the second operation" and the vertical axis indicating "the integral value of the difference from the reference value of the iron tapping amount." [Figure 8B] This is a graph corresponding to determination method 2, with the horizontal axis indicating "the timing of switching from the first operation to the second operation" and the vertical axis indicating "the integral value of the difference from the reference value of the iron tapping amount." [Figure 9A] 13 is a graph corresponding to determination method 2, with the horizontal axis indicating "the timing of switching from the first operation to the second operation" and the vertical axis indicating "the integral value of the difference from the reference value of the molten iron temperature." [Figure 9B] 13 is a graph corresponding to determination method 2, with the horizontal axis indicating "the timing of switching from the first operation to the second operation" and the vertical axis indicating "the integral value of the difference from the reference value of the molten iron temperature." DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Outline of blast furnace structure> 1 is a schematic diagram of a blast furnace in this embodiment. The blast furnace 1 is a bell-less type blast furnace, and includes a tuyere 2, an annular pipe 3, a blowpipe 4, a pulverized coal injection lance 5, a rotating chute 6, and a tap hole 7. The present disclosure can also be applied to a bell-type blast furnace that does not have a rotating chute.

[0013] The tuyere 2 is an inlet for blowing hot air generated in a hot stove (not shown) into the blast furnace 1, and a plurality of tuyere are provided along the circumferential direction of the blast furnace 1. From the tuyere 2, pulverized coal, which will be described later, can be blown into the furnace together with the hot air.

[0014] The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. A plurality of blowpipes 4 are provided at predetermined intervals in the circumferential direction of the annular pipe 3. The annular pipe 3 supplies hot air sent from the hot stove to the blowpipes 4.

[0015] Each blowpipe 4 is connected to the annular pipe 3 and is also connected to a different tuyere 2. The blowpipe 4 blows hot air sent from the annular pipe 3 into the blast furnace 1 through the tuyere 2.

[0016] The pulverized coal injection lance 5 is provided to inject pulverized coal into the furnace from the tuyere 2. The pulverized coal injection lance 5 penetrates the wall of each blowpipe 4 and extends into the inside of each blowpipe 4. The pulverized coal injected from the pulverized coal injection lance 5 into the blowpipe 4 is injected into the furnace through the tuyere 2 together with the hot air flowing into the blowpipe 4 from the annular pipe 3.

[0017] The rotating chute 6 charges the iron raw materials and coke alternately in layers while rotating around an axis extending in the vertical direction. The iron raw materials can be lump ore, sintered ore, pellets, unburned carbon-containing agglomerated ore, etc., but when reduced iron operation is performed, part of the iron raw materials can be replaced with reduced iron. The iron raw materials may also contain a reduction auxiliary material such as small lump coke. The coke may contain ferro-coke. The blast furnace raw materials can be charged at a desired position by controlling the driving method (forward tilting / reverse tilting) of the rotating chute 6, the tilting angle, and the rotation speed. Note that forward tilting refers to a driving method in which the rotating chute 6 is driven from the furnace wall side toward the furnace center side, and reverse tilting refers to a driving method in which the rotating chute 6 is driven from the furnace center side toward the furnace wall side.

[0018] The tap hole 7 is provided at the bottom of the blast furnace 1 and taps the molten iron produced by reducing the iron raw material. A plurality of tap holes 7 are provided around the periphery of the furnace, and the molten iron can be tapped continuously or intermittently.

[0019] When reduced iron is added to the iron raw material charged into a blast furnace, operational parameters such as the pig iron production rate, molten iron temperature, and top gas temperature change unsteadily. In order to respond to the change in operational parameters, in normal operation of a blast furnace, the blast parameters and pulverized coal ratio are also changed a predetermined time after the charge amount of reduced iron is changed. This aims to make the pig iron production rate, molten iron temperature, and top gas temperature approximately the same before and after the charge amount of reduced iron is changed. However, when the fluctuations in the pig iron production rate and molten iron temperature are significant, if the timing of changing the blast parameters and pulverized coal ratio is not appropriate, the blast furnace operation may become unstable.

[0020] In the blast furnace operation method according to the present embodiment, the state before the charge amount of reduced iron is changed is called the standard operation. The standard operation is an operation performed under the operation specifications that are prerequisites for the analysis. The state after all of the charge amount of reduced iron, the blast specifications, and the pulverized coal ratio are changed from the standard operation values ​​is called the second operation. And, the state in which the charge amount of reduced iron is changed from the standard operation values, but the blast specifications and the pulverized coal ratio are not changed from the standard operation values ​​is called the first operation. Detailed definitions of the standard operation, the first operation, and the second operation will be described later. In the blast furnace operation method according to the present embodiment, the first operation is provided to delay the change of the blast specifications and the pulverized coal ratio.

