Method of manufacturing sintered ore and sintered ore for hydrogen gas injection blast furnace

Abstract

According to the present invention, provided is a method for manufacturing sintered ore enabling the manufacture of highly reducible sintered ore, independent of a trade-off relationship between reducibility and reduction disintegration, in a reducing gas atmosphere containing hydrogen gas. In particular, the invention is characterized in that the oxygen concentration of gas supplied by a gas supply device, the added amount of powdered coke and / or anthracite to be added to sinter feed, and the firing speed satisfy (1). (1): (10+0.3×CO2+0.2×CC) / FS>1.00. In (1), CO2 is the oxygen concentration (vol%) of gas, CC is the added amount (mass%, added externally) of powdered coke and / or anthracite relative to 100 mass% of the sinter feed, and FS is the firing speed (mm / min).

Description

Manufacturing method of sintered ore and sintered ore for hydrogen gas-injected blast furnace

[0001] The present invention relates to a method for producing sintered ore suitable for use in a hydrogen gas-injected blast furnace, and to sintered ore for a hydrogen gas-injected blast furnace.

[0002] From the perspective of preventing global warming, CO ２ There is a demand for reducing CO emissions, and in the steel industry, the molten iron production process in blast furnaces ２ For this reason, in blast furnace operation, not only carbon derived from coke and pulverized coal is used as a reducing agent, but also H ２ The reduction of iron oxide using H is being investigated. ２ When using CO in blast furnace operation compared with CO ２ In addition to the benefit of reduced emissions, other benefits include a faster reduction rate of iron oxide.

[0003] On the other hand, in blast furnaces, ２ and C and O ２ Indirect reduction by CO gas generated in the ２ There is direct reduction via CO, which is generated when the reaction occurs. Direct reduction is an endothermic reaction, so if direct reduction increases, it becomes necessary to increase the amount of heat input to the blast furnace.

[0004] Direct reduction is caused by a reaction in the lower part of the blast furnace where the raw material, iron ore or sinter, is melted. To suppress direct reduction, it is important to promote indirect reduction of the raw material, iron ore or sinter, in the upper part of the blast furnace before the reaction occurs in the lower part of the blast furnace. ２ It is important to improve the reducibility (JIS M 8713:2021) of sintered ore by reducing gases such as CO and CO. On the other hand, sintered ore undergoes a phenomenon called reduction disintegration, in which the ore is disintegrated during reduction. Patent Document 1 discloses a reduction disintegration rate measurement method that can measure the reduction disintegration rate of ore while reflecting the conditions inside a blast furnace.

[0005] JP 2012-247289 A

[0006] The reduction and disintegration of sintered ore is caused by the hematite (Fe ２ O ３ ) is magnetite (Fe ３O ４ It is believed that this phenomenon occurs when the sinter ore expands during reduction to 0.25°C, causing internal cracks and resulting in the pulverization of the sinter ore. As the reduction of the sinter ore progresses, the reduction and pulverization become more pronounced, which poses a trade-off between the reducibility and pulverization of the sinter ore. As mentioned above, there is also the issue that no studies have been conducted in terms of sinter ore suitable for hydrogen-gas-injected blast furnaces, which inject hydrogen gas, which has a high iron oxide reduction ability.

[0007] The present invention has been made in view of the above problems of the prior art, and its object is to provide a method for producing sintered ore that can produce highly reducible sintered ore in a reducing gas environment containing hydrogen gas, which is free from the trade-off between reducibility and reduction disintegration. Another object of the present invention is to provide sintered ore for hydrogen gas-injected blast furnaces that is suitable for hydrogen gas-injected blast furnaces.

