JPH06145728A - Blast furnace operation method - Google Patents

Abstract

PURPOSE:To reduce raw material costs and fuel ratio in the operation method for substituting highly reactive coke for a part of ordinary coke by adjusting the amt. of the porous lumped ore and non-calcined agglomerate, etc., to be charged in such a manner that the utilization factor furnace top gaseous hydrogen attains a prescribed value or above. CONSTITUTION:The ordinary coke for metallurgy is substituted with the highly reactive coke having >=30% JIS(Japanese Industrial Standards) reactivity. The highly reactive coke is mixed with at least either of the ore or the ordinary coke for metallurgy. Further, the non-calcined agglomerate and/or the porous lumped ore, in which <=1% consists of <=3mm size adjusted to >=30% porosity and >=3% water of crystallization and the ore are mixed, and the mixture is charged into a blast furnace. The utilization factor etaH2 of the furnace top gaseous hydrogen is measured in this operation method and the amt. of the porous lumped ore and non-calcined agglomerate, etc., to be charged is adjusted in such a manner that the factor etaH2 attains the preset lower limit value or above. As a result, the temp. of a heat retaining zone is controlled to 750 to 1000 deg.C and the reaction efficiency is maintained even when the quality of the sintered ore degrades. The fuel ratio is lowered and the safe operation under high reduction efficiency is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a large amount of water of crystallization and a large amount of vein ore components when the coke for metallurgical charging from the furnace top is partially replaced with coke having a higher reactivity. The present invention relates to a blast furnace operating method for reducing raw material cost and fuel ratio by charging an inexpensive porous lump ore in a lump state into a blast furnace.

[0002]

2. Description of the Related Art In an ordinary blast furnace, iron ore and coke are charged in layers from the furnace top, and after this iron ore is reduced in the furnace, it is reduced and melted into a metallic state to produce hot metal. ing. At this time, in order to improve the reduction efficiency of iron ore, in Japanese Patent Publication No. 52-43169, iron ore and small coke are premixed, and this mixture and ordinary metallurgical coke are charged in layers. It is disclosed. By using the iron ore previously mixed with the coke in this way, the air permeability in the furnace is improved and the reducing property thereof 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, if the temperature of the heat preservation zone is high, the indirect reduction of iron ore cannot be effectively utilized because the permeation of the reducing gas becomes insufficient, 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 the CO ₂ produced by the CO reduction of the iron ore is closer to the coke because it is mixed with the iron ore, the reduction of the heat preservation zone temperature is not accompanied only by the advantage that the reaction is fast. There was a limit to efficiency improvement.

In order to improve this limit, it has been practiced to replace the high-reactivity coke with all or 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 promote the reaction of reducing it to the lower oxide or metal state. This C + C
The reaction of O ₂ = 2CO is an endothermic reaction and can lower the heat preservation zone temperature in the blast furnace. According to the conventional method, a heat storage zone of about 1000 ° C. is generated and its value hardly changes, whereas the temperature of the heat storage zone is lowered to 900 to 950 ° C. by using a highly reactive coke. Is possible. As a result, the reduction equilibrium point can be afforded, so that the reduction progresses further, the reduction efficiency is improved, and the coke ratio can be reduced.

Regarding the lump ore charged into the blast furnace, humusley ore, Newman ore, etc., which are excellent iron ores having relatively good reducing properties and less heat cracking, are usually used.
It uses about 20%. In addition, a heat-cracking ore such as MBR ore, or an ore with little heat-cracking property, which is porous and contains a large amount of crystal water and adhering powdered ore (3 mm or less), and an inexpensive lobe river with many vein ore components. Porous lump iron ore such as gore ore has a large amount of pulverization in the shaft part of the blast furnace and it is feared that it will not be able to maintain stable operation due to poor ventilation, and this kind of ore will be directly added to the blast furnace. It was crushed and used as a sintering raw material without charging. However, in recent years, JP-A 1-219
As can be seen in Japanese Patent Publication No. 111, a method has been proposed in which a heat cracking ore is charged in the side of the furnace wall and the excellent iron ore is charged in the center of the furnace.

