JP4244340B2 - Coke charging method to blast furnace - Google Patents

Description

  The present invention relates to a raw material charging technique that can contribute to stabilization and efficiency of blast furnace operation, and specifically, a coke center charging technique (also referred to as “coke shaft core charging technique”) developed by the present applicant. Regarding improvement.

  The present applicant has established a coke center charging technique for improving the stabilization or certainty of the so-called central flow operation in order to realize stabilization and efficiency improvement of the blast furnace operation (see, for example, Patent Document 1), and further lower coke. An improved technology that can reliably demonstrate the effect of coke-centered charging operation even under specific operation has been completed (see Patent Document 2).

  The invention described in the above-mentioned patent document 2 is “Coke shaft core charging means for intensively charging coke into the shaft core (center portion) of the blast furnace, and peripheral device for charging coke and ore to the periphery of the blast furnace. In the method of charging coke and ore into a blast furnace comprising a charging means, the coke shaft core charging means increases the coke ratio of the blast furnace shaft core (center part) and the peripheral charging means. The coke layer charged in a mountain shape so as to have a peak height at a position of 0.02R to 0.6R (where R is the blast furnace radius) from the furnace wall is charged at least in the initial stage of ore charging. By setting the ore charging position to the centrifugal side with respect to the peak position by the peripheral charging means, the high altitude part including at least the summit part of the mountain-shaped charging coke layer is destroyed and the blast furnace shaft core part side (center To the department side) Raw material charging method to become configured so as to flow to the blast furnace which is characterized. "It is.

  According to the present invention, the O / C of the shaft core portion (center portion) is lowered and the O / C of the furnace wall portion is raised, and the O / C is smoothed in the middle portion thereof, and the change is gentle. Yes, O / C does not go up and down suddenly on the way, so the rising gas in the furnace can be concentrated on the shaft core (center), and stable central flow operation can be continued. Stable and economical operations have been carried out.

  By the way, as the peripheral charging means, in the case of a blast furnace of the bell charging method, a bell method charging device consisting of a combination of a bell and a movable armor is used, and by displacing the plate of the movable armor (armor plate), The peak position of the coke layer is controlled.

  The movable armature is generally an extrusion type in which the plate surface reflecting the raw material is fixed vertically and can be pushed out into the furnace or pulled into the furnace wall side, and the plate surface is inclined obliquely upward from the vertical. Swing type that can be changed within the range up to is used.

  When an extruded type movable armor is used, the peak of the coke layer is clearly formed, and the coke layer is sufficiently scraped by the subsequent ore charging to form a mixed layer in the vicinity of the furnace center. It has been confirmed that a sufficient effect can be obtained.

  However, when a swing-type movable armor is used, the coke layer has a gentle deposit shape, and peaks are not clearly formed. It has been found that a mixed layer having a sufficient thickness is not formed, and the effects of the invention are not sufficiently exhibited. The reason for the difference in the formation of the coke layer peaks between the extrusion type and the swing type is assumed as follows. That is, when the coke is charged so as to form a peak at a predetermined position in the furnace, the coke particles descend from the lower bell toward the plate surface, are reflected by the plate surface, and fall near the predetermined position. At this time, if the plate surface is inclined upward, the coke particles reflected by the plate surface have a higher velocity component in the horizontal direction than when the coke particles are reflected by the plate surface maintained vertically. Even if such coke particles are supplied in the vicinity of the predetermined position, the coke particles try to flow further into the furnace center due to the inertial force in the horizontal direction. It is thought that it becomes a shape.

  In addition, when reducing the amount of coke charged per charge in high O / C operations, the coke center is used to stabilize the coke accumulation on the furnace wall and to stabilize the gas flow distribution in the furnace. A method that does not use charging technology is as follows: “In the coke charging method in an operation in which a single charge of coke is charged into multiple batches in a bell-type blast furnace, when reducing the amount of charged coke, "A coke charging method in a blast furnace characterized in that the amount of coke in the batch to be charged is 95 to 90% of the amount of coke in the batch to be charged last" is disclosed (see Patent Document 3).