[0008] The means for solving the above problems are as follows: [1] A granulation step of adding at least one of coke fines and anthracite to sintering raw materials containing an iron-containing raw material and a CaO-containing raw material, and granulating them in a granulator to form granulated particles, a charging bed formation step of charging the granulated particles onto an endless moving pallet in a raw material supply device of a Dwight Lloyd type sintering machine to form a charging bed, and a step of igniting at least one of the coke fines and anthracite contained in the surface layer of the charging bed in an ignition furnace provided downstream of the raw material supply device, and supplying gas from a gas supply device provided downstream of the ignition furnace. The method for producing sintered ore includes a sintering step of burning at least one of the coke fines and anthracite by supplying the gas to the sintering bed and sucking the gas introduced into the sintering bed with a wind box provided below the pallet to turn the sintered bed into a sintered cake, and a crushing step of crushing the sintered cake into sintered ore, wherein the oxygen concentration of the gas supplied from the gas supply device, the amount of at least one of the coke fines and anthracite added to the sintering raw materials, and the firing rate satisfy the following (1): (10 + 0.3 x C Ｏ２ +0.2 x C Ｃ ) / FS>1.00 (1) In the above formula (1), C Ｏ２is the oxygen concentration (vol %) of the gas, and C Ｃ is the amount (outer percentage by mass) of at least one of coke breeze and anthracite added relative to 100% by mass of the sintering raw material, and FS is the firing speed (mm / min). [2] A method for producing sintered ore according to [1], wherein the oxygen concentration of the gas is equal to or higher than air, the firing speed is 17 mm / min or less, and the amount (outer percentage) of at least one of coke breeze and anthracite added relative to 100% by mass of the sintering raw material is 3.5% to 4.0% by mass. [3] A method for producing sintered ore according to [1], wherein the oxygen concentration of the gas is 25% by volume or more, the firing speed is 19 mm / min or less, and the amount (outer percentage) of at least one of coke breeze and anthracite added relative to 100% by mass of the sintering raw material is 3.5% to 4.5% by mass. [4] Sintered ore for hydrogen gas injection blast furnace, having a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less.

[0009] The sintered ore produced by the method for producing sintered ore according to the present invention is sintered ore in which the decrease in reduction disintegration property is suppressed more than conventionally in a reducing gas environment containing hydrogen gas, and the sintered ore has improved reducibility. This makes it possible to provide sintered ore with high reducibility that is free from the trade-off relationship between reducibility and reduction disintegration property in a reducing gas environment containing hydrogen gas.

[0010] Fig. 1 is a schematic diagram showing a sintered ore production facility in which the sintered ore production method according to the present embodiment can be implemented. Fig. 2 is a graph showing the reaction rate constant and the diffusion rate constant in the gas reduction of sintered ore.

[0011] The present invention will be described below with reference to an embodiment. Fig. 1 is a schematic diagram showing a sintered ore production facility 10 in which a sintered ore production method according to the present embodiment can be implemented. The sintered ore production facility 10 includes a granulator 16, a sintering machine 20, and a crusher 30.

[0012] The granulator 16 adds coke breeze to the sintering raw material 12 containing the iron-containing raw material and the CaO-containing raw material, and granulates them to form granulated particles 18. This process is the granulation step. Anthracite may be used in place of the coke breeze added to the sintering raw material, or in addition to the coke breeze. That is, at least one of the coke breeze and the anthracite is added to the sintering raw material 12. In the following embodiments and examples, an example in which coke breeze is added to the sintering raw material 12 will be described.

[0013] The sintering raw materials 12 and coke fines are granulated in a granulator 16. When the sintering raw materials 12 and coke fines are granulated in the granulator 16, granulation water 14 is added to the sintering raw materials 12 and coke fines. Granulated particles 18 granulated by the granulator 16 are transported to a sintering machine 20. The iron-containing raw materials are, for example, iron ore and dust generated in a steel mill. The CaO-containing raw materials are, for example, quicklime, limestone, and slag.

[0014] The sintering machine 20 is, for example, a Dwight Lloyd type sintering machine and includes a raw material supply device 21, a pallet 22, a cutoff plate 23, an ignition furnace 24, a gas supply device 25, and a wind box 26. The raw material supply device 21 charges the granulated particles 18 into the pallet 22.

[0015] The pallet 22 is an endlessly movable pallet. When the granulated particles 18 are charged into the pallet 22 from the raw material supply device 21, a charging layer is formed in the pallet 22. The cut-off plate 23 flattens the surface of the charging layer and adjusts the thickness of the charging layer to a predetermined target layer thickness. This process is the charging layer formation step.

[0016] The ignition furnace 24 is provided downstream of the raw material supply device 21 and ignites the coke powder contained in the surface layer of the charging bed. The gas supply device 25 supplies gas to the surface side of the charging bed. For example, the gas may be air or oxygen-enriched air which has been enriched with oxygen to have a higher oxygen concentration than air.

