Method for producing sintered ore

Abstract

To provide a method for producing a sintered ore capable of improving the RDI of the sintered ore while maintaining productivity of the sintered ore.SOLUTION: Provided is a method for producing a sintered ore, in which a high-combustibility carbonaceous material is used as part of a carbonaceous material for sintering. The carbonaceous material for sintering comprises 20 to 60 mass% of the high-combustibility carbonaceous material having a particle size distribution such that particles with a size of 2.8 mm or more account for 25 mass% or more, particles with a size of 5 mm or more account for 15 mass% or less, and particles with a size of less than 0.6 mm account for 40 mass% or less. The remainder of the carbonaceous material for sintering is a low-combustibility carbonaceous material having a particle size distribution in which particles with a size of less than 1 mm account for 40 mass% or more. The carbonaceous material for sintering is blended into a sintering raw material to form a blended material A, and the blended material is charged using a segregation charging device 14 that, in the blended material, segregates coarse particles toward a bottom side of a pallet 17.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The manufacturing method for sintered ore is outlined as follows. First, the sintering raw material and sintering carbonaceous material are blended to form a blended raw material, which is then transported to a hopper on a belt conveyor. The sintering raw material is composed of iron ore, which is the main raw material, auxiliary raw materials (limestone, etc.) required for the sintering reaction and composition adjustment, miscellaneous raw materials (steelmaking dust, etc.), and return ore. The sintering carbonaceous material is used as a heat source, and is, for example, coke for steelmaking or anthracite.

[0003] The blended raw materials stored in the hopper are loaded onto the pallet through a drum feeder and a chute. This forms a raw material packed layer on the pallet. The surface of the raw material packed layer is then ignited in an ignition furnace. The raw material packed layer is then sintered by being sucked downward, and after sintering is complete, it is discharged from the pallet as sintered ore (discharged ore).

[0004] In such a method for producing sintered ore, in order to improve the productivity of sintered ore, it is necessary to improve the yield and the firing rate.

[0005] In order to improve the productivity of sintered ore, attempts have been made to improve the combustion properties of carbonaceous materials for sintering. Specifically, the use of highly combustible carbonaceous materials has been considered.

[0006] Here, highly combustible carbonaceous materials refer to carbonaceous materials whose combustion initiation temperature is 550°C or less when measured using the combustion initiation temperature measurement method described below. Examples of highly combustible carbonaceous materials include some plant-derived carbonaceous materials and some carbonized products (part of coal char) of allochthonous and suballochthonous coals. Note that commonly used coke for steelmaking and anthracite are often classified as low combustible carbonaceous materials. Low combustible carbonaceous materials refer to carbonaceous materials whose combustion initiation temperature is higher than 550°C when measured using the above-mentioned method.

[0007] Here, we explain the method for measuring the combustion initiation temperature. A 10 mg sample was placed on a thermobalance (Rigaku Thermo Plus Evo2 TG-DTA8120 / H-IR Smart Loader) and heated at a heating rate of 100 °C / min with air flowing at 200 mL / min. The weight loss was measured, and the reaction rate dX / dt at each reaction rate was calculated from the resulting data on reaction time t and reaction rate X (X = weight loss at each time / initial sample weight). The temperature at which dX / dt = 0.00015 was measured and defined as the combustion initiation temperature. (Note: Weight loss at temperatures below 250 °C was excluded because it may be due to the removal of moisture contained in the carbonaceous material.)

[0008] It is said that the use of highly combustible carbon materials can improve the firing speed and the yield by reducing unburned carbon.

[0009] For example, in Patent Document 1, palm kernel shell charcoal, a highly combustible carbonaceous material, is used as coarse particles. By using palm kernel shell charcoal as coarse particles, the firing rate of the entire raw material packed bed is adjusted so that it does not become too fast, thereby improving the yield.

