Method for producing sintered ore

Abstract

To provide a method for producing sintered ore excellent in productivity.SOLUTION: A method for producing sintered ore according to an embodiment of the present disclosure involves preparing a first granulate and a second granulate so as to satisfy requirements A through C below. Requirement A: Let the mass ratio of CaO particles with a particle diameter of 1 mm or less to Fe2O3 particles with a particle diameter of 1 mm or less in the first granulate be Q1, and let the above mass ratio in the second granulate be Q2. The weight average of Q1 and Q2 shall be 0.115 or more. Requirement B: Let the content of lime raw material in the first granulate be L1 [mass%], and in the second granulate be L2 [mass%]. It shall satisfy L1≥L2. Requirement C: When the average content of coarse coal particles with a particle diameter of more than 1 mm and up to 6 mm in the first and second granulates is CAVE [mass%], the content C1 [mass%] of such coarse coal particles in the first granulate shall satisfy C1≥1.2CAVE.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing sintered ore. [Background technology]

[0002] Sintered ore is formed by melting and assimilating granules together and solidifying them. The melting and assimilating of granules is achieved by igniting the surface of a raw material layer containing, for example, carbonaceous material (coke fines), drawing in gas from below, and propagating the combustion.

[0003] Most granules have a core with a particle diameter of more than 1 mm and an adhesion layer surrounding the core. The adhesion layer includes, for example, fine ore, fine carbonaceous material, etc. with a particle diameter of 1 mm or less.

[0004] During the production of sintered ore, the sintering reaction progresses as the calcium ferrite melt generated from the adhesion layer melts and assimilates with the core and surrounding granules. A carbonaceous material is used as the heat source during this process. If an insufficient amount of carbonaceous material is used as the heat source, the amount of melt becomes insufficient, weakening the bonding strength between the granules. This results in a decrease in yield and productivity. Therefore, currently, technologies for promoting the melting and assimilation of the granules are being investigated (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2016-020521 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-313614 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 describes that a fine particle mixture obtained by crushing quicklime or the like with iron ore has excellent binder effects. Patent Document 1 also describes a separate granulation method in which a separate granulation line for granulating fine powder raw materials that are difficult to granulate and a main line for granulating the remaining sintering raw materials, auxiliary raw materials, coagulants, etc. are provided in parallel, and the two lines are combined and charged into a sintering machine. Patent Document 1 also describes kneading the above fine particle mixture with the raw materials for the separate granulation system in a high-speed stirring kneader.

[0007] Patent Document 2 describes a method of classifying various fine ores into at least two series according to their Al2O3 contents, and adjusting the amount of CaO source added according to the Al2O3 content of the fine powder fraction with a particle size of 1 mm or less in each series of fine ore so that the basicity CaO / SiO2 of all sintering raw materials becomes the required value, thereby ensuring the required amount of melt.

[0008] However, in the separate granulation methods described in Patent Documents 1 and 2, there is room for further improvement in terms of promoting melting and assimilation of the granulated materials together and increasing productivity.

[0009] The present disclosure has been made in light of the above circumstances, and has an object to provide a method for producing sintered ore with excellent productivity. [Means for solving the problem]

[0010] A method for producing sintered ore according to one embodiment of the present disclosure includes a step of producing a first granulated material and a second granulated material in separate granulators, and a step of firing a mixture of the first granulated material and the second granulated material, wherein the first granulated material and the second granulated material have a core portion and an adhesion layer adhering to the periphery of the core portion, and in the production step, the first granulated material and the second granulated material are produced so as to satisfy the following requirements A to C. Requirement A: If the mass ratio [CaO / Fe2O3] of CaO particles with a particle diameter of 1 mm or less to Fe2O3 particles with a particle diameter of 1 mm or less in the first granule is Q1, and the same mass ratio in the second granule is Q2, the weighted average of Q1 and Q2 based on the mass-based mixing ratio of the first granule and the second granule must be 0.115 or more. Requirement B: When the content of the lime raw material in the first granule is L1 [mass %] and the content of the lime raw material in the second granule is L2 [mass %], L1≧L2. Requirement C: The average content of coarse carbonaceous material, which is carbonaceous material with a particle diameter of more than 1 mm and less than 6 mm in the first granulated material and the second granulated material, is C AVE When the content C1 [mass%] of the coarse carbonaceous material contained in the first granules is set to C1 ≧ 1.2C AVE Let's say. [Effects of the Invention]

