JP2021070832A - Compounding method of raw materials for sinter - Google Patents

Abstract

To provide a compounding method of novel and improved raw materials for sinter capable of heightening a content of a needle-shaped CF in a sinter ore and resultantly capable of heightening reducibility of the sinter ore.MEANS FOR SOLVING THE PROBLEM: In order to solve the above problem, according to a certain aspect of the present invention, a compounding method of raw materials for sinter characterized such that a content of dense iron ore having an average particle size of 0.1 to 1.0 mm and the porosity of 10 vol.% or smaller becomes 5 mass% or larger relative to a total mass of the new material, and, among the new raw materials excluding the dense iron ore, the new raw materials having particle size of 1.0 mm or smaller satisfy the following conditions (1), (2) is provided. (1) Basicity (mass ratio of CaO/SiO2) is 1.65 or larger. (2) A concentration of Al2O3 is 1.5 mass% or larger, or a concentration of MgO is 1.0 mass% or smaller.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for blending raw materials for sintering.

The method for producing sinter is as follows. First, a raw material for sintering, which is a raw material for sinter, is blended in a predetermined blending ratio to obtain a blended raw material, and then granulated with water. Here, the raw material for sintering is composed of an iron-based raw material as a main raw material, an auxiliary raw material necessary for the sintering reaction and component adjustment, a carbonaceous material (solid fuel) as a heat source, a miscellaneous raw material, a return ore, and the like. Will be done. The iron-based raw material is, for example, iron ore such as powder ore and fine powder ore. Auxiliary raw materials are, for example, limestone, dolomite, converter slag, serpentinite, silica stone and dolomite. The carbonaceous material is, for example, coke powder and anthracite. The miscellaneous raw materials are iron-containing recycled raw materials such as iron-making dust, steel-making dust, and scales. Of these sintering raw materials, the sintering raw materials excluding coal and return ore are also referred to as new raw materials.

Then, the granulated material of the compounding raw material is charged into the sintering pallet of the sintering machine in layers. Here, the granulated product of the compounding raw material contains coarse nuclear particles and an adhering powder layer adhering to the surface of the nuclear particles. Then, the solid fuel in the raw material filling layer is ignited from the surface of the raw material filling layer, and suction ventilation is performed in the thickness direction from the top to the bottom of the raw material filling layer. As a result, the combustion zone of the raw material filling layer is sequentially shifted to the lower layer side, and the sintering reaction proceeds (sintering process). The sinter cake in the sinter pallet after firing is crushed and sized so as to have a predetermined particle size suitable for sinter for a blast furnace. Sintered ore is produced by the above steps.

The porosity and pores of the raw material packing layer can be increased by charging the compounded raw material into a sintering machine after making it into a granulated product. Therefore, since the air permeability of the raw material packing layer is improved, it is expected that the productivity of the sinter is improved.

By the way, in the sintering process, a liquid phase sintering reaction in which the remaining solid portion (that is, the non-assimilated portion) is bonded by the fluid generated at a volume ratio of about 50 to 70% proceeds. On the other hand, the reactivity (reduction) of the sinter in the blast furnace is affected by the pore structure of the sinter and the reactivity of the dough portion (the portion other than the pores). Therefore, in order to produce a sinter having excellent reducibility, it is important to control the characteristics of the fluid generated in the sintering process to build the pore structure and the dough portion.

Japanese Unexamined Patent Publication No. 58-039746

Sasaki et al., "Structure and quality of sinter from the viewpoint of sinter reaction" (Iron and Steel, 1982, Vol. 68, No. 6, p.563-571) Sato et al., "Relationship between sinter structure and reducing properties" (Iron and Steel, 1982, Vol. 68, No. 15, p.2215-2222) Sakamoto et al., "Reduction kinetics of sinter structure" (Iron and Steel, 1984, Vol. 70, No. 6, p. 504-511) Hida et al., "Mechanism of needle-like calcium-ferrite formation in sinter" (Iron and Steel, 1987, Vol. 73, No. 15, p.1893-1900)

Here, it is known that the reactivity of needle-shaped calcium ferrite (CF) having a width of about 10 μm is better than the reactivity of columnar CF with respect to the structure of the dough portion (Non-Patent Documents 1 to 3). Therefore, the more needle-shaped CF contained in the dough portion, the higher the reactivity of the dough portion and, by extension, the higher the reducibility of the sinter.

