WO2015011981A1 - Method for manufacturing briquettes and reduced iron - Google Patents

Abstract

Provided is a method for manufacturing briquettes through pelletization such that a fine iron oxide-containing powder wherein 50% of particles are 2 μm or smaller can be utilized as starting material for iron manufacture. Another purpose is to provide a technique for manufacturing reduced iron from briquettes obtained by briquetting. The method for manufacturing briquettes includes a step of heat treating an iron oxide-containing powder wherein 50% of particles are 2 μm or smaller at a temperature of 900-1,200°C, and a step of pelletizing the resulting heat-treated powder as a starting material for manufacturing briquettes.

Description

[Name of invention determined by ISA based on Rule 37.2] Method for producing agglomerates and reduced iron

The present invention relates to a technique for effectively using a fine iron oxide-containing powder having a 50% particle diameter of 2 μm or less as an iron source.

As a method for producing reduced iron from an iron oxide-containing substance such as iron ore, for example, a gas reduction method using natural gas is known. As a method for producing reduced iron developed in recent years, an agglomerate obtained by mixing an iron oxide-containing substance and a carbonaceous reducing agent such as a carbonaceous material is heated at a high temperature of 1300 ° C. or more to produce a reduced agglomerate. There are a FASTMET method and an ITmk3 method in which the reduced agglomerate is further heated to reduce and separate reduced iron and slag to produce granular reduced iron.

Thus, when producing reduced iron from an iron oxide-containing substance, water and a binder are mixed in the mixer using the iron oxide-containing substance as a raw material, and granulated by a granulator to obtain an agglomerate having a diameter of 13 to 18 mm. Things are used.

As the agglomeration method of the powder, for example, a pelletizing method and a sintering method are known, and an appropriate granulation method as a pretreatment is determined according to the particle size range of the powder (for example, non-patent document). 1). Specifically, in the rolling granulation method in the pelletizing method, it is recommended that the 50% particle size is 4 μm or more, and in the sintering method, the 50% particle size is about 0.11 mm to about 3 mm. It is recommended that there be.

By the way, valuable metals other than iron include Ni, Al, Ti and the like. These valuable metals are separated and recovered as Ni, Al, and Ti from Ni-containing ores such as saprolite, Al-containing ores such as red mud, and Ti-containing ores such as ilmenite. For example, the HPAL method (High Pressure Acid Leach) is known as a method for separating and recovering Ni from Ni-containing ores. In this method, Ni can be extracted and recovered by stably reacting Ni-containing ore with sulfuric acid in a high-temperature and high-pressure state. After extracting and recovering Ni, a precipitate separation product is generated as a residue. This residue contains a large amount of iron oxide, and this oxide is mainly hematite (Fe ₂ O ₃ ). Further, the amount of water contained in the residue is 20% or more, the form is mud, and the 50% particle size is very fine as about 0.6 μm.

As described above, the residue from which the target component is recovered by the beneficiation operation (hereinafter sometimes referred to as tailing) may contain a large amount of iron oxide such as hematite, for example. Therefore, it is conceivable to reduce the iron oxide contained in the tailings and use it as an iron source. However, since tailings are usually very fine, it is difficult to granulate by the tumbling granulation method described above and use it as an iron-making raw material. That is, when the particles are very fine, the particles easily stick to each other during the stirring process in the mixer, and the particles form pseudo particles. When these pseudo particles are granulated by a granulator, the pseudo particles are bonded to each other and grow to form a pellet having protrusions on the surface like konpeito. The pellet having such a shape cannot be used as an iron-making raw material because the internal structure is not uniform and the strength is low. Therefore, it is difficult to agglomerate tailings and use it as a raw material for iron making and effectively use it as an iron source.

The present invention has been made paying attention to the above-mentioned circumstances, and its purpose is to granulate a fine iron oxide-containing powder having a 50% particle size of 2 μm or less so that it can be used as an iron-making raw material. The object is to provide a method for producing the composition. Another object of the present invention is to provide a technique for producing reduced iron from an agglomerate obtained by agglomeration.

