CN107419093B

CN107419093B - Granulated particle of carbon-encapsulated material for use in producing sintered ore, method for producing same, and method for producing sintered ore

Info

Publication number: CN107419093B
Application number: CN201710549802.1A
Authority: CN
Inventors: 岩见友司; 大山伸幸; 山本哲也; 樋口隆英; 岩瀬一洋
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2013-07-10
Filing date: 2014-07-02
Publication date: 2021-12-21
Anticipated expiration: 2034-07-02
Also published as: JP2015129353A; CN105308194B; CN107419093A; JP6620850B2; AU2014288374A1; AU2014288374B2; KR20170106513A; AU2014288374B9; WO2015005190A1; PH12015502818A1; JP2018168476A; CN105308194A; JP6414493B2; PH12015502818B1; KR20160003860A; KR102110643B1; EP3020834A1; EP3020834A4; JP5790966B2; EP3020834B1

Abstract

The present invention provides a granulated particle containing a carbon material, which is a pseudo particle prepared by: a method for producing pseudo particles, which comprises charging a coke briquette having a carbon core particle diameter of 3 to 15mm, an iron ore powder having an outer layer particle diameter of 250 [ mu ] m or less, and a CaO-containing raw material into a granulator, mixing the coke briquette with the iron ore powder, and the CaO-containing raw material, granulating the mixture, and coating the outer layer around the carbon core. Further, a sintering raw material obtained by mixing the above-mentioned granulated particles of the carbon-encapsulated material with ordinary granulated particles is charged into a sintering bed of a sintering machine to form a charged layer, and sintered ore (sintered ore of the carbon-encapsulated material) is produced by utilizing combustion heat of the carbon material contained in the ordinary granulated particles. Further, the production amount of the carbon material-containing sintered ore in which the iron-containing raw material and the carbon material are arranged adjacent to each other can be obtained without using iron oxide powder containing metallic iron such as iron-making ore powder and mill scale.

Description

Granulated particle of carbon-encapsulated material for use in producing sintered ore, method for producing same, and method for producing sintered ore

The present application is a divisional application of the present application entitled "granulated particles of a carbon-containing material for use in producing sintered ore, a method for producing the same, and a method for producing sintered ore" filed as 2/7/2014 and having an application number of 201480033411.9.

Technical Field

The present invention relates to a technique for producing sintered ore used as an iron-making raw material in a blast furnace or the like, and more particularly, to granulated particles of a carbon-encapsulated material used for producing sintered ore, a method for producing the same, and a method for producing sintered ore using the granulated carbon-encapsulated material.

Background

In the blast furnace iron-making process, at present, iron-containing raw materials such as iron ore and sintered ore are mainly used as an iron source. Here, the above sintered ore is one of lump ores, which are obtained by recovering particles, as a finished product, prepared by: adding an appropriate amount of water to a granulation raw material comprising iron ore having a particle size of 10mm or less and SiO-containing SiO such as silica, serpentine and nickel-making slag to granulate, mixing and granulating the mixture with a drum mixer to obtain a sintering raw material as pseudo particles, charging the sintering raw material into a circulating sintering carriage (pallet) of a sintering machine, burning and sintering a carbon material contained in the pseudo particles, and pulverizing and granulating the obtained sintered cake to obtain particles having a particle size of at least a predetermined particle size₂Raw materials, auxiliary raw materials including CaO-containing raw materials such as limestone and quicklime, and solid fuels (carbon materials) as condensed materials such as powdery coke and anthracite.

In recent years, as the lump ore, a lump ore in which an iron source such as iron ore or mineral powder is disposed adjacent to a carbon material such as coke has been attracting attention. This is because, for example, when an iron source such as iron ore and a carbonaceous material are disposed adjacent to each other in a lump ore, a reduction reaction (exothermic reaction) on the iron source side and a gasification reaction (endothermic reaction) on the carbonaceous material side rapidly repeat, and thus iron making efficiency is improved and the temperature in a blast furnace or the like can be reduced.

As the lump ore, for example, patent document 1 discloses a lump ore produced as follows: an iron-containing powder raw material produced in an iron-making process such as blast furnace/converter ore powder, rolled iron scale, slime (slurry), iron ore powder, or the like alone or a raw material obtained by mixing these materials is mixed with a carbon material such as coal or coke, and starch, and then the mixture is mixed and kneaded, and then a starch solution is supplied to a granulator to granulate the mixture. However, in the lump ore disclosed in patent document 1, since the carbon material in the pellet is burned off during the production of the sintered ore, it is not actually realized to dispose the iron-containing raw material such as iron ore adjacent to the carbon material. Further, simply reducing the particle sizes of the iron ores and carbon materials for the purpose of adjacent arrangement excessively increases the movement resistance of the heat transfer gas, and conversely, reduces the reaction rate, thereby lowering the iron making efficiency.

