JP3485787B2 - How to charge raw materials for blast furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the operation of ores (O) and agglomerated coke, in particular, under the condition that the fuel ratio is constant.
Regarding the charging method of the blast furnace raw material suitable for the bell-type blast furnace that performs high O / C operation with the in-furnace weight ratio O / C of (C) of 4.5 or more,
The present invention relates to a blast furnace raw material charging method capable of segregating and charging small and medium sized coke into the periphery of a furnace.

[0002]

2. Description of the Related Art In the blast furnace method in the iron-making industry, ores (a mixture of iron ore, sinter, pellets, limestone, etc.) and iron-making raw material granules such as coke are sequentially charged into the furnace. A material layer is formed, and a high-temperature heat source gas is circulated from the lower part of the furnace to cause a reduction reaction of iron. For this reason, it is important to control the gas distribution in the furnace that guarantees the reduction reaction, and control of the distribution and filling state of the charge layer of the iron-making raw material powder particles, which greatly affects this gas distribution, is an economical and stable operation. Has become important to continue.

In the recent operation of a blast furnace, conventional all-coke operation (all reducing materials are installed as coke from the top of the furnace) for the purpose of drastically reducing fuel costs, reducing the burden on the coke oven, and extending the life of the furnace. How to enter)
In addition to the charging of coke from the top of the furnace, the operation is in the process of blowing in auxiliary fuel such as pulverized coal, heavy oil, and natural gas from the tuyere of the blast furnace. And in recent years, 150kg / t −
A large amount of auxiliary fuel such as pulverized coal of pig iron (pig) or more is blown into the furnace to increase the ratio Ore / Coke (hereinafter simply referred to as O / C) of ore (O) and coke (C) in the furnace. It is common to operate at high O / C, which is 4.5 or higher.

On the other hand, usually, the coke lumps produced in the coke oven are crushed by a crusher to prepare a particle size distribution preferable for use in the blast furnace, for example, 35 to 100 mm, and these lump cokes are charged into the blast furnace. Form a coke layer and play an important role in ensuring the air permeability of the charge layer.

In the process of obtaining coke having the above particle size distribution, 35
A relatively large amount of small and medium sized coke with a particle size of less than mm is generated. These small and medium sized cokes, compared to the lump coke having a particle size of 35 mm or more, because the effect of ensuring the air permeability of the charge layer is low, are not used directly for blast furnace,
Some powder coke was used during the sintering of powder ores or as an additive for briquettes.
However, in recent years, it has been attempted to improve the coke production yield by using these small and medium-sized coke directly for a blast furnace.

For example, in Japanese Patent Publication No. 52-43169,
Small lump coke with a particle size of 15 mm or less is mixed with ores in advance before charging to the blast furnace, and the mixed ore and normal lump coke are charged in layers to operate the blast furnace. . And, in this technology, not only the improvement of the coke production yield, but because the mixed ores premixed with small lump coke and normal lump coke are charged in layers,
It is said that since the permeability and reduction rate of the mixed ores in the blast furnace are improved and the permeability of the entire charge layer is improved, the fall of the charge is stable.

Further, Japanese Patent Publication No. 4-42443 and the like disclose, as an improvement of Japanese Patent Publication No. 52-43169, a technique for allowing small coke to uniformly exist in a deposited ore layer in a furnace. There is. That is, in the publication, the Japanese Patent Publication No. 52-43169
As described in Japanese Patent Publication, even if a mixed ore in which small coke is uniformly and completely mixed with ores is charged into the furnace from the large bell hopper in advance, the small coke is uniformly distributed in the deposited ore layer in the furnace. When the mixed ores are falling from the large bell hopper, and while descending on the lump coke slope that has already been deposited, re-separation of ore and small lump coke occurs, resulting in a specific gravity It is disclosed that the small coke of small size does not enter into the deposited ore layer and is unevenly distributed near the surface of the deposited ore layer.

