JPH0796688B2 - Pretreatment method for sintering raw material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pretreatment method for a sintering raw material, and particularly by improving the mixed state of iron ore and limestone among the sintering raw materials, high quality self-fluxing sintering is performed. The present invention relates to a pretreatment method that enables the production of ore.

Conventional technology As is well known, self-fluxing sinter is manufactured by sintering limestone by decomposing and slagging it by firing limestone by adding limestone to raw materials such as iron ore and coke. However, it is not easy to obtain a product having both reduction powder resistance and cold strength. That is, if the reduction pulverization resistance is improved, the cold strength is deteriorated, and it is difficult to improve both of these qualities at the same time.

Among the qualities of this sinter, in order to improve resistance to reduction pulverization, a method of dividing the raw material in advance is known (iron and steel v
ol.73 1987). This is based on the principle that a calcium ferrite-based melt is positively generated in a high CaO concentration environment.

This melt generation region has a low melting point composition by adding a large amount of limestone, and as an iron ore brand, it is rich in pellet feed and granulation rich in fine powder to increase the contact area between iron ore and limestone. Melt generation is promoted by the method of selecting the ore. This is based on the principle that melt generation is promoted by increasing the contact area between iron ore and limestone at the start of the reaction.

On the other hand, it is recognized that uneven distribution of limestone deteriorates the cold strength.

Therefore, in order to improve both reduction pulverization resistance and cold strength, it is necessary to improve the reactivity of limestone and increase the amount of calcium ferrite-based melt.

However, there is a limit in dealing with only the above-mentioned stock selection method. That is, it is expected that the fine iron ore or the fine limestone fills the space between the coarse iron ores to suppress the melting reaction, or the unreacted portion remains in the coarse grains, thereby lowering the reactivity.

As a countermeasure for this, for example, a method of mixing fine ores (Japanese Patent Publication No. 62-7253) has been proposed, but the phenomenon that the sintering raw material contains a few percent of water causes a phenomenon such as pseudo-particle formation between the same particles. Therefore, even if a mixer is specially installed, it becomes difficult to uniformly mix the raw materials as the particle size decreases, which causes a problem that the reactivity of limestone with iron ore deteriorates.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the case of a sintering raw material, when the particle size becomes larger than a certain level,
An unreacted part that does not contribute to the melting reaction remains, and particles having a small particle size are clogged between particles having a large particle size, thereby lowering the reactivity. In particular, the decrease in reactivity of limestone leads to deterioration of cold strength of sinter. Therefore, in order to improve the quality of sinter, it is necessary to increase the reactivity of limestone.

Furthermore, the calcium ferrite-based melt produced by the reaction between iron ore and limestone is in a state where unreacted fine particles are suspended. For this reason, if the unreacted fine particles have a large particle size, the fluidity of the melt decreases, and the cold strength of the sintered ore deteriorates as in the above case.

In order to increase the reactivity of limestone and increase the fluidity of the melt, conditions such as narrowing the particle size distribution of limestone, reducing the particle size to below a certain level, increasing the contact area with iron ore, etc. It is necessary to satisfy.

Therefore, crushing or classifying all or part of the sintering raw material in advance can be considered as a countermeasure, but this method requires equipment for crushing or classifying for each brand, which increases the cost in terms of equipment. Not only inviting it, but when directly mixing the pulverized raw materials, there is a problem that the same raw materials become pseudo-particles and the reactivity of limestone deteriorates during firing, which is an effective measure. Absent.

In view of such an actual situation, the present invention improves the mixed state of iron ore and limestone among the sintering raw materials,
With the aim of obtaining a self-fluxing sinter with excellent reducing properties (reducibility and resistance to reduction pulverization) and cold strength, it is possible to effectively improve the mixed state of iron ore and limestone with inexpensive equipment cost. The present invention is intended to propose a pretreatment method for a sintering raw material which can increase the reactivity of limestone.

Means for Solving the Problems This invention is a method of mixing iron ore and limestone in advance for granulation and then granulating the mixture, and then mixing the remaining other sintering raw materials for sintering. And are mixed in a weight ratio of iron ore and limestone in the range of 30% or more and 60% or less, and the mixture is crushed to a particle size of 250 μm or less and 80% by weight, and water is added for granulation treatment. The gist is to use the raw material obtained by performing as a part of the sintering raw material.

Action Iron ore and limestone were selected as pretreatment raw materials.
This is because both the cold strength and the reducing property are improved by promoting the sintering-melting reaction.

The weight ratio of limestone in the blended raw material of iron ore and limestone
If it is less than 30%, the melting of the raw material is insufficient. On the other hand, if it exceeds 60%, the CaO component in the remaining raw material is extremely reduced and the cold strength of the sintered ore is reduced. This is because I will let you.

After the iron ore and the limestone are blended, the blended raw material is crushed for the reason described below.

