Blast furnace operation method, charging method control device, and charging method control program

Abstract

To control ore terrace length in a proper range, achieving the stable operation of a blast furnace.SOLUTION: In a blast furnace operation method, an ore layer and a coke layer are alternately and laminarly formed in a furnace, and the deposition shape at the furnace top is inclined downward to the furnace center. A length evaluation value for evaluating the ore terrace length of the ore layer formed in the furnace is acquired for each of a plurality of furnace radial directions. A representative value determined on the basis of the acquired length evaluation values is used as an operation management index to conduct operation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method of operating a blast furnace in which ore layers and coke layers are alternately formed in the furnace. [Background technology]

[0002] In a blast furnace, layers of ore and coke are alternately stacked, and the shape of the stacked material has a great influence on the operation of the blast furnace. The ore raw material charged in layers is melted in the lower part of the blast furnace, so the reducing gas introduced from the tuyere rises in the furnace through the coke layer. For stable operation of the blast furnace, it is preferable to distribute the gas uniformly in the furnace radial direction, and it is necessary to form a coke layer that can achieve this.

[0003] In the ore layer near the furnace wall, an ore terrace is formed that is sufficiently smaller than the angle of repose of the ore. In the ore layer, coke is likely to accumulate on the ore terrace. However, if the length of the ore terrace is too short, the amount of coke accumulated near the furnace wall will be small, and gas may not be distributed sufficiently in the furnace. Therefore, in order to achieve stable operation of the blast furnace, it is important to properly manage the length of the ore terrace.

[0004] Here, in the past, in order to realize stable operation of a blast furnace, for example, a method of controlling the ore layer thickness ratio (Lo / (Lc+Lo)) so that it satisfies a predetermined condition has been adopted. Patent Documents 1 and 2 disclose a technique of measuring a pile shape in a specific furnace radial direction and controlling the ore layer thickness ratio (Lo / (Lc+Lo)) obtained from the measured pile shape to be within a predetermined value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-095761 A [Patent Document 2] JP 2018-193579 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, even if the ore layer thickness ratio (Lo / (Lc+Lo)) is used as a control index for operational control, it does not necessarily mean that a coke layer with a layer thickness distribution capable of properly distributing gas in the furnace is formed. Even if the ore layer thickness ratio (Lo / (Lc+Lo)) satisfies a predetermined condition, if the thickness of the coke layer near the furnace wall is insufficient, gas may not be distributed sufficiently in the furnace, which may lead to fluctuations in the operation of the blast furnace.

[0007] In view of the above, the present invention aims to control the coke layer thickness, particularly in the vicinity of the furnace wall, by managing the ore terrace length of the ore layer within an appropriate range, thereby achieving stable operation of the blast furnace. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a blast furnace operation method, which comprises: (1) forming ore layers and coke layers in an alternating layered manner inside the furnace and causing the deposition shape at the top of the furnace to slope downward toward the center of the furnace, obtaining length evaluation values ​​for evaluating the ore terrace length of the ore layer formed inside the furnace for each of a plurality of furnace radial directions, and operating the furnace using a representative value determined based on the obtained length evaluation values ​​as an operation management index.

[0009] (2) A method for operating a blast furnace according to the above (1), characterized in that the length evaluation value in each radial direction of the furnace is calculated based on the deposition shape of the ore layer obtained using a two-dimensional profile meter.

[0010] (3) A method for operating a blast furnace according to the above (1), characterized in that the length evaluation value in each furnace radial direction is calculated based on the deposition shape of the ore layer obtained using a three-dimensional profile meter.

[0011] (4) A method for operating a blast furnace according to any one of (1) to (3) above, characterized in that: relationship information, which is the relationship between an index for evaluating the stability of blast furnace operation and a length evaluation value, is investigated in advance; an appropriate range of length evaluation values ​​for which the stability of the blast furnace is evaluated to be high is determined based on the relationship information; and if the representative value falls outside the appropriate range, an action is taken to increase the ore terrace length.

[0012] (5) The method for operating a blast furnace according to (4) above, characterized in that the index for evaluating the stability of the blast furnace operation is a coke ratio, which is the amount of coke consumed per unit weight of pig iron.

[0013] (6) The method for operating a blast furnace according to (4) or (5) above, wherein the length evaluation value is a dimensionless ore terrace length, which is the ore terrace length when the furnace throat diameter is set to 1, and when the ore layer charging raw materials for forming the ore layer are charged at one dump per charge, the appropriate range is 0.16 or more.

