JPS5818413B2 - A method for producing sintered ore that enables high blending of ores containing high Al↓2O↓3 - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing sintered ore, in which a large amount of ore containing high Al2O3 can be blended without reducing the quality or productivity of the sintered ore. The purpose is to

Blast furnace operation (in order to stabilize furnace conditions and increase productivity, the reducibility of the charged raw material must be as high as possible,
Moreover, it must have properties that allow it to maintain sufficient strength and ventilation inside the furnace.

The main sources of iron in blast furnace charging raw materials are lump iron ore, pellets, and sintered ore, but in recent years, the charging ratio of sintered ore has been 80 to 90%.
It is no exaggeration to say that the quality of sintered ore affects blast furnace operation. Therefore, sintered ore that has good reducibility and can maintain sufficient strength in the furnace is desired.

However, sintered ore generally contains 400 to 60
The property of pulverizing in the so-called low-temperature reduction region t of 0°C (
It has the disadvantage of significantly inhibiting ventilation in the upper part of the blast furnace.

The main cause of low-temperature reduction powdering is Al2O3°T during the sintering process.
i02. It is thought that this is due to the multi-component system crystallized from the melted bath containing MnO, etc., but in particular, the high content of Al2OψS in the maquite causes the multi-component system to crystallize.
This is the most problematic.

During crystallization of this multi-component system (Al2O3 etc. are precipitated inside hematite, strain due to crystal transition when hematite changes to magnetite concentrates in this part and cracks occur).

As the reduction progresses, cracks will grow starting from this area and turn into powder, so the means to prevent this is to increase the 60% partial pressure of the sintering atmosphere by adding more coke to suppress the re-oxidation of the multi-component magnetite. It is possible to do so.

However, this method worsens the coke consumption rate,
Currently, efforts are being made to suppress the amount of Al2O3 that enters maquito into multicomponent systems, that is, to limit the amount of Al2O3 in the blended raw materials.

An increase in Al2O3 contained in the blended raw materials not only deteriorates the low-temperature reduction powdering properties of the sintered ore, but also reduces the amount of melt produced (hereinafter referred to as bond) since Al2O3-containing ores have poor slagability.

For this reason, the amount of bond required to maintain the strength of the sintered ore decreases, which deteriorates the product yield of the sintered ore.

From this point of view as well, Al2O3 is a harmful component, and the amount of Al2O3 in sintered ore is limited.

However, Al2O3 is not specifically added to the blended raw materials, but is brought in from the ore as gangue, and has a high Al2 content.
In recent years, large quantities of O3-based ores have been imported, and when these ores have to be used extensively, an increase in Al2O3 in sintered ore is unavoidable, leading to deterioration in low-temperature reduction powdering properties and product yield. It is desired to develop a technology that can prevent this and use large quantities of high-Al2O3 ore.

The present invention was made in view of these circumstances, and
In a blended raw material containing 25% by weight or more of fine particles with a particle size of less than 1 mm, the amount of 5i02 contained in the fine powder part with a particle diameter of less than 0.25 mm in the blended raw material is 0.85% of the total components constituting the blended raw material. At least % by weight and the A of the fine powder portion
Adjust the weight ratio of 403/S i 02 to 0.25 or less,
This is a method for producing sintered ore that enables a high blending of ore containing high Al2O3, which is characterized by sintering the blended raw materials prepared in this way.

The present invention will be explained in detail below.

Generally, soluble sintered ore is agglomerated by so-called fusion bonding in which iron oxide particles are bonded together by a molten body.

The quality of sintered ore, productivity, etc. are greatly influenced by this bond, so how to generate the bond is extremely important.

However, in the current sintering process of the packed bed suction type, which is typified by the sintered ore production method using a Dwight Lloyd type sintering machine (hereinafter referred to as DL type sintering machine).

Since the reaction time at high temperatures is extremely short, it is necessary to quickly generate the necessary melt in a short period of time.

As a result of various studies on this point, the present inventors found that the fine powder portion of less than 0.25 mm in the blended raw materials.

The Al2O3 and S i 02 contents are important, and controlling these values promotes rapid melt formation, which in turn improves the AJl? It has been found that the 203 content can be increased.

Generally, blended raw materials contain about 6% water.

The aim is to improve the ventilation of the raw material layer by promoting pseudo-granulation.

