JP2007284728A - Method of granulating raw material for iron manufacture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of granulating a raw material for iron manufacture into a predetermined appropriate grain size in a high granulation yield, when producing an agglomerate for the iron manufacture. <P>SOLUTION: This granulation method includes granulating the raw material for iron manufacture containing two or more types of raw iron oxides having different wettability with water from each other, under the presence of water, wherein the two or more types of the raw iron oxides have a contact angle with water of 25 degrees or less. The granulation method includes granulating the raw iron oxides having close wettability to each other, and accordingly can provide a granulated substance having a uniform and adequate grain size distribution in an improved granulation yield. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for granulating a raw material for iron making, and particularly to a granulating method suitable for producing an agglomerate for iron making used in a vertical iron making furnace such as a blast furnace.

  In a pig iron manufacturing process performed using a solid iron furnace such as a blast furnace (hereinafter described as an example of a blast furnace), the porosity in the raw material packed bed is used to distribute the reducing gas in the raw material packed bed in the furnace. It is important to keep the above a certain value. For this reason, it is desirable that the furnace interior inclusions such as iron raw materials have a large particle size distribution, and it is necessary to increase the strength of the charges that may be pulverized after charging to suppress pulverization.

For this reason, particularly in large blast furnaces, granulated by adding water to the raw material in which a binder, carbonaceous material, etc. are blended with powdered ore, and this granulated material is baked and hardened by the combustion heat of the carbonaceous material. A calcined agglomerate such as calcined pellets obtained by forming ore into a spherical shape with a pelletizer or the like and then heat-curing it at 1000 ° C. or higher is widely used.
On the other hand, studies on non-fired agglomerated minerals that are not heat-treated at high temperatures are also being promoted, particularly for the purpose of energy saving. For example, Patent Document 1 discloses a technique for pelletizing or briquetting by adding a binder and moisture to fine ore. Has been.
JP-A-53-129113

In general, calcined agglomerated or non-calcined agglomerated minerals include iron ore of various origins and brands (sintered ore), sinter-returned powder that is generated under sinter ore, and various dusts. Various iron oxide raw materials such as various iron powders are used.
In the production process of agglomerated minerals using such an iron oxide raw material, when the iron oxide raw material (usually an iron oxide raw material to which auxiliary materials such as a binder are added) is granulated in the presence of water, the molding yield is reduced. There is a problem that the particle size distribution of the granulated product cannot be ensured sufficiently, and it is difficult to control the particle size to an appropriate particle size.
Accordingly, an object of the present invention is to provide a granulation method capable of granulating an ironmaking raw material in which a plurality of types of iron oxide raw materials are blended into an appropriate particle size distribution at a high molding yield when producing an agglomerate for iron making. Is to provide.

The present inventor examined the cause of the decrease in the molding yield of the granulated product and the failure of the particle size distribution in the production process of the agglomerate for iron making using the various iron oxide raw materials described above, and measures for that. As a result, the following knowledge was obtained.
The bonding force between the particles that make up the granulated product obtained by granulating the powder in the presence of water is mainly a physical force such as the surface tension or adhesive force of water, or bonding due to unevenness of the powder. It can be roughly classified into a primary binding force that plays a role of temporary fixing and a secondary binding force that strongly bonds particles mainly due to changes in the properties of water and powder. In the granulation step of the powder, the powder is first molded with a primary bonding force, and further the bonding force is strengthened with a secondary bonding force, whereby a molded body (granulated product) having a predetermined bonding strength is obtained. It is known that the bonding force due to the surface tension of water plays an important role in the molding by the primary bonding force. When the powder particles are bonded by water, the bonding force due to the surface tension of water can be calculated by the following formula ("Granulation Technology" by Kenji Hashimoto, published by Epoch, 1991).

