JP2017048464A - Method for raw material charge to blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a raw material charge method for improving permeability in an operation of coke layer thickness.SOLUTION: A charge of iron raw material in charged raw materials is divided and carried out two or more times, and at the second charge or later, at least 80 mass% of the gross quantity of block ore is charged as iron raw material in an area of no dimension radius (r/R):0.2-0.8 in which a radius position (r) in a blast furnace throat is made dimensionless by a throat radius (R).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a raw material charging method for a blast furnace in which the raw material is charged into the blast furnace with a turning chute.

In recent years, reduction of CO ₂ emissions has been demanded from the viewpoint of suppressing global warming.
In the steel industry, about 70% of CO ₂ emissions are from blast furnaces, so reduction of CO ₂ emissions in blast furnaces is required. Reduction of CO ₂ emissions in the blast furnace is possible by reducing reducing materials (coke, pulverized coal, natural gas, etc.) used in the blast furnace. In order to reduce this reducing material, it is necessary to improve the reduction efficiency of the ore layer.

  According to Non-Patent Document 1, it is considered effective to reduce the thickness of the ore layer and reduce the thickness of the unreduced portion in order to improve the reduction efficiency of the ore layer.

However, when the thickness of the ore layer is reduced as described above, the coke layer thickness is also reduced at the same time. It is empirically known that when the coke layer thickness is reduced in the blast furnace, the airflow resistance in the cohesive zone where the ore softens and melts increases, thereby hindering stable operation.
For example, Non-Patent Document 2 shows that the ventilation resistance of the blast furnace increases when the coke layer thickness is 180 mm or less as an average value in the flank of the blast furnace.

Accordingly, various operations have been proposed for securing the coke layer thickness to a specified value or more against the destabilization of the blast furnace operation due to such an increase in ventilation resistance.
For example, Patent Document 1 defines a lower limit of the coke layer thickness that should be secured in order to prevent local occurrence of a portion having a thin coke layer thickness. Here, if a furnace port average of 600 mm or more is secured, the coke layer thickness in the furnace is not locally lower than the lower limit.

  Further, Patent Document 2 proposes to secure an average coke layer thickness of 250 mm or more in the furnace belly in order to prevent an increase in ventilation resistance in the cohesive zone.

  Furthermore, in Patent Document 3, the charging of the raw material is divided into the furnace center part and the furnace peripheral part, and the ratio of the iron raw material and coke having a high reduced powdering index in the furnace peripheral part is made higher than those in the furnace central part. It has been proposed to improve the breathability in the furnace.

Japanese Patent Laid-Open No. 7-18310 JP-A-6-136414 JP 2012-113032 A

Materials and Processes Vol.13, p.894 (2000) Iron and Steel, Vol. 87, No. 5, 342 (2001)

  However, the techniques described in Patent Documents 1 and 2 described above only define the average layer thickness of the coke layer to be secured, and do not consider the air permeability on the ore layer side. In addition, the technique described in Patent Document 3 gives the mixing ratio of coke in the ore layer where air permeability is not hindered from the standpoint of reduced powdering, and also defines the ratio of coke. It was not.

  The present invention has been developed to solve the above-described problems, and an object of the present invention is to provide a raw material charging method for improving air permeability in an operation with a thin coke layer thickness.

The inventors diligently investigated the air permeability in an operation with a thin coke layer, and found that considering the softening and melting behavior on the ore layer side is extremely effective for improving the air permeability, and completed the present invention. Arrived. That is, the gist configuration of the present invention is as follows.
1. In a raw material charging method for alternately charging coke and iron raw material into a blast furnace using a turning chute from the top of the blast furnace, an ore raw material containing at least sintered ore and at least 10% by mass of lump ore In the blast furnace as an iron raw material,
Performing the charging of the iron raw material in two or more steps,
In the second and subsequent charging of the iron raw material, a dimensionless radius (at which the radius position (r) at the blast furnace furnace mouth is made dimensionless by the furnace mouth radius (R) at least 80% by mass of the total mass of the ore. r / R): A raw material charging method into a blast furnace, characterized by charging in a range of 0.2 to 0.8.

  Here, the ore raw material refers to ores that are iron raw materials such as sintered ore other than lump ore, iron oxide pellets, and iron scrap.

