JP3171066B2 - 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, and more particularly to a method for charging a raw material by controlling the deposition state of the raw material in the lower part of the blast furnace and the bottom of the furnace to suppress wear of the refractory at the bottom of the furnace due to hot metal flow. Blast furnace operation method.

[0002]

2. Description of the Related Art In recent years, the size of blast furnaces for producing pig iron has been increasing, and the cost of repairs has been enormous.
For this reason, in the recent blast furnace operation, prolonging the furnace life has become an important issue in addition to stable production of pig iron.

[0003] The service life of a blast furnace is judged based on the degree of damage to the furnace body, except for the blow stopper in accordance with the production plan. It depends on whether the inner surface of the furnace is seriously damaged.

[0004] In recent blast furnace operations, after the operation is started, the air is periodically or as required, and repair is performed from the inner surface of the furnace. Due to the progress of the repair technology, a certain degree of furnace body can be maintained in the side wall portion above the tuyere in the blast furnace body. However, the furnace body side wall portion and bottom portion below the tuyere (hereinafter, referred to as “hearth bottom wall” and “hearth bottom portion”, respectively) are portions where molten iron slag exists, and the contents below the tuyere It is not possible to make a radical repair for the damage of the part because it is not easy to discharge.
Therefore, it can be said that the damage condition of the furnace bottom side wall and the furnace bottom bottom determines the life of the blast furnace, and the main point of extending the furnace life is to prevent the damage of this part.

[0005] The blast furnace furnace body is composed of a steel shell constituting an outer wall, furnace body cooling means such as a stave, a cooling board, and a cooling pipe installed on the inner side thereof, and a refractory brick laid inside the furnace body. However, the suppression of damage to the furnace bottom and the furnace bottom side wall specifically means suppressing wear of refractory bricks on the furnace inner surface.

The mechanism of brick wear on the bottom and bottom walls of the hearth is complicated, but the main cause of the wear is the loss due to the flow of hot metal in contact with the brick surface. The more the hot metal flows, the more the brick wears. Therefore, in order to suppress brick wear on the furnace bottom and the furnace bottom side wall, it is necessary to control the liquid permeability of the furnace bottom and reduce the flow rate of hot metal near the furnace bottom and the furnace bottom side wall.

[0007] Conventionally, the charging of a Ti-containing iron source material into a blast furnace or the injection of tuyeres containing Ti ore into a blast furnace, which has been performed to suppress brick wear on the furnace bottom side wall or the furnace bottom, increase the Ti concentration. The purpose is to increase the viscosity of the hot metal, thereby reducing the flow velocity of the hot metal near the same portion. However, including
Ti ore is expensive, and its regular use will increase iron making costs. In addition, if a large amount of Ti-containing ore is used, there is a risk that the tapping and slagging conditions will deteriorate.

By the way, the falling behavior of the charge in the blast furnace is as follows (for example, the final report of the Blast Furnace Reaction Subcommittee of the Iron and Steel Institute of Japan and the Joint Research Group for Iron and Steel (July 1982): And its analysis ”in“ Comprehensive Examination Results of Demolition Surveys ”).

FIG. 7 is a schematic cross-sectional view for explaining a state inside the furnace determined by a conventional blast furnace dismantling survey.

[0010] The lump 29 in the upper half of the blast furnace 1 shown in the figure is a region where the alternately stacked coke layer and ore layer descend while maintaining the layered state. The lower softening zone 30 is an area where the ore layer softens and finally melts. When the ore layer dissolves and disappears, coke descent is accelerated,
A coke band 31 is formed between the lower part of the softening cohesive zone 30 and the coke deposit layer of the furnace core 32. This coke belt 31
Is a region where most of the coke is supplied to the combustion zone 24 at the tip of the tuyere 21 and part of the coke is supplied to the furnace core 32.

The furnace core 32 is a cone-shaped coke deposit (hereinafter referred to as "furnace coke deposit"), and coke in this region is mostly involved in the reaction except that it is consumed for dissolving carbon in molten iron. Not stay in the furnace for a long time. The space near the bottom 19 of the furnace bottom is not completely occupied by the core coke layer, but is occupied solely by hot metal without coke (hereinafter referred to as “coke-free layer (28)
") Can exist.

Since the coke-free layer 28 is a free space for the flow of hot metal, its liquid permeability is significantly higher than that of the core coke layer. For this reason, the presence or absence of the coke-free layer or its thickness is a factor that largely controls the flow of hot metal. In other words, this coke-free layer
If the 28 can be eliminated, the flow rate of the hot metal in the vicinity of the bottom 19 of the furnace bottom can be reduced, and the progress of the wear of bricks in the same portion can be suppressed.