The inventors of the present invention have intensively studied to granulate and agglomerate fine iron oxide-containing powder and use it as a raw material for iron making. As a result, it was found that if the iron oxide-containing powder having a 50% particle size of 2 μm or less is heat-treated at a predetermined temperature, the particles can be granulated because they are sintered together and coarsened, and an agglomerate can be produced. The present invention has been completed.

That is, the method for producing an agglomerate according to the present invention, which was able to solve the above problems, was obtained by heat-treating an iron oxide-containing powder having a 50% particle size of 2 μm or less at a heating temperature of 900 to 1200 ° C. And a step of producing an agglomerate by granulating the heat-treated powder.

The granulation may be performed by a rolling granulation method.

The heat treatment is preferably performed so that the 50% particle diameter of the heat treated powder is 4 μm or more, and the heating time may be, for example, 30 minutes or more. The heat treatment is preferably performed while rolling the iron oxide-containing powder.

As the iron oxide-containing powder, tailings can be used. As the tailing, for example, a residue after recovering Ni from Ni-containing ore can be used.

The present invention also includes a method of producing reduced iron by using the agglomerate obtained by the above production method as a raw material and heating it to reduce iron oxide. The agglomerate may further contain, for example, a carbonaceous reducing agent.

According to the present invention, the iron oxide-containing powder having a 50% particle size of 2 μm or less is heat-treated at a heating temperature of 900 to 1200 ° C., whereby the particles can be coarsened. The composition can be manufactured. The obtained agglomerate can be used as a raw material for iron making.

FIG. 1 is a drawing-substituting photograph in which a heat-treated powder obtained by heat treatment at a heating temperature of 400 ° C. is photographed. FIG. 2 is a drawing-substituting photograph in which a heat-treated powder obtained by heat treatment at a heating temperature of 1200 ° C. is photographed. FIG. 3 is a graph showing the particle size distribution of the heat-treated powder. FIG. 4 is a drawing-substituting photograph in which an agglomerated product obtained by granulating a heat-treated powder obtained by heat treatment at a heating temperature of 400 ° C. with a ball mill is photographed. FIG. 5 is a drawing-substituting photograph in which an agglomerated product obtained by granulating a heat-treated powder obtained by heat-treating at a heating temperature of 1200 ° C. with a ball mill is photographed.

The method of the present invention
A step of heat-treating an iron oxide-containing powder having a 50% particle size of 2 μm or less at a heating temperature of 900 to 1200 ° C. (hereinafter sometimes referred to as a heat treatment step);
A step of granulating the obtained heat-treated powder as a raw material to produce an agglomerate (hereinafter sometimes referred to as an agglomeration step);
Is included. Hereinafter, each step will be described in detail.

[Heat treatment process]
In the method of the present invention, it is premised that an iron oxide-containing powder having a 50% particle diameter of 2 μm or less is used. For the purpose of granulating and agglomerating such fine iron oxide powder, it can be effectively used as an iron source. Yes.

As the iron oxide-containing powder having a 50% particle size of 2 μm or less, tailing can be used. The tailing means a residue obtained by recovering the target component by the beneficiation operation, and the type of mineral before the beneficiation is not particularly limited. As tailings, for example, residues after beneficiation from iron ore, residues after recovering Al from Al-containing ores, residues after recovering Ti from Ti-containing ores, and after recovering Ni from Ni-containing ores Residues, etc. can be used.

Red mud is used as the Al-containing ore, ilmenite is used as the Ti-containing ore, and saprolite is used as the Ni-containing ore. For example, as a method for recovering Ni from Ni-containing ore, the above-described HPAL method is known, and the residue after separating and recovering Ni has a 50% particle size of 2 μm or less.

