Sinter manufacturing method

Abstract

To improve productivity by a two-stage ignition sintering method.SOLUTION: A manufacturing method of sintered ore includes: a step for forming a lower-stage raw material packed bed by charging a blended raw material for a lower stage into a sintering machine; a step for forming an upper-stage raw material packed bed by charging a blended raw material for an upper stage onto the lower-stage raw material packed bed; and a step for igniting the surface of the lower-stage raw material packed bed and the upper-stage raw material packed bed individually, and also sucking oxygen-containing gas in the lower-stage raw material packed bed and the upper-stage raw material packed bed downward. In the manufacturing method of sintered ore, the calorific volume of an iron-containing substance having an oxidation heat generation property, blended in the blended raw material for the upper stage, per unit new raw material is made larger than the calorific volume of an iron-containing substance having an oxidation heat generation property, blended in the blended raw material for the lower stage, per unit new raw material.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing sintered ore for use as a blast furnace raw material. [Background technology]

[0002] Currently, the main raw material for blast furnace pig iron production is sintered ore. Sintered ore is usually produced as follows. First, raw materials for sintered ore production, such as iron ore (powder), iron-containing miscellaneous raw materials such as scale and iron-making dust, MgO-containing auxiliary raw materials such as olivine, CaO-containing auxiliary raw materials such as limestone, return ore, and carbonaceous material (agglomeration material) that serves as fuel for sintering (agglomerating) sintered ore by combustion heat, are mixed in a specified ratio. The mixed raw materials are granulated to form a granulated raw material mixture. Next, the granulated raw material mixture is loaded from a hopper onto a pallet (sintering pallet) of a downward suction type Dwight Lloyd (DL) sintering machine to form a raw material packed bed. The carbonaceous material in the raw material packed bed is ignited from the top (surface) of the formed raw material packed bed by an ignition furnace (igniter). Then, air is sucked from below the pallet while the pallet is continuously moved. Oxygen is supplied into the raw material packed bed by suction, and the combustion of the carbonaceous material in the raw material packed bed proceeds from the top to the bottom, and the raw material packed bed is successively sintered by the combustion heat of the carbonaceous material. The sintered part 3 (sinter cake) obtained by sintering is crushed to a specified grain size, sized by sieving, etc., and becomes sintered ore, which is the raw material for blast furnaces.

[0003] In the manufacturing method of sintered ore using such DL-type sintering machines, a multi-stage charging and multi-stage ignition sintering method has been proposed, in which the formation of raw material packed beds and ignition are performed in two or more stages. In the multi-stage charging and multi-stage ignition sintering method, granulated mixed raw materials are charged in sequence in the layer height direction of the sintering machine to form multiple stages (two or more stages) of raw material packed beds, and the surface of each raw material packed bed is ignited and air is sucked in from below, allowing the sintering reaction in each layer to proceed simultaneously in parallel.

[0004] Fig. 1 is a schematic diagram of a DL-type sintering machine used for a two-stage charging two-stage ignition sintering method, which is an example of a multi-stage charging multi-stage ignition sintering method. With reference to Fig. 1, the two-stage charging two-stage ignition sintering method will be described, in which granulated blended raw materials are charged in two stages to form an upper raw material packed layer (hereinafter referred to as the upper layer) and a lower raw material packed layer (hereinafter referred to as the lower layer), and sintering is performed by igniting each of the upper layer and the lower layer.

[0005] In the example shown in FIG. 1, the upper-stage blended raw material forming the upper layer 20 and the lower-stage blended raw material forming the lower layer 10 are prepared in separate systems (two systems) and are charged onto a pallet (not shown) of the sintering machine 100 in the separate systems. Specifically, the raw material for the lower stage is fed to each raw material tank (1D1 to 1D X The raw materials for the upper stage are stored in the drum mixer 1A, and the required types and amounts of raw materials are extracted and blended in a predetermined ratio. The blended raw materials for the lower stage (blended raw materials for the lower stage) are fed into the drum mixer 1A for the lower stage, mixed, and granulated by adding moisture. The raw materials for the upper stage are fed into each raw material tank (2D1 to 2D y The raw materials are stored in the upper drum mixer 2A, and the required types and amounts of raw materials are cut out in a specified ratio and mixed. The mixed raw materials for the upper stage (upper stage mixed raw materials) are fed into the upper drum mixer 2A, mixed, and granulated by adding water.