Therefore, several techniques have been proposed for the purpose of disposing iron ore and a carbonaceous material adjacent to each other (see, for example, patent documents 2 to 5). These disclosed techniques basically use an iron-containing raw material such as iron ore and a carbon material such as coke mixed together and then thermally molded to form a lump, and use the formed lump as a raw material for iron making in a blast furnace or the like, or use the raw particles as they are without firing as a raw material for iron making in a blast furnace or the like. However, since these agglomerates are non-sintered ores formed of a homogeneous mixture or a multi-layer granulated material and have insufficient strength and are seriously pulverized, when they are charged into a blast furnace or the like, they are pulverized by dehydration and reduction, and the permeability of the blast furnace is impaired, so that there is a problem that the amount of use is limited.

As a technique for solving the technical problems of patent documents 2 to 5, for example, patent document 6 proposes an iron-making lump ore in which a core is formed from a raw material containing 5 wt% or more of metallic iron and/or 5 wt% or more of carbon, one or more outer circumferential layers are formed by including the core in a raw material containing 10 wt% or more of metallic iron and 5 wt% or less of carbon, and then the core is fired and agglomerated in an oxidizing gas atmosphere at 300 to 1300 ℃. However, the lump ore disclosed in patent document 6 also requires the use of metallic iron as a raw material, and there is a problem that the amount of the iron-making lump ore that can be produced is limited because the amount of the raw material used is limited.

Therefore, as a technique for overcoming the above problems of patent documents 1 to 6, a technique of lump ore containing a carbonaceous material inside has been proposed. For example, patent document 7 discloses the following technique: coating iron oxide powder containing metallic iron such as iron making powder and rolling mill scale around a carbon material core made of small coke by using a granulator to form an iron oxide shell with a low degree of oxidation, and then performing oxidation treatment by heating at a temperature of 200 ℃ or higher and less than 300 ℃ for 0.5 to 5 hours in the atmosphere, thereby forming a hard thin layer made of iron oxide with a high degree of oxidation only on the surface of the iron oxide shell, thereby obtaining a lump ore containing a carbon material; patent document 8 discloses the following technique: a lump ore containing coke powder having a size of 3mm or less dispersed in iron oxide powder or iron ore powder is obtained by mixing and granulating iron oxide powder such as iron-making powder or rolling mill scale or iron ore powder and a carbonaceous material using a granulator, and then coating the outer surface of the granulated product with iron oxide powder containing metallic iron to form an iron oxide shell having a low oxidation degree.

In addition, non-patent document 1 reports the results of evaluating a sintered ore containing a carbon material in a blast furnace atmosphere, the sintered ore containing a carbon material being obtained as follows: anthracite was coated on the green pellets to produce green pellets in which pellets (pellet feed) were coated with anthracite, which were then loaded onto layered ore in a pan test apparatus, and sintering raw material was loaded thereon and sintered.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2001 and 348625

Patent document 2: japanese patent No. 3502008

Patent document 3: japanese patent No. 3502011

Patent document 4: japanese patent laid-open publication No. 2005-344181

Patent document 5: japanese laid-open patent publication No. 2002-241853

Patent document 6: japanese laid-open patent publication No. 10-183262

Patent document 7: japanese patent laid-open publication No. 2011-195943

Patent document 8: japanese patent laid-open publication No. 2011-

Non-patent document

Non-patent document 1: CAMP-ISIJ vol.24(2011),194

Disclosure of Invention

Problems to be solved by the invention

According to the techniques disclosed in patent documents 7 and 8, it is possible to obtain a lump ore containing a carbon material having a suitable size and a sufficient strength as an iron-making raw material, and having a structure in which an iron-containing raw material is disposed adjacent to the carbon material, an iron-making reaction easily occurs, and low-temperature reduction is possible. However, in the above-mentioned techniques, since wettability with the carbon material is deteriorated when the amount of metallic iron is large, it is difficult to form a coating of the surface of the carbon material core with the iron oxide powder containing metallic iron, and it is necessary to perform oxidation treatment after granulation in order to form the iron oxide shell having a low oxidation degree, thereby increasing production cost, and there is a problem that production amount is limited because the amount of iron oxide powder containing metallic iron such as iron ore powder and mill scale is small.

