Method for producing sintered ore

Abstract

Provided is a method for producing sintered ore, which produces sintered ore by means of downward suction, and which is provided with an ignition furnace that performs initial ignition and a reignition furnace that performs reignition and is disposed downstream of the ignition furnace at a prescribed interval, using a Trulosi sintering machine that performs sintering by means of downward suction, a low-combustibility carbon material having a combustion initiation temperature of more than 550 DEG C and a high-combustibility carbon material having a combustion initiation temperature of 550 DEG C or less are used as the congealing material for the raw materials, and the ratio of particles having a particle size of 2.8 mm or more in the high-combustibility carbon material is 30-80 mass%.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing sintered ore used as a raw material for a blast furnace. Background Art

[0002] The main raw material for blast furnace ironmaking is sintered ore. In recent years, as a method for manufacturing sintered ore, a re-ignition sintering method (hereinafter referred to as Patent Document 1) for performing two-stage (twice) ignition for the purpose of improving the sintering yield has been proposed. The re-ignition sintering method is a technique in which, after the first ignition is completed, air is sucked in the air suction region for a predetermined time, and then the second ignition (re-ignition) is performed. In addition, as a technique for improving the re-ignition sintering method, a method for strengthening the segregation of carbonaceous materials (condensing materials) in the layer thickness direction of the raw material filling layer (hereinafter referred to as Patent Document 2), and a method using a char (hereinafter referred to as a highly combustible carbonaceous material) obtained by dry-distilling coal having a Roga index of 10 or less as the original coal as the condensing material (hereinafter referred to as Patent Document 3) have been proposed.

[0003] Regarding the ordinary single-stage (once) ignition sintering method, various techniques using highly combustible carbonaceous materials (carbonaceous materials having a lower combustion start temperature than low-combustible carbonaceous materials such as coke or anthracite) have been shown. For example, techniques regarding the appropriate mixing ratio of highly combustible carbonaceous materials and low-combustible carbonaceous materials (hereinafter referred to as Patent Document 4), techniques regarding the preferred particle size of highly combustible carbonaceous materials (hereinafter referred to as Patent Document 5), and addition methods in the granulation process (hereinafter referred to as Patent Documents 4 and 6) have been proposed.

[0004] Patent Document 1 discloses a method for manufacturing sintered ore (re-ignition sintering method) using a Dwight-Lloyd (DL) type sintering machine, the Dwight-Lloyd (DL) type sintering machine including: a plurality of pallets that are continuously arranged in the forward direction from upstream to downstream and into which sintering raw materials are charged; an igniter that ignites the raw material filling layer in the upstream pallet in the forward direction among the plurality of pallets from above; a wind box that sucks air from below the plurality of pallets; a flame heating device that is separately arranged on the downstream side of the igniter and performs flame heating on the entire width of the upper surface of the raw material filling layer; and an air suction region that is formed between the igniter and the flame heating device, sucks air by suction from below, and does not directly heat from above. It is described that the reducibility can be maintained, and both the sintering yield and the cold strength of the sintered ore can be improved.

[0005] A method for manufacturing sintered ore is disclosed in Patent Document 2. The method uses a Dwight-Lloyd sintering machine. For a plurality of pallets that cyclically move in the forward direction from upstream to downstream, a raw material filling layer is formed by dividing it into a lower layer and a surface layer respectively. When manufacturing sintered ore with the concentration of solid combustibles in the lower layer being lower than that in the surface layer, the raw material filling layer in the pallet on the upstream side of the forward direction is ignited from above. After the ignition part of the raw material filling layer moves to the downstream side of the forward direction, the ignition part is reignited. It is described that: even if the concentration of solid combustibles in the surface layer is increased, unburned components can be reduced and effectively utilized as heat, thereby the firing speed can be increased, the yield can be increased, and the productivity can be further increased.

[0006] A technique is disclosed in Patent Document 3. The technique uses a Dwight-Lloyd (DL) type sintering machine equipped with an igniter and a flame heating device. The flame heating device is separately provided on the downstream side of the igniter and flame-heats the upper surface of the raw material filling layer. Among them, the charged compound raw material is a substance obtained by removing a part or the total amount of only carbonaceous material and then adding the removed carbonaceous material to the above raw material during or after granulation by adding moisture. The later-added carbonaceous material is set as a coke (coke) obtained by dry-distilling coal with a Roga index of 10 or less as raw coal. It is described that: in the granulation process of the re-ignition sintering method, by adding coke later, the yield and productivity are increased.

[0007] A method for manufacturing sintered ore is disclosed in Patent Document 4 as a technique for increasing the yield of sintering. Among them, as the coagulant for sintering raw materials, a low-combustibility carbonaceous material containing at least one of pulverized coke and anthracite and a high-combustibility carbonaceous material with a combustion start temperature lower than that of the low-combustibility carbonaceous material are used. The mass ratio of the carbon component of the high-combustibility carbonaceous material to the carbon component of the coagulant is 25% by mass to 75% by mass, and at least one of the low-combustibility carbonaceous material and the high-combustibility carbonaceous material is added in the latter half of the granulation process of the sintering raw materials.

[0008] A technique is disclosed in Patent Document 5. In a method for manufacturing sintered ore in which pseudo-particle segregation obtained by granulating sintering raw materials including iron ore, auxiliary raw materials, return fines, and solid carbonaceous materials is charged into a pallet of a sintering machine and firing is performed by creating a carbon concentration difference in the height direction of the raw material layer, as part or all of the solid carbonaceous materials in the sintering raw materials, when blending oil palm shell carbon, which is a solid carbide manufactured by heat-treating oil palm shells, oil palm shell carbon having an average particle size adjusted to 2.7 mm to 6.0 mm is blended. By using oil palm shell carbon as the solid carbonaceous material for sintering, the emission amount of carbon dioxide, which is a global warming gas, is suppressed, and the sintering productivity is increased through appropriate operation techniques. In addition, it is pointed out that: as part of the solid carbonaceous materials in the sintering raw materials, when blending oil palm shell carbon, it is preferable to blend oil palm shell carbon having an average particle size adjusted to be coarser in the range of 1.0 mm to 4.5 mm compared to the average particle size of pulverized coke or anthracite, which is the solid carbonaceous material.

[0009] Patent Document 6 discloses: a method for manufacturing a carbonaceous material for sintering in which the Roga index of coal is calculated and a coal having a Roga index of 10 or less is used to manufacture the carbonaceous material for sintering; and in the granulation step of the sintering raw materials, at least a part of the predetermined blending amount of the carbonaceous material for sintering is post-added during or at the end of the granulation step. It is described that the emission amount of NOx generated during the manufacture of sintered ore can be reduced.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-2457

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-29603

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-84204

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 2022-33594

[0016] Patent Document 5: Japanese Patent Application Laid-Open No. 2014-218713

[0017] Patent Document 6: Japanese Patent Application Laid-Open No. 2020-56086 Summary of the Invention

[0018] Problems to be Solved by the Invention

[0019] High combustibility carbon materials refer to carbon materials with high combustibility, that is, carbon materials with a fast combustion rate. Regarding the combustion rate of carbon materials (condensation materials), various measurement methods and measurement results have been published. However, if the measurement is not carried out under sufficient management, there is a problem that the obtained measurement results deviate greatly. Therefore, as an index representing the combustion rate, the ignition start temperature (ignition temperature) having a substantial correspondence with the combustion rate is adopted. In the present invention, low combustibility carbon materials refer to carbon materials with a high ignition start temperature such as coke and anthracite (carbon materials with an ignition start temperature exceeding 550 °C), and high combustibility carbon materials refer to carbon materials with an ignition start temperature lower than that of low combustibility carbon materials (carbon materials with an ignition start temperature of 550 °C or lower).

[0020] As described above, it has been pointed out that in the single-point ignition sintering method, by using high combustibility carbon materials, the yield and productivity are improved due to the increase in the combustion rate of the carbon materials in the raw material filling layer, and it has also been pointed out that in the re-ignition sintering method, by using coke as a high combustibility carbon material, the yield and productivity are improved. However, so far, in the re-ignition sintering method, the preferred necessary conditions for using high combustibility carbon materials have not been studied in detail. The inventors of the present invention have conducted in-depth research on the necessary conditions and as a result, found that under specific conditions, the productivity is further improved, thus completing the present invention. The object of the present invention is to provide a method for manufacturing sintered ore with further improved productivity when adopting the technology of the re-ignition sintering method.

[0021] Means for solving the problem

[0022] According to several aspects of the present invention, the following is provided.

[0023] [1] A method for manufacturing sintered ore, which uses a Dwight-Lloyd sintering machine to manufacture sintered ore. The Dwight-Lloyd sintering machine is equipped with an ignition furnace for initial ignition and a re-ignition furnace that is arranged at a prescribed interval on the downstream side of the ignition furnace and performs re-ignition, and sintering is carried out by downward suction, wherein

[0024] As the condensation material for the blending raw materials, low combustibility carbon materials with an ignition start temperature exceeding 550 °C and high combustibility carbon materials with an ignition start temperature of 550 °C or lower are used,

[0025] The ratio of the particle size of 2.8 mm or more in the above high combustibility carbon materials is 30 mass% to 80 mass%.

[0026] [2] The method for manufacturing sintered ore according to [1], wherein for the above high combustibility carbon materials, a pulverized material obtained by pulverizing a compression molded product obtained by compressing and molding an aggregate of wood carbide is used.

[0027] [3]The method for manufacturing sintered ore according to [2], wherein the manufacturing of the crushed material obtained by crushing the compression molded product obtained by compressing and molding the aggregate of wood carbide has the following steps: a carbide manufacturing step of manufacturing wood carbide by carbonizing wood; an aggregate manufacturing step of crushing the wood carbide as needed to form wood carbide particles, and manufacturing an aggregate of wood carbide by kneading the wood carbide particles alone or with a binder; a compression step of manufacturing a compression molded product obtained by compressing the aggregate; and a compressed product crushing step of crushing the compression molded product.

[0028] [4]The method for manufacturing sintered ore according to any one of [1] to [3], wherein the mass ratio of the carbon component of the highly combustible carbon material to the carbon component of the coagulant is 25% by mass to 75% by mass.

[0029] [5]The method for manufacturing sintered ore according to [4], wherein the average particle size of the low combustibility carbon material is in the range of 0.8 mm to 1.2 mm.

[0030] [6]The method for manufacturing sintered ore according to [5], wherein a segregation-enhanced charging device is used as the charging device for the mixed raw materials.

[0031] [7]The method for manufacturing sintered ore according to [5], wherein only the low combustibility carbon material in the coagulant is added in the latter half of the granulation step.

[0032] [8]The method for manufacturing sintered ore according to any one of [1] to [3], which suppresses the amount of air suction downward only in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering strand.

[0033] [9]The method for manufacturing sintered ore according to [8], which sets the average free cylinder air volume of the atmosphere sucked in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering strand to 60% to 80% of the average free cylinder air volume of the atmosphere sucked in the section on the downstream side of the outlet of the re-ignition furnace.

[0034]

[10] The method for manufacturing sintered ore according to [8], which sets the average negative pressure in the wind box or wind box branch pipe in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering strand to 40% to 70% of the average negative pressure in the wind box or wind box branch pipe in the section on the downstream side of the outlet of the re-ignition furnace.

[0035]

[11] The method for manufacturing sintered ore according to [8], which sets the separation time, that is, the time required for the pallet to pass through the section between the ignition furnace and the re-ignition furnace, to 30 seconds to 2 minutes.

[0036]

[12] In the method for manufacturing sintered ore according to any one of [1] to [3], the separation time, which is the time required for the pallet car to pass through the section between the ignition furnace and the re-ignition furnace, is 1 minute or more, and the oxygen concentration of the suction gas sucked downward from the surface side of the sintered layer in the above section is 30% by volume or more.

[0037]

[13] In the method for manufacturing sintered ore according to

[12] , the separation time is 5 minutes or less, and the oxygen concentration of the suction gas is 40% by volume or less.

[0038]

[14] In the method for manufacturing sintered ore according to any one of [1] to [3], the start of oxygen enrichment of the suction gas sucked downward from the surface side of the sintered layer is set after the end of re-ignition. The oxygen enrichment time from the start of the oxygen enrichment to the end of the oxygen enrichment is 30 seconds or more, and the oxygen concentration of the suction gas sucked downward during the oxygen enrichment time is 30% by volume or more.

[0039]

[15] In the method for manufacturing sintered ore according to

[14] , the oxygen enrichment time is 2 minutes or less, and the oxygen concentration of the suction gas is 40% by volume or less.

[0040]

[16] In the method for manufacturing sintered ore according to

[14] , the start of the oxygen enrichment is more than 0 seconds and within 30 seconds from the end of re-ignition.

[0041]

[17] In the method for manufacturing sintered ore according to

[16] , the start of the oxygen enrichment is more than 0 seconds and within 10 seconds from the end of re-ignition.

[0042]

[18] In the method for manufacturing sintered ore according to any one of [1] to [3], in the pallet car charged with the above-mentioned mixed raw materials, a support member having a sinter cake support surface is vertically provided on the grate bar in a manner buried in the raw material filling layer.

[0043] According to the present invention, in the method for manufacturing sintered ore using a Dwight-Lloyd sintering machine that has an ignition furnace for initial ignition and a re-ignition furnace that is arranged at a prescribed interval downstream of the ignition furnace and performs re-ignition, and performs sintering by suction from below, by using a low-combustibility carbon material and a high-combustibility carbon material as the binding material, and setting the ratio of the high-combustibility carbon material with a particle size of 2.8 mm or more to 30 mass% to 80 mass%, the productivity can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1It is a schematic diagram showing an example of a DL type sintering machine used in the manufacturing method of sintered ore (re-ignition sintering method) of the first embodiment.

[0045] Figure 2 It is a schematic diagram showing an example of a segregation strengthening type charging device.

[0046] Figure 3 It is a graph showing the particle size distribution of sintering raw materials in each layer (the first layer to the fifth layer) of the raw material packed bed where segregation strengthening type charging is implemented.

[0047] Figure 4 It is a graph showing the ratio of the average particle size of each layer (the first layer to the fifth layer) in the raw material packed bed where segregation strengthening type charging is implemented to the average particle size of the whole.

[0048] Figure 5 It is a graph showing the carbon concentration distribution in each layer (the first layer to the fifth layer) of the raw material packed bed where segregation strengthening type charging is implemented.

[0049] Figure 6 Relating to the second embodiment, it is a schematic diagram showing an example of air volume control in a DL type sintering machine used in the manufacturing method of sintered ore (re-ignition sintering method).

[0050] Figure 7 Relating to the third embodiment, it is a schematic diagram showing an example of oxygen enrichment in a DL type sintering machine used in the manufacturing method of sintered ore (re-ignition sintering method).

[0051] Figure 8 Relating to the fourth embodiment, it is a schematic diagram showing another example of oxygen enrichment in a DL type sintering machine used in the manufacturing method of sintered ore (re-ignition sintering method).

[0052] Figure 9 Relating to the fifth embodiment, it is a schematic diagram showing an example of a sintering trolley used in the manufacturing of sintered ore using a stand to support the sintering technology.

[0053] Figure 10 Relating to Example 1, it is a graph showing the relationship between the ratio of the particle size +2.8 mm of a highly combustible carbon material and the productivity.

[0054] Figure 11 Relating to Example 1, it is a graph showing the relationship between the mass ratio of the carbon component of a highly combustible carbon material to the carbon component of a binder material and the productivity.

[0055] Figure 12 Relating to Example 1, it is a graph showing the relationship between the average particle size of a low combustibility carbon material (pulverized coke) and the productivity.

[0056] Figure 13 Referring to Example 2, it is a graph showing the relationship between the air volume ratio of the empty cylinder and the productivity.

[0057] Figure 14 Referring to Example 3, it is a graph showing the relationship between the oxygen concentration and the productivity.

[0058] Figure 15 Referring to Example 4 (Test 1), it is a graph showing the relationship between the oxygen concentration and the productivity.

[0059] Figure 16 Referring to Example 4 (Test 2), it is a graph showing the relationship between the oxygen enrichment time and the productivity.

[0060] Figure 17 Referring to Example 5 (the high-combustibility carbon material is 50% by mass (carbon component mass ratio)), it is a graph showing the relationship between the separation time and the productivity.

[0061] Figure 18 Referring to Example 5 (the high-combustibility carbon material is 0% by mass), it is a graph showing the relationship between the separation time and the productivity. Detailed implementation manners

[0062] Hereinafter, the present invention and its preferred embodiments will be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the accompanying drawings, for components having substantially the same function, the same or similar names or the same or similar symbols are used, thereby omitting repeated descriptions.

[0063] 《First Embodiment》

[0064] First, a Dravo (DL) type sintering machine used in the re-ignition sintering method and a method for manufacturing sintered ore using the same will be described. In the DL type sintering machine used in the re-ignition sintering method, at the downstream side in the advancing direction of the pallet of the igniter for the first ignition, a re-igniter for the second ignition is provided with a prescribed interval (corresponding to the "separation distance" described later) left open. The re-igniter is a flame heating device that heats the upper surface (surface) of the raw material filling layer after the first ignition by a flame.

