JP2853557B2 - 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 of operating a blast furnace, and more particularly, to a method of operating a blast furnace in which the lower portion of the blast furnace is kept in a healthy state during operation, thereby ensuring stable operation of the blast furnace. The present invention relates to a method for operating a blast furnace for controlling a distribution in a furnace radial direction.

[0002]

2. Description of the Related Art In the operation of a blast furnace, it is important to smoothly reduce and melt an iron source material and to stably produce an imposed amount of pig iron over time.

[0003] The inside of a blast furnace is separated from a region where the iron source material is softened and melted by raising the temperature (hereinafter referred to as a "cohesive zone"), and upper and lower portions thereof (hereinafter referred to as "furnace upper portion" and "furnace portion"). The lower part is markedly different. That is, in the upper part of the furnace, the iron source material exists in a solid state together with the coke, and is reduced and heated by the gas which descends downward and rises through the void. On the other hand, in the lower part of the furnace, the hot metal and slag generated by the reduction and melting of the iron source material drop downward through the gap in the coke packed bed, and the gas blown from the tuyere blows into the gap in the coke packed bed. Through the furnace and rising toward the center of the furnace.

Most of the coke in the lower part of the furnace moves toward the tuyere combustion zone and disappears, but a part of the coke stays in the central part of the furnace where the logistics are very slow, and becomes so-called "core coke". . This core coke is the part corresponding to the "dead zone" in the logistics field in the blast furnace, and directly contributes to the pig iron production process because it is not involved in the supply of heat by combustion or the generation of reducing gas. Although not important, it has important implications for the stable operation of blast furnaces.

That is, when the core coke is viewed from inside the tuyere through the combustion zone (hereinafter referred to as "raceway") in front of the tuyere, the permeability of the core coke deteriorates. For example, the flow path of the gas generated in the raceway narrows, and the blowing pressure increases. This causes irregular coke lowering at the lower part of the furnace or, in severe cases, blow-through, which hinders stable operation. For this reason, in many blast furnaces, coke sampling is performed when the wind is shut off to periodically monitor the state of the core coke.

[0006] The coke temperature detected by the measurement of the degree of graphitization of the collected coke is the most important index for evaluating the state of the core coke, and it has been empirically known that a decrease in the coke temperature leads to a malfunction in the furnace condition. . That is, if the core coke temperature is maintained at about 1400 ° C. or higher, the molten iron slag dripping from the cohesive zone can pass through the core coke, but if the temperature drops significantly, the molten iron slag becomes Since the fluidity deteriorates and stays in the voids of the core coke, the air permeability of the core coke is impaired. The following can be considered as a cause of such a decrease in the core coke temperature.

The coke powder generated by the reduction of the strength of the charged coke during the unloading in the furnace or the coke powder generated by the pulverization in the raceway accumulates in the periphery of the core coke, and the core coke is generated from the raceway generated gas. Heat supply to the power supply is obstructed.

[0008] Low-temperature unreduced material enters the furnace core coke due to slippage or the like, so that the amount of direct reduction, which is an endothermic reaction, rises rapidly, and the temperature of molten iron slag dripping at the lower part of the furnace decreases.

As described above, the core coke temperature is an important isolation item in the operation of a blast furnace, and various methods have conventionally been adopted to suppress a decrease in the core coke temperature.

For example, it is possible to reduce the amount of powder generated by suppressing the deterioration of coke strength due to the reaction with CO ₂ gas, or to reduce the amount of powder generated on the raceway by controlling the tuyere front temperature and the tuyere wind speed to appropriate values. There is a method of ensuring heat permeability of the furnace core coke and promoting heat exchange with gas by reducing the amount.

In the invention of Japanese Patent Publication No. 64-9373, coke flowing into the furnace core is mainly coke charged near the furnace center axis at the top of the layer (the uppermost layer of the furnace interior charge). The coke is charged into the center of the furnace through a dedicated charging route, the amount of coke deposited in the center of the furnace is increased, and the weight ratio between the iron source material and coke (ore / coke; ,
By lowering the "O / C ratio", a porosity of the furnace core coke is secured, and a so-called central flow is strengthened. However, in this method, the central part of the furnace is mostly occupied by coke, and the air permeability is excessively increased, and as a result, the furnace top gas temperature becomes too high, and a burden is imposed on ancillary facilities. Further, since there is almost no ore in the center of the furnace, this region does not contribute to the production of hot metal, which is disadvantageous in terms of equipment efficiency.

