JPH05295412A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To reduce the fuel ratio with a high reducing efficiency and to stably operate a blast furnace with excellent productivity by replacing a part of lump cokes for blast furnace with a small lump high reactive coke. CONSTITUTION:A part of the metallurgical lump coke as heat source in the blast furnace operation and the reducing agent to iron ore is replaced with the small lump high reactive coke having >=30% JIS reactivity and <=25mm the average grain size and charged into the blast furnace by mixing the coke with the iron ore or making a layer state with the raw material of the iron ore, etc. In this case, the heat load over the part from a shaft lower part to a belly part in the blast furnace is measured and at least one side of the charging quantity or the JIS reactivity of the small lump high reactive coke into the furnace is adjusted so that the measured value exceeds the preset lower limited value. The bad burden permeability and the lowering of the reducing efficiency by stagnation, etc., of the descendent speed of the charged raw material caused by the lowering of the heat load are prevented, and molten iron is produced with a high reducing efficiency and excellent productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the fuel ratio and improves productivity by replacing a part of the coke for ordinary metallurgy charged from the furnace top with coke having a higher reactivity. Blast furnace operation method.

[0002]

2. Description of the Related Art In a normal blast furnace, iron ore and ordinary metallurgical coke are charged in layers from the furnace top, and the iron ore is reduced in the furnace and then melted into a metallic state to produce hot metal. is doing. At this time, in order to increase the reduction efficiency of iron ore, in Japanese Patent Publication No. 52-43169, iron ore and small lump coke are mixed in advance, and this mixture and ordinary metallurgical coke are charged in layers. It is disclosed. By using iron ore pre-mixed with coke in this way, the air permeability in the furnace is improved,
Its reducibility is improved.

By the way, the heat preservation zone temperature of the blast furnace is 1000
The temperature is about ℃, and this temperature corresponds to the gasification start temperature of coke. In other words, a temperature of about 1000 ° C. or higher is necessary for the gasification reaction of coke of C + CO ₂ = 2CO in the blast furnace. About 70% of the reduction of iron ore occurs in the higher temperature region than the heat preservation zone, but the reduction equilibrium gas composition becomes high CO side as the temperature rises, and the melt generation from iron ore is about 1100 ° C or more. However, since the infiltration of reducing gas becomes insufficient, the indirect reduction of iron ore cannot be effectively utilized when the temperature of the heat preservation zone is high, and the reduction efficiency does not improve beyond a certain value.

By the way, since small lump coke mixed with iron ore usually has the same properties as metallurgical coke, the reaction with CO ₂ is more active due to the smaller particle size. However, since it is mixed with iron ore, CO ₂ generated by CO reduction of iron ore is closer to coke, and the reduction of the heat storage zone temperature is not accompanied by the advantage that the reaction is fast. There was a limit.

In order to improve this limit, it is practiced to replace the highly reactive coke with the whole amount or a part of the metallurgical coke as an operation. Since this highly reactive coke is highly reactive, CO ₂ in the blast furnace comes into contact with the surface of the coke, and the reaction of C + CO ₂ = 2CO is actively performed from a lower temperature. Further, as a result, the CO gas generated in the furnace effectively reacts with the iron ore to reduce the reaction to the lower oxide or metal state.

The reaction of C + CO ₂ = 2CO is an endothermic reaction and can lower the heat preservation zone temperature in the blast furnace. When the conventional method is used, a heat storage zone of about 1000 ° C. is generated and its value hardly changes, whereas the heat storage zone temperature is set to 900 by using highly reactive coke.
It is possible to lower the temperature to 950 ° C. as a result,
Since there is a margin at the reduction equilibrium reaching point, the reduction proceeds further, the reduction efficiency is improved, and the coke ratio can be reduced.

[0007]

By the way, in the conventional blast furnace operation, since the charge distribution adjustment range at the furnace top is not so wide and the charge distribution varies widely,
When the O / C around the furnace becomes high, insufficient heating and reduction of the ore in this region occurs, and there is a stagnation of charge drop from the lower part of the shaft to the abdomen of the furnace or it causes deposit formation for a long time, resulting in poor ventilation and reduction. Inefficiency occurs. When this phenomenon occurs, the heat load from the lower part of the shaft of the blast furnace to the upper part of the furnace decreases. Therefore, normally, the heat load from the lower part of the shaft of the blast furnace to the furnace belly is monitored, and when the heat load falls below a certain value, the charge distribution adjustment is performed to reduce the O / C around the furnace. Since this adjustment brings about an increase in the O / C in the central part of the furnace, there is a limit to the extent of the decrease, and as a result, the overall O / C must be reduced, and the fuel ratio rises.
Production was declining.