[0006] The granulated lower-stage raw material mixture (granulated lower-stage raw material mixture) is charged from the lower-stage hopper 1B onto a pallet covered with bedding ore, forming a lower layer 10 (lower-stage raw material packed layer). The lower layer 10 moves to below the lower-stage igniter 1C by moving the pallet in the pallet travel direction 5, where the carbonaceous material on the surface of the lower layer 10 is ignited by the lower-stage igniter 1C. After ignition, sintering of the lower layer 10 is started by downward suction 6, which draws air from below through a wind box (not shown) below the pallet. The sintering of the lower layer 10 progresses downward by the continued downward suction 6, forming a lower-stage layer combustion zone 10A.

[0007] When the lower layer 10 where sintering has started moves to below the upper hopper 2B, the upper mixed raw material (upper mixed raw material granules) granulated by the upper drum mixer 2A is charged from the upper hopper 2B onto the ignited lower layer 10 to form the upper layer 20 (upper raw material packed layer). The upper layer 20 moves to below the upper igniter 2C by moving the pallet in the pallet traveling direction 5, where the carbonaceous material on the surface of the upper layer 20 is ignited by the upper igniter 2C. After ignition, sintering of the upper layer 20 starts by downward suction 6. The sintering of the upper layer 20 progresses downward by the continued downward suction 6, forming an upper layer combustion zone 20A.

[0008] The lower layer combustion zone 10A of the lower layer 10 and the upper layer combustion zone 20A of the upper layer 20 are simultaneously sintered and move down due to further downward suction 6. When the lower layer combustion zone 10A and the upper layer combustion zone 20A reach the bottom of each layer, sintering by combustion of carbonaceous materials ends, and the lower layer 10 and the upper layer 20 become the sintering section 3. Finally, the sintering section 3 where sintering is completed is discharged from the end of the pallet.

[0009] In the two-stage charging two-stage ignition sintering method, the raw material packed bed is arranged in two stages, and sintering proceeds simultaneously in two stages, so that the production volume can be almost doubled. Also, the exhaust gas used in sintering the upper stage layer 20 is reused for sintering the lower stage layer 10 by downward suction, so that the amount of exhaust gas can be reduced (halved).

[0010] The multi-stage charging and multi-stage ignition sintering method is disclosed in Patent Documents 1 and 2. Patent Document 1 describes that the multi-stage charging and multi-stage ignition sintering method can change the supply ratio of the raw materials in each layer, and therefore, by adjusting the particle size of the raw materials in the upper layer 20 and the lower layer 10, it is possible to improve the yield.

[0011] Patent Document 2 points out that the two-stage ignition sintering method has an essential drawback in that the fuel mixed in the intake side layer is prone to incomplete combustion due to the low oxygen concentration of the gas flowing from the intake side layer to the intake side layer, and the combustion heat generation amount decreases, so the temperature in the layer drops, and sufficient melting and sintering cannot be performed, resulting in a deterioration in the strength of the sintered ore product. In the two-stage charging two-stage ignition sintering method, the gas (exhaust gas) used for sintering the upper layer 20 and with a reduced oxygen partial pressure is supplied to the lower layer 10 by downward suction 6 and used for sintering the lower layer 10. Therefore, sintering is performed under low oxygen partial pressure in the lower layer 10, and the combustion of the carbonaceous material in the lower layer 10 is incomplete, resulting in a shortage of heat required for sintering. Due to the shortage of heat, the progress of the sintering reaction in the lower layer 10 is hindered, and the strength of the sintered ore in the lower layer 10 is reduced.

