JP2822862B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace in which charging of coke alone and charging of ore and coke are repeated, and more particularly, the particle size ratio of ore and coke charged simultaneously, and more particularly, Ore / coke weight ratio at the center of the blast furnace (hereinafter referred to as O / C
The present invention relates to a method of operating a blast furnace in which the blast furnace core is controlled to a low level to ensure the air permeability and liquid permeability of the blast furnace core and an appropriate gas flow rate in the center of the furnace, thereby maintaining a stable furnace condition.

[0002]

2. Description of the Related Art In order to operate a blast furnace stably and efficiently, it is important to appropriately control a gas flow distribution rising in the furnace. The ore is gradually heated and reduced by the action of the high-temperature reducing gas (CO, H ₂ ) generated by the reaction between the hot air blown from the tuyere installed at the lower part of the furnace and the coke, and softened and melted. It becomes hot metal after forming a bandage. The hot metal accumulates at the furnace bottom along the gap between the core coke layers and is intermittently or continuously extracted from the tap hole. It has been empirically known that it is effective to centralize the blast furnace ascending gas in order to enhance the efficiency and stability of such blast furnace operation.

[0003] Many proposals have been made on a raw material charging distribution control method for appropriately securing a rising gas in the center of a blast furnace. For example, in the invention described in Japanese Patent Publication No. 64-9373, a dedicated charging route is provided to charge a part of coke into the center of the blast furnace, thereby increasing the coke abundance ratio with respect to the ore in the center. To increase the central flow. According to this method, the central flow is strengthened while maintaining a good cohesive zone shape and gas utilization rate.Therefore, effects such as stabilization of blast furnace operation, reduction of molten iron Si, and reduction of furnace wall heat load are obtained. Is shown.

Japanese Patent Application Laid-Open No. 4-63212 discloses a method in which a mixture in which a part of coke charged in ore is mixed into ore and the remaining coke are alternately charged into a blast furnace by mixing into an ore layer. By increasing the particle size of the mixed coke according to the coke weight fraction, the property that coke is unevenly distributed in the center of the blast furnace and near the furnace wall when a mixed layer of ore and coke is deposited in the furnace A method for securing a gas flow in a central portion is disclosed. According to this method, it is said that stabilization of tapping slag, reduction of furnace pressure loss, and reduction of fluctuations in the Si concentration in the hot metal are achieved.

On the other hand, the coke particle size in the mixed layer of coke and ore, which is a part of the charged coke amount, is reduced to 1.4% of the ore particle size.
The mixed coke supports the load of the upper charge, thereby avoiding close contact between reduced iron and coke in the softened cohesive zone, thereby avoiding carburization of reduced iron. Japanese Patent Application Laid-Open No. S61-153211 discloses a method of producing hot metal with low Si by suppressing the transfer of Si to reduced iron accompanying this.

However, each of the above methods has the following problems. In other words, in the method disclosed in Japanese Patent Publication No. 64-9373, it is necessary to provide a charging device dedicated to coke in the upper space of the charge accumulation level at the furnace top in order to charge coke into the center of the furnace. is there. However, in the case of this charging method, particularly, the central part of the furnace top is always exposed to a high-temperature rising gas, so that maintenance of the apparatus may be hindered.

[0007] Furthermore, during the high tapping operation, the number of times of charging increases and the time required for one time of charging is limited, so that the number of times of charging from another system is added to the number of times of normal charging. In the above-mentioned method, it is conceivable that smooth high tapping operation is hindered.