In the technique disclosed in non-patent document 1, since no sintering material is present around the briquette, anthracite coal is wrapped around the green briquette, but the briquette layer coated with anthracite coal melts and exposes the anthracite coal inside, causing a problem of burning and disappearance.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide granulated particles of a carbon-encapsulated material that can obtain lump ore (sintered ore) of a carbon-encapsulated material in which a raw material containing iron and a carbon material are arranged adjacent to each other without using iron oxide powder containing metallic iron such as iron-making ore powder or mill scale, and to provide a method for producing the same, and a method for producing a sintered ore using the granulated particles of a carbon-encapsulated material.

Means for solving the problems

The inventors have conducted intensive studies to solve the above problems. As a result, it has been found that it is effective to produce sintered ore (lump ore) by using a small lump coke as a core of a carbon material in the center, using an iron ore powder (pellet (PF)) containing a CaO raw material to which a melting point modifier is added and having a particle size of 250 μm or less as an outer layer raw material, performing quasi-particle granulation to obtain a granulated material containing a carbon material for producing sintered ore, and charging the granulated material into a sintering machine as a part of a sintering raw material, thereby producing sintered ore (lump ore), and the present invention has been completed.

That is, the present invention relates to a granulated particle of a carbon-containing material for use in the production of a sintered ore, which is a pseudo particle comprising a core of a carbon material and an outer layer formed around the core of the carbon material, wherein the outer layer is mainly composed of iron ore powder and a raw material containing CaO.

The iron ore powder in the granulated particles containing a carbon material is characterized in that it is a pellet having a particle diameter of 10 to 1000 μm.

The pellet of the granulated particle containing a carbon-encapsulated material of the present invention is characterized in that the particle diameter thereof is 250 μm or less.

The outer layer in the granulated particle containing a carbon-encapsulating material of the present invention is characterized in that the melting point thereof is 1200 ℃ to 1500 ℃.

In the granulated particles of the carbon-encapsulated material of the present invention, the carbon material to be the core of the carbon material is characterized by being a coke particle having a particle diameter of 3mm or more.

The outer layer in the granulated particle containing a carbon material of the present invention is characterized in that the thickness thereof is 2mm or more.

The granulated particles of the carbon-encapsulated material of the present invention are characterized in that the particle diameter thereof is 8mm or more.

The present invention also relates to a method for producing carbon-encapsulated granulated particles for use in producing sintered ores, the method being any one of the above-described methods for producing carbon-encapsulated granulated particles, the method comprising: the carbon material core, iron ore powder as an outer layer and a raw material containing CaO as a melting point regulator are put into a granulator, mixed and granulated, and the periphery of the carbon material core is coated to form an outer layer, thereby preparing the pseudo-particles.

Further, the present invention relates to a method for producing a sintered ore containing a carbon material inside, the method including: the sintering raw material obtained by mixing the carbon material-containing granulated particles of any one of the above-described methods with normal granulated particles is charged into a sintering bed of a sintering machine to form a charged layer, and a sintered ore is produced by using the combustion heat of the carbon material contained in the normal granulated particles.

The method for producing a sintered ore containing a carbon-containing material according to the present invention is characterized in that a large amount of the granulated particles of the carbon-containing material are charged into the lower layer side of the charged layer.

In the method for producing a sintered ore containing a carbon-encapsulated material according to the present invention, the above-mentioned usual granulated particles are granulated by a drum mixer, and have a particle diameter smaller than that of the granulated particles containing a carbon-encapsulated material.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, iron ore powder (pellet (PF)) having low cost and high purity can be used in place of low-oxidation-degree iron oxide powder having a limited amount of production, such as various iron ore powders and mill scale produced in iron works, and thus, the production amount can be kept from limitation, and moreover, since oxidation treatment is not required, granulated particles of a carbon-encapsulated material for producing sintered ore can be produced at low cost. In addition, since the granulated particles of the carbon-encapsulated material of the present invention can be produced into sintered ore by using a conventional sintering machine, sintered ore of the carbon-encapsulated material can be produced in a large amount at low cost. In addition, since the sintered ore containing a carbon material of the present invention has a sufficient strength when used as a raw material for a blast furnace or the like, and has a structure in which an iron-containing raw material and a carbon material are disposed adjacent to each other, the reaction efficiency of an iron-making reaction is improved, the temperature in the furnace is lowered, the fuel ratio is lowered, and the manufacturing cost is reduced.

Drawings

Fig. 1 is a graph illustrating the effect of the distance between an iron-containing raw material and a carbon material on the reaction rate.

