Method for producing sintered ore

Abstract

To aim to improve productivity by utilizing wood carbide that is biomass charcoal, when producing a sintered ore.SOLUTION: In a method for producing sintered ore by advancing sintering through downward suction of granulated mixed raw materials, a firing furnace and a re-ignition furnace, which is arranged at a predetermined distance downstream of the firing furnace, are used to perform ignition by the firing furnace and re-ignition by the re-ignition furnace. For the binder of the mixed raw materials, low combustibility carbon materials (powdered coke and / or smokeless coal) and ground products of compressed molded bodies formed by compressing aggregates of wood charcoal are used based on a predetermined mixing ratio.SELECTED DRAWING: Figure 4

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] The main raw material for blast furnace pig iron production is sintered ore. In recent years, a reignition sintering method (Patent Document 1 below) has been proposed as a method for producing sintered ore, in which two-stage ignition is performed to improve the sinter yield. The reignition sintering method is a technique in which, after the first ignition is completed, air is sucked in for a predetermined time in an air suction area, and then a second ignition (reignition) is performed. In addition, as improved techniques of the reignition sintering method, a method for enhancing segregation of carbonaceous material in the layer thickness direction of the raw material packed bed (Patent Document 2 below) and a method for utilizing char (highly combustible carbonaceous material described later) obtained by carbonizing raw coal with a Roga index of 10 or less as a coagulating material (Patent Document 3 below) have been proposed.

[0003] For the one-stage ignition and sintering method, which involves only one normal stage (one time) of ignition, various techniques have already been proposed that utilize highly combustible carbonaceous materials (carbonaceous materials with a lower combustion start temperature than low combustible carbonaceous materials such as coke and anthracite. For example, techniques related to the blending ratio of highly combustible carbonaceous materials (Patent Documents 4 and 7 below), techniques related to the preferred particle size of highly combustible carbonaceous materials (Patent Documents 5 and 8 below), and methods of addition in the granulation process (Patent Documents 4 and 6 below) have been proposed.

[0004] Patent Document 1 discloses a method for producing sintered ore (reignition sintering method) using a Dwight Lloyd (DL) type sintering machine, which includes a number of pallets arranged in succession in the traveling direction from upstream to downstream and on which sintering raw materials are charged, an igniter for igniting the raw material packed bed in the upstream pallet in the traveling direction from above among the pallets, a wind box for drawing in air from below the pallets, a frame heating device arranged at a distance downstream of the igniter and for frame heating the entire width of the upper surface of the raw material packed bed, and an air suction area formed between the igniter and the frame heating device, in which air is drawn in by downward suction and no direct heating is performed from the upper surface. It is described that it is possible to improve both the yield and cold strength of sintered ore while maintaining reducibility.

[0005] Patent Document 2 discloses a method for producing sintered ore using a Dwight Lloyd sintering machine, in which a raw material packed layer is divided into a lower layer and a surface layer on each of multiple pallets that circulate in the traveling direction from upstream to downstream, and the concentration of solid combustibles in the lower layer is made lower than that of solid combustibles in the surface layer to produce sintered ore, in which the raw material packed layer in the upstream pallet in the traveling direction is ignited from above, and after the ignition part of the raw material packed layer moves downstream in the traveling direction, the ignition part is reignited. It describes that by increasing the concentration of solid combustibles in the surface layer while reducing unburned content so that it can be effectively used as heat, it is possible to increase the sintering speed and increase the yield, thereby further improving productivity.

[0006] Patent Document 3 discloses a technology in which a Dwight Lloyd (DL) type sintering machine equipped with an igniter and a frame heating device provided at a distance downstream from the igniter for flame heating the upper surface of the raw material packed bed is used, the blended raw material to be charged is a raw material from which only a part or all of the carbonaceous material has been removed, and the removed carbonaceous material is added to the raw material during or after granulation by adding moisture, and the carbonaceous material to be added later is char (coal char) obtained by carbonizing coal having a Roga index of 10 or less as raw coal. It is described that by adding coal char later in the granulation process of the reignition sintering method, yield and productivity are improved.

[0007] Patent Document 4 discloses a method for producing sintered ore as a technique for improving the sintering yield, which uses a low combustibility carbonaceous material consisting of at least one of powdered coke and anthracite, and a highly combustible carbonaceous material having a lower combustion start temperature than the low combustibility carbonaceous material, and the carbon content of the highly combustible carbonaceous material is 25% by mass to 75% by mass relative to the carbon content of the agglomeration material, and at least one of the low combustibility carbonaceous material and the highly combustible carbonaceous material is added in the latter half of the granulation process of the sintering raw material.

[0008] Patent Document 5 discloses a technique for producing sintered ore in which pseudo-particles obtained by granulating sintering raw materials consisting of iron ore, auxiliary raw materials, return ore and solid carbonaceous material are segregated and charged into the pallet of a sintering machine, and then fired while generating a carbon concentration difference in the height direction of the raw material layer. When oil palm kernel shell charcoal, which is a solid carbide produced by heat-treating oil palm kernel shell, is blended as part or all of the solid carbonaceous material in the sintering raw material, the technique blends oil palm kernel shell charcoal with an average particle size adjusted to 2.7 mm to 6.0 mm. By using oil palm kernel shell charcoal as the solid carbonaceous material for sintering, it is possible to suppress the emission of carbon dioxide, a global warming gas, and to improve sintering productivity through appropriate operating techniques. In addition, when blending oil palm kernel shell coal as part of the solid carbonaceous material in the sintering raw material, it is preferable to blend oil palm kernel shell coal whose average particle size is adjusted to be coarser within the range of 1.0 mm to 4.5 mm than the average particle size of the solid carbonaceous material, coke powder or anthracite.

[0009] Patent Document 6 discloses a method for producing carbonaceous material for sintering, which calculates the Roga index of coal and produces carbonaceous material for sintering using coal with a Roga index of 10 or less, and a method for adding at least a part of a predetermined blend amount of carbonaceous material for sintering during or at the end of the granulation process in the granulation process of raw materials for sintering. It also discloses that the amount of NOx emissions generated during the production of sintered ore can be reduced.

[0010] Patent Document 7 discloses the production of sintered ore in a downward suction sintering machine using a sintering raw material containing 0.1 to 9.0 mass% of biomass carbide containing less than 2.3 mass%-dry nitrogen and less than 1 mass%-dry sulfur, with the remainder being iron ore, coke, and other auxiliary raw materials. Patent Document 7 uses as the biomass carbide a solid content (residue) generated when biomass is pyrolyzed in an oxygen-free or low-oxygen state. It discloses that by mixing 0.1 to 9.0 mass% of the biomass raw material with the sintering raw material, NOx and SOx in the exhaust gas can be reduced compared to conventional methods.