Therefore, in the present invention, when the small lump highly reactive coke is replaced with a part of the metallurgical coke and charged into the blast furnace, the heat load from the lower part of the shaft to the belly part of the blast furnace is reduced. , In order to prevent stagnation of deposits in this region or generation of deposits, and to prevent ventilation failure and reduction of reduction efficiency, do not carry out the distribution adjustment of the deposits to reduce the O / C around the furnace, The purpose is to adjust the charging amount of small lump highly reactive coke and the JIS reactivity to operate the blast furnace stably with high productivity under high reduction efficiency.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, in which a part of coke for metallurgy is usually JIS.
Blast furnace operation in which a small lump highly reactive coke having a reactivity of 30% or more and an average particle size of 25 mm or less is replaced, and the small lump highly reactive coke is mixed with at least one of ore and ordinary metallurgical coke and then charged into a blast furnace. When performing, measure the heat load from the bottom of the shaft of the blast furnace to the furnace belly,
It is characterized in that at least one of the charging amount of the small lump highly reactive coke and the JIS reactivity is adjusted so that the heat load exceeds a preset lower limit value.

[0010]

[Function] The highly reactive coke used in the present invention is JIS
It is necessary that the JIS reactivity as measured by the reactivity test method of K2151-1977 is 30% or more.
The numerical limitation of 30% or more is due to the fact that as shown in Japanese Patent Laid-Open No. 1-36710, the results are hardly seen when the actual furnace test results are less than 30%. Further, the highly reactive coke used in the present invention needs to be a small block having an average particle size of 25 mm or less. The numerical limitation of 25 mm or less is due to the fact that the effect is hardly seen with the average particle size exceeding 25 mm according to the operation test result of the present invention. Japanese Patent Application Laid-Open No. 1-36710 discloses, as a method for adjusting highly reactive coke, a catalyst that accelerates the reaction by partially blending a raw coal with a highly reactive slightly non-caking coal or steam coal that is not suitable for the production of coke for metallurgy. Small amount of limestone and alkalis, which have the role of
A method of blending with raw coal has been disclosed. Molded coke also belongs to this category.

When the small lump highly reactive coke is replaced with a part of the coke for ordinary metallurgy and charged into the blast furnace, the temperature of the heat preservation zone is lowered and the reduction equilibrium point can be afforded. Results in C + CO
₂ = 2CO solution loss reaction (endothermic reaction) is suppressed. Therefore, the furnace heat of the blast furnace has a margin, and it is possible to prevent reduction of the reduction efficiency from the lower part of the shaft of the blast furnace to the furnace belly. Moreover, since it is not necessary to adjust the distribution of the charge to reduce the O / C in the peripheral area of the furnace, the O / C in the central area of the furnace
It does not cause rise and does not fall into poor ventilation. Therefore, the blast furnace can be stably operated with high productivity under high reduction efficiency.

In the operation of the blast furnace in the present invention, the decrease of the heat load from the lower part of the shaft to the belly part of the furnace is monitored,
When this heat load falls below the preset lower limit value, there is a stagnant drop in the charge in this region, and this phenomenon continues to deposit formation, poor ventilation, and reduction in reduction efficiency. In order to improve the reduction efficiency in this area before deposit formation, poor ventilation, and reduction of reduction efficiency in order to cut off the continuation, a small lump highly reactive coke equipment that is usually replaced with a part of metallurgical coke is used. Adjust the dosage and JIS reactivity. The degree of improvement of the reduction efficiency in this region can be adjusted by adjusting the charging amount of the small lump highly reactive coke and the JIS reactivity. The nodule highly reactive coke can be used in admixture with iron ore, or in admixture with conventional metallurgical coke, and in admixture with both iron ore and conventional metallurgical coke.

As a method for monitoring the heat load from the lower part of the shaft of the blast furnace to the belly part, the brick embedding temperature in this region is measured, the temperature of the stave cooler is measured, and the difference between the cooling water flow rate of the stave cooler or the cooling plate and the water supply / drainage temperature difference is obtained. A heat removal amount measurement or the like can be used. The lower limit of these monitoring methods is set in advance based on the drop stagnation condition by an operation test, and the charging amount of the small lump highly reactive coke or JIS required depending on the degree of falling below this lower limit. The relationship of the range of change in reactivity is also obtained in advance by an operation test.

FIG. 1 shows the relationship between the range of decrease from the lower limit value thus obtained by the operation test and the range of change in the JIS reactivity of the small-lump highly-reactive coke required for it. 1 and 2 show a case where the brick embedding temperature measurement in this region is used as a method for monitoring the heat load from the lower part of the shaft to the furnace belly.