Japanese Patent Application Laid-Open No. 4-63212 discloses that the average particle size dp (mm) of 20% by weight of the coke to be mixed with the ore is changed to the charging amount W (% by weight) of the coke mixed into the ore. ), It is shown to be (W + 20) mm or more. However, in order to control the abundance ratio of coke and ore in the radial direction by utilizing the uneven distribution phenomenon in the coke-deposited ore layer in the furnace, the particle size ratio between coke and ore particles that greatly contribute to the uneven distribution amount , And density ratio need to be defined. Since the latter is usually a constant value, it is important to determine the particle size ratio of coke and ore mixed with the ore. However, in the method disclosed in this publication, since the particle size ratio of coke and ore is not taken into account, the controllability of the uneven distribution amount of coke and ore determined by the density ratio between particles and the particle size ratio is not always good. Further, it is necessary to further improve the controllability of the coke abundance distribution in the blast furnace radial direction with respect to securing the rising gas in the center of the blast furnace in order to improve the efficiency and stabilization of the blast furnace operation.

On the other hand, according to the method disclosed in Japanese Patent Application Laid-Open No. S61-153211, low Si hot metal is manufactured by specifying the ratio between the coke particle size and the ore particle size in the coke mixed ore layer. However, this method is intended to make mixed coke exist in the softened cohesive zone layer, to support the load of the upper charge, and to avoid close contact between reduced iron and coke.
In the coke mixed ore layer, the mixed coke needs to exist uniformly in the blast furnace radial direction, and this is not a method intended to control the distribution of the coke abundance in the blast furnace radial direction in which coke is unevenly distributed in the center of the blast furnace.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blast furnace operation in which coke is charged alone and ore and coke are charged simultaneously. Control the O / C ratio of the blast furnace to a low level to secure the amount of gas rising in the center of the blast furnace and reduce the reaction amount of coke supplied to the center of the blast furnace to secure the particle size and strength of the furnace core coke. It is another object of the present invention to provide a blast furnace operating method capable of maintaining good air permeability and liquid permeability of a blast furnace core and maintaining a stable furnace state.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a blast furnace operation in which coke is charged alone and ore and coke are charged at the same time. By properly selecting the charging pattern and utilizing the classification and deposition of mixed raw material particles when entering the blast furnace, the above-mentioned object has been achieved.
The blast furnace operation method is described in (1).

(1) When a blast furnace is operated by repeating charging of coke alone and charging of ore and coke at the same time, coarse ore occupying 10% by volume% of the total ore in order of coarser ore particle size. The bulk-volume ratio weighted average particle size is determined from the finer particle size of the coke charged at the same time as the ore.
A blast furnace operating method characterized in that the bulk volume ratio of fine-grained coke occupying 10 volume percent by volume is 1.2 times or less the weighted average particle size.

In the method of the present invention, as a method for simultaneously charging ore and coke, ore and coke are cut out from a small bell in a mixed state into a large bell storage, and then the mixture is introduced from a large bell into a furnace. You can use the charging method,
Alternatively, coke and ore may be separately discharged from the small bell into the ore storage section of the large bell, and then charged into the furnace from the large bell. When the latter is adopted, coke is first deposited at the bottom of the reservoir between the Great Bell Cup and the Great Bell, and ore is deposited on top of it, giving priority to the ore loading at the beginning of simultaneous charging. It is desirable to adopt a charging pattern that completes charging of coke.

[0014]

The operation of the present invention will be described below based on the results of a charging experiment of a blast furnace model and the simulation results of a mixed raw material uneven distribution prediction model according to the probability theory.

FIG. 1 shows the actual blast furnace (internal volume) used in the charging experiment.
1850m ³ ) 1/7 scale blast furnace top half cut model
(A) is a three-dimensional perspective view, (b) is a half cut vertical sectional view.

The raw material in the ore storage section between the bell cup 3 and the bell 2 shown in FIG. 1 is cut out by lowering the bell 2 and is charged into the furnace after colliding with the armor 5 and is charged into the coke layer 6 for several charges. And a layer of ore alone or a mixed layer of coke and ore 7
Are laminated. With such raw material charging, the radial distribution of the weight ratio of ore to coke after being deposited in the furnace (hereinafter referred to as the deposited O / C ratio) was measured.

The apparent densities of the ore (particle size is D _O ) and coke (particle size is D _C ) used in the charging experiment are as follows:
Each 3.2 g / cm ^3, a 1.08 g / cm ^3, co-charging coke amount was 2.7% certain ore weight.

