JP2008214715A - Method for manufacturing nonfired agglomerated ore for iron manufacture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture nonfired agglomerated ore for iron manufacture having high strength and high reducibility. <P>SOLUTION: A mixture, in which a carbonaceous material B and a binding material C are blended with an iron raw material A, is pelletized into a primary pellet X<SB>1</SB>to be a core part. The outer side of this primary pellet X<SB>1</SB>is coated with a mixture in which the binding material C is blended with the iron raw material A to prepare a secondary pellet X<SB>2</SB>. Subsequently, the secondary pellet X<SB>2</SB>solidified using the binding material C as a binder is subjected to microwave heating to preliminarily reduce iron oxide in the core part using the carbonaceous material B as a main reducing material. Even if the coating layer is densified to increase the strength of the pellet, reducibility in the central part of nonfired agglomerated ore can be increased. As a result, the nonfired agglomerated ore having high strength and reducibility on the whole can be manufactured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an unfired agglomerated ore for iron making used as an iron raw material in an iron making furnace such as a blast furnace.

  In a pig iron manufacturing process performed using a solid iron furnace such as a blast furnace (hereinafter described as an example of a blast furnace), a void in the raw material packed bed is used to distribute reducing gas in the raw material packed bed in the furnace. It is important to keep the rate above a certain value. For this reason, it is desirable that the furnace interior inclusions such as iron raw materials have a large particle size distribution, and it is necessary to increase the strength of the charges that may be pulverized after charging to suppress pulverization. For this reason, especially in large blast furnaces, sintered ore obtained by baking powdered ore with the heat of combustion of carbonaceous materials, or fired pellets obtained by forming powdered ore into a spherical shape with a pelletizer and then heat-hardening at 1000 ° C or higher Is widely used.

  On the other hand, studies on non-fired agglomerated minerals that are not heat-treated at high temperatures have been promoted, particularly for the purpose of energy saving. This non-calcined agglomerated mineral is cured for a certain period of time at a relatively low temperature of several hundred degrees C or less using normal or waste heat with iron ore powder or ironmaking dust as a binder and a hydraulic binder such as cement. Manufactured. Such unfired agglomerated ore is also desired to be as strong as possible to prevent pulverization. Therefore, it is desirable to make the structure as dense as possible (increase the packing density) when granulating. However, on the other hand, if the structure of the granulated product is densified, the reducing gas will not easily penetrate into the granulated product, and the reduction inside the granulated product will be delayed. When unreduced iron oxide is supplied to the lower part of a solid furnace such as a blast furnace, the ratio of direct reduction (endothermic reaction) between solid carbon and iron oxide increases, resulting in an increase in the ratio of reducing materials and a decrease in productivity. Because it causes, it is not preferable.

Patent Document 1 discloses a non-fired agglomerated mineral using fine sintered ore having a particle diameter of 5 mm or less as a core particle. In such a non-fired agglomerated mineral, a relatively porous sintered ore is disclosed. It is said that the reducing structure of the unfired agglomerated ore center improves because the ore structure helps the reductive gas to penetrate into the center of the granulated product.
JP-A-9-170033

  Patent Document 1 is a technique for improving the reducibility of the central part of the non-fired agglomerated mineral, but no matter how porous the fine sintered ore of the core part is porous and has good air permeability, When the granulated structure of the part is densified, the reducing gas is blocked and cannot reach the central part. On the other hand, if the filling rate of the outer peripheral portion is lowered in order to improve the air permeability, the strength of the granulated product is lowered and pulverized in the blast furnace. Therefore, the conventional technique is not a drastic measure for improving the reduction of the central portion of the unfired agglomerated ore.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a method for producing a non-fired agglomerate for iron making that has high strength that is difficult to be pulverized in a furnace and has high reducibility. There is.

  If the inventors preliminarily reduce only the central part of the unfired agglomerated ore in advance, even if the permeability of the reducing gas is reduced by densifying the outer peripheral part to ensure strength, The necessary reducibility of the agglomerate as a whole could be ensured, and it was thought that this could achieve both high strength and high reducibility, and the specific measures were examined. As a result, the granulated product to be a non-fired agglomerated mineral is composed of a core portion and a coating layer on the outer side of the granulated material. It has been found that by heating, a high-strength, highly reducible non-fired agglomerated mineral that can solve the above-mentioned problems can be obtained. That is, the carbonaceous material (carbon) is a material that absorbs microwaves well and is easily heated, and also functions as a reducing material for iron oxide. Therefore, if carbonaceous material is blended in the core part of the granulated product that will be unfired agglomerated ore, the core part is preferentially heated in microwave heating, and the iron oxide contained in the core part is Since it will be reduced, the reducibility of the central part of the unfired agglomerated ore can be enhanced. On the other hand, since the iron oxide is easily reduced by the reducing gas in the furnace, the pre-reduction like the core part is necessary for the outer layer of the granulated product (the outer peripheral part of the granulated product). On the contrary, if carbon material is contained in the same manner as the core part, not only the energy and material cost required for reduction are increased, but also the coating layer is brought about by contact with reducing gas in the furnace in advance and microwave heating. Is strongly reduced, resulting in the formation of a layer of metallic iron in the coating layer, which prevents the reduction of the central part of the unfired agglomerate. Based on the above, the granulated product to be a non-fired agglomerated mineral is composed of a core portion and a coating layer on the outer side of the granulated material. If the non-fired agglomerated mineral is produced, the entire agglomerated ore is necessary by increasing the reducibility of the central part of the non-fired agglomerated mineral, even if the coating layer is densified to increase the strength of the granulated product. As a result, it is possible to obtain a non-fired agglomerated mineral with high strength and high reducibility.