[0011] The method for producing sintered ore according to one embodiment of the present disclosure has excellent productivity for sintered ore. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram showing a method for producing sintered ore according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing a manufacturing apparatus capable of carrying out the sintered ore manufacturing method of FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view of a first granule produced by the method for producing sintered ore of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of a second granulated material produced by the method for producing sintered ore of FIG. [Figure 5] FIG. 5 is a schematic diagram showing the progress of melting and assimilating the first granules and the second granules in the method for producing sintered ore of FIG. [Figure 6] FIG. 6 is a schematic diagram showing a large pot test device used in the examples. [Figure 7] Figure 7 is a graph showing the change in productivity when C1 / CAVE is changed. [Figure 8]FIG. 8 is a graph showing the relationship between C / F and rotation strength in the adhesion layer of the granulated material. [Figure 9] FIG. 9 is a graph showing the relationship between C / F and rotation strength in the adhesion layer of the granulated material. [Figure 10] FIG. 10 is a graph showing the relationship between the blending ratio of low-alumina ore and the proportion of granules with particle diameters of 5 mm or more and 1 mm or less in the entire granules. [Figure 11] FIG. 11 is a graph showing the relationship between the crystal water content in the adhesion layer and the variation in rotation strength. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0014] (1) A method for producing sintered ore according to one embodiment of the present disclosure includes a step of producing a first granulated material and a second granulated material in separate granulators, and a step of firing a mixture of the first granulated material and the second granulated material, wherein the first granulated material and the second granulated material have a core portion and an adhesion layer adhering to the periphery of the core portion, and in the production step, the first granulated material and the second granulated material are produced so as to satisfy the following requirements A to C: Requirement A: If the mass ratio [CaO / Fe2O3] of CaO particles with a particle diameter of 1 mm or less to Fe2O3 particles with a particle diameter of 1 mm or less in the first granule is Q1, and the same mass ratio in the second granule is Q2, the weighted average of Q1 and Q2 based on the mass-based mixing ratio of the first granule and the second granule must be 0.115 or more. Requirement B: When the content of the lime raw material in the first granule is L1 [mass %] and the content of the lime raw material in the second granule is L2 [mass %], L1≧L2. Requirement C: The average content of coarse carbonaceous material, which is carbonaceous material with a particle diameter of more than 1 mm and less than 6 mm in the first granulated material and the second granulated material, is C AVE When the content C1 [mass%] of the coarse carbonaceous material contained in the first granules is set to C1 ≧ 1.2C AVE Let's say.

[0015] In the method for producing sintered ore, the weighted average of Q1 and Q2 based on the mass-based mixing ratio of the first granules and the second granules is set to 0.115 or more (requirement A), thereby ensuring the amount of melt required for the first granules and the second granules as a whole. Furthermore, in the method for producing sintered ore, the content L1 of the lime raw material contained in the first granules is set to L1≧L2 (requirement B), and the content C1 of the coarse carbonaceous material contained in the first granules is set to C1≧1.2C. AVE By satisfying requirement B (requirement C), the first granules can function as a melt supply medium that preferentially supplies melt to the second granules. More specifically, by satisfying requirement B relative to the second granules, the first granules facilitate melting of the adhesion layer, and by satisfying requirement C, combustion of the coarse carbonaceous material in the core portion is promoted, making it easier for the temperature to rise. As a result, the sinter ore manufacturing method can promote melting and assimilation of the first granules and the second granules. Therefore, the sinter ore manufacturing method is excellent in productivity.

[0016] (2) In the above (1), the second granules may be prepared in the preparation step so as to further satisfy the following requirement D. Requirement D: Q2 ≧ 0.08.

[0017] According to this configuration, it is possible to easily prevent the second granules from having insufficient meltability.

[0018] (3) In the above (1) or (2), the first granules and the second granules may be prepared in the preparation step so as to further satisfy the following requirements E1 and E2. Requirement E1: When the content of the low-alumina ore in the first granule is A1 [mass %] and the content of the low-alumina ore in the second granule is A2 [mass %], A1>A2. Requirement E2: In the granulator that produces the first granules, the amount of low-alumina ore mixed is 30 mass % or less.

[0019] According to the requirement E1, the viscosity of the melt in the first granules can be reduced, and as a result, the melt assimilation of the first granules and the second granules can be further promoted. Also, according to the requirement E2, the yield of the sintered ore obtained can be improved.

[0020] (4) In any of the above (1) to (3), the first granules and the second granules may be prepared in the preparation step so as to further satisfy the following requirements F1 and F2. Requirement F1: When the content of the high crystal water ore in the first granule is W1 [mass %] and the content of the high crystal water ore in the second granule is W2 [mass %], W1 > W2. Requirement F2: The content of water of crystallization in the adhesive layer of the first granules is 4.0% by mass or less.

[0021] According to the requirement F1, the amount of melt of the first granules can be increased, and as a result, the melt assimilation of the first granules and the second granules can be further promoted. Also, according to the requirement F2, the strength of the obtained sintered ore can be increased.

[0022] (5) In any of the above (1) to (4), in the firing step, the raw material layer containing the mixture may be ignited and gas may be drawn into the raw material layer from the outside. This configuration reduces the amount of carbonaceous material (coke fines) used and improves the production efficiency of sintered ore.