[0014] (7) A method for operating a blast furnace according to any one of (1) to (6) above, characterized in that the representative value is the minimum value of the obtained length evaluation values.

[0015] (8) In order to solve the above problems, the charging method control device of the present invention is a charging method control device used in the operation of a blast furnace in which ore layers and coke layers are formed alternately in layers inside the furnace and the deposition shape at the furnace top is inclined downward toward the center of the furnace, the charging method control device having: an acquisition unit that acquires length evaluation values ​​for evaluating the ore terrace length of the ore layer formed in the furnace for each of a plurality of furnace radial directions; and an operation control unit that operates using a representative value determined based on the plurality of length evaluation values ​​acquired by the acquisition unit as an operation management index.

[0016] (9) In order to solve the above problems, the charging method control program of the present invention is a charging method control program used in the operation of a blast furnace in which ore layers and coke layers are formed alternately in layers inside the furnace and the deposition shape at the furnace top is inclined downward toward the center of the furnace, and causes a process computer to execute an acquisition step of acquiring length evaluation values ​​for evaluating the ore terrace lengths of the ore layer formed in the furnace for each of a plurality of furnace radial directions, and an operation step of operating using a representative value determined based on the plurality of length evaluation values ​​acquired in the acquisition step as an operation management index. Effect of the Invention

[0017] According to the present invention, the ore terrace length is controlled within an appropriate range, so that the coke layer thickness, particularly that in the vicinity of the furnace wall, can be appropriately controlled, thereby realizing stable operation of the blast furnace. [Brief description of the drawings]

[0018] [Figure 1] This is a schematic diagram of a blast furnace (bell-less type blast furnace). [Diagram 2] 1 is a graph showing the relationship between the coke rate (kg / t) of a blast furnace and the dimensionless ore terrace length (-). [Diagram 3] FIG. 2 is a functional block diagram of a charging method control device. [Figure 4] 1 is a flowchart showing a sequence of a charging method control program. [Diagram 5] The data shows the dimensionless ore terrace length (-) before and after the implementation of improvement actions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 is a schematic diagram of a blast furnace used in a method of operating a blast furnace according to an embodiment of the present invention. The blast furnace 1 is a bell-less type blast furnace, and includes a tuyere 2, an annular pipe 3, a blowpipe 4, a lance 5 for injecting pulverized coal, a swivel chute 6, a profile meter 7, and a controller 8. A plurality of tuyere 2 are provided in the lower part of the blast furnace 1 along the circumferential direction of the blast furnace 1. The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. The blowpipes 4 are provided intermittently in the circumferential direction of the annular pipe 3, and each is connected to a different tuyere 2. The lance 5 for injecting pulverized coal is inserted through each blowpipe 4, and the tip of the lance 5 for injecting pulverized coal extends into the inside of each blowpipe 4.

[0020] The rotating chute 6 rotates around an axis extending in the vertical direction, and charges the ore layer charging raw material and the coke layer charging raw material so that the ore layer and the coke layer are alternately formed in the furnace. The ore layer charging raw material and the coke layer charging raw material may be charged in multiple batches, or each may be charged in one batch. Here, the ore layer and the coke layer are alternately formed in the furnace, and the raw material charging performed to form one layer of the ore layer is defined as ore charging, and the ore charging achieved by one raw material charging is defined as "one dump charging", and the ore charging achieved by multiple raw material charging is defined as "multiple dump charging". Therefore, "the ore layer charging raw material for forming the ore layer is charged in one dump per charge" in claim 6 means the above-mentioned "one dump charging". Sintered ore, pellets, lump ore, and unsintered carbon-containing agglomerated ore can be used as the ore layer charging raw material. The ore layer charging material may contain materials other than ore (e.g., reduction aids such as small lump coke). The coke layer charging material may contain ferro coke. The driving method of the rotating chute 6 may be any of forward tilting, reverse tilting, and a combination of forward tilting and reverse tilting. 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.

[0021] Here, by driving the rotating chute 6, an ore terrace is formed in the region of the ore layer near the furnace wall. It is known that there is a certain correlation between the ore terrace length and an index for evaluating the stability of blast furnace operation. That is, if the ore terrace length is too short, the amount of coke deposited near the furnace wall is reduced, and gas cannot be distributed sufficiently in the furnace.

