JP7130904B2 - Granulation method by thin and uniform watering - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique of granulating raw materials used in producing sintered ore.

Sintered ore, which is the main raw material for blast furnaces, is made by adding a solvent such as limestone to powdered iron ore and sintering it in a sintering machine.
In the sintering machine, sintered ore raw materials (raw materials for sintering), mainly iron ore, are filled on a pallet truck, and the air is sucked from below to continuously burn the coke fine in the raw materials. Calcium ferrite-based melt is produced by heating to produce sintered ore in which fine ores are bonded together by the melt.

Therefore, the air permeability of the filled sintering raw material affects the amount of air sucked (oxygen supply amount) passing through the pallet, that is, the combustion rate (productivity) of coke breeze.
Therefore, in the sintering process, water is generally added to the raw material, and a granulator (e.g., drum mixer, pan pelletizer, etc.) is used to close the voids in the raw material packed bed and deteriorate the air permeability during sintering. Pseudo-particles (granules) are obtained by adhering the fine ore to the coarse-grained ore, which is the core, to ensure the air permeability of the raw material packed bed (raw material for sintering filled on the pallet truck).

Techniques for producing raw materials for sintering are disclosed in Patent Documents 1 to 3, for example.
Patent Document 1 improves productivity by improving air permeability and yield in the sintering bed by reducing coarse pellets and pellets without nuclei to improve the particle size and state of existence of the raw material for sintering. It is intended to

Specifically, when the raw material for sintering is produced using a drum mixer, fine ore containing 80% or more of particles having a particle size of 250 μm or less accounts for 40% or more. Further, when water is sprinkled from a water sprinkling port provided in the drum mixer, the relationship between the rotation speed of the drum mixer, the water sprinkling distance, the water sprinkling flow rate, the spray angle, and the solid angle of water sprinkling satisfies the following equation.
・0<(Q×tan(θ/2))/((√2)×d×ω×Ω×D)<1.10
Patent Literature 2 is a technique relating to a watering method and apparatus, and aims to reduce variations in the water content of raw materials.

Specifically, a water sprinkler is arranged on each of the raw material charging side and the discharging side of the drum mixer, and water is sprinkled on an arbitrary region in the longitudinal direction of the mixer. It is said that the raw materials are mixed in the upstream mixing section, then conditioned in the midstream humidity control section, and then granulated in the downstream, so that each process is performed efficiently, and as a result, the variation in the raw material moisture content is reduced.
In Patent Document 3, when granulating fine ore or the like containing coke into pseudo-particles, the fine powder remaining after granulation is suppressed, the air permeability of the sintering machine is improved, and sintered ore is produced. The purpose is to improve the quality and yield.

Specifically, in a method of granulating a sintering raw material in which coke-blended ore powder or the like is charged into a drum mixer and granulated by stirring, water is added at the initial stage of granulation, and the fine ore powder is added in advance. After granulating a part into pseudo-particles, a binder is added and granulated.
In Patent Document 4, when granulating into a mass with a granulator, water is added in a spray state to the raw material for sintering prior to charging into the kneader, and is uniformly added to the raw material to improve mixing efficiency and The purpose is to significantly improve the granulation effect.

Specifically, the raw material for sintering is continuously charged into a kneader in which a cylindrical rod vibrates in a circular motion, kneaded at a high density to form flakes, and then charged into a granulator to form lumps. At the time of granulation, water is added by spraying a mist stream of water sprayed with high-pressure air onto the surface and/or the back surface of the sintering raw material supplied to the kneader.

JP 2016-172903 A JP-A-2001-316730 JP-A-2000-273553 JP-A-03-219026

By the way, in recent years, the Al ₂ O ₃ content of sintered ore has been on the rise due to the deterioration of the quality of sintering raw materials. It is feared that it will get worse.
Therefore, as a new low Al ₂ O ₃ source, crushed and beneficiated high-grade ore (for example, Canadian concentrate) is attracting attention. However, this ore has medium-sized particles compared to conventional raw materials, and has a surface property with high wettability, so there is a problem that if water is unevenly distributed during granulation, it tends to become coarse particles.

These coarse particles are weak in strength and pulverize during the transportation process. Therefore, the difference between the particle size of the generated powder and the particle size of the coarse particles reduces the porosity of the raw material packed bed after being supplied to the sintering machine.
Since such a decrease in porosity deteriorates the permeability of the raw material packed bed, the productivity of sintered ore decreases. Therefore, means for producing granules having a uniform particle size distribution are required.

In Patent Document 1, the target ore is a fine ore called a pellet feed, which is different in properties from the medium-grain ore targeted by the present invention. Since the medium-grained ore targeted by the present invention has high wettability, sufficient water dispersion cannot be performed with the mixing time and watering density of the raw materials specified under the conventional conditions as in Patent Document 1. The effect of optimizing the particle size distribution of the granules has not been obtained.

In addition, as for Patent Document 2, there is no description or suggestion about the mixing time, which is the necessary condition for granulating the raw material for sintering using medium-grained ore, and the watering density and droplet diameter when watering. However, the conditions required to granulate raw materials for sintering using medium-grained ores are not clear.
As for Patent Document 3, since water is sprinkled immediately after the drum mixer is charged, a sufficient mixing time required for dispersing the initial moisture content of the raw materials cannot be ensured. In addition, since there is no description or suggestion regarding the method of adding water to the raw material, such as the water spray density and droplet size, it does not correspond to the technique of granulating using medium-grained ore.

Patent Document 4 is directed to a kneader, and is not a technology applicable to a granulator (drum mixer) targeted by the present invention. In addition, the diameter of droplets of the mist is finer than the conditions of the present invention, and it does not correspond to the technique of granulating using medium-grained ore.
Therefore, in view of the above problems, the present invention suppresses the generation of coarse particles caused by "uneven distribution of water" when granulating using medium-grain ore, and sintered due to the coarse particles. It is an object of the present invention to provide a granulation method using thin and uniform watering that can avoid a decrease in ore productivity.

In order to achieve the above object, the present invention has taken the following technical measures.
The granulation method by thin and uniform water spraying according to the present invention uses a drum mixer with a residence time of 150 seconds or more for the raw material to be granulated, and the particles with a particle size of 1.0 mm or less are 70% by mass or more of the whole, and When granulating a raw material for sintering containing medium-grained ore in which particles having a particle size of 0.5 mm or more account for 50% by mass or more of the total, after charging the raw material into the drum mixer, only rolling is performed for 60 seconds or more without sprinkling water. After 60 seconds or more have passed, water is sprinkled until the watering density is 0.25 kg/s/m ² or less (excluding 0) and the target moisture content according to the raw material is reached with rolling, and the target moisture content is reached. After that, the sintering raw material is discharged from the drum mixer after watering is stopped and rolling is continued for 90 seconds or more.

