JP7024648B2 - Granulation method of raw material for sintering - Google Patents

Description

The present invention relates to a method for granulating a raw material for sintering.

The method for producing sinter is as follows. First, a raw material for sinter, which is a raw material for sinter, is blended in a predetermined ratio, and then granulated together with water. Here, the raw material for sintering is composed of an iron-containing raw material as a main raw material, an auxiliary raw material necessary for the sintering reaction and component adjustment, a carbonaceous material (solid fuel) as a heat source, a return ore, and the like. The iron-containing raw material is, for example, iron ore such as powder ore, fine powder ore, iron-making dust (iron-making dust, steel-making dust, scale, etc.) and the like. Auxiliary raw materials are limestone, dolomite, converter slag, serpentinite, silica stone and peridotite. The charcoal material is, for example, coke powder and anthracite.

Then, the granulated material for sintering is charged into the sintering pallet of the sintering machine in layers. Then, the solid fuel in the packed bed is ignited from the surface of the packed bed, and is sucked and ventilated in the thickness direction from the top to the bottom of the packed bed. As a result, the combustion points of the packed bed of the raw material are sequentially shifted to the lower layer side, and the sintering reaction proceeds. The sinter cake in the sinter pallet after firing is crushed and sized so as to have a predetermined particle size suitable for sinter for a blast furnace. By the above steps, sinter is produced.

By charging the sintering raw material into a granulating product and then charging the sintering machine, the porosity and pores of the raw material packed bed can be increased. Therefore, since the air permeability of the packed bed of the raw material is improved, it is expected that the productivity of the sinter is improved.

Patent No. 5644955 Japanese Unexamined Patent Publication No. 2016-79467 Japanese Unexamined Patent Publication No. 2016-191122 International Publication No. 2012/102265 Japanese Unexamined Patent Publication No. 2016-3167

Kawachi et al./Nippon Steel Corporation, Tetsu to Hagane, Vol. 94 (2008), No. 11, p. 15-22 "Quantitative effect of fine particles in iron ore on optimum granulated moisture" Shibata et al., Resource Processing Technology, Vol. 40 (1993), p. 99-104 "Study on Viscosity Reduction of High Concentration Slurry"

By the way, in recent years, the iron content in iron ore has decreased and the gangue component has increased. As a countermeasure, it is considered effective to increase the amount of fine powder ore whose iron content has been increased by mineral processing. Has been done. In this case, the powdered ore is used as the core particles, and the fine powdered ore is attached to the powdered ore to prepare a granulated product. However, since the fine powder ore is inferior in granulation property, if the amount of the fine powder ore used is increased, the grain size of the granulated product becomes smaller. As a result, there is a problem that the air permeability of the raw material packed bed described above is lowered, and eventually the productivity of the sinter is lowered.

Therefore, Non-Patent Document 1 discloses a technique of using iron ore fine particles having a particle size of less than 10 μm as a binder as a technique for improving the granulation property of fine ore.

The present inventor has further studied the above findings and found a method for wet-crushing iron ore as a method for producing iron ore fine particles (Patent Documents 1 and 2). In this method, iron ore is wet-crushed with, for example, a tower mill to prepare a slurry containing crushed ore having a particle size of less than 10 μm. Then, by kneading this slurry with the raw material for sintering, a raw material kneaded product is produced. Then, the granulated product is produced by granulating the raw material kneaded product. Furthermore, the present inventor has a preferable mass ratio of the crushed ore added to the raw material for sintering, which is 3% by mass or more and less than 7% by mass with respect to the total mass of the raw material for sintering and the crushed ore, that is, the total mass of the granulated product. (Patent Document 3).

By the way, as a result of further studies on the techniques disclosed in Patent Documents 1 to 3, it was found that the technique for adding a slurry to a raw material for sintering has the following problems. Iron ore, which is a raw material for sintering, is temporarily stored in the yard after it arrives at the steelworks. After that, the iron ore is appropriately discharged to the sintering factory and brought to the granulation line. Here, the iron ore brought into the granulation line retains a certain amount of water due to rainfall during storage in the yard and watering carried out from the viewpoint of preventing dust generation. Therefore, the water contained in the iron ore is brought into the granulation line. Hereinafter, the water brought into the granulation line together with the iron ore is also referred to as "moist brought in ore".

Further, in the methods disclosed in Patent Documents 1 to 3, the slurry is added to the raw material for sintering. The slurry contains crushed ore and water. Therefore, in addition to the water brought into the ore, the water in the slurry is brought into the granulation line. Hereinafter, the water brought into the granulation line by the slurry is also referred to as "slurry brought-in water". The mass of the crushed ore added to the raw material for sintering by the slurry is automatically determined by the slurry concentration and the amount of the slurry added. Here, the slurry concentration is the solid concentration of the slurry. That is, the slurry concentration is the mass% of the crushed ore with respect to the total mass of the slurry. In this way, the ore carry-in moisture and the slurry carry-in moisture are brought into the granulation line.

