JPH06145730A - Operation method for blast furnace - Google Patents

Abstract

PURPOSE:To improve the reaction efficiency of a blast furnace and to lower a fuel ratio in the operation method using an iron source mainly consisting of sintered ore, ordinary coke and specific highly reactive coke by adjusting the ratio of using the highly reactive coke, etc., according to the reducibility of the sintered ore. CONSTITUTION:The blast furnace operation is executed by charging the sintered ore, pellets, lumped ore, ordinary coke for metallurgy and the highly reactive coke having <=25mm average grain size and >=30% JIS(Japanese Industrial Standards) reactivity into the blast furnace. One or more among the ratio of using the highly reactive coke, the grain size and JIS reactivity thereof are adjusted according to the reducibility of the sintered ore in this operation method. As a result, the temp. of a heat retaining temp. is controlled to an optimum value and the reduction reaction is accelerated, by which the safe operation is executed with the high reaction efficiency at the low fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace efficiently and stably by controlling the temperature of the heat preservation zone in the blast furnace according to the reducibility of sinter.

[0002]

2. Description of the Related Art In a blast furnace, a sinter ore or an agglomerated iron ore (70% or more) as an iron source and ordinary metallurgical coke are charged in layers, and after reducing the iron source, the metal It is melted into a state and pig iron is manufactured. At this time, in order to improve the reduction efficiency of the iron source, for example, as proposed in Japanese Patent Publication No. 52-43169, the iron source and the small coke (average particle size 20 m
m) is mixed in advance, and this small lump coke mixed iron source and ordinary metallurgical coke are charged in layers to improve the air permeability in the furnace to improve the reducibility.

The temperature of the heat preservation zone above the fusion zone is about 1000 ° C. in the blast furnace in which this ordinary metallurgical coke (JIS reactivity is about 20%) is used. It is equivalent to the temperature at which the gasification reaction of C + CO ₂ = 2CO is started. On the other hand, the softening start temperature of the iron source is 110
The temperature is about 0 ° C., and when this softening starts, the gas permeability in the furnace deteriorates and the permeation of the reducing gas becomes insufficient. For this reason,
If only normal metallurgical coke is used, the heat preservation zone temperature is 1
Since the temperature is as high as about 000 ° C, CO generated in the gasification reaction cannot be effectively utilized, and the air source is deteriorated due to softening of the iron source, resulting in uneven contact between the iron source and the reducing gas. As a result, the indirect reduction of the iron source in the heat preservation zone cannot be effectively utilized, and it is difficult to significantly improve the reduction efficiency even if the iron source and the small coke are mixed as described above.

In order to improve this, Japanese Patent Laid-Open No. 1-3617
As proposed in Japanese Patent No. 0, the highly reactive coke having a size of 25 mm or less is replaced with a part of the ordinary metallurgical coke, and the substituted highly reactive coke is mixed with an iron source or the ordinary metallurgical coke and loaded into a blast furnace. There is something to enter. This highly reactive coke is produced by partially mixing highly reactive, slightly non-caking coal into the metallurgical coke-producing coal, or by incorporating limestone and alkalis as a reaction-promoting catalyst into the metallurgical coke-producing carbon. Is. Then, the JIS reactivity is adjusted by adjusting the blending amounts of the slightly non-caking coal, limestone, and alkalis.

This highly reactive coke is usually more reactive than metallurgical coke and has a relatively small particle size, so that CO ₂ in the furnace comes into contact with the highly reactive coke surface and C + CO ₂ = 2CO. The gasification reaction of is carried out actively from a lower temperature. As a result, the CO gas generated in the furnace effectively reacts with the iron source to accelerate the reduction reaction of the iron source. In addition, C +
The gasification reaction of CO ₂ = 2CO is an endothermic reaction (-38.8k
cal / mol), it is possible to lower the temperature of the heat preservation zone formed in the massive zone in the blast furnace.
Therefore, the temperature difference between the softening temperature of the iron source becomes large,
Since the air permeability does not deteriorate, the generated C
The contact between O and the iron source becomes even, the reduction efficiency is improved, and the coke ratio can be reduced.

