JP5821778B2 - Pretreatment method of sintering raw material - Google Patents

Description

  The present invention relates to a pretreatment method for a sintered material when the sintered material is mixed (stirred) and granulated.

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, Patent Document 1 discloses a method of controlling the amount of water sprayed by a mixer in combination with a feedforward control system and a feedback control system in order to adjust the water content of the sintering raw material (mixed raw material) to a target water value. Has been. As a result, the moisture in the sintered raw material can be accurately controlled to the target value continuously without a time delay, so that a sintered ore with stable quality can be efficiently produced.

Japanese Patent Laid-Open No. 10-17946

  However, in recent years, the number of difficult-to-granulate powdered ores obtained by crushing inferior iron ore and flotation processing (that is, raw materials for fine powder) has increased. Then, it was necessary to significantly increase the amount of expensive binder added.

  The present invention has been made in view of such circumstances, and without increasing the amount of binder used, efficiently improves the granulation properties during the production of sintered ore, and provides a fine powder material having difficult granulation properties. It aims at providing the pre-processing method of the sintering raw material which makes it usable.

In the present invention that meets the above-mentioned purpose, the total amount of the iron ore is 70 to 100% by mass, the coagulating material composed of coke powder and / or coal powder, and the auxiliary material that is the raw material for component adjustment is 30% by mass or less. A sintering raw material pretreatment method in which a sintering raw material and quick lime are charged into a stirrer,
The iron ore is a fine powder material in which 500 μm under has a particle size of 50% by mass or more and 10 μm under has a particle size of 5% by mass or less, and 30 to 60% by mass of high crystal water ore containing 4% by mass or more of crystal water is blended. Become
And the sintered material and quicklime, when stirred was charged with the stirrer, the peripheral speed of the stirring blade of the stirrer was more than 2m / s, during stirring, a mass of CaO component in the quicklime M (18/56 × 2 × M) or more and (18/56 × 6 × M) or less of water is added.

In the pretreatment method of the sintered raw material according to the present invention, the mass of the CaO component in the quick lime is M when stirring the quick lime and the sintered raw material using a fine powder material having a particle size that is difficult to granulate as iron ore ( 18/56 × 2 × M) or more (18/56 × 6 × M) of water is added, so that digestion and uniform dispersion of quick lime can be achieved while suppressing and further preventing aggregation of slaked lime due to excessive addition of moisture. Can supply enough water to make it possible.
In addition, a stirrer is used to stir the quick lime and the sintering raw material using a fine powder raw material having a particle size that is difficult to granulate, and the peripheral speed of the stirring blade is set to 2 m / second or more. This slaked lime can be dispersed as much as possible on the particle surface of each sintered raw material while being dispersed throughout the sintered raw material.
Therefore, it is possible to efficiently improve the granulation property at the time of producing the sintered ore and to use a fine powder material having difficult granulation property without increasing the amount of the binder used.

It is a graph which shows the influence which the kind of binder to add has on the granulation property of a granulated material. It is a graph which shows the influence which the amount of water added to a raw material and the peripheral speed of a stirring blade have on the granulation property of a granulated material.

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 property of the fine powder raw material which shows difficult granulation property among powder ores (iron ore) is demonstrated.
The sintering raw material to be granulated according to the present invention has extremely small particles (fine particles) with a mesh size of 10 μm or less as 5% by mass or less, and very few particles with 500 μm or less as 50% by mass or more. Is a fine powder raw material (iron ore). This fine powder raw material is different from ordinary iron ore in that the number of fine particles under 10 μm is extremely small. For example, this feature can be obtained by repeating iron ore crushing treatment and specific gravity beneficiation treatment with water. all right. 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.
More generally, the powdered ore is granulated using water. However, when the high-crystal water ore containing 4% by mass or more of crystal water is contained in the fine powder raw material by 30 to 60% by mass, the pores of the high-crystal water ore There is also a problem that water is absorbed and the strength of the granulated material deteriorates (decreases) with time.
In the above situation, it was conceived that the binder used for the granulation of the fine powder raw material is preferably one that can supply fine particles of under 10 μm and can fill the space described above.

In addition, although there exist bentonite, calcium carbonate, etc. in a solid binder, it turned out that it is difficult to disperse | distribute a solid binder uniformly to the above-mentioned fine powder raw material by the normal stirring process grade.
This is because, as described above, the particle size of the fine powder raw material is almost uniform in the size of about 10 μm over and under 500 μm, and generally the mixing of the raw material by stirring (kneading) progresses due to the wide particle size distribution. It is considered that dispersion does not proceed even when bentonite, calcium carbonate, or the like, in which the particles are not atomized and dissolved, is added, and from this viewpoint, it is preferable to add fine particles under 10 μm by another means. It was.
From the above, the present inventors, as iron ore, agitation and agitation were performed when granulating a sintered raw material using a fine powder raw material having a particle size of 500 μm under 50% by mass and 10 μm under 5% by mass. We came up with quicklime as a binder to facilitate granulation. In addition, the addition amount of quicklime is usually 0.1 mass% or more and 6.0 mass% or less by the outer coating with respect to a sintering raw material.