  In this method, when reducing the amount of coke charged per charge, the amount of coke in the batch to be charged first is reduced preferentially, and the amount of coke in the batch charged last is secured to some extent. An attempt is made to stabilize the gas flow distribution in the furnace by suppressing an increase in the inclination angle of the coke layer to prevent an excessive increase in O / C in the central portion and maintaining the central gas flow. . And when the pulverized coal ratio is raised from 120 kg / thm to 150 kg / thm, it is shown that the above-mentioned effect can be obtained (see [Example] in Patent Document 3).

However, with this coke charging method, if the pulverized coal ratio is further increased beyond 150 kg / thm, the amount of coke charged per charge further decreases, giving priority to the amount of coke in the batch that is initially charged. Even if it is reduced, the amount of coke in the batch charged last cannot be secured sufficiently, and the increase in the inclination angle of the coke layer cannot be suppressed. In addition, Patent Document 3 does not describe any kind of ore, but if ore containing a large amount of pellets is used, the pellets are spherical, so that they tend to flow into the central part and the central ore layer tends to be thick. . Therefore, in the operation of high pulverized coal ratio exceeding 150 kg / thm and the operation of multiple blending of pellets, even if this coke charging method is used, the central gas flow can be maintained and the central gas flow can be maintained. There is a high possibility that the stabilization of the gas flow distribution in the furnace cannot be maintained.
JP-A-64-65207 Japanese Examined Patent Publication No. 6-27283 Japanese Patent Laid-Open No. 10-17910

  Therefore, the present invention is a bell-type blast furnace that employs coke center charging, even when performing a high pulverized coal ratio operation exceeding 150 kg / thm or a pellet multiple compounding operation, regardless of the displacement method of the armor plate, The objective is to establish a method for charging coke into a blast furnace that can secure stable central flow operation and maintain stable furnace conditions.

  The present invention relates to a coke charging method in a coke center charging operation in which coke is charged separately at the center and the peripheral side of the blast furnace. The coke amount corresponding to 5% by mass is charged, and the remaining coke amount is charged in multiple batches on the peripheral side, and the coke amount of the last charged batch is the total coke per charge. The gist is to make the amount more than 49 mass% and 69 mass% or less.

  According to the present invention, in a bell-type blast furnace that employs coke center charging, even when a high pulverized coal ratio operation exceeding 150 kg / thm is performed or when a pellet multi-mixing operation is performed, the armor plate displacement method is adopted. Regardless, stable central flow operation can be secured, stable furnace conditions can be maintained, and more economical blast furnace operation can be realized.

Embodiment
Hereinafter, the present invention will be described in more detail with reference to a longitudinal sectional view for explaining the raw material charging state at the top of the blast furnace furnace of FIG. In the following description, only a blast furnace having a swing-type movable armor with a bell charging method that can exhibit the effects of the present invention most significantly will be described, but the present invention is not limited to this. In addition, the present invention can naturally be applied to a blast furnace having an extrusion type movable armor and a bell-less charging type blast furnace.

  As shown in FIG. 1, the blast furnace 1 according to the present embodiment is a central charging chute 2 for intensively charging coke into the center of the blast furnace 1 and for charging coke and ore to the periphery of the blast furnace. The bell type charging device 3 comprising a combination of a lower bell 3a and a swing type armor plate 3b is provided.

  First, the coke layer is formed by dividing the coke charging into two times of C1 ↓ C2 ↓ by using the bell type charging device 3 (a combination of the lower bell 3a and the armor plate 3b). Specifically, for example, at C1 ↓, the armor plate 3b is set in a vertical state, a drop point is set in the vicinity of the furnace wall, and a predetermined amount of coke is introduced to form a base coke layer C1 thickness. Next, at C2 ↓, the armor plate 3b is tilted obliquely upward to set a drop point at a position P closer to the center of the blast furnace than C1 ↓, and the remaining coke is charged, and the final surface shape of the coke layer C2 is obtained. Form. Here, a symbol without ↓ (for example, C1) means a deposited layer formed by raw material charging (for example, C1 ↓), and so on.