[0021] Table 1 is a comparison table showing an overview of the standard operation, the first operation, and the second operation. When switching from the standard operation to the first operation, the charged amount of reduced iron is increased or decreased by α, but the blast specifications and the pulverized coal ratio conditions are not changed. When switching from the first operation to the second operation, the charged amount of reduced iron is not changed, but the blast specifications and the pulverized coal ratio conditions are changed.

[0022] [Table 1]

[0023] The inventors have found that blast furnace operation can be stabilized by optimizing the delay time for changing the blast specifications and pulverized coal ratio with respect to the change in the amount of charged reduced iron, that is, the length from the start of the first operation to the start of the second operation. The delay time, that is, the length from the start of the first operation to the start of the second operation, can be optimized by the following steps of estimating specifications, acquiring change information, repeating, and acquiring the minimum delay time. The optimal delay time is a value acquired by simulation before the start of the second operation. The start of the first operation refers to the time when the amount of charged reduced iron is changed from the value in the standard operation. The start of the second operation refers to the time when one or both of the blast specifications and the pulverized coal ratio are changed from the value in the first operation.

[0024] <Flow of blast furnace operation> An embodiment of the blast furnace operation method of the present disclosure will be described with reference to Fig. 2. Fig. 2 is a flowchart for explaining the blast furnace operation method of the present embodiment. The blast furnace operation method of the present embodiment has a standard operation, a first operation, and a second operation.

[0025] The method includes a specification estimation step (S1), a change information acquisition step (S2), a repeat step (S3), and a minimum delay time acquisition step (S4). Each step will be described in detail below.

[0026] (S1: Parameter estimation step) The blast furnace operation method of this embodiment is an operation method in which the standard operation is switched to the first operation, and then the first operation is switched to the second operation. Therefore, before describing the contents of the parameter estimation step, the definitions of the standard operation, the first operation, and the second operation will be described.

[0027] "Reference operation" refers to operation performed under the operating specifications that are prerequisites for analysis. Reference operation may be operation that does not include reduced iron as an iron raw material, or it may be operation that includes reduced iron. In addition, it is preferable that the reference operation is an operation performed during a stable operation period. A stable operation period is a period during which blast furnace operation is stable, avoiding periods immediately before and after blast shutdown, periods in which rapid increases in ash occur, periods in which rapid increases or decreases in pig iron production occur, and periods in which blast specifications fluctuate greatly.

[0028] In the present disclosure, the blast specifications and pulverized coal ratio in the standard operation are applied to the first operation described below. In the present disclosure, the pig iron production rate, molten iron temperature, and top gas temperature in the standard operation are used in the specification estimation step. These values ​​can be approximately constant during the stable operation period. The blast specifications and pulverized coal ratio, as well as the pig iron production rate, molten iron temperature, and top gas temperature at any time during the stable operation period can be used in the subsequent operation. Preferably, the blast specifications and pulverized coal ratio, as well as the pig iron production rate, molten iron temperature, and top gas temperature immediately before the standard operation is ended and the first operation is started are used in the subsequent operation. Immediately before the start of the first operation means, for example, a period up to 8 hours before the start of the first operation.

[0029] "First operation" refers to a blast furnace operation that has the same blast specifications and pulverized coal ratio as the reference operation, but has a different amount of reduced iron charged from the reference operation. The first operation may be an operation in which the amount of reduced iron charged is greater than that of the reference operation, or may be an operation in which the amount of reduced iron charged is less than that of the reference operation. An operation in which the amount of reduced iron charged is not substantially the same as that of the reference operation is considered to be the first operation. "Blow parameters" refer to the blowing volume, oxygen enrichment rate, and blowing moisture. Therefore, when the amount of reduced iron charged in the standard operation is 0, the amount of reduced iron charged in the first operation is greater than 0. Also, when the amount of reduced iron charged in the standard operation is k (k>0), the amount of reduced iron charged in the first operation is greater than k or less than k.

[0030] However, it is preferable to set the mixing ratio of reduced iron in the first operation and the second operation to 0.5 mass % or more and 50 mass % or less.

[0031] When the blending ratio in the first operation is 0.5% by mass or more, the tapping rate and the molten iron temperature tend to fluctuate greatly at the start of the first operation and the second operation. Therefore, the effect of the operating method according to the present disclosure is more preferably exhibited. The blending ratio of reduced iron in the first operation may be 1% by mass or more, 5% by mass or more, or 10% by mass or more.

