JPH07228904A - Operation of blast furnace - Google Patents

Abstract

PURPOSE:To prolong the service life of a furnace lining by restraining wearing of a brick at the furnace bottom part of a blast furnace. CONSTITUTION:At the time of charging alternately coke and iron source raw material into the furnace from the furnace top part of the blast furnace, a part of the charging quantity of the coke is substituted with lumpy material 12 having >=1.3 apparent sp. gr., >=80wt.% of fixed carbon, <=1wt.% of volatile matter and 30-200mm of grain diameter. The above lumpy material 12 can be charged into the furnace at the same time of charging the coke 13 but it is desirable to charge the lumpy material, separately with the coke 13 concentrically in the furnace center range. By this method, as a part or a large part of the coke deposited layer 25 at the furnace core is constituted with the larger apparent sp. gr. of lumpy material 12 than the coke 13, the float-up of the coke deposited layer at the furnace core is restrained. Further, the liquid permeability of the deposited layer itself is improved and molten iron flowing speeding at the furnace bottom part is lowered and the brick wearing of the furnace bottom part 19 and the side wall 20 can be restrained.

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 charging a raw material for controlling the filling / depositing state of the raw material in the lower part and the bottom of the blast furnace to suppress wear of refractory at the bottom of the furnace due to hot metal flow The present invention relates to a blast furnace operating method characterized by the method.

[0002]

2. Description of the Related Art Blast furnaces for producing pig iron have become larger in size in recent years, and the repair cost has been enormous accordingly.
Therefore, in recent blast furnace operation, stable production of pig iron and extension of furnace life have become important issues.

The life of the blast furnace is judged based on the degree of damage to the furnace body, except for the blow-off in accordance with the production plan. However, the point cannot be dealt with by repairing by a temporary blast. It depends on whether the inner surface of the furnace is seriously damaged.

In blast furnace operation in recent years, after the start of operation, the blast furnace is blown off periodically or as needed, and repair is performed from the inside of the furnace. Due to the progress of this repair technique, it is possible to maintain the side wall of the blast furnace furnace body above the tuyere to some extent. However, the side wall and bottom of the furnace body below the tuyere (hereinafter referred to as “furnace bottom side wall” and “furnace bottom bottom”, respectively) are the parts where the molten pig iron is present, and the contents below the tuyere Since it is not easy to discharge, it is impossible to radically repair damage to the area.
Therefore, it can be said that the damage condition of the bottom wall of the furnace bottom and the bottom part of the furnace bottom determines the life of the blast furnace, and the main point of extending the life of the furnace is to prevent damage to the same part.

The furnace body of the blast furnace is composed of an iron shell constituting the outer wall, a furnace body cooling means such as a stave, a cooling plate, and a cooling pipe installed on the inner side thereof, and a refractory brick laid inside thereof. However, the above-mentioned suppression of damage to the bottom of the furnace bottom and the side wall of the furnace bottom specifically means suppression of wear of the refractory bricks on the inner surface of the furnace.

Although the mechanism of brick wear at the bottom of the furnace bottom and the side wall of the furnace bottom is complicated, the main cause of the wear is the melt loss due to the flow of hot metal in contact with the brick surface. Brick wear progresses as the molten pig iron flows strongly. Therefore, in order to suppress the brick wear of the bottom of the furnace bottom and the side wall of the furnace bottom, it is necessary to control the liquid permeability of the furnace bottom to reduce the hot metal flow rate in the vicinity of the bottom of the furnace bottom and the side wall of the furnace bottom.

[0007] Conventionally, in order to suppress the brick wear of the bottom wall of the furnace bottom or the bottom of the furnace bottom, the charging of the Ti-containing iron source raw material into the blast furnace or the blowing of the ore-bearing ore of the Ti-containing ore into the blast furnace is performed by increasing the Ti concentration. It is intended to increase the viscosity of the hot metal and thereby reduce the hot metal flow rate in the vicinity thereof. However, including
Ti ore is expensive, and using it regularly increases the cost of ironmaking. Furthermore, if a large amount of Ti-containing ore is used, there is a risk that the status of tapping and slag 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 Japan Iron and Steel Institute and the Iron and Steel Foundation Joint Research Group (July 1982): "Blast furnace phenomena"). And "Analysis" in "Comprehensive Investigation Results of Demolition Survey"). FIG. 9 is a schematic cross-sectional view for explaining the in-furnace state found by the conventional blast furnace disassembly study.