[0011] Patent Document 8 discloses a method for producing sintered ore by using a raw material containing fine iron ores, a composition-adjusting solder, return ore, and solid carbonaceous material, and distributing the concentration of the solid carbonaceous material in the pallet height direction, in which the raw material containing the fine iron ores, the composition-adjusting solder, and return ore is mixed with oil palm kernel shell charcoal (PKS charcoal), which is a solid carbide produced by heat-treating oil palm kernel shell (PKS), and one or more of coke and anthracite, which have a particle size smaller than that of the solid carbide, are also mixed. Specifically, PKS charcoal, which is produced by heat-treating dried PKS in an electric furnace at 700°C for one hour, is used as the sintered raw material. The document discloses that PKS charcoal is a carbon-neutral material, has low volatility, and has good combustibility, and therefore suppresses the emission of carbon dioxide, a greenhouse gas, during the production of sintered ore, and significantly improves the combustibility in the lower layer of the sintered layer, thereby improving the productivity of the sintering machine. It is also described that although PKS coal has excellent combustibility due to its micropores, if the combustibility is not controlled, the product yield will decrease (paragraph

[0044] ). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2020-2457 A [Patent Document 2] JP 2020-29603 A [Patent Document 3] JP 2020-84204 A [Patent Document 4] JP 2022-33594 A [Patent Document 5] JP 2014-218713 A [Patent Document 6] JP 2020-56086 A [Patent Document 7] JP 2003-328044 A [Patent Document 8] JP 2013-237876 A Summary of the Invention [Problem to be solved by the invention]

[0013] In light of global environmental issues (reducing CO2 emissions), there is a demand to utilize carbon-neutral biomass charcoal instead of coal-based coke breeze and anthracite.

[0014] As described in the above-mentioned Patent Document 8, biomass charcoal (hereinafter referred to as biomass charcoal) produced by heat treatment (carbonization) of biomass is a porous body (low density) and has excellent combustibility, so that the sintering speed can be increased. However, if the sintering speed becomes too fast, the high-temperature holding time for progressing the sintering reaction becomes shorter, which may result in a decrease in the product yield and productivity of sintered ore.

[0015] In addition, when biomass charcoal is used as a coagulant, there are also the following problems. It is known that in the manufacturing method of sintered ore using a Dwight Lloyd sintering machine, the upper part of the sintered bed is quenched with low-temperature air supplied by downward suction, and the high-temperature holding time is shortened. In addition, the Dwight Lloyd sintering machine is configured so that the upper part of the raw material packed bed (sintered bed) is charged with raw materials of finer particle size. Therefore, the upper part of the raw material packed bed is characterized in that low-density particles are easily charged and the mixing ratio thereof increases (hereinafter also referred to as thickening). Therefore, when biomass charcoal is used as a coagulant, the low-density biomass charcoal is thickened in the upper part of the raw material packed bed (sintered bed). Due to the high combustibility of the biomass charcoal thickened in the upper part of the raw material packed bed, the high-temperature holding time in the upper part is further shortened. The reduction in the high-temperature holding time causes a decrease in the yield in the upper part of the sintered bed, thereby reducing the production rate. [Means for solving the problem]

[0016] (1) A method for producing sintered ore in which sintering of granulated raw materials is promoted by downward suction, Using an ignition furnace and a re-ignition furnace arranged at a predetermined interval downstream of the ignition furnace, ignition by the ignition furnace and re-ignition by the re-ignition furnace are performed, A method for producing sintered ore, characterized in that powdered coke and / or anthracite and a crushed product obtained by compressing and molding an aggregate of wood carbonized material are used as a coagulant for the mixed raw materials in a predetermined mixing ratio. (2) A method for producing sintered ore according to (1), characterized in that a part or all of the coagulant mixed based on the predetermined blending ratio is added later during the granulation process. (3) A method for producing sintered ore according to (2), characterized in that, in the case of post-addition during the granulation process, the mass ratio of the post-added coagulation agent is 30 mass% or more relative to the total mass of the coagulation agent, and the granulation time until the post-added coagulation agent is added is 80% or more and 96% or less relative to the total granulation time. Effect of the Invention

[0017] According to the method for producing sintered ore of the present invention, an aggregate of wood carbonized material is compressed and molded into a compressed product, which is then pulverized and used as part of the coagulation material. In addition, the re-ignition sintering method is used, thereby improving the productivity. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a schematic diagram showing an example of sintering equipment used in the first embodiment. [Diagram 2] FIG. 11 is a schematic diagram showing an example of sintering equipment used in a second embodiment. [Diagram 3] 1 is a graph showing the cumulative undersize particle size distribution in which the particle size distribution shown in Table 4 is expressed as a cumulative ratio (mass%). [Figure 4] 1 is a graph showing test results (production rate) for a single-stage ignition test case and a reignition test case. [Diagram 5] 1 is a graph showing the test results (productivity rate) of a test case in which the entire amount of the coagulant was added later. [Figure 6] 1 is a graph showing test results (productivity) of test cases in which the particle size conditions of compressed and pulverized charcoal were changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The inventors have found that processing biomass charcoal and using it is an effective solution to the excessive combustibility of biomass charcoal, and that using a reignition sintering method in combination with biomass charcoal and low combustibility carbonaceous material (coke fines and / or anthracite) is an effective solution to the problem that the concentration of biomass charcoal in the upper layer of the raw material packed bed (sintered layer) causes a decrease in the yield in the upper layer. That is, they have found that by using compressed and crushed charcoal, whose combustibility has been adjusted by processing biomass charcoal, as part of the coagulation material and sintering using the reignition sintering method, the shortened high temperature retention time of the upper layer of the sintered layer caused by the compressed and crushed charcoal can be restored, thereby improving the productivity.

[0020] The present invention is a method for producing sintered ore in which sintering of granulated blended raw materials is promoted by downward suction, using an ignition furnace and a reignition furnace arranged downstream of the ignition furnace with a predetermined distance (corresponding to the "separation distance" described later), ignition by the ignition furnace and reignition by the reignition furnace, and using coke powder and / or anthracite and a crushed product (hereinafter, for convenience, also simply referred to as charcoal compressed molded product) obtained by crushing a compressed molded product (hereinafter, for convenience, also simply referred to as charcoal compressed molded product) obtained by compressing and molding an aggregate of wood charcoal, based on a predetermined blending ratio as the coagulating material of the blended raw materials. A crushed product (charcoal compressed molded crushed product) obtained by crushing a compressed molded product (charcoal compressed molded product) made mainly of wood charcoal, which is biomass charcoal (biochar), is used as the coagulating material of the sintered raw materials. Here, the terms used in this specification are defined as follows. "Wood" refers to the trunk or branch of a tree, or a material made of these, including, for example, construction waste. "Wood charcoal" refers to a charcoal obtained by heat-treating (dry distilling) the above-mentioned "wood." "Aggregate of wood charcoal" refers to an aggregate of wood charcoal particles, or an aggregate of wood charcoal particles bonded with a binder, and the size and shape of the wood charcoal particles are not limited. "Molded by compression" refers to molding that involves compression, and includes not only compression molding, but also extrusion molding in which pressure is applied when extruding. "Main raw material" refers to the raw material that is used in the largest proportion (mass ratio) of the total solid raw materials among the solid raw materials. "Crushing" refers to reducing the particle size using a crusher (e.g., rod mill, hammer crusher, roll crusher, super sander, jaw crusher, fret mill, etc.).

