JPH09143516A - Operating method of vertical furnace - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To set the basicity (CaO / SiO ₂ ), SiO ₂ content and MgO content of a sintered ore charged from the furnace top of a vertical furnace such as a blast furnace to a certain level. Use the one in the specified range and maintain its operation stably. SOLUTION: (1) 1.4 ≦ CaO / SiO ₂ ≦ 1.8, 4.0 ≦
SiO ₂ content (%) ≦ 6.0, and MgO content (%)
≤ 1.4, (2) 1.8 ≤ CaO / SiO ₂ ≤ 2.3 and 4.0 ≤ S
iO ₂ content (%) ≦ 10.55-2.75 × (CaO / SiO ₂ ), (3)
1.8 ≦ CaO / SiO ₂ ≦ 2.3, 6.0 ≧ SiO ₂ content (%) ≧ 1
0.55-2.75 × (CaO / SiO ₂ ) and MgO content (%)
A sintered ore satisfying any of the conditions ≧ 2.0 is charged from the furnace top. [Effects] A blast furnace using a sinter that satisfies the conditions of the present invention has improved air permeability, can maintain stable operation, and can achieve improved productivity and reduced fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention focuses on a sinter ore charged from the top of a furnace when performing a blast furnace operation such as a blast furnace in which a large amount of pulverized coal is injected, and the operation is stably performed. Regarding how to maintain.

[0002]

2. Description of the Related Art In the operation of a vertical furnace such as a blast furnace, it is necessary to keep the high-temperature property of the sintered ore charged from the top of the furnace in order to keep the operation stable. In particular, it is indispensable to stably maintain high-load operations such as blowing a large amount of pulverized coal. For that, "Iron and Steel" (1955, P185
0) and "Steel and Steel-Steel Association Lecture Meeting" (Showa 58, S
755), the sinter ore is charged into a crucible, the crucible is placed in an electric furnace, and a reducing gas is introduced from below the electric furnace to heat and reduce the sinter. Therefore, a measuring method for measuring high-temperature properties such as reduction rate, softening shrinkage rate, in-layer pressure loss and the like of the sintered ore at a temperature from room temperature to around 1500 ° C. is required.

By the way, in order to produce a sinter having a good high-temperature property, the conventional method for measuring a high-temperature property of a sinter is used, and the data obtained therefrom is fed back. Therefore, it has not been attempted to optimize the raw material composition adjustment in the sinter production process.
At present, only the high temperature properties of the sintered ore produced by the actual machine are measured. The reason is that the accuracy of these measurement methods is not so good, and it cannot be said that the high temperature properties of the sintered ore in the furnace of the actual blast furnace are faithfully reproduced.

The conventional measuring method is a measuring method using one electric furnace, in which a reducing gas is introduced from a reducing gas inlet below the electric furnace, and a measured value of a thermometer installed in the electric furnace is set to a preset value. Since it is a method of heating and reducing the sinter in the crucible arranged in the electric furnace by increasing the temperature according to the temperature program, the sinter softens and melts, and the reduction of the molten FeO (endothermic reaction) occurs, Even if the temperature of the sinter decreases, the temperature of the electric furnace rises according to the temperature increasing program, so that the heat reduction proceeds in the form of forcibly applying heat to the sinter.

However, in the actual vertical furnace, when the sinter ore softens and melts and the molten FeO is reduced (endothermic reaction), and the temperature of the sinter decreases, it differs from the above-mentioned measurement method. Since heat is not forcibly applied to the sinter, the fluidity of the melt deteriorates due to the temperature decrease, and the reduction of the molten FeO is delayed, which delays the thermal reduction.