According to the present invention, when granulating using medium-grained ore, the generation of coarse particles caused by "uneven distribution of water" is suppressed, and the productivity of sintered ore caused by the coarse particles is reduced. can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically the outline|summary of the granulation method by thin uniform water spraying concerning this invention. FIG. 3 is a diagram schematically showing the concept of each area (1) to (3) of the drum mixer; It is the graph which showed the particle size distribution of each ore. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically the outline|summary of a permeation rate measuring apparatus. FIG. 4 is a diagram showing changes in particle size distribution of granules when medium-grained ore is blended. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically the outline|summary of the air permeability measuring apparatus of a raw material packed bed. It is the figure which showed the influence on the air permeability of a medium-grained ore. 1 is a diagram schematically showing an overview of a sintering machine having drum mixers arranged in parallel; FIG. It is the figure which showed typically the movement of the raw material during drum mixer rolling. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically the outline|summary of a sintering pot test apparatus. 4 is a graph showing changes in water content σ inside the drum mixer. FIG. 4 is a diagram schematically showing the concept of the watering range when the spray nozzle is watering. It is a graph showing the relationship between the water spray density and the generation (existence) ratio of coarse particles. It is the graph which showed typically the water content change in a drum mixer. FIG. 2 is a diagram schematically showing structure types of pseudo-particles; 4 is a graph showing the relationship between rolling time and strength of pseudo-particles. It is the figure which showed the tumbler tester typically. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing an outline of a drum mixer that satisfies the prescribed scope of the present invention; 2 is a graph showing the particle size distribution of granules in an actual drum mixer (2-line side using 30% medium-grain ore). It is the figure which showed the productivity improvement effect in the real machine (drum mixer) in this invention.

Hereinafter, an embodiment of the granulation method by thin and uniform water spraying according to the present invention will be described with reference to the drawings.
The embodiment described below is an example of the present invention, and the specific example does not limit the configuration of the present invention.
Further, in the following description, the sintering raw material 1 granulated by rolling of the drum mixer 8 may be referred to as pseudo-particles or granules. The raw material 2 that is the source of the raw material 1 for sintering is sometimes called a granulated raw material.

First, the outline of the granulation method by thin and uniform water spraying of the present invention will be described.
As shown in FIG. 1, in the present invention, in the case of granulating the raw material 1 for sintering using the drum mixer 8, the granulated raw material 2 is added as a pre-process of adding granulation water 7 (addition water). A mixing region (1) is provided, the initial moisture 6 (attached water) is promoted in the mixing region (1), and the granulation water 7 is added in the granulation region (2) thinly and uniformly. This was the case when an ore with high wettability (medium-grained ore 3) was used by dispersing the granulation water 7 over time, stopping water sprinkling in the rolling area (3), and rolling. Even so, it is possible to suppress coarse particles caused by "maldistribution of water" during granulation, and to produce granules 1 having a uniform particle size distribution.

That is, as shown in FIG. 1, the granulation method by thin and uniform water spraying of the present invention does not cause "uneven distribution of water" when using the granulation raw material 2 containing the medium-grain ore 3 with high wettability. First, the drum mixer 8 is rolled for a certain period of time without sprinkling water to disperse the adhering water 6 of the granulated raw material 2 . Thereafter, a predetermined amount of granulation water 7 is evenly sprinkled over the granulated raw material 2 while the drum mixer 8 is being rolled. Further, the water spray is stopped and the drum mixer 8 is rolled for a certain period of time to disperse the granulation water 7 so as not to cause "maldistribution of water", thereby producing the granules 1 having a uniform particle size.

For example, in the case of a high spraying density (comparative example), the granulated raw material 2 is charged into the drum mixer 8 in a state where the initially adhered water 6 is unevenly distributed. After that, when the granulation water 7 with a high spraying density is locally added to the granulation raw material 2 in a short time while the adhered water 6 remains unevenly distributed, the high water content portion aggregates and becomes coarse, resulting in a broad ( A granulate having a particle size distribution is produced.
On the other hand, in the case of a low spraying density (the present invention), after charging the granulated raw material 2 into the drum mixer 8, the granulated raw material 2 is mixed before adding the granulating water 7, thereby dispersing the adhering water 6. It is urged to avoid "uneven distribution of adhering water 6". Furthermore, the granulation water 7 is added thinly and evenly over a long period of time at a low watering density, thereby strengthening the dispersion of the granulation water 7 to avoid "uneven distribution of the granulation water 7" and sharply Granules 1 having a particle size distribution (with uniform particle sizes) are produced.

Next, the granulation method by thin and uniform water spraying of the present invention will be described in detail.
Sintered ore is the main raw material for blast furnaces, and is obtained by adding a solvent such as limestone to powdered iron ore and sintering the mixture in the sintering machine 15 .
In the sintering machine 15, the sintered ore raw material (sintering raw material 1) mainly composed of iron ore is filled on a pallet truck, and the air is sucked from below to remove coke fine in the sintering raw material 1. Calcium ferrite-based melt is generated with the heat of combustion resulting from the continuous combustion of the powder, and sintered ore is produced by bonding fine ores with the melt.

Therefore, the air permeability of the filled sintering material 1 affects the amount of air sucked (oxygen supply amount) passing through the pallet, that is, the combustion rate (productivity) of coke breeze.
Therefore, in the sintering process, generally, a granulator (for example, a drum mixer 8, a pan pelletizer, etc.) is used to add granulation water 7 to the granulated raw material 2, and during sintering, the voids in the raw material packed bed are filled. By granulating the granules 1 that are made into pseudo-particles by attaching the fine ore that clogs and deteriorates the air permeability during firing to the coarse-grained ore that serves as the core, the raw material packed bed (on the pallet truck Ensure air permeability of the filled granules 1).

As the size of the sintering machine 15 increases, it is common to employ a drum mixer 8 with high throughput. As for the arrangement of the drum mixers 8, two drum mixers 8 are arranged in series, mainly for the primary purpose of mixing the granulated raw material 2 and the secondary purpose of granulating the granulated material 1 .
On the other hand, in one drum mixer 8, the above operations (mixing and granulation) may be divided into the first half section and the second half section. In this case, it is important to adjust the addition of the granulation water 7 (reference: iron ore handbook page of sintering equipment).