[0065] Figure 1 It is a schematic diagram showing an example of the Dravo (DL) type sintering machine used in the re-ignition sintering method. It should be noted that in the following description, based on the advancing direction 5x of the pallet, the feeding side ( Figure 1 the left side) is set as the upstream side, and the discharging side ( Figure 1 the right side) is set as the downstream side. As Figure 1As shown in FIG. 1 , in the DL type sintering machine 101, a re-ignition furnace 4 is provided at a predetermined interval (separation distance) on the downstream side of the ignition furnace 3. Figure 1 As shown in , the ignition furnace 3 has an igniter 31 for performing the first (initial) ignition (initial ignition) and an outer cover 32 covering it. In addition, the re-ignition furnace 4 has a re-igniter 41 for performing the second (second) ignition (re-ignition) and an outer cover 42 covering it. For example, the ignition furnace 3 is an ignition furnace equipped with a burner and the like used in the one-stage ignition sintering method, and the re-ignition furnace 4 may also be an ignition furnace similar to the ignition furnace used in the one-stage ignition sintering method. Figure 1 As shown in FIG. 1 , the outer cover 32 of the ignition furnace 3 and the outer cover 42 of the re-ignition furnace 4 are independent of each other, and an atmosphere suction area 7 is provided between the ignition furnace 3 and the re-ignition furnace 4 which are arranged at a predetermined interval (separation distance) in the carriage forward direction 5x.

[0066] The atmospheric suction area 7 is a section (area) where the raw material filling layer 10 in the trolley is not heated by a burner or the like, and the atmosphere (air) is sucked in by the lower suction 6x and supplied to the raw material filling layer 10. Figure 1 As shown in , the interval between the partition wall 32a on the downstream side of the outer cover 32 of the ignition furnace 3 and the partition wall 42a on the upstream side of the outer cover 42 of the re-ignition furnace 4 is the atmosphere suction area 7. Here, in this specification, the distance between the partition wall 32a and the partition wall 42a in the trolley forward direction 5x, that is, the distance of the trolley forward direction 5x of the atmosphere suction area 7 is called the separation distance, and the time required for the trolley (a plurality of trolley frames connected to move on a circulating track, not shown) of the DL type sintering machine 101 to pass through the separation distance (atmospheric suction area passing time) is called the separation time. It should be noted that in this specification, the raw material filling layer 10 has nothing to do with the presence or absence of ignition (including initial ignition) and re-ignition, and refers to a layer of mixed raw materials formed on the trolley, including a combustion zone 10A in which a sintering reaction is carried out by ignition and a sintered block 10B in which the sintering reaction is completed. In addition, in the following description, the raw material filling layer 10 after the initial ignition (after the start of firing) is also referred to as a sintering layer.

[0067] Here, the lower limit value (minimum value) of the appropriate range of the above-mentioned separation time is the limit at which the expansion of the combustion zone 10A can be fully obtained, and the upper limit value (maximum value) of the appropriate range of the separation time is dominated by the cooling of the upper layer of the sintering layer after the initial ignition. Therefore, the appropriate range of the separation time varies according to the embodiment (the first embodiment to the fifth embodiment) (the details will be described below), and can be set within the range of 0.5 minutes to 6 minutes. In the case of being lower than the lower limit value of the appropriate range, sufficient oxygen cannot be supplied to the combustion zone 10A of the upper layer of the sintering layer, and the expansion of the combustion zone 10A is suppressed. On the other hand, if the upper limit value of the appropriate range is exceeded, the upper layer of the sintering layer is reduced to a temperature below the sintering reaction, and it is difficult to obtain the productivity improvement effect of the re-ignition technology. Secondly, the separation distance is obtained by multiplying the separation time by the transfer speed (trolley speed) of the raw material filling layer 10 brought by the trolley. If the trolley speed of a standard commercial sintering machine is 3m / min, the appropriate range of the separation distance becomes 1.5m to 18m. Of course, the appropriate separation distance also changes according to the trolley speed. Therefore, the separation distance is different in each sintering machine.

[0068] The method for producing sintered ore using the re-ignition sintering method is a technology that adds a re-ignition process to the one-stage ignition sintering method (details will be described below). For the raw materials of the sintered ore (sintering raw materials), it is appropriate to use iron raw materials such as iron ore (powder), iron-containing miscellaneous raw materials such as oxide scale / ironmaking dust, auxiliary raw materials containing MgO such as peridotite, auxiliary raw materials containing CaO such as limestone, return ore, and condensing materials (carbon materials) that serve as fuel for sintering (condensation). Figure 1 As shown in FIG. 1 , each sintering raw material is stored in each raw material tank (11 to 1 X ), are cut out and mixed in a specified ratio. The mixed raw materials (mixed raw materials) are put into the drum mixer 2 for granulation to produce pseudo particles. The mixed raw materials after granulation (hereinafter, the mixed raw materials after granulation are also referred to as mixed raw material granules) are loaded from the mixed raw material buffer hopper 81 onto a trolley covered with bottom ore (not shown in the figure) to form a raw material filling layer 10.

[0069] The raw material filling layer 10 is continuously moved in the forward direction 5x of the trolley by the movement of the trolley. When the raw material filling layer 10 is moved under the ignition furnace 3, the carbon material on the surface of the raw material filling layer 10 is ignited by the flame of the igniter 31, and the sintering of the raw material filling layer 10 begins. A lower suction device 6 (see FIG. 1 ) is provided on the lower side of the trolley moving in the forward direction 5x of the trolley. Figure 6) The atmosphere (air) is sucked from below the pallet car. Through this downward suction, oxygen is supplied into the raw material filling layer 10. The combustion of the coagulant in the raw material filling layer 10 (combustion zone 10A) advances from the upper part to the lower part, and the raw material filling layer 10 is fired in sequence by the combustion heat of the coagulant. If the raw material filling layer 10 moves to below the re-ignition furnace 4 while passing through the atmosphere suction area 7, the raw material filling layer 10 is re-ignited by the flame of the re-igniter 41. The sintered cake 10B obtained by sintering the raw material filling layer 10 is discharged at the downstream end in the advancing direction 5x of the pallet car of the DL type sintering machine 101, and is sized by crushing, screening, etc. The sintered ore with a particle size that can be charged into the blast furnace becomes the raw material for blast furnace ironmaking.

[0070] As described above, in the re-ignition sintering method, after ignition by the ignition furnace 3 and after passing through the atmosphere suction area 7, that is, after a prescribed time interval (corresponding to the above-mentioned separation time) has elapsed, the raw material filling layer 10 is re-ignited using the re-ignition furnace 4. In the atmosphere suction area 7 on the downstream side of the ignition furnace 3, since heating from above, that is, combustion using a flame burner such as an igniter, is not performed, oxygen is sufficiently supplied into the raw material filling layer 10, and the coagulant in the combustion zone 10A burns. In addition, since the atmosphere suction area 7 is provided between the ignition furnace 3 and the re-ignition furnace 4, the combustion of the coagulant proceeds to a lower part due to an increase in the superficial gas velocity in the empty tower. As a result, the thickness of the combustion zone 10A expands in the upper part of the raw material filling layer 10. Then, on the basis of the expansion of the thickness of the combustion zone 10A in the atmosphere suction area 7, the upper surface of the raw material filling layer 10 is re-ignited by the flame of the re-ignition furnace 4 provided on the downstream side of the atmosphere suction area 7. By re-ignition, the residual coagulant (residual coagulant) that did not ignite and burn during ignition using the ignition furnace 3 can be burned without remainder. In addition, the gas heated by re-ignition and the combustion of the residual coagulant is sucked into the raw material filling layer 10, whereby the high-temperature holding time (for example, the time held at 1200 °C or higher) of the upper part of the raw material filling layer 10 increases, promoting the sintering reaction, and an effect of improving the yield can be obtained. The separation time is, as described above, the time required for the pallet car to move in the atmosphere suction area 7, that is, the time from the end of primary ignition to the implementation of re-ignition. In the present embodiment, it can be set to, for example, 0.5 minutes to 3.5 minutes. Furthermore, by promoting combustion by using a highly combustible carbon material, it is preferably 30 seconds or more and 2 minutes or less.

[0071] Similar to the single-stage ignition sintering method, in the re-ignition sintering method, a charging device equipped with a segregation mechanism is also used when charging the compound raw material granulated product onto the pallet car, and usually Figure 1The inclined flat chute type charging device 8 shown in [figure number] etc. The inclined flat chute type charging device 8 includes: a compound raw material buffer hopper 81 that accumulates the compound raw material granulated product, and an inclined flat chute 82 that is installed inclined downward in a direction opposite to the traveling direction 5x of the trolley. By charging the compound raw material granulated product in the compound raw material buffer hopper 81 onto the trolley using the inclined flat chute 82, an inclined surface 10x is formed on the upstream side of the raw material filling layer 10. Through the rolling classification action of the compound raw material granulated product on this inclined surface 10x, particle size segregation is caused in the layer thickness (layer height) direction of the raw material filling layer 10. Specifically, the smaller particles are more likely to be charged to the upper layer side of the raw material filling layer 10, and the larger particles are more likely to be charged to the lower layer side of the raw material filling layer 10.

[0072] Here, the granulation treatment of the above compound raw materials is for the purpose of ensuring the air permeability of the raw material filling layer 10. Generally, as described in the 3rd Edition of the Iron and Steel Handbook II, Ironmaking and Steelmaking, P84 ( Figure 2 .4) [October 15, 1979], it is pointed out that: for the fine powder raw materials with a particle size below 0.25mm, which are the main objects of the granulation treatment, pseudo-particles are formed by attaching to the surrounding of particles with a particle size of 1.00mm or more as core particles. However, the intermediate particle size particles with a particle size above 0.25mm and below 1.00mm are difficult to granulate and are not easily formed into pseudo-particles. Therefore, even in the case of granulation treatment, by adjusting the particle size of the added binder and using the above-mentioned inclined flat chute type charging device 8 for charging, the distribution of the binder in the height direction of the raw material filling layer can be adjusted.

[0073] For the binder, coke and anthracite are usually used. The coke for sintering is obtained by crushing the coke with a particle size not suitable for blast furnace use (usually below 40mm) to a particle size suitable for sintering, which is below 10mm, during the process of manufacturing coke for blast furnace. However, since there are cases where screening is not performed after crushing, there may also be some particles above 10mm remaining. The coke for sintering is called powdered coke compared to the lump coke for blast furnace. Anthracite is one of the classifications of coal (lignite, bituminous coal, anthracite), and it is the coal with the most advanced carbonization. Coal with a fuel ratio (fixed carbon / volatile component (mass ratio)) of 4 or more, simply speaking, coal with a carbon content of 90 mass% or more is classified as anthracite. It should be noted that anthracite is also crushed in the same way as powdered coke so that the particle size becomes generally below 10mm.

[0074] The inventors focused on the following two points in the above-described re-ignition sintering method. The first point is that, as the agglomerant, in addition to using a low-combustibility carbon material, a high-combustibility carbon material is also used, and by coarsening the high-combustibility carbon material and making it unevenly present in the lower layer of the raw material filling layer 10, the effect of reducing the ventilation resistance brought about by coarsening can be enjoyed from the start to the end of sintering. In addition, the second point is that it is considered that if the object of coarsening is set as the high-combustibility carbon material, due to its high combustibility, the influence of the reduction in sinter output caused by the delay in the combustion end time due to coarsening is small. The inventors focused on these two points, conducted in-depth research, and completed the present invention. In addition, the inventors also studied the influencing factors applicable in the present invention (such as the type of high-combustibility carbon material, the particle size of the low-combustibility carbon material, the segregation charging method, etc.).

[0075] The present invention is a method for manufacturing sintered ore, which uses a Dwight-Lloyd sintering machine to manufacture sintered ore. The Dwight-Lloyd sintering machine is equipped with an ignition furnace for initial ignition and a re-ignition furnace that is arranged at a prescribed interval downstream of the ignition furnace and performs re-ignition, and sintering is carried out by suction from below. Among them, as the agglomerant for the compound raw material, a low-combustibility carbon material with a combustion start temperature exceeding 550°C and a high-combustibility carbon material with a combustion start temperature of 550°C or lower are used, and the ratio of the particle size of 2.8 mm or more in the high-combustibility carbon material is 30 mass% to 80 mass%. Initial ignition refers to initially igniting the agglomerant on the surface of the raw material filling layer 10 loaded into the trolley (the first ignition). Re-ignition refers to the re-ignition (the second ignition) carried out after the initial ignition is completed. Suction from below refers to sucking air (oxygen-containing gas) from below the trolley and inhaling the oxygen-containing gas above the raw material filling layer 10 into the raw material filling layer 10 to supply oxygen to the raw material filling layer 10. Hereinafter, first, the low-combustibility carbon material and the high-combustibility carbon material used as the agglomerant will be described in turn. It should be noted that in this specification, "particle size" refers to the value (particle diameter) measured by sieving using a sieve according to JIS Z8801-1:2019.

[0076] (Low-combustibility carbon material and high-combustibility carbon material)

[0077] The agglomerant (carbon material) of the sintering raw material is classified into a low-combustibility carbon material and a high-combustibility carbon material.

[0078] Low-combustibility carbon materials such as coke and anthracite, and high-combustibility carbon materials are carbon materials with a higher combustibility than low-combustibility carbon materials (carbon materials with a lower combustion start temperature). Specifically, low-combustibility carbon materials and high-combustibility carbon materials are classified based on the combustion start temperature obtained by differential thermal balance analysis. Low-combustibility carbon materials are carbon materials with a combustion start temperature exceeding 550 °C, and high-combustibility carbon materials are carbon materials with a combustion start temperature of 550 °C or lower. The combustion start temperature (ignition temperature) is defined as the temperature at which a sharp weight reduction begins, using a differential thermal balance-mass analysis device (TG-DTA / MS) based on the temperature-weight change curve obtained by thermogravimetry in an air stream (TG: Thermogravimetry).

[0079] For high-combustibility carbon materials, there are, for example, coal tar coke, biomass carbon (oil palm kernel shell carbon, wood carbide produced by dry distillation of wood, etc.). The combustion start temperatures (ignition temperatures) of coke and anthracite, which are low-combustibility carbon materials, are approximately 670 °C and approximately 690 °C, respectively. In contrast, high-combustibility carbon materials have a lower combustion start temperature. The combustion start temperature of coal tar coke (semicokes, lignite coke, and sub-bituminous coal coke) is 430 °C to 550 °C, the combustion start temperature of oil palm kernel shell carbon is approximately 470 °C, and the combustion start temperature of wood carbide is around 400 °C to 450 °C. Since the ignition temperatures of coal tar coke and biomass carbon are at approximately the same temperature, they have the same combustibility. In addition, although the details will be described below, a compression molded product using wood carbide, which is a biomass carbon (biochar), as the main raw material is also a high-combustibility carbon material, and the crushed product obtained by crushing it can also be used. The combustion start temperature of this compression molded product is a low temperature of around 250 °C to 450 °C, and the same applies to the crushed product of the compression molded product. It should be noted that the combustion rate of high-combustibility carbon materials is 1.03 to 30.00 times that of coke.

[0080] Here, coal tar coke refers to a carbon material (coke) produced by dry distilling raw coal such as low-adhesion bituminous coal, lignite, and sub-bituminous coal at a temperature of 700 °C to 900 °C. The carbon materials produced by dry distilling low-adhesion bituminous coal, lignite, and sub-bituminous coal are respectively called semicoke, lignite coke, and sub-bituminous coal coke. Regarding these carbon materials, the coal (including mixed carbon) used as the raw material is dry-distilled using a thermal decomposition furnace (such as a rotary kiln).

[0081] In addition, biomass carbon refers to carbon materials manufactured by, for example, using biological resources (biomass) such as oil palm kernel shells and wood as materials and subjecting them to heat treatment (dry distillation). Palm kernel shell carbon (PKS carbon) is a solid carbide manufactured by subjecting palm kernel shells to heat treatment (dry distillation). It should be noted that the manufacturing method of PKS carbon can be implemented by referring to documents such as the above-mentioned Patent Document 5, etc., so detailed description is omitted here.

