Method for manufacturing sintered ore

Abstract

To provide a method of producing a sintered ore, which can improve strength and productivity of the sintered ore by designing appropriate granule components in a granulating step that produces multiple types of granules differently, taking into consideration characteristics of raw materials used.SOLUTION: In operating a sintering process that produces a sintered ore by differently producing granules A and B in each of which an adhesion layer 3 surrounds a core particle 2 and then mixing and firing these granules A and B, granules A and B are produced by meeting the following conditions: a proportion of low-alumina ore blended in each of granules A and B is ≤30 mass%; and a weighted average [C / F] in the adhesion layers of the granules A and B is ≥0.115, performing gradient blending of low-alumina ore to the granule A, performing gradient blending of limestone 4 to the granule A so that [C / F] in the adhesion layer 3 of the granule B is ≥0.08, and performing gradient blending of high crystallization water ore to the granule A so that a crystallization water component in the adhesion layer 3 of the granule A is ≤4.0 mass%.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for producing sintered ore by mixing iron ore and auxiliary raw materials, granulating them, and sintering the granulated product.

Background Art

[0002] Generally, in the sintering process (the process of producing sintered ore), first, in a granulator, iron ore and auxiliary raw materials (such as limestone) are mixed, a carbonaceous material serving as a heat source is added, and a granulated product serving as a sintering raw material is produced. Then, the granulated product is filled into a sintering machine and fired to obtain sintered ore as a finished product.

[0003] Among these, in the granulation process, the above raw materials charged into the granulator from the raw material hopper are rolled while adding water, so that fine ore, limestone, etc. adhere around the ore serving as the core to form an adhesion layer. In this way, a granulated product with an adhesion layer formed is produced. Regarding the granulator, a method using a drum mixer or a pan pelletizer is generally used. The granulated product is fired in a sintering machine to produce sintered ore. As a technique for producing such sintered ore, for example, those disclosed in Patent Documents 1 to 3 are available.

[0004] Patent Document 1 aims to stably and surely improve the yield and productivity of sintered ore without changing the chemical composition of the sintered ore that affects blast furnace operation in the method for producing sintered ore.

[0005] Specifically, various powdered ores used as sintering raw materials are classified into two series (high Al2O3 content series (A), low Al2O3 content series (B)) according to their Al2O3 content. CaO sources (4A, 4B) and powdered fuels (7A, 7B) are then added to the powdered ores of each series (A, B). After mixing and granulating these mixtures (8A, 8B), the granulated materials of each series are mixed. (9) In a method for producing sintered ore by (10) firing the total sintered raw material, the basicity (mass ratio CaO / SiO2) of the fine powder portion of 0.5 mm or less in the first series (A) formulation is set to be in the range of 4.4 to 7.3, and the mixing ratio of the first series (A) formulation (excluding the returned ore and powdered fuel) and the second series (B) formulation (excluding the powdered fuel) is set to be in the range of 2:8 to 8:2 by mass ratio.

[0006] Patent Document 2 aims to improve the productivity of sintered ore and the strength of sintered ore when a large amount of fine ore powder (pellet feed) is incorporated into the manufacturing method of sintered ore.

[0007] Specifically, the method for producing sintered ore involves a main granulation process and a secondary granulation process, which are carried out in parallel, in which the sintering raw material is divided into a main sintering raw material and a secondary sintering raw material, and each is mixed and granulated; the granules produced in the main granulation process and the secondary granulation process are combined; and the combined granules are fired. In the secondary granulation process, the ratio of fine ore to powdered ore, which is part of the secondary sintering raw material, is 1.5 / 1 or more and less than 3 / 1; the binder is quicklime and crushed ore; and the crushed ore is 3% by mass or more and less than 7% by mass relative to the secondary sintering raw material.

[0008] Patent Document 3 aims to suppress the formation of strip-shaped CaF with poor reducibility, promote the formation of amorphous slag with excellent room-temperature strength and resistance to reduction and pulverization, and enable the production of sintered ore with excellent room-temperature strength, reduction and pulverization resistance, and reducibility in a high yield.

[0009] Specifically, in the pretreatment method for sintering raw materials, the {average Al2O3 weight content / (average Al2O3 weight content + average Fe2O3 weight content)} value and average SiO2 weight content value of the total powdered ore are calculated from the chemical composition and blending ratio of the various powdered ore materials to be blended as binding materials. The various powdered ore materials are classified based on these average values, and for powdered ore materials that have an {Al2O3 weight content / (Al2O3 weight content + Fe2O3 weight content)} value lower than the average value and an SiO2 weight content value higher than the average value, the CaO source to be blended as a solvent is blended so that it is higher than the average (CaO weight content / SiO2 weight content) value of the total sintering raw materials, and this blend is mixed and granulated prior to the mixing and granulation of the total sintering raw materials. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2009-114485 [Patent Document 2] Japanese Patent Publication No. 2016-191122 [Patent Document 3] Japanese Patent Publication No. 63-076825 [Overview of the project] [Problems that the invention aims to solve]

[0011] Now, Figure 1 schematically shows the sintering process for producing sintered ore by granulating granulation raw material 1. As shown in Figure 1, when producing sintered ore, granulation raw material 1 (hereinafter referred to as granules 1), which has been pre-processed in granulation equipment 7 such as a drum mixer 8, is supplied to a pallet trolley on a sintering machine 10, the surface of the raw material packed bed containing carbon material is ignited, and gas is drawn in from below to propagate the combustion. While this combustion is occurring, multiple granules 1 are melted and assimilated and solidified together to produce the finished sintered ore.

[0012] Figure 2 schematically shows the outline of granule 1. As shown in Figure 2, many granules 1 have a structure in which a core ore 2 of +1 mm is covered with limestone 4 and -1 mm fine ore 5 (or auxiliary material). In other words, granule 1 has an adhesive layer 3 formed around it and is also called a pseudo-particle.

[0013] Incidentally, when granules melt due to combustion on a sintering machine, the melting point of the granules is the part of the adhesion layer with a large specific surface area. The molten calcium ferrite (CF) generated from the molten adhesion layer incorporates and assimilates the surrounding granules as the sintering reaction progresses. At this time, the better the melt assimilation between the granules, the stronger the connective tissue becomes, and the stronger the resulting sintered ore product will be.