Therefore, research on the generation mechanism of needle-shaped CF is being enthusiastically conducted. For example, in the above-mentioned sintering process, it is easy to generate needle-shaped CF by firing the compounded raw material at a low temperature of 1300 ° C. or lower, and a certain amount of SiO ₂ or Al ₂ O ₃ veins is generated for forming needle-shaped CF. It is known that a stone component is required (Non-Patent Documents 1 and 4).

However, the conventional findings are limited to qualitative evaluation, and the quantitative conditions for increasing the content of needle-shaped CF in the dough have not been clarified. In particular, the mineral morphology of iron ore has changed compared to the time when the findings of Non-Patent Documents 1 to 4 were obtained, and the deterioration of iron ore resources is progressing in the medium to long term. Therefore, increasing the reducibility of the sinter is a very important issue. On the other hand, Patent Document 1 discloses a technique for controlling the components of a fluid produced in the sintering process. However, Patent Document 1 does not examine the effect of each component of the fluid on the formation of needle-shaped CF.

The present invention has been made in view of the above problems, and an object of the present invention is to increase the content of acicular CF in the sinter, and thus to increase the reducibility of the sinter. It is an object of the present invention to provide a new and improved method for blending a raw material for sintering.

In order to solve the above problems, according to a certain viewpoint of the present invention, the content of the dense iron ore having an average particle size of 0.1 to 1.0 mm and a porosity of 10% by volume or less is a new raw material. Baking so that the new raw material having a particle size of 1.0 mm or less among the new raw materials excluding dense iron ore, which is 5% by mass or more based on the total mass, satisfies the following conditions (1) and (2). Provided is a method for blending a sintering raw material, which comprises blending a binder raw material.
(1) The basicity ( _{mass ratio of CaO / SiO 2} ) is 1.65 or more.
(2) The Al ₂ O ₃ concentration is 1.5% by mass or more, or the MgO concentration is 1.0% by mass or less.

According to the above viewpoint of the present invention, it is possible to increase the content of acicular CF in the sinter, and thus to increase the reducibility of the sinter.

It is a schematic diagram which shows an example of the granulation line which concerns on this embodiment.

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

<1. Examination by the present inventor>
In order to find a method for quantitatively evaluating the content of needle-shaped CF in the dough part, the present inventor first observed the dough part structure and element distribution of the sinter by image analysis. Here, the dough part structure is composed of silicate slag (SS) and the like in addition to the above-mentioned needle-shaped CF and columnar CF. As a result, it was found that a large amount of needle-shaped CF in the sinter was generated in the region where the concentration gradient of Ca was large. Therefore, if many regions having a large Ca concentration gradient can be formed in the sinter, it is presumed that many acicular CFs are generated in the sinter.

The conditions for increasing the Ca concentration gradient are "low temperature firing", "addition of dense iron ore (hereinafter, also referred to as" dense ore ")", "increased viscosity of the fluid generated in the sintering process", and " "Cooling rate increase" was considered. Therefore, the present inventor conducted a basic experiment (tablet firing experiment) in order to know the magnitude of these contributions to the formation of needle-shaped CF. Here, in the tablet firing experiment, the following processing was performed. First, the iron-based raw material and limestone were mixed based on the blending ratio of the blended raw materials. Then, the mixture was formed into tablets, and the produced tablets were fired with a heat pattern simulating an actual sintering reaction. Then, the cross section of the sintered body was image-analyzed to observe the dough structure and element distribution of the sintered ore. As a result, the present inventor states that the addition of the densified ore greatly contributes to the formation of the needle-shaped CF, and that the content of the needle-like CF is further increased by increasing the fluid viscosity in addition to the addition of the densified ore. Was found. Furthermore, the present inventor conducted a tablet firing experiment by variously changing the amount of the densified ore added, the particle size, and the fluid viscosity, and measured the high temperature reducibility (R1200) of the obtained sintered body. A suitable range of parameters was identified. Based on the above findings, the present inventor has come up with a method for blending a raw material for sintering according to the present embodiment.