[0022] The profile meter 7 acquires the deposition shape of the ore layer. Specifically, the profile meter 7 acquires a waveform of the distance between the profile meter 7 and the surface of the ore layer for each measurement point. The profile meter 7 may be a two-dimensional profile meter or a three-dimensional profile meter. In the case of a two-dimensional profile meter, a deposition shape in a specific furnace radial direction is acquired by one measurement. Therefore, by installing a plurality of two-dimensional profile meters, the deposition shapes of the ore layer in a plurality of furnace radial directions can be acquired. In addition, by providing a traveling mechanism for traveling the two-dimensional profile meter in the furnace circumferential direction, the deposition shapes of the ore layer in a plurality of furnace radial directions can be acquired with one two-dimensional profile meter. In addition, when a two-dimensional profile meter is used, the deposition shapes of the ore layer may be estimated by interpolating the deposition shapes of the unmeasured areas using the deposition shapes acquired for a plurality of furnace radial directions.

[0023] The three-dimensional profile meter acquires the deposition shape of the ore layer in the radial direction of the furnace for each predetermined angle in the circumferential direction. The measurement interval (predetermined angle) of the three-dimensional profile meter can be set appropriately. When the measurement interval of the three-dimensional profile meter is wide, the deposition shape of the unmeasured area may be interpolated as in the case of using the above-mentioned two-dimensional profile meter. Furthermore, the measurement data of the three-dimensional profile meter is not limited to that acquired according to the circumferential angle, and may be measured, for example, at a lattice-shaped measurement point. In this case, the measurement data can be processed into measurement data for the circumferential angle and then used in the subsequent process.

[0024] Here, acquiring the deposition shape includes not only receiving raw measurement data from the profile meter 7, but also acquiring the raw data by appropriately processing (for example, interpolating) it.

[0025] The controller 8 calculates a length evaluation value for evaluating the length of the ore terrace based on the deposition shape of the ore layer acquired by the profile meter 7. The ore terrace length is the length in the furnace radial direction from the shoulder of the ore terrace (in other words, the point where the waveform of the distance acquired by the profile meter 7 switches from a substantially horizontal state to an inclined state) to the furnace wall. Specifically, the acquired deposition shape is approximated by a polynomial, and the point where the value obtained by the second differentiation is the smallest in the vicinity of the furnace wall (that is, the position corresponding to the shoulder of the ore terrace) is calculated, and the distance in the furnace radial direction between this point and the furnace wall can be set as the ore terrace length. It goes without saying that the point that specifies the ore terrace length and the position of the furnace wall are on the same plane. Here, the vicinity of the furnace wall can be, for example, in the range of 0.7 to 1.0 in terms of a dimensionless radius when the furnace throat diameter is 1. The furnace throat diameter refers to the radius of the furnace throat.

[0026] The processing performed by the controller 8 can be realized by a program, and is realized by storing programs prepared in advance in an auxiliary storage device to realize various processes, and having a process computer such as a CPU read the programs stored in the auxiliary storage device into a main storage device, and having the process computer execute the programs read into the main storage device.

[0027] The above program can also be provided to a process computer (for example, a server) in a state in which it is recorded on a computer-readable recording medium. Examples of computer-readable recording media include optical disks such as CD-ROMs, phase-change optical disks such as DVD-ROMs, magneto-optical disks such as MO (MagnetOptical) and MD (Mini Disk), magnetic disks such as floppy (registered trademark) disks and removable hard disks, and memory cards such as CompactFlash (registered trademark), smart media, SD memory cards, and memory sticks. Also included as recording media are hardware devices such as integrated circuits (IC chips, etc.) specially designed and configured for the purpose of the present invention.

[0028] The inventors have found that a blast furnace is operated by acquiring length evaluation values ​​for evaluating the ore terrace length for each of a plurality of furnace radial directions, and using a representative value determined based on these acquired length evaluation values ​​as an operation management index. Here, the plurality of furnace radial directions refers to imaginary lines extending from the furnace center toward the furnace wall. On the furnace diameter, there exists a first furnace radial direction extending from the furnace center toward the furnace wall, and a second furnace radial direction extending from the furnace center toward the furnace wall and having a direction 180 degrees different from the first furnace radial direction, but in this specification, these two furnace radial directions existing on the furnace diameter are treated as independent furnace radial directions. Therefore, acquiring length evaluation values ​​for each of the first furnace radial direction and the second furnace radial direction aligned on the furnace diameter is also included in the above-mentioned "acquiring length evaluation values ​​for evaluating the ore terrace length for each of a plurality of furnace radial directions".