[0023] In this disclosure, the term "first granules" generally refers to a collection of granules produced by a granulator (first granulator) that produces the first granules. In this disclosure, the term "second granules" generally refers to a collection of granules produced by a granulator (second granulator) that produces the second granules. "Particle size" refers to a value measured using a sieve with a specified mesh size in accordance with JIS-Z8801-1:2019. For example, a particle size of 1 mm or less refers to a particle size that passes through a sieve with a mesh size of 1 mm. In this disclosure, carbonaceous material with a particle size of more than 1 mm and 6 mm or less is referred to as "coarse carbonaceous material," carbonaceous material with a particle size of 1 mm or less is referred to as "fine carbonaceous material," and coarse carbonaceous material and fine carbonaceous material are collectively referred to as "coke fines." "Low-alumina ore" refers to ore with an alumina content of less than 1.0% by mass. "High water of crystallization ore" means an ore with a water of crystallization content of 10% by mass or more. "Water of crystallization content" means the value measured according to JIS-K0068 "Method for measuring water content in chemical products."

[0024] [Details of the embodiments of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Regarding the numerical values ​​described in this specification, only one of the upper and lower limit values ​​described may be used, or the upper and lower limit values ​​may be combined in any desired manner. Furthermore, in this disclosure, the terms "first" and "second" are used to distinguish the components to which they are attached, and do not limit the number, order, priority, etc. Figures 2 to 6 are schematic and may not correspond to actual dimensions, shapes, etc.

[0025] [Sintered ore manufacturing method] The method for producing sintered ore shown in Fig. 1 includes a step S1 of producing first granules and second granules in separate granulators, and a step S2 of firing a mixture of the first granules and the second granules. The first granules and the second granules have a core and an adhesion layer adhering to the periphery of the core. In the production step S1, the first granules and the second granules are produced so as to satisfy the following requirements A to C: Requirement A: If the mass ratio [CaO / Fe2O3] of CaO particles with a particle diameter of 1 mm or less to Fe2O3 particles with a particle diameter of 1 mm or less in the first granule is Q1, and the same mass ratio in the second granule is Q2, the weighted average of Q1 and Q2 based on the mass-based mixing ratio of the first granule and the second granule must be 0.115 or more. Requirement B: When the content of the lime raw material in the first granule is L1 [mass %] and the content of the lime raw material in the second granule is L2 [mass %], L1≧L2. Requirement C: The average content of coarse carbonaceous material, which is carbonaceous material with a particle diameter of more than 1 mm and less than 6 mm in the first granulated material and the second granulated material, is C AVE When the content C1 [mass%] of the coarse carbonaceous material contained in the first granules is set to C1 ≧ 1.2C AVE Let's say.

[0026] In the method for producing sintered ore, the weighted average of Q1 and Q2, which are the mass-based mixing ratios of the first granules and the second granules, is set to 0.115 or more (requirement A), thereby ensuring the amount of melt required for the first granules and the second granules as a whole. Furthermore, in the method for producing sintered ore, the content L1 of the lime raw material contained in the first granules is set to L1≧L2 (requirement B), and the content C1 of the coarse carbonaceous material contained in the first granules is set to C1≧1.2C. AVEBy satisfying requirement C, the first granules can function as a melt supply medium that preferentially supplies melt to the second granules. This sinter ore manufacturing method employs a separate granulation method for separately producing the first granules, which melt easily during firing and melt and assimilate surrounding granules while incorporating them in firing step S2, and the second granules, which receive the melt from the first granules. In the separate granulation method, it is desirable that the first granules have low viscosity and can supply a large amount of melt. On the other hand, it is sufficient that the second granules have a higher viscosity than the first granules and can secure a necessary amount of a small amount of melt. By satisfying requirement B relative to the second granules, the first granules are more likely to melt the adhesion layer, and by satisfying requirement C, combustion of the coarse carbonaceous material in the core is promoted, facilitating a temperature rise. As a result, the method for producing sintered ore can promote melting and assimilation of the first granules and the second granules, and therefore the method for producing sintered ore is excellent in productivity of sintered ore.

[0027] <Production process> In the preparation step (a step of preparing a granulated material) S1, the first granulated material is prepared in a first granulator, and the second granulated material is prepared in a second granulator. That is, in the preparation step S1, raw materials discharged from multiple raw material processes (not shown) are distributed to parallel granulators (first granulator and second granulator), and these granulators prepare the granulated materials (first granulated material and second granulated material).

[0028] In the preparation step S1, the first granules and the second granules are prepared so that the first granules serve as a melt supply medium that supplies a low-melting-point, low-viscosity melt to the second granules, and the second granules serve as a melt receiving medium that receives the melt from the first granules. This sintered ore production method produces sintered ore in which the first granules are melted and assimilated into the second granules by melting the first granules and flowing the melt while entraining the second granules. That is, this sintered ore production method separately produces the first granules and the second granules by varying the blending ratio of specific raw materials between the first granulator and the second granulator while maintaining the total amount of the raw materials. This allows the first granules to serve as a melt supply medium and the second granules to serve as a melt receiving medium.

[0029] The first granules and the second granules each have a core and an adhesive layer attached to the periphery of the core. More specifically, the first granulator produces an aggregate of the first granules, and many of the individual first granules contained in this aggregate have the core and the adhesive layer. The second granulator produces an aggregate of the second granules, and many of the individual second granules contained in this aggregate have the core and the adhesive layer.