<2. Mixing method of raw materials for sintering ＞
Next, a method of blending the sintering raw material according to the present embodiment will be described. Here, as described above, the raw materials for sintering include iron-based raw materials as main raw materials, auxiliary raw materials necessary for sintering reaction and component adjustment, carbonaceous materials (solid fuel) as heat sources, miscellaneous raw materials, and so on. It is composed of return ore. The iron-based raw material is, for example, iron ore such as powder ore and fine powder ore. Although details will be described later, the iron ore in the present embodiment contains a dense ore having an average particle size of 0.1 to 1.0 mm and a porosity of 10% by volume or less. Auxiliary raw materials are, for example, limestone, dolomite, converter slag, serpentinite, silica stone and dolomite. The carbonaceous material is, for example, coke powder and anthracite. The miscellaneous raw materials are iron-containing recycled raw materials such as iron-making dust, steel-making dust, and scales. Of these sintering raw materials, sintering raw materials excluding carbonaceous materials and return ore are also referred to as new raw materials. In the present embodiment, the raw materials for sintering are blended so that the following conditions A and B are satisfied.

(Condition A)
In the present embodiment, the content of the dense ore having an average particle size of 0.1 to 1.0 mm and a porosity of 10% by volume or less is 5% by mass or more with respect to the total mass of the new raw material. Mix raw materials for sintering.

Here, the average particle size of iron ore is measured by a dry, stepped, discontinuous mechanical sieving method in accordance with JIS-M8706 (2008) "Iron ore and reduced iron-measurement method of particle size distribution by sieving". The sieves used are 5 stages of 0.25 mm, 0.5 mm, 1.0 mm, 2.0 mm and 4.0 mm, and the representative particle sizes of the 6 particle size categories are 0.125 mm, 0.375 mm and 0. It is 75 mm, 1.5 mm, 3 mm, and 7 mm. The calculation of the average particle size is in accordance with Annex J. That is, the arithmetic mean is obtained by multiplying the representative particle size by the mass ratio of each particle size category.

The porosity of iron ore is measured by image analysis of its cross section. That is, the sample is buried and polished, the cross section of the obtained sample is image-analyzed, and the area ratio (%) of the pore portion to the total area of the observation field of view is obtained. This area ratio is taken as the porosity of the sample. The same treatment is performed for some observation fields, and the arithmetic mean value of the obtained area ratio is used as the representative porosity of the sample. The number of observation fields shall be such that one digit of the representative value obtained as the arithmetic mean is sufficiently accurate. In the examples described later, the average particle size and porosity were measured by these methods.

As described above, in this embodiment, a relatively fine dense ore having an average particle size of 0.1 to 1.0 mm is used. As a result, many regions having a large Ca concentration gradient can be formed in the sinter. More specifically, the number of regions having a large Ca concentration gradient is large, and the total area of the regions is large. In the sintering process, a part of the raw material packing layer is assimilated into a fluid, and this fluid bonds the remaining solid parts (that is, non-assimilated parts) to each other (liquid phase sintering reaction). After that, the fluid is cooled and solidified to become an assimilation part. Therefore, the dough portion in the sinter contains an assimilated portion in which the fluid is solidified and a non-assimilated portion in which the fluid is not assimilated. The dense ore having an average particle size of 0.1 to 1.0 mm is difficult to assimilate with the fluid during the liquid phase sintering reaction, and often remains in the dough part as a non-assimilated part (in other words, a residual source ore part). Therefore, the Fe concentration gradient becomes large around such a dense ore. That is, the Fe concentration in each region in the dough portion increases as the region is closer to the dense ore. Then, a Ca concentration gradient is formed in a form that trades off with such an Fe concentration gradient. That is, the Ca concentration in each region in the dough portion becomes lower as the region is closer to the dense ore. Further, in the present embodiment, since the dense ore forming a large Ca concentration gradient is dispersed in the sinter, many regions having a large Ca concentration gradient can be formed in the sinter.

The average particle size of the dense ore needs to be 0.1 to 1.0 mm. When the average particle size of the dense ore is less than 0.1 mm, the dense ore is immediately assimilated with the fluid in the sintering process, and a Ca concentration gradient is hardly formed. When the average particle size of the dense ore exceeds 1.0 mm, the dense ore is difficult to assimilate with the fluid, so that a large Ca concentration gradient is formed around the dense ore. However, since the number of particles of the dense ore is reduced, the region where the Ca concentration gradient is formed is reduced.