[0012] As a method for solving this problem, Patent Document 2 discloses a technology in which the fixed carbon concentration in the blended raw material layer on the intake outlet side of the two layers (the lower raw material packed layer) is set to 0 or 2 wt% or less, and instead raw materials containing one or more of metallic iron, FeO, and Fe3O4, which are iron-containing substances that can be oxidized as fuel, are blended. The technology discloses that by blending raw materials containing an iron-containing substance that generates oxidation heat in the blended raw material in the intake outlet side layer, it is possible to obtain a sufficient amount of heat for melting and sintering even with a gas with a low oxygen concentration, and to significantly improve the productivity of the sintering machine. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 47-26304 [Patent Document 2] Japanese Patent Application Publication No. 09-279261 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention is a method for producing sintered ore that has been newly invented in consideration of the above problems. The object of the present invention is to provide a method for producing sintered ore that enables further improvement in productivity (production rate) in a two-stage charging two-stage ignition sintering method (hereinafter also simply referred to as the two-stage ignition sintering method). [Means for solving the problem]

[0015] The present invention has been made to solve the above problems, and the gist of the present invention is as follows. (1) A step of charging a lower-stage raw material mixture into a sintering machine to form a lower-stage raw material packed bed; forming an upper-stage raw material packed bed by charging an upper-stage raw material blend onto the lower-stage raw material packed bed; igniting the surfaces of the lower-stage raw material packed bed and the upper-stage raw material packed bed, respectively, and sucking the oxygen-containing gas in the lower-stage raw material packed bed and the upper-stage raw material packed bed downward, the calorific value per unit new raw material of the iron-containing substance having oxidative exothermic properties blended in the upper raw material is greater than the calorific value per unit new raw material of the iron-containing substance having oxidative exothermic properties blended in the lower raw material; A method for producing sintered ore, comprising: (2) In the case where a single raw material containing an iron-containing substance having oxidative exothermic properties is used in the upper-stage raw material mix and the lower-stage raw material mix, the blending ratio (mass%) of the raw material containing the iron-containing substance having oxidative exothermic properties blended in the raw material for the upper stage in the new raw material is greater than the blending ratio (mass%) of the raw material containing the iron-containing substance having oxidative exothermic properties blended in the raw material for the lower stage in the new raw material; The method for producing sintered ore according to (1), (3) The particle size of the carbonaceous material blended in the upper raw material mixture is larger than the particle size of the carbonaceous material blended in the lower raw material mixture. The method for producing sintered ore according to (1) or (2), Effect of the Invention

[0016] According to the present invention, the amount of the iron-containing material having oxidative heat generation property mixed in the upper layer is made larger than that in the lower layer, thereby making it possible to improve the productivity by the two-stage ignition sintering method. [Brief description of the drawings]

[0017] [Figure 1] This is a schematic diagram of a DL-type sintering machine used in the two-stage ignition sintering method. [Diagram 2] FIG. 2 is a diagram showing a raw material processing step of a two-stage ignition sintering method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] As described above, the two-stage ignition sintering method has a problem of a decrease in sinter strength of sintered ore in the lower raw material packed bed (lower layer 10). Unlike Patent Document 2, the present inventor came up with a new perspective on the two-stage ignition sintering method in which a decrease in strength of sintered ore in the lower layer is a problem: to use a heat source in the upper layer 20 that can supply exhaust gas with a high oxygen concentration to the lower layer 10.

[0019] The present invention is characterized in that in the two-stage ignition sintering method, the calorific value per unit of new raw material of the iron-containing material having oxidative exothermicity blended in the upper stage blended raw material is larger than the calorific value per unit of new raw material of the iron-containing material having oxidative exothermicity blended in the lower stage blended raw material. In addition, when a single raw material containing an iron-containing material having oxidative exothermicity is used in the upper stage blended raw material and the lower stage blended raw material, the blending ratio (mass %) of the raw material containing the iron-containing material having oxidative exothermicity blended in the upper stage blended raw material in the new raw material may be larger than the blending ratio (mass %) of the raw material containing the iron-containing material having oxidative exothermicity blended in the lower stage blended raw material. Here, the iron-containing material having oxidative exothermicity (hereinafter also referred to as iron-containing material F) is a material containing at least one of metallic iron (Fe), wustite (FeO), and magnetite (Fe3O4), which are iron components having oxidative exothermicity. Raw materials containing iron-containing material F having oxidative heat generating properties (hereinafter referred to as exothermic raw materials) include reduced iron powder, scale, converter dust, steel can chips, etc. Also included in raw materials containing iron-containing material F are iron ores that contain at least one of metallic iron (Fe), wustite (FeO), and magnetite (Fe3O4), which are iron components having oxidative heat generating properties.