[0030] The core portion is composed of, for example, ore (coarse ore) having a particle size of more than 1 mm or carbonaceous material (coarse carbonaceous material) having a particle size of more than 1 mm. The adhesion layer is an aggregate containing, for example, ore (fine ore) having a particle size of 1 mm or less, carbonaceous material (fine carbonaceous material) having a particle size of 1 mm or less, and other auxiliary materials. The adhesion layer functions as a melting starting point in the firing step S2.

[0031] The preparation step S1 can be performed, for example, using raw material tanks (first raw material tank 10a and second raw material tank 10b) and granulators (first granulator 20a and second granulator 20b) in the manufacturing apparatus 1 shown in FIG. 2. First, in the preparation step S1, granule-forming raw materials, which are extracted from multiple raw material processes (not shown) and placed in the raw material tanks 10a and 10b, are fed into the first granulator 20a and the second granulator 20b. Next, in the preparation step S1, as shown in FIGS. 3 and 4, the first granule 40 is produced in the first granulator 20a, and the second granule 50 is produced in the second granulator 20b. In the first granulator 20a and the second granulator 20b, the granule-forming raw materials are tumbled while water is added. As a result, in the first granulator 20a and the second granulator 20b, a first granule 40 and a second granule 50 are produced, in which the fine ore and the fine carbonaceous materials are attached around the core portions 41 and 51. As the first granulator 20a and the second granulator 20b, for example, a drum mixer, a pan pelletizer, etc. can be used.

[0032] 2 illustrates a configuration having one first granulator 20a and one second granulator 20b. However, in this sinter ore manufacturing method, for example, the first granulator 20a and the second granulator 20b may each be configured with a plurality of granulators. When the first and second granulators include a plurality of granulators, the blending ratio of the granulated material raw materials fed into the plurality of granulators included in the first granulator 20a or the plurality of granulators included in the second granulator 20b may or may not be the same. When the first and second granulators include a plurality of granulators, the granulated material produced by the plurality of granulators included in the first granulator 20a is the first granulated material, and the granulated material produced by the plurality of granulators included in the second granulator 20b is the second granulated material.

[0033] (Requirement A) In the preparation step S1, if the mass ratio [CaO / Fe2O3] of CaO particles with a particle size of 1 mm or less to Fe2O3 particles with a particle size of 1 mm or less in the first granulated material 40 is Q1 and the same mass ratio in the second granulated material 50 is Q2, the weighted average of Q1 and Q2 based on the mass-based mixing ratio of the first granulated material 40 and the second granulated material 50 is 0.115 or more. In Q1 and Q2, [Fe2O3] is a value based only on iron ore, and [CaO] is a value based only on limestone and quicklime. That is, Q1 can be calculated by the following equation in the first granulator 20a: Σ(lime raw material blend amount [% by mass] × fraction of 1 mm or smaller particles in the lime raw material [% by mass] × CaO fraction in the 1 mm or smaller particles in the lime raw material [% by mass]) / Σ(iron ore raw material blend amount [% by mass] × fraction of 1 mm or smaller particles in the iron ore raw material [% by mass] × Fe2O3 fraction in the 1 mm or smaller particles in the iron ore raw material [% by mass]). Q2 can be calculated by the following equation in the second granulator 20b: Σ(lime raw material blend amount [% by mass] × fraction of 1 mm or smaller particles in the lime raw material [% by mass] × CaO fraction in the 1 mm or smaller particles in the lime raw material [% by mass]) / Σ(iron ore raw material blend amount [% by mass] × fraction of 1 mm or smaller particles in the iron ore raw material [% by mass] × Fe2O3 fraction in the 1 mm or smaller particles in the iron ore raw material [% by mass]). The lower limit of the weighted average is 0.115, as described above. On the other hand, the upper limit of the weighted average is not particularly limited, but can be set to, for example, 0.35 from the viewpoint of preventing overmelting.

[0034] Both FeO particles with a particle size of 1 mm or less and CaO particles with a particle size of 1 mm or less are contained in the adhesion layers 42, 52. The melt generation starting point in the first granulated material 40 and the second granulated material 50 is the adhesion layers 42, 52 with a large specific surface area. Therefore, the melt properties in the first granulated material 40 and the second granulated material 50 can be controlled by the components of the adhesion layers 42, 52.

[0035] An index of the melting and assimilation properties of granulated materials is the ratio [CaO / Fe2O3] of coal-derived CaO (calcium oxide) with particle diameters of 1 mm or less to iron ore-derived Fe2O3 (iron (III) oxide) with particle diameters of 1 mm or less (hereinafter, this ratio is also referred to as "C / F"). The larger the C / F, the greater the relative amount of melt generated, indicating high melting properties, while the smaller the C / F, the less melt there is, indicating low melting properties. In this sintered ore manufacturing method, by setting the weighted average of Q1 and Q2 to 0.115 or more, melting and assimilation of the first granulated material 40 and the second granulated material 50 can be promoted and a decrease in the rotational strength of the resulting sintered ore can be suppressed.