[0007]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
-In place of the heat cracking ore proposed in Japanese Patent No. 219111,
If the porous massive iron ore that has been used as the sintering raw material is charged as it is as described above, clogging of the charge due to the powdered ore occurs even in the blast furnace wall. Even if it could be used, it was a very small amount of about 1% of the total amount of iron source charged. Further, as a method of lowering the heat preservation zone temperature and improving the reaction efficiency of the blast furnace, it is effective to use highly reactive coke mixed with ore or coke, and a reduction in the fuel ratio can be achieved. In blast furnace operation, although it has been confirmed that the temperature of the heat preservation zone decreases, the temperature of the heat preservation zone has not been controlled yet. When using highly reactive coke, the lower limit level of the heat storage zone temperature is about 9
It was about 00 ° C.

Regarding the effect of changes in the properties of the sinter on the operation of the blast furnace, the reducibility of the sinter changes depending on the raw material conditions such as the Al ₂ O ₃ component, and the reduction index JIS-
When the RI decreases, the operation of the blast furnace becomes unstable and the fuel ratio increases. Therefore, it is an issue to maintain the reaction efficiency and reduce the fuel ratio increase amount as much as possible even when the quality of the sintered ore deteriorates. In order to reduce the raw material cost and the fuel ratio, the present invention can maintain a stable blast furnace operation even if a large amount of the above-mentioned porous lump iron ore is charged, and at any position in the furnace. In consideration of the mixed use with the non-calcined agglomerated ore, the heat preservation zone temperature is set to 750 to 10
The purpose is to adjust the temperature within the range of 00 ° C. and to stably produce hot metal with high productivity under high reaction 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.
High reactivity coke having reactivity of 30% or more, mixing the high reactivity coke with at least one of ore and ordinary metallurgical coke, and further reducing 3 mm or less to 1% or less, high crystal with porosity of 30% or more Mixing water (3% or more) -containing porous lump ore and / or uncalcined agglomerated ore with the ore;
In the blast furnace operation method of charging into a blast furnace, the furnace top hydrogen gas utilization rate ηH ₂ is measured, and high crystallization water (3% or more) -containing porous lump ore is set so that the ηH ₂ is equal to or higher than a preset lower limit value. And / or adjusting the amount of uncalcined agglomerate charge or the amount of highly reactive coke used to increase the thermal storage zone temperature to 7
It is characterized in that it is controlled within the range of 50 to 1000 ° C. to further improve the reaction efficiency of the blast furnace.

[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 because, as shown in Japanese Patent Laid-Open No. 1-36710, when the actual furnace test result is less than 30%, the effect is hardly seen. Japanese Patent Laid-Open No. 1-36
No. 710 discloses a highly reactive coke that is not suitable for the production of coke for metallurgy, as a method for adjusting highly reactive coke,
A method has been disclosed in which steam coal is partially blended with raw coal or a small amount of limestone and alkalis which play a role of a catalyst for accelerating the reaction is blended with raw coal. Molded coke also belongs to this category. When the high-reactivity coke is replaced with a part of normal metallurgical coke and charged into the blast furnace, the heat preservation zone temperature decreases and a reduction equilibrium point can be afforded, so that the reduction progresses further and the reduction efficiency improves. As a result, the solution loss reaction (endothermic reaction) of C + CO ₂ = 2CO 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.

First, a method for lowering the heat storage zone temperature will be described. The heat preservation zone temperature corresponds to the reaction start point of the coke, and in the current coke properties, the heat preservation zone temperature is about 100.
Although the temperature is 0 ° C, the lower limit of the thermal storage zone temperature is about 9 when the highly reactive coke as shown in Japanese Patent Application No. 62-193457 is used.
It is 00 ° C. Fig. 1 shows the relationship between the usage method, particle size and usage ratio of the highly reactive coke and the decrease width of the heat storage zone temperature. The thermal storage zone temperature decreases depending on the particle size, and due to the increase in the proportion of highly reactive coke used or the reduction in particle size. In other words, the reactivity of highly reactive coke,
By adjusting the particle size and usage ratio, 900-100
It is possible to control the heat storage zone temperature within the range of 0 ° C.