[0020] In the sintering process, which is carried out at high temperatures, metallic iron (Fe), wustite (FeO), and magnetite (Fe3O4) are oxidized; for example, metallic iron (Fe) and wustite (FeO) change to magnetite (Fe3O4) and hematite (Fe2O3), and magnetite (Fe3O4) changes to hematite (Fe2O3). These oxidation reactions are exothermic. In conventional sinter manufacturing methods, exothermic raw materials such as scale are generally mixed into the raw material mix as iron-containing miscellaneous raw materials to make effective use of the iron components, and are used at a uniform concentration throughout the raw material packed bed. In addition, as mentioned above, iron-containing substances F undergo exothermic reactions during the sintering process, so exothermic raw materials can also be used as a heat source instead of a coagulant.

[0021] The inventors have studied various ways to improve the two-stage ignition sintering method, and have found that by using an exothermic raw material as the heat source in the upper layer, the combustibility of the carbonaceous material in the lower layer can be improved, and productivity can be improved. As shown in the embodiment (Experiment 2) described later, when an exothermic raw material is used as the heat source, a higher concentration of oxygen remains in the sintering exhaust gas than when a carbonaceous material (coke, etc.) is used. By using an exothermic raw material as the heat source in the upper layer and reducing the amount of carbonaceous material corresponding to the iron-containing substance F contained therein, the sintering exhaust gas in the upper layer is supplied to the lower layer in a state where a high concentration of oxygen remains, and the amount of heat required for sintering in the lower layer can be secured, thereby improving productivity.

[0022] Scales and the like, which are exothermic raw materials, are commonly used as iron-containing miscellaneous raw materials, not limited to the two-stage ignition sintering method. In the conventional two-stage ignition sintering method, the exothermic raw materials are considered to be mixed in the same ratio in the new raw materials for the lower stage and the new raw materials for the upper stage. In the present invention, as described above, the calorific value per unit new raw material of the iron-containing material F mixed in the upper stage raw material is made larger than the calorific value per unit new raw material of the iron-containing material F mixed in the lower stage raw material, or the blending ratio (mass%) of the iron-containing material F mixed in the upper stage raw material is made larger than the blending ratio (mass%) of the iron-containing material F in the new raw materials mixed in the lower stage raw material, thereby increasing the oxygen concentration in the sintering exhaust gas from the upper stage layer supplied to the lower stage.

[0023] When multiple exothermic raw materials are used, the calorific value per unit of new raw material is used as an indicator instead of the blending ratio in the new raw materials. The calorific value per unit of new raw material of the iron-containing material F blended in the upper raw material mix is ​​made larger than the calorific value per unit of new raw material of the iron-containing material F blended in the lower raw material mix. Here, it is advisable to adjust the blending ratio of the carbonaceous material blended in the upper-stage raw material based on the calorific value of the iron-containing material F blended in the upper-stage raw material. Furthermore, it is also preferable to adjust the blending ratio of iron ore and CaO-containing auxiliary materials blended in the upper-stage blended raw material based on the basicity (CaO / SiO2: mass%) of the lower-stage blended raw material. This makes it possible to stabilize the quality of the sintered ore.

[0024] Fig. 2 is a diagram showing an example of a raw material processing process for carrying out a method for producing sintered ore by the two-stage charging, two-stage ignition and sintering method of the present invention. The process after the lower-stage blended raw material is charged into the lower-stage drum mixer 1A and the upper-stage blended raw material is charged into the upper-stage drum mixer 2A is the same as the sintered ore production process described above using Fig. 1, and a DL-type sintering machine 100 shown in Fig. 1 is used for sintering.