[0014] The fusion assimilation between these granules depends on the amount and viscosity of the melt generated, which are influenced by the composition of the adhering layer, i.e., the properties of the raw materials used during granulation. For example, when using iron ore with a high proportion of fine powder, the iron content in the adhering layer of the granules becomes relatively high, while the CaO content in the melt decreases relatively, resulting in a reduction in the amount of melt generated. Conversely, when using ore with a high alumina content, even if the amount of melt generated is sufficient, the viscosity of the melt increases, leading to poor assimilation and a fragile structure.

[0015] Furthermore, the productivity of sintered ore is primarily determined by the yield within the sintering machine and the permeability of the raw material packing bed. Good permeability in the raw material packing bed shortens the sintering time, thereby increasing production volume. To ensure good permeability within the sintering machine, it is necessary to increase the porosity (reduce the density) of the raw material packing bed.

[0016] If a highly viscous molten material is generated from the granules, it becomes difficult for the molten material to flow when gas is drawn in from below the sintering machine, hindering the formation of gas passages, worsening permeability, and reducing the productivity of sintered ore. Conversely, if the amount of molten material is too small, unfired material will occur, reducing the yield in the sintering machine and lowering the productivity of sintered ore. On the other hand, if the amount of molten material is too large, it will hinder gas flow and cause uneven firing.

[0017] In other words, appropriate melt volume and viscosity are important for improving the permeability within the sintering machine. To control the melting during firing as described above, it is important to appropriately design the adhesion layer components of the granulated material by selecting the raw materials used in granulation. However, the properties of ore are generally fixed, and due to the supply and demand constraints of ore, it is difficult to control the selection and quantity of raw materials.

[0018] Patent Document 1 does not specify the blending of highly crystalline water ore. In other words, the upper limit of the crystalline water component in the adhering layer is unknown. Furthermore, Patent Documents 2 and 3 do not specify the [C / F] (=CaO / Fe2O3) value of the adhering layer of the granulated material. In other words, Patent Documents 2 and 3 make it difficult to design the appropriate composition of the granulated material.

[0019] Therefore, in view of the above problems, the present invention aims to provide a method for producing sintered ore that can improve the strength and productivity of sintered ore by designing the appropriate composition of granules that take into account the characteristics of the raw materials used in the granulation process for producing multiple types of granules. [Means for solving the problem]

[0020] To achieve the above objectives, the present invention employs the following technical means.

[0021] The present invention provides a method for producing sintered ore, which involves separately producing granules A and granules B, each having an attached layer around the outer surface of a core particle, and then mixing and firing these granules A and granules B to produce sintered ore. In this sintering process, the present invention provides granules A and granules B that satisfy the following conditions (1) and (2). Granules A and granules B are manufactured by performing a "gradual blending of raw materials," which involves changing the amount of predetermined raw materials charged to each granulator. The low-alumina ore is blended in a gradual manner to ensure that granules A contain a large amount of low-alumina ore, and the limestone is blended in a gradual manner to ensure that granules A contain a large amount of limestone, while the [C / F] of the adhesion layer of granules B is set to ≥ 0.08, and the high-crystallinity water ore is blended in a gradual manner to ensure that granules A contain a large amount of high-crystallinity water ore, while the crystalline water content in the adhesion layer of granules A is set to ≤ 4.0 mass%. It is characterized by the following:

[0022] (1) The proportion of low-alumina ore in each of granules A and B is ≤30 mass% (2) Weighted average [C / F] of the adhesion layer between granules A and B ≥ 0.115 Note that [C / F] refers to CaO (mass%) / Fe2O3 (mass%). Furthermore, the term "low-alumina ore" refers to iron ore with a low alumina content of less than 1.0 mass%, while "high-crystal-water ore" refers to iron ore with a high crystal-water content of 10.0 mass% or more.

Advantages of the Invention

[0026] According to the method for producing sintered ore of the present invention, in the granulation step of separately producing a plurality of granulated products, by performing appropriate component design of the granulated products in consideration of the characteristics of the raw materials used, it is possible to improve the strength and productivity of the sintered ore.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram schematically showing an outline of a sintering process for producing sintered ore. [Figure 2] It is a diagram schematically showing an outline of a granulated product produced by a sintering process. [Figure 3] It is a diagram schematically showing an outline of the granulation step (granulation equipment) of the present embodiment. [Figure 4] It is a diagram showing an example of the divided granulation method in the granulation step. [Figure 5] It is a diagram showing the relationship between [C / F] of the adhesion layer of the granulated product in single granulation and the sintering rotation strength. [Figure 6] It is a diagram showing the relationship between the concentrate blend from Canada (low-alumina ore) and the granulation property. [Figure 7] It is a diagram showing the relationship between the crystal water in the adhesion layer and the variation in the sintering rotation strength. [Figure 8] It is a diagram schematically showing an outline of the uniform blending of limestone and the inclined blending of limestone. [Figure 9] It is a diagram showing the relationship between [C / F] of the adhesion layer of the divided granulated product B and the sintering rotation strength. [Figure 10] It is a diagram showing the influence in the sintering machine when raw materials such as concentrate from Canada (low-alumina ore) or ore from Australia (high-crystal water ore) are unevenly distributed in the granulated product 1 on one side. [Figure 11] It is a diagram showing the evaluation of the results of the sintering strength and the productivity of the sintered ore by the angle pot test. [Figure 12]This is a flowchart illustrating the procedure for the manufacturing method of sintered ore according to the present invention. [Modes for carrying out the invention]

[0028] Hereinafter, embodiments of the method for producing sintered ore according to the present invention will be described with reference to the figures. Note that the embodiments described below are merely examples of the present invention, and these specific examples do not limit the configuration of the present invention.

[0029] The present invention relates to a method for producing sintered ore. Through the following investigations, we have found that by designing the appropriate components of granules A and B in the granulation process, which involves creating multiple granules 1 (granule A and granule B in this embodiment) that serve as sintering raw materials, taking into account the characteristics of the raw materials used, it is possible to improve the strength and productivity of the sintered ore.