As a means for lowering the heat storage zone temperature to 900 ° C. or lower, in addition to the use of highly reactive coke, lump iron ore containing 3% or more of water of crystallization (for the technique of using lump iron ore, see Japanese Patent Application No. 3-42406) and / or uncalcined agglomerates. This is because the decomposition endothermic reaction of the crystal water contained in the agglomerated iron ore and the non-calcined agglomerated ore occurs at around 750 ° C., and the decomposition and endothermic reaction of CaCO _{3 in} the cement contained in the uncalcined agglomerated ore is about It takes advantage of the fact that the endothermic reaction of the internal carbon in the non-calcined agglomerate occurs at around 800 to 850 ° C, and that it occurs near 850 ° C.
As described above, when a highly reactive coke is used, the temperature of the heat preservation zone can be lowered by mixing an object that causes an endothermic reaction at around 750 to 850 ° C. in the shaft portion. About the control range of heat preservation zone temperature,
The range is valid. 1000 ° C. corresponds to the current heat preservation zone temperature level, and at 1000 ° C. or higher, the reaction efficiency decreases and the fuel ratio cannot be reduced. Also, below 750 ° C,
Reduction powder of sinter is remarkable, which hinders stable operation.

Next, the necessity of controlling the furnace top hydrogen gas utilization rate η H ₂ proposed in Japanese Examined Patent Publication No. 3-27604 and Japanese Examined Patent Publication No. 63-61366 will be described. When the temperature range of 400 to 700 ° C. becomes long in a part of the radial direction in the blast furnace, reduction pulverization of the sinter occurs, the gas flow in the shaft portion of the blast furnace is diverted, and the reduction delay in the low temperature region causes the blast furnace It reduces the reaction efficiency of and causes instability in blast furnace operation. When the low temperature region becomes long, a water gas shift reaction (H ₂ O + CO = CO ₂ + H ₂ ) occurs in that region, and ηH ₂ decreases. Therefore, by constantly measuring the furnace top gas utilization ratio ηH ₂ , The length of the 700 ° C region can be monitored. In normal operation, there is a high heat flow ratio part in a part of the radial direction, and the upper part of the furnace is heated by the cross flow from the central part or the peripheral part to 400 to 700 ° C.
It is known that the low temperature region of becomes long, but as directed in the present invention, when the heat preservation zone temperature is lowered,
The low temperature region may become long. Therefore, in order to stabilize the operation of the blast furnace, it is necessary to control ηH ₂ .

Next, a method of controlling the heat preservation zone temperature will be described. The heat storage zone temperature can be controlled within the range of 900 to 1000 ° C. depending on the reactivity of the highly reactive coke, the use ratio, and the particle size. For heat storage zone temperature control of 900 ° C. or less, in addition to the use of highly reactive coke, by adjusting the amount of agglomerated iron ore and / or uncalcined agglomerated ore containing 3% or more water of crystallization, It is controllable. In the blast furnace operation in the present invention, the blast furnace top hydrogen gas utilization rate ηH ₂ is monitored, and when this value is below a preset lower limit, a low temperature region of 400 to 700 ° C. is present in a part of the blast furnace radial direction. Spreading, the reduction rate of sinter ore is promoted and reduction powdering is promoted, and this phenomenon leads to deterioration of the air permeability in the furnace and poor condition of the furnace, so to cut off the connection,
The amounts of the agglomerated iron ore, uncalcined agglomerated ore, and highly reactive coke containing 3% or more of water of crystallization are adjusted.

The spread is a low temperature region of 400 to 700 ° C. in a blast, blast furnace top hydrogen gas utilization rate ItaH ₂ for promoting reduction degradation
Varies depending on the operating conditions, so it is obtained in advance by an operating test, and the agglomerated iron ore containing 3% or more of water of crystallization required depending on the degree of falling below this lower limit, uncalcined agglomerated The relationship between changes in the use of ore and highly reactive coke should also be obtained in advance by operation tests. Fig. 2 shows the hydrogen gas utilization rate ηH _{2 at the} top of the blast furnace determined by the operation test.
Fig. 3 shows the relationship between the range of decrease from the lower limit and the range of change in the amounts of the aforementioned massive iron ore, non-calcined agglomerated ore, and highly reactive coke required for recovering to the lower limit. FIG. 3 is a lump containing uncalcined agglomerated ore and / or 3% or more of water of crystallization under the operation in which 20% of the normal coke by weight is replaced with highly reactive coke having a JIS reactivity of 70 and a particle size of 10 mm. The relationship between the amount of iron ore used and the width of decrease in the temperature of the heat storage zone is shown.