[0029] "Operating a blast furnace as an operation management index" means performing operation management so that the representative value is a value that satisfies the stability of blast furnace operation. This makes the gas flow in the furnace more uniform, and operation can be stabilized. In the following explanation, the length evaluation value that realizes the stability of blast furnace operation is also referred to as the appropriate range.

[0030] For example, the minimum value of the length evaluation value can be used as the representative value. That is, the controller 8 can compare the length evaluation values ​​in each furnace radial direction with each other and use the minimum value as the representative value. By using the minimum value of the length evaluation value as the representative value, the length evaluation value in the pile shape part with the smallest length evaluation value among the acquired data is improved to the appropriate range, so that the entire furnace circumferential direction can be shifted toward the appropriate range. As a result, the above-mentioned effect (uniform distribution of gas) can be enhanced. In addition, the uniformity of gas distribution can be further improved by further taking action to make the ore terrace lengths in each direction uniform. However, the representative value is not limited to the minimum value of the length evaluation value, but may be the average value of the bottom X% of the smallest length evaluation values, or may be the simple average of the entire circumference. X% may be, for example, 30%.

[0031] In addition, the length evaluation value of the direction in which the furnace pressure is the highest may be used as the representative value. As described above, when the ore terrace is shortened, the amount of coke deposited near the furnace wall is reduced, and the furnace pressure in this area increases. Therefore, even if the length evaluation value of the direction in which the furnace pressure is the highest is used as the representative value, the entire furnace circumferential direction can be shifted toward the appropriate range. Furthermore, the length evaluation value of the direction with the lowest molten iron temperature may be used as the representative value. In an area with insufficient gas flow, reduction does not progress easily, and the molten iron temperature becomes low. Therefore, even if the length evaluation value of the direction with the lowest molten iron temperature is used as the representative value, the entire circumferential direction of the furnace can be shifted toward the appropriate range.

[0032] The appropriate range can be determined, for example, by investigating the relationship between the length evaluation value and the index for evaluating the stability of the blast furnace operation (hereinafter, also referred to as the relationship information) in advance and determining the range based on the relationship information. Specifically, an evaluation index corresponding to the target stability is determined, and the range of the dimensionless ore terrace length (-) (corresponding to the length evaluation value) that satisfies the range below the determined evaluation index is determined. This point will be described in detail by taking the case where the relationship information of FIG. 2 is obtained as an example. FIG. 2 shows the relationship between the coke ratio (kg / t) of the blast furnace and the dimensionless ore terrace length (-), which is an example of the "index for evaluating the stability of the blast furnace operation" obtained based on many operation results in which ore charging was performed at one dump per charge, with the horizontal axis being the coke ratio (kg / t) of the blast furnace and the vertical axis being the dimensionless ore terrace length (-). It goes without saying that the dimensionless ore terrace length (-) corresponds to the length evaluation value, but the length evaluation value does not necessarily have to be a dimensionless value and may be a value converted into the actual ore terrace length. Coke ratio (kg / t) is the amount of coke consumed per unit weight of pig iron, also called CR (kg / t).

[0033] The coke rate (kg / t) indicates the quality of the blast furnace operation, and when the coke rate (kg / t) is low, stable operation can be considered to be realized. For example, a coke rate (kg / t) of 310 (kg / t) or less can be considered as one criterion for stable operation. In other words, when the coke rate (kg / t) is 310 (kg / t) or less, even if there is little coke as a spacer, it can be considered that the gas in the furnace is properly distributed and the ore raw material is uniformly reduced in the furnace radial direction. If the operation is not stable, the coke rate needs to be increased, so the coke rate (kg / t) exceeds 310 (kg / t). Therefore, in the example of Figure 2, the evaluation index corresponding to the target stability can be set to 310 (kg / t). As shown in Figure 2, the range of the dimensionless ore terrace length (-) when the coke rate (kg / t) satisfies 310 (kg / t) or less is 0.16 or more. Therefore, in the example of Fig. 2, the range in which the dimensionless ore terrace length (-) is 0.16 or more can be set as the appropriate range. In this embodiment, the "coke ratio (kg / t)" is exemplified as the "index for evaluating the stability of blast furnace operation", but the present invention is not limited to this, and other indexes such as the reducing agent ratio (RAR) and indexes showing the stability of permeability (σ blast pressure, air resistance index, etc.) can be used. Even when other indexes are used, the relationship between the other indexes and the dimensionless ore terrace length (-) can be obtained and an appropriate range can be set in advance, thereby applying the method for operating a blast furnace of the present invention.