In FIGS. 3 and 4, as a method of monitoring the heat load from the lower part of the shaft to the furnace abdomen, when the temperature measurement of the stave cooler in this region is used, it is necessary to reduce the lower limit value and the lower limit value. Fig. 2 shows the relationship between the charging amount of highly reactive coke and the change range of JIS reactivity.

In FIGS. 5 and 6, as a method of monitoring the heat load from the lower part of the shaft to the furnace belly, the amount of decrease from the lower limit value and the necessary amount of decrease in the amount of heat removal of the stave cooler in this region are used. The relationship between the charging amount of the small lump highly reactive coke and the change width of JIS reactivity is shown.

As shown in FIGS. 7 and 8, as a method of monitoring the heat load from the lower part of the shaft to the furnace belly, the range of decrease from the lower limit value and the necessary amount when the heat removal amount measurement of the cooling board in this region is used are necessary. Charge of small lump highly reactive coke, J
The relationship of the change width of IS reactivity is shown.

[0018]

EXAMPLES The features of the present invention will be specifically described below with reference to examples. Table 1 shows the operation results of the blast furnace according to the present invention using the small lump highly reactive coke in comparison with the conventional method. The target blast furnace is a medium-sized blast furnace with an internal volume of 3000 m ³ ,
/C=4.2 at a ratio of iron ore and ordinary metallurgical coke (J
IS reactivity 20%) was charged in layers, and usually 20 kg / t-pig of a small lump of metallurgical coke (JIS reactivity 20%, average particle size 20 mm, mixed with iron ore) was charged. The tuyere front frame temperature is 2180 ° C (blast temperature 1200 ° C,
Blast humidity 25g / Nm ³ -air, oxygen enrichment 0.01
3Nm ³ / Nm ³ -air, pulverized coal injection amount 100g /
The hot metal was produced at 6000 t / day while maintaining Nm ³ -air).

[0019]

[Table 1]

Example 1 When a brick embedding temperature was measured in this region as a method of monitoring the heat load from the lower part of the shaft to the furnace belly, the lower limit value obtained in advance by an operation test was 60 ° C. Since this monitored temperature dropped to 50 ° C (-10 ° C), -5 ° C was added in accordance with Fig. 1 in the amount of the small amount of highly reactive coke charged to +16 kg / t-pig (36 kg / t-).
Pig) (16 kg / t-pig increase to 36 kg / t
-Pig, the same applies to the following description), and -5 ° C is set to + 18% (38%) in JIS reactivity of the small-lump highly-reactive coke according to Fig. 2. 24 mm) was replaced with small coke for ordinary metallurgy, and when mixed with iron ore and charged, the monitoring temperature was 65
This is an example of operation that has recovered to ℃. Compared to Comparative Example 1 described later, the fuel ratio is low and the amount of tapped iron is large.

Example 2 When the temperature measurement of the stave cooler in this region was used as a method for monitoring the heat load from the lower part of the shaft to the furnace belly, the lower limit value obtained in advance by the operation test was 50 ° C. This monitored temperature dropped to 35 ° C (-15 ° C)
Therefore, according to Fig. 4, the JIS reactivity of the small-lump highly-reactive coke was set to + 33% (53%) according to Fig. 4 (the charging amount remains 20 kg / t-pig). This is an example of operation in which the monitoring temperature was recovered to 60 ° C. when (average particle size 20 mm) was replaced with small coke for ordinary metallurgy, and the mixture was charged with mixed coke for ordinary metallurgy. Compared to Comparative Example 2 described later, the fuel ratio is low and the amount of tapped iron is large.

Example 3 As a method of monitoring the heat load from the lower part of the shaft to the furnace abdomen, when the heat removal amount measurement of the stave cooler in this region was used, the lower limit value previously obtained by the operation test was 150.
It was 0,000 kcal / h. This monitoring heat removal amount is 1000
Decreased to 10,000 kcal / h (-5 million kcal / h)
Therefore, the amount of −3 million kcal / h is +18 kg / t-pi as the charging amount of the highly reactive coke of small particles according to FIG.
g (38 kg / t-pig), -2 million kcal / h
According to Fig. 6, JIS of small reactive coke
The reactivity was + 16% (36%), and when this small lump highly reactive coke (average particle size 18 mm) was replaced with normal metallurgical small lump coke and mixed with iron ore and charged, the heat removal amount monitored This is an example of operation that recovered to 17 million kcal / h.