[0016]

EXAMPLES The features of the present invention will be specifically described below with reference to examples. Table 1 shows highly reactive coke with 3 mm or less as 1
A blast furnace operation using a porous agglomerated iron ore and a non-calcined agglomerated ore having a porosity of 30% or more and a water of crystallization of 3% or more, which are made less than or equal to%, is shown in comparison with a conventional method. The target blast furnace has an internal volume of 3000 m ^3.
This is a medium-sized blast furnace in which iron ore and normal metallurgical coke (JIS reactivity 20%) are charged in layers at a ratio of O / C = 4.2 from the furnace top, and a small lump of normal metallurgical coke (JIS reaction) 20%, average particle size 20 mm, mixed with iron ore)
/ T was charged. The normal lump ore usage ratio is 13% and the pellet usage ratio is 9%. Hue front frame temperature 21
80 ° C (Blower temperature 1200 ° C, added moisture 25g / Nm
³ , the oxygen enrichment amount was 0.013 Nm ³ / Nm ³ -air, and the pulverized coal blowing amount was 100 g / Nm ³ -air), and hot metal was produced at 6000 t / day (Comparative Example 1).
The quality of sinter is JIS-RI 68%.

The heat preservation zone temperature during normal operation was 980 ° C. From this state, 20% of the normal coke in weight ratio was replaced with highly reactive coke having a JIS reactivity of 70 and a particle size of 5 to 10 mm, and the highly reactive coke was mixed with iron ore and charged (Comparative Example 2). ). 400-in the shaft part of the blast furnace
The lower limit of the blast furnace top hydrogen gas utilization rate ηH ₂ when the low temperature region was generated at 700 ° C. and destabilized the operation of the blast furnace was 42%. Here, the porous lump iron ore having crystal water of 8.1% and 3 mm or less made 1% or less is indicated as A lump ore, and the crystal water of 8.1%, 3 mm or less and porous lump iron ore made 1% or less Display the stone as a B block ore.

In Example 1, under the use of the highly reactive coke shown in Comparative Example 2, the A mass ore was used in place of the total amount of the normally used mass ore and a part of the sintered ore, and the usage amounts were sequentially. When the amount of use increased to 16%, ηH ₂ was 40%, which was below the lower limit value of 42%. Therefore, according to FIG. 1, the amount of the lump ore used was reduced by 4%, and ηH ₂ was 42 to 43%. It is an example of the operation when it was restored to. Heat preservation zone temperature is about 860 ℃
Stable in. The reaction efficiency of the blast furnace was improved compared to Comparative Example 2, and the fuel ratio was reduced.

In Example 2, the highly reactive coke shown in Comparative Example 2 was used, and the entire amount of the pellets was used in the non-calcined agglomerated ore (9
%), Under the operation of replacing the whole amount of the normally used lump ore and part of the sintered ore with A lump ore, the usage amount is gradually increased until the usage amount reaches 14%, since ItaH ₂ is below 42% 40% becomes the lower limit value, according to FIG. 1, to reduce the amount of該塊ore 4%, the ηH ₂ 42~
It is an example of operation when it is recovered to 43%. The heat storage zone temperature was stable at 850 ° C. In operation, the reaction efficiency is improved and the fuel ratio is reduced as compared with Comparative Example 2.

In Example 3, the highly reactive coke shown in Comparative Example 2 was used, the whole amount of pellets and a part of the sintered ore were replaced with non-calcined agglomerated ore, and the use ratio of the non-calcined agglomerated ore was 15 %, And the total amount of normally used lump ore and part of the sinter ore
Replaced lump ore 10% and B lump ore 7%, and changed the usage rate to 1
When it was set to 5%, ηH ₂ was 40%, which was below the lower limit. Therefore, according to Fig. 1, A lump ore was reduced by 4% and ηH ₂
Is an example of operation when it is recovered to 42 to 43%. The temperature of the heat preservation zone around the furnace dropped to about 825 ° C.