The present applicant has disclosed a method of supplying not only coke but also ore to a furnace center from a dedicated charging route and freely adjusting the O / C ratio near the furnace center. No. has proposed.

[0013]

In order to increase the air permeability in the center of the furnace and keep the temperature of the core coke high, the above-mentioned Japanese Patent Application Laid-Open
Conventionally known methods such as the method disclosed in JP-A 61-227109 are effective. However, the method of charging only the coke into the central portion of the furnace has the above-mentioned problems. Also, once the temperature of the core coke is lowered, the movement of the core coke is extremely slow. Therefore, in the above-mentioned conventional method, it takes a considerable time to recover the desired state of the core coke, during which time the blast furnace is operated in an unstable manner.

An object of the present invention is to provide a method for quickly increasing the temperature of a reduced core coke so that the furnace condition can be recovered in a short time, and in which only coke is deposited at the center of the furnace. An object of the present invention is to provide a method of operating a blast furnace without the above-mentioned problems.

[0015]

The gist of the present invention is a method of operating a blast furnace in which coke and an iron source material are alternately charged into the furnace from the furnace top in a layered manner. It is in the operation method of the blast furnace.

As a part of the iron source material, the reducibility index is
Using a highly reducible sintered ore of 65% or more, and charging a mixture of the above highly reducible sintered ore and coke into the center of the furnace separately from a normal iron source material; Separately from normal coke, coke shall be charged into the center of the furnace, and the mixture and coke charged into the center of the furnace shall be deposited in a layer of normal iron source material.

The amount of coke to be mixed with the highly reducible sintered ore is 0.05 to 0.1 with respect to 1 part by weight of the highly reducible sintered ore.
It is desirable to use 10 parts by weight. The coke has a strength index after reaction of 50% or less and an average particle size of 40%.
It is desirable to use coke of less than mm.

The reducibility index of the sintered ore is measured by the following test method (see JIS M 8713 for details). That is, a reaction tube (made of heat-resistant metal with an inner diameter of 75 ± 1 mm,
Inside has a hole with a hole diameter of 2 to 3 mm, and under the hole is filled with a heat exchange material consisting of alumina balls.) Inside, 500 g of sintered ore with a grain size of 19 to 22.4 mm Charge the temperature 90
At 0 ° C, 3% with a reducing gas of 30% CO and 70% N ₂
Time reduction. After the reduction, the reduction rate is determined from the weight loss due to the reduction and the contents of the total iron and iron oxide (divalent) in the sample before the reduction, and used as the reducibility index. The sinter having a high reducibility index is evaluated as an iron source raw material with less unreduced FeO flowing into the core coke. In the present specification, a sinter having a reducing index of 65% or more is referred to as a highly reducible sinter.

The post-reaction strength index of coke is determined, for example, by the following test method (for details, see the 3rd edition “Steel Handbook II”).
(See page 02). That is, the reaction tube (87.1 m inside diameter)
m, 250 mm in length), 200 g of coke sample sized to 20 ± 1 mm was charged, reacted at 1100 ° C, CO ₂ flow rate of 5 L / min for 120 minutes, and reacted. The above sample is abraded into powder by an I-type drum tester (tube diameter 130 mm, tube length 700 mm, rotation speed 20 rpm, total number of rotations 600).
The coke sample after the test is sieved, and the weight% of a portion having a particle size of 10 mm or more is defined as a post-reaction strength index. Coke
Coke having a lower strength index after the reaction is evaluated as a highly reactive coke that easily converts CO ₂ into CO, since the more the CO ₂ reacts easily with CO ₂ , the greater the strength deterioration.

Normally, in the blast furnace operation, a bell type charging device or a bellless type charging device provided at the furnace top is used. Coke and an iron source material are alternately charged using this normal charging device, and are deposited in a layered manner in a furnace. Hereinafter, the raw material charged in layers by the normal charging device is referred to as “normal charging iron source” or “normal charging coke”.

The main material of the iron source material is sinter ore or sinter, but in the method of the present invention, a part of the iron source material forming one layer (hereinafter referred to as "one charge iron source material"). Instead, a sinter having a reducing index of 65% or more, that is, a highly reducible sinter is used. Then, a mixture obtained by mixing coke with the highly reducible sintered ore (hereinafter referred to as "coke mixed sintered ore") is mainly charged into the center of the furnace. The iron source material for one charge excluding the portion replaced by the highly reducible sintered ore (the amount charged as the iron source material alone) is referred to as the “single charge iron source material” for convenience. ].