2. 2. The raw material charging method to the blast furnace according to 1 above, wherein the lump ore has a crystal water content of 6% by mass or more.

3. 3. The raw material charging method to the blast furnace according to 1 or 2 above, wherein Lc / Dc is 2 or less, where Lc is the layer thickness (mm) of the coke and Dc is the average particle size (mm). .

4. A dimensionless radius (r / R) obtained by making the radial position (r) at the furnace mouth of the blast furnace non-dimensional with the furnace mouth radius (R) of 60% by mass or more of the lump ore charged after the second time. ) Is charged in the range of 0.2 or more and less than 0.58, The raw material charging method to the blast furnace according to any one of the above 1-3.

  According to the present invention, for example, even in an operation for reducing the thickness of the coke layer, the air permeability of the blast furnace can be improved by charging the lump ore which causes the deterioration of air permeability at an appropriate position. . Therefore, it becomes possible to stabilize the blast furnace operation even under low coke ratio operation, which is an operation to reduce the coke layer thickness.

It is a schematic diagram of an experimental apparatus. It is a figure which shows the experimental result which showed the influence which crystallization water content has on the ventilation resistance of a cohesive zone. It is a figure which shows the experimental result which showed the influence which coke slit layer thickness has on the ventilation resistance of a cohesive zone. (A), (b) is a schematic diagram which shows the melting behavior in a cohesive zone.

Hereinafter, the present invention will be specifically described.
First, the elucidation process of the segregation charging condition of the lump ore will be described among the conditions of the present invention.
The inventors conducted reduction tests simulating conditions in the blast furnace in order to investigate the influence of various block ores on the permeability of the cohesive zone in the blast furnace, and confirmed the behavior of the block ore.

FIG. 1 shows a schematic diagram of an apparatus used for investigating the relationship between the coke layer thickness and the gas flow resistance of the cohesive zone. In the figure, reference numeral 1 denotes a sample heating furnace, and the sample heating furnace 1 includes a sample filling container 2 and a heating device 3 therein. Inside the sample filling container 2, a sample filling layer 6 in which the coke layer 4 and the sample layer 5 (iron raw material layer) are filled in layers is formed. The temperature of the sample packed layer 6 is controlled by the heating device 3.
Reference numeral 7 denotes a gas heating furnace, and the gas heating furnace 7 also includes a heating device 8 therein. 9 is a gas mixer, 10 is a gas distribution pipe, 11 is a pressure gauge, 12 is a thermocouple, 13 is a holding plate, 14 is a pedestal, and 15 is a connecting rod. This connecting rod is made of graphite or metal. It is preferable that

Further, reference numeral 16 denotes a load means, and a weight is used in FIG. The weight 16 applies a load simulating the inside of the blast furnace to the sample packed layer 6.
In this measuring apparatus, the sample heating furnace 1 and the gas heating furnace 7 are arranged in parallel. Thus, since it was arranged in parallel, the gas heated in the gas heating furnace 7 enters the sample heating furnace 1 from the lateral direction. As a result, as shown in FIG. 1, since the invading heated gas flows horizontally through the sample packed bed 6 in the sample packed container 1, the gas flow in the blast furnace cohesive zone can be reproduced.

  Ventilation resistance of the cohesive zone was measured using the above test apparatus while changing the state of loading of the block ore in the sample layer 5 in various ways. Table 1 shows the experimental conditions at that time. The lump ore used in this experiment had a particle size of 4.8 to 6.7 mm, and the sintered ore had a particle size of 4.8 to 6.7 mm. In Table 1, the upper layer is a region above the center of the total thickness of the sample layer 5 (iron raw material layer), and the lower layer is a region below the center of the total thickness of the sample layer 5 (iron raw material layer). is there. Similarly, “block ore + sintered ore” indicates a mixture of the block ore and the sintered ore uniformly (the block ore is uniformly dispersed in the target upper layer or lower layer).

  Here, the experiment was conducted by changing the lump ore charging method (mixed uniformly in the sample layer, segregated in the upper layer of the sample layer, segregated in the lower layer of the sample layer), the crystal water content of the lump ore, and the coke layer thickness. It was. When the coke layer thickness was changed, the gas flow rate was also changed so that the initial gas flow rate per unit volume was constant. Lc represents the coke layer thickness (mm), and Dc represents the coke average particle diameter (mm).