By the way, the larger the amount of water added to the raw material for sintering, the more the particle size of the granulated product (strictly speaking, the average particle size obtained from the particle size distribution, etc. Book J)) tends to be larger. The larger the particle size of the granulated product, the larger the porosity and pores of the raw material packed bed. However, when the water content becomes a predetermined value or more, the particle size of the granulated product becomes excessive, and particles having a diameter of more than 20 mm, for example, begin to be generated. Such coarse pseudo-particles are not sufficiently heated to the center of the particles even after being filled in a sintering machine and undergoing a firing step, resulting in a fired body having insufficient melting and thus insufficient strength, which causes a decrease in product yield. Therefore, there is an appropriate value in the mass ratio of the water content of the granulated product. Hereinafter, such an appropriate value is also referred to as an appropriate moisture ratio. It is known that the appropriate water content of the granulated product containing the fine ore is about 9 to 12% by mass with respect to the total mass of the granulated product. Here, the appropriate water content is shown as a so-called external number. Each moisture ratio in the following description is an external number.

As described above, in the methods disclosed in Patent Documents 1 to 3, the ore-carrying water and the slurry-carrying water are brought into the granulation line. Therefore, if the total of the water content of the ore brought in and the water content of the slurry brought in is insufficient for the appropriate ratio, if the insufficient water content is brought into the granulation line (that is, if it is added to the raw material for sintering). good. The ore carry-in water content is the mass% of the ore carry-in water content with respect to the total mass of the granulated matter. The slurry carry-in water content is the mass% of the slurry carry-in water with respect to the total mass of the granulated product. Hereinafter, the water brought into the granulation line separately from the water brought in by the ore and the water brought in by the slurry is also referred to as the water added to the granulation.

Here, the fine powder ore has a high water retention capacity, and when it is brought from the iron ore yard to the granulation line, it contains a large amount of water compared to other powder ores. It reaches about 10% by mass with respect to the total mass of the ore.

The present inventor has presented in Patent Document 3 that it is preferable to add crushed ore to a raw material for sintering in a mass ratio of 3% by mass or more and less than 7% by mass. However, due to restrictions on the appropriate water content and the water content brought in by the ore, it may not be possible to add the crushed ore to the raw material for sintering in a preferable mass ratio. Hereinafter, this problem will be taken as an example of producing a granulated product having a water content of 10.5% by mass using iron ore having an ore carry-in moisture content of 6.0% by mass and a slurry having a slurry concentration of 40% by mass. To explain.

In this example, the raw materials for sintering are powder ore and fine powder ore. The water content of the fine powder ore often reaches about 10% by mass with respect to the total mass of the fine powder ore, but the water content of the fine powder ore is less than that of the fine powder ore. Therefore, the water content brought in by the ore is lower than 10% by mass, and in this example, it is 6% by mass.

Further, in this example, it is necessary to bring 4.5% by mass of water into the granulation line. When all of the water content of 4.5% by mass is covered by the water content brought in by the slurry, the mass% of the crushed ore added to the raw material for sintering is about 3.0% by mass with respect to the total mass of the granulated product. Become. Therefore, the mass% of the crushed ore is the lower limit of the above-mentioned preferable range. However, when the water content of the granulated product is further reduced within the range of the appropriate water content, or when the water content of the ore brought in is higher than 6.0% by mass, the amount of crushed ore added is 3.0% by mass. Will be smaller than.

That is, the upper limit of the water content of the slurry brought in is determined by the appropriate water content and the water content of the ore brought in. Therefore, it is necessary to add 3% by mass or more and less than 7% by mass with respect to the total mass of the granulated material within the range where the water content of the slurry brought in does not exceed the upper limit. However, when the slurry concentration is low, such a process may not be possible.

As a method for solving this problem, there is a method of increasing the slurry concentration. In the above example, when it is necessary to further reduce the water content of the granulated product, or when the water content of the ore brought in is more than 6.0% by mass, the slurry concentration may be increased to more than 40% by mass.

However, when the slurry concentration is increased, the fluidity of the slurry decreases. Therefore, when the slurry concentration is high, it is necessary to sufficiently knead the sintering raw material and the slurry before granulation. Insufficient kneading causes the crushed ore in the slurry to form dense agglomerates. In this case, there is a concern that the crushed ore may suppress or extinguish the effect as a binder that improves the strength of the granulated product by dispersing and entering between the fine ore particles. As a result, the particle size of the granulated product may be reduced. Conversely, it is assumed that a granulated product having a large particle size can be produced by sufficiently kneading the raw material for sintering and the slurry.

Therefore, the present inventor focused on a high-speed stirring mixer as a mixer used for kneading, and attempted to lengthen the stirring time by the high-speed stirring mixer. This is because it was assumed that the particle size of the granulated product could be increased because the slurry and the raw material for sintering were sufficiently kneaded by lengthening the stirring time. However, simply lengthening the stirring time may result in a smaller particle size of the granulated product.