[0082] In addition, as described above, as the coagulant for the sintering raw material, a pulverized product of a compression molded product mainly made of wood carbide as biomass carbon (bio-carbon) can also be used. This compression molded product is a compression molded product obtained by compressing and molding an aggregate of wood carbide (hereinafter, for convenience, also simply referred to as charcoal compression molded product), and a pulverized product obtained by pulverizing it (hereinafter, for convenience, also simply referred to as charcoal compression molded pulverized product) is used as the coagulant. Here, the so-called "wood carbide" refers to the carbide obtained by subjecting "wood" to heat treatment (dry distillation), and the above-mentioned "wood" refers to the trunk and branches of a tree or the substances made from them, and for example, also includes construction waste, etc. In addition, the so-called "aggregate of wood carbide" refers to an aggregate of wood carbide particles or an aggregate of wood carbide particles in a state joined with an adhesive, and the size and shape of the wood carbide particles are not limited. The so-called "compressing and molding" means that compression is accompanied during molding, and includes not only compression molding, but also, for example, extrusion molding in which pressure is applied during extrusion. The so-called "main raw material" refers to the raw material with the largest usage ratio (mass ratio) among all the solid raw materials in this solid raw material. The so-called "pulverizing" means using a pulverizer (such as a rod mill, hammer crusher, roll crusher, super sandblaster, jaw crusher, edge runner mill, etc.) to reduce the particle size.

[0083] The pulverized product of the above-mentioned charcoal compression molded product is manufactured as follows. First, obtain the wood used as the material, and subject the wood to dry distillation to manufacture wood carbide (carbide manufacturing process). Next, the manufactured wood carbide is pulverized as needed to make wood carbide particles, and the wood carbide particles are kneaded alone or with an adhesive, etc., to manufacture an aggregate of wood carbide (hereinafter, referred to as wood carbide aggregate) (aggregate manufacturing process). The adhesive is used to form a firm aggregate. Next, manufacture a compression molded product (charcoal compression molded product) obtained by compressing and molding the wood carbide aggregate (compression process). Then, pulverize the charcoal compression molded product to manufacture a pulverized product of the charcoal compression molded product (charcoal compression molded pulverized product) (compressed product pulverizing process).

[0084] In the carbide manufacturing process, wood carbide is manufactured using wood as a raw material by appropriately setting carbonization conditions (temperature, time, etc.) through a carbonization device (such as an externally fired rotary kiln, internally fired rotary kiln, fluidized bed reactor, moving bed reactor (shaft furnace), etc.). The volatile components of the manufactured wood carbide (measured in accordance with JIS M8812:2006) are preferably 15% by mass or less. For example, in the case of cedar wood chips, by carbonizing at 800 °C for 1 hour, the volatile components of the carbide (wood carbide) can be reduced to 4.8% by mass.

[0085] In the aggregate manufacturing process, the wood carbide manufactured in the carbide manufacturing process is crushed as needed (for example, the average particle size is crushed to 1 mm or less). The wood carbide particles are kneaded alone, together with a binder, together with a binder and water, or together with a binder, water, and an additive to manufacture a wood carbide aggregate. As the binder, corn starch (starch), bentonite, coal tar, biomass tar, petroleum pitch, cement, etc. are used. In addition, for some binders (such as corn starch), additives such as alkalis and acids are added to manufacture a strong formed body. It should be noted that a device (such as an extruder) that can also crush wood carbide during kneading can also be used. When the wood carbide is set to 100% by mass, the amount of binder added is preferably added at a mixing ratio of 1% to 10% by mass (excluded from the total).

[0086] In the compression process, the wood carbide aggregate (kneaded product) manufactured in the aggregate manufacturing process is compressed and formed to manufacture a charcoal compressed formed body as a compression molded product. As the compression forming method, a compression forming machine can be used, or an extrusion forming machine can be used. For example, a roll pressing method using a roll rotary compression forming machine (ring punch mode, flat mode, etc.) or a tablet pressing method using a twin screw compression forming machine (screw type extrusion forming machine) can be adopted. The shape of the charcoal compressed formed body is arbitrary, for example, formed into pellets (cylindrical) or briquettes (pillow shape).

[0087] In the compressed product crushing process, the charcoal compressed formed body manufactured in the compression process is crushed using a crusher to manufacture a crushed product of the charcoal compressed formed body (charcoal compressed formed crushed product). Examples of the crusher include a rod mill, hammer crusher, roll crusher, super sandblaster, jaw crusher, edge runner mill, etc. After crushing, for example, screening is performed using a sieve in accordance with JIS Z8801-1:2019, and the crushed product with a specified particle size is used as a highly combustible carbon material. For example, the crushed product with a particle size of less than 10 mm in diameter (undersize of a sieve with a sieve hole of 10 mm), more preferably less than 5 mm in diameter (undersize of a sieve with a sieve hole of 5 mm).

[0088] Here, in the compression process, it is preferable to manufacture a charcoal compression molded article having the following properties. It should be noted that the volatile components and apparent density of the charcoal compression molded article do not change before and after pulverization in the compression molded article pulverization process, and the pulverized product of the charcoal compression molded article also has the same properties.

[0089] The volatile components of the charcoal compression molded article (measured according to JIS M8812:2006) are preferably 20% by mass or less. Generally, when manufacturing sintered ore, in order to suppress failures of the exhaust electrostatic precipitator that collects dust from the exhaust gas generated during manufacturing, the volatile components of the coagulant are managed to be below a specified value (for example, 10% by mass). Therefore, it is preferable to specify the upper limit value of the volatile components of the charcoal compression molded article. The increase in the volatile components of the charcoal compression molded article relative to those of the wood carbide depends on the use of adhesives in the aggregate manufacturing process. It should be noted that in the present invention, a charcoal compression molded article (highly combustible carbon material) is used in combination with a low combustibility carbon material (pulverized coke / anthracite). Here, in particular, the volatile components of pulverized coke are mostly extremely low compared to the above-mentioned specified value (10% by mass). In addition, the volatile components of anthracite are also as low as around 5% by mass. Considering these aspects, the upper limit of the volatile components of the charcoal compression molded article is set to 20% by mass, which is higher than 10% by mass. By setting the upper limit value higher, materials with high volatile components can be used as materials for the charcoal compression molded article. It should be noted that the mixing ratio of the charcoal compression molded article and the low combustibility carbon material (pulverized coke or / and anthracite) is also preferably determined based on the volatile components of the charcoal compression molded article and the low combustibility carbon material used, so as not to exceed the specified value of the volatile components corresponding to the capacity of the exhaust electrostatic precipitator.

[0090] In addition, the apparent density of the charcoal compression molded article is preferably 0.6 g / cm 3 or more, more preferably 0.7 g / cm 3 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 it is a volume displacement method using beads with high fluidity, namely DryFlо (pseudo-fluid), for the measurement sample. Specifically, it is the following method: First, measure the volume of only the beads placed in the sample chamber, then put the sample into the layer of beads in the sample chamber and measure the volume, and calculate the volume including the pores and voids of the measurement sample from the difference between the two volumes. The apparent density is the value obtained by dividing the mass of the measurement sample by the calculated volume. By setting the apparent density of the charcoal compression molded article to 0.6 g / cm 3 or more, the atmosphere temperature near the combustion of the coagulant increases during the manufacture of sintered ore. Therefore, through an increase in the yield rate, the sintering productivity can be improved. However, if the apparent density exceeds 1.3 g / cm 3, the burning rate of the charcoal compressed compact decreases, and the sintering rate decreases.

[0091] (Particle size of highly combustible carbon material)

[0092] The particle size of the highly combustible carbon material is determined as follows. After drying the highly combustible carbon material at 105 °C for 2 hours or more, a Ro-tap sieve shaker equipped with a sieve having a sieve opening of 2.8 mm specified in JIS Z8801-1:2019 is used, and it is vibrated by tapping for 5 minutes to investigate the ratio of the particle size of 2.8 mm or more on the sieve. In the present invention, a highly combustible carbon material having a ratio of 2.8 mm or more of 30 mass% to 80 mass% is used. If the ratio of the particle size of 2.8 mm or more is less than 30 mass%, the yield rate decreases and the productivity decreases. In addition, if the ratio of the particle size of 2.8 mm or more exceeds 80 mass%, the productivity decreases due to uneven sintering.

[0093] According to the present invention, by coarsening the highly combustible carbon material and unevenly distributing it in the lower layer, the air permeability in the lower layer can be improved. By improving the air permeability in the lower layer, the sintering rate during sintering becomes faster, and as a result, the productivity is improved. Here, the coarsened condensed material is only the highly combustible carbon material. Since the highly combustible carbon material has a fast burning rate, the influence of the decrease in the burning rate caused by coarsening is small. Therefore, it is not easy to cause a decrease in the sintering rate. Furthermore, by increasing the sintering rate, the cooling rate of the combustion zone 10A increases. As a result, the hematite (Fe2O3) particles crystallized from the liquid phase generated by the high-temperature sintering reaction become finer. When the sintered ore in the blast furnace is reduced from hematite to magnetite (Fe3O4), crystal expansion occurs. At this time, pulverization occurs due to the cracks generated. This pulverization phenomenon is reduction pulverization, but here, as described above, since the hematite (Fe2O3) particles become finer and the amount of crystal expansion decreases, an effect of suppressing the reduction pulverization of the sintered ore can be obtained.

[0094] (Use of pulverized charcoal compressed compact)

[0095] In the present invention, for the highly combustible carbon material, it is preferable to use a pulverized product of a charcoal compressed compact. The reason for this can be cited as follows: Compared with directly using a wood carbide or a pulverized product of a wood carbide, when a wood carbide or a pulverized product of a wood carbide is once compressed and formed and then pulverized for use, the yield rate is increased by an increase in the apparent density, and as a result, the productivity is increased. This is because: Although a wood carbide or a pulverized product of a wood carbide has excellent combustibility because it is a porous body (generally, the apparent density is less than 0.6 g / cm 3 ), the yield rate and productivity of the sintered ore are decreased due to an excessive increase in the sintering rate.

[0096] (Mass ratio of carbon component)

[0097] In the present invention, the mass ratio of the carbon component of the high-combustibility carbon material to the carbon component of the entire condensing material is preferably set to 25% to 75% by mass. The mass ratio of the carbon component of the high-combustibility carbon material to the carbon component of the entire condensing material is adjusted based on the carbon component of each carbon material (low-combustibility carbon material, high-combustibility carbon material) according to the industrial analysis of the low-combustibility carbon material and the high-combustibility carbon material. This is because it is believed that if the proportion of the high-combustibility carbon material is lower than 25% by mass, the effect of the high-combustibility carbon material combination, that is, the effect of improving the sintering speed (combustion front descent speed) cannot be obtained. If the proportion of the high-combustibility carbon material exceeds 75% by mass, the high-speed combustion unique to the high-combustibility carbon material will lead to a decrease in the yield.

[0098] (Average particle size of low-combustibility carbon materials)

[0099] In the present invention, the average particle size of the low-combustibility carbon material is also preferably set to a range of 0.8 mm to 1.2 mm. By making the average particle size of the low-combustibility carbon material finer, the number of carbon material particles is increased, so that the heat source supply in the cubic area with a length of one side of more than a few mm and less than 10 mm in each part of the combustion zone 10A is uniform, thereby improving the yield. In addition, by segregation loading, the amount of condensing material can be increased in the upper layer of the raw material filling layer that is insufficient in heat, and the yield is further improved. As a result, the productivity improvement effect is accelerated.

[0100] The average particle size of the low-combustibility carbon material is calculated as follows. After drying the low-combustibility carbon material at 105°C for more than 2 hours, use 5 sieves with different mesh sizes (mesh sizes) and a Rotap sifter to classify them by tapping them to vibrate for 5 minutes, and measure the sample mass wi of each particle size classification i. As shown in Table 1, the particle sizes (0.5mm, 1.0mm, 2.8mm, 4.76mm, 10.0mm) that serve as the boundary values ​​of the particle size classification are the mesh sizes of the sieves used in the classification. For example, particle size classification 2 "0.5-1.0" means that when sieving with a sieve with a mesh size of 0.5mm, it is on the sieve, and when sieving with a sieve with a mesh size of 1.0mm, it is under the sieve.

[0101] [Table 1]

[0102] Particle size classification i 1 2 3 4 5 Particle size (mm) 0-0.5 0.5-1.0 1.0-2.8 2.8-4.76 4.76-10.0 <![CDATA[Representative value x i > 0.25 0.75 1.9 3.8 7.5

[0103] The average particle size (mm) is an arithmetic mean particle size calculated by loading the representative value xi (≈median value) of the particle size fractions as the mass fraction (mass ratio) of each particle size fraction as shown in the following formula (1).

[0104] Average particle size = Σwixi / Σwi Formula (1)

[0105] xi: Representative value of particle size classification i

[0106] wi: Sample mass of particle size classification i

[0107] (Segregation-strengthened charging device)

[0108] In the present invention, instead of the usual charging device 8, it is also preferable to use a segregation-strengthened charging device. Here, when charging the compound raw material granulated product onto the trolley using the segregation-strengthened charging device, when the charged raw material filling layer is divided into five equal intervals in the layer thickness (layer height) direction, it is also preferable to perform the charging in such a manner that the average particle size of the raw material in the uppermost layer of the five-divided raw material filling layer becomes 0.3 to 0.5 times that of the raw material in the lowermost layer. In addition, when the charged raw material filling layer is divided into five in the layer thickness (layer height) direction, it is also preferable to perform segregation charging in such a manner that the carbon ratio in the uppermost layer of the five-divided raw material filling layer becomes 1.10 to 1.16 times that of the entire raw material filling layer.

[0109] The segregation-strengthened charging device (segregation-strengthened charging device) compared with Figure 1 the inclined flat chute 82 shown in Figure 2 is a charging device capable of increasing the particle size segregation in the layer thickness direction of the raw material filling layer, such as the slit bar type charging device (Ohne et al., Materials and Processing 10 (1997), P. 191, Iron and Steel Institute of Japan), the slit wire type charging device (Takai et al., Materials and Processing 6 (1993), P. 916), the ISF (Intensified Sifting Feeder) type charging device as a rectifying and dispersing type (Nagai et al., Materials and Processing 29 (2016), P. 563), the hybrid magnetic segregation charging device (Oyama et al., Materials and Processing 11 (1998), P. 225), the wind segregation device (Shibata et al., Materials and Processing 14 (2001), P. 193), etc. As Figure 2As shown in [reference], the sieve member of the slit rod charging device 8A is a member in which wires 82A (or rods) parallel to the width direction of the trolley are arranged such that the interval becomes wider as it goes from the upper part to the lower part of the trolley (Yoshinaga et al., Iron and Steel (1987), Vol. 73, Proceedings of the 114th Lecture Meeting of the Iron and Steel Institute of Japan, Summary of Lectures, S846). The wires (or rods) may also be arranged in a manner parallel to the vertical direction of the trolley. The sieve member of the rectifying and dispersing charging device is configured by arranging a plurality of rods along the raw material flow direction, and setting adjacent rods such that the step difference becomes larger as it goes from the upstream to the downstream (Inakaku et al., Iron and Steel 77 (1991), P. 63 - 70). It should be noted that the configurations of the respective segregation strengthening type charging devices are described in the above-mentioned respective documents and can be implemented by referring to the respective documents, so detailed descriptions are omitted here.

[0110] Here, an example of the results of investigating the raw material particle size distribution and carbon concentration distribution in the height direction of the raw material filling layer when the compound raw material (refer to Table 6) used in the following Invention Examples 1 - 10 is charged into a practical machine using a slit rod charging device (One et al., Materials and Processing 10 (1997), P. 191, Iron and Steel Institute of Japan), which is a type of segregation strengthening type charging device, is shown. Sampling of the specimens in the height direction of the raw material filling layer is carried out by a method using a sampling device (described in Japanese Patent Application Laid-Open No. 2018 - 044188). Specifically, the compound raw material granulates are charged into the bottom cover placed on the laying layer, and then a cylindrical sampling tube is driven in from directly above the bottom cover and plugged with the bottom cover to collect the specimens. It should be noted that the sampling method of the specimens can be implemented by referring to the above-mentioned document (Japanese Patent Application Laid-Open No. 2018 - 044188), so detailed descriptions are omitted here.

[0111] The collected samples were divided into five equal parts at equal intervals in the height direction of the raw material filling layer (set as the first layer to the fifth layer in order from the top) and used for analysis respectively. The analysis results of each layer (the first layer to the fifth layer) are shown in Table 2. As shown in Table 2, starting from the upper layer (the first layer) side, the mass of each layer is 4.30 kg, 5.16 kg, 4.88 kg, 4.62 kg, and 5.33 kg in turn, and the mass ratio becomes 18%, 21%, 20%, 19%, and 22%. The recovered mass in each layer is almost equal. The mass fraction in Table 2 was obtained by taking 300 g of the granulated product of the mixed raw materials of each layer (the first layer to the fifth layer), drying it at 105 °C for more than 2 hours, and then using sieves with each sieve hole shown in the horizontal axis (particle size classification), using a Ro-Tap sieve shaker, and vibrating the sieve for 15 seconds without tapping for classification. It should be noted that through this operation, the particle size distribution in the state of the sintering raw material before granulation treatment can be grasped, and the mass ratio of each particle size classification of the sintering raw material in each layer is expressed as the existence ratio (mass %). The average particle size of each layer in Table 2 is the arithmetic mean particle diameter calculated almost in the same way as the above formula (1) based on the representative value of the particle size classification and the mass fraction of each particle size classification. It should be noted that in Table 2, the particle size classification "+8.0" means the oversize when screening with a sieve with a sieve hole of 8.0 mm. In addition, the particle size classification "~4.0" means the oversize when screening with a sieve with a sieve hole of 4.0 mm, and the undersize when screening with a sieve with a sieve hole of 8.0 mm shown in the particle size classification "+8.0" in the left column. The same applies to the particle size classifications "~2.0", "~1.0", "~0.5", "~0.25", and "~0.125". The particle size classification "-0.125" means the undersize when screening with a sieve with a sieve hole of 0.125 mm.

