Method for manufacturing sintered ore

Abstract

To improve a yield and a production rate in a two-stage loading and two-stage ignition method.SOLUTION: A manufacturing method of sintered ore includes a step for loading a lower-stage blended granular raw material in a sintering machine to form a lower-stage raw material packed bed, a step for loading an upper-stage blended granular raw material on the lower-stage raw material packed bed to form an upper-stage raw material packed bed, and a step for igniting each of the surface of the lower-stage raw material packed bed and the surface of the upper-stage raw material packed bed and introducing a gas containing oxygen at atmospheric pressure into the lower-stage raw material packed bed and the upper-stage raw material packed bed by downward suction. At least part of the gas downward suctioned from the surface side of the upper-stage raw material packed bed after the upper-stage raw material packed bed is ignited is oxygen-enriched gas of an oxygen concentration of 26 vol.% or more and 46 vol.% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing sintered ore for blast furnace raw materials, particularly a two-stage charging and two-stage ignition sintering method.

Background Art

[0002] Sintered ore, which is the main raw material for blast furnace ironmaking, is usually produced as follows. First, as raw materials for sintered ore production, iron raw materials such as iron ore (powder), iron-containing miscellaneous raw materials such as scale and steelmaking dust, MgO-containing auxiliary raw materials such as peridotite, CaO-containing auxiliary raw materials such as limestone, return ore, and carbonaceous materials (condensing materials) that serve as fuels for sintering (condensing) sintered ore by combustion heat are mixed at a predetermined ratio. The mixed blended raw materials are granulated to obtain blended raw material granules. Next, the blended raw material granules are loaded onto a pallet (sintering pallet) of a downward suction type Dwight Lloyd (DL) sintering machine from a hopper to form a packed bed of the blended raw materials (hereinafter referred to as the raw material packed bed or raw material layer). From the upper part (surface) of the formed raw material packed bed, ignition is carried out on the carbonaceous material inthe raw material packed bed by an ignition furnace. Then, while continuously moving the pallet, air is sucked from below the pallet. By suction, oxygen is supplied into the raw material packed bed, and the combustion of the carbonaceous material in the raw material packed bed proceeds from the upper part to the lower part, and the raw material packed bed is sequentially sintered by the combustion heat of the carbonaceous material. The sintered part (sinter cake) obtained by sintering is sized by crushing, screening, etc. to a predetermined particle size to become sintered ore, which is a raw material for a blast furnace.

[0003] In such a method for producing sintered ore by a DL type sintering machine, Patent Document 1 proposes a multi-stage charging and multi-stage ignition sintering method in which the formation and ignition of the raw material packed bed are carried out in two or more stages. In a two-stage charging and two-stage ignition sintering method (hereinafter also referred to as the two-stage charging and two-stage ignition method), which is an example of the multi-stage charging and multi-stage ignition sintering method, the granulated blended raw materials are charged in two steps in the layer height direction of the sintering machine in order to form two-stage raw material packed beds (upper-stage raw material packed bed and lower-stage raw material packed bed), and ignition is carried out on the surface of each raw material packed bed, and air is sucked from below to cause the sintering reaction of each layer to proceed simultaneously and in parallel for sintering.

[0004] In the two-stage charging, two-stage ignition sintering method, the raw material packing bed is divided into two stages, and sintering proceeds simultaneously in both stages, resulting in nearly double the production volume. Furthermore, the exhaust gas used for sintering the upper raw material packing bed (hereinafter referred to as the upper layer) is reused for sintering the lower raw material packing bed (hereinafter referred to as the lower layer) by downward suction, which has the advantage of reducing (halving) the amount of exhaust gas. On the other hand, the gas (exhaust gas) used for sintering the upper layer, which has a reduced oxygen partial pressure, is used for sintering the lower layer, resulting in sintering under low oxygen partial pressure conditions in the lower layer. Therefore, the combustion of the carbon material in the lower layer becomes incomplete, the amount of heat required for sintering is insufficient, the progress of the sintering reaction is hindered, and the strength of the sintered ore in the lower layer is reduced.

[0005] In response to this, a proposal has been made to enrich the aspirated gas with oxygen. Patent Document 2 discloses a technique for measuring the oxygen concentration in the main exhaust gas drawn from the entire sintering machine and adjusting the oxygen concentration in the gas drawn from the surface of the raw material layer (hereinafter referred to as "drawn gas") so that the oxygen concentration is 6% or higher. In the examples, the range of oxygen concentrations of the drawn gas from 21% to 25% was verified, and the effect of improving strength through oxygen enrichment was confirmed.

[0006] Furthermore, Patent Document 3 discloses a method for supplying pressurized oxygen-containing gas in a two-stage charging, two-stage ignition sintering method. It states that the oxygen concentration of the pressurized oxygen-containing gas is preferably 12 to 40%.