  FIG. 2 shows the influence of the lump ore charging method and the lump ore crystal water content on the ventilation resistance under the conditions of Lc / Dc = 2 in Table 1 and the temperature of the sample packed bed 6 being 1400 ° C. Since the coke layer thickness and the coke average particle size both affect the airflow resistance, the coke layer thickness (Lc) was evaluated by an index (Lc / Dc) normalized by the coke average particle size (Dc). . In addition, in FIG. 2, ◯: represents one in which the lump ore is uniformly mixed in the sample layer, □: represents one in which the lump ore is segregated in the upper layer of the sample layer, and Δ represents one in which the lump ore is segregated in the lower layer of the sample layer. ing.

  As can be seen from FIG. 2, when the massive ore is segregated on the upper layer of the sample layer 5, the airflow resistance of the sample packed layer 6 is greatly improved. In particular, when a high crystal water block ore having a crystal water content of 6% by mass or more is used, when the block ore is segregated in the upper layer of the sample layer 5, the increase in ventilation resistance is sufficiently suppressed. Recognize.

  In addition, the higher the crystallization water content, the higher the airflow resistance improvement effect in the cohesive zone. Since the deterioration becomes remarkable, the effect of improving the ventilation resistance as the whole blast furnace is lowered. Therefore, it is preferable to use a lump ore having a crystal water content of 10% by mass or less.

Further, FIG. 3 shows that the lump ore charging method and index (Lc / Dc) are the sample packed bed 6 under the condition that the crystal water content of the massive ore is 8 mass% and the temperature of the sample packed bed 6 is 1400 ° C. The effect on the ventilation resistance is shown. From FIG. 3, it can be seen that when the massive ore is segregated in the upper layer of the sample layer 5, the airflow resistance is greatly improved. In particular, it is understood that when the coke having Lc / Dc of 2 or less is segregated to the upper layer of the sample layer 5, the increase in the airflow resistance is sufficiently suppressed. In addition, (circle), (square), and (triangle | delta) in FIG. 3 means the charging method similar to the code | symbol in FIG.
From the above, it has been found that segregating (mixing) the lump ore into the upper layer of the sample layer 5, that is, the iron raw material layer, is effective in improving the air permeability in the blast furnace under the condition that the coke layer is thin.

Next, the raw material of the present invention, the raw material charging procedure, and the raw material charging position will be described.
The present invention is a method of charging iron raw material and coke into a blast furnace, and the raw material charging into the blast furnace can use a bellless type charging device equipped with a publicly known swivel chute.

The iron raw material and coke are respectively stored in the furnace top bunker. And the raw material charging order from these furnace top bunkers is as follows.
First, charge coke. That is, when the raw material charging destination of the swirl chute is moved from the center of the blast furnace toward the inner peripheral portion of the blast furnace wall, only the coke is charged from the furnace top bunker storing only the coke. Form.
At that time, a central coke layer is formed in the central part of the blast furnace, or the central axis part (furnace port dimensionless radius: 0) from the furnace wall part (furnace port dimensionless radius: 1.0) to the inner peripheral part of the furnace wall. ), A peripheral coke layer may be formed.

  In addition, when the raw material charging destination of the turning chute is facing the furnace wall of the blast furnace, the flow rate adjustment gate of the furnace top bunker where the iron raw material is stored is closed, and the flow adjustment of only the furnace top bunker where only the coke is stored By opening the gate and supplying only the coke stored in the furnace top bunker to the turning chute, a coke layer can be formed or a central coke layer can be formed at the center of the blast furnace.

  Next, the iron raw material is cut out from the top bunker and charged into the blast furnace. In this case, the blast furnace is moved from the position near the center axis of the blast furnace, that is, the dimensionless radius of the furnace port is zero. It is preferable to leave the outer side from the central axis and finally charge the furnace wall (furnace port dimensionless radius: 1.0) side.