Fig. 2(a) to (b) are diagrams illustrating iron-making reactions (reduction reactions and gasification reactions) between iron-containing raw materials and carbon materials in comparison with the sintered ore containing carbon materials of the present invention in a conventional blast furnace.

Fig. 3(a) to (b) are diagrams illustrating a reduction reaction and a gasification reaction in the sintered ore containing the carbon material.

FIG. 4 is Fe₂O₃CaO binary phase diagram.

Fig. 5 is a diagram illustrating a reaction in the outer layer during sintering of the granulated particles containing a carbon material.

FIG. 6 is SiO₂-Fe₂O₃-CaO ternary phase diagram.

Fig. 7 is a view showing an example of the method for producing granulated particles of a carbon-encapsulated material and a sintered ore of a carbon-encapsulated material according to the present invention.

FIG. 8 is a view illustrating a sintering test pot used in the examples.

FIG. 9 is a photograph showing the appearance of a sintered ore (lump ore) obtained in the sintering test of the example.

FIG. 10 is a microphotograph showing a cross section of a sintered ore containing a carbon material of the present invention.

FIG. 11 is a graph showing the results of EPMA analysis of a cross section of a sintered ore containing a carbon-containing material of the present invention.

Fig. 12(a) to (b) are diagrams showing the reduction index RI and the reduction pulverization index RDI of the sintered ore containing a carbon material of the present invention in comparison with those of a conventional sintered ore.

Detailed Description

For example, in a blast furnace iron-making process, iron-containing raw materials such as iron ore and sintered ore are heated to a high temperature by combustion heat of a carbon material such as coke and are reduced to produce pig iron. In this case, the iron-containing material and the carbon material, which are generally granulated to have a size of about 20 to 40mm, are charged in layers from the top of the blast furnace. In this case, it is considered that if the layer thicknesses of the iron-containing raw material layer and the carbon material layer are reduced, the distance between the iron-containing raw material and the carbon material is reduced, and therefore the above-mentioned reduction reaction rate can be improved. However, when only the iron-containing raw material and the carbon material are mixed and charged as described above, the movement resistance of the heat transfer gas increases, and the reaction rate becomes slow.

Therefore, in recent years, as a method for increasing the reaction rate, there have been studied technologies such as iron coke, lump ore containing a carbon material, and ultrafine powder, as schematically shown in fig. 1. Here, the ferro coke is a technique of mixing and burning a carbon material and iron ore (iron-containing material) as an iron-making raw material, the lump ore containing a carbon material is a technique of filling the iron ore with a carbon material and using the material as an iron-making raw material, and the ultra-refining is a technique mainly used for refining the carbon material.

The idea of these techniques is based on the theory shown in fig. 2. Fig. 2 shows the relationship between heat exchange, reduction reaction of iron ore, and gasification reaction of carbon material (coke) when iron ore and carbon material are made to adjoin each other. On the iron ore side, Fe occurs₂O₃Reacts with CO to form Fe and CO₂And (3) reduction reaction of (2). The reaction is exothermic. On the other hand, on the carbon material side, a gasification reaction (gas modification reaction) called "budeson reaction" occurs, which is CO₂Reaction with C to form CO. This reaction is an endothermic reaction (hereinafter, both reactions are also referred to as "iron making reactions").

Here, as shown in fig. 2(a), when the iron-containing raw material and the carbon material are charged in a layered manner in the blast furnace, the reduction reaction as the exothermic reaction and the gasification reaction as the endothermic reaction occur at different sites, and therefore, heat conduction, CO, and CO necessary for the above reactions occur₂The supply of (2) requires movement of gas. On the other hand, as shown in fig. 2(b), when iron ore is adjacent to the carbonaceous material, the reduction reaction, which is an exothermic reaction, and the gasification reaction, which is an endothermic reaction, are repeated at a high rate, so that the iron making reaction efficiency is improved.

Therefore, it is considered that it is effective to bring the iron-containing raw material and the carbon material close to each other, that is, to arrange the iron-containing raw material and the carbon material adjacent to each other, for improving the iron-making reaction. According to such a technical idea, a lump ore containing a carbon material is obtained by mixing an iron-containing raw material and a carbon material in advance and embedding the carbon material in the iron-containing raw material.

In addition, in the lump ore containing the carbon material obtained by disposing such carbon material-iron-containing raw material adjacently, when the heat necessary for the gasification reaction reaches the inside of the lump ore containing the carbon material, as shown in fig. 3, CO generated by the gasification reaction is generated to cause Fe_nO_mReduction reaction of reduction, and CO produced by the reduction reaction₂Trigger the next gasification reactionIn this way, a chain reaction occurs from the inside to the outside of the lump ore, and Fe in the inside_nO_mAnd is sequentially self-reduced to generate Fe (metallic iron). As described above, since the reduction reaction and the gasification reaction are carried out inside the lump ore, a small amount of heat may be supplied from the outside, and only this portion can reduce the temperature in the furnace.