It should be noted that a method of increasing the particle size of the granulated product by increasing the fluidity of the slurry is also conceivable. As a method for increasing the fluidity of the slurry, as disclosed in Patent Documents 4, 5 and Non-Patent Document 2, the slurry is raised by raising the slurry temperature, optimizing the pH of the slurry, adding a dispersant to the slurry, and the like. A method of reducing the interaction force between the solid particles in the slurry is known. However, these methods increase the production cost of the slurry, which in turn increases the production cost of the granulated product.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a novel and improved method capable of increasing the particle size of a granulated product containing fine powder ore at low cost. It is an object of the present invention to provide a method for granulating a raw material for sintering.

In order to solve the above problems, according to a certain viewpoint of the present invention, among all sintering raw materials, a sub-granulation step for granulating a sub-sintering raw material including powder ore and fine sinter, and a total sintering raw material. Of these, the main granulation step of granulating the main sintering raw material other than the sub-sintering raw material is included, and the sub-granulation step includes the sub-sintering raw material and the iron ore for binder having a particle size of less than 10 μm. The solid concentration of the slurry is 40% by mass or more and less than 80% by mass , including a step of producing a raw material kneaded product and a step of granulating the raw material kneaded product by kneading the containing slurry with a high-speed stirring mixer. When the solid concentration of the slurry is 40% by mass or more and less than 70% by mass, the stirring time by the high-speed stirring mixer is set to 30 seconds or more and less than 120 seconds, and when the solid concentration of the slurry is 70% by mass or more and less than 80% by mass, Provided is a method for granulating a raw material for sintering, which comprises setting the stirring time by a high-speed stirring mixer to 60 seconds or more and less than 120 seconds.

Here, the iron ore for binder contained in the raw material kneaded material may be 3% by mass or more and less than 7% by mass with respect to the total mass of the raw material for subsintering and the iron ore for binder.

Further, the raw material for subsintering may contain fine powder ore in an amount of 50 to 85% by mass with respect to the total mass of the raw material for subsintering.

As described above, according to the present invention, the granulation property of the fine powder ore is enhanced by adding the slurry to the raw material for subsintering containing the fine powder ore. Further, the stirring time by the high-speed stirring mixer is adjusted according to the slurry concentration. This makes it possible to increase the average particle size of the granulated product, specifically, the secondary granulated product. Further, since the treatment for increasing the fluidity of the slurry is not required, the particle size of the granulated product can be increased at low cost.

It is explanatory drawing which shows the outline of the granulation line which concerns on embodiment of this invention. It is a graph which shows the relationship between the slurry concentration and the average particle size of a granulated product for each stirring time.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Examination by the present inventor>
As a result of diligent studies on the slurry concentration and the stirring time, the present inventor came up with the granulation method of the raw material for sintering according to the present embodiment. Therefore, first, the study conducted by the present inventor will be described.

When the powdered ore and the fine powdered ore are used as a raw material for sintering to prepare a granulated product, the powdered ore functions as a core particle of the granulated product. That is, among the powder ore, particles having a particle size of 1 mm or more become nuclear particles, and the fine powder ore adheres to the surface of the nuclear particles. As a result, a granulated product is produced. Here, since the fine powder ore is inferior in granulation property, a crushed ore having a particle size of less than 10 μm is used as a binder. Specifically, a binder in which crushed ore is dispersed is added to the powder ore and the fine powder ore.

Here, the upper limit of the water content of the slurry brought in is determined by the appropriate water content ratio and the water content of the ore brought in. Therefore, it is necessary to add 3% by mass or more and less than 7% by mass with respect to the total mass of the granulated material within the range where the water content of the slurry brought in does not exceed the upper limit. However, when the slurry concentration is low, such a process may not be possible.

As a method for solving this problem, increasing the slurry concentration can be mentioned. However, when the slurry concentration is increased, the fluidity of the slurry decreases. Therefore, when the slurry concentration is high, it is necessary to sufficiently knead the sintering raw material and the slurry before granulation. This is because if the kneading of the sintering raw material and the slurry is insufficient, the average particle size of the granulated product may become small.

Therefore, the present inventor focused on a high-speed stirring mixer as a mixer used for kneading, and attempted to lengthen the stirring time by the high-speed stirring mixer. This is because it was assumed that the particle size of the granulated product could be increased because the slurry and the raw material for sintering were sufficiently kneaded by lengthening the stirring time. However, the average particle size of the granulated product may be rather small simply by lengthening the stirring time.

The present inventor examined the reason for this. The average particle size of the granulated product also depends on the average particle size of the powdered ore, which is a nuclear particle. Therefore, the present inventor considered that the powdered ore was crushed by stirring and the average particle size of the powdered ore became small, so that the average particle size of the granulated product became small.