The block portion 28 in the upper half of the illustrated blast furnace 1 is an area where the coke layers and the ore layers, which are alternately stacked, descend while maintaining the layered state. The softening cohesive zone 29 at the lower part is a region where the ore layer is softened and fused and finally melted. When the ore layer melts and disappears, coke fall is promoted,
A coke zone 30 is formed between the lower part of the softening fusion zone 29 and the coke deposit layer of the furnace core section 31. This coke belt 30
Is an area 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 31.

The furnace core portion 31 is a conical coke deposit layer (hereinafter referred to as "furnace core coke deposit layer"), and the coke in this region is mostly involved in the reaction except that it is consumed to dissolve carbon in molten iron. Instead, it stays in the furnace for a long time. Then, the vicinity of the bottom 19 of the furnace bottom is not completely occupied by the core coke deposit layer, but is a space occupied only by the hot metal without coke (hereinafter, referred to as "coke-free layer (27)".
It is confirmed that there can be a).

Since the above-mentioned coke-free layer 27 is a free space for hot metal flow, its liquid permeability is significantly higher than that of the core coke deposit layer. Therefore, the presence or absence of the coke-free layer or the thickness of the layer is a factor that largely controls the hot metal flow. That is, if this coke-free layer can be eliminated, the hot metal flow rate in the vicinity of the bottom 19 of the furnace bottom can be reduced, and the progress of brick wear in the same can be suppressed.

In the coke free layer 27, the buoyancy of the hot metal acting on the core coke deposit layer and the upward drag force due to the gas exceed the dead weight of the core coke deposit layer and the load applied to the core coke deposit layer. It is thought to occur. Therefore, increasing the dead weight of the core coke deposit layer,
Alternatively, by increasing the top load applied to this, it is possible to prevent the core coke deposit layer from floating and eliminate the coke-free layer. From this latter point of view, the iron source material / coke weight ratio (hereinafter, “O / C ratio”) in the center of the furnace
Japanese Patent Publication No. 5-7443 discloses a method of suppressing the floating of the coke deposit layer in the vicinity of the bottom of the furnace bottom by increasing the load of the charge in the center of the furnace. However, increasing the O / C ratio in the center of the furnace is
While exerting the above effect on the bottom of the furnace, it also affects the radial gas flow distribution above the tuyere, which hinders the efficient progress of the pig iron reaction in the blast furnace and further hinders the stable operation of the blast furnace. There is a risk of

On the other hand, when the coke and the iron source material (hereinafter, also referred to as "ores") are charged alternately from the top of the furnace, coke, air permeability, and liquid permeability are provided in the center of the ore layer or coke layer. Japanese Patent Publication No. 5-8245 discloses a method of charging a solid reducing agent suitable for improvement to make the radial distribution of air permeability and liquid permeability of the core coke deposit layer uniform. According to this method, the shape of the softened cohesive zone in the furnace can be improved to improve the efficiency and stability of the operation, and the hot metal flows at a uniform flow rate on the bottom of the furnace during tapping, It is said that the brick erosion rate on the peripheral wall of the furnace bottom due to the peripheral flow of the hot metal flow due to the reduced liquid permeability of the coke deposit layer is suppressed. However, as described above, a coke-free layer exists between the blast furnace bottom and the core coke deposit layer. For this reason,
The flow velocity of the hot metal flowing on the furnace bottom is controlled by the liquid permeability of the coke free layer, that is, the thickness of the coke free layer rather than the liquid permeability of the core coke deposit layer. Therefore, this method seems to be effective for reducing the erosion of the bricks on the bottom wall of the furnace bottom, but it is not intended to reduce the erosion of the bricks on the bottom of the furnace bottom by controlling the thickness of the coke-free layer.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to increase the dead weight of the core coke deposit layer and prevent the core coke deposit layer from rising due to the buoyancy of the hot metal, so that an efficient and stable blast furnace can be obtained. It is an object of the present invention to provide a method for operating a blast furnace that can suppress brick wear on the bottom of the furnace bottom and the side wall of the furnace bottom without hindering pig iron production.

[0015]

The summary of the present invention is as follows.
It is in the blast furnace operation method of (1) and (2).

(1) When alternately charging coke and iron source material into the furnace from the top of the blast furnace, a part of the charging amount of the above coke has an apparent specific gravity of 1.3 or more and a fixed carbon content of 80%. If the content of volatile matter is 1% by weight or more and the particle size is
A blast furnace operating method characterized by substituting 30-200 mm lumps.

