JP3284908B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of charging ore and coke repeatedly into a blast furnace by stratification, wherein coke is charged alone, and ore is coke and MgO source auxiliary material. And a blast furnace operating method for mixing and charging (simultaneous charging).

[0002]

2. Description of the Related Art In a blast furnace, ore is produced by the action of a reducing gas (CO, H ₂ ) generated by a reaction between hot air blown from tuyeres installed in the lower part of the furnace and coke.
Heated and reduced gradually while descending in the furnace, forming a softening and melting zone (the area from the start of ore melting to the dropping), then passes through the gap in the core coke layer and accumulates as hot metal at the furnace bottom . The hot metal is withdrawn from the taphole periodically or continuously.

In recent years, the operation of this blast furnace has shifted to a high PCI operation in which pulverized coal is blown together with hot air from tuyeres in order to reduce the coke ratio, and the amount of ore charged from the furnace top is smaller than that of coke. It is increasing. Therefore, in particular, there is a situation in which the ventilation resistance of the ore softening and melting zone tends to increase.

Under these circumstances, in order to operate the blast furnace stably and efficiently, it is important to properly control the gas flow distribution rising in the furnace, and for that purpose, ventilation of the ore softening and melting zone is required. It is effective to maintain good properties.

[0005] In order to maintain good permeability of the ore softening zone, there is a method of reducing the amount of ore charged at a time and reducing the thickness of the softening zone.

[0006] A method of mixing and charging coke into ore has also been proposed. For example, JP-A-59-4140
In Japanese Unexamined Patent Publication No. 2, when ore and coke are alternately stratified and charged, coke or coal of up to 20% of the charged coke amount is mixed and charged into the ore layer, so that a softened molten zone having high ventilation resistance is charged. To allow gas to enter the
Methods for improving furnace conditions are disclosed. Further, in Japanese Patent Application Laid-Open No. 4-63212, the particle size of coke is increased in accordance with the amount of coke mixed into the ore, and the coke having a coarse particle size is ubiquitously used in the center of the furnace to utilize the gas flow in the center. And a method for reducing the ventilation resistance in the furnace is disclosed.

On the other hand, the coke in the mixed layer of coke and ore
The mixed coke supports the load of the upper charge by 1.4 to 9.0 times the ore particle size, and the reduced iron and coke in the softening molten zone are tightly packed. Japanese Patent Publication No. 63-65727 discloses a method for producing hot metal with low Si by avoiding contact, thereby suppressing carburization of reduced iron and accompanying transfer of Si to reduced iron.

However, each of the above methods has the following problems. That is, in the method of reducing the amount of ore to be charged at a time and reducing the thickness of the softening zone, the thickness of the coke layer in the softening zone also decreases at the same time. However, there is a problem that the distribution deviation in the circumferential direction is apt to occur due to the small amount of charging at a time.

In the method described in JP-A-59-41402, the particle size ratio between the ore and coke charged at the same time is not specified. As a result, a particle segregation phenomenon occurs, and the particle size distribution in the radial direction in the furnace is governed by the particle segregation phenomenon, so that the gas flow distribution in the furnace becomes unstable, and there is a risk that the furnace condition may deteriorate.

In the method described in the above-mentioned Japanese Patent Application Laid-Open No. 4-63212, the coke to be mixed with the ore has two particles from the coarser one.
The average particle size dp (mm) of 0% by weight is determined according to the charging amount W (% by weight) of coke mixed into the ore by dp> (W + 2
0). However, since the particle size ratio of coke and ore is not taken into account, the controllability of the uneven distribution of coke and ore is determined by the particle size ratio and density ratio between particles (which is usually constant). Is not always good.

In the method described in Japanese Patent Publication No. 63-65727, the ratio between the coke grain size and the ore grain size in the ore layer mixed with coke is defined. However, this method involves the presence of the mixed coke in the softening molten zone to support the load of the upper charge and avoid intimate contact between the reduced iron and the coke. However, when the mixed coke does not completely disappear in the softening and melting zone and is supplied to the furnace core in a finely divided state, the permeability of the core coke to the liquid is impaired, and the furnace condition deteriorates. Can cause.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and keeps the ore molten state in the blast furnace radial direction in a good and uniform state, thereby improving the air permeability and liquid permeability of the blast furnace. The purpose of the present invention is to provide a blast furnace operating method for maintaining the furnace condition stably.