[0025] 2, in this embodiment, a heat-generating raw material containing an iron-containing substance F is stored in raw material vessel 1D1 of lower raw material vessel group 1D and raw material vessel 2D1 of upper raw material vessel group 2D. The amount of heat-generating raw material in raw material vessel 2D1 discharged when blended with other upper-stage blended raw materials, and the amount of heat-generating raw material in raw material vessel 1D1 discharged when blended with other lower-stage blended raw materials are appropriately adjusted to set the blending ratio of iron-containing substance F in the upper-stage blended raw material and the blending ratio of iron-containing substance F in the lower-stage blended raw material to predetermined blending ratios.

[0026] The storage of the exothermic raw materials in the upper-stage blended raw materials and the lower-stage blended raw materials is not limited to the above-mentioned form, and may be configured so that the blending ratio of the iron-containing material F in the upper-stage blended raw materials and the blending ratio of the iron-containing material F in the lower-stage blended raw materials are predetermined amounts. For example, when a plurality of types of exothermic raw materials are blended as the upper-stage blended raw materials, they may be stored in the raw material tanks 2Dn (1≦n≦y) by type, and the amount of the raw material discharged from the raw material tank 2Dn may be adjusted for each type, or a mixed raw material in which a plurality of types of exothermic raw materials are mixed in advance at a predetermined ratio may be stored in one raw material tank 2Dm (1≦m≦y), and the amount of the mixed raw material discharged from the raw material tank 2Dm may be adjusted. The same applies to the lower-stage blended raw materials. In addition, the lower-stage blended raw materials may not be provided with raw material tanks 1Dn (1≦n≦x) or raw material tanks 2Dm (1≦m≦y) for storing exothermic raw materials. This is because the lower-stage blended raw materials do not need to be blended with exothermic raw materials.

[0027] In the embodiment shown in FIG. 2, an upper-stage raw material tank group 2D and a lower-stage raw material tank group 1D are provided, and the upper-stage raw material blended material and the lower-stage raw material blended material are prepared in separate systems and charged onto a pallet to produce sintered ore by a two-stage ignition and sintering method. However, after the raw materials are mixed at a predetermined blending ratio, they may be separated into the upper-stage raw material and the lower-stage raw material, and an exothermic raw material may be added to the lower-stage raw material to make it the lower-stage raw material blended material, and the upper-stage raw material may be used as it is as the upper-stage raw material blended material, and each of them may be granulated and charged into the sintering machine.

[0028] It is preferable that the particle size of the carbonaceous material blended in the upper layer is larger than that of the lower layer. Coarse carbonaceous material consumes less oxygen per unit of suction air. By making the particle size of the carbonaceous material blended in the upper layer larger than that of the lower layer, the oxygen consumption in the upper layer is reduced. The oxygen concentration in the gas supplied to the lower layer is increased, which further improves the yield of sintered ore in the lower layer. Here, the carbonaceous material is a solid fuel containing carbon, and examples thereof include coke powder, anthracite, carbon-containing dust, etc. Although the carbonaceous material may contain volatile matter, it is preferable that the content of volatile matter is small.

[0029] It is preferable to use coke with a particle size of less than 5 mm as the carbonaceous material. Here, the particle size of the carbonaceous material is defined as the mass ratio of particles with a diameter of 3 mm or more (hereinafter also referred to as the mass ratio of particles with a diameter of 3 mm or more). For example, the mass ratio of particles with a diameter of 3 mm or more is determined by classifying the carbonaceous material with a 3 mm sieve (a sieve with a mesh size of 2.8 mm of a JIS standard sieve (JIS Z 8801)), measuring the mass of the particles on the sieve and the particles on the sieve, and calculating the mass ratio of the particles on the sieve to the total carbonaceous material. Furthermore, it is preferable that the mass ratio of the carbonaceous material with a particle size of 3 mm or more and less than 5 mm is 10 mass% or less, and the mass ratio of the carbonaceous material with a particle size of 3 mm or more and less than 5 mm is 10 mass% or less, and more preferably 10 mass% or more and 25 mass% or less, and more preferably 10 mass% or more and 22 mass% or less. Here, a particle size of 3 mm or more but less than 5 mm refers to the part that is on the 2.8 mm sieve and below the 4.75 mm sieve when classified using JIS standard sieves (JIS Z 8801) with sieve meshes of 2.8 mm and 4.75 mm. Note that when classifying particle sizes, the approximate values ​​of 3 mm and 5 mm are usually used for the 2.8 mm and 4.75 mm sieve meshes. The particle size of carbonaceous materials can be adjusted by shortening or extending the grinding time or changing the sieve mesh.