(2) A blast furnace characterized in that the agglomerates specified in (1) above are replaced with a part of the charging amount of the coke, and the agglomerates are mainly charged into the central region of the furnace. Operating method.

The above-mentioned lumps are carbon-based or graphite-based as shown in the following examples, and act as a reducing agent. As a standard, the amount of substitution by the agglomerates is about 2 to 15% by weight of the charged coke. This amount of lumps will be replaced with the same amount of coke before use.

In the blast furnace operation, a bell type charging device or a bellless type charging device provided at the top of the furnace is usually used. Coke and iron source raw materials are alternately charged using this normal charging device and deposited in layers in the furnace. Main sources of the iron source raw material are iron ore and sinter, but in the present specification, these may be collectively referred to as “ore”. In the method of the present invention, a coke substitute lump (hereinafter referred to as “substitute lump”) is used as a part of the coke to be charged.

The above-mentioned alternative agglomerates may be simultaneously charged with coke and mixed in the coke layer, but may be charged mainly in the central region of the furnace.

FIG. 1 is a schematic sectional view of an upper part of a blast furnace for explaining an example of an embodiment in which an alternative lump of the method of the present invention is simultaneously charged with coke and a raw material deposition state. (A) is a bellless blast furnace,
(B) is a bell-type blast furnace.

As shown in FIG. 1 (a), the alternative lumps 12 and coke 13 stored in the fixed hopper 4 of the bellless charging device 2 are simultaneously charged into the furnace while the distribution chute 3 is swirling. It Then, the tilt angle of the distribution chute is changed to shift the raw material drop trajectory 18 from the furnace peripheral side to the furnace center side. At this time, by setting the relationship between the tilt angle β ° in the latter half of turning and the tilt angle α ° in the latter half of turning when ore is charged to β ° <α °, the alternative lump mixture coke layer 14 in the central region of the furnace
It is desirable that the ore layer 15 be thicker and the ore layer 15 be thinner so as to increase the amount of the alternative lumps in the central region of the furnace.

As shown in FIG. 2 (b), the alternative lumps stored inside the large bell 6 and bell cup 7 of the bell type charging device 5.
The coke 12 and the coke 13 are repelled by the movable armor 8 and are simultaneously charged into the furnace according to the raw material falling trajectory 18.
In this control of the tilt angle of the movable armor, the falling position of the charging raw material is limited to the peripheral side of the furnace, so that it is difficult to make the alternative mass-mixed coke layer 14 in the furnace central region particularly thick. Therefore, by using an alternative lump having a particle size that does not inhibit combustibility on the large diameter side of the particle size range specified in the present invention, by utilizing the reclassification phenomenon that the larger diameter particles are deposited on the furnace center side, It is desirable to increase the abundance of alternative agglomerates in the central region of the furnace.

FIG. 2 is a schematic cross-sectional view of the upper part of the blast furnace for explaining an example of the embodiment of the method of the present invention in which an alternative mass alone is centrally charged and a raw material deposition state. )
Is a bell-type blast furnace.

As shown in the figure, the alternative lump 12 uses a charging device 9 of a different route from the normal charging device, and a charging chute 10
It is charged into the central area of the furnace via. On the other hand, the ore and coke 13 are charged into the furnace from the bellless charging device 2 or the bell charging device 5 in the same manner as in FIG. At this time, as shown in the drawing, the order of charging the raw materials in one cycle is set to the order of “alternative lumps” → “coke” → “ore”, thereby suppressing the infiltration of the coke layer 16 into the furnace central region, It is desirable to prevent the centrally charged alternative mass layer 17 from being buried in the coke layer 16 so as to increase the ratio of alternative mass existing in the central region of the furnace.

Although not shown in the drawing, the ore layer is formed by setting the raw material charging order as “coke” → “alternative lump” → “ore”.
Alternate agglomerates may be deposited to replace the fifteen core areas. However, in this case, it is preferable to appropriately bury the alternative lump layer in the ore layer 15 in order to suppress the air permeability in the central part of the furnace and minimize the decrease in productivity of the part. In addition,
In the same figure (a), the central charging of the alternative lumps may be performed by using the bellless charging device 2 instead of the separate route charging device 9 and by making the tilt angle of the distribution chute 3 small and constant. .

[0027]

FIG. 3 is a schematic cross-sectional view for explaining the state of the inside of a blast furnace in which an alternative lump and coke are simultaneously charged for explaining the method of the present invention. As shown in the figure, in the agglomerate portion of the upper half of the blast furnace, the alternative agglomerate mixture coke layers 14 and ore layers 15 charged from the normal charging device are alternately laminated, and the inside of the furnace is maintained while maintaining the layered state. To descend.