[0013]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventor has found that when coke and MgO source auxiliary material are mixed with ore charged in a blast furnace,
By adjusting the particle size ratio and weight ratio of the ore and coke to be charged at the same time, and the particle size ratio of the ore and the MgO source auxiliary material to be charged at the same time, the furnace radius in the ore layer after the charging is adjusted. The distribution of the weight ratio of ore to coke in the direction (hereinafter, referred to as O / C ratio) is controlled, and the coke in the ore layer charged at the same time from the start of melting of the ore to the dropping of the coke (that is, softening melting). Band), it was confirmed that the ore could be maintained in a good molten state at the same time as the reaction disappeared. This makes it possible to maintain good air permeability and liquid permeability of the blast furnace and to stabilize the furnace condition.

The present invention has been made based on the above findings, and the gist of the invention resides in the following blast furnace operating method.

A method for operating a blast furnace in which ore and coke are repeatedly charged into a blast furnace by layer, wherein the ore and the coke satisfy the following equations (1), (2) and (3) simultaneously. And a blast furnace operating method comprising mixing an MgO source auxiliary material.

1.20 <D _O / D _C <1.60 (1) 1.10 <D _O / D _F <1.15 (2) X <3.2 − ｛(D _(C- 20) / 25} (3) where D _O : Weighted average particle size of ore (mm) D _C : Weighted average particle size of coke (mm) D _F : Weighted average particle size of MgO source auxiliary material (Mm) X: weight ratio of coke to ore mixed with ore (%)

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a blast furnace operating method of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing a half-cut model that is vertically cut around the top of a blast furnace of 1/7 scale of an actual blast furnace (internal volume: 1850 m ³ ) used in a raw material charging experiment. FIG. 4B is a perspective view, and FIG.

In FIG. 1, the raw material in the ore storage portion between the bell cup 3 and the bell 2 is cut out by lowering the bell 2 by using a bell lifting / lowering drive device 4 and colliding with an armor 5 after the collision in the furnace. The coke layer 6 for several charges and the coke mixed or single ore layer 7 are stacked.

For two kinds of particles having different densities, that is, ore and MgO source auxiliary material, or coke and ore, a raw material charging experiment was performed using the above blast furnace top model, and the particles were deposited in the furnace. Were measured in the radial direction in the furnace. Hereinafter, an experiment using coke and ore having a large density difference will be described.

The apparent densities of the ore (particle size is D _O ) and coke (particle size is D _C ) used in the raw material charging experiment were 3.2 g / cm ³ and 1.08 g / cm ³ , respectively. cm
^The amount of coke mixed with the ore and charged at the same time was constant at 2.7% by weight of the ore weight. The ore and coke particle size ratios (D _O / D _C ) were 0.6, 1.0,
There were five cases of 1.2, 1.6 and 1.8.

FIG. 2 shows the state of uneven distribution of the raw material in the blast furnace furnace in the radial direction and the ore and coke particle size ratios (D _O / D).
_C ) (represented by symbols such as ● and ○ in the figure). (Charged O / C ratio) in (Deposited O / C ratio) / (Charged O / C ratio) on the vertical axis is a weight ratio of charged ore to charged coke, and (Deposited O / C ratio) Ratio) is the weight ratio of similarly deposited ore to coke deposited in the furnace. When the charged ore and coke are deposited in the furnace in a state of being uniformly mixed without uneven distribution, the (deposited O / C ratio) becomes the same value as the (charged O / C ratio). Therefore, when the value of (deposition O / C ratio) / (charge O / C ratio) on the vertical axis of FIG. 2 is 1, it indicates that there is no uneven distribution of the raw material, and when it exceeds 1, the ore is unevenly distributed.
If it is less than 1, it indicates that coke is unevenly distributed. The horizontal axis is a dimensionless distance where the distance between the furnace center and the furnace wall of the model furnace used in the experiment is 1.0.

[0023] As shown in FIG. 2, (in the case of 0.6 and 1.0) D _O / D when _C is small, the coke is unevenly distributed in the region of the furnace center side, the furnace wall near the furnace middle portion There is a lot of ore throughout the part, and the degree of uneven distribution increases as D _O / D _C decreases. On the other hand, when D _O / D _C is large (in the cases of 1.6 and 1.8), conversely, ore is ubiquitous in the furnace center region and coke is unevenly distributed in the region near the furnace wall. Therefore, the degree of the reverse segregation increases as D _O / D _C increases.