As described above, in the conventional measuring method, since the phenomenon different from the phenomenon occurring in the actual furnace should cause a difference in the high-temperature property of the sintered ore in the actual furnace, according to the above measuring method, There was no difference in the high-temperature properties, so even if the measurement results thus obtained were used, the constituent conditions of the sintered ore for maintaining stable operation were inaccurate.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention enables accurate measurement of a phenomenon occurring in a real furnace at the time of heat reduction of a sinter, in particular, a temperature rising rate, a reduction rate, a layer pressure loss, and the like. In order to do so, we improved the measurement method so that the difference in the high-temperature properties of the sintered ore occurring in the actual furnace can be detected even in the measurement,
Clarify the composition conditions of sinter having good high-temperature properties from the data obtained by making full use of this, and insert sinter that satisfies these conditions into the blast furnace to maintain stable operation. With the goal.

[0008]

Means for Solving the Problems In the present invention, when a pulverized coal blowing operation is carried out in a vertical furnace such as a blast furnace, the component composition is such that the basicity (CaO / SiO ₂ ) is 1.4 to 1. 8, SiO
₂ content 4.0 to 6.0 wt% and MgO content 1.
4 wt% or less, basicity (CaO / SiO ₂ ) of 1.8 to 2.3,
Further, the SiO ₂ content (wt%) satisfies the formula 4.0 ≤ [SiO ₂ content (wt%)] ≤ 10.55-2.75 × (CaO / SiO ₂ ), and the basicity (CaO / SiO ₂ ) 1 .8 to 2.3,
The SiO ₂ content (wt%) must satisfy the formula 10.55-2.75 × (CaO / SiO ₂ ) ≦ [SiO ₂ content (wt%)] ≦ 6.0, and the MgO content must be 2.0 wt% or more. The method for operating a vertical furnace is characterized in that sinter ore satisfying any one of the above three conditions is charged from the furnace top.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to clarify the constituent conditions of the above-mentioned sinter, the present inventor has disclosed in Japanese Patent Laid-Open No. 7-2762.
As disclosed in Japanese Patent Publication No. 3, the number of electric furnaces is two, one electric furnace is used for heating, and the other electric furnace is used for temperature control. We have developed a measuring device and a measuring method that can measure the thermal reduction phenomenon occurring in an actual furnace by applying the same heat as in the vertical furnace.

That is, as described above, the electric furnaces are arranged in upper and lower two stages, both electric furnaces are connected by a flange, and the lower stage electric furnace is emptied while introducing the reducing gas from the lower side of the lower stage electric furnace. While raising the temperature as it is, place the crucible in which the packed bed of the sintered ore to be measured is formed in the upper electric furnace, and the furnace temperature of the upper electric furnace and the temperature of the sintered ore in the crucible are simultaneously measured. The electric power applied to the upper electric furnace is measured and measured so that the temperature difference between the two becomes a preset constant value.

When measuring using such a measuring device,
The measurement data as shown in FIG. 1 is obtained. The horizontal axis of FIG. 1 represents the elapsed time (minutes) of the experiment, the left vertical axis represents the reduction rate (%) of the sintered ore, and the right vertical axis represents the pressure loss (mmH ₂ O) of the packed bed of the sintered ore. Here, as an index for evaluating the high temperature properties of the sinter,
The following five are adopted. Maximum layer pressure loss (ΔPmax (mmH ₂ O), see Fig. 1)
Temperature range where pressure loss of the layer is 200 mmH ₂ O or more (ΔT
(° C), see Fig. 1), pressure loss of the layer (ΔP
E (mmH ₂ O), see Fig. 1), drop start temperature (TD
(℃)), Metal drop yield at the end of the experiment (Ratio of M
et al Dropping [abbreviated as RMD] (%)).

The inventor of the present invention has found that the sintered ores satisfying all of the following five ranges are excellent in high-temperature properties and are effective even in the operation of blowing a large amount of pulverized coal. I found that. That is, ΔPmax ≦ 4,5
00mmH ₂ O, ΔT ≦ 250 ° C, ΔPE ≦ 125mm
H ₂ O, TD ≧ 1,400 ° C., RMD ≧ 50%.

