JP2003129139A - Method for treating raw material prior to sintering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a raw material prior to sintering, which improves granulation properties of iron ore raw materials abundantly containing blended goethite ore. SOLUTION: This prior treatment method comprises adding free water to the iron ore raw material, which includes blended goethite ore of 70 mass% or more containing crystal water of 4 mass% or more, and mixing and granulating these by using a blender with built-in high-speed stirring blades. Thereby, the raw material is appropriately granulated by the blender, the granulation properties are maintained even when granulated substances are charged on a sintering pallet, and air permeability of a packed bed during sintering can be improved, because the free water invades pores of the goethite ore during granulation and the water thoroughly adheres inside the pores of the goethite ore and to the surfaces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for a sintering raw material in a granulation step of a sinter production process.

[0002]

2. Description of the Related Art In the production of iron ore sintered ore, first, a sintering raw material such as iron ore, limestone, serpentine, coke powder, etc. is blended in a predetermined ratio, and then a necessary amount of water is added to the sintering raw material. Then, the mixture is granulated and charged into a sintering pallet to form a sintering material filling layer. Next, in the ignition furnace, the surface (surface layer portion) of this sintering raw material filled layer is ignited, and the charging raw material (sintering raw material filling) is carried out by the blower through the wind box.
Aspirate air above the bed. As a result, the coke blended in the sintering raw material burns, and the heat is used to sequentially calcine, and then the calcined product (also referred to as a sintered cake) in the mine discharge section.
Are discharged from the pallet. The discharged fired product is crushed and cooled, and then a product having a certain particle size or more is supplied to the raw material for the blast furnace as a sinter. It should be noted that a powder or granular material having a particle size smaller than a certain size (hereinafter referred to as return ore) is used again as a sintering raw material. In this sinter production process, the granulation of the sintering raw material influences the air permeability of the packed bed at the time of firing and greatly affects the productivity of the sinter. Therefore, many studies have heretofore been made on the improvement of the granulation process.

As a granulating apparatus for producing the above-mentioned sintering raw material, a drum mixer which has been widely used in the world was generally used, but in recent years, for example, a mixer having a built-in pan pelletizer or a high speed stirring blade (hereinafter referred to as a mixer). , Abbreviated as high-speed stirring mixer) and the like, and a mixing granulator is also put into practical use. Patent No. 27
In 90008, fine powder of 0.5 mm or less is 30 wt%
As a pretreatment method for the sintering raw material including the above, a method is disclosed in which the water content of the sintering raw material is adjusted to 6.5 to 10.0% and mixed by using a high-speed stirring mixer. This is to regulate the amount of granulated water in order to bring out the specific treatment effect (effect of mixing while applying shearing force) unique to a high-speed stirring mixer, and the granulated water content is measured by the centrifugal separation method for each iron ore. It is a method of increasing the water absorption index by 1.0 to 3.0%. Further, in recent years, as an iron ore raw material used as a sintering raw material, a goethite ore such as a pisolite ore or a mara mamba ore, which is less expensive than conventionally used hematite ores, is increasingly used.

[0004]

However, when the goethite ore is to be treated in the same manner as the hematite ore treatment method by using the above-mentioned pretreatment method for the sintering raw material, the goethite ore is the hematite ore and the water-absorbing substance. Since the mechanism is different, when mixing and granulating with a high-speed stirring mixer, the water content becomes insufficient, and the granulation property of the iron ore raw material deteriorates, which may cause problems such as deterioration of aeration during firing. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pretreatment method for a sintering raw material that improves the granulation property of an iron ore raw material containing a large amount of goethite ore.

[0005]

A method for pre-treating a sintering raw material according to the present invention, which is in accordance with the above object, comprises a raw material for iron ore containing 70% by mass or more of goethite ore containing 4% by mass or more of water of crystallization. Is added, and this is mixed and granulated using a mixer with a built-in high-speed stirring blade. Here, in the pretreatment method for a sintering raw material according to the present invention, water may be added to the iron ore raw material so that the water content of the iron ore raw material is more than 10.0% by mass and 12.5% by mass or less. preferable. In the pretreatment method for a sintering raw material according to the present invention, it is preferable that the rotation speed of the high-speed stirring blade is 100 to 300 rpm.