Ｆ：粒子間の結合力
ｄ：粒子径
Ｔ：水の表面張力
θ：粉体と水の接触角

F: Bonding force between particles d: Particle diameter T: Surface tension of water θ: Contact angle between powder and water

  From the above formula, when multiple types of iron oxide raw materials with different wettability with water are mixed in the raw material for iron making to be granulated, the bond between the particles of the raw material with high wettability (= small θ) The force is larger than the bonding force between the raw material particles having low wettability (= θ is large). In other words, when granulation is performed by mixing these iron oxide raw materials, a raw material with high wettability is easy to be granulated because of its strong bonding force between particles, while a raw material with low wettability has a strong bonding force between particles. Since it is weak, it is difficult to granulate, and the raw material having high wettability is segregated in the granulated product component. In addition, since water adheres preferentially to raw materials with high wettability, water does not spread sufficiently to raw materials with low wettability, making it difficult to granulate raw materials with low wettability. The particle size distribution tends to be divided into two poles, a small particle size close to the raw material particles and a very large particle size. As a result, the molding yield for an appropriate particle size range as agglomerated ore is greatly reduced.

  In order to solve the above problems, the iron oxide raw materials having close wettability may be combined and granulated. Specifically, since the wettability of the iron oxide raw material can be evaluated based on the contact angle with water, when multiple types of iron oxide raw materials are blended, the oxidation in which the difference in contact angle with water is within a predetermined numerical range. What is necessary is just to use an iron raw material, and this can raise a shaping | molding yield and can obtain the granulated material which has a homogeneous and appropriate particle size distribution (narrow particle size distribution range).

The present invention has been made on the basis of the above findings, and the gist thereof is as follows.
[1] When granulating an iron-making raw material containing two or more types of iron oxide raw materials having different wettability with water in the presence of water, the contact angle with water is used as the two or more types of iron oxide raw materials. A method for granulating a raw material for iron making, characterized in that the difference between the two is within 25 degrees.
[2] A granulation method for a raw material for iron making, wherein the iron oxide raw material is fine-grained sintered ore and / or fine-grained iron ore in the granulation method of [1].

  According to the method for granulating a raw material for iron making according to the present invention, the raw material for iron making can be granulated to an appropriate particle size distribution with a high molding yield when producing the agglomerate for iron making.

In the present invention, when granulating an iron-making raw material containing two or more types of iron oxide raw materials having different wettability with water in the presence of water, a combination of iron oxide raw materials having as close wettability as possible is used. It is what makes the grain.
In addition to iron ore of various origins and brands (sintered ore), various raw materials for iron making include various types of oxidation, such as sinter-returned powder, various dusts, various iron powders, etc. An iron raw material is used. Such wettability of the iron oxide raw material with water can be evaluated by the contact angle between the iron oxide raw material and water.

The contact angle between the liquid and the solid can be directly measured by dropping a droplet on a solid surface cut into a flat surface and polished. However, when the solid is a granular particle, measurement of such a contact angle is possible. However, it is difficult to measure the contact angle indirectly. Regarding the method of measuring the contact angle θ between the liquid and the powder, Yoshinaga et al. Have shown a detailed measuring method (permeation rate method) (Wednesday Society, 18 (1977) p561).
That is, in the test apparatus shown in FIG. 2, the lower end of the sample tube 2 is closed with the filter paper 4, the finely pulverized granule sample 3 is charged therein, and then the liquid kept at a constant temperature by the temperature controller 6. Gently immerse in sample 7 (water). The rising speed of the liquid level at this time is expressed by the following equation.

ｔ：浸透時間
ｈ：液面高さ
ｒ：毛管半径
ｇ：重力加速度
γ_Ｌ：液体の表面張力
η：液体の粘度
θ：粉体−液滴の接触角

t: Penetration time h: Liquid surface height r: Capillary radius g: Gravity acceleration γ _L : Liquid surface tension η: Liquid viscosity θ: Powder-droplet contact angle

Then, the reciprocal (1 / h) of the observed liquid level is arranged on the X axis, the rising speed (dh / dt) of the liquid level is arranged on the Y axis, and the contact angle θ is calculated by obtaining the odor distribution of the graph. Can be calculated. Specifically, first, the iron oxide raw material is finely pulverized and adjusted to a particle size range of 53 to 105 μm. Next, 3 g of this finely pulverized sample (powder sample) is loaded into the sample tube 2 (inner diameter of about 6 mm) of the test apparatus shown in FIG. 2, and the tapping operation is performed 200 times in order to sufficiently compact the powder sample. . Further, the sample tube 2 is gently immersed in the liquid surface as shown in FIG. 2, and the liquid surface height is measured at regular intervals until the rising speed of the liquid surface becomes almost zero, and the contact angle θ is determined by the above method. calculate.
As a particle size measuring method of the particles, in addition to a particle size measuring method by sieving, a laser diffraction scattering method shown in JIS Z 8825-1 can be used.