Simultaneous charging of ore and coke is based on a pattern in which a mixed raw material of coke and ore (hereinafter simply referred to as mixed raw material) is charged into the furnace from bell 3 (hereinafter referred to as raw material mixed charging). , First deposit coke on the bottom of the storage,
The coke was preferentially charged into the furnace from bell 3 by depositing the ore on the top of the ore (hereinafter referred to as preferential charging of coke). The experimental conditions were A and B below.
Shown in

Experiment A: D _O / D _C ... 0.6, 1.0, 1.2 and 1.6 Charge pattern: Raw material mixed charge Experiment B: D _O / D _C .0.4 Charge pattern: Raw material mixed charge or preferential charging of coke FIG. 2 shows the relationship between the uneven distribution of raw materials in the blast furnace radial direction and the ore to coke particle size ratio.

The charged O / C ratio corresponds to the O / C ratio when the charged ore and coke are deposited in the furnace in a state of being uniformly mixed without uneven distribution. Therefore, the vertical axis of the figure
When the value of (deposition O / C ratio) / (charge O / C ratio) is 1, it indicates that there is no uneven distribution of raw materials. When it exceeds 1, there is uneven distribution of ore. When it is less than 1, there is uneven distribution of coke. Indicates that

As shown in the figure, by making D _O / D _C smaller than 1.2, the dimensionless distance from the furnace center (the dimension obtained by dividing the actual distance by the inner radius of the furnace to make it dimensionless) is about 0.2. The coke can be unevenly distributed in the furnace center area (hereinafter referred to as the furnace center area), and the ore can be unevenly distributed in the furnace intermediate area with a dimensionless distance of 0.3 to 0.8. The degree of these uneven distribution increases as D _O / D _C decreases. On the other hand, D
_{When O} / D _C is 1.6, ore is unevenly distributed in the furnace center area, and coke is unevenly distributed in the area near the furnace wall with a dimensionless distance of 0.8 or more. When D _O / D _C was 1.2, uneven distribution of the raw material was hardly observed.

Usually, the raw material used in the blast furnace has a particle size distribution. In the case of ore charging alone, coarse ore occupying 10% by volume of the total ore (hereinafter simply referred to as coarse ore) Ore) are unevenly distributed in the central region of the furnace due to the difference in particle size. On the other hand, when charging the ore and coke simultaneously, the bulk volume ratio weighted average particle diameter (hereinafter, referred to as coarse D _O ) of the coarse ore deposited in the furnace center region is simultaneously charged based on the above results. Weight-average particle size (hereinafter referred to as fine D) of fine coke (hereinafter simply referred to as fine coke) occupying 10 bulk% of the coke in the order of finer coke roughness. _C ), it was found that it is possible to replace coarse-grained ores unevenly distributed in the furnace center area with co-charged coke in the case of ore charging alone.

FIG. 3 shows the influence of the charging pattern on the raw material uneven distribution in the blast furnace radial direction. As shown, D _O /
Since D _C is lower than that of FIG. 2, the degree of uneven distribution of ore to uneven distribution Oyohi furnace intermediate region of the coke into the furnace center region is made stronger than that of FIG. When the preferential charging of coke is performed, the uneven distribution of coke in the furnace center region can be enhanced as compared with the case of the raw material mixed charging.

The mechanism in which ore and coke having a difference in density and a difference in particle size are simultaneously charged and the above-described uneven distribution of the raw material occurs in the deposited layer after the deposition in the furnace is considered as follows.

FIGS. 4A and 4B are conceptual diagrams for explaining the classifying and depositing action in the process of depositing mixed particles having a particle size difference and a density difference in a furnace. FIG. Is the case where there is a density difference.