The present invention has been made based on the above findings, and the features thereof are as follows.
[1] In a method for producing an unfired agglomerated ore for iron making using an iron raw material (A) containing iron oxide, a mixture in which a carbonaceous material (B) and a binder (C) are blended with the iron raw material (A) Is made into a primary granulated product (X ₁ ) that becomes a core part, and then a mixture in which the binder (C) is blended with the iron raw material (A) outside the primary granulated product (X ₁ ). The secondary granulated product (X ₂ ) is coated to be coated, and then the secondary granulated product (X ₂ ) solidified with the binder (C) as a binder is heated by microwaves. A method for producing agglomerates.

[2] In the production method of [1], the iron raw material (A) is composed of at least one selected from fine-grained sintered ore, fine-grained iron ore, and dust generated in the steel production process. A method for producing an unfired agglomerated ore for iron making.
[3] In the production method of the above-mentioned [1] or [2], that radius R and primary granules of KatamariNaruko (X ₁₎ and the radius R ₁ of the formed nuclei part satisfies the formula The manufacturing method of the non-baking agglomerate for iron making characterized.
0.4 ≦ R ₁ /R≦0.5
[4] In the production method according to any one of [1] to [3], the carbon content of the primary granulated product (X ₁ ) is 2 to 30 mass%, and the unfired agglomerated ore for iron making Manufacturing method.

  According to the present invention, a granulated product that forms a non-fired agglomerated mineral is composed of a core portion and a coating layer on the outer side thereof, and a form in which carbonaceous materials are blended only in the core portion. Even if the coating layer is densified by heating to increase the strength of the granulated product, the reducibility required for the entire agglomerated ore is ensured by increasing the reducibility of the central part of the unfired agglomerated ore. be able to. For this reason, the non-baking agglomerate which has high intensity | strength and reducibility can be manufactured. Moreover, since a carbon material is mix | blended only in the nucleus part, a reducing material ratio can also be reduced.

  The present invention is a method for producing an unfired agglomerated ore for iron making using an iron raw material (A) containing iron oxide, and the iron raw material (A) is a fine-grain sintered ore, fine-grain iron ore, steel Examples thereof include dust generated in the manufacturing process, and one or more of these can be used. However, the iron raw material (A) is not limited thereto, and may be a fine granular material that can serve as an iron raw material for an iron making furnace and cannot be charged into a blast furnace as it is. The particle size of the iron raw material (A) for iron is generally less than 5 mm.

  A typical example of the fine-grained sintered ore is a sintered ore powder called return ore in the iron ore sintering process. In the conventional general sintering process, this sintered ore powder is sent back to the sintering process. It is used as a sintering raw material. Most of the sintered ore powder is generated in the particle size selection process when obtaining the product sintered ore, but there are also those generated in the transport process to the blast furnace and around the blast furnace. In the conventional sintering process, the product yield is about 70 to 80 mass%, and the remaining 20 to 30 mass% is returned to the sintering process as return mineral (sintered ore powder) (that is, the product sintered ore). Circulates within the process without becoming). Therefore, by using such sintered ore powder as the iron raw material (A) of the non-fired agglomerated mineral of the present invention, the total yield of agglomerated minerals including the sintered ore can be greatly improved.

The fine-grained iron ore includes iron ore powder. Moreover, any of iron ore having a small particle size and iron ore having a small particle size generated in the sizing process may be used.
Examples of the dust generated in the steel manufacturing process include blast furnace dust, refining dust, and the like, and these dusts also contain a considerable amount of iron oxide.
Blast furnace dust is dust recovered from blast furnace gas by dust collection. Further, the refining dust is dust collected by collecting dust from the exhaust gas generated in the refining process. For example, refining dust generated in the hot metal pretreatment process, refining dust generated in the converter decarburization process (converter OG dust). and so on.

