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

Abstract

To control coke terrace length in a proper range, achieving the stable operation of a blast furnace.SOLUTION: In a blast furnace operation method, ore raw material and coke are alternately and laminarly formed, and the deposition shape at the furnace top is inclined downward to the furnace center. A length evaluation value for evaluating the coke terrace length of the coke 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 raw ore and coke are alternately layered. [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 coke layer near the furnace wall, a coke terrace is formed that is sufficiently smaller than the angle of repose of the coke. If the length of the coke terrace becomes excessively long, the thickness of the coke layer near the furnace wall becomes relatively thin, and there is a possibility that gas cannot be distributed sufficiently in the furnace. Therefore, it is important to properly manage the length of the coke terrace.

[0004] In addition, since the length of the coke terrace varies depending on the orientation in a plan view, adjusting the length of the coke terrace in only one direction cannot sufficiently distribute the gas in the furnace. Patent documents 1 and 2 disclose techniques for measuring the deposition shape in a specific furnace radial direction and controlling the parameters obtained from the measurement 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] An object of the present invention is to realize stable operation of a blast furnace by controlling the coke terrace length within an appropriate range. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a blast furnace operation method, which comprises: (1) forming alternating layers of ore raw material and coke so that the pile shape at the top of the furnace is inclined downward toward the center of the furnace; obtaining length evaluation values ​​for evaluating the coke terrace length of the coke layer formed in the furnace for each of a plurality of furnace radial directions; and operating the furnace using a representative value determined based on the plurality of length evaluation values ​​obtained as an operation management index.

[0008] (2) A method for operating a blast furnace according to the above (1), characterized in that a length evaluation value in each radial direction of the furnace is calculated based on the deposition shape of the coke layer obtained using a two-dimensional profile meter.

[0009] (3) A method for operating a blast furnace according to the above (1), characterized in that a length evaluation value in each furnace radial direction is calculated based on the deposition shape of the coke layer obtained using a three-dimensional profile meter.

[0010] (4) A method of operating a blast furnace according to any one of (1) to (3) above, characterized in that: relational information representing 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 relational information; and if the representative value falls outside the appropriate range, an action is taken to shorten the coke terrace length.

[0011] (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.

[0012] (6) The method for operating a blast furnace according to (4) or (5) above, characterized in that the length evaluation value is a dimensionless coke terrace length, which is a coke terrace length when a furnace throat diameter is set to 1, and the appropriate range is 0.18 or less.

[0013] (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 maximum value of the acquired length evaluation values.

[0014] (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 raw materials and coke are formed in alternating layers and the deposition shape at the top of the furnace is inclined downward toward the center of the furnace, and the charging method control device has: an acquisition unit that acquires length evaluation values ​​for evaluating the coke terrace lengths of the coke 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 multiple length evaluation values ​​acquired by the acquisition unit as an operation management index.

[0015] (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 raw materials and coke are formed in alternating layers and the deposition shape at the top of the furnace 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 coke terrace lengths of the coke 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

[0016] According to the present invention, the coke terrace length is controlled within an appropriate range, so that stable operation of the blast furnace can be achieved. [Brief description of the drawings]

[0017] [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 coke 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 coke terrace length (-) before and after the implementation of improvement actions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] The rotating chute 6 rotates around an axis extending in the vertical direction, and charges the ore material and coke alternately in layers. The ore material and coke may each be charged in a number of separate charges, or each may be charged in one charge. The ore material may be sintered ore, pellets, lump ore, or unburned carbon-containing agglomerated ore. The coke 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.

[0020] Here, a coke terrace is formed near the furnace wall of the coke layer, depending on the driving method of the rotating chute 6. It is known that there is a certain correlation between the length of the coke terrace and an index for evaluating the stability of blast furnace operation. That is, if the length of the coke terrace becomes excessively long, the thickness of the coke layer on the furnace wall becomes relatively thin, and gas cannot be distributed sufficiently inside the furnace.

[0021] The profile meter 7 acquires the deposition shape of the coke layer. Specifically, the profile meter 7 acquires the waveform of the distance between the profile meter 7 and the surface of the coke 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 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 coke 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 coke layer may be estimated by interpolating the deposition shapes of the unmeasured areas using the deposition shapes acquired in a plurality of furnace radial directions.

[0022] The three-dimensional profile meter acquires the deposition shape of the coke 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. If 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 grid-like measurement point. In this case, the data can be processed into measurement data for the circumferential angle before being used in the subsequent steps.