As shown in FIG. 4 (a), when particles having different particle sizes flow down the slope in a mixed state, particles A having a small particle size pass through gaps between particles B having a large particle size. Move to lower level. At this time, the probability that the particles A pass through the gaps between the particles B is proportional to the size of the gaps between the particles B with respect to the particles A and the frequency at which the particles A encounter the gaps of the particles B while flowing down the slope. Is, the larger the particle size difference between the particles A and B,
The latter is larger as the velocity gradient in the direction perpendicular to the slope of the mixed particles flowing down is larger, and classification based on the particle size difference is actively performed. Therefore, particles A having a small particle size undergo classification in the vicinity of the drop point and accumulate near the furnace wall upstream of the slope, and particles B having a large particle size float near the drop point and are transported downstream of the slope. It will be unevenly distributed in the center.

On the other hand, as shown in FIG. 4 (b), when particles having different densities flow down the slope in a mixed state, of the collisions between the particles flowing down, compared with those at the same density. ,
Since the recoil when the low-density particles B collide with the high-density particles A is large, coarse voids are generated by the particles B in the vicinity of the high-density particles A. And the probability of moving to the lower part increases. Therefore, high-density particles A are subjected to classification near the drop point and accumulate near the furnace wall upstream of the slope, and low-density particles B float near the drop point and are transported downstream of the slope. Will be unevenly distributed.

The present inventor has considered that the above-described uneven distribution of the raw material in the mixed raw material deposition layer is determined by the probability that the mixed raw material particles flowing down the slope are classified and deposited in the deposition process. It was also considered that this probability changes depending on the density ratio of the mixed particles, the particle size ratio in consideration of the particle size distribution, the charging ratio, the charging speed, and the charging pattern. Then, the probability of classification and sedimentation was quantified based on the measured raw material uneven distribution values in the charging model experiment with these changed, and a mixed raw material uneven distribution prediction model in the radial direction of the sedimentary layer was created. The calculated values of the mixed raw material uneven distribution prediction model are also shown in FIGS. 2 and 3, but the measured values and the calculated values are almost the same, and it is possible to simulate the radial distribution of the deposited O / C ratio of the actual blast furnace. I understood.

Using the above mixed raw material uneven distribution prediction model, a numerical simulation was conducted for an actual blast furnace (internal volume: 2700 m ³ , air flow: 4400 Nm ³ / min). Table 1 shows the charging conditions and the raw material particle size conditions of the actual blast furnace. FIG. 5 shows the particle size distribution of the charged raw material, wherein (a) is ore, (b) is coke, and the particle size conditions are as shown in Table 1.

[0030]

[Table 1]

FIG. 6 shows the O / C deposited in the radial direction of the blast furnace of the embodiment.
The result of model calculation of the ratio distribution is shown. In case 1, ordinary ore alone charging without mixing coke was performed. In addition Case 2, 3 and 4, mixed bulk volume ratio of coke for ore (hereinafter, simply referred to as coke mixed bulk volume ratio) as a constant, coarse ore average particle径粗D _O In the case 2 granules 1.3 times the coke average particle径細D _C, were simultaneously charging coke and ores in the case 3 and the 2 1.1. As for the charging method, the movable armor was used in each case.
Is a raw material mixed charging, and Case 4 is a coke priority charging.

As shown in FIG. 6, in the cases 2 and 3 in which coke is mixed in the ore layer, compared with the case 1 in which coke is not mixed in the ore layer, the accumulation O /
C ratio is low. Then, 1.1 crude D _O is fine D _C
In case 3, the deposition O / C ratio in the furnace central region is controlled to be lower than in case 2 in which the coarse D _O is 1.3 times the fine D _C. This is because the lower limit particle size of the coke charged at the same time is larger than the upper limit particle size of the ore, which promotes the classification and deposition of coarse ore during the in-furnace deposition process. This is because the part is unevenly distributed in the furnace central region. Therefore, by setting the coarse D _O to 1.2 times or less of the fine D _C , the ore abundance in the central region of the furnace becomes low, and the amount of CO ₂ gas and H ₂ O gas generated by ore reduction is suppressed to a low level. Can be. For this reason, the reaction deterioration of the coke due to the CO ₂ gas and the H ₂ O gas, and the resulting powdering of the coke are suppressed, and the air permeability and liquid permeability of the furnace core coke are maintained satisfactorily.