FIG. 1 shows an outline of the production method of the present invention.
In the production method of the present invention, first, as shown in FIG. 1 (a), a mixture in which a carbon material (B) and a binder (C) are blended with an iron raw material (A) is granulated, and the core portion of the agglomerated ore. A primary granulated product (X ₁ ) is formed. Granulation is performed with the mixture in a humidified state. Usually, the mixture (iron raw material (A) + carbonaceous material (B) + binding material (C) + other components as necessary. The same applies hereinafter) and water are mixed. and stirring (mixing), and then subjected to granulation, to obtain primary granules of (X _1).

In the present invention, the carbonaceous material (B) is blended as a raw material for the primary granulated product (X ₁ ), as described later. This is because the core portion composed of (X ₁ ) is preferentially heated, and the carbon material (B) is preliminarily reduced with the iron oxide contained therein as the reducing material. Examples of the carbon material (B) include pulverized coke and pulverized coal, and one or more of them can be used. In addition, when using pulverized coal, it is desirable to use so-called anthracite with little volatile content. When coal with a large amount of volatile matter is used, the volatile matter is gasified during heating, and the granulated structure is destroyed by the gas pressure, which may cause weakening of the granulated matter.
Primary granules (X ₁₎ is no particular restriction on the carbon-containing (blending) ratio in but about 2～30Mass%, more preferably it is appropriate to be about 10~15mass%. If the carbon content is less than 2 mass%, the degree of preliminary reduction is small, while if it exceeds 30 mass%, there is a possibility of causing a problem in the strength of the unfired agglomerated ore.

The binding material (C) is not particularly limited as long as it can exhibit sufficient strength in the cold, but a hydraulic binding material is particularly preferable in terms of manufacturing cost. The hydraulic binder is not particularly limited as long as it can express sufficient strength in the cold by hydration hardening, for example, various cements such as blast furnace cement, Portland cement, fly ash cement, alumina cement, Examples include blast furnace granulated slag fine powder, and one or more of these can be used.
The binding material (C) may be a minimum necessary amount for obtaining a sufficient cold strength, and usually about 2 to 10 mass% is appropriate.
The granulation method is arbitrary, but as a typical method, there are a rolling granulation method using a disk pelletizer or a drum type granulator, a compression granulation method using a briquette molding machine, etc. However, the rolling granulation method is preferred from the standpoints of productivity and manufacturing cost.

Next, as shown in FIG. 1B, a coating layer (y) was formed by coating a mixture of the iron raw material (A) and the binder (C) on the outside of the primary granulated product (X ₁ ). A secondary granulated product (X ₂ ) is obtained.
Carbonaceous materials are not significantly added to the raw material for forming the coating layer (y). Since the iron oxide of the coating layer (y) is easily reduced by the reducing gas in the furnace, pre-reduction such as the core portion is not necessary. In addition to increasing the energy and material costs required for the reduction, the coating layer is strongly reduced by the contact between the microwave heating and the reducing gas in the furnace, resulting in the formation of a metallic iron layer in the coating layer. This will hinder the reduction of the central part of the unfired agglomerate. Therefore, although this coating layer (y) can also use the dust generated in the steel production process as the iron raw material (A), it is preferable to avoid the use of dust containing a relatively large amount of powdered coke and carbon.
The type of the binder (C) used for the coating layer (y) is the same as that of the primary granulated product (X ₁ ) described above, but the blending amount is more blended for higher strength. May be. However, since it is not desirable for the iron making furnace to increase the binder that is not an iron source, the upper limit of the amount of the binder is preferably about 20 mass%.

Although formation of a coating layer (y) can be performed by arbitrary methods, it is normally performed by the rolling granulation method. That is, the above mixture (iron raw material (A) + binding material (C) + and other components as necessary, the same applies hereinafter) is added to the primary granulated product (X ₁ ), and a disk pelletizer or drum type granulator Mix granulation in a humidified state by the rolling granulation method using Thus deposited mixture on the surface layer of the primary granules (X _1), is intended to obtain the coating layer (y) secondary granules formed of mixture (X _2).
Therefore, in the method of the present invention, the primary granulated product (X ₁ ) is formed by primary granulation by the rolling granulation method, and then the primary granulated product (X ₁ ) by secondary granulation by the rolling granulation method. The method of forming the coating layer (y) on the outer side of the slag to obtain the secondary granulated product (X ₂ ) is most preferable.