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In this specification and the drawings, components having substantially the same functions are given the same or similar names or symbols, and duplicate descriptions are omitted.

[0022] First Embodiment An example of an embodiment of the present invention will be described below. First, the reignition sintering method will be described, and then the low combustibility carbonaceous material, the high combustibility carbonaceous material, and the compressed and pulverized charcoal classified into the high combustibility carbonaceous material will be described in order.

[0023] (Reignition sintering method) First, a method for producing sintered ore using the reignition sintering method used in the present invention will be described. The reignition sintering method is a technology in which a reignition process is added to the one-stage ignition sintering method. Although details will be described later, a Dwight Lloyd (DL) type sintering machine used in the reignition sintering method is provided with a reigniter that performs a second (second) ignition (reignition) at a predetermined interval (separation distance) downstream in the pallet traveling direction of the igniter that performs the first ignition (initial ignition). The reigniter is a frame heating device that heats the upper surface of the raw material packed bed with a flame, and the flame (flame) is blown onto the uppermost surface (surface) of the raw material packed bed, which is the object to be heated.

[0024] FIG. 1 is a schematic diagram showing an example of a sintering facility used in this embodiment. As shown in FIG. 1, this sintering facility includes a raw material tank group 1, a granulator 2 (such as a drum mixer), and a Dwight Lloyd (DL) type sintering machine 100. The DL type sintering machine 100 is provided with a re-ignition furnace 4 at a predetermined interval (separation distance) downstream of the ignition furnace 3 in the pallet traveling direction 5. The ignition furnace 3 has an igniter 3a that performs the first ignition (initial ignition) and a hood 3b that covers it, and the re-ignition furnace 4 has a re-igniter 4a that performs the second (second) ignition (re-ignition) and a hood 4b that covers it. For example, the ignition furnace 3 is an ignition furnace used in a one-stage ignition sintering method, and the re-ignition furnace 4 can also be the same as the ignition furnace used in the one-stage ignition sintering method. The hoods 3b and 4b are independent of each other, and between the ignition furnace 3 and the re-ignition furnace 4 in the pallet travel direction 5 (between the partition wall downstream of the hood 3b of the ignition furnace 3 and the partition wall upstream of the hood 4b of the re-ignition furnace 4), there is provided an air suction area 7, which is a section (area) where direct heating by a burner or the like is not performed from above and where air is sucked in by downward suction 6. Here, in this specification, the distance in the pallet travel direction 5 between the partition wall downstream of the hood 3b and the partition wall upstream of the hood 4b of the ignition furnace 4, that is, the distance in the pallet travel direction 5 of the air suction area 7 shown in FIG. 1 is referred to as the separation distance, and the time required for the pallet (a plurality of connected pallet carts moving on an endless track, not shown) of the DL-type sintering machine 101 to pass through this separation distance (air suction area passing time) is referred to as the separation time. Therefore, the separation distance can be obtained by multiplying the separation time by the transfer speed (pallet speed) of the raw material packed bed 10 by the pallet.

[0025] The raw materials for sintering (sintering raw materials) include iron raw materials 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 agglomeration materials (carbon materials) that serve as fuel for sintering (agglomeration). In the present invention, as agglomeration materials, low-combustible carbon materials (coke powder and / or anthracite) and crushed products (compressed and crushed charcoal products) obtained by crushing a compressed molded product obtained by compressing an aggregate of wood charcoal are used. Each sintering raw material is fed to each raw material tank (11-1) of raw material tank group 1. XThe raw materials are stored in a granulator 20, cut out at a predetermined ratio, and blended. The blended raw materials (blended raw materials) are fed into a granulator 2 and granulated. The granulated blended raw materials (hereinafter, the blended raw materials after granulation are also referred to as blended raw material granules) are charged from a blended raw material surge hopper 21 onto a pallet (not shown) covered with bedding ore, forming a raw material packed bed 10.

[0026] The raw material packed bed 10 is continuously moved in the pallet moving direction 5 by the pallet. When the raw material packed bed 10 moves to the bottom of the ignition furnace 3, the igniter 3a ignites the carbonaceous material on the surface of the raw material packed bed 10, and sintering of the raw material packed bed 10 is started. A wind box (not shown) is provided below the pallet that moves in the pallet moving direction 5 after ignition, and air is sucked from below the pallet. This downward suction 6 supplies oxygen into the raw material packed bed, and the combustion of the condensed material in the raw material packed bed (combustion zone 10A) progresses from the top to the bottom, and the raw material packed bed 10 is successively sintered by the combustion heat of the condensed material. When the raw material packed bed 10 passes through the air suction area 7 and moves to the bottom of the re-ignition furnace 4, the raw material packed bed 10 is re-ignited by the frame of the re-igniter 4a. The sinter cake 11 obtained by sintering the raw material packed bed 10 is discharged at the downstream end of the pallet travel direction 5 of the DL-type sintering machine 100, and is crushed, sieved, etc., so that the sintered ore of a particle size suitable for blast furnace charging becomes the raw material for blast furnace pig iron production. In this specification, the raw material packed bed 10 refers to a layer of blended raw materials formed on a pallet (a plurality of linked pallet carts moving on a caterpillar track, not shown) regardless of whether ignition (initial ignition) or re-ignition is performed, and includes a combustion zone 10A in which a sintering reaction is progressing due to ignition, and a sinter cake 11 in which the sintering reaction is completed. In the following description, the raw material packed bed 10 after initial ignition is performed (after the start of sintering) is also referred to as a sintered layer.

[0027] As described above, in the reignition sintering method, after the ignition heating by the ignition furnace 3, the material passes through the atmosphere suction region 7, that is, after a predetermined time interval (corresponding to the above-mentioned separation time), reignition is performed by the reignition furnace 4. In the atmosphere suction region 7 downstream of the ignition furnace 3, since no combustion heating is performed from the top by a flame burner such as an igniter, sufficient oxygen is supplied to the raw material packed bed 10, and the combustion of the condensed material in the combustion zone 10A progresses. In addition, since the atmosphere suction region 7 is provided between the ignition furnace 3 and the reignition furnace 4, the combustion of the condensed material progresses to a lower part due to the increase in superficial tower wind speed. As a result, the thickness of the combustion zone 10A expands in the upper part of the raw material packed bed 10. Then, after the thickness of the combustion zone 10A expands in the atmosphere suction region 7, reignition is performed by the frame of the reignition furnace 4 provided downstream of the atmosphere suction region 7. By re-ignition, the remaining condensed material that was not burned by the ignition by the ignition furnace 3 can be burned without leaving any residue, and the air warmed by re-ignition is drawn into the raw material packed bed 10, which promotes the sintering reaction in the upper layer of the raw material packed bed 10, thereby improving the yield. As described above, the separation time (predetermined time interval) is the time required for the pallet to move through the air suction area 7 (the time from the end of the initial ignition to the execution of re-ignition), and is preferably 0.5 minutes or more and 3.5 minutes or less. The lower limit (minimum value) of this separation time is the limit at which the combustion zone 10A can be sufficiently expanded, and the upper limit (maximum value) of the preferable separation time is governed by the cooling of the upper layer of the sintered layer after the initial ignition. If the separation time is less than 0.5 minutes, sufficient oxygen cannot be supplied to the combustion zone 10A of the upper layer of the sintered layer, and if it exceeds 3.5 minutes, the upper layer of the sintered layer will drop to a temperature below the sintering reaction, making it difficult to obtain the productivity improvement effect of the re-ignition technique. Here, as described above, the separation distance can be obtained by multiplying the separation time by the pallet speed. If a standard commercial sintering machine has a pallet speed of 3 m / min, the optimum range of separation time is 0.5 to 3.5 minutes, so the optimum range of separation distance is 1.5 to 10.5 m. Of course, the optimum separation distance changes depending on the pallet speed. Therefore, the separation distance differs for each sintering machine.