[0036] (Requirement B) In the preparation step S1, when the content of the lime raw material in the first granules 40 is L1 [mass %] and the content of the lime raw material in the second granules 50 is L2 [mass %], L1≧L2 is satisfied. That is, in the preparation step S1, the coal raw material is blended in the first granulator 20a at an inclined angle so that the blending amount [mass %] in the first granulator 20a is greater than the blending amount [mass %] in the second granulator 20b.

[0037] In the preparation step S1, satisfying requirement B facilitates melting of the first granules 40. As a result, by firing the mixture of the first granules 40 and the second granules 50 in step S2, the highly fluid molten liquid 40a generated from the first granules 40 can be caused to flow while entraining the second granules 50, as shown in FIG. 5, for example. In this sintered ore manufacturing method, the first granules 40 can flow so as to avoid the gas flow path, thereby forming a ventilation path P along the gas suction direction. As a result, high-strength, homogeneous sintered ore 60 can be manufactured. While FIG. 5 illustrates a configuration in which the entire first granules 40 are melted, it is sufficient that the adhesion layer 42 of the first granules 40 melts preferentially. Furthermore, although FIG. 5 illustrates a configuration in which the number of second granules 50 and the number of sintered ore 60 are equal, one sintered ore 60 may contain multiple second granules 50.

[0038] Examples of the lime raw material include limestone, quicklime, and slaked lime. Among these, limestone, which is relatively inexpensive, is preferred. The limestone, quicklime, and slaked lime may be used alone or in combination of two or more.

[0039] (Requirement C) In the preparation step S1, the average content of coarse carbonaceous material, which is a carbonaceous material with a particle diameter of more than 1 mm and 6 mm or less, in the first granules 40 and the second granules 50 is C AVE When the content C1 [mass %] of the coarse carbonaceous material contained in the first granules 40 is expressed as C1≧1.2C AVE That is, in the preparation step S1, the coarse carbonaceous materials are blended in the first granulator 20a so that the blending amount [mass%] of the coarse carbonaceous materials in the first granulator 20a is 1.2 times or more with respect to the average value of the blending amount [mass%] of the coarse carbonaceous materials in the first granulator 20a and the blending amount [mass%] of the coarse carbonaceous materials in the second granulator 20b. In the preparation step S1, C1≧1.5C AVE C1≧2.0C AVE On the other hand, the upper limit of C1 is not particularly limited, but can be set to, for example, 15 mass % from the viewpoint of preventing overmelting.

[0040] In the preparation step S1, the coarse carbonaceous material forms the core of the granules. Furthermore, in the firing step S2, the coarse carbonaceous material comes into contact with oxygen as the melting of the adhesion layers 42, 52 progresses, thereby increasing the combustion rate. In the firing step S2, the combustion of the coarse carbonaceous material improves thermal efficiency and promotes the melting and assimilation of the first granules 40 and the second granules 50. In the firing step S2, the adhesion layer 42 of the first granules 40 melts preferentially. Therefore, by incorporating a large amount of the coarse carbonaceous material into the first granules 40, the combustion rate can be easily maintained or increased. As a result, the molten liquid generated by the melting of the first granules 40 flows, entraining the second granules 50, making it easier to produce sintered ore 60 in which the first granules 40 are melted and assimilated into the second granules 50. Furthermore, this configuration allows for a reduction in the amount of coke fines used in the entire first granules 40 and the second granules 50. As a result, when the sintered ore 60 is produced, CO2 emissions can be reduced.

[0041] (Other requirements) In the preparation step S1, it is also preferable to prepare the first granules 40 and the second granules 50 so as to satisfy one or more of the following requirements D, E, and F. Each condition will be explained below.

[0042] (Requirement D) In the preparation step S1, it is preferable that Q2 ≧ 0.08. As described above, in the preparation step S1, the content L1 of the lime raw material contained in the first granules 40 is set to L1 ≧ L2 (requirement B), thereby improving the melting property of the first granules 40. On the other hand, as will be described later, the first granules 40 in which low-alumina ore is preferentially blended has a reduced C / F of the adhesion layer 42. Therefore, if the C / F falls below Q2, it may be necessary to further increase the lime raw material L1 as necessary. Even in such cases, by setting Q2 ≧ 0.08, the reduction in the C / F can be compensated for, and the melting property of the second granules can be more reliably prevented from becoming insufficient.

[0043] (Requirement E) In the preparation step S1, when the content of the low-alumina ore in the first granulated material 40 is A1 [mass%] and the content of the low-alumina ore in the second granulated material 50 is A2 [mass%], it is preferable that A1 > A2 (requirement E1). Also, in the preparation step S1, it is preferable that the blending amount of the low-alumina ore in the granulator (first granulator 20a) that prepares the first granulated material 40 is 30 mass% or less (requirement E2). In the preparation step S1, it is possible to satisfy only one of requirements E1 and E2, but it is preferable that both requirements E1 and E2 are satisfied.

