JP5799892B2 - Granulation method of sintering raw material - Google Patents

Description

  The present invention relates to a method for granulating a sintered raw material as a raw material for producing a sintered ore which is one of raw materials for producing steel.

Sintering raw material is powdered ore made of iron ore, blending auxiliary materials and coagulants to adjust the ingredients as necessary, and mixing and granulating this powdered ore with water and binder before firing, The amount of fine powder charged into the sintering machine is reduced. This granulation is an important operation for maintaining and improving sintering productivity, and various granulation techniques have been proposed.
For example, in Patent Document 1, when granulating water by adding granulated water to a sintering raw material using a drum mixer, the pH of the granulated water is increased to more than 7, thereby improving the productivity of sintered ore. Is disclosed. This is because the mixing of the quick lime as a binder and the sintering raw material can be improved by adjusting the charging state of the sintering raw material.

Japanese Patent Laid-Open No. 10-226825

In the conventional method, although mixing of quicklime into the sintering raw material can be improved to some extent, grasping the dispersion state of quicklime in the kneaded product and granulated product obtained after addition of granulated water The strength of the produced granulated product is low. In this way, if the strength is low, for example, when the granulated material is charged into the sintering machine, the granulated material is broken and pulverized, and the productivity of the sintered ore cannot be improved.
In the future, it is expected that the amount of fine powder in the sintering raw material will increase as the quality of the powdered ore deteriorates. is expected. This powder ore is an ore containing only fine powder, and is a hardly granulated powder ore with a low content of fine particles effective for granulation (that is, a fine powder raw material). The effect is limited.

  This invention is made | formed in view of this situation, and it aims at providing the granulation method of the sintering raw material which can ensure the intensity | strength of a granulated material high.

  In the granulation method for a sintered raw material according to the first aspect of the present invention, either 1 or 2 of quicklime and slaked lime containing 50% by mass or more of 250 μm under is added to a sintered raw material used for steel production, and water is added. When granulating in the presence, the pH value of the granulated product obtained by the granulation treatment is adjusted to 11 or more and 12.6 or less.

  The granulation method of the sintered raw material according to the second invention in accordance with the above object is to add either 1 or 2 of quick lime and slaked lime containing 50% by mass or more of 250 μm under to the sintered raw material used for steel production, When kneading and granulating in the presence, the pH value of the kneaded product obtained by the kneading treatment or the granulated product obtained by the granulating treatment is adjusted to 11 or more and 12.6 or less.

  In the granulation method of the sintering raw material according to the first and second inventions, the sintering raw material uses a fine powder raw material having a particle size of 500 μm under 50 μm or more and 10 μm under 5% by mass as iron ore. It is preferable from the viewpoint that the effect of the present invention becomes more remarkable.

  In the granulation method of the sintered raw material according to the present invention, either 1 or 2 of quick lime and slaked lime containing 50% by mass or more of 250 μm under is added to the sintered raw material, and the pH value of the sintered raw material of the kneaded product or granulated product It can confirm that quick lime and slaked lime fully melt | dissolved in water by making it into 11 or more and 12.6 or less. Thereby, since the fine particles of quick lime and slaked lime can be uniformly dispersed in the kneaded product or the granulated product, the strength of the granulated product to be produced can be secured at a high level.

  In addition, when using a fine powder raw material having a particle size of 50% by mass or more and 10 μm under 5% by mass as iron ore as the iron ore, the sintered raw material having a particle size that is difficult to granulate is granulated. By doing so, the effect of the present invention becomes more remarkable.

It is a graph which shows the relationship between the pH value of a granulated material, and intensity | strength.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, the background to the present invention will be described.
First, the granulation mechanism of fine ore composed of iron ore by quick lime or slaked lime (hereinafter also referred to as sintered raw material) will be described.
Quick lime is considered to be partly hygroscopic and digested (slaked calcification) and atomized by contact with water during kneading and granulation, and easily mixed with powdered ore together with water. In addition, as quicklime, that whose CaO is 84 mass% or more is used abundantly.
Here, a part of the generated slaked lime is easily mixed with the fine ore even by dissolving in water.
In addition, it is the same also when adding slaked lime to a powdered ore instead of a quicklime, or with a quicklime, and a part of slaked lime melt | dissolves in water, and it becomes easy to mix uniformly in a powdered ore.