Therefore, the present inventor investigated in detail the correlation between the slurry concentration and the stirring time. As a result, it was found that when the slurry concentration was 40% by mass or more and less than 70% by mass, the shorter the stirring time, the larger the average particle size of the granulated product. It is considered that when the stirring time is long, the powder ore, which is a nuclear particle, is crushed and the average particle size of the powder ore becomes small. As a result, it is considered that the average particle size of the granulated product becomes smaller. On the other hand, when the slurry concentration was 70% by mass or more and less than 80% by mass, the average particle size of the granulated product did not increase unless the stirring time was lengthened to some extent. If the stirring time is short, it is considered that the crushed ore in the slurry forms a dense agglomerate. As a result, it is considered that the average particle size of the granulated product becomes smaller.

As a result of the above examination, when the slurry concentration is 40% by mass or more and less than 70% by mass, the stirring time is 30 seconds or more, and when the slurry concentration is 70% by mass or more and less than 80% by mass, the stirring time is 60 seconds or more. By doing so, it was found that the average grain size can be increased. On the other hand, the upper limit of the stirring time is less than 120 seconds regardless of the slurry concentration. This is because if the stirring time is too long, the powder ore, which is a nuclear particle, is crushed regardless of the slurry concentration, and the average particle size of the powder ore is considered to be small.

As described above, the slurry concentration is set to a high value due to restrictions on the appropriate water content ratio and the ore carry-in water content ratio. In other words, the slurry concentration is a predetermined value depending on the appropriate water content ratio and the ore carry-in water content ratio. Therefore, the stirring time is adjusted according to the predetermined slurry concentration. Based on the above findings, the present inventor has come up with a method for granulating a raw material for sintering according to the present embodiment. Hereinafter, the present embodiment will be described in detail.

<2. Configuration of sinter manufacturing system>
First, the configuration of the sinter manufacturing system 1 according to the present embodiment will be described with reference to FIG. The sinter ore production system 1 includes a main granulation line 10, a sub-granulation line 20, and a sinter machine 30. Although the number of sub-granulation lines 20 is one in FIG. 1, a plurality of sub-granulation lines 20 may be prepared.

The main granulation line 10 is a line for producing a main granulated product by granulating the main raw material for sintering among all the raw materials for sintering. Here, the raw material for sintering is composed of an iron-containing raw material as a main raw material, an auxiliary raw material necessary for the sintering reaction and component adjustment, a carbonaceous material (solid fuel) as a heat source, a return ore, and the like. The iron-containing raw material is, for example, iron ore such as powder ore, fine powder ore, iron-making dust (iron-making dust, steel-making dust, scale, etc.) and the like. Auxiliary raw materials are limestone, dolomite, converter slag, silica stone and peridotite. The charcoal material is, for example, coke powder and anthracite.

The powder ore is, for example, an iron ore having a particle size of less than 10 mm. The average particle size of the powder ore may be about 2 to 3 mm. The average particle size is, for example, an arithmetic mean value of the particle size. Of course, the powder ore applicable to this embodiment is not limited to this example, and any iron ore referred to as powder ore in the field of sinter is applicable to this embodiment. The particle size in this embodiment is measured by a sieve. The particle size is measured by sieves with different openings. For example, when the raw material for sintering is placed on a sieve having an opening of X mm, the particle size of the particles remaining on the sieve is X mm or more, and the particle size of the particles dropped from the sieve is less than X mm.

The fine powder ore is, for example, an iron ore having a particle size of 10 μm or more and less than 100 μm. As mentioned above, the fine powder ore is inferior in granulation property. Therefore, in the present embodiment, the fine powder ore is firmly adhered to the powder ore by the iron ore for binder (details will be described later, for example, crushed ore).

The main sintering raw material means a sintering raw material other than the sub-sintering raw material described later among all sintering raw materials. The details will be described later, but the raw material for subsintering includes, for example, powder ore and fine powder ore. Further, the raw material for subsintering contains fine powder ore in an amount of 50 to 85% by mass with respect to the total mass of the raw material for subsintering. Therefore, the raw materials for sintering other than these are the main raw materials for sintering. The mass% of the main sintering raw material is preferably larger than 50% by mass with respect to the total mass of the total sintering raw materials.

The main granulation line 10 includes drum mixers 11 and 12. Here, the drum mixers 11 and 12 are arranged on the main granulation line 10 because the drum mixers 11 and 12 have a large processing amount per unit time. The granulation method of the main sintering raw material using the main granulation line 10 may be the same as the conventional granulation method. That is, the raw material for main sintering is charged into the drum mixer 11. Quicklime may be added to the main sintering raw material as a binder for improving the granulation property of the main sintering raw material. As a result, the particle size of the main granulated product is increased, and the air permeability of the raw material packed bed is improved. Further, fine powder ore may be added to the raw material for main sintering to the extent that the air permeability of the packed bed of the raw material is not deteriorated. The amount of fine ore added to the main sinter raw material may be approximately less than 10% by mass with respect to the total mass of the main sinter raw material.