Since the coke mixed sintered ore described above needs to be deposited at the center of the furnace, prior to the normal charging of the single charged iron source material, preferably from a charging route different from the normal charging device, Charge in the center of the furnace.

In the method of the present invention, in addition to charging the coke mixed sintered ore into the center of the furnace, a measure for reducing the O / C ratio in the center of the furnace is also used. This can be done by increasing the thickness of the coke layer in the center of the furnace. Specifically, a part of the coke forming one layer (hereinafter, referred to as "one charge coke") is charged into the center of the furnace prior to the charging of the single charged iron source material. It is desirable to use a charging device of a different route from the normal charging device for this charging.

FIGS. 1 to 5 are longitudinal sectional views of a central portion of a blast furnace schematically illustrating the deposition state (pattern) of a raw material layer charged by the method of the present invention. The symbol D indicates a heat-affected zone described later.

I Pattern of FIG. 1: In FIG. 1, C ₀
Is a coke bed normally charged during normal operation. O ₀
Is an iron source raw material layer in which a single charged iron source raw material is usually charged collectively. In this case, one iron source material layer is formed with O ₀ . “One layer” in this specification refers to this layer. M is a layer of coke mixed sintered ore charged mainly in the center, and Cc is a coke layer mainly charged in the center. The above-mentioned M and Cc are continuously charged into the center with priority given to either one. That is, the material layers are formed in the order of C ₀ → M → Cc → O ₀ ((a) in FIG. 1) or C ₀ → Cc → M → O ₀ ((b)). Note that C ₀ may be divided and charged two or more times. On the raw material layer formed as described above, the raw material layers in the same charging order starting from C ₀ are stacked as needed.

II Pattern of FIG. 2: In FIG.
₁ and C ₂ are the coke layers normally charged after being divided into two times ( _one coke layer is formed by C ₁ and C ₂ )
. O ₁ and O ₂ are iron source raw material layers which are usually divided into two and charged. In this case, O ₁ and O ₂ form one iron source material layer. Prior to the normal charging of O ₁ and O ₂ , M and Cc are continuously charged in the center with priority on one of them. That is, after normal charging of C ₁ → C ₂ , M → Cc → O ₁ → M → Cc → O ₂ ((a) in FIG. 2), Cc → M → O ₁ → Cc → M → O ₂ (same as above). (b)), forming a raw material layer in the order of _{Cc → M → O 1 → M} → Cc → O 2 ( the (c)) or _{M → Cc → O 1 → Cc} → M → O 2 ( the (d)) I will do it. Note that C ₁ and C ₂ may be charged together without being divided.

III Pattern of FIG. 3: As shown in FIG. 3, prior to the normal charging of O ₁ or O ₂ , M and C
Perform center charging of c. That is, after normal charging of C ₁ → C ₂ , M → Cc → O ₁ → M → O ₂ ((a) in FIG. 3), Cc → O ₁ → Cc → M → O ₂ (same (b)), _{cc → M → O 1 → M} → O 2 ( the (c)) or _{M → cc → O 1 → cc} → O 2 is going to form a raw material layer in this order (the (d)).

IV Pattern of FIG. 4: As shown in FIG. 4, prior to the normal charging of O ₁ or O ₂ , M or C
Perform single center charging of c. That is, after the normal charging of C ₁ → C ₂ , the raw material layers are arranged in the order of M → O ₁ → Cc → O ₂ ((a) in FIG. 4) or Cc → O ₁ → M → O ₂ (same (b)). Is formed. Note that O ₁ and O
₂ may be further divided and charged two or more times. For example, O ₂
When charging is divided into two or more times, charging Cc or M may be performed before each divided charging.

On the raw material layer formed as described above,
Stacking up as necessary raw material layer of the same charging order starting from C ₁ again.

As described above, there are various types of central charging of coke mixed sintered ore and coke. In any case, the core charged in this way must be deposited in the layer of the iron source raw material normally charged. Must. If these are present in the normally charged coke layer, the above-described object of the present invention cannot be achieved.

[0031]

It is considered that heat is supplied to the core coke in the blast furnace by heat exchange with hot gas generated by combustion of coke in the raceway or by heat exchange with dripping molten iron slag. Therefore, an experimental study was conducted using a reduced model of a blast furnace to investigate whether any of these heat supply factors could more effectively affect the temperature rise of the core coke.