In order to accelerate the melting reaction of limestone, it is important to increase the contact area between iron ore and limestone as described above. Further, in order to maintain good fluidity of the generated melt, it is important to reduce the particle size of fine particles suspended in the melt. As a measure against these, it is necessary to properly adjust the particle size of the raw material. However, the conventional method of classifying or crushing each material brand requires classification and crushing equipment for each brand, resulting in high equipment cost.

On the other hand, in the case of the method of crushing the target raw material after blending, there is no need for equipment for classification and crushing for each brand, and since crushing processing also serves as a mixing effect, no equipment for mixing is particularly necessary. It is an economically effective means. Also,
The pretreatment using crushing as a means is less affected by the initial particle size of the raw material as compared with the pretreatment using classification as a means,
Furthermore, since the initial particle size composition of the sintering raw material naturally differs for each brand, the method of crushing the pre-treated raw materials at once after compounding is superior to the crushing means for each brand in terms of crushing efficiency.

For this reason, the present invention employs a method of crushing iron ore and limestone in a mixed state.

The reason why the particle size after crushing is limited to 80% or more when the particle size is 250 μm or less is to avoid deterioration of granulation property after crushing treatment.

Embodiment FIG. 1 is a process diagram showing a pretreatment method of the present invention.

That is, a mixture of iron ore and limestone such that limestone accounts for 30 to 60% of the total particle size of 250 μm in the crushing process.
It is crushed so that the following is 80% or more, and granulated while adding water to the raw material after the crushing treatment in the next granulation step. This granulated product is mixed with another sintering raw material mixed and granulated in another process and supplied to the sintering process.

Example 1 Hamasley of the particle size composition shown in Table 1 and limestone were blended,
After crushing up to 80% with a particle size of 250 μm or less, sinter ore is produced using a sintering raw material in which the granulated material and other raw materials are blended under the conditions shown in Table 2, and the productivity and firing at that time are performed. With respect to the yield and quality, the case where all the compounded raw materials shown in Table 1 were mixed and granulated with a drum mixer (Comparative Example 1),
In the case of using the Hamasley and the limestone having the particle size constitution shown in the table, which was simply granulated separately (Comparative Example 2), the same as the above, the Hamasley and the limestone were each crushed and then mixed with another sintering raw material which was separately granulated When using one (Comparative Example 3)
It is shown in FIG.

As is clear from FIG. 2, by using the pretreated raw material of the present invention, quality, productivity and yield were all improved. On the other hand, in Comparative Example 3, a large improvement effect is not obtained even though the complicated pretreatment is performed as compared with the present invention.

Example 2 The results of investigating the influence of the weight ratio of the particle size after crushing of 250 μm or less on the cold strength and the reduction pulverization property of the sinter using the compounded raw material using the same pretreatment raw material as in Example 1 It is shown in FIG.

From FIG. 3, it can be seen that the quality of the sinter becomes good when the particle size of 250 μm or less is 80% or more.

Example 3 When the same raw materials as in Example 1 were used and the pretreatment was carried out by the method of the present invention, the mixing ratio of humusley and limestone having the grain size composition shown in Table 2 was changed as shown in Table 3. Fig. 4 shows the influence of the weight ratio of limestone in the pretreatment raw material on the cold strength and the reduction powdering property when fired by firing.

It can be seen from FIG. 4 that good quality is obtained in the range where the weight ratio of limestone is 30% or more and 60% or less, and that the limestone weight ratio of 40% is most effective.

EFFECTS OF THE INVENTION As described above, according to the method of the present invention, the mixed state of iron ore and limestone is improved, so that it is possible to manufacture a sintered ore having excellent reducing properties and cold strength. In addition, it is not necessary to install a crushing facility for each brand, and since the crushing process also serves as a mixing effect, no equipment for mixing is required, and the equipment cost is low. Therefore, it becomes possible to manufacture a high-quality sintered ore at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram showing a pretreatment method according to the present invention, and FIG. 2 is a diagram showing productivity, yield and quality of sinter according to an embodiment of the present invention. A) is the production rate, (B) is the product yield, (C) is the reduction powderability, and (D) is the cold strength. FIG. 3 is a diagram showing the influence of the weight ratio of the particle size after crushing of iron ore and limestone on the cold strength and reductive pulverization property of the sintered ore in the above-mentioned Example, and FIG. 4 is the sintered ore in the above-mentioned Example. It is a figure which shows the influence of the weight ratio of the limestone in a pretreatment raw material which affects the cold strength and reduction powderability of.

Claims (1)

[Claims] 1. A method of mixing iron ore and limestone in advance to granulate them, and then mixing the remaining other sintering raw materials and sintering the mixture, wherein iron ore and limestone are mixed with each other. After blending the limestone in a weight ratio of the mixture with 30% or more and 60% or less, the mixture is crushed to a particle size of 250 μm or less and 80% by weight, and water is added for granulation treatment. A pretreatment method for a sintering raw material, characterized in that the raw material subjected to the above step is used as a part of the sintering raw material.