Table 1 below shows typical examples of iron ore. Among these examples, iron ores D and FG are classified as dense ores. Further, iron ores F and G are the dense ores used in the present embodiment. In Table 1, the value of each component means mass% with respect to the total mass of iron ore. The mass% of each component is a value measured according to the general rule of JIS M8202 (2000). The Al ₂ O ₃ concentration is measured according to M8220: aluminum quantification method, the SiO ₂ concentration is measured according to M8214: silicon quantification method, or M8205: fluorescent X-ray analysis method corrected by them. The method for measuring the porosity and the average particle size is as described above.

In the present embodiment, the mass% of the dense ore having an average particle size of 0.1 to 1.0 mm is 5% by mass or more with respect to the total mass of the new raw material. It is preferably 10% by mass or more. When the mass% of the dense ore is less than 5% by mass, the Ca concentration gradient is not sufficiently formed. When the mass% of the dense ore is 5% by mass or more, preferably 10% by mass or more, many regions having a large Ca concentration gradient can be formed.

(Condition B)
In the present embodiment, among the new raw materials excluding the densified ore, the raw material for sintering is blended so that the new raw material having a particle size of 1.0 mm or less satisfies the following conditions (1) and (2).
(1) The basicity ( _{mass ratio of CaO / SiO 2} , so-called C / S) is 1.65 or more.
(2) The Al ₂ O ₃ concentration is 1.5% by mass or more, or the MgO concentration is 1.0% by mass or less.

Condition B defines the conditions to be satisfied by a new raw material having a particle size of 1.0 mm or less (excluding densified ore; the same applies hereinafter). The volume ratio of the fluid produced in the sintering process is considered to be about 50 to 70% of the total volume of the raw material packing layer. Considering the volume ratio of such a fluid and the particle size distribution of a general compounded raw material, it is considered that a new raw material having a particle size of 1.0 mm or less is almost completely assimilated in the sintering process and becomes a fluid. Therefore, it can be said that the condition B defines the conditions to be satisfied by the new raw material as a fluid. The new raw material having a particle size of 1.0 mm or less can be obtained by classifying all the new raw materials except the densified ore with a sieve having a mesh size of 1.0 mm.

Condition (1) defines the basicity of the new raw material. The basicity is the mass ratio of _{CaO and SiO 2} contained in the new raw material having a particle size of 1.0 mm or less. The mass of the CaO component is measured according to JIS M8221: Calcium Quantification Method. The mass of the SiO ₂ component is measured by the method described above. According to _CaO-SiO 2 _-Fe 2 _{O 3} phase diagram which is disclosed in the German Steel Institute book "Slag Atlas" or the like, if the basicity is 1.65 or more, CF is produced.

_{Condition (2) defines the conditions that the Al 2} O ₃ concentration or Mg O concentration of the new raw material having a particle size of 1.0 mm or less should be satisfied. The Al ₂ O ₃ concentration is measured by the method described above. The MgO concentration is measured according to JIS M8222: Magnesium quantification method. When the condition (2) is satisfied, the viscosity of the fluid generated in the sintering process becomes high, so that many regions having a large Ca concentration gradient can be formed in the dough portion. More specifically, when the condition (2) is satisfied, a highly viscous fluid surrounds the dense ore that is difficult to assimilate. Such a highly viscous fluid solidifies while maintaining the Ca concentration gradient formed around the dense ore. Therefore, many regions having a large Ca concentration gradient can be formed in the sinter, and many needle-shaped CFs can be formed in the sinter.

Conventionally, the viscosity of the fluid has been reduced as much as possible for reasons such as increasing the strength of the sinter. On the other hand, the present inventor has found that by increasing the viscosity of the fluid, many needle-shaped CFs can be formed in the sinter, and by extension, the reducibility of the sinter can be increased. It was. Therefore, the findings of the present inventor have not been considered at all in the past.

_{The upper limit of the Al 2} O ₃ concentration and the lower limit of the Mg O concentration under the condition (2) are not particularly limited. However, if the Al ₂ O ₃ concentration is too high or the Mg O concentration is too low, the viscosity of the fluid may become very high and the strength of the sinter may decrease. From this point of view, _{the upper limit of the Al 2} O ₃ concentration is preferably 2.2%, and the lower limit of the Mg O concentration is preferably 0.5%.