In the heat treatment step, the iron oxide-containing powder having a 50% particle size of 2 μm or less is heat-treated at a heating temperature of 900 to 1200 ° C. By heat-treating the fine iron oxide-containing powder in this temperature range, the iron oxide-containing powder is oxidized, sintered, and coarsened. As a result, it can be grown to a size that allows granulation in the steps described below. When the heating temperature is lower than 900 ° C., the effect of coarsening cannot be obtained, and granulation cannot be performed or even if granulation can be performed, a spherical agglomerate cannot be obtained. Therefore, the heating temperature is 900 ° C. or higher, preferably 950 ° C. or higher, more preferably 1000 ° C. or higher. However, when the heating temperature exceeds 1200 ° C., there is a problem that a coarse agglomerate is formed or the agglomerate adheres to the surface of the heat treatment apparatus. Therefore, the heating temperature is 1200 ° C. or lower, preferably 1150 ° C. or lower, more preferably 1100 ° C. or lower.

The heating temperature may be controlled based on this temperature by inserting a thermocouple into the furnace and measuring the ambient temperature in the center of the furnace.

In the heat treatment, the heating time may be controlled in consideration of the heating temperature so that the 50% particle diameter of the heat treated powder is 4 μm or more. The heating time is preferably 30 minutes or longer, for example. The heating time is more preferably 40 minutes or more, and further preferably 50 minutes or more. The upper limit of the heating time is not particularly limited, but even if the heating time is increased, the effect of coarsening the particle diameter is saturated, but the productivity is lowered. Therefore, the heating time may be 60 minutes or less, for example.

The heat treatment may be performed in an oxidizing atmosphere, for example, in an air atmosphere.

The heat treatment is preferably performed while rolling to uniformly heat the iron oxide-containing powder. A rotary heating furnace may be used as the heating furnace. The rotary heating furnace refers to a furnace in which a furnace surface that is a heating surface rotates around a rotation axis, and the rotation axis is horizontal or more and less than vertical.

[Agglomeration process]
In the agglomeration step, the heat treated powder obtained in the heat treatment step is used as a raw material, and the heat treated powder is granulated to produce an agglomerated product.

As a method for granulating the above heat treated powder, for example, a rolling granulation method can be mentioned.

The above heat-treated powder is preferably granulated so that the particle size of the agglomerate is, for example, 10 to 16 mm.

The heat-treated powder may be pulverized or pulverized prior to granulation. A well-known thing can be used as a crusher or a grinder, for example, a ball mill, a roller mill, a roll crusher etc. can be used.

[Other]
The agglomerate obtained in the agglomeration process can be used as a raw material for iron making. For example, after heat-curing the obtained agglomerate, by putting in a blast furnace or heat-cured product obtained by heat-curing treatment, further reducing the iron oxide by heating in a reducing gas atmosphere, Reduced iron can be produced.

Also, reduced iron can be produced by blending the heat-treated powder with a carbonaceous reducing agent or binder to form an agglomerate and heating it in a heating furnace.

As described above, according to the present invention, since the iron oxide-containing powder having a 50% particle size of 2 μm or less can be coarsened to a granulated particle size by heat treatment in a predetermined temperature range, When granulated as a raw material, an agglomerate having a uniform structure in which the heat-treated powder has grown in a snowball manner can be produced.

This application claims the benefit of priority based on Japanese Patent Application No. 2013-154793 filed on July 25, 2013. The entire contents of the specification of Japanese Patent Application No. 2013-154793 are incorporated herein by reference.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with modifications within a range that can meet the above and the gist described below. Of course, these are all possible and are included in the technical scope of the present invention.

An iron oxide-containing powder having a 50% particle size of 2 μm or less was heat-treated, and the obtained heat-treated powder was granulated to produce an agglomerate. Details will be described below.

As the iron oxide-containing powder having a 50% particle diameter of 2 μm or less, a residue after recovering Ni from Ni-containing ore was used. This residue was tailing and the water content was about 27%. The component composition of the residue after Ni recovery is shown in Table 1 below. In Table 1 below, LOI represents the amount of ignition loss (loss of ignition).