Here, a low ΔPmax and a small ΔT means that the width of the fusion layer is narrow and a ventilation resistance is small, and a low ΔPE means that the temperature is high (155).
It shows that the fusion resistance of the fusion layer at about 0 ° C.) is small. Also, the high TD means that the fusion layer has a high temperature (1400 ° C).
The above shows that the hot metal temperature is high and the furnace heat of the blast furnace is kept high. Further, a large RMD means that the melt generated in the fusion layer of the sintered ore has a good fluidity and rapid melt dripping occurs, and as a result, the ventilation resistance of the fusion layer becomes small.

The present inventor measured the sintered ore produced by various actual machines and test pots by the measuring method using the above-mentioned measuring device, and satisfied all of the above five index ranges specified in the present invention. The components of sinter having good high-temperature properties are basicity (CaO / SiO ₂ ), SiO ₂ content, and M
It has been found that the gO content is used and arranged into the following three ranges. That is, (1) 1.4 ≦ CaO / S
iO ₂ ≦ 1.8, 4.0 ≦ SiO ₂ content (wt%) ≦
6.0, and MgO content (wt%) ≦ 1.4, (2)
1.8 ≦ CaO / SiO ₂ ≦ 2.3, and 4.0 ≦ S
iO ₂ content (wt%) ≤ 10.55-2.75 x (Ca
O / SiO ₂ ), (3) 1.8 ≦ CaO / SiO ₂ ≦
2.3, 6.0 ≧ SiO ₂ content (wt%) ≧ 10.55
_{-2.75 × (CaO / SiO 2)} , and MgO content (wt%) ≧ 2.0. In FIG. 2, these three ranges are indicated by diagonal lines.

When the basicity (CaO / SiO ₂ ) of (1) is low, the fluidity of the melt formed in the fused layer of the sinter is good, so that it is not necessary to increase the MgO content. If it is rather high, the liquidity deteriorates. Further, it is not preferable that the SiO ₂ content be limited to the upper and lower limits because the strength required for producing a sintered ore cannot be maintained if it is less than 4.0 wt%, and 6.0 wt%. If it exceeds, the amount of the melt produced in the fused layer of the sinter becomes too large, and the ventilation resistance becomes large, which is not preferable. Further, the lower limit of CaO / SiO ₂ is that if it is less than 1.4, the reducibility of the sinter deteriorates and FeO melts in the melt, increasing the apparent melt amount. Therefore, ventilation resistance increases, which is not preferable.

When the basicity (CaO / SiO ₂ ) of ( ₂ ) is high, if the SiO ₂ content is set to a value lower than the SiO ₂ content determined by CaO / SiO ₂ , the fused layer of sinter ore Since the amount of the melt having a high melting point generated therein can be reduced, the ventilation resistance is small. Also SiO ₂
It is not preferable to limit the content to the lower limit if the content is less than 4.0 wt% in the above-mentioned case because the strength required for producing a sintered ore cannot be maintained. Further Ca
The upper limit of O / SiO ₂ is 2.3.
If it exceeds, the melt is hardly generated in the fused layer of the sinter, and therefore the metal does not drop and the ventilation resistance increases. In this case, the MgO content is not specified, but it is desirable to lower it in order to reduce the amount of the high-melting-point melt generated in the fused layer of the sintered ore.

When (3) the basicity (CaO / SiO ₂ ) is high, the SiO ₂ content is set to a value higher than the SiO ₂ content determined by CaO / SiO ₂ and the MgO content is increased. As a result, the fluidity of the melt generated in the fused layer of the sinter becomes good and the ventilation resistance becomes small. Further, the upper limit of the SiO ₂ content is limited, because if it exceeds 6.0 wt%, the amount of the melt produced in the fusion layer of the sinter becomes too large, and the ventilation resistance becomes large. Absent. Further, the upper limit of CaO / SiO ₂ is limited. In the same manner as above, when 2.3 is exceeded, almost no melt is formed in the fusion layer of the sintered ore, and therefore metal dripping occurs. It is not preferable because the ventilation resistance becomes large.

[0018]

EXAMPLES The features of the present invention will be specifically described with reference to the following examples. Table 1 shows the component conditions of the sinter and the results of its use in the blast furnace.