[0030] In the two-stage charging two-stage ignition sintering method, the layer thicknesses of the upper and lower layers are adjusted so that the upper and lower layers finish sintering at approximately the same time. As a result, the layer thicknesses of the upper and lower layers are approximately equal. However, when different raw materials are used for the upper and lower layers, or when the simultaneous completion of sintering of the upper and lower layers is not important, a wider layer thickness ratio of the upper layer to the lower layer can be selected. In the embodiment of the two-stage charging two-stage ignition sintering method shown in FIG. 2, a layer thickness ratio of 1:2 to 2:1 can be adopted without impairing the equipment efficiency. EXAMPLES

[0031] Examples that demonstrate the effects of the present invention will be described below. Note that the present invention is not limited to the following examples.

[0032] <Experiment 1> The inventors confirmed the effect of the present invention by a sintering pot test (diameter 300 mm) that can simulate sintering by a DL sintering machine. The sintering pot test device does not move the raw material packed bed by a pallet like the DL sintering machine, but it is a test device that charges a container of a specified size with blended raw materials, ignites from the top, and advances sintering by downward suction. As shown in Table 3 below, five tests were conducted: a comparative example, a reference example, and examples 1 to 3.

[0033] (Raw material blend) Scale was used as the exothermic raw material (FeO: 65.9 mass%, M-Fe (metallic iron Fe): 3.98 mass%). Table 1 shows the blending ratio of the raw materials used as the blended raw materials. As shown in Table 1, two types of blended raw materials were prepared: blended raw material 1 without scale, and blended raw material 2 with scale. Silica was used in blended raw material 2 to match the SiO2 content with blended raw material 1. The blended amount of limestone was 12 mass% in all cases so that the target basicity of the sintered ore would be 1.8. Iron ores A to D are not exothermic raw materials, and each comes from a different place of origin.

[0034] For the raw material blend 2 containing scale, the amount of carbonaceous material (mixing ratio) was adjusted to reduce the amount of scale so that the estimated heat generation in both raw material blends was the same, based on the raw material blend 1 not containing scale. Specifically, the amount of oxidation heat generation of the iron-containing substance F in the scale was calculated from the amount of scale (mixing ratio 40 mass%) and its chemical components, and the amount of carbonaceous material equivalent to this amount of oxidation heat generation was determined. The amount of carbonaceous material in the raw material blend 2 was determined by subtracting the amount of carbonaceous material equivalent to the calculated amount of oxidation heat generation (mixing ratio 2.2 mass%) from the amount of carbonaceous material in the raw material blend 1 (mixing ratio 4.5 mass%) (mixing ratio 2.3 mass%). Coke was used as the carbonaceous material (aggregating agent). The blending ratio of coke in blended raw materials 1 and 2 was 4.5% by mass and 2.3% by mass, respectively, with the new raw materials being 100% by mass.

[0035] [Table 1]

[0036] Three types of coke (coke 1 to coke 3) with different particle size distributions were used. Table 2 shows the particle size distributions of the three types of coke. As shown in Table 2, coke 1 to coke 3 all have a particle size of -5 mm (less than 5 mm). For example, coke 1 contains 90 mass% of coke with a particle size of less than 3 mm, and 10 mass% of coke with a particle size of 3 mm or more and less than 5 mm. The particle size of the coke was adjusted by classification using a sieve.

[0037] [Table 2]

[0038] (Test case) The test conditions are shown below (see the upper part of Table 3). As shown in Table 3, five tests were carried out for the Comparative Example, Reference Example, and Examples 1 to 3, which imitate the two-stage charging, two-stage ignition sintering method. Comparative example (reference conditions for two-stage charging and two-stage ignition) : Both the upper and lower layers use raw materials that do not contain scale (mixed raw materials 1). Coke 1 is used. Reference example: Only the lower layer uses raw material containing scale (mixed raw material 2). Coke is the same as the reference condition. Example 1: Raw material containing scale (mixed raw material 2) was used only in the upper layer. Coke is the same as the reference condition. Example 2: Raw material containing scale (mixed raw material 2) was used only in the upper layer. Coke 2 is used only in the upper layer. Example 3: A raw material containing scale (mixed raw material 2) was used only in the upper layer. Coke 3 is used only in the upper layer.

