Blast furnace operation method

Abstract

To provide an operation method for a blast furnace that can reduce CO2 emissions using hydrogen-based reducing gas containing hydrocarbons.SOLUTION: In an operation method for a blast furnace according to the present invention, a hydrogen-based gas, which is a gas containing hydrocarbons, is blown through a tuyere at a blowing temperature higher than normal temperature and by a predetermined blowing amount. The blowing temperature is a temperature set according to the blowing amount, or the blowing amount is a blowing amount set according to the blowing temperature.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for operating a blast furnace. [Background technology]

[0002] In the steel industry, the blast furnace process is the mainstream of pig iron manufacturing processes. In the blast furnace process, ferrous raw materials for the blast furnace (raw materials containing iron oxide, mainly sintered ore, hereinafter also simply referred to as "ferrous raw materials") and coke are charged alternately and in layers into the blast furnace from the top of the blast furnace, while hot air is blown into the blast furnace from the tuyere at the bottom of the blast furnace. High-temperature reducing gas (mainly CO gas in this case) is generated by reacting with the pulverized coal blown in with the hot air and the coke in the blast furnace. That is, the hot air gasifies the coke and pulverized coal. The reducing gas rises in the blast furnace and reduces the ferrous raw materials while heating them. The ferrous raw materials descend in the blast furnace, while being heated and reduced by the reducing gas. The ferrous raw materials are then melted and dripped into the blast furnace while being further reduced by the coke. The ferrous raw materials are finally stored in the hearth as molten pig iron (pig iron) containing just under 5% by mass of carbon. The molten iron in the hearth is taken out from a tap hole and is used in the next steelmaking process. Therefore, in the blast furnace process, carbonaceous materials such as coke and pulverized coal are used as reducing agents.

[0003] In recent years, global warming has become a social issue, and as a countermeasure, there is a demand for reducing emissions of carbon dioxide, which is one of the greenhouse gases. In the above-mentioned blast furnace process, a large amount of pig iron is produced using carbonaceous material as a reducing agent, which generates a large amount of CO2. Therefore, the steel industry is one of the major industries in terms of CO2 emissions, and must respond to this social demand. In order to reduce CO2 emissions, it is important to reduce the amount of reducing material used in blast furnace operation.

[0004] The reducing agent has two roles: to heat the charge in the furnace and to raise the temperature of the charge, and to reduce the iron-based raw materials in the furnace. In order to reduce CO2 emissions, it is important to prevent the direct reduction reaction by solid carbon (reaction formula: FeO+C⇒Fe+CO) from occurring as much as possible. To do this, it is important to reduce the reducing agent ratio. In order to reduce the reducing agent ratio, it is necessary to increase the reduction efficiency in the furnace. The reduction reaction in the furnace can be expressed by various reaction formulas, among which the direct reduction reaction by solid carbon is an endothermic reaction with a large amount of heat absorption. Since this direct reduction reaction occurs in the lower part of the blast furnace, if the iron-based raw materials can be sufficiently reduced with gases such as CO and H2 before they reach the lower part of the furnace, the amount of iron-based raw materials that are the subject of the direct reduction reaction can be reduced. However, since this direct reduction reaction is an endothermic reaction, the reduction efficiency in the blast furnace decreases, so the amount of iron-based raw materials that reach the lower part of the blast furnace without being reduced increases, and the amount of direct reduction reaction by coke increases. As a result, a lot of reducing agent is required to reduce the iron-based raw materials, and the amount of CO2 reduction cannot be increased.

