JP2008260984A - Blast furnace operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blast furnace operation method with which balance in the circumferential direction of charged material level in a furnace, is uniformly held by controlling the fine coal blowing quantity, and the stable operation can be continued, in the blast furnace performing fine powdery coal blowing. <P>SOLUTION: In the blast furnace operation method for blowing the fine powdery coal from a tuyere 9 in the blast furnace 1, a difference 3 between the maximum value and the minimum value of the measured values is found by measuring a distance from the furnace top part to the charged material surface in the blast furnace in the circumferential direction, and the fine powdery coal quantity is adjusted so that this difference becomes the preset reference value or lower and particularly, it is preferable that the fine powdery coal blowing quantity at the lower part of a region of the maximum value in the distance from the furnace top to the measured charged material surface or at the tuyere in its vicinity is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

In the present invention, by adjusting the amount of pulverized coal blown from the tuyere of the blast furnace, the circumferential deviation of the distance (hereinafter referred to as the charge level) to the charge surface charged in the furnace is eliminated. It relates to blast furnace operation method.

To stabilize the blast furnace operation, it is important to make the circumferential balance of the gas flow in the furnace uniform. To that end, it is necessary to make the charge distribution from the top of the furnace uniform in the circumferential direction. . The charge level in the blast furnace is measured at multiple detection ends called the index finger, but the increase in the level difference (hereinafter also referred to as ΔSTL) increases the deviation in the amount of charge flow, and the operation There is a problem that the furnace condition becomes unstable due to fluctuations.
Conventionally, for example, in order to reduce this ΔSTL, the hot air control valve of the tuyere corresponding to the furnace top circumference part of the part where the measured value of the index finger is high is throttled to reduce the branch pipe air volume. A method of delaying the unloading speed of the charged material (see, for example, Patent Document 1) has been proposed.

Japanese Patent Laid-Open No. 1-156411

In order to reduce the deviation of the charge level in the circumferential direction of the charge, when the branch air volume of the tuyere is reduced as in Patent Document 1, the raceway region and oxygen formed at the tip of the tuyere Since the supply amount decreases, the reduction of hot metal partially stagnate.
On the other hand, since the amount of pulverized coal injected is constant, the pulverized coal ratio (hereinafter also referred to as PCR) is partially increased, and the reducing agent ratio (hereinafter also referred to as RAR) is increased. Due to this partial increase in RAR, a difference in height occurs in the position of the cohesive zone in the furnace, so that the gas flow rate rising in the furnace varies in the circumferential direction (is drifted), and the furnace condition deteriorates.
In addition, since the root of the cohesive zone hangs down due to a decrease in RAR, the unreduced melt easily falls to the lower part of the blast furnace, and a direct reduction reaction (hereinafter also referred to as an SLC reaction) that is an endothermic reaction occurs in the lower part of the blast furnace. It may become difficult to continue stable operation due to the progress of the heat in the furnace (hereinafter also referred to as furnace heat).
Therefore, the present invention maintains stable operation by maintaining the circumferential balance of RAR so that ΔSTL generated in the furnace interior does not exceed a preset reference value, and continues stable operation by reducing ΔSTL. Is an issue.

The present invention has been made to solve the above-described problems, and the features thereof are as follows:
(1) In the blast furnace operation method in which pulverized coal is blown from the blast furnace tuyeres, the distance from the top of the blast furnace to the charge surface is measured in the circumferential direction, and the difference between the maximum value and the minimum value is measured. This is a blast furnace operation method in which the amount of pulverized coal is adjusted so that the difference is equal to or less than a preset reference value.
(2) The blast furnace operating method according to the above (1), wherein the amount of pulverized coal blown into the tuyere below or near the maximum portion of the measured distance to the charged surface is reduced.
(3) In the blast furnace operating method according to (1) or (2) above, the amount of pulverized coal blown into the tuyere below or near the minimum portion of the measured distance to the charged surface is increased. is there.

