JP3995380B2 - Raw material charging method to blast furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a raw material charging method for a blast furnace having a bell-less charging device.
[0002]
[Prior art]
In general, in the operation of a blast furnace, ores and coke such as lump ore, sintered ore, and pellets, which are raw materials, are alternately charged from the top of the blast furnace to deposit the ore and coke in layers. On the other hand, hot reducing gas generated by burning hot air blown from the tuyeres below the blast furnace raises the gap between the raw materials deposited in the blast furnace, raising the temperature of the raw material and reducing the ore. The pig iron is manufactured by doing.
[0003]
The coke deposited in the blast furnace burns and the ore is reduced or melted and descends downward in the blast furnace. Accordingly, ore and coke are alternately charged from the top of the furnace, and pig iron is continuously produced while maintaining the raw material in the blast furnace at a substantially constant height.
In this way, the charging amount for one cycle (hereinafter referred to as “one charge”) of ore and coke alternately and repeatedly charged from the top of the furnace is controlled to be a predetermined amount. In order to further improve the productivity of the blast furnace, by maintaining the consumption of the raw material in the radial direction and the circumferential direction in the blast furnace in an appropriate state, the rising gas flow in the blast furnace is maintained in an appropriate state. It is necessary to adjust so that it descends continuously.
[0004]
Although this rising gas flow in an appropriate state varies depending on the production volume and the particle size distribution of the raw material, basically the gas flow in the furnace center is strong and the gas flow in the furnace wall is in the middle of the furnace. It is said that it is preferable to make it slightly stronger. For this reason, in normal operation, the raw material in the blast furnace is charged in a mortar shape with the furnace center lower than the furnace wall. When the raw material is deposited in the shape of a mortar, the raw material layer in the furnace center becomes thin, so that a strong gas flow can be secured in the furnace center.
[0005]
In order to maintain the ascending gas flow in the blast furnace in an appropriate state, raw materials such as ore and coke for one charge are divided and charged according to properties such as particle size (hereinafter referred to as batch). The batch needs to be charged into place in the furnace.
In the bell-less charging device, raw materials such as coke and ore discharged from a furnace bunker disposed at the top of the blast furnace are charged into the blast furnace through a charging chute. The charging chute swivels around the central axis of the blast furnace and can change an angle (hereinafter referred to as a tilt angle) between the central axis of the blast furnace and the direction in which the raw material of the charging chute flows. Therefore, when charging the raw material, the raw material deposition position in the radial direction in the blast furnace can be adjusted by changing the tilt angle while turning the charging chute.
[0006]
That is, when the tilt angle is increased, the raw material jumps out in the direction close to the furnace wall and accumulates in the vicinity of the furnace wall, and when the tilt angle is decreased, the raw material jumps out downward and accumulates in the center of the furnace. By changing the tilt angle in this way, the raw material can be charged at an arbitrary position in the radial direction in the blast furnace.
When charging the raw material while rotating the charging chute, if the tilt angle is changed from larger to smaller and the charging chute is tilted from the furnace wall side toward the furnace center, the raw material is removed from the furnace wall side. It is deposited on the furnace center side. Conversely, when the tilt angle is changed from a smaller one to a larger one and the charging chute is tilted from the furnace center side toward the furnace wall, the raw material is deposited from the furnace center side to the furnace wall side.
[0007]
In operation, the ore layer thickness / coke layer thickness ratio in the blast furnace radial direction is controlled by the combination of the tilt angle of the charging chute and the number of turns. This distribution control of the ore layer thickness / coke layer thickness ratio in the blast furnace radial direction is called charge distribution control and is an important technology for stabilizing the blast furnace operation by controlling the gas flow distribution in the blast furnace radial direction. It is.
Generally, the charging chute for charging the raw material tilts from the furnace wall side toward the furnace center. At that time, the discharge of the raw material from the furnace top bunker is adjusted in flow rate at the gate below the furnace top bunker so that the charging chute is completed in a time required for performing a predetermined number of turns. However, if the discharge time changes due to a change in the properties of the raw material or the like, the charging amount at the position of turning at the final tilt angle becomes excessive or insufficient.
[0008]
Since the charging chute tilts from the furnace wall side toward the furnace center, excessive or insufficient charging at the final tilt angle changes the ratio of ore layer thickness / coke layer thickness at the center of the furnace. It causes the flow distribution to change. Specifically, if the turning at the final tilt angle at the time of charging the ore is increased more than the predetermined number of times, or the turning at the final tilt angle at the time of charging the coke is reduced from the predetermined number of times, The ore layer thickness / coke layer thickness ratio increases and the gas flow decreases.
