JP3058015B2 - Granulation method of sintering raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a sinter to be charged into a blast furnace for iron making, wherein a sinter having a high cold strength is produced with a high product yield and a low unit air volume. The present invention relates to a method for granulating a sintering raw material for the purpose.

[0002]

2. Description of the Related Art Sinter is generally produced as follows. First, various sintering raw materials such as iron ore, limestone and coke breeze are granulated by adding an appropriate amount of moisture, and then charged into a sintering pallet. Then ignite the upper part of the sintering raw material packed layer,
Baking is performed in order from the upper layer while sucking air downward. After firing, the pallet is tilted to crush and cool the fired product (referred to as a sintered cake), and then a product having a certain particle size or more is provided as a blast furnace raw material.

[0003] The granulation step in the above-mentioned sinter production process is as follows:
It is important for ensuring the air permeability of the sintering material packed layer when the sintering material is charged into the sintering pallet and fired. That is, when the air permeability increases, the sintering time is shortened, and the production rate (tons / day of sintered product) increases.

[0004] In order to ensure high air permeability of the sintering raw material packed layer, it is necessary to increase the particle size of the particles after sintering raw material granulation (hereinafter referred to as pseudo particles). Since the pseudo particles have a structure in which coarse particles having a particle diameter of about 1 mm or more serve as nuclei and fine powder adheres around the cores, the pseudo particle diameter is increased by adhering more fine powder to the coarse particles.

Therefore, as a method for increasing the adhesion of the fine powder, for example, Japanese Patent Application Laid-Open No. Sho 57-174420 proposes a method in which a sintering raw material is treated before granulation with a drum mixer or a pan pelletizer. The sticking treatment is an operation of kneading the powder by applying an external force in a wet state, and aims to uniformly disperse the added water by the external force. However, when the thickness of the adhered layer of the adhering powder in the pseudo particles increases, fine coke powder is buried in the adhering layer of the adhering powder during granulation. As a result, the buried coke breeze causes combustion delay, incomplete combustion, or unburned during firing.

For this reason, the maximum temperature of the raw material at the time of firing is lowered, and the high-temperature holding time of 1200 ° C. or more is shortened, and the product yield of sintering is lowered.

On the other hand, Japanese Patent Publication No. 55-9047 discloses an invention for promoting the burial of coke breeze into pseudo particles for the purpose of reducing nitrogen oxides (NO _x ) generated during sintering. Is disclosed. The method is a method of granulating a sintering raw material with a primary pelletizer, adding coke breeze to the granulated material, and granulating with a secondary pelletizer. In this way, by localized coke breeze to the pseudo particles inner layer portion, the coke by incomplete combustion, and to be able to reduce NO _X generation amount. The problem here is that if coke breeze is unevenly distributed in the inner layer of the pseudo-particles,
The adhesive strength of the unevenly distributed layer is weakened, and when the granulated material is conveyed between the primary pelletizer and the secondary pelletizer or between the secondary pelletizer and the sintered pallet, it collapses from the part of the unevenly distributed layer, and the granulation step is stopped. Retention is reduced. Further Japanese Patent
Japanese Patent Application Laid-Open No. 52-71305 proposes a method in which a binder is used in combination in the divided addition and the subsequent addition of coke breeze. However, the mere sintering of a binder with a binder has a limited effect of increasing the quasi-particle strength.

[0008]

As described above, in the conventional method, when the particle size of the pseudo particles is increased in order to improve the production rate, the coke breeze is buried in the pseudo particles and the sintering process is started. Retention deteriorates. Also, in the method described in JP-B-55-9047 and JP-A-52-71305, the coke powder is buried in the pseudo particles, and the strength of the pseudo particles is also increased. The problem is the decrease and incomplete combustion of coke breeze during firing.

An object of the present invention is to improve the granulation process of a sintering raw material so that coke breeze is adhered to the surface layer of the pseudo-particles, and high-strength pseudo-particles that do not easily collapse are formed. It is an object of the present invention to provide a granulation method capable of improving the yield and the cold strength of a sintered ore, and reducing the basic unit of air flow to increase the productivity of sintering.

[0010]

The present invention provides the following (1)
The method for granulating sintering raw materials up to (4) is summarized.

