JP2790008B2 - Pre-processing method for sintering raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pre-treating a sintering raw material, which is performed prior to a granulation step in a sinter ore manufacturing step.

[0002]

2. Description of the Related Art In the production of sintered ore, first, iron ore,
Some sintering raw materials such as limestone are appropriately blended, an appropriate amount of water is added, granulation is performed, and the resultant is charged into a sintering pallet to form a sintering raw material packed layer. Next, the upper portion of the sintering material-filled layer is ignited, and air is sucked from below to fire sequentially from the upper portion. After firing, the sintering pallet is tilted to crush and cool the fired product (called a sintered cake), and then a product having a certain particle size or more is supplied as sinter to the blast furnace raw material. The powder having a certain particle size or less (referred to as ore return) is again used as a raw material for sintering.

In this sinter ore production process, granulation is particularly
It affects the air permeability of the raw material filling layer during firing, and greatly affects the productivity of sinter. Therefore, improvement of the granulation efficiency in the granulation step is an important means for improving productivity.

Conventionally, drum mixers have been the mainstream used for granulation. However, in recent years, sintering raw materials, especially iron ore, tend to become finer, and a granulation technology that uses a high-performance mixer or granulator other than a drum mixer to further promote pseudo-particles has also been reported. Have been.

For example, it has been proposed to use a vibrating kneader and a vibrating granulator as a granulator of such a sintering raw material. In this method, first, the sintering raw material is condensed and kneaded using a vibrating kneader having a consolidation medium in a container, so that moisture is oozed on the surface of the raw material. Further, the raw materials are combined using a vibrating granulator that performs circular vibration or horizontal oscillating vibration. As a result, the pseudo particle size increases, and the gas permeability of the raw material packed layer increases.

Another example is disclosed in Japanese Patent Application Laid-Open No. 57-17442.
No. 0 proposes a method of treating a sintering raw material by using a fret mill, a ball mill, an Erich mixer, a twin-shaft kneader, or the like. In each of these methods, a mechanism is used in which the surface of the raw material is evenly coated with moisture to increase the capillary force of the raw material, and as a result, the pseudo particle diameter increases.

However, in these methods, when an external force such as a shearing force is applied to the sintering raw material, the granular material itself may be crushed and the particle size may be reduced. Japanese Patent Laid- Open Publication No. 3-166322 discloses that the raw material after kneading is in the form of flakes, but is strictly an aggregate of fine powder. It is naturally expected that such an aggregate of fine powder contains fine limestone and coke breeze inside. Therefore, it is expected that the reaction of the fine limestone and the coke breeze is delayed or remains unreacted. As a result, the sintering time is prolonged or the sintering yield is reduced. As a result, there is a concern that productivity may be reduced.

Therefore, it is important to consider a mixing method in consideration of the particle size of the raw material after mixing, but this point has not been clarified. Furthermore, the amount of suitable moisture when using such a mixer or granulator is not quantified, and the combined effect of a high-performance granulator or mixer and moisture is not clarified.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for improving the productivity of sinter by improving the granulation efficiency in the granulation step of a sintering raw material. It is. When the ratio of particles with a particle size of 0.5 mm or less in the sintering raw material increases, the granulation state deteriorates in the drum mixers that have been widely used so far, and the ratio of the particles with a particle size of 0.5 mm or less coalescing with other particles is reduced. To a lesser extent, a more specific object of the present invention is to provide a method for improving the granulation efficiency of such sintering raw materials.

[0010]

As described above, in the production of sintered ore, improvement of granulation efficiency is an important factor for improving the productivity. To cope with recent sintering raw material refinement, it is necessary to use a high-performance granulator or mixer other than a drum mixer. However, depending on the model, the sintering raw material is crushed, resulting in a decrease in productivity. Also, the appropriate amount of water has not been clarified. To clarify the suitability moisture content when using the granulator or mixer without crushing the raw material selection and these granulator or mixer are required.

The inventors of the present invention have studied the techniques so far to achieve the above-mentioned object, and found that the stirring blade is required from the viewpoint that the pretreatment of the granulated raw material is necessary and the sintering raw material is not crushed. The inventors have found that more efficient granulation can be achieved by further adjusting the water content to a predetermined value using the built-in mixer, and completed the present invention.

