JP3536509B2 - Blast furnace operation method for producing low Si pig - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a blast furnace operating method for producing low Si pig iron.

[0002]

2. Description of the Related Art As one method of producing low-Si pig iron in a blast furnace, the basicity distribution of a blast furnace charge deposit layer is set so that the basicity is higher near the furnace periphery than in the center of the furnace. how adjusted to perform operations in (JP 59-1500 0 3
No. Gazette). In general, it is known that in a Si transfer in a blast furnace, in a high-temperature region in front of a tuyere, SiO gas is generated by SiO ₂ + C → SiO + CO, and Si enters the hot metal by SiO + C → Si + CO.

[0003] In the above method of adjusting the basicity distribution of the charged material so that the basicity is higher near the periphery of the furnace than in the center of the furnace, the melt passing through the high-temperature region in front of the tuyere is required. To lower the activity of SiO ₂ ,
The purpose is to suppress the transfer reaction of Si to hot metal by suppressing the generation of gas.

[0004]

However, in the above-mentioned method, as shown in FIG. 2, the raw material (ore layer 2) deposited on the coke layer 3 in the blast furnace 1 has a high basicity raw material 2a on the furnace wall side.
Is charged into the core side with the low basicity raw material 2b. In the inert state where the core 5 has poor liquid permeability, the melt 7 generated at the center of the cohesive zone 4 flows on the surface layer of the core 5 toward the tuyere 6, so that the high temperature region in front of the tuyere is high. However, there is a problem that the average basicity of the charged raw material is eventually reached and the effect of reducing Si is reduced.

That is, when the ventilation and liquid permeability at the center of the blast furnace 1 decrease, that is, when the so-called furnace core inactivation occurs, the Si lowering effect is lost as shown in FIG. An object of the present invention is to provide a technique for producing low Si pig iron that has solved the above-mentioned problems.

[0006]

According to the present invention, in order to solve the above-mentioned problems, the basicity of the raw material to be deposited in the blast furnace is CaO.
The raw material and the charging method are adjusted so that the radial distribution of / SiO ₂ is higher than the basicity of the raw material near the furnace center by 0.5 or more than the basicity of the raw material near the furnace center; It is an object of the present invention to provide a blast furnace operating method for producing low Si pig iron, characterized by charging coke in the center and increasing the coke layer thickness in the center. In this case, it is preferable that the boundary between the vicinity of the furnace periphery and the vicinity of the center has a dimensionless radius of 0.7 ± 0.1.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown schematically in FIG. 1, the basicity distribution of the charge is adjusted so that the basicity distribution is higher at the periphery than at the center of the furnace, and the conventional method is used. By intensively charging coke 8 in the center in addition to the coke layer 3, the furnace core 5 was activated and liquid permeability was maintained high. Flow through the wick 5,
The high basicity melt at the periphery flows through the high temperature region in front of the tuyere at the periphery. In the high temperature region before the tuyere, SiO
_{(2) The} activity is reduced, the amount of generated SiO gas is suppressed, and the amount of Si transferred into the hot metal is also reduced. By the above operation, the tapping Si is eventually reduced.

[0008] The dimensionless radius of 0.7 ± 1 is 0.7
This is because the effect of the present invention is enhanced when the basicity level is divided on the boundary of 0.7 ± 0.1 because the high temperature region of the raceway exists on the furnace peripheral side of ± 0.1. Although the raceway depth of the blast furnace changes depending on the air volume, tuyere diameter, and coke particle size, it has been about 1.0 to 2.5 m from the wall in the measurement examples so far. FIG. 6 shows [S] when the basicity difference is 0.8 and the central charging coke is 2 t / ch.
i] and the boundary position. If it deviates from 0.7 ± 0.1, [Si] sharply increases. CaO / SiO
_As shown in FIG. 5, the difference between the _two basicities was set to 0.5 or more.
When the basicity difference is 0.5 or more, the activity a _{sio2 of} SiO ₂ is about 2
This is because the difference is doubled and the intended effect of reducing Si is obtained.

The basicity of the basicity distribution in the radial direction is adjusted by, specifically, (a) a high basicity adjusted sintered ore, pellet (b) dolomite, converter slag, continuous cast slag, etc., having a high CaO concentration. High basicity raw materials such as auxiliary raw materials are charged into the periphery, and (a) sintered ore adjusted to low basicity, pellets (b) raw ore (c) silica raw materials with high SiO ₂ concentration, etc. What is necessary is just to charge a low basicity raw material to a center part. Further, in order to charge the raw materials having different basicities to desired positions, the basicity of the ore charging batch was changed in a blast furnace having a bellless charging device or a blast furnace having a bell movable armor charging device. Divide into two or more batches and adjust the angle of the bell-less charging chute or the position of the movable armor so that the low basicity raw material accumulates at the center and the high basicity raw material accumulates more at the periphery. Good. If there is not enough time to make multiple batches of ore or the number of top bunker in Bellless Blast Furnace is insufficient, or if multiple batches are not possible in the sequence, the order of cutting from the ore storage tank should be changed from high basicity material to low basicity material. By sequentially cutting out the basicity raw materials, it may be adjusted so that the high basicity raw materials are charged into the furnace first, and the raw materials may be sequentially charged from the periphery of the furnace. Alternatively, the reverse may be performed.