Further, in case 4 in which the simultaneous charging pattern is the coke priority charging, the deposition O / C ratio in the furnace central region can be controlled to be lower than in case 3 in which the raw material mixture is charged. This means that by performing preferential charging of coke, the amount of ore in co-charged coke in the initial stage of charging can be reduced, and therefore, the probability of ore being classified and deposited in the in-furnace deposition process increases, This is because coke is unevenly distributed to the central region.

The coke charged simultaneously with the ore is
Because it is part of a predetermined amount of all charged coke,
When the ore bulk volume fraction ratio of coke exceeds 0.2, the amount of coke charged alone becomes small, the coke layer thickness becomes thin, and the furnace central region with low deposited O / C ratio expands in the radial direction. . For this reason, the deposition O / C ratio from the middle of the furnace to the vicinity of the furnace wall is increased, and the unbalance of the gas flow distribution in the radial direction is promoted.

Therefore, it is desirable that the coke to be charged at the same time has an ore bulk volume fraction ratio of 0.2 or less.

Hereinafter, the effects of the present invention will be specifically described with reference to examples.

[0037]

[Example] In a blast furnace having a furnace inner volume of 2700 m ³ , in the operation of Examples and Comparative Examples, charging of coke alone and simultaneous charging of coke and ore were alternately repeated and laminated in the furnace, and the conventional operation was performed. In this study, the coke charging and the ore charging were alternately repeated and laminated in a furnace, and the operation was performed at a blowing rate of 4400 Nm ³ / min. The raw material charging conditions and the raw material particle size conditions are as shown in Table 1 above. Cases 1 to 4 in Table 1 correspond to the conventional example, comparative example, Example 1 and Example 2 in Table 2.

Table 2 shows the conditions in the furnace during operation, that is, the blowing pressure, the number of slip occurrences, and the fluctuations in the Si concentration in the hot metal, together with the main charging conditions and raw material particle size conditions of the examples, comparative examples and conventional examples. Rate, the measured value of the weighted average particle size of the core coke by the tuyere coke sample, and the variation of the hot metal temperature are shown. FIGS. 7 and 8 show the furnace top gas temperature distribution and the CO gas utilization rate distribution [= CO ₂ volume% / (CO + CO ₂ ) volume%] measured at the furnace top, respectively.

[0039]

[Table 2]

As shown in Table 2 and FIGS. 7 and 8, coke and ore were charged at the same time, but the comparative example in which the coarse D _O was 1.3 times the fine D _C was Due to the uneven distribution, the rise of the top gas temperature and the decrease of the CO gas utilization rate in the central region of the furnace were observed as compared with the conventional example in which coke was not mixed with the ore (not shown). However, fluctuations in the Si concentration in the hot metal and the hot metal temperature, which are thought to be caused by the ore uneven distribution in the furnace central region, were observed, and the number of slips was only slightly reduced, and the degree of improvement in operation stabilization was insufficient. this is,
Because the co-charged coke has a low particle size ratio to the coarse ore, the co-charged coke does not sufficiently classify and deposit the coarse ore, and the ore is unevenly distributed in the central region of the furnace.
As shown in Fig. 7, the deposition O / C ratio in the furnace center region was not controlled to a low level.

Incidentally, for example, the conditions of the comparative example satisfy the relationship between the coke mixing ratio and the mixed coke particle size described in the claims of JP-A-4-63212.
That is, the coke mixing ratio with respect to the ore is 4.2% by weight, and as shown in FIG. 5, the average particle size of the 20% by weight of the coke of the comparative example mixed with the ore is 52.6 mm.
Therefore, the value sufficiently exceeds the minimum value shown in JP-A-4-63212, that is, 20 + 4.2 = 24.2 mm. However, as described above, the degree of improvement in operation stabilization was insufficient. This indicates that the range defined by the invention of Japanese Patent Application Laid-Open No. 4-63212 is insufficient as charging conditions for maintaining stable blast furnace operation.

[0042] In contrast, example was 1.1 times the crude D _O fine D _C 1, Example 2 further simultaneous charging pattern was coke priority charging is slip occurrence count is reduced, furnace conditions Was stable. In Examples 1 and 2, as shown in FIG. 7, the furnace top gas temperature in the central part of the blast furnace was increased, and the gas flow in the central part of the blast furnace was stabilized. Further, as shown in FIG. 8, the gas utilization rate in the central part has decreased, and C + CO ₂ →
Deterioration of the core coke caused by the reaction of 2CO, C + H ₂ O → CO + H ₂ was suppressed, and the decrease in the core coke particle size by the tuyere coke sample measurement shown in Table 2 was small.

Embodiment 2 in which coke priority charging was performed
The effect of improving the conditions inside the furnace was greater than that of Example 1. As shown in FIG. 6, in Examples 1 and 2, the deposition O / C ratio in the furnace center region can be controlled to a low level, so that coke powdering due to reaction deterioration is suppressed, and air permeability and liquid permeability are good. The furnace core coke is formed. For this reason, a stable gas flow to the furnace central region is secured, and the blowing pressure is reduced, so that stable operation can be maintained. And the fluctuation of Si concentration and hot metal temperature in hot metal could be reduced.

[0044]

According to the method of the present invention, the O / C ratio at the center of the blast furnace can be controlled to a low level without newly providing a charging device. Therefore, it is possible to reduce the amount of coke reaction deterioration in the central part of the blast furnace, maintain the rising gas flow rate in the central part of the blast furnace at a higher level than before, secure the air permeability and liquid permeability of the blast furnace core, and improve the furnace condition. It can be kept stable.

[Brief description of the drawings]

1 shows a 1/7 scale blast furnace top half-cut model of an actual blast furnace used in a charging experiment, wherein (a) is a three-dimensional perspective view and (b) is a half-cut vertical cross-sectional view.

FIG. 2 is a diagram showing a relationship between a raw material uneven distribution state in a blast furnace radial direction and an ore to coke particle size ratio.

FIG. 3 is a diagram showing an influence of a charging pattern on a raw material uneven distribution state in a blast furnace radial direction.

FIG. 4 is a diagram illustrating a classifying deposition effect in a process of depositing mixed raw material particles in a furnace.

FIG. 5 is a diagram showing a particle size distribution of a charged material.

FIG. 6 is a diagram showing a distribution of deposited O / C in a blast furnace radial direction under various test conditions.

FIG. 7 is a diagram showing a furnace top gas temperature distribution in a blast furnace radial direction of an example in comparison with a conventional example.

FIG. 8 is a diagram showing a distribution of a CO gas utilization rate in a blast furnace radial direction of an example in comparison with a conventional example.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiro Kashiwada 1850 Minato, Wakayama City Wakayama Steel Works, Sumitomo Metal Industries, Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C21B 5/00 311 C21B 5/00 301

Claims (2)

(57) [Claims] When a blast furnace is operated by repeating charging of coke alone and charging of ore and coke at the same time, the volume of coarse-grained ore occupying 10% by volume of the total ore is determined by the size of the ore. The volume ratio weighted average particle size is calculated as the bulk volume ratio of fine coke occupying 10% by volume of the coke, starting from the finer particle size of the coke charged at the same time as the ore.
A blast furnace operating method characterized in that the blast furnace is not more than 1.2 times. 2. In the simultaneous charging of ore and coke, coke is firstly deposited on the bottom of the reserve between the large bell cup and the large bell, and the ore is deposited on the upper portion thereof. 2. The blast furnace operating method according to claim 1, wherein the charging pattern is a charging pattern in which charging of coke is completed prior to charging of ore.