The coke-free layer 28 is considered to be generated when the buoyancy of the hot metal acting on the core coke layer exceeds the dead weight of the core coke layer and the load of the charge above the core layer. Therefore, by increasing the own weight of the core coke layer or increasing the upper load applied thereto, the floating of the core coke layer can be prevented and the coke-free layer 28 can be eliminated. From this latter point of view, by increasing the iron source material / coke weight ratio (hereinafter referred to as “O / C ratio”) in the center of the furnace and increasing the load of the charge in the center of the furnace, the vicinity of the bottom of the furnace is increased. A method of suppressing the floating of the coke deposit layer is disclosed in Japanese Patent Publication No. 5-7443. However, raising the O / C ratio in the center of the furnace gives the above-mentioned effect to the bottom of the furnace and also affects the gas flow distribution in the radial direction above the tuyere. Hinders the efficient progress of
Furthermore, there is a risk that stable operation of the blast furnace may be impaired.

On the other hand, when coke and an iron source material (hereinafter, also referred to as "ore") are charged alternately from the furnace top, coke or air permeability and liquid permeability are improved in the ore layer or the central part of the coke layer. Japanese Patent Publication No. 5-8245 discloses a method in which a solid reducing agent suitable for the process is charged to make the radial distribution of air permeability and liquid permeability in the core coke deposition layer uniform. According to this method, the shape of the softening cohesive zone in the furnace becomes an inverted V-shape and a central flow can be obtained, which leads to stabilization of the operation. In addition, since molten iron slag flows at a uniform velocity at the bottom of the furnace at the time of tapping, the erosion rate of the peripheral wall of the furnace bottom due to the peripheral flow of molten iron due to reduced permeability of the core coke deposition layer is said to be suppressed. . However, as described above, a coke-free layer exists between the blast furnace furnace bottom and the core coke deposition layer. In this case, it is considered that the flow velocity of the molten iron slag flowing in the furnace bottom is governed by the thickness of the coke-free layer because the liquid permeability of the coke-free layer is much better than that of the core coke deposition layer. . Therefore, this method is effective for reducing the erosion of the bottom wall brick, but is not intended to reduce the erosion of the bottom brick by controlling the thickness of the coke-free layer.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the dead weight of a core coke layer, or further increase the load on the furnace upper part, thereby increasing the core coke deposition due to the buoyancy of molten iron. By preventing the levitation of the layer,
Without hindering efficient and stable pig iron production in the blast furnace,
An object of the present invention is to provide a method of operating a blast furnace, which can suppress brick wear on a furnace bottom and a furnace bottom side wall.

[0016]

The gist of the present invention resides in the following blast furnace operating method.

When the coke and the iron source material are alternately charged into the furnace from the top of the blast furnace, a part of the charged amount of the coke has an apparent specific gravity of 1.3 or more and a fixed carbon content of 80% by weight or more. Having a volatile content of 1% by weight or less and a particle size of 30 to
A method for operating a blast furnace to be replaced with a 200-mm lump, comprising:

[0018] Prior to the loading of the coke, usually
Using the charging device on a route different from the charging device, charging the above lump in the furnace central region with emphasis.

[0019] is prior to the loading of the iron source material, usually
Using a charging device with a different route from the charging device, (a) charging the lump or a part of the coke into the furnace central region with a focus, or (b) transferring iron scrap or reduced iron into the furnace Focusing on the central area.

The above-mentioned lump is obtained by crushing carbon-based or graphite-based bricks or electrodes, and acts as a reducing agent for an iron source material. The amount replaced by this agglomerate is the amount required to form one coke layer with normal charging.
Approximately 2 to 15% by weight of the coke amount per charge (hereinafter referred to as "coke base") is a standard. This amount of lumps will be replaced by the same amount of coke and will be used for focused charging into the furnace center area. Hereinafter, this lump is referred to as “alternate lump”.

The iron scrap used in the method of the present invention may be a commercial iron scrap, but it is desirable to use scrap from a steel mill that does not contain impurities such as Cu, Ni and Sn. The reduced iron may be of a generally high quality having a Fe purity of about 85% or higher, or a low quality of reduced iron produced from, for example, dust generated from an ironworks.

