JP7620192B2 - Blast furnace operation method, charging method control device, and charging method control program - Google Patents

Description

The present invention relates to a method of operating a blast furnace in which raw ore and coke are alternately layered.

Inside a blast furnace, layers of ore and coke are stacked alternately, and the pile shape of the blast furnace charge has a huge impact on the operation of the blast furnace. The ore raw materials charged in layers are melted in the lower part of the blast furnace, so the reducing gas introduced from the tuyere rises inside the furnace through the coke layer. For stable operation of the blast furnace, it is preferable to distribute the gas evenly in the radial direction of the furnace, and it is necessary to form a coke layer that can achieve this.

In the coke layer near the oven wall, coke terraces are formed that are much smaller than the angle of repose of the coke. If the length of the coke terraces becomes excessively long, the thickness of the coke layer near the oven wall becomes relatively thin, which may result in insufficient distribution of gas within the oven, so it is important to properly manage the length of the coke terraces.

In addition, the length of the coke terrace varies depending on the orientation in a plan view, so adjusting the length of the coke terrace in only one direction cannot adequately distribute the gas inside the furnace. Patent documents 1 and 2 disclose techniques for measuring the deposition shape in a specific furnace radial direction and managing the parameters found from the shape to be within predetermined values.

JP 2017-095761 A JP 2018-193579 A

The purpose of the present invention is to achieve stable operation of the blast furnace by controlling the coke terrace length within an appropriate range.

In order to solve the above problems, the present invention provides a blast furnace operation method that (1) forms alternating layers of raw ore and coke and tilts the pile shape at the top of the furnace downward toward the center of the furnace, in which length evaluation values that evaluate the coke terrace length of the coke layer formed in the furnace are obtained for each of a number of furnace radial directions, and a representative value determined based on the obtained length evaluation values is used as an operational management index.

(2) A method for operating a blast furnace as described in (1) above, 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 two-dimensional profile meter.

(3) A method for operating a blast furnace as described in (1) above, 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.

(4) A method of 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 examined in advance; an appropriate range of length evaluation values for which the stability of the blast furnace is evaluated as high is determined based on the relationship information; and, if the representative value falls outside the appropriate range, an action is taken to shorten the coke terrace length.

(5) The method of operating a blast furnace described in (4) above, characterized in that 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.

(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 the coke terrace length when the furnace throat diameter is set to 1, and the appropriate range is 0.18 or less.

(7) A method of 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.

(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 alternately formed in layers and the pile shape at the furnace top is tilted downward toward the center of the furnace, and has an acquisition unit that acquires length evaluation values for evaluating the coke terrace length of the coke layer formed in the furnace for each of multiple 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.

(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 alternately formed in layers and the pile 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 coke terrace length of the coke layer formed in the furnace for each of multiple furnace radial directions, and an operation step of operating using a representative value determined based on the multiple length evaluation values acquired in the acquisition step as an operation management index.

According to the present invention, the coke terrace length is controlled within an appropriate range, making it possible to achieve stable operation of the blast furnace.

FIG. 1 is a schematic diagram of a blast furnace (bell-less blast furnace). 1 is a graph showing the relationship between the coke rate (kg/t) of a blast furnace and the dimensionless coke terrace length (-). FIG. 2 is a functional block diagram of a charging method control device. 1 is a flowchart showing a sequence of a charging method control program. This shows data on the dimensionless coke terrace length (-) before and after the implementation of improvement actions.

Figure 1 is a schematic diagram of a blast furnace used in a method of operating a blast furnace according to one 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 arranged 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.

The rotating chute 6 rotates around an axis extending in the vertical direction, and charges the ore raw material and coke in alternating layers. The ore raw material and coke may each be charged in multiple batches, or each may be charged in one batch. The ore raw material may be sintered ore, pellets, lump ore, or uncalcined 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.

Here, depending on the driving method of the rotating chute 6, a coke terrace is formed in the vicinity of the furnace wall of the coke layer. 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.

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 in one measurement. Therefore, by installing multiple two-dimensional profile meters, deposition shapes in multiple furnace radial directions can be acquired. In addition, by providing a traveling mechanism that travels the two-dimensional profile meter in the furnace circumferential direction, the deposition shapes of the coke layer in multiple furnace radial directions can be acquired with one two-dimensional profile meter. Note that when a two-dimensional profile meter is used, the deposition shape of the coke layer may be estimated by interpolating the deposition shapes of areas not measured using the deposition shapes acquired for multiple furnace radial directions.

The three-dimensional profile meter acquires the deposition shape of the coke layer in the radial direction of the furnace for each specified angle in the circumferential direction. The measurement interval (specified 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 two-dimensional profile meter described above. Furthermore, the measurement data of the three-dimensional profile meter is not limited to being acquired according to the circumferential angle, but may be measured, for example, at a grid-like measurement point, in which case it can be processed into measurement data for the circumferential angle before being used in subsequent processes.