[0005] As a conventional technique for solving the above problems, as disclosed in Patent Documents 1 to 4, for example, a technique is known in which a reducing gas containing hydrogen atoms (hereinafter, a gas containing hydrogen atoms may be referred to as a hydrogen-based reducing gas) is blown from a tuyere together with hot air, such as COG (Cokes Oven Gas), natural gas, LPG (liquefied petroleum gas), methane gas, or hydrogen gas. By blowing a hydrogen-based reducing gas into a blast furnace, the hydrogen in the reducing gas contributes to the reduction of iron-based raw materials, promoting the hydrogen reduction reaction and suppressing the direct reduction reaction. In the following description, unless otherwise specified, "carbon" and "hydrogen" mean carbon atom and hydrogen atom, respectively. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-28984 A [Patent Document 2] JP 2006-233332 A [Patent Document 3] JP 2020-66753 A [Patent Document 4] JP 2020-45508 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, hydrogen-based reducing gases such as COG, natural gas, LPG, methane gas, or hydrogen gas are generally injected into the blast furnace through the tuyere at room temperature. As the amount of the reducing gas at room temperature injected into the blast furnace through the tuyere increases, the pre-tuyere temperature, which is the furnace temperature at the inner end of the tuyere, decreases. In order to suppress the decrease in the pre-tuyere temperature caused by the reducing gas being injected at room temperature, it is necessary to increase the oxygen enrichment rate of the hot blast injected into the blast furnace through the tuyere. The oxygen enrichment rate of the hot blast is adjusted by changing the flow rate of air mixed with enriched oxygen in the hot blast stove to keep the productivity constant.

[0008] As described above, increasing the amount of hydrogen-based reducing gas such as COG, natural gas, LPG, methane gas, or hydrogen gas injected increases the oxygen enrichment rate. Therefore, increasing the oxygen enrichment rate reduces the flow rate of hot air and the amount of bosh gas (the amount of mixed gas of nitrogen gas, hydrogen gas, and CO gas in the blast furnace). As a result, the flow rate of nitrogen gas decreases relative to the amount of ore flowing in the furnace. When the flow rate of nitrogen gas decreases, the sensible heat of the nitrogen gas decreases. As a result, the temperature in the blast furnace decreases, the reduction of the iron-based raw materials becomes insufficient, and the operation of the blast furnace may become unstable.

[0009] In addition, when the oxygen enrichment rate is increased and the amount of bosh gas is decreased, the temperature of the upper part of the furnace decreases due to the decrease in the sensible heat of the gas flowing through the furnace, and as a result, the temperature of the exhaust gas discharged from the top of the furnace decreases. It is empirically known that the operation of the exhaust gas cleaning equipment installed in the blast furnace becomes unstable when the temperature of the exhaust gas discharged from the top of the blast furnace falls below 100°C. For this reason, when increasing the injection amount of COG, natural gas, LPG, methane gas, or hydrogen-based reducing gas such as hydrogen gas, it is important to adjust the oxygen enrichment rate so that the temperature of the exhaust gas is maintained at 100°C or higher.

[0010] Furthermore, when a reducing gas containing a hydrocarbon such as COG, natural gas, LPG, or methane gas is injected into a blast furnace through a tuyere, the temperature in front of the tuyere decreases due to endothermic heat caused by the decomposition of the hydrocarbon in front of the tuyere. When a reducing gas containing a hydrocarbon is used, it is necessary to further increase the oxygen enrichment rate in order to suppress the decrease in the temperature in front of the tuyere caused by the endothermic heat caused by the decomposition of the hydrocarbon.

[0011] On the other hand, for hydrogen gas, since no endothermic heat is generated by decomposition, the decrease in the temperature before the tuyere is small compared to when a reducing gas containing a hydrocarbon is used. Therefore, the adjustment amount of the oxygen enrichment rate is small, and the decrease amount of the bosh gas amount is small. However, the production cost of hydrogen gas is high compared to hydrogen-based gas, which is a gas containing a hydrocarbon. Therefore, the production cost of pig iron produced by operating a blast furnace using hydrogen gas is high. Therefore, there has been a demand for reducing CO2 emissions by using a cheaper reducing gas in the operation of a blast furnace.

[0012] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a method for operating a blast furnace that can reduce CO2 emissions by using a hydrogen-based reducing gas containing a hydrocarbon. [Means for solving the problem]