However, in order to realize the above technical idea, it is a condition that lump ore (sintered ore) containing a carbon material can be stably produced. However, in the production of agglomerate containing a carbon material, there is a problem that small coke particles contained in granulated particles (pseudo particles) are burned and lost during sintering, and if this problem cannot be solved, sintered ore containing a carbon material cannot be obtained stably.

Therefore, in the present invention, the above problems are solved by providing a granular coke having a small lump of coke as a core of a carbon material in the center, coating the periphery of the core of the carbon material with an iron ore powder having an adjusted over-melting point to prepare a pseudo particle, and using the pseudo particle as a granulated particle of a carbon-encapsulated material for producing a lump ore, i.e., a sintered ore, for encapsulating a carbon material.

That is, the lump ore containing a carbon material of the present invention is the same as the lump ore containing a carbon material of the related art in that the lump coke is used as the core of a carbon material in the center of the granulated particle (pseudo particle). However, the present invention is different from the conventional art in that the periphery of the carbon material core is covered with iron ore powder, and the melting point is lowered by adding quicklime to the iron ore powder, and a dense outer layer is formed during sintering, so that the carbon material core is prevented from burning and disappearing during sintering.

Here, as the iron ore powder, a pellet having a particle size of preferably 10 to 1000 μm, more preferably 250 μm or less is used. The pellet is a fine particle ore having a particle size of 1mm or less and 90% or more, contains high-grade (high Fe and low gangue) hematite and magnetite as main components, and is excellent in that it can be obtained at a low cost in a large amount.

The iron ore powder used in the present invention may be rolled iron scale, converter off-gas recovered ore powder (OG ore powder), tailings generated during ore dressing, or the like, or may be mixed into a pellet, as long as the particle size is within the above range.

However, Fe as shown in FIG. 4₂O₃The binary phase diagram of CaO shows that the melting point of the magnetite, especially high-grade magnetite, is as high as about 1580 ℃, which is far higher than the preferred sintering temperature for obtaining high-quality sintered ore, and the magnetite does not melt at the normal sintering temperature, i.e. does not generate sintering reaction.

Therefore, the present invention is characterized in that the melting point of the outer layer is lowered by adding a CaO-containing raw material to the iron ore powder, the resultant is melted at a temperature (1200 ℃ or higher) at the time of sintering to form a melt-adhered layer, and the melt-adhered layer functions as an oxygen barrier layer, thereby preventing burning and disappearance of the carbon material core encapsulated in the granulated particle encapsulating the carbon material and retaining the carbon material core.

In addition, by adopting the above-described structure, even if air is introduced during sintering, the core of the encapsulated carbon material can be made to exist. This is because, as shown in fig. 5, it is considered that the outer layer formed around the central core of the granulated particles (pseudo particles) containing the carbon material has an oxygen barrier effect, and C forming the central core and O entering the core are formed ₂The CO gas of the reducing gas atmosphere can be substantially maintained inside the outer layer, and thus the carbon material can be retained.

The temperature of the melting point to be adjusted is preferably in the range of 1200 to 1500 ℃, and more preferably in the range of 1200 to 1400 ℃ from the viewpoint of promoting melting on a sintering machine. If the temperature is less than 1200 ℃, the molten metal is not formed, and the calcium ferrite having the highest strength and high reducibility among the constituent minerals of the sintered ore is not formed. On the other hand, if the temperature exceeds 1500 ℃, the sintering material will not melt and adhere to the sintered ore structure mainly composed of the ferrite.

In addition, the amount of CaO added as a melting point modifier is small in the Pellet (PF) used for the outer layer, and the amount of the gangue component (hematite (Fe) such as Anglo American-PF is small₂O₃) 97.7 mass%) of oreThe Fe represented in FIG. 4 may be used₂O₃-a CaO binary phase diagram. In the case of using PF having a large gangue component, SiO which is considered as the gangue component as shown in FIG. 6 can be used₂SiO of (2)₂-Fe₂O₃A CaO ternary phase diagram to determine the addition amount of CaO. The quicklime functions as a binder in addition to the melting point modifier.