Since the types of iron ores used as sintering raw materials are diverse, and the water absorption mechanism is different for each ore type, the optimum water content (water content) can be obtained only by the evaluation test results based on the simple water absorption mechanism. Rate) cannot be determined. That is, when performing good granulation, it is required to set an appropriate amount of water in consideration of the influence of this type of iron ore. The present inventors have made detailed studies on the granulation property of goethite ores, such as pisolite ores and maramanba ores, whose use amounts have been increasing in recent years. As a result, it was found that the goethite ore contained 4% by mass or more of water of crystallization (derived from goethite mineral), and thus had higher wettability and higher porosity than hematite ore. When these high wettability and high porosity goethite ore are mixed and granulated, for example, with a high-speed stirring mixer, by performing mixing at a higher water level than when a hematite ore is granulated with a normal drum mixer or the like, We have found a phenomenon in which a remarkable effect of improving the granulation property is obtained.

That is, when the goethite ore is granulated by a drum mixer, the water adheres to the surface of the ore without entering into the pores of the goethite ore, so that high water content (water content: 10.0 mass % To 12.5% by mass), the water content becomes excessive during granulation and good granulation cannot be achieved. Further, it is possible to perform good granulation by having a low water content equivalent to that of hematite ore, but because the wettability is good, water gradually enters the pores over time, so firing At the time of charging on the binding pallet, the water content on the surface of the goethite ore becomes insufficient, and the granulated product is pulverized to deteriorate the air permeability. On the other hand, when the goethite ore is granulated with a high-speed stirring mixer, the water enters the pores during the granulation, and the water uniformly adheres to the pores and the surface of this goethite ore, so that the high water state is obtained. If this is done, the granulation will be carried out properly, and moisture will not invade into the pores of the goethite ore even after a lapse of time. It is maintained and does not cause deterioration of breathability.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to the attached drawings, an embodiment in which the present invention is embodied will be described to provide an understanding of the present invention. 1A and 1B are explanatory views of a granulation method to which the pretreatment method for a sintering raw material according to an embodiment of the present invention is applied, and FIG. 2 is a pretreatment for the sintering raw material. Explanatory diagram showing the relationship between the water of crystallization contained in the goethite ore used in the method and the heat of wetting, FIG. 3 is an explanatory diagram showing the influence of the water content of the ore raw material used in the pretreatment method of the sintering raw material. .

As shown in FIG. 1A, a pretreatment method for a sintering raw material according to one embodiment of the present invention is a goethite ore containing 4% by mass or more of water of crystallization (for example, pisolite ore, maramanba). (Ore or the like) is added to the iron ore raw material containing 70% by mass or more, and the mixture is granulated using a high speed stirring mixer (Eirich mixer), which is an example of a mixer having a high speed stirring blade. Is. The details will be described below.

First, an iron ore raw material containing 70% by mass or more of pisolite ore and mara mamba ore having a particle diameter of 10 mm or less (average particle diameter in dry state is 2 mm) has a water content of 10.0%. Water is added so as to exceed 12.5% by mass and not more than 12.5% by mass, and this is mixed and granulated with a high-speed stirring mixer for, for example, about 0.5 to 2 minutes to granulate the iron ore raw material. The rotation speed of the high-speed stirring blade (agitator) of the high-speed stirring mixer was set to 100 to 300 rpm,
The number of rotations of the bread is 10 to 70 rpm (the above is the pretreatment process).

The iron ore raw material thus mixed and granulated contains iron ore (for example, hematite ore) containing less than 4% by mass of crystallization water, and miscellaneous raw materials (for example, sintered ore having a particle size smaller than a predetermined particle size). , Ore with small particle size that cannot be put into the blast furnace),
By adding an auxiliary material (for example, limestone having a particle size of 7 mm or less, 5 mm or less serpentine, etc.) and 1 mm or less of quicklime, a raw iron ore material is made into a sintering material containing, for example, about 20 to 50% by mass. In addition, this sintering raw material includes the sintering raw material 1
In the outer frame with respect to 00% by mass, for example, about 10 to 20% by mass of the returned ore (other, iron ore) and, for example, about 2 to 5% by mass of powder coke are further added. The amount can be included in the amount of miscellaneous raw materials. The rotation speed of this sintering raw material is, for example, 5 to 50 using a drum mixer.
After rolling granulation with rpm and residence time of, for example, about 2 to 5 minutes to obtain a granulated product (above, granulation process), the granulated product is sintered with a sintering machine to obtain a sintered ore. To do. Here, the drum mixer is subjected to tumbling granulation without adding water or by adding 1 to 2% by mass of water (added water) as shown in FIG. When water is added to the sintering raw material with this drum mixer, the addition is performed in consideration of the water content of the iron ore raw material.