Normally, in the blast furnace operation, coke and an iron source material are charged alternately using a bell-type charging device or a bell-less type charging device provided at the furnace top, and deposited in a layered manner in the furnace. Hereinafter, this charging method is referred to as “conventional method”. The iron source material is mainly iron ore and sintered ore, and in the present specification, these are collectively referred to as “ore”.

FIG. 1 is a schematic cross-sectional view of the upper portion of a blast furnace for explaining an example of a raw material deposition state when the method of the present invention is carried out. (B) Similarly, iron scrap or reduced iron is charged into the center of the furnace.

As shown in FIG. 1 (a), the substitute mass is transferred to a charged object falling locus 9 via a hopper 8 and a charging chute 7 by using a charging device 6 on a different route from the normal charging device. Along the furnace center region, it is mainly charged to form the alternative lump deposit layer 11. Next, the coke 10 stored in the large bell 3 and the bell cup 4 of the bell-type charging device 2 is repelled by the movable armor 5 and charged into the periphery of the furnace as a charged material falling trajectory 9 '. The coke layer 12 is formed. At this time, the infiltration of the coke layer 12 into the coke layer 12 (hereinafter, referred to as “D region”) of the coke and the substitute lump is suppressed so that the substitute lump deposit layer 11 is not buried in the coke layer 12. Therefore, it is desirable to increase the ratio of the alternative mass in the D region. Then, from the charging device 6 on another route, as described above,
The alternative lump or coke is mainly charged into the furnace center region, and the alternative lump or coke deposition layer 13 is formed. Thereafter, the ore is supplied from the bell-type
The ore layer 15 is formed by charging 10 around the furnace. At this time, in order to control the air permeability in the D region and minimize the decrease in productivity, it is preferable that the alternative lump deposit layer or the coke deposit layer 13 is appropriately buried in the ore layer 15 (see FIG. (a)).

In the example of FIG. 1 (b), after forming the alternative lump deposit layer 11 in the furnace center region of the coke layer 12 as described above,
Scrap or reduced iron is mainly charged into the furnace central region from the charging device 6 of another route, and a scrap deposit layer or a reduced iron deposit layer 14 is formed. Thereafter, the ore 10 is charged from the bell-type charging device 2 into the periphery of the furnace.

On the raw material layer formed as described above, the raw material layers in the same charging order are again stacked as needed.

The coke or ore 10 charged from the bell type charging device 2 may be charged by dividing the charging amount per charge into a plurality of batches. Further, a bellless type charging device may be used instead of the bell type charging device.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic sectional view showing one of the inside states of a blast furnace for explaining the method of the present invention.
The figure shows a case of an embodiment in which the alternative lump is charged prior to charging coke, and coke is charged prior to charging ore into the furnace central region. In the following description, the method of charging only coke as center is described as the `` conventional method, '' where the alternative mass is centered before charging coke, but the center is charged before charging ore. The method that does not perform is referred to as a “comparison method”.

As shown in the figure, in the bulk portion of the upper half of the blast furnace, in the region from the periphery of the furnace to the middle of the furnace, for example, a coke layer 12 and an ore layer 15 charged from a bell-type charging device are alternately arranged. The layers are stacked and descend in the furnace while maintaining the layered state. In the furnace center region, the alternative lump deposit layer 11 and the coke deposition layer 16 charged from different route charging devices are lowered in the furnace in a state of being alternately stacked.

Here, the coke in the coke layer 12, the coke in the coke deposit layer 16 and the coherent material in the substitute clump deposit layer 11 which flowed into the area D shown in FIG.
17 fall into the furnace core coke deposition layer 25 and stay in the furnace for a long time. On the other hand, the coke 18 existing in the region from the furnace periphery to the furnace middle portion descends in the mortar-shaped region 23 formed by the core coke deposition layer 25 and the ore softening fusion layer 22, and the tuyere
It flows toward the tip of 21 and is burned and consumed in the coke combustion zone 24.

As described above, in the embodiment shown in FIG. 2 of the method of the present invention, the core coke deposited layer 25 has a coke 18 having an apparent specific gravity of about 1 and a substitute lump 17 having an apparent specific gravity of 1.3 or more.
And the gravity of the core coke layer 25
25 W can be increased compared to a case where only the conventional coke is charged. Accordingly, the gravity of the core coke layer 25
25W exceeds the buoyancy of the hot metal 26F and the core coke layer
25 can be reduced and the thickness of the coke-free layer 28 at the furnace bottom can be reduced. Accordingly, the flow velocity of the hot metal in the vicinity of the bottom 19 of the furnace bottom is reduced, and brick wear on the bottom 19 of the furnace bottom can be reduced.