[0019]

[Table 1]

[Example 1] Basicity of sinter (CaO / S
iO ₂ ) = 1.68, SiO ₂ content = 5.74 wt%,
Sintered ore was manufactured by adjusting the components so that the MgO content = 1.38 wt%. When this sinter is used in a blast furnace, the blast pressure showing ventilation resistance is lower than in Comparative Example 1 described later.

[Example 2] Basicity of sinter (CaO / S
Sintered ore was manufactured by adjusting the components so that i0 ₂ ) = 2.13 and SiO ₂ content = 4.22 wt%. At this time, the MgO content was 0.95 wt%. When this sinter is used in a blast furnace, the blast pressure showing ventilation resistance is lower than in Comparative Example 2 described later.

[Example 3] Basicity of sinter (CaO / S
iO ₂ ) = 1.94, SiO ₂ content = 5.60 wt%,
Sintered ore was manufactured by adjusting the components so that the MgO content = 3.05 wt%. When this sinter is used in a blast furnace, the blast pressure indicating ventilation resistance is lower than in Comparative Example 3 described later.

[Comparative Example 1] As a result of producing a sinter by only adjusting the conventional raw material composition, the basicity (CaO / SiO ₂ )
= 1.67, SiO ₂ content = 5.71 wt%, MgO content = 1.75 wt%. When this sinter is used in a blast furnace, the blast pressure exhibiting ventilation resistance is higher than in Example 1.

[Comparative Example 2] As a result of producing a sintered ore only by adjusting the conventional raw material mixture, the basicity (CaO / SiO ₂ )
= 2.15, SiO ₂ content = 4.95 wt%, MgO content = 1.60 wt%. When this sinter is used in a blast furnace, the blast pressure showing ventilation resistance is higher than in Example 2.

[Comparative Example 3] As a result of producing a sintered ore only by adjusting the conventional raw material composition, the basicity (CaO / SiO ₂ )
= 1.93, SiO ₂ content = 5.62 wt%, MgO content = 1.80 wt%. When this sinter is used in a blast furnace, the blast pressure showing ventilation resistance is higher than in Example 3.

[0026]

As described above, in the present invention, by adjusting the basicity (CaO / SiO ₂ ), SiO ₂ content and MgO content of the sinter to a certain set range, The fusion resistance layer formed from this sinter has a low air flow resistance, a high dropping temperature, and a large amount of metal drops, resulting in good high-temperature properties. As a result, the blast furnace using this sinter has a high air permeability. It will be improved and it will be possible to maintain stable operation of the blast furnace. This improves productivity,
A fuel ratio reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of data measured by a measuring method using a high temperature property measuring device, and clearly shows five indexes for evaluating the high temperature property of a sintered ore.

FIG. 2 is a diagram showing the ranges of basicity (CaO / SiO ₂ ), SiO ₂ content, and MgO content of sinter ore used in the present invention with good high-temperature properties.

Claims (3)

[Claims] 1. The composition of components is basicity (CaO / Si
O ₂ ) 1.4 to 1.8, SiO ₂ content 4.0 to 6.0
A method for operating a vertical furnace, characterized in that sinter having a wt% and an MgO content of 1.4 wt% or less is charged from the furnace top. 2. The composition of components is basicity (CaO / Si
O ₂ ) 1.8 to 2.3, and the SiO ₂ content (wt%) is expressed by the formula 4.0 ≦ [SiO ₂ content (wt%)] ≦ 10.55-2.75 × (CaO / SiO ₂ ). A method for operating a vertical furnace, which comprises charging a satisfactory sinter from the top of the furnace. 3. The composition of components is basicity (CaO / Si
O ₂ ) 1.8 to 2.3 and SiO ₂ content (wt%)
However, a sinter that satisfies the formula 10.55-2.75 × (CaO / SiO ₂ ) ≦ [SiO ₂ content (wt%)] ≦ 6.0 and has a MgO content of 2.0 wt% or more is charged from the furnace top. A method for operating a vertical furnace characterized by: