JP5817643B2 - 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, in Patent Document 1, in the method for producing sintered ore, when using quicklime as a binder, the temperature of water added at the time of mixed granulation is set to 40 ° C. or higher so that the granulation property of the sintered raw material is increased. A method for improving the productivity of sintered ore is disclosed. This is because the activity (digestion) of quicklime increases as the temperature of the water to be added increases, that is, as it increases to 40 ° C, 60 ° C, and 80 ° C.

Japanese Patent Publication No.58-38494

However, in recent years, the number of difficult-to-granulate powdered ores obtained by crushing inferior iron ore and flotation processing (that is, fine powder raw material) has increased, and quick lime is used as a binder for this fine powder raw material. At that time, even if the above-described conventional method is applied, the granulation property is lowered and the necessary granulation property cannot be maintained. Although the activity of quick lime can be improved by increasing the temperature of the water to be added to 40 ° C. or higher, it has an effect of improving granulation for fine powder raw materials having difficult granulation. This is considered to be limited.
For this reason, it becomes difficult to use a fine powder material having difficult granulation properties, and even if used, it is necessary to greatly increase the amount of binder used in order to improve granulation properties.

  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, at the time of stirring, the temperature range of less than 20 ° C. or higher 40 ° C. Add water.

The pretreatment method of the sintered raw material according to the present invention uses a stirrer for stirring quick lime and the sintered raw material using a fine powder material having a particle size that is difficult to granulate as iron ore, Since the peripheral speed is 2 m / sec or more, quick lime (generated slaked lime) can be uniformly dispersed in the sintered raw material, and the granulation property of the sintered raw material can be improved.
Moreover, since the temperature of the water added at the time of agitation with quick lime and the sintering raw material using the fine powder raw material of the particle size which becomes difficult granulation is made into the range of 20 degreeC or more and less than 40 degreeC, digestion reaction of quick lime fully progresses In addition, it is possible to suppress and further prevent the evaporation of moisture accompanying digestion of quicklime. Thereby, the uniform dispersion | distribution effect of the generated slaked lime by melt | dissolving in water can be expressed, the variation in the generation amount of the fine powder after granulation can be reduced, and the stable granulation property can be exhibited.
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 temperature of the water added at the time of stirring and the peripheral speed of a stirring blade has 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).

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. When mixing and stirring the granular fine powder raw material) in a stirrer, the peripheral speed of the stirring blade of the stirrer is set to 2 m / second or more, and water in a temperature range of 20 ° C. or more and less than 40 ° C. is added during stirring. It is a method to do. 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.

In order to granulate the sintered raw material, it is important not only to have the activity (digestion) of quick lime but also to disperse the quick lime (generated slaked lime) uniformly in the sintered raw material. They made clear for the first time by various experiments.
As a result, it has been devised that high-speed stirring (hereinafter also referred to as strong stirring) using a stirrer is effective in improving granulation properties. The stirrer is not particularly limited as long as the peripheral speed of the stirring blade can be 2 m / second or more. For example, the above-described universal mixer can be used.

However, it has been clarified that by vigorous stirring for the purpose of uniform dispersion of quicklime, the reactivity of quicklime is also improved and the temperature of water rises, so that water evaporates. For this reason, the following effects, that is, quick lime is atomized by contact with water, and part of the generated slaked lime dissolves in water, so that it is easily mixed with the sintering raw material. It has been found that the effect of improving the granulation property of the powder becomes difficult to express.
As a countermeasure against these problems, the inventors have invented that the temperature of water added during stirring can be adjusted to the above-described temperature range to prevent water evaporation and improve granulation.

That is, the present invention regulates the peripheral speed of the stirring blade of the stirrer as described above, and further regulates the temperature of water added during stirring, thereby preventing evaporation of moisture and producing slaked lime. It was conceived to improve the granulation properties of the sintered raw material by uniformly dispersing it throughout the sintered raw material and adhering it as much as possible to the particle surface of each sintered raw material.
Hereinafter, the reason why the peripheral speed of the stirring blade of the stirrer and the temperature of water added during stirring are specified will be described with reference to test results.

  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 conditions for moisture and granulation are the same as the detailed conditions described above. 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 conditions described above, the temperature of the water added during stirring with the universal mixer is variously changed, and the peripheral speed of the stirring blade of the universal mixer is adjusted to 0.5 m / second and 2 m / second (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 calculated as “1.0” when the easily granulated raw material is stirred and the peripheral speed of the stirring blade is 0.5 m / second and the temperature of the water to be added is 40 ° C. The powder rate (dotted line in FIG. 2) or less was regarded as acceptable.

First, the effect of high-speed stirring on the granulation property will be described with reference to FIG.
As shown in FIG. 2, after granulation, compared with the case where the difficult-to-granulate fine powder raw material was stirred at a high speed (●: 2 m / second) and not stirred at a high speed (■: 0.5 m / second). It was confirmed that the powder rate of the powder can be significantly reduced. This is because the slaked lime generated by strong stirring is uniformly dispersed in the hardly granulated fine powder raw material, that is, the generated slaked lime is dispersed (macro dispersed) throughout the hardly granulated fine powder raw material. This is because it was adhered to the surface of the raw material particles as much as possible (dispersed microscopically).

Therefore, when the quick lime and the hardly granulated fine powder 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.
On the other hand, the upper limit value of the peripheral speed of the stirring blade is not particularly limited from the above description, but it is, for example, about 35 m / second in consideration of a stirrer generally used in the world.
In addition, the diameter of the stirring blade of the stirrer to be used is about 0.1 to 1.5 m.

Next, the influence of water temperature on the granulation property will be described.
As the temperature of water increases, the degree of activity of quicklime increases, and the production of slaked lime that contributes to granulation is promoted. For this reason, when the temperature of water was less than 20 degreeC, while the temperature fell, the digestion reaction of quicklime was suppressed, and as shown in FIG. 2, the tendency for the powder rate after granulation to become high was obtained.
Therefore, the temperature of the water added at the time of stirring was set to 20 ° C. or more at which the average (plot point) of the powder ratio was 1.0 or less. In addition, when the temperature of water is 20 degreeC, the dispersion | variation in a powder rate (deviation: the upper end of the error bar shown by "I" in FIG. 2) is also 1.0 or less.

Moreover, as mentioned above, the activity of quicklime increases as the temperature increases, but under conditions of high-speed stirring, evaporation of moisture was confirmed at a water temperature of 40 ° C. or higher. This evaporation phenomenon became more prominent as the water temperature increased.
As described above, since the occurrence of uniform dispersion effect due to the generated slaked lime being dissolved in water becomes difficult due to the occurrence of evaporation, as shown in FIG. 2, the variation in the amount of fine powder after granulation becomes large and stable. It was difficult to produce a granulated product (the upper limit of the variation in the powder rate at 40 ° C. was over 1.0).
Therefore, the temperature of the water added at the time of stirring was set to less than 40 ° C. at which the upper limit of the variation in the powder rate was 1.0 or less.

  From the above results, the peripheral speed of the stirring blade of the stirrer was set to 2 m / second, and the temperature of water added during stirring was set to 20 ° C. or more and less than 40 ° C., but the granulation property was further improved (the average of the powder rate was further increased). In order to further reduce the variation in the powder rate, the upper limit is preferably set to 38 ° C.

The water added at the time of stirring can be adjusted to the above temperature range by, for example, heating using a heating device. However, since this temperature range is not high as in Patent Document 1, a special heating device is used. It is also possible to adjust without using (without making new capital investment).
For example, there is a method in which the piping through which the water to be added flows passes through the facility (in the vicinity of the facility) that holds heat installed in the factory, and the water in the piping is heated in the atmosphere of the facility. is there. Here, as the equipment, for example, an exhaust gas chimney can be used. In this case, a pipe is provided on the side of the chimney, and the temperature of the water is adjusted to the above temperature range simply by flowing water into the pipe. it can.
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.
The test was performed by adding 2% by mass of quick lime to the hardly granulated fine powder raw material (500 μm under: 50% by mass, 10 μm under: 5% by mass) used in FIG. After stirring with the above-mentioned universal mixer, it was granulated with a drum mixer. The conditions for moisture and granulation are the same as the detailed conditions described above.
Under the conditions described above, the temperature of water added during stirring with the universal mixer is adjusted to 35 ° C. and 40 ° C., and the peripheral speed of the stirring blade of the universal mixer is set to 2 m / second (stirring time: 90 seconds). ), And investigated the variation in the powder rate after granulation. The results are shown in Table 2.

  In the investigation of variation, the powder rate was defined as the mass ratio of 0.5 mm under. Further, the powder rate was calculated as “1.0” when the easily granulated raw material was stirred when the peripheral speed of the stirring blade was 0.5 m / second and the temperature of the water to be added was 40 ° C. And the investigation of the variation in the powder rate was performed three times at 35 ° C and 40 ° C. Furthermore, this investigation was conducted for the case where the average value of the powder ratio at each temperature was the same (0.78).

As is apparent from Table 2, when water with a temperature of 35 ° C. is added during stirring of the hardly granulated fine powder raw material, the powder ratio is 1.0 or less (maximum 0.93), which can be adopted in the actual machine. Level (evaluation: ○). On the other hand, when water at a temperature of 40 ° C. is added during stirring of the hardly granulated fine powder raw material, the powder ratio may exceed 1.0 (1.03), resulting in a variation in the powder ratio that cannot be adopted in the actual machine. (Evaluation: x).
From the above, it was confirmed that by using the sintering raw material pretreatment method of the present invention, the generation amount and variation of fine powder after granulation can be reduced and stable granulation can be exhibited. 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.

  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, at the time of stirring, the temperature range of less than 20 ° C. or higher 40 ° C. A pretreatment method of a sintering raw material characterized by adding water.

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