Here, according to the present invention, when the iron raw material is charged into the blast furnace, 10% by mass or more in one charge of the iron raw material is required to be the lump ore.
This is because, conventionally, when the use ratio of the lump ore becomes 10% by mass or more, the reduction material ratio has been inevitably increased. However, if the present invention is applied, the air permeability is improved and the reduction efficiency is improved, so that an increase in the reducing material ratio, which was conventionally unavoidable when the use ratio of the lump ore is 10% by mass or more, is avoided. Can do. In addition, when the usage-amount of a lump ore exceeds 30 mass%, there exists a possibility that a raise of ventilation resistance may not be suppressed, Therefore It is desirable that the lump ore mixed with an iron raw material is 30 mass% or less.

In the present invention, the iron raw material includes an ore raw material containing at least sintered ore and a lump ore. The ore raw material occupying the iron raw material is the remainder excluding the above-mentioned massive ore.
The ore raw material used in the present invention includes at least sintered ore, but may include those normally used as blast furnace charging raw materials such as iron oxide pellets and iron scrap. In addition, it is preferable that the ratio of the sintered ore in an ore raw material is 50-100 mass% at the point which ensures the reducibility of an iron raw material.

  And, as explained in the above elucidation process, the greatest feature of the present invention is to segregate the lump ore. As a specific procedure, the charging of the iron raw material is divided into two or more times. In the second and subsequent iron raw material charging, at least 80% by mass of the total amount of ore of one charge is charged as the iron raw material, and the second and subsequent iron raw materials are radiused at the blast furnace furnace mouth. Dimensionless radius (r / R) obtained by making the position (r) dimensionless with the furnace port radius (R) is charged in the range of 0.2 to 0.8. By setting it as this procedure, the said lump ore can be segregated and charged to the upper layer of the said iron raw material layer.

In general, when performing blast furnace operation, air permeability is maintained by ensuring a gas flow in the central part of the blast furnace and a gas flow in the peripheral part. That is, in order to ensure the gas flow, the operation is performed by reducing the thickness of the iron raw material layer having a large ventilation resistance. Therefore, the central portion and the peripheral portion of the blast furnace are regions where the thickness of the iron raw material layer is thin, and the middle portion thereof is a region where the iron raw material layer is thick. Specifically, the region where the dimensionless radius r / R of the blast furnace is 0.2 to 0.8 is usually a region where the iron raw material layer is thick.
Therefore, in the present invention, the raw material charging procedure in this region is defined as described above. By complying with such regulations, it is possible to effectively improve the air permeability of the blast furnace even under low coke ratio operation. Furthermore, among these, the region where the radius r / R of the blast furnace is 0.2 or more and less than 0.58 is a region where the iron material layer is particularly thick. Therefore, it is preferable to segregate the lump ore into the upper layer of the iron raw material layer in this region, and it is preferable to charge 60% or more of the raw material charging after the second time into this region.

  It is desirable that the iron raw material charged for the first time does not contain lump ore, but if less than 20% by mass of the total lump ore charge in one charge, an increase in ventilation resistance is suppressed. In addition, it may be contained in the iron material charged in the first time for forming the lower layer.

Furthermore, the schematic diagram in a blast furnace when an iron raw material fuse | melts in FIG. 4 is shown. FIG. 4A shows a state in which the lump ore is segregated in the lower layer of the iron raw material layer, and FIG. 4B shows a state in which the lump ore is segregated in the upper layer of the iron raw material layer.
As shown in FIG. 4 (a), when the lump ore is segregated in the lower layer of the iron raw material layer, the molten lump ore is in contact with the coke layer, so that the melt falls and enters the coke layer. Go. Therefore, when the ore is segregated in the lower layer of the iron raw material layer, if the coke layer is thin, the coke layer is blocked and the ventilation resistance in the blast furnace is increased.

  On the other hand, as shown in FIG. 4B, when the lump ore is segregated in the upper layer of the iron raw material layer, the iron raw material layer mixed with the lump ore is in the upper layer of the iron raw material layer and the coke layer. Since it is not in contact, even if the lump ore softens from a low temperature to form a melt, the melt does not enter the coke layer. For this reason, the coke layer does not block, and therefore, when the ore is segregated and mixed with the upper layer of the iron raw material layer, the ventilation resistance does not increase. Furthermore, the effect that the ventilation resistance is maintained even under the condition that the coke layer is thin is also exhibited. The same applies to the case where the lower part of the iron raw material layer contains lump ore less than 20% by mass of the total lump ore. When the lump ore amount is small, the lump ore softens and melts. Even if produced, the coke layer is prevented from being blocked by staying in the iron raw material layer formed in a large amount of sintered ore.