This pseudo-particle has a core of coarse raw material of about 1 to 5 mm,
It takes the form of fine particles of less than 1 u attached around it.

However, studies conducted by the present inventors have revealed that the production of the problematic melt starts from the part of the adhered fine particles smaller than 0.25 mm.

This initial melt gradually increases in volume while melting the surrounding coarse grains, but because the high temperature residence time during sintering is short, the coarse grains do not completely melt, and the melt is not uniform. Without mixing, solidification is completed and a bond is formed while retaining the strong influence of the composition of the initial melt. Therefore, in order to quickly secure the required amount of melt,
．． It is necessary to increase the starting point of the low melting point composition in the fine powder portion of less than 25 mm.

On the other hand, it is well known that as the amount of Al2O3 in the sintered ore increases, the low temperature reduction index (hereinafter referred to as RDI) tends to deteriorate.

However, although it is said that there is an adverse effect of Al2O3 as a statistical tendency, there are some cases where the RDI does not necessarily worsen even if the Al2O3 content increases, so there are some unclear points.

As mentioned above, the present inventors believe that the particle size of the blended raw materials that forms the bond is 0.25a! The fine powder part with a particle size of less than m
Most of the coarse grains with r/L of 11L or more are not dissolved and remain as residual ore (hereinafter referred to as original ore), so A
Various experiments were conducted focusing on the influence of 403 not on the average composition including coarse particles, but on the amount of Al2O3 in the fine powder portion.

As a result, it was found that there is a positive correlation between the Al2O3 content of the fine powder portion with a particle size of less than 0.25 mm in the blended raw materials and RDI.

It was also found that the partially contradictory relationship between the average Al2O3 amount and RDI can be explained by the Al2O3 content of the fine powder portion less than 0.25 mm.

Therefore, the amount of Al2O3 in the blended raw materials varies with the average composition (
It is also necessary to control the amount of Al2O3 in the fine powder part of less than 0.25 mm, and when iron ores are crushed to be used as raw materials for sintering, it is important to avoid crushing ores with high Al2O3 content. This is important for maintaining the RDI of the concretion.

From the above study results, the amount of fine powder part less than 0.25 mm in the blended raw materials and the composition include S i 02 , Al2O3
It is known that the content has an important effect on the quality of sintered ore.

It was also found that most of the Al2O3 in the coarse grain portion of 1rILm or more remains unreacted, or even if reacted, only a portion contributes to the reaction.

Therefore, 5i02 of the fine powder part less than 0.25 mm
If each value is maintained appropriately to increase the Al2O3 content and reduce the Al2O3 content, the quality and productivity of the sintered ore will not be impaired even if the amount of Al2O3 in the coarse grain portion increases by 1 or more. can produce sintered ore.

In other words, if the appropriate conditions for the amount and composition (SiO2, A1203) of the fine powder part less than 0.25 mm in the blended raw material are satisfied, it is necessary and sufficient for the quality and productivity of the sintered ore. Al2O3 contained in the coarse part of
Even if the amount is increased, the quality and productivity of the sintered ore will not be impaired.

Figure 1 shows the experimental results of producing sintered ore using a DL type sintering machine with a length of 460 m.It shows the weight ratio of Al2O3 and 5i02 contained in the fine powder portion with a particle size of less than 0.25 mm in the blended raw materials (hereinafter this value will be referred to as FIG. 2 is a diagram showing how the EtDI of sintered ore and product yield are affected by -0,25 tomon [Al2O3/5i02].

As shown in Figure 1, [Al2O3/
There is a strong correlation between S i 02 ), RDI, and product yield, with CAA203 /S i 02 in -0.25 mm
: ] increases, RDI and product yield deteriorate, respectively.

Especially when -0,25 [Al2O3/SiO2] is 0
．． It can be seen that below 25, the RDI and product yield tend to deteriorate gradually, but when it exceeds 0.25, both RDI and product yield deteriorate rapidly.

This phenomenon occurs when the particle size of the initial melt during sintering is 0.25 mm.
If Al2O3 is present in a large amount (more than 25% of SiO2) in the fine powder portion, the adverse effects of Al2O3 will be noticeable.

On the other hand, the relationship between the amount of 5i02 in the portions less than 0 and 25 mm, which greatly affects the initial melt amount, and the quality of the sintered ore was investigated using a 40 mm test pot, and the results shown in FIG. 2 were obtained.

