JPWO2010032466A1 - Method for producing sintered ore - Google Patents

Abstract

Mixing and granulating iron-containing raw materials containing multiple brands of iron ore, secondary raw materials, solid fuel, and return ore into sintered raw materials, mixing and granulating these sintered raw materials, and then charging them onto a sintering pallet The sintered ore manufacturing method for firing, wherein the weight average of the melt penetration distance from the iron ore of the plurality of brands based on the melt penetration distance measured for each brand of the iron ore The high-melt-penetrating iron ore selected or blended to have a thickness of 4.0 mm or more is 5 to 12 in a layer thickness ratio with respect to the total layer thickness from the upper surface of the raw material filled layer formed on the sintered pallet. %, The other iron ore is charged in the lower layer of the raw material packed bed, and the auxiliary raw material, the solid fuel, and the return ore are added to the upper layer of the raw material packed layer. And charging the lower layer.

Description

The present invention relates to a method for producing sintered ore used as an ironmaking raw material, and more particularly to a method for producing sintered ore for improving the product yield and strength of the upper part of the raw material packed bed formed in the sintering pallet. .
This application claims priority on September 17, 2008 based on Japanese Patent Application No. 2008-238448 for which it applied to Japan, and uses the content here.

  In recent years, Australia's iron ore, which is the main iron ore used in Japan, has been depleted of high-quality hematite ore. At present, the development of the pisolite deposit, the Maramamba deposit and the high phosphorus block man deposit has been developed. Progressing.

  Iron ore produced from the Maramamba deposit or the high phosphorus block man deposit has a smaller particle size and a higher content of crystal water than a good quality hematite ore. Therefore, at the time of sintering, these iron ores cause a decrease in air permeability and a deterioration in sintering reactivity.

  The existing pisolite ore from the pisolite deposit is a high crystal water ore. Ninety percent of the iron ore produced from this psolite deposit, the Maramamba deposit and the high phosphorus block man deposit is iron ore with a crystal water content of 4% by mass or more.

  The influence on the sintering operation when a large amount of high crystal water ore is added as a sintering raw material will be described below.

  In general, the production of sintered ore using a lower suction type sintering machine is performed as follows.

  Sintering materials include iron-containing materials such as iron ore as the main material and iron-making dust generated in the iron-making process, auxiliary materials such as limestone and serpentine required for the sintering reaction, coke powder as a heat source, etc. These are used in combination with solid fuel.

  The sintered raw material is mixed and granulated while adding water using a mixing / granulating machine such as a drum mixer before being charged into the lower suction type sintering machine, and processed into pseudo particles. . The pseudo particles are mainly composed of core particles having a particle diameter of 1 mm or more and adhering powder having a particle diameter of 0.5 mm or less attached around the core particles.

  By inserting the sintering raw material processed into the pseudo particles into the sintering machine, the air permeability in the sintered packed bed formed in the sintering pallet is maintained, and the sintering reaction of the sintering raw material is promoted. And high productivity can be secured.

  The sintered raw material processed into pseudo particles is charged into the sintering pallet from the feeding section of the sintering machine to form a raw material packed layer. Thereafter, in the ignition furnace, the coke powder on the surface of the raw material packed bed is ignited and air is sucked from the lower part of the sintering machine, thereby moving the combustion point of the coke powder to the lower side of the raw material packed bed.

  Sintering reaction proceeds sequentially from the upper layer to the lower layer of the raw material packed bed by the combustion heat of the coke powder, and the sintering is completed by the time the sintering pallet moves and reaches the waste ore section. The sintered cake (lumps) in the sintering pallet is discharged from the waste ore section and then crushed to produce a sintered ore for a blast furnace with a predetermined particle size.

  Since the sintered ore powder having a particle size smaller than the predetermined particle size generated in the production of the sintered ore cannot be used as the sintered ore for the blast furnace, it is blended in the sintering raw material as a return ore and sintered again.

The sintering reaction of the sintering raw material proceeds at around 1200 ° C. mainly by the following initial melt generation and subsequent assimilation reaction. That is, an initial melt of calcium ferrite (CaO—Fe ₂ O ₃ ) is generated by a reaction between Fe ₂ O ₃ in the iron-containing raw material and CaO in limestone. Thereafter, an assimilation reaction in which the components in the iron ore and the components in the auxiliary raw material dissolve in the initial melt proceeds.

  This sintering reaction is an extremely fast reaction that is completed within a few minutes after the formation of the initial melt. This reaction greatly affects the product yield and productivity of the sintered ore and the quality of the sintered ore.

  For example, if the sintering reaction proceeds excessively and the amount of melt produced is extremely increased, the air permeability in the sintered layer deteriorates during the sintering operation. Due to the deterioration of the air permeability, uneven burning occurs, so that the product yield and productivity are lowered, and the quality of sintered ore such as strength is also deteriorated.

  On the other hand, if the sintering reaction does not proceed sufficiently, the melt for bonding unmelted parts such as residual iron ore (residual source ore) decreases, so the product yield decreases, and the strength and reduced powder The quality of sintered ore such as chemical conversion (RDI) deteriorates.

  This sintering reaction is the main raw material in the blended raw material, and sinterability (assimilability) due to the mineral composition and properties of iron ore, which accounts for more than 60% of the total, and the air permeability of the sintered raw material packed layer It is greatly influenced by the granulation property that affects

  When high crystal hydrous ores such as pisolite ore are blended as iron ore, the crystal water derived from the goethite structure in the iron ore starts pyrolysis and dehydration at around 300 ° C. Cracks occur in the site structure.

  For this reason, pores are generated in the initial melt, a solidified binder phase is generated with the generated pores remaining, or unmelted original ore containing cracks remains. As a result, the sintered ore becomes a brittle and porous structure, the product yield of the sintered ore decreases, and the quality of the sintered ore such as strength deteriorates.

  In addition, in the case of blending iron ore with a high particle size such as maramanba ore and high phosphate ore as a sintering raw material, in addition to the above-mentioned problems caused by crystal water, the granulation property is deteriorated. . Therefore, it is difficult to generate pseudo particles, and the pseudo particles are liable to collapse during transportation or charging of raw materials.

  For this reason, when the raw material is charged into the pallet, finely divided iron ore that has not been granulated or finely divided particles of iron ore that have been disintegrated are segregated and distributed on the upper layer side of the raw material packed bed, so Air permeability is reduced. Further, since the goethite structure containing crystal water is brittle, there are many iron ore particles having a small particle size.

