JPH09125114A - Operation of blast furnace at the time of blowing a large quantity of pulverized fine coals - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blast furnace operation at the time of blowing a large quantity of pulverized fine coal which promotes high temp. reduction by charging low slag sintered ore having much fine pores into the blast furnace and can control so that the thickness of a softening and cohesive zone forms to thinner than the conventional method. SOLUTION: In the blast surface blowing >=150kg/t-p pulverized fine coal, the sintered ore having much fine pores and 8.0-10.0mass% Fe, 4.2-4.9mass% SiO2 and 0.18-0.29 Al2 O3 /FeO ratio, is charged into the blast furnace to improve the high temp. reducibility and thus, the pulverized fine coal is stably blown in a large quantity by controlling so that the thickness of the softening and cohesive zone becomes thin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention introduces sinter having improved high-temperature reducibility into a blast furnace and controls it so that the width of the softening cohesive zone becomes thin, whereby a large amount of pulverized coal is injected. The present invention relates to a blast furnace operation method aiming at stabilization of blast furnace operation.

[0002]

2. Description of the Related Art The replacement of coke has a great effect of reducing the cost of hot metal, and blowing pulverized coal, which is important as a countermeasure against the deterioration of coke ovens, has recently attracted attention and has been adopted in almost all blast furnaces in Japan. For example, “Materials and Processes” 7 (19
94), p124, the blowing operation with a pulverized coal ratio of 180 kg / tp or more was maintained stably by improving the charge distribution (maintaining a sharp inverted V-shaped cohesive zone) and pre-tuyere conditions. The results have been reported. Also, in “Materials and Processes” 7 (1994), p126, an operation test result of a pulverized coal ratio of 200 kg / tp for one week is reported, which shows improvement in coke DI, high oxygen enrichment operation, and low Al ₂ O.
_{3. The} contents achieved by using highly reducible sinter ore and controlling the distribution of the charge without forming a local high O / C part are described.

Here, since it is reported that low Al ₂ O ₃ / highly reducible sinter is used in order to suppress deterioration of the air permeability of the lower part of the furnace due to an increase in the thickness of the cohesive zone, It is considered that the increase in the thickness of the cohesive zone was suppressed by reducing the Al ₂ O ₃ content of the material. Furthermore, "Materials and Processes" 8 (1995), p3
In Fig. 19, as a result of monthly pulverized coal ratio of 218 kg / tp, the slag ratio was reduced (320 → 280 kg / tp) and the high RI of agglomerated ore was improved to improve the permeability of the lower part of the furnace.
It has been reported that (reducible) (using the entire surface of HPS) and improving coke strength were carried out. It is well known that HPS ore is a low SiO ₂ and low Al ₂ O ₃ ore, and it is possible to increase the thickness of the cohesive zone by reducing the SiO ₂ content and the A content of the charge.
It is considered that this was suppressed by conversion into l ₂ O ₃ .

[0004]

It is considered necessary to solve the following technical problems in order to blow a large amount of pulverized coal in the pulverized coal blowing operation. That is, since the coke amount decreases (coke slit size reduction) due to the increase in the pulverized coal ratio, the ore / coke ratio (O / C) increases, which increases the thickness of the cohesive zone and is located below it. Since the air permeability in the lower part of the furnace deteriorates and the amount of pulverized coal combustion in the tuyere increases, the gas flow flows down to the periphery, the heat dissipated from the furnace body increases and the thermal efficiency decreases, and the heat flow ratio (solid heat capacity (/ Heat capacity of gas body) lowers the temperature of gas in the furnace, so that the sensible heat of gas from the top of the furnace increases, which lowers the thermal efficiency. It has been reported that when the pulverized coal ratio is 150 kg / tp or more, the operation becomes unstable due to deterioration of the load unloading, increased pressure loss, and increased heat load on the furnace body. Solving problems is considered important.

Among them, it is considered that there is a big problem that the ore / coke ratio (O / C) is increased due to the increase of the pulverized coal ratio, which increases the thickness of the cohesive zone. At the same time as the pressure loss in the lower part of the furnace increases, the central flow of gas is suppressed and the peripheral flow is promoted, so that the unloading becomes unstable and the heat load on the furnace body increases. However, as described above, regarding the measures for improving the charge against the increase in the thickness of the cohesive zone due to the higher O / C and the deterioration of the air permeability of the lower part of the furnace located therebelow, as described above, Al ₂ O ₃ conversion (1.7 ma
Only less than ss%) can be seen. However, A in the sinter in the entire 1994 Japanese steel industry
The average value of l ₂ O ₃ is in the range of 1.75 to 1.85 mass%, and it is expected that Al ₂ O ₃ in the sinter will gradually increase in the future. Therefore, it is considered difficult for many blast furnaces to produce and use low Al ₂ O ₃ sinter for a long time.