FIG. 5 is a schematic sectional view of a model test apparatus for examining the influence of the heat supply factor on the temperature rise of the core coke. This experimental device simulates the inside of a blast furnace above the tuyere. From the furnace top, a coke and a simulated ore (commonly referred to as “metal soap”) are fed through a charge hopper 8, a bell 1, and a movable armor 2. The discharge device 4 discharges the charge from the cutout below the tuyere to the discharge reservoir 6. In this way, the charge is lowered sequentially. Reference numeral 7 denotes an exhaust gas pipe.

On the other hand, the charge is heated by blowing hot air from the tuyere 3. As a result, the simulated ore dissolves in the course of descent, becomes a liquid, and drops on the bottom of the apparatus. That is, this apparatus can simulate the basic phenomena in the blast furnace excluding the reaction. Further, a large number of thermocouple temperature measuring points 5 are installed in the furnace, so that the movement of the furnace temperature can be understood.

The experiment was performed under the conditions shown in Table 1. First, the inside of the furnace was filled with coke, and blowing was started. While discharging coke from under the tuyere, charging only coke from the furnace top and continuing this charging / discharging for a certain period of time, then charging from the furnace top alternately with coke and simulated ore Then, the experiment was continued in that state, and the transition of the temperature of the tuyere-level furnace center, that is, the core coke, was investigated.

[0035]

[Table 1]

FIG. 6 is a diagram showing the influence of the heat supply factor on the temperature rise of the core coke.

The left half in the figure is the time of charging the coke alone, and the temperature of the core coke is raised only by heat exchange with gas from the tuyere. On the other hand, the right half in the figure corresponds to the time of alternate charging of coke and artificial ore, where the furnace exchanges heat with gas from the tuyeres and exchanges heat with the artificial ore that melts and drops. The core coke is heated.

As shown in the figure, the rate of temperature rise of the furnace core coke rapidly increased from the time when the charged artificial ore started melting, and the heating of the furnace core coke was caused by the heat of the artificial ore dropped. It is clear that is promoted. In other words, the promotion of heat exchange with dropped hot metal is effective in raising the temperature of the core coke, and by dropping a large amount of high-temperature hot metal onto the core, the core coke can be heated quickly. is there.

The present invention has been made based on the knowledge obtained in the above-described model experiment. Hereinafter, the mode of carrying out the method of the present invention in an actual blast furnace will be described.

In order to obtain the above-mentioned effect in the actual blast furnace, a certain amount of iron source material is deposited at the center of the furnace of the raw materials charged in layers, this is melted, and the temperature is raised to a high temperature. Need to be dropped into the furnace core coke. Usually, iron is contained in the iron source material in the form of iron oxide, and in order to melt and reduce these to produce hot metal, a large amount of heat of melting and heat required for reduction must be supplied. The heat is supplied by heat exchange with the gas in the lump zone and by heat exchange with the gas and coke in the dripping zone in the dripping zone. However, the rate of descent (dropping) in the dropping zone after dissolution is much faster than that in the blocky zone of the iron source material, so it is estimated that the heat exchange efficiency in the dropping zone is considerably worse than that in the blocky zone. You.

Therefore, when the direct reduction reaction, which is an endothermic reaction, proceeds after the melting of the iron source material, that is, when the smelting reduction occurs in the dropping zone, the heat exchange efficiency is poor. It is not easy to make hot metal. Furthermore, the coke deteriorates due to the reaction with CO ₂ and H ₂ O gas generated by the reduction, so that the strength at the time of reaching the furnace core decreases. And, if the reaction deterioration of the core supply coke becomes large, the permeability itself of the core coke deteriorates,
The furnace core becomes inactive, which leads to a malfunction of the furnace condition.

In the method of the present invention, a part of the iron source material usually charged in a layer is replaced with a sinter having a reducibility index of 65% or more (highly reducible sinter), and A coke mixed sintered ore obtained by mixing coke with ore is charged into the furnace center. In this case, the particles of the highly reducible sinter and the coke particles are present adjacent to each other. CO generated by reduction of sinter
₂ or H ₂ O causes a gasification reaction with adjacent coke particles, and is soon regenerated into CO and H ₂ , thereby accelerating the progress of reduction. As a result, the reduction rate of the meltdown of the iron source material is increased, and the unreduced Fe in the dropping zone is reduced.
Since the smelting reduction of O 2 can be suppressed, the temperature of the hot metal can be increased. The reducibility index of a general sinter used in a blast furnace is about 55 to 65%.