Slaked lime produced by digestion of quicklime and slaked lime recrystallized by evaporation of water, etc. are fine particles with a particle size of less than 10 μm, and also contain many fine particles of submicron order. It greatly contributes to the improvement of the granulation property of the ore and the strength of the granulated product.
Therefore, a large amount of slaked lime that contributes to granulation can be generated by digesting as much quick lime as possible, reducing the particle size of the generated slaked lime, dissolving as much slaked lime as possible in the granulated water, etc. It is important to disperse the generated slaked lime throughout the powder ore (macro disperse) and adhere as much as possible to the particle surface of the powder ore (disperse microscopically).
From the above, when mixing fine powder raw materials having particularly difficult granulation properties with other raw materials (for example, easy granulating raw materials that are easy to granulate), it is difficult to granulate fine powder. It is also important to add quick lime and slaked lime that have been processed to reduce the particle size, increase the amount of addition, and the like.

In addition, calcium carbonate (molecular formula: CaCO ₃ ) contains CaO similarly to quick lime and slaked lime, and has a CaO content of about 56% by mass, and may be referred to as limestone or simply lime. However, calcium carbonate is a chemically stable substance, and digestion due to moisture absorption and dissolution in water hardly occur.
Therefore, calcium carbonate is not contained in the above-mentioned quick lime and slaked lime.
From the above, when calcium carbonate is added to the fine ore, the improvement in granulation is small, whereas when quick lime or slaked lime is added to the fine ore, the granulation is remarkably improved. The present inventors discovered for the first time.
This is because quick lime is atomized by contact with water, and part of the generated slaked lime (added slaked lime) dissolves in water, making it easy to mix evenly in the powdered ore, and by the solid cross-linking This is thought to be due to the great contribution to the improvement of graininess and the strength of the granulated product.

Then, the characteristic of the fine ore which this invention makes the object of granulation is demonstrated.
The granulation target is not particularly limited as long as it is a fine ore, but among the fine ores, if the raw material is a fine powder material having a particle size of 500 μm under 50 μm or more and 10 μm under 5% by mass, The effect of the invention becomes more remarkable.
The fine powder raw material described above is a raw material exhibiting difficult granulation properties, in which particles (fine particles) having a mesh size of 10 μm or less are extremely small as 5% by mass or less and particles having a particle size of 500 μm or less are very large as 50% by mass or more. This fine powder raw material is different from ordinary iron ore in that the number of particles under 10 μm is extremely small. For example, it is understood that this feature can be obtained by repeating iron ore crushing and specific gravity beneficiation with water. It was.

When measuring the mass% of particles having a size of 500 μm or less, the fine powder material (2 kg) was dried at 150 ° C. for 1 hour, and then sieved with 0.5 mm (500 μm) (JIS Z8801-1 “Test sieve—No. 1 part: according to “metal mesh sieve”), and the mass% under the sieve was determined. Further, when measuring the mass% of fine particles under 10 μm, the measurement device of the laser diffraction scattering method (MICROTRAC (registered trademark) MT3300, manufactured by Nikkiso Co., Ltd., measurement range: 0.02) is used for the fine powder raw material after drying. ˜1400 μm) was used.
Here, the iron ore containing at least one or more kinds of fine ores (including fine powder raw materials) is a sintered raw material, and the auxiliary raw materials (component adjusting raw materials) and coagulants are included in this sintered raw material. Whether or not (for example, coke powder or coal powder) is included is arbitrary, and the sintering raw material in the present embodiment refers to a material that does not include quick lime and slaked lime (binder). In addition, when the auxiliary material and the coagulant are included in the sintered raw material, the total amount of the auxiliary material and the coagulant in the sintered material is about 30% by mass or less (the amount of iron ore in the sintered material: The auxiliary raw material and the coagulant may be added to the iron ore so as to be about 70 to 100% by mass of the sintered raw material). It is difficult to improve by the amount.

When the above-mentioned particle size configuration, that is, a fine raw material that is roughly aligned to about 10 μm and under 500 μm is granulated, a space is formed between adjacent raw material particles.
However, as described above, since the fine powder raw material has very few 10 μm-undersized fine particles filling the space, the fine powder raw material is granulated while enclosing the space, and the strength of the granulated product becomes extremely low. For this reason, even if the fine powder raw material is granulated using an adhesive binder such as cellulose, and even if the particles of the adjacent fine powder raw material can be adhered to each other, a space remains in the granulated product. Hard to improve strength.
In the above situation, it has been conceived that it is preferable that the binder used for the granulation of the fine ore, particularly the fine powder raw material exhibiting difficult granulation, can supply fine particles of under 10 μm and can fill the above-mentioned space.