On the other hand, Japanese Patent Laid-Open No. 6-100911 discloses that in a blast furnace operation in which pulverized coal is blown, the amount of pulverized coal blown is 150 kg / tp or more and the amount of hydrogen fed is 15 to 20.
It describes a blast furnace operating method at the time of blowing a large amount of pulverized coal, which is characterized in that it is set to kg / tp and that oxygen is enriched by 3 to 5%. This is a method to improve the air permeability by changing the cohesive zone into an inverted V shape by increasing the amount of steam injected and enriching oxygen, but since steam and oxygen are manufactured separately and blown into the blast furnace, the blast furnace operating cost is reduced. It has the drawback of rising significantly.

Further, in Japanese Patent Laid-Open No. 61-56211, the basicity of the sintered ore charged in the blast furnace operation is set to 2 or more, and the amount that is higher than the target basicity of the blast furnace slag is SiO 2 in the blast furnace. A blast furnace operating method is described which is characterized in that it is adjusted by charging a _two- source auxiliary material and that the Si concentration in the hot metal is lowered by lowering the level of the softening cohesive zone. This method improves the shrinkage rate and the ventilation resistance of the softening cohesive zone by using a sinter having a high basicity and excellent in high-temperature properties, but it has the drawback of increasing the amount of blast furnace slag. It is difficult to apply to the operation in which a large amount of pulverized coal is injected, which requires improvement of the air permeability of the lower part.

The present invention has been made in order to solve the above-mentioned problems, and it is intended to significantly improve the air permeability of the cohesive zone formed in the blast furnace by focusing only on the charged material. I'm aiming. That is, a low-slag sinter having many fine pores is charged into a blast furnace to promote high-temperature reduction, and the width of the softening cohesive zone can be controlled so as to be thinner than in the conventional method. The purpose is to provide.

[0009]

In the present invention, the above object is specifically achieved by any of the following three means. That is, the amount of pulverized coal blown is 150 kg / tp
In order to enable stable operation of the blast furnace even when a large amount of the above is blown, (1) FeO component in the blast furnace is 8.0 to 10.0 mass.
%, SiO ₂ component is 4.2 to 4.9 mass%, Al ₂
The width of the softening cohesive zone is controlled to be thin by charging a sinter having an O ₃ / FeO ratio of 0.18 to 0.29 to improve the high-temperature reducibility. (2) In addition to the above (1), the amount of blast furnace slag is further set to 3
Operate while adjusting to less than 00 kg / tp. (3) An iron ore containing 5 mass% or more of water of crystallization is mixed in a new raw material in an amount of 25 mass% or more and manufactured, and a sinter that satisfies the above component condition (1) is charged to improve the high temperature reducibility. As a result, the width of the softening cohesive zone is controlled to be thin.

Assuming that the fuel ratio is 500 kg / tp, the pulverized coal ratio is 150 kg / tp (hence the coke ratio is 35).
0 kg / tp), the ore / coke ratio (O / C) rises to the 4.5 level. Furthermore, the pulverized coal ratio is 200 kg / tp (so the coke ratio is 300 k
g / tp), O / C rises to 5.5.
O / C in normal operation is less than 4.0, so pulverized coal ratio is 1
If it is 50 kg / tp or more, the ore layer thickness will be significantly increased, and the shape of the cohesive zone will be enlarged.

FIG. 1 shows a pulverized coal ratio of 60 kg / tp and 2
The change of the cohesive zone shape in a furnace based on the simulation result in 00 kg / tp blowing operation is shown. It can be seen that the cohesive zone is enlarged as the pulverized coal ratio increases. If the enlargement of the cohesive zone can be suppressed, the air permeability in the furnace will be improved. According to the present invention, by increasing the fine pores of the sinter and reducing the slag, the width of the cohesive zone in the blast furnace is controlled to be thin so that a large amount of pulverized coal can be injected. On the other hand, SiO ₂
Component is 4.2 to 4.9 mass%, FeO component is 8 to 1
0 mass%, Al ₂ O ₃ / FeO ratio is 0.18 to 0.
It has been found that in the sintered ore in the range of 29, the melt amount decreases and the viscosity of the melt increases, and the fine pores formed in the sintered ore are uniformly dispersed without gathering. Also, iron ore containing 5 mass% or more of water of crystallization produces fine pores after the water of crystallization disappears.
It was also found that when s% or more of this iron ore is blended, the formation of fine pores becomes remarkable. The present invention is based on such findings.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION First, the results of a test for producing a low slag sinter having many fine pores will be described. 500m ^{2 of} sinter
It was manufactured with a sintering machine of. In order to compare the conventionally used sinter with the sinter used in the present invention, the measurement result of the fine pore distribution measured by the mercury intrusion method, the reduction pulverization index (RD)
The measurement results of I) are shown in Table 1, and the high temperature property measurement results are shown in FIG. It can be seen that the sintered ore used in the present invention has many fine pores, and the effect of lowering the slag is also added, and the high temperature reducing property and the softening and melting property are significantly improved. That is, the sinter used in the present invention is characterized by high FeO, high Al ₂ O ₃ and low SiO ₂ , and has a SiO ₂ component of 4.2 to 4.9 mass%.
In the range of, the Al ₂ O ₃ / FeO ratio is 0.18 to 0.29.
FeO component is 8.0 to 10.0 mass% so that
It has been found that the fine pores of the sintered ore can be increased without lowering the strength of the sintered ore and the yield at the time of production by maintaining the above.