And, in this publication, this problem is solved,
In order to make the small coke uniformly exist in the deposited ore layer in the furnace, the coke charged into the furnace is divided and charged, and the small coke is used as the final charging coke,
This small coke is charged near the dropping position of the initially charged ore in the furnace, while the ore is also divided and charged, and only the ore is charged at the beginning of the ore charging, and the second ore after the ore insertion. In the charging of No. 2, the small coke is deposited in the lower part of the large bell hopper, and the ore is then deposited from the upper part, and the upper ore and the lower small coke are simultaneously charged into the furnace.

[0009]

[Problems to be Solved by the Invention] Usually, the above-mentioned high O / C
In the operation, the fuel ratio of the blast furnace (lump coke ratio + small and medium sized coke + pulverized coal ratio + Oil ratio) is constant. Therefore, for such high O / C operations, when using mixed ores mixed with the above ores and small coke with a particle size of 15 mm or less, the amount of small and medium sized coke is naturally commensurate with the amount used. A large amount of agglomerated coke (agglomerated coke ratio) is reduced to operate.

The Japanese Patent Publication No. 52-43169 and Japanese Patent Publication No. 4-
As in Japanese Patent No. 42443, the small coke is uniformly present in the sedimentary ore layer in the furnace, that is, the ore and the small coke mixed ore and the normal coke are uniformly layered in the furnace. When charging, the amount of small coke used increases considerably, so in blast furnace operation under the above-mentioned constant fuel ratio,
The amount of agglomerated coke used (agglomerated coke ratio) will be significantly reduced.

However, the high O /
In the C operation, as described above, the ratio of lump coke to ore decreased, and as a result, the weight ratio of ore and lump coke was increased.
O / C increases, so in the situation of raw material deposition in the blast furnace,
The local high O / C portion is likely to occur in the radial or circumferential direction of the blast furnace.

[0012] Therefore, for example, when small medium sized coke having a particle size of 35 mm or less is used for high O / C operation under the condition of constant fuel ratio, the blast furnace is greatly reduced in the ratio of lump coke to ore. The generation of local high O / C in the radial direction or the circumferential direction is more likely to occur, and the tendency that the O / C in the peripheral area of the furnace becomes high becomes remarkable. As a result, the phenomenon in which the temperature rise or reduction of the ore occurs in the peripheral portion of the furnace and the smooth melting and dropping is hindered becomes remarkable. This phenomenon is further promoted by a decrease in the amount of gas rising in the bed due to the increase in the ore layer thickness due to the high O / C and the decrease in the coke layer thickness.

Further, this phenomenon increases the ventilation resistance in the blast furnace during operation of the blast furnace, and in particular, the gas flow in the center of the blast furnace decreases, and conversely the gas flow on the furnace wall side rises. The disadvantage is that the amount of heat loss increases. Also,
When the gas flow on the furnace wall side rises significantly, troubles such as bending of tuyere occur.

Thus, if the small and medium-sized coke can be directly used for the blast furnace, it can be expected to improve the yield of coke production, but in particular, the high O / C operation under the condition of a constant fuel ratio. Then, the operation trouble is likely to occur. That is, as in the above-mentioned prior art, instead of the ordinary ores, mixed ores of ores and small and medium sized coke are used, and the mixed ores and ordinary lump coke are layered throughout the furnace. In the case of high O / C blast furnace operation under the condition that the fuel ratio is constant, the O / C especially in the peripheral area of the furnace becomes high due to the large decrease in the ratio of lump coke to ore. In the above, the phenomenon in which the temperature rise or reduction of the ore occurs and the smooth melting and dropping is hindered becomes remarkable. Therefore, it can be said that the prior art does not intend to operate a high O / C blast furnace under the condition of a constant fuel ratio, and targets a low O / C blast furnace operation.