Next, the granulation mechanism of the sintering raw material using the fine powder raw material by quick lime is demonstrated.
Quick lime is considered to be partly hygroscopic and digested (slaked calcification) and atomized by contact with water during stirring and granulation, and easily mixed with the fine powder raw material 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 powder raw material even by dissolving in water.

Slaked lime produced by digestion of quick lime and slaked lime recrystallized by evaporation of water, etc. are fine particles with a particle size of under 10 μm, and also contain many fine particles of submicron order. This greatly contributes to the improvement of the granulation properties of the raw materials and the strength of the granules.
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 slaked lime generated, dissolving as much slaked lime as possible in granulated water, etc. It is important to disperse the slaked lime to be produced throughout the fine powder raw material (macro dispersion) and to adhere as much as possible to the particle surface of each fine powder raw material (disperse into the micro).
From the above, when mixing a difficult-to-granulate fine powder raw material and other raw materials (for example, easy-to-granulate raw material that is easy to granulate), It is also important to add quick lime that has been subjected to a treatment for reducing the amount of the lime, and to increase the amount of addition.

Calcium carbonate (molecular formula: CaCO ₃ ) contains CaO in the same manner as quicklime, 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 quicklime.
Here, the influence which the kind of binder to add has on the granulation property of a granulated material is demonstrated, referring FIG.

In addition, the test is a difficult structure in which 500 μm under which high crystal water ore containing 4% by weight or more of crystal water is blended with 0 or more than 0 and 10% by weight is 50 μm or more and 10 μm under is 5% by weight or less. 2% by mass of binder (calcium carbonate, quicklime) was added to the granular fine powder raw material (sintered raw material) and stirred with a universal mixer (a vertical mixer that revolves the axis of the rotating stirring blade). Then, it was granulated with a drum mixer. Here, as an evaluation standard for adding a binder, only a hardly granulated fine powder raw material (raw material) to which a binder was not added was stirred with a universal mixer and then granulated with a drum mixer.
Detailed conditions are: moisture: constant in the range of 9 to 12% by mass, stirring: peripheral speed 2.2 m / sec, treatment time 90 seconds, granulation: peripheral speed 1.0 m / sec, treatment time 60 seconds. In addition, the water | moisture content contained in the used raw material is the range of 3-10 mass% normally. This moisture was calculated by (Moisture content in raw material) / {(Mass of raw material after absolutely dry) + (Moisture content in raw material)} × 100 (mass%). Further, the peripheral speed means the speed of the fastest part of the universal mixer (stirrer) and drum mixer (granulator) that rotate (blades, drums, etc.).

And evaluation was performed in the following procedures.
First, the above granulated fine powder material (2 kg) was dried at 150 ° C. for 1 hour, and then passed through a 0.5 mm sieve mesh (JIS Z8801-1 “Test sieve—Part 1: Metal mesh sieve”). The ratio of 0.5 mm under was defined as the powder rate. The powder ratio was calculated by setting the powder ratio of only the fine powder raw material to which no binder was added to “1.0”.
From FIG. 1, when calcium carbonate is added to the fine powder material, the improvement in granulation is small (powder rate: 0.70), whereas when quick lime is added to the fine powder material, the granulation property is The present inventors discovered for the first time that it improved remarkably (quick lime: 0.41).
This is because quick lime is atomized by contact with water, and part of the generated slaked lime is dissolved in water, so that it can be easily mixed into the fine powder raw material. This is thought to be due to the significant contribution to improving the strength of the granules.

The powder ratio is an average value, and the powder ratio value varied by about 5% when any binder was used.
On the other hand, when the fine powder raw material used in the above test was blended with 30 to 60% by mass of high crystal water ore containing 4% by mass or more of crystal water, the powder rate was deteriorated (increased) as a whole. When calcium carbonate is used as the binder, it shows a variation of about 20 to 30%, whereas when quick lime is used as the binder, it is about 10% smaller than the variation of the powder rate value of calcium carbonate. It was. This is because even when using a high crystal water ore that can absorb water into the pores during granulation or after granulation, the above-mentioned solid cross-linking is not stable when calcium carbonate is used as a binder, whereas when quick lime is used, It was estimated that the solid cross-linking was stable, and when digestion due to moisture absorption and dissolution in water occurred, it was presumed that the solid cross-linking was relatively stable even if water absorption into the pores occurred.