[0032] On the other hand, the reason why the upper limit of the blending ratio in the first operation is preferably set to 50 mass% is that if the amount of reduced iron is excessively large, the amount of oxygen to be reduced decreases, resulting in a decrease in reducing gas in terms of operational design, which has the disadvantage of making it difficult to maintain the furnace top gas temperature, etc. The blending ratio of reduced iron in the first operation may be set to 45 mass% or less, 40 mass% or less, or 30 mass% or less.

[0033] In normal operation, the higher the blending ratio of reduced iron in the first operation, the greater the fluctuations in the amount of iron produced and the temperature of the molten iron, which may cause the blast furnace operation to become unstable. However, in the blast furnace operation method according to the present disclosure, the blast furnace can be stably operated while suppressing the fluctuations in the amount of iron produced and the temperature of the molten iron. Therefore, the higher the blending ratio of reduced iron in the first operation, the more remarkable the effect of the blast furnace operation method according to the present disclosure, which is preferable.

[0034] The "second operation" refers to an operation in which the amount of reduced iron charged is the same as that in the first operation, but the blast specifications and pulverized coal ratio are different. Therefore, the example of the blend ratio of reduced iron in the first operation described above can also be applied to the second operation. The purpose of the "parameter estimation step" described below is to search for optimal blast specifications and pulverized coal ratio for this second operation.

[0035] In the parameter estimation step, the blast parameters and pulverized coal ratio in the second operation that will result in the same iron tapping rate, molten iron temperature, and top gas temperature as those in the standard operation are estimated.

[0036] "The same as standard operation" also includes "substantially the same." For example, if the difference in pig iron production rate between standard operation and second operation is about ±100 (t / d), it is not considered to be an operational variation that requires operational action, so it can be considered that "the pig iron production rate is the same." If the difference in molten iron temperature between standard operation and second operation is about ±2°C, it is not considered to be an operational variation that requires operational action, so it can be considered that "the molten iron temperature is the same." If the difference in top gas temperature between standard operation and second operation is about ±10 (°C), it is not considered to be an operational variation that requires operational action, so it can be considered that "the molten iron temperature is the same."

[0037] The parameter estimation step can be realized, for example, by an analysis process using a blast furnace mathematical model. Specifically, the process of estimating the iron production rate, molten iron temperature, and top gas temperature of the standard operation and the process of estimating the blast parameters and pulverized coal ratio of the second operation are realized by an analysis process using a blast furnace mathematical model. A blast furnace mathematical model (see, for example, Non-Patent Document 1) is a mathematical model in which the internal region of a blast furnace is divided into a mesh, and preset conditions are substituted into the formulas for material balance, momentum balance, and energy balance to perform calculation processing, thereby estimating state variables (output values) and comprehensively simulating the state inside the furnace.

[0038] A method for estimating the pig iron production rate, molten iron temperature, and top gas temperature of standard operation using a blast furnace mathematical model will be described. Setting conditions such as the blast specifications, pulverized coal ratio (PC), reduced iron blend ratio, reduced iron consumption rate, blast moisture, and O / C of the standard operation are input into the blast furnace mathematical model to estimate state variables. The estimated state variables include at least the pig iron production rate, molten iron temperature, and top gas temperature. The reduced iron blend ratio (mass%) is the ratio of the mass of reduced iron to the mass of the iron raw material. The reduced iron consumption rate (kg / t) is the weight of reduced iron consumed to produce 1 ton of molten iron. O / C is the weight ratio of the ore layer and the coke layer. The estimated state variables may further include the theoretical combustion temperature at the tuyere tip, the bosh gas amount, the reducing agent ratio, the coke ratio, the PCI ratio, the slag ratio, ηCO, ηH2, SLC, and the pressure loss in the furnace.

[0039] In the standard operation, the state variables are estimated in a steady state (operation time is set to infinity).

[0040] A method for acquiring the blast specifications and pulverized coal ratio in the second operation by the blast furnace mathematical model will be described. The set conditions such as the reduced iron blend ratio, reduced iron consumption unit, blast moisture, and O / C in the second operation are input to the blast furnace mathematical model, and the simulation conditions are set to "the amount of pig iron produced, the molten iron temperature, and the top gas temperature are the same as those in the standard operation." In this case, the amount of pig iron produced, the molten iron temperature, and the top gas temperature in the second operation can be estimated as state variables. In this case, the amount of pig iron produced, the molten iron temperature, and the top gas temperature outputted may be completely the same as the amount of pig iron produced, the molten iron temperature, and the top gas temperature in the standard operation, or may be substantially the same. The range of the substantially same can be appropriately set by adjusting the parameters of the blast furnace mathematical model. The meaning of "substantially the same" will not be explained again. The operating conditions of the second operation, such as the blast moisture content and O / C, may be the same as those of the standard operation, or may not be the same.

[0041] In the second operation, the state variables at steady state (operation time set to infinity) are to be estimated.