In addition, although there exist bentonite, calcium carbonate, etc. in a solid binder, it became clear that it was difficult to disperse | distribute a solid binder uniformly to a fine ore by the normal kneading | mixing process grade.
This is because, as described above, for example, the particle size of the fine powder raw material is roughly aligned with a size of about 10 μm over and under 500 μm, and generally the mixing of the raw material by kneading proceeds by having a wide particle size distribution. Even if bentonite or calcium carbonate, which does not atomize or dissolve, is added, it is considered that the dispersion does not proceed. From this point of view, it is considered preferable to add fine particles under 10 μm by another means. It was.
In view of the above, the present inventors, when granulating a sintered raw material using a fine ore, particularly a fine powder raw material having a particle size of 500 μm under 50% by mass and 10 μm under 5% by mass, As a binder for facilitating grains, quick lime and slaked lime were conceived. In addition, the sintering raw material put into a sintering pallet may not knead | mix.

As mentioned above, it is necessary to ensure the uniform dispersion of quicklime and slaked lime in order to stably secure the strength of the granulated material against the increase of fine ore, particularly fine powder raw materials having difficult granulation properties. For this purpose, it is important to dissolve quick lime and slaked lime sufficiently in water. As an indicator of the dissolved state, the present inventors have conceived of using the pH value of the kneaded product or the granulated product.
Specifically, when quick lime or slaked lime dissolves in water, it becomes alkaline and the pH value of water rises. Therefore, if this pH value can be maintained at a predetermined value, the strength of the granulated product can be stably secured. The pH value of the kneaded product or granulated product was measured in accordance with the change in the addition amount of quicklime and slaked lime.

That is, when either 1 or 2 of quicklime and slaked lime containing 50% by mass or more of 250 μm under is added to powdered ore used for steel production (hereinafter also referred to as a sintering raw material) and granulated in the presence of water, In this method, the pH value of a granulated product (a mixture after granulation of a sintered raw material and quick lime and / or slaked lime) obtained by grain treatment is adjusted to 11 or more and 12.6 or less. In addition, when kneading before granulation, the pH value of the kneaded product (mixture after sintering raw material and quicklime and / or slaked lime kneaded) or granulated product obtained by kneading is adjusted to the above-described value. To do. In particular, the effect of the present invention can be achieved when granulating a fine powder raw material (difficult-to-granulate fine powder raw material) that is a fine ore (iron ore) with a particle size of 500 μm under 50 mass% or more and 10 μm under 5 mass% or less Become more prominent.
This will be described in detail below.

First, the relationship between the pH value and strength of a granulated product obtained by adding quick lime to powdered ore, kneading and granulating will be described with reference to FIG.
The powder ore used in FIG. 1 is of two types, a hardly granulated raw material (●) and an easily granulated raw material (Δ). The easily granulated raw material is a raw material having a particle size in which 500 μm under is less than 50% by mass and 10 μm under is more than 5% by mass, and the hardly granulated raw material is 500 μm under with 50% by mass or more and 10 μm under. Is a raw material having a particle size of 5% by mass or less.
Moreover, the particle size of quicklime contains 50 mass% or more of 250 μm under.
And the intensity | strength of the granulated material was calculated | required by extracting the thing about 7-9 mmphi from the produced granulated material, and measuring the crushing strength after drying completely.

From FIG. 1, it was confirmed that the strength of the granulated product increased as the pH value of the granulated product increased for both the easily granulated raw material and the hardly granulated raw material. In particular, the strength of the hardly granulated fine powder material was greatly improved from about pH 11 (0.8 MPa or more).
In addition, even at pH 11 or higher, an increase in strength was confirmed as the pH value increased, and it was confirmed that the strength improved to pH 12.6.
From the above, the pH value of the granulated product is defined as 11 or more and 12.6 or less, but the lower limit is preferably 11.5.
This test result was obtained by granulating without kneading even when slaked lime was used instead of quick lime, or when the pH value of the kneaded material was measured instead of the granulated material. The same tendency was obtained when the pH value of the obtained granulated product was measured.

Here, as means for ensuring the pH value of the above-mentioned kneaded product and granulated product, since the amount of quick lime and the amount of slaked lime affect the stirring conditions during kneading and granulation, those Any one or a combination of the adjustments is effective. In addition, in order to adjust the pH value, it is necessary to make fine particles so that quick lime and slaked lime can be easily dissolved in water. Therefore, the particle size is more than 50% by mass (more than 60% by mass) of 250 μm under. It was stipulated to include. The reason why the upper limit value of 250 μm under is not specified is that it may be 100% by mass.
In addition, since it is necessary to measure an object directly on the sintering machine side so as not to change the dissolved state of quick lime and slaked lime, the pH measuring means is commercially available for kneaded materials and granulated materials. There is a method of measuring by inserting a general-purpose soil pH measurement sensor.