Here, in the present invention, the core portion of the secondary granulated product (X ₂ ) is preliminarily reduced using the mixing of the carbonaceous material (B) and the microwave heating described later, thereby reducing the reducibility of the agglomerate. Therefore, even if a dense coating layer (y) having a low permeability of reducing gas is formed, the reducibility required for the entire agglomerate can be ensured. For this reason, a dense coating layer (y) can be formed by a tumbling granulation method or the like to obtain a high-strength non-fired agglomerated mineral that hardly causes pulverization. In order to form a dense coating layer (y), for example, the following method is effective.
(1) By increasing the blending amount of the binder (C), the strength is increased and the generation of cracks is suppressed.
(2) Adjust the particle size distribution of the raw materials constituting the coating layer and increase the packing density.
(3) In rolling granulators such as disk pelletizers, increase the residence time in the granulator and increase the packing density. In a compression granulator such as a briquette molding machine, the packing force is increased by increasing the compression force.
The secondary granulated product (X ₂ ) thus obtained is usually solidified with the binder (C) as a binder by curing for an appropriate period. The primary granulated product (X ₁ ) may be cured before forming the coating layer (y).

Next, as shown in FIG. 1C, the solidified secondary granulated product (X ₂ ) is irradiated with microwaves and heated by microwaves. Here, the carbonaceous material (B) blended in the core portion of the secondary granulated product (X ₂ ) (portion formed by the primary granulated product (X ₁ )) absorbs microwaves well and is easily heated. It is a material and functions as a reducing material for iron oxide. Therefore, by blending the carbonaceous material (B) only in the core part of the secondary granulated product (X ₂ ), the core part is preferentially heated by microwave heating, and the iron oxide contained in the core part is converted into carbon. The material (B) is efficiently reduced (preliminary reduction) using the reducing material, whereby an unfired agglomerate for iron production in which iron oxide contained mainly in the core portion is preliminarily reduced is obtained.
In the microwave heating step, the microwave generated by the microwave generator 1 is usually guided by the waveguide 2 as shown in FIG. 1 (c) and irradiated to the secondary granulated product (X ₂ ).
In addition, since the irradiated microwave is absorbed and attenuated by the secondary granulated product (X ₂ ), for example, when the stacked secondary granulated product (X ₂ ) is irradiated with microwaves from above A sufficient heating effect may not be obtained for the secondary granulated product (X ₂ ) on the lower layer side. Therefore, in that case, it is desirable that the stacked height of the secondary granulated product (X ₂ ) is 2 meters or less, more preferably 1 m or less.

The secondary granulated product (X ₂ ) is mainly composed of the iron raw material (A), the carbonaceous material (B), and the binder (C). (X ₁ ) and / or other components in the coating layer (y), for example, one or more of various dispersants, curing accelerators, limestone fine powder, fly ash, silica fine powder, etc., do not impair the effects of the present invention. An appropriate amount can be blended at the limit. The total amount of these other components in the primary granulated product (X ₁ ) and / or the coating layer (y) is preferably about 10 mass%, particularly preferably about 5 mass%.
The particle size of the unfired agglomerated mineral produced according to the present invention (sphere-converted particle size in a normal temperature atmosphere) is preferably about 8 to 30 mm. If the particle size of the unfired agglomerated mineral is less than 8 mm, the air permeability of the raw material packed layer when charged in the furnace may be reduced. On the other hand, if the particle size exceeds 30 mm, the reducibility may be reduced. .

In the non-fired agglomerated mineral produced according to the present invention, it is preferable that the radius R of the agglomerated mineral and the radius R _{1 of the} core part formed of the primary granulated product (X ₁ ) satisfy the following formula. Here, the radius R of the agglomerated mineral and the radius R _{1 of the} core part are the sphere equivalent radius in a normal temperature atmosphere.
0.4 ≦ R ₁ /R≦0.5
FIG. 2 schematically shows the reduction behavior of a non-fired agglomerated ore produced by the method of the present invention in a vertical furnace, and is reduced in a solid furnace (hereinafter, a blast furnace will be described as an example). The state of the agglomerated mineral just before melting after being reduced by the property gas is shown. If any radial position of the non-calcined mass Naruko was r, uncalcined masses Naruko by prereduction (secondary granules) in the range of 0 ≦ r / R ≦ R ₁ is reduced. On the other hand, although the outer peripheral portion is reduced in the blast furnace, a non-fired agglomerate containing no carbonaceous material is prepared, and a reduction test is performed in a reducing atmosphere and a temperature rising pattern in the blast furnace. Gas reduction was observed in the range of 5 ≦ r / R ≦ 1. Therefore, the range of the radius R ₁ of the core portion is preferably R ₁ /R≦0.5. If the core portion is larger than this, the preliminary reduction is performed up to the region where the gas is reduced, so that the energy required for the preliminary reduction is lost. Also, tissue containing a carbonaceous material strength is weak, the thickness of the In R ₁ /R>0.5 much coating layer is thin, there is a tendency that the cold strength decreases. On the other hand, when the radius R _{1 of the} core portion decreases, a layer (shaded portion in FIG. 2) that is not reduced by either preliminary reduction or gas reduction in the blast furnace is generated in the range of R ₁ ≦ r / R ≦ 0.5. When this layer becomes thick, the ratio of reducing material increases and the operation becomes unstable. However, if 0.4 ≦ R ₁ / R, there is almost no operational problem.