Example 4 As a method of monitoring the heat load from the lower part of the shaft to the furnace abdomen, in the case of using the heat removal amount measurement of the cooling board in this region,
The lower limit value obtained by the operation test in advance is 12 million kca
It was 1 / h. This monitored heat removal is 8 million kcal /
-40 because it fell to h (-4 million kcal / h)
According to FIG. 8, the JIS reactivity of high-reactivity coke of small knots of all 0,000 kcal / h was set to + 22% (42%) (charge was 20 kg / t-pig). (Average particle size 22 mm) was replaced with small coke for ordinary metallurgy and charged, and when mixed with iron ore and coke for ordinary metallurgy by half each, the monitored heat removal amount was 1
This is an example of an operation that recovered to 10 million kcal / h.

In Comparative Example 1, as a method of monitoring the heat load from the lower part of the shaft to the furnace belly, the brick embedding temperature measurement in this region was used, and this monitoring temperature was the lower limit value 60.
Since the temperature fell below 50 ° C and dropped to 50 ° C, the distribution of charges was adjusted to lower the O / C around the furnace, but the monitored temperature did not recover and the overall O / C was reduced. Is. Since the air permeability fluctuated and deteriorated, action was taken to further increase the fuel ratio. Compared with Example 1, the fuel ratio is high and the amount of tapped metal is small.

Comparative Example 2 uses a temperature measurement of a stave cooler in this region as a method for monitoring the heat load from the lower part of the shaft to the furnace belly, and the monitored temperature falls below the lower limit value of 50 ° C. to 35 ° C. Because of this, O / around the furnace
This is an example of the operation of the conventional method in which the charged temperature distribution was adjusted to reduce C, but the monitored temperature did not recover, and the overall O / C was reduced. The fuel ratio is higher and the amount of tapped iron is smaller than that in the second embodiment.

[0026]

As described above, in the present invention, the decrease in the heat load from the lower part of the shaft to the furnace belly is monitored, and when this heat load falls below the preset lower limit value, the deposit formation In order to improve the reduction efficiency in this area before it causes poor ventilation and reduction in reduction efficiency, the charging amount and JIS reactivity of small lump highly reactive coke, which is a part of the metallurgical coke, is adjusted. .. Since this operation method does not need to adjust the distribution of the charge for lowering the O / C in the peripheral portion of the furnace, it does not cause an increase in O / C in the central portion of the furnace.
It does not cause poor ventilation. As a result, the fuel ratio can be reduced under high reduction efficiency, and the blast furnace can be operated stably with high productivity.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the range of decrease in the heat load from the lower part of the shaft to the furnace belly below the lower limit of monitoring and the range of change in the charging amount of small lump highly reactive coke.

[Fig. 2] JIS of high-reactivity coke of small lumps and reduction width from the lower limit of monitoring of heat load from the lower part of the shaft to the furnace belly
Graph showing the relationship of the change range of reactivity

FIG. 3 is a graph showing the relationship between the range of decrease in the thermal load from the lower part of the shaft to the furnace belly below the lower limit of monitoring and the range of change in the charging amount of small-lump highly reactive coke.

[Fig. 4] JIS level of a small-lump highly-reactive coke and a reduction range from the lower limit of monitoring of heat load from the lower part of the shaft to the furnace belly.
Graph showing the relationship of the change range of reactivity

FIG. 5 is a graph showing the relationship between the lower limit of the thermal load from the lower part of the shaft to the furnace belly, which is lower than the monitoring lower limit, and the range of change in the charging amount of the small lump highly reactive coke.

[Fig. 6] JIS width of a high-reactivity coke of small lumps and the width of decrease from the lower limit of monitoring of the heat load from the lower part of the shaft to the furnace belly
Graph showing the relationship of the change range of reactivity

FIG. 7 is a graph showing the relationship between the range of decrease in the heat load from the lower part of the shaft to the furnace belly below the lower limit of monitoring and the range of change in the charging amount of small lump highly reactive coke.

[Fig. 8] JIS of high-reactivity coke of small lumps and reduction width from the lower limit of monitoring of heat load from the lower part of the shaft to the furnace belly
Graph showing the relationship of the change range of reactivity

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Seiichi Morimoto 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corp. Technology Development Division

Claims (1)

[Claims] 1. A part of the ordinary metallurgical coke is replaced with a small lump highly reactive coke having a JIS reactivity of 30% or more and an average particle size of 25 mm or less, and the small lump highly reactive coke is an ore or ordinary metallurgical coke. At the time of performing the blast furnace operation in which the blast furnace is charged after being mixed with at least one of the above, the heat load from the lower part of the shaft of the blast furnace to the furnace belly is measured, and the nodule height is increased so that the heat load exceeds a preset lower limit value. A blast furnace operating method characterized by adjusting at least one of the charging amount of reactive coke and JIS reactivity.