[0030] In other words, the present invention's method for producing sintered ore is characterized by producing granules A and granules B, each having an attached layer 3 formed around the outer periphery of a core particle 2, and then operating a sintering process to produce sintered ore by mixing and firing these granules A and granules B, while satisfying the following conditions (1) and (2).

[0031] (1) The proportion of low-alumina ore in each of granules A and B is ≤30 mass% (2) Weighted average [C / F] of the adhesion layer between granules A and B ≥ 0.115 Note that [C / F] refers to CaO (mass%) / Fe2O3 (mass%).

[0032] More preferably, when producing granules A and granules B separately by "gradual blending of raw materials," which involves changing the amount of predetermined raw materials charged to each granulator (drum mixers 8 and 9 in this embodiment), it is preferable to blend the low-alumina ore in a gradual manner towards granules A so that a larger amount of low-alumina ore is incorporated into granules A.

[0033] More preferably, the limestone 4 is blended into granule A in a gradual manner so that a large amount of limestone 4 is incorporated into granule A, and the [C / F] ratio of the adhering layer of granule B is set to ≥ 0.08.

[0034] More preferably, the amount of highly crystalline water ore is blended into granule A in a gradual manner so that a large amount of highly crystalline water ore is incorporated into granule A, and the amount of crystalline water in the adhering layer of granule A is set to ≤4.0 mass%.

[0035] The method for producing sintered ore according to the present invention will be described in more detail below.

[0036] When manufacturing granules 1, the overall properties of the granules 1 are largely determined by the ore and auxiliary materials used. For example, if a single type of granule 1 is produced, all granules 1 will exhibit almost the same melting behavior, making it impossible to control the melt assimilation state.

[0037] Therefore, by providing multiple granulation systems to produce different types of granules 1 and assigning specific functions to each granule 1, melt assimilation is promoted, improving sintering strength and the permeability of the raw material packing bed, thus increasing productivity.

[0038] Specifically, one of several granules, 1 (hereinafter referred to as granule A), is preferentially blended with secondary raw materials such as limestone, low-alumina ore, and high-crystallinity water ore (in greater quantities than other granules 1 (hereinafter referred to as granule B)) to produce easily meltable granule A. Because granule A, which contains a large amount of low-alumina ore, has low viscosity and generates a large amount of melt, it can assimilate during sintering, incorporating the remaining difficult-to-melt granule B and forming a strong sintered body (sintered ore).

[0039] Figure 1 schematically shows the sintering process for producing sintered ore. Figure 2 schematically shows granule 1 produced in the sintering process (granulation process).

[0040] Generally, in the sintering process, iron ore is mixed with auxiliary materials (such as limestone 4), carbon material is added as a heat source, granules 1 which will be used as the sintering material are produced in a granulator (drum mixer 8, 9), and these granules 1 are packed into a sintering machine 10 and fired to produce sintered ore, which will be the finished product.

[0041] In the granulation process, as shown in Figure 1, the raw materials are charged into the granulator from the raw material layer 6 (raw material hopper 6) and tumbled while water is added. As shown in Figure 2, limestone 4 and fine ore 5 adhere to the core ore 2, forming an adhesion layer 3. In this way, granulated material 1 with the adhesion layer 3 is produced. For the granulator, it is common to use, for example, a drum mixer 8 or a pan pelletizer 11. The granulated material 1 is then fired in a sintering machine 10 to produce sintered ore.

[0042] In this embodiment, during the sintering process in which the materials are mixed and fired, multiple granules 1 (granule A, granule B) that will serve as raw materials for the sintered ore are produced separately using multiple granulators (drum mixers 8, 9).

[0043] Figure 3 schematically shows the granulation process (granulation equipment 7) of this embodiment.

[0044] As shown in Figure 3, in this embodiment, raw materials extracted from a raw material process with multiple systems are processed in a granulation facility 7 equipped with two parallel systems to produce two types of granules 1. Specifically, the drum mixer 8 of system II granulates easily melted granule A, and the drum mixer 9 of system I granulates difficult-to-melt granule B. These granules A and B are mixed and fired in a sintering machine 10 to produce sintered ore.

[0045] Figure 4 shows an example of a divided granulation method in the granulation process.

[0046] As shown in Figure 4, in the granulation process, raw materials are cut from raw material processes (raw material layers 6a, 6b) which have multiple systems, and granules 1 are produced separately using multiple granulation equipment 7 (drum mixer 8, pan pelletizer 11, etc.). Each granule 1 is then mixed and fed into the sintering machine 10 (this is known as the divided granulation method).

[0047] In the example shown in Figure 4, one granule 1 is granulated in a drum mixer 8, the other granule 1 is granulated in a pan pelletizer 11, the two types of granules 1 are mixed, and sintered ore is produced by firing in a sintering machine 10. The present invention is also applicable to the example shown in Figure 4.

[0048] Such a divided granulation method is known as a technique aimed at improving permeability by changing the melting behavior between multiple granules 1 within the sintering machine 10. The granules 1 produced by the divided granulation method can be divided into two types: granules 1 on the melt supply side (granule A in this embodiment), which melt easily during firing and assimilate by incorporating surrounding granules 1; and granules 1 on the melt receiving side (granule B in this embodiment). In other words, it is important to design granule A on the melt-sharing side to have low viscosity and generate a large amount of melt. That is, it is necessary to produce granules A that melt easily and granules B that do not melt easily.

[0049] Inside the sintering machine 10, ignition occurs from the surface of the raw material packing bed containing carbon material, and combustion is propagated by drawing in air from below. As the combustion propagates to the packed granules 1, a portion of the granules 1 melts, and the heat of combustion from burning the powdered coke generates a molten calcium ferrite (CF) mixture. This mixture flows downward along the flow of the suctioned gas, agglomerating the powdered ore particles through slag bonding by the molten mixture and assimilating the other granules 1. As the molten and assimilated granules 1 cool, a sintered body (sintered ore) is obtained.