Since microwave heating consumes electric power, it is desirable that the irradiation with microwaves should be performed with a minimum irradiation amount that can provide a sufficient reduction effect. FIG. 3 shows the amount of microwave power and the non-calcined agglomerated when the secondary granulated product (X ₂ ) is microwave-heated when producing the unfired agglomerated R ₁ /R=0.5. This shows the relationship with the preliminary reduction rate. Here, the preliminary reduction rate is an index of how much the amount of oxygen to be reduced contained in the iron oxide before the preliminary reduction has been removed by the preliminary reduction, and is defined as follows.
γ = {(0.43F−0.112Fo) − (0.43F′−0.112Fo ′)} / (0.43F−0.112Fo)
Where γ: preliminary reduction rate (-)
F: Total iron content (mass%) in the sample before preliminary reduction
Fo: Ferrous oxide content (mass%) in the sample before preliminary reduction
F ′: Total iron content (mass%) in the sample after preliminary reduction
Fo ′: Ferrous oxide content (mass%) in the sample after preliminary reduction

According to FIG. 3, the microwave power per ton of unfired agglomerated ore is about 150 kWh / t- (agglomerated ore), and the preliminary reduction rate is almost the maximum (preliminary reduction rate: about 0.125). The amount of wave power is further increased, and the preliminary reduction rate is constant.
Since the non-fired agglomerated ore used in FIG. 3 is R ₁ /R=0.5, the volume of the core portion containing the carbonaceous material is about 12.5% of the entire non-fired agglomerated particles. The preliminary reduction rate of 0.125 indicates that the reduction rate of the core portion has reached almost 100%. From the above results, the amount of electric power of the microwave to be irradiated is preferably 100 to 200 kWh / t- (agglomerated ore), and particularly preferably around 150 kWh / t- (agglomerated ore). When the amount of power is below the above range, preliminary reduction is insufficient, while when the amount of power is above the above range, power that does not contribute to reduction is consumed, resulting in a loss of energy.

FIG. 4 shows a manufacturing flow of a specific embodiment of the manufacturing method of the present invention.
In the hopper group 3 (raw material storage tank), as the raw material for the core portion, fine iron ore a ₁ , fine sinter ore ₂ which is an iron raw material (A), ironworks generated dust a ₃ , carbon material (B ), Powder coke b, and cement c, which is a binder (C), are stored. Further, in the hopper group 4 (raw material storage tank), as the raw material for the coating layer, fine iron ore a ₁ and fine sintered ore a ₂ that are iron raw materials (A), and cement c that is a binder (C). Are stored respectively. Here, the fine particle iron ore a ₁ may be used in combination of a plurality of brands. The powder coke b can be replaced with powdered anthracite. Note that the above raw materials may be mixed in advance and cut out from one hopper. Although not shown, there may be a pulverization step for adjusting the particle size in advance, a step for removing foreign matter, and the like as necessary.

The raw material for the core part stored in the hopper group 3 is cut out by a quantitative cutting device, transported by the raw material transport device 5, and introduced into the humidification mixer 6 (for example, a drum mixer, an Eirich mixer, etc.). In the humidifying mixer 6, water is added to the raw material, and mixed and stirred. Although there is no special restriction | limiting in the function of the humidification mixer 6, etc., a thing with high mixing stirring ability is desirable. When a thing with low mixing stirring ability is employ | adopted, it will be necessary to take long mixing time, and productivity will fall.
The humidified and mixed raw material (mixture) is conveyed to the primary granulator 8 by the raw material conveying device 7, and is granulated by the primary granulator 8 to obtain a primary granulated product (X ₁ ). In the present embodiment, a dish type rolling granulator (disk pelletizer) is used as the primary granulator 8, but other types of granulators such as a drum granulator may be used. Good.

The primary granulated product (X ₁ ) is transported to the secondary granulator 10 by the raw material transport device 9. On the other hand, the raw material for the coating layer stored in the hopper group 4 is cut out by a quantitative cutting device, conveyed by the raw material conveying device 11 and introduced into the secondary granulator 10. These raw materials may be mixed in advance and cut out from one hopper.
In the secondary granulator 10, the primary granulated product (X ₁ ) and the raw material for the coating layer are mixed and granulated, and the coating layer comprising the raw material for the coating layer (mixture) outside the primary granulated product (X ₁ ). (Y) is formed and becomes a secondary granulated product (X ₂ ). This secondary granulated product (X ₂ ) is cured at a curing site 12 for a predetermined period, and then preliminarily reduced by a microwave heating process as shown in FIG. 1 (c) to obtain an unfired agglomerated ore.
The non-fired agglomerated ore produced as described above is used as an iron raw material in a vertical ironmaking furnace represented by a blast furnace.