[0039] [Table 3]

[0040] (Granulation method) The blended raw materials 1 and 2 were granulated together. The granulation was carried out by mixing for 4 minutes with a test drum mixer (diameter 600 mm, rotation speed 25 rpm), adding 6.5% by mass of water to the blended raw materials, and processing for another 4 minutes.

[0041] (Charging / ignition method) Two pots were prepared: a cylindrical lower pot (φ300mm) with a height of 500mm, and a cylindrical upper pot (φ300mm) with a height of 300mm. First, the granulated lower layer mixed raw materials and upper layer mixed raw materials were charged into the lower pot and upper pot, and the layer height of the lower layer was set to 500mm and the layer height of the upper layer was set to 300mm. Then, the lower pot with a layer height of 500mm was set, and the surface of the lower layer was ignited for 1 minute. After that, the upper pot with a layer height of 300mm was set on top of the lower pot, and the surface of the upper layer was ignited for 1 minute after confirming the temperature rise at a position 290mm from the bottom surface of the lower layer in order to realize the progress of sintering in two layers, upper and lower. The suction pressure was kept constant at 1500mmAq (14.7kPa) from the start of ignition, and the oxygen concentration in the sintering exhaust gas exhausted from below the lower pot was also measured. The oxygen concentration is a value measured by a gas analyzer (magnetic wind analyzer) and is an average value until the completion of sintering.

[0042] (sintering time) The sintering time was measured as follows. Thermocouples were inserted 380 mm from the bottom of the lower pan and at the wind box position to measure the temperature inside the layer. The later of the completion of sintering of the upper layer or the lower layer was considered to be the completion of sintering for the entire raw material packed layer (upper and lower layers), so the sintering time for the entire raw material packed layer was determined as the longer of the time required for the second temperature rise of the thermocouple at 380 mm (completion of sintering of the upper layer) and the time required for the first peak of the thermocouple at the wind box (completion of sintering of the lower layer). Suction was stopped 3 minutes after the completion of sintering, and sintering was considered to be finished.

[0043] (Yield) The yield was measured as follows. After sintering, the obtained sintered cake was dropped from a height of 2 m four times, and the mass of the sintered product was calculated as the particle size + 5 mm (5 mm or more). The ratio (mass%) of this sintered product to the total mass of the sinter cake was defined as the product yield (+5 mm%).

[0044] (Production rate) The productivity was calculated from the sintering time measured as described above using the following formula (5). Production rate = product amount (t) / sintering area (0.07m 2 ) / sintering time (days) ···(5)

[0045] (Test Results) The test results are shown in the lower part of Table 3. As shown in Table 3, the yield and production rate (productivity) were improved in the Examples compared to the Comparative Examples. Note that, although the Reference Example also used the blended raw material 2 containing scale, the Examples in which the blended raw material 2 was used in the upper layer showed a greater improvement in production rate. Furthermore, in Examples 1 and 2, the yield was also improved. This is believed to be because, as shown in Table 3, the oxygen concentration in the exhaust gas was low in the Examples, and the oxygen in the oxygen-containing gas sucked downward was effectively used for sintering.

[0046] Moreover, as shown in Table 3, in Example 2, coke 2 (mass ratio of particles of 3 mm or more being 22 mass%) was used in the upper layer. By increasing the particle size of the coke used, the yield and productivity were improved compared to Example 1 (coke 1 with a mass ratio of particles of 3 mm or more being 10 mass%). This is believed to be because the oxygen concentration in the exhaust gas supplied to the lower layer was increased. In the case of Example 3, in which the particle size of the coke used in the upper layer was even larger than that of Example 2, a higher yield and productivity were still obtained than in the comparative example, but the yield and productivity were lower than in Example 2. This is believed to be because the presence of extremely large coke left unburned particles, which reduced the yield in the upper layer.