The above tailings were left outdoors and exposed to the sun to make the water content about 19%. The tailing whose water content was adjusted to about 19% was reddish brown. This was charged in 2 kg into a rotary heating furnace and heat-treated while rolling the tailing to dry and sinter. As shown in Table 2 below, the heating temperature during the heat treatment was set to 400 ° C., 800 ° C., 1100 ° C., or 1200 ° C. As shown in Table 2 below, the heating time was about 60 minutes when the heating temperature was 400 ° C, and about 30 minutes when the heating temperature was 800 ° C, 1100 ° C, or 1200 ° C. The heating atmosphere was under air circulation.

The powder obtained by heat treatment remained reddish brown when the heating temperature was 400 ° C, 800 ° C or 1100 ° C, but changed to blackish brown when the heating temperature was 1200 ° C. For reference, FIG. 1 shows a drawing-substituting photograph in which a powder obtained by heat treatment at a heating temperature of 400 ° C. is photographed. Moreover, the drawing substitute photograph which image | photographed the powder obtained by heat-processing with 1200 degreeC heating temperature is shown in FIG.

Next, after the heat treatment, the heat-treated powder cooled to room temperature was crushed or pulverized with a ball mill, and this was used as a granulation sample. For heat-treated powder obtained by heat treatment at a heating temperature of 400 ° C., 800 ° C. or 1100 ° C., for a heat treatment powder obtained by crushing for about 30 seconds with a ball mill and heat treatment at a heating temperature of 1200 ° C. For about 20 minutes.

The particle size distribution of each heat-treated powder was measured, and the results are shown in FIG. The horizontal axis in FIG. 3 indicates the particle diameter (μm), and the vertical axis indicates the total sieve mass (mass%). As shown in FIG. 3, when the particle size distribution is determined with the mass of the heat treated powder as a whole being 100%, the particle size at which the integrated sieve mass becomes 50% is called the 50% particle size.

Further, 50% particle diameter (μm), integrated sieve mass (mass%) having a particle diameter of less than 1 μm, and integrated sieve mass (mass%) having a particle diameter of less than 10 μm were calculated, and the results are shown in Table 2 below. Show.

As is clear from FIG. 3 and Table 2, the powder obtained by heat treatment at a heating temperature of 400 ° C. or 800 ° C. has a 50% particle size almost the same as the raw material powder before the heat treatment, and the particle size is less than 1 μm. The total sieve mass of was also almost the same. Therefore, the raw material powder and the powder obtained by heat treatment at a heating temperature of 400 ° C. or 800 ° C. all had a particle size of less than 10 μm and almost the same particle size constitution. In contrast, the powder obtained by heat treatment at a heating temperature of 1100 ° C. has a 50% particle size that is approximately 8.6 times larger than the raw material powder before the heat treatment, and the particles are coarsened by the heat treatment. I understand that. In addition, the powder obtained by heat treatment at a heating temperature of 1200 ° C. has a 50% particle size that is about 53.5 times larger than the raw material powder before the heat treatment, and the cumulative sieving mass with a particle size of less than 1 μm is It can be reduced to 4.4% by mass, and it can be seen that the particles are coarsened by the heat treatment.

The coarsening of the particles can also be read from the results of the accumulated sieving mass with a particle size of less than 1 μm and the accumulated sieving mass with a particle size of less than 10 μm. That is, when the raw material powder or the heating temperature was heat treated at 400 ° C. or 800 ° C., the particle diameter was only less than 10 μm, whereas the heat treatment was carried out at a heating temperature of 1200 ° C. so that the particle diameter was less than 10 μm. The ratio of the powder was 20.9%, and the ratio of the coarse powder having a particle diameter of 10 μm or more could be about 80%.

Next, based on the particle size distribution value for each particle size range of the heat-treated powder, the specific surface area (cm ² / g) was calculated by assuming that the particle diameter was spherical. The results are shown in Table 2 below.