[0009]
Conversely, if the turning at the final tilt angle at the time of charging the coke increases more than the predetermined number of times, or the turning at the final tilt angle at the time of charging the ore decreases below the predetermined number of times, the ore at the center of the furnace The layer thickness / coke layer thickness ratio decreases and the gas flow increases. Blast furnace operation is known to become unstable even if the gas flow at the center of the furnace is insufficient or excessive, in order to stabilize the operation of the blast furnace by maintaining an appropriate gas flow It is necessary to perform charge distribution control.
[0010]
The ore has a bulk specific gravity of about 4 times that of coke. Since the ore is heavier than the coke, when the ore is charged, the impact causes the phenomenon that the upper layer of the coke layer already deposited is dug up and the coke layer is scraped off. Moreover, since the charging chute tilts from the furnace wall side toward the furnace center, ore has not yet accumulated on the slope on the furnace center side of the position where the coke has been scraped off. For this reason, the scraped coke flows along the mortar-shaped slope into the furnace center.
[0011]
When inflow of coke scraped by ore charging occurs, the position at which the coke is scraped and the distribution of the ore layer thickness / coke layer thickness ratio in the center of the furnace change. As a result, the control of the gas flow distribution in the blast furnace is hindered.
As described above, the normal charging chute tilts from the furnace wall side toward the furnace center, and Japanese Patent Publication No. 8-11804 discloses a method for charging different types of raw materials in a bell-less blast furnace. In this method, the charging chute is tilted from the furnace center side toward the furnace wall, and the iron source and the reducing agent are divided into a plurality of batches and charged, thereby improving the controllability of the deposition amount distribution in the furnace. It is what. However, in this method, when the discharge time of the raw material from the furnace top bunker changes, it affects the fluctuation of the ore layer thickness / coke layer thickness ratio of the furnace wall, causing the gas flow of the furnace wall to fluctuate. Become. That is, even if a method of charging the raw material by tilting the charging chute from the furnace center side toward the furnace wall is used, fluctuations in the gas flow in the furnace wall cannot be avoided.
[0012]
It is known that not only the gas flow at the center of the furnace but also the control of the gas flow at the furnace wall is important for maintaining stable operation of the blast furnace, because the gas flow fluctuates with conventional charging methods. There was a problem of disturbing the operation of the blast furnace.
[0013]
[Problems to be solved by the invention]
The present invention solves the above problems, and when charging the raw material into a blast furnace having a bell-less charging device, the change in the material discharge time from the top bunker is the ore layer thickness of the furnace center and the furnace wall. An object of the present invention is to provide a raw material charging method that stabilizes the operation of a blast furnace by reducing the influence on the coke layer thickness ratio and gas flow fluctuation.
[0014]
[Means for Solving the Problems]
The present invention, the raw material charging to the blast furnace to be deposited in each layer bell-less charging device ore and coke each 2 ore by entering divided into batch instrumentation and coke with having charging chutes In the method, the ore is divided into two batches of coarse ore and fine ore, and when charging the first batch of coke and coarse ore, the furnace starts from the midpoint between the furnace center and the furnace wall in the radial direction of the blast furnace. Starting charging at the center side, charging the charging chute from the furnace center side toward the furnace wall, charging the second batch of coke and fine-grained ore. a raw material charging process of the charging chutes from the furnace wall side to the blast furnace which is charged while tilting the furnace center direction to start charging in the furnace wall side of the midpoint of the furnace wall.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing an example in which coke is divided into two batches and charged using the raw material charging method of the present invention, (a) is an example of charging of the first batch 5, (b) Shows an example of charging the second batch 6.
When charging one charge of coke in two batches according to properties such as particle size, the charging chute 3 is first rotated about the central axis of the blast furnace 1 as shown in FIG. While tilting from the furnace center side toward the furnace wall, the first batch 5 of coke is charged halfway in the radial direction. The charging of the batch is started on the furnace center side from a half position in the radial direction of the blast furnace 1 (hereinafter referred to as an intermediate point), so that the charging chute 3 is tilted from the furnace center side toward the furnace wall. . The arrow in FIG. 1 (a) indicates the tilting direction of the charging chute 3. The fluctuation of the discharge time of the first batch 5 of the coke from the furnace top hopper 2 is the thickness of the position where the swirl is swung at the final tilt angle of the charging chute 3 which is closest to the furnace wall 4 of the first batch 5 layer. Appears as a change.