The drum mixer 11 kneads the main sintering raw material and additives together with water. The drum mixer 12 produces a main granulated product by granulating the kneaded product of the main sintering raw material discharged from the drum mixer 11. Through the above steps, the raw material for main sintering is granulated. As described above, the drum mixer 11 (primary mixer) has a function of kneading the main sintering raw material, and the drum mixer 12 (secondary mixer) has a function of granulating the main sintering raw material.

Here, the drum mixers 11 and 12 may be anything as long as they are used for granulating the raw material for sintering. Further, in the present embodiment, the main sintering raw material is granulated by the drum mixers 11 and 12, but any device can be used as long as it can granulate the main sintering raw material. Is also good.

The sub-granulation line 20 is a line for producing a sub-granulation product by granulating the sub-sintering raw material among all the raw materials for sintering. Here, the raw material for subsintering includes, for example, powder ore and fine powder ore. The subsintering raw material preferably contains fine powder ore in an amount of 50 to 85% by mass with respect to the total mass of the subsintering raw material. That is, it is preferable that the fine powder ore occupies the majority of the raw material for subsintering. As described above, by separating the iron ore, which is relatively difficult to granulate, from the main granulation line 10 and granulating it, granulation can be efficiently performed. That is, by concentrating the fine powder ore that is difficult to granulate on the sub-granulation line 20, it is sufficient to add the slurry only on the sub-granulation line 20.

A slurry containing iron ore for binder is added to the raw material for subsintering. Here, the iron ore for binder is an iron ore having a particle size of less than 10 μm, and is, for example, the above-mentioned crushed ore. The slurry containing the crushed ore can be produced, for example, by the production method disclosed in Patent Documents 1 and 2.

Since the raw material for subsintering contains fine ore, the granulation property is inferior. Therefore, by adding a slurry containing iron ore for binder to the raw material for subsintering, the granulation property of the raw material for subsintering is enhanced. That is, the iron ore for binder adheres to the surface of the powder ore which is a nuclear particle, and further binds the powder ore to the fine powder ore or the fine powder ore to each other.

Here, the slurry concentration is preferably 40% by mass or more and less than 80% by mass. As described above, since the raw material for subsintering contains fine powder ore, the water content of the raw material for subsintering brought in is high. Therefore, the slurry concentration is preferably a relatively high value, that is, 40% by mass or more. As a result, the amount of iron ore added for the binder can be reduced to 3% by mass or more and less than 7% by mass. Here, the ratio of the ore carry-in water content of the raw material for subsintering is the mass% of the ore carry-in water content with respect to the total mass of the by-granulation products. In this embodiment, each water content is a so-called external number. The mass% of the amount of iron ore added for the binder is mass% with respect to the total mass of the by-granulation. When the slurry concentration is less than 40% by mass, the ratio of the iron ore for binder to the slurry is small, and it is difficult to add the iron ore for binder to 3% by mass or more and less than 7% by mass. Further, when the slurry concentration is 80% by mass or more, the slurry loses its fluidity as a slurry and becomes a state close to a solid, and it is judged that the fluidity reaches the so-called flow limit value. The present inventor produced a slurry by wet-crushing iron ore and verified the slurry concentration. As a result, the present inventor confirmed that the fluidity was lost at a concentration of about 80% by mass, which was almost the same in some iron ore species.

Here, the slurry concentration and the slurry addition amount are determined by the following steps. That is, the water content ratio of the by-granulation (mass% of water with respect to the total mass of the by-granulation) is determined. For example, when the water content is 10 kg with respect to 100 kg of the by-granulated product, the water content is 10% by mass. The water content of the by-granulation is preferably about 9 to 12% by mass with respect to the total mass of the by-granulation.

Then, the water content of the ore brought in is specified. Next, the difference between the water content of the by-granulation and the water content of the ore brought in is set as the upper limit of the water content of the slurry brought in. The ore carry-in water content is the mass% of the ore carry-in water content with respect to the total mass of the by-granulation. The slurry carry-in water content is the mass% of the slurry carry-in water content with respect to the total mass of the by-granulated products. Then, the water content of the slurry brought in does not exceed the upper limit, and the amount of iron ore added for the binder is 3.0% by mass or more and less than 7.0% by mass with respect to the total mass of the by-granulated matter. Determine the slurry concentration and the amount of slurry added. If the water content of the by-granulation is insufficient due to the water content brought in by the slurry, the water content may be added separately to the raw material for sub-sintering. Further, quicklime may be further added as a binder to the raw material for subsintering. In addition, when the sub-sintering raw material and quicklime alone are insufficient in Ca content as a melt source and C content as a heat source during the sintering reaction, auxiliary raw materials, dust and slag are used to supplement the melt source and heat source. May be added to the raw material for subsintering.