[0044] [Requirement E1] The low-alumina ore has a low viscosity when melted. Therefore, by setting the content A1 of the low-alumina ore contained in the first granulated material 40 so that A1 > A2, the viscosity of the melt of the first granulated material 40 can be reduced. That is, in the preparation step S1, the low-alumina ore is blended in the first granulated material 20a at an inclined blending rate so that the blending amount [mass%] in the first granulated material 20a is greater than the blending amount [mass%] in the second granulated material 20b, thereby reducing the viscosity of the melt of the first granulated material 40. As a result, in the firing step S2, the melting and assimilation of the first granulated material 40 and the second granulated material 50 can be further promoted.

[0045] [Requirement E2] A typical example of the low-alumina ore is Canadian concentrate. Many Canadian concentrates have particle diameters of 1 mm or less, with 90% or more by mass being 1 mm or less. That is, the low-alumina ore accounts for 80% or more by mass, or even 90% or more by mass, of the total. Therefore, if the content of the low-alumina ore in the first granulated material 40 increases, the iron content in the adhesion layer 42 increases, and the C / F ratio decreases, resulting in a decrease in the amount of melt. Furthermore, the low-alumina ore increases the thickness of the adhesion layer 42, making the adhered powder more likely to peel off. Additionally, because the Canadian concentrate has a smooth surface and good wettability, it tends to agglomerate and inhibit the dispersion of granulation water. Therefore, if the amount of the low-alumina ore in the first granulator 20a exceeds 30% by mass, the amount of ungranulated powder may increase. In contrast, by setting the blending amount of the low-alumina ore in the first granulator 20a to 30 mass% or less, it is possible to improve the yield of the first granulated material 40 and, in turn, the sintered ore 60. In accordance with the above requirement E2, it is preferable that the blending amount of the low-alumina ore containing 90 mass% or more of fine powder of 1 mm or less in the first granulator 20a be 30 mass% or less.

[0046] (Requirement F) In the preparation step S1, when the content of the high crystal water ore in the first granulated material 40 is W1 [mass%] and the content of the high crystal water ore in the second granulated material 50 is W2 [mass%], it is preferable that W1 > W2 (requirement F1). Also, in the preparation step S1, it is preferable that the content of the crystal water component in the adhesion layer 42 of the first granulated material 40 is 4.0 mass% or less (requirement F2). In the preparation step S1, it is possible to satisfy only one of requirements F1 and F2, but it is preferable that both requirements F1 and F2 are satisfied.

[0047] [Requirement F1] A typical example of the high-water-of-crystallization ore is Australian ore. Compared to the Canadian concentrate, the Australian ore has a wider particle size distribution and a higher content of water of crystallization. Because the Australian ore contains ultrafine particles, it has a large specific surface area and is easily melted. Therefore, the inclusion of the high-water-of-crystallization ore in the granulated material can increase the amount of melt. Meanwhile, the decomposition reaction of the water of crystallization is an endothermic reaction, which inhibits the generation of melt. Furthermore, with Australian ore, bubbles are generated in the melt due to the decomposition reaction of water of crystallization, increasing the structural viscosity of the melt. Here, since the high-water-of-crystallization ore contributes to an increase in the amount of melt, using it together with the low-alumina ore makes it possible to produce a large amount of melt with low viscosity. Therefore, by setting the content W1 of the high-water-of-crystallization ore contained in the first granulated material 40 to W1 > W2, the function of the first granulated material 40 as a melt supply medium can be improved. In other words, in the production process S1, the high crystal water ore is inclined and blended into the first granulator 20a so that the blending amount [mass %] in the first granulator 20a is greater than the blending amount [mass %] in the second granulator 20b, thereby enhancing the function of the first granulated material 40 as a melt supply medium.

[0048] [Requirement F2] If the content of the water of crystallization component in the adhesion layer 42 of the first granules 40 exceeds 4.0 mass%, there is a risk of large variations in the strength of the obtained sintered ore 60. Therefore, it is preferable that the content of the water of crystallization component in the adhesion layer 42 of the first granules 40 be 4.0 mass% or less.

[0049] It is preferable to simultaneously satisfy the requirements E and F. By simultaneously satisfying the requirements E and F, it is possible to easily prevent a local shortage of melt due to uneven distribution of the low-alumina ore and a local deterioration in air permeability due to collapse of the granules in the firing step S2. Furthermore, by simultaneously satisfying the requirements E and F, it is possible to easily prevent uneven burning and a deterioration in air permeability due to the local generation of high-viscosity melt in the firing step S2.

[0050] <Firing process> The firing step S2 can be performed using, for example, the sintering machine 30 shown in FIG. 2. In the firing step S2, the raw material layer 30a containing the mixture of the first granulated material 40 and the second granulated material 50 is ignited, and gas is drawn into the raw material layer 30a from the outside. In this method for producing sintered ore, the first granulated material 40 functions as a melt supply medium and the second granulated material 50 functions as a melt receiving medium, thereby reducing the overall amount of coke fines used. Furthermore, in this method for producing sintered ore, the first granulated material 40 functions as a melt supply medium and the second granulated material 50 functions as a melt receiving medium, thereby improving the production efficiency of sintered ore 60.