[0013] The gist of the present invention, which has been completed based on the above findings, is as follows. [1] According to one aspect of the present invention, a hydrogen-based gas, which is a gas containing a hydrocarbon, is injected from a tuyere at a blowing temperature higher than room temperature and at a predetermined blowing amount, and the blowing temperature is a temperature set according to the blowing amount, or the blowing amount is an injection amount set according to the blowing temperature. A correlation between the injection amount according to the injection temperature and a reduction rate of a carbon consumption unit is obtained, and the hydrogen-based gas is injected from the tuyere at the injection temperature and the injection amount determined based on the correlation. A method for operating a blast furnace is provided. 。 [2 ] Above [1 ] In the described blast furnace operation method, a correlation between the injection amount according to the injection temperature and the reduction rate of carbon consumption intensity is obtained, and based on the obtained correlation, a reduction rate of the carbon consumption intensity at a desired injection temperature of 100°C or higher is derived by linear interpolation for each injection amount, and using the injection temperature, the injection amount, and the reduction rate of the carbon consumption intensity, a range of the injection amount is determined so that the reduction rate of the carbon consumption reduction unit is equal to or greater than the maximum value of the reduction rate of the carbon consumption intensity when the injection temperature is at room temperature, and the hydrogen-based gas is injected from the tuyere at the desired injection temperature and the determined injection amount. [ 3 ] Above [1] Or [2] In the blast furnace operation method described in the above, when the hydrogen-based gas is natural gas and the injection temperature is 300°C, the injection amount of the natural gas is 140 Nm 3 / t or more, 160Nm 3 When the injection temperature is set to 600°C, the injection amount of the natural gas is set to 90 Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 900°C, the injection amount of the natural gas is set to 70 Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 1200°C, the injection amount of the natural gas is set to 50 Nm 3 / t or more, 200Nm 3 It is preferable to set it in the range of / t or less. [ 4 ] Above [1] Or [2]In the method for operating a blast furnace described in the above, the hydrogen-based gas is coke oven gas, and when the injection temperature is 300°C, the injection amount of the coke oven gas is 200 Nm 3 / t, and when the injection temperature is 600°C, the injection amount of the coke oven gas is 140 Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 900°C or less, the injection amount of the coke oven gas is set to 100 Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 1200°C or less, the injection amount of the coke oven gas is set to 80 Nm 3 / t or more, 200Nm 3 It is preferable to set this to less than / t. Effect of the Invention

[0014] According to the present invention, it is possible to provide a method for operating a blast furnace that can reduce CO2 emissions by using a hydrogen-based reducing gas containing a hydrocarbon. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing an example of a molten iron production facility equipped with a blast furnace to which a method for operating a blast furnace according to an embodiment of the present invention can be applied. FIG. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a molten iron production facility to which the blast furnace operation method according to the embodiment can be applied. [Diagram 3] 1 is a graph showing the correlation between the amount of each gas injected and the reduction rate Input ΔC of the carbon consumption intensity when natural gas, COG, and hydrogen gas are injected into a blast furnace with the injection temperature at room temperature. [Figure 4] 1 is a graph showing the correlation between the amount of each gas injected and the oxygen enrichment rate when natural gas, COG, and hydrogen gas are used as the reducing gas. [Diagram 5] 1 is a graph showing the correlation between the amount of each gas injected and the temperature before the tuyere when natural gas, COG, and hydrogen gas are used as the reducing gas. [Figure 6] 1 is a graph showing the correlation between the total input hydrogen amount, which is the amount of hydrogen generated by decomposition of reducing gas, pulverized coal, and moisture in hot air, and the reduction rate Input ΔC of carbon consumption intensity. [Figure 7] 1 is a graph showing the correlation between the amount of natural gas injected as a reducing gas and the reduction rate Input ΔC of the carbon consumption intensity for each reducing gas injection temperature. [Figure 8] 1 is a graph showing the correlation between the amount of COG injected as a reducing gas and the reduction rate Input ΔC of the carbon consumption intensity for each reducing gas injection temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The dimensions and ratios of each component in the drawings do not represent the actual dimensions and ratios of each component.

[0017] <Outline of molten iron production facility> First, prior to describing the blast furnace operation method according to the present embodiment, an example of a molten iron production facility to which the blast furnace operation method according to the present embodiment can be applied will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing an example of a molten iron production facility equipped with a blast furnace to which the blast furnace operation method according to an embodiment of the present invention can be applied. Figure 2 is a schematic diagram showing an example of a blast furnace to which the blast furnace operation method according to the present embodiment can be applied.

[0018] The molten iron production facility includes a blast furnace 1, a gas tank 2 for storing reducing gas, a heater 3 provided in the gas tank 2 for heating the reducing gas, and a hot stove 4 for producing hot air.