[0050] In this process, the melt assimilation characteristics between each granule 1 change depending on the properties of the melt generated from each granule 1. For example, if a high-alumina raw material is used for granule 1, the viscosity of the generated melt increases, making it difficult to flow downwards. This makes it difficult to assimilate with other granules 1 and can also create a barrier that obstructs gas flow, potentially leading to poor permeability of the raw material packed bed. In other words, it can lead to a decrease in productivity. Furthermore, if a difficult-to-melt raw material is used, the amount of melt generated will be insufficient, resulting in poor assimilation (i.e., the occurrence of unburned portions) and a decrease in productivity.

[0051] Thus, in the process of manufacturing sintered ore, it is necessary to ensure the permeability of the raw material packed bed in the sintering machine 10 and to stably supply the air necessary for combustion to the raw material packed bed. To achieve this, it is necessary to appropriately mix and granulate raw materials such as iron ore and limestone 4 in the granulation process, which is a pretreatment step before sintering, in order to produce granulated material 1 that has been converted into pseudo-particles.

[0052] Therefore, in this invention, one of the granules A is formulated with a gradient blend of limestone 4 and fine ore 5 such as low-alumina ore or high-crystallinity hydro ore (more limestone 4 and high-crystallinity hydro ore 5 than in granule B). The "gradient blending" of the auxiliary raw materials (limestone 4 and fine ore 5 such as low-alumina ore or high-crystallinity hydro ore) used in the production of granules A and B will be explained in detail later.

[0053] Table 1 shows the definitions of the parameters used in this embodiment.

[0054] [Table 1]

[0055] For example, as shown in Table 1, the "low-alumina ore" in this embodiment uses iron ore with a low alumina content of less than 1.0 mass%. A typical example of this low-alumina ore is Canadian concentrate, which is characterized by its fine particle size (approximately 90% of the powder is -1 mm). However, because of the low alumina content, the viscosity of the resulting melt is low, but other ores In comparison, the particle size range of -1 mm, which forms the adhesion layer 3, has relatively large particle sizes, resulting in poor reactivity and a large amount of undissolved material. Furthermore, the ore surface is smooth, and granulation is not good.

[0056] Note that particle size is measured using the sieving method; -1mm means "under 1mm, passing through a sieve with a 1mm mesh," and +1mm means "over 1mm, unable to pass through a sieve with a 1mm mesh."

[0057] Furthermore, the "highly crystalline water ore" in this embodiment uses iron ore with a high water content of 10.0 mass% or more. A typical example of this highly crystalline water ore is aubergine ore, which has a wide grain size distribution. However, because highly crystalline water ore contains a large amount of micro-order powder, it has good meltability and generates a large amount of melt, but when water is released it forms bubbles that remain in the melt, resulting in high structural viscosity of the melt.

[0058] In this embodiment, the weighted average [C / F] (=CaO / Fe2O3) of all granules 1 (granules A and granules B) in the adhesion layer 3 is set to be 0.115 or higher. This will be explained in detail below.

[0059] The weighted average [C / F] in the adhesion layer 3 for granules A and B can be calculated using the following formula.

[0060] • Weighted average [C / F] of granule A and granule B = Weight of granule A / (Weight of granule A + Weight of granule B) × [C / F] of the adhesion layer 3 of granule A + Weight of granule B / (Weight of granule A + Weight of granule B) × [C / F] of the adhesion layer 3 of granule B Incidentally, the melting point of the granulated material 1 during sintering is the adhesive layer 3, which has a large specific surface area. By controlling the composition of this adhesive layer 3 during granulation, the properties of the melt generated during sintering are determined. In this embodiment, the adhesive layer 3 refers to an aggregate of adhesive powder composed of -1 mm fine particles.

[0061] The mass ratio of CaO to Fe2O3 in the adhering layer 3, [C / F] (= CaO (mass%) / Fe2O3 (mass%)), is used as an indicator of the melt assimilation properties of the pseudo-particleized granule 1. The higher the weighted average [C / F] value of the adhering layer 3, the greater the relative amount of melt generated, indicating good meltability. On the other hand, if the weighted average [C / F] value of the adhering layer 3 is low, the amount of melt is small, and therefore the meltability can be judged as poor.

[0062] Here, the strength effect of the weighted average [C / F] of the adhesion layer 3 of granule 1 was investigated using a small pot test. The test method and conditions are described in the "Implementation Conditions" section (Experiment 1) in Tables 2 and 3. Furthermore, this test example uses a single granulation method with a constant suction airflow during sintering, making it a method that can investigate the average component effect of granule 1.

[0063] Table 2 shows the conditions for conducting the small-scale sintering pot tests (Experiment 1, Experiment 2).

[0064] [Table 2]

[0065] Table 3 shows the raw material blending conditions (Experiment 1) during the single granulation test.

[0066] [Table 3]

[0067] Figure 5 shows the weighted average [C / F] of the adhesion layer 3 of granule 1 in single granulation, and the results for sintering rotation strength.

[0068] As shown in Figure 5, it was found that when the weighted average [C / F] of the adhesion layer 3 falls below 0.115, the amount of melt becomes insufficient, melt assimilation between each granule 1 does not progress, and the rotational strength of the resulting sintered ore decreases sharply. In other words, the weighted average [C / F] of the average adhesion layer 3 of granule 1 necessary for improving melt assimilation The value of ] must be 0.115 or higher.

[0069] Therefore, in this invention, the weighted average [C / F] in the adhesion layer 3 of granules A and granules B is set to ≥ 0.115.

[0070] In this embodiment, when charging low-alumina ore into the granulator (drum mixer 8) for granulating a specific granule 1 (granule A), the mixing ratio of low-alumina ore is limited to 30 mass%, and the low-alumina ore is mixed in a tiered manner. This will be explained in detail below.

[0071] The mixing ratio of low-alumina ore can be calculated using the following formula.

[0072] • Low alumina ore content = (Amount of low alumina ore in granule A / Total amount of raw materials in granule A) × 100 (mass%) Low-alumina ore refers to ore with an alumina content of less than 1.0 mass%. A typical example of this low-alumina ore is Canadian concentrate, which is characterized by its fine particle size (approximately 90% of the particles are -1 mm). Because it is low-alumina, the viscosity of the resulting melt is low, but compared to other ores, the particle size in the -1 mm particle size range that forms the adhesion layer 3 is relatively large, resulting in poor reactivity and a large amount of undissolved material. The surface is smooth and the granulation properties are poor. In this embodiment, Canadian concentrate is used as the low-alumina ore. However, Canadian concentrate is just one example.