(Method of adjusting _{Al 2} O _{3 concentration)}
If the condition (2) is not satisfied, the Al ₂ O ₃ concentration may be adjusted by, for example, the following treatment. That is, the Al ₂ O ₃ component is mainly brought in from iron ore. Therefore, the blending amount of the iron ore having a high _{Al 2} O _{3 concentration may be increased, or the iron ore having a high Al 2} O ₃ concentration may be pulverized so that the particle size of the iron ore is 1.0 mm or less.

(How to adjust MgO concentration)
If the condition (2) is not satisfied, the MgO concentration may be adjusted by, for example, the following treatment. That is, the MgO component is abundantly contained in some MgO-containing auxiliary raw materials (for example, peridotite). Therefore, the blending amount of the MgO-containing auxiliary raw material may be reduced. Alternatively, the MgO-containing auxiliary material may be classified with a sieve having a mesh size of 1.0 mm to reduce the blending amount of the MgO-containing auxiliary material having a particle size of 1.0 mm or less. Alternatively, the MgO-containing auxiliary material having a particle size of 1.0 mm or less may be agglomerated to have a particle size of more than 1.0 mm.

As described above, according to the method for blending the sinter raw material according to the present embodiment, by blending the sinter raw material so as to satisfy the conditions A and B, a region having a large Ca concentration gradient in the sinter ore Can be formed in large numbers. As a result, many needle-shaped CFs can be formed in the sinter, and by extension, the reducibility of the sinter can be enhanced.

<3. Example of granulation line>
Next, an example of a granulation line for realizing the above-mentioned blending method of the sintering raw material will be described. FIG. 1 is an example of a sinter manufacturing process according to the present embodiment. The sinter manufacturing process (more specifically, equipment for realizing the sinter manufacturing process) 10 includes a granulation line 1 and a sinter 20. In the sinter manufacturing step 10, the raw material for sinter is granulated on a single granulation line.

The granulation line 1 includes a plurality of raw material hoppers 11, a granulator 12, and belt conveyors 1a and 1b. Each raw material hopper 11 supplies different sintering raw materials to the belt conveyor 1a. Here, as described above, the raw materials for sintering include iron-based raw materials as main raw materials, auxiliary raw materials necessary for sintering reaction and component adjustment, carbonaceous materials (solid fuel) as heat sources, miscellaneous raw materials, and so on. It is composed of return ore. The iron-based raw material is, for example, iron ore such as powder ore and fine powder ore. Auxiliary raw materials are, for example, limestone, dolomite, converter slag, serpentinite, silica stone and dolomite. The carbonaceous material is, for example, coke powder and anthracite. The miscellaneous raw materials are iron-containing recycled raw materials such as iron-making dust, steel-making dust, and scales.

The particle size of the powdered ore for sintering is, for example, 10 mm or less. The average particle size is about 2 to 3 mm. Fine powder ore is iron ore whose iron content has been increased by mineral processing. Its particle size is about 500 μm or less. Of course, the powder ore and fine powder ore applicable to this embodiment are not limited to these examples, and all iron ores referred to as powder ore and fine powder ore in the field of sinter are applicable to this embodiment. Further, the iron-based raw material in the present embodiment contains a dense ore having an average particle size of 0.1 to 1.0 mm and a porosity of 10% by volume or less.

Each raw material hopper 11 supplies each sintering raw material to the belt conveyor 1a in a predetermined compounding ratio. Here, each raw material hopper 11 supplies each sintering raw material to the belt conveyor 1a so that the above-mentioned conditions A and B are satisfied. On the belt conveyor 1a, these sintering raw materials are blended and used as a blending raw material.

Then, the belt conveyor 1a supplies the compounding raw material to the granulator 12. The granulator 12 produces a granulated product of the compounded raw material by granulating the compounded raw material. The granulator 12 may be any device as long as it can granulate the compounded raw material. Examples of the granulator 12 include a drum mixer, a pan pelletizer, and the like. The granulator 12 discharges the granulated material of the compounding raw material to the belt conveyor 1b. The belt conveyor 1b charges the granulated material of the compounding raw material into the sintering machine 20. The sinter 20 produces a sinter by firing the granulated material of the compounding raw material. The granulation line in the present embodiment is not limited to the granulation line 1, and any granulation line may be used as long as the above-mentioned method for blending the sintering raw material can be realized. For example, a granulation line having a plurality of granulation lines (main granulation line and sub-granulation line) may be used.