From the results shown in FIG. 1 described above, since the strength of the granulated material was increased with an increase in the pH value for the easily granulated raw material, the type of the powdered ore is not particularly limited. Absent.
However, since the effect on the difficult-to-granulate fine powder material was remarkable, in particular, the difficult-to-granulate fine powder material, that is, 500 μm under is 50% by mass (further 60% by mass) and 10 μm under is 5% by mass ( Furthermore, it is preferable to treat a raw material of 4% by mass or less since the effects of the present invention can be obtained more remarkably. The reason why the upper limit value of 500 μm under is not specified is 100% by mass, and the reason why the lower limit value of 10 μm under is not specified is that 0% by mass may be used.
Here, the easily granulated raw material is not limited to the raw material having the above-mentioned particle size, and is a raw material other than the hardly granulated raw material, that is, 500 μm under is less than 50 mass% or 10 μm under is more than 5 mass%. A raw material having a particle size of

As described above, in the present invention, the pH value is specified to be 11 or more and 12.6 or less. However, the fact that the measurement object is different from the pH value described in Patent Document 1 will be described below. .
Moisture is usually attached to the sintered raw material, and the ratio of the granulated water added to the sintered raw material is about 10 to 50% by mass of the water attached to the sintered raw material. The water adhering to the sintering raw material includes, for example, water already adhering at the time of receiving (importing) the sintering raw material, and rain water adhering to the sintering raw material loaded in the raw material yard.
For this reason, as in Patent Document 1, for example, granulated water having a pH of 11 is used as the granulated water to be added to the sintering raw material, and this granulated water is added in a common sense amount within the above range. However, since the pH value of the produced granulated product is 8 or less, the strength of the granulated product is low from the above results. Even if 10% of the adhering water having a pH of 7 and 90% of the granulated water having a pH of 11 are mixed, the pH value is only about 8. This is because pH is a function of hydrogen ion concentration, and it is difficult to easily raise the pH value with granulated water, and it is substantially difficult to raise the pH value of the granulated product with pH control of the granulated water. It is shown that.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, in the step of separating 20% by mass of a difficult-to-granulate fine powder raw material (hereinafter also referred to as a sintered raw material) from the whole powder ore, and adding water (pH 7 to 9) to this and kneading at high speed, The relationship between the added amount of particle size: 50 μm or more under 250 μm) and the resulting granulated product was investigated. In the test, a sample after kneading (kneaded material) was collected, the pH value was measured by inserting the above-mentioned soil pH measurement sensor, and a granulated material of 7 to 9 mmφ was sampled and completely removed at 150 ° C. It was dried and its crushing strength was measured.
Test conditions and test results are shown in Table 1. In addition, the addition amount of quicklime is the quantity (outer coating) with respect to a hardly granulated fine powder raw material.

As shown in Table 1, the pH value was 10 or less and the crushing strength was relatively low (less than 0.8 MPa) when the amount of quicklime added was up to 0.5 mass%.
On the other hand, when the addition amount of quicklime was 1% by mass, the pH value was 11, and the strength increased dramatically with this (0.8 MPa or more). Furthermore, when the amount of quicklime added was 2% by mass, the pH value further increased and the strength also increased. When the addition amount of quicklime was 3% by mass, the pH value did not change to 12.6, but the strength slightly increased.
This test result is obtained by granulating without kneading even when slaked lime is used instead of quick lime, or when the pH value of the granulated product is measured instead of the kneaded product. The same tendency was obtained when the pH value of the obtained granulated product was measured.

  From the above, by using the granulation method of the sintered raw material of the present invention, the strength of the granulated material produced using the powdered ore, especially using the sintered raw material using the difficult-to-granulate fine powder material It was confirmed that the strength of the granulated product could be secured at a high level.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the granulating method for a sintered raw material of the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.

Claims (3)

When either 1 or 2 of quick lime and slaked lime containing 50% by mass or more of 250 μm under is added to the sintering raw material used for steel production, and granulated in the presence of water, A granulation method of a sintering raw material, wherein the pH value is 11 or more and 12.6 or less. When either 1 or 2 of quicklime and slaked lime containing 50% by mass or more of 250 μm under is added to a sintering raw material used for steel production, and kneaded in the presence of water and granulated, the kneaded product obtained by the kneading process Or the granulation method of the sintering raw material characterized by making pH value of the granulated material obtained by the said granulation process into 11 or more and 12.6 or less. 3. The method for granulating a sintered raw material according to claim 1 or 2, wherein the sintered raw material is a fine powder raw material having a particle size of not less than 50% by mass and not more than 5% by mass of 10 μm under as the iron ore. A method for granulating a sintered raw material.

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