Here, acquiring the deposition shape includes not only receiving raw measurement data from the profile meter 7, but also processing the raw data appropriately (e.g., interpolating) to acquire the data.

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 waveform of the acquired distance 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 second-order differentiation is the smallest near 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 position of the point that defines the coke terrace length and the position of the furnace wall are on the same axis. Here, the vicinity of the furnace wall can be, for example, a dimensionless radius in the range of 0.7 to 1.0 when the furnace opening diameter is 1. The furnace opening diameter refers to the radius of the furnace opening.

The processing performed by the controller 8 can be realized by a program. Programs prepared in advance to realize various processes are stored in an auxiliary storage device, and a process computer such as a CPU reads the programs stored in the auxiliary storage device into a main storage device, and the process computer executes the programs read into the main storage device.

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) that are specially designed and configured for the purposes of the present invention.

The 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 diameter directions, and using a representative value determined based on the acquired length evaluation values as an operation management index. Here, the plurality of furnace diameter directions refers to imaginary lines extending from the furnace center toward the furnace wall. On the furnace diameter, there exists a first furnace diameter direction extending from the furnace center toward the furnace wall, and a second furnace diameter direction extending from the furnace center toward the furnace wall, which is 180 degrees different from the first furnace diameter direction. In this specification, these two furnace diameter directions existing on the furnace diameter are treated as independent furnace diameter directions. Therefore, acquiring length evaluation values for each of the first furnace diameter direction and the second furnace diameter 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 diameter directions".

"Operating a blast furnace as an operational management index" means managing operations so that the representative value is a value that satisfies the stability of blast furnace operation. This makes the gas flow inside the furnace more uniform, stabilizing operation. In the following explanation, the range of length evaluation values that realizes stable blast furnace operation is also referred to as the appropriate range.

The representative value may be, for example, the maximum value of the length evaluation value. That is, the controller 8 may compare the length evaluation values in each furnace radial direction and use the maximum value as the representative value. By using the maximum value of the 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 enhanced. In addition, the uniformity of gas distribution can be further improved by further taking an 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%.

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.

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 blast furnace operation (hereinafter also referred to as the relationship information) in advance and determining the appropriate range 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 explained in detail using an example of the case where the relationship information in Figure 2 is obtained. Figure 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 an "index for evaluating the stability of blast furnace operation" obtained based on a large number of operational 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 calculated 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.

The coke rate (kg/t) indicates the quality of the operation of the blast furnace, and when the coke rate (kg/t) is low, stable operation can be considered to have been achieved. 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 inside the furnace is properly distributed and the ore raw material is uniformly reduced in the furnace diameter 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 appropriate range of the dimensionless coke terrace length (-) can be set to be 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 indices such as the reducing agent ratio (RAR) and an index showing the stability of permeability (σ blast pressure, air resistance index, etc.) can be used. Even when using other indices, the relationship between the other indices and the dimensionless coke terrace length (-) can be found and the appropriate range can be set in advance, making it possible to apply the method of operating a blast furnace of the present invention.

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 put into the furnace wall side increases, and the length of the coke terrace can be shortened.

In addition, an improvement action may be taken by adjusting 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, when charging raw materials before coke is charged, the opening 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, so that the coke in the maximum direction is 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 with the highest furnace pressure or the direction with the lowest molten iron temperature may also be adjusted.

In this embodiment, a bell-less blast furnace has been used 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, which collides with the coke falling inside the furnace and corrects its falling trajectory, or by adjusting the opening speed of the bell.

From another perspective, 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 explanation will not be repeated.

Figure 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 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 the 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 the "acquisition step" described in claim 9, and steps S103 to S105 correspond to the "operation step" described in claim 9.

The blast furnace operating method of the present invention will be described in detail with 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 investigated. 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 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.

The deposition shape of the coke 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 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 was implemented. The open plots (circles) are before the improvement action was implemented, and the filled plots (circles) are after the improvement action was implemented. The appropriate range was set to a dimensionless value of 0.00 to 0.18, with 0.18 indicated by a dotted line.

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.

As shown in Figure 5, by implementing improvement actions, the dimensionless coke terrace length (-) was improved to within the appropriate range in all directions.

In addition, by implementing improvement actions, the standard deviation σ improved from 0.027 to 0.014, and the variation in the dimensionless coke terrace length (-) decreased. Therefore, by implementing improvement actions, it is possible to operate the blast furnace with an aim to make the gas flow inside the furnace more uniform.

Based on the results obtained by the 1/3 bell-less test device, an actual blast furnace was operated with the coke dump changed to examine whether operation would be stable. The target blast furnace was a ^4000-5000m3 class blast furnace, and 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. Since 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 was improved to 0.09, which was within the appropriate range. It was also confirmed that the overall air flow resistance in the furnace was reduced by about 3%, and the gas flow in the furnace was made uniform, enabling stable operation.

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 (4)

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