  For this reason, the fine powder particles of iron ore that are segregated and distributed on the upper layer side of the raw material packed bed also cause a problem caused by the crystal water.

  In general, in the production of sintered ore using a lower suction type sintering machine, the temperature of the surface layer portion of the raw material packed layer after ignition is lowered by suction of air close to room temperature. For this reason, a decrease in product yield of sintered ore in the upper layer and deterioration in quality such as strength have been problems.

  The problem of quality such as product yield and strength of the sintered ore in the upper layer is remarkable in the recent sintering operation in which high crystal hydrous ore and fine iron ore are blended as a sintering raw material.

  In the production of sintered ore using the lower suction type sintering machine, many methods have been proposed so far for improving the quality such as the product yield and strength of the upper layer of the sintered raw material packed layer. Yes.

  For example, a method for increasing the solid fuel in the upper layer portion of the raw material packed bed (for example, see Patent Document 1) has been proposed.

  Also, a method of charging a surface layer portion of a raw material packed bed with a high FeO ferromagnetic raw material such as return mineral, mill scale, and magnetite and a granulated product of a ferromagnetic raw material and a carbonaceous material using a magnetic charging device. (For example, refer to Patent Documents 2 to 6).

  In addition, in consideration of the assimilation and melting properties of iron ore to be blended with the sintering raw material, a method of charging easily fusible iron ore into the upper layer of the raw material packed layer and charging poorly fusible iron ore into the lower layer ( For example, Patent Document 7, see) has also been proposed.

That is, in order to increase the temperature of the surface layer portion of the raw material packed layer after ignition, the solid fuel in the surface layer portion of the raw material packed layer is increased, or CaO and SiO ₂ in the auxiliary raw material in the surface layer portion of the raw material packed layer and For example, a ferromagnetic raw material containing a large amount of FeO that easily forms a melt (CaO—SiO ₂ —FeO), or an easily meltable iron ore is charged. These methods are intended to improve the product yield and quality of the sintered ore in the upper layer portion of the raw material packed bed.

  However, according to these methods, it is difficult to appropriately control the amount of heat and the amount of melt generated in the upper layer of the raw material packed layer, so that the amount of heat is too high and the amount of melt increases excessively. Therefore, the air permeability of the entire raw material packed bed is deteriorated, the productivity is lowered, and the quality of sintered ore such as reducibility is lowered.

JP 2000-144266 A JP 2000-328148 A JP 2001-234257 A JP 2001-271122 A JP 2001-335849 A JP 2002-130957 A Japanese Patent Publication No. 60-47887

  In view of the above-mentioned problems of the prior art, the present invention is a method for producing a sintered ore using a lower suction type sintering machine, and has a brand excellent in melt permeability to the fine powder portion in the upper layer of the raw material packed layer. By selectively charging iron ore, the melt of the upper layer of the raw material packed bed is prevented from excessively increasing, the air permeability of the entire raw material packed layer is deteriorated, and reducible and other sintered ore It is an object of the present invention to provide a method for producing a sintered ore that can improve the product yield and strength of the upper layer of the raw material packed layer and improve the productivity of the sintered ore without reducing the quality of the ore.

  The present inventors diligently studied a method for improving the product yield and strength of the upper layer of the raw material packed layer formed on the sintered pallet in the production of sintered ore.

  As a result, among the multiple brands of iron ore constituting the sintering raw material, an iron ore having a melt penetration distance of 4.0 mm or more measured by a melt penetration evaluation test into the iron ore powder is obtained from a sintering pallet. It was confirmed that the product yield and strength of the sintered ore in the upper layer of the raw material packed layer can be improved by selectively charging the upper layer of the raw material packed layer in a predetermined range.

  In addition, according to this method, compared to a conventionally proposed method of increasing the solid fuel and FeO source in the upper layer of the raw material packed bed, and a method of charging easily meltable iron ore into the upper layer of the raw material packed bed, It has been found that the product yield and strength of the sintered ore in the upper layer of the raw material packed layer can be improved without generating an excessive melt in the upper layer of the raw material packed layer and reducing the air permeability of the entire raw material packed layer.

  The present invention has been made based on the above findings, and the gist of the invention is as follows.

  (1) Mixing iron-containing raw materials containing multiple brands of iron ore, auxiliary raw materials, solid fuel, and return ore into sintered raw materials, mixing and granulating these sintered raw materials, and then placing them on the sintering pallet A method for producing sintered ore to be charged and fired, based on the melt penetration distance measured for each brand of the iron ore, from the iron ore of the plurality of brands, the melt penetration distance of The high melt permeable iron ore selected or blended so that the weighted average value is 4.0 mm or more is the layer thickness ratio with respect to the total layer thickness from the upper surface of the raw material packed layer formed on the sintered pallet. The upper layer in the range of 5 to 12% is charged, the other iron ore is charged in the lower layer of the raw material packed layer, and the auxiliary raw material, the solid fuel, and the return ore are supplied to the raw material packed layer. In the upper layer and the lower layer.

(2) In the method for producing a sintered ore according to (1) above, the Al ₂ O ₃ content of the high melt-permeable iron ore may be 0.6% by mass or less.

  (3) In the method for producing a sintered ore according to (1) above, in addition to the high melt-permeable iron ore, the iron-containing raw material is scaled in the iron making process above the raw material packed bed. You may insert in the upper layer of the range of 5-12% by the layer thickness ratio with respect to the total layer thickness from the surface.

  (4) In the method for producing a sintered ore according to (1), the solid fuel and the return ore may be charged in the same mixing ratio in the upper layer and the lower layer of the raw material packed bed. .

  (5) In the method for producing a sintered ore described in (1) above, with respect to the auxiliary material charged into the raw material packed layer, the mixing ratio of the upper layer may be equal to or less than the mixing ratio of the lower layer.

  (6) In the method for producing a sintered ore according to (1), the high-melt-penetrating iron ore and the other iron ore are the secondary raw material, the solid fuel, and the return ore. After blending, mixing, and granulating, each of the upper layer and the lower layer of the raw material packed layer may be charged.

  (7) In the method for producing a sintered ore according to (6), the highly melt-permeable iron ore is blended with the scale generated in the iron making process as the iron-containing raw material, After blending, mixing, and granulating the solid fuel and the return mineral, the solid fuel may be charged into the upper layer of the raw material packed bed.

  According to the present invention, in the method for producing sintered ore using the lower suction type sintering machine, the melt permeability to the fine powder portion of each brand iron ore to be blended with the sintering raw material is evaluated, and this evaluation result Based on the iron ore of each brand, select the iron ore of the brand excellent in melt penetration into the fine powder part and selectively insert it into the upper layer of the raw material packed bed, so that the upper layer of the raw material packed bed The yield and strength of the product can be improved, and the productivity of sintered ore can be improved.