The residence time T(s) of the granulated raw material 2 in the drum mixer 8 varies depending on equipment specifications such as the length and diameter of the drum mixer 8, and is obtained as follows.
For example, in the reference (Suzuki et al., Tetsu to Hagane, Vol. 73 (1987), No. 15, p. 130), 300 g of the granulated raw material 2 is packed in a cloth bag and charged from the inlet of the drum mixer 8, and the granulated product 1 is fed from the outlet. The retention time T is measured as the time until it is discharged as .

The residence time T can also be calculated by measuring the raw material weight W (kg) staying in the drum mixer 8 and then dividing it by the raw material processing amount Q (kg/s).
That is, the residence time of the granulated raw material 2 can also be determined by T=W/Q.
As for the raw material weight W (kg), the weight of the raw material 2 discharged from the drum mixer 8 may be measured. The raw material weight W can also be obtained by measuring the volume V (m ³ ) of the accumulated granulated raw material 2 and multiplying it by the bulk density ρ (kg/m ³ ) of the granulated raw material 2 .

That is, the weight of the deposited raw material: W=V×ρ can also be obtained.
Further, the size of the drum mixer 8 for producing sintered ore varies from φ=2 m to 5 m in diameter and from 10 m to 30 m in length. The drum mixer 8 has a residence time T of a wide range from 90 seconds (see, for example, Japanese Unexamined Patent Publication No. 2003-328042) to 600 seconds (see, for example, Japanese Unexamined Patent Publication No. 62-225238). It's becoming

By the way, when mixing and granulating the granulated raw material 2 in one drum mixer 8, the role inside the drum mixer 8 is considered as follows.
FIG. 2 schematically shows the concept of each area within the drum mixer 8. As shown in FIG.
As shown in FIG. 2, there is a "mixing area (1)" at the inlet of the drum mixer 8, and a "hydrolysis granulation area" following the mixing area where granulation water 7 is added to the granulation raw material 2 to proceed with granulation. (2)” and a “non-hydrostatic rolling region (3)” in which the granules 1 are rolled after the granulation water 7 is added to finish them with high strength.

In order to ensure proper residence time T in these three regions (details will be described later), the drum mixer 8 must have a residence time T of at least 150 seconds or longer.
That is, in the present invention, the drum mixer 8 is used in which the residence time T of the granulated raw material 2, which is the source of granulation, is 150 seconds or longer.
Here, the characteristics of the medium-grained ore 3 used in the present invention will be described.

FIG. 3 shows the particle size distribution of each ore.
As shown in FIG. 3, the high-grade medium-grained ore 3 undergoes crushing and beneficiation processes in order to improve the iron grade at the mine. etc.), it has a feature in granularity.
That is, it is difficult for the medium-grained ore 3 to become a nucleus (with a grain size larger than 1 mm (+1 mm)) in the granulation step of the sintering process, and alone, the adhered powder 4 (with a grain size of 0.5 mm or less ( -0.5 mm)), often containing many intermediate grain sizes. That is, the medium-grained ore 3 having a particle size larger than 0.5 mm and 1.0 mm or less is a difficult-to-process raw material.

On the other hand, as shown in Table 1, the medium-grained ore 3 has a low gangue component such as Al ₂ O ₃ due to beneficiation and has a high iron grade.
Table 1 shows the components of each ore.

In addition, the medium-grained ore 3 is easily wetted with water, and has a water absorption index of 5 mm ² /s or more, which indicates the permeation rate of water.
Therefore, when the granules 1 are granulated, if water (attached water 6, granulation water 7) is unevenly distributed in the portion where the medium-grained ore 3 exists, the medium-grained ore 3 becomes the nucleus. It has the property that fine powder around the outer periphery tends to adhere and become coarse particles.

Here, the particle size (mm) will be described.
For example, according to the Handbook of Powder Technology (Edited by Society of Powder Technology, Nikkan Kogyo Shimbun, First Edition (February 28, 1986), P.1), ``Powder consists of many particles of various sizes. The concept of the average size of this constituent particle group is called particle size, and the representative size of individual particles is called particle diameter.Since actual particles have a complicated shape, they are spherical. and representative dimensions reduced to simple ones such as rectangular parallelepipeds are used." For this reason, the particle size is also expressed as a particle diameter, and is a representative dimension indicating the size of particles.

Moreover, as one of the methods for measuring the particle size, there is a “sieving method”. In the "sieving method", when powder is separated by two kinds of sieves with known openings, the particle groups remaining on the finer sieve have a size between the two openings. Here, particles remaining on the sieve mesh are defined as particle sizes exceeding the sieve mesh size, and particles passing through the sieve mesh are defined as particle sizes equal to or smaller than the sieve mesh size.

The existence ratio (%) of coarse particles is as follows.
It refers to the existence ratio of particles having a particle size of +5 mm in the granulated material 1 sieved by the above-mentioned "sieving method". Coarse particles are weak in strength and difficult to conduct heat to the inside, so they collapse when the raw material is charged into the sintering machine 15 or collapse during the firing process to generate powder, which deteriorates the air permeability of the raw material packed bed. Let As a result, the firing time is extended and the productivity is lowered. Therefore, it is desirable that the number of coarse particles is as small as possible.

The method for measuring the permeation rate of water is as follows.
Techniques for measuring the wettability of powder such as fine ore and water include, for example, the "penetration rate method". In the case of this method, the permeation rate of water can be calculated using the following "Lucas-Washburn equation", considering the voids in the powder packed bed as a collection of capillaries.
・l2/ ^t =(r×γ×cosθ)/2η
However, l: height of penetration into the powder layer (m), t: time (s), r: capillary radius (m), γ: liquid surface tension (m N/m), θ: wetting angle ( °), η: liquid clay (m・Pa・s).

The left side [l ² /t] of the above formula is a value that can be measured, and a high-precision surface tension meter (for example, manufactured by Interface Kyowa Chemical Co., Ltd., model number: DY-700) or a penetration rate measuring device (for example, , Peneto Analyzer manufactured by Hosokawa Micron Corporation) or the like.
Alternatively, the measurement can be performed simply by assembling a permeation rate measuring device 9 as shown in FIG.

On the other hand, γ and η in the right side of the above equation [(r×γ×cos θ)/2η] are determined by the physical properties of the permeating liquid (water in this embodiment). is determined by θ and r.
For example, the wettability θ between water and ore can be calculated by using isopropyl alcohol or the like with extremely high wettability instead of water, setting θ=0, and obtaining the capillary diameter r in advance.