In the comparative method described above, only the coke in the coke layer flowing into the D region and the substitute lump in the substitute lump deposit fall into the core coke deposit. On the other hand, in the embodiment shown in FIG. 2, the coke in the coke deposition layer 16 drops further. Therefore, the substitute mass composition ratio of the furnace core coke deposition layer 25 is low, and its own gravity 25 W is lower than that of the comparative method. Further, since the coke deposition layer 16 having a lower bulk density than the ore layer is formed in the central region of the ore layer 15, the load on the furnace top in the central region of the furnace is also lower than that of the comparative method. For this reason, as can be seen from the calorific value at the bottom of the furnace shown in FIG. 5 described later, the floating suppression effect of the coke-free layer 28 is slightly lower than that of the comparative method.

On the other hand, since the coke deposition layer 16 is formed in the central region of the ore layer 15, the ore abundance in the D region is
Less than the comparison method, the amount of CO ₂ gas generated in the ore reduction is also reduced. For this reason, the coke and the substitute lump that fall in the D region are less susceptible to particle size deterioration (hereinafter referred to as “reaction deterioration”) due to reaction with CO ₂ gas. In addition, since the substitute mass is denser and stronger than coke, particle size deterioration (hereinafter, referred to as “wear deterioration”) due to abrasion received when descending in the furnace is smaller than that of coke. Furthermore, since the volatile content is as low as or less than that of coke, gas is not generated in the furnace and self-destructed to cause powdering (hereinafter referred to as “self-destructing powdering”).

Accordingly, the coke and the substitute lump in the region D fall into the core coke deposition layer 25 in a state where the particle size deterioration is suppressed. Thereby, the furnace core coke deposition layer 25
Is better than that of a conventional core coke deposition layer composed of only coke that has been strongly affected by reaction deterioration and abrasion deterioration, even if the charged particle size is the same. Also, the increase in the flow rate of hot metal near the furnace bottom side wall 20 due to the deterioration of the liquid permeability of the furnace core coke deposition layer seen when only the conventional coke is charged, and the progress of brick wear on the furnace bottom side wall 20 associated therewith It can be suppressed at the same time. Further, the liquid permeability of the furnace core coke deposition layer 25 is slightly better than that of the comparative method composed of the coke subjected to the reaction deterioration and the substitute lump. For this reason, as can be seen from the calorific value of the flow through the furnace bottom side wall in FIG. 5 described later, the effect of reducing the hot metal flow velocity near the furnace bottom side wall 20 is slightly improved as compared with the comparative method.

As described above, the reason why the coke deposited layer 16 is formed in the central region of the ore layer 15 although the effect of suppressing the coke-free layer is slightly inferior to that of the comparative method is as follows. That is, since the lower limit particle size of the substitute lump is set to a value equal to the lower limit particle size of the coke charged in the blast furnace, the substitute lump deposit layer 11 does not deteriorate the air permeability in the central region of the furnace. Ore layer with poor ventilation
Since the coke deposited layer 16 having good air permeability is deposited in the central region of the furnace 15, air permeability in the central region of the furnace is improved. Since the thickness of the coke deposition layer 16 is controlled by the charged amount, the permeability of the charged material in the central region of the furnace is properly secured. In addition, since the amount of ore is smaller than that of the comparative method, the amount of CO ₂ gas generated by the reduction is reduced, and the reaction deterioration of the alternative lump or coke is suppressed. Therefore, the core coke deposition layer
The liquid permeability of 25 is better than the liquid permeability of the core coke deposition layer of the comparative method and the conventional method because the amount of the reaction deterioration is small even if the particle size of the charge is the same.

FIG. 3 is a view showing another state of the inside of the blast furnace for explaining the method of the present invention. This figure shows a mode in which the alternative lump is mainly charged into the furnace central region before charging the coke and before charging the ore. In addition,
The description overlapping with FIG. 2 is omitted.

As shown in the figure, in the furnace center region, the alternative lump deposit layers 11 charged from another route charging device are lowered in the furnace in a state where they are successively stacked. The coke in the coke layer 12 flowing into the region D shown in FIG. 1 (a) and the substitute lump 17 in the substitute lump deposit layer 11 descend into the core coke deposit 25 and become longer. Stay in the furnace for hours.