(1) Mixing sintering raw materials such as iron ore and limestone excluding particulate fuel using a mixer incorporating a high-speed rotating blade
A method of granulating a sintering raw material, characterized in that, after granulation, granulated fuel is added to the mixture and granulated by a granulator having a rolling function (hereinafter referred to as the first invention) Method).

(2) Sintering raw materials such as iron ore and limestone excluding powdered and granular fuels are mixed by using a mixer having a built-in high-speed rotating blade, and then granulated by a granulator having a rolling function. After that, a granulated fuel is added to the granulated material, and the granulated material is granulated again by a granulator having a rolling function. Method).

In the above method (1) or (2), 90% or more of the total water added at the time of mixing and granulating the sintering raw materials is added at the time of mixing by a mixer having a built-in high-speed rotating blade. It is desirable to do.

(3) Mixing sintering raw materials such as iron ore, limestone and the like except for the particulate fuel using a mixer incorporating a high-speed rotating blade.
A method of granulating a sintering raw material, characterized in that after granulation , a granulated fuel and quick lime are added to the mixture and granulated by a granulator having a rolling function (hereinafter referred to as a third method). Inventive method).

(4) The sintering raw materials such as iron ore and limestone excluding the particulate fuel are mixed by using a mixer having a built-in high-speed rotating blade and then granulated by a granulator having a rolling function. A method for granulating a sintering raw material, comprising adding a granular fuel and quick lime to the granulated material and granulating again with a granulator having a rolling function (hereinafter referred to as the fourth invention). Method).

In the above method (3) or (4), 70% of the total water added when mixing and granulating the sintering raw materials is used.
It is desirable to add the above-mentioned water at the time of mixing by a mixer incorporating a high-speed rotating blade.

The mixer having a built-in high-speed rotary blade used in the method of the present invention is a mixer in which a blade for stirring is installed in a cylindrical pan, and both the pan and the blade rotate. For example, a mixer called an Erich mixer is a typical example. This type of mixer has a high rotation speed of the blades of several hundred rpm and does not have a compaction effect, so it is possible to mix sufficiently evenly, and even fragile components such as limestone can be unnecessarily crushed. Absent.

As a granulator having a rolling function, a drum mixer, a pan pelletizer and the like which are usually used in a granulation process of fine iron ore can be used.

[0019]

Next, the function and effect of the present invention will be described in detail. Incidentally, the “pulverized fuel” used in the method of the present invention is:
It is a granular fuel mainly composed of carbon such as coke breeze or anthracite powder. Generally, coke breeze is often used, so in the following description, coke breeze is represented.

FIG. 1 is a schematic diagram illustrating the granulation step of the present invention. As shown in the drawing, in the methods of the first and third inventions, after sintering raw materials other than coke breeze are cut out from the cutting hopper 3 and the sintering raw materials are mixed and granulated using the high-speed rotary blade built-in mixer 1, The coke breeze (or coke breeze and quick lime) cut out from the coke breeze cutting hopper 4 is added to the mixed / granulated material , and the mixture is granulated using the rolling granulator 2.

In the method of the second and fourth inventions, sintering raw materials other than coke breeze are mixed using a high-speed rotary blade built-in mixer 1 and the mixture is formed using a rolling granulator 2. After granulation, coke breeze (or coke breeze and quick lime) is added to the granulated product, and granulation is performed again using the rolling granulator 2.

As shown in FIG. 1, the basis of the present invention is a "post-addition granulation method" for coke breeze. in this way,
A relatively small particle size (e.g., 0.5 mm
The following coke breeze is present in the surface layer of the pseudo-particles, and the coke breeze having a relatively large particle size (for example, 0.5 mm or more) is present alone without pseudo-granulation. As a result, it is possible to increase the burning speed of the coke particles (more precisely, to shorten the burning start time) and to improve the utilization efficiency thereof, thereby improving the unit air volume and the yield. In this method, a granulation technique in which powder coke having a relatively small particle size is present in the surface layer of the pseudo particle is important. The present invention is characterized in that the granulation technique is devised with a new idea.