The gasification reaction of coke with CO ₂ or H ₂ O described above proceeds preferentially with coke mixed with highly reducible sintered ore. For this reason, the coke in the coke layer near the center of the furnace hardly undergoes deterioration due to the reaction with CO ₂ and H ₂ O gas, and the strength of the coke supplied to the furnace core can be maintained at a high level.

The mixing weight ratio of coke to high reducible sinter in the method of the present invention is 0.05 to 0.10 (0.05 to 0.10 parts by weight of coke for 1 part by weight of high reducible sinter). It is desirable to do. This is a desirable condition for the coke particles mixed with the sinter to completely disappear by gasification before entering the dropping zone. If the mixing amount of coke is excessively increased, low-strength coke finely divided remains after the gasification reaction, which falls into the furnace core and impairs the air permeability of the core coke. If the mixing amount is too small, the gasification reaction of CO ₂ and H ₂ O does not proceed sufficiently,
Promotion of reduction is inhibited. In addition, if the gasification reaction amount of the mixed coke is not sufficient, the coke in the coke layer usually charged must cover this, and the strength of the coke supplied to the furnace core decreases.

In the method of the present invention, the coke to be mixed with the highly reducible sintered ore is more preferably a coke having a post-reaction strength index of 50% or less and an average particle size of 40 mm or less.
This is also a desirable condition for completely eliminating the mixed coke. By doing so, the gasification reactivity of the mixed coke can be increased, and a situation in which finely divided low-strength coke remains can be avoided. Therefore,
Good permeability of the furnace core coke is maintained. The post-reaction strength index of a general coke used in a blast furnace is about 50 to 60%, and the average particle diameter is about 50 to 55 mm.

As described above, by mixing coke with highly reducible sintered ore having a reducibility index of 65% or more and charging the mixed ore into the furnace center, the gasification reaction of coke by CO ₂ and H ₂ O is performed. The mixed coke was selectively performed, while suppressing the strength deterioration due to the reaction of coke in the coke layer near the center of the furnace supplied to the furnace core, ensuring the permeability of the furnace core coke, and sufficiently raising the temperature. Hot metal can be dropped onto the furnace core.

Next, the significance of charging coke mixed sintered ore and coke into the center of the furnace in the method of the present invention will be described with reference to FIGS.

From the measurement by coke sampling when the blast furnace is shut off, the dimensionless distance from the center axis of the furnace (the amount obtained by dividing the actual distance by the radius of the furnace opening to make it dimensionless) is more than about 0.2 (furnace center). It has been empirically known that the coke temperature in the area (side of D) in the figure (the "heat-affected area" indicated by D in the figure) is an important index for core condition evaluation, and that heating in this area is not easy. Have been.

In the method of the present invention, the amounts of the coke mixed sintered ore and coke charged in the center of the furnace are adjusted so that at least the center of the furnace does not normally have a charged iron source. As shown in the drawing, coke mixed sintered ore and coke are mainly deposited at the center of the furnace of the normally charged iron source material layer formed subsequently. Therefore, the abundance of the normally charged iron source having a low reducibility in the heat-affected zone can be reduced as compared with the normal charging method in which the central charging is not performed. Further, the O / C ratio or the coke layer thickness at the center of the furnace can be accurately controlled. This makes it possible to increase the temperature of the hot metal at the center of the furnace to promote the heating of the core coke, maintain good air permeability of the core, and avoid a furnace condition malfunction.
Furthermore, since highly reducible sintered ore, which is replaced by a normal iron source, is centrally charged, it is possible to contribute more effectively to pig iron production in the heat-affected zone compared to central charging of coke alone. it can.

FIGS. 1 and 2 show coke mixed sintered ore.
This is a pattern of continuous center charging of (M) and coke (Cc).

[0051] Figure 1 a continuous center charged in preference to M to Cc (a), in FIG. 2 (a), the normal between the instrumentation Nyutetsu source material layer O ₀ or O _1, O ₂ and M, A Cc layer is formed diagonally upward from the furnace wall side end of the heat-affected zone D toward the furnace center.
If the temperature of the exhaust gas in the center of the furnace becomes too high, the temperature can be adjusted by increasing the amount of M charged and reducing the thickness of the Cc layer.

FIG. 1 in which iron source materials are charged at one charge.
2A can reduce the abundance of the normally charged iron source having a low reducibility in the D region as compared with FIG. On the other hand, in FIG. 2A, the thickness of the M layer divided into two at the furnace center is smaller than the thickness of the M layer in FIG.
Split charging is more advantageous for promoting reduction of M at the center of the furnace.