According to the present invention, since ΔSTL can be reduced while maintaining the circumferential balance of the RAR in the blast furnace furnace, the position of the cohesive zone can be kept constant in the circumferential direction. As a result, the circumferential balance of the gas flow in the furnace is made uniform and the furnace heat drop is suppressed, and the stable operation of the blast furnace continues at a high level, which has a great effect in this field.

First, the mechanism by which ΔSTL occurs in the charge level charged in the blast furnace will be described with reference to FIG.
This is because when the charge descending speed on one side of the blast furnace 1 (the right side in FIG. 1) becomes slow for some reason, the charge flows into the relatively fast side (the left side in FIG. 1). The recessed portion of the charge is shifted from the center. When the concave portion of the charge is shifted from the center, the portion where the charge level 4 is deep (right side of the drawing) is reduced compared to the portion where the charge level 4 is shallow (left side of the drawing). As a result, the RAR increases. Here, if an equivalent amount of pulverized coal is blown from all tuyere 9, the RAR rise in the portion where the charge level 4 is deep is promoted, and the charge drop in that portion is further delayed and measured with the index finger 2. It is considered that ΔSTL3, which is a level difference of charge level 4, is generated. In FIG. 1, reference numeral 5 is a pulverized coal distributor, reference numeral 6 is a ring for adjusting the amount of pulverized coal injection, reference numeral 7 is a pulverized coal flow meter, and reference numeral 8 is a burner for pulverized coal injection.

Next, a method for reducing ΔSTL in the blast furnace operating method according to the first embodiment of the present invention will be described.
In order to reduce ΔSTL so that it is below the preset reference value, the amount of pulverized coal injection at the part where the charge level is deep (right side of the drawing) is reduced to increase the charge lowering speed (coke consumption) Need to be promoted).
For this reason, in the present embodiment, by reducing the amount of pulverized coal blown in the tuyere below or near the portion where the charging level is deep, and reducing the amount of oxygen consumed by the combustion of the pulverized coal, The amount of oxygen for burning the coke at the front tuyere raceway is increased, and ΔSTL generated at the charge level in the circumferential direction of the furnace is reduced.

Furthermore, in the above-described embodiment, the method of reducing the ΔSTL of the charged material by increasing the level of the portion where the charging level is deep has been described. However, in the blast furnace operating method according to the second embodiment of the present invention, On the other hand, the level of the portion where the charge level is shallow is lowered to reduce the ΔSTL of the charge.
In order to reduce ΔSTL, it is necessary to increase the amount of pulverized coal injection at the portion where the charge level is shallow (the left side of the drawing) to reduce the charge lowering speed (reduction of coke consumption).
For this reason, in the present embodiment, by increasing the amount of pulverized coal blown in the tuyere below or near the portion where the charging level is shallow, and increasing the amount of oxygen consumed by the combustion of the pulverized coal, The amount of oxygen for burning coke in the front tuyere raceway is reduced, and ΔSTL generated at the charge level in the circumferential direction of the furnace is reduced.
This is because when the amount of pulverized coal blown in the tuyere below or near the portion where the charging level is shallow (the left side of the drawing) is increased, the amount of oxygen in the furnace gas rising above this portion is reduced. By reducing the consumption, the charge lowering speed of this portion is reduced, and ΔSTL generated at the charge level in the circumferential direction in the furnace is reduced.
Furthermore, by simultaneously performing the method for increasing the level of the portion having a deep charge level and the method for decreasing the level of the portion having a low charge level, ΔSTL generated in the charge at an early stage can be reduced. Therefore, it is preferable.
The adjustment of the amount of pulverized coal injection for each tuyere is preferably performed by increasing or decreasing the amount of protrusion of the ring 6 in the distributor 5 of the pulverized coal injection facility, as proposed in Japanese Patent Publication No. 1-20685.

In addition, for example, if there are about 40 tuyere in the vicinity, the tuyere in the vicinity refers to 3 to 4 on the left and right below the charging level measurement site, and adjustment is performed by one or more of them. .
Furthermore, since the reference value of ΔSTL varies depending on the structure of the blast furnace, the operation design, etc., it is determined in advance from the operation results. In an actual furnace, it is desirable to set the value of ΔSTL when the gas flow fluctuation or operation fluctuation suddenly occurs to the reference value.