[0112] [Table 2]

[0113]

[0114] Figures 3 to 5 is a chart made based on Table 2. Figure 3 It shows the particle size distribution in the state of the sintering raw material before granulation in each layer (the first layer to the fifth layer) of the raw material filling layer. In addition, Figure 4 It shows the ratio of the average particle size of each layer (the first layer to the fifth layer) to the average particle size of the whole. Figure 5 It shows the carbon concentration distribution in each layer (the first layer to the fifth layer) of the raw material filling layer. It should be noted that this carbon concentration is the free carbon value participating in combustion except for the carbon contained in carbonates, etc., and is calculated based on the combustion-infrared absorption method (JIS G1211-3: 2018).

[0115] As Figure 3As shown in [reference], the mass fraction of the coarse-grained sintering raw material in the lower layer, that is, the particle size classification of "+8.0 mm" (particle size of 8.0 mm or more) and "~4.0 mm" (particle size less than 8.0 mm and 4.0 mm or more), becomes higher relative to the upper layer. As a result, as shown in Table 2, the average particle size of the blended raw material in the lowermost layer (the 5th layer) is in the range of 3 mm to 5 mm, and the average particle size of the uppermost layer (the 1st layer) is 2 mm or less. In addition, as Figure 4 shown, there are differences in the average particle size of each layer, and the average particle size of the 1st layer is 0.4 times that of the 5th layer. On the other hand, regarding the carbon concentration, as Figure 5 shown, the uppermost layer (the 1st layer) reaches up to 5.06 mass%, which is 1.13 times the average carbon concentration of the whole layer. In this way, by coarsening the ratio of the high-combustibility carbon material with a particle size of 2.8 mm or more to 30 mass% or more and making the average particle size of the low-combustibility carbon material in the range of 0.8 mm to 1.2 mm to make the particle size finer, the blended raw material is charged using a segregation-strengthening type charging device, so that the agglomerated material with a particle size of 0.25 mm or more and less than 1.00 mm segregates in the upper layer where it becomes fragile after sintering, and thus the carbon concentration is concentrated. As a result, as shown in Invention Examples 1-10 described later, heat required for the sintering reaction is supplied to the upper layer to promote an increase in the yield, and the productivity is also increased. It should be noted that if the ratio of the high-combustibility carbon material with a particle size of 2.8 mm or more increases excessively, due to the decrease in the number of agglomerated material particles, temperature unevenness occurs in the raw material filling layer. Therefore, it is preferable to set the upper limit value of the ratio of the particle size of 2.8 mm or more to 80 mass%. It should be noted that it is considered that here, because a segregation-strengthening type charging device is used, the segregation of coarse particles and fine particles is significantly shown, but the segregation of coarse particles and fine particles also occurs in the segregation charging using a normal inclined flat chute.

[0116] (Post-adding method)

[0117] In the present invention, it is also preferable to add a part of the sintering raw material, that is, the total amount of only the low-combustibility carbon material, in the latter half of the granulation process. Here, the "latter half of the granulation process" refers to the latter half of the time domain when the following "total granulation time" is divided into the front and the back. In the granulation process of granulating the sintering raw material using a granulator, first, the sintering raw material other than the low-combustibility carbon material cut out from the raw material tank is first put into the granulator for mixing, humidified, and granulation is started (hereinafter, the substance obtained by granulating the sintering raw material other than the low-combustibility carbon material is referred to as the pre-granulated material). After a certain period of time, the low-combustibility carbon material (hereinafter, also referred to as the post-added coagulant) is put into the granulator (during the granulation process) to produce a granulated material of the compound raw material. By adding the post-added coagulant at an appropriate timing later, the post-added coagulant is externally coated on the pre-granulated material, that is, it is not encapsulated in the pre-granulated material, and adheres to the surface layer of the pre-granulated material or exists as unadhered independent particles. By using the granulated material of the compound raw material externally coated with the post-added coagulant, the start timing of combustion of the post-added coagulant in the sintering process can be adjusted.

[0118] The post-adding in the granulation process is carried out as follows, for example. For granulation, a cylindrical granulator in the form of a plug flow inclined downward in the central axis direction toward the downstream side is used, and it is set in a state where a small conveyor is inserted into a specified position inside the granulator from the downstream outlet. If the sintering raw material other than the post-added coagulant (hereinafter, also referred to as the pre-sintering raw material before post-adding) is put in from the upstream inlet, the put-in pre-sintering raw material before post-adding is mixed and then water is added, and it moves downstream while granulating. The post-added coagulant is loaded on the conveyor and is carried into the upstream side inside the granulator from the downstream outlet of the granulator. The post-added coagulant is added to the pre-granulated material moving while granulating from the upstream side in the granulator at a specified position, and all the sintering raw materials (pre-granulated material and post-added coagulant) are further granulated and discharged as a granulated material of the compound raw material from the downstream outlet.

[0119] Preferably, the granulation time of the post-addition pre-sintering raw materials until the addition of the coagulant is set to 80% to 96% relative to the total granulation time of the sintering raw materials, that is, the timing of the post-addition is set to a time within the range of 80% to 96% of the total granulation time of the sintering raw materials in the granulation process. For example, when the total granulation time is 240 seconds, the compound raw materials (post-addition pre-sintering raw materials) other than the low-combustibility carbon material can be granulated for 225 seconds, and then the low-combustibility carbon material can be added and granulated for 15 seconds. If the post-addition is earlier than 80% of the total granulation time, it is impossible to sufficiently prevent the post-added coagulant from being encapsulated in the granulated material. In addition, if the post-addition is later than 96% of the total granulation time, the granulation treatment of the post-added coagulant becomes insufficient. Here, the total granulation time in the granulation process does not include the time for simple mixing (mixing time) until the sintering raw materials are put into the granulator and water is added. In sintering, a drum mixer is mainly used, but it is a constant-speed plug flow type. Therefore, the post-addition position can be implemented by making the above granulation time correspond to the distance in the machine length direction of the drum mixer.

[0120] As described above, if the low-combustibility carbon material is post-added, the low-combustibility carbon material is externally mounted on the granulated material of the compound raw materials, so the reaction with the oxygen in the air supplied to the raw material filling layer can be promoted. In addition, sufficient heat supply is received from the heated air for combustion. As a result, the combustion speed of the coagulant is increased, and thus the productivity is further improved. If it is encapsulated by co-granulation, it is difficult to receive the supply of oxygen and heat required for the combustion of the low-combustibility carbon material. On the other hand, the high-combustibility carbon material that is not post-added is encapsulated in the compound raw material granulated material, but the combustion start temperature of the high-combustibility carbon material is low and the combustion speed is also fast. By making the timing of the start of combustion of the coagulant shift from the externally mounted low-combustibility carbon material to the encapsulated high-combustibility carbon material and utilizing the difference in the combustion characteristics of the coagulant, the overall combustion speed increases and the productivity is further improved.

[0121] 《Second Embodiment》

[0122] For a preferred embodiment of the present invention that uses an air volume control technique, the following description will be given as the second embodiment. As shown in the first embodiment, in the present invention, by using a specified amount (30% to 80% by mass) of coarse-grained highly combustible carbonaceous materials, the productivity is improved. However, since the highly combustible carbonaceous materials having a particle size of less than 2.8 mm are included in the compounding raw materials, the highly combustible carbonaceous materials (especially fine particles) exist in the upper layer of the raw material filling layer. Since the highly combustible carbonaceous materials have a fast burning rate, there are the following problems: the temperature reduction in the upper layer of the sintering layer (from the surface layer to a depth of about 100 mm) becomes faster from the start of ignition to the start of re-ignition, the yield is reduced, and the effect of improving productivity is reduced. The inventors believe that as a countermeasure, using an air volume control technique is effective. Hereinafter, first, the air volume control technique will be described, and the objectives of the inventors will be described.

[0123] (Air volume control technique)

[0124] Figure 6 It is a schematic diagram showing an example of the air volume control in the DL type sintering machine used in the re-ignition sintering method. As Figure 6 shown, below the trolley of the DL type sintering machine 101, a downward suction device 6 for causing the sintering reaction to proceed downward is provided ( Figure 1 the illustration is omitted). The downward suction air volume in the sintering belt machine direction (the same as the trolley forward direction 5x) is controlled by the downward suction device 6. Specifically, the downward suction device 6 has a plurality of groups of air boxes 61 and air box branch pipes 62 continuously provided in the sintering belt machine direction below the raw material filling layer 10, and the air boxes 61 and the air box branch pipes 62 are respectively connected to a blower 65 via a flue 64. An adjusting damper 63 is provided at the connection part of each group of air boxes 61 and the air box branch pipes 62 or in the middle of the air box branch pipes 62. By adjusting the opening degree of the adjusting damper 63, the suction air volume using each air box 61 can be adjusted, and the suction air volume distribution in the sintering belt machine direction (the trolley forward direction) can be controlled.

[0125] Regarding the above problems of the present invention using the re-ignition sintering method, the inventors believe that by limiting the air volume suppression area to the re-ignition furnace outlet on the upstream side of the sintering belt machine and not suppressing the air volume after the re-ignition, the sintering speed reduction in the upper layer of the sintering layer can be suppressed and the yield can be greatly improved, and the effect of improving productivity can be obtained. Repeated sintering experiments were carried out, and the following preferred embodiments were found. In addition, the constitution for optimizing the reduced air volume or pressure in the air volume suppression area and the timing of re-ignition (separation time) was also studied. Hereinafter, these contents will be described.

[0126] In implementing the present invention, it is preferable to suppress the air volume drawn downward only in the section from the upstream end of the sintering belt conveyor on the upstream side of the sintering belt conveyor to the outlet of the re-ignition furnace ( Figure 6 section S). This is because: in the section S up to the outlet of the re-ignition furnace on the upstream side of the sintering belt conveyor, suppressing the air volume drawn downward compared to the section on the downstream side of the outlet of the re-ignition furnace is effective for improving productivity (refer to Example 2 described later). It should be noted that, as Figure 6 shown in, when in the direction of the sintering belt conveyor, the air box 61 on the most upstream side is disposed directly below the inlet of the ignition furnace 3 (disposed in such a way that the upstream end of the air box 61 on the most upstream side is directly below the upstream end of the ignition furnace 3), the above-mentioned section S corresponds to the section from the inlet of the ignition furnace 3 of the sintering belt conveyor to the outlet of the re-ignition furnace 4.

[0127] In addition, a preferred solution for reducing the air volume is to set the average empty cylinder air volume of the atmosphere drawn in the section S up to the outlet of the re-ignition furnace on the upstream side of the sintering belt conveyor to 60% - 80% of the average empty cylinder air volume of the atmosphere drawn in the section on the downstream side of the outlet of the re-ignition furnace, or to set the average negative pressure in the air box 61 or the air box branch pipe 62 in the section S to 40% - 70% of the average negative pressure in the air box 61 or the air box branch pipe 62 in the section on the downstream side of the outlet of the re-ignition furnace.

[0128] Here, the empty cylinder air volume in the air box 61 or the air box branch pipe 62 is measured, for example, using a pitot tube to calculate the average empty cylinder air volume. It should be noted that in the air box 61 or the air box branch pipe 62, since the gas contains dust, the measurement environment is not necessarily good. Therefore, it can also be measured on the surface of the raw material filling layer 10 using a hot wire anemometer or the like. Setting the average empty cylinder air volume of the atmosphere drawn in the section S to 60% - 80% after the re-ignition is because: when it is less than 60%, the reduction in the sintering speed becomes large and the productivity deteriorates, and if it exceeds 80%, the productivity improvement effect brought about by the increase in the yield due to the reduction in the air volume cannot be obtained.

[0129] However, there are also cases where it is difficult to measure the empty cylinder air volume. In this case, it can be managed by the average negative pressure in each section. There is the following relationship between the air volume passing through the raw material filling layer 10 and the suction negative pressure, which is described by the formula (2) of JPU (Japanese Permeability Unit). JPU is the ventilation resistance index of the raw material filling layer and is an index indicating the ventilation property (ease of gas passage) of the raw material filling layer.

[0130] JPU = (Q / A)·(H / P) 0.6 (2)

[0131] Q: Air volume (suction air flow rate) (Nm 3 / min)

[0132] A: Suction area (m 2 )

[0133] H: Thickness of packed bed layer (m)

[0134] P: Negative pressure (mH2O)

[0135] The following can be derived from the above formula (2): 60% of the air volume (40% reduction) is equivalent to 40% of the negative pressure (60% reduction), and 80% of the air volume (20% reduction) is equivalent to 70% of the negative pressure (30% reduction).

[0136] In addition, in the present embodiment, the separation time, which is the time required for the trolley to pass through the section (atmospheric suction area 7) between the ignition furnace 3 and the re-ignition furnace 4, can be set, for example, to 0.5 minutes to 3.5 minutes, and a more preferable separation time is 0.5 minutes to 2.0 minutes (30 seconds to 2 minutes). If it is less than 0.5 minutes, sufficient oxygen cannot be supplied to the combustion zone 10A in the upper layer of the sintered bed. If it exceeds 2.0 minutes, the temperature of the upper layer of the sintered bed drops below the sintering reaction temperature, and it is difficult to obtain the effect of improving the productivity of the re-ignition technology. It should be noted that "the trolley passes through the section" means that the trolley moves between a certain position and other positions.

[0137] 《Third Embodiment》

[0138] For a preferred embodiment of the present invention using the oxygen enrichment technology, the following description is given as the third embodiment. In the present invention using the re-ignition sintering method, when it is desired to extend the high-temperature holding time of the sintered bed and further improve the productivity, if it is desired to extend the separation time, which is the time from the completion of the initial ignition to the implementation of re-ignition (the time for the trolley to move through the section between the ignition furnace and the re-ignition furnace), the temperature of the upper layer of the sintered bed drops excessively before the re-ignition is implemented. Therefore, there is a limit to the extension of the separation time. Especially when using highly combustible carbon materials, even if coarsening is carried out (the particle size is 30 mass% to 80 mass% of 2.8 mm or more), since the combustion time is short, the cooling rate also increases. The inventors believe that as a countermeasure, instead of extending the separation time, it is effective to adopt the oxygen enrichment technology. Hereinafter, the oxygen enrichment technology is described, and the objectives of the inventors are described.

[0139] (Oxygen Enrichment Technology)

[0140] The oxygen enrichment technology is a technology for enriching oxygen in the air sucked from below and supplying it into the raw material packed bed. Specifically, for example, as described later Figure 7 、 Figure 8As shown, an oxygen-enriched gas supply device 9 is provided above the raw material filling layer 10. Using this oxygen-enriched gas supply device 9, an oxygen-enriched gas with an oxygen concentration higher than that of the air supplied during normal operation is supplied as the gas (suction gas) attracted downward. By increasing the oxygen concentration, the combustion amount of the coagulant per unit time can be increased.

[0141] Regarding the above problems of the present invention, the inventors believe that by supplying an oxygen-enriched gas in the atmosphere suction area 7 provided in the re-ignition sintering method, the high-temperature holding time of the sintered layer can be extended to improve productivity, and repeated sintering experiments were carried out, and the following preferred solutions were found. In addition, a configuration for optimizing the separation time and the oxygen concentration of the oxygen-enriched gas supplied in the atmosphere suction area 7 was also studied. Hereinafter, these will be described.

[0142] Figure 7 is a schematic diagram showing an example of a DL type sintering machine of the present embodiment (oxygen enrichment). As Figure 7 shown, in addition to the components of the above-mentioned DL type sintering machine 101, the DL type sintering machine 103 further includes an oxygen-enriched gas supply device 9 above the raw material filling layer 10. The oxygen-enriched gas supply device 9 supplies an oxygen-enriched gas (such as a gas obtained by mixing oxygen in the air) with an oxygen concentration higher than that of the air into the raw material filling layer 10. The oxygen-enriched gas supply device 9 has, for example, a ventilation hood 91 and a trachea 92 for supplying the oxygen-enriched gas into the ventilation hood 91, and is configured to continuously supply the oxygen-enriched gas. The supplied oxygen-enriched gas is attracted downward by the lower suction device 6 and is introduced into the raw material filling layer 10 to carry out a sintering reaction in the combustion zone 10A, and then is recovered as exhaust gas through the lower suction device 6 (wind box 61). By adjusting the supply amount of oxygen ejected from the trachea 92, the oxygen concentration of the oxygen-enriched gas can be set to a specified concentration with an oxygen content higher than that of the atmosphere.