[0051] In the calcining step S2, for example, the coke powder contained in the first granules 40 and the second granules 50 is used as a heat source. In the calcining step S2, the surface of the raw material layer 30a is ignited, and the air is sucked in from below to spread the combustion. As the combustion spreads in the raw material layer 30a, some or all of the first granules 40 (individual first granules) melt to produce a calcium ferrite-based melt, which flows downward along the flow of the suction gas and melts and assimilates with the second granules 50. The melted and assimilated granules are cooled to produce sintered ore 60.

[0052] As shown in Fig. 5, in the firing step S2, the first granulated material 40 generates a large amount of low-viscosity melt. This melt can flow so as to avoid the gas flow path, and therefore can form a ventilation path P along the gas suction direction (vertical direction). As a result, high-strength and homogeneous sintered ore 60 can be produced.

[0053] [Other embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as falling within the scope of the present invention. [Example]

[0054] The present disclosure will be described in detail below based on examples, but the present disclosure should not be construed as being limited based on the description of these examples.

[0055] [Sintering pot test] (Productivity test) The productivity of sintered ore was investigated using a large-scale pot test apparatus 100 (Figure 6) equipped with a large sintering pot 101 (280 mm x 280 mm x 590 mm square). The specific test procedure is as follows. First, sintered ore with a particle size of 6 mm or less was charged as a bedding to protect the floor of the sintering pot 101 to a layer thickness of 70 mm. Next, 80 kg of granulated raw materials, including iron ore, auxiliary raw materials such as coal stone, and coke fines as a coagulant, were added with water and granulated in a drum mixer. The resulting granulated materials were packed on the bedding up to the level, forming a raw material packed layer approximately 500 mm thick. In this test, first and second granulated materials were produced. The auxiliary raw materials for the first and second granulated materials were adjusted so that the SiO2 content of the sintered product was 5.4 mass% and the CaO / SiO2 basicity was 2.1. First, as shown in Table 1, a coke fines ratio of 4.2% in the granulated raw materials was used as the reference condition. The coke breeze ratio was reduced by 0.2% from the standard condition, and the blending amount of coarse carbonaceous material with a particle diameter of more than 1 mm and less than 6 mm was changed. In Table 1, C1 means the content [mass%] of coarse carbonaceous material in the first granules, and C AVEThe coarse carbonaceous material content [mass%] in the first granules and the coarse carbonaceous material content [mass%] in the second granules are averaged. The components contained in the first and second granules, as well as the C / F of the adhesion layers of the first and second granules, are shown in Table 2. The components and qualities of the low-alumina ore, high-crystallization water ore, and limestone in Table 2 are shown in Table 3. The surface of the raw material packed bed was then ignited using an ignition burner, and the exhaust fan connected to the wind box was used to draw in air at a suction pressure of -1.0 kPa at the time of ignition, and then at a suction pressure of -1.6 kPa to combust the coke fines in the raw material packed bed. The ignition time using the ignition burner was 90 seconds. The time when the CO2 concentration in the exhaust gas reached 0.2 vol% or less was defined as the end of the firing. The fired sintered cake was dropped twice from a height of 2 m using a drop strength tester (JIS-M8711:1993). After the drop, the fired product was sieved and those 10 mm or larger were weighed as finished products. The productivity of the sintered ore was calculated using the following formula (1). Productivity [t / h / m 2 ] = Amount of product over 10 mm [t] ÷ Firing time [h] ÷ Bottom area of ​​sintering pot [m 2 ] ···(1)

[0056] [Table 1]

[0057] [Table 2] *The distribution ratio [mass %] of the entire raw materials for forming the granules was granule A: granule B = 35:65.

[0058] [Table 3]

[0059] Figure 7 shows C1 / C AVE This shows the change in productivity in the firing of a mixture of the first and second granules when the temperature is changed. 2 ], C1 / CAVE It can be seen that productivity tends to be high when the ratio is 1.2 or more.

[0060] (Rotational strength test 1) Using the large-pot test apparatus 100 shown in Figure 6, several types of sintered ore with different C / F ratios were produced by separate granulation of the first and second granules. The C / F ratio in the sintered ore was changed by adjusting the blending ratio. The rotational strength of these sintered ores was measured using an eye-type rotational strength tester. First, 500 g of each sintered ore was weighed and packed into a 500 mm long cylinder. This cylinder was rotated at a rotation speed of 20 rpm for 1 minute to impact the sintered ore. After the rotation test, the sintered ore was removed and sieved, and the rotational strength [%] was calculated using the following formula (2). Rotation strength [%] = remaining amount of particles with a diameter of 10 mm or more [g] ÷ initial filling amount [g] × 100 (2) The test results are shown in Figure 8.

[0061] As shown in FIG. 8, it is clear that the rotation strength can be improved by setting the C / F in the adhesion layer of the entire granulated material to 0.115 or more.