On the other hand, when the SiO ₂ component is less than 4.2 mass%, the yield of the sintered ore is significantly decreased due to the decrease of the melt amount, and when it exceeds 4.9 mass%, the melt amount is increased. There was a tendency that the number of fine pores decreased. Further, since the Al ₂ O ₃ level is high, it is necessary to set the FeO component to be 8.0 mass% or more in order to maintain the strength.
However, when the FeO component exceeds 10.0 mass%,
As the melt volume increased, the number of fine pores decreased and the adverse effect of reduced reducibility became apparent. Furthermore, it is important to maintain the Al ₂ O ₃ / FeO ratio at 0.18 to 0.29, and when this value is less than 0.18, the amount of fine pores generated becomes insufficient and exceeds 0.29. On the contrary, the decrease in strength and yield became conspicuous. Since the sintered ore used in the present invention is a high FeO sintered ore, the value of the reduction powdering index (RDI) is lower than that of the conventionally used sintered ore, and the RDI value is further increased with the increase of FeOmass%. improves. This low RDI contributes to the improvement of the air permeability of the upper part of the blast furnace shaft.

[0014]

[Table 1]

Next, a blast furnace (internal volume: 3200 m ³ ) was charged with sinter having many fine pores, and the amount of pulverized coal injected was 170.
An example in the case of increasing to kg / tp will be described. Examples of the present invention are summarized in Table 2 in comparison with the conventional method. In the conventional method, the operation level of the pulverized coal ratio of 130 kg / tp (Comparative example 1) is changed to the operation level of the pulverized coal ratio of 170 kg / tp (Comparative example 2, period A) to the pulverized coal large usage level. During the process, ventilation resistance increased, slippage began to occur, the amount of heat dissipated in the furnace body also increased, and blast furnace operation fell into distress. This is because the O / C increased due to the increase in the pulverized coal ratio, the high temperature properties of the sintered ore layer deteriorated, and the total pressure loss in the furnace became large, and this tendency was especially observed at a pulverized coal ratio of 160 kg / tp or more. It was remarkable. On the other hand, in the case of the present invention in which the low slag sinter having increased fine pores is replaced with the conventional sinter (period B), the pulverized coal blowing rate is 170 kg / t.
Even though it was -p, the ventilation resistance value and the amount of heat dissipated in the furnace body decreased, and the slip did not occur. This is RDI
It is thought that this is because in addition to improving the air permeability of the upper part of the furnace due to the decrease in the value, it was also possible to prevent the enlargement of the root of the cohesive zone, which is a factor that particularly deteriorates the ventilation resistance, and there was no abnormality in the lower part of the furnace. There wasn't.

[0016]

[Table 2]

[0017]

As described above, the amount of pulverized coal blown is 15
Even if it is increased to 0 kg / tp or more, the present invention allows the blast furnace stable operation to be continued without deteriorating the ventilation resistance of the cohesive zone. The present invention, in the operation of blowing a large amount of pulverized coal, there are many fine pores, and by charging a low-slag sinter, the width of the softening cohesive zone is controlled to be thinner than before, and the furnace bottom By suppressing deterioration of ventilation resistance, it becomes possible to stabilize blast furnace operation even when a large amount of pulverized coal of 150 kg / tp or more is blown.

[Brief description of the drawings]

FIG. 1 is a diagram simulating a cohesive zone in a blast furnace.

FIG. 2 is a diagram showing measurement results of high temperature properties of a conventionally used sintered ore and a sintered ore used in the present invention.

Claims (3)

[Claims] 1. A FeO component in a blast furnace is 8.0 to 10.0.
mass%, SiO ₂ component is 4.2 to 4.9 mass
%, Al ₂ O ₃ / FeO ratio of 0.18 to 0.29 is charged, and pulverized coal is blown in at a rate of 150 kg / t-p or more for operation. Time blast furnace operation method. 2. The FeO component in the blast furnace is 8.0 to 10.0.
mass%, SiO ₂ component is 4.2 to 4.9 mass
%, Al ₂ O ₃ / FeO ratio of 0.18 to 0.29 was charged, and the pulverized coal blowing amount was set to 150 kg / t-p or more, and the blast furnace slag amount was 300 kg / t-p.
A method for operating a blast furnace when a large amount of pulverized coal is injected, which is characterized in that the operation is performed while adjusting the amount to less than 1. 3. A FeO component produced by blending iron ore containing crystal water of 5 mass% or more in a new raw material in an amount of 25 mass% or more in a blast furnace, wherein FeO component is 8.0 to 10.0 mass% and SiO.
₂ components are 4.2 to 4.9 mass%, Al ₂ O ₃ / Fe
A method for operating a blast furnace at the time of blowing a large amount of pulverized coal, which comprises charging a sinter having an O ratio of 0.18 to 0.29 and operating a pulverized coal blowing amount of 150 kg / tp or more.