[0028] When the blended raw material granules are charged onto the pallet, a charging device equipped with a segregation mechanism is used. Usually, an inclined flat plate chute type charging device 20 shown in FIG. 1 is used, and the blended raw material granules are charged onto the pallet using an inclined flat plate chute 22 installed with a downward inclination in the opposite direction to the pallet travel direction 5, forming a slope 10x on the upstream side of the raw material packed bed 10. Due to the rolling classification action of the blended raw material granules on this slope 10x and the movement of the pallet, particle size segregation occurs in the layer thickness (layer height) direction of the raw material packed bed 10. Specifically, small particle sizes tend to be charged into the upper layer side of the raw material packed bed 10, and large particle sizes tend to be charged into the lower layer side of the raw material packed bed 10.

[0029] Here, the granulation process of the blended raw materials is aimed at ensuring the permeability of the raw material packed bed, and generally, as described in the 3rd Edition Iron and Steel Handbook II, Pig Iron and Steelmaking, p. 84 (Fig. 2.4) [October 15, 1979], fine raw materials with a particle size of less than 0.25 mm, which are the main target of the granulation process, form pseudo-particles by adhering to the periphery of particles of 1.00 mm or more as core particles, but particles of intermediate particle size of 0.25 mm or more and less than 1.00 mm are difficult to granulate and do not easily become pseudo-particles. Therefore, even when the granulation process is performed, it is possible to adjust the distribution of the granulation material in the height direction of the raw material packed bed by adjusting the particle size of the blended granulation material and charging it using the inclined plate chute type charging device 20 described above.

[0030] Next, the low combustibility carbonaceous material and the high combustibility carbonaceous material used as the agglomerating material, and the compressed molded pulverized charcoal classified as the high combustibility carbonaceous material will be described in detail.

[0031] (setting material) The sintering raw material, agglomerate (carbonaceous material), is classified into low combustibility carbonaceous material and high combustibility carbonaceous material. Examples of low combustibility carbonaceous materials include coke and anthracite, and coke and anthracite are usually used as agglomeration materials in sintered ore production. High combustibility carbonaceous materials are carbonaceous materials with higher combustibility (low combustion initiation temperature) than low combustibility carbonaceous materials. Specifically, low combustibility carbonaceous materials and high combustibility carbonaceous materials are classified based on the combustion initiation temperature obtained by differential thermogravimetry analysis. Low combustibility carbonaceous materials are carbonaceous materials with a combustion initiation temperature of over 550°C, and high combustibility carbonaceous materials are carbonaceous materials with a combustion initiation temperature of 550°C or less. The combustion initiation temperature (ignition temperature) is defined as the temperature at which a rapid weight loss begins based on the temperature-weight change curve obtained by thermogravimetry (TG: Thermogravimetry) in an air stream using a differential thermogravimetry-mass spectrometry (TG-DTA / MS).

[0032] (Low flammability carbon material) As mentioned above, low-combustibility carbonaceous materials include coke and anthracite. The combustion start temperature (ignition temperature) of coke and anthracite is about 670℃ and about 690℃, respectively. Coke for sintering is made by crushing coke of a particle size unsuitable for blast furnace use (usually 40mm or less) to a particle size suitable for sintering during the process of manufacturing coke for blast furnaces. Sintering coke is also called breeze coke, as opposed to lump coke for blast furnaces. Anthracite is one of the classifications given to coal (brown coal, bituminous coal, anthracite), and is the most carbonized coal. Coal with a fuel ratio (fixed carbon / volatile matter (mass ratio)) of 4 or more, or simply coal with a carbon content of 90% or more by mass, is classified as anthracite. Both anthracite and breeze coke are crushed to a particle size suitable for sintering (generally less than 10mm). In this specification, the term "particle size" refers to a value (particle size) measured by sieving using a sieve in accordance with JIS Z8801-1:2019.

[0033] (Highly combustible carbonaceous material) Examples of highly combustible carbonaceous materials include coal char and biomass charcoal (oil palm kernel shell charcoal, wood charcoal, etc.). The combustion start temperature of coal char (semi-coke, lignite char, and subbituminous coal char) is 430°C or higher and 550°C or lower, that of oil palm kernel shell charcoal is about 470°C, and that of wood charcoal is about 400°C or higher and 450°C or lower. Coal charcoal and biomass charcoal have roughly the same ignition temperature, and therefore have similar combustibility. In addition, a compressed product (compressed charcoal product) made mainly from wood charcoal, which is biomass charcoal (biochar), and the crushed product (compressed charcoal crushed product) obtained by crushing this product are also highly combustible carbonaceous materials. The combustion start temperature of compressed charcoal product is a low temperature of about 250°C or higher and 450°C or lower, and the crushed product (compressed charcoal crushed product) is the same. It is known that the combustion rate of highly combustible carbonaceous materials is 1.03 to 30.00 times that of coke.

[0034] Coal char, which is a highly combustible carbonaceous material, is a carbonaceous material (char) produced by carbonizing low-caking bituminous coal, lignite, and subbituminous coal at 700 to 900°C. The carbonaceous materials produced by carbonizing low-caking bituminous coal, lignite, and subbituminous coal are called semi-coke, lignite char, and subbituminous char, respectively. These carbonaceous materials are produced by carbonizing raw coal (including mixed coal) in a pyrolysis furnace (e.g., a rotary kiln).

[0035] Biomass charcoal, which is a highly combustible carbonaceous material, is a carbonaceous material produced by heat-treating (carbonizing) biological resources (biomass) such as oil palm kernel shell and wood. Oil palm kernel shell charcoal (PKS charcoal) is a solid charcoal produced by heat-treating (carbonizing) oil palm kernel shell. Compressed molded and pulverized charcoal used as a coagulant in the present invention is also biomass charcoal, and is made from wood charcoal, which is a solid charcoal produced by heat-treating (carbonizing) wood. Compressed molded and pulverized charcoal will be described in detail below.

[0036] (Compressed and crushed charcoal) The compressed wood pulverized product is produced as follows. First, wood material is obtained and carbonized to produce charcoal (charcoal production process). Next, the produced charcoal is crushed as necessary to produce charcoal particles, and these charcoal particles are kneaded alone or with a binder to produce an aggregate of charcoal (hereinafter referred to as charcoal aggregate) (aggregate production process). The binder is used to form a strong aggregate. Next, the charcoal aggregate is compressed and molded to produce a charcoal compressed product (compression process). Then, the charcoal compressed product is crushed to produce a crushed product of the charcoal compressed product (crushed charcoal compressed product) (compressed product crushing process).