Next, an embodiment of the present embodiment will be described. In this example, it was confirmed that the reducibility of the sinter is enhanced when the conditions A and B of the present embodiment are satisfied. First, iron ores A to G shown in Table 1 were prepared as iron-based raw materials. These iron ores A to G, limestone, quicklime, peridotite, return ore, and carbonaceous material were blended to prepare a blended raw material. The compounding ratio of each sintering raw material was adjusted so as to satisfy the conditions shown in Tables 2 and 3. The specific compounding ratios are as shown in Tables 4 to 6. _{Here, the Al 2} O ₃ concentration in the new raw material having a particle size of 1.0 mm or less is 0, 10, 20, 30% by mass (total mass in the new raw material) of the blending ratio of iron ore A having a high _{Al 2} O _{3 concentration.} It was adjusted by setting it to one of (mass% with respect to). The MgO concentration in the new raw material having a particle size of 1.0 mm or less was adjusted by setting the blending ratio of peridotite to either 1.0 or 1.5% by mass (mass% with respect to the total mass in the new raw material). The mass% of the carbonaceous material was 4.7% by mass with respect to the total mass of the new raw material. In Tables 4 to 6, the numerical value of each sintering raw material is mass% with respect to the total mass of the new raw material. Therefore, the mass% of the new raw material is an internal number, and the mass% of the return ore and coke is an external number.

Then, the mixed raw material and 7% by mass (mass% with respect to the total mass of the mixed raw material) of water were added to the drum mixer, and granulation was performed in 1 minute of mixing and 4 minutes of granulation. Then, a pot test was conducted. The pan test was carried out under the conditions of a layer thickness of the raw material filling layer: 600 mm, a negative pressure of 1500 mm Aq, and an ignition time of 60 sec. After the baking was completed, the sinter cake was crushed by dropping it from a height of 2 m four times. The sinter after crushing was classified by a sieve, and iron ore having a particle size of more than 15 mm and 20 mm or less was recovered. Next, the reducibility (R1200) of the recovered iron ore was described by Hosoya et al., "Development of a method for evaluating the softening and melt properties of sinter" (Iron and Steel, 1997, Vol. 83, No. 2, p. 97-102). The measurement was performed according to the measurement method described in. The results are shown in Tables 2 and 3.

As is clear from Tables 2 and 3, in Comparative Examples 1 to 8 using iron ore D (average particle size 0.057 mm) that does not satisfy the condition A of the present embodiment, the reducibility (R1200) of the sinter is 60. It was as low as 0.8 to 64.5%. In Comparative Examples 9 and 10, iron ore F satisfying the condition A of the present embodiment is used, but the condition B is not satisfied. Therefore, the reducibility (R1200) of the sinter was as low as 63.5 to 65.8. In Comparative Examples 11 to 12, iron ore G satisfying the condition A of the present embodiment is used, but the condition B is not satisfied. Therefore, the reducibility (R1200) of the sinter was as low as 62.8 to 65.3. In Comparative Examples 13 to 20, the C / S is less than 1.65, and the condition B is not satisfied. Therefore, the reducibility (R1200) of the sinter was as low as 62.1 to 64.3. In Comparative Examples 21 and 22, although the C / S is 1.65 or more _{, neither the Al 2} O ₃ concentration nor the Mg O concentration satisfies the condition B. On the other hand, in Examples 1 to 18 in which both conditions A and B were satisfied, the reducibility (R1200) of the sinter was as high as 66.7 to 67.5. Therefore, it was confirmed that a highly reducible sinter can be produced by blending the sinter raw materials so as to satisfy the conditions A and B.

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

10 Granulation system 1 Granulation line 11 Raw material hopper 12 Granulation machine 20 Sintering machine

Claims (1)

The content of dense iron ore having an average particle size of 0.1 to 1.0 mm and a porosity of 10% by volume or less is 5% by mass or more with respect to the total mass of the new raw material, and
Among the new raw materials excluding the dense iron ore, the sintering raw material is blended so that the new raw material having a particle size of 1.0 mm or less satisfies the following conditions (1) and (2). How to mix raw materials for sintering.
(1) The basicity ( _{mass ratio of CaO / SiO 2} ) is 1.65 or more.
(2) The Al ₂ O ₃ concentration is 1.5% by mass or more, or the MgO concentration is 1.0% by mass or less.

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