In view of the above, the present inventors have come up with a pretreatment method for a sintered material that can improve the granulation property of a fine powder material having difficult granulation properties. That is, a sintered raw material (difficulty) using quick lime and a fine raw material having a particle size of not less than 50% by mass (more than 60% by mass) and not more than 5% by mass (more than 4% by mass) of 10 μm under as iron ore. (Granular fine powder raw material) is charged into a stirrer and stirred, the peripheral speed of the stirring blade of the stirrer is set to 2 m / second or more, and the mass of the CaO component in quicklime is M (18 / 56 × 2 × M) or more (18/56 × 6 × M) of water is added. 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.
This will be described in detail below.

Assuming that the amount of water consumed for the hydration reaction (digestion reaction) of quicklime is the theoretical amount of water and the mass of the CaO component in quicklime is M, the theoretical amount of water is “18/56 × M” (CaO + H ₂ O
→ Ca (OH) ₂ ) Therefore, the above-mentioned (18/56 × 2 × M) means twice the theoretical amount of water, and (18/56 × 6 × M) means six times the theoretical amount of water. The amount of water added during stirring by the stirrer is 2 to 6 times the amount of theoretical water used for the hydration reaction with quicklime.

Here, if the amount of water added during stirring is less than twice the theoretical amount of water, a large amount of unreacted quicklime is generated. That is, by setting the amount of water more than twice the theoretical amount of water, water necessary for digestion and uniform dispersion of quick lime can be sufficiently supplied, digesting as much quick lime as possible, and reducing the particle size of slaked lime produced. It is possible to dissolve as much slaked lime as possible in the granulated water.
However, when the amount of water added at the time of stirring exceeds 6 times the theoretical amount of water, after the quick lime is digested, the generated slaked flocculates due to excessive moisture, and the uniform diffusion is inhibited.
In addition, about the water | moisture content contained in the sintering raw material from the beginning, the water | moisture content on the partial surface of a sintering raw material contributes to the digestive reaction of quicklime, but the effect is compared with the water added above. Remarkably small. That is, the digestion reaction greatly depends on the amount of added water.

As described above, according to the present invention, the amount of water added at the time of stirring is defined by a multiple thereof based on the theoretical amount of water.
On the other hand, the above-described Patent Document 1 has a description that “the calculated amount of moisture brought in by each raw material uses a value obtained by subtracting the amount of water consumed by the hydration reaction by quick lime in each raw material”. If this description is presumed from the viewpoint of the present invention, the amount of water added at the time of stirring can be considered to be one time the theoretical amount of water.
However, as described above, since Patent Document 1 is a control method for adjusting the water content of the sintering raw material to the target water value, the amount of water to be added is defined by the theoretical water amount as in the present invention. There is no technical idea of this, and therefore there is no concept of prescribing it as a multiple of the theoretical water volume.
Therefore, the present invention is an extremely excellent invention obtained by conceiving that the present inventors define the amount of water to be added at the time of stirring by a multiple thereof based on the theoretical amount of water.

Further, when the quick lime and the sintered raw material are stirred using a stirrer, the peripheral speed of the stirring blade is set to 2 m / second (more preferably 3 m / second) or more.
Here, by setting the peripheral speed of the stirring blade to 2 m / second or more, the generated slaked lime is dispersed in the entire sintered raw material (macro) and adhered to the surface of each sintered raw material as much as possible (dispersed microscopically). Can do.
Therefore, the stirrer is not particularly limited as long as the peripheral speed of the stirring blade can be 2 m / second or more, and for example, the above-described universal mixer can be used. Although the upper limit value of the peripheral speed of the stirring blade is not particularly limited from the above description, it is, for example, about 35 m / second in consideration of a stirrer generally used in the world. The diameter of the stirring blade is about 0.1 to 1.5 m.

From the above, when the quick lime and the sintered raw material are stirred using a stirrer, the peripheral speed of the stirring blade is set to 2 m / second or more, and the amount of water added during stirring is used for the quick lime digestion reaction. A slaked lime that contributes to granulation is produced in a large amount by making it 2 times or more and 6 times or less of the theoretical water volume, and the produced slaked lime is dispersed throughout the sintered raw material and adhered to the surface of each sintered raw material as much as possible. It is possible to improve the granulation property of the sintering raw material.
The amount of water added at the time of stirring is 2.5 times, further 3 times, and the upper limit is 5.5 times, further 5 times, in order to improve the granulation property of the sintering raw material. It is desirable to do.
After stirring quick lime and a sintering raw material by the above-described method, the mixture is further granulated with a granulator (for example, a drum mixer) and charged into a sintering pallet to produce a sintered ore.