[0037] In the charcoal production process, wood charcoal is produced by appropriately setting the charcoal distillation conditions (temperature, time, etc.) using a carbonization device (external combustion rotary kiln, internal combustion rotary kiln, fluidized bed reactor, moving bed reactor (shaft furnace), etc.). The volatile content of the produced wood charcoal (measured in accordance with JIS M8812:2006) is preferably 15 mass% or less. For example, in the case of cedar wood chips, the volatile content of the charcoal (wood charcoal) can be reduced to 4.8 mass% by carbonizing at 800°C for 1 hour.

[0038] In the aggregate manufacturing process, the wood charcoal produced in the charcoal manufacturing process is crushed as necessary (for example, to an average particle size of 1 mm or less). The wood charcoal particles are mixed alone with a binder, with the binder and water, or with the binder, water, and additives to produce a wood charcoal aggregate. Corn starch (starch), bentonite, coal tar, biomass tar, petroleum pitch, cement, etc. are used as the binder, and additives such as alkali and acid are added to some binders (such as corn starch) to produce a strong molded product. Note that a device (for example, an extruder) that can simultaneously crush the wood charcoal may be used for the kneading. The amount of binder added is preferably 1% by mass or more and 10% by mass or less (excluding numbers) when the wood charcoal is 100% by mass.

[0039] In the compression step, the wood carbonized aggregate (kneaded material) produced in the aggregate production step is compressed and molded to produce a compressed and molded charcoal product. As the compression molding method, a compression molding machine or an extrusion molding machine may be used, and for example, a roll press method using a roll rotation type compression molding machine (ring die type, flat die type, etc.) or a tableting method using a two-axis compression molding machine (screw type extrusion molding machine) can be used. The shape of the charcoal compressed product is arbitrary, and it is molded into, for example, a pellet (cylindrical) or a briquette (pillow shape).

[0040] In the compressed product crushing step, the charcoal compressed molded product produced in the compression step is crushed by a crusher to produce a crushed product of the charcoal compressed molded product (crushed charcoal compressed molded product). Examples of crushers include rod mills, hammer crushers, roll crushers, super sanders, jaw crushers, and fret mills. After crushing, the material is sieved using a sieve conforming to JIS Z8801-1:2019, for example, and a material of a predetermined particle size is used as the highly combustible carbonaceous material. For example, the crushed product has a particle size of less than 10 mm (sieve size of 10 mm), more preferably less than 5 mm (sieve size of 5 mm).

[0041] Here, in the compression step, it is preferable to produce a charcoal compression-molded product having the following properties. The volatile content and apparent density of the charcoal compression-molded product do not change before and after the compression-molding step, and the pulverized product of the charcoal compression-molded product has similar properties.

[0042] The volatile content of the charcoal compression molded product (measured according to JIS M8812:2006) is preferably 20% by mass or less. Usually, when sintered ore is produced, the volatile content of the coagulating material is controlled to be a predetermined value (for example, 10% by mass) or less in order to suppress failure of the exhaust gas electric dust collector that collects the exhaust gas generated during production, so it is preferable to specify the upper limit of the volatile content of the charcoal compression molded product. The increase in the volatile content of the charcoal compression molded product relative to the volatile content of the wood carbonized product is due to the use of a binder in the aggregate production process. In the present invention, the charcoal compression molded product (high combustibility carbonaceous material) is used in combination with a low combustibility carbonaceous material (coke powder and / or anthracite). Here, the volatile content of the coke powder in particular is often much lower than the above-mentioned predetermined value (10% by mass). In addition, the volatile content of anthracite is also low, around 5% by mass. In consideration of these points, the upper limit of the volatile content of the charcoal compression molded product is set to 20% by mass, which is higher than 10% by mass. By increasing the set upper limit, it becomes possible to use wood charcoal with a high volatile content as a material for the compressed charcoal. It is also preferable to determine the blending ratio of the compressed charcoal and the low combustibility carbonaceous material (coke powder and / or anthracite) based on the volatile content of the compressed charcoal and the volatile content of the low combustibility carbonaceous material used so as not to exceed a predetermined value of the volatile content according to the capacity of the exhaust gas electric dust collector.

[0043] The apparent density of the compressed charcoal is 0.6 g / cm 3 It is preferable that the content is 0.7 g / cm or more. 3 More preferably, the apparent density is 0.6 g / cm or more. The apparent density is measured by the bead volume displacement method. The bead volume displacement method is a measurement method adopted by Micromeritics, and is a volume displacement method using DryFlо (pseudo fluid), which is a highly fluid bead, as a measurement sample. Specifically, the volume of only the beads placed in the sample chamber is measured first, and then the sample is placed in the bead layer in the sample chamber and the volume is measured, and the volume of the measurement sample, including the pores and cavities, is calculated from the difference between the two volumes. The apparent density is the mass of the measurement sample divided by the calculated volume. The apparent density of the charcoal compression molded product is 0.6 g / cm 3By setting the temperature at or above this level, the atmospheric temperature in the vicinity of the combustion of the agglomeration agent during the production of sintered ore is increased, and the sintering productivity can be improved through the improvement of the yield. However, if the apparent density is less than 1.3 g / cm 3 If the temperature exceeds this range, the burning rate of the compressed charcoal product decreases, and the sintering rate decreases.

[0044] (Particle size of biomass charcoal (compressed and crushed charcoal)) The average particle size of the compressed charcoal crushed product is preferably 2.0 mm or more. If it is less than 2.0 mm, the time required for combustion is too short. As a result, the high-temperature retention time of the sintered layer is shortened, which reduces the yield and the productivity. The average particle size of the compressed charcoal crushed product is calculated as follows. After drying the compressed charcoal crushed product at 105°C for 2 hours or more, it is shaken for 5 minutes using a rotary tap shaker, and the arithmetic mean diameter is calculated based on the mass measurement of each particle size division, which is the average particle size. The arithmetic mean diameter is calculated by determining a representative diameter (the median value of the particle size division) for each particle size division, and multiplying this representative diameter by the mass fraction (≦1) of each particle size division.

[0045] (carbon mass ratio) In the present invention, the low combustible carbonaceous material and the compressed charcoal pulverized material can be used based on a predetermined blending ratio. In the predetermined blending ratio, the mass ratio of the carbon content of the compressed charcoal pulverized material to the carbon content of the total aggregate is preferably 10% by mass or more and 50% by mass or less. The mass ratio of the carbon content of the compressed charcoal pulverized material to the carbon content of the total aggregate is adjusted based on the carbon content of each carbonaceous material (low combustible carbonaceous material, compressed charcoal pulverized material) from industrial analysis of the low combustible carbonaceous material and the compressed charcoal pulverized material. If the blending ratio of the compressed charcoal pulverized material is less than 10% by mass, the effect of improving the sintering speed (combustion front descent speed), which is the blending effect of the high combustible carbonaceous material, cannot be obtained, and if the blending ratio of the compressed charcoal pulverized material exceeds 50% by mass, it is considered that the product yield will decrease due to the high-speed combustion of the compressed charcoal pulverized material.