In other words, Fig. 2 shows -0.25 mm [Al2O3/5i02
] is fixed at 0.20 and the coke blending ratio is fixed at 3.2% by weight, respectively, and the particle size is expressed as 100%, where the total of the components constituting the entire blended raw material (dry weight excluding water) is 100%. 25
SiO2 weight% contained in the portion less than rILrIL (hereinafter this value will be referred to as -0.25mff1 SiO2 (%)
5i0 in -0.25Wtm by variously changing
2 (to) shows the influence on the RDI and product yield of sintered ore.

As shown in Figure 2, [5i02 (%) in 0.25 mm]
Both RDI and product yield are improved with an increase in S i 02 (%) in -0,25r ILTIL.
．． 85 or higher, the RDI and product yield are significantly improved.As shown in Figures 1 and 2, the RDI of sintered ore,
In order to maintain a good product yield, -0.2
[Al2O3/SiO□] in 5rItm should be 0.25 or less, and 5in2 (%) in -0.25van should be 0.25 or less.
It can be seen that it is important to set the score to 85 or higher.

- 0.25 mm (A407S i02) or less, 5iO2 (%) in 0.25 rILm
In order to make the value 0.85 or more, it is effective to adjust it by finely pulverizing the raw material added as the S i 02 source, such as sand stone, or by preventing the fine crushing of ores with a large Al2O3 content.

In this way, by adjusting the amount of SiO3 and Al2O3/S i 02 contained in the fine powder part with a particle size of less than -0.25 mm in the mixed raw material, the Al2O3 content in the coarse part with a particle size of 1 mm or more in the mixed raw material can be increased. A of sintered ore is obtained.
A high A content containing about 3.3% Al2O3, which was conventionally considered undesirable with an Al2O3 content of 2.0% or more,
Al2 of sintered ore by blending 60% or more of l2O3-containing ore
It is possible to have an O3 content of more than 2.0%.

The Al2O3 content of the sintered ore is determined by the A403 content of the blended raw materials.

Generally, Al2O3 is concentrated approximately 1.1 times by sintering the blended raw materials, so taking this concentration degree into account, the Al2O3 content of the sintered ore can be determined at the stage of blending raw materials, and this value can be used thereafter. This will be referred to as the Al2O3 content converted to sintered ore.

In addition, although the particle size of the blended raw materials is 1, ordinary blended raw materials have a particle size distribution as shown in Table 7, of which the weight proportion of fine particles with a particle size of less than 1 mm is usually 25 to 60%. is within the range of

If this value is less than 25%, bond formation will be insufficient during sintering, making it impossible to maintain the strength of the sintered ore.

Furthermore, if this value exceeds 60%, a problem arises in that the air permeability during sintering is deteriorated, so countermeasures such as strengthening the granulation are required.

In the present invention, from the viewpoint of maintaining the strength of the sintered ore and breathability during sintering, the fine grain portion with a grain size of less than 1rILm is reduced to 25%.
A compounding raw material containing the above, preferably having a particle size distribution of 25% or more and 60% or less is used.

Example Water was added to a mixed raw material of iron ore, limestone, sandstone, coke and return ore to granulate it, and the sintered ore was produced using a negative pressure of 1700 mm in a 40 mm test pot.

Tables 1 to 4 show the compositions of ore, sandstone, limestone, juite, return ore, and coke, which are the raw materials to be blended.

The blending ratios, including comparative examples, are shown in Table 5, the test conditions are shown in Table 6, and the particle size distribution of the blended raw materials is shown in Table 7.

In addition, [Al2O3/5i02] in -0,25 mm and 5iO2 (%) in -0,25 nm, including comparative examples,
It is shown in Table 8.

The raw materials for Comparative Example 1 were A as shown in Tables 1 and 5.
37.2% iron ore C with low l2O3 content and Al2
Since 26.7% of iron ore with a high O3 content was blended, and the iron ore was crushed, -0.25 mm (A403
/S i 02] is as high as 0.36, and the blending ratio of sandstone is 2.
．． 0 wt% -0.25 Maronaka Si02 (%) is 0.96, Al2O3 content converted to sintered ore is 2.0
It was expressed as weight%.