However, when D _O / D _C is 1.2, there is no uneven distribution of coke and ore, and coke and ore are evenly mixed in the radial direction in the blast furnace. This indicates that the particle segregation effect caused by the density difference between coke and the ore cancels out the particle segregation effect caused by the particle size difference, and that a state where the two are not separated even when mixed is realized.

The above-described uneven distribution of the raw materials in the deposited layer after the ore and the coke having the density difference and the particle size difference are simultaneously charged and deposited in the furnace is caused by the following mechanism. It is considered something.

FIGS. 3A and 3B are conceptual diagrams for explaining the classifying and depositing action in the process of depositing mixed particles having a difference in particle size or density in a furnace. FIG. Is the case where there is a density difference.

As shown in FIG. 3 (a), when the particles having different particle sizes flow down the slope in a mixed state, the small particles A pass through the gaps between the large particles B. Then move to the lower layer. 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. The larger the particle size difference between the particles A and the particles B, the larger the latter as the velocity gradient in the direction perpendicular to the slope of the mixed particles flowing down becomes larger, and the classification by the particle size difference is promoted. Therefore, the particles A having a small particle size are classified near the falling point and deposited near the furnace wall on the upstream of the slope, and the particles B having a large particle float near the falling point and are transported to the downstream of the slope. Will be unevenly distributed.

On the other hand, as shown in FIG. 3B, when particles having different densities flow down the slope in a mixed state, when particles having the same density collide with each other among particles flowing down. The repulsion when the low-density particles B collide with the high-density particles A is greater than that of the high-density particles A, so that coarse voids due to the particles B are generated near the high-density particles A. As a result, the probability that the particles A pass through the gap and move to the lower layer increases. Therefore, the high-density particles A are subjected to the classification action near the drop point and accumulate near the furnace wall upstream of the slope, and the low-density particles B float near the drop point and are transported downstream of the slope to the furnace center. Will be unevenly distributed.

The inventor of the present invention has determined that the above-mentioned uneven distribution of a specific raw material in the deposition layer of the mixed raw material is determined by the probability that the mixed raw material particles flowing down the slope are classified and deposited in the deposition process. It is considered that the ratio varies depending on the density difference of the mixed particles, the particle size ratio in consideration of the particle size distribution, the charging ratio, and the charging speed. Then, the probability of classification and deposition was quantified based on the measured values of the uneven distribution of the raw materials in the charging model experiment in which these were changed, and a mixed raw material uneven distribution prediction model in the radial direction of the furnace in the furnace was created.

Using the mixed raw material uneven distribution prediction model, the results of calculating the distribution of the raw material particles in the radial direction in the furnace for each case of the raw material charging experiment performed with the above blast furnace furnace top model are shown in FIG. Shown.

The calculated values indicated by the solid line and the broken line in FIG. 2 substantially coincide with the measured values described above, and it is possible to simulate the distribution of the raw materials deposited in the blast furnace in the radial direction inside the furnace. I found it to be.

Therefore, using the above mixed raw material uneven distribution prediction model, an actual blast furnace (internal volume 2700 m ³ , air flow: 4400 N
(m ³ / min). Table 1 shows the raw material charging conditions and raw material particle size conditions at this time.

[0033]

[Table 1]

FIG. 4 shows the calculation results of the radial distribution in the furnace of the coke abundance ratio in the ore and coke simultaneous charging layers. The horizontal axis is the furnace radius, where the distance between the furnace center and the furnace wall is 1.0.

As is apparent from this figure, in the case where coke A having a large particle size is simultaneously charged with ore (case 1), or in the case where coke B having a small particle size is simultaneously charged with ore (case 2). In the same manner as in the results of the basic experiment using the blast furnace top model described above, coke A was unevenly distributed from the center of the furnace to the middle, and coke B was unevenly distributed around the furnace wall. Even if the ratio is 3% by weight, there is a portion locally exceeding 5% by weight.

On the other hand, when coke C having a particle diameter D _O / D _C of 1.23 is simultaneously charged with ore at a mixing ratio of 3% by weight (case 3), similarly, coke C is mixed at a mixing ratio of 5% by weight. The coke abundance in the furnace in the radial direction after charging when the ore and the ore were charged simultaneously (case 4) was almost the same as the ratio at the time of charging (3% by weight and 5% by weight, respectively). There are no uneven parts.

Case 5 is a highly reactive coke D
Was mixed with ore at a mixing ratio of 3% by weight. However, since the particle size was the same as that of coke C, the distribution pattern in the radial direction did not change, and the same result as in Case 3 with a mixing ratio of 3% by weight was obtained. .

From the above numerical study results, it is necessary to satisfy the condition of the following formula (1) in order to cancel the effect of segregation of particles between coke (particle diameter D _C ) and ore (particle diameter D _O ). I understand. However, this condition is a condition corresponding to a case where the particle density ratio (the ratio of the apparent density between ore and coke) is 3.0.

1.20 <D _O / D _C <1.60 (1) The coke mixed in the ore layer is heated while descending in the blast furnace, and is generated by the ore reduction reaction. Coke gasification reaction due to carbon dioxide gas (CO ₂ ) occurs, the strength is deteriorated (reaction deterioration) and powdered,
The particle size gradually decreases.

The coke gasification reaction reaches a peak in the ore softening and melting zone, but when the coke whose particle size is particularly reduced due to the reaction deterioration reaches the lower part of the furnace, it deteriorates gas permeability and liquid permeability, adversely affecting the furnace condition. give. Therefore, for coke having a relatively small particle size and the same size as ore, it is effective to completely extinguish the coke by the gasification reaction in the ore softening and melting zone in order to enhance gas permeability and liquid permeability.
In addition, by activating the coke gasification reaction in the ore softening and melting zone, the ore reduction reaction is also activated, so that the ore's burn-through properties are improved and the increase in airflow resistance due to fusion of the ore is moderated. be able to.

The conditions under which the coke mixed in the ore layer is eliminated by the reaction in the ore cohesive zone are determined by the initial particle size of the coke and the mixing ratio of the ore.

The behavior of particle size deterioration of coke due to the coke gasification reaction has been clarified by Iwanaga et al. (Sumitomo Metals, Vol. 32, No. 1, p1). Under the in-furnace conditions estimated in each case of Table 1 above, it was determined whether or not coke mixed with ore and charged at the same time would disappear in the ore cohesive zone.

FIG. 5 shows the result. The horizontal axis in the figure is the particle size (D _C ) of coke mixed in the ore layer, and the vertical axis is the maximum coke mixing ratio allowable when charging the ore and coke simultaneously. Cases 1 to 5 correspond to cases 1 to 5 in Table 1.
Corresponding to 5. ○ and ○, □ and の, and △ and の in the figure represent coke existing at the center, the middle, and the periphery of the furnace wall of the furnace, respectively. The determination as to whether or not the coke reacted and disappeared was performed twice in each case to examine the degree of variation.

In FIG. 5, the shaded portion is the range in which coke charged simultaneously with the ore in the ore softening and melting zone disappears due to the gasification reaction, and the coke remains in other portions. The value of C in the figure is an index representing the reactivity of coke, and the larger the value, the better the reactivity. The larger the value of C (ie, the greater the reactivity of coke). It can be seen that the shaded area is enlarged and the coke is easily extinguished.

The maximum allowable coke mixing ratio X at the time of simultaneous charging is expressed by the following equation (2) when C = 27% in consideration of the reactivity of ordinary coke. That is, the allowable mixing ratio X as the coke particle size D _C is increased is reduced.

X <3.2 − {(D _C −20) / 25} (2) As is apparent from FIG. 5, in case 1, the furnace is located from the center of the furnace where coke A having a large particle size is unevenly distributed. In the middle, there is coke that does not disappear in the reaction. In Case 2, unreacted coke B remains around the furnace wall because the amount of uneven distribution around the furnace wall is large despite the small particle size of coke B. In Case 3, since coke C satisfies the above formula (1), there is no uneven distribution in the furnace in the radial direction after charging, and the coke C is uniformly distributed at the initial mixing ratio and mixed in the ore layer. All the coke that has been reacted disappears in the ore softening and melting zone. However, in Case 4, although coke C is used, there is no uneven portion of coke in the radial direction in the furnace, but the mixing ratio at the time of charging is high, and the reaction does not disappear in the cohesive zone.

In case 5, the particle size and the mixing ratio were the same as in case 3, but coke D (C = 3) having high reactivity was used.
Since 3) is used, the maximum coke mixing ratio X that can be eliminated in the ore softening and melting zone increases. This means that by using highly reactive coke, it is possible to increase the amount of coke that can be mixed into the ore.

Therefore, in order to extinguish coke charged together with ore by the coke gasification reaction in the ore softening and melting zone and to maintain good air permeability, the condition for canceling the particle segregation effect in the blast furnace radial direction is (1). ), It is necessary to simultaneously satisfy the expression (2) that defines the coke disappearance amount.

As in the case of the above equation (1), the condition for offsetting the particle segregation effect between the MgO source auxiliary material (particle diameter D _F ) and the ore is determined by the particle density ratio (the ratio of the apparent density between the ore and the MgO source auxiliary material). ) Is 1.8, the following equation is obtained.

1.10 <D _O / D _F <1.15 (3) By satisfying the condition of the expression (3), the MgO source auxiliary material is uniformly distributed in the ore in the furnace radial direction. Due to the slagging action of MgO during softening and melting of the ore, the viscosity of the melt is reduced uniformly in the radial direction in the furnace, the ore's molten state is kept good, and the pressure loss at the time of dropping slag is reduced. be able to. That is, by mixing and charging the MgO source auxiliary material with the ore under the condition satisfying the expression (3), the high-temperature properties of the ore can be made uniform in the radial direction in the furnace, and the ventilation resistance in the furnace can be reduced. As a result, it is possible to suppress an increase in ventilation resistance due to an increase in the charged O / C ratio when the operation is shifted to the high PCI operation.

As described above, the coke and the MgO source auxiliary material are mixed with the ore charged into the blast furnace so that the above-mentioned equations (1) to (3) are simultaneously satisfied, whereby the coke and the ore in the furnace radial direction are mixed. At the same time, the coke in the ore layer reacts and disappears in the softening and melting zone, and at the same time, the high-temperature properties of the ore are uniformly improved in the radial direction inside the furnace, maintaining good air permeability and liquid permeability of the blast furnace. , Stable operation can be performed.

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

[0053]

EXAMPLE A blast furnace operating method of the present invention was carried out using a blast furnace having a furnace inner volume of 2700 m ³ , and a conventional operating method and an operating method under conditions deviating from the provisions of the present invention for comparison were carried out. In the furnace.

In the operation of the example and the comparative example, the coke alone was charged, and the ore was mixed with coke and Mg mixed therewith.
The simultaneous charging of the O-source auxiliary material was alternately repeated and laminated in the furnace. In the operation of the conventional example, the coke-only charging and the ore-only charging were alternately repeated and laminated in the furnace. The air volume was 4400 Nm ³ / min in each case.

Table 2 shows the raw material charging conditions and the raw material particle size conditions of the examples, comparative examples 1 to 4, and the conventional example. In addition, the conditions inside the furnace during operation, that is, blast pressure fluctuation, number of slip occurrences, ventilation resistance index, fluctuation rate of hot metal Si concentration, furnace core
The table also shows the weighted average particle size (measured value of tuyere coke sample) and fluctuation range of hot metal temperature.

[0056]

[Table 2]

[0057] As shown in Table 2, is performed simultaneously charging of ore and coke and MgO sources adjuncts, D _O is D
_In Comparative Example 1, which is 0.35 times _C , compared to the conventional example in which coke was not mixed into the ore, the Si concentration of the hot metal and the hot metal temperature fluctuated, and the number of slip occurrences also increased. Operations have turned to instability. The reason is that the coke is co-distributed to the furnace center region because the particle size ratio of the ore to the co-charged coke is smaller than the stipulation in the present invention, and the coke of reduced strength is supplied to the furnace lower part. This is considered to be due to the deterioration of the liquid permeability of the air.
Although not shown, due to the uneven distribution of coke in the furnace center region, an increase in the furnace top gas temperature and a decrease in the CO gas utilization rate in the furnace center region were observed as compared with the conventional example.

The conditions of Comparative Example 1 are as described in JP-A-4-63.
No. 212 satisfies the relationship between the coke mixing ratio and the mixed coke particle size described in the method described in JP-A-212. That is, the mixing ratio of coke to ore is 3% by weight,
From the coarser coke of the comparative example mixed with the ore,
The average particle size of 0% by weight is 52.6 mm.
This is well above the minimum value shown in the method described in JP-A-63212, that is, 20 + 3.0 = 23.0 mm. However, as described above, the degree of improvement in operation stabilization was insufficient. This is disclosed in Japanese Unexamined Patent Publication No. 4-63.
This shows that the range specified by the method described in Japanese Patent Publication No. 212 is insufficient as charging conditions for maintaining stable blast furnace operation.