Here, the coke 13 and the alternative lump 12 descending in the center of the furnace enter the furnace core coke deposit layer 25 and stay in the furnace for a long time, while the remainder and the middle of the furnace radial direction from the furnace. Coke 13 and alternative mass 12 present in the surrounding area
Is descended through a mortar-shaped region 23 formed by the furnace core coke deposit layer 25 and the ore softening and fusing layer 22, flows toward the tip of the tuyere 21, and is burned and consumed in the coke combustion zone 24. .

As described above, in the method of the present invention, the core coke deposit layer 25 can be composed of the coke 13 having an apparent specific gravity of about 1 and the alternative lump 12 having an apparent specific gravity of 1.3 or more. Since the alternative lump composition ratio is increased to a value close to the coke replacement ratio, the deadweight 25 W of the core coke deposit layer 25 can be increased compared to the case where only normal coke is charged. Therefore, the core weight of the core coke deposition layer 25 is 25 W
Is relatively increased with respect to the buoyancy 26F of the hot metal 26, the floating of the core coke deposit layer 25 can be suppressed and the thickness of the coke free layer 27 can be reduced. This allows
The flow velocity of the hot metal in the vicinity of the bottom 19 of the furnace bottom is reduced, and the brick wear of the bottom 19 of the furnace bottom is reduced.

The above-mentioned alternative lump must be denser and stronger than coke and less deteriorated in the furnace than coke. When such an alternative lump is used, the liquid permeability of the core coke deposit layer 25 becomes better than the liquid permeability of the core coke deposit layer composed only of coke having the same charging particle diameter. For this reason, the increase in the hot metal flow velocity in the vicinity of the furnace bottom side wall 20 due to the deterioration of the liquid permeability of the furnace core coke deposit layer observed when only the coke is charged, and the accompanying brick wear of the furnace bottom side wall 20 are also suppressed at the same time. can do.

Here, the characteristics to be possessed by the coke substitute lump used in the method of the present invention will be specifically described. The apparent specific gravity must be 1.3 or higher in order to suppress the generation of coke-free layer by charging the coke with a specific gravity higher than that of the coke deposit layer. The fixed carbon content is set to 80% by weight or more because the substitute lump must have the same combustibility and reducibility as coke as the reducing agent for the blast furnace. The volatile content of the alternative mass of 1% by weight or less means that
This is a condition necessary for preventing self-destruction and powdering due to gas generation in the furnace.

Further, the particle size of the substitute lumps is set within the range of 30 to 200 mm, and the lower limit value is determined from the lower limit particle size of the blast furnace charging coke, which is a part of the charging coke. It is a value that does not deteriorate the air permeability in the furnace even if the substitute is replaced with the substitute lump. On the other hand, the upper limit is not restricted by equipment such as transportation, storage, charging, etc. where the alternative lump is designed assuming normal coke, and when the alternative lump enters the coke combustion zone in the furnace. , Is set to enable smooth combustion disappearance.

FIG. 4 is a view similar to FIG. 3 showing a preferred embodiment of the method of the present invention, and showing a case where the alternative lumps are mainly charged in the central region of the furnace separately from the coke.

As shown, the ore is charged from the normal charging device to form the ore layer 15, and then the alternative mass 12 or the bellless charging device is used to replace the alternative mass 12 with the central region of the furnace. Into the coke 13 after forming the alternative mass layer 17 into the
Is charged from a normal charging device to form the coke layer 16.

As described above, the alternative lump 12 charged in the central region of the furnace is supplied to the core coke deposit layer 25, and the alternative lump of the core coke deposit layer 25 (apparent specific gravity of 1.3 or more) is formed. Is increased to 3 to 5 times the coke substitution ratio.
Therefore, by increasing the own weight 25W of the core coke deposit layer 25, it is possible to prevent the core coke deposit layer 25 from floating and eliminate the coke-free layer. As a result, the hot metal flow velocity near the bottom 19 of the furnace bottom is further reduced as compared with the case of FIG. 3 described above, and the effect of suppressing brick wear of the bottom 19 and bottom side wall 20 of the furnace can be further enhanced.