[0034] If the representative value does not fall within the appropriate range, the controller 8 performs processing to implement improvement actions to improve this. For example, in the ore dump, the improvement action can be performed by shifting all notches by one notch toward the center of the furnace and changing the dump to an inward swing. Also, the improvement action can be performed by raising the stock line of the blast furnace. By raising the stock line, the amount of ore charged toward the center of the furnace increases, and the length of the ore terrace can be increased.

[0035] Also, the improvement action may be to adjust the amount of raw material charged in the direction in which the ore terrace length is the shortest (hereinafter also referred to as the minimum orientation). Specifically, in advance, in the raw material charging before ore charging, the opening degree of the discharge gate is adjusted while the rotating chute is rotating, thereby increasing the amount of raw material charged in the minimum orientation. As a result, the charging surface in the minimum orientation becomes higher than the other charging surfaces, and as a result, the ore in the minimum orientation turns inward, and the length of the ore terrace can be increased. Note that, instead of the ore terrace length, the amount of raw material charged in the direction in which the furnace pressure is the highest or the molten iron temperature is the lowest may be adjusted.

[0036] In this embodiment, a bell-less blast furnace has been described as an example, but the present invention can also be applied to a bell blast furnace. In the case of a bell blast furnace, improvement actions can be taken by adjusting the angle of the movable armor that collides with the ore layer charge material falling inside the furnace to correct the falling trajectory, or by adjusting the opening speed of the bell.

[0037] After the improvement action is taken, it is judged again whether the representative value falls within the appropriate range. If the result shows that the representative value does not fall within the appropriate range, further improvement action is taken. In other words, improvement action is repeatedly taken until the representative value falls within the appropriate range.

[0038] According to another aspect, the present invention is realized by a charging method control device shown in FIG. 3. The charging method control device 10 has an acquisition unit 11 and an operation control unit 12. The acquisition unit 11 acquires a length evaluation value for evaluating the ore terrace length of the ore layer formed in the furnace for each of a plurality of furnace radial directions. That is, the acquisition unit 11 acquires the deposition shape of the ore layer and calculates the length evaluation value in each furnace radial direction. The acquisition unit 11 is realized by the profile meter 7 and the controller 8 working together. The operation control unit 12 operates using a representative value determined based on the plurality of length evaluation values ​​acquired by the acquisition unit 11 as an operation management index. The operation control unit 12 is realized by the controller 8. The details of the process have been described above, so the description will not be repeated.

[0039] FIG. 4 is a flowchart showing the process realized by the above-mentioned program. To avoid duplication, only an outline of the process will be described. The acquisition unit 11 (profile meter 7) acquires the deposition shape of the ore layer (step S101). The acquisition unit 11 (controller 8) calculates a length evaluation value for evaluating the ore terrace length for each furnace radial direction based on the acquired deposition shape (step S102). The operation control unit 12 (controller 8) determines a representative value based on the calculated length evaluation value (step S103). The operation control unit 12 (controller 8) determines whether the determined representative value belongs to an appropriate range (step S104). If the representative value belongs to the appropriate range (step S104 Yes), the process returns to step S101. If the representative value does not belong to the appropriate range (step S104 No), the process proceeds to step S105. In step S105, the operation control unit 12 (controller 8) executes the above-mentioned action, and the process returns to step S101. Steps S101 to S102 correspond to an "acquisition step" in claim 9, and steps S103 to S105 correspond to an "operation step" in claim 9. EXAMPLES

[0040] The blast furnace operation method of the present invention will be described in detail with reference to examples. Using a 1 / 3 bell-less test device, blast furnace raw materials were charged in layers under the same conditions as in an actual blast furnace, and the dimensionless ore terrace length (-) in multiple furnace radial directions was examined. The 1 / 3 bell-less test device is a model experimental device (radius about 1800 mm) that is 1 / 3 the size of an actual furnace and imitates a bell-less type furnace top charging device. The average particle size of the blast furnace raw materials was about 1 / 3 of that of an actual furnace, and the charging amount was about 1 / 27 of that of an actual furnace. Coke was charged at one dump per charge, and the charging amount of coke per charge was about 1.3 t. In addition, ore was charged at one dump per charge, and the charging amount of ore per charge was about 7.3 t.