In the third and fourth inventions, quicklime is added together with coke breeze. This is to strengthen the bond between the particulate sintered fuel and the pseudo particles. Quick lime is usually added to the sintering raw material, but if the entire amount is blended into the sintering raw material from the beginning, this quick lime is used to bind particles in pseudo particles formed by granulation before adding coke breeze. As a result, the amount of quicklime involved in the binding of the coke breeze and the pseudo particles in the subsequent stage is reduced. If the purpose is to use quick lime for strengthening the cohesion of coke breeze, it is desirable that quick lime be present in the surface layer of the pseudo-particles, and to achieve this, granulation is performed by adding quick lime together with coke breeze at a later stage. Is effective. By this method, finally, the coke breeze is in a state where it is present in the surface layer of the pseudo particle and does not easily peel off and collapse.

It is not necessary to add the whole amount of quick lime to be mixed with the sintering raw material together with coke breeze. It is only necessary to add the amount of quicklime necessary to allow the coke breeze to adhere to the surface of the pseudo particles, and the remaining quicklime is blended with the sintering material other than the coke breeze to enhance granulation before adding the coke breeze. You can use it.

It is important that the coke breeze does not peel off from the surface of the pseudo-particles and that the pseudo-particles themselves are strong. This is because even if the target pseudo-particles can be generated by the latter stage addition of the coke breeze, the pseudo-particles must not collapse during the transportation process from the granulator to the sintering pallet.

FIG. 2 is a view for explaining the relationship between the pulverization of the pseudo particles and the granulation step in the transport step. In the figure, the generated powder rate is the particle size 2 under the same raw material mixing conditions and different granulation methods.
Pseudo-particles of ~ 10 mm were sealed in a bag of synthetic resin film, charged into the raw material tank outlet, transported from there to the sintering section of the sintering machine, where the bags were collected and examined. Shows the rate of occurrence under a 1 mm sieve.

As shown in the figure, when the Erich mixer, which is a mixer incorporating a high-speed rotating blade, is used, compared with the case of using a drum mixer or a pan pelletizer, which is a tumbling granulator, the granulated material is used. Of the pseudo-particles in the transporting step can be reduced.

In particular, when the Erich mixer and the drum mixer are combined, the pseudo particles hardly collapse in the transporting step. This is because the high-speed rotating blade built-in mixer has a good kneading action between the water and the raw material, whereby the adhesive force of the fine powder raw material is increased and a strong bond is obtained. When a high-speed rotating blade built-in mixer is used and a rolling type granulator is used, the shape of the pseudo particles becomes spherical and the amount of powder is further reduced. As described above, the use of the mixer with a built-in high-speed rotary blade makes it possible to form dynamically strong pseudo particles.

In the particle size composition of the raw material, if fine powder (particles having a particle size of 0.5 mm or less) is present in an amount larger than necessary for forming pseudo particles, the fine powder becomes an adhering powder on the surface layer of the pseudo particles, and pseudo particles are formed. Go. At this time, according to the method of the present invention, the fine powder is stirred at a high speed to disperse the moisture uniformly, and the moisture is oozing on the surface of the fine powder.
Therefore, the adhered fine powder on the surface layer of the pseudo particle can come into contact with the fine powder that is not a pseudo particle, adsorb the fine powder, and the pseudo particle diameter increases. For this reason, coke breeze
It is adsorbed without being buried in the surface layer of the pseudo particles, and the combustion of coke breeze is promoted during firing.

As described above, the mixer having the built-in high-speed rotating blades has the function of extruding water on the surface of the raw material particles by vigorously stirring the raw material and water. On the other hand, the surface layer portion of the pseudo particles before the addition of coke breeze is a fine powder functioning as an adhering powder in forming the pseudo particles. The surface of the fine powder functioning as the adhering powder has oozed water, and as a result, the surface of the pseudo particle has oozed water. By adding quicklime to the pseudo-particles in a state where water has oozed out, the adhesive strength of the surface layer of the pseudo-particles increases. This is because quicklime (CaO) is slaked lime [C
a (OH) ₂ ], which functions as a binder.

As described above, raising the pseudo particle strength at the stage of adding coke breeze can be achieved by mixing with a mixer having a built-in high-speed rotating blade. By mixing the sintering raw materials and then granulating with a granulator having a rolling function, the pseudo particle strength is further increased.