It is a figure which shows the micro structure of the pseudo-particle cross section of the sintering raw material extract | collected from the raw material filling layer of a sintering machine. It is a figure which shows the relationship between the melt penetration distance of an iron ore, and intensity | strength SI of the sintered ore in an actual machine sintering operation. It is a figure which shows the relationship between the melt penetration distance of an iron ore, and the product yield of the sintered ore in an actual machine sintering operation. It is a figure which shows the measurement position of the melt penetration distance in the tablet after baking. It is a figure which shows the comparison of the melt penetration distance of the iron ore of a main brand. It is a figure which shows the relationship between the melt penetration distance of an iron ore, and the intensity | strength parameter | index (+0.5 mm% value) by the drop test in a tablet baking test. It is a figure which shows the relationship between an upper charging layer thickness ratio and the intensity | strength SI of the sintered ore in a sintering pot test. It is a figure which shows the relationship between an upper charging layer thickness ratio and the product yield of the sintered ore in a sintering pot test. The melt infiltration distance iron ore is a diagram showing the relationship between the Al ₂ O ₃ content. It is a figure which shows the relationship between the limestone ratio in an upper layer, and the product yield of the sintered ore in a sintering pot test. It is a figure which shows the relationship between the limestone ratio in an upper layer, and the intensity | strength SI of the sintered ore in a sintering pot test. It is a figure which shows the charging conditions of the sintering raw material of the sintering pot test of an Example. It is a figure which shows an example of the method of charging a highly melt-permeable iron ore and other iron ores in the upper layer and lower layer of a raw material packed layer, respectively.

  First, the technical idea of the present invention will be described.

  FIG. 1 is a diagram showing an optical microscope structure of a cross section of pseudo particles of a sintered raw material collected from a raw material packed layer of a sintering machine.

In the sintering process, the initial melt is considered to be generated at a portion where iron ore (Fe ₂ O ₃ ) and limestone (CaO) are in contact with each other. However, as shown in FIG. 1, the adhering powder part (fine powder part) of the pseudo raw material of the sintering material (consisting of core particles having a particle diameter of 1 mm or more and the adhering powder part having a particle diameter of 0.5 mm or less around it) According to the micro observation of), iron ore (Fe ₂ O ₃ ) and limestone (CaO) are irregularly distributed, and therefore there are few portions in contact with each other.

From this, in the actual sintering process, it is considered that the sintering reaction proceeds as follows. That is, an initial melt of calcium ferrite (CaO—Fe ₂ O ₃ ) is generated at the portion where the iron ore (Fe ₂ O ₃ ) and limestone (CaO) in the adhering powder portion of the pseudo raw material of the sintering material are in contact To do. Thereafter, the initial melt penetrates into the adhering powder part, comes into contact with surrounding iron ore and auxiliary materials, and repeats assimilation and coalescence. In this way, the amount of melt increases and a binder phase of sintered ore is formed.

  The inventors of the present invention have found that the behavior of the initial melt produced in the sintering process penetrates into the iron ore packed bed, that is, the melt permeability depends on the mineral characteristics of the iron ore, and the bonding of the sintered ore. It has been clarified that phase formation is greatly affected (see ISIJ-Int. 43 (2003), p. 1384).

The temperature of the upper layer of the sintering raw material packed bed during the sintering operation tends to be low, and the sintering reaction (anabolic reaction) starts from the formation of the initial melt of iron ore (Fe ₂ O ₃ ) and limestone (CaO). The time to complete is short. Therefore, the present inventors selectively charged iron ore with high melt permeability into the upper layer of the raw material packed bed in order to improve the product yield of the sintered ore in the upper layer of the raw material packed layer. Then, it was considered effective to promptly infiltrate the produced initial melt into the raw material fine powder part to promote the anabolic reaction.

  The present invention is made on the basis of this technical idea, and includes iron-containing raw materials including iron ores of a plurality of brands (iron ore brands), secondary raw materials (such as limestone), solid fuel (such as coke), and return ore. The sintered raw material is mixed, granulated, charged on a sintering pallet, and fired. The manufacturing method of the sintered ore has the following characteristics. That is, a melt permeability evaluation test is performed for each iron ore brand, and the melt penetration distance is 4.0 mm from the plurality of brand iron ores based on the measured value of the melt penetration distance of each brand. One or more types of iron ore are selected or blended so as to have the above, and the layer thickness ratio (upper charge layer thickness ratio) to the total layer thickness from the upper surface of the raw material packed layer formed on the sintered pallet is The upper layer is charged so as to be in the range of 5 to 12%.

In the present invention, the melt permeability of the iron ore (ease of spreading when the initial melt penetrates into the iron ore powder having a particle size of 0.5 mm or less), and the melt penetration distance (of the melt in the iron ore powder) The permeation distance) can be evaluated and measured by an evaluation test proposed by the present inventors in Japanese Patent Application Laid-Open No. 2002-62290 (hereinafter referred to as “iron ore melt permeability evaluation test”).
This melt penetration distance is a weighting of the measured melt penetration distance for each brand of iron ore in order to simplify the measurement when two or more brands of iron ore are blended as the iron ore of the sintering raw material. Average values were used. Hereinafter, when using iron ore containing two or more types of iron ore, the weighted average value is also expressed as the melt penetration distance. A plurality of brand iron ores may be blended and the melt penetration distance may be measured as one brand iron ore.
The melt penetration distance in the present invention is evaluated by the melt permeability evaluation test of the present invention. The melt penetration distance in the present invention is evaluated by evaluating the melt permeability by other evaluation tests. May be converted into For example, evaluation is performed by changing the molding pressure of the iron ore melt permeability test, the size and shape of the iron ore tablet and the initial melt material tablet, the test procedure, etc., and converted into the melt penetration distance in the present invention. May be. In addition, for example, the time during which the melt has permeated a predetermined distance may be measured and converted to the melt penetration distance in the present invention. Any physical quantity that can be converted may be used.

  The melt penetration evaluation test of iron ore in the present invention is performed as follows, and the melt penetration distance is measured.

  Adjust the particle size of the iron ore sample so that the ratio of particle size: 0.25 to 0.5 mm is 50% by mass, and the ratio of particle size: 0.25 mm or less is 50% by mass, and mix well. . Thereafter, an iron ore sample was molded at a molding pressure of 4 MPa using a mold forming die, and an iron ore tablet having a diameter of 15 mm and a height of 5 mm (porosity (open porosity) by mercury intrusion method): about 30% ).