[0007] Furthermore, Patent Document 4 discloses a technique for realizing a two-stage ignition sintering method by igniting the upper surface of a charge layer (raw material packed layer) formed in a single-stage charge with an ignition furnace, and also igniting the middle section of the upstream end of the charge layer from the side with a burner. It also proposes resolving insufficient combustion of the lower layer by enriching the intake gas with oxygen downstream of the ignition furnace. In the examples, the range of intake gas oxygen concentration from 21% to 46% was verified, and improvements in production rate and strength due to oxygen enrichment were confirmed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 47-26304 [Patent Document 2] Japanese Patent Application Publication No. 62-60828 [Patent Document 3] Japanese Patent Publication No. 2000-17343 [Patent Document 4] Japanese Patent Publication No. 2015-157980 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the verification of the two-stage charging and two-stage ignition method described in Patent Document 2 does not examine the region where the oxygen concentration of the aspirated gas exceeds 25%. Furthermore, the oxygen-containing gas aspirated in Patent Document 3 is under pressurized conditions, and there is no indication of a two-stage charging and two-stage ignition method using gas aspirated gas at normal atmospheric pressure.

[0010] Furthermore, Patent Document 4 discloses verification results when applying two-stage ignition technology to a single-stage charging method, which involves charging the raw materials all at once to form a single charging layer. When the blended raw materials are filled into the sintering machine pallet via the charging chute, they are charged with particle size segregation, where smaller particles are mostly placed on the upper side of the raw material layer, and larger particles are mostly placed on the lower side. As a result, for example, carbon material consisting of fine particles is mostly distributed on the upper side of the raw material layer. In the single-stage charging method, the lower layer has a coarser particle size and a lower carbon material concentration compared to the lower layer in the two-stage charging method, where each charging layer is formed in two stages. On the other hand, it is generally known that such differences in particle size segregation and carbon material distribution in the layer thickness (layer height) direction change firing conditions such as the internal layer temperature and permeability during sintering, affecting yield and productivity.

[0011] Furthermore, in the technology described in Patent Document 4, the lower layer is ignited by applying a flame from the side to the middle section of the upstream end of the charging layer. Since the charging layer on the pallet moves toward the discharge end along with the pallet, the ignition time is inevitably shorter compared to ignition by an ignition furnace in the two-stage ignition method. In addition, the granulated raw material supplied from the hopper enters the space between the lower layer and the flame during ignition. Therefore, in actual operation, the amount of heat input to the lower layer decreases, and there is a risk that the sintering reaction will not proceed sufficiently. Since the flame is blown toward the slope which is the upstream end of the charging layer, it is thought that it may also affect particle size segregation. For the reasons described above, the inventors concluded that the effect of oxygen enrichment of the suction gas in the two-stage charging and two-stage ignition method cannot be assumed from the findings of Patent Document 3.

[0012] In view of the above problems, the inventors attempted to investigate the impact on yield and productivity (production rate) when the oxygen concentration of the gas drawn in at atmospheric pressure is set to a high oxygen concentration range of over 25% in a two-stage charging, two-stage ignition method.

[0013] The object of the present invention is to provide a method for producing sintered ore that enables improvement in yield and production rate in a two-stage charging and two-stage ignition method. [Means for solving the problem]

[0014] This invention was made to solve the above-mentioned problems, and its gist is as follows. (1) A step of forming a lower raw material packed layer by charging the lower system's blended raw material granules into the sintering machine, The process involves loading the upper-stage blended raw material granules onto the lower-stage raw material packed layer to form the upper-stage raw material packed layer, The process includes igniting the surface of the lower raw material packed layer and the surface of the upper raw material packed layer, respectively, and introducing an oxygen-containing gas into the lower raw material packed layer and the upper raw material packed layer at atmospheric pressure by downward suction. A method for producing sintered ore, characterized in that at least a portion of the gas drawn downward from the surface side of the upper raw material packed bed after the ignition of the upper raw material packed bed is completed is an oxygen-enriched gas with an oxygen concentration of 26% by volume or more and 46% by volume or less. (2) The method for producing sintered ore according to (1), characterized in that, in the machine length direction of the sintering machine, the intermediate position is defined as the middle of the section from the outlet of the upper ignition furnace to the end of the ore discharge, and the section from the outlet of the upper ignition furnace to the intermediate position is defined as the first half section, and the region to which the oxygen-enriched gas is supplied is a region that includes a part of the first half section. (3) In the direction of the length of the sintering machine, when the intermediate position in the section from the outlet of the upper ignition furnace to the end of the ore discharge is defined as the intermediate position, the section from the outlet of the upper ignition furnace to the intermediate position is defined as the first half section, and the section from the intermediate position to the end of the ore discharge is defined as the second half section, The method for producing sintered ore according to (1), characterized in that the region to which the oxygen-enriched gas is supplied includes at least the portion corresponding to the first half section, and the portion corresponding to the first half section is longer than the portion corresponding to the second half section. (4) In the length direction of the sintering machine, when the intermediate position between the upper ignition furnace outlet and the ore discharge end is defined as the intermediate position, and the section from the upper ignition furnace outlet to the intermediate position is defined as the first half section, The method for producing sintered ore according to (1), characterized in that the region to which the oxygen-enriched gas is supplied is the first half section or a part of the first half section. (5) A method for producing sintered ore according to any one of (1) to (4), characterized in that a highly combustible carbon material with a combustion rate of 0.0022 (1 / sec) or more at 700°C is blended as a blending material for the lower raw material packed bed. (6) The method for producing sintered ore according to (5), characterized in that the highly combustible coal material includes char obtained by carbon distillation of coal with a logger index of less than 10. (7) The method for producing sintered ore according to (5), characterized in that the highly combustible carbon material includes oil palm kernel shell carbon. [Effects of the Invention]