[0062] (Rotational strength test 2) Using the large pot test apparatus 100 shown in Figure 6, a general single granule and the first and second parallel divided granules were produced. The general single granule and the first and second parallel divided granules each contained the low-alumina ore, high-crystallization water ore, and limestone shown in Table 3, and the granule-forming raw materials were distributed in a gradient manner so that the C / F of the second granule was smaller than that of the first granule. Figure 9 shows the relationship between the C / F and rotational strength [%] of the first and second parallel divided granules. In Figure 9, the mass ratio of the first granule to the second granule was first granule:second granule B = 35:65.

[0063] As shown in Figure 9, it can be seen that the rotation strength decreases when the weighted average C / F in the adhesion layer of the first and second parallel divided granules is below 0.115. It can also be seen that the rotation strength decreases when the C / F of a general single granule is below 0.08. From this, it can be seen that good rotation strength can be obtained by setting the weighted average C / F of the adhesion layer of the first and second parallel divided granules to 0.115 or more and setting the C / F of the adhesion layer of the second granule to 0.08 or more.

[0064] (Canadian concentrate blending ratio) Figure 10 shows the relationship between the blending ratio (mass%) of Canadian concentrate and the proportion (mass%) of granules with particle diameters of 5 mm or more (left axis) and 1 mm or less (right axis) in the total granules. As shown in Figure 10, when the blending ratio of Canadian concentrate exceeds 30%, granulation performance deteriorates and the amount of ungranulated powder with a particle diameter of 1 mm or less increases.

[0065] (Relationship between crystal water content and rotational strength) Using the large pot test apparatus 100 shown in FIG. 6, the first granules (C1 / C2) shown in Tables 1 to 3 were AVE The relationship between the variation in rotational strength and the amount of crystal water in the adhesion layer of the entire granule was investigated by varying the blending ratio of high crystal water ore to the total particle size of the sintered ore (constant at 1.1). The results are shown in Figure 11. The rotational strength R [%] in Figure 11 represents the difference between the maximum and minimum values ​​calculated by dividing the particle size of the sintered ore obtained by the particle size of 10 mm or more by the total particle size of the sintered ore obtained.

[0066] As shown in FIG. 11, it can be seen that when the crystal water content in the adhesion layer exceeds 4.0 mass %, variations in strength occur. [Explanation of symbols]

[0067] 1 Manufacturing equipment 10a 1st raw material tank 10b 2nd raw material tank 20a 1st granulator 20b 2nd granulator 30 Sintering machine 30a Raw material layer 40 First granulate 40a melt 41 Core 42 Adhesion layer 50 Second granulate 51 Core 52 Adhesion layer 60 Sinter 100 Large pot testing equipment 101 Sintering pot P Ventilation path

Claims

1. A step of preparing the first granule and the second granule in separate granulators; baking the mixture of the first granules and the second granules; Equipped with the first granule and the second granule each have a core portion and an adhesive layer attached to the periphery of the core portion, A method for producing sintered ore, wherein the first granules and the second granules are produced in the producing step so as to satisfy the following requirements A to C: Requirement A: Fe having a particle diameter of 1 mm or less in the first granule ２ O ３ The mass ratio of CaO particles with a particle diameter of 1 mm or less to the particles [CaO / Fe ２ O ３ ] to Q １ The mass ratio in the second granule is Q ２ In this case, Q １ and Q ２ The weighted average of the mixing ratio of the first granules and the second granules based on mass is 0.115 or more. Requirement B: The content of the lime raw material in the first granule is L １ [mass%], the content of the lime raw material in the second granules is L ２ When expressed as [mass %], L １ ≧L ２ Let's say. Requirement C: The average content of coarse carbonaceous material having a particle diameter of more than 1 mm and not more than 6 mm in the first granule and the second granule is C ＡＶＥ When expressed as [mass%], the content C of the coarse carbonaceous material contained in the first granules １ [mass%] is C １ ≧1.2C ＡＶＥ Let's say.

2. 2. The method for producing sintered ore according to claim 1, wherein the second granules are produced in the producing step so as to further satisfy the following requirement D: Requirement D: Q ２ ≧0.

08.

3. 2. The method for producing sintered ore according to claim 1, wherein in the producing step, the first granules and the second granules are produced so as to further satisfy the following requirements E1 and E2. Requirement E1: The content of low alumina ore in the first granule is A １ [mass%], the content of the low alumina ore in the second granules is A ２ When expressed as [mass%], A １ >A ２ Let's say. Requirement E2: In the granulator that produces the first granules, the amount of low-alumina ore containing 90% by mass or more of fine powder of 1 mm or less is 30% by mass or less.

4. 2. The method for producing sintered ore according to claim 1, wherein in the producing step, the first granules and the second granules are produced so as to further satisfy the following requirements F1 and F2. Requirement F1: The content of high crystal water ore in the first granule is W １ [mass%], the content of the high water of crystallization ore in the second granules is W ２ When expressed as [mass %], W １ >W ２ Let's say. Requirement F2: The content of water of crystallization in the adhesion layer of the first granules is 4.0% by mass or less.

5. 5. The method for producing sintered ore according to claim 1, wherein in the firing step, a raw material layer containing the mixture is ignited, and gas is sucked into the raw material layer from the outside.

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