[0046] The present embodiment has been described above. In the present invention, as a part of the agglomeration material, instead of using pulverized wood charcoal in its original state, pulverized wood charcoal compressed by compressing the wood charcoal is used. The apparent density of the pulverized charcoal compressed by compressing and pulverizing the wood charcoal increases more than that of the charcoal used as is. The pulverized charcoal compressed by compressing and pulverizing the wood charcoal increases the apparent density. The pulverized charcoal compressed by compressing the wood charcoal increases the combustibility suitable for sintering (the combustibility can be controlled), and the product yield improves, and as a result, the productivity improves. Although the charcoal compressed by compressing is still low density compared to other sintering raw materials, it is likely to be charged in the upper layer of the raw material packed bed (sintering layer). The pulverized charcoal compressed by compressing the wood charcoal charged in the upper layer has better combustibility than low combustible carbonaceous material, so the high temperature retention time is shorter and the sintering reaction does not proceed, and there is a concern that the yield of the upper layer of the sintering layer will deteriorate, resulting in a decrease in the productivity. However, in the present invention, the decrease in the productivity can be suppressed by supplying heat to the upper layer by reignition.

[0047] Second Embodiment Hereinafter, an example of another embodiment of the present invention will be described. This embodiment differs from the first embodiment only in the granulation process of the blended raw materials. Below, only the differences from the first embodiment will be described with reference to the drawings, and duplicated explanations will be omitted.

[0048] (Post-addition) In this embodiment, a part or all of the coagulant mixed based on a predetermined blending ratio is added later (post-added) during the granulation process. FIG. 2 is a schematic diagram showing an example of a sintering facility used in the second embodiment. As shown in FIG. 2, the sintering facility of the second embodiment is equipped with a post-added carbonaceous material tank 30. The post-added carbonaceous material tank 30 stores a mixture (mixed coagulant) of low combustibility carbonaceous material (coke powder and / or anthracite) and wood carbonized compressed powder based on a predetermined blending ratio (the blending ratio of each sintering raw material determined when the sintering raw material is blended to prepare a blended raw material). From the post-added carbonaceous material tank 30, the mixed coagulant is cut out in an amount corresponding to at least a part of the blending amount of the coagulant determined based on the predetermined blending ratio, transported to the granulator 2, and post-added.

[0049] The granulation process of this embodiment will be described in detail below. First, the sintering raw materials, excluding the coagulant (low combustibility carbonaceous material and wood carbonized compressed powder) that are added later, that are cut out from the raw material tank group 1, are first charged into the granulator 2, mixed, and granulation is started after humidity adjustment (hereinafter, the granulated sintering raw materials excluding the coagulant that is added later are referred to as the pre-granulated material). After a certain time has passed (during the granulation process), the post-added coagulant is charged into the granulator 2 to produce the blended raw material granulated material. By adding the post-added coagulant later at an appropriate timing, the post-added coagulant is coated on the pre-granulated material, that is, it is not included in the pre-granulated material, but exists as an independent particle attached or not attached to the surface layer of the pre-granulated material. By using the blended raw material granulated material coated with the post-added coagulant, it is possible to adjust the timing of the start of combustion of the post-added coagulant in the sintering process.

[0050] The post-addition during the granulation process is carried out, for example, as follows. As shown in FIG. 2, a piston-flow type cylindrical granulator 2 with a central axis inclined downward toward the downstream side is used, and a small transport conveyor is inserted from the downstream outlet to a predetermined position inside the granulator 2. When the sintering raw materials excluding the post-addition coagulant (hereinafter also referred to as the pre-post-addition sintering raw materials) are charged from the upstream inlet, the pre-post-addition sintering raw materials are mixed and then water is added, and the charged materials move downstream while being granulated. The post-addition coagulant is carried on the transport conveyor and carried from the downstream outlet of the granulator 2 to the internal upstream side. The post-addition coagulant is added at a predetermined position to the pre-granulated material that has been granulated and moved from the upstream side inside the granulator 2, and all the sintering raw materials are further granulated and discharged from the downstream outlet as a blended raw material granulated material.

[0051] As described above, when the mixed coagulant is added later, the mixed coagulant is wrapped around the granulated material of the blended raw materials, which promotes the reaction with the oxygen in the air supplied to the raw material packed bed. In addition, the heated circulating gas supplies sufficient heat for combustion, which results in an improved combustion speed of the coagulant, leading to improved productivity. If the mixed coagulant is encapsulated by the batch granulation, it is difficult for it to receive the oxygen and heat required for combustion. Specifically, the heat transfer of the heated circulating gas proceeds from the surface layer of the granulated material to the inside, which delays the timing at which the coagulant starts to burn. As a result, the progress of sintering is delayed, which reduces the production rate.

[0052] Here, in the case of post-addition during the granulation process, the mass ratio of the post-added coagulating agent may be 30% or more by mass relative to the total mass of the coagulating agent, and the granulation time until the post-added coagulating agent is added may be 80% to 96% of the total granulation time. The ratio of the post-added coagulating agent must be 30% or more by mass in order to obtain the post-addition effect. It is preferable to post-add the entire amount of the coagulating agent (100% by mass). Regarding the timing of post-addition, it is preferable that the granulation time of the pre-post-addition sintering raw material before the post-addition coagulating agent is 80% to 96% of the total granulation time of the sintering raw material, that is, the timing of post-addition is within the range of 80% to 96% of the total granulation time of the sintering raw material in the granulation process. For example, when the total granulation time is 240 seconds, the mixed raw material (pre-post-addition sintering raw material) excluding the post-addition coagulating agent may be granulated for 225 seconds, and then the post-addition coagulating agent may be added and granulated for 15 seconds. If the post-addition is earlier than 80% of the total granulation time, it is not possible to sufficiently prevent the post-added coagulant from being included in the granulated material. Also, if the post-addition is later than 96% of the total granulation time, the granulation process of the post-added coagulant will be insufficient. Here, the total granulation time in the granulation process does not include the time during which the sintering raw materials are simply mixed (mixing time) from when they are put into the granulator 2 until water is added. In sintering, a drum mixer 2 is mainly used, which is a piston flow type with a constant speed. Therefore, the post-addition position can be implemented by making the above-mentioned granulation time correspond to the distance in the machine length direction of the drum mixer 2. EXAMPLES

[0053] In the examples, verification was performed using a method commonly known as the sintering pot test. The sintering pot test is a test in which sintering raw materials (mixed raw materials) containing a fuel coagulant are charged into a container of a specified size, ignited from the top, and sucked downward to advance sintering. The sintering pot test device does not move the raw material packed bed using a pallet like the Dwight Lloyd (DL) type sintering machine, but it is a test device that can simulate sintering using a DL type sintering machine. As shown in Tables 3 and 5 below, a total of 20 tests were performed, including 5 comparative examples and 15 invention examples. First, the raw materials used in the tests and the test method are explained in order, and then the test results are described.