  The peak position P of C2 ↓ is recommended to be 0.02R to 0.6R (where R is the blast furnace radius) from the furnace wall. When it is smaller than 0.02R, the coke layer on the furnace wall side becomes relatively thick. As a result, the ore layer on the furnace wall side becomes relatively thin and a part of the rising gas flow drifts to the furnace wall side, resulting in a large amount of heat dissipation. growing. On the other hand, when it is larger than 0.6R, the coke layer on the furnace wall side becomes too thin. As a result, the ore layer on the furnace wall side becomes too thick, the gas flow to the furnace wall side is insufficient, and the reduction of the ore is delayed. This is because there are concerns about an increase in the fuel ratio due to an increase in the direct reduction amount.

  Next, the ore layer and coke column are formed. For example, after the coke layers C1 and C2 are formed, the central charging chute 2 and the bell type charging device 3 are alternately used, so that the coke charging CC1 ↓ at the center and the ore charging at the peripheral portion are performed. The charging is performed in the order of input O1 ↓, coke charging CC2 ↓ to the center, ore charging O2 ↓ to the peripheral portion, and coke charging CC3 ↓ to the center. Thus, by alternately performing the coke charging to the central part and the ore charging to the peripheral part, the central charging coke CC1, CC2, CC3 is not divided by the ore layer, and the above coke layer C1, C2 and the central charging coke CC1, CC2, CC3 are continuous, and a complete coke column can be formed at the center.

Upon raw material charging of the first charge amount, 2-7 center charging coke weight W _CC total amount of coke W _TC per charged (= [CC1 + CC2 + CC3 ] total amount of coke) (= [C1 + C2 + CC1 + CC2 + CC3] total amount of coke). The C2 coke amount W _C2 (= C2 coke amount), which is the last batch to be charged, is set to more than 49% by mass and less than 69% by mass of the total coke amount W _TC per charge.

The reason why the ranges of the center charge coke amount W _CC and the C2 coke amount W _C2 are limited as described above will be described below.

First, the reason for limiting the range of the central charge coke amount W _CC will be described. If the central charge coke amount W _CC is too small, the central charge coke CC1, CC2, CC3 is divided by the ore layers O1, O2, and a complete coke column is not formed at the center. Increased risk of being unable to do so. On the other hand, if the amount of core charge coke W _CC is increased too much, the gas flow to the center becomes excessive and the gas flow to the periphery is insufficient, and the reduction of the ore at the periphery is delayed. Concerns such as an increase in the fuel ratio due to an increase in the volume arise. Accordingly, there is an appropriate range for the center charge coke amount W _CC , and the appropriate range is 2 to 7.5% by mass of the total coke amount W _TC per charge, and a more preferable range is 5 to 6% by mass. It is.

Next, the reason for limiting the range of the C2 coke amount W _C2 will be described. If the amount of C2 coke W _C2 is too small, the flow of coke to the center will be insufficient, the inclination angle of the surface of the C2 coke layer after charging will increase, and the thickness of the coke layer near the center will decrease. There is an increased risk that the flow cannot be secured. On the other hand, when the C2 coke amount W _C2 is excessively increased, the inclination angle of the C2 coke layer surface is excessively decreased, and the thickness of the coke layer near the center is excessively increased. As a result, the central flow becomes excessive and the furnace top temperature rises excessively, so that the actual gas volume increases and the total pressure loss of the blast furnace rises rather. Accordingly, there is an appropriate range for the C2 coke amount W _C2 , and the appropriate range is more than 49% by mass and less than 69% by mass of the total coke amount W _TC per charge, and a more preferable range is 50 to 66% by mass. A more preferable range is 52 to 62% by mass.

  According to the method of the present invention, since a coke column is formed in the center, even if a pellet-mixed ore is used, the pellet is prevented from flowing into the center and the center flow is maintained. The present invention is not limited by the type of ore, but the effect of the present invention is more effective in operations where the blending ratio of the pellet in the ore is 15% or more, further 20% or more, especially 25% or more. To be demonstrated.

[Modification]
In the above embodiment, the central charging chute and the bell type charging device are used as the means for charging the coke into the central portion and the peripheral side, but in the blast furnace having the bellless type charging device, the swirling A chute may be used to serve both functions.