[0023] 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.

[0024] The controller 8 calculates a length evaluation value for evaluating the coke terrace length based on the acquired deposition shape. The coke terrace length is the length in the furnace radial direction from the shoulder of the coke terrace (in other words, the point where the acquired distance waveform 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 a point where the value obtained by second-order differentiation is the smallest in the vicinity of the furnace wall (i.e., the shoulder of the coke terrace) is calculated, and the distance in the furnace radial direction between this point and the furnace wall can be set as the coke terrace length. It goes without saying that the point that defines the coke 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.

[0025] 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.

[0026] The above program can also be provided to a process computer (e.g., 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 (Magnet Optical) and MD (Mini Disk), magnetic disks such as floppy (registered trademark) disks and removable hard disks, and memory cards such as Compact Flash (registered trademark), Smart Media, SD memory cards, and memory sticks. Also included as recording media are hardware devices such as integrated circuits (e.g., IC chips) specially designed and configured for the purpose of the present invention.

[0027] The present inventors have found that a blast furnace is operated by acquiring length evaluation values ​​for evaluating the coke terrace length for each of a plurality of furnace radial directions, and using a representative value determined based on the 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 coke terrace length for each of a plurality of furnace radial directions".

[0028] "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 range of length evaluation values ​​that realizes the stability of blast furnace operation is also referred to as the appropriate range.

[0029] For example, the maximum 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 and use the maximum value as the representative value. By using the maximum length evaluation value as the representative value, the length evaluation value in the deposition shape part with the longest coke terrace length in the furnace radial direction where the length evaluation value is obtained 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 improved. In addition, the uniformity of gas distribution can be further improved by further taking action to make the coke terrace length in each direction uniform. However, the representative value is not limited to the maximum value of the length evaluation value, but may be the average value of the top X% of the length evaluation values, or may be the simple average of the entire circumference. X% may be, for example, 30%.

[0030] 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 coke terrace becomes longer, the thickness of the coke terrace becomes thinner, and the furnace pressure in this portion becomes higher. 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.

[0031] The appropriate range can be determined, for example, by investigating in advance 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), and based on the relationship information. Specifically, an evaluation index corresponding to the target stability is determined, and the range of the dimensionless coke 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 as an example the case where the relationship information of FIG. 2 is obtained. FIG. 2 shows the relationship between the coke ratio (kg / t) of the blast furnace and the dimensionless coke terrace length (-), which is an example of the "index for evaluating the stability of the blast furnace operation" obtained based on a large number of operation records, with the horizontal axis being the coke ratio (kg / t) of the blast furnace and the vertical axis being the dimensionless coke terrace length (-). The coke ratio (kg / t) is the amount of coke consumed per unit weight of pig iron, and is also called CR (kg / t). The dimensionless coke terrace length is the length of the coke terrace when the furnace throat diameter is set to 1, and can be obtained by dividing the coke terrace length (calculated actual measurement value) by the furnace throat diameter. Note that instead of the dimensionless coke terrace length (-), the actual measurement value of the coke terrace can also be used as the length evaluation value.

[0032] The coke rate (kg / t) indicates the quality of the blast furnace operation, and when the coke rate (kg / t) is low, stable operation is considered to be realized. For example, a coke rate (kg / t) of 320 (kg / t) or less can be considered as one criterion for stable operation. In other words, when the coke rate (kg / t) is 320 (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 320 (kg / t). Therefore, in the example of Figure 2, the evaluation index corresponding to the target stability can be set to 320 (kg / t). As shown in Figure 2, the range of the dimensionless coke terrace length (-) when the coke rate (kg / t) satisfies 320 (kg / t) or less is 0.00 or more and 0.18 or less. Therefore, in the example of Fig. 2, the range of the dimensionless coke terrace length (-) can be set to be the appropriate range of 0.00 or more and 0.18 or less. 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 permeability resistance index, etc.) can be used. Even when other indexes are used, the relationship between the other indexes and the dimensionless coke 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.

[0033] 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 coke dump, the improvement action can be to shift all notches by one notch toward the furnace wall side and change it to an outward swing. Also, the improvement action can be to lower the stock line of the blast furnace. By lowering the stock line, the amount of coke charged to the furnace wall side increases, and the length of the coke terrace can be shortened.