[0017] The wind box 26 is provided below the pallet 22 and sucks gas downward from within the sintering bed formed within the pallet 22. This causes the fine coke contained in the sintering bed to combust, forming a combustion and molten zone within the sintering bed. When the wind box 26 sucks the gas downward from within the sintering bed, the combustion and molten zone within the sintering bed moves downward within the sintering bed. As the air within the sintering bed is sucked downward, the gas supplied from the gas supply device 25 is introduced into the sintering bed from the surface layer of the sintering bed. As the pallet 22 moves, the combustion and molten zone within the sintering bed moves downward, sintering the sintering raw materials 12. A sintered cake is obtained by sintering the sintering raw materials 12. This process is the sintering step.

[0018] The crusher 30 crushes the sintered cake discharged from the sintering machine 20 into crushed sintered cakes. The crushed sintered cakes are cooled and sized to produce sintered ore. This process is the crushing step.

[0019] In the method for producing sintered ore according to the present embodiment, a decrease in reduction disintegration property is suppressed and sintered ore with improved reducibility is produced in a reducing gas environment containing hydrogen gas. ２ The reaction rate constant and diffusion rate constant of the reduction reaction were confirmed.

[0020] 2A and 2B are graphs showing the reaction rate constant and the diffusion rate constant in the gas reduction of sintered ore. ２ 2(b) is a graph showing the reaction rate constant (m / sec) of CO and H ２ The diffusion rate constant (m ２ 2(a) and 2(b), H ２ The reaction rate constant of H is about three times that of CO. ２ It was confirmed that the diffusion rate constant of H is more than five times that of CO. ２We realized that to improve the reducibility of sintered ore during gas reduction, it is important to increase the reducibility of the sintered ore matrix, rather than increasing the pores in the sintered ore that contribute to gas diffusion. Increasing the reducibility of the sintered ore matrix means adjusting the constituent minerals (hematite, calcium ferrite, and magnetite) of sintered ore so as to increase the proportion of hematite, which is more easily reduced.

[0021] On the other hand, in order to prevent deterioration of the reduction disintegration property of sintered ore, it is necessary to maintain the strength of the sintered ore structure. For this reason, the inventors came up with the idea of ​​reducing the cumulative pore volume contained in the sintered ore and increasing the hematite content in the sintered ore to densify the sintered ore, thereby preventing deterioration of the reduction disintegration property of sintered ore.

[0022] In the method for producing sintered ore according to this embodiment, the amount of coke powder added to the sintering raw material is reduced, or the oxygen concentration of the gas supplied from the gas supply device 25 is increased. The coke powder is a heat source, and when heat is applied during the firing process of the sintering raw material, hematite in the sintering raw material is thermally decomposed into magnetite. Therefore, by reducing the amount of coke powder added to the sintering raw material, the hematite content in the produced sintered ore can be increased.

[0023] Thermal decomposition reaction of hematite at high temperatures (3Fe ２ O ３ →2Fe ３ O ４ +1 / 2O ２ The reoxidation during sintering (the reverse reaction described above) and the reoxidation during cooling are affected by the oxygen concentration of the gas supplied from the gas supply device 25. As the oxygen concentration of the supplied gas increases, reoxidation is promoted, and the hematite content in the sintered ore produced increases. On the other hand, in the sintering process in which combustion is performed while suction is performed in the wind box 26, the fire spreads vertically. Therefore, even if the oxygen concentration of the supplied gas is increased, the sintering temperature does not increase significantly, and the thermal decomposition reaction of hematite is not promoted. Therefore, increasing the oxygen concentration of the supplied gas increases the hematite content in the sintered ore.

[0024] Furthermore, in the method for producing sintered ore according to this embodiment, the firing rate of the sintering raw materials is slower than in the past. The slower the firing rate of the sintering raw materials, the slower the combustion and movement speed of the molten zone in the sintering bed. This ensures time for the molten liquid to wet and spread within the sintering bed, promoting the densification of the sintered ore. Here, the firing rate is calculated by dividing the thickness of the sintering bed by the firing time. The firing time is calculated by dividing the effective length of the sintering machine 20 by the moving speed of the pallet 22. The effective length of the sintering machine 20 is the length from when the sintered cake leaves the ignition furnace 24 until it is discharged.

[0025] Specifically, the oxygen concentration of the gas supplied from the gas supply device 25, the amount of coke powder added to the sintering raw material, and the firing rate are determined so as to satisfy the following formula (1), and sintered ore is produced. This allows the production of sintered ore having a hematite content of 40 mass% or more and a cumulative pore volume of 0.030 mL / g or less.