However, in the present embodiment, it is considered that the capillary ^diameter r, which is affected by the particle size of the ore, also affects the granulation characteristics. Compare each difference.
Table 2 shows the results of measuring the time required for water to permeate between 10 mm and 20 mm of the raw material packed bed and calculating the water permeation rate [l ² /t].

As shown in Table 2, it can be seen that medium grain ore 3, which is the target brand of the present invention, has a faster water permeation rate than other ores.
Although the details will be described later, the effect of "dilute and uniform watering ⁽ watering the granulation water 7 in the drum mixer 8 in a thin and uniform manner)" is as follows. No effect was observed when only ores other than 3 (Australian ore B and South American ore A) were used.

That is, the uneven distribution of the granulation water 7 (addition water) is caused by the ease with which water permeates the ore layer (due to wettability). It can be said that it occurs remarkably in
FIG. 5 shows the change in particle size distribution of the granules 1 when the medium-grained ore 3 is blended.
As shown in FIG. 5, under the condition (0% by mass) in which the medium-grained ore 3 is not blended, there are few coarse particles with a particle size larger than 5 mm (+5 mm) and particles with a particle size of 1 mm or less (-1 mm). It has a sharp particle size distribution with less ungranulated powder, that is, a uniform particle size distribution.

On the other hand, when medium-grained ore 3 is increased (10% by mass, 30% by mass), no increase in ungranulated ore with a particle size of -1 mm is observed, but coarse particles with a particle size of +5 mm increase. It has a broad particle size distribution, that is, an irregular particle size distribution.
The reason for this is that the granulation water 7 tends to be unevenly distributed at the locations where the medium-grained ore 3 exists due to the high wettability that is a feature of the medium-grained ore 3, so that the fine powder (adherent powder 4) aggregates on the medium-grained ore 3. This is because the particles are attached to the core particles 5 in a state where they are stuck, and coarse particles with a high moisture content are formed in which the attached layer is enlarged.

FIG. 6 schematically shows an overview of the raw material packed bed permeability measuring device 10 .
As shown in FIG. 6, in order to evaluate the air permeability of the raw material packed bed, an acrylic cylindrical model was used as the air permeability measuring device 10 to form a raw material packed bed with a diameter of 130 mm inside, and the raw material packed The pressure loss of the layer (thickness = 100 mm) was measured, and the air permeability of the raw material packed bed was evaluated using the JPU index represented by the following formula (1).

・JPU=Q/A(h/ΔP) ^0.6 (1)
FIG. 7 shows the effect of the medium-grained ore 3 on air permeability.
As shown in FIG. 7, as a result of the increase in coarse particles, the average particle size of the granules 1 increases from about 3.5 mm to about 4.8 mm. Dropped from 25 to 20.

As mentioned above, the decrease in air permeability of the raw material packed bed affects the decrease in the amount of air sucked (oxygen supply) passing through the pallet, that is, the decrease in the combustion rate (productivity) of coke breeze. becomes.
The compounding ratio of the medium-grained ore 3 is the compounding ratio per drum mixer 8 .
FIG. 8 schematically shows an outline of a sintering machine 15 having drum mixers 12 and 14 arranged in parallel.

In the present invention, the compounding ratio (%) of the medium-grained ore 3 is set by parallel mixing of the drum mixer 12 (DM1) of the first-line granulation equipment 11 and the drum mixer 14 (DM2) of the two-line granulation equipment 13 as shown in FIG. In granulation equipment, it is defined as follows.
For the compounding ratio of the medium-grained ore 3 in the case described as average, the sintering machine 15 with respect to the total amount of all raw materials supplied to the sintering machine 15 (in addition, the sintering pot test device 18 in the case of a laboratory) (10/100×100=100% in FIG. 8).

Regarding the compounding ratio of the medium-grained ore 3 when described as one system, it means the ratio of the medium-grained ore 3 that passes through the one-system drum mixer 12 to the granulated raw material 2 that passes through the one-system drum mixer 12 (in FIG. 8, , 0/63 × 100 = 0%).
The compounding ratio of the medium-grained ore 3 when described as two systems means the ratio of the medium-grained ore 3 that passes through the two-system drum mixers 14 to the granulated raw material 2 that passes through the two-system drum mixers 14 (in FIG. 8, , 10/37 × 100 = 27%).

The above can be considered in the same way, for example, when two or more drum mixers 12 and 14 are arranged in parallel or in series.
In order to investigate the effect of the compounding ratio of the medium-grained ore 3 described above, a sintering pot test was conducted in a laboratory.

Table 3 shows the test conditions in the lab. The unit of the mixing ratio in Table 3 is % by weight, and the proportion of particles is % by mass. Also, Table 3 is a continuous one, and is divided and arranged vertically for easy viewing.

The laboratory equipment is as follows.
FIG. 9 schematically shows the state of the granulated raw material 2 while the drum mixer 8 is rolling. 9 indicates the movement of the granulated raw material 2. As shown in FIG.
The details of the granulation operation test conducted in the laboratory are as follows.
A drum mixer 8 was used as a testing device. The drum mixer 8 has a diameter of φ=820 mm, a length of 800 mm, and a rotational speed of 13 rpm. In addition, the raw material charging amount is 65 kg.

Note that the actual drum mixer 8 has a length of about 20 m and is inclined by about 2° from the inlet toward the outlet (for example, see FIG. 2).
Therefore, the actual drum mixer 8 is a continuous operation in which the granulated raw material 2 moves from the inlet toward the outlet.
On the other hand, in the laboratory, a drum mixer 8 having a short length is installed horizontally, and the granulated raw material 2 is rolled in the same place to reproduce the actual machine by batch operation.

At this time, the mixing time of the granulated raw material 2, the watering time of the granulating water 7, the rolling time of the granulated raw material 2 after watering, and the Fr number were matched with the conditions of the actual machine to match the granulation conditions. .
The Fr number is an index that determines the behavior of the granulated raw material 2 inside the drum mixer 8, and is calculated by the following formula.

Details of the granulation procedure are as follows.
In each of the one-system drum mixer 12 and the two-system drum mixer 14 (see FIG. 8), the granulated raw material 2 having a predetermined composition was mixed with a stirrer (described later) for 60 seconds.
The granulated raw material 2 after mixing was charged into drum mixers 12 and 14, and tumbling granulated while adding granulation water 7 to the granulated raw material 2 at a predetermined spraying density. The water spray nozzle used had a droplet size with a Sauter mean diameter of 1.0 mm.