Next, examples carried out for confirming the effects of the present invention will be described.
In the test, a highly granulated fine raw material containing 30 to 60% by mass of high crystal water ore containing 4% by mass or more of crystal water and 30 to 60% by mass of high crystal water ore containing 4% or more of crystal water by weight. Each of the easily granulated raw materials was added with 2% by mass of quick lime on the outside, added with water, stirred with the above-mentioned universal mixer (stirrer), and granulated with a drum mixer. The detailed conditions are as follows: the amount of water contained in the raw material used: 7 to 8% by mass; the amount of water during granulation: 8 to 12% by mass; and the peripheral speed during granulation: 1.0 m / second (treatment time 60 Second). Also, the hardly granulated fine powder raw material (500 μm under is 50% by mass or more and 10 μm under is 5% by mass or less, granulation property: difficult) and easily granulated raw material (particle size excluding the particle size of the difficult granulated fine powder raw material, That is, iron ore having the particle size conditions shown in Table 1 was used for less than 50% by mass of 500 μm under or more than 5% by mass of 10 μm under, granulation property: easy).

Under the above-mentioned conditions, the amount of water (water temperature: 15 ° C. (room temperature)) added at the time of stirring with the universal mixer is variously changed, and the peripheral speed of the stirring blade of the universal mixer is 0.5 m / second, 2 m / G, and 6 m / s (stirring time: 90 seconds), and the powder rate after granulation was evaluated.
The evaluation was performed by defining the above-described mass ratio of 0.5 mm under as the powder rate. Here, the powder rate is a value α (= (mass of added water) / () obtained by dividing the amount of water added to the raw material by the theoretical amount of water when the peripheral speed of the stirring blade is 2 m / sec. The case where the mass of theoretical water)) was “1” was calculated as the powder rate “1.0”, and the powder rate (dotted line in FIG. 2) or less was regarded as acceptable.

As shown in FIG. 2, the slope (gradient) of the reduction in the powder ratio in the range of the value α from 1 to 2 is more difficult to granulate raw material (◯) than the easily granulated raw material (▲). (3), x) was found to be larger.
For any of the stirring of the difficult-to-granulate fine powder material and the easily-granulated material, by adding a water amount having a value α of 2 or more, the digestion of quick lime occurs to the same extent and fine particles are generated. However, as described above, the hardly granulated fine powder raw material has very few under 10 μm particles, and therefore the powder rate extremely increases or decreases depending on whether or not quick lime is digested. On the other hand, since the easily granulated raw material originally contains particles under 10 μm, there is no sudden increase or decrease in the powder rate even if the digestion amount of quick lime is slightly increased or decreased.
Thus, from FIG. 2, when stirring the hardly granulated fine powder raw material, the value α is set to 2 or more and 6 or less, whereby the decrease in the powder rate becomes remarkable (granulation property changes remarkably). was gotten.

Moreover, it turned out that the generation amount of the powder rate after granulation can be lowered | hung by speeding up the peripheral speed of the stirring blade using a universal mixer in stirring difficult-to-granulate fine powder raw material. In particular, by setting the peripheral speed of the stirring blade to 2 m / second or more, the powder rate could be reduced to the same extent as when the easily granulated raw material was stirred (granulation property could be improved).
This is achieved by using a universal mixer and setting the peripheral speed of the stirring blade to 2 m / second or more to disperse the slaked lime produced throughout the sintered raw material, and the slaked lime on the surface of each sintered raw material particle. By being able to adhere as much as possible.

  From the above, by using the sintering raw material pretreatment method of the present invention, without increasing the amount of binder used, efficiently improve the granulation properties during the production of sintered ore, It was confirmed that a fine powder material having difficult granulation properties can be used.

  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 in which the sintering raw material pretreatment method of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.

Claims (1)

A sintered raw material in which the amount of iron ore is 70 to 100% by mass, a coagulating material composed of coke powder and / or coal powder and a total amount of auxiliary raw materials as component adjusting raw materials is 30% by mass or less, and quicklime A pre-treatment method for sintering raw material charged in a stirrer,
The iron ore is a fine powder material in which 500 μm under has a particle size of 50% by mass or more and 10 μm under has a particle size of 5% by mass or less, and 30 to 60% by mass of high crystal water ore containing 4% by mass or more of crystal water is blended. Become
And the sintered material and quicklime, when stirred was charged with the stirrer, the peripheral speed of the stirring blade of the stirrer was more than 2m / s, during stirring, a mass of CaO component in the quicklime M (18/56 × 2 × M) or more and (18/56 × 6 × M) or less water is added as a sintering raw material pretreatment method.

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