JPH02236210A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve the productivity by charging large lump of high reactive coke into center part of a furnace and small lump thereof into circumferential part together with agglomerated ore and further, replacing ordinary sintered ore to the agglomerated ore from difference between the measured values and set values of distributions of temp. and gaseous hydrogen utilizing ratio in the blast furnace. CONSTITUTION:In the blast furnace where the high reactive coke is charged while separating into the large lump and the small lump, together with the agglomerated ore combining plural pieces of pellets having 3-10mm grain diameter, the large lump coke into center part in the furnace and the small lump coke into the circumferential part in the furnace, are charged. Further, the temp. distribution in the height direction or the distribution of hydrogen utilizing ratio in the radius direction in the blast furnace is measured, and when the difference between this value and the reference value comes to the preset value, the whole ordinary sintered ore is replaced to the agglomerated ore. By this method, the productivity of the blast furnace operation can be improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention improves production by using agglomerate, which is made by combining a plurality of pellets with a particle size of 3 to 10 square meters, together with coke that has been made highly reactive in a blast furnace. Concerning a blast furnace operating method with improved performance.

(Prior art) In a normal blast furnace, iron ore and coke are charged in layers from the furnace stage, and the iron ore is reduced in the furnace, and then reduced and melted into a metallic state to produce smelt. are doing.

At this time, in order to operate the blast furnace stably,
In the -174403 publication, in a blast furnace operating method in which iron raw material and coke are sequentially charged into a blast furnace and refined, when charging coke into the blast furnace, 15 to 25 me A blast furnace operating method is disclosed in which small coke having an average particle size is charged into the center of the furnace and large coke having an average particle size of 35 to 70 calM is charged for operation.

In addition, the present inventors have disclosed in Japanese Patent Application No. 193457/1983 that using small pieces of highly reactive coke of 15 mm or less,
We proposed a blast furnace operating method in which the highly reactive coke is mixed with ordinary coke or ore and charged into the blast furnace, thereby lowering the temperature of the thermal reserve zone of the blast furnace and increasing the reaction efficiency of the blast furnace.

Furthermore, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 62-40322 an agglomerate ore for iron-making, which is characterized in that voids are provided inside the agglomerate made by combining a plurality of pellets with a grain size of 3 to 10 w+m. Proposed.

(Problem to be solved by the invention) However, in blast furnace operation, 35 to 70 a.m.
Large lump coke with an average particle size of s is placed around the furnace.
By charging small coke with an average particle size of 25 mm, ventilation and liquid permeability of the furnace core in the center of the furnace can be ensured, and stable operation is thought to be possible. The reaction efficiency cannot be improved.

On the other hand, in order to improve the reaction efficiency of blast furnaces, it is effective to use small-sized highly reactive coke mixed with ore or coke, but in normal operation, small-sized highly reactive coke has a low m content. Since it is charged so that it does not reach the center of the furnace, the reduction efficiency in the center of the furnace is not improved, and the reaction efficiency in the entire radial direction of the blast furnace is difficult to improve. In addition, by controlling the charge distribution, if small lump highly reactive coke is charged into the center of the furnace,
Although the overall reaction efficiency in the radial direction of the blast furnace can be improved, there is a problem in terms of ventilation and liquid permeability of the furnace core in the center of the furnace, which hinders stable operation.

In addition, even if the reaction efficiency can be improved and low fuel ratio operation becomes possible, the gas flow will be unbalanced and a region of low gas flow will be created in the blast furnace shaft, as is often seen during low fuel ratio operation. As a result, a low-temperature thermal storage zone of 600 to 700°C is likely to be generated, but this region promotes sinter reduction and pulverization, resulting in poor ventilation of the blast furnace shaft, resulting in a delay in ore reduction and charging problems. There are many cases where stable operation of the blast furnace is hindered, such as due to poor descent of materials.