On the other hand, the initial melt material is close to the eutectic composition of the binary system phase diagram of _{CaO-Fe 2 O 3 CaO:} 26 _wt%, Fe ₂ O 3: As will become 74% by weight of the composition, _Fe 2 O ₃ reagents and CaO reagent are mixed and mixed in an automatic mortar for 20 minutes. Thereafter, similarly to the iron ore tablet, the initial melt material is molded at a molding pressure of 4 MPa using a mold forming die to produce an initial melt material tablet having a diameter of 5 mm and a height of 5 mm.

  Furthermore, the initial melt material tablet is placed on the center of the upper surface of the iron ore tablet, charged into a Ni cylindrical crucible (inner diameter 20 mm, height 15 mm), and heated in an air stream in an electric furnace. , Fire. Then, melt penetration distance is measured by cross-sectional observation of the tablet after baking.

  In the measurement of the melt permeation distance in the tablet after baking, the tablet is cut vertically at the center in the radial direction of the tablet, the cut surface is polished, and the mineral structure of the cut surface as shown in FIG. 4 is observed with an optical microscope. In the photographed cross-sectional structure, the width direction (tablet radial direction) central portion (3) of the portion infiltrated with the melt shown in FIG. 4, each of the central portion (3) and the outer ends (1) and (5). It is preferable to actually measure the permeation distance at three points (2) and (4), which are intermediate points, and obtain the melt permeation distance from the average value thereof.

  In the evaluation test, the sintering heat pattern similar to that of the actual machine is used as the tablet baking condition. That is, the tablet is heated from 1100 ° C. to 1290 ° C. (maximum temperature) in 1 minute, then cooled from 1290 ° C. to 1100 ° C. in 3 minutes, and the tablet is immediately taken out of the furnace and air-cooled.

  FIG. 2 shows the relationship between the melt penetration distance of the iron ore and the strength SI of the sintered ore, and FIG. 3 shows the relationship between the iron ore in the actual sintering operation using the iron-containing raw material containing multiple brands of iron ore. The relationship between melt penetration distance and product yield of sintered ore is shown.

  SI, which is an index indicating the strength of sintered ore, samples 10 kg of sintered ore having a particle size of 10 to 25 mm from the sintered ore after the following product yield measurement, and drops 4 times from a height of 2 m. Is measured. This SI indicates the ratio (mass%) of the mass (kg) of the sintered ore having a particle diameter of 5 mm or more after dropping to the mass (kg) of the sintered ore before dropping.

  The product yield of sintered ore is measured by dropping the sintered cake (lumps) 5 times from a height of 2 m. The product yield of this sintered ore is the sintered ore with a particle size of 5mm or more after dropping with respect to the mass (kg) of the sintered cake (lumb) before dropping (excluding the bedding ore) , The ratio (mass%) of the mass (kg) of the bedding ore is excluded.

  2 and 3, it can be seen that the product yield and SI of the sintered ore are improved when the melt penetration distance is increased in the sintered raw material including a plurality of brands of iron ore.

  That is, these results are based on the melt penetration distance as an index of the melt permeability of iron ore, and the method of adjusting the composition of each brand of iron ore in the sintering raw material is a sintering machine manufactured by an actual machine. This suggests that it is effective for improving the yield and strength of the ore.

  As shown in FIGS. 2 and 3, in the actual machine sintering operation, the strength SI of the sintered ore is required to be 90.5% or more, and the product yield is required to be 80.0% or more.

  Next, in the present invention, it is required to improve the strength and product yield of the upper-layer sintered ore (strength SI: 90.5% or more, product yield: 80.0% or more). An appropriate range of the melt permeability of the iron ore, that is, the melt penetration distance measured in the melt permeability evaluation test will be described.

  Table 1 shows the chemical composition of the main brand iron ore to be blended with the sintered raw material and the melt penetration distance measured in the melt permeability evaluation test.

  In Table 1, B (a) and B (b) are two Brazilian ores, H (a) and H (b) are two Australian hematite ores, M (a) and M (b) Shows two types of Australian maramamba ore. HP (a) and HP (b) are two Australian high phosphate rocks, P (a) and P (b) are two Australian pisolite ores, HPM is a new Australian blended ore, I ( a) and I (b) represent two types of Indian ores. S1 and S2 indicate scales generated in two types of iron making processes.

  FIG. 5 is a diagram showing a comparison of melt penetration distances of main brand iron ores shown in Table 1. According to Table 1 and FIG. 5, among the main brands of iron ore, two Brazilian ores B (a) and B (b) both have a high melt penetration distance of 4.0 mm or more. I understand.

  On the other hand, two Australian hematite ores H (a) and H (b), two Australian high-phosphorus ores HP (a) and HP (b), and two Australian pisolite ores P (a) As for P and (b), the melt penetration distance is as low as 2.0 mm or less.

  In addition, Australian new blended ore HPM, two Australian maramamba ores M (a) and M (b), and two Indian ores I (a) and I (b) have a melt penetration distance. It turns out that it exists in the range of more than 2.0 mm-less than 4.0 mm.

  Australian pisolite ores P (a) and P (b) are known as easily meltable iron ores that have a high crystallization water content and are easily assimilated and melted in the sintering reaction. However, it can be seen that Australian pisolite ores P (a) and P (b) have a low melt penetration distance of 2.0 mm or less and have poor melt permeability. In addition, it can be seen that the scales S1 and S2 generated in the iron making process differ greatly in the melt permeability distance depending on the type of scale.

  Next, using multiple grades of iron ore with different melt permeability shown in Table 1 and improving the strength and product yield of the sintered ore when these are selectively charged into the upper layer of the sintered raw material packed bed The effect was confirmed by a tablet baking test.

  As a sample for tablet firing test, the iron ore of plural brands shown in Table 1 is pulverized, and iron ore having a particle size of 0.25 to 0.25 mm is 50% by mass, and iron ore having a particle size of 0.25 mm or less is used. The particle size was adjusted to 50% by mass, and limestone of 0.25 mm or less was mixed with each iron ore so that the CaO concentration was 10% by mass.

  These samples were molded into tablets (porosity of about 30%) having a diameter of 8 mm and a height of 10 mm using a mold forming die at a molding pressure of 4 MPa.