[0073] Furthermore, "graded blending" refers to a method of producing multiple granules 1 (granules A and granules B in this embodiment) where the blending ratio of a specific raw material in granule 1 (granule A in this embodiment) is higher than that of the other granules 1 (granules B).

[0074] More specifically, "gradual blending" of auxiliary raw materials (limestone 4, fine powdered ore 5 such as low-alumina ore or high-crystallinity hydro ore) is a method of blending auxiliary raw materials in parallel-arranged granulation equipment 7 (drum mixers 8 and 9 in this embodiment) by changing the amount of auxiliary raw materials for each drum mixer 8 and 9 while keeping the total amount of auxiliary raw materials used constant (without changing the total amount of auxiliary raw materials).

[0075] For example, one method involves blending a large amount of auxiliary raw materials into drum mixer 8 on one side (system A) and a small amount of auxiliary raw materials into drum mixer 9 on the other side (system B). By blending the auxiliary raw materials in a "gradual" manner (changing the amount of auxiliary raw materials) for drum mixers 8 and 9 in this way, it is possible to simultaneously produce granule A (which contains a large amount of auxiliary raw materials and is easily soluble in solvent) and granule B (which contains a small amount of auxiliary raw materials and is not easily soluble in solvent) (see Table 1).

[0076] In the following explanation, varying the amount of auxiliary materials used in each drum mixer (8, 9) will be referred to as "gradual blending" of auxiliary materials. For example, blending a large amount of low-alumina ore into granule A produced by drum mixer 8 will be called "gradual blending" of low-alumina ore.

[0077] In other words, in drum mixers 8 and 9, using different amounts of low-alumina ore in each mixer, rather than the same amount, is called "graded blending of low-alumina ore."

[0078] Low-alumina ore generates a large amount of melt due to the low viscosity of its melt, while high-crystalline water ore generates a large amount of melt despite having a high viscosity. When low-alumina ore is blended in a specific granule 1 (granule A in this embodiment), the meltability of granule A is improved.

[0079] Granule A functions as a melt donor for the other granule 1 (granule B). In other words, by making the low-alumina ore blending granule A > granule B (graded blending), the viscosity of granule A on the melt supply side is reduced.

[0080] However, a typical example of low-alumina ore is Canadian concentrate, which has a fine grain size and is characterized by a high percentage of -1mm powder (approximately 90%). When the low-alumina ore is Canadian concentrate, most of it exists as an adhering layer 3 within the granulated material 1.

[0081] Therefore, when the amount of low-alumina ore concentrate from Canada is increased, the iron content in the adhesion layer 3 increases, and the [C / F] ratio of the adhesion layer 3 decreases, resulting in a deterioration of meltability. Furthermore, as the thickness of the adhesion layer 3 increases, the fine powder of low-alumina ore that adheres in the drying zone inside the sintering machine 10 becomes more likely to peel off, which contributes to a deterioration of the permeability inside the sintering machine 10.

[0082] Figure 6 shows the relationship between the composition of Canadian concentrate and granulation properties. However, Canadian concentrate is shown as an example of low-alumina ore.

[0083] As shown in Figure 6, Canadian concentrate has a smooth surface and good wettability, resulting in poor granulation properties. Therefore, if the proportion of Canadian concentrate in the granulator (drum mixer 8,9) exceeds 30 mass%, the amount of ungranulated powder increases, and the granulation process fails. For this reason, the upper limit for the proportion of Canadian concentrate (low-alumina ore) in the granulator (drum mixer 8,9) is 30 mass%.

[0084] In other words, in this invention, the blending ratio of low-alumina ore in granule A is set to ≤30 mass%. Furthermore, the low-alumina ore is blended into granule A in a tiered manner so that a large amount of low-alumina ore is blended into granule A.

[0085] In other words, the alumina concentration in the adhesion layer 3 of granule A, which is blended with low-alumina ore having an alumina content of 1.0 mass% or less, is set to be lower than the alumina concentration in the adhesion layer 3 of other granules B. Furthermore, the upper limit for the blending of low-alumina ore in granule A is set to 30 mass%. That is, in granule A, low-alumina ore is preferentially blended to satisfy the condition of low-alumina ore blending ratio ≤ 30 mass% to the greatest extent possible.

[0086] In this embodiment, the high-crystallinity water ore is blended in a gradual manner so that the amount of crystal water in the adhering layer 3 of granule A does not exceed 4.0 mass%. This will be explained in detail below.

[0087] The water crystallization component in the adhering layer 3 of granule A can be calculated using the following formula. However, the standard for the water crystallization component is based on the adhering layer 3.

[0088] • Crystalline water content = Percentage of crystalline water contained in the adhering layer 3 of granule A (mass%) A typical example of a highly crystalline water ore is Australian ore, and in this embodiment, ore with a crystal water content of 10 mass% or more is referred to as highly crystalline water ore. Australian ore has a wider particle size distribution and a higher crystal water content compared to Canadian concentrate (low alumina ore). Because highly crystalline water ore (Australia ore) contains ultrafine particles, it has a large surface area and is easily soluble. Highly crystalline water ore has a large amount of micro-order powder, so it has good melting properties and generates a large amount of melt, but when crystal water is released it forms bubbles that remain in the melt, so the structural viscosity of the melt is high.

[0089] In other words, Australian ore has a large volume of melt. However, the decomposition reaction of the water of crystallization is an endothermic reaction, and this endothermic reaction inhibits melt formation. As a result of this decomposition reaction of water of crystallization, bubbles are generated in the melt, and the melt has a high structural viscosity.

[0090] However, since the amount of melt produced by high-crystallinity water ore is relatively large, by combining it with granule A, which is a graded blend of Canadian concentrate of low-alumina ore as mentioned earlier, a large amount of low-viscosity melt is generated, allowing it to function effectively as a melt donor. From this, it can be concluded that granule (high-crystallinity water ore) has a melt-promoting effect.