In the granulated particles (pseudo particles) encapsulating a carbon material according to the present invention, it is preferable that the size of the carbon material core is 3mm or more, the thickness of the outer layer formed around the carbon material core is 2mm or more, and the particle diameter is controlled to be within an appropriate range, from the viewpoint of preventing burning and disappearance of the carbon material core during sintering. Here, the size of the carbon material refers to the major diameter of the carbon material.

That is, in the carbon material core used as the granulation core in the carbon material-coated granulated particle of the present invention, it is preferable to use a carbon material having a small volatile content, such as anthracite coal, e.g., hard coke and Hongyy (Hongyy) coal. Particularly, small coke is preferable because it is easy to obtain and does not generate gas by heating. In addition, in order to prevent burning and disappearance of the core of the carbon material during the sintering process, it is preferable to use particles of 3mm or more, not small particles, as the particle diameter of the carbon material as the core. More preferably 4mm or more, and still more preferably 5mm or more.

In addition, the outer layer formed around the carbon material core preferably has a thickness of 2mm or more. If the thickness is less than 2mm, there is a possibility that the core does not sufficiently function as an oxygen barrier layer even if it is melted during sintering to form a dense outer layer, and there is a possibility that the core cannot be completely coated because of many irregularities of the core. In general, since the granulated particles are heated from the outside, the temperature is less likely to rise when the granulated particles are heated on the center side. Therefore, the thicker the thickness of the outer layer is, the more preferably the melting point of the outer layer is adjusted to be low. Therefore, the thickness is more preferably in the range of 3 to 7 mm.

In addition, the particle size of the carbon material-encapsulated granulated particles (pseudo particles) of the present invention formed with a carbon material as a core is preferably set to a particle size that is sufficiently increased to the particle center in the sintering process, that is, 8mm or more, in consideration of the temperature distribution in the granulated particles, from the viewpoint of suppressing the reaction of the carbon material on the sintering machine, because the minimum particle size is 7mm in terms of the size of the minimum carbon material core and the minimum outer layer thickness, but the temperature of the carbon material core does not need to be increased. More preferably 10mm or more, and still more preferably 20mm or more.

In addition, when charging the sintering material into the sintering machine described later, it is also preferable to make the particle diameter larger than that of the usual sintering material (granulated particles) from the viewpoint of charging more to the lower layer side of the sintered layer. Here, the above-mentioned usual granulated particles are pseudo particles (hereinafter, referred to as the same meaning) prepared by granulating an iron ore powder, a carbonaceous material and a secondary raw material containing a CaO-containing raw material as a granulation raw material by a drum mixer, a granulator or the like to a particle diameter of 2 to 4mm (arithmetic mean particle diameter). The particle size in the present invention refers to a particle size measured by sieving.

Next, the granulated particles of the carbon-encapsulated material of the present invention and a method for producing a sintered ore using the granulated particles as a sintering raw material will be described.

Fig. 7 shows an example of a method for producing granulated particles of a carbon-encapsulated material and a sintered ore of a carbon-encapsulated material according to the present invention. Coke particles having a diameter of 3mm or more and serving as core particles, a Pellet (PF) having a diameter of 250 μm or less and a quicklime CaO serving as a melting point modifier are charged into a granulator and mixed, and granulated to obtain granulated particles (pseudo particles) containing a carbon material having a size of 8mm or more. The above-mentioned raw materials can be added simultaneously because the granulation is carried out with coke particles having a large particle diameter as nuclei. The charging ratio of the coke particles to PF is determined so that the thickness of the PF layer as the outer layer is 2mm or more relative to the coke particles as the core particles.

Next, the granulated particles (pseudo particles) of the carbon-encapsulated material obtained as described above are combined with ordinary granulated particles (pseudo particles) for sintering obtained by stirring and granulating conventional raw materials with a drum mixer or the like, and both kinds of granulated particles are mixed and conveyed to a hopper (charge hopper) of a sintering machine, and are charged from the hopper onto a sintering cart which is circulated and moved by the sintering machine. Since the particle diameter of the granulated particles (pseudo particles) of the carbon-encapsulating material is larger than that of the usual granulated particles (pseudo particles) for sintering, the sintering reaction can be sufficiently progressed because the content of the middle layer and the lower layer which are more likely to rise in temperature than the upper layer side is large due to uneven loading at the time of loading.

As described above, the sintered ore (lump ore) containing a carbon material of the present invention can be produced by using a sintering machine, and thus can be mass-produced at low cost. Further, since the Pellet (PF) as a raw material of the outer layer can be obtained at low cost and in large quantities, there is no production limitation.

Example 1

Using a sintering test pot as shown in fig. 8, a sintering test was performed in which granulated particles of the carbon-encapsulated material of the present invention in which lump coke was coated with PF and ordinary granulated particles were used as sintering raw materials.