[0017]
Next, as shown in FIG. 1 (b), the charging chute 3 is tilted from the furnace wall side toward the furnace center while rotating around the central axis of the blast furnace 1, and the second batch 6 of coke is coke. To the outer periphery of the first batch of 5 layers. Since the charging of the batch is started on the furnace wall side from the radial intermediate point of the blast furnace 1, the charging chute 3 is tilted from the furnace wall side toward the furnace center. The arrow in FIG. 1 (b) indicates the tilting direction of the charging chute 3. The variation in the discharge time of the second batch 6 of coke from the furnace top hopper 2 is caused by the change in the thickness of the swivel position at the final tilt angle of the charging chute 3 that is closest to the furnace center of the second batch 6 layer. Appears as Therefore, the thickness of the coke layer at the furnace center and the furnace wall is not affected even if the discharge time from the furnace top hopper 2 varies.
[0018]
Further, as shown in FIG. 2, when charging ore for one charge by dividing into two batches according to properties such as particle size, the furnace is operated while rotating the charging chute 3 around the central axis of the blast furnace 1. Tilt in the furnace wall direction from the center side and charge the first batch 7 of ore halfway in the radial direction. Since the charging of the batch is started on the furnace center side from the radial intermediate point of the blast furnace 1, the charging chute 3 is tilted from the furnace center side toward the furnace wall. The fluctuation of the discharge time of the first batch 7 of ore from the furnace top hopper 2 is the thickness of the position where the swirl is swung at the final tilt angle of the charging chute 3 which is closest to the furnace wall 4 of the layer of the first batch 7. Appears as a change.
[0019]
Next, the charging chute 3 is tilted from the furnace wall side toward the furnace center while rotating about the central axis of the blast furnace 1, and the second batch 8 of ore is loaded to the outer periphery of the first batch 7 layer of ore. Enter. Since the charging of the batch is started on the furnace wall side from the radial intermediate point of the blast furnace 1, the charging chute 3 is tilted from the furnace wall side toward the furnace center. The fluctuation of the discharge time of the second batch 8 of ore from the top hopper 2 is caused by the thickness of the swirl position at the final tilt angle of the charging chute 3 which is the most furnace center side of the layer of the second batch 8. Appears as a change.
[0020]
Therefore, the thickness of the ore layer at the furnace center and the furnace wall is not affected even if the discharge time from the furnace top hopper 2 varies. In addition, the arrow in FIG. 2 shows the direction where a raw material is deposited.
In this way, charging is possible in which the ore layer thickness / coke layer thickness ratio of the furnace center and the furnace wall is not affected by the change in the discharge time from the furnace top hopper 2.
[0021]
In the charging method described above, the first batch 5 of coke and the first batch 7 of ore charged in the furnace wall direction from the furnace center portion are not charged in the furnace wall portion, but from the furnace wall portion to the furnace center direction. The second batch 6 of coke and the second batch 8 of ore charged to the center are not charged in the center. This charging method is most effective for the present invention.
On the other hand, when one batch of charging starts from the furnace wall side from the radial intermediate point of the blast furnace 1 and is charged to the center of the furnace, or one batch of charging starts from the radial intermediate point of the blast furnace 1 It may start from the center side and be charged to the furnace wall. An example is shown in FIG. The arrows in FIG. 3 indicate the direction in which the raw material is deposited.
[0022]
In FIG. 3, the charging chute 3 is tilted from the furnace wall side toward the furnace center while rotating about the central axis of the blast furnace 1 to load the first batch 5 of coke from the furnace wall to the furnace center. Enter. Next, the charging chute 3 is tilted from the furnace center side toward the furnace wall while rotating about the central axis of the blast furnace 1, and the second batch 6 of coke is charged from the furnace center to the middle in the radial direction. To do. Further, the charging chute 3 is tilted from the furnace center side toward the furnace wall while rotating around the central axis of the blast furnace 1 to charge the first batch 7 of ore from the furnace center to the furnace wall. Then, the charging chute 3 is tilted from the furnace wall side toward the furnace center to charge the second batch 8 of ore from the furnace wall part to the middle in the radial direction.
[0023]
In this case, a change in discharge time from the top hopper 2 of the first batch 5 of coke appears as a variation in the thickness of the center portion of the furnace of the first batch 5. However, by charging the second batch 6 of coke from the furnace center, fluctuations in the layer thickness of one charge can be suppressed. Further, the change in discharge time from the top hopper 2 of the first batch 7 of ore appears as a variation in the thickness of the furnace wall portion of the first batch 7. However, by charging the second batch 8 of ore from the furnace wall, fluctuations in the layer thickness of one charge can be suppressed.