[0042] In this embodiment, the specification estimation step is realized by an analysis process using a blast furnace mathematical model, but the present disclosure is not limited to this, and the specification estimation step may be realized by a method other than the blast furnace mathematical model.

[0043] For example, the parameter estimation step may be performed by an analysis process using the RIST model. The RIST model is known as a partial balance model based on thermodynamics, and the details thereof are disclosed in, for example, Non-Patent Document 2, and therefore a detailed description thereof will be omitted.

[0044] (S2: Change information acquisition step) In the change information acquisition step, information on the change over time of one or both of the molten iron temperature and the tapping rate is acquired when the second operation is carried out based on the blast parameters and the pulverized coal ratio estimated in the parameter estimation step with a delay of a predetermined time after switching from the standard operation to the first operation. Preferably, in the change information acquisition step, information on the change over time of both the molten iron temperature and the tapping rate is acquired. The "predetermined time" is, for example, a candidate value for the optimal delay time, and is any value greater than 0. The predetermined time is, for example, within a range of 1 hour to 10 hours. The time point of switching from the standard operation to the first operation refers to the time point at which the first operation is started.

[0045] In the parameter estimation step, by inputting the following setting conditions: "The blast parameters, pulverized coal ratio, blast moisture, and O / C for the first operation are the same as those for the standard operation," "The reduced iron blend ratio for the first operation is the same as that for the second operation," and "A specified time (delay time)," it is possible to obtain, as a state variable, "information regarding the changes over time in either or both of the molten iron temperature and the amount of molten iron produced when switching to the second operation based on the blast parameters and pulverized coal ratio estimated in the parameter estimation step after a specified time has elapsed since the first operation."

[0046] In this embodiment, the change information acquisition step is realized by an analysis process using a blast furnace mathematical model, but the present disclosure is not limited to this, and a method other than the blast furnace mathematical model may be used. For example, information on a change over time when the operation is switched to the second operation after a predetermined time has elapsed from the first operation may be acquired based on the operation record.

[0047] (S3: Repeat step) The change information acquisition step is performed multiple times by changing the predetermined time, and "information regarding the change over time of the molten iron temperature and the tapping rate" is acquired for each "predetermined time." The repetition step estimates the results brought about by each of multiple candidate values ​​for the optimal delay time. The change information acquisition step is preferably repeated, for example, three or more times, four or more times, or five or more times.

[0048] (S4: Optimal delay time acquisition step) Based on the information acquired in the repeating step, a predetermined time at which the change over time of one or both of the molten iron temperature and the amount of tapping is minimum is determined as the optimum delay time from among the "predetermined times". Whether it is "minimum" or not can be determined by comparing the molten iron temperature during standard operation (hereinafter also referred to as the molten iron temperature reference value) and the amount of tapping during standard operation (hereinafter also referred to as the amount of tapping reference value). Hereinafter, the molten iron temperature reference value and the amount of tapping reference value will be collectively referred to as "reference values". An example of a method for determining the optimum delay time is given below.

[0049] Determination method 1: The molten iron temperature and / or the amount of tapping is calculated from the start of the first operation until the operation is stabilized, and the predetermined time of the second operation at which the maximum value of the difference between the molten iron temperature and the reference value of the molten iron temperature or the maximum value of the difference between the amount of tapping and the reference value of the amount of tapping is the smallest is determined as the "optimum delay time." Note that "operation is stabilized" means that the amount of tapping and the molten iron temperature recover to the levels of the reference operation, for example, 24 hours after the start of the first operation.

[0050] Determination method 2: The difference between the molten iron temperature and / or the tapping amount from the start of the first operation until the operation stabilizes is calculated from their respective reference values, and the predetermined time of the second operation at which the integral value of the difference between the molten iron temperature and the molten iron temperature reference value or the integral value of the difference between the tapping amount and the tapping amount reference value is minimized is determined as the "optimum delay time."

[0051] Determination method 3: Calculate the average values ​​of the molten iron temperature and the amount of tapping from the start of the first operation until the operation stabilizes, and determine the predetermined time of the second operation at which the difference between the average value of the molten iron temperature and the reference value for the molten iron temperature or the difference between the average value of the amount of tapping and the reference value for the amount of tapping is the smallest as the "optimum delay time."

[0052] Selection can be made appropriately among Determination Method 1, Determination Method 2, and Determination Method 3 depending on the operational state. For example, since a sudden change in the molten iron temperature or the amount of tapping, even for a short period of time, has a high risk of destabilizing the operation, it is desirable to select Determination Method 1 when such a phenomenon is observed.