  In the tablet firing test, the sample tablet was placed in a Ni cylindrical crucible having an inner diameter of 20 mm and a height of 15 mm and fired in an air stream in an electric furnace. A sintering heat pattern similar to that of the actual machine is used as the tablet baking condition. That is, the tablet was heated from 1100 ° C. to 1290 ° C. (maximum temperature) in 1 minute, then cooled from 1290 ° C. to 1100 ° C. in 3 minutes, and the tablet was immediately taken out of the furnace and air-cooled.

  For the strength evaluation of the baked tablet after baking, a drop test was performed in which 300 g of iron weight was dropped three times for each baked tablet. After mixing the sample (baked tablet) after this test, it was classified with a 0.5 mm sieve. As a strength index (+0.5 mm% value), a mass percentage of a sample of 0.5 mm or more with respect to the mass of all samples was obtained.

  In the actual machine sintering operation, the strength SI of the sintered ore is required to be 90.5% or more, and the product yield is required to be 80.0% or more.

  In order to determine the evaluation criteria for the strength of the fired tablet, a sinter with an intensity SI of 90.5% or more and a product yield of 80.0% or more produced in advance by actual machine sintering operation is collected and dropped. The test was conducted. In this drop test, a sample processed into the same shape as the pot test tablet, that is, a tablet shape having a diameter of 8 mm and a height of 10 mm was used. The strength index (+0.5 mm% value) measured in this drop test was used as an evaluation standard.

  In addition, the strength index (+0.5 mm% value) measured by the above drop test using a sintered ore having a strength SI of 90.5% or more and a product yield of 80.0% or more manufactured by an actual machine sintering operation is 88%. Therefore, in the strength evaluation of the fired tablet, the fired tablet satisfying the drop test strength index (+0.5 mm% value) of 88% or more was evaluated as having good sintered ore strength and product yield.

  FIG. 6 shows the relationship between the melt penetration distance of each brand iron ore by the tablet firing test and the strength index (+0.5 mm% value) by the drop test.

  As shown in FIG. 6, the above drop test strength index (+0.5 mm% value) of 88% or more corresponding to the target sinter strength (SI is 90.5% or more) in actual machine sintering operation is achieved. In order to achieve this, melt permeability having a melt penetration distance of 4.0 mm or more is required.

  Specific examples of the iron ore brand having melt permeability having a melt penetration distance of 4.0 mm or more include Brazilian ores B (a) and B (b) shown in Table 1.

  In the present invention, in order to improve the strength and product yield of the sintered ore in the upper layer of the sintered material packed layer (strength SI is 90.5% or more, product yield is 80.0% or more) One or more types of iron ore are charged into the upper layer in a predetermined range of the packed bed so that the melt penetration distance is 4.0 mm or more.

As described above, when the iron ore charged in the upper layer of the predetermined range of the sintering raw material packed layer contains two or more brands of iron ore, each brand of iron ore measured by the melt permeability evaluation test The blending ratio of two or more brands of iron ore is adjusted so that the weighted average value of the stone melt penetration distance is 4.0 mm or more.
Below, the iron ore which consists of 1 or more types selected or mix | blended so that a melt penetration distance may be set to 4.0 mm or more is defined as a high melt penetration iron ore.

  FIG. 7 shows the relationship between the ratio of the thickness of the upper charged layer in which the high melt permeability iron ore is charged and the strength SI of the sintered ore. Similarly, FIG. 8 shows the relationship between the upper charge layer thickness ratio and the product yield of sintered ore.

  SI, which is an index indicating the strength of sintered ore, is obtained by collecting 10 kg of sintered ore having a particle size of 10 to 25 mm from the sintered ore after measurement of the following product yield, and measuring 4 kg from the height of 2 m. It is measured by dropping it twice. This SI indicates the ratio (mass%) of the mass (kg) of the sintered ore having a particle diameter of 5 mm or more after dropping to the mass (kg) of the sintered ore before dropping.

  The product yield of sintered ore is measured by dropping the sintered cake (lumps) 5 times from a height of 2 m. The product yield of this sintered ore is the sintered ore with a particle size of 5mm or more after dropping with respect to the mass (kg) of the sintered cake (lumb) before dropping (excluding the bedding ore) , The ratio (mass%) of the mass (kg) of the bedding ore is excluded.

7 and FIG. 8 show the high melt permeability iron ore and other iron ores in the upper layer (A part) and the lower layer (B part) of the sintering pot having a height of 600 mm and a diameter of 300 mm shown in FIG. The test results when stones are charged and fired are shown. The average values of the upper layer (A layer) and the lower layer (B layer) are constant in SiO ₂ : 5.01% by mass, CaO / SiO ₂ : 1.89, and coke: 4.3% by mass in the sintering raw material. Limestone, coke, and return are blended. These sintered raw materials are used after granulation at a granulation moisture of 7.0% by mass. Here, the other iron ores mean iron ores excluding the iron ore charged in the upper layer.

  The firing conditions of the sintering pot test were as follows: layer thickness: 600 mm, suction negative pressure: 14.7 KPa, firing time: 27 minutes.

  The strength of the sintered ore and the product yield in this sintering pot test were evaluated based on the strength of the sintered ore SI: 77% and the product yield: 76%. These evaluation criteria are shown in Table 2 in which it is confirmed in advance that the strength SI of the sintered ore is 90.5% or more and the product yield is 80.0% or more when the actual machine sintering operation is performed. It was obtained by carrying out a main sintering pot test using a sintering raw material under blending conditions. Therefore, these evaluation criteria correspond to the strength SI (90.5% or more) and the product yield (80.0% or more) of the sintered ore targeted in the actual machine sintering operation.

  That is, in the sintering pot test, when the strength SI of the sintered ore was 77% or more and the product yield was 76% or more, the strength of the sintered ore and the product yield were evaluated as good.

  As shown in FIGS. 7 and 8, in order to achieve the strength SI of 77% or more and the product yield of 76% or more in the above-mentioned sintering pot test, high melt-permeable iron ore is installed. The upper charging layer thickness ratio (layer thickness ratio with respect to the total layer thickness of the raw material-filled layer) needs to be in the range of 5 to 12%.

  Sintering of the upper layer of the raw material packed layer by selective charging of iron ore with excellent melt permeability when the upper charging layer thickness ratio for charging high melt-permeable iron ore is lower than 5% The effect of improving the product yield, strength, and production rate of the ore cannot be obtained sufficiently.

  When the upper charge layer thickness ratio for charging the high melt permeability iron ore is higher than 12%, the iron ore with high melt permeability has a low granulation property as described later. Pseudoparticles collapse at the time of entering and in the firing process, and the air permeability in the raw material packed layer tends to be lowered. Therefore, the sinterability of the entire raw material packed layer is deteriorated, and the product yield, strength, and production rate of the sintered ore are deteriorated.