[0010] In Patent Document 2, palm kernel shell charcoal, a highly combustible carbonaceous material, is also used as coarse particles. However, in Patent Document 2, palm kernel shell charcoal is used as coarse particles, and coke breeze is used that is finer than palm kernel shell charcoal, thereby adjusting the firing rate of the upper layer to be slow and the firing rate of the lower layer to be fast, thereby achieving an improvement in yield. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-78397 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-237876 Summary of the Invention [Problem to be solved by the invention]

[0012] Sintered ore is required to suppress reduction disintegration when used in a blast furnace. That is, sintered ore is also required to improve its RDI (reduce its RDI value). The RDI value is measured by the method described in JIS M 8720.

[0013] However, the techniques disclosed in Patent Documents 1 and 2 may not improve the RDI value of sintered ore, especially that produced on the bottom side of the pallet, and it has been desired to obtain a stable improvement effect.

[0014] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a method for producing sintered ore that can improve the RDI of sintered ore while maintaining or improving the productivity of sintered ore. [Means for solving the problem]

[0015] The gist of the present invention is as follows. (1) A method for producing sintered ore using a highly combustible carbonaceous material as part of a carbonaceous material for sintering, The carbonaceous material for sintering contains 20 to 60 mass% of a highly combustible carbonaceous material having a particle size distribution in which particles having a particle size of 2.8 mm or more: 25 mass% or more, particles having a particle size of 5 mm or more: 15 mass% or less, and particles having a particle size of less than 0.6 mm: 40 mass% or less, and the remainder of the carbonaceous material for sintering is a low combustible carbonaceous material having a particle size distribution in which particles having a particle size of less than 1 mm: 40 mass% or more, A method for producing sintered ore, characterized in that the carbonaceous material for sintering is mixed with a sintering raw material to form a blended raw material, and the blended raw material is charged using a segregation charging device that segregates coarse particles to the bottom side of a pallet. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for producing sintered ore that can improve the RDI of sintered ore while maintaining or improving the productivity of sintered ore. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a side cross-sectional view showing an overview of a sintering machine according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0019] First, a method for producing sintered ore according to this embodiment will be described with reference to Fig. 1. The method for producing sintered ore is performed by a sintering machine 1 shown in Fig. 1. The sintering machine 1 has a belt conveyor 10, a hopper 11, a drum feeder 12, a chute 13, a segregation charging device 14, a ventilation bar 15, a stand 16, a pallet 17, and an ignition furnace 18.

[0020] First, the sintering raw material and the sintering carbonaceous material are blended to form blended raw material A, which is then transported to a hopper 11 by a belt conveyor 10. The sintering raw material is composed of an iron-based raw material as the main raw material, auxiliary raw materials necessary for the sintering reaction and component adjustment, miscellaneous raw materials, and return ore. The iron-based raw material is, for example, iron ore such as fine ore. The auxiliary raw materials are, for example, limestone, quicklime, dolomite, converter slag, serpentine, silica, and peridotite. The miscellaneous raw materials are, for example, recycled iron-containing raw materials such as iron-making dust, steel-making dust, and scale.

[0021] Instead of simply blending the sintering raw material and the carbonaceous material for sintering, the sintering raw material may first be granulated in a drum mixer or the like, and the surface of the granulated material may be coated with the carbonaceous material for sintering. In this case, the same effect as in this embodiment can be obtained.

[0022] The carbonaceous material for sintering is contained in about 2.0 to 6.0 mass% of blended raw material A and is composed of a high combustibility carbonaceous material and a low combustibility carbonaceous material. A high combustibility carbonaceous material refers to a carbonaceous material whose combustion initiation temperature is 550°C or less when measured using the combustion initiation temperature measurement method described below.