  FIG. 1 shows that when two types of iron oxide raw materials having different wettability with water are granulated in the presence of water, the difference in contact angle between both iron oxide raw materials and water and the molding yield during granulation (10 This shows the relationship with the mass ratio of the molded product granulated to ˜40 mm. In this granulation test, the granulation test was performed using the raw materials for iron making blended by combining two of the iron oxide raw materials (iron ores A to E and sintered ore) shown in Table 1. As granulation conditions, two types of iron oxide raw materials (each 10 kg) were pulverized and the particle size was adjusted to 100 μm or less, 0.6 kg of water, and alumina cement as a binder for strengthening the secondary bond strength was set to 0. 6 kg was added and stirred with a mixer for 30 minutes, and then granulated at 30 rpm using a disk pelletizer having a diameter of 50 cm.

  According to FIG. 1, if the difference in contact angle between two or more iron oxide raw materials and water is within 25 degrees, an excellent molding yield is obtained. For this reason, in the present invention, when granulating an iron-making raw material containing two or more types of iron oxide raw materials having different wettability with water in the presence of water, as the two or more types of iron oxide raw materials, water and A mixture having a contact angle difference of 25 degrees or less is granulated. Thereby, a granulated product having a uniform and proper particle size distribution can be obtained.

The method for granulating a raw material for iron making according to the present invention can be applied to both a production process of a fired agglomerated mineral such as sintered ore and a process of producing a non-fired agglomerate without heat treatment.
It goes without saying that raw materials other than iron oxide raw materials such as a binder can be blended in the raw material for iron making to be granulated. In general, lime, carbonaceous material, silica, serpentine, nickel slag, dolomite and the like are blended in addition to the iron oxide raw material as a raw material for the sintered agglomerate such as sintered ore. Moreover, in order to reinforce the strength of the granulated material by the secondary binding force, for example, cement, lime, or the like may be blended with the raw material for the unfired agglomerated mineral. Moreover, you may mix | blend the iron oxide fine powder etc. for ensuring hot strength by sintering in a high temperature area in a furnace. Examples of the iron oxide fine powder include steel pickling line recovery powder (so-called Rusner iron oxide and the like), refining dust generated in the steel manufacturing process, iron ore fine powder, and the like, and one or more of these can be used.

As granulation methods, (1) pelletizing method using disc pelletizer, rotary granulation method such as drum granulation method using drum mixer, (2) extrusion molding method, briquette molding method, tablet compression molding method, etc. However, the present invention is particularly effective for granulation by the rotary granulation method.
The treatment after granulation is arbitrary. In general, in the case of calcined agglomerated minerals, secondary granulation or the like is performed as necessary, and then calcined (sintered) to obtain calcined agglomerated minerals. In the case of non-calcined agglomerated minerals, secondary granulation is performed as necessary, followed by drying and curing to obtain non-calcined agglomerated minerals.

The granulation test was performed using the iron-making raw material which mix | blended and mix | blended two types of the iron oxide raw materials (iron ore AE, sintered reverse sinter) shown by Table 1. FIG. The contact angle of each iron oxide raw material shown in Table 1 with water was measured by the penetration rate method described above.
In the granulation test, two types of iron oxide raw materials (10 kg each) were crushed and the particle size was adjusted to 100 μm or less, water was 0.6 kg, and alumina cement as a binder for strengthening the secondary bond strength was 0.6 kg. The mixture was added and stirred for 30 minutes with a mixer, and then granulated under a granulation condition of 30 rpm using a disk pelletizer having a diameter of 50 cm to obtain a granulated product.

The granulation property and strength of each granulated product were measured and evaluated by the following methods. The results are shown in Table 2. In addition, N / P in Table 2 shows the magnitude | size of the force required when destroying one granulated material.
For the evaluation of the granulation property, the particle size distribution of the obtained granulated product is measured, and the mass ratio of the granulated product in the particle size range of 10 to 40 mm which is the target particle size is obtained as the molding yield, and the mass ratio is 70 mass%. The case above was evaluated as “◯” and the case of less than 70 mass% was evaluated as “x”.
As for the strength of the granulated material, after drying and curing the granulated material for 24 hours, 20 granulated materials having a particle size of 25 mm are selected, and the crushing strength is measured at a rate of about 1 mm / min by an autograph tester. Measurements were made to determine the minimum strength, maximum strength, and average strength of 20 granules.