[0091] In other words, by using a gradient blend of high-crystallinity water ore, where granule A > granule B (graded blending), the amount of melt generated by granule A, which is the melt supply side, is increased. The definition of gradient blending is as described above: it means that the blending ratio of a specific raw material in granule A is higher than that of the other granules B. That is, a large amount of high-crystallinity water ore is blended into granule A, which is granulated in the drum mixer 8.

[0092] In this embodiment, as described above, austrocite is used as the highly crystalline hydrolite. However, austrocite is just one example.

[0093] Figure 7 shows the relationship between crystalline water in the adhering layer 3 and the variation in sintering rotational strength.

[0094] As shown in Figure 7, Table 2, and Table 3, the results of the single granulation pot test (Experiment 1) indicate that when the crystalline water content in the adhering layer 3 exceeds 4.0 mass%, strength variation occurs. Therefore, 4.0 mass% is the upper limit for the crystalline water content in the adhering layer 3.

[0095] In other words, in this invention, the crystalline water content in the adhering layer of granule A is satisfied to be ≤ 4.0 mass%. Furthermore, limestone 4 is blended into granule A in a graded manner so that a large amount of limestone 4 is incorporated into granule A.

[0096] In other words, the concentration of crystal water in the adhering layer 3 of granule A, which is made by blending highly crystal water-containing ore with a crystal water content of 10 mass% or more, is set to be higher than the concentration of crystal water in the adhering layer 3 of other granules B. Furthermore, the upper limit for the crystal water component in the adhering layer 3 of one granule A is 4.0 mass%.

[0097] In this embodiment, limestone 4 is added to granule A in a graded blending manner, such that the [C / F] ratio in the adhesion layer 3 of granule B, other than granule A, does not fall below 0.08. This will be explained in detail below.

[0098] The [C / F] ratio in the adhesion layer 3 of granule B can be calculated using the following formula. However, the standard for the [C / F] ratio of granule B is based on the adhesion layer 3.

[0099] • Granule B's [C / F] = Percentage of CaO in the adhering layer 3 within granule B / Percentage of Fe2O3 in the adhering layer 3 within granule B (-) Figure 8 schematically shows the uniform distribution of limestone 4 and the gradient distribution of limestone 4 according to the present invention.

[0100] As shown in Figure 8, the gradient mixing of limestone 4 is a technique that aims to achieve both permeability and sintering strength in the raw material packed bed by creating a state where limestone 4 is more easily melted by concentrating the limestone 4 on a specific granule A (a gradient mixing with more limestone 4 on granule A) compared to the normal uniform mixing of limestone 4. The highly fluid molten liquid generated from the preferentially melted granule A promotes melt assimilation by entraining the surrounding granule B as the molten liquid flows.

[0101] In other words, since limestone 4 is dominant in determining the meltable properties of granule 1, the meltable properties of granule A on the molten supply side are improved by adjusting the proportion of limestone 4 so that granule A > granule B (graded proportions).

[0102] As mentioned earlier, granule A, which is primarily composed of Canadian concentrate, a low-alumina ore, exhibits a decrease in the [C / F] value of the adhesion layer 3, resulting in poor meltability. Therefore, by adding limestone 4 to granule A, it is possible to increase the [C / F] value of the adhesion layer 3 and ensure the meltability of granule A.

[0103] The effect of the [C / F] ratio of the adhering layer 3 in the divided granulation method was investigated using a small pot test. The test method and conditions are described in the "Implementation Conditions" section (Experiment 2) in Tables 2 and 4.

[0104] Table 4 shows the raw material blending conditions (Experiment 2) during the parallel granulation test. In this embodiment, the granulation equipment 7 was divided into two systems, System I and System II, and the granulation method was a drum mixer system (two drum mixers 8 and 9) (see Figure 3). The total amount in System I : Total amount in System II was set to 65:35.

[0105] [Table 4]

[0106] In this test example, two types of granules, A and B, were produced. Granule 1 on one side was granule A, which had a high [C / F] value in the adhesion layer 3 and was easily soluble. Granule 1 on the other side was granule B, which had a low [C / F] value in the adhesion layer 3 and was not easily soluble. Here, the effect of granule B (granule 1 with low [C / F]) on strength was investigated. The total amount of raw materials used was the same under each condition; only the distribution ratio between granule A and granule B was changed.

[0107] Figure 9 shows the relationship between the [C / F] of the adhering layer 3 of the divided granulated material B and the sintering rotation strength.

[0108] As shown in Figure 9, when the [C / F] of the adhesion layer 3 of granule B falls below 0.08, the rotational sintering strength decreases. In other words, the sintering strength can be maintained if the weighted average [C / F] of the average adhesion layer 3 of granule A / granule B is maintained > 0.115, while the [C / F] of the adhesion layer 3 of granule B is > 0.08.

[0109] The reason the lower limit of the weighted average [C / F] on the granule B side could be relaxed from 0.115 is due to the effect of the split granulation method. When blending Canadian concentrate (low alumina ore) and limestone 4 into granule A in a gradient manner, the design ensures that the [C / F] value of the adhesion layer 3 of granule B does not fall below 0.08.

[0110] In other words, in this invention, the adhering layer of granule B satisfies the condition [CaO / Fe2O3] ≥ 0.08. Furthermore, high-crystallinity hydro ore is blended into granule A in a graded manner so that a large amount of high-crystallinity hydro ore is incorporated into granule A.

[0111] In other words, the limestone 4 is distributed according to the proportions of the adhering layers 3 of granules A and B. Adjust the ratio. Also, set the [C / F] value of the adhering layer 3 of granule B on the side where limestone 4 is not mixed in a gradient so that it does not fall below 0.08.

[0112] Granules A and B, which are granulated while satisfying the above constraints, are mixed and fired to produce sintered ore.

[0113] Regarding granule B, it may also be granule 1 produced in granulation equipment 7 equipped with multiple systems (which can be arranged in parallel).