[0023] Here, we explain the method for measuring the combustion initiation temperature. A 10 mg sample was placed on a thermobalance (Rigaku Thermo Plus Evo2 TG-DTA8120 / H-IR Smart Loader) and heated at a heating rate of 100 °C / min with air flowing at 200 mL / min. The weight loss was measured, and the reaction rate dX / dt at each reaction rate was calculated from the resulting data on reaction time t and reaction rate X (X = weight loss at each time / initial sample weight). The temperature at which dX / dt = 0.00015 was measured and defined as the combustion initiation temperature. (Note: Weight loss at temperatures below 250 °C was excluded because it may be due to the removal of moisture contained in the carbonaceous material.)

[0024] Highly combustible carbonaceous materials have a particle size distribution in which particles with a particle size of 2.8 mm or larger are 25% by mass or more, particles with a particle size of 5 mm or larger are 15% by mass or less, and particles with a particle size of less than 0.6 mm are 40% by mass or less. Examples of highly combustible carbonaceous materials include some plant-derived carbonaceous materials and some carbonized products (parts of coal char) of allochronic and sub-allochronic coals. The mass percentages here are values ​​relative to the total mass of the highly combustible carbonaceous materials. Furthermore, the particle size is the value obtained by sieving. When carbonaceous materials are sieved through a sieve with an opening size of X mm, the particles remaining on the sieve have a particle size of X mm or larger, and the particles that fall through the sieve have a particle size of less than X mm. Highly combustible carbonaceous materials begin to burn at a relatively low temperature, which allows for a fast burning rate when firing raw materials for sintering, and reduces the amount of unburned carbon remaining.

[0025] The highly combustible carbonaceous material according to this embodiment is relatively coarse-grained, containing 25% by mass or more of particles with a particle size of 2.8 mm or more and 40% by mass or less of particles with a particle size of less than 0.6 mm. However, the highly combustible carbonaceous material is not extremely coarse-grained, containing 15% by mass or less of particles with a particle size of 5 mm or more.

[0026] Details will be described later, but in this embodiment, coarse particles (for example, particles with a particle size of 2.8 mm or more, particles with a particle size of 5 mm or more) of the highly combustible carbonaceous material are segregated to the lower layer side of the raw material packed bed B (the bottom side of the pallet 17).

[0027] The lower layer of the raw material packed bed B is prone to overheating due to the high-temperature exhaust gas passing through it during suction, making it difficult to cool. For this reason, the RDI of the sintered ore produced at the lower layer of the raw material packed bed B tends to deteriorate. Therefore, in this embodiment, coarse-grained highly combustible carbonaceous material is segregated at the lower layer of the raw material packed bed B. This improves air permeability around the coarse-grained highly combustible carbonaceous material (the large gaps between the coarse particles improve air permeability). Therefore, the sintered body after sintering, i.e., the sintered ore, is quickly cooled (quenched) even if the cooling gas is high-temperature exhaust gas. Furthermore, the highly combustible carbonaceous material is quickly combusted and disappears, so the sintered ore is also quickly cooled in this respect. This improves the RDI.

[0028] The mechanism by which rapid cooling improves RDI is due to changes in the sinter structure. Specifically, magnetite present in sinter is oxidized during cooling to form secondary hematite, and rapid cooling significantly reduces the amount of secondary hematite formed. During reduction in the blast furnace, magnetite is re-formed from the secondary hematite, but the volume expansion at this time causes cracks, which lead to reduction disintegration. Therefore, if the amount of secondary hematite formed is reduced in advance by rapid cooling during sinter production, it is possible to suppress the amount of reduction disintegration in the blast furnace.

[0029] Furthermore, improved air permeability means that the firing reaction itself proceeds faster, improving the firing rate. Furthermore, since unburned carbon is less likely to remain, the yield also improves. Therefore, the productivity of sintered ore (firing rate x yield) also improves.

[0030] Furthermore, in the highly combustible carbonaceous material according to this embodiment, the content of particles having a particle size of 5 mm or more is 15% by mass or less, so the particles are not extremely coarse. Therefore, the coarse particles are evenly charged in the lower layer of the raw material packed bed B. Therefore, uneven ventilation is suppressed, and the above-mentioned effect is evenly achieved in the lower layer of the raw material packed bed B.