[0010] In order to charge coke into the center, it is common to use a dedicated center charging chute in a bell blast furnace. In the bellless blast furnace, a method of charging coke in a state where the charging chute is vertical or nearly vertical may be used.

[0011]

Next, an embodiment of the present invention will be described. Table 1
The operating conditions and results of Examples and Comparative Examples of the present invention are shown together. The method of adjusting the basicity distribution in Examples 1 to 3 and Comparative Examples 1 to 3 is to divide the ore into two parts of high / low basicity raw material and adjust the angle of the bellless chute to surround the high basicity raw material. The low basicity raw material was charged near the center. In Examples 1 to 3, the central charging of coke was performed by charging coke with the bellless charging chute standing upright.

In Comparative Examples 1 to 3, the central charging of coke was not performed. Example 1 shows a high basicity batch with a basicity of 2.0.
Raw ore was used for the low basicity batch.
In Example 2, the raw ore in the low basicity batch was increased from that in Example 1, and converter slag was charged in the high basicity batch to adjust the average basicity to be approximately equal to Example 1. It is an example. Example 3 is an example in which the high / low basicity is roughly divided into 50:50, and the basicity is adjusted using the mixing ratio of the sinter ore and the raw ore and the continuous cast slag.

FIG. 4 shows the results of the measurements of the basicity distribution in the radial direction of the raw materials charged to the furnace top in Examples 1 to 3. In each case, the basicity is high near the furnace wall, and the basicity is low at the center. As is clear from Table 1, Examples 1 to 3 are compared with Comparative Examples 1 to 3 in which coke center charging was not performed.
The tapping Si was reduced by 0.05%, and a low Si pig could be stably obtained by the present invention.

By changing the bellless charging pattern in Table 2, the difference between the basicity on the peripheral side and the basicity on the center side of the charged raw material when divided by a dimensionless radius of 0.7 is shown in Examples 1 to 3. The operation test result when the lower limit is set is shown. In Comparative Examples 4 to 6, the basicity differences of the charged raw materials were 0.2 and 0.2, respectively.
0.4, 0.4, the tapping Si is 0.24 to 0.2
5%, and 0.18 to 0.20% of Examples 1 to 3
Higher and less effective.

Table 3 shows Examples 4 to 7 in which the boundary between the center portion and the peripheral portion is 0.5 to 0.9. Table 1 also shows Example 1 again. These are plotted in FIG. 6 and shown as a graph. As shown in FIG. 6, when the dimensionless radius is 0.6 to 0.8, [Si] is 0.204 to
While the dimensionless radius is 0.5, Example 6 has a low dimension of 0.5, whereas Example 7 has a non-dimensional radius of 0.9.
21, 0.225, and the dimensionless radius is 0.7 ± 0.2.
Somewhat higher than the embodiment of FIG. 1 and therefore, if the boundary between the center and the periphery is in the range of 0.7 ± 0.1,
It is known that a more excellent effect is obtained and preferable.

Although only the test results in the bellless blast furnace are shown here, similar results were obtained in the bell movable armor blast furnace.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

According to the present invention, the basicity distribution of the blast furnace charge is high at the periphery of the furnace, low at the center, and the center of coke is charged to maintain the liquid permeability of the furnace core. Low Si pig can be produced stably.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a furnace liquid flow when a core in a blast furnace is activated.

FIG. 2 is a view schematically showing a furnace liquid flow when a core in a blast furnace is inactive.

FIG. 3 is a graph showing a relationship between tapping Si, furnace core coke powder, and the like.

FIG. 4 is a graph showing a charge basicity distribution.

FIG. 5 is a graph showing a relationship between _basicity and activity a _{sio2 of} SiO ₂ .

FIG. 6 is a graph showing a relationship between tapping Si and a dimensionless radius.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Ore layer 2a High basicity raw material 2b Low basicity raw material 3 Coke layer 4 Cohesive zone 5 Core 6 Tuyere 7 Melt 8 Coke

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-150003 (JP, A) JP-A-58-61202 (JP, A) JP-A-7-138624 (JP, A) JP-A-1- 263207 (JP, A) JP-A-6-271908 (JP, A) JP-A-3-232912 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21B 5/00 313

Claims (2)

(57) [Claims] 1. The basicity CaO of a raw material deposited in a blast furnace
The raw material and the charging method are adjusted so that the radial distribution of / SiO ₂ is higher than the basicity of the raw material near the furnace center by 0.5 or more than the basicity of the raw material near the furnace center; A blast furnace operating method for producing low Si pig, characterized by charging coke in the center and increasing the coke layer thickness in the center. 2. A blast furnace operation for producing low Si pig according to claim 1, wherein a boundary between the vicinity of the furnace and the vicinity of the center has a dimensionless radius of 0.7 ± 0.1. Method.