The sintering raw materials are prepared as follows: in general granulated particles (pseudo particles), iron ore powder, limestone having a CaO amount of 10 mass% as an auxiliary material, and coke powder having a char amount of 5 mass% as a char material were charged into a drum mixer as a granulation raw material, and were stirred and mixed to granulate particles having a particle diameter of 2.9mm in terms of arithmetic average particle diameter.

On the other hand, as the granulated particles (quasi-particles) containing a carbon material, those obtained as follows were used: 3 kinds of small coke with particle size of 3mm, 4mm and 8mm as carbon material core and Anglo American-PF (hematite (Fe) with particle size of 250 μm or less as outer layer raw material (iron ore powder) ₂O₃): 97.7%), and CaO (quicklime) as a melting point modifier were charged into a granulator and mixed, and granulated to obtain granules having an outer layer thickness of 2mm or more and a particle diameter of 8 to 20mm, and quasi-granules of T1 to T7 shown in Table 1 were prepared.

[ Table 1]

In the production of the above-described granulated particles of the carbon-encapsulated material, hematite (Fe) of PF used as an outer layer material₂O₃) Substantially 100%, therefore, Fe shown in FIG. 5 was used₂O₃And a binary phase diagram of CaO, wherein the amount of CaO (quicklime) added is 5 mass% (T6) when the melting point is 1500 ℃, the amount of CaO (quicklime) added is 10 mass% (T1 to T3) when the melting point is 1450 ℃, and the amount of CaO (quicklime) added is 17 mass% (T4, T5) when the melting point is 1300 ℃. The granulated particles of T4 in table 1 are comparative examples in which 2 mass% of a carbon material was mixed in the PF of the outer layer in the same manner as in the case of the usual granulated particles. T7 in Table 1 is a comparative example in which the melting point of the outer layer was not adjusted (melting point: 1580 ℃ C. without CaO added).

In the sintering test, a sintering pot having a raw material charging section shown in fig. 8 and an inner diameter of 300mm phi and a height of 400mm was used, granulated particles of the carbon-encapsulated material and normal granulated particles were uniformly mixed and charged on the lower layer side 1/3(133mm) of the raw material charging section so that the mass ratio of the granulated particles of the carbon-encapsulated material to the normal granulated particles was 1: 1, the granulated particles of the carbon-encapsulated material were embedded in the normal granulated particles, the normal granulated particles were charged on the upper layer side 2/3(267mm) of the sintering pot, and then the sintering pot was ignited on the upper layer surface of the charging layer, and air above the testing pot was sucked by a blower provided below the testing pot and introduced into the charging layer to burn the carbon material in the sintering raw material. Here, the reason why the granulated particles of the carbon-encapsulated material are embedded in the normal granulated particles in the lower layer side 1/3 is that the sintering reaction is performed between the normal granulated particles and the outer layer of the granulated particles of the carbon-encapsulated material by using only the combustion heat of the surrounding normal granulated particles, whereby the encapsulated sintered ore can be obtained without burning the carbon material of the central core, and therefore, the lower layer side 1/3 in which the temperature is easily increased at the time of sintering is advantageous.

Fig. 9 shows an appearance photograph of the sintered ore (lump ore) obtained in the above sintering experiment.

As can be seen from the figure, the T1 to T3, T5 and T6 granulated particles according to the present invention can obtain a sintered ore containing a carbonaceous material and also moderately melt-adhere to the surrounding normal sintered ore. That is, in this example, in addition to the sintered ore in the state of the carbon-encapsulated material, the sintered ore of the carbon-encapsulated material integrated with the sintered ore existing in the periphery can be obtained, and it is estimated that the sintered ore is charged into the sintering machine as the sintering material without adverse effect.

In contrast, the sintered ore obtained from the granulated particles T7 without melting point adjustment was not completely melt-adhered to the surrounding ordinary sintered ore, remained as a single sphere, and was in an unsintered state. Therefore, when the granulated particles of the carbon-encapsulated material in which the outer layer melting point is not adjusted are charged into the sintering machine, not only the sintered ore of the carbon-encapsulated material cannot be obtained, but also the granulated particles of the carbon-encapsulated material are not sintered with the surrounding sintered ore, and therefore, the sintered ore becomes a fracture site, the pulverization rate is increased, and the yield is greatly lowered.

When granulated particles T4 of 2 mass% of coke were mixed in the outer layer, the mixture was rather in an excessively molten state and did not remain as granules in the obtained sintered ore.