[0034] Also, the improvement action may be to adjust the amount of raw material charged in the direction in which the coke terrace length is maximum (hereinafter also referred to as the maximum direction). Specifically, in advance, in the raw material charging before coke charging, the opening degree of the discharge gate is adjusted while the rotating chute is rotating, thereby reducing the amount of raw material charged in the maximum direction. As a result, the charging surface in the maximum direction becomes lower than the other charging surfaces, and the coke in the maximum direction ends up being swung outward, thereby shortening the coke terrace length. Note that, instead of the coke 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.

[0035] 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 coke falling inside the furnace and corrects the falling trajectory, or by adjusting the opening speed of the bell.

[0036] 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 coke terrace length of the coke 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 coke layer and calculates the length evaluation value in each furnace radial direction. The acquisition unit 11 is realized by the cooperation of the profile meter 7 and the controller 8. 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.

[0037] FIG. 4 is a flow chart showing the process realized by the above-mentioned program. To avoid repetition, only the outline of the process will be described. The acquisition unit 11 (profile meter 7) acquires the deposition shape of the coke layer (step S101). The acquisition unit 11 (controller 8) calculates a length evaluation value for evaluating the coke 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

[0038] 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 coke terrace length (-) in multiple furnace radial directions was examined. The 1 / 3 bell-less test device is a model experimental device (radius approximately 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 approximately 1 / 3 of that of an actual furnace, and the charging amount was approximately 1 / 27 of that of an actual furnace. The charging amount of coke per charge was approximately 1.3 t, and the charging amount of ore per charge was approximately 7.3 t.

[0039] The deposition shape of the coke layer was measured by 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 coke terrace length (-) in each direction was calculated. Specifically, the obtained deposition shape was approximated by a polynomial, and the point where the second-order differential value was minimum near the furnace wall was calculated, and the distance between this point and the inner wall of the device was non-dimensionalized with the furnace throat diameter set to 1 to obtain the dimensionless coke terrace length (-). The representative value was the maximum value of the dimensionless coke terrace length (-). Figure 5 plots the dimensionless coke terrace length (-) before and after the improvement action. The open plot (circle) is before the improvement action, and the filled plot (circle) is after the improvement action. The appropriate range is a dimensionless value of 0.00 to 0.18, and 0.18 is indicated by a dotted line.

[0040] The maximum value of the dimensionless coke terrace length (-) was in the azimuth 23, which greatly exceeded 0.18, so improvement action was implemented. The improvement action was simulated by shifting all notches by one notch toward the inner wall of the equipment (corresponding to the furnace wall of an actual blast furnace) and changing the coke dump to an outward swing.

[0041] As shown in Fig. 5, by implementing the improvement actions, the dimensionless coke terrace length (-) could be improved to within the appropriate range in all directions.

[0042] In addition, by implementing the improvement action, the standard deviation σ improved from 0.027 to 0.014, and the variation in the dimensionless coke terrace length (-) became smaller. Therefore, by implementing the improvement action, it is possible to operate the blast furnace with a view to uniforming the gas flow inside the furnace.

[0043] Based on the results obtained by the 1 / 3 bell-less test device, we performed operations at an actual blast furnace with a modified coke dump to examine whether operation would be stable. 3The 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 coke terrace length (-) calculated from the measurement results of a profile meter installed in a specific furnace diameter direction was 0.21. Because the dimensionless coke terrace length (-) exceeded the upper limit of the appropriate range, an improvement action was taken to shift the coke dump outward by one notch. As a result, the dimensionless coke terrace length improved to 0.09, which was within the appropriate range. It was also confirmed that the overall air flow resistance in the furnace decreased by about 3%, and the gas flow in the furnace became uniform, enabling stable operation. [Explanation of symbols]

[0044] 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 Department

Claims

1. A method for operating a blast furnace in which ore raw materials and coke are alternately layered and the pile shape at the top of the furnace is inclined downward toward the center of the furnace, investigating in advance relational information relating to the relationship between an index for evaluating the stability of blast furnace operation and a length evaluation value for evaluating the length of a coke terrace of a coke layer formed in the furnace, and determining an appropriate range of the length evaluation value for evaluating the stability of the blast furnace as being high 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 length evaluation values ​​is used as an operation management index, and when the representative value falls outside the appropriate range, an action is taken to shorten the coke terrace length; The length evaluation value is a dimensionless coke terrace length, which is a coke terrace length when a furnace throat diameter is set to 1, and the appropriate range is 0.18 or less. 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 a length evaluation value in each of the furnace radial directions is calculated based on a deposition shape of the coke layer obtained using a two-dimensional profile meter.

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

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

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