The sub-granulation line 20 includes a high-speed stirring mixer 21 and a pan pelletizer 22. The high-speed stirring mixer 21 kneads the raw material for subsintering and the additive of the raw material for subsintering (slurry or the like described above) to prepare a raw material kneaded product.

Here, the high-speed stirring mixer 21 has a stirring blade (agitator) and a similar mechanism inside, and is a mixer that exerts a large mixing, stirring, and shearing force on the sample. Normally, the peripheral speed of the stirring blade (agitator) is adjusted to 3 to 30 m / sec (Ikuo Yusa: "Basics and Applications of Powder Technology", September issue of Chemical Equipment, Supplement, Industrial Communication Co., Ltd., 2005). As the high-speed stirring mixer 21, for example, a vertical high-speed stirring mixer (manufactured by Nippon Eirich Co., Ltd.) that generates a large mixing stirring force by rotating the mixer container and the internal stirring blade (agitator) in opposite directions. Can be mentioned. Further, as another example of the high-speed stirring mixer 21, a Ladyge mixer / Proshare mixer (manufactured by Pacific Kiko Co., Ltd.), a Dow mixer and the like can be mentioned. Of course, the high-speed stirring mixer 21 is not limited to these examples, and any one called a high-speed stirring mixer in the field of sinter can be applied to the present embodiment. Since the raw material for subsintering contains a large amount of fine ore, it has a large specific surface area and is difficult to granulate. Therefore, the drum mixer may not be able to sufficiently knead the raw material for subsintering. Therefore, in the present embodiment, the high-speed stirring mixer 21 is used as a device for kneading the raw material for subsintering.

The drive system of the high-speed stirring mixer 21 may be a batch system or a continuous system. When the high-speed stirring mixer 21 is a batch type, the following processing is performed. That is, the raw material (here, the raw material for subsintering and the additive) is put into the mixer inlet and the lid is closed. Then, the raw materials are mixed in the high-speed stirring mixer 21. Then, the mixed raw material is discharged from the same mixer inlet.

When the high-speed stirring mixer 21 is a continuous type, the following processing is performed. That is, the raw material before kneading (that is, the raw material for subsintering and the additive) is charged from one end of the high-speed stirring mixer 21, for example, from the top, and discharged from the other end, for example, the bottom.

The stirring time by the high-speed stirring mixer 21 (in other words, the residence time in the high-speed stirring mixer 21) differs depending on the slurry concentration. That is, when the slurry concentration is 40% by mass or more and less than 70% by mass, the stirring time is set to 30 seconds or more and less than 120 seconds. On the other hand, when the slurry concentration is 70% by mass or more and less than 80% by mass, the stirring time is set to 60 seconds or more and less than 120 seconds.

When the slurry concentration is 40% by mass or more and less than 70% by mass, the slurry concentration is relatively low. In this case, if the stirring time is too long, it is considered that the powder ore, which is a nuclear particle, is crushed and the average particle size of the powder ore becomes small. Therefore, if the stirring time is too long, the average particle size of the granulated product becomes small. Therefore, when the slurry concentration is 40% by mass or more and less than 70% by mass, the stirring time is set to 30 seconds or more and less than 120 seconds. Even in this case, a certain amount of stirring time is required. Therefore, the lower limit of the stirring time was set to 30 seconds or more. If the stirring time is less than 30 seconds, it is considered that the crushed ore in the slurry forms a dense agglomerate. As a result, it is considered that the average particle size of the by-granulated product becomes smaller.

On the other hand, when the slurry concentration is 70% by mass or more and less than 80% by mass, the slurry concentration is relatively high. In this case, sufficient stirring is required. If the stirring time is short, it is considered that the crushed ore in the slurry forms a dense agglomerate. Therefore, when the stirring time is short, the average particle size of the granulated product becomes small. Therefore, when the slurry concentration is 70% by mass or more and less than 80% by mass, the stirring time is set to 60 seconds or more. Even in this case, if the stirring time is too long, many powdered ores are crushed and the average particle size of the powdered ore is lowered. Therefore, the upper limit of the stirring time is set to less than 120 seconds.

Here, the stirring time differs depending on the driving method of the high-speed stirring mixer 21. When the high-speed stirring mixer 21 is a batch type, the stirring time is the time when the high-speed stirring mixer 21 is operated. That is, the stirring time does not include the time required for loading and unloading operations. Therefore, the stirring time can be adjusted by adjusting the operating time of the high-speed stirring mixer 21.

On the other hand, when the high-speed stirring mixer 21 is a continuous type, the stirring time is the time from when the raw material is charged into the high-speed stirring mixer 21 to when it is discharged, that is, the time when the raw material is present in the high-speed stirring mixer 21. That is, the continuous high-speed stirring mixer 21 is operated in a so-called steady state. In the steady state, the supply and emission of raw materials are almost constant. If the supply amount exceeds the discharge amount, the raw material overflows from the high-speed stirring mixer 21, and if the supply amount exceeds the discharge amount, the inside of the high-speed stirring mixer 21 becomes empty, so that the high-speed stirring mixer 21 does not function. In order to operate the high-speed stirring mixer 21 in a steady state, the raw material supply amount, the mixer device conditions, the operating conditions and the like may be appropriately adjusted.