[0006]

However, the sintered ore as the iron source cannot always be manufactured with a constant raw material,
The quality changes depending on the raw material situation at that time.
For example, if the components of the raw materials to be mixed, especially Al ₂ O ₃ , change, the reducibility of the sinter changes.
For example, if Al ₂ O ₃ is high, the reducibility tends to deteriorate, and conversely, if Al ₂ O ₃ is low, the reducibility tends to be good. When the reducibility of this sinter changes, if the heat preservation zone temperature is kept constant, the reduction reaction efficiency changes and the furnace condition becomes unstable, and the fuel ratio changes accordingly. Have the problem of rising.

The present invention promotes the reduction reaction of the entire furnace by controlling the temperature of the heat preservation zone in the furnace to an optimum value in accordance with the reducibility of the sinter, and at a high reaction efficiency, a low fuel ratio is achieved. The challenge is to carry out stable operations in the area.

[0008]

Means for Solving the Problems The present invention is to solve the above-mentioned problems by means of an iron source mainly composed of sinter, ordinary metallurgical coke, JIS reactivity of 30% or more and average grain size. In a method of operating a blast furnace in which a highly reactive coke having a diameter of 25 mm or less is charged and operated, a use ratio of the highly reactive coke, a particle size, J
The temperature of the heat preservation zone in the blast furnace is controlled by adjusting at least one of the IS reactivity.

[0009]

The highly reactive coke used in the present invention has a JIS reactivity of 30% or more (value measured by the reactivity test method of JIS K2151-1977) and an average particle size of 25 m.
m or less is required. This is the above-mentioned Japanese Patent Laid-Open No. 1-36.
As disclosed in Japanese Patent No. 710, when the JIS reactivity is less than 30% or the average particle size exceeds 25 mm, the effect of lowering the thermal storage zone temperature is not observed.

Next, a method of controlling the heat storage zone temperature will be described. As a method of measuring this heat preservation zone temperature,
The method of inserting the sonde from the furnace wall of the blast furnace is generally used, but the method is not limited to this. Figure 1 shows the relationship between the average particle size of highly reactive coke, JIS reactivity, increase in usage ratio (usage ratio with ordinary metallurgical coke) and the extent of decrease in heat storage zone temperature. As you can see
As the use ratio of the highly reactive coke is increased, the particles are made finer, or the JIS reactivity is improved, the temperature decrease width of the heat preservation zone becomes larger. In other words, by adjusting the usage ratio of highly reactive coke, particle size, and JIS reactivity,
It will be appreciated that it is possible to control the heat storage zone temperature.

Furthermore, the reducibility of sintered ore (hereinafter simply referred to as JI
The relationship between S-RI) and the heat storage zone temperature will be described. FIG. 2 shows the relationship between the JIS-RI and the reduction reaction efficiency of the sintered ore when the heat preservation zone temperature is 1000 ° C. From this figure, it can be seen that the reduction reaction efficiency drops sharply when the JIS-RI of the sinter decreases.

On the other hand, it is desirable to lower the temperature of the heat preservation zone as much as possible in order to improve the efficiency of the reduction reaction, but since the temperature of the upper part of the shaft is lowered, the heat preservation zone temperature should be set appropriately from the top of the blast furnace to set the heat preservation zone temperature appropriately. The low-temperature reducibility of sinter is important. Therefore, in order to obtain the proper heat preservation zone temperature of each sintered ore with JIS-RI of 55% and 62%, the present inventor has
Tests were carried out using the blast furnace reaction simulator proposed in Japanese Patent No. 27038. This is filled with lump iron ore from the upper part and conducts reducing gas from the lower part, and a furnace core tube that makes countercurrent contact between the reducing gas and the lump iron ore, and surrounds a part of the furnace core tube to downstream the reducing gas. It is an apparatus having a heater provided so as to be movable in the lateral direction.