Also in the case of Comparative Example 2 in which D _O was 1.7 times as large as D _C , gas leak and slip occurred particularly on the furnace wall side due to deterioration of air permeability, resulting in deterioration of the furnace condition. In this case, coke mixed with ore and co-charged around the furnace wall remained in the area below the cohesive zone and became finer, resulting in poor air permeability and fluctuations in gas flow. Is thought to be the cause.

On the other hand, in the embodiment in which D _O is 1.23 times D _C , the number of slips is reduced, the air permeability is improved, the blast pressure fluctuation is reduced, and the furnace condition is extremely stabilized. .

On the other hand, as in Comparative Example 3, when the particle size of the MgO source auxiliary material is smaller than that of the ore (D _O / D _F = 1.
In the case of 51), when the mixed raw material in which the coke and the MgO source auxiliary material were mixed into the ore was charged, the MgO source auxiliary material was deposited near the furnace wall near the drop point due to particle size segregation, so that the ore high-temperature properties in the peripheral portion improved. However, especially in the middle part of the furnace in the radial direction with a high O / C ratio, the ventilation resistance at the time of ore fusion increased, and the furnace condition deteriorated as seen in the increase in the blast pressure fluctuation.

On the contrary, as in Comparative Example 4,
When the particle size of the MgO source auxiliary material is larger than the ore (D _O
/ D _F = 0.82) means that when the mixed raw material is charged, the MgO source auxiliary raw material is unevenly distributed in the center of the furnace due to the synergistic effect of the difference in particle size and the difference in density, and extends from the intermediate portion in the radial direction inside the furnace to the vicinity of the furnace wall. However, the increase in air flow resistance at the time of ore fusion caused fluctuations in load drop, leading to deterioration of the furnace condition due to an increase in the number of slips.

On the other hand, in the embodiment in which D _O / D _F = 1.12, the ventilation resistance at the time of ore fusion was uniformly reduced in the radial direction in the furnace. Was completed.

[0064]

According to the blast furnace operating method of the present invention, the distribution of the O / C ratio in the furnace radial direction in the ore layer is controlled, and the coke in the ore layer charged at the same time reacts and disappears in the softening and melting zone. At the same time, the high-temperature properties at the time of ore fusion are improved, and the air permeability and liquid permeability of the blast furnace can be kept good, and the furnace condition can be stably maintained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a half-cut model of a top blast furnace of 1/7 scale of an actual blast furnace used for a charging experiment, (a) is a perspective view in three dimensions,
(B) is a half-section vertical sectional view.

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

FIGS. 3A and 3B are diagrams illustrating a classification and deposition effect in a process of depositing mixed raw material particles in a furnace, wherein FIG. 3A is a diagram illustrating a classification effect due to a difference in particle diameter, and FIG. .

FIG. 4 is an estimation diagram of a distribution state of a coke abundance ratio in a furnace radial direction in a layer deposited in the furnace after simultaneous charging of ore coke.

FIG. 5 is a view for explaining conditions for extinguishing coke simultaneously charged with ore by a reaction in a softening and melting zone.

[Explanation of symbols]

 1: Blast furnace top half cut model 2: Bell 3: Bell cup 4: Bell lift drive unit 5: Armor 6: Coke layer 7: Coke mixed or single ore layer 8: Furnace top side wall 9: Acrylic plate half cut surface 10: Charge material

Claims (1)

(57) [Claims] A blast furnace operating method in which ore and coke are repeatedly charged into a blast furnace by layer, wherein the ore satisfies the following expressions (1), (2) and (3) simultaneously. A blast furnace operating method comprising mixing coke and an MgO source auxiliary material into the blast furnace. 1.20 <D _O / D _C <1.60 (1) 1.10 <D _O / D _F <1.15 (2) X <3.2 − ｛(D _C −20) ) / 25} · (3) where, D _O: weighted average particle size of the ore (mm) D _C: weighted average particle size of the coke (mm) D _F: weighted average particle size (mm of MgO source auxiliary material) X: weight ratio of coke to ore mixed with ore (%)