Although not shown in the figure, the raw material charging sequence is "coke" → "alternative lump center charging" → "ore" to form an alternative lump layer in the central region of the ore layer. Good. In this case, there is almost no ore in the central area of the furnace,
There will be alternative mass and coke layer coke. Therefore, the alternative lumps and coke in the central area of the furnace are
Since it does not undergo reaction deterioration due to CO ₂ gas generated by ore reduction, it has the effect of enhancing the air permeability and liquid permeability of the core coke deposit layer. However, since the core coke deposit layer is composed of the alternative lumps and the coke, the coke-free layer generation suppressing effect is inferior to that in the case of FIG. 4 described above.

FIG. 5 is a graph showing the relationship between the core composition ratio and the coke replacement ratio of the substitute lump obtained in the example of the present invention. The numbers in the figure indicate the case numbers of the examples. Also,
● indicates bell type blast furnace, △ indicates bellless type blast furnace, which is mainly charged with alternative lumps from another route charging equipment, ◎ indicates bellless type blast furnace, which is mainly charged alternative lumps from distribution chute Cases, ○ marks are cases in which alternative lumps and coke were simultaneously charged in a bell-type blast furnace.

As shown in FIG. 5, it can be seen that as the replacement ratio is increased, the core composition ratio of the alternative lumps is increased. And, while the simultaneous charging gives a core composition ratio close to the equiweight ratio line, the furnace core charging gives a core composition ratio higher than that of the equiweight ratio line. In the case of center charging, if the substitution ratio is less than 2% by weight, the substitution lump layer 17 is buried in the coke layer 16 and the infiltration of the coke layer into the furnace central region increases. Therefore, the composition ratio of the alternative lumps in the core coke deposit layer becomes low, and the effect of suppressing the formation of the coke free layer cannot be sufficiently obtained. In addition, Case22 exceeding 15% by weight
In, an abnormal combustion condition in the coke combustion zone 24 was observed, which is considered to be due to an excessive increase in the alternative lumps entering the mortar-shaped region 23. From this result, it is desirable to set the replacement ratio to 2 to 15% by weight in the operation mode in which the replacement lump is mainly charged.

Further, in the operation mode in which the substitute lump and the coke are simultaneously charged, it is not possible to expect the substitute lump to be unevenly distributed in the central part of the furnace. Therefore, the coke substitution ratio of the substitute lump is economically considered. As a guide, it is recommended to use about 5 to 10% by weight to obtain the core composition ratio equivalent to that of Case 19 of central charging.

[0040]

Example 1 The method of the present invention was carried out using a blast furnace (Fig. 1 (a)) having a furnace volume of 4800 m ³ and equipped with a bellless charging device.
Table 1 shows the properties of the coke substitute lumps used. As shown in the table, all the alternative lumps used have the characteristics defined in the present invention. Specifically, the alternative lumps A and B are carbon-based refractory materials, C is a carbon electrode, and D is a carbon electrode. Is a graphite electrode crushed and adjusted to each particle size. Using these, operation was performed under the operating conditions shown in Table 2 and the bellless charging conditions shown in Table 3.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

Next, a method of evaluating the effect will be described. When the hot metal flow velocity near the bottom of the furnace bottom and the side wall of the furnace bottom changes, the heat transfer between the hot metal at the furnace bottom and the furnace bottom refractory also changes accordingly, so the hot metal flow velocity is estimated from the heat flux in the furnace bottom refractory. can do. Therefore, the bottom of the furnace bottom and the furnace bottom wall and the furnace are calculated based on the temperature gradient in the refractory of the bottom bottom and the bottom wall obtained from the data of the thermometer embedded in the refractory bricks of the bottom bottom and the side wall of the furnace bottom. The heat flux values of the bottom side wall (hereinafter referred to as "heat flow through the bottom of the furnace bottom" and "heat flow through the bottom of the furnace bottom", respectively) were used as evaluation indices for the hot metal flow velocity at the bottom of the furnace and near the side wall of the furnace.

As shown in Table 4, the actual furnace test was performed by changing the type, particle size and alternative ratio of the alternative lumps, and the operation period in each case was 30 days, and the bottom of the furnace bottom for the last 5 days was set. And the amount of heat flow through the bottom wall of the furnace was used as the evaluation index. Also, the blast pressure fluctuation index at this time (a value obtained by dividing the length of the blast pressure recording curve on the continuous blast pressure recording chart by the chart feed length)
Was used as an index showing the stability of the operation. The state before applying the method of the present invention (hereinafter referred to as “Base”) was used for comparison.