As a result, as shown in FIG. 3, JIS-RI
In the case of 62% sinter, the heat preservation zone temperature with the highest reduction reaction efficiency (hereinafter referred to as the proper heat preservation zone temperature) is 900 ° C.
(In this case, the temperature of the heat preservation zone cannot be lowered to 900 ° C. or lower, and the reduction reaction efficiency of the sintered ore below this is unknown), and in the case of the sintered ore of JIS-RI of 55%, It was 930 ° C. In other words, JIS-RI of sinter
It indicates that the appropriate heat storage zone temperature varies depending on the value of.

FIG. 4 is based on FIG.
The relationship between S-RI and the proper heat storage temperature at which the reaction efficiency is the best is investigated. As can be seen from this figure, the optimum heat storage temperature is 900 ° C. when the JIS-RI of the sinter is 60% or more, and the optimum heat storage zone is as the JIS-RI decreases when the JIS-RI is 60% or less. The temperature rises.

As described above, the present invention is based on JIS-RI of sintered ore.
By adjusting the usage ratio, particle size, and JIS reactivity of the highly reactive coke charged into the furnace based on the above, the reduction reaction that maximizes the temperature of the heat preservation zone formed above the cohesive zone in the furnace Although it is controlled to an appropriate value that can enjoy efficiency, when the control width of the heat preservation zone temperature is small, any one of the use ratio of the highly reactive coke, the particle size, and the JIS reactivity is independently used. When the control width is large, it is preferable to make a plurality of adjustments by combining the use ratio, particle size, and JIS reactivity.

Further, it is preferable to adjust the use ratio of the high-reactivity coke because the control range of the heat preservation zone temperature is the largest as compared with the case of adjusting the particle size and JIS reactivity. It is usually complicated because it is necessary to adjust the amount of metallurgical coke or sintered ore. On the other hand, it is preferable to adjust the particle size of the highly reactive coke without causing the above-mentioned complication, but if the particle size is too fine, the yield will deteriorate due to scattering with the blast furnace gas, or in the in-furnace agglomerate part. It may cause clogging and deteriorate air permeability. Furthermore, if the JIS reactivity of the highly reactive coke is adjusted, the air permeability in the furnace does not change, and usually there is no need to adjust the amount of coke for metallurgy or sinter, which is most preferable as a blast furnace, but the desired JIS reaction Has skill in making highly reactive coke. As described above, since each has its advantages and disadvantages, the usage ratio, particle size, JI
It is necessary to properly use the means for adjusting the S reactivity.

[0017]

EXAMPLES Examples of the present invention will be specifically described below.
Table 1 shows the highly reactive coke and JIS-R
An example in which the blast furnace is operated by controlling the heat preservation zone temperature according to I is shown.

[0018]

[Table 1]

The target blast furnace is a medium-sized blast furnace with an internal volume of 3000 m ³ , and an iron source mainly composed of sinter (80% sinter, 10% pellets, 10% fine ore (Hamasley ore, Newman ore, etc.)) ) And normal large metallurgical coke (JI
S reactivity 20%, average particle size 50 mm) is charged in layers. Further, the tuyere temperature is 2180 ° C (hot air temperature 120
0 ° C., blowing moisture 25g / Nm ³ -air, oxygen-enriched amount 0.013Nm ³ / Nm ^{3 -air,} pulverized coal blowing amount 1
The operation is carried out while maintaining the value of 00 g / Nm ³ -air).

Example 1 has a JIS reactivity of 70% and a particle size of 5
It is an example of a case where JIS-RI of the sinter changes from 68% to 62% in a state where 10% of highly reactive coke of 10 mm is mixed with a large coke for ordinary metallurgy and is operating. . “Before adjustment” indicates that the furnace started to become unstable by continuing operation even if the JIS-RI of the sinter changed, and “after adjustment” indicates that the furnace began to become unstable. JIS-R of the sinter in order to stabilize the situation
The heat preservation zone temperature is controlled by adjusting the usage ratio of the highly reactive coke according to the change in I.

In this adjustment, the control width of the optimum heat preservation zone temperature is first calculated by the following procedure. That is, (1) the optimum heat preservation zone temperature when the JIS-RI of the sintered ore is 62% is 900 ° C. from FIG. (2) The current heat preservation zone temperature (before adjustment) is 950 ° C. (3) This (1),
From (2), the temperature reduction width of the heat preservation zone is 50 ° C.