[0015] According to the present invention, in the two-stage ignition method, after the completion of the upper-stage ignition, by sucking an oxygen-enriched gas having an oxygen concentration of 26% by volume (vol%) or more and 46% by volume (vol%) or less from the surface of the upper-stage layer, the yield and productivity can be improved.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic diagram showing a sintered ore manufacturing process by a two-stage charging two-stage ignition sintering method which is an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a two-stage charging two-stage ignition sintering method which is an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing a sintered ore manufacturing process by a two-stage charging two-stage ignition sintering method in which granulated blended raw materials are charged in two stages to form an upper-stage raw material filling layer (hereinafter referred to as the upper-stage layer) and a lower-stage raw material filling layer (hereinafter referred to as the lower-stage layer), and ignition is performed on each of the upper-stage layer and the lower-stage layer to carry out sintering.

[0018] First, an example of a two-stage charging two-stage ignition sintering method as a conventional technique will be described. In the example shown in FIG. 1, the upper-stage blended raw materials for forming the upper-stage layer 20 and the lower-stage blended raw materials for forming the lower-stage layer 10 are prepared in separate lines (two lines) and charged onto the pallet (not shown) of the sintering machine 100 in separate lines. Specifically, the raw materials for the lower stage are stored in each raw material tank (1D1 to 1D X ) of the lower-stage raw material tank group 1D, and the required types and amounts of raw materials are cut out and blended at a predetermined ratio. The blended lower-stage raw materials (lower-stage blended raw materials) are put into the lower-stage drum mixer 1A and mixed, and moisture is added for granulation. Also, the upper-stage raw materials are in each raw material tank (2D1 to 2D) of the upper-stage raw material tank group 2D yThe raw materials are stored in the ) and the required types and quantities are cut out in predetermined proportions and blended. The blended raw materials for the upper stage (upper stage blended raw materials) are put into the upper stage drum mixer 2A, mixed, and then water is added to granulate them. Powdered coke and anthracite are used as the carbon material for the lower and upper stage raw materials. For example, when both powdered coke and anthracite are used as raw materials, they may be stored in separate raw material tanks, or powdered coke and anthracite may be mixed in predetermined proportions and stored in one raw material tank.

[0019] The granulated lower-stage blending material (granulated lower-stage blending material) is charged from the lower-stage hopper 1B onto a pallet covered with bedding ore to form the lower-stage layer 10 (lower-stage raw material packed layer). The lower-stage layer 10 moves to below the lower-stage ignition furnace 1C by moving the pallet in the direction of pallet movement 5, where the carbon material on the surface of the lower-stage layer 10 is ignited by the lower-stage ignition furnace 1C. After ignition, sintering of the lower-stage layer 10 is started by downward suction 6, which draws air from below through a wind box (not shown in the figure) below the pallet. The sintering of the lower-stage layer 10 progresses downward due to the subsequent downward suction 6, forming the lower-stage combustion zone 10A.

[0020] When the lower layer 10, which has begun sintering, moves to below the upper hopper 2B, the upper blending material (upper blending material granules) granulated by the upper drum mixer 2A is charged from the upper hopper 2B onto the ignited lower layer 10, forming the upper layer 20 (upper raw material filled layer). The upper layer 20 moves to below the upper ignition furnace 2C by moving the pallet in the direction of pallet movement 5, where the carbon material on the surface of the upper layer 20 is ignited by the upper ignition furnace 2C. After ignition, sintering of the upper layer 20 begins due to downward suction 6. The sintering of the upper layer 20 proceeds downward due to the subsequent downward suction 6, forming the upper layer combustion zone 20A.