[0046]

[Table 4]

FIG. 6 is a diagram showing the effect and operation stability of Example 1 in which the alternative lumps of the present invention were simultaneously charged into the furnace together with the coke, and (a) is the amount of heat flow through the bottom of the furnace,
(B) is the amount of heat flowing through the bottom wall of the furnace bottom, and (c) is the blast pressure fluctuation index.

Any condition (Case) to which the method of the present invention is applied
Also in 1 to 8), the amount of heat flowing through both the bottom of the furnace bottom and the side wall of the furnace bottom is lower than that of Base. Except for Case 2, which is the lower limit of the fixed carbon content of the alternative lumps in the range defined by the present invention, the degree of decrease in the amount of heat flowing through the bottom of the furnace bottom increases as the apparent specific gravity of the alternative lumps increases (Case 4 → Case 3
→ Case 1). This is because when the apparent specific gravity of the alternative lumps that form a part of the core coke deposit layer increases, the self-weight of the core coke deposit layer increases and its floating is suppressed, and the thickness of the coke-free layer becomes thin. This is because the hot metal flow rate at the bottom of the furnace decreased.

On the other hand, the degree of decrease in the amount of heat flowing through the bottom wall of the furnace is
The higher the fixed carbon content and the lower the volatile content, the higher the fixed carbon content, and the lower the blast pressure fluctuation index (Case 2).
→ Case 1 → Case 3 → Case 4). This means that when the volatile content of the alternative lumps decreases, the particle size deterioration in the furnace decreases,
This is because the liquid permeability of the core coke deposition layer is improved and the hot metal flow velocity around the side wall of the furnace bottom is reduced.

Next, in Case 5 in which the particle size is reduced to the lower limit of the particle size range of the alternative lumps defined by the present invention, the effect of lowering the amount of heat flowing through is recognized as compared with Base, although the degree is small. As the particle size is increased from the lower limit value to the upper limit value, the degree of decrease in the amount of heat flowing through becomes larger (Case 5 → Ca
se1 → Case8) This is because, when the alternative lump and the coke are charged at the same time, the alternative lump having a larger particle size is unevenly distributed in the central region of the furnace due to the reclassification phenomenon. Therefore, the core ratio of the alternative lumps becomes high, the coke-free layer becomes thin, and the hot metal flow rate at the bottom of the furnace bottom decreases. It is also interpreted that the increase in particle size improves the liquid permeability of the core coke deposit layer and reduces the hot metal flow rate around the side wall of the furnace bottom.

As in Case 6, Case 1 and Case 7, increasing the replacement ratio of the alternative lumps enhances the effect of lowering the heat flow through the bottom of the furnace bottom, while the amount of the alternative lumps flowing into the coke combustion zone increases. In Case 7, there is an upward trend in blast pressure fluctuation that is presumed to be due to the inability to maintain smooth combustion disappearance in the coke combustion zone. This phenomenon also appears in Case 8 where the particle size of the alternative lumps is the upper limit value, but in all cases, the control upper limit value of the blast pressure fluctuation index of the actual blast furnace is 1.35 or less, and stable operation of the blast furnace is possible. It didn't hurt him.

[0052]

Example 2 Using the same furnace as in Example 1, an alternative lump was charged separately from the coke and deposited in the central area of the furnace (FIG. 2 (a) above). The order of charging raw materials into the furnace is in the order of "central charging of alternative lumps" → "coke" → "ore", and charging of ore and coke is performed under the bellless charging conditions shown in Table 3 above. It was Center loading of alternative lumps is Case 9-Case
In case 13, the distribution chute is tilted at a small fixed angle under the bellless charging condition, and in cases 14 to 16,
It carried out using the different route charging device. The particle size of the alternative mass
The type A shown in the above Table 1 adjusted to 50 mm was used.

As shown in Table 5, in the actual furnace test, in the coke substitution ratio of the substitute lump and the center charging by the distribution chute, the tilt angle of the distribution chute was changed and the operation conditions shown in Table 2 were performed. Then, in the same manner as in Example 1, the amount of heat flowing through the bottom of the furnace bottom and the side wall of the furnace bottom and the fluctuation of the blown pressure were investigated for each Case. Furthermore, the deposition range of the alternative lumps in the central region of the furnace was also measured for each case using a profiler.

The results are also shown in Table 5. In addition, Case11,
For Case14, core coke sampling was performed at the end of the test, and the core composition ratio (% by weight) of the alternative lump was also investigated. The results are shown in FIG. 5 described above.