[0053] Figure 1 a continuous center charged give priority to Cc to M (b), FIG. 2 (b), O ₀ or O _1, O ₂ and Cc
And an M layer is formed between them. Therefore, the thickness of the M layer is made uniform in the radial direction. On the other hand, carbon monoxide (C
O) The rich gas flow can be controlled by adjusting the charge of Cc. Therefore, the reduction of M can be more effectively promoted than in the case of the continuous center charging in which M is prioritized over Cc.

FIG. 2 (c) in which a continuous center charging in which Cc has priority over M and a continuous center charging in which M has priority over Cc are combined.
In FIG. 2D, an average effect of each of the effects described above is obtained.

FIG. 3 shows a pattern of a combination of continuous central charging of coke mixed sinter (M) and coke (Cc) and single central charging of coke mixed sinter or coke.

The effect of the continuous center charging giving priority to either M or Cc is as described above. This continuous center charging is performed prior to the charging of the normal charging iron source O ₁ , and M
FIG went before the single central charging the charging of the normal instrumentation Nyutetsu source O ₂ 3 (a), in FIG. 3 (c), the previously described FIG. 2 (a), 2
In the case (c), the abundance of M in the heat-affected zone D is increased, and the zone D can be effectively contributed to pig iron production. On the other hand, the charging amount of Cc decreases, and carbon monoxide (C
O) Since the ascending flow of the rich gas in the furnace center is weakened, it is suitable for the operation of lowering the exhaust gas temperature in the center of the furnace.

3 (b) and 3 (d) in which the single center charging of Cc and the continuous center charging of Cc and M are combined, the coke layer thickness at the center of the furnace can be increased. The ascent flow of the carbon dioxide (CO) rich gas in the furnace center can be enhanced. Therefore, reduction of M can be promoted. However, since the amount of M charged is small, the contribution to the pig iron production in the D region is inferior to FIGS. 3 (a) and 3 (c).

FIG. 4 shows a pattern of a combined charging of a single center charging of coke mixed sintered ore (M) and a single center charging of coke (Cc).

As shown in FIGS. 4 (a) and 4 (b), M and Cc are mainly charged in the center of the furnace of the normally charged iron source material layer, and carbon monoxide (CO) The furnace center ascending flow of the rich gas can be enhanced to promote the reduction of M. Also,
The region D can also contribute to pig iron production. In this method, although the amount of M in the D region and the suppression width of the upward flow of the carbon monoxide (CO) rich gas in the center of the furnace are narrow, the number of times of center charging or the number of times of changing the center charging amount is limited by the iron source divided into two parts. In this case, the number of the M and Cc is smaller than that in the case of the continuous center charging, so that the operability is suitable for the actual operation.

As shown in FIG. 7 to be described later, the coke mixed sintered ore and coke are charged into the center of the furnace by charging a separate route in addition to a normal bell-type charging device or a bellless-type charging device. It may be provided by means of a device.

According to the method of the present invention, even if the temperature of the core coke drops during operation, the temperature of the core coke can be raised quickly, and the furnace condition can be quickly recovered to maintain stable operation. Further, since the furnace center also contributes to the melting and reduction of the iron source, there is no possibility that the productivity of the furnace will decrease.

[0062]

Embodiments of the present invention will be described below. In this example, a blast furnace having a furnace volume of 2700 m ³ and equipped with a bell-type charging device was used.

FIG. 7 is a longitudinal sectional view for explaining a charging device for an upper portion of a blast furnace used in the embodiment. As shown in the drawing, in addition to the ordinary bell-type charging device 9, another route charging device 14 for charging the central part of the furnace is provided. Raw materials charged from another route are supplied to the upper hopper by the bucket conveyor 15.
After being temporarily stored in the lower hopper 19 and the exhaust pressure in the lower hopper 19 is completed, the upper seal valve 18 and subsequently the upper gate 17 are opened and transferred to the lower hopper 19.

Next, after the upper gate 17 and the upper seal valve 18 are closed, the pressure in the lower hopper 19 is equalized to the furnace pressure, and the preparation for the furnace interior is completed. Then, when the charging timing to the center of the furnace comes, the lower seal valve 21 and then the lower gate
The opening operation of 20 causes the raw material to drop to the center of the furnace via the charging chute 23, and is deposited like 24. Reference numeral 25 denotes a raw material charged from a normal charging route, which is generally deposited in a layer having a hollow central portion as shown in the figure.

Table 2 shows the main operation data of the embodiment. Here, the raw materials were charged as follows.