[0047] <Experiment 2> To complement the above tests, sinter pot tests were carried out to compare the oxygen availability in oxygen-containing gas during the sintering process for coke and scale.

[0048] The raw materials 1 and 2 shown in Table 1 were prepared by granulation in the same manner as in the above-mentioned experimental example, and a sintering experiment was carried out using the single-stage charging and single-stage ignition method. Each raw material was charged to a bed height of 500 mm in a cylindrical lower-stage pot (φ300 mm) with a height of 500 mm, and ignition was carried out for one minute. The suction pressure was constant at 1500 mmAq from the start of ignition. The oxygen concentration in the sintering exhaust gas (exhaust gas oxygen concentration) was measured, and the relationship with the raw material blending conditions was examined. As a result, the exhaust gas oxygen concentration was 9.5% in the raw material 1 that did not contain scale. On the other hand, the exhaust gas oxygen concentration was 11.9% in the raw material 2 that contained scale, which was higher than that of the raw material 1. In other words, the amount of oxygen consumed (oxygen consumption) was less when a heat-generating raw material (scale was used in this example) was used as a part of the heat source in the sintering process than when only the carbonaceous material, which is a coagulating material, was used.

[0049] In Experiment 1, as shown in Table 3, Example 1, in which raw material blend 2 (scale blend) was used only in the upper layer, had a lower exhaust gas oxygen concentration than the Reference Example, in which raw material blend 2 (scale blend) was used only in the lower layer, and Example 1 effectively utilized the oxygen in the oxygen-containing gas sucked downward in the entire upper and lower layers for sintering. Also, from the results of Experiment 2, it is considered that the oxygen consumption in the upper layer was less in Example 1 than in the Reference Example. Therefore, it is assumed that in the Reference Example, the oxygen in the exhaust gas from the upper layer could not be effectively utilized for sintering in the lower layer. On the other hand, in Example 1, exhaust gas with a relatively high oxygen concentration from the upper layer was supplied to the lower layer, and in the lower layer, the oxygen in the exhaust gas was effectively utilized for sintering, and it is assumed that the yield and productivity were further improved. [Explanation of symbols]

[0050] 100... sintering machine, 1A... lower stage drum mixer, 1B... lower stage hopper, 1C... lower stage igniter, 1D... lower stage raw material tank group (lower stage raw material tanks 1D1 to 1D X), 2A... upper drum mixer, 2B... upper hopper, 2C... upper igniter, 2D... upper raw material tank group (upper raw material tanks 2D1 to 2D y ), 3...sintering section, 5...pallet travel direction, 6...downward suction, 10...lower layer, 10A...lower layer combustion zone, 20...upper layer, 20A...upper layer combustion zone

Claims

1. A step of forming a lower-stage raw material packed bed by charging a lower-stage raw material blend into a sintering machine; forming an upper-stage raw material packed bed by charging an upper-stage raw material blend onto the lower-stage raw material packed bed; igniting the surfaces of the lower-stage raw material packed bed and the upper-stage raw material packed bed, respectively, and sucking the oxygen-containing gas in the lower-stage raw material packed bed and the upper-stage raw material packed bed downward, the calorific value per unit new raw material of the iron-containing substance having oxidative exothermic properties blended in the upper raw material is greater than the calorific value per unit new raw material of the iron-containing substance having oxidative exothermic properties blended in the lower raw material; A method for producing sintered ore, comprising:

2. In the case where a single raw material containing an iron-containing substance having oxidative exothermic properties is used in the upper stage raw material mix and the lower stage raw material mix, the blending ratio (mass%) of the raw material containing the iron-containing substance having oxidative exothermic properties to be blended in the raw material for the upper stage in the new raw material is greater than the blending ratio (mass%) of the raw material containing the iron-containing substance having oxidative exothermic properties to be blended in the raw material for the lower stage in the new raw material; The method for producing sintered ore according to claim 1 .

3. The particle size of the carbonaceous material blended in the upper stage raw material is larger than the particle size of the carbonaceous material blended in the lower stage raw material. The method for producing sintered ore according to claim 1 or 2.

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