Therefore, the gist of the present invention is that when a sintering raw material having a particle size of 0.5 mm or less and 30 wt% or more is granulated, a shear force is applied in advance without substantially crushing the raw material. It is a method for pre-treating a sintering raw material, wherein the water content of the sintering raw material is adjusted to 6.5 to 10.0% during the mixing.

From another aspect, the present invention provides a method for producing a powder having a particle size of 0.5
Before granulating a sintering raw material having a diameter of 30 mm% or less, the water content of the sintering raw material should be 1.0 to 3.0% larger than the water absorption index (%) measured by the centrifugal separation method. This is a sintering raw material pretreatment method, characterized in that the raw material is humidified and mixed while applying a shearing force without substantially crushing.

The present invention is directed to a sintering raw material having a grain size of 0.5 mm or less and 30 wt% or more, which is used to improve the granulation properties of the sintering material thus refined, particularly iron ore. Is a problem.

The raw material having a coarser particle size may be granulated according to a conventional method. In addition, even such coarse particles may be classified and subjected to the pretreatment of the present invention for fine particles having a particle size of 0.5 mm or less and 30 wt% or more. Although there has been a conventional method of applying a shearing force to a raw material using a mixer as a pretreatment method for the raw material for sintering, adjustment of the water content has not been clarified.

In this regard, in the present invention, for example, by using a mixer having a built-in stirring blade, moisture is added in a state where a shearing force is applied to perform humidity control mixing. Specifically, the water content is adjusted to 6.5 to 10.0% while mixing using a mixer such as an Erich mixer, or the water content is adjusted to 1.0 to 3.0% higher than the water absorption index.

At this time, the reason why the water content is set to 6.5 to 10.0% is that if the water content is less than 6.5% by weight, the water content is insufficient, while if it exceeds 10.0%, the water content is excessive.
Further, according to a preferred embodiment of the present invention, the humidity of the raw material is adjusted by using a mixer having a built-in high-speed stirring blade at a value of 1 to 3% larger than a water absorption index (%) measured by a centrifugal separation method. By mixing, the adhesive force of the fine powder raw material further increases. However, if the amount is out of the range of 1 to 3%, the amount of water present on the surface of the particles of the sintering raw material may be insufficient or excessive, so that the effect of the pretreatment method based on the method of the present invention is not sufficient. I can't get it.

In the present invention, when regulating the amount of water,
Compared with the case of performing with the water content, when performed with the water absorption index, the water content that contributes to granulation is clear,
Considered more practical. In addition, the water absorption index is obtained by measuring each blended raw material in advance and integrating them.

[0019]

The present invention will now be described in more detail by taking a mixer incorporating a high-speed stirring blade as an example of a suitable mixer capable of applying a shearing force without substantially crushing the sintering raw material at the time of mixing. The function and effect will be described below.

First, FIGS. 1 (a) and 1 (b) compare the quasi-particle structure in a case where a mixer having a built-in high-speed stirring blade is used and in a case where a vibratory kneader is used. As shown in FIG. 1 (a), when a mixer having a built-in high-speed stirring blade is used, fine powder adheres around coarse particles as nuclei.
On the other hand, as shown in FIG. 1 (b), when a vibrating kneader is used, the raw materials are finely pulverized and then interconnected.

[0021] Here and coke as a heat source Importantly in sintering, der that also contains many following fine grain size 0.5mm for limestone as a flux
You . When a mixer incorporating a high-speed stirring blade is used, particles having a small particle size are distributed on the surface of the pseudo particles. Considering that the sintering reaction is due to gas heat transfer from above, the pseudo-particle structure using a mixer incorporating a high-speed stirring blade has a higher reaction speed.

On the other hand, when a vibrating kneader is used, a large amount of coke breeze or limestone having a small particle size exists in the pseudo particles. For this reason, the reaction rate becomes slow, or in some cases, the unburned material remains. As a result, there is a fear that the yield or the cold strength of the sintered ore is reduced.

The pseudo particles after each mixing were decomposed to the constituent particle level, completely dried, and the particle size distribution was measured. When a vibrating kneader was used, -0.125 was used.
While the particle size was reduced to about 30% and -1.0 mm to 90%, when a mixer having a high-speed stirring blade was used, almost no change in the particle size was observed.