As shown in FIG. 1 (B), the iron ore raw material has a water content of more than 10.0% by mass and 1 or more.
Water was added to 2.5% by mass or less, and this was mixed and granulated with a high-speed stirring mixer, and then the iron ore raw material was further granulated by rolling using, for example, a pan pelletizer, and the other sintering described above. It is also possible to add the raw materials to a drum mixer for rolling granulation.

As shown in FIG. 2, in the above-described goethite ore (Fe ₂ O ₃ .nH ₂ O), when the water of crystallization is 4% by mass or more, the goethite having good wettability increases on the surface of the ore. It was found that the heat of wetting started to increase, while below that, the amount of hematite with poor wettability increased and the heat of wetting decreased. Note that the heat of wetting is the amount of heat generated when the ore surface is changed from a dry state to a wet state,
It is the value measured using a commercially available twin type microcalorimeter. Further, the chemical components and ore properties of Australian pisolite ore A and Australian maramanba ore B, which are typical of the goethite ores targeted by the present invention, are the same as those used in Australia or Brazil. Table 1 shows the produced hematite ores C and D.

[0014]

[Table 1]

As can be seen from Table 1, Pisolite Ore A and Mara Mamba Ore B contain about 4 to 9 mass% of water of crystallization, and the heat of wetting is higher than that of Hematite Ore C and D. , Shows that the ore surface has good wettability.
In addition, the BET specific surface area in Table 1 is one of the indexes showing the substantial porosity, and this also shows a high value. Therefore, when the goethite ore such as the pisolite ore A and the maramanba ore B is mixed and granulated by the high-speed stirring mixer, the water rapidly enters the pores of the ore, and the inner wall surface in the pores and Water adheres evenly to the surface of the ore. The specific surface area is a value measured by the BET method. The BET method is a general measurement method for determining the specific surface area from the amount of adsorbed nitrogen (for example, Teruichiro Kubo, Eiji Mizuwata, Yuzo Nakagawa, Sohachiro Hayakawa, “Powder Theory and Applications” Maruzen, P134 (S37). Published annually)).

Next, the reasons for limiting the compounding ratio of goethite ore to the iron ore raw material, the water content of the iron ore raw material, and the rotational speed of the high-speed stirring blade to the above-described numerical values will be described. The mixing ratio of the goethite ore to the iron ore raw material is set to 70% by mass or more. When the mixing ratio is less than 70% by mass, the influence of the goethite ore on the iron ore raw material is not dominant and This is because it is strongly influenced by the characteristics. On the other hand, although the upper limit value is not specified, it is possible even when all the iron ore raw materials are goethite ores. Therefore, in order to reveal the effect of goethite ore on iron ore raw material more significantly,
Also, considering that the amount of goethite ore used will increase in the future by considering economic efficiency, the compounding ratio of goethite ore to the iron ore raw material is 75 mass% or more, and further 80% or more.
It is preferable that the content is at least mass%.

Further, after changing the compounding amount of the pisolite ore A in the iron ore raw material and adjusting the water content (water content) of the iron ore raw material in various ways, the iron ore raw material is charged into a high-speed stirring mixer and stirred. Then, the granulation property of the iron ore raw material was examined. The rotation speed of the high-speed stirring blade of this high-speed stirring mixer was 200 rpm. As shown in FIG. 3, it was confirmed that when the water content of the iron ore raw material is more than 10 mass% and 12.5 mass% or less, the granulation property of the iron ore raw material can be improved. It should be noted that it is found that the peak of the curve of the maramanba ore B slightly moves in the direction of lower water content than that of the pisolite ore A, but shows a tendency similar to that of the pisolite ore A.

Here, the water content of the iron ore raw material is 10% by mass.
When the amount is below, water penetrates into the pores of the goethite ore, so that surface water required for granulation is insufficient, so that the granulation property of the iron ore raw material deteriorates. On the other hand, when the water content of the iron ore raw material exceeds 12.5% by mass, fine powder particles flow due to excess moisture, resulting in granules having no strength and rather granules having an appropriate particle size. Decrease. Therefore, in order to secure surface water necessary for granulation and to obtain a granulated product with an appropriate particle size, the water content of the iron ore raw material should be 10.5% by mass or more and 1 or more.
2.5 mass% or less, further 10.5 mass% or more 12.0
It is preferable that the content is not more than mass%. The water content of the iron ore raw material, that is, more than 10% by mass and 12.5% by mass or less is out of the range of the optimum water content determined from the water absorption index in the above-mentioned Japanese Patent No. 2790008. Even if a high water infiltration is taken into consideration, it corresponds to the range that can be regarded as excess water.