The temperature distribution in the height direction inside the blast furnace is measured by a vertical sonde as disclosed in JP-A-59-16917, and in JP-A-62-054006, the temperature distribution at the top of the blast furnace or A method of detecting the temperature distribution in the furnace by measuring the hydrogen gas utilization rate or the hydrogen gas utilization rate/CO gas utilization rate at the upper part of the shaft is disclosed, and this information is used to adjust the pellet usage amount. It has not yet reached that point.

Figure 4 compares the reduction pulverization index (hereinafter referred to as RDI) and the indirect reduction rate when reduced under blast furnace conditions between low-reduced pulverizable sintered ore, pellets, and regular sintered ore. , low-reduction pulverizable sintered ore, and vered all have lower RDI than normal sintered ore, suppressing the hair ratio of the blast furnace shaft,
It is possible to eliminate poor ventilation, and stable operation is expected under low fuel ratio operation.

However, the reducibility of both low-reduced pulverizable sintered ore and pellets is inferior to that of normal sintered ore, and the amount of fuel ratio reduction that can be achieved by using highly reactive coke cannot be utilized to the fullest extent. do not have.

Therefore, in the present invention, by increasing the reactivity of the coke charged into the blast furnace and charging it separately into large lumps and small lumps, the temperature of the heat reserve zone is lowered and the iron ore in the entire blast furnace is reduced. To promote the reduction reaction of sinter and reduce the powder ratio in the furnace as much as possible to efficiently produce smelt, and to reduce the increase in t rate due to reduction and powdering of sinter which tends to occur under low fuel ratio operation. The purpose is to control the blast furnace and operate the blast furnace stably with high reaction efficiency and high productivity.

(Means and effects for solving the problem) In order to achieve the object, the blast furnace operating method of the present invention is to charge highly reactive coke into large lumps in a blast furnace in which coke is charged after being separated into large lumps and small lumps. When charging the large highly reactive coke into the center of the furnace and the small highly reactive coke from the middle to the periphery of the furnace, along with the highly reactive coke, particles with a particle size of 3 to 3 It is characterized by charging agglomerate (hereinafter referred to as new agglomerate) consisting of a plurality of 10 mm pellets, and when operating by charging highly reactive coke into the blast furnace, the blast furnace inside the blast furnace is The temperature distribution in the horizontal direction or the hydrogen gas utilization rate distribution in the radial direction inside the blast furnace is measured, and when the difference between the measured temperature or hydrogen gas utilization rate and the standard value reaches a preset value, the new sintered ore is It is characterized by replacing the entire amount with agglomerate ore.

First, we will discuss highly reactive coke.

The highly reactive coke used in the present invention is JISK2151
It is desirable that the JIS reactivity is 30% or more when measured by the reactivity test method of -1977. Its value is 30
If it is less than %, the temperature of the thermal storage zone, which will be described later, will hardly decrease. Furthermore, even with highly reactive coke, it is necessary to maintain high strength, and it is desirable to maintain the same strength as normal coke.

Methods for preparing highly reactive coke with high strength include a method of adding an alkaline aqueous solution to high-strength ordinary coke, or a method of molding steam coal and carbonizing it.

Highly reactive coke replaces part or all of the coke normally charged from the top of the furnace, and the highly reactive coke is separated into large lumps and small lumps, and the large lumps are mixed with normal coke, or It is charged alone in layers in the center of the furnace, alternating with iron ore. The nodules are charged from the middle of the furnace to the periphery of the furnace in a mixture with iron ore and/or coke, or alone in layers alternating with iron ore.

In the present invention, the furnace center is defined as 20 mm of the furnace mouth radius of the blast furnace.
For example, if the radius of the furnace mouth is 5 m, the area within the radius lm is called the furnace center.

The area outside the furnace wall excluding the furnace center is called the furnace middle area to the furnace periphery area.

It is desirable that the degree of ablation of the iron ore charged from the middle part of the furnace to the peripheral part of the furnace and/or the highly reactive coke mixed with the normal coke is 15 mm or less. This particle size is l5
If it is less than lIII1, the surface area of the coke per unit weight increases, and the proportion contributing to the reaction increases.