[0031] Furthermore, the content of the highly combustible carbonaceous material relative to the total carbonaceous material for sintering is 20 to 60% by mass. If the content of the highly combustible carbonaceous material is less than 20% by mass, the above-mentioned effects cannot be fully achieved. If the content of the highly combustible carbonaceous material exceeds 60% by mass, the combustion start temperature of the carbonaceous material for sintering tends to decrease, which leads to a shortening of the holding time of the sintering raw material in the firing temperature range (also called high-temperature holding time). Therefore, if the high-temperature holding time is insufficient, the firing of the sintering raw material does not progress, leading to a decrease in yield and a deterioration in RDI.

[0032] The remainder of the carbonaceous material for sintering is composed of low combustibility carbonaceous material. Low combustibility carbonaceous material refers to carbonaceous material whose combustion start temperature is higher than 550°C as measured by the above-mentioned method. The low combustibility carbonaceous material according to this embodiment has a particle size distribution in which particles with a particle size of less than 1 mm account for 40% by mass or more. Here, the mass % is a value relative to the total mass of the low combustible carbonaceous material. The particle size is a value obtained by classification using a sieve. Details are as described above. Examples of low combustibility carbonaceous material include coke for steelmaking and anthracite.

[0033] Since the low combustibility carbonaceous material is fine-grained, it is layered on the upper side of the raw material packed bed. As mentioned above, the high combustibility carbonaceous material tends to segregate on the lower side of the raw material packed bed B, so the upper side of the raw material packed bed B is prone to heat shortage. Therefore, by layering the low combustibility carbonaceous material on the upper side of the raw material packed bed B, the heat shortage on the upper side of the raw material packed bed B is compensated for.

[0034] Furthermore, by stacking low combustible carbonaceous material on the upper layer side of the raw material packed bed B, the high temperature retention time of the upper layer side of the raw material packed bed B is extended, thereby improving the yield. In this way, in this embodiment, by including not only high combustible carbonaceous material but also low combustible carbonaceous material in the carbonaceous material for sintering, the drawbacks of high combustible carbonaceous material can be compensated for and the yield can be improved.

[0035] The blended raw material A stored in the hopper 11 is fed onto the pallet 17 through the drum feeder 12 and the chute 13 .

[0036] The blended raw material A sliding down the chute 13 is charged onto a pallet 17 via a segregation charging device 14 provided at the tip of the chute 13, and is stacked to a depth of about 400 to 800 mm. This forms a raw material packed bed B.

[0037] Here, the segregation charging device 14 may be, for example, one that uses a rod arranged parallel to the direction in which the sintering raw material or the like slides down, as disclosed in Japanese Patent Application Laid-Open No. 2014-077573, or one that uses a rod arranged perpendicular to the direction in which the sintering raw material or the like slides down, as disclosed in Japanese Patent Application Laid-Open No. 2018-48360, or any other device that segregates the blended raw material A according to the particle size of the blended raw material A that slides down.

[0038] In particular, in this embodiment, coarse particles (especially coarse highly combustible carbonaceous materials) of the blended raw material A are segregated to the lower layer side of the raw material packed bed B. This achieves the above-mentioned effect, i.e., the effect of improving the RDI while maintaining high productivity. Note that the coarse particles in this embodiment include particles having a particle size of at least 2.8 mm or more.

[0039] Here, a segregation charging device may be used to segregate the coarse particles to the lower layer side of the raw material packed bed B. When a known segregation charging device such as that disclosed in JP 2014-077573 A or JP 2018-48360 A is used, when the depth direction of the pallet 17 is divided into six equal parts, the highly combustible carbonaceous material in the sixth layer (the lowest layer) tends to account for 30 mass % or more of the total mass of the sixth layer, and can be increased to 43 mass % or more by optimizing the position and angle of the rods constituting the segregation charging device 14.