The blast furnace used as an example in the present invention is a bell-type super large blast furnace with an internal volume of 5000 m ³ , the number of tuyere is 40, and as shown in FIG. 1, the charge level (that is, from the top of the blast furnace). The distance to the surface of the charge) is continuously measured in the circumferential direction with a plurality of differential fingers, and ΔSTL is calculated from the difference between the maximum value and the minimum value. Figure 2 shows the connection between the index finger and the tuyere.
Table 1 below shows Examples 1 to 3 of the present invention.

Example 1 is a case in which the amount of pulverized coal injection near the portion where the distance to the charge surface is the maximum value is reduced and the amount of pulverized coal injection near the portion where the distance to the charge surface is the minimum value is increased. .
For the No. 2 index finger with the maximum distance to the charge surface, adjust the protrusion amount of the ring to reduce the amount of # 10 tuyere in the lower part of the No. 2 index finger. The amount of per tuyere per blow was reduced from 123 g / Nm ³ to 110 g / Nm ³ . On the other hand, for the No. 4 differential finger with the minimum distance to the charge surface, adjust the amount of protrusion of the ring in order to increase the blowing amount of # 27 and 28 tuyere near the lower side of the No. 4 differential finger. In addition, since the amount of air blown per tuyere was increased from 97 g / Nm ³ to 110 g / Nm ³ , the unstable furnace condition was stabilized.
Example 2 is a case in which the amount of pulverized coal injection in the vicinity of the part where the distance to the charge surface is the minimum is increased, and the case where the distance to the charge surface of No. 1 and 3rd finger is minimized. It is. For # 1, 39, 40 near the lower part of the No.1 forefinger and # 16, 17 near the lower part of the No.3 forefinger, the protrusion amount of the ring is adjusted to increase the amount of blown air at the tuyere, and the number of feathers Since the injection amount per mouth was increased from 80 to 90 g / Nm ³ to 95 g / Nm ³ , the unstable furnace condition was stabilized.
Example 3 is a case in which the amount of pulverized coal in the vicinity of the part where the distance to the charge surface is the maximum value is reduced, and the distance from the No. 2 index finger to the charge surface is maximized. , by adjusting the amount of projection of the ring to reduce blow amount of # 4,5,6 birds port near No.2 Sayubi downward, the tuyere every blow amount per blast volume from 124g / Nm ³ 110g / The reactor condition was unstable because it was reduced to Nm ³ .
In the table, “after adjustment” means the average for 3 days after adjusting the pulverized coal injection amount, and “before adjustment” means the average for 3 days before adjustment.
In both cases, it was confirmed that ΔSTL was improved, and the index indicating the gas flow fluctuation (also called the gas flow fluctuation index) was greatly improved, and the furnace condition was stabilized.

It is explanatory drawing which shows the state of the furnace interior entrance of a blast furnace. It is explanatory drawing which shows the relationship between the position of the index finger of a blast furnace and the tuyere of the Example of this invention.

Explanation of symbols

1: blast furnace, 2: differential finger, 3: ΔSTL, 4: charge level, 5: pulverized coal distributor, 6: ring for adjusting the amount of pulverized coal injection, 7: pulverized coal flow meter, 8: pulverized coal injection Burner, 9: tuyere

Claims (3)

In the blast furnace operation method in which pulverized coal is blown from the tuyere of the blast furnace, the distance from the top of the blast furnace to the charge surface is measured in the circumferential direction to determine the difference between the maximum value and the minimum value, A blast furnace operating method, wherein the amount of pulverized coal is adjusted so that the difference is equal to or less than a preset reference value. 2. The blast furnace operation method according to claim 1, wherein the amount of pulverized coal injected into the tuyere below or near the portion of the measured maximum distance to the charged surface is reduced. 3. The blast furnace operating method according to claim 1, wherein the amount of pulverized coal injection in the tuyere below or near the portion of the minimum value of the distance to the charged surface is increased.

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