In Example 4, while the operation of Example 3 was continued, the sinter ore RDI increased, and due to the effect, ηH ₂ was 41%, which was below the lower limit of 42%, and blast furnace operation began to become unstable. Therefore, according to FIG. 1, this is an operation example in which the usage ratio of highly reactive coke is reduced by 3% and η H ₂ is recovered to 42%. The heat preservation zone temperature of the peripheral part rose to about 840 ° C, and the operation was stabilized.

In Example 5, from the operation of Comparative Example 1, 20% by weight of normal coke was JIS reactive 60 and particle size 10.
Replaced with ~ 15 mm highly reactive coke, which was mixed and charged with iron ore. This is an operation example when the entire amount of the normally used lump ore is replaced with the A lump ore from this operating state (used amount 13%). Although η H ₂ was 44%, which was close to the lower limit, the blast furnace operation was stable, and the temperature of the heat preservation zone around the furnace was about 910 ° C. The fuel ratio is lower than in Comparative Example 1.

[0023]

[Table 1]

[0024]

As described above, in the present invention, when using highly reactive coke, porous lump iron ore with 3% or more of water of crystallization, or non-calcined agglomerate, the hydrogen gas utilization rate at the top of the furnace ηH ₂ is monitored, and before this ηH ₂ falls below the preset lower limit value and aeration fluctuation due to promotion of reduction powdering is reached, the above-mentioned porous lump iron ore, uncalcined agglomerated ore use ratio or high reactivity Adjust coke usage. This operation method uses a highly reactive coke, the above-mentioned porous lump iron ore, and non-calcined agglomerated ore to keep the heat preservation zone temperature at 750 to 1000 ° C.
The fuel ratio can be reduced and the blast furnace can be operated stably under high reduction efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a method of using highly reactive coke, a particle size, a usage ratio, and a decrease width of a heat preservation zone temperature

[Fig. 2] Amount of decrease in the hydrogen gas utilization rate ηH _{2 from} the top of the blast furnace and an agglomerated iron ore containing 3% or more of crystallization water necessary for recovering to the lower limit, uncalcined agglomerated ore, high The figure which shows the relationship of the variation width of the charging amount of the reactive coke,

FIG. 3 is an uncalcined agglomerated ore and an agglomerated iron ore containing 3% or more of crystallization water under the operation in which 20% of normal coke by weight is replaced with highly reactive coke having a JIS reactivity of 70 and a particle size of 10 mm. It is a figure which shows the relationship between the usage amount of stones and the fall width of heat preservation zone temperature.

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

Claims (2)

[Claims] 1. A part of the ordinary metallurgical coke is replaced with a highly reactive coke having a JIS reactivity of 30% or more, the highly reactive coke is mixed with at least one of ore and ordinary metallurgical coke, and further unfired. In a blast furnace operating method in which agglomerated ore and / or a porous lump iron ore having a porosity of 30% or more and water of crystallization of 3% or more in which 1% or less is 3 mm or less is mixed with ore and charged into a blast furnace, the furnace top is Hydrogen gas utilization rate η
Of H ₂ were measured, as the ItaH ₂ is equal to or greater than the lower limit value set in advance, blast furnace operation method characterized by adjusting the charging amount of the porous mass of iron ore and / or uncalcined masses Naruko . 2. A part of the ordinary metallurgical coke is replaced with a highly reactive coke having a JIS reactivity of 30% or more, the highly reactive coke is mixed with at least one of ore and ordinary metallurgical coke, and further unfired. In a blast furnace operating method in which agglomerated ore and / or a porous lump iron ore having a porosity of 30% or more and water of crystallization of 3% or more in which 1% or less is 3 mm or less is mixed with ore and charged into a blast furnace, the furnace top is Hydrogen gas utilization rate η
Of H ₂ were measured, as in the ItaH ₂ is equal to or greater than the lower limit value set in advance, blast furnace operation method characterized by adjusting the charging amount of the highly reactive coke.