When the high-speed stirring mixer 21 is operated in a steady state, a substantially constant amount of raw materials are retained and mixed in the high-speed stirring mixer 21.

Therefore, the stirring time is calculated from the amount of raw material supplied and the amount of raw material retained in the mixer. For example, when the supply amount and the discharge amount of the raw material are 1 t / min and the retention amount is 2 t, the raw materials are replaced in 2 min. Therefore, the stirring time is 2 min. In reality, some raw materials stay in the mixer for a longer period of time, and some of them pass through. Therefore, the stirring time is preferably an average value. For example, the stirring time is measured a plurality of times within a certain period, and these arithmetic mean values are used as the stirring time. The stirring time can be adjusted, for example, by adjusting the raw material input rate and the raw material discharge rate, adjusting the mixer capacity, and the like.

The pan pelletizer 22 produces a by-granulation product by granulating the raw material kneaded product discharged from the high-speed stirring mixer 21. The device capable of granulating the raw material kneaded product is not limited to the pan pelletizer 22. That is, any apparatus may be used as long as it can construct a raw material kneaded product.

After the sub-granulation is produced, the sub-granulation line 20 merges with the main granulation line 10. As a result, the sub-granulation is mixed with the main granulation. After that, the main granulation product and the sub-granulation product are charged into the sintering machine 30. The sinter 30 produces a sinter by firing the main granulation and the sub-granulation.

<3. Granulation method of raw material for sintering ＞
Next, a method for granulating a raw material for sinter using the above-mentioned sinter manufacturing system 1 will be described. The method for granulating the raw material for sintering includes a main granulation step of granulating the raw material for main sintering and a sub-granulation step of granulating the raw material for sub-sintering. The main granulation step is performed on the main granulation line 10, and the sub-granulation step is performed on the sub-granulation line 20. The main granulation step may be the same as before.

The sub-granulation step includes a step of producing a raw material kneaded product by kneading the sub-sintering raw material and the slurry with a high-speed stirring mixer 21, and a step of granulating the raw material kneaded product with a pan pelletizer 22. Here, the slurry contains the above-mentioned iron ore for binder.

Here, the slurry concentration and the slurry addition amount are determined by the following steps. That is, the water content ratio of the by-granulation is determined. The water content of the by-granulation is preferably about 9 to 12% by mass with respect to the total mass of the by-granulation.

Then, the water content of the ore brought in is specified. Next, the difference between the water content of the by-granulation and the water content of the ore brought in is set as the upper limit of the water content of the slurry brought in. Then, the water content of the slurry brought in does not exceed the upper limit, and the amount of iron ore added for the binder is 3.0% by mass or more and less than 7.0% by mass with respect to the total mass of the by-granulated matter. Determine the slurry concentration and the amount of slurry added. If the water content of the by-granulation is insufficient due to the water content brought in by the slurry, the water content may be added separately to the raw material for sub-sintering.

Further, in the step of producing the raw material kneaded product, the stirring time by the high-speed stirring mixer is adjusted according to the slurry concentration. That is, when the slurry concentration is 40% by mass or more and less than 70% by mass, the stirring time is set to 30 seconds or more and less than 120 seconds. On the other hand, when the slurry concentration is 70% by mass or more and less than 80% by mass, the stirring time is set to 60 seconds or more and less than 120 seconds.

As described above, in the present embodiment, the granulation property of the fine powder ore is enhanced by adding the slurry to the raw material for subsintering containing the fine powder ore. Further, the stirring time by the high-speed stirring mixer 21 is adjusted according to the slurry concentration. Specifically, when the slurry concentration is 40% by mass or more and less than 70% by mass, the stirring time by the high-speed stirring mixer 21 is set to 30 seconds or more and less than 120 seconds, and when the slurry concentration is 70% by mass or more and less than 80% by mass, the stirring time is set to 30 seconds or more and less than 120 seconds. The stirring time by the high-speed stirring mixer 21 is set to 60 seconds or more and less than 120 seconds. This makes it possible to increase the average particle size of the by-granulated product. Further, since the treatment for increasing the fluidity of the slurry is not required, the particle size of the by-granulated product can be increased at low cost.

In this example, an experiment simulating the sub-granulation line 20 was performed. Specifically, first, a slurry containing crushed ore was prepared. The slurry was prepared according to the methods disclosed in Patent Documents 1 and 2. Here, the slurry concentration was changed from 40% by mass to 80% by mass in increments of 10% by mass. Then, the raw material for subsintering and the slurry were put into the high-speed stirring mixer 21 (manufactured by Nippon Eirich Co., Ltd., Eirich mixer, model number R02). Here, the breakdown and mass ratio of the raw material for substituting and the crushed ore were 24% by mass of the powdered ore, 71% by mass of the fine powdered ore, and 5% by mass of the crushed ore. That is, the mass ratio of the crushed ore was kept constant, and the slurry concentration was changed. The water content of the by-granulation was 9.0% by mass. When the water content was insufficient only by adding the slurry, the insufficient water was added to the high-speed stirring mixer 21 as so-called granulation-added water content.