Moreover, the iron ore having high melt permeability is an ore having a low Al ₂ O ₃ content and a relatively high price, as will be described later. Therefore, it causes an increase in the manufacturing cost of the sintered ore.

  For the above reasons, the product yield and strength of the upper layer of the raw material packed layer are sufficiently improved without reducing the air permeability of the entire raw material packed layer (strength SI is 90.5% or more, and the product yield is 80.%). Therefore, a high melt permeable iron ore selected or blended from multiple brands of iron ore so that the weighted average value of the melt infiltration distance is 4.0 mm or more is applied to the raw material packed bed. The upper layer in the range of 5 to 12% of the total layer thickness from the surface is charged, the other iron ore is charged in the lower layer of the raw material packed bed, and the auxiliary raw material, solid fuel, and return ore Was charged into the upper and lower layers of the raw material packed layer. Unless otherwise specified, the mixing ratio of the auxiliary raw material, the solid fuel, and the return ore is the same in the upper layer and the lower layer of the raw material packed bed.

  In addition to the high melt permeable iron ore, the scales S1 and S2 generated in the iron making process may also be charged as an iron-containing raw material into the upper layer in the range where the upper charging layer thickness ratio is 5 to 12%. Good. Similarly, the scales S1 and S2 may be added to the lower layer as an iron-containing raw material in addition to other iron ores. Below, only the high melt permeability iron ore, or the iron-containing raw material combining the high melt permeability iron ore and the scale will be referred to as the high melt permeability iron-containing raw material. Moreover, only the other iron ore or the iron-containing raw material combining the other iron ore and the scale is used as the other iron-containing raw material.

FIG. 9 shows the relationship between the melt penetration distance of each brand of iron ore and the Al ₂ O ₃ content. As shown in FIG. 9, there is a correlation between the melt infiltration distance and the Al ₂ O ₃ content, and as the iron ore having the melt infiltration distance: 4.0 mm or more, the Al ₂ O ₃ content is 0.6% by mass. It is preferable to select the following iron ore brands.

The melt permeability of iron ore is not determined only by the Al ₂ O ₃ content, but is also affected by the structure of the iron ore such as pores. However, when the Al ₂ O ₃ content in the iron ore increases, the Al ₂ O ₃ content in the assimilated melt to be generated also increases. Therefore, the viscosity of the melt increases and the melt permeability decreases.

Therefore, in the present invention, the iron ore having a melt penetration distance of 4.0 mm or more charged in the upper layer of the raw material packed layer preferably has an Al ₂ O ₃ content of 0.6% by mass or less.

  Furthermore, as described above, in order to maintain the air permeability of the entire raw material packed layer, it is necessary to prevent the melt of the upper layer of the raw material packed layer from excessively increasing. Moreover, in order to reduce cost, it is preferable to reduce auxiliary materials. For this reason, the influence of the auxiliary raw materials required for melt formation, particularly the proportion of limestone in the upper layer, on the sinterability was investigated.

  FIG. 10 shows the relationship between the limestone ratio in the upper layer and the product yield of the sintered ore in the sintering pot test. Moreover, in FIG. 11, the relationship between the limestone ratio in an upper layer and the intensity | strength SI of the sintered ore in a sintering pot test is shown. In the examples of the present invention, Brazilian ore B (b) was used as the high melt-permeable iron ore in the upper layer, and the upper charge layer thickness ratio was 11.7%. Moreover, the sintering raw material of the mixture ratio shown in Table 2 was used.

As shown in FIGS. 10 and 11, SI and product yield were improved by using high melt permeability iron ore as the iron ore in the upper layer. In addition, reducing the proportion of limestone in the upper layer increased SI and product yield.
Therefore, with respect to the auxiliary raw material charged in the raw material packed layer, it is preferable that the mixing ratio of the upper auxiliary material is equal to or less than the mixing ratio of the lower auxiliary material from the viewpoint of cost reduction.

  In the present invention, the method of charging the high melt-permeable iron-containing raw material and other iron-containing raw materials into the upper layer of the raw material packed layer on the sintering pallet and the lower layer of the raw material packed layer, respectively, Although not limited, for example, a method as shown in FIG. 13 is used.

  A first surge hopper (for other iron-containing raw materials) 1 and a second surge hopper (for high melt-permeable iron-containing raw materials) 2 are arranged in series in the machine length direction in the feed section of the downward suction type sintering machine. Has been. From this first surge hopper 1, a sintered raw material 3 made up of other iron-containing raw materials excluding the high melt-permeable iron-containing raw material and limestone, coke, and return ore is placed on a sintering pallet 4. Then, the lower layer 5 of the raw material packed layer is formed. Thereafter, the second surge hopper 2 is charged with a raw material containing high melt permeability iron and a sintering raw material 6 made of limestone, coke and return ore, and on the lower layer 5, a raw material packed layer The upper layer 7 can be formed.

  In addition, the sintering raw material 6 which consists of a highly melt-permeable iron-containing raw material, limestone, coke and return ore, and the other iron-containing raw material, sintering which consists of limestone, coke and return ore The raw material 3 is mixed and granulated using granulators 8 and 9 such as a drum mixer and a pan pelletizer, respectively, to obtain pseudo particles. Thereafter, the respective sintered raw materials are supplied to a second surge hopper (for high melt-permeable iron-containing raw material) 2 and a first surge hopper (for other iron-containing raw materials) 1.

  Moreover, the sintering raw material 6 which consists of a highly melt-permeable iron-containing raw material, limestone, coke and return ore, and the sintering which consists of other iron-containing raw materials, limestone, coke and return ore As described above, the raw material 3 is blended so that limestone, coke, and return ore are in a predetermined blending ratio.

[First embodiment]
The effects of the present invention will be described below with reference to examples.
As a sintering raw material, a sintering pot test was carried out using a sintering pot having a height of 600 mm and a diameter of 300 mm as shown in FIG. 12 based on the average blending conditions during actual operation shown in Table 2. .

  In addition, when an actual machine sintering operation is performed using sintering raw materials having the blending conditions shown in Table 2, a sintered ore having a strength SI of 90.5% or more and a product yield of 80.0% or more is obtained. Is confirmed in advance.

Moreover, the production rate in the sintering pot test, the product yield of the obtained sinter, the cold strength SI, the reduction powder resistance index RDI, and the reduction ratio JIS-RI (%) were measured. The results are shown in Table 3 together with the production conditions. In addition, a production rate shows the value which divided | segmented the mass (t) of the sintered ore of 5 mm or more except the bed covering ore by the pan area (m < ² >) and sintering time (day).