[0019] (Blast Furnace 1) The blast furnace 1 is a facility for producing molten iron by reducing iron-based raw materials. As shown in Fig. 2, the blast furnace 1 includes a furnace body 10, a tuyere 11, a main blast pipe 12, a branch blast pipe 13, a pulverized coal injection lance 14, a reducing gas injection lance 15, a tap hole 16, and a rotating chute 17.

[0020] The furnace body 10 is a vertical reaction vessel with an open top. The furnace body 10 is formed of a hollow iron shell and a refractory material or stave attached to the inner surface of the iron shell. A reservoir 101 for storing molten iron produced by reducing iron-based raw materials inside the furnace body 10 is provided below the furnace body 10 (hearth). Iron-based raw materials and coke are charged into the furnace body 10 from the opening at the top end of the furnace body 10 by various known methods, and the iron-based raw materials are reduced inside the furnace body 10 to produce molten iron.

[0021] The tuyere 11 is provided on the lower side of the side of the furnace body 10, and is an inlet for blowing the hot air, reducing gas, and pulverized coal produced in the hot stove 4 into the inside of the furnace body 10. The furnace body 10 may be equipped with a plurality of tuyere 11. In addition to the mixed gas, reducing gas and pulverized coal, which will be described later, can be blown into the furnace through the tuyere 11.

[0022] The main air duct 12 is an annular pipe provided so as to surround the furnace body 10, and a branch air duct 13 is connected to the main air duct 12. The main air duct 12 supplies hot air sent from the hot stove 4 to the branch air duct 13.

[0023] The branch air duct 13 is connected to the main air duct 12 and the tuyere 11. The branch air duct 13 supplies the hot air sent from the main air duct 12 through the tuyere 11 into the furnace.

[0024] The pulverized coal injection lance 14 has a tubular shape and supplies pulverized coal to the inside of the furnace body 10 through the tuyere 11. The pulverized coal injection lance 14 is inserted into the inside of the blast branch pipe 13, for example, from the wall surface of the blast branch pipe 13. The pulverized coal injection lance 14 is not particularly limited as long as it injects a predetermined amount of pulverized coal into the furnace, and for example, a circular pipe, a square pipe, or a multiple pipe in which pipes of different diameters are concentrically arranged can be used.

[0025] The reducing gas injection lance 15 has a tubular shape and supplies reducing gas to the inside of the furnace body 10 through the tuyere 11. The reducing gas injection lance 15 is inserted into the blast branch pipe 13, for example, from the wall surface of the blast branch pipe 13. In FIG. 2, the pulverized coal injection lance 14 is inserted into the blast branch pipe 13 closer to the tuyere 11 than the reducing gas injection lance 15, but the reducing gas injection lance 15 may be inserted into the blast branch pipe 13 closer to the tuyere 11 than the pulverized coal injection lance 14.

[0026] The reducing gas injection lance 15 may be, for example, a circular tube, a square tube, or a multi-tube structure in which tubes of different diameters are arranged concentrically. When the reducing gas injection lance 15 is a multi-tube lance, a different reducing gas can be supplied to each of a plurality of spaces formed inside the reducing gas injection lance 15, thereby allowing a plurality of types of reducing gas to be injected into the furnace simultaneously.

[0027] The tap hole 16 is provided in the reservoir 101 and discharges the molten iron and molten slag produced by the reduction of the iron-based raw materials. A plurality of tap holes 16 are provided, allowing the molten iron and slag to be tapped continuously or intermittently.

[0028] The rotating chute 17 is provided above the furnace body 10 and charges the iron-based raw materials and coke into the furnace body 10. The inclination angle and rotation speed of the rotating chute 17 are controlled so that the iron-based raw materials and coke are charged at a desired position in a desired furnace.

[0029] So far, the outline of the blast furnace 1 has been described. In the blast furnace 1 during operation, iron-based raw materials and coke are charged into the furnace body 10 from the furnace top, and hot air, pulverized coal, and reducing gas are blown into the furnace body 10 from the tuyere 11. The oxygen in the hot air burns the coke, pulverized coal, and reducing gas to generate bosh gas, which contains carbon monoxide and hydrogen gas, as well as nitrogen gas contained in the hot air. The generated bosh gas reduces Fe2O3, Fe3O4, and the like contained in the iron-based raw materials to generate molten pig iron. In the furnace body 10 where the molten pig iron is produced in this way, a lumpy zone 20, a cohesive zone 30 formed below the lumpy zone 20, and a dripping zone 40 formed below the cohesive zone 30 are formed.