As is apparent from Table 2 below, the specific surface area (calculated value) of the powder obtained by heat treatment at a heating temperature of 400 ° C. or 800 ° C. was 27400 to 29380 cm ² / g. In contrast, the specific surface area (calculated value) of the powder obtained by heat treatment at a heating temperature of 1100 ° C. is 8520 cm ² / g, and the specific surface area of the powder obtained by heat treatment at a heating temperature of 1200 ° C. (calculated value). Was 1920 cm ² / g. From these results, it can be seen that the higher the heating temperature, the smaller the specific surface area and the larger the particles.

Next, the heat treated powder was charged into a granulator made of rubber tire having a diameter of about 35 cm, and granulated by adding an appropriate amount of water. As a result, when the pulverized product of heat treated powder obtained by heat treatment at 400 ° C. or 800 ° C. is used, the pellet shape does not become spherical, and there are protrusions on the surface like confetti became. FIG. 4 shows a drawing-substituting photograph in which an agglomerate obtained by granulating a pulverized product of heat-treated powder obtained by heat treatment at a heating temperature of 400 ° C. is photographed.

On the other hand, when the pulverized product of the heat-treated powder obtained by heat treatment at 1100 ° C. or 1200 ° C. was used, the shape of the pellet was spherical. FIG. 5 shows a photograph substituted for a drawing of a pellet obtained by granulating a pulverized product of the heat-treated powder obtained by heat treatment at a heating temperature of 1200 ° C.

Next, regarding pellets obtained by granulating a heat-treated powder obtained by heat treatment at 1100 ° C. or 1200 ° C., the moisture content (%), crush strength per pellet (kg), and voids The rate (%) was measured.

The crushing strength may be referred to as a crushing load (hereinafter referred to as a crushing load) by placing one pellet between two flat plates and applying a load to the flat plate so that the pellet is compressed. kg) was measured with a strength tester. The crush load was measured for 10 pellets, and the average value was obtained. The results are shown in Table 2 below.

The porosity (%) was obtained by calculation from the apparent specific gravity value measured based on the buoyancy of the pellet immersed in mercury and the true specific gravity value of the mixed raw material powder. The results are shown in Table 2 below.

When the heat-treated powder obtained by heat treatment at a heating temperature of 1100 ° C. or 1200 ° C. is granulated, the moisture content, crushing strength, and porosity contained in the resulting pellet are manufactured by a conventional pelletizing plant. It was confirmed that it was almost the same as the raw pellet.

These iron pellets can be produced after heat-curing treatment, for example, by heating in a reducing gas atmosphere. Also, reduced iron can be produced by preparing pellets by mixing a carbonaceous reducing agent, a binder or the like with the heat-treated powder and heating the pellets.

As described above, according to the present invention, an iron oxide-containing powder having a 50% particle size of 2 μm or less can be heat treated at a heating temperature of 900 to 1200 ° C. to obtain a granulated particle size. Can be manufactured. This agglomerate can be effectively used as an iron source.

Claims (9)

1. A step of heat-treating an iron oxide-containing powder having a 50% particle size of 2 μm or less at a heating temperature of 900 to 1200 ° C .;
   A process of granulating the obtained heat-treated powder as a raw material to produce an agglomerate;
   The manufacturing method of the agglomerate characterized by including.
2. The production method according to claim 1, wherein the granulation is performed by a rolling granulation method.
3. The manufacturing method according to claim 1 or 2, wherein the heat treatment is performed such that a 50% particle diameter of the heat treated powder is 4 µm or more.
4. The manufacturing method according to claim 1 or 2, wherein the heat treatment is performed for a heating time of 30 minutes or more.
5. The manufacturing method according to claim 1 or 2, wherein the heat treatment is performed while rolling the iron oxide-containing powder.
6. The method according to claim 1 or 2, wherein the iron oxide-containing powder is tailing.
7. The manufacturing method according to claim 6, wherein the tailings are residues after recovering Ni from Ni-containing ores.
8. A method for producing reduced iron, wherein the agglomerates obtained by the production method according to claim 1 or 2 are heated to produce reduced iron.
9. The production method according to claim 8, wherein the agglomerate further contains a carbonaceous reducing agent.

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