  The strength SI of the sinter is measured by collecting 10 kg of sintered ore with a particle size of 10 to 25 mm from the sinter after the following product yield measurement and dropping it 4 times from a height of 2 m. The This SI indicates the ratio (mass%) of the mass (kg) of the sintered ore having a particle diameter of 5 mm or more after dropping to the mass (kg) of the sintered ore before dropping.

  The product yield of sintered ore is measured by dropping a sintered cake (lumps) 5 times from a height of 2 m. The product yield of this sintered ore is calculated based on the mass (kg) of the sintered cake (lumps) before dropping (excluding the bedding ore), but the grain size after dropping: , The ratio (mass%) of the mass (kg) of the bedding ore is excluded.

The reduction powder resistance index (RDI) of the sintered ore was measured according to the test method specified in JIS M 8720. That is, 500 g of sintered ore having a particle size of 15 to 19 mm is collected and reduced at 550 ° C. for 30 minutes in a mixed gas of N ₂ : 70% and CO: 30%. Thereafter, the reduced sintered ore is charged into a drum and subjected to 900 rotation tests in 30 minutes. The ratio (mass%) of the mass (g) of the sintered ore powder having a particle diameter after rotation of 3 mm or less to the mass (g) of the sintered ore after reduction before the rotation is the reduction dust resistance index (RDI). is there.

The JIS reduction rate (JIS-RI) of the sintered ore was measured according to a test method defined in JIS M 8713. That is, 500 g of sintered ore having a particle size of 19 to 21 mm is collected and reduced at 900 ° C. for 180 minutes in a mixed gas of N ₂ : 70% and CO: 30%. The ratio (mass%) of the reduction amount (g) of the mass of sintered ore due to the reduction to the mass (g) of oxygen contained in the iron oxide of the sintered ore before reduction is the JIS reduction rate (JIS-RI). .

  The high melt permeable iron-containing raw material charged into the upper layer of the raw material packed bed is mixed with limestone, return mineral, and coke and granulated to form pseudo particles, which are shown in FIG. The upper layer). In addition, the mixture ratio of limestone, coke, and return mineral is the same as the mixture ratio in the whole charging raw material.

  In addition, the other iron-containing raw materials were mixed with limestone, return mineral, coke, and granulated to form pseudo particles, and charged into part B (lower layer of the raw material packed layer) shown in FIG. . The proportions of coke and limestone (CaO) and return ore in the A part and the B part of the sintered raw material packed layer are the same.

  In addition, the high melt permeable iron-containing raw material to be charged into part A is shown in Table 1, two kinds of Brazilian ores B (a) and B (b) having different melt penetration distances, and melt penetration. Two Australian pisolite ores P (a) and P (b) with different distances, and iron ores mixed with these, and Australia's new blended ore HPM, and two types of steel making with different melt penetration distances Scales S1 and S2 generated in the process.

  In this example, B part was charged 530 mm from the great surface of the sintered pallet, and A part was placed on B part with a layer thickness of 70 mm (layer thickness ratio to total layer thickness (600 mm): 11.7). %).

Further, SiO _{2 in} the blending raw materials of part A and B: 5.01% by mass, CaO / SiO ₂ : 1.89, coke blending: 4.3% by mass (each equal to the ratio of the entire sintered raw material) The granulation conditions were granulated moisture: 7.0% by mass. Furthermore, the firing conditions of this sintering pot test were as follows: layer thickness: 600 mm, suction negative pressure: 14.7 KPa, firing time: 27 minutes. Each test result shown in Table 3 is an average value of n = 2 measured values.

  Reference Example 1 is a base test in which a plurality of brand iron ores shown in Table 2 as the sintering raw material were uniformly charged in the packed bed thickness direction. Evaluation of strength SI, product yield, production rate and the like of the sintered ore of Examples and Comparative Examples shown below was evaluated based on Reference Example 1.

  In Example 1, a Brazilian ore B (a) having a melt penetration distance: 4.65 mm shown in Table 1 was selectively charged into part A (upper layer of the raw material packed bed), and the remaining iron-containing raw material ( This is an example in which the other iron-containing raw material) is charged into part B (lower layer of the raw material packed layer).

  In Example 2, the Brazilian ore B (b) having a melt penetration distance: 4.22 mm shown in Table 1 was selectively charged in part A, and the remaining iron-containing raw material was charged in part B. It is an example.

  In Example 1 and Example 2, the product yield and strength SI of the sintered ore were improved and the production rate compared with Reference Example 1 without impairing the reduction-resistant powdered RDI and the reduction rate JIS-RI. Improved.

  Example 3 is a mixture ratio P of Brazilian ore B (a) having a melt penetration distance: 4.65 mm shown in Table 1 and Australian pisolite ore P (a) having a melt penetration distance: 1.12 mm. (A): B (a) = 15: 85 In this example, the mixture was selectively charged in part A, and the remaining iron-containing raw material was charged in part B.

  Melt penetration distance (B (a) and P (a) melt penetration distances of the iron ore mixture of B (a) and P (a) selectively charged in part A of Example 3 The weighted average value according to the mixing ratio was 4.12 mm. Therefore, the product yield and strength SI of the sintered ore were improved and the production rate was improved as compared with Reference Example 1 without impairing the reduction-resistant powdered RDI and the reduction rate JIS-RI.

  In Example 4, the Brazilian ore B (a) having a melt penetration distance: 4.65 mm shown in Table 1 and the scale S1 generated in the iron making process having a melt penetration distance: 4.21 mm are mixed with a mixing ratio B (a ): S = 85: 15 In this example, the mixture was mixed and selectively charged in part A, and the remaining iron-containing raw material was charged in part B.

  In Example 5, the Brazilian ore B (a) having a melt penetration distance: 4.65 mm shown in Table 1 and a scale S2 generated in an iron making process having a melt penetration distance: 1.66 mm are mixed with a mixing ratio B (a ): S2 = 85: 15 In this example, the mixture was mixed and selectively charged in part A, and the remaining iron-containing material was charged in part B.