[0143] As Figure 7 shown, the oxygen-enriched gas supply device 9 is disposed in the section between the ignition furnace 3 and the re-ignition furnace 4 (refer to the atmosphere suction area 7, Figure 6 ), and the oxygen-enriched gas is supplied from the surface side of the raw material filling layer 10 (sintered layer) passing through the atmosphere suction area 7 and attracted downward. That is, in the present embodiment, the atmosphere suction area 7 that supplies the atmosphere in the first embodiment and the second embodiment becomes an oxygen-enriched gas suction area 7x that supplies the oxygen-enriched gas (refer to Figure 6 and Figure 7 ). It should be noted that in Figure 7In the illustration, an example is shown in which a safety gap is slightly provided between the ventilation hood 91 of the oxygen-enriched gas supply device 9 provided in the atmospheric suction region 7, the outer casing 32 (partition wall 32a) of the ignition furnace 3, and the outer casing 42 (partition wall 42a) of the re-ignition furnace 4. In this case, the section where the ventilation hood 91 of the oxygen-enriched gas supply device 9 is provided is the oxygen-enriched gas suction region 7x. However, as long as there are no safety problems, it is preferable to arrange the outer casings 32, 42, and 91 without leaving such a gap, or to continuously arrange the ventilation hood 91 of the oxygen-enriched gas supply device 9 with the outer casing 32 of the ignition furnace 33 and / or the outer casing 42 of the re-ignition furnace 4. It should be noted that the gap between the ignition furnace 3 (the downstream partition wall 32a) and the oxygen-enriched gas supply device 9 (the upstream side wall of the ventilation hood 91) and the gap between the oxygen-enriched gas supply device 9 (the downstream side wall of the ventilation hood 91) and the re-ignition furnace 4 (the upstream partition wall 42a) are provided only when required for safety, and even in this case, it is preferable to set them not longer than the necessary minimum distance. This is because if the oxygen enrichment time is reduced, the productivity improvement effect is reduced.

[0144] Here, the oxygen input amount in the suction gas supplied to the oxygen-enriched gas suction region 7x can be controlled by methods such as the following: a method of measuring and adjusting the oxygen concentration on the sintered layer surface by providing a collection pipe on the sintered layer surface in the oxygen-enriched gas suction region 7x; or a method of adjusting according to the air volume of the air box 61 of the DL type sintering machine 103. Moreover, regarding the oxygen input method, for example, oxygen (such as industrial oxygen) is directly supplied into the ventilation hood 91 provided above the oxygen-enriched gas suction region 7x and supplied into the raw material filling layer 10 together with the atmosphere (hereinafter, also referred to as the outer hood atmosphere) sucked from the periphery of the ventilation hood 91 (outside the ventilation hood 91). At this time, it is preferable to supply from multiple positions in the width direction (the direction perpendicular to the trolley forward direction 5x) of the DL type sintering machine 103. In addition, an oxygen-enriched gas with a specified oxygen concentration obtained by pre-mixing oxygen and air can also be supplied from the gas pipe 92 into the ventilation hood 91. It should be noted that industrial oxygen can use the oxygen produced in the oxygen plant in the ironworks.

[0145] When implementing the present invention, the time required for the trolley to pass through the section between the ignition furnace 3 and the re-ignition furnace 4 (separation time) can be set, for example, to 0.5 minutes to 6 minutes (refer to Table 8 described later). In addition, preferably, the separation time is set to 1 minute or more, and the oxygen concentration of the suction gas sucked downward from the surface side of the sintered layer in this section is set to 30% by volume or more. Here, the separation time includes the time passed in the interval set for safety (for example, more than 0 seconds and within 2 seconds). This is because, as shown in the embodiments described later, when the oxygen concentration in the suction gas is less than 30% by volume or the separation time is less than 1 minute, the oxygen supply amount is insufficient and the effect of improving productivity sufficiently cannot be obtained.

[0146] It should be noted that the separation time is preferably 6 minutes or less. If it exceeds 6 minutes, even if oxygen enrichment is performed, the sintered layer has already been cooled by the suction gas and the effect of re-ignition cannot be obtained. On the other hand, the oxygen concentration in the suction gas is preferably 50% by volume or less. For the method of supplying pure oxygen and the outside atmosphere of the hood together as the suction gas into the raw material filling layer 10, when the oxygen concentration in the suction gas is 50% by volume, the ratio of the amount of pure oxygen gas to the amount of outside atmosphere gas of the hood (outer number) reaches 60% by volume. On the other hand, the amount of gas sucked into the raw material filling layer is determined by the air permeability of the raw material filling layer and the power of the sintering machine blower (blower 65), so the amount of suction gas changes in minutes and seconds. Therefore, if the supply ratio of pure oxygen in the suction gas increases, the change in the oxygen concentration in the suction gas becomes obvious due to the change in the amount of suction gas. (The supply amount of pure oxygen is adjusted according to the change in the amount of suction gas, but the control becomes difficult.) As a result, it hinders the stable supply of the oxygen concentration in the suction gas to the sintered layer.

[0147] Furthermore, more preferably, the oxygen concentration in the suction gas is 40% by volume or less, and the separation time is 5 minutes or less. This is because, as shown in the embodiments described later, if the oxygen concentration exceeds 40% by volume or the separation time exceeds 5 minutes, the increase in productivity accompanying the increase in the oxygen supply amount becomes slow, and the effect brought about by oxygen enrichment cannot be effectively exhibited.

[0148] The oxygen enrichment in the oxygen-enriched gas suction area 7x of the present invention, as confirmed in the following embodiments, has the effect that although the sintering speed increases, the yield and productivity also increase, and the appropriate separation time extends to the long-time side. As the reason for the increase in the former productivity, the following can be cited: By re-igniting immediately after oxygen enrichment, heat is supplied to the coke combustion field activated by oxygen enrichment, and the activation of the coke combustion field is continuously maintained. Therefore, even short-term oxygen enrichment can improve the yield and productivity. As the reason for the extension of the latter appropriate separation time, it can be cited that the temperature of the sintering layer rises due to the activation of coke combustion brought about by oxygen enrichment. Although re-ignition needs to be carried out before the sintering layer cools, since it becomes difficult to cool due to the implementation of oxygen enrichment in the oxygen-enriched gas suction area 7x, even a long separation time shows an effect. Moreover, if the separation time is long, the high-temperature holding time of the sintered ore is extended, resulting in an increase in the yield. On the other hand, oxygen enrichment without re-ignition is to suppress the degree of productivity reduction caused by the increase in the general sintering speed.

[0149] <<Fourth Embodiment>>

[0150] Regarding other preferred embodiments of the present invention using the oxygen enrichment technique, the following is described as the fourth embodiment. The inventors believe that the oxygen enrichment technique shows an effect even when it is implemented not in the above-described atmosphere suction area 7 but immediately after re-ignition. Hereinafter, the objectives of the inventors are described, and then the preferred embodiments are explained.

[0151] In the re-ignition method, the upper part of the high-temperature zone (region of approximately 1000 °C or higher) of the sintering layer formed by the initial ignition is reheated by re-ignition, and the condensed material (carbon material) that remained unburned in the initial ignition burns. As shown in the following Figure 8 As shown, combustion reactions occur at two positions in the layer height direction by 1) combustion of the remaining condensed material in the combustion zone formed by re-ignition (hereinafter, also referred to as the re-ignition combustion zone 10A2) and 2) combustion of the condensed material in the combustion zone formed by the initial ignition (hereinafter, also referred to as the initial ignition combustion zone 10A1). In the sintering machine, the atmosphere containing oxygen required for combustion is sucked downward, and vertically flows from the upper part to the lower part in the layer height direction of the sintering layer. In order to promote the combustion reactions at the above two positions, a large amount of oxygen is required. Especially when using a highly combustible carbon material, even when coarsened (particle size of 2.8 mm or more is 30 mass% to 80 mass%), more oxygen is required due to the fast combustion speed.

[0152] In addition, immediately after the re-ignition ends, a re-ignition combustion zone 10A2 is generated at another position in the layer height direction in addition to the initial ignition combustion zone 10A1. As a result, the high-temperature zone expands in the layer height direction. In the re-ignition combustion zone 10A2, since heat propagates within the sintered mass with a high porosity that has been sintered during the initial ignition, the surface area of the solid (sintered mass) in contact with the gas attracted downward is small. In contrast, in the initial ignition combustion zone 10A1, since heat propagates within the sintering raw material containing fine powder with a particle size of less than 1 mm, the surface area of the solid (sintering raw material) in contact with the gas attracted downward is large. Therefore, the descent speed of the re-ignition combustion zone 10A2 is faster than that of the initial ignition combustion zone 10A1, and the re-ignition combustion zone 10A2 merges with the initial ignition combustion zone 10A1 at an early stage after the re-ignition ends (refer to Figure 8 ). It should be noted that the high-temperature zone during sintering includes the combustion zone, which is the region from the start to the end of the combustion of the setting material, and the region where the temperature is cooled to the temperature at which the subsequent metallurgical reaction continues (approximately 1000 °C).

[0153] In this way, in the re-ignition sintering method, due to the increase in the required oxygen amount, the problem of a decrease in the sintering speed during the suction below the normal atmosphere becomes apparent. Thus, the inventors considered that in the present invention using the re-ignition method, it is precisely by implementing the oxygen enrichment technique immediately after the re-ignition that it becomes possible to increase the sintering speed and the productivity brought about thereby, and repeated sintering experiments were conducted, and the following preferred solutions were found. In addition, a configuration for optimizing the timing of starting oxygen enrichment, the oxygen enrichment time, and the oxygen concentration of the oxygen enrichment gas supplied in the oxygen enrichment region was also studied. Hereinafter, these contents will be described.

[0154] Figure 8 It is a schematic diagram showing another example of the DL type sintering machine for explaining the present embodiment (oxygen enrichment). Hereinafter, using Figure 8The above phenomenon is described in detail. In the manufacture of sintered ore using the re-ignition sintering method, an atmosphere suction area 7 is provided between the ignition furnace 3 and the re-ignition furnace 4, and sufficient oxygen (atmosphere) is supplied to the combustion zone 10A formed on the surface of the raw material filling layer 10 by the initial ignition, and the surface layer is subjected to combustion of the unignited and residual condensate by the subsequent re-ignition. In addition, in addition to the confluence of the above-mentioned two combustion zones (the initial ignition combustion zone 10A1 and the re-ignition combustion zone 10A2), the circulating gas attracted from above and passing through the initial ignition combustion zone 10A1 is heated to a high temperature by the combustion of the residual condensate caused by the re-ignition, and the combustion of the condensate directly below the initial ignition combustion zone 10A1 is promoted, so that the width of the combustion zone 10A and the high temperature zone is further expanded. In addition, by re-igniting before the sintered block 10B is cooled by the supply of the atmosphere in the atmosphere suction area 7, the high temperature holding time of the upper layer (for example, the time kept at above 1200°C) is increased. By supplying heat by re-igniting at an appropriate timing, the high temperature holding time can be increased, and improvements in yield and productivity can be expected.

[0155] In this embodiment, the area (oxygen-enriched gas suction area) where oxygen-enriched gas is supplied to the surface of the raw material filling layer 10 (sintering layer) and suction is performed downward is set as a predetermined interval after the re-ignition is completed. Therefore, in addition to the above-mentioned various components of the DL type sintering machine 101, the DL type sintering machine 104 of this embodiment is also equipped with an oxygen-enriched gas supply device 9 with the same structure as that described in the third embodiment on the downstream side of the trolley forward direction of the re-ignition furnace 4. It should be noted that the separation time in this embodiment can be set to, for example, 0.5 minutes to 3.5 minutes.

[0156] exist Figure 8 In the embodiment, although there is a slight gap between the re-ignition furnace 4 and the oxygen-enriched gas supply device 9, the re-ignition furnace 4 and the oxygen-enriched gas supply device 9 can also be set continuously as long as there is no problem in safety. The oxygen-enriched gas supply device 9 is configured to set the specified time as the oxygen enrichment time and continuously supply the oxygen-enriched gas. It should be noted that the time for the trolley to move in the gap between the re-ignition furnace 4 (the downstream partition 42b) and the oxygen-enriched gas supply device 9 (the upstream side wall of the ventilation hood 91), that is, the time from the end of re-ignition to the start of oxygen enrichment is preferably short. For example, even if safety issues are taken into consideration, it is preferably more than 0 seconds and less than 30 seconds, more preferably more than 0 seconds and less than 10 seconds, and further preferably to start oxygen enrichment just after the re-ignition is completed (more than 0 seconds and less than 2 seconds). If it exceeds 30 seconds, the effective time domain of oxygen enrichment is reduced, so the effect is reduced (refer to Test 2 of Example 4 described later).

[0157] In implementing the present invention, preferably, in the above-described oxygen-enriched gas suction region (the section provided with the oxygen-enriched gas supply device 9 in the traveling direction 5x of the trolley), the oxygen concentration in the suction gas suctioned from the surface layer of the sintering layer by bottom suction is 30% by volume or more, and the oxygen-enriched time using the oxygen-enriched gas supply device 9 after the end of re-ignition is set to 30 seconds or more. Here, the oxygen-enriched time refers to the time required for the trolley to move in the oxygen-enriched gas suction region, that is, the time from the start to the end of the supply of the oxygen-enriched gas when the supply of the oxygen-enriched gas is carried out after the end of re-ignition. This is because when the oxygen concentration in the suction gas is less than 30% by volume or the oxygen-enriched time is less than 30 seconds, the oxygen supply amount is insufficient, and the effect of improving the sintering speed and productivity cannot be obtained sufficiently (refer to Test 2 in Example 4 described later).

[0158] Furthermore, the oxygen concentration in the suction gas in the oxygen-enriched gas suction region is preferably 40% by volume or less. In addition, the oxygen-enriched time using the oxygen-enriched gas supply device 9 is preferably within 2 minutes. This is because if the oxygen concentration exceeds 40% by volume or the oxygen-enriched time exceeds 2 minutes, the increase in the sintering speed and productivity due to the increase in the oxygen supply amount becomes slow, and the oxygen enrichment becomes ineffective. The timing at which the two combustion zones (the initial ignition combustion zone 10A1 and the re-ignition combustion zone 10A2) merge has not been clear so far, but based on the appropriate oxygen-enriched time obtained from the experimental results (refer to Test 1 in Example 4 described later), it is presumed that the merger occurs at a time exceeding 2 minutes and within 3 minutes from the end of re-ignition.

[0159] In the present embodiment, through the oxygen enrichment after re-ignition, as confirmed in Example 4 described later, the sintering speed increases significantly. This increase amplitude is greater than the increase in the sintering speed in the oxygen enrichment without re-ignition described in the prior art (Iron and Steel Vol. 92 (2006), p. 417-426) and the like. As a reason for the increase in the sintering speed increase amplitude, since there are two sites where the combustion zones are activated by the oxygen enrichment after the end of re-ignition, oxygen is effectively utilized. Therefore, even a short-time oxygen enrichment can bring about an increase in the sintering speed and an increase in productivity.

[0160] 《Fifth Embodiment》

[0161] The inventors focused on the productivity improvement effect in the upper part of the sintering layer in the above-described second to fourth embodiments. However, on the other hand, the productivity improvement effect in the lower part of the sintering layer is extremely small. As an effect on the lower part of the sintering layer in the present embodiment, the inventors focused on the scaffold-supported sintering technique effective in increasing the firing speed of the lower part of the sintering layer. Hereinafter, the scaffold-supported sintering technique will be described, and the inventors' objectives regarding the preferred embodiments will be described.

[0162] According to the support sintering technology of the support, by supporting the sintered block formed in the upper part of the raw material filling layer with the support, when sintering the lower part of the raw material filling layer (hereinafter, also referred to as the lower part), by reducing the upper load of the lower part, the voids in the lower part can be ensured. As a result, the ventilation resistance in the lower part is reduced and the sintering speed is increased (refer to Japanese Patent Laid-Open No. 4-168234). The inventors believe that when implementing the present invention, by applying the support sintering technology with the effect of improving the productivity of the lower layer, it becomes possible to improve the overall productivity of the sintered ore. However, the increase in the width of the combustion zone in the upper part generated by the present invention also affects the sintering conditions in the lower part. The inventors repeatedly conducted sintering experiments and found that, as shown in Example 5 described later, the synergistic effect of the present invention and the support sintering technology exceeding the prediction can be obtained. In addition, when the support sintering technology is used in combination in the present invention, the appropriate range of the separation distance (the interval between the ignition furnace and the re-ignition furnace) has also been studied. Hereinafter, these contents will be described.