[0030] As shown in FIG. 2, the lumpy zone 20 is an area formed by alternately stacking an ore layer 201 made of iron-based raw materials and a coke layer 202 made of coke. The lumpy zone 20 is formed, for example, by alternately charging iron-based raw materials and coke from the top of the furnace body 10 by a rotating chute 17. As shown in FIG. 2, the lumpy zone 20 is formed in the upper part of the furnace. In the lumpy zone 20, the iron-based raw materials are reduced by the bosh gas rising from the bottom of the furnace body 10. The reduction reaction of the iron-based raw materials in the lumpy zone 20 starts at around 500°C and is reduced to FeO at about 900°C to 1000°C.

[0031] The cohesive zone 30 is a region where the reduction and heating of the iron-based raw materials present below the lumpy zone 20 progresses and the raw materials are in a semi-molten state. In the cohesive zone 30, the iron-based raw materials are reduced by bosh gas and carbon contained in coke or pulverized coal. In the cohesive zone 30, FeO and slag components generated during the reduction of the iron-based raw materials are in a semi-molten state. In the cohesive zone 30, there is a coke layer (coke slit 50) which is a passage for gas to move from the dripping zone 40 to the lumpy zone 20. The bosh gas in the lower part of the furnace moves to the lumpy zone 20 through the coke slit 50.

[0032] The dripping zone 40 is mainly formed of coke, and is a region where the molten iron and molten slag drip downward through the gaps between the coke. The molten iron and molten slag are stored in the reservoir 101.

[0033] (Gas Tank 2) The gas tank 2 is a facility for storing reducing gas. The temperature of the reducing gas stored in the gas tank 2 is adjusted by a heater (heat exchanger) 3 provided in the gas tank 2. The reducing gas whose temperature has been adjusted by the heater (heat exchanger) 3 is sent to a tuyere 11 provided in the lower part of the blast furnace 1. The reducing gas sent to the tuyere 11 is mixed with hot air and blown into the furnace body 10 from the tuyere 11.

[0034] (hot stove 4) The hot stove 4 is a facility that produces the hot air that is blown into the stove. The hot air is produced by heating air or a mixture of air and oxygen-enriched gas. The oxygen-enriched gas is oxygen used to adjust the oxygen enrichment rate of the hot air. The temperature of the hot air produced by the hot stove 4 is adjusted by controlling the amount of heat stored and the amount of hot air supplied.

[0035] Here, the increase in oxygen concentration after mixing enriched oxygen relative to the oxygen concentration of the air before mixing the enriched oxygen is called the oxygen enrichment rate. More specifically, the oxygen enrichment rate is the value obtained by subtracting the oxygen content of the air, 21% by volume, from the oxygen content (volume %) contained in the hot air. This oxygen enrichment rate can be calculated from the flow rate of the hot air and the flow rate of enriched oxygen fed into the hot air stove.

[0036] Up to this point, an example of a molten iron production facility to which the blast furnace operation method according to the present embodiment can be applied has been described with reference to Figures 1 and 2, but it goes without saying that the molten iron production facility to which the blast furnace operation method according to the present embodiment can be applied is not limited to the above-mentioned one. The blast furnace operation method according to the present embodiment may be applied to a molten iron production facility in which some of the components of the above-mentioned molten iron production facility are omitted or to which another component is added. In addition, the blast furnace operation method according to the present embodiment may be applied to a molten iron production facility in which some of the components of the blast furnace 1 are omitted or to which another component is added.