On the other hand, if the small and medium sized coke is segregated into the peripheral area of the furnace (segregated and accumulated in the peripheral area of the furnace) and the amount of the small and medium sized coke used is reduced, the lump coke for the ore is reduced. The ratio does not decrease so much, and since the agglomerated coke deposit layer in the furnace ensures air permeability, the O / C in the peripheral area of the furnace does not become so high, and the peripheral area of the furnace, especially the root of the cohesive zone The pressure loss can be reduced, and the ore reduction rate can be improved.

More specifically, iron ore raw material powder particles such as iron ore and coke are usually charged alternately into the blast furnace from the top of the blast furnace to form a multi-layered charge layer. At this time, the particle size of the ore is very small compared with the particle size of the coke and has a high density, so when the ore is charged on the sedimentary layer of the coke, the ore flowing into the central part of the furnace is The upper part of the coke layer is scraped off and accumulated while entrained in the ore layer, causing an unstable phenomenon such as coke collapse, and a mixed layer of coke and ore having a high packing density between the coke layer and the ore layer ( The closest packed layer) is formed.

The mixed layer has poorer air permeability in the solid state and the softened and molten state than the coke layer and the ore layer, and has a great influence on the gas distribution in the furnace. As mentioned above,
Especially in high O / C operation, the ratio of coke to ore decreases and the weight ratio O / C of ore to coke increases, so in the situation of raw material deposition in the blast furnace, in the radial or circumferential direction of the blast furnace, Above all, the local high O / C portion is likely to occur especially in the periphery of the furnace, especially in the root of the cohesive zone.

On the other hand, if the small and medium sized coke or mixed ore having a particle size of 35 mm or less is segregated and charged into the peripheral area of the furnace, and the amount of the small and medium sized coke used is reduced, In particular, in the periphery of the furnace, especially in the root of the cohesive zone,
It is possible to prevent the occurrence of local high O / C portions, reduce pressure loss and improve air permeability. In the reducing zone in the furnace, the ore in the mixed ore (mixed ore layer) is heated and reduced by the reducing gas in the furnace, and the ore in the mixed ore is directly converted by the small and medium sized coke contained in the mixed ore. Since the reduction is accelerated, the reduction rate of the ore is increased and the progress of metallization is accelerated.

However, when the small and medium sized coke is directly used for the blast furnace, it is effective to segregate the small and medium sized coke into the peripheral portion of the furnace as described above, but the actual blast furnace is not charged. In charging blast furnace raw materials, it is difficult to segregate small and medium sized coke into the periphery of the furnace itself.
The actual situation is that the technology that enables segregation of small and medium sized coke into the peripheral area of the furnace has not been established so far.

In view of these problems of the prior art, the present invention relates to a method for charging a blast furnace raw material into a bell-type blast furnace operating under a constant fuel ratio condition and a high pulverized coal ratio (low coke ratio). It enables segregation charging of small and medium sized coke to the inside of the furnace and reduction of the amount of small and medium sized coke to be used, thus operating without causing troubles such as pressure loss in the inside of the furnace and cohesive zone. In addition to the above, it is an object of the present invention to provide a blast furnace raw material charging method capable of exerting the advantages of using small and medium sized coke, such as improving the coke production yield and improving the permeability and reduction rate of ores in the blast furnace. And

[0021]

In order to achieve the above object, the present invention provides a method for charging a blast furnace raw material into a bell- type blast furnace, in which a lower region of ores loaded in a large bell hopper is provided. , Ore mixed with small and medium sized coke having a particle size of 35 mm or less in advance, and this lower region is loaded with the weight of the lower ore mixed with small and medium sized coke (WOL) and loaded in a large bell hopper. As a percentage of total weight (WO) (WOL
/ WO) is 0.2 or less, and by charging these ores into the furnace from the large bell hopper, it is the gist to segregate the small and medium sized coke into the peripheral area of the furnace. is there.