Next, based on the above (3), the increase in the use ratio of the highly reactive coke having a JIS reactivity of 70% and a particle size of 5 mm to 10 mm is calculated according to FIG. 1 to be 15%. Then, by adding the increase in the usage rate calculated above to the high reactivity coke before adjustment so that the total becomes 25%, large coke for normal metallurgy (1% compared to before adjustment)
5% reduction) and charged into the furnace. As a result, the heat preservation zone temperature was controlled to 900 ° C. calculated as above, and the operation was carried out. As a result, the furnace condition became stable and the fuel ratio fell to 485 kg / t-pig.

Examples 2 and 3 are JIS of sintered ore.
-This is the case where RI changed from 62% to 68%. “Before adjustment” indicates that the furnace started to become unstable by continuing operation even if the JIS-RI of the sinter changed, and “after adjustment” indicates that the furnace began to become unstable. In order to stabilize the situation, according to the change in JIS-RI of the sinter,
The heat storage zone temperature was controlled by adjusting the JIS reactivity (Examples 2 and 3) and particle size (Example 2) of the highly reactive coke.

This adjustment will be described with reference to the second embodiment. Similar to the above, first, the control width of the optimum heat storage zone temperature is calculated by the following procedure. (1) The optimum heat preservation zone temperature after the change of JIS-RI of this sinter is 900 ° C. as shown in FIG. 4 since the JIS-RI of the sinter reached 68%.
(2) The current heat preservation zone temperature (before adjustment) is 940 ° C. (3) From these (1) and (2), the temperature reduction range of the heat preservation zone is 40 ° C.

Therefore, as shown in "after adjustment", the high reactivity coke JIS reactivity (60%) calculated according to FIG.
% → 70%) and particle size (10-15 mm → 5-10 m)
m) and the heat preservation zone temperature is controlled and maintained at 900 ° C. which is the optimum heat preservation zone temperature.

In Example 4, JIS-RI of the sintered ore is 62%.
From the JIS-
JIS reactivity (60% → 70%) and particle size (5-10 mm → 10) of highly reactive coke depending on RI change.
15 mm) and the usage ratio (20% → 25%) were adjusted to control and maintain the thermal storage zone temperature at 930 ° C. calculated from FIG.

In Example 5, JIS-RI of the sintered ore is 62%.
From the JIS-
Depending on the change of RI, the particle size of highly reactive coke is 10 to 1
It was adjusted (fine-grained) from 5 mm to 5-10 mm and the heat preservation zone temperature was controlled and maintained at 930 ° C. calculated from FIG.

[0028]

As described above, according to the present invention, the JIS reactivity, particle size, and amount of the highly reactive coke are adjusted according to the reducibility of the sinter to obtain an appropriate heat preservation zone temperature. By controlling, the fuel ratio can be reduced and efficient blast furnace operation becomes possible, and the effect in this field is great.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the JIS reactivity of highly reactive coke, the increase in the usage ratio by particle size, and the decrease width of the heat storage zone temperature.

[Fig. 2] JIS of sinter with heat preservation zone temperature of 1000 ° C
-A graph showing reaction efficiency when RI (reducibility index) changes

FIG. 3 is a graph showing the relationship between reaction efficiency and heat preservation zone temperature when JIS-RI of sinter is 55% and 62%.

FIG. 4 is a graph showing the relationship between JIS-RI of sintered ore and the optimum heat storage zone temperature.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tetsuzo Haga 1 Nishinosu, Oita City, Oita Prefecture Nippon Steel Co., Ltd. Oita Steel Works Ltd.

Claims (1)

[Claims] 1. An iron source mainly composed of sinter, ordinary coke for metallurgy, JIS reactivity of 30% or more, and an average particle size of 25 m.
In a method of operating a blast furnace in which a highly reactive coke having a volume of m or less is charged and operated, at least one of the use ratio, particle size and JIS reactivity of the highly reactive coke is determined according to the reducibility of the sinter. The method for operating a blast furnace is characterized in that the temperature of the heat preservation zone in the blast furnace is controlled by adjusting one of the two.