[0053] By carrying out the above S1 to S4, it is possible to estimate the optimal delay time from the start of the first operation until switching to the blast specifications and pulverized coal ratio estimated in the specification estimation step. By operating the blast furnace based on such an estimation result, it is possible to stably operate the blast furnace while suppressing fluctuations in the pig iron production rate and molten iron temperature.

[0054] That is, by switching from the standard operation to the first operation and then starting the second operation after the optimal delay time has elapsed, the blast furnace can be stably operated while suppressing fluctuations in the pig iron tapping rate and the molten iron temperature. Note that "starting the second operation after the optimal delay time has elapsed after switching from the standard operation to the first operation" means that the length of the first operation is made to match the optimal delay time. Here, the length of the first operation and the optimal delay time may be substantially the same. For example, when the length of the first operation is within a range of, for example, the optimal delay time ±30 minutes, the length of the first operation and the optimal delay time are considered to be substantially the same, and the blast furnace operation method characterized by "starting the second operation after the optimal delay time has elapsed after switching from the standard operation to the first operation" is considered to be implemented. When the sensitivity of the pig iron tapping rate and the molten iron temperature to the delay time is small, it is permissible to increase the difference between the optimal delay time and the actual delay time.

[0055] As explained by exemplifying the determination methods 1, 2, and 3, in the optimal delay time acquisition step, the optimal delay time may be specified based on the change over time of the molten iron temperature, or the optimal delay time may be specified based on the change over time of the amount of iron tapped. When the change over time of the molten iron temperature is used, it is not essential to acquire the change over time of the amount of iron tapped in the change information acquisition step. When the change over time of the amount of iron tapped is used, it is not essential to acquire the change over time of the molten iron temperature in the change information acquisition step.

[0056] On the other hand, in the change information acquisition step, information on the change over time of both the molten iron temperature and the amount of tapped iron may be acquired, and in the optimum delay time acquisition step, any one of the change over time of the molten iron temperature and the change over time of the amount of tapped iron may be used to determine the optimum delay time. For example, of the change over time of the molten iron temperature and the change over time of the amount of tapped iron, the one having a higher sensitivity to delay time may be used to determine the optimum delay time.

[0057] For example, in the change information acquisition step of the embodiment described later, both the change over time of the molten iron temperature and the change over time of the tapping rate were acquired. An example of the results is shown in Figures 4A and 4B. A more preferable method for determining the optimum delay time will be described with reference to this data.

[0058] In this embodiment, both the graph of the time-dependent change in the amount of pig iron tapped shown in Fig. 4A and the graph of the time-dependent change in the molten iron temperature shown in Fig. 4B have a downwardly convex shape. On the other hand, the graph of the time-dependent change in the amount of pig iron tapped shown in Fig. 4B has a steeper downward shape than the graph of the time-dependent change in the amount of pig iron tapped shown in Fig. 4A. In other words, the sensitivity of the time-dependent change in the molten iron temperature to the delay time is higher than that of the time-dependent change in the amount of pig iron tapped. In the examples shown in Fig. 4A and Fig. 4B, it is preferable to determine the predetermined time at the data point where the time-dependent change in the molten iron temperature is minimum as the optimum delay time.

[0059] In the above-described blast furnace operation method, the opportunity to increase the amount of reduced iron charged in the standard operation is only one. When switching from the standard operation to the first operation, the amount of reduced iron charged is increased, but when switching from the second operation to the third operation, the amount of reduced iron charged is not increased. However, in the blast furnace operation method according to the present disclosure, the opportunity to increase the amount of reduced iron charged may be two or more times. For example, when the second operation satisfies the definition of the standard operation, the second operation is regarded as the standard operation, and the above-mentioned procedure is performed again, so that the opportunity to increase the amount of reduced iron charged can be two times. Of course, the above-mentioned procedure can also be performed further. This makes it even easier to stably operate the blast furnace while suppressing fluctuations in the amount of pig iron produced and the temperature of the molten iron. Below, a specific example of an embodiment in which the opportunity to increase the amount of reduced iron charged is two or more times will be described.

[0060] (A. An embodiment for recalculating the optimal delay time) In the blast furnace operation method according to the present disclosure, a third operation and a fourth operation may be further performed. The third operation is defined as an operation having the same blast specifications and pulverized coal ratio as the second operation and a larger amount of reduced iron charged than the second operation. The fourth operation is defined as an operation having the same amount of reduced iron charged as the third operation and a different blast specifications and pulverized coal ratio. When the second operation is considered as a reference operation, the definition of the third operation is substantially the same as that of the first operation, and the definition of the fourth operation is substantially the same as that of the second operation.