[0163] (Support sintering technology)

[0164] Figure 9 is a schematic diagram for explaining an example of the trolley used in the present embodiment (applying the support sintering technology). As Figure 9 shown, the trolley 5 includes a main frame 52 provided with grate bars 51 and trolley side walls 53 erected at opposite end portions of the main frame 52. In addition, the trolley 5 is provided with a substantially plate-shaped member, i.e., a support 16 (support member) having a substantially isosceles trapezoidal shape, at the central portion above the grate bars 51. The support 16 has a sintered block support surface 16a and is vertically provided in a manner parallel to the trolley advancing direction 5x in the raw material filling layer 10. During the firing of the raw material filling layer 10, as Figure 9 shown, the upper part of the sintered layer (raw material filling layer 10) in the trolley 5 becomes the sintered block 10B that has been sintered, and the lower part (the lower part of the combustion zone 10A) is in the original state of the unsintered sintering raw material. Here, the upper part (sintered block support surface 16a) of the support (support member) 16 supports the sintered block 10B in the upper part and suppresses the densification of the sintering raw material in the lower part. By suppressing the densification, the ventilation resistance of the sintered layer during sintering of the lower part is reduced and the sintering speed is increased. Furthermore, it also has the effect of suppressing the uneven flow of the gas flowing in the sintered layer, reducing the amount of the unburned part, and increasing the sintering yield.

[0165] In implementing the present invention, it is preferable to use the above-described support technology of the support. That is, preferably, in the trolley 5 for loading the compounding raw materials, the support member (support 16) having the sintered block support surface 16a is vertically provided on the grate 51 in such a manner as to be buried in the raw material filling layer 10. In the present embodiment, the configuration of the support member (support 16) may be such that it can support the sintered block 10B formed in the upper layer portion. For example, two rows of support brackets may be provided in the trolley width direction. By providing a plurality of support members (support 16), when sintering the lower layer portion, by supporting the sintered block 10B formed in the upper layer portion, the load applied to the unburned lower layer portion is reduced, so that the voids in the lower layer portion can be ensured, and the gas flow rate in the trolley width direction can be made uniform.

[0166] In the present invention using the re-ignition sintering method, the effects when applying the support sintering technology of the support are considered as follows.

[0167] (Yield)

[0168] As a feature of the support sintering technology, the effects of improving the sintering speed and the yield are limited to the lower layer portion. In the present embodiment, the time (separation time) required for the trolley to pass through the section (atmospheric suction region 7) between the ignition furnace 3 and the re-ignition furnace 4 can be set, for example, to 0.5 minutes to 3.5 minutes, and preferably set to less than 3.0 minutes (refer to Table 12 described later). By combining with the re-ignition sintering method having the effect of improving the yield of the upper layer portion, when the separation time is within a specified range (less than 3.0 minutes), the effect of improving the yield of the entire layer from the upper layer to the lower layer can be obtained. From the above, additivity holds in terms of the yield. If the separation time exceeds 3.0 minutes, the effect of improving the yield brought about by re-ignition is dulled, and the yield deteriorates due to the influence of the shortening of the sintering time brought about by the support.

[0169] (Sintering speed)

[0170] By performing two ignitions in the re-ignition sintering method, the width of the combustion zone in the sintered layer increases. The increase in the width of the combustion zone in the sintered layer brings about an improvement in the yield in the upper layer. However, in the lower layer, even in the case of the single-ignition sintering method, the width of the combustion zone is sufficiently ensured, so no further improvement effect is expected. Instead, in the lower layer, the increase in the width of the combustion zone leads to an increase in the ventilation resistance, and as a result, the sintering speed (BTS: Burn through speed) decreases. Especially when using highly combustible carbon materials, even if coarsening is carried out (the particle size of 2.8 mm or more is 30 mass% to 80 mass%), since the combustion start temperature is low and the combustion speed is fast, the width of the combustion zone also becomes large. Here, if the scaffold-supported sintering technique is applied, the upper sintered block supports it, so that the increase in the ventilation resistance is reduced during the sintering of the lower layer part, and the sintering speed of the lower layer increases. By increasing the sintering speed of the lower layer, an increase in the width of the combustion zone in the lower layer can be suppressed. As a result, the sintering speed is accelerated. Through the above, a synergistic effect can be obtained in terms of the sintering speed.

[0171] (Productivity)

[0172] The productivity is proportional to the product of the yield and the sintering speed. Through the additive effect in the yield and the synergistic effect in the sintering speed as described above, a synergistic effect of the re-ignition sintering method and the scaffold-supported sintering technique exceeding the prediction can be obtained (refer to Example 5 described later).

[0173] Examples

[0174] Regarding the tests related to the above-described present invention and each preferred configuration applicable to the above-described present invention, the following will be described. Examples 1 to 5 respectively correspond to the above-described first to fifth embodiments. In addition, in Example 4, it is described in two tests (Test 1 and Test 2).

[0175] Here, in all the examples (Examples 1 to 5), the mixing ratio of the sintering raw materials other than the coagulant (refer to Table 4 described later) is set to be common. In addition, for the lower suction conditions (suction pressure or air volume) during sintering, in Examples 1 and 5, it is set to be constant at 1300 mmAq (12.7 kPa) based on the measured value under the pot, and in Examples 3 and 4, it is set to be constant at 1.80 Nm 3 / min based on the air volume (exhaust). In addition, in Example 2, based on 1.80 Nm 3 / min as the basis, the air volume control shown in the test conditions described later is carried out.

[0176] 《Example 1》

[0177] (Test level)

[0178] An experiment related to each condition of the composition ratio of the carbon materials (low-combustibility carbon materials and high-combustibility carbon materials), the average particle size of the low-combustibility carbon materials, and the particle size of the high-combustibility carbon materials described in the first embodiment will be described. In the following experiments, only pulverized coke was used as the low-combustibility carbon material, but even if both anthracite and coke, or only anthracite, are used as the low-combustibility carbon material, the same effect can be obtained. In addition, in the following experiments, only semicoke or only charcoal compacts (substances obtained by pulverization) were used as the high-combustibility carbon material, but it is not limited to these. For example, even if any one of other high-combustibility carbon materials is used, or a mixture of multiple types of high-combustibility carbon materials is used, the same effect can be obtained.

[0179] In the examples, a method commonly known as the sintering pot test was used for verification. The sintering pot test is the following test: A sintering raw material (compounded raw material) containing a coagulant as a fuel is charged into a container of a specified size, and sintering is performed by igniting from above and performing downward suction. Regarding the device for the sintering pot test, it is a test device that does not have the movement of the raw material filling layer using a trolley like the DL (Dravo Lime) type sintering machine but can simulate the sintering using the DL type sintering machine. As shown in Table 6 described later, 17 tests of Comparative Examples 1-0 to 1-3 and Invention Examples 1-1 to 1-13 were conducted. First, the raw materials used in the experiments and the test methods will be described in sequence, and then the test results will be described.

[0180] (Raw materials)

[0181] Table 3 shows the results of the proximate analysis and ultimate analysis of the low-combustibility carbon materials and high-combustibility carbon materials used in the experiments. Pulverized coke shown in Table 3 was prepared as the low-combustibility carbon material, and semicoke and charcoal compacts (pulverized) were prepared as the high-combustibility carbon materials.

[0182] [Table 3]

[0183]

[0184] (Raw material compounding)

[0185] In Tables 4 and 5, the compounding ratios (mass %) of each sintering raw material are shown for the compounded raw materials used in the experiments. As shown in Table 4, the ratios of the new raw materials (iron ore, limestone, quicklime, and olivine) and the return fines were set to be constant in all test examples. Iron ores A to E are iron ores of different brands (origins). The new raw materials (iron ore, limestone, quicklime, and olivine) were set to 100 mass %, and the compounding ratio of the return fines was set to 15.0 mass % in terms of the number. It should be noted that the compounding ratios of the raw materials other than the coagulant were set to be common in Examples 1 to 5.

[0186] Table 5 shows the blending ratio (mass %) of the binder materials in the blended raw materials used in the experiments. For the low-combustibility carbon materials, pulverized coke was used in all the test examples. For the high-combustibility carbon materials, crushed charcoal compacts were used in Invention Examples 1-12 and 1-13, and semicoke was used in the other test examples. In the test examples (Comparative Examples 1-0 and 1-2) where only low-combustibility carbon materials (pulverized coke) were used as the binder material, the new raw material was set to 100% by mass, and the amount other than the blending ratio of the binder material (pulverized coke) was set to 4.5% by mass. In the test examples (test examples other than Comparative Examples 1-0 and 1-2) where high-combustibility carbon materials (semicoke or charcoal compacts) were blended, based on the blending amount of the binder material (pulverized coke at 4.5% by mass) in Comparative Examples 1-0 and 1-2, and based on the mass ratio of the carbon components of the low-combustibility carbon materials (pulverized coke) and the high-combustibility carbon materials (semicoke, charcoal compacts) (upper part of Table 5) and the fixed carbon content of the low-combustibility carbon materials (pulverized coke) and the high-combustibility carbon materials (semicoke, charcoal compacts) (Table 3), the blending ratio of the binder materials (low-combustibility carbon materials and high-combustibility carbon materials) relative to the new raw material was adjusted so that the fixed carbon content (carbon component) of the industrial analysis of all the binder materials (pulverized coke, semicoke, charcoal compacts) contained in the blended raw materials became constant in all the test examples. It should be noted that the lower part of Table 5 shows the blending ratio of the low-combustibility carbon materials and the high-combustibility carbon materials relative to the total amount of the binder materials.

[0187] [Table 4]

[0188]

[0189] [Table 5]

[0190]

[0191] The upper part of Table 6, which will be described later, shows the test conditions. The mass ratio of the carbon components shown in Table 6 is the same as the mass ratio of the carbon components shown in the upper part of Table 5. As shown in Tables 5 and 6, Comparative Example 1-0 is a case where re-ignition was not carried out and only low-combustibility carbon materials (pulverized coke) were used as the binder material without blending high-combustibility carbon materials. In addition, Invention Examples 1-12 and Invention Example 1-13 are cases where crushed charcoal compacts were used for the high-combustibility carbon materials.

[0192] As shown in Table 6, the average particle size of the low-combustibility carbon material (refer to the last paragraph on page 16 of the specification, i.e., the paragraph of the above-mentioned (average particle size of the low-combustibility carbon material)) was set to 0.6 mm, 0.8 mm, 1.2 mm, and 1.4 mm in Invention Examples 1-6 to 1-9 respectively, 1.2 mm in Invention Examples 1-12 and 1-13, and 1.0 mm in other test cases. The ratio of the high-combustibility carbon material with a particle size of 2.8 mm or more (the ratio of the high-combustibility carbon material with a particle size of 2.8 mm or more to the entire high-combustibility carbon material) was set to 20% by mass, 50% by mass, and 70% by mass in Comparative Example 1-3, Invention Examples 1-4, and 1-5 respectively, 80% by mass in Invention Examples 1-12 and 1-13, and 30% by mass in other test cases. In Invention Examples 1-11 and 1-13, the total amount of only the low-combustibility carbon material in the sintering raw material was added in the latter half of the granulation process of the sintering raw material. In addition, Invention Examples 1-10 and 1-13 used a segregation-strengthening type charging device to charge the granulated mixed raw materials.

[0193] [Table 6]

[0194]

[0195] (Granulation method)

[0196] As the granulator, an intermittent drum mixer with a diameter of 600 mm and a length of 800 mm (rotation speed: 25 rpm) was used. In the test cases of co-granulation other than Invention Examples 1-11 and 1-13, all the sintering raw materials composed of new raw materials, binders, and return fines were put into the granulator, and after 4 minutes of mixing treatment, water was added (humidification) in such a way as to reach the target moisture value and further mixed for 4 minutes (granulation). In addition, for Invention Examples 1-11 and 1-13 (the case of post-adding only the low-combustibility carbon material), the sintering raw materials except for the low-combustibility carbon material were put into the granulator, and after 4 minutes of mixing treatment, water was added (humidification) in such a way as to reach the target moisture value and mixed for 3 minutes and 45 seconds (granulation), the granulator was temporarily stopped, the low-combustibility carbon material (pulverized coke) was added, and further mixed for 15 seconds (granulation) (refer to the second paragraph on page 20 of the specification, i.e., the paragraph above the above-mentioned (post-adding method)). It should be noted that the final target moisture value was set to 7.5% by mass based on the mass of all the sintering raw materials including all the binders and return fines.

[0197] (Charging method)

[0198] The pot test apparatus used is a cylindrical pot with a diameter of 300 mm and a height of 500 mm. In addition, for Invention Examples 1-10 and Invention Example 1-13 (in the case of segregation-enhanced feeding), as shown below, loading was carried out in accordance with the method of the slit rod type classification device described in Materials and Processes 24 (2011), P.795 (original etc.), simulating segregation-enhanced loading using the above-mentioned segregation-enhanced type loading device (slit rod type loading device, refer to the second paragraph on page 18 of the specification). In the case of the test of normal loading other than Invention Examples 1-10 and Invention Example 1-13, a flat plate was used instead of the slit rod type classification device.

[0199] (Segregation-enhanced loading)

[0200] In Invention Examples 1-10 and Invention Example 1-13, the granulated mixed raw material after classification using the slit rod type classification device was loaded into the sintering pot. Specifically, the granulated mixed raw material was put into the slit rod type classification device, and the granulated mixed raw material that fell between the slit rods was recovered using a recovery box with 4 boxes arranged from the upstream side to the downstream side directly below the slit rods. Furthermore, the granulated mixed raw material that slid on the slit rods was recovered using another recovery box. Since the granulated mixed raw material had been classified and recovered into 5 recovery boxes, first, the granulated mixed raw material that slid on the slit rods and then the granulated mixed raw material that fell between the slit rods were sequentially dropped and loaded from the upper part of the pot from the downstream side recovery box.

[0201] (Firing conditions)

[0202] After the granulated mixed raw material was loaded, the surface of the raw material filling layer was first ignited for 1.0 minute (initial ignition) using an ignition device (flame heating). 1.0 minute after the ignition ended, re-ignition was carried out for 1.0 minute. It should be noted that the time (separation time) of 1.0 minute from the end of ignition to the start of re-ignition, when converted to the actual machine, becomes 4% of the length of the entire belt machine. The ignition time and the re-ignition time were both set to 1.0 minute (heat: as the sensible heat of the suction gas, it was 25 MJ / t of mixed raw material). It should be noted that in the pot test, due to large heat losses, the LPG gas combustion amount was about 100 MJ / t of mixed raw material. In addition, the suction negative pressure during sintering was adjusted by the valve opening on the suction side of the blower so as to be constant at 1300 mmAq (12.7 kPa) based on the measured value under the pot.

[0203] Temperature measurement was also carried out with a thermocouple under the pot together with the pressure. During sintering, if the combustion zone reaches the bottom of the raw material filling layer, the exhaust temperature under the pot starts to rise, soon reaches a peak, and then decreases as the combustion of coke ends. The suction of the blower is stopped 3 minutes after the exhaust temperature reaches the peak. It should be noted that the sintering time is set as the time from the ignition start time to the time when the exhaust temperature reaches the peak. The sintering speed (BTS: Burn through speed) is obtained by dividing the raw material layer thickness by the sintering time.

[0204] (Yield rate)

[0205] After sintering, the obtained sintered ore is dropped 4 times from a height of 2 m. The sintered ore with a particle size of +5 mm (more than 5 mm) excluding the bottom layer ore is recovered as the sintered product and its mass is measured, which is regarded as the mass of the sintered product. Then, the value obtained by dividing the mass of the sintered product by the mass of the sintered ore excluding the bottom layer ore is defined as the yield rate.

[0206] (Productivity)

[0207] The productivity is calculated as shown in the following formula (3), by dividing the mass of the sintered product (finished product amount (tons; ton)) by the above-mentioned sintering time (converting the time into days) and the firing area (bottom area of the pot (m 2 )).

[0208] Productivity (t / (Dm 2 )) = finished product amount (t) / {sintering time (Day) · bottom area of the pot (m 2 )}

[0209] Formula (3)

[0210] (Reduction degradation property)

[0211] The reduction degradation property of the sintered ore represents the degree of pulverization of the sintered ore under the conditions simulating the low-temperature reduction zone of a blast furnace, and the method specified in the JIS method (JIS M8720:2017 "Iron ores - Test method for reduction degradation") is adopted. That is, 500 g of the sintered ore with a particle size exceeding 15 mm and less than 20 mm is passed through a gas composed of CO (30 vol%) - N2 (70 vol%) at a flow rate of 15 L / min, and is subjected to a reduction treatment at 550 °C for 30 minutes. Then, using a cylindrical rotary drum (diameter 130 mmφ × 200 mmL), it is rotated at 30 rpm for 30 minutes, and the particle size -2.8 mm ratio (the mass ratio of the iron ore passing through the sieve with a 2.8 mm sieve hole) is used as an index (RDI: Reduction Degradation Index) of the reduction degradation property.

[0212] (Test results)

[0213] The test results are shown in the lower column of Table 6. In the test results, the productivity became 29.5 t / (Dm 2 ) or more, which is the invention example of Example 1.