  In particular, when a high crystal water block ore with a crystal water content of 6% by mass or more is used, softening of the block ore starts from a low temperature, and a melt is generated to reduce the amount of intrusion into the coke layer. Therefore, the thickness of the intrusion layer of the molten iron material increases. As a result, the coke layer through which the gas can easily flow is reduced and the ventilation resistance is increased. Even in this case, according to the present invention, the mass ore is segregated to the upper layer of the iron raw material layer, so that the melt does not enter the coke layer as shown in FIG. Is suppressed. Therefore, when using a high crystal water block ore, the effect by this invention is remarkable.

Here, in the experiments shown in FIGS. 2 and 3, the upper layer is an area above the center of the total thickness of the iron raw material layer and the lower layer is an area below the center of the total thickness of the iron raw material layer. However, the region for segregating the lump ore is not limited to this. That is, if at least 80% by mass of the total amount of the lump ore is charged after the second time of the iron raw material, an upper layer portion in which the lump ore is segregated is formed above the iron raw material layer. This segregation area of the lump ore is formed within a range within 70% of the total thickness from the surface of the iron raw material layer.
Further, when segregating the lump ore, it is not necessary that the lump ore is mixed evenly in the sintered ore, and it is sufficient if they are simply mixed.

In this example, a blast furnace having an internal volume of 5000 m ³ was used, and coke and iron raw materials were alternately charged into the blast furnace using a turning chute.
In addition, as an iron raw material used for the present Example, all ore raw materials used the sintered ore whose iron content is 58 mass%, and a lump ore has an iron content of 60 mass% and has the crystallization water content shown in Table 2. A thing was used. The coke contained 88% by mass of carbon.
Furthermore, the charging method of the lump ore was changed, and the ventilation resistance index was evaluated for each charging method.
Specifically, in Comparative Examples 1, 2, 4, 6 and 7, 10 to 30% by mass of the iron raw material in one charge is uniformly mixed as a lump ore and the balance as a sintered ore. It was charged at once without splitting.

In Comparative Examples 3 and 5 and Invention Examples 1 to 6, 10 to 30% by mass of the iron raw material in one charge was used as a lump ore, and the iron raw material was charged in two portions.
The first time, the ore raw material and the iron raw material containing 30% by mass or 20% by mass or less of the total mass of ore in one charge are charged,
The second time, the remaining iron raw material (including the remaining lump ore not included in the first charging) was charged. The iron raw material was charged by discharging a predetermined amount of lump ore and ore raw material from the storage tank, transporting them to the furnace top bunker with a belt conveyor, and then charging them into the blast furnace. The ratio of the lump ore in the iron raw material was adjusted by changing the discharge amount of the lump ore in the first time and the second time. (Please check the description on the left because it seems to be inconsistent with the claims. 30% of the first time seems to be out of the scope of the invention, and the figures include the first and second times instead of the first time. Please confirm and answer.)
The second raw material charging position in each example was as shown in Table 2.

[Ventilation resistance index]
The ventilation resistance index can be obtained by the following equation.
Ventilation resistance index = (P _B ² −P _T ² ) / V ^1.7 × 100
Here, P _B : blowing pressure (kPa), P _T : furnace top pressure (kPa), and V: blowing amount (Nm ³ / min). The larger the ventilation resistance index, the higher the pressure loss in the furnace and the worse the air permeability, and the lower the air resistance index, the better the air permeability in the furnace.
Table 2 shows each experimental condition and experimental result.