[0040] When the blended raw material A is loaded into the pallet 17, means for improving ventilation during sintering, such as ventilation bars 15 and stands 16 inside the pallet 17, may be used. The ventilation bars 15 and stands 16 may be omitted.

[0041] The surface of the raw material packed bed B is ignited in an ignition furnace 18, fired, and after firing is completed, the sintered ore (sinter cake C) is discharged from a pallet 17 (discharged).

[0042] The raw material packed bed B is fired by sucking gas, mainly air, from above the raw material packed bed B (atmospheric suction) and utilizing the heat generated by oxidation of the sintering carbonaceous material contained in the raw material packed bed B.

[0043] Here, the sintering raw materials in the raw material packed bed B are first heated by gas drawn in from above (exhaust gas heated by passing through the red hot zone during firing). Then, the sintering raw materials reach a maximum temperature (1200-1600°C) as they pass through the red hot zone descending through the raw material packed bed B, completing the firing and becoming sintered ore, and then are cooled by gas drawn in from above (atmosphere).

[0044] In this way, sinter (sinter raw material) undergoes a thermal history of starting heating, heating, reaching the maximum temperature, and cooling. The inventors noticed that the RDI value (the degree of reduction and disintegration of sinter in a blast furnace; a low RDI value means that reduction and disintegration in a blast furnace is less likely to occur) changes depending on the cooling rate (slow or rapid cooling). For this reason, the highly combustible carbonaceous material is segregated as coarse particles in the lower layer of the raw material packed bed B, and the less combustible carbonaceous material is segregated as fine particles in the upper layer of the raw material packed bed B.

[0045] As described above in detail, the lower layer of the raw material packed bed B is difficult to cool because high-temperature exhaust gas passes through it. Therefore, by segregating coarse-grained highly combustible carbonaceous material to the lower layer of the raw material packed bed B, the permeability of the lower layer of the raw material packed bed B is improved. As a result, even if the cooling gas is high-temperature exhaust gas, the sintered body after sintering is quickly cooled (quenched). This improves the RDI.

[0046] Furthermore, improved air permeability means that the firing reaction itself proceeds faster, improving the firing rate. Furthermore, since unburned carbon is less likely to remain, the yield also improves. Therefore, the productivity of sintered ore (firing rate x yield) also improves.

[0047] Furthermore, in the highly combustible carbonaceous material according to this embodiment, the content of particles having a particle size of 5 mm or more is 15% by mass or less, so the particles are not extremely coarse. Therefore, the coarse particles are evenly charged in the lower layer of the raw material packed bed B. Therefore, uneven ventilation is suppressed, and the above-mentioned effect is evenly achieved in the lower layer of the raw material packed bed B.

[0048] On the other hand, in the upper layer of the raw material packed bed B, the high combustibility carbonaceous material segregates to the lower layer, which easily causes a heat shortage. Therefore, by stacking the low combustibility carbonaceous material on the upper layer of the raw material packed bed B, the heat of the upper layer of the raw material packed bed B is compensated for. In particular, by stacking the low combustibility carbonaceous material on the upper layer of the raw material packed bed B, the high temperature retention time of the upper layer of the raw material packed bed B is extended, thereby improving the yield. In this way, in this embodiment, by including not only the high combustibility carbonaceous material but also the low combustibility carbonaceous material in the carbonaceous material for sintering, the shortcomings of the high combustibility carbonaceous material can be compensated for and the yield can be improved.

[0049] As described above, according to this embodiment, it is possible to provide a method for producing sintered ore that can improve the RDI of sintered ore while maintaining or improving the productivity of sintered ore. [Example]

[0050] Next, an example of this embodiment will be described. In the example, a sintering test was carried out using a sintering pot with a diameter of 300 mm and a height of 500 mm. First, the raw materials used in the test and the test method will be explained, and then the test results will be described.