In order to segregate the small and medium sized coke into the peripheral portion of the furnace, the present inventors premix the small and medium sized coke in the lower region of the ores loaded in the large bell hopper, That is, the ores in the lower region of the ores loaded in the large bell hopper are mixed ores pre-mixed with small and medium sized coke, and the weight of the lower ores mixed with small and medium sized coke (WOL) , The total weight of ore loaded
By setting the ratio (WOL / WO) to (WO) to 0.2 or less and charging this ore into the furnace from the large bell hopper, it is possible to reduce the amount of small and medium sized coke used and reduce the amount of small and medium sized coke. We have found that it is possible to charge segregated into the peripheral area of the furnace.

Then, as in the present invention, if the small and medium sized coke or mixed ore having a particle size of 35 mm or less is segregated and charged into the peripheral portion of the furnace, and the amount of the small and medium sized coke used is reduced, the furnace the inner periphery, particularly in the cohesive zone root, elementary and junior high Mukuro
Coke acts to compensate for the breathability. In the reducing zone in the furnace, the ore in the mixed ore (mixed ore layer) is heated and reduced by the reducing gas in the furnace, and the ore in the mixed ore is directly converted by the small and medium sized coke contained in the mixed ore. Since the reduction is accelerated, the reduction rate of the ore is increased and the progress of metallization is accelerated.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method of segregating small and medium sized coke into the peripheral portion of the furnace in the present invention will be described.

In the present invention, in order to charge the small and medium sized coke into the peripheral portion of the furnace, it is necessary to first mix the small and medium sized coke with the lower part of the ores loaded in the large bell hopper. is there. Normally, the charging of the iron-making raw material into the bell-type blast furnace is carried out with 2 batches of lump coke and 2 batches of ore C ₁ ↓ C ₂
↓ O ₁ ↓ O ₂ ↓ (C: coke,: O ores), and each ironmaking raw material is sequentially loaded into the large bell hopper and charged into the furnace. Therefore, according to this common law,
In the present invention, the small or medium corpse coke is premixed with the ores under the ores O ₁ ↓ and / or O ₂ ↓ loaded in the large bell hopper.

At this time, the proportion of the small or medium sized coke mixed in the lower region of the ore loaded in the large bell hopper is determined by the weight of the lower ore mixed with the small or medium sized coke.
The ratio of (WOL) to the total weight of loaded ores (WO) (WOL / WO) is 0.2 or less. As described below, the ratio of the weight (WOL) of the lower ore mixed with small and medium sized coke to the total weight (WO) of the loaded ore (WOL /
When (WO) exceeds 0.2, it becomes close to or the same as the mixing of small and medium sized coke over the entire ores O ₁ ↓ and O ₂ ↓ as in the above-mentioned respective prior arts. Segregation charging itself into the peripheral area of the coke inside the furnace is not possible. It also leads to the inability to reduce the amount of small and medium sized coke used.

As the method of preliminarily mixing the small and medium sized coke with the ores, the mixing method disclosed in the above Japanese Patent Publication No. 52-43169 can be appropriately used. In particular,
Before placing in the ore tank, in the transportation system between the ore tank and the blast furnace top charging device, or by installing another mixing device in the furnace top charging device and mixing in the furnace top charging device There is a way.

Further, the mixing amount of the small and medium sized coke into the ore in the lower region loaded on the large bell hopper is determined by segregating the small and medium sized coke into the peripheral portion of the furnace to obtain the above-mentioned breathability. As a lower limit amount for exerting a compensating action or a reducing action of ore, preferably 5 kg / t-pig or more, more preferably 10
More than kg / t-pig.

On the other hand, if the amount of small and medium-sized coke to the lower ores is too large, the amount of agglomerated coke will be remarkably reduced under the constant fuel ratio operation of the blast furnace. / C occurs. Therefore, from this point of view, it is preferable that the amount of the small and medium sized coke to be premixed with the ore is as small as possible, and therefore,
The upper limit of the small and medium sized coke mixed with the ores is preferably 100 kg / t-pig or less, more preferably 30 kg / t-pig or more.