[0026] (10 + 0.3 x C Ｏ２ +0.2 x C Ｃ ) / FS>1.00 (1) In the above formula (1), C Ｏ２ is the oxygen concentration of the gas (volume %), and C Ｃ is the amount of coke powder added (mass % outer percentage) with the sintering raw material being 100 mass %, and FS is the firing speed (mm / min).

[0027] Sintered ore having a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less is sintered ore in which the decrease in reduction disintegration property is suppressed more than conventionally in a reducing gas environment containing hydrogen gas, and the sintered ore has improved reducibility. Therefore, sintered ore having a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less is sintered ore with high reducibility that is free from the trade-off between reducibility and reduction disintegration property in a reducing gas environment containing hydrogen gas.

[0028] An example of a sintered ore production condition that satisfies the above formula (1) is that the oxygen concentration of the gas supplied from the gas supply device is equal to or higher than that of air (oxygen concentration of 21% by volume or higher), the firing speed is 17 mm / min or lower, and the amount of coke powder added (outer percentage) based on 100% by mass of the sintering raw material is 3.5% by mass or higher and 4.0% by mass or lower. By producing sintered ore under these production conditions, it is possible to produce sintered ore with a hematite content of 40% by mass or higher and a cumulative pore volume of 0.030 mL / g or lower. The firing speed needs to be faster than 0 mm / min, and the oxygen concentration needs to be 100% by volume or lower.

[0029] Another example of sintered ore production conditions that satisfy the above formula (1) is that the oxygen concentration of the gas supplied from the gas supply device is 25% by volume or more, the firing rate is 19 mm / min or less, and the amount of coke powder added (outer percentage) based on 100% by mass of the sintering raw material is 3.5% by mass or more and 4.5% by mass or less. By producing sintered ore under these production conditions, sintered ore with a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less can be produced. The firing rate needs to be faster than 0 mm / min, and the oxygen concentration needs to be 100% by volume or less.

[0030] Next, an example will be described in which sintered ore was produced and the reducibility and reduction disintegration properties of the produced sintered ore were confirmed. The iron ore, quicklime, limestone, and return ore, excluding coke fines, were kept constant in the mass ratios shown in Table 1 below, and the amount of coke fines mixed was varied to prepare a sintering raw material. This sintering raw material was granulated using a drum mixer to obtain granulated particles. In granulating the sintering raw material, granulation water was added to the sintering raw material to adjust the moisture content of the sintering raw material to 7.5 mass%. When granulating the sintering raw material, the amount of coke fines added was adjusted so that the ratio of coke fines to 100 mass% of the sintering raw material was 3.5 to 6.5 mass%. The blending of each raw material was adjusted so that the basicity of the sintering raw material was 2.1.

[0031]

[0032] A pot test was conducted as a firing test. In the pot test, the firing rate was adjusted by adjusting the suction air volume. The oxygen concentration of the suction gas was adjusted to three levels: 21 vol% (air), 25 vol%, and 30 vol% to confirm the effect of oxygen-enriched air. The sintered cake produced in the pot test was dropped four times from a height of 2 m, and those with a particle size of +10 mm were designated as product sintered ore. A particle size of +10 mm means the particle size that can be sieved through a sieve with a nominal mesh size of 10 mm as specified in JIS Z 8801-1:2019. The firing rate was calculated by dividing the layer thickness of the sintering raw material layer by the time from the start to the end of firing.

[0033] The product sinter recovered in the ladle test was subjected to a reducibility test and a low-temperature reduction disintegration test. The reducibility test and the low-temperature reduction disintegration test were carried out in accordance with JIS M 8713:2021 (reducibility test method) and JIS M 8720:2023 (low-temperature reduction disintegration test method). However, some conditions (reduction temperature, reduction time, CO concentration, H ２ Concentration, N ２ Regarding the test conditions for the reduction gas containing hydrogen gas in a hydrogen gas-injected blast furnace, the test conditions specified in JIS were changed as shown in Table 2 below.