As described above, in order to carry out mixing in the presence of a shearing force according to the present invention, specifically, a mixer (for example, an Erich mixer) having a built-in high-speed stirring blade is used. As another example, a blade that rotates in the reverse direction to the drum may be mounted in the drum mixer.

Taking an Erich mixer as an example, the shearing force at that time is such that the rotation speed of the stirring blade is 100 to 700 rp.
m, and mixing at a pan rotation speed of 30 to 70 rpm is sufficient to achieve the intended object of the present invention. There are the following two effects on granulation by applying a strong external force as a shear force to the particles by using a mixer equipped with a high-speed stirring blade.

The first is to uniformly disperse the water in the raw material, that is, to make the water supplied to each particle uniform. Second, the moisture contained in the particles is oozed to the surface to increase the adhesion of the particles. In other words, the specific degree is not limited as long as the above-described action is exerted and as a result a shearing force for performing high-strength granulation is applied.

At this time, as for the particle size condition under which the effect of using the mixer incorporating the high-speed stirring blade is exhibited, as described above, the particle size distribution measured in the particle size configuration before granulation and measured after complete drying. Particle size 0.5mm or less is 30wt
% Or more. At that time, it is appropriate that the water content is 6.5% or more and 10.0% or less, and from another point of view, the water absorption index is more than 1.0% and 3.0% or less than the water absorption index measured by centrifugation. Is appropriate.

With respect to powder having a particle size of 0.5 mm or less and less than 30 wt%, the ratio of particles functioning as adhering powder in granulation is low. Sufficiently high air permeability can be ensured by granulation using a drum mixer that is widely used.

Further, up to a certain value of the moisture contained in the particles, even if they are mixed with a high-speed stirring blade, they cannot ooze out on the surface. In short, when water is absorbed into the particles at a certain value or more, the distribution state of the water in the particles becomes a problem. If the water content is 6.5% or more and 10.0% or less, or the water absorption measured by the centrifugation method is greater than the water absorption index in the range of 1.0% or more and 3.0% or less, a mixer with a built-in high-speed stirring blade The distribution state of water in the particles differs depending on whether or not water is used. When a mixer with a built-in high-speed stirring blade is used, water seeps out onto the surface of the raw material. Moisture content
If the water content exceeds 10.0% or exceeds 3.0% of the water absorption measured by the centrifugal separation method, the water content will be excessive regardless of the use of a mixer with a built-in high-speed stirring blade. A part of the water may rise to the surface of the particles to form a thick water film, or if the amount of the water is too high, the particles may not be adsorbed to the particles and fill the voids between the particles. Then, although the pseudo particle diameter increases, the strength of the pseudo particles decreases. As a result, the pseudo particles collapse during firing, and the air permeability deteriorates.

That is, if the water content is less than 6.5% or the water absorption measured by a centrifugal separation method is less than + 1.0%, the effect of using a mixer having a built-in high-speed stirring blade is not exhibited. When the water content exceeds 10.0% or when the water absorption measured by centrifugation exceeds + 3.0%, the air permeability itself deteriorates. Next, an embodiment of a mixer incorporating a high-speed stirring blade in an actual sintering operation will be described.

The grain size of all raw materials for sintering is 0.5 mm
When the following composition ratio is 30 wt% or more, all the raw materials are humidified and mixed by a mixer having a built-in high-speed stirring blade. Alternatively, if all the raw materials cannot be processed by the mixer with the built-in high-speed stirring blades due to circumstances such as the supply of all the raw materials of the sintering is larger than the processing capacity of the mixer with the built-in high-speed stirring blades, a part of the raw material is adjusted. Wet mixing alone is also effective.

The grain size of all raw materials for sintering is 0.5 mm
If the following composition ratio is less than 30 wt%, the particle size is 0.5
It is sufficient to select a brand with a fine particle size of the raw material so that the composition ratio of not more than 30 mm% is 30 wt% or more, and supply it to a mixer having a built-in high-speed stirring blade to mix and control the humidity.