After the end of watering, the drum mixers 12 and 14 were rolled without watering so that the rolling time was 2 minutes. After granulation, the granules were sieved in a wet state to investigate the proportion of coarse particles (+5 mm).
The details of the mixing operation of the granulated raw material 2 performed in the laboratory are as follows.
A stirrer was used as a test device. For the stirrer, capacity = 70 L, speed = 25 rpm. In addition, the raw material charging amount is 45 kg.

The granules 1 of the above-described 1st and 2nd systems were weighed in accordance with the compounding ratio of the 1st and 2nd systems (1st system/2nd system) so that the total weight was 45 kg.
For example, if 1 system/2 systems = 67/33, 1 system = 30 kg and 2 systems = 15 kg.
Combining the granules 1 of these 1st system and 2nd system, simulating the mixing action in the transport belt transfer from the drum mixers 12 and 14 of the actual machine to the sintering machine 15, after mixing for 30 seconds with a concrete mixer, sintering It was subjected to a pot test.

Details of the sinter pot tests performed in the lab are as follows.
FIG. 10 shows an outline of the sintering pot test apparatus 18. As shown in FIG.
・Test equipment: Large sintering pot (sintering area = 280mm x 280mm)
・Ore layer thickness: 500mm
・Raw material charging amount: 80kg
・Firing conditions: Atmospheric suction (at ignition = -1.0 kPa, at firing = -1.6 kPa)
・Ignition time: 90sec
First, sintered ore having a particle size of 10 mm to 20 mm is charged into a large rectangular sintering pot 19 as a bedding for protection of pallets. Onto the sintered ore, auxiliary raw materials such as iron ore and limestone, and sintering raw material 1 obtained by pulverizing powdered coke as a coagulant were charged.

The compounding conditions were adjusted so that the SiO ₂ content in the sintered product was 5.4% by mass and the basicity [CaO/SiO ₂ ] was 2.1.
Next, an exhaust fan 21 (suction machine) connected to the wind box 20 was used to ignite the surface of the raw material packed bed with an ignition burner under a constant suction pressure of -1.0 kPa. After that, the air was sucked under a constant condition of suction pressure = -1.6 kPa to burn the coke fine in the raw material 1 for sintering.

The end of the firing was defined as the time when the CO ₂ concentration in the exhaust gas reached 0.5% or less.
Using a drop strength tester (JIS M8711:1993), the baked sintered cake was dropped from a height of 2m four times, and the remaining particle size was 10mm or more. was the final product.
After that, a drop test was conducted by dropping a product with a particle size of 10 mm to 50 mm four times from a height of 2 m.

The firing time (min) is defined as the time from the ignition of the ignition burner to the end of firing (when the CO ₂ concentration in the exhaust gas is 0.5% or less).
Further, the productivity (t/h/m ² ) can be calculated by the following formula.
・Productivity (t/h/m ² ) = {product weight (kg) ÷ 1000 (kg/t)} ÷ {firing time (min)/60 (min/hr)} ÷ sintering pot firing area (m ² )
Further, the drop strength (%) can be obtained by the following formula.

・Drop strength (%) = Remaining amount (kg) of 10 mm or more after drop test ÷ Product weight (kg) of 10 mm to 50 mm × 100
Now, in laboratory tests, in equipment simulating parallel granulation equipment 11 and 13 (see Fig. 8), 1 system (accounting for 67% by mass of all raw materials) and 2 systems (33 mass% of all raw materials) %) and the granules 1 were separately prepared, and after the granules 1 were combined and mixed, they were supplied to a sintering pot 19 and sintered.

Comparative Example 1 in Table 3 shows the results of granulation and sintering under conditions where the medium-grained ore 3 was not blended. In this embodiment, Comparative Example 1 is used as a base condition.
Comparative Examples 2 to 4 are the results of granulation and sintering under conditions in which medium-grained ore 3 was evenly distributed between the 1st system and the 2nd system.
Comparative Example 5 shows the results of granulation and sintering under conditions in which medium-grained ore 3 is concentrated in two lines and the ratio is increased (more is blended).

For example, as shown in Comparative Examples 2 to 4, when the granulated raw material 2 containing the medium-sized ore 3 was granulated at a high spraying density S, the number of coarse particles increased and the air permeability of the raw material packed bed deteriorated. As a result, the extension of the firing time resulted in a decrease in productivity.
In addition, as shown in Comparative Example 5, even under the condition that medium-grained ore 3 is concentrated (more) in either one of the 1st system or the 2nd system (one of the systems), the productivity similarly decreases. became.

In other words, the point of the present invention is to suppress the formation of coarse particles due to "maldistribution of water", which is a problem when blending medium-grained ore 3, and to produce granules 1 having a uniform particle size distribution.
As described above, in the present invention, the sintering raw material 1 containing the medium-grained ore 3 in which 70% by mass or more of the total particles have a particle size of 1.0 mm or less and 50% or more by mass of the total particles have a particle size of 0.5 mm or more is to be granulated.

In addition, for example, in the case of medium-grained ore 3 with a particle size of 0.7 mm, it is counted as 70% by mass or more of the whole, and is also counted as 50% by mass or more of the whole (adhesive powder 4 and core in FIG. 3). range between). That is, the particle size of the medium-grained ore 3 may be included in both and counted.
Now, the granulated raw material 2 is exposed to the rain in stock yards of loading ports (mines, ports) and unloading ports (steel mills). In addition to the above, the granulated raw material 2 is sprinkled with water to prevent dust generation. Therefore, depending on the ore brand, it has 3% to 9% of adhered water 6 (initial moisture).

At the inlet of the drum mixer 8 (see, for example, FIG. 2), the granulated raw materials 2 with different moisture contents are charged into the drum mixer 8 without being sufficiently mixed, so that the adhered water 6 is unevenly distributed in the granulated raw materials 2. state.
Therefore, in the drum mixer 8, in order to disperse the adhering water 6 in the mixing area (1) before adding the granulating water 7, only mixing is performed without sprinkling water.

As a method for evaluating the dispersed state of this moisture (attached water 6), there is a method in which a plurality of granulated raw materials 2 are locally sampled in the drum mixer 8 and the variation in water content in the granulated raw materials 2 is measured. .
For example, the drum mixer 8 is stopped while the granulated raw material 2 remains inside, and 50 g of the granulated raw material 2 is sampled evenly in the width direction (radial direction) and also in the machine length direction (full length direction), and dried. The water content of the granulated raw material 2 is measured, and the standard deviation of the water content is obtained.