  Moreover, in the said embodiment, although the example in which the coke charged to a peripheral part was divided | segmented into 2 times was shown, you may divide | segment and divide into 3 or more times. However, if charging is performed once, the thickness of the coke layer is likely to be uneven, and if the number of divisions is increased, the charging sequence becomes complicated and troubles are likely to occur.

  Moreover, in the said embodiment, although the example in which the coke charged to the center part is divided into three times was shown, it may be charged in two or four times or more. However, as the number of divisions increases, the charging sequence becomes complicated and troubles are likely to occur as described above, so about 2 to 3 times are recommended.

  Moreover, in the said embodiment, although the example which charges an ore in 2 steps was shown, it may be charged in 1 time or may be charged in 3 or more times. However, like the coke charging to the peripheral part, if the charging is performed once, the thickness of the ore layer is likely to be uneven, and if the number of divisions is increased, the charging sequence becomes complicated and troubles are likely to occur. Therefore, about twice is recommended.

In order to confirm the effect of the present invention, in a bell charging blast furnace having a swing type armor plate (internal volume: 4500 m ³ , coke ratio: 340 kg / thm, pulverized coal injection ratio: 160 to 165 kg / thm), For each of the two levels of coke charging into the center, operations were carried out with the C2 coke amount changed in sequence. In addition, the pellet mixing rate in the charging ore was 27 mass%, the sintered ore mixing rate was 50 mass%, and the lump ore mixing rate was 23 mass%.

  FIG. 2 shows the relationship between the ratio of the C2 coke amount to the total coke amount per charge and the blast furnace total pressure loss (= tuyere pressure-furnace top pressure). In the figure, ◯ and ♦ indicate the cases where the ratio of the central charge coke amount to the total coke amount per charge is 4.5% by mass and 7.5% by mass, respectively.

  In the figure, points A1 and A2 indicate a comparative example, where the C1 coke amount and the C2 coke amount are equal. When the ratio of the C2 coke amount is sequentially increased with respect to these comparative examples, the total pressure loss of the blast furnace is within the comparative example within the scope of the present invention in which the ratio exceeds 49 mass% and is 69 mass% or less. In comparison, a significant decrease of about 0.7 to 3.0 kPa was exhibited. Among them, in the range of the C2 coke amount ratio of 50 to 66 mass%, a pressure loss reduction of about 2.0 to 3.0 kPa is ensured, and in particular, in the range of the C2 coke amount ratio of 52 to 62 mass%, It was found that the maximum pressure loss reduction effect of about 2.7 to 3.0 kPa was obtained. However, if the proportion of the C2 coke amount further increases and exceeds 69 mass% outside the range of the present invention, the total pressure loss of the blast furnace returns almost to the level of the comparative example, and the effect of the present invention may not be obtained. all right.

  Therefore, according to the present invention, a stable central flow operation is ensured even if a swing type armor plate is used in a pellet multiple blending operation with a high pulverized coal ratio exceeding 150 kg / thm and a pellet blending ratio exceeding 25%. It was confirmed that the air permeability in the furnace was greatly improved.

It is a longitudinal cross-sectional view explaining the raw material charging condition in a blast furnace top part. It is a graph which shows the relationship between the ratio of the C2 coke amount with respect to the total coke amount per charge, and a blast furnace total pressure loss.

Explanation of symbols

1: Blast furnace 2: Chute for exclusive use of center charging 3: Bell type charging device 3a: Lower bell 3b: Armor plate O1 ↓, O2 ↓: Ore charging C1 ↓, C2 ↓: Coke charging CC1 ↓ to the periphery CC2 ↓, CC3 ↓: Coke charge O1, O2 at the center: Ore layer C1, C2: Coke layer CC1, CC2, CC3: Center charge coke P: Peak position of the coke layer C2

Claims (1)

In the coke charging method in the coke center charging operation in which the coke is divided into the central part and the peripheral side of the blast furnace,
The center portion is charged with a coke amount corresponding to 2 to 7.5% by mass of the total coke amount per charge, and the peripheral portion is charged with the remaining coke amount divided into a plurality of batches. A coke charging method into a blast furnace, characterized in that the amount of coke in the batch to be charged last is more than 49% by mass and less than 69% by mass of the total amount of coke per charge.

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