Since this highly reactive coke has high reactivity, the interfacial reaction in which the coke in the furnace comes into contact with the surface of the coke and becomes CO takes place smoothly. In addition, as a result, the C generated in the furnace
The O gas effectively reacts with the iron ore to promote the reaction of reducing it to a lower oxide or metal state.

The C+GO,=2GO coke gasification reaction can reduce the temperature of the zone. For example, when using the conventional method, a heat reserve zone of about 1000°C is generated, and its value hardly changes, but by using highly reactive coke, the temperature of the heat reserve zone is increased to 900 to 950°C.
It is possible to reduce the As a result, the margin ratio can be lowered to reach the reduction equilibrium point.

Also, as large block highly reactive coke, the particle size is 35-70mm+
By charging highly reactive coke into the center of the furnace, ventilation and liquid permeability of the furnace core in the center of the furnace is ensured, stable operation is possible, and iron ore charged into the center of the furnace is Since the reduction is promoted, the reduction efficiency in the entire blast furnace radial direction can be improved.

In addition, as shown in Figure 1, new agglomerated ore has a lower reduction pulverizability index (RD I ) than normal sintered ore, and is effective in reducing the reduction rate and improving the reduction efficiency in the blast furnace. It is an effective means to reduce the fuel ratio.

Next, we will discuss the phenomenon of reduction and pulverization of sintered ore.

The use of highly reactive coke improves the reduction efficiency, but as a result of promoting reduction at low temperatures, reduction powdering of the sintered ore is promoted, the amount of powder generated increases, and the ventilation inside the blast furnace is reduced. Unless measures are taken to suppress this deterioration, the effects of highly reactive coke cannot be maximized and high productivity cannot be ensured.

When the air permeability deteriorates, the temperature distribution in the height direction inside the blast furnace changes.
A low-temperature thermal storage zone of 0 to 700 degrees Celsius occurs, and a temperature range of 600 degrees to
As the water gas shift reaction progresses in the 700°C low-temperature thermal storage zone, the hydrogen gas utilization rate decreases.

Figure 2 shows the relationship between the length of the low-temperature heat storage zone of 600 to 700°C and the increase in the powder ratio in the furnace. .

Moreover, FIG. 3 shows the relationship between the furnace top hydrogen gas utilization rate and the in-furnace powder rate increase, and as the hydrogen gas utilization rate decreases, the sinter reduction powder rate increases.

The absolute value of the increase in reduction powdering rate usually differs depending on the RD■ of the sintered ore, but for example, when a low-temperature thermal preservation zone of about 4 m is detected according to Figure 2, an increase of about 10% according to Figure 3 is detected. When a decrease in the hydrogen gas utilization rate is detected, it is determined that the in-furnace powder rate has increased by 5% compared to the reference value during normal stable operation.

As shown in Figure 1, new agglomerated ore has a lower reduction pulverizability index (RD I ) than normal sintered ore. By replacing it with mature ore, it is possible to suppress an increase in the powder ratio in the furnace, and it is possible to eliminate operational fluctuations due to deterioration of air permeability in the blast furnace. Also,
Since it has good reducibility, the use of new agglomerated ore can also contribute to improving the reduction efficiency in the blast furnace. In the process of forming a low-temperature thermal reserve zone, the criteria for determining the complete replacement of normal sintered ore with new agglomerated ore differs depending on the sintered ore RDI, but the in-furnace powder ratio is 5% compared to the standard value during normal stable operation. % increase.

In the present invention, the entire amount of normal sintered ore is replaced with new agglomerated ore, which is charged together with highly reactive coke. Or, normally, normal sintered ore is charged, and while detecting whether or not a low-temperature thermal storage zone occurs at 600 to 700°C, when the low-temperature thermal storage zone occurs, charging of normal sintered ore is started. By stopping the blast furnace and charging the entire amount of new agglomerated ore, the amount of reduction and powdering can be suppressed, the above-mentioned low-temperature heat storage zone and/or poor ventilation zone can be eliminated, and stable blast furnace operation can be performed.