[0214] Figure 10 is a graph showing the test results of Comparative Example 1-1 (using only highly combustible carbon material as the binder) in Table 6, Invention Examples 1-1 to 1-3 (carbon component mass ratio of highly combustible carbon material: 75 mass%, 50 mass%, 25 mass%), Comparative Example 1-3 (carbon component mass ratio of highly combustible carbon material: 50 mass%), Invention Examples 1-4 to 1-5 (carbon component mass ratio of highly combustible carbon material: 50 mass%), and Invention Examples 1-12 to 1-13 (carbon component mass ratio of highly combustible carbon material: 20 mass%, 25 mass%, highly combustible carbon material: charcoal compressed product) in the graph, and is a graph showing the relationship between the ratio of the particle size +2.8 mm of the highly combustible carbon material and the productivity. Figure 11 is a graph showing the test results of Comparative Example 1-0 (one-stage ignition), Comparative Examples 1-1 to 1-2 (using only highly combustible carbon material as the binder, using only low-combustible carbon material as the binder) in Table 6, Comparative Example 1-3 (ratio of the particle size of semicoke being 2.8 mm or more: less than 30 mass%), Invention Examples 1-1 to 1-5 (average particle size of pulverized coke: 1.0 mm, highly combustible carbon material: semicoke), and Invention Examples 1-12 to 1-13 (average particle size of pulverized coke: 1.2 mm, highly combustible carbon material: charcoal compressed product) in the graph, showing the relationship between the mass ratio (mass%) of the carbon component of the highly combustible carbon material to the carbon component of the binder and the productivity (t / (Dm 2 )) Figure 12 is a graph showing the test results of Invention Examples 1-6 to 1-11 (carbon component mass ratio of semicoke: 50 mass%, ratio of the particle size of semicoke being 2.8 mm or more: 30 mass%) in Table 6, showing the relationship between the average particle size (mm) of pulverized coke and the productivity (t / (Dm 2 ))

[0215] As shown in Table 6, Figure 10 , Figure 11 and Figure 12As shown in , in Invention Examples 1-1 to 1-13 where the mass ratio of the carbon component of the highly combustible carbon material to the carbon component of all the agglomerated materials is 25% by mass to 75% by mass and the ratio of the particle size of the highly combustible carbon material (semicoke) being 2.8 mm or more is 30% to 80%, the productivity is improved. Since the charcoal compression molded product has a low combustion start temperature, the productivity is improved in the same way as the semicoke. Furthermore, since the combustion start temperature of the charcoal compression molded product is lower than that of the semicoke, even when the mass ratio to the carbon component of the agglomerated material is as low as 20% by mass (Invention Example 1-12), it has the same productivity as 25% by mass in the semicoke (Invention Example 1-3). In addition, as shown in Figure 12 As shown in , in Invention Examples 1-7 and 1-8 where the average particle size of pulverized coke as the low combustibility carbon material is 0.8 to 1.2 mm, the productivity and reduction degradation property are further improved (comparison with Invention Examples 1-6 and 1-9). Furthermore, for Invention Example 1-10 where segregation enhanced feeding was carried out, the yield increase was large and the productivity was further improved. For Invention Example 1-11 where pulverized coke was added later, the combustion front descent speed (sintering speed) and the yield increase were remarkable, and the productivity was greatly improved. It should be noted that through the comparison between Comparative Example 1-0 (one-stage ignition sintering method) and Comparative Example 1-2 (re-ignition sintering method), it was confirmed that the implementation of re-ignition can maintain the sintering speed and increase the yield, and the improvement effect of productivity can be obtained.

[0216] 《Example 2》

[0217] (Test level)

[0218] In this example, the same sintering pot test as in Example 1 was used to verify the application of the air volume control technology in the present invention. Hereinafter, for the test conditions of Example 2 (Comparative Examples 2-1 to 2-2, Invention Examples 2-1 to 2-3), different test conditions and the like from Example 1 will be described using Table 7 described later. In addition, in the following description, the same conditions, the same test methods, etc. as in Example 1 will be appropriately omitted from repeated description.

[0219] (Raw material blending, etc.)

[0220] The raw material composition, except for the binder, was set to be the same as in Table 4 of Example 1. The composition of the binder (carbonaceous material) in the sintering raw materials and the particle size of the binder (the ratio of the average particle size of the low-combustibility carbonaceous material and the particle size of the high-combustibility carbonaceous material being 2.8 mm or more) were set to the same conditions as in Comparative Example 1-2 or Inventive Example 1-2 of Example 1. Specifically, as shown in Tables 5 to 7, in Comparative Examples 2-1 to 2-2, similar to the former (Comparative Example 1-2), only 4.5 mass% of pulverized coke (low-combustibility carbonaceous material) was used based on the number excluding the new raw materials (the mass ratio of the carbon component of the binder was 0 mass% for semi-coke and 100 mass% for pulverized coke), and the average particle size of the pulverized coke was set to 1.0 mm. In addition, in Inventive Examples 2-1 to 2-3, similar to the latter (Inventive Example 1-2), the mass ratio of the carbon component was set to 50 mass% for pulverized coke (low-combustibility carbonaceous material) and 50 mass% for semi-coke (high-combustibility carbonaceous material), and the average particle size of the pulverized coke and the ratio of the particle size of the high-combustibility carbonaceous material being 2.8 mm or more were set to 1.00 mm and 30 mass%, respectively. It should be noted that in all test cases of Example 2, the granulation method was set to co-granulation, and the charging method was set to normal charging.

[0221] (Firing conditions)

[0222] In all test cases of Example 2, the ignition time (equivalent to the ignition (primary ignition) using the ignition furnace 3) and the re-ignition time (equivalent to the re-ignition using the re-ignition furnace 4) were both set to 1 minute (heat: 25 MJ / ton of the combined raw materials as the sensible heat of the suction gas). In addition, as shown in the column of the two ignition intervals in Table 7, the re-ignition start time was set to 1 minute after the ignition completion time (separation time: 1 minute).

[0223] The suction air volume was adjusted by the valve opening on the suction side of the blower so that the air volume in the empty cylinder in the pot became one of the following Conditions 0 to 2.

[0224] Condition 0. Air volume control off: The air volume was 1.80 Nm 3 / min and constant

[0225] Condition 1. Air volume control on 1:

[0226] The air volume was 1.35 Nm 3 / min before the end of re-ignition and 1.80 Nm 3 / min after that

[0227] Condition 2. Air volume control on 2:

[0228] The air volume was 1.20 Nm 3 / min before the end of re-ignition and 1.80 Nm3 / min

[0229] As shown in the air volume control column of Table 7, in Comparative Examples 2-1 and 2-2, they were set to Condition 0 (off) and Condition 2 (open 2) respectively. In addition, in Invention Example 2-1, the test was carried out under Condition 0 (off), in Invention Example 2-2, the test was carried out under Condition 1 (open 1), and in Invention Example 2-3, the test was carried out under Condition 2 (open 2).

[0230] [Table 7]

[0231]

[0232] (Test results)

[0233] The test results (sintering speed, yield, productivity of each test case) are shown in the right column of Table 7. In the test results, the cases where the productivity is 36.0 t / (Dm 2 ) or more are Invention Examples of Example 2. It should be noted that the sintering speed, yield, and productivity are obtained by the same method as in Example 1. In addition, Figure 13 is a figure showing the test results in a graph, representing the relationship between the empty cylinder air volume ratio (a / b) and the productivity (t / (Dm 2 ).

[0234] As shown in Table 7 and Figure 13 , compared with Comparative Examples 2-1 and 2-2 that did not use highly combustible carbon materials, the productivity of Invention Examples 2-1 to 2-3 that used highly combustible carbon materials increased. In addition, for Invention Example 2-2 (empty cylinder air volume is 1.35 Nm 3 / min) and Invention Example 2-3 (empty cylinder air volume is 1.20 Nm 3 / min) where the air volume was suppressed in the interval just before the re-ignition ended, compared with Invention Example 2-1 where the air volume was not suppressed, the yield increased significantly, the decrease in the sintering speed could be compensated for, and the productivity was improved to 0.3 t / (Dm 2 ) and 0.4 t / (Dm 2 ) respectively.

[0235] 《Example 3》

[0236] (Test level)

[0237] In this example, the same sintering pot test as in Example 1 was used to verify the application of the oxygen enrichment technology in the present invention. Hereinafter, for the test cases of Example 3 (Invention Examples 3-1 to 3-10), for the test conditions different from those in Example 1, Table 8 described later will be used for explanation. In addition, in the following description, for the same conditions, the same test methods, etc. as in Example 1, the repeated description will be appropriately omitted.

[0238] (Raw material composition, etc.)

[0239] The raw material composition other than the binder is set to be the same as that in Table 4 of Example 1. The binder (carbon material) composition in the raw materials and the particle size of the binder (the average particle size of the low-combustibility carbon material and the ratio of the particle size of the high-combustibility carbon material being 2.8 mm or more) are set to the same conditions as those in Invention Example 1-2 of Example 1 in all test cases of Example 3 (except for Comparative Example 2-1 shown for reference in Table 8). It should be noted that in all test cases of Example 3, the granulation method is set to be the same, and the charging method is set to be normal. It should be noted that semicoke is used as the high-combustibility carbon material.

[0240] (Firing conditions)

[0241] In all test cases of Example 3, the ignition time (equivalent to the ignition (initial ignition) using the ignition furnace 3) and the re-ignition time (equivalent to the re-ignition using the re-ignition furnace 4) are both set to 1 minute (heat: 25 MJ / ton of the combined raw materials as the sensible heat of the suction gas). As shown in Table 8, for each test case (Invention Examples 3-1 to 3-10), the time (separation time) between ignition and re-ignition (equivalent to the movement of the oxygen-enriched gas suction region) and the oxygen concentration of the suction gas are changed at the levels shown as test conditions in Table 8.

[0242] During the firing after ignition, the suction air volume is set to a constant condition, and the air volume is adjusted to be 1.80 Nm 3 / min in terms of the exhaust gas. Similar to Examples 1 and 2, the suction of the blower is stopped 3 minutes after the exhaust gas temperature reaches the peak, and the firing is ended. Here, the sintering time is set to the time from the start moment of ignition to the moment when the exhaust gas temperature reaches the peak.

[0243] In the inventive examples 3-1 and 3-4, oxygen enrichment was not performed, and the atmosphere (air) was used for the suction gas. The oxygen feeding method in the inventive examples 3-2 to 3-3, 3-5 to 3-10 is to mix the atmosphere and oxygen in a manner to obtain a specified oxygen concentration (oxygen concentration in Table 8) using a gas mixer, and to supply the mixed gas for a specified time (oxygen enrichment time in Table 8) using a hood covering the pot. It should be noted that the supply and suction of the oxygen-enriched gas is limited to the period from immediately after the ignition is completed (after a time of more than 0 seconds and less than 2 seconds from the time of the ignition end) to immediately before the re-ignition (before a time of more than 0 seconds and less than 2 seconds from the time of the re-ignition start). That is, the hood is set at the same time as the ignition is completed to supply the oxygen-enriched gas of the specified oxygen concentration, and the oxygen-enriched gas is sucked, and the hood is immediately removed after a specified time to re-ignite. Here, the inlet gas volume (=suction gas volume) is determined in such a way that all the mixed gas passes through the gas mixer. It should be noted that the inlet gas volume is obtained from the inlet gas nitrogen concentration, the exhaust nitrogen concentration and the exhaust air volume. This is because the nitrogen volume at the inlet and outlet is equal. Furthermore, the exhaust nitrogen concentration is obtained from the exhaust gas analysis (CO, CO2, O2) by subtraction (N2≈100-(CO+CO2+O2)). In this embodiment, since the exhaust air volume is set to a constant condition, it is easy to adjust the suction gas.

[0244] [Table 8]

[0245]

[0246] (Test results)

[0247] The right column of Table 8 shows the test results (sintering rate, yield, and productivity) of each test case. In the test results, the productivity was 36.0 t / (Dm 2 ) The above situation is an inventive example of Example 3. It should be noted that the sintering speed, yield rate and productivity are obtained by the same method as in Example 1. In addition, Figure 14 The test results are shown in a graph, showing the oxygen concentration (vol.%) of the suction gas during the separation time (equivalent to the time domain in which the carriage passes through the oxygen-enriched gas suction area 7x of the actual machine) and the productivity (t / (Dm 2 ))’s relationship.

[0248] As shown in the test results of Inventive Examples 3-1 to 3-3, when the separation time is set to 0.5 minutes, the oxygen concentration increases. The resulting increase in sintering speed, yield and productivity is not significant. This is believed to be due to the short separation time and the oxygen enrichment time, which is as short as 0.5 minutes.

[0249] On the other hand, as shown in the test results of Invention Examples 3-4 and 3-5, when the separation time was set to 1.0 minute, by increasing the oxygen concentration from 21% by volume to 30% by volume the increase in the yield and productivity became significant.

[0250] In addition, as shown in the test results of Invention Examples 3-5 and 3-6, by increasing the separation time from 1.0 minute to 2.0 minutes at the same oxygen concentration (30% by volume) the sintering speed, yield, and productivity increased significantly. This is the effect of the increase in the oxygen enrichment time accompanying the increase in the separation time.

[0251] As shown in the test results of Invention Examples 3-6 and 3-7, when the separation time was 2.0 minutes, by increasing the oxygen concentration from 30% by volume to 40% by volume the sintering speed and productivity increased significantly.

[0252] In addition, as shown in the test results of Invention Examples 3-7 and 3-8, by increasing the separation time from 2 minutes to 5 minutes the sintering speed, yield, and productivity increased.

[0253] However, as shown in the test results of Invention Examples 3-8 to 3-10, if the oxygen concentration exceeds 40% by volume or if the separation time exceeds 5 minutes the improvement effects of the sintering speed, yield, and productivity reach a limit.

[0254] 《Example 4》

[0255] (Test level)

[0256] In this example, using the same sintering pot test as in Example 1, the application of the oxygen enrichment technology in the present invention was verified. Hereinafter, using Tables 9 to 11 described later, the test conditions and test results of Test 1 (a total of 15 test cases of Invention Examples 4-1 to 4-15, refer to Table 9) and Test 2 (a total of 6 test cases of Invention Examples 4-16 to 21, refer to Table 11) will be described. It should be noted that Invention Example 4-1 in Table 9 described later is the same test case as Invention Example 2-1. In addition, Comparative Example 2-1 of Example 2 is shown for reference in Table 9, and Invention Example 4-10 of Test 1 is shown for reference in Table 11. In the following description, the same conditions, the same test methods, etc. as in Example 1 will be appropriately omitted from repeated description.

[0257] "Experiment 1"

[0258] (Raw material formulation, etc.)

[0259] The raw material formulation, except for the binder, is set to be the same as that in Table 4 of Example 1. The binder (carbon material) formulation in the raw materials and the particle size of the binder (the average particle size of the low-combustibility carbon material and the ratio of the particle size of the high-combustibility carbon material being 2.8 mm or more) are set to the same conditions as those in Invention Example 1-2 of Example 1 in all test cases (Experiment 1 and Experiment 2 (Invention Examples 4-1 to 4-21)) of Example 4. In addition, in all test cases of Example 4, the granulation method is set to be the same, and the charging method is set to be normal.

[0260] (Firing conditions)

[0261] In all test cases of Example 4, the combustion time in ignition (corresponding to the ignition (initial ignition) using the ignition furnace 3) and re-ignition (corresponding to the re-ignition using the re-ignition furnace 4) is set to 1 minute (heat: as the sensible heat of the suction gas, it is 25 MJ / t of the mixed raw materials). In addition, as shown in Table 9, the interval between ignition and re-ignition (separation time: corresponding to the time of movement in the atmospheric suction region 7) is set to 1 minute. Under the condition of starting oxygen enrichment just after re-ignition (more than 0 seconds and within 2 seconds from the end time of re-ignition), the oxygen enrichment time and oxygen concentration are changed at the levels shown as test conditions.

[0262] The firing air volume after ignition is set to a constant condition, and its air volume is adjusted to 1.80 Nm 3 / min in terms of exhaust gas. Similar to Examples 1 to 3, the suction of the blower is stopped 3 minutes after the exhaust gas temperature reaches the peak, and the firing is ended. Here, the sintering time is set to the time from the start time of ignition to the time when the exhaust gas temperature reaches the peak.

[0263] In Invention Example 4-1, no oxygen enrichment was carried out, and atmospheric air was used for the suction gas. The oxygen input method in Invention Examples 4-2 to 4-15 is the same as that in Example 3. The atmosphere and oxygen are mixed by a gas mixer to form a specified oxygen concentration (the oxygen concentration in Table 9), and this mixed gas is supplied for a specified time (the oxygen enrichment time in Table 9) using a ventilation hood covering the pot. Specifically, the ventilation hood is set up simultaneously with the end of re-ignition to supply the oxygen enrichment gas with a specified oxygen concentration, the oxygen enrichment gas is sucked, and the ventilation hood is immediately removed after a specified time. Here, the inlet-side gas air volume (= suction gas volume) is determined so that all of it becomes the mixed gas passing through the gas mixer.

[0264] [Table 9]

[0265]

[0266] (Test results)

[0267] The test results (sintering speed, yield, productivity) of each test case are shown in the right column of Table 9. In the test results, the productivity becomes 36.0 t / (Dm 2 ) or more in the invention example of Example 4 (Test 1). It should be noted that the sintering speed, yield, and productivity are obtained by the same method as in Example 1.

[0268] (Sintering speed)

[0269] Effect of oxygen concentration: The oxygen concentration rises to 40 vol.% (volume %), but there is a tendency to reach a limit at an oxygen concentration of 50 vol.% (invention examples 4-9, 4-13).

[0270] Effect of oxygen enrichment time: If observed under the condition of an oxygen concentration of 30 vol.%, the effect increases until 2.0 minutes (invention example 4-11), but even if extended to 3.0 minutes (invention example 4-14) and 4.0 minutes (invention example 4-15), the effect reaches a limit.

[0271] (Yield)

[0272] It is 76.2 mass% (mass %) under the condition of no oxygen enrichment in the re-ignition method (invention example 4-1), and all test levels fall within 76.2 ± 0.5 mass% under the condition of oxygen enrichment in the re-ignition method. Therefore, no effect on the yield is shown.

[0273] (Productivity)

[0274] Figure 15 This test result is shown in the graph in the figure, showing the relationship between the oxygen concentration (vol.%) and the productivity (t / (Dm 2 ). As Figure 15 shown, the following results are obtained.

[0275] Effect of oxygen concentration: The oxygen concentration rises to 40 vol.% (volume %), but there is a tendency to reach a limit at an oxygen concentration of 50 vol.% (invention examples 4-9, 4-13).

[0276] Effect of oxygen enrichment time: If observed under the condition of an oxygen concentration of 30 vol.%, the effect increases until 2.0 minutes (invention example 4-11), but even if extended to 3.0 minutes (invention example 4-14) and 4.0 minutes (invention example 4-15), the effect reaches a limit.

[0277] Here, the results obtained by calculating the oxygen utilization rate and oxygen consumption rate for the above-described Invention Examples 4-1 and 4-14 are shown in Table 10. In Table 10, for the case of Invention Example 4-14 (oxygen concentration: 30 vol.%, oxygen enrichment time: 3.0 minutes) where the productivity improvement effect is the greatest, the test conditions and results of Comparative Examples 4-1 and 4-2 conducted for comparative evaluation with the effects in one-stage ignition are also shown. In Comparative Example 4-2, oxygen enrichment was carried out for 3.0 minutes starting immediately after ignition. It should be noted that the time domain for evaluating the oxygen utilization rate and oxygen consumption rate is 3 minutes starting immediately after ignition in Comparative Examples 4-1 and 4-2 (one-stage ignition sintering method). In addition, in Invention Examples 4-1 and 4-14 (re-ignition sintering method), it is set to 3 minutes starting immediately after re-ignition. That is, for Comparative Example 4-2 and Invention Example 4-14, the oxygen utilization rate and oxygen consumption rate in the oxygen enrichment time domain are shown. In addition, the exhaust gas oxygen release rate (b) shown in Table 10 is calculated from the exhaust gas analysis results obtained using a magnetic oxygen concentration meter. The oxygen consumption rate (a) is obtained by subtracting the exhaust gas oxygen release rate (b) from the oxygen flow rate drawn into the sintering layer. It should be noted that the oxygen flow rate drawn into the sintering layer can be obtained by multiplying the inlet-side gas flow rate by the oxygen concentration.

[0278] [Table 10]

[0279]

[0280] As shown in Table 10, when comparing those without oxygen enrichment (Invention Example 4-1 and Comparative Example 4-1), the oxygen consumption rate and oxygen utilization rate are higher 3 minutes after re-ignition than 3 minutes after ignition in one-stage ignition. Moreover, when comparing those with re-ignition (Invention Example 4-1 and Invention Example 4-14), for Invention Example 4-14 where oxygen enrichment was carried out for 3 minutes after re-ignition, the oxygen utilization rate is maintained and the oxygen concentration increases, resulting in an increase in the oxygen consumption rate.

[0281] 《Test 2》

[0282] In this experiment, taking Invention Examples 4-10 of Experiment 1 as a reference, only the oxygen enrichment start time was changed at 10-second intervals starting from the end of re-ignition, and its influence was investigated. That is, the test conditions of Invention Examples 4-16 to 4-21 were the same as those of Invention Example 4-10 except for the oxygen enrichment start time. Table 11 shows the test conditions and test results of Invention Example 4-10 and Invention Examples 4-16 to 4-21. The oxygen enrichment start time in Table 11 represents the elapsed time (in seconds) from the end of re-ignition to the start of re-ignition. The "0 seconds" of Invention Example 4-10 where oxygen enrichment starts immediately after re-ignition represents a time exceeding 0 seconds and within 2 seconds including the operation time from the end of re-ignition to the start of oxygen enrichment. In addition, "10 seconds" of Invention Example 4-16 represents a time exceeding 10 seconds and within 12 seconds including the operation time from the end of re-ignition to the start of oxygen enrichment. For each second of the oxygen enrichment start time of Invention Examples 4-17 to 4-21, it is the same as that of Invention Example 4-10 and Invention Example 4-16.

[0283] [Table 11]

[0284]

[0285] (Test Results)

[0286] The test results (sintering speed, yield, productivity) of each test case are shown in the right column of Table 11. In the test results, the cases where the productivity is 36.0 t / (Dm 2 ) or more are Invention Examples of Example 4 (Experiment 2). It should be noted that the sintering speed, yield, and productivity are obtained by the same method as in Example 1. Figure 16 is a graph made from the test results in the right column of Table 4, showing the relationship between the oxygen enrichment time and the productivity. From Figure 16 and the test results (sintering speed and productivity) in the right column of Table 4, it can be seen that it is preferable to start oxygen enrichment within 10 seconds from the end of re-ignition, but even within 30 seconds from the end of re-ignition, a considerable effect can be obtained. In addition, even after 60 seconds, the effect is greater compared to Invention Examples 4-1 to 4-3 shown in Table 9.

[0287] 《Example 5》

[0288] (Test Level)

[0289] In this embodiment, the same sintering pot test as in Embodiment 1 was used to verify the application of the support sintering technology in the present invention. Hereinafter, Table 12 described later is used to explain the test conditions and test results of the test cases of Embodiment 5 (Comparative Examples 5-1 to 5-2, Invention Examples 5-1 to 5-6). It should be noted that in the following description, the same conditions, the same test methods, etc. as in Embodiment 1 are appropriately omitted from repeated description.

[0290] (Raw material formulation, etc.)

[0291] The raw material formulation was set to be the same as that in Table 4 of Embodiment 1 except for the binder. The binder (carbon material) formulation in the raw materials and the particle size of the binder (the average particle size of the low-combustibility carbon material, the ratio of the particle size of the high-combustibility carbon material being 2.8 mm or more) were set to the same conditions as those in Comparative Example 1-2 or Invention Example 1-2 of Embodiment 1. In Comparative Examples 5-1 to 5-2, similar to the former (Comparative Example 1-2), only 4.5 mass% of pulverized coke (low-combustibility carbon material) was used in terms of the number other than the new raw materials (the mass ratio of the carbon component of the binder was 0 mass% for semicoke and 100 mass% for pulverized coke), and the average particle size of the pulverized coke was set to 1.0 mm. In addition, in Invention Examples 5-1 to 5-6, similar to the latter (Invention Example 1-2), in terms of the mass ratio of the carbon component, the formulation was set to 50 mass% for pulverized coke (low-combustibility carbon material) and 50 mass% for semicoke (high-combustibility carbon material), and the average particle size of the pulverized coke and the ratio of the particle size of the high-combustibility carbon material being 2.8 mm or more were set to 1.00 mm and 30 mass%, respectively. It should be noted that in all test cases of Embodiment 5, the granulation method was set to be the same, and the charging method was set to be normal.

[0292] (Firing conditions)

[0293] In all test cases of Embodiment 5, the ignition time in both ignition (equivalent to the ignition (initial ignition) using the ignition furnace 3) and re-ignition (equivalent to the re-ignition using the re-ignition furnace 4) was set to 1 minute (the heat was 25 MJ / t of the mixed raw materials). In addition, as shown in the column of the separation time in Table 12, the separation time was set to one of 0.5 minutes, 1 minute, 2.5 minutes, and 3.5 minutes. For the suction pressure, the same as in Embodiment 1, in all test cases of Embodiment 5, it was adjusted by the valve opening of the suction side of the blower so that the measured value under the pot became a constant 1300 mmAq (12.75 kPa).

[0294] Table 12 shows the test conditions and test results for each test case of this embodiment. As shown in Table 12, for the semicoke (highly combustible carbon material) blend of 50% by mass, the effect of the support sintering technology of the bracket was evaluated at three levels of the separation time (0.5 minutes, 2.5 minutes, 3.5 minutes) (Inventive Examples 5-1 to 5-6). In addition, for comparison, for the semicoke blend of 0% by mass, the evaluation was carried out under the condition that the separation time was 0.5 minutes (Comparative Examples 5-1 to 5-2). For reference, Comparative Example 1-2 and Inventive Example 1-2 of Example 1 are also shown.

[0295] [Table 12]

[0296]

[0297] (Test results)

[0298] Table 12 shows the test results (sintering speed, yield, productivity) for each test case. In the test results, the case where the productivity is 29.5 t / (Dm 2 ) or more is the inventive example of Example 5. It should be noted that the sintering speed, yield, and productivity are obtained by the same method as in Example 1. In addition, Figure 17 (semicoke blend of 50% by mass) and Figure 18 (semicoke blend of 0% by mass) are the graphs showing the test results in Table 12, indicating the relationship between the separation time (min) and the productivity (t / (Dm 2 ).

[0299] As shown in Table 12 and Figure 17 , for the semicoke blend of 50% by mass, in terms of the sintering speed, yield, and productivity, if the support sintering technology of the bracket is applied at the separation times of 0.5 minutes and 2.5 minutes, the productivity becomes a high value and the improvement effect is significant.

[0300] On the other hand, as shown in Table 12 and Figure 18 , for the semicoke blend of 0% by mass, the effect of the support sintering technology of the bracket is weakened for the sintering speed, yield, and productivity. In this way, an unexpected synergistic effect between the highly combustible carbon material (semicoke) blend and the support sintering technology was confirmed in the re-ignition sintering method.

[0301] It should be noted that, in the present test case (Examples 1 to 5), the ignition time and the re-ignition time are both implemented with 1 minute (heat: sensible heat of the attracted gas, 25 MJ / t of mixed raw material), but the present embodiment is not limited to this example. This is because the ignition time in the test case is set in consideration of the heat loss in the pot test. In an actual machine (commercial sintering machine), for example, if the operation is performed with an ignition time of 30 seconds, it is not necessary to set the ignition time to 1 minute, and the re-ignition sintering method can be performed by maintaining the ignition time of the actual operation. In addition, for the re-ignition time, it is also not necessary to set it to 1 minute in an actual machine.

[0302] The preferred embodiments and examples of the present invention are described in detail with reference to the accompanying drawings, but the present invention is not limited to the examples. Anyone with ordinary knowledge in the technical field to which the present invention belongs can obviously think of various variations or modifications within the scope of the technical ideas recorded in the claims, and they are of course understood to belong to the technical scope of the present invention.

[0303] Explanation of symbols

[0304] 1 raw material tank group, 2 drum mixer, 3 ignition furnace, 31 igniter, 32 outer cover of ignition furnace, 32a partition (downstream side), 4 re-ignition furnace, 41 re-igniter, 42 outer cover of re-ignition furnace, 42a partition (upstream side), 42b partition (downstream side), 5 trolley, 5x trolley forward direction, 51 grate bar, 52 main frame, 53 trolley side wall, 6 lower suction device, 6x lower suction, 61 bellows, 62 bellows branch pipe, 63 damper, 64 flue, 65 blower, 7 large gas suction area, 7x oxygen-enriched gas suction area, 8 inclined flat plate chute type loading device, 81 mixed raw material buffer hopper, 82 inclined flat plate chute, 9 oxygen-enriched gas supply equipment, 91 ventilation hood of oxygen-enriched gas supply equipment, 92 gas pipe, 10 raw material filling layer, 10x inclined surface, 10A combustion zone, 10A1 initial ignition combustion zone, 10A2 re-ignition combustion zone, 10B sintering block, 16 bracket, 16a sintering block support surface, 101, 103, 104 DL sintering machine, S section

Claims

1. A method for manufacturing sintered ore, which uses a Dravo sintering machine to manufacture sintered ore. The Dravo sintering machine is equipped with an ignition furnace for initial ignition and a re-ignition furnace that is arranged at a prescribed interval downstream of the ignition furnace and performs re-ignition, and sintering is carried out by downward suction. Among them, As the setting material for the blending raw materials, a low-combustibility carbon material with a combustion start temperature exceeding 550 °C and a high-combustibility carbon material with a combustion start temperature of 550 °C or lower are used. In the high-combustibility carbon material, the ratio of particles with a particle size of 2.8 mm or more is 30 mass% to 80 mass%.

2. The manufacturing method of the sintered ore according to claim 1, wherein, For the high-combustibility carbon material, a crushed material obtained by crushing a compression molded product obtained by compressing and molding an aggregate of wood carbide is used.

3. The method for manufacturing sintered ore according to claim 2, wherein, The manufacture of the crushed material obtained by crushing the compression molded product obtained by compressing and molding the aggregate of wood carbide has the following processes: A carbide manufacturing process for manufacturing wood carbide by carbonizing wood; An aggregate manufacturing process, which crushes the wood carbide as needed to form wood carbide particles, and manufactures an aggregate of wood carbide by mixing the wood carbide particles alone or with a binder; A compression process for manufacturing a compression molded product obtained by compressing and molding the aggregate; And A compressed product crushing process for crushing the compression molded product.

4. The method for manufacturing sintered ore according to any one of claims 1 to 3, wherein, The mass ratio of the carbon component of the high-combustibility carbon material to the carbon component of the setting material is 25 mass% to 75 mass%.

5. The manufacturing method of sintered ore according to claim 4, wherein, The average particle size of the low-combustibility carbon material is in the range of 0.8 mm to 1.2 mm.

6. The manufacturing method of sintered ore according to claim 5, wherein, As the charging device for the blending raw materials, a segregation-enhanced charging device is used.

7. The method for manufacturing sintered ore according to claim 5, wherein, Only the low-combustibility carbon material in the setting material is added in the latter half of the granulation process.

8. The method for manufacturing sintered ore according to any one of claims 1 to 3, which suppresses the air volume of downward suction only in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering belt conveyor.

9. The method for manufacturing sintered ore according to claim 8, which sets the average empty cylinder air volume of the atmosphere sucked in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering belt conveyor to 60% to 80% relative to the average empty cylinder air volume of the atmosphere sucked in the section on the downstream side of the outlet of the re-ignition furnace.

10. The method for manufacturing sintered ore according to claim 8, which sets the average negative pressure in the wind box or wind box branch pipe in the section up to the outlet of the re-ignition furnace on the upstream side of the sintering belt conveyor to 40% to 70% relative to the average negative pressure in the wind box or wind box branch pipe in the section on the downstream side of the outlet of the re-ignition furnace.

11. The method for manufacturing sintered ore according to claim 8, which sets the separation time, that is, the time required for the trolley to pass through the section between the ignition furnace and the re-ignition furnace, to 30 seconds to 2 minutes.

12. The method for manufacturing sintered ore according to any one of claims 1 to 3, wherein, The separation time, that is, the time required for the trolley to pass through the section between the ignition furnace and the re-ignition furnace, is 1 minute or more. In this section, the oxygen concentration of the suction gas sucked from the surface side of the sintered layer downward is 30% by volume or more.

13. The method for manufacturing sintered ore according to claim 12, wherein, The separation time is less than 5 minutes, and the oxygen concentration of the suction gas is 40% by volume or less.

14. The method for manufacturing sintered ore according to any one of claims 1 to 3, wherein, The start of oxygen enrichment of the suction gas sucked downward from the surface layer side of the sintered layer is set after the end of re-ignition. The oxygen enrichment time from the start of the oxygen enrichment to the end of the oxygen enrichment is 30 seconds or more. During the oxygen enrichment time, the oxygen concentration of the suction gas sucked downward is 30% by volume or more.

15. The method for manufacturing sintered ore according to claim 14, wherein, The oxygen enrichment time is 2 minutes or less, and the oxygen concentration of the suction gas is 40% by volume or less.

16. The method for manufacturing sintered ore according to claim 14, wherein, The start of the oxygen enrichment is more than 0 seconds and within 30 seconds from the end of the re-ignition.

17. The method for manufacturing sintered ore according to claim 16, wherein, The start of the oxygen enrichment is more than 0 seconds and within 10 seconds from the end of the re-ignition.

18. The method for manufacturing sintered ore according to any one of claims 1 to 3, wherein, In the trolley loaded with the compound raw material, a support member having a sintered block support surface is vertically provided on the grate in a manner buried in the raw material filling layer.

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