[0021] The lower layer combustion zone 10A of the lower layer 10 and the upper layer combustion zone 20A of the upper layer 20 undergo sintering simultaneously and descend due to further downward suction 6. When the lower layer combustion zone 10A and the upper layer combustion zone 20A reach the bottom of their respective layers, sintering due to the combustion of the carbon material is completed, and the lower layer 10 and the upper layer 20 become sintered sections 3. Finally, the sintered sections 3, once sintering is complete, are discharged from the end of the pallet.

[0022] The present invention relates to a method for producing sintered ore, comprising the steps of: forming a lower raw material packed layer by charging lower-stage blended raw material granules into a sintering machine; forming an upper raw material packed layer by charging upper-stage blended raw material granules onto the lower raw material packed layer; and igniting the surfaces of the lower and upper raw material packed layers, respectively, while introducing oxygen-containing gas into the lower and upper raw material packed layers at atmospheric pressure by downward suction. The gas drawn downward at atmospheric pressure from the surface side of the upper raw material packed layer after ignition of the upper raw material packed layer is an oxygen-enriched gas with an oxygen concentration of 26 vol% to 46 vol%. Specifically, as shown in Figure 1, the sintering machine 100 is equipped with an oxygen-enriched gas supply device 7. The oxygen-enriched gas supply device 7 has a hood 8 and a gas pipe 9 that supplies oxygen-enriched gas into the hood 8, and supplies oxygen-enriched gas with an oxygen concentration of 26 vol% to 46 vol% above (surface side of) the upper raw material packed layer. The supplied oxygen-enriched gas is guided into the raw material packed bed by the downward suction 6 of the wind box, where the sintering reaction proceeds, and is recovered as exhaust gas by the wind box. Alternatively, without providing the hood 8, oxygen gas may be injected from the gas pipe 9 toward the surface of the upper raw material packed bed and drawn in along with the atmosphere. In this case, the amount of oxygen gas injected from the gas pipe 9 is adjusted so that the oxygen concentration on the surface of the upper raw material packed bed is between 26 vol% and 46 vol%.

[0023] The preferred range (region) for supplying oxygen-enriched gas will be described below, with the intermediate position Z defined as the middle position of the section from the upper ignition furnace outlet X to the ore discharge end Y (the entire section) in the machine length direction (pallet travel direction 5) of the sintering machine 100, the section from the upper ignition furnace outlet X to the intermediate position Z as the first half section, and the section from the intermediate position Z to the ore discharge end Y as the second half section.

[0024] The section where the hood 8 is provided, that is, the area where oxygen-enriched gas is supplied to the surface of the raw material packed bed (oxygen-enriched region), is preferably a region that includes a part of the first half section (the section from the upper ignition furnace outlet X to the intermediate position Z) in the longitudinal direction of the sintering machine 100. Furthermore, it is preferable that it includes at least a portion corresponding to the first half section, and that the portion corresponding to the first half section is longer than the portion corresponding to the second half section (the section from the intermediate position Z to the ore discharge end Y). Moreover, it is more preferable that the area where oxygen-enriched gas is supplied to the surface of the raw material packed bed (oxygen-enriched region) is the first half section, or a part of the first half section.

[0025] The basis for this is that, in the examples described later, it was found that the supply range of oxygen-enriched gas was more effective when it was limited to the range from the upper ignition furnace outlet X to the intermediate position Z (the first half of the process), or a part of that range (a part of the first half of the process), rather than the range from the intermediate position Z to the end of the mine discharge Y (the second half of the process). Furthermore, when the oxygen-enriched region is limited to a part of the entire process, the reason why oxygen enrichment in the first half of the process is more effective than oxygen enrichment in the second half of the process is thought to be as follows.

[0026] Oxygen enrichment is performed to improve the situation where carbon combustion in the lower layer is inactive (incomplete) due to oxygen deficiency. In sections where oxygen enrichment is performed, carbon combustion becomes more active, and the temperature inside the sintering machine can be maintained at an appropriate high temperature. If oxygen enrichment is performed in the first section, the high temperature maintained in the first section will keep the temperature inside the sintering machine high even if oxygen enrichment is not performed in the second section, allowing the sintering reaction to proceed. On the other hand, if oxygen enrichment is not performed in the first section but is performed in the second section, carbon combustion will be inactive in the first section, causing the temperature inside the sintering machine to drop. Therefore, even if oxygen enrichment is performed in the second section, it will be difficult to sufficiently recover the temperature inside the sintering machine. For this reason, oxygen enrichment in the first section is preferable.