From Table 2, Invention Example 1 is compared with Comparative Example 2 using a lump ore with the same crystallization water content, and even compared with Comparative Example 1 using a lump ore with a low crystallization water content, It can be seen that the ventilation resistance is improved. Therefore, the raw material charging method according to the present invention is not limited to the case where the lump ore having the same crystallization water content is mixed in the entire iron raw material layer, but the lump ore having a low crystallization water content is applied to the entire iron raw material layer. It was found that the coke ratio can be reduced compared to the case of mixing.
In addition, compared with the comparative example 1, the comparative example 2 is a case where the lump ore with much crystal water content is mixed with the whole iron raw material layer. As shown in Table 2, it can be seen that Comparative Example 2 has a high airflow resistance index because of the high crystal water content of the lump ore.

  In Comparative Example 3, the charging position of 80% by mass or more of the total mass of the ore is outside the scope of the present invention, and the ventilation resistance of Inventive Example 1 is improved when compared with Inventive Example 1 having the same furnace coke layer thickness. I understand that. That is, in Comparative Example 3, the lump ore was segregated in the upper layer, but since the raw material charging position was outside the range of the present invention, the airflow resistance index was comparable to that of Comparative Example 2.

  Next, when Comparative Example 4 is compared with Invention Examples 2 and 3 in which the furnace coke layer thickness is thin and ventilation is relatively poor, the ventilation resistance of Invention Examples 2 and 3 is greatly improved. I understand. In particular, as in Invention Example 3, when 60% of the whole ore out of the second and subsequent iron raw material charges is charged into the area of dimensionless radius r / R 0.2 or more and less than 0.58 of the blast furnace. It can be seen that the ventilation resistance is further improved, and the reducing material ratio can be reduced. This is because the presence of the lump ore particularly in the region where the ore layer is thick has a remarkable effect of suppressing the infiltration of the melt into the coke layer and suppressing the increase of the airflow resistance.

Further, when Invention Example 4 and Comparative Example 5 having different upper-layer lump ore ratios are compared, it can be seen that the ventilation resistance of Invention Example 4 satisfying the upper-layer lump ore ratio of 80% or more is improved.
Furthermore, when Invention Example 5 is compared with Comparative Example 6 where the mass ore ratio is 20% and the ventilation is relatively poor, it can be seen that the ventilation resistance of Invention Example 5 is improved. Furthermore, when Invention Example 6 and Comparative Example 7, which have a mass ore ratio of 30% and have poor ventilation, are compared, it can be seen that the ventilation resistance of Invention Example 6 is improved.

  From the above, it was confirmed that by increasing the segregation and mixing of the lump ore at an appropriate position in the upper layer of the iron raw material layer, it is possible to suppress an increase in ventilation resistance when using the lump ore with a high crystallization water content. . And suppression of the raise of this ventilation resistance leads to the stable blast furnace operation.

DESCRIPTION OF SYMBOLS 1 Sample heating furnace 2 Sample filling container 3 Heating device 4 Coke layer 5 Sample layer (iron raw material layer)
6 Sample packed bed 7 Gas heating furnace 8 Heating device 9 Gas mixer 10 Gas distribution pipe 11 Pressure gauge 12 Thermocouple 13 Presser plate 14 Base 15 Connecting rod 16 Load means (weight)

Claims (4)

In a raw material charging method in which coke and iron raw material are alternately charged into a blast furnace using a turning chute from the top of the blast furnace, an ore raw material including at least a sintered ore, and at least 10% by mass of lump ore In the blast furnace as an iron raw material,
Performing the charging of the iron raw material in two or more steps,
In the second and subsequent charging of the iron raw material, a dimensionless radius (at which the radius position (r) at the blast furnace furnace mouth is made dimensionless by the furnace mouth radius (R) at least 80% by mass of the total mass of the ore. r / R): A raw material charging method into a blast furnace, characterized by charging in a range of 0.2 to 0.8.   The method for charging a raw material into a blast furnace according to claim 1, wherein the lump ore has a crystal water content of 6 mass% or more.   The raw material charge to the blast furnace according to claim 1 or 2, wherein Lc / Dc is 2 or less, where Lc is the layer thickness (mm) of the coke and Dc is the average particle size (mm). Method. A dimensionless radius (r / R) obtained by making the radial position (r) at the blast furnace outlet non-dimensional with the furnace outlet radius (R) of 60% by mass or more of the lump ore charged after the second time is obtained. The raw material charging method to the blast furnace according to any one of claims 1 to 3, wherein the charging is performed in a range of 0.2 or more and less than 0.58.

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