(A) Charging Coke 15.5 tons (Examples 1 and 3) and 15.7 tons (Example 2) of one charge (16 tons) were divided into two equal parts and divided into two parts 250 kg (Example 1), 300 kg (Example 2), remaining
500 kg (Example 3) was charged into the furnace center from another route charging device 14.

(B) Charging of Iron Source Material One charge (63 tons) of the iron source material (sinter ore or iron ore) is divided into two equal parts, and divided into two parts from the furnace top by the normal route. 550 kg, 500 kg
(Example 1), 400 kg, 1050 kg (Example 2), 1050 kg
(Example 3) was replaced with a sinter having a reducing index shown in Table 3 and used for coke mixed sinter. That is, coke having an average particle size and a post-reaction strength index shown in Table 3 was blended with the sintered ore to obtain a coke mixed sintered ore. The mixing weight ratio is also shown in Table 3. The coke mixed sintered ore was charged from a separate route charging device 14 into the furnace center.

(C) Order of charging Example 1 (as shown in FIG. 2 (b)) Coke (first time) 2. 2. Coke (second time) 3. Central charging of coke from another route 4. Central charging of coke mixed sinter from another route 5. Iron source material (first time) 6. Central charging of coke from another route 7. Central charging of coke mixed sinter from another route Iron source material (second time) Example 2 (as shown in FIG. 3 (a)) Coke (first time) 2. 2. Coke (second time) 3. Central charging of coke mixed sinter from another route 4. Central charging of coke from another route 5. Iron source material (first time) 6. Central charging of coke mixed sinter from another route Iron source material (second time) Example 3 (as shown in FIG. 4 (b)) Coke (first time) 2. 2. Coke (second time) 3. Central charging of coke from another route Iron source material (first time) 5. 5. Central charging of coke mixed sinter from another route The iron source material (second time) was used, and this was repeated as one cycle.

As shown in Table 3, the coke mixed sintered ore charged centrally from another route has a reducibility index of 65.
% Of the sintered ore, and the operation was performed while changing the post-reaction strength index and particle size of the coke mixed only in Example 3 and the mixing weight ratio of the mixed coke to the sintered ore. As a comparative example of Example 3, a sintered ore having a reducibility index of 60% was used.

In Table 3, the mixing ratio by weight of coke was 0.10.
Is a condition in which a coke amount commensurate with the direct reduction amount is mixed based on the direct reduction ratio (40%) in the central part of the furnace before the method of the present invention is carried out.

The operation of the example and the comparative example was carried out between normal charging operations without using the method of the present invention (conventional example without center charging by another route charging device in FIG. 7). The operation period was about three weeks. Then, core coke was sampled from the tuyeres at the time of the wind break after the end of each operation period.

In order to evaluate the powdered state and the temperature rise state of the core coke during the operation, it was estimated from the measured data of the average particle size and the degree of graphitization of the core coke collected near the tuyere level center of the furnace. The history temperature (maximum temperature reached) of core coke was investigated.

[0073]

[Table 2]

[0074]

[Table 3]

FIG. 8 shows the state of powdering and heating of core coke in Examples 1, 2 and 3 of Table 3 and the conventional example in which only normal charging of raw materials was performed. (A) shows the average core coke particle size, and (b) shows the core coke hysteresis temperature (maximum attained temperature).

As shown in the figure, the sinter ore reducibility index of the coke mixed sinter is the value determined in the present invention, and the mixed weight ratio, particle size and post-reaction strength index of the mixed coke are desirable values. In Cases 1 and 2 of Examples 1, 2 and 3, the average particle size and hysteresis temperature of the core coke were higher than those of the conventional example in which normal charging was performed. The improvement of the furnace condition by the improvement of the air permeability and the temperature rise of the core coke is seen.

The comparative example is an example operated under the same conditions as in Case 1 of Example 3 except that the reducibility index of the sinter mixed with coke was set to 60%. In this comparative example, the coke and the mixed coke charged at the center supply the core coke with the normally charged coke having little particle size deterioration. In addition, mixed coke finely divided after the reaction remains,
Since the coke mixing weight ratio is determined so that this is not supplied to the furnace core coke, the average particle size of the furnace core coke is higher than that of the conventional example. However, since the reducibility of the sinter ore charged in the center is lower than in Case 1, the inflow of unreduced FeO into the core coke increases, and thus the improvement of the hysteresis temperature of the core coke is not observed. From the results, it was found that coke mixed sinter ore and part of coke were charged at the center to achieve the rapid heating of the core coke and the recovery of the furnace condition, which are the objects of the present invention. It turns out that the sinter ore reducibility index of the condensate should be 65% or more.