[0027] Furthermore, in sintering machines, particle size segregation is introduced during the charging of the blending materials, resulting in a higher concentration of finer-grained carbon materials compared to the main raw materials such as iron ore at the top. For this reason, in a two-stage charging and two-stage ignition system, the upper layer contains more carbon materials than the lower layer in both the lower and upper layers. Since a larger amount of carbon materials requires more oxygen for combustion, it is preferable to enrich the oxygen in the first half of the combustion section, which corresponds to the upper part of the layer. If the oxygen enrichment region is limited to reduce the cost of oxygen gas, it is preferable for the above reasons to include at least a portion of the first half of the region (each region described in paragraph 0024).

[0028] The formulations for the upper and lower layers of the mixture may be the same or different. Furthermore, if the formulations are the same, the upper and lower layers of the mixture may be prepared in the same system rather than in separate systems (two systems).

[0029] Here, as will be shown in the examples described later, in the method for producing sintered ore of the present invention, it is preferable to use a highly combustible carbon material for part or all of the carbon material used as raw material for the lower stage. A highly combustible carbon material is a carbon material (coagulant) with a combustion rate at 700°C (combustion rate (700°C)) of 0.0022 (1 / sec) or higher, as illustrated in Table 1, and includes coal char, oil palm kernel shell char (PKS char), and charcoal char produced by carbon distillation of wood. It should be noted that highly combustible carbon materials have a lower combustion start temperature than coke and anthracite.

[0030] [Table 1]

[0031] PKS coal is a solid carbide produced by heat treatment (carbonization) of oil palm kernel shells. Coal char, on the other hand, is a sintering material (char) produced by carbonization of low-fluidity coal, such as coal with a logger index of less than 10, as the raw material. Coal char is produced by carbonization of raw coal (including mixed coal) in a pyrolysis furnace (e.g., a rotary kiln). By using low-fluidity coal with a logger index of less than 10 as the raw material, highly combustible coal char can be produced. The fluidity of coal is a characteristic that results from the degree of molecular decomposition during heating, and low-fluidity coal is coal that has the characteristic of not easily undergoing molecular decomposition during heating.

[0032] The Logger index is calculated according to the Logger test method specified in JIS-M8801. The Logger test method is described below. First, 1 g of low-grade coal with a particle size of 200 μm or less and 5 g of standard anthracite are thoroughly mixed in a crucible. The standard anthracite used has an ash content (anhydrous basis) of 4.0% or less, a volatile matter (anhydrous basis) of 5.0-6.5%, and a particle size of 300-400 μm. Next, a constant load (59 N) is applied to the low-grade coal and standard anthracite in the crucible using a heat-resistant steel weight for a predetermined time (at least 30 seconds).

[0033] Next, the crucible described above is placed in an electric furnace set to a furnace temperature of 850±10℃, and low-grade coal and standard anthracite are heated (carbonized) for 15 minutes. After the heated crucible is placed on a heat-resistant plate and cooled for 45 minutes, the mass of the contents of the crucible (hereinafter sometimes referred to as carbonized material) is measured, and the mass of the carbonized material on the sieve is measured using a 1 mm perforated plate sieve.

[0034] Next, the contents of the crucible (carbonized product) are placed in a drum, and the drum is rotated at a predetermined speed (50 rpm) for 5 minutes to destroy the carbonized product. The inner diameter of the drum is 200 mm, the depth of the drum is 70 mm, and two vanes, each 70 mm long and 30 mm wide, are symmetrically arranged on the inner circumferential wall of the drum.

[0035] Next, the carbonized product after the destruction treatment is sieved using a 1 mm perforated sieve, and the mass on the sieve is measured. The destruction treatment described above is repeated three times, and the Loga index is calculated based on the following formula (1). In formula (1), RI is the Loga index. m1 is the total mass of the contents of the crucible (carbonized product) after carbonization [g], m2 is the mass of the carbonized product on the sieve before the first destruction treatment [g], m3 is the mass of the carbonized product on the sieve after the first destruction treatment [g], m4 is the mass of the carbonized product on the sieve after the second destruction treatment [g], and m5 is the mass of the carbonized product on the sieve after the third destruction treatment [g].

[0036]

number

[0037] The combustion rate (700°C) shown in Table 1 is calculated as follows: First, 10 mg of the sample to be measured is placed in the thermobalance inside the apparatus. After thoroughly purging the inside of the apparatus with nitrogen, the sample is heated at a heating rate of 100°C / min while circulating nitrogen at 200 ml / min. Once the sample temperature reaches 700°C, the circulating gas is immediately switched from nitrogen to air at 200 ml / min, and the weight loss is measured. The reaction time t (time elapsed since the circulating gas was switched from nitrogen to air) and the reaction rate X (X = [weight loss at each time - weight of unburned material at the end of measurement] / [initial weight of sample - weight of unburned material at the end of measurement]) are obtained. The reaction rate dX / dt is then calculated for each reaction rate, and the average value from X = 0 to 0.5 is calculated and taken as the combustion rate at 700°C.