In the embodiment shown in FIG. 3 of the method of the present invention, as compared with the above-described comparative method, the amount of the substitute lump increases by the amount of the fallout from the substitute lump deposit layer 11 formed in the central region of the ore layer 15. For this reason, the alternative lump constituent ratio of the core coke deposition layer 25 is higher than that of the embodiment shown in FIG. 2 or the comparative method, and the gravity of the core coke deposition layer 25 of 25 W is further increased. Therefore, the floating of the core coke deposited layer 25 due to the buoyancy 26F of the hot metal 26 is prevented, and the thickness of the coke-free layer can be further reduced. Thereby, the flow velocity of the hot metal in the vicinity of the furnace bottom 19 is further reduced as compared with the embodiment shown in FIG. 2 or the comparative method, and the effect of suppressing the brick wear of the furnace bottom 25 can be further enhanced.

On the other hand, the reaction deterioration and the wear deterioration of the substitute mass falling in the region D are smaller than those of the conventional method and the comparative method. Therefore, the liquid permeability of the furnace core coke deposition layer 25 having a high substitute lump composition ratio becomes better than the conventional method and the comparative method. And
The increase in the flow velocity of the hot metal near the furnace bottom side wall 20 due to the deterioration of the permeability of the core coke deposit layer can simultaneously suppress the progress of brick wear on the furnace bottom side wall 20.

FIG. 4 is a view showing still another state in the furnace of the blast furnace for explaining the method of the present invention. The figure shows a mode in which the alternative lump is charged prior to charging coke, and iron scrap or reduced iron is charged prior to charging ore into the furnace central region. The description that overlaps with FIG. 2 will be omitted.

As shown in the figure, in the furnace central region, the alternate lump deposit layer 11 and the iron scrap deposit layer or the reduced iron deposit layer 14 charged from the different route charging device are alternately stacked in the furnace. Descend. Then, D shown in FIG.
The coke in the coke layer 12 that has flowed into the region and the substitute lump in the substitute lump deposit layer 11 form a core coke deposit layer.
It falls into 25 and stays in the furnace for a long time.

Therefore, in the embodiment shown in FIG. 4, the substitute lump constituting ratio of the furnace core coke deposition layer 25 is equivalent to that of the comparative method, and can be higher than that of the conventional method or the embodiment shown in FIG. The self-gravity 25 W of the furnace core coke deposition layer 25 increases. Furthermore, as shown in Table 3 below, the bulk density of the iron scrap deposit is 3.8 times or more that of the coke deposit and 2.2 times or more that of the alternative lump deposit. The bulk density of the reduced iron sedimentary layer is 1.6 times higher than that of the iron scrap sedimentary layer. Accordingly, the load 27 in the furnace center region in the lump portion in the upper half of the furnace is increased as compared with the embodiment shown in FIGS. For this reason, the floating of the furnace core coke deposition layer 25 due to the buoyancy 26F of the hot metal 26 is prevented, and the coke-free layer can be almost eliminated. Accordingly, the flow velocity of the hot metal in the vicinity of the furnace bottom 19 is further reduced, and the effect of suppressing the brick wear of the furnace bottom 19 can be further enhanced. Since iron scrap and reduced iron have already been reduced, there is almost no reaction deterioration of the substitute mass due to CO ₂ gas generated by the reduction.

Therefore, the liquid permeability of the furnace core coke deposition layer 25 is better than the conventional method, the comparative method or the embodiment shown in FIG. 2, as in the embodiment shown in FIG.
At the same time, the progress of wear of the 20 bricks can be suppressed.

In the embodiment shown in FIGS. 2 and 3,
When producing molten iron from the ore present in the D region, heat supply for direct reduction (endothermic reaction) is required in addition to the temperature increase of the ore.

On the other hand, in the embodiment shown in FIG. 4, only heat supply for raising the temperature of iron scrap or reduced iron is required. Therefore, a high temperature and a large amount of molten iron can be generated, and heat is exchanged with a large amount of hot metal, so that the temperature of the core coke deposition layer 25 is maintained higher than the conventional method, the comparative method, and the case of FIGS. 2 and 3. You. And hot metal dripped in the core coke deposition layer 25,
The fluidity of the slag is improved, and it is possible to stably produce hot metal with a target tapping amount.

[0046]

Example 1 A bell type charging apparatus with a furnace volume of 2700 m ³ and FIG.
The method of the present invention was carried out using a blast furnace provided with a charging device from another route as shown in FIG. The coke substitute lump used was obtained by crushing a carbon-based refractory and adjusting the particle size, and having the following properties having the characteristics defined by the present invention.

Average particle size: 50 mm, apparent specific gravity: 1.73 Fixed carbon content: 92% by weight, volatile matter: 0.6% The raw material charging to the blast furnace was performed by replacing the substitute mass with the ore charging before charging the coke. Prior to the charging, coke or an alternative lump was mainly charged into the furnace central region (FIG. 1 (a)).
The charging of coke and the charging of ore were performed by dividing one charge into two batches and charging into two batches. Conventional example (base)
Was charged by a conventional method in which coke and ore were charged alternately from a bell type charging device. Further, the comparative example (case 1) is a charging method in which the alternative mass is mainly charged before charging the coke, but the central charging is not performed before charging the ore.

In the actual furnace test, the weight fraction (hereinafter, referred to as the “alternative ratio”) of the alternative mass to be charged centrally with respect to the coke base prior to the charging of coke was kept constant at 7% by weight, and the ore charging was performed. The weight fraction (hereinafter referred to as “replacement ratio”) with respect to the coke base charged centrally or the replacement ratio of the substitute mass is changed as shown in Table 2,
The operation was performed under the operating conditions shown in Table 1.

[0049]

[Table 1]

[0050]

[Table 2]

Next, a method for evaluating the effect will be described. When the flow velocity of the hot metal near the bottom and the bottom wall changes, the heat transfer between the hot metal at the bottom and the refractory changes accordingly, so the hot metal flow rate is estimated from the heat flux in the refractory. can do. Therefore, the furnace bottom obtained from the data of the thermometer buried at a plurality of places in the refractory brick of the furnace bottom and the furnace bottom wall, and the furnace bottom calculated based on the temperature gradient in the refractory of the furnace bottom wall and The heat flux value of the hearth side wall portion (hereinafter, referred to as the "heat volume flowing through the hearth bottom" and the "heat volume flowing through the hearth side wall," respectively) was used as an evaluation index of the hot metal flow velocity near the hearth bottom and the hearth side wall.

In the actual furnace operation, the operation in each case was continued for a certain period of time, and the through-flow calorific value of the furnace bottom and the bottom wall of the last 5 days of the operation period was used as an evaluation index. Further, the blast pressure fluctuation index at this time (a value obtained by dividing the length of the blast pressure recording curve on the continuous recording chart of the blast pressure by the chart feed length) was used as an index indicating the stability of operation. The fuel ratio was also investigated. The state before application of the method of the present invention (hereinafter referred to as “base”) was used for comparison as a conventional example.

FIG. 5 is a diagram showing the measurement results of the calorific value at the bottom of the furnace bottom, the calorific value at the side wall of the furnace bottom, the blast pressure fluctuation index and the fuel ratio in Example 1 of the method of the present invention in comparison with the conventional example and the comparative example. is there.

As shown in the figure, regarding the calorific value of the flow through the bottom of the furnace bottom, coke was charged also in Case 1 of the comparative example in which the alternative lump was charged in the central area of the coke layer, and further, in the central area of the ore layer ( Case 2 of Example)
5, or the cases 6 to 9 in which the substitute lump was charged (indicated by the substitute ratio) were lower than the base of the conventional example, and a decrease in the hot metal flow velocity near the bottom of the furnace bottom was observed.

In contrast to Case 1, the replacement ratio of coke charged centrally in the ore layer was changed to Case 2 (1% by weight) →
Case 3 (2% by weight) → Case 4 (4% by weight) → Case 5 (8% by weight), the amount of heat flowing through the bottom of the furnace bottom increased slightly, and the flow rate of hot metal near the bottom of the furnace bottom increased slightly. . This is due to the fact that the substitute mass composition ratio of the core coke deposit decreases with the increase of the replacement ratio and its own gravity decreases, or the upper burden load decreases due to the decrease of ore abundance in the core region of the furnace Thus, it is determined that the thickness of the coke-free layer was slightly increased.

The replacement ratio of the replacement lump to be charged centrally in the ore layer is changed from case 6 (1% by weight) to case 7 (3% by weight).
→ Case 8 (10% by weight) increased and the calorific value flowing through the bottom of the furnace bottom decreased, and a decrease in the flow rate of hot metal near the bottom of the furnace bottom was observed. This is because, compared to Case 1, the increase in self-gravity due to the increase in the substitute mass composition ratio of the core coke deposits exceeds the decrease in the upper burden load due to the decrease in ore abundance,
It is determined that the thickness of the coke-free layer was reduced. In Case 9 (15% by weight), the effect of the decrease in the load of the upper charge was strongly exhibited, and the flow rate of the hot metal near the bottom of the furnace bottom increased to about the same level as in Case 1.

On the other hand, regarding the calorific value flowing through the bottom wall of the furnace and the blast pressure variation index, the replacement ratio of coke was increased (Case 1).
→ Case 2 → Case 3 → Case 4 → Case 5) or decrease as the substitute ratio of substitute mass increases (Case 1 → Case 6 → Case 7 → Case 8 → Case 9). A decrease and stabilization of the blast pressure were observed. This is because the ore abundance in the core region of the furnace decreases with an increase in the substitution ratio or substitution ratio, so that coke or substitute lump with less reaction degradation falls to the core coke deposition layer, and the coke-free layer rises It is considered that the air permeability and the liquid permeability of the furnace core coke deposition layer in a state where the temperature was suppressed were improved.

Cases 7 to 9 in which the composition ratio of the substitute lump in the furnace core coke deposition layer was high were cases 1 to 9 in which the composition ratio was low.
5, the calorific value flowing through the bottom wall of the furnace and the blowing pressure fluctuation index are lower. This is because the substitute agglomerates have less wear deterioration than coke and do not self-destruct, so that the permeability and liquid permeability of the core coke deposited layer of cases 7 to 9 having a high substitute lump constituent ratio are high. Is better than that of Cases 1-5.

Regarding the fuel ratio, Case 1 (Comparative Example) was about 10 kg / t higher than the base (Conventional Example). Then, the replacement ratio of coke is increased (case 1 → case 2).
→ Case 3 → Case 4 → Case 5) or the increase in the substitute ratio of substitute lump (Case 1 → Case 6 → Case 7 → Case 8 → Case 9), the fuel ratio slightly increases, and in Cases 5 and 9 Is more than case 1
Deteriorated by about 10 kg / hot metal t. It is considered that this is because the ore abundance in the furnace center region decreases with the increase of the replacement ratio or the substitution ratio, and the utilization efficiency of the reducing gas that rises in the lump in the furnace center region decreases. Therefore, in order to suppress the deterioration of the fuel ratio to approximately the same level as in the comparative example, the replacement ratio of coke should be in the range of 2% by weight or more and less than 8% by weight, and the replacement ratio of the lump substitute should be in the range of 2% by weight or more and less than 15% by weight. It turns out that it is good to do.

[0060]

EXAMPLE 2 Using the same furnace as in Example 1, the alternative mass equivalent to 7% by weight of the coke base was charged before charging the coke and reduced iron or scrap was charged before charging the ore. Focused charging was performed in the central area (Fig. 1 (b)).
Table 3 shows the particle size or dimensions of the raw materials used and the bulk density of each raw material deposited layer.

[0061]

[Table 3]

In the actual furnace test, as shown in Table 5, the weight fraction of reduced iron or scrap with respect to the total iron source material (hereinafter referred to as
The operation was performed under the operating conditions shown in Table 4 while changing the “iron replacement ratio”. Then, in the same manner as in Example 1, the through-flow calorie of the furnace bottom and the furnace bottom side wall and the blowing pressure fluctuation index were investigated for each case. In addition, coke sampling was carried out from the tuyere at the time of wind shut down after the operation of each case,
The particle size of the core coke collected from the furnace core was measured, and the reduction rate of the coke charged from the furnace top and the particle size reduction ratio with respect to the particle size of the substitute lump were investigated.

[0063]

[Table 4]

[0064]

[Table 5]

FIG. 6 is a diagram showing the measurement results of the calorific value of the bottom of the furnace bottom, the calorific value of the side wall of the furnace bottom, the blowing pressure fluctuation index and the particle size reduction rate in Example 2 of the present invention in comparison with the conventional example and the comparative example. It is.

As shown, cases 10 to 15 of the second embodiment
Compared with the base of the conventional example and the case 1 of the comparative example, the amount of heat flowing through the bottom of the furnace bottom and the side wall of the furnace bottom are both reduced.

The decrease in the amount of heat flowing through is caused by an increase in the replacement ratio of reduced iron or scrap with the iron source (Case 1 → Case 10 →
Case 11 → Case 12 or Case 1 → Case 13 → Case
14 → Case 15) Both increase. This reduction in the amount of heat flowing through is mainly due to the case where reduced iron, which has a large bulk density, is centrally charged.
In particular, the decrease in the amount of heat flowing through the bottom of the furnace bottom has a positive correlation with the load applied to the furnace core coke layer from the upper part of the furnace center. Further, the particle diameter reduction rate of the core coke is lower than that of the base and the case 1. This is considered to be due to the fact that the substitute agglomerates with little abrasion deterioration descended to the furnace core without undergoing strong reaction deterioration and constituted a core coke deposited layer.