[0061] Furthermore, the method for operating a blast furnace according to the present disclosure includes: (S11) a second parameter estimation step of estimating blast parameters and a pulverized coal ratio in the fourth operation, in which the iron tapping rate, the molten iron temperature, and the furnace top gas temperature in the fourth operation are the same as those in the second operation; (S12) a second change information acquisition step of acquiring information regarding a change over time in one or both of the molten iron temperature and the amount of tapped iron when a fourth operation based on the blast parameters and the pulverized coal ratio estimated in the second parameter estimation step is carried out with a delay of a predetermined time after switching from the second operation to the third operation; (S13) a second repeating step of performing the second change information acquisition step a plurality of times with different predetermined times; (S14) a second optimum delay time acquisition step of determining, based on the information acquired in the second repetition step, a predetermined time at which a change with time in the molten iron temperature or the amount of tapped iron is minimized as a second optimum delay time; When the second operation is regarded as the reference operation, the configurations of the second parameter estimation step, the second change information acquisition step, the second repetition step, and the second optimum delay time acquisition step are substantially the same as the configurations of the parameter estimation step, the change information acquisition step, the repetition step, and the optimum delay time acquisition step described above. In other words, in the blast furnace operation method according to the present disclosure, these steps may be repeated again.

[0062] In the second optimum delay time acquisition step, the second optimum delay time is calculated. Then, after switching from the second operation to the third operation, the fourth operation based on the blast parameters and the pulverized coal ratio estimated in the second parameter estimation step is started with a delay of the second optimum delay time. This increases the number of opportunities to increase the amount of reduced iron charged to two. Naturally, the fourth operation can be regarded as the standard operation and the above-mentioned procedure can be carried out again. By gradually increasing the amount of reduced iron charged, it becomes easier to stably operate the blast furnace while suppressing fluctuations in the amount of pig iron produced and the temperature of the molten iron.

[0063] (B) An embodiment in which the optimal delay time for the second operation is diverted to the fourth operation) In the blast furnace operation method according to the present disclosure, a third operation and a fourth operation may be further performed. The third operation is defined as an operation having the same blast specifications and pulverized coal ratio as the second operation and a larger amount of reduced iron charged than the second operation. The fourth operation is defined as an operation having the same amount of reduced iron charged as the third operation and a different blast specifications and pulverized coal ratio. When the second operation is considered as a reference operation, the definition of the third operation is substantially the same as that of the first operation, and the definition of the fourth operation is substantially the same as that of the second operation.

[0064] Furthermore, the method for operating a blast furnace according to the present disclosure includes: (S21) A second parameter estimation step for estimating blast parameters and pulverized coal ratio in the fourth operation, in which the iron production rate, molten iron temperature, and furnace top gas temperature in the fourth operation are the same as those in the second operation. When the second operation is regarded as a reference operation, the configuration of the second parameter estimation step is substantially the same as the configuration of the parameter estimation step described above.

[0065] Then, after switching from the second operation to the third operation, a fourth operation based on the blowing parameters and the pulverized coal ratio estimated in the second parameter estimation step is started with a delay of the optimal delay time. Here, the optimal delay time applied to the fourth operation is the same as the optimal delay time applied to the second operation. In other words, the optimal delay time applied to the second operation is diverted to the fourth operation.

[0066] Comparing the embodiment A in which the optimal delay time is recalculated with the embodiment B in which the optimal delay time for the second operation is diverted to the fourth operation, the second change information acquisition step, the second repetition step, and the second optimal delay time acquisition step are omitted in the embodiment B. Therefore, the calculation process in the embodiment B is simpler than that in the embodiment A.

[0067] The embodiment A is suitable for the case where the blending ratio of reduced iron is increased non-uniformly. For example, when the blending ratio of reduced iron in the reference operation is 0%, the blending ratio of reduced iron in the first and second operations is 10%, and the blending ratio of reduced iron in the third and fourth operations is 40%, it is preferable to recalculate the optimal delay time to be applied to the fourth operation.

[0068] The embodiment B is suitable for the case where the blending ratio of reduced iron is uniformly increased. For example, when the blending ratio of reduced iron in the reference operation is 0%, the blending ratio of reduced iron in the first and second operations is 20%, and the blending ratio of reduced iron in the third and fourth operations is 40%, it is preferable to divert the optimal delay time applied to the second operation to the fourth operation.

[0069] (Example) The present disclosure will now be described in more detail with reference to examples. According to the method described in the embodiment, the parameter estimation step was performed by carrying out an analysis process using a blast furnace mathematical model. The set values ​​given to the blast furnace mathematical model and the output state variables are shown in Table 2. In this example, an operation in which reduced iron is not included in the iron raw material is set as a reference operation, and the blending ratio of reduced iron in the second operation is set to about 10 mass % (10.3 mass %).