[0041] The deposition shape of the ore layer was measured with a three-dimensional profile meter, and the measured three-dimensional deposition shape was cut out at 10° intervals in the furnace circumferential direction to obtain the deposition shape in each direction (corresponding to the furnace radial direction). After obtaining the deposition shape in each direction, the dimensionless ore terrace length (-) in each direction was calculated. Specifically, the obtained deposition shape was approximated by a polynomial, and the point where the value obtained by the second-order differentiation was the smallest near the furnace wall was calculated, and the distance between this point and the inner wall of the device (distance in the furnace radial direction) was non-dimensionalized with the furnace opening diameter set to 1, and the non-dimensional ore terrace length (-) was taken as the representative value. The dimensionless ore terrace length (-) before and after the implementation of the improvement action is plotted in Figure 5. The open plot (circle) is before the improvement action is implemented, and the filled plot (circle) is after the improvement action is implemented. The appropriate range is set to 0.16 or more in dimensionless value, and 0.16 is indicated by a dotted line.

[0042] At this time, the minimum value of the dimensionless ore terrace length (-) was in the orientation 4, which was smaller than 0.16. Therefore, in order to expand the ore terrace length, the improvement action was simulated by shifting all notches in the ore dump by one notch toward the center of the equipment (changing to an inward tilt). This allowed the ore to be charged closer to the center of the equipment.

[0043] As a result, as shown in Fig. 5, the minimum value of the dimensionless ore terrace length (-) was in the orientation 13, but the dimensionless ore terrace length (-) in the orientation 13 was 0.16 or more. In other words, the dimensionless ore terrace length (-) was able to be kept within the appropriate range in all orientations.

[0044] In addition, by implementing the improvement action, the standard deviation σ improved from 1.3 to 0.9, and the variation in the dimensionless ore terrace length (-) became smaller. Therefore, it became clear that by implementing the improvement action, it is possible to operate the blast furnace with a view to uniforming the gas flow inside the furnace.

[0045] Based on the results obtained by the 1 / 3 bell-less test device, we performed operations at an actual blast furnace with the ore dump changed to examine whether operation would be stable. 3 The blast furnace was operated under the same charging conditions as in the 1 / 3 bell-less test before the improvement action was implemented. At this time, the dimensionless ore terrace length (-) calculated from the measurement results of a profile meter installed in a specific furnace diameter direction was 0.15. Because the dimensionless ore terrace length (-) was below the lower limit of the appropriate range, an improvement action was taken to shift the ore dump inward by one notch. As a result, the dimensionless ore terrace length improved to 0.22, falling within the appropriate range. It was also confirmed that the overall air flow resistance in the furnace decreased by about 2%, and the gas flow in the furnace became uniform, enabling stable operation. [Explanation of symbols]

[0046] 1 blast furnace 2 tuyere 3 annular pipe 4 blowpipe 5 Pulverized coal injection lance 6 Swivel chute 7 Profile meter 8 Controller 10 Charging method control device 11 Acquisition unit 12 Operation control unit

Claims

1. A method for operating a blast furnace in which ore layers and coke layers are alternately formed in a furnace and the pile shape at the top of the furnace is inclined downward toward the center of the furnace, A relational information is previously obtained which is a relation between an index for evaluating the stability of a blast furnace operation and a length evaluation value for evaluating the length of an ore terrace of an ore layer formed in the furnace, and an appropriate range of the length evaluation value for evaluating the stability of the blast furnace as being high is determined based on the relational information; A length evaluation value is obtained for each of a plurality of furnace radial directions; a representative value determined based on the acquired plurality of length evaluation values ​​is used as an operation management index, and if the representative value falls outside the appropriate range, an action is taken to increase the length of the ore terrace; The index for evaluating the stability of the blast furnace operation is the coke ratio, which is the amount of coke consumed per unit weight of pig iron; How to operate a blast furnace.

2. The method for operating a blast furnace according to claim 1, characterized in that the length evaluation value in each radial direction of the furnace is calculated based on the deposition shape of the ore layer obtained using a two-dimensional profile meter.

3. The method for operating a blast furnace according to claim 1, characterized in that the length evaluation value in each radial direction of the furnace is calculated based on the deposition shape of the ore layer obtained using a three-dimensional profile meter.

4. The length evaluation value is a dimensionless ore terrace length when the furnace throat diameter is set to 1, 2. The method of operating a blast furnace according to claim 1, wherein the optimum range is 0.16 or more when the ore layer charging material for forming the ore layer is charged at one dump per charge.

5. 5. The method for operating a blast furnace according to claim 1, wherein the representative value is a minimum value of the acquired length evaluation values.

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