[0038] In the two-stage charging and two-stage ignition method, the oxygen concentration of the supplied gas is lower in the lower stage compared to the upper stage. High-combustibility carbon materials have a low combustion start temperature, so they can burn even in low-oxygen environments and low-temperature conditions, thus suppressing combustion failure (unburned carbon material). As shown in the examples described later, combining the use of high-combustibility carbon materials in the lower stage with oxygen enrichment significantly improves production rate and yield. The following reasons are thought to be for this effect. As shown in Table 1, high-combustibility carbon materials have a fast combustion rate. However, even when using high-combustibility carbon materials, if oxygen enrichment is not implemented, combustion failure can be suppressed, but the combustion rate will not be fast enough due to insufficient oxygen, making it difficult to maintain an appropriate high temperature inside the sintering machine. On the other hand, by implementing oxygen enrichment, the combustion rate of high-combustibility carbon materials can be adjusted by controlling the oxygen concentration. By implementing oxygen enrichment, the sintering rate can be increased, the combustion of the carbon material can be made more active, and the temperature inside the sintering machine can be maintained at an appropriate high temperature. Furthermore, because highly combustible carbon materials have a fast combustion rate (700°C), using them in the sintering process shortens the time required for the complete combustion of the carbon material, and thus shortens the time required for sintering to be completed. A shorter time to complete sintering increases the amount of sintered ore produced per unit time, resulting in a higher production rate (t-sintered ore / day / m). 2 (t / d / m 2The sintering rate increases. Therefore, actively incorporating highly combustible carbon material into the lower layer is effective in improving productivity (improving the sintering rate).

[0039] The high-combustion carbon material should be added to the lower layer as follows: As shown in Figure 1, the raw materials for the upper layer forming the upper layer 20 and the raw materials for the lower layer forming the lower layer 10 are separate systems (2 systems). Then, the raw material tanks (1D1~1D) of the lower raw material tank group 1D X A raw material tank for storing highly combustible carbon materials is provided within the ). For example, raw material tank 1D1 (first carbon material tank) of the lower raw material tank group 1D stores carbon materials other than highly combustible carbon materials (e.g., coke and / or anthracite), and raw material tank 1D2 (second carbon material tank) stores highly combustible carbon materials (e.g., coal char and / or PKS coal). If two or more types of carbon materials other than highly combustible carbon materials, or two or more types of highly combustible carbon materials are used, a raw material tank for storing each type may be provided. [Examples]

[0040] Examples demonstrating the effects of the present invention will be described below. However, the present invention is not limited to the following examples.

[0041] The inventors verified the effectiveness of the present invention by conducting a sintering pot test (300 mm in diameter) that simulates sintering using a DL sintering machine. The sintering pot test apparatus does not involve the movement of the raw material filling layer by a pallet like a DL sintering machine, but it is a test apparatus in which the blended raw materials are placed in a container of a predetermined size, ignited from the top, and sintering is carried out by downward suction. As shown in Table 3 below, 13 experiments were conducted, including Comparative Examples 1-4 and Invention Examples 1-10.

[0042] (Raw material blend) Table 2 shows the raw materials and their mixing ratios. As shown in Table 2, two types of mixing materials were prepared: mixing material a and mixing material b. Of the mixing materials, the new raw materials, iron ore A-D, olivine, quicklime, and limestone, were mixed in the proportions shown in Table 2. Iron ore A-D were sourced from different locations. In addition, the setting agent (carbon material) was added at an additional 4.5% by mass, with the new raw materials accounting for 100% by mass. As the carbon material, powdered coke was added to mixing material a, while mixing material b consisted of equal parts powdered coke and PKS carbon, a highly combustible carbon material. Furthermore, as shown in Table 3 below, mixing material b was used only in the lower layer of Comparative Example 4 and Invention Examples 9 and 10. That is, in Comparative Example 4 and Invention Examples 9 and 10, PKS carbon was added as a setting agent to the lower layer.

[0043] [Table 2]

[0044] (Granulation method) The raw materials for the upper and lower layers were granulated separately. Granulation was performed by mixing the materials for 4 minutes using a drum mixer (600 mm diameter, 25 rpm rotation speed), then adding 7.2% by mass of water to the mixture, and processing for another 4 minutes.

[0045] (Test level) The test levels are shown below. As shown in the upper part of Table 3, in Comparative Examples 1-4 and Invention Examples 1-10, the oxygen concentration of the suction gas supplied from the surface side of the upper layer and drawn downward at atmospheric pressure was varied within the range of 21 vol% (no oxygen enrichment) to 50 vol% when performing two-stage charging and two-stage ignition. Furthermore, as will be described in detail later, the supply of oxygen-enriched gas was set to the layer height range (position) corresponding to the first half section (the first half of the section from the upper ignition furnace outlet to the ore discharge end) in the sintering pot tests of Comparative Examples 2-3 and Invention Examples 1-3, 7-10; to the layer height range corresponding to the second half section (the second half of the section from the upper ignition furnace outlet to the ore discharge end) in Invention Example 4; to the layer height range corresponding to a part of the first half section in Invention Example 5; and to the layer height range corresponding to both the first and second half sections (the entire section) in Invention Example 6. Note that oxygen enrichment was not performed in Comparative Example 1.