[0054] (raw materials) Table 1 shows the results of proximate and elemental analyses of the low and high combustibility carbon materials used in the test, as well as the apparent densities. In the proximate analyses, the ash, volatile matter, and fixed carbon contents [mass%-dry] were measured in accordance with the provisions of JIS M8812:2006. In the elemental analyses, the contents [mass%] of carbon (C), hydrogen (H), nitrogen (N), and total sulfur (Total-S) were measured in accordance with the provisions of JIS M8813:2006. The apparent densities were measured by the bead volume displacement method described above. In this test, the coke powder (low combustibility carbon material), lignite char (high combustibility carbon material), and charcoal compression molding (high combustibility carbon material), which is biomass charcoal, shown in Table 1, were used as agglomerates (see Table 3A below). Note that data for other high combustibility carbon materials (semi-coke, subbituminous coal char) are listed for reference. As shown in Table 1, the apparent density of the compressed charcoal is smaller than that of coke breeze and other highly combustible carbonaceous materials. Therefore, the compression molding process is necessary.

[0055] The lignite char used was made by carbonizing coal with a Roga index of 0.0 as raw coal. The Roga index is calculated by the Roga test method specified in JIS-M8801-1:2019. The calculation method can be performed by referring to the above-mentioned document (JP 2020-56086 A), so a detailed explanation will be omitted here.

[0056] [Table 1]

[0057] (Raw material blend) Tables 2 and 3 show the mixing ratio (mass%) of each sintering raw material for the mixed raw materials used in the test. As shown in Table 2, the ratio of new raw materials (iron ore, limestone, quicklime, and olivine) and return ore was constant in all test examples. Iron ores A to E are iron ores of different brands (origins). The mixing ratio of return ore was 15.0 mass%, with the new raw materials (iron ore, limestone, quicklime, and olivine) being 100 mass%.

[0058] [Table 2]

[0059] Table 3 shows the mixing ratio (mass%) of the coagulant in the mixed raw materials used in the test. As shown in column B of Table 3, in the test examples (Comparative Examples 0-1 and 1-1) in which only low combustibility carbonaceous materials (coke powder) were used, the new raw materials were taken as 100 mass%, and the mixing ratio of the low combustibility carbonaceous materials was 4.5 mass%. In the test examples (test examples other than Comparative Examples 0-1 and 1-1) in which highly combustible carbonaceous materials (biomass coal or lignite char) were blended, as shown in column C of Table 3, the fixed carbon content of the agglomerate (4.5% by mass of powdered coke) in Comparative Examples 0-1 and 1-1 was used as a basis, and the blending ratio of the low combustible carbonaceous material (powdered coke) and the high combustible carbonaceous material (biomass coal or lignite char) was adjusted based on the mass ratio of the carbon content (coke powder) (coke powder) and the high combustible carbonaceous material (biomass coal or lignite char) (column B of Table 3) and the fixed carbon content (carbon content) of the low combustible carbonaceous material (powdered coke) and the high combustible carbonaceous material (biomass coal or lignite char) in industrial analysis (Table 1) so that the fixed carbon content (carbon content) of all the agglomerates (low combustible carbonaceous materials and high combustible carbonaceous materials) contained in the blended raw materials in the industrial analysis was constant in all test examples. The blending ratios (of low combustibility carbonaceous materials and high combustibility carbonaceous materials) to the total aggregate in column D of Table 3 are values ​​calculated based on the blending ratios of low combustibility carbonaceous materials and high combustibility carbonaceous materials in column C of Table 3. The blending ratios of each sintering raw material shown in Tables 2 and 3 are examples of the above-mentioned "predetermined blending ratios."

[0060] [Table 3]

[0061] (Test conditions) The test conditions for each test example are shown in the upper part of Table 5 below. The test results shown in the lower part of Table 5 will be described later.

[0062] (Adjustment of aggregate particle size) As shown in Table 5, the average particle size of the agglomerate was one level for coke powder (arithmetic mean diameter 1.2 mm), one level for lignite charcoal (arithmetic mean diameter 3.6 mm), and three levels for biomass charcoal (compressed charcoal) (arithmetic mean diameter 1.2 mm, 2.4 mm, 3.6 mm). The compressed charcoal was crushed using compressed charcoal crushed material. The particle size of the agglomerate was adjusted by completely drying each sample (each agglomerate) in a dryer adjusted to 105 ° C, and then sieving with head beating using a rotary tap shaker for 5 minutes or more to adjust it to the specified average particle size shown in Table 5. For the sieving, nine types of sieves with different sieve meshes (opening dimensions) specified in JIS Z8801-1:2019 were used.

[0063] Table 4 shows the particle size distribution at each level of each aggregate (arithmetic mean diameter 1.2 mm, 2.0 mm, 2.4 mm, 3.6 mm). Also, FIG. 3 is a graph of the undersieve cumulative particle size distribution, which shows the particle size distribution shown in Table 4 as a cumulative ratio (mass%). In Table 4, the particle size category "+9.5 mm" is the oversieve when sieved with a 9.5 mm sieve. Also, the particle size category "8.0 mm-9.5 mm" is the oversieve when sieved with a 8.0 mm sieve and the undersieve when sieved with a 9.5 mm sieve. The same applies to the particle size categories "4.75 mm-8.0 mm" to "0.125 mm-0.25 mm". The particle size category "-0.125" refers to the particle size that falls below the sieve size when sieved through a sieve with 0.125 mm mesh.

[0064] [Table 4]

[0065] [Table 5]

[0066] (Mixing of coagulant) Prior to granulation, only the coagulant was put into the drum mixer in the ratio shown in column D of Table 3, and mixed for 4 minutes to prepare the test sample (mixed coagulant). In the test case in which post-addition was performed, a predetermined ratio (see post-addition ratio in Table 5) was taken from the coagulant after mixing (hereinafter also referred to as mixed coagulant) to prepare the coagulant for post-addition (hereinafter also referred to as post-addition coagulant).

[0067] (Granulation method) A cylindrical batch drum mixer (25 rpm) with a diameter of 600 mm and a length of 800 mm was used as the granulator. In the test case of lump-sum granulation, all sinter raw materials consisting of new raw materials, coagulant (mixed coagulant), and return ore were put into the granulator, mixed for 4 minutes, then water was added (humidity control) to reach the target moisture value, and mixed (granulated) for another 4 minutes. In the test case of post-addition, the sinter raw materials except for the post-addition coagulant were put into the granulator, mixed for 4 minutes, then water was added (humidity control) to reach the target moisture value, mixed (granulated) for a specified time, the granulator was stopped once, the post-addition coagulant was added, and mixed (granulated) for a specified time. Here, the total granulation time before and after the addition of the post-addition coagulant in the test case of post-addition was the same as that of lump-sum granulation (4 minutes). The target moisture value was set to 7.5 mass% of the mass of all sinter raw materials including all coagulant and return ore.

[0068] (Charging method) The pot test equipment used was a cylindrical pot with a diameter of 300 mm and a height of 500 mm. 68 kg of the granulated raw material was dropped into the sinter pot from above.