From the above results, it can be seen that the decrease in the calorific value at the bottom of the furnace in Example 2 is due to the fact that most of the core coke deposited layer is composed of a lump substitute which is heavier than coke. It is presumed that the coke-free layer disappeared due to an increase in the load applied to the furnace, and the flow velocity of the hot metal at the bottom of the furnace bottom decreased. In addition, the decrease in the calorific value of the flow through the bottom wall of the hearth is due to the improved liquid permeability of the core coke layer itself and the increase in the flow rate of hot metal near the furnace bottom wall, which is observed when the liquid permeability of the layer is deteriorated. It is inferred.

The blow pressure fluctuation index increases with an increase in the iron source replacement ratio.
The following is not a hindrance to stable operation.

[0070]

According to the method of the present invention, the dead weight of the core coke layer and the load on the upper part thereof are increased.
As a result, the coke-free layer disappears. Further, the particle size deterioration due to the reaction is suppressed, and the liquid permeability of the core coke deposited layer is improved. Therefore, at the time of tapping, it is possible to reduce the flow velocity of the molten metal near the bottom of the furnace and the side wall of the furnace bottom. This suppresses the progress of brick wear on the furnace bottom and the furnace bottom side wall,
Blast furnace life can be greatly extended.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an upper part of a blast furnace illustrating an embodiment of the method of the present invention and a raw material deposition state, in which (a) charges an alternative lump or coke into the center of the furnace prior to charging of ore. (B) Similarly, the case where iron scrap or reduced iron was charged into the furnace center.

FIG. 2 is a schematic cross-sectional view showing a state inside a blast furnace for explaining one method of the present invention.

FIG. 3 is a schematic cross-sectional view showing an inside state of a blast furnace for explaining another method of the present invention.

FIG. 4 is a schematic cross-sectional view showing a state inside a blast furnace for explaining still another method of the present invention.

FIG. 5 shows the calorific value of the bottom of the furnace in one embodiment of the present invention;
It is a figure which shows the calorie | heat amount which flows through a furnace bottom wall, the measurement result of blast pressure fluctuation | variation index, and a fuel ratio.

FIG. 6 is a diagram showing the measurement results of the calorific value of the bottom of the furnace bottom, the calorific value of the side wall of the furnace bottom, the blowing pressure fluctuation index, and the particle size reduction rate in another embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view illustrating a furnace state of a general blast furnace.

[Explanation of symbols]

 1: Blast furnace 2: Bell type charging device 3: Large bell 4: Bell cup 5: Movable armor 6: Separate route charging device 7: Charging chute 8: Hopper 9, 9 ': Load drop locus 10: Coke Or ore 11: Alternate lump deposit 12: Coke layer 13: Alternate lump or coke deposit 14: Scrap or reduced iron deposit 15: Ore layer 16: Coke deposit 17: Alternate lump 18: Coke 19: Furnace bottom 20: Furnace bottom wall 21: Tuyere 22: Ore softening cohesive zone 23: Mortar-shaped area 24: Coke combustion zone 25: Core coke deposit 26: Hot metal 26F: Buoyancy 27: Charge Load 28: Coke-free layer 29: Lumped part 30: Soft cohesive zone 31: Coke band 32: Furnace core D: Core fall area of coke and alternative lump

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-228904 (JP, A) JP-A-7-173513 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21B 5/00

Claims (1)

(57) [Claims] When the coke and the iron source material are alternately charged into the furnace from the top of the blast furnace, a part of the charged amount of the coke has an apparent specific gravity of 1.3 or more and a fixed carbon content of 80% by weight. % Or more, the volatile matter content is 1% by weight or less, and the particle size is 30 to
A method for operating a blast furnace to be replaced with a 200-mm lump, comprising: Prior to charging the above coke, a different route from the normal charging equipment
Using the charging device, the mass is mainly charged into the furnace central region. Is prior to the loading of the iron source material, usually
Using a charging device with a different route from the charging device, (a) charging the lump or a part of the coke into the furnace central region with a focus, or (b) transferring iron scrap or reduced iron into the furnace Focusing on the central area.