[0070] Through analysis, the blast specifications and pulverized coal ratio for the second operation were estimated to be blast volume: 5235 (Nm3 / min), oxygen enrichment rate: 2.95 (%), and pulverized coal ratio (PC): 47.1 (t / hr). [Table 2]

[0071] The predetermined time for the "change information acquisition step" was set to three patterns: 4 hours, 6 hours, and 8 hours, and "information on the change over time in the molten iron temperature and the amount of tapped iron" was acquired for each pattern. Figure 3 shows the results of these acquisitions, and is a graph with the horizontal axis representing time and the vertical axis representing the amount of tapped iron or the molten iron temperature. The time when the first operation started is set as "0".

[0072] From FIG. 3, the graphs of FIG. 4A, FIG. 4B, FIG. 5A, and FIG. 5B were obtained. FIG. 4A is a graph with the horizontal axis representing “the timing of switching from the first operation to the second operation” and the vertical axis representing “the maximum difference from the reference value of the iron tapping rate,” and corresponds to determination method 1. FIG. 4B is a graph with the horizontal axis representing “the timing of switching from the first operation to the second operation” and the vertical axis representing “the maximum value of the difference from the reference value of the molten iron temperature,” and corresponds to determination method 1. FIG. 5A is a graph in which the horizontal axis indicates “the timing of switching from the first operation to the second operation” and the vertical axis indicates “the integral value of the difference from the reference value of the iron tapping rate,” and corresponds to determination method 2. FIG. 5B is a graph with the horizontal axis representing “the timing of switching from the first operation to the second operation” and the vertical axis representing “the integral value of the difference from the reference value of the molten iron temperature,” and corresponds to determination method 2. The definitions of determination methods 1 and 2 will not be repeated.

[0073] Furthermore, in addition to the patterns in which the predetermined time shown in FIG. 3 was set to 4 hours, 6 hours, and 8 hours, patterns in which the predetermined time was set to 5 hours and 7 hours were also examined. From the results, the graphs shown in FIGS. 6A to 5B were obtained. These graphs will be explained below. Note that the markers with the caption "X%→Y%" in FIGS. 6A to 9B are data on an operation in which the charged amount of reduced iron in the reference operation was X%, and the charged amount of reduced iron in the first operation and the second operation was Y%. For example, the markers with the caption "0%→5%" are data on an operation in which the charged amount of reduced iron in the reference operation was 0%, and the charged amount of reduced iron in the first operation and the second operation was 5%.

[0074] 6A and 6B are graphs with the horizontal axis representing the "timing of switching from the first operation to the second operation" and the vertical axis representing the "maximum difference from the reference value of the iron tapping rate," and correspond to determination method 1. Note that FIG. 6A is a vertical expansion of FIG. 6B with the "0%→50%" series removed from the five data series shown in FIG. 6B.

[0075] 7A and 7B are graphs with the horizontal axis representing the "timing of switching from the first operation to the second operation" and the vertical axis representing the "maximum difference from the reference value of the molten iron temperature," and correspond to determination method 1. Note that FIG. 7A is a vertical expansion of FIG. 7B with the "0%→50%" series omitted from the five data series shown in FIG. 7B.

[0076] 8A and 8B are graphs with the horizontal axis representing "the timing of switching from the first operation to the second operation" and the vertical axis representing "the integral value of the difference from the reference value of the iron tapping rate," and correspond to determination method 2. Note that FIG. 8A is a vertical expansion of FIG. 8B with "0%→50%" omitted from the five data series shown in FIG. 8B.

[0077] 9A and 9B are graphs with the horizontal axis representing the "timing of switching from the first operation to the second operation" and the vertical axis representing the "integral value of the difference from the reference value of the molten iron temperature," and correspond to determination method 2. Note that FIG. 9A is a vertical expansion of FIG. 9B with the "0%→50%" series omitted from the five data series shown in FIG. 9B.

[0078] As shown in Table 2, in the case where the operation in which the iron raw material does not contain reduced iron is set as the reference operation and the blending ratio of reduced iron in the second operation is set to about 10 mass% (10.3 mass%), it was found that the maximum value and integral value of "6 hours" were smallest regardless of whether determination method 1 or 2 was used, as shown in Figures 4A to 5B. Therefore, it was found that the change over time in the molten iron temperature and the amount of tapped iron was minimized by setting "6 hours" as the optimal delay time.

[0079] 4A to 5B also show the results of performing a similar analysis under the conditions shown in Table 2, but changing the blending ratio of reduced iron contained in the iron raw material in the reduced iron operation to about 2 mass% (2.1 mass%). Even when the blending ratio of reduced iron contained in the iron raw material was changed to about 2 mass%, the optimal delay time was 6 hours.