The microwave heating process shown in FIG.1 (c) was applied to the manufacturing flow as shown in FIG. 4, and the unbaking agglomerate for iron manufacture was manufactured. Table 1 shows the component composition of the raw materials used. The iron raw material (A1) is fine-grained iron ore, the iron raw material (A2) is a sinter ore powder and the iron raw material (A3) is blast furnace dust. It is suitable as an iron raw material. Moreover, powder coke was used as the carbonaceous material (B), and Portland cement was used as the binder (C).
The produced uncalcined agglomerated ore was charged into a blast furnace (internal volume 3223 m ³ ) as a part of the iron raw material and operated. The results are shown in Table 2 together with the raw material blending ratio, cold strength, blast furnace operating conditions and operating results of the unfired agglomerated ore.
In each Example, the mixing ratio of the iron raw material to the blast furnace was set to non-fired agglomerated ore: 20 mass%, sintered ore: 70 mass%, and ore: 10 mass%.
In each Example, the preliminary reduction was performed by microwave heating for 30 minutes for each ton of uncalcined agglomerate using a 300 kW microwave generator.

  In order to investigate the cold strength of each unfired agglomerated ore of the inventive example and the comparative example, the powder rate at the yard and the powder rate at the top of the blast furnace were measured, and the powdered amount at the time of transportation was determined from the difference. If the agglomerate has a particle size of 5 mm or more, it can be used as a raw material for a blast furnace. Therefore, particles of −5 mm (= particle size less than 5 mm) are defined as powder, and the mass ratio is set to a powder rate of −5 mm. . The larger the cold strength of the agglomerate, the lower the amount of powder during transportation. The non-fired agglomerated mineral was sized through a sieve of 12 to 25 mm. This is because the pressure loss of the gas passing through the raw material packed bed in the furnace is smaller when the particle size distribution of the unfired agglomerated mineral is narrow.

  Also, the “blow-out phenomenon” of the number of blow-throughs shown in Table 2 means that the flow of reducing gas is stopped by increasing the pressure loss in the blast furnace, the pressure in the furnace rises, and reaches a certain pressure. When this happens, it means a phenomenon in which the rising of the reducing gas explosively resumes. In this case, since the charge in the furnace moves with the gas simultaneously with the resumption of the gas flow, the distribution of the charge deposited in layers is disturbed. If the distribution of the charge is disturbed, the air permeability is further deteriorated, and problems such as poor reduction of iron oxide are caused. There is also concern about thermal adverse effects on various facilities due to mechanical damage to the furnace body due to the rise and rapid hot gas ejection.

Invention Example 1 is the raw material blending ratio of the granulated product, and the iron part (A1): 78 mass%, the carbonaceous material (B): 15 mass for the core part (core part composed of the primary granulated product (X ₁ )). %, Binder (C): 7 mass%, and the coating layer is made of iron raw material (A1): 93 mass% and binder (C): 7 mass%. The unfired agglomerated ore obtained in this example is bonded by the binder (C) and has sufficient cold strength (the amount of powder during transportation is as small as 0.6 mass%). Also, when looking at the operation of the blast furnace, there is a large amount of tapping, the ratio of reducing material is low, and no blow-through phenomenon has occurred. This is because the preliminary reduction of the core part including the carbonaceous material was sufficiently performed, and the coating layer was appropriately reduced by the reducing gas in the blast furnace, so that the reduction of the unfired agglomerated ore was performed well. It is thought that.

Invention Example 2 is the raw material blending ratio of the granulated product, and the iron material (A1): 37 mass%, the iron material (A2): 40 mass for the core part (the core part composed of the primary granulated product (X ₁ )). %, Carbon material (B): 16 mass%, binder (C): 7 mass%, and the coating layer is iron raw material (A1): 43 mass%, iron raw material (A2): 50 mass%, binder (C): 7 mass %. The unfired agglomerated ore obtained in this example is bonded by the binder (C) and has sufficient cold strength (the amount of powder during transport is as small as 0.5 mass%). Also, when looking at the operation of the blast furnace, there is a large amount of tapping, the ratio of reducing material is low, and no blow-through phenomenon has occurred. This is because the preliminary reduction of the core part including the carbonaceous material was sufficiently performed, and the coating layer was appropriately reduced by the reducing gas in the blast furnace, so that the reduction of the unfired agglomerated ore was performed well. It is thought that. Moreover, the secondary effect which improves the yield of a sintering process is also acquired by using as a raw material the fine grain sintered ore returned to the sintering machine as a sieve.