The method of the present invention is characterized by utilizing the strength of the pseudo-particles and the properties of the adhered fine powder (moisture seepage on the surface of the pseudo-particles). That is, in the method of the first invention and the third invention, after mixing the sintering raw material with the high-speed rotary blade built-in mixer, adding coke breeze and granulating with the tumbling granulator, the pseudo particle surface is obtained. The coke breeze can be firmly adhered to the sintering pallet, and the collapse during the transportation process before charging the sintering pallet can be suppressed.

In the method of the second and fourth inventions, the sintering raw materials are mixed by a high-speed rotary blade built-in mixer, granulated by a tumbling granulator, and then crushed by adding coke breeze. By performing granulation with a mold granulator, the strength of the pseudo-particles further increases, and collapse during the transportation process before loading into the sintering pallet can be further suppressed.

In granulation, there are major problems in the amount of water that functions as a binder and the distribution of added water to the mixer or granulator used. As for the amount of water addition, an appropriate amount varies depending on the raw material mixing conditions, and thus the amount of water added may be determined according to the raw material mixing conditions.

First, when quicklime is not added together with the coke breeze (the method of the first and second inventions), the water content of the high-speed rotating blade built-in mixer before addition of the coke breeze is set to 90% or more of the total added water. It is desirable that the content be less than 10% of the total added water in the tumbling granulator after the addition. Also,
When adding quicklime together with coke breeze (the method of the third and fourth inventions), the amount of water added in the high-speed rotary blade built-in mixer is preferably 70% or more of the total added water amount. The reason will be described below in detail.

When water is added to the high-speed rotary blade built-in mixer before the coke breeze addition, as described above, the moisture is also humidified and mixed into the fine powder in the raw material, and strong pseudo particles can be formed. In addition, a state in which moisture has oozed out to the surface of the pseudo-particles during granulation after the addition of coke is obtained, and the coke breeze can be satisfactorily coated.

On the other hand, when the amount of water added to the tumbling granulator is increased, the total amount of added water is set to an appropriate value. Decreases the amount of water added. For this reason, at the time of granulation after the addition of coke breeze, the seepage of moisture on the surface of the pseudo particles becomes insufficient, and the coating of coke breeze becomes insufficient.

In particular, when a large amount of water is added during granulation after adding coke breeze, the following problems occur. First, the pseudo particles are combined with the coke breeze, and a part of the coke breeze is buried in the newly formed pseudo particles, and the burning state of the buried coke is deteriorated, and the sintering yield is deteriorated. . Second, when mixing with a high-speed rotating blade built-in mixer, after adding appropriate moisture to make the surface of the pseudo-particles seep moisture,
Further, when water is added by a tumbling granulator, the water content becomes excessive and the pseudo particle strength is reduced, so that the pseudo particles are easily broken down during the transportation process to the sintering pallet.

Therefore, the added water is basically unnecessary in the granulation after the addition of the coke breeze. However, if the water content of the coke breeze to be added is low before granulation, the coke breeze having a relatively large particle size, which cannot be the adhering powder of the pseudo particles, comes into contact with the pseudo particles, and the surface of the pseudo particles is reduced. Water is expected to be robbed. In this case, added water is required to such an extent that the water content of the pseudo particles does not decrease. However, even in this case, considering that the blending amount of the coke breeze with the sintering raw material is several percent, the added water of less than 10% of the total added water content is sufficient.

When quicklime is added together with coke breeze (the method of the third and fourth inventions), as described above, quicklime (CaO) is converted into slaked lime [Ca (O
H) ₂ ] to form a binder, so that slightly more water may be present. Therefore, it is preferable that the amount of water to be added in the mixer having the high-speed rotating blades is set to 70% or more of the total amount of water added, and that the remaining water be added to the tumbling granulator.

Hereinafter, the method of the present invention will be specifically described with reference to examples.

[0042]

【Example】

[Common conditions] Table 1 shows the mixing ratio of the sintering raw material and coke breeze used in the test, and Table 2 shows the particle size distribution of coke breeze.