[0080] The results of similar analysis processing under multiple conditions in which the blending ratio of reduced iron in the standard operation and the blending ratio of reduced iron in the second operation were changed are shown in Figures 6A, 6B, 7A, and 7B, as well as Figures 8A, 8B, 9A, and 9B. The optimal delay time changed depending on the conditions under which the blending ratio of reduced iron was changed. When the optimal delay time was determined using Determination Method 1 with a focus on the molten iron temperature (see Figures 7A and 7B), the optimal delay time under each condition was as shown in Table 3.

[0081] [Table 3] [Explanation of symbols]

[0082] 1 blast furnace 2 tuyere 3 Circular Pipe 4 Blowpipes 5 Pulverized coal injection lance 6 Swivel Shot 7 Taphole

Claims

1. An operation having the same blast specifications and pulverized coal ratio as the standard operation but a different amount of reduced iron charged than the standard operation is defined as a first operation, When an operation in which the charged amount of reduced iron is the same as that in the first operation and the blowing specifications and the pulverized coal ratio are different from those in the first operation are defined as a second operation, a parameter estimation step of estimating blast parameters and a pulverized coal ratio in the second operation, which will result in a pig iron tapping rate, a molten iron temperature, and a furnace top gas temperature being the same as those in the standard operation; a change information acquisition step of acquiring information regarding a change over time in one or both of a molten iron temperature and a tapping rate when the second operation based on the blast specifications and the pulverized coal ratio estimated in the specification estimation step is carried out with a delay of a predetermined time after switching from the standard operation to the first operation; a repeating step of performing the change information acquiring step a plurality of times while changing the predetermined time period; an optimal delay time acquisition step of determining, as an optimal delay time, the predetermined time at which a change with time of the molten iron temperature or the amount of tapped iron is minimized, based on information acquired in the repeating step; having After switching from the standard operation to the first operation, the second operation based on the blowing specifications and the pulverized coal ratio estimated in the specification estimation step is started with a delay of the optimal delay time. A method for operating a blast furnace comprising the steps of:

2. The amount of reduced iron charged in the first operation is greater than that in the standard operation. A method for operating a blast furnace according to claim 1 .

3. In the second operation, the blending ratio of reduced iron contained in the iron raw material is 0.5 mass% or more and 50 mass% or less. A method for operating a blast furnace according to claim 1 or 2.

4. In the change information acquisition step, information on changes over time of both the molten iron temperature and the amount of tapped iron is acquired, In the optimum delay time acquisition step, the predetermined time at which the change over time of the molten iron temperature or the amount of tapping iron, whichever is more sensitive to the delay time, is minimized is determined as the optimum delay time. A method for operating a blast furnace according to claim 1 or 2.

5. An operation having the same blast specifications and pulverized coal ratio as the second operation and a larger amount of reduced iron charged than the second operation is defined as a third operation, When an operation in which the charged amount of reduced iron is the same as that in the third operation and which has different blast specifications and pulverized coal ratio is defined as a fourth operation, a second parameter estimation step of estimating blast parameters and a pulverized coal ratio in the fourth operation, which will result in a pig iron tapping rate, a molten iron temperature, and a furnace top gas temperature being the same as those in the second operation; a second change information acquisition step of acquiring information regarding a change over time in one or both of a molten iron temperature and a tapping rate when the fourth operation is carried out based on the blast parameters and the pulverized coal ratio estimated in the second parameter estimation step with a delay of a predetermined time after switching from the second operation to the third operation; a second repeating step of performing the second change information acquiring step a plurality of times while changing the predetermined time period; a second optimum delay time acquisition step of determining, based on information acquired in the second repetition step, the predetermined time at which a change in the molten iron temperature or the amount of tapped iron over time is minimized as a second optimum delay time; and After switching from the second operation to the third operation, the fourth operation is started with a delay of the second optimal delay time based on the blowing specifications and the pulverized coal ratio estimated in the second specification estimation step. A method for operating a blast furnace according to claim 1 or 2.

6. An operation having the same blast specifications and pulverized coal ratio as the second operation and a larger amount of reduced iron charged than the second operation is defined as a third operation, When an operation in which the charged amount of reduced iron is the same as that in the third operation and which has different blast specifications and pulverized coal ratio is defined as a fourth operation, A second parameter estimation step of estimating blast parameters and a pulverized coal ratio in the fourth operation, in which the amount of hot metal tapped, the hot metal temperature, and the furnace top gas temperature in the fourth operation are the same as those in the second operation. and After switching from the second operation to the third operation, the fourth operation is started with a delay of the optimal delay time based on the blowing specifications and the pulverized coal ratio estimated in the second specification estimation step. A method for operating a blast furnace according to claim 1 or 2.

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