Melt penetration distance of a mixture of B (a) and S1 iron ore selectively charged in part A of Example 4 (weighted average value by mixing ratio of each melt penetration distance between B (a) and S1 ) Was 4.28 mm. Therefore, the product yield and strength SI of the sintered ore were improved and the production rate was improved as compared with Reference Example 1 without impairing the reduction-resistant powdered RDI and the reduction rate JIS-RI.
Further, the melt penetration distance of the mixture of B (a) and S2 iron ore selectively charged in part A of Example 5 (weighting by the mixing ratio of the melt penetration distances of B (a) and S2) The average value) was 4.28 mm. Therefore, the product yield and strength SI of the sintered ore were improved and the production rate was improved as compared with Reference Example 1 without impairing the reduction-resistant powdered RDI and the reduction rate JIS-RI.

  On the other hand, Comparative Example 1 is a mixture of the Brazilian ore B (b) with a melt penetration distance: 4.22 mm shown in Table 1 and the Australian pisolite ore P (b) with a melt penetration distance: 1.23 mm. This is an example in which the mixture was mixed so that the ratio P (b): B (b) = 45: 55 was selectively charged into part A, and the remaining iron-containing raw material was charged into part B.

  The melt penetration distance (B (b) and P (b) of each melt penetration distance of the iron ore mixture of B (b) and P (b) selectively charged in part A of Comparative Example 1 The weighted average value by the mixing ratio) was as low as 2.87 mm. Therefore, compared with the reference example 1, the product yield and intensity | strength SI of the sintered ore fell, and the production rate also fell.

  Comparative Example 2 is a method of selectively charging Australian Pisolite ore P (a) having a melt penetration distance: 1.12 mm shown in Table 1 into part A and charging the remaining iron-containing raw material into part B. This is an example.

  In Comparative Example 3, Australian Pisolite ore P (b) having a melt penetration distance: 1.23 mm shown in Table 1 was selectively charged in part A, and the remaining iron-containing raw material was charged in part B. This is an example.

  In both Comparative Example 2 and Comparative Example 3, the melt penetration distances of P (a) and P (b) iron ores selectively charged in part A were as low as 1.12 mm and 1.23 mm, respectively. It was. Therefore, compared with the reference example 1, the product yield and intensity | strength SI of the sintered ore fell, and the production rate also fell.

[Second Example]
Next, the upper charge layer thickness of the Brazilian ore B (a) charged in the part A (the upper layer of the raw material packed bed) under the same conditions as in the first example carried out in the [first example]. The test was performed in the same manner except that the ratio (layer thickness ratio with respect to the total layer thickness from the upper surface) was the same, except that only the upper charge layer thickness ratio was changed. Reference Example 1 has the same conditions as [First Example].

  Further, as in [First Example], the production rate in the sintering pot test, the product yield of the obtained sintered ore, and the cold strength SI were measured. The results are shown in Table 4.

  Examples 1 to 3, in which Brazilian ore B (a) was charged into part A so that the upper charge layer thickness ratio was in the range of 5 to 12%, were reduced powder-resistant RDI and reduction rate JIS- Without impairing RI, the product yield and strength SI of the sintered ore were improved and the production rate was improved as compared with Reference Example 1.

  On the other hand, Brazilian ore B (a), Comparative Examples 1 and 2 in which the upper charge layer thickness ratio is less than 5% in the A part, and Brazilian ore B (a), In the case of Comparative Examples 3 and 4 where the portion A was charged so that the thickness ratio of the upper charge layer was greater than 12%, both the product yield and strength of the sintered ore as compared with Reference Example 1 SI decreased and production rate also decreased.

  As described above, according to the present invention, in the method for producing sintered ore using the lower suction type sintering machine, the melt permeability to the fine powder portion of each brand of iron ore to be blended with the sintering raw material is evaluated. Based on this evaluation result, among each brand iron ore, select a brand iron ore with excellent melt penetration into the fine powder part, and selectively insert it into the upper layer of the raw material packed bed, The product yield and strength of the upper layer of the raw material packed bed can be improved, and the productivity of the sintered ore can be improved. Therefore, the present invention has high applicability in the steel industry.

1 First surge hopper (for other iron-containing raw materials)
2 Second surge hopper (for high melt-permeable iron-containing raw materials)
3 Sintered raw materials consisting of other iron-containing raw materials, auxiliary raw materials, coke and return ore 4 Sintering pallet 5 Lower layer of raw material packed bed 6 High melt permeable iron-containing raw materials, auxiliary raw materials, coke and returned ores Sintered raw material consisting of 7 Upper layer of raw material packed bed 8 Granulator 9 Granulator

Claims (7)

Mixing and granulating iron-containing raw materials containing multiple brands of iron ore, secondary raw materials, solid fuel, and return ore into sintered raw materials, mixing and granulating these sintered raw materials, and then charging them onto a sintering pallet A method for producing a sintered ore to be fired,
Based on the melt penetration distance measured for each brand of the iron ore, the weight average value of the melt penetration distance is selected or blended from the plurality of brand iron ores to 4.0 mm or more. High melt-permeable iron ore is charged from the upper surface of the raw material packed layer formed on the sintered pallet to the upper layer in the range of 5 to 12% in the layer thickness ratio to the total layer thickness;
Charging other iron ore into the lower layer of the raw material packed bed;
And charging the secondary raw material, the solid fuel, and the return ore into the upper layer and the lower layer of the raw material packed bed;
The manufacturing method of the sintered ore characterized by the above-mentioned. Method for producing sintered ore according to claim 1, the content of Al ₂ O ₃ the KoTorueki permeable iron ore is equal to or less than 0.6 wt%.   In addition to the high melt permeability iron ore, as the iron-containing raw material, the scale generated in the iron making process is in the range of 5 to 12% in the layer thickness ratio with respect to the total layer thickness from the upper surface of the raw material packed layer. The method for producing a sintered ore according to claim 1, wherein the upper layer is charged.   2. The method for producing a sintered ore according to claim 1, wherein the solid fuel and the return ore are charged in the same mixing ratio in the upper layer and the lower layer of the raw material packed bed.   2. The method for producing a sintered ore according to claim 1, wherein a mixing ratio of the upper layer is equal to or less than a mixing ratio of the lower layer with respect to the auxiliary material charged in the raw material packed layer.   The high melt permeable iron ore and the other iron ore are mixed with the auxiliary raw material, the solid fuel, and the return mineral, mixed, granulated, and then the upper layer of the raw material packed bed and The method for producing a sintered ore according to claim 1, wherein the lower layer is charged respectively.   The high melt permeability iron ore is blended with the scale generated in the iron making process as the iron-containing raw material, blended with the auxiliary raw material, the solid fuel, and the return mineral, mixed, and granulated. 7. The method for producing a sintered ore according to claim 6, wherein after that, the upper layer of the raw material packed bed is charged.