[0034]

[0035] During hydrogen gas reduction, the temperature inside the blast furnace drops. For this reason, the reduction temperature was lowered to 800°C compared to the JIS test conditions of 900°C as shown in Table 2. The reducibility under these conditions was designated as "N-RI." Similarly, the H ２ In gas reduction, the low-temperature time is long. For this reason, the reduction time was extended to 40 minutes compared to the JIS test condition of 30 minutes, as shown in Table 2, and the low-temperature reduction disintegration test was carried out. The low-temperature reduction disintegration under these conditions was designated "N-RDI."

[0036] The reducibility test was carried out using approximately 500 g of sintered ore with a particle size of 19 to 21 mm, as specified in JIS. The reducibility test was carried out using a TG furnace, and the reduction rate was calculated from the change in weight during the reduction test. The calculation method for the reduction rate was the same as that specified in JIS.

[0037] The low-temperature reduction disintegration test was conducted using approximately 500 g of sintered ore with a particle size of 16 to 20 mm, as specified in JIS. In the low-temperature reduction disintegration test, a drum test was conducted after reduction, and the weight before the drum test was taken as 100%, and the weight percentage of sintered ore whose particle size was -2.8 mm after the rotation test was used as the reduction disintegration index. A particle size of -2.8 mm means a particle size that can be sieved through a sieve with a nominal mesh size of 2.8 mm as specified in JIS Z 8801-1:2019.

[0038] The cumulative pore volume of the sintered ore was measured using a general mercury porosimeter, and the cumulative pore volume was measured as the sum of the pore volume of 200 μm or less. The hematite content in the sintered ore was quantified by XRD-Rietveld analysis to determine the amount of α-hematite. In this example, the hematite content was measured using Rietveld analysis, but the hematite content may also be measured using an internal standard method using a reference such as NaF. The hematite content may also be measured using analytical methods capable of mineralogical classification, such as optical microscopy, SEM, and EBSD, in addition to XRD techniques. The production conditions for the sintered ore, the quality of the produced sintered ore, and the results of the reducibility test and low-temperature reduction disintegration test are shown in Table 3 below.

[0039]

[0040] The baking index in Table 3 is a value calculated by the following formula (2): As can be seen from the following formula (2), the baking index is the value on the left side of the above formula (1).

[0041] Firing index = (10 + 0.3 x C Ｏ２ +0.2 x C Ｃ ) / FS (2) In the above formula (2), C Ｏ２ is the oxygen concentration of the gas (volume %), and C Ｃ is the amount of coke powder added (mass % outer percentage) with the sintering raw material being 100 mass %, and FS is the firing speed (mm / min).

[0042] As described above, N-RI and N-RDI have traditionally been considered to have a trade-off relationship, so in this example, the value of N-RI / N-RDI was used as an index. A larger value of N-RI / N-RDI means that reducibility has been improved while suppressing a deterioration (increase) in reduction disintegration property. Therefore, the value shown in the N-RI / N-RDI column can be used to determine whether or not highly reducible sintered ore has been produced that has escaped the trade-off relationship between reducibility and reduction disintegration property.

[0043] The "standard" in Table 3 is the evaluation result of sintered ore sampled from an actual machine. The firing rate in the actual machine was calculated by dividing the effective length of the sintering machine used by the moving speed of the pallet, which was the firing time, and dividing the layer thickness of the charging layer formed on the pallet by the firing time. The N-RI and N-RDI of the sintered ore produced by this actual machine were measured under the same conditions as above. The N-RI / N-RDI value of this actual sintered ore was used as a criterion for determining whether or not highly reducible sintered ore that escaped the trade-off relationship between reducibility and reduction disintegration property could be produced.

[0044] Comparative Examples 1 to 6 are examples of producing sintered ore with a firing index of 1.00 or less. That is, Comparative Examples 1 to 6 are examples of producing sintered ore that does not satisfy the above formula (1).

[0045] The N-RI / N-RDI values ​​of the sintered ores produced in Comparative Examples 1 to 6 were below the "standard" of 2.4. From these results, it was confirmed that the sintered ores produced in Comparative Examples 1 to 6 did not become highly reducible sintered ores that escaped the trade-off between reducibility and reduction disintegration in a reducing gas environment containing hydrogen gas. When the quality of the sintered ores produced in Comparative Examples 1 to 6 was confirmed, they did not satisfy at least one of the following conditions: a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less.

[0046] Inventive Examples 1 to 6 are examples of producing sintered ore with a firing index of more than 1.00. That is, Inventive Examples 1 to 6 are examples of producing sintered ore that satisfies the above formula (1).