[0069] (Firing conditions) After the granulated raw materials were charged, the surface of the raw material packed bed was ignited for 1.0 minute using an ignition device (flame heating). 1.0 minute after the end of ignition, re-ignition was performed for 1.0 minute. The time from the end of ignition to the start of re-ignition (separation time) of 1.0 minute corresponds to 4% of the length of the total strand when converted to an actual machine. The ignition time and re-ignition time were both 1.0 minute (calorie amount of 25 MJ / ton of raw materials as suction gas sensible heat). Since the heat loss is large in the pot test, the amount of LPG gas required to be fired is about 100 MJ / ton of raw materials. The suction negative pressure during sintering was adjusted by the valve opening on the blower suction side so that the measured value below the pot was constant at 1300 mmAq (12.7 kPa).

[0070] Below the pot, temperature was measured with a thermocouple along with the pressure. During sintering, when the combustion zone reached the bottom of the raw material packed bed, the exhaust gas temperature below the pot began to rise, eventually reaching a peak, and then decreasing as the coke combustion ceased. Three minutes after the exhaust gas temperature reached its peak, the blower suction was stopped. The sintering time was defined as the time from the start of ignition to the time the exhaust gas temperature reached its peak. The sintering speed (BTS) was calculated by dividing the raw material layer thickness by the sintering time.

[0071] (finished product yield) After sintering, the obtained sinter cake was dropped four times from a height of 2 m, and the sintered ore with a grain size of +5 mm (over 5 mm) excluding the bedding ore was collected as the sintered product, and its mass was calculated and defined as the sintered product mass. The sintered product mass divided by the sinter cake mass excluding the bedding ore was defined as the product yield.

[0072] (Production rate) The productivity is calculated by multiplying the amount of sintered product (amount of product (tons)) by the above-mentioned sintering time (time converted into days) and the firing area (pot bottom area (m 2 )) and divided by.

[0073] (Test Results) The test results are shown in the lower column of Table 6 and in Figures 4 to 6. Figure 4 is a graph showing the test results (productivity) of Comparative Example 0 series, which is a test case of one-stage ignition, and the test cases of Inventive Example 1 series and Comparative Example 1 series, which are test cases of reignition, with the horizontal axis showing the blending ratio (carbon mass ratio) of the highly combustible carbonaceous material (compressed charcoal or lignite charcoal) to the total aggregated material. Figure 5 is a graph showing the test results (productivity) of the test cases (Inventive Examples 2-1 to 2-5) in which the aggregated material was added in its entirety after reignition and after addition was performed, and the test case of Comparative Example 2-1, in which lignite charcoal char was used as the highly combustible carbonaceous material instead of compressed charcoal, under the same conditions as Inventive Example 2-3, with the horizontal axis showing the ratio of the granulation time until after addition to the total granulation time. For reference, the value of the productivity of Inventive Example 1-3, in which lump granulation was performed instead of after addition under the same conditions as Inventive Example 2-3, is shown by a broken line. Figure 6 is a graph showing the test results (productivity rate) of the test cases of Invention Example 3 series, which is a test case in which re-ignition and lump-sum granulation were performed and the average particle size conditions of the charcoal compression molded product were changed, and the test cases of Invention Examples 1-3, which are similar to Invention Example 3 series but differ only in the average particle size conditions of the charcoal compression molded product, with the horizontal axis representing the average particle size (arithmetic mean diameter) of the charcoal compression molded product.

[0074] As shown in Table 5 and FIG. 4, in the test cases of the one-stage ignition sintering method (Comparative Examples 0-1 and 0-2), although the sintering speed is improved by using biomass charcoal, the product yield is significantly affected, and the production rate is reduced. In contrast, in the test cases of the reignition sintering method (Invention Example 1 Series: Invention Examples 1-1 to 1-5), the product yield is recovered, so the production rate is improved (especially Invention Examples 1-3 and 1-4). In addition, when comparing the test cases using the reignition sintering method, and Comparative Example 1-1, which did not use a highly combustible carbonaceous material, with Invention Example 1-3, which used a highly combustible carbonaceous material (biomass charcoal), and Comparative Example 1-2, which used a highly combustible carbonaceous material (brown coal char), Invention Example 1-3, which used biomass char, has a greater improvement in sintering speed (BTS) than Comparative Example 1-2, which used brown coal char, and as a result of maintaining the product yield, the production rate is improved. In addition, in the first series of invention examples, by using powdered coke, which is a low-combustibility carbonaceous material, in combination with a highly combustible carbonaceous material (biomass charcoal), the combustion area is expanded, ensuring product yield, and the sintering speed, which is determined by the combustion of the highly combustible carbonaceous material, is improved, which is thought to improve productivity.

[0075] As shown in Table 5 and Figure 5, in the invention examples 2-1 to 2-5 in which the entire amount of the coagulating agent was added later, the sintering speed was significantly improved and the productivity was improved compared to the invention example 1-3 in which no later addition was performed (lump granulation). In particular, as shown in Table 5, when the ratio of the later addition of the coagulating agent is 30 mass% or more (see invention examples 2-3, 2-6, and 2-7), and when the granulation time until the later addition of the coagulating agent is 80% or more and 96% or less of the total granulation time (see invention examples 2-1 to 2-5), the productivity improvement effect is large.

[0076] As shown in Table 5 and Figure 6, in the invention example 3 series and invention examples 1-3, when the average particle size of biomass charcoal (compressed molded pulverized charcoal) is coarsened up to 3.6 mm, the sintering speed and productivity improve as the particles become coarser. This is thought to be because the gas flow rate increases due to the improved breathability caused by the coarse particles, and because compressed molded pulverized charcoal is a highly combustible carbon material, it burns quickly even when the particles are coarse. [Explanation of symbols]

[0077] 1: raw material tank group, 2: granulator, 3: ignition furnace, 4: reignition furnace, 5: pallet travel direction, 6: downward suction, 7: atmospheric suction area, 10: raw material packed bed, 10A: combustion zone, 10x: slope, 11: sinter cake, 20: inclined flat plate chute type charging device, 21: blended raw material surge hopper, 22: inclined flat plate chute, 30: post-added carbonaceous material tank, 100: DL type sinter machine

Claims

1. In a method for producing sintered ore, sintering of granulated raw materials is promoted by downward suction, Using an ignition furnace and a re-ignition furnace arranged at a predetermined interval downstream of the ignition furnace, ignition by the ignition furnace and re-ignition by the re-ignition furnace are performed, A method for producing sintered ore, characterized in that powdered coke and / or anthracite and a crushed product obtained by compressing and molding an aggregate of wood carbonized material are used as a coagulant for the blended raw materials in a predetermined blending ratio.

2. 2. The method for producing sintered ore according to claim 1, wherein a part or all of the coagulating agent mixed based on the predetermined blending ratio is added later during the granulation process.

3. The method for producing sintered ore according to claim 2, characterized in that, in the case of post-addition during the granulation process, the mass ratio of the post-added coagulation agent is 30 mass% or more relative to the total mass of the coagulation agent, and the granulation time until the post-added coagulation agent is added is 80% or more and 96% or less relative to the total granulation time.

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