[0033]

EXAMPLES (Example 1) The ratio of the particle size of all the sintered raw materials to the particle size of 0.5 mm or less was 30%.
The effect of the granulation method based on the present invention under the precondition of not less than wt% was confirmed by a pot firing test. The firing was performed using a pot having a diameter of 300 mm, a layer thickness of 500 mm, a suction pressure of 1050 mm, and a constant water column. The ignition conditions were LPG 70 Nl / min for 2 minutes, and the firing was completed at BTP at the exhaust gas temperature.

Tables 1 and 2 show the raw material composition along with the water absorption index and the particle size in the dry state (ratio of -0.5 mm particles).
Shown in Here, the water absorption index was a water value measured by a drying method after centrifugation at 2300 RPM for 30 minutes at a rotation radius of 140 mm after immersing the raw material in water for 24 hours. FIG. 2 shows a list of granulation methods employed in this example, and Table 3 shows specifications of the granulator. An Erich mixer was used as a mixer incorporating high-speed rotating blades.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

The present invention was carried out under the conditions shown in Table 4 in order to evaluate the effects of the mixing and granulation methods and the amount of water on the air permeability and the production rate.

[0039]

[Table 4]

The results are shown in FIGS. 3 and 4. 6.5 moisture
When ア イ 10% or 1 to 3% more than the water absorption index was used, when the Erich mixer was used, the raw material permeability was improved, and the production rate was improved. An improvement was also observed in the method of supplying 50% of the raw material to Erich (granulation method).

Next, the present invention was carried out under the conditions shown in Table 5 in order to evaluate the effects of the mixed granulation method on air permeability, production rate, and yield.

[0042]

[Table 5]

Table 6 shows the results. Compared with the case using only the drum mixer, the case using the Eirich mixer or the rod mill has improved air permeability. However, in the case using the rod mill, the product yield is deteriorated and the production rate is lower than in the case using the Erich mixer.

[0044]

[Table 6]

Example 2 The raw material particle size conditions under which the effect of the granulation method according to the present invention is exhibited were confirmed by a pot firing test. The pot firing test conditions are the same as in Example 1. Table 7 shows the raw material conditions.

[0046]

[Table 7]

Here, the present invention was carried out under the conditions shown in Table 8 in order to evaluate the influence of the selected granulation product on the air permeability production rate. The formulations shown in Table 7 were divided as follows, and the air permeability and the production rate were compared. Table 8 shows the test conditions.

[0048]

[Table 8]

The water content of the system A in cases I and II is from the water absorption index of + 0% to the water absorption index of + 4.0%.
To the B system in cases I and II, and the case
For III and IV, the water absorption index was fixed at + 2.0%.
Table 9 shows the results.

[0050]

[Table 9]

SF Hamasley and SF Lidose are selected for the A system, and the A system water content is 6.5 to 10%, or the water absorption index is +1.0.
When adjusted to ~ 3.0%, the air permeability became 20 JPU or more, and the production rate was improved.

[0052]

According to the present invention, when the particle size of the sintering raw material is low, the permeability of the raw material packed layer can be increased, and the productivity can be improved. Also, regardless of the particle size of the raw material, by pre-treating the fine-grain raw material, the air permeability can be increased and the productivity can be improved. This is because the proper mixing and granulation method was achieved by selecting the model and optimizing the water content.

[Brief description of the drawings]

FIG. 1 is a comparison diagram of a pseudo particle structure in a case where a mixer having a built-in high-speed stirring blade is used and in a case where a vibration type kneader is used.

FIG. 2 is a comparison table of the granulation methods of the present invention example and the conventional example used in the examples.

FIG. 3 is a graph showing a result in an example.

FIG. 4 is a graph showing a result in the example.

Claims (2)

(57) [Claims] 1. A portion having a particle size of 0.5 mm or less is 30 wt%.
When granulating the above-mentioned sintering raw materials, the raw materials are mixed in advance while applying a shearing force without substantially crushing, and the water content of the sintering raw materials is 6.5 to 10.0% during this mixing. A method for pre-processing a sintering raw material, characterized in that: 2. When granulating a sintering raw material in which a portion having a particle size of 0.5 mm or less has a content of 30 wt% or more, the water content of the sintering raw material is set to be smaller than the water absorption index (%) measured by a centrifugal separation method in advance. ~ 3.
A sintering raw material pretreatment method, characterized in that the raw material is subjected to humidity control and mixing while applying a shearing force without substantially crushing the raw material so as to increase the value by 0%.