The drying method is a method of calculating the water content X using the following formula (2) from the raw material weight W (g) before drying and the raw material weight D (g) after drying.
・Moisture content X=(WD)÷W×100 (2)
FIG. 11 shows the result of measuring the change in water content σ in the mixing region (1) in the stage prior to adding the granulation water 7 in the drum mixer 8 of the actual machine.

As shown in FIG. 11, at the inlet of the drum mixer 8, the water content σ is high, but the mixing time of the granulated raw material 2 is prolonged, that is, the granulated raw material 2 moves toward the outlet of the drum mixer 8. It can be seen that the water content σ is lowered accordingly.
Depending on the conditions of the granulated raw material 2, the moisture content σ at the inlet of the drum mixer 8 varies (σ=0.4 to 1.1). However, it was found that the decrease in water content σ was saturated by providing a mixing time of 60 seconds or more in the mixing region (1) in the drum mixer 8 as in the present invention.

As described above, when the uneven distribution of the water 6 (initial water content) adhered to the granulation raw material 2 is large, even if the water content (including the water 6 adhered) is dispersed in the process of adding the water 7 for granulation later, water Diversification effect weakens. Therefore, for 60 seconds or longer after the granulated raw material 2 is put into the drum mixer 8, only mixing is performed without sprinkling water, so that the adhering water 6 is dispersed.
Based on the above, in the present invention, after charging the granulated raw material 2 into the drum mixer 8, only rolling is performed for 60 seconds or longer without sprinkling water.

By the way, in the hydrostatic granulation region (2) in the drum mixer 8, the granulation water 7 is added to the granulation raw material 2 from the spray nozzle 16 (watering nozzle) "thin and uniform watering (spraying the granulation water 7 thinly and evenly). is effective in dispersing water.
The amount of the granulation water 7 added to the granulation raw material 2 at one time can be represented by the water spray density per area and time.

FIG. 12 schematically shows the concept of the spraying range of the spray nozzle 16. As shown in FIG.
As shown in FIG. 12, for example, when using a spray nozzle 16 that sprays water so as to spread out in a conical shape, the spraying density can be calculated as follows.
That is, the water spray density S (kg/s/m ² ) is determined by the spray nozzle 16, the amount of water added N (kg/s) per nozzle, the spray angle θ (°), and the granulated raw material 2 in the drum mixer 8. It can be obtained from the distance L (m) between the spray nozzles 16 using the equation (3).

・Watering density S=N÷(3.14×(L×tan(θ/2)) ² ) ・・・（３）
At this time, if the space factor of the granulated raw material 2 (the volume ratio of the granulated raw material 2 inside the drum mixer 8 to the volume of the drum mixer 8) is 5% to 15%, the granulated raw material 2 during rolling is When the drum mixer 8 is viewed from the front, it rolls at about 90° from the 6 o'clock direction to the 9 o'clock direction.
Further, the spray angle θ of the spray nozzle 16 must be set so that the added water 7 (granulation water) does not spread beyond the width of the granulated raw material 2 that is moving.

The configuration of the spray nozzle 16 that sprays the granulating water 7 in a conical shape shown in FIG. 12 is an example, and if the spraying density S of the present invention can be realized, the spray nozzle 16 that sprays in an elliptical or square shape can be used. May be adopted. In other words, the configuration of the spray nozzle 16 is not particularly limited as long as it satisfies the spraying density of the present invention.
FIG. 13 shows the effect of water spraying density S when the compounding ratio of medium-grained ore 3 is 0% by mass, 10% by mass, and 30% by mass.

As shown in FIG. 13, when the blending ratio of medium-grained ore 3, which has high wettability and unevenly distributes water, is 0% by mass, the effect of water spray density S on the existence ratio of coarse particles (+5 mm) was not observed. (◆ mark).
However, when the medium-grained ore 3 was mixed (10% by mass and 30% by mass), the lower the water spraying density S, the lower the abundance of coarse particles (+5 mm) decreased (marked ▴, marked ▪).

In this way, when medium-grained ore 3 is used, the existence ratio of coarse particles (+5 mm) is set to the original state, that is, when medium-grained ore 3 is not blended (0 mass% blended) uniform particle size distribution level In order to reduce it to 0.25 kg/s/m 2 , the water spray density S must be 0.25 kg/s/m ² or less.
From the viewpoint of facilitating dispersion of water, a lower watering density S is preferable, and granulation may be performed at 0.25 kg/s/m ² or less.

The watering density S here needs to be uniform on the area scale of interest.
For example, even if the watering density S is the same, when watering is uniformly distributed over 1m2 ⁽ uniformly over a wide area) and when watering is concentrated in the center of ^1m2 (more water is sprinkled in the middle), Naturally, the state of dispersion of water in the whole granulated raw material 2 is different.
For granules 1 with an average particle size of about 3 mm, which are to be sprayed, in a sufficiently narrow region (0.1 cm ² = projected area of granules with an average particle size) in order to increase water dispersion , it is necessary to control the aforementioned watering density S.

In addition, it is considered that the smaller the droplet diameter, the easier the water is dispersed. rice field.
The Sauter mean diameter (mm) is an average particle diameter that takes into consideration not only the droplet size but also the distribution of the number of droplets present.

The arithmetic mean particle size may be the same in the case where most of the particles are medium-sized and in the case where the particles are evenly distributed from small particle size to large particle size. However, the reality of the average is different.
Therefore, when there are n _i droplets with a diameter of d _i , the Sauter mean diameter D (mm) can be obtained by the formula (4).

・Sauter mean diameter D=Σ(n _i ×di ³ )÷Σ(n _i ×d _i ² ) (4)
Note that the laser Doppler method is generally used as a method for measuring the droplet diameter. According to this method, the particle size, velocity and concentration of spherical particles, droplets, bubbles, etc. floating in gas or liquid can be measured.
In addition, the laser Doppler method intersects two lasers against the water flow, detects the scattered light generated by the particles passing through the formed buffer stripes with multiple light receivers, and determines the particle diameter from the phase difference. (Reference: Toyota Central R&D Labs. R&D Review vol.28 No.2 p4).

Tables 4 and 5 show the results of the granulation test when the medium-grained ore 3 was blended. The unit of the mixing ratio in Tables 4 and 5 is % by weight, and the proportion of particles is % by mass. Also, Tables 4 and 5 are continuous, and are divided and arranged vertically for easy viewing.