[0114] As described above, if the Canadian concentrate (low-alumina ore) is unevenly distributed in the granules 1 on one side, the [C / F] value of the adhering layer 3 will decrease, resulting in a localized molten metal shortage within the sintering machine 10. In addition, this may lead to a deterioration in the permeability of the raw material packing layer due to the collapse of the granules 1.

[0115] Furthermore, if the Australian ore (highly crystalline hydrolite) is unevenly distributed in the granules 1 on either side, the formation of a localized highly viscous melt may lead to uneven burning during sintering and impaired gas flow, potentially resulting in poor air permeability of the raw material packed bed.

[0116] Figure 10 shows the effect within the sintering machine 10 when Canadian concentrate (low alumina ore) or Australian concentrate (high crystalline hydro ore) is unevenly distributed in one of the granules 1.

[0117] As shown in Figure 10, compared to the case where the raw material distribution is uniform, if the Canadian concentrate is concentrated to one side (i.e., there is an imbalance in the raw material distribution), the fine low-alumina ore attached in the dry zone becomes more prone to detachment. When this happens, it fills the voids in the sintering tank (raw material packed bed) of the sintering machine 10, worsening the permeability of the raw material packed bed. This is thought to potentially lead to a decrease in the productivity of sintered ore.

[0118] Furthermore, in the combustion zone, the decrease in [C / F] of the adhesion layer 3 of granule 1 and the increase in the crystalline water component can lead to localized molten material shortages and increased molten material viscosity in the combustion zone. By distributing the raw materials of granule A / granule B in a way that satisfies the above constraints on granulation and firing, it is possible to improve sintering strength and productivity.

[0119] In a large-scale pot test, the effects of graded blending of limestone 4 and the preferential blending of low-alumina ore and high-crystallinity water ore were investigated. The test methods and conditions are described in the "Implementation Conditions" section (Experiment 3) of Table 5 below.

[0120] Table 5 shows the conditions for the large sintering pot test (Experiment 3).

[0121] [Table 5]

[0122] In this experiment, the suction pressure was kept constant during sintering. Furthermore, the large pot test simulated the actual sintering machine 10, and the sintering strength and productivity were also evaluated.

[0123] Tables 6 and 7 show examples and comparative examples carried out according to the method for producing sintered ore of the present invention. Note that Table 6 is a single continuous table, but for ease of viewing, it has been divided and arranged vertically.

[0124] [Table 6]

[0125] [Table 7]

[0126] Figure 11 shows the results and evaluation of sintering strength and sintering ore productivity obtained from the pan test.

[0127] As shown in Figure 11, Table 6, and Table 7, for condition a, the amount of limestone 4 was adjusted so that the [C / F] of the adhering layer 3 on the I system side (granulated material B) was less than 0.08. For conditions b and c, the amount of limestone 4 was adjusted so that the [C / F] of the adhering layer 3 of granulated material 1 in the I system and II system were equivalent. For condition d, the amount of limestone 4 was equal, and the [C / F] of the adhering layer 3 of granulated material 1 in the I system and II system were equivalent. Furthermore, for conditions e, d', and f, a gradient blend of limestone 4 was applied to the II system. However, the [C / F] of the adhering layer 3 of granulated material 1 in the I system and II system for conditions b to d were kept the same.

[0128] Here, we decided to granulate granule B using the drum mixer 9 on the I system side, and granule A using the drum mixer 8 on the II system side. However, when granulation is performed under condition a (where the constraint on the [C / F] of the adhesion layer 3 of granule B on the I system side is not observed, resulting in a [C / F] of the adhesion layer 3 of granule B granulated in the I system drum mixer 9 is approximately 0.07), both the sintering strength and productivity are low.

[0129] Therefore, when granulation was performed under condition b, which adhered to the constraint of [C / F] of the adhering layer 3, the sintering strength improved. When Canadian concentrate of low-alumina ore, which contains a large amount of fine powder, was shifted from conditions a and b, which biased the blending towards system I, to conditions c and then d, prioritizing the blending towards system II, productivity improved.

[0130] In this embodiment, the preferred formulation means unevenly distributing the mixture to the extent that the aforementioned granulation constraint (upper limit of Canadian concentrate (low-alumina ore): 30 mass%) is satisfied to the greatest extent possible. For example, the proportion of low-alumina ore is set to 29 mass%, or close to 30 mass%.

[0131] By applying a gradient blending of limestone 4 and prioritizing the blending of granule A (highly crystalline water ore) containing a large amount of crystalline water into the II system, the melting acceleration effect described above was obtained, maximizing both productivity and sintering strength. Details of the blending conditions are described in the experimental conditions tables, such as Tables 6 and 7 shown above.

[0132] Herein, this embodiment and comparative example will be described.

[0133] As shown in Table 6, in comparative example condition a, the low alumina ore content in granule B (system I) is 32.2 mass%, which does not meet the specified blending conditions, and the [C / F] of the adhering layer 3 of granule B is 0.07, which does not meet the specified component conditions, resulting in low productivity and rotational strength. Consequently, the desired results were not obtained in the overall evaluation.

[0134] In comparative example b, the low alumina ore content in granule B (System I) is 30.7 mass%, which does not meet the specified mixing conditions, resulting in low productivity and rotational strength. Consequently, the desired results were not obtained in the overall evaluation.

[0135] Comparative Example Condition c does not meet the specified blending conditions, and therefore the desired results were not obtained in the overall evaluation. In this experimental example, Comparative Example Condition c, in which the blending amounts of low-alumina ore and the [C / F] of the adhering layer 3 are equivalent for granules B (System I) and granules A (System II), is used as the base condition.

[0136] In comparative example condition d, the gradient of the [C / F] of the adhering layer 3 is smaller compared to condition f (this example). That is, the difference in [C / F] between granule B (system I) and granule A (system II) of the adhering layer 3 is small at 0.01, and considering the fluctuations in the actual process, a difference of at least 0.02 or more is required to obtain a significant effect. As a result, the rotational strength is low, and the desired results were not obtained in the overall evaluation.

[0137] In comparative example e, the mixing ratio of highly crystalline water ore in granule B (System I) is 0, which does not meet the specified mixing conditions, resulting in low rotational strength. Consequently, the desired results were not obtained in the overall evaluation.