[0024]
In the present invention, the ore is divided into two batches of coarse ore and fine ore. The coarse ore starts charging at the center of the furnace from the radial center of the blast furnace 1, and the fine ore is The charging is preferably started on the furnace wall side from the radial intermediate point of the blast furnace 1.
That is, as shown in FIG. 2, coarse ore is charged as the first batch 7 of ore. At that time, the charging chute 3 is swung around the central axis of the blast furnace 1 while being tilted from the furnace center side toward the furnace wall, and the first batch 7 of the ore (that is, coarse ore) is brought to the middle in the radial direction. Insert. Since the charging of the batch is started on the furnace center side from the radial intermediate point of the blast furnace 1, the charging chute 3 is tilted from the furnace center side toward the furnace wall.
[0025]
Since the bulk density of the ore is larger than that of coke, when the coarse ore falls on the coke layer, the coke layer is scraped off by the impact. When charging coarse ore, the charging chute 3 is tilted from the furnace center side toward the furnace wall, so the coarse ore is placed on the furnace center side from the position where the coarse ore is charged and the coke is scraped off. Is deposited. Coarse ore deposited on the furnace center side prevents scraped coke from flowing into the furnace center. Therefore, it is possible to suppress fluctuations in the position where the coke scraping occurs or the ratio of the ore layer thickness / coke layer thickness at the furnace center.
[0026]
The fine ore is charged as a second batch 8 of ore as shown in FIG. At that time, the charging chute 3 is swiveled around the central axis of the blast furnace 1 while being tilted from the furnace wall side toward the furnace center, and the second batch 8 of ore (that is, fine-grained ore) is made into the first batch of ore. Charge to the outer periphery of 7 (ie coarse ore) layer. Since the charging of the batch is started on the furnace wall side from the radial intermediate point of the blast furnace 1, the charging chute 3 is tilted from the furnace wall side toward the furnace center.
[0027]
When charging fine-grained ore, the scraping phenomenon of the coke layer like coarse-grained ore is not remarkable. When charging the fine ore, the charging chute 3 is tilted from the furnace wall side toward the furnace center, so that the fine ore is not deposited on the furnace center side from the position where the fine ore is charged. . Therefore, the coarse ore layer in which the relatively large-diameter ore in the fine-grained ore flows from the charged position to the furnace center along the mortar-shaped slope and is charged as the first batch 7 of ore. It flows into the outer periphery of. On the other hand, the small-diameter ore accumulates at the charged position, and the coke layer is not significantly scraped off. In this way, fluctuations in the ore layer thickness / coke layer thickness ratio can be suppressed.
[0028]
As shown in FIG. 3, coarse ore is charged as the first batch 7 of ore. At that time, the charging chute 3 is swung around the central axis of the blast furnace 1 and tilted in the direction of the furnace wall from the furnace center side, so that the first batch 7 of ore (that is, coarse ore) is removed from the furnace center. Insert to the wall. The fine ore is then charged as the second batch 8 of ore. At that time, the charging chute 3 is swung around the central axis of the blast furnace 1 while being tilted from the furnace wall side toward the furnace center to bring the second batch 8 of ore (that is, fine-grained ore) halfway in the radial direction. Insert.
[0029]
Even if such a charging method is used, it is possible to suppress the fluctuation of the ratio of the ore layer thickness / coke layer thickness in the center of the furnace and the position where the coke scraping has occurred.
Here, coarse ore refers to ore having a particle size of 5 mm or more, and fine ore refers to ore having a particle size of less than 5 mm. In addition, as the second batch 8 of ores, fine ores with a total particle size of less than 5 mm may be charged, or coarse ores with a particle size of 5 mm or more may be mixed with fine ores with a particle size of less than 5 mm. good.
[0030]
【Example】
Coke and ore were each divided into 2 batches (1 charge total 4 batches) and charged into the blast furnace 1 for operation.
First, raw materials were charged by a conventional charging method as shown in FIG. That is, as shown in FIG. 4, the charging chute 3 is tilted from the furnace wall side toward the furnace center while rotating the charging chute 3 about the central axis of the blast furnace 1, and the first batch 5 of coke is fed from the middle in the radial direction to the furnace. Then, the charging chute 3 was tilted from the furnace wall side toward the furnace center, and the second batch 6 of coke was charged from the furnace wall to the outer periphery of the first batch 5 layers.