As shown in Tables 4 and 5, based on the results of the existence ratio of coarse particles (+5 mm) with respect to the water spray density S, the coarse particles when changing the blending ratio of medium-grain ore 3 and the water spray density S at the time of granulation A trial calculation was made of the change in the existence ratio of particles (+5mm).
Comparative Examples 6 to 9 show the results of granulation under conditions in which the medium-grained ore 3 is mixed (more) in the drum mixer 14 on the side of the second system and granulated at a water spraying density S higher than the specified range of the present invention. .

Examples 1 and 2 show the results of granulation under the condition that the drum mixer 14 on the two-line side containing the medium-grained ore 3 was granulated at an appropriate water spraying density S.
Note that the drum mixer 12 on the first system side does not contain the medium-grained ore 3, so the spraying density S was set to 0.5 kg/s/m ² and kept constant.
Comparative Examples 10 to 13 are the results of granulation under the condition that the medium-grained ore 3 was evenly blended and the granulation was carried out at a water spraying density S higher than the specified range of the present invention.

Examples 3 and 4 are the results of granulation under the condition that granulation was performed with the drum mixer 12 of one system and the drum mixer 14 of two systems at an appropriate spraying density S.
In Comparative Examples 6 to 9 and Comparative Examples 10 to 13, the existence ratio of coarse particles (+5 mm) after mixing is higher than in Comparative Example 1, which is the base condition. A decrease in productivity is expected due to deterioration. Note that, under the base conditions, the existence ratio of coarse particles after mixing is 16.7%.

On the other hand, in Examples 1 to 4, since coarse particles were suppressed by granulation at an appropriate watering density S, it can be expected to avoid a decrease in productivity.
Therefore, under the conditions of Comparative Example 9 and Example 2, a sintering pot test was conducted in a laboratory. In addition, the experimental equipment in the laboratory is as described above.
Table 6 shows the test results of granulation and firing of Comparative Example 9 and Example 2.

At this time, in the equipment simulating the parallel granulation equipment 11, 13, granules 1 in 1 system (accounting for 67% by mass of all raw materials) and 2 systems (accounting for 33% by mass of all raw materials) were prepared separately, and the granules 1 were combined and mixed, and then sintered in a sintering pot 19 (see FIG. 8).
Comparative Example 9 shows the result of sintering under conditions in which the medium-grained ore 3 is concentrated (mixed more) in the two-system drum mixer 14 and granulated with a water spraying density S higher than the specified range of the present invention.

Example 2 shows the result of sintering under conditions in which medium-grained ore 3 is concentrated (mixed more) in two systems of drum mixers 14 and granulated at an appropriate watering density S.
In Comparative Example 9, suppression of coarse particles was insufficient, and the productivity decreased as the firing time was extended.
On the other hand, in Example 2, due to the effect of suppressing coarse particles, the firing time was not extended, and the productivity was improved. Note that the productivity is 1.51 t/h/m ² under the base conditions (Comparative Example 1).

By granulating the medium-grained ore 3 at a spraying density S of 0.25 kg/s/m ² or less in this way, it is possible to suppress the generation of coarse particles and improve productivity.
By the way, if the water content during granulation becomes too low, ungranulated powder (-1 mm) will remain. On the other hand, if the water content during granulation is too high, the raw material 2 will be slurried. As described above, in either case, since the gaps in the raw material packed bed are closed, the permeability of the raw material packed bed is lowered.

There are various methods for determining the target moisture content of the granulation water 7 according to the granulation raw material 2 . For example, there is a method in which a granulation test is performed with different water contents, the air permeability [JPU index] of the raw material packed bed is measured by the method described above, and the maximum water content is determined as the target water content.
This target moisture content is a value that can be easily determined by those skilled in the art, and is usually about 6% to 8%.

In addition, in the implementation conditions of the present invention, the target moisture content was 6.5±0.2%.
That is, if the raw material adhering water 6 at the inlet of the drum mixer 8 is 4.5% on average, water corresponding to the difference of 2.0% is added as the granulation water 7 within the drum mixer 8 .
FIG. 14 shows changes in water content in the drum mixer 8. As shown in FIG.
At this time, as shown in FIG. 14, the change in the water content of the granulated raw material 2 in the drum mixer 8 can be adjusted by, for example, adding the granulation water 7 using two spray nozzles 16, thereby extending the time required to reach the target water content. , the watering density S becomes lower.

As described above, in the present invention, after 60 seconds or more have elapsed, the drum mixer 8 is rolled, and the water spray density S is 0.25 kg/s/m ² or less (excluding 0) and according to the granulation raw material 2 Water is sprinkled until the target moisture content is reached.
Now, regarding the role of the no-water-water rolling region (3) of the drum mixer 8, the strength of the whole granules 1 is improved by rolling the granules with weak strength to break them down and regranulate them. The point is to let

FIG. 15 shows a schematic diagram of the structure type of the pseudo-particle 1. As shown in FIG.
As shown in FIG. 15, in general, the pseudo-particles 1 (called C-type) in which the adhered powder 4 is uniformly adhered to the outer peripheral side of the core particles 5 have high strength due to the aggregate effect.
On the other hand, quasi-particles without core particles 5 (called P-type) generated in high-moisture areas due to "uneven distribution of water", and quasi-particles (C type hypertrophy) is weak.

In addition, the low-moisture pseudo-particles caused by the "uneven distribution of water" are also weak in strength, and collapse in the no-water-water rolling region (3), and are re-granulated in such a manner that they are incorporated into other pseudo-particles.
FIG. 16 shows the results of investigating the intensity change of the pseudo-particles 1 in the actual drum mixer 8 using an eye-type tumbler tester 17 .
As shown in FIG. 16, the strength of the pseudo-particles 1, which once decreased during the water-sprinkling granulation in the hydro-rolling region (2), increases in the rolling time. It will improve when you move.

Since the granules 1 discharged from the drum mixer 8 are fed to the sintering machine 15 via a plurality of conveying belts, the higher the strength, the better.
Therefore, the rolling time of the drum mixer 8 after the completion (stop) of watering is set to 90 seconds or more so that the strength improvement of the pseudo-particles 1 is saturated by the no-water-water rolling region (3).
Here, a method for measuring the strength of the granules 1 will be described.