[0138] In the comparative example, condition d' has a smaller gradient in the blending ratio of high-crystallinity water ore compared to condition f (this example), and the crystalline water component in the adhering layer is higher in granule B (system I). In other words, the difference between granule B (system I) and granule A (system II) in the blending ratio of high-crystallinity water ore is small. As a result, the rotational strength is low, and the desired results are not obtained in the overall evaluation. If the crystalline water component in the adhering layer is higher on the granule A (system II) side, the same effect as condition f in this example can be obtained.

[0139] Condition f in this embodiment satisfies the specified blending conditions for the gradient blending of low-alumina ore, high-crystallinity water ore, and limestone 4 with respect to granule A (system II), and has a sufficient difference in blending compared to granule B (system I). As a result, productivity and rotational strength were improved. This allowed us to obtain the desired good results in the overall evaluation.

[0140] In a sintering process (granulation process) that produces multiple granules A and B, setting thresholds for the composition design of granules A and B, taking into account the characteristics of the raw materials used (such as setting an upper limit (≤30 mass%) for the blending ratio of a specific raw material (low alumina ore), and setting upper and lower limits for the [C / F] of the adhesion layer 3 (weighted average [C / F] of the adhesion layer 3 of all granules 1 ≥0.115, crystal water content of the adhesion layer 3 of granule A ≤4.0 mass%, [C / F] of the adhesion layer 3 of granule B ≥0.08)), improves the melt assimilation between each granule A and B during firing, thereby improving the quality and productivity of the finished product (sintered ore).

[0141] The following outlines the design considerations for granulation when producing granule 1.

[0142] At least one of the multiple granules 1 is blended in a gradual manner, containing Canadian concentrate (low alumina ore), limestone 4, and Australian ore (high crystalline water ore). The reason for this is to create granule A, which is low in alumina and has a high [C / F] value in the adhering layer 3, so that this granule A can function as a melt donor.

[0143] The upper limit for the amount of Canadian concentrate (low-alumina ore) in each granulator (drum mixers 8 and 9 in this embodiment) is 30 mass%. This is because granulation performance deteriorates when the amount of low-alumina ore exceeds 30 mass%.

[0144] The upper limit of the crystalline water content in the adhering layer 3 of each granule 1 shall be 4.0 mass%. This is because the formation of localized highly viscous melts may cause uneven firing.

[0145] Figure 12 shows the procedure for the method of producing sintered ore according to the present invention.

[0146] As shown in Figure 12, first, it is confirmed that the weighted average [C / F] of the adhering layer 3 of the average granule 1 produced from the raw materials used is 0.115 or higher, and that the crystalline water content of the adhering layer 3 is less than 4.0 mass%. In other words, if the weighted average [C / F] of the adhering layer 3 is less than 0.115, or if the crystalline water content of the adhering layer 3 is 4.0 mass% or higher, the present invention cannot be applied, so this is confirmed.

[0147] (i) Low-alumina ore is preferentially blended into one of the granules (granule A). At this time, the blending ratio of low-alumina ore in granule A is set to the maximum possible value, and not to exceed 30 mass%.

[0148] (ii) Granule A, which has a priority blend of low-alumina ore, is blended with high-crystallinity water ore in a gradual manner. The water content of the crystalline water in the attached layer 3 is set so that it does not reach 4.0 mass%.

[0149] (iii) Limestone 4 is added in a gradient to the granulator that has been used to blend the low-alumina ore (in this embodiment, the drum mixer 8 on the II system side). At this time, the [C / F] of the remaining granules B adhesion layer 3 is set to the maximum possible value so that it does not fall below 0.08.

[0150] According to the present invention's method for producing sintered ore, in the granulation process that produces multiple granules A and B, by designing the appropriate components of granules A and B while considering the characteristics of the raw materials used, it is possible to improve the strength and productivity of the sintered ore.

[0151] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. In particular, matters not explicitly stated in the embodiments disclosed herein, such as operating conditions, various parameters, dimensions, weights, and volumes of components, do not deviate from what is normally practiced by those skilled in the art, and the values ​​adopted are those that can be easily anticipated by those skilled in the art.

[0152] Furthermore, the granules A and B described in detail in this embodiment are merely names used for convenience in explanation, and the naming convention is arbitrary. In other words, with respect to granule 1, A may be referred to as B, and B as A. Similarly, with respect to the granulation equipment 7 which has multiple systems, the names System I and System II are merely names used for convenience in explanation, and are arbitrary. [Explanation of Symbols]

[0153] 1. Granulated material A Granules B Granules 2 nuclear particle 3. Adhesion layer 4 limestone 5. Fine ore 6. Raw material layer (raw material hopper) 7 Granulation equipment 8. Drum Mixer (Two Systems) 9. Drum Mixer (System I) 10 Sintering machine 11. Pan Pelletizer

Claims

1. In operating a sintering process to produce sintered ore by separately creating granules A and B, in which an adhesive layer is formed around the outer surface of the core particles, and then mixing and firing granules A and B, granules A and B that satisfy the following conditions (1) and (2) are produced by "graded raw material blending," which involves changing the amount of predetermined raw materials charged into each granulator. The low-alumina ore is blended into granule A in a gradual manner so that a large amount of low-alumina ore is incorporated into granule A, and the limestone is blended into granule A in a gradual manner so that a large amount of limestone is incorporated into granule A, and the [C / F] of the adhering layer of granule B is set to ≥ 0.

08. The high-crystallinity water ore is blended into granule A in a graded manner so that a large amount of high-crystallinity water ore is incorporated into granule A, and the crystalline water content in the adhering layer of granule A is set to ≤4.0 mass%. A method for producing sintered ore, characterized by the above. (1) The proportion of low-alumina ore in each of granules A and B is ≤30 mass% (2) Weighted average [C / F] in the adhesion layer of granules A and B ≥ 0.115 Note that [C / F] stands for CaO(mass%) / Fe 2 O 3 This refers to (mass%). Furthermore, the term "low-alumina ore" refers to iron ore with a low alumina content of less than 1.0 mass%, while "high-crystal-water ore" refers to iron ore with a high crystal-water content of 10.0 mass% or more.

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