[0030]

EXAMPLES Next, examples of the present invention will be described. Internal volume 45
Using a two-dimensional cold model machine with a scale of 1 / 10.6 of a large blast furnace of 50 m ³ and simulating high O / C operation at a constant fuel ratio, 0 / C: 5.
5 (however, C is the volumetric weight of the coke only in the coke), the coke ratio of the coke: 290 kg / t-pig, the coke ratio of the small and medium coke is 5 kg / t
-Pig, pulverized coal blowing ratio of 230kg / t-pig,
A segregation charging test of small and medium sized coke was conducted. The ironmaking raw materials used in the test were agglomerated coke with a particle size of 4.0 to 5.6 mm, small and medium-sized coke with a particle size of 4.0 to 5.6 mm, ore [sintered ore (particle size
1.0 to 3.35 mm) 56% + Alumina ball (particle size 1.0 to 1.4 m
m) 44%].

Lump coke, which is the usual charging of ironmaking raw materials
Assuming 2 batches of ore and 2 batches of C ₁ ↓ C ₂ ↓ O ₁ ↓ O ₂ ↓ (C: coke,: O ore), mix small and medium sized coke with the above particle size into O ₁ ore. I went in advance. The mixing amount (concentration) for ores was fixed at 5 kg / t-pig, and the amount of ores mixed with small and medium sized coke was changed. In other words, the ores mixed with this small and medium sized coke were mixed in the lower region of the large bell hopper 5 which is composed of the large bell 1 and bell cup 2 of the cold model machine, as shown schematically in Fig. 3. Ore
_No. 4 is deposited first, and then the ore that does not mix the small and medium sized coke is deposited as the O ₁ ore, and the weight of the lower ore mixed with the small and medium sized coke (WOL) is loaded. Proportion of total ore (WOL / W)
O) was changed variously.

Then, the ores with varying mixing ratios of these small and medium sized cokes are loaded into the furnace by lowering the large bell 1, and at the same time, the small and medium sized solids of the ores accumulated at each WOL / WO are loaded. The segregation degree of the coke in the furnace radial direction was investigated.
Note that the segregation degree was investigated by aspirating the ores from each part of the deposited ore in the radial direction of the furnace by the suction method to obtain the amount of small and medium sized coke in the ores and segregating them. The degree (the weight ratio of small and medium sized coke to the weight of ore when collecting the sedimentary layer in the furnace / the weight ratio of small and medium sized coke to the weight of ore at the time of charging) was obtained. The results are shown in Figure 2.

FIG. 2 shows O ₁ at each portion in the radial direction in the furnace.
Shows the segregation degree of small and medium sized coke in the ore layer of. As is clear from Fig. 2, ore layers with WOL / WO of 0.0 (marked ○ in the figure) and 0.1 (marked △ in the figure), that is, small or medium in the lower part of the ore loaded in the large bell hopper. It can be seen that the small and medium wreck coke is segregated to the periphery of the furnace by mixing the wreck coke and charging the ore with WOL / WO of 0.2 or less into the furnace from the large bell hopper. On the other hand, WOL / WO
0.2 (□ mark in the figure), 0.3 (◇ mark in the figure), 1.0 (▽ mark in the figure)
In the ore layer (indicated by ()), small and medium sized coke is not segregated to the periphery of the furnace. In particular, the conventional example where WOL / WO was 1.0 and small or medium coke coke was mixed with all the ore loaded in the large bell hopper, segregation toward the center of the furnace was avoided, instead of segregating to the periphery of the furnace. is doing.