[0043]

[Table 1]

[0044]

[Table 2]

FIG. 3 is a process chart showing a granulation method at the time of the test. (A), (b), (c) and (d) are examples of the present invention, and (e), (f) and (G) is a comparative example, (h)
Indicates a conventional method. In the figure, α ₁ and α ₂ indicate the added water distribution ratio before addition of coke breeze, and β, β ₁ and β ₂ indicate the added water distribution ratio after addition of coke breeze.

An Erich mixer was used as a high-speed rotating blade built-in mixer, and a drum mixer and a pan-paytizer were used as a rolling granulator. The specifications of these three types of mixers and granulators are as follows.

Erich mixer: dimensions: 630 mm in diameter,
Height 460mm, number of rotations: pan 30 rpm, agitator 500 rpm residence time: 1 minute Drum mixer ……… Dimensions: diameter 600mm, length 1000mm Number of rotations: pan 30 rpm, residence time: 4 minutes Pan pelletizer …… Dimensions: Diameter 600 mm, depth 200 mm Number of rotations: 15 to 30 rpm, inclination angle: 45 ° Residence time: 5 minutes [Example 1] A sintering pot test was performed on raw materials granulated by changing the granulation method. The cold strength (tumbler index, TI) of sinter and product yield of sinter were investigated. Table 3
The following shows the granulation process and the added water distribution ratio of the inventive examples, comparative examples and conventional examples. The moisture content of the sintering raw material before granulation is
Water was added to the mixer and granulator in accordance with the added water distribution ratio so that the raw material moisture value after granulation was constant at 8.0%.

[0048]

[Table 3]

The raw material after granulation was dropped eight times using a drop strength tester. This was carried out for the purpose of reproducing the phenomenon in which the granulated raw material is subjected to impact force and the pseudo-particles are powdered in the transportation process from the granulator to the sintering pallet in the sinter production facility. The number of drops was determined by the following method. That is, the granulated product was sealed in a bag of a synthetic resin film, transported from the raw material tank outlet of the sintering machine to the roll feeder outlet, and the powder generation rate under a 1 mm sieve was measured. And
The number of drops corresponding to the powder generation rate under a 1 mm sieve in an actual machine was determined.

In the sintering test, the powdered raw material corresponding to the powdering in the conveying step after granulation was charged into a cylindrical pot having a diameter of 300 mm, the bed height was 500 mm, and the superficial tower wind speed was 21.8 Nm ³ / m ² min
Was fired as a constant condition. The reason why the air tower wind speed was constant was that the product yield and cold strength were reduced only by the bond strength of the sintered raw material granules, eliminating the effect of the sintering speed which had an effect on the product yield and the sintered ore cold strength. Is to be able to be reflected.
The sintering was completed when the temperature of the exhaust gas measured by a thermocouple provided under the great reached the maximum value.

FIG. 4 is a graph showing the relationship between the granulation process of the present invention, the comparative example and the conventional example, the product yield of sintering and the cold strength of the sintered ore. As shown in the drawing, in the present invention example 1 and the present invention example 2, the product yield and the cold strength are increased as compared with the conventional example and the comparative example. In particular, in Example 2 of the present invention in which the mixture was granulated with an Erich mixer and a tumbling granulator (drum mixer or pan pelletizer) before adding coke breeze, a remarkable improvement in product yield was obtained.

FIG. 5 is a diagram showing the relationship between the product yield of sintering and the cold strength of the sintered ore and the distribution of added water during mixing and granulation, comparing the present invention example with the comparative example. is there.

As shown in the figure, when the granulation process of Examples 1 and 2 of the present invention was used, higher product strength and cold strength were observed as compared with the case where the granulation process of the comparative example was used. Was obtained over the entire range. In particular, No. 1 and No. 2 of Inventive Example 1 and Nos. 8 and 9 of Inventive Example 2 which were added when 90% or more of the total added water were mixed by the Erich mixer, particularly high product yield and cooling. The interstrength was obtained.

Embodiment 2 In this embodiment, a part of quicklime shown in Table 1 was added together with coke breeze in the granulation method of FIGS. 3 (a) to 3 (g). on the other hand,
In the granulation method of (h) and the granulation methods of (a) to (g), a case where quicklime is not added together with coke breeze is
Here is a comparative example.

In this case, in addition to the cold strength (tumbler index, TI) and the product yield of sintering, the FFS (frame front speed) of the sintered ore of [Example 1] was also investigated.