[0051] <1.Combination conditions> The composition of the blended raw materials is shown in Table 1. The iron-based raw materials (iron ore) and auxiliary raw materials are also referred to as new raw materials. The values ​​for new raw materials in Table 1 indicate the mass% of the total mass of new raw materials. The values ​​for return ore and sintering carbonaceous material indicate the mass% of the total mass of new raw materials (excluded figures).

[0052] The proportions of new raw materials (iron ore A to E, limestone, quicklime, peridotite powder, dolomite), sintering carbonaceous material, and return ore were kept constant throughout all tests. Moisture (6.5 to 8.0 mass% of the raw material mixture, with the raw material mixture being 100 mass%) was added to the raw materials, and then the materials were granulated using a drum mixer.

[0053] [Table 1]

[0054] <2. Blending conditions of carbonaceous materials for sintering> The blending conditions for the carbonaceous material for sintering are shown in Table 2. Coke breeze was used as the low combustibility carbonaceous material, and carbonized coal from all ages (also called semi-coke or semi-coke) was used as the high combustibility carbonaceous material, and each was granulated under the blending conditions shown in Table 2. In the particle size notation in Table 2, "+" indicates "more than" and "-" indicates "less than."

[0055] [Table 2]

[0056] <3. Creating a raw material packed bed> In the test conditions other than Comparative Example 7, the segregation charging device used was an example of the invention described in JP 2014-077573 A, with zero water supply (the blended raw material adhering to the bar was manually removed for each pot test). Specifically, the granulated material was dropped through a chute from above the segregation charging device, and the granulated material was collected in five collection boxes lined up below the segregation charging device from the upstream side to the downstream side of the chute. The granulated material of the blended raw material, classified and collected in the five collection boxes, was then charged into the test pot in order, starting with the downstream collection box. In Comparative Example 7, the segregation charging device was not used, and the granulated material of the blended raw material was charged directly into the test pot.

[0057] <4. Firing> The surface of the packed bed of raw materials was ignited for 1 minute (heat amount 25 MJ / ton of raw material) and fired. The suction negative pressure during ignition was adjusted with the motor inverter on the suction side of the blower so that it was constant at 1200 mmAq (11.8 kPa) as measured below the pot. After ignition, firing was carried out under constant airflow conditions, with the exhaust gas flow rate being 1.8 Nm 3 / min. Below the pot, the temperature was measured with a thermocouple along with the pressure. During the sintering reaction process, when the combustion zone reaches the bottom of the raw material packed bed, the exhaust gas temperature below the pot begins to rise, eventually peaks, and then drops as the combustion of the sintering carbonaceous material is completed. Three minutes after the exhaust gas temperature reaches its peak, the suction of the blower is stopped and the firing is completed. The firing rate is calculated by dividing the layer thickness by the time from the start of ignition to the time when the exhaust gas temperature reaches its peak, as shown in the following formula (Equation 1). Firing speed (mm / min) = layer thickness (mm) / time from ignition start to peak exhaust gas (min)...Equation 1

[0058] After sintering was completed, the resulting sinter cake was dropped four times from a height of 2 m, and the mass percentage of particles with a particle size of 5 mm or more, excluding bedding ore, was taken as the yield. Furthermore, the production index was calculated using the following formula 2. The production index is the value obtained by dividing the productivity (sintering rate x yield) in each example by the base productivity. Production index = {firing speed (mm / min) x yield (mass%)} / {base firing speed (mm / min) x base yield (mass%)} ... Equation 2

[0059] <5. Test Results> The test results are shown in Table 2. A production index of 1.02 or more was considered a pass level, and an RDI drop of 1 or more compared to the base RDI was considered a pass level. When both were pass levels, the evaluation was rated as O (pass). Inventive Examples 1 and 2 and Comparative Examples 4 and 5 were tests in which only the use ratio of the highly combustible carbonaceous material was changed, and when the use ratio was 20 to 60 mass%, both the effects of improving the production index and reducing (improving) the RDI were obtained. In other words, Inventive Examples 1 and 2 were evaluated as O.