Further, the coke mixed weight ratio of the coke mixed sintered ore was set to 0.20 higher than 0.10 corresponding to the direct reduction amount at the furnace center.
Case 3 where the post-reaction strength index of the mixed coke was 55% or less than 50% or less, and Case 5 where the average particle size was 50 mm or less and less than 40 mm or less. Since the reducibility index of the condensate is as high as 65%, the reduction is promoted, the inflow of unreduced FeO into the core coke is reduced, and the hysteresis temperature of the core coke is improved. However, in the coke-sintered ore layer charged at the center, coke refined by increasing the reducibility of the sinter by the gasification reaction remains, and this coke flows into the core coke, and the average particle size is reduced. Causes a decrease in From this result, to promote the temperature rise of the furnace core coke, to improve the furnace conditions, and to maintain the ventilation and liquid permeability of the furnace core coke, the coke mixing weight ratio with respect to the sinter is 0.05 to 0.10, Further, it can be seen that it is desirable to operate the mixed coke with the post-reaction strength index of 50% or less and the average particle size of 40 mm or less.

[0079]

According to the method of the present invention, it is possible to promote the heat exchange between the core coke and the ascending flow of hot hot metal and a high temperature carbon monoxide (CO) rich gas in the furnace core. Higher temperatures can be maintained. Further, even when the core coke cools down, the temperature of the core coke is quickly raised, and the furnace condition can be quickly and normally recovered. Therefore, stable operation of the blast furnace can be easily maintained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a central portion of a blast furnace schematically showing a raw material deposition state according to the method of the present invention.

FIG. 2 is a vertical sectional view of a central portion of a blast furnace schematically showing another example of a raw material deposition state according to the method of the present invention.

FIG. 3 is a vertical sectional view of a central portion of a blast furnace schematically showing still another example of a raw material deposition state according to the method of the present invention.

FIG. 4 is a vertical sectional view of a central portion of a blast furnace schematically showing still another example of a raw material deposition state according to the method of the present invention.

FIG. 5 is a schematic cross-sectional view of a model test apparatus for examining the influence of a heat supply factor on the temperature rise of the core coke.

FIG. 6 is a diagram showing the influence of the heat supply factor on the temperature rise of the core coke.

FIG. 7 is a schematic sectional view of an upper part of a blast furnace having a separate route charging device for a central part of a furnace used for carrying out the present invention.

8A and 8B are diagrams showing, in comparison, the state of powdered and elevated temperature of the core coke confirmed in the examples, wherein FIG. 8A shows the average particle diameter of the core coke, and FIG. FIG.

[Explanation of symbols]

1: Bell, 2: Movable armor, 3:
Tuyere, 4: Charge discharger, 5: Thermocouple temperature measuring point,
6: Exhaust reservoir, 7: Exhaust gas pipe, 8: Charge hopper, 9: Bell type charging device, 10: Small bell,
11: Large bell, 12: Movable armor, 13: Blast furnace furnace, 14: Separate route charging device, 15: Bucket conveyor, 16: Upper hopper, 17: Upper gate,
18: Upper seal valve, 19: Lower hopper, 20:
Lower gate, 21: Lower seal valve, 22: Equalizing pipe,
23: Charging chute, 24: Alternative route charging material,
25: Normal route charge.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-35610 (JP, A) JP-A-1-290708 (JP, A) JP-A-6-256819 (JP, A) 9373 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21B 5/00

Claims (3)

(57) [Claims] 1. A method for operating a blast furnace in which coke and an iron source material are alternately charged into a furnace from the furnace top in a layered manner, wherein a high reducible index having a reducibility index of 65% or more as part of the iron source material is provided. Using a highly sinterable ore, charging the mixture of this highly reducible sinter and coke into the center of the furnace separately from the normal iron source material, and separately from the normal coke A method of operating a blast furnace, comprising: charging coke to the center of the furnace; and depositing the mixture and coke charged to the center of the furnace in a layer of ordinary iron source material. 2. A method for operating a blast furnace according to claim 1, wherein the amount of coke in said mixture is 0.05 to 0.10 parts by weight based on 1 part by weight of the highly reducible sintered ore. . 3. A coke mixed with the highly reducible sintered ore having a strength index after reaction of not more than 50% and an average particle size of not more than 50%.
2. A coke of 40 mm or less is used.
Or the method for operating a blast furnace according to item 2.