Invention example 3 is the raw material compounding ratio of the granulated material, and the iron material (A1): 77 mass%, the carbonaceous material (B): 16 mass for the core part (the core part composed of the primary granulated product (X ₁ )). %, Binder (C): 7 mass%, and the coating layer is made of iron raw material (A1): 93 mass% and binder (C): 7 mass%. The unfired agglomerated ore obtained in this example is bonded by the binder (C) and has sufficient cold strength (the amount of powder during transportation is as small as 0.6 mass%). Also, when looking at the operation of the blast furnace, there is a large amount of tapping, the ratio of reducing material is low, and no blow-through phenomenon has occurred. This is because the preliminary reduction of the core part including the carbonaceous material was sufficiently performed, and the coating layer was appropriately reduced by the reducing gas in the blast furnace, so that the reduction of the unfired agglomerated ore was performed well. It is thought that. Moreover, the secondary effect which improves the yield of a sintering process is also acquired by using as a raw material the fine grain sintered ore returned to the sintering machine as a sieve.

Invention example 4 is the raw material compounding ratio of the granulated product, and the iron material (A1): 23 mass% and the iron material (A2): 45 mass for the core part (the core part composed of the primary granulated product (X ₁ )). %, Iron material (A3): 10 mass%, Charcoal material (B): 15 mass%, Binder (C): 7 mass%, and the coating layer is iron material (A1): 58 mass%, Iron material (A2): 35 mass %, Binder (C): 7 mass%. The uncalcined agglomerated mineral obtained in this example is bonded by the binder (C) and has sufficient cold strength (the amount of powder during transportation is as small as 0.7 mass%). Also, when looking at the operation of the blast furnace, there is a large amount of tapping, the ratio of reducing material is low, and no blow-through phenomenon has occurred. This is because the preliminary reduction of the core part including the carbonaceous material was sufficiently performed, and the coating layer was appropriately reduced by the reducing gas in the blast furnace, so that the reduction of the unfired agglomerated ore was performed well. It is thought that. In addition, blast furnace dust is generally put into a sintering machine as a sintering raw material, and is made into a sintered ore by applying energy such as combustion heat of powdered coke. A secondary effect is also obtained.

Invention example 5 is the raw material compounding ratio of the granulated product, and the iron part (A1): 78 mass%, the carbonaceous material (B): 15 mass for the core part (core part composed of the primary granulated product (X ₁ )). %, Binder (C): 7 mass%, and the coating layer is made of iron raw material (A1): 93 mass% and binder (C): 7 mass%. The non-fired agglomerated mineral obtained in this example has a slightly small core region, R ₁ /R=0.35. This unfired agglomerated mineral is sufficiently bonded with the binding material (C) and has sufficient cold strength (the amount of powdered powder during transportation is as small as 0.6 mass%). On the other hand, when looking at the operation of the blast furnace, the amount of slag decreased slightly compared to Invention Examples 1 to 4, and the reducing material ratio increased. Although the operation of the blast furnace was stable, it was confirmed that the blow-through phenomenon slightly worsened, such as once a day. This is because the preliminary reduction of the core portion including the carbonaceous material is sufficiently performed, and the coating layer is reduced by the reducing gas in the blast furnace, and the reduction of the unfired agglomerated ore is performed. It is considered that the unreduced portion generated in the layer of <R ₁ /R≦0.5 reaches the lower part of the blast furnace, causing a direct reduction reaction that is a large endothermic reaction, which slightly deteriorates the operation of the blast furnace.

Invention example 6 is the raw material compounding ratio of the granulated product, and iron material (A1): 78 mass%, carbonaceous material (B): 15 mass for the core part (core part composed of primary granulated product (X ₁ )). %, Binder (C): 7 mass%, and the coating layer is made of iron raw material (A1): 93 mass% and binder (C): 7 mass%. The non-fired agglomerated ore obtained in this example has a slightly large core region and R ₁ /R=0.7. This unfired agglomerated ore tends to have a slight decrease in cold strength (the amount of powdering during transport is a little high at 2.0 mass%). The reducing material ratio was high. Although the operation of the blast furnace was stable, it was confirmed that the blow-through phenomenon slightly worsened, such as once a day. This is presumably because the core portion was thick and the coating layer was thin, so that the cold strength was slightly reduced, powder was brought into the blast furnace, and the airflow resistance was slightly deteriorated.