[0046] [Table 3]

[0047] (Firing conditions) The thickness of each layer in the two-tiered setup was set at 500mm for the lower layer and 300mm for the upper layer. Two pots were prepared: a cylindrical pot for the lower layer (300mm in diameter) with a height of 500mm, and a cylindrical pot for the upper layer (300mm in diameter) with a height of 300mm. First, the granulated lower and upper mixing materials were placed in the lower and upper pots, respectively, to create a lower layer height of 500 mm and an upper layer height of 300 mm. Then, the lower pot with a height of 500 mm was set in place, and the surface of the lower layer was ignited for 1 minute. After that, the upper pot with a height of 300 mm was set on top of the lower pot, and in order to achieve sintering in both upper and lower layers, after confirming the temperature rise at a height of 320 mm (320 mm from the bottom surface of the lower layer) (by temperature measurement using a thermocouple as described later), the surface of the upper layer was ignited for 1 minute. The suction pressure was kept constant at 1200 mmAq (11.8 kPa) from the start of ignition.

[0048] (Sintering time) Thermocouples were inserted at layer heights of 440mm, 320mm, 230mm, and 170mm to measure the temperature inside the layer. To determine the completion of sintering for the entire raw material-packed bed (upper and lower layers) at the later of the completion of sintering in the upper layer and the lower layer, the longer of the two times—the time until the second temperature rise of the thermocouple at 440mm (completion of sintering in the upper layer) and the time until the peak of the exhaust gas temperature at the wind box (completion of sintering in the lower layer)—was used as the sintering time for the entire raw material-packed bed. Suction was stopped 3 minutes after the time of completion of sintering, and the sintering process was considered complete.

[0049] (Oxygen enrichment) As shown in Table 3, oxygen enrichment was carried out in four patterns: a portion of the first half, the entire first half, the second half, and the entire experiment. Under the conditions for a portion of the first half, oxygen enrichment was carried out from immediately after the start of upper stage ignition until the temperature rose to 230 mm. Under the conditions for the entire first half, oxygen enrichment was carried out from immediately after the start of upper stage ignition until the temperature rose to 170 mm, which corresponds to approximately half the height of the upper layer. Under the conditions for the second half, oxygen enrichment was carried out from the temperature rise to 170 mm until the end of the experiment. Under the conditions for the entire experiment, oxygen enrichment was carried out from immediately after the start of upper stage ignition until the end of the experiment.

[0050] (Yield) The yield was measured as follows: After sintering, the resulting sintered cake was dropped four times from a height of 2m, and the mass of sintered products with a particle size of +5mm (greater than 5mm) was determined. The ratio (mass %) of these sintered products to the total mass of the sintered cake was defined as the product yield (+5mm%).

[0051] (Production rate) The production rate was calculated using the following formula (2), based on the sintering time measured as described above. Production rate = Quantity of finished product (t) / Sintering area (0.07m²) 2 ) / Sintering time (days) ···(2)

[0052] (Sintered ore strength) The strength of the sintered ore was measured as cold strength (rotational strength index TI) based on JIS M8712 (2009). The mass of the test sample was 15 kg (15 mm - 40 mm size). In addition, only the lower sintered ore (sintered ore in the lower pot) was measured for strength. The apparatus used for measurement was a cylindrical container (diameter 1000 mm, depth 500 mm), in which the test sample was placed and rotated at a rotation speed of 25 rpm for 8 minutes. The mass of the sintered ore recovered after rotation, plus 6 mm, was determined, and the ratio of this sintered ore to the 15 kg test sample (mass %) was defined as the cold strength.

[0053] (Test results) The test results are shown in the lower section of Table 3. In the test results for cases where high-combustibility carbon material was not used, as shown in Table 3, Invention Examples 1-8 showed a significant improvement in both yield and production rate compared to Comparative Examples 1 and 2. Regarding strength, Invention Example 1 was approximately the same as Comparative Examples 1 and 2, but Invention Examples 2-8 showed improvement. Comparative Example 3, with an oxygen concentration of 50 vol%, showed lower yield, strength, and production rate than Invention Example 8, with an oxygen concentration of 46 vol%. This indicates that excessive oxygen enrichment is unnecessary, and an oxygen concentration of 26 vol% to 46 vol% is desirable. Furthermore, from the results of Invention Examples 3-5, where the oxygen concentration was kept constant at 36 vol% and the oxygen enrichment location was changed, the following was found: Oxygen enrichment is more effective in the first half of the process than in the second half (comparison of Invention Examples 3 and 4). While the effect is less pronounced in a portion of the first half than in the entire first half, when calculating the improvement rate of yield, strength, and production rate relative to the length of the oxygen enrichment section (based on Comparative Example 1), a portion of the first half is more efficiently utilized (comparison of Invention Examples 3 and 5).