Further, FIG. 1 shows the WOL / WO of the O ₁ ore layer and the degree of segregation of small and medium sized coke only in the peripheral area of the furnace. In Fig. 1, the WOL / WO of the O ₁ ore layer on the horizontal axis is shown.
Is described as the mixing position of the small and medium sized coke in the large bell hopper. From this Figure 1, WOL / WO (horizontal axis) is 0.2
Below, the degree of segregation of the small and medium sized coke in the ore layer to the periphery of the furnace
It is clear that (vertical axis) rises sharply. Therefore, from these results, when the small medium sized coke is mixed with the ore layer of the present invention, the degree of segregation greatly changes to the peripheral part of the small medium sized coke depending on how it is loaded into the large bell hopper. That is, the small ore body coke is mixed with the lower part of the ore loaded in the large bell hopper, and the weight of the lower ore mixture (WOL) with the small ore body coke is mixed.
As a percentage of the total weight of ores loaded (WO)
(WOL / WO) Technical significance of specifying (WOL / WO)
The critical significance of setting WO to 0.2 or less is clear.

Therefore, this example demonstrates that it is possible to segregate small and medium sized coke into the peripheral portion of the furnace by the charging method of the raw material for blast furnace according to the present invention. Further, this segregation charging improves the air permeability and the reduction rate of the mixed ores in the blast furnace, and can exhibit the advantages of using small and medium sized coke such as improving the coke production yield.

[0036]

As described above, the method for charging the raw material for the blast furnace of the present invention is not limited to the high pulverized coal ratio operation (low coke ratio operation) particularly under the condition that the fuel ratio is constant. It is possible to charge the segregation into the periphery of the furnace. Therefore, even if small and medium sized coke is used, it can be operated without causing troubles such as pressure loss in the peripheral area of the furnace and in the cohesive zone, the coke production yield is improved, the permeability of ores in the blast furnace and the The advantages of using small and medium sized coke, such as improvement of the reduction rate, can be exhibited. Therefore, for the operation of high pulverized coal ratio under the condition of constant fuel ratio, it opens the way for direct use of small and medium sized coke to the blast furnace, and this effect greatly expands the conventional blast furnace operation method. It is of great industrial significance in that it can be easily achieved without changing to.

[Brief description of drawings]

FIG. 1 shows an example of the present invention, and is an explanatory view showing WOL / WO of an O ₁ ore layer only in the peripheral portion of the furnace and a segregation degree of small and medium sized coke.

FIG. 2 is an explanatory view showing an example of the present invention and showing the degree of segregation of small and medium sized coke in an O ₁ ore layer at each site in the furnace radial direction.

FIG. 3 is an explanatory view schematically showing a large bell hopper.

[Explanation of symbols]

1: Large bell, 2: Bell cup, 3: Ore not mixed with small and medium sized coke, 4: Mixed ore with small and medium sized coke,
5: Large bell hopper

Continuation of the front page (56) Reference JP-A-8-277405 (JP, A) JP-A-5-86408 (JP, A) JP-A-51-138501 (JP, A) JP-A-6-248311 (JP , A) Japanese Patent Publication 4-42443 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21B 5/00 311 C21B 7/18 306

Claims (4)

(57) [Claims] 1. A method for charging raw materials for a blast furnace into a bell-type blast furnace, wherein small coke having a particle size of 35 mm or less is premixed in a lower region of ores loaded in a large bell hopper, and , The ratio of the weight of the lower ore mixed with small and medium sized coke (WOL) to the total weight of the ore loaded in the large bell hopper (WO) (WOL /
(WO) is 0.2 or less, and by charging these ores into the furnace from the large bell hopper, the small and medium sized coke is segregated and charged into the periphery of the furnace. Charging method. 2. The bell-type blast furnace is operated under the condition of a constant fuel ratio, and the ratio O / C of ore (O) and agglomerated coke (C) in the furnace is 4.5 or higher O / C. The method for charging a raw material for a blast furnace according to claim 1, wherein C operation is performed. 3. The bell-type blast furnace operating method according to claim 2, wherein the high O / C operation is performed by blowing pulverized coal of 150 kg / t-pig iron or more into the blast furnace. 4. The small premixed with the ore
The amount of medium Mukuro coke, 5 ~ 100kg / t - bell type blast furnace method according to any one of claims 1 to 3, pig.