Invention example 7 is the raw material compounding ratio of the granulated product, and the iron material (A1): 57 mass% and the iron material (A2): 35 mass for the core part (the core part composed of the primary granulated product (X ₁ )). %, Carbon material (B): 1 mass%, binder (C): 7 mass%, and about covering layer, iron raw material (A1): 45 mass%, iron raw material (A2): 48 mass%, binder (C): 7 mass %. In this example, the carbon content of the primary granulated product (X ₁ ) constituting the core portion is 0.9 mass%. The unfired agglomerated ore obtained in this example is bonded by the binder (C) and has sufficient cold strength (the amount of powder during transportation is as small as 0.6 mass%). On the other hand, when we looked at the operation of the blast furnace, the output amount decreased slightly and the ratio of reducing materials increased. Although the operation of the blast furnace was stable, it was confirmed that the blow-through phenomenon slightly worsened, such as twice a day. This is because the carbon necessary for the preliminary reduction is insufficient, and unreduced iron oxide remains in the core part, so that this unreduced part reaches the lower part of the blast furnace and performs a direct endothermic reaction that is a large endothermic reaction. It is thought that the operation of the blast furnace was slightly deteriorated.

Invention example 8 is the raw material compounding ratio of the granulated product, and the iron material (A1): 23 mass% and the iron material (A2): 25 mass for the core part (core part composed of the primary granulated product (X ₁ )). %, Carbon material (B): 45 mass%, binder (C): 7 mass%, and the coating layer is made of iron raw material (A1): 93 mass%, binder (C): 7 mass%. In this example, the carbon content of the primary granulated material (X ₁ ) constituting the core portion is 38.9 mass%. The non-fired agglomerated mineral obtained in this example has a tendency to slightly decrease the cold strength (the amount of powdering during transportation is slightly high at 2.8 mass%). The amount decreased slightly and the reducing material ratio increased. Although the operation of the blast furnace was stable, it was confirmed that the blow-through phenomenon slightly worsened, such as three times a day. This is because the carbon content of the core portion was increased to 38.9 mass%, which reduced the strength of the unfired agglomerated minerals, which resulted in powder in the blast furnace and a slight deterioration in ventilation resistance. It is considered a thing.

In Comparative Example 1, the raw material blending ratio of the granulated product was determined. Regarding the core part (the core part composed of the primary granulated product (X ₁ )), the iron raw material (A1): 93 mass%, the binder (C): 7 mass. The coating layer is also made of iron raw material (A1): 93 mass% and binder (C): 7 mass%. In the granulated product of this example, the composition of the core portion and the coating layer is the same, and the core portion does not contain carbon necessary for the prereduction, so it is considered that prereduction does not occur even if microwave heating is performed. . However, the unfired agglomerated ore obtained in this example has strong cold strength (the amount of powdered powder during transportation is 0.6 mass%), and can be used in a blast furnace as an iron oxide raw material. It was. However, when looking at the operation of the blast furnace, it was confirmed that the amount of brewing decreased, the ratio of the reducing material increased, and the phenomenon that the blow-through phenomenon occurred 12 times a day was considerably worsened. This is because the reducing gas in the blast furnace reduces only the non-calcined agglomerated coating layer, and the core part reaches the lower part of the furnace without reduction, causing a direct reduction reaction that is a large endothermic reaction. It is thought that deteriorated.

Explanatory drawing which shows the outline of the manufacturing method of this invention Explanatory drawing which represented typically the reduction | restoration behavior in the furnace of the non-baking agglomerate manufactured with the manufacturing method of this invention Graph showing the relationship between the microwave power amount and the non-calcined mass Naruko prereduction rate in the case where the secondary granules of (X ₂₎ and microwave heating Explanatory drawing which shows the manufacture flow of specific embodiment of the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microwave generator 2 Waveguide 3, 4 Hopper group 5, 7, 9, 11 Raw material conveyance apparatus 6 Humidification mixer 8 Primary granulator 10 Secondary granulator 12 Curing place X ₁ Primary granulated material X ₂ Secondary granulated materials a ₁ Fine-grained iron ore a ₂ Fine-grained sintered ore a ₃ Steelworks generated dust ₃
b Powder coke c Cement

Claims (4)

In a method for producing an unfired agglomerated ore for iron making using an iron raw material (A) containing iron oxide,
After the carbonaceous material (B) and a binder (C) The mixture was granulated primary granules comprising a core portion containing a combination (X ₁₎ in the iron raw material (A), said primary granules (X ₁ ) Is coated with a mixture of the iron raw material (A) and the binder (C) to form a secondary granulated product (X ₂ ), and then the secondary solidified using the binder (C) as a binder. A method for producing a non-fired agglomerated ore for iron making, wherein the granulated product (X ₂ ) is heated by microwaves.   The iron raw material (A) is composed of one or more kinds selected from fine grain sintered ore, fine grain iron ore, and dust generated in a steel production process. A method for producing agglomerates. Uncalcined masses for steel according to claim 1 or 2 radius R and primary granules of KatamariNaruko (X ₁₎ and the radius R ₁ of the core portion formed in is characterized by satisfying the following formula Method for producing ore.
0.4 ≦ R ₁ /R≦0.5 Steel for uncalcined masses Naruko method according to claim 1, the carbon content is characterized in that it is a 2～30Mass% of primary granules (X _1).

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