[0054] The test results for cases using highly combustible carbon materials are as follows. As shown in Comparative Example 4, when highly combustible carbon materials (PKS coal) were blended into the lower layer without oxygen enrichment, both the yield and production rate were lower than in Comparative Example 1, which did not contain PKS coal. In contrast to this result, in Invention Example 9, where PKS coal was blended into the lower layer and oxygen enrichment was performed, the production rate and yield were significantly improved compared to Comparative Example 4, where highly combustible carbon materials (PKS coal) were blended into the lower layer without oxygen enrichment, and Comparative Example 1, which did not use oxygen enrichment or PKS coal. Furthermore, in Invention Example 10, where the oxygen concentration of the supply gas was increased, the strength of the lower layer was improved while maintaining a high yield, and productivity was further significantly improved compared to Invention Example 8, where oxygen enrichment was performed without PKS coal. Similar effects were observed not only with PKS coal but also with coal char, which is a highly combustible carbon material. These results indicate that the combination of using highly combustible carbon materials and oxygen enrichment is effective. [Explanation of Symbols]

[0055] 100...Sintering machine, 1A...Lower drum mixer, 1B...Lower hopper, 1C...Lower ignition furnace, 1D...Lower raw material tank group (Lower raw material tanks 1D1~1DX ), 2A... Upper drum mixer, 2B... Upper hopper, 2C... Upper ignition furnace, 2D... Upper raw material tank group (upper raw material tanks 2D1~2D y ), 3...Sintering section, 5...Pallet forward direction, 6...Downward suction, 7...Oxygen-enriched gas supply equipment, 8...Hood, 9...Gas pipe, 10...Lower layer, 10A...Lower layer combustion zone, 20...Upper layer, 20A...Upper layer combustion zone, X...Ignition furnace outlet for upper layer, Y...Mine discharge end, Z...Intermediate position

Claims

1. The process involves loading the lower-stage raw material granules into the sintering machine to form a lower-stage raw material packed layer, The process involves loading the upper-stage blended raw material granules onto the lower-stage raw material packed layer to form the upper-stage raw material packed layer, The process includes igniting the surface of the lower raw material packed layer and the surface of the upper raw material packed layer, respectively, and introducing an oxygen-containing gas into the lower raw material packed layer and the upper raw material packed layer at atmospheric pressure by downward suction. A method for producing sintered ore, characterized in that at least a portion of the gas drawn downward from the surface side of the upper raw material packed bed after the ignition of the upper raw material packed bed is completed is an oxygen-enriched gas with an oxygen concentration of 26% by volume or more and 46% by volume or less.

2. In the longitudinal direction of the sintering machine, when the intermediate position between the upper ignition furnace outlet and the ore discharge end is defined as the intermediate position, and the section from the upper ignition furnace outlet to the intermediate position is defined as the first half section, The method for producing sintered ore according to claim 1, characterized in that the region to which the oxygen-enriched gas is supplied includes a part of the first half section.

3. In the longitudinal direction of the sintering machine, when the intermediate position between the upper ignition furnace outlet and the ore discharge end is defined as the intermediate position, the section from the upper ignition furnace outlet to the intermediate position is defined as the first half section, and the section from the intermediate position to the ore discharge end is defined as the second half section, The method for producing sintered ore according to claim 1, characterized in that the region to which the oxygen-enriched gas is supplied includes at least a portion corresponding to the first half section, and the portion corresponding to the first half section is longer than the portion corresponding to the second half section.

4. In the longitudinal direction of the sintering machine, when the intermediate position between the upper ignition furnace outlet and the ore discharge end is defined as the intermediate position, and the section from the upper ignition furnace outlet to the intermediate position is defined as the first half section, The method for producing sintered ore according to claim 1, characterized in that the region to which the oxygen-enriched gas is supplied is the first half section or a part of the first half section.

5. A method for producing sintered ore according to any one of claims 1 to 4, characterized in that a highly combustible carbon material having a combustion rate of 0.0022 (1 / sec) or more at 700°C is blended as a blending material for the lower raw material packed bed.

6. The method for producing sintered ore according to claim 5, characterized in that the highly combustible coal material includes char obtained by carbon distillation of coal with a logger index of less than 10.

7. The method for producing sintered ore according to claim 5, characterized in that the highly combustible carbon material includes oil palm kernel shell carbon.

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