FIG. 17 schematically shows an outline of an eye-shaped tumbler tester 17. As shown in FIG.
As shown in FIG. 17 , the strength of the granules 1 was measured with an eye-shaped tumbler tester 17 . The conditions for the measurement were a drop of 500 mm, 20 rpm, 2 min, and so on.
First, after sieving and drying the granules 1 by particle size = (3 mm to 5 mm) and (5 mm to 10 mm), 500 g of each sample was charged into an eye-shaped tumbler tester 17, and after the test (+3mm) and (+5mm) survival rates were evaluated as tumbler strength.

If the strength of the granules is weak, the granules 1 collapse when charged into the sintering machine 15 or collapse during the firing process to generate powder, thereby deteriorating air permeability. As a result, the sintering time is extended, and the productivity is lowered. Therefore, it is desirable that the strength of the granules 1 is as high as possible.
FIG. 18 shows granulation conditions by "thin and uniform watering" that satisfies the stipulations of the present invention described above.

As shown in FIG. 18, by satisfying the stipulations of the present invention, the generation of coarse particles that occur when granulating medium-grained ore 3 with high wettability is suppressed, and the particle size distribution of granules 1 is sharpened. In other words, by making the particle size uniform, a decrease in productivity can be avoided.
Finally, the implementation conditions in the actual machine will be explained.
In the sintering machine 15 having the drum mixers 12 and 14 arranged in parallel as shown in FIG. show.

Incidentally, the residence time T is 360 sec.
The medium-grained ore 3 was used intensively in the drum mixer 14 on one side (hereinafter referred to as the 2-system (DM2) side). Therefore, the compounding ratio of the medium-grained ore 3 in the two-system drum mixer 14 is 27% by mass, which is within the specified range in which the effects of the present invention are exhibited.
Two spray nozzles 16 (manufactured by Ikeuchi Co., Ltd., material: alumina, model number: 3/4MAJP90AL92) are installed in two systems of the drum mixer 14, and the water spray density S is reduced from the conventional 2.5 kg/s/m ² to 0.25 kg. /s/ ^m2 .

The droplets from the spray nozzle 16 used in this experiment have a Sauter mean diameter of 950 μm to 1250 μm.
At this time, the watering nozzle 16 was arranged so that the mixing time before watering was 70 seconds and the rolling time of the drum mixer 14 after watering was completed was 220 seconds. The total residence time T of the drum mixer 14 is 360 seconds.

Furthermore, supplementary information is provided for FIG.
The blended powder shown in FIG. 8 indicates a raw material obtained by blending a plurality of iron ores and products (converter furnace slag, scale, etc.) from steelworks in a yard.
In addition, coke fine and return ore are blended according to the granulation ratio of the 1st system and the 2nd system according to the quality and quantity balance of the product sintered ore (in the case of Fig. 8, 1 system / 2 systems = 63/37).

In addition, the return ore was blended at 20% to 25% with respect to the new raw material. In addition, the coke fine was blended at 4.0% to 4.5% with respect to the combined raw material of new raw material and return ore.
FIG. 19 shows the particle size distribution of the granules 1 in the actual drum mixer 14 (2-system side using 30% by mass of medium-grained ore).
FIG. 20 shows the productivity improvement effect of the actual machine (drum mixer 14) according to the present invention.

As shown in FIG. 19, the granulated product 1 granulated by the two-system drum mixer 14 changed to a sharp (uniform particle size) particle size distribution by reducing the water sprinkling density S.
As a result, as shown in FIG. 20, when medium-grained ore 3 was added (30% by mass), the productivity decreased (approximately 1.63 (t/h/ ^m2 ) → about 1.59 (t/h/ ^m2 )).

On the other hand, when carried out according to the provisions of the present invention, the effect of improving productivity (production efficiency) to the original level (when medium-grained ore 3 was not mixed (0% by mass)) or more was obtained. (About 1.67 (t/h/ ^m2 )).
In summary, the granulation method by thin and uniform water spraying according to the present invention uses a drum mixer 8 having a residence time T of 150 seconds or more for the granulated raw material 2 that is the source of granulation, and the particles having a particle size of 1.0 mm or less are all mixed. In granulating the raw material 1 for sintering containing medium-grained ore 3 in which 70% by mass or more of After that, only rolling without watering is performed for 60 seconds or more, and after 60 seconds or more, the watering density S is 0.25 kg / s / m ² or less (excluding 0) with rolling, and the granulated raw material 2 Water is sprinkled until the target moisture content is reached, and after reaching the target moisture content, watering is stopped and the raw material 1 for sintering is discharged from the drum mixer 8 by rolling for 90 seconds or longer.

As described above, if the raw material 1 for sintering is granulated according to the present invention, when the medium-grained ore 3 is granulated, the generation of coarse particles caused by "uneven distribution of water" is suppressed, A decrease in productivity of sintered ore due to the coarse particles can be avoided.
It should be noted that the embodiments disclosed this time should be considered as examples and not restrictive in all respects.

In particular, matters not specified in the embodiments disclosed this time, such as operating conditions, operating conditions, various parameters, dimensions, weights, volumes, etc. of components, do not deviate from the range normally performed by those skilled in the art. Instead, values that can be easily assumed by those of ordinary skill in the art are adopted.

1 Raw material for sintering (pseudoparticles, granules)
2 raw material (granulation raw material)
3 medium-grained ore 4 adhering powder 5 nuclear particles 6 adhering water (initial moisture)
7 Granulation water (added water)
8 drum mixer 9 permeation rate measuring device 10 air permeability measuring device 11 1-system granulating equipment 12 1-system drum mixer 13 2-system granulating equipment 14 2-system drum mixer 15 sintering machine 16 nozzle (spray nozzle)
17 tumbler tester 18 sintering pan test device 19 sintering pan 20 wind box 21 exhaust fan

Claims (1)

Using a drum mixer with a residence time of 150 seconds or more for the raw material that is the basis of granulation, particles with a particle size of 1.0 mm or less account for 70% by mass or more of the total, and particles with a particle size of 0.5 mm or greater account for 50% by mass of the total. In granulating the raw material for sintering containing the above medium-grained ore,
After charging the raw material into the drum mixer, only rolling is performed for 60 seconds or more without watering,
After 60 seconds or more have passed, water is sprinkled until the watering density is 0.25 kg/s/m ² or less (excluding 0) and the target moisture content according to the raw material is reached with rolling,
After reaching the target moisture content, the granulation method by thin and uniform water spraying is characterized in that water spraying is stopped and the raw material for sintering is discharged from the drum mixer by rolling for 90 seconds or more.

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