[0060] In Comparative Example 4, the ratio of highly combustible carbonaceous material used was low, and almost no improvement in the production index was confirmed. In Comparative Example 5, the ratio of highly combustible carbonaceous material was high, and the firing of the sintering raw materials did not progress due to a shortened high-temperature holding time, and the effects of improving the production index and RDI due to improved yield were not obtained.

[0061] Comparative Example 1 is an example in which the ratio of highly combustible carbonaceous particles with a particle size of 2.8 mm or more was reduced compared to Invention Example 1, and almost no improvement in RDI or production index was confirmed. This is thought to be because the effect of improving air permeability and segregation due to the reduction in particle size was reduced.

[0062] In Comparative Example 2, the ratio of highly combustible carbonaceous particles with a particle size of 5 mm or more was increased compared to Invention Example 1, and a deterioration in RDI was confirmed. Although ventilation in the raw material packed bed before and during firing tends to be ensured through the gaps around the coarse-grained carbonaceous material for sintering, this is thought to be because an increase in the coarse particles caused uneven ventilation.

[0063] In Comparative Example 3, the ratio of highly combustible carbonaceous particles with a particle size of less than 0.6 mm was increased compared to Invention Example 1, and no improvement in RDI or production index was confirmed. In Comparative Example 3, the ratio of particles with a particle size of 2.8 mm or more was not changed compared to Invention Example 1, but the ratio of intermediate-sized particles (less than 2.8 mm, 0.6 mm or more) was reduced, and the ratio of particles with a particle size of less than 0.6 mm, which make it relatively difficult to ensure air permeability and to obtain the segregation effect in the lower layer of the raw material packed bed, increased, which is thought to be the reason for the reduced air permeability improvement effect and segregation effect due to the reduced particle size.

[0064] In Comparative Example 6, the ratio of low combustibility carbonaceous particles with a particle size of less than 1 mm was reduced compared to Invention Example 1, and almost no improvement in RDI or productivity index was confirmed. This is thought to be because in Comparative Example 6, the low combustibility carbonaceous materials were segregated to the lower layer of the raw material packed bed, causing a heat shortage in the upper layer and resulting in a deterioration in yield.

[0065] In Comparative Example 7, segregation by the segregation charging device was omitted from the test of Invention Example 1, and the RDI and production index decreased. This is thought to be because the segregation effect of the highly combustible carbonaceous material to the lower layer of the raw material packed bed became smaller, and the effects of improving the air permeability and RDI decreased.

[0066] The same effect was also obtained when raw materials other than carbonaceous materials for sintering, i.e., sintering raw materials, were first granulated in a drum mixer, and then the sintering raw materials were coated on the surface of the granulated material. This is thought to be because the particle size of the highly combustible carbonaceous materials was large, and in this case too, the highly combustible carbonaceous materials were segregated to the lower layer of the raw material packed bed.

[0067] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0068] 1. Sintering machine 10 conveyor belt 11 Hopper 12 Drum Feeder 13 Shoot 14 Segregation charging device 15 Ventilation bar 16 Stand 17 Palettes 18 Ignition furnace A Mixed raw materials B Raw material packed bed C Sinter cake

Claims

[Claim 1] A method for producing sintered ore using a highly combustible carbonaceous material as part of a carbonaceous material for sintering, The carbonaceous material for sintering contains 20 to 60 mass% of a highly combustible carbonaceous material having a particle size distribution in which particles having a particle size of 2.8 mm or more: 25 mass% or more, particles having a particle size of 5 mm or more: 15 mass% or less, and particles having a particle size of less than 0.6 mm: 40 mass% or less, and the remainder of the carbonaceous material for sintering is a low combustible carbonaceous material having a particle size distribution in which particles having a particle size of less than 1 mm: 40 mass% or more, A method for producing sintered ore, characterized in that the carbonaceous material for sintering is mixed with a sintering raw material to form a blended raw material, and the blended raw material is charged using a segregation charging device that segregates coarse particles to the bottom side of a pallet.

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