[0031]
Next, while rotating the charging chute 3 around the central axis of the blast furnace 1, the first batch 7 of ore is charged from the middle of the radial direction to the furnace center by tilting from the furnace wall side toward the furnace center. Then, the charging chute 3 was tilted from the furnace wall side toward the furnace center, and the second batch 8 of ore was charged from the furnace wall portion to the outer periphery of the first batch 7 layers. The first batch 7 of ore was an ore having a particle size of 5 mm or more, and the second batch 8 of ore was an ore having a particle size of less than 5 mm. The arrows in FIG. 4 indicate the direction in which the raw material is deposited.
[0032]
According to this charging method, when each batch is charged, the charging chute 3 tilts from the furnace wall 4 side toward the furnace center, so that there is an excess or deficiency in the charging amount at the position of turning at the final tilt angle. If this occurs, or if the coke layer is scraped off due to ore charging, the ratio of the ore layer thickness / coke layer thickness at the center of the furnace or where the scraping has occurred changes. The flow fluctuates.
[0033]
Further, the operation of the blast furnace 1 was continued while charging the raw material by the charging method of the present invention as shown in FIG. The first batch 7 of ore was an ore having a particle size of 5 mm or more, and the second batch 8 of ore was an ore having a particle size of less than 5 mm. In the charging method of the present invention, the charging order of each batch and the tilting direction of the charging chute 3 are the same as those described above with reference to FIGS.
[0034]
While operating the blast furnace 1 in this way, a sample is taken from the gas in the furnace at the center of the furnace using a shaft gas sonde, the sample is analyzed by gas chromatography, and the volume concentrations of CO gas and CO ₂ gas are determined. The gas utilization rate η _CO was measured (3 times / day). The gas utilization rate η _CO (%) is expressed by the following equation (1).
_{η CO (%) = 100 ×} CO 2 vol% / (COvol% + CO 2 vol%) ··· (1)
The results are shown in FIG. 5 together with the transition of the daily deviation of the ventilation resistance index σ. The ventilation resistance index σ is expressed by the following equation (2). The pressure loss in the furnace was obtained by subtracting the furnace top pressure from the blowing pressure.
[0035]
σ (10 ^-3 kpa / Nm ³ / min) = Furnace pressure loss / Air flow ... (2)
As is clear from FIG. 5, the gas utilization rate η _CO varies greatly during the period of operation while charging the raw material by the conventional charging method, but after the charging method of the present invention is applied, the η _CO variation varies. Is getting smaller. Thus, since the gas distribution is stabilized by applying the charging method of the present invention, the ventilation fluctuation in the blast furnace 1 is reduced, and the blast furnace 1 can be operated stably. This is apparent from the fact that after applying the charging method of the present invention, the ventilation resistance index σ decreases and maintains a constant level.
[0036]
【The invention's effect】
In the present invention, when a raw material is charged into a blast furnace using a bell-less charging device having a charging chute, the ore layer thickness / coke at the furnace center and the furnace wall due to the change in the material discharge time from the top bunker The fluctuation of the layer thickness ratio was suppressed, and as a result, the fluctuation of the gas flow was reduced and stable operation of the blast furnace was achieved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example in which coke is divided into two batches and charged using the raw material charging method of the present invention, (a) is an example of charging of the first batch, (b) is An example of charging the second batch is shown.
FIG. 2 is a schematic view showing an example in which ore is divided into two batches and charged using the raw material charging method of the present invention.
FIG. 3 is a schematic diagram showing another charging example according to the raw material charging method of the present invention.
FIG. 4 is a schematic diagram showing an example of charging by a conventional raw material charging method.
FIG. 5 is a graph showing changes in gas utilization rate and ventilation resistance index.
[Explanation of symbols]
1 Blast Furnace 2 Top Bunker 3 Charge Chute 4 Furnace Wall 5 1st Batch of Coke 6 2nd Batch of Coke 7 1st Batch of Ore 8 2nd Batch of Ore

Claims (1)

In ore and coke each second source charging method is divided into batch by charging to the ore and the coke into a blast furnace to be respectively deposited in layers using a bell-less charging device having a charging chutes The ore is divided into two batches of coarse ore and fine ore, and when charging the first batch of coke and the coarse ore, the intermediate point between the furnace center and the furnace wall in the radial direction of the blast furnace start the charging at the furnace center side charged while tilted furnace wall direction the charging chute from the furnace center side, the radial direction of the blast when charged the second batch and the fine ore of coke start the charged at a furnace wall side of the midpoint between the furnace center and the furnace wall material instrumentation to blast, which comprises charging while tilting the charging chute from the furnace wall side of the furnace center direction in How to enter .

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