[0047] The N-RI / N-RDI values ​​of the sintered ores produced in Examples 1 to 6 were greater than the "standard" value of 2.4. This result confirmed that the sintered ores produced in Examples 1 to 6 became highly reducible sintered ores that escaped the trade-off between reducibility and reduction disintegration in a reducing gas environment containing hydrogen gas.

[0048] When the sintered ores produced in Examples 1 to 6 were examined, they were found to have a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less. These results confirmed that sintered ores with a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less are highly reducible sintered ores that overcome the trade-off between reducibility and reduction disintegration in a reducing gas environment containing hydrogen gas. In other words, it can be seen that these sintered ores are suitable for hydrogen gas-injected blast furnaces.

[0049] Examples 1 to 3 are examples of sintered ore production under the following conditions for producing sintered ore: the oxygen concentration of the gas supplied from the gas supply device 25 is equal to or higher than that of air, the firing speed is 17 mm / min or less, and the amount of coke powder added (outer percentage) is 3.5 mass% to 4.0 mass% based on 100 mass% of the sintering raw material. It was confirmed that by setting the sintered ore production conditions in this way, it is possible to produce sintered ore with high reducibility that overcomes the trade-off between reducibility and reduction disintegration property in a reducing gas environment containing hydrogen gas.

[0050] Inventive Examples 4 to 6 are examples of sintered ore production conditions in which the oxygen concentration of the gas supplied from the gas supply device 25 is 25% by volume or more, the firing speed is 19 mm / min or less, and the amount of coke powder added (outer percentage) relative to 100% by mass of the sintering raw material is 3.5% by mass or more and 4.5% by mass or less. It was confirmed that by setting the sintered ore production conditions in this way, it is possible to produce highly reducible sintered ore in a reducing gas environment containing hydrogen gas, which overcomes the trade-off between reducibility and reduction disintegration.

[0051] REFERENCE SIGNS LIST 10 Sinter ore manufacturing equipment 12 Sinter raw material 14 Granulation water 16 Granulator 18 Granulated particles 20 Sinter machine 21 Raw material supply device 22 Pallet 23 Cut-off plate 24 Ignition furnace 25 Gas supply device 26 Wind box 30 Crusher

Claims

1. A granulation step of adding at least one of coke fines and anthracite to sintering raw materials containing an iron-containing raw material and a CaO-containing raw material, and granulating them in a granulator to form granulated particles; a charging bed formation step of charging the granulated particles onto an endless moving pallet by a raw material supply device of a Dwight Lloyd type sintering machine to form a charging bed; a sintering step of igniting at least one of the coke fines and anthracite contained in the surface layer of the charging bed by an ignition furnace provided downstream of the raw material supply device, supplying gas to the charging bed from a gas supply device provided downstream of the ignition furnace, and burning at least one of the coke fines and anthracite by sucking the gas introduced into the charging bed by a wind box provided below the pallet, thereby turning the charging bed into a sintered cake; and a crushing step of crushing the sintered cake to form sintered ore. The method for producing sintered ore, wherein the oxygen concentration of the gas supplied from the gas supply device, the amount of at least one of coke fines and anthracite added to the sintering raw material, and the firing rate satisfy the following (1): (10 + 0.3 x C Ｏ２ +0.2 x C Ｃ ) / FS>1.00 (1) In the above formula (1), C Ｏ２ is the oxygen concentration (vol %) of the gas, and C Ｃ is the amount (mass % outer percentage) of at least one of coke fines and anthracite added, with the sintering raw material being 100 mass %, and FS is the firing speed (mm / min).

2. A method for producing sintered ore as described in claim 1, wherein the oxygen concentration of the gas is equal to or higher than that of air, the firing speed is 17 mm / min or less, and the amount (outer percentage) of at least one of fine coke and anthracite added relative to 100% by mass of the sintering raw material is 3.5% by mass or more and 4.0% by mass or less.

3. A method for producing sintered ore as described in claim 1, wherein the oxygen concentration of the gas is 25% by volume or more, the firing speed is 19 mm / min or less, and the amount (outer percentage) of at least one of fine coke and anthracite added to 100% by mass of the sintering raw material is 3.5% by mass or more and 4.5% by mass or less.

4. Sintered ore for hydrogen gas-injected blast furnaces, having a hematite content of 40% by mass or more and a cumulative pore volume of 0.030 mL / g or less.

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