[Invention Example 1]
As the iron oxide raw material, sintered ore (contact angle with water of 74 degrees) and iron ore C (contact angle with water of 68 degrees) were used. The difference in contact angle between both iron oxide raw materials and water is 6 degrees.
In this example of the invention, a granulated product having a narrow particle size range and a large number of granulated products having a target particle size of 10 to 40 mm was obtained. In addition, it is considered that the granulated product having an almost uniform composition was obtained because the difference between the minimum and maximum strengths of the granulated product after curing was small.

[Invention Example 2]
Sintered ore (contact angle with water of 74 degrees) and iron ore A (contact angle with water of 52 degrees) were used as iron oxide raw materials. The difference in contact angle between both iron oxide raw materials and water is 22 degrees.
In this example of the invention, a granulated product having a narrow particle size range and a large number of granulated products having a target particle size of 10 to 40 mm was obtained. In addition, it is considered that the granulated product having an almost uniform composition was obtained because the difference between the minimum and maximum strengths of the granulated product after curing was small.

[Invention Example 3]
As iron oxide raw materials, iron ore D (contact angle with water of 55 degrees) and iron ore A (contact angle with water of 52 degrees) were used. The difference in contact angle between both iron oxide raw materials and water is 3 degrees.
In this example of the invention, a granulated product having a narrow particle size range and a large number of granulated products having a target particle size of 10 to 40 mm was obtained. In addition, it is considered that the granulated product having an almost uniform composition was obtained because the difference between the minimum and maximum strengths of the granulated product after curing was small.

[Invention Example 4]
As iron oxide raw materials, iron ore D (contact angle with water of 55 degrees) and iron ore E (contact angle with water of 30 degrees) were used. The difference in contact angle between both iron oxide raw materials and water is 25 degrees.
In this example of the invention, a granulated product having a narrow particle size range and a large number of granulated products having a target particle size of 10 to 40 mm was obtained. In addition, it is considered that the granulated product having an almost uniform composition was obtained because the difference between the minimum and maximum strengths of the granulated product after curing was small.

[Comparative Example 1]
Sintered ore (contact angle with water of 74 degrees) and iron ore B (contact angle with water of 37 degrees) were used as iron oxide raw materials. The difference in contact angle between both iron oxide raw materials and water is 37 degrees.
In this comparative example, the particle size distribution of the granulated material is divided into two, a small diameter that is hardly granulated and a large diameter that has undergone granulation. Only a small amount of granules was obtained. Moreover, since the crushing strength after curing of the granulated product shows a large variation in strength depending on the particles, it is considered that the composition of the granulated product is biased.

[Comparative Example 2]
As iron oxide raw materials, iron ore B (contact angle with water of 37 degrees) and iron ore C (contact angle with water of 68 degrees) were used. The difference in contact angle between both iron oxide raw materials and water was 31 degrees. .
In this comparative example, the particle size distribution of the granulated material is divided into two, a small diameter that is hardly granulated and a large diameter that has undergone granulation. Only a small amount of granules was obtained. Moreover, since the crushing strength after curing of the granulated product shows a large variation in strength depending on the particles, it is considered that the composition of the granulated product is biased.

Graph showing the relationship between the difference in contact angle between two types of iron oxide raw materials and water and the molding yield when two types of iron oxide raw materials with different wettability with water are granulated in the presence of water Explanatory drawing showing a test device that measures the contact angle θ between powder and liquid

Claims (2)

  When granulating an iron-making raw material containing two or more types of iron oxide raw materials having different wettability with water in the presence of water, the difference in contact angle with water as the two or more types of iron oxide raw materials is A method for granulating a raw material for iron making, characterized in that a material within 25 degrees is blended.   The method for granulating a raw material for iron making according to claim 1, wherein the iron oxide raw material is fine-grained sintered ore and / or fine-grained iron ore.

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