Note that the low-temperature heat storage zone of 600 to 700° C. can be detected by measuring the temperature with a vertical sonde or measuring the hydrogen gas utilization rate in the radial direction at the top of the furnace or the upper part of the shaft using a horizontal sonde. In addition, RDI uses a reducing gas (CO30
%-N, 70%, 1 5 N12/win) 55
It was reduced at 0° C. for 30 minutes, and was then rotated at 900 revolutions (30 rpm x 30 minutes) using a rotation tester, which was then shown as a weight percentage of -3 ms.

(Example) Hereinafter, the features of the present invention will be specifically explained with reference to Examples.

Table 1 shows a comparison of blast furnace operation using highly reactive coke and agglomerate ore made by bonding a plurality of pellets with a particle size of 3 to 101 with a conventional method.

The target blast furnace is a medium-sized blast furnace with an internal volume of 3000 + O3, and in the conventional method, iron ore and normal coke are charged at a ratio of O/C = 3.2 from the furnace term in terms of weight ratio, and the flame temperature before the tuyere is set to 22
70℃ (hot air temperature 1100℃, added moisture 35z/
Nm', without pulverized coal injection).
A sintered ore containing 0% I4 was used to produce melt (comparative example).

In Example 1, the entire amount of normal coke was replaced with highly reactive coke (JI
In this example, the particle size was 5 (1
+m or more is 20%, particle size less than 50Ilm is 80%, and the total amount of normal sintered ore with RD 140%, particle size 3-1
This is an example of operation when replacing a plurality of 0 mm pellets with agglomerated ore (referred to as new agglomerate). In Example 1, the operational results when normal sintered ore was charged are added (
(Example of operation before using new agglomerate ore) is shown in comparison with the operation results when the entire amount of new agglomerate is charged (Example of operation after using new agglomerate ore)
.

The production of new agglomerated ore is based on the raw material composition Fetu3, which is approximately 94% by weight.
．． 0%, SiO*2.0%, Ca02.5% iron ore powder is milled to make raw pellets of 4 to 6 cm, and coke powder is blended so that the maximum firing temperature is 300℃. , After firing in a sintering machine, it is passed through a crusher for 3 to 6
The agglomerated ore had an average diameter of about 25a+a+ when the pieces were combined. The new agglomerate properties used in Examples 2 to 4 are also the same.

In Example 2, 50% by weight of normal coke was replaced with highly reactive coke (JIS reactivity 50%), of which the weight m
The ratio is 70% for particles exceeding 151Ilm, and 30% for particles with a particle size of 15mm or less.
In the example, RD 14 0% normal sintered ore 16
Of 15 Kg/pig-t, T. 5 in terms of Fe
685Kg of new agglomerated ore (T.Fe66%) equivalent to 0%
This is an example of operation when replacing with /pig-t. Example 2
Inside, the operational results when using normal sintered ore are appended (example of operation before using fr agglomerate ore) and compared with the operational results when new agglomerate ore is charged (new agglomerate ore). Example of operation after use).

In Example 3, 35% by weight of normal coke was replaced with highly reactive coke (JIS reactivity 45%), of which 50% by weight was more than 15n+m and 50% was less than 15mm in particle size.
In this example, a vertical sonde detected a low-temperature thermal storage zone of 600 to 700°C over approximately 4 m above the blast furnace shaft (an example of operation before using new agglomerated ore), so all of the normal sintered ore was replaced with new agglomerated ore. This shows the operational status when replaced with mature ore (an example of operation after using new agglomerated ore).