Then, the raw material for subsintering and the slurry were kneaded with the high-speed stirring mixer 21. Here, the peripheral speed of the agitator of the high-speed stirring mixer 21 was set to 10 m / sec, and the kneading time was set to any of 30 seconds, 60 seconds, and 120 seconds. The raw material kneaded product thus produced was charged into the pan pelletizer 22, and the raw material kneaded product was granulated with the pan pelletizer 22 for 300 seconds. The average particle size of the granulated product was measured, and the average particle size was used as an evaluation index. Here, the average particle size was measured in the following steps. (1) About 500 g of the granulated product was collected and kept in a dryer kept at 105 ° C. for 5-10 minutes. This is an operation of reducing the water content on the surface of the granulated product in order to prevent the granulated product from adhering to the net and making the sieving difficult when sieving later. (2) The granulated product taken out from the dryer was sieved through several open sieves. (Uses a JIS standard compliant 200 mmφ round sieve of 9.5, 8.0, 4.75, 2.8, 2.0, 1.0 mm) (3) The arithmetic mean diameter was obtained from the mass ratio of each particle size category. As described above, in this example, the by-granulation was prepared by changing the slurry concentration and the stirring time, and the average particle size of the by-granulation was measured. The results are shown in FIG.

As is clear from FIG. 2, when the slurry concentration was 40 to 60% by mass, the shorter the stirring time, the larger the average particle size of the by-granulated product. It is considered that the longer the stirring time, the more the powder ore is crushed, and the average particle size of the powder ore becomes smaller. As a result, it is considered that the average particle size of the granulated product becomes smaller. It was found that the stirring time is preferably 30 seconds or more and less than 120 seconds because the by-granulated product having an average particle size that does not cause any problem in practical use was obtained in any of the stirring times.

On the other hand, when the slurry concentration is 70 to 80% by mass, the average particle size of the by-granulation is the smallest when the stirring time is 30 seconds, and the average of the by-granulation is when the stirring time is 60 seconds. The grain size was the largest. Therefore, when the stirring time is 30 seconds, it is considered that the stirring of the slurry is insufficient and the crushed ore in the slurry forms a dense agglomerate. As a result, a small number of coarse particles and a large number of small particles are generated as the by-granulation, and it is considered that the average particle size of the by-granulation becomes smaller. The average particle size when the stirring time was 60 seconds was larger than the average particle size when the stirring time was 120 seconds. Therefore, when the slurry concentration is 60 seconds or more, it is considered that more powder ore is crushed as the stirring time is longer. In any of the stirring times, a by-granulated product having an average particle size that did not cause any problem in practical use was obtained, but it was found that the stirring time was preferably 60 seconds or more. It was also found that the upper limit is preferably less than 120 seconds.

According to FIG. 2, it is considered that the boundary value at which the correlation between the stirring time and the average particle size changes exists in the range where the slurry concentration is 60 to 70% by mass. Was actually changed to 70% by mass.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Granulation system 10 Main granulation line 11, 12 Drum mixer 20 Sub-granulation line 21 High-speed stirring mixer 22 Pampletizer

Claims (3)

Of all raw materials for sintering, a sub-granulation process for granulating sub-sintering raw materials including powdered ore and fine powdered ore, and
Among the total sintering raw materials, the main granulation step of granulating the main sintering raw material other than the sub-sintering raw material is included.
The sub-granulation step includes a step of producing a raw material kneaded product by kneading the sub-sintering raw material and a slurry containing iron ore for a binder having a particle size of less than 10 μm with a high-speed stirring mixer.
Including the step of granulating the raw material kneaded product,
The solid concentration of the slurry is 40% by mass or more and less than 80% by mass.
When the solid concentration of the slurry is 40% by mass or more and less than 70% by mass, the stirring time by the high-speed stirring mixer is set to 30 seconds or more and less than 120 seconds.
A method for granulating a raw material for sintering, which comprises setting the stirring time by the high-speed stirring mixer to 60 seconds or more and less than 120 seconds when the solid concentration of the slurry is 70% by mass or more and less than 80% by mass. The binder iron ore contained in the raw material kneaded material is characterized in that it is 3% by mass or more and less than 7% by mass with respect to the total mass of the subsintering raw material and the binder iron ore. The method for granulating a raw material for sintering according to the description. The method for granulating a raw material for sintering according to claim 1, wherein the raw material for subsintering contains the fine ore in an amount of 50 to 85% by mass with respect to the total mass of the raw material for subsintering.

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