When high water content is added in this way, the rotation speed of the rotary blades of the high speed stirring mixer is 100 to 300 rp.
About m is preferable. Here, when the rotation speed is less than 100 rpm, the shearing force peculiar to the high-speed agitation mixer is insufficient, the granulation conditions are close to those of normal tumbling granulation, and the effect of effectively contacting the water with the ore is lost, and the water content is reduced. It will not be able to fully penetrate the pores of goethite ore. Further, if strong stirring exceeding 300 rpm is performed under such a high water content condition, the mixing action is strengthened rather than the granulation action and the disintegration action of the pseudo particles is promoted, which is not desirable. Therefore, in order to apply a sufficient shearing force to the iron ore raw material and suppress the collapse of the pseudo particles, it is preferable to set the rotation speed to 150 to 300 rpm, and further 150 to 250 rpm.

[0020]

[Examples] The results of tests conducted by using a granulation method to which the sintering raw material pretreatment method according to the present invention is applied will be described. The iron ore raw material was prepared by varying the composition of the iron ore raw material and the water content of the iron ore raw material, and the iron ore raw material was prepared as shown in FIG.
The iron ore raw material was tumbled and granulated by using each of the methods (B), and the effect of the granulation method was confirmed by an operation test using a sintering machine. Here, a goethite ore containing 4% by mass or more of water of crystallization, that is, a pisolite ore and a maramamba ore,
Tables 2 and 3 show the compounding conditions of hematite ore C and hematite ore D containing less than 4 mass% of water of crystallization, and the test results thereof, respectively. In addition, Pisolite ore, Mara Mamba ore,
Hematite Ore C and Hematite Ore D are shown in Table 1 respectively.
It means the ore inside.

[0021]

[Table 2]

[0022]

[Table 3]

The preconditions for the operation test, that is, the types of mixers used in the pretreatment step iron and the granulation step (Eirich mixer (A), pan pelletizer (B), drum mixer (C)), and each Table 4 shows the operating conditions of the mixer and the sintering machine for sintering the iron ore raw material.

[0024]

[Table 4]

As shown in Table 2, the iron ore raw material of Inventive Example 1 is 100% by mass of pisolite ore, and the iron ore raw material of Inventive Example 2 is 40% by mass of pisolite ore and 60% by mass of Maramanba ore. % (The goethite ore is 100% by mass), and the iron ore raw materials of Invention Examples 3 and 4 are 40% by mass of the pisolite ore and 30% by mass of the Mara Mamba ore.
(Gaysite ore is 70% by mass) and hematite ore C is 30% by mass. Here, Examples 1 to 3 of the present invention are the methods of FIG. 1A described above, and Examples 4 of the present invention are the methods of FIG.
The method of (B) is used respectively.

Regarding the added water necessary for granulation,
Considering the raw material moisture before mixed granulation, that is, about 4.0% by weight of the moisture contained in the goethite ore, and the moisture that has penetrated into the pores of the ore when the ore is left (water content in Table 1), By mixing and granulating in a mixer, the total amount is further added, and by adjusting the added water content (3.7 to 4.1% by mass), mixing with an Erich mixer (the stirring blade rotation speed is 150 rpm or 250 rpm). The water content after granulation, that is, the water content of the iron ore raw material (water content of the granulated product) is 1
It was changed within the range of 1.2 to 12.2% by mass. By adding the miscellaneous materials (other miscellaneous materials), auxiliary materials (limestone, serpentine), quick lime, etc. to this iron ore material, a sintering material containing 30 to 45 mass% of the iron ore material was produced. This sintering raw material contains an external component with respect to 100% by mass of the sintering raw material,
The returned ore and powder coke are further added to add water (0.6
.About.1.2% by mass), and the water content of the granulated product was adjusted to 6.7% by mass using a pan pelletizer or a drum mixer.

On the other hand, as shown in Table 2, the iron ore raw materials of Comparative Examples 1 to 3 have substantially the same composition of the iron ore raw material and the operating conditions of the granulation step as those of Example 1 of the present invention. When the iron ore raw material of Comparative Example 1 is different in the type of mixer (drum mixer) used in the pretreatment step, the iron ore raw material of Comparative Example 2 has a water content of the iron ore raw material of the lower limit value of the present invention, that is, When it is below 10% by mass (9.2% by mass), Comparative Example 3
In the iron ore raw material of No. 1, the rotation speed of the stirring blade of the Erich mixer was below the lower limit of the present invention, that is, 100 rpm (90r.
pm) in each case. The granulated product produced by the above method was fired by a sintering machine to produce a sintered ore.