The blended raw materials of Comparative Example 2 had the ore blending ratio almost the same as Comparative Example 1, the sandstone blending ratio was reduced by 1.8% by weight, and the Al
A part of iron ore A with a high 2O3 content is crushed and 51.7% of the crushed iron ore is blended, -
〇, S i 02 (%) in 25WtrIL is 0.93
, the Al2O3 content converted to sintered ore is as high as 2.6% by weight, and in -0.25rnm [Al2O3/SiO2]
has a high value of 0.49.

On the other hand, the blended raw materials of Example 1 have the same proportion of ore as Comparative Example 1, contain coarse particles of iron ore with a high Al2O3 content, and have a blended proportion of sand and stone of 2.0. It was converted to sintered ore in weight percent.

The Al2O3 content is 2.0% by weight, which is the same as in Comparative Example 1, but the [Al2O3/SiO2] in -0.25 mm is 0.
23 and 1 area, and S A in -025rnrIL
02 (%) is 0.95 The blended raw materials of Example 2 are as follows.
Less than IL (this is a mixture of finely pulverized ore with high Al2O3 content in coarse particles, and the Al2O3 content converted to sintered ore is 2.6% by weight, which is the same as Comparative Example 2, but -〇 ,
[Al2O3/5i02] in 25rn7IL is 0.20
The S i 02 (%) at -0.25 mm is as low as 0.
It was maintained at 85.

In addition, 5i02 of sintered ore is 5.6% in both the comparative example and the example.
And so.

The results of sintering such blended raw materials are summarized in Table 9 and are shown in a graph in FIG.

As shown in Table 9 and FIG. 3, in Comparative Example 1, in which blended raw materials commonly used at present were sintered, and in Comparative Example 2, in which a large number of high Al2O3 raw materials were blended, -0.25 rnrrt was used.
[Al2O3/5i02] could not be reduced to 0.25 or less, and the RDI and product yield showed a deteriorating trend, and the falling strength and coke consumption showed a similar trend.

On the other hand, in -0,25Inrn (A 1j207S
i 02) to 0.23 and -0.25rnr
In Example 1, in which Si, 0si (%) in n was maintained at 0.95, the S i 02 content of the sintered ore was set to 5.6 coulometric test, and the Al2O3 content converted to the sintered ore was set to 2.0. Even though the N amount% was made the same as that of the comparative example↓, the RDI and product yield were improved, and the coke consumption rate and falling strength were improved without extending the sintering time or decreasing the production rate.

Also, in -0,25mm [Al2O3/SiO□] is 0
．． 20-5i92 in 0,25rILrIL(
:%) was 0.85 and the Al2O3 content was 2.6% by weight in terms of sintered ore.
, product yield, and falling strength as well as sintering time, production rate, and coke consumption were able to match the values of Example 1 and Corridor.

As described above, according to the present invention, the Al2O3 of sintered ore is maintained without deteriorating the low-temperature reduction powdering index while maintaining productivity, coke consumption, falling strength, etc. at the same or higher level than conventional ones. can be more than 2.0% by weight.

That is, the Al2O content of sintered ore was conventionally set at about 2.0% as an upper limit.
However, according to the method of the present invention, it is possible to increase the Al2O3 content to over 2.0%. It is possible to produce sintered ore with good concretion quality, and if the conventional quality is maintained, high Al2O3 is possible.
It becomes possible to mix ores at a high level, increasing the degree of freedom in mixing.
Gain AφS, which is important for sintering operations, can be obtained.

[Brief explanation of the drawing]

Figure 1 shows A7203/S of the fine powder portion of less than 0.25 vtw of the sintered ore blend raw material obtained from the 460mDL sintering machine data.
Figure 2 shows the relationship between the iO2 weight ratio, the low-temperature reduction pulverization index of sintered ore, and the product yield. Figure 3 shows the relationship between i02% by weight, the low-temperature reduction powdering index of sintered ore, and the product yield. /l! 20s/S i 02 weight ratio, low temperature reduction powdering index c, product yield 2, sintering time e, production rate,
FIG. 3 is a graph showing coke consumption rate and falling strength.

Claims (1)

[Scope of Claims] 1. In a blended raw material containing 25% by weight or more of a fine part with a particle size of less than 1 mm, the amount of 5i02 contained in the fine part with a particle diameter of less than 0.25 mm in the blended raw material constitutes the blended raw material. High Al2O3 is characterized by adjusting the Al2O3/5i02 weight ratio of the fine powder part to 0.25 or less and sintering the blended raw materials adjusted in this way. A method for producing sintered ore that allows for a high content of ore.