[0055]

[Table 5]

FIG. 7 is a diagram showing the effect and operation stability of Example 2 in which the alternative lump of the present invention was charged separately from the coke and charged in the central region of the furnace, and (a) shows the furnace. The amount of heat flow through the bottom of the bottom, (b) is the amount of heat flow through the bottom wall of the furnace bottom, and (c) is the blast pressure fluctuation index.

Simultaneously, in the furnace, Case10, Case11 and Case14 in which an alternative lump (particle size 50 mm, substitution ratio 5% by weight) was centrally charged, and an alternative lump (particle size 50 mm, substitution ratio 7% by weight) together with coke. Comparing with the charged Case 1 of Example 1, in Cases 10, 11 and 14, although the substitution ratio is low, the amount of heat flowing through the bottom of the furnace bottom and the side wall of the furnace bottom is Case 1.
Is lower. This is because the core coke deposit layer is mostly composed of alternative lumps charged in the central region of the furnace, the floating of the core coke deposit layer due to its own weight increase is prevented, and the coke-free layer disappears. It is presumed that the hot metal flow rate was decreased, or the deterioration of the particle size of the alternative lumps in the furnace was smaller than that of coke, which improved the liquid permeability of the core coke deposit layer and decreased the hot metal flow rate around the bottom wall of the furnace bottom. .

In the bell-less system center charging, when the deposition area of the alternative lumps is concentrated toward the center axis of the furnace (Case
9 → Case10 → Case11), there is an effect of reducing the fluctuation of blast pressure, which is estimated to be due to the decrease of the inflow amount of the alternative lumps into the coke combustion zone at the tip of the tuyere. At the same time, the composition ratio of the alternative lumps in the core coke deposit layer increases, the disappearance of the coke-free layer and the improvement of the liquid permeability of the core coke deposit layer increase the effect of reducing the heat flow through the bottom and side walls of the furnace bottom. Is recognized. In particular, when the dimensionless distance from the furnace central axis, that is, the distance from the furnace central axis / furnace opening radius is within 0.3, the above-mentioned effect can be enhanced.

On the other hand, when the replacement ratio of the alternative lumps (in other words, the charging amount) is increased as in Case 11 → Case 12 → Case 13, the deposition range of the substitute lumps expands accordingly, and An upper limit of 15% by weight is to place the alternative lumps within the optimum deposition range.

On the other hand, when the central charging is performed by the charging device of another route even with the same alternative ratio (Case11 → Case14, Ca
Se13 → Case15) can be reliably deposited in the center of the core. In addition, core coke sampling results (Case1
(1: 18% by weight, Case 14: 33% by weight), the core ratio of the alternative reducing agent increases as the deposition range decreases. Therefore, it is desirable to surely charge the core core region by the charging device of another route in order to efficiently increase the dead weight of the core coke deposit layer. However, in Case 16 where the deposition range is 0.3 or less, but the substitution ratio is as high as 20% by weight, the O / C decreases due to the thickening of the substitution mass deposit layer in the furnace central region, and the ventilation resistance of the furnace core Due to the decrease, the core temperature at the top of the furnace rose significantly compared to normal operation. Since this is not preferable for each equipment at the top of the furnace, the upper limit of the substitution ratio should be set to about 15% by weight even in the case of the separate route center charging method.

[0061]

Example 3 The method of the present invention was carried out using a blast furnace having a furnace capacity of 2700 m ³ and equipped with a bell-type charging device.

The alternative lumps used are the method of simultaneously charging with coke (FIG. 1 (b) above) and the method of central charging from a charging device of another route separate from coke (FIG. 2 (b) above). ) 2
It charged by the method and compared. As alternative reducing agent, A in Table 1
Was used and the particle size was 50 mm. The evaluation method was the same as in Example 1, and the investigation of the core ratio of the alternative lumps was also conducted in the same manner as in Example 2. The results are shown in FIG. 5 described above.

When centrally charging the alternative lumps, the order of charging the raw materials into the furnace is as follows: "central charging of the alternative lumps"->"coke"->"ore", with the ore and coke charging The charging was performed using a bell type charging device. As shown in Table 7, the actual furnace test was performed under the operating conditions shown in Table 6 by changing the coke substitution ratio of the substitute lump. The state before applying the method of the present invention (hereinafter referred to as “Base”) was used for comparison.