Fig. 10 is a photomicrograph of a sintered ore T5 containing a carbon material, which is moderately sintered and integrated with a sintered ore existing in the periphery. From this figure, it can be seen that the PF layer of the sintered ore subjected to moderate sintering is coated with the carbon material core, and a fusion layer is observed between the PF layer on the surface layer of the PF layer and the other sintering material, that is, the PF layer is fusion-bonded to the surrounding sintering material in a state where coke forming the central core remains. Therefore, the existence of the sintered ore containing the carbon material does not cause a risk of lowering the strength of the sintered ore.

Fig. 11 shows the result of element mapping of the cross section of the sintered ore T5 of the carbon-encapsulated material that has been moderately sintered using EPMA. It is found that carbon, i.e., the encapsulated carbon material, remains in the particles remaining in the sintered ore, and that the local Fe concentration around the carbon increases, and metallic iron is produced by reduction.

The reason why such a reduction reaction occurs is considered as follows.

In the case of the granulated particles containing a carbon material inside, the carbon material core composed of small coke particles is located at the center, and therefore, the structure of the carbon material inside is completed. Therefore, similarly to the iron-making reaction of the sintered ore shown in fig. 2(b), the reduction reaction between the iron oxide powder and the coke particles present in proximity to each other inside the granulated particles and the gasification reaction of the coke are considered to proceed simultaneously, and metallic iron is generated in the sintered ore production stage.

Therefore, when the sintered ore containing a carbon material of the present invention is charged into a blast furnace, the iron-making reaction can be expected to proceed at a higher speed, a higher efficiency, and a lower temperature than those of the normal sintered ore.

Example 2

The granulated particles T5 of the carbon-encapsulated material produced in example 1 and the usual granulated particles were put into a sintering test pot shown in fig. 8 in the same manner as in example 1, and a sintering test was carried out, and the reduction degree index (reduction ratio) RI was measured by a method specified in JIS M8713 with respect to the sintered ore of the carbon-encapsulated material obtained from the lower layer side 1/3(133mm) of the raw material charging section and the usual sintered ore obtained from the upper layer side 2/3(267mm) of the raw material charging section, and the reduction degradation index RDI was measured by a method specified in JIS M8720.

Fig. 12(a) shows the change in the reduction index (reduction rate) RI with the reduction time, and it is understood that the reduction rate of the sintered ore containing a carbonaceous material of the present invention is higher than that of a normal sintered ore, that is, the reduction reaction rate is higher.

Fig. 12(b) shows a comparison between the reduction index RI and the reduction degradation index RDI of the sintered ore with a carbonaceous material encapsulated therein according to the present invention and the reduction index RI and the reduction degradation index RDI of a normal sintered ore.

Industrial applicability

The technique of the present invention is not limited to the above-described embodiment, and can be applied to, for example, a sintering technique in which a gas fuel is supplied as a sintering heat source in addition to a carbon material added to a sintering raw material, and a sintering technique in which oxygen is supplied.

Claims

1. A granulated particle of a carbon-containing material for use in the production of a sintered ore, which is a pseudo particle comprising a core of a carbon material and an outer layer formed by covering the periphery of the core of the carbon material,

the outer layer is composed of iron ore powder and a raw material containing CaO, the addition amount of the CaO is 5-17% by mass, no carbon material is mixed in the outer layer, the melting point of the outer layer is more than 1200 ℃ and less than 1500 ℃,

the carbon material core is a small coke particle having a particle diameter of 3mm to 8 mm.

2. The granulated particle of the carbon-included material for producing a sintered ore according to claim 1, wherein the iron ore powder is a pellet having a particle size of 10 to 1000 μm.

3. The granulated particle of the carbon-included material for producing a sintered ore according to claim 2, wherein the particle diameter of the pellet is 250 μm or less.

4. The granulated particle of the carbon-encapsulated material for producing a sintered ore according to any of claims 1 to 3, wherein the thickness of the outer layer is 2mm or more.

5. The granulated particles of the carbon-encapsulated material for use in the production of sintered ore according to any one of claims 1 to 3, wherein the particle diameter of the granulated particles is 8mm or more.

6. The granulated particle of the carbon-encapsulated material for use in the production of a sintered ore according to claim 4, wherein the particle diameter of the granulated particle is 8mm or more.

7. A method for producing the carbon-encapsulated granulated particles for use in the production of sintered ore, which comprises the steps of:

a carbon material core, iron ore powder for forming an outer layer, and a raw material containing CaO as a melting point modifier are charged into a granulator, mixed and granulated, and the outer layer is formed by coating the carbon material core to form a pseudo particle.