As the sintering machine, a DL type sintering machine as shown in Table 4 was used, and a pallet speed of 3.6 m / min and a pallet sintering area of 600 m ² were used, and a sintering material charging layer (filling layer) was filled. The granulated product was fired under the operating conditions in which the thickness of (layer) was 600 mm. As can be seen from the operation results shown in Table 3, Invention Examples 1 to 4
When using the granulated product of, the production of sinter is 17800
~ 18200 (t / day), the air permeability of the packed bed during firing is about 31 to 32, and the yield in this operation is 7
It was 8.5 to 78.9%. On the other hand, when the granules of Comparative Examples 1 to 3 are used, the production amount of sinter is 15200 to 1
About 6000 (t / day), the air permeability was about 28 to 30, and the yield in this operation was 74.1 to 75.1%. As can be seen from this, in the comparative example,
Since the mixer selection, the water content of the iron ore raw material, and the rotation speed of the stirring blade of the Eirich mixer could not be adjusted properly, granulation of the sintering raw material became defective, and the air permeability of the packed bed during firing was deteriorated, and firing was performed. It is considered that the productivity of the ore was greatly reduced as compared with the present invention, and the yield was also reduced.

Although the present invention has been described with reference to one embodiment, the present invention is not limited to the structure described in the above embodiment and is described in the scope of claims. Other embodiments and modifications that are conceivable within the scope of the matters described above are also included. For example, in the above-described embodiment, the particle size of limestone, serpentine, quicklime, and the amount of coke dust are shown, but the present invention is not limited to the above-mentioned values, and other values are applicable. To be done.

[0030]

In the pretreatment method for sintering raw materials according to claims 1 to 3, since a mixer having a high-speed stirring blade is used, water penetrates into the pores of goethite ore during granulation. Thus, water can be evenly adhered to the pores and the surface of the goethite ore. Therefore, the granulation is properly performed by the mixer, and since moisture does not enter the pores of the goethite ore even after a lapse of time, the granulated product produced based on the iron ore raw material is Even at the time of charging on a sintering pallet, the granulating property is maintained, and there is no possibility that the air permeability of the filling layer during sintering is deteriorated. Therefore, it is economical because the granulation property can be improved and the productivity of the sinter can be improved.

Particularly, in the pretreatment method for a sintering raw material according to claim 2, the water content adhering to the surface of the iron ore raw material is controlled by limiting the water content of the iron ore raw material to a predetermined range.
It becomes possible to adjust to an appropriate amount. Therefore, even when using a goethite ore having a different water absorption mechanism from the conventionally used hematite ore, it is possible to improve the granulation property, so that more goethite ore can be blended in the iron ore raw material, and thus It is economical because the raw material cost of iron ore raw material can be suppressed. In the pretreatment method for a sintering raw material according to claim 3, the shearing force generated by the rotation of the high-speed stirring blade can be sufficiently applied to the iron ore raw material, and a large particle size can be obtained in the iron ore raw material. It becomes possible to form pseudo particles to which the ore having a small particle size is attached, around the ore having the ore. Therefore, even when using a goethite ore that has a different water absorption mechanism from the conventionally used hematite ore, it is possible to evenly attach water to the pores and the surface of the goethite ore, and thus more in the iron ore raw material. It is possible to mix the goethite ore of the above, which makes it possible to reduce the raw material cost of the iron ore raw material, which is economical.

[Brief description of drawings]

1A and 1B are explanatory views of a granulation method to which a pretreatment method for a sintering raw material according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram showing the relationship between the water of crystallization contained in the goethite ore used in the pretreatment method for the sintering raw material and the heat of wetting.

FIG. 3 is an explanatory diagram showing the influence of the water content of the ore raw material used in the pretreatment method for the sintering raw material.

Claims (3)

[Claims] 1. Water is added to an iron ore raw material containing 70% by mass or more of goethite ore containing 4% by mass or more of water of crystallization, and this is mixed and granulated by using a mixer equipped with a high-speed stirring blade. A pretreatment method for a sintering raw material, comprising: 2. The pretreatment method for a sintering raw material according to claim 1, wherein the water content is added to the iron ore raw material so that the water content of the iron ore raw material exceeds 10.0% by mass and 12.5% by mass. % Or less, a pretreatment method for a sintering raw material, characterized in that 3. The pretreatment method for a sintering raw material according to claim 1, wherein the rotational speed of the high-speed stirring blade is 100 to 100.
A pretreatment method for a sintering raw material, which is characterized in that the speed is 300 rpm.