[0064]

[Table 6]

[0065]

[Table 7]

Under all of the conditions, the amount of heat flowing through both the bottom of the furnace bottom and the side wall of the furnace bottom was lower than that of Base. Especially, when the charging was carried out at the center using the charging device of another route ( In Cases 19 to 22), the decrease is remarkable. Although the bell type charging device uses a movable armor to control the charge distribution, it is generally impossible to selectively charge the raw material only in the central region of the furnace. Therefore, as shown in FIG.
As shown in, Cases 17 and 18 have the same substitution ratio.
It is considered that the core ratio of the alternative lumps decreased compared to 19 and 20, and there was a difference in effect. In Case 22, which has a high substitution ratio of 20% by weight in the center charge, a large temperature rise in the center of the furnace was confirmed as in Case 16 of Example 2 described above.

From the above, by concentrating and depositing the alternative lumps satisfying the requirements of the present invention in the central region of the furnace, a higher effect can be obtained than in the case of simultaneously charging the alternative lumps with coke into the furnace. I found out that Furthermore, in the case of central charging, the substitution ratio of the substitute lumps is 2 to 15% by weight.
It was found that by setting the above range, it is possible to effectively reduce the heat flow through the furnace bottom without significantly deteriorating the blast pressure fluctuation level under normal operation.

[0068]

According to the method of the present invention, the dead weight of the core coke deposit layer increases, and as a result, the coke free layer disappears, and the hot metal flow rate at the bottom of the furnace bottom can be reduced. Also,
The liquid permeability of the core coke deposit is also improved, and the hot metal flow velocity around the bottom wall of the furnace is reduced. As a result, the progress of brick wear on the bottom of the furnace bottom and the side wall of the furnace bottom is suppressed, and the life of the blast furnace can be significantly extended.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an upper part of a blast furnace for explaining an example of an embodiment of simultaneously charging an alternative lump and coke of the method of the present invention and a raw material deposition state.

FIG. 2 is a schematic cross-sectional view of an upper part of a blast furnace for explaining an example of an embodiment of centrally charging an alternative lump of the method of the present invention and a raw material deposition state.

FIG. 3 is a schematic cross-sectional view for explaining the in-core state of the blast furnace in the case of the charging method of FIG.

FIG. 4 is a schematic cross-sectional view illustrating a furnace state of a blast furnace in the case of the charging method of FIG.

FIG. 5 is a diagram showing a relationship between a core constituent ratio of a substitute lump and a coke replacement ratio obtained in an example of the present invention.

FIG. 6 (a) is a heat flow through the bottom of the furnace bottom in one embodiment of the present invention, FIG. 6 (b) is a heat flow through the bottom of the furnace bottom, and FIG.
The figure is also a diagram showing the measurement result of the blast pressure fluctuation index.

FIG. 7 is a diagram showing the measurement results of the amount of heat flowing through the bottom of the furnace bottom, the amount of heat flowing through the side wall of the furnace bottom, and the blast pressure variation index in another example of the present invention.

FIG. 8 is a diagram showing the measurement results of the amount of heat flowing through the bottom of the furnace bottom, the amount of heat flowing through the side wall of the furnace bottom, and the blast pressure variation index in another embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view for explaining the in-furnace state of a general blast furnace.

[Explanation of symbols]

1: Blast furnace, 2: Bell-less type charging device, 3: Swirling chute 4: Fixed hopper, 5: Bell type charging device, 6: Large bell 7, Bell cup, 8: Movable armor, 9: Separate route charging device 10: Charging chute, 11: Hopper, 12: Alternative lump 13: Coke, 14: Alternative lump mixed coke layer,
15: Ore layer 16: Coke layer, 17: Alternative lump layer, 18: Raw material falling locus 19: Furnace bottom bottom part, 20: Furnace bottom side wall, 21: Tuyere 22: Softening fusion layer, 23: Mortar-shaped region, 24: Coke combustion zone 25: Core coke deposit layer, 25 W: Gravity, 26: Hot metal 26 F: Buoyancy, 27: Coke-free layer, 28: Bulk part 29: Softening cohesion zone, 30: Coke zone, 31: Furnace core Department

Claims (2)

[Claims] 1. When alternately charging coke and iron source raw material into the furnace from the top of the blast furnace, a part of the charging 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 content is 1% by weight or less, and the particle size is 30 to
Operation method of blast furnace characterized by substituting 200 mm lumps. 2. When alternately charging coke and iron source material into the furnace from the top of the blast furnace, a part of the charging 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 content is 1% by weight or less, and the particle size is 30 to
A blast furnace operation method characterized by replacing with a 200 mm lump and placing this lump in the central area of the furnace.