Table 4 shows the test conditions in which the granulation method and the amount of quick lime added together with the coke breeze were changed, and FIG. 6 shows the test results.
Shown in

[0057]

[Table 4]

FIG. 6 shows that when quicklime was added together with coke breeze, the product yield and the cold strength increased, and
It can be seen that the FFS also increases. The increase in the FFS under the condition where the air tower wind speed is constant reflects the improvement in the combustibility of the coke breeze, and means a reduction in the unit air volume.

Looking at the influence of the granulation method, a granulator with a built-in high-speed rotary blade (granularizer (drum mixer or pan pelletizer) as a granulator used before adding coke breeze) was used. In particular, when using an Erich mixer and a rolling type granulator in series, the product yield, cold strength and FFS
The rise is large.

Further, when an Erich mixer was used, a test was conducted in which the timing of adding water was changed. The test conditions are shown in Table 5, and the results are shown in FIG. From FIG.
In the method of the present invention, it is apparent that particularly when the water content of 70% or more with respect to the total added water is added by the Erich mixer, the product yield, the cold strength and the FFS increase. This supports that the humidity control effect of the Erich mixer is strongly exhibited when a large amount of water is added.

[0061]

[Table 5]

[0062]

According to the method of the present invention, coke breeze can be adhered to the surface layer of the pseudo-particles, and high-strength pseudo-particles can be formed without being powdered in the transportation step.
Thereby, the flammability of the coke breeze during sintering is improved, and not only the product yield of sintering and the cold strength of the sinter are improved, but also the productivity of sintering is improved. Further, by using the sintered ore produced by this method, the effect of stabilizing the operation of the blast furnace can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the outline of the method of the present invention.

FIG. 2 is a diagram illustrating a relationship between pulverization of pseudo particles and a granulation method in a transport step.

FIG. 3 is a diagram showing a granulation method in an example,
(A) to (d) are examples of the present invention, (e) to (g) are comparative examples,
(H) shows a conventional method.

FIG. 4 shows granulation steps of the present invention example, comparative example and conventional example,
It is a figure which shows the relationship between the product yield of sintering, and the cold strength of a sinter.

FIG. 5 is a diagram showing the relationship between the product yield of sintering and the cold strength of sinter, and the distribution of added water during mixing and granulation.

FIG. 6 is a graph showing the relationship between the product yield of sintering, the cold strength of FFS and sinter, and the amount of quicklime added together with the granulation method and coke breeze.

FIG. 7 is a view showing the relationship between the product yield of sintering, the cold strength of FFS and sintered ore, and the distribution ratio of added moisture when quick lime is added together with coke breeze.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (6)

(57) [Claims] 1. A sintering raw material excluding a particulate fuel is mixed and granulated by using a mixer having a built-in high-speed rotary blade, and then the particulate fuel is added to the mixture to form a mixture having a rolling function. A method for granulating a sintering raw material, comprising granulating with a granulator. 2. A sintering raw material excluding a particulate fuel is mixed by using a mixer having a built-in high-speed rotary blade, and then granulated by a granulator having a rolling function. A method for granulating a sintering raw material, comprising adding a granular fuel and granulating again with a granulator having a rolling function. 3. The method according to claim 1, wherein 90% or more of the total water added at the time of mixing and granulating the sintering raw materials is added when mixing using a mixer having a built-in high-speed rotating blade. The method for granulating a sintering raw material according to claim 1 or 2. 4. A sintering raw material excluding a particulate fuel is mixed and granulated by using a mixer having a built-in high-speed rotating blade, and then the particulate fuel and quicklime are added to the mixture to provide a rolling function. A method for granulating a sintering raw material, comprising granulating with a granulator having the same. 5. A sintering raw material excluding a particulate fuel is mixed by using a mixer having a built-in high-speed rotating blade, and then granulated by a granulator having a rolling function. A method for granulating a sintering raw material, comprising adding a granular fuel and quick lime and granulating again with a granulator having a rolling function. 6. The method according to claim 4, wherein 70% or more of the total water added at the time of mixing and granulating the sintering raw materials is added at the time of mixing using a mixer having a built-in high-speed rotating blade. A method for granulating the sintering raw material according to claim 5.