In Example 4, 50% by weight of normal coke was replaced with highly reactive coke (JIS reactivity 50%), of which 70% by weight was more than 15III1. In an example where 30% of grain size is 151 mm or less, in an operation in which the hydrogen gas utilization rate (-Hto/(Ht+H,O)) distribution in the radial direction inside the blast furnace was detected using a horizontal sonde, hydrogen at a position lm from the blast furnace wall It was detected that the gas utilization rate was lower than the standard value (hydrogen gas utilization rate of 50%) by IO% (an example of operation before using new agglomerate ore), so the normal sintered ore was completely replaced with new agglomerate ore. This shows the operating status when the plant was operated (example of operation after using new agglomerated ore).

In the case of Example 1, the charging method was such that a large lump of highly reactive coke was charged in the center, small lumps were charged from the middle part of the furnace to the peripheral part, and the sintered ore was alternately charged. In the case of Example 2.3.4, the large highly reactive coke is mixed with normal coke and charged into the center of the furnace, and the small coke is mixed with normal coke and new agglomerated ore.
Two parts were mixed and charged from the middle part to the peripheral part of the furnace.

In the examples shown in Table 1, the gas utilization rate was improved and the coke ratio was lowered, and the fuel ratio was lowered, compared to the comparative example. In addition, the operation results before using new agglomerate ore in Examples 1 to 4 show a smaller degree of decrease in coke ratio than the operation results after using new agglomerate ore, and the blast furnace operation is not efficient. .

(Effect of the invention) As explained above, in the present invention, highly reactive coke is separated into large lumps and small lumps, and the large highly reactive coke is placed in the center of the furnace, and the small highly reactive coke is placed in the center of the furnace. By charging from the middle of the furnace to the periphery of the furnace, it is possible to ensure ventilation and liquid permeability of the furnace core in the center of the furnace, and also to lower the temperature of the heat storage zone, thereby increasing shaft efficiency. This increases the overall gas utilization efficiency of the blast furnace and enables blast furnace operation with a small coke ratio. Even when a low-temperature thermal storage zone near 600 to 700 degrees Celsius is generated, which is likely to occur at low fuel ratios, by charging agglomerate made by bonding multiple pellets with a particle size of 3 to 10 nua, ventilation can be achieved by increasing the powder ratio. Defects can be suppressed and stable operation can be performed for a long period of time.

In this way, according to the present invention, the productivity of blast furnace operation can be improved.

[Brief explanation of drawings]

Figure 1 shows a comparison of the RDI of agglomerated ore made of a plurality of pellets with a grain size of 3 to 10 mm combined with normal sintered ore, and the indirect reduction rate when reduced under blast furnace conditions. 60
Figure 3 is a diagram showing the relationship between the length of the low-temperature heat storage zone of 0 to 700°C and the increase in the powder ratio in the furnace. Figure 4 is a diagram showing a comparison of the RDI of low-reduced pulverizable sintered ore, pellets, and normal sintered ore, and the indirect reduction rate when reduced under blast furnace conditions. Fig. i Fig. 2 Applicant Nippon Steel Corporation Kishitetsu 4G-naL}Female (g))

Claims (1)

[Claims] 1) In a blast furnace in which coke is charged after being separated into large lumps and small lumps, the highly reactive coke is separated into large lumps and small lumps, and the large highly reactive coke is placed in the center of the furnace. When charging the small highly reactive coke from the middle part of the furnace to the peripheral part of the furnace, it is characterized in that agglomerate ore, which is a combination of a plurality of pellets with a grain size of 3 to 10 mm, is charged together with the highly reactive coke. Blast furnace operation method. 2) When charging highly reactive coke into a blast furnace and operating it, measure the temperature distribution in the height direction inside the blast furnace or the hydrogen gas utilization rate distribution in the radial direction inside the blast furnace, and compare it with the measured temperature or hydrogen gas utilization rate. A blast furnace operating method characterized in that when the difference from a reference value reaches a preset value, the entire amount of normal sintered ore is replaced with agglomerated ore made by combining a plurality of pellets with a grain size of 3 to 10 mm.