[0037] <Findings of the Inventors> Next, with reference to Figs. 3 to 6, the findings obtained by the present inventors when inventing the blast furnace operation method according to the present invention will be described. Fig. 3 is a graph showing the correlation between the amount of each gas injected and the reduction ratio Input ΔC of the carbon consumption unit when natural gas, COG, and hydrogen gas are used as the reducing gas. Fig. 4 is a graph showing the correlation between the amount of each gas injected and the oxygen enrichment rate when natural gas, COG, and hydrogen gas are used as the reducing gas. Fig. 5 is a graph showing the correlation between the amount of each gas injected and the temperature before the tuyere when natural gas, COG, and hydrogen gas are used as the reducing gas. Fig. 6 is a graph showing the correlation between the total amount of hydrogen injected, which is the amount of hydrogen generated by decomposition of the reducing gas, pulverized coal, and moisture in the hot blast, and the reduction ratio Input ΔC of the carbon consumption unit.

[0038] "Reduction rate of carbon consumption intensity, Input ΔC" refers to the reduction rate (%) of carbon consumption intensity relative to the amount of carbon consumption in base operation, which is operation without injecting reducing gas. "Carbon consumption intensity (Input C)" is the carbon input to produce 1 ton of molten iron, i.e., the amount of carbon input per ton of molten iron. Therefore, if Input C in base operation is A (kg / t) and Input C when operation is performed with reducing gas injected is B (kg / t), the reduction rate of carbon consumption intensity, Input ΔC, is expressed by the following formula (1). Input △C=(AB) / A×100...Equation (1)

[0039] Here, referring to FIG. 1, the blowing temperature of the reducing gas will be described. As described above, the reducing gas is heated by the heater 3 in the gas tank 2, and then blown into the furnace body 10 through the tuyere 11 provided at the bottom of the blast furnace 1. Specifically, the reducing gas sent to the tuyere 11 is mixed with the hot air produced in the hot stove 4, and then blown into the furnace body 10 from the tuyere 11. The blowing temperature is the temperature of the reducing gas before being mixed with the hot air when being blown into the furnace body 10 from the tuyere 11. In actual operation, for example, the set temperature of the heater 3 that heats the reducing gas can be set as the blowing temperature. The temperature of the reducing gas rises as the hot air and the reducing gas are mixed, but the temperature at this time is not the blowing temperature in this embodiment. In this embodiment, "room temperature" means the temperature in an unheated state. "Room temperature" is, for example, 20°C±15°C, and may be 25°C. In addition, a temperature higher than room temperature means a temperature of approximately 100°C or higher. In particular, it refers to temperatures above 300°C.

[0040] The temperature before the tuyere is the temperature of a combustion space called a raceway formed at the tip of the tuyere inside the furnace. The temperature before the tuyere can be calculated as the theoretical combustion temperature at the tuyere tip according to the Lamm formula described in "Ironmaking Handbook" (Chijin Shokan) by Akitoshi Shigemi. The method of calculating the temperature before the tuyere is not limited to this, and for example, the inflow temperature of the coke into the raceway used in the calculation may be calculated by analyzing the heat exchange with the gas in the furnace during the process of the coke descending from the time it is charged into the furnace top to the time it is in front of the tuyere. In this embodiment, the latter method was used.

[0041] First, the inventors performed a blast furnace operation simulation to investigate the correlation between the amount of each gas injected and the reduction rate Input ΔC of carbon consumption intensity when natural gas, COG, and hydrogen gas are used as reducing gas. In detail, the blast furnace operation simulation was performed using the so-called "blast furnace mathematical model" shown in Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, p. 15-22, etc. This blast furnace mathematical model roughly divides the internal region of the blast furnace in the height direction, radial direction, and circumferential direction to define a plurality of meshes (small regions), and simulates the behavior of each mesh.

[0042] In the blast furnace mathematical model, the reducing gas injection amount is set as the amount of reducing gas injected from the tuyere. The reducing gas injection temperature is set as the temperature of the reducing gas when it is injected from the tuyere. The top gas temperature is calculated by subtracting the heat loss from the gas temperature at the top layer of the furnace contents to the top gas temperature measurement point. The temperature before the tuyere is calculated as a result of considering the combustion heat of various gases, the sensible heat of the blast, the temperature of the coke flowing into the tuyere, the heat of various reactions, etc.

[0043] Table 1 shows the base operation conditions without reducing gas injection for the reduction rate Input ΔC of specific carbon consumption. The pig iron production rate in Table 1 is the amount of pig iron discharged from the blast furnace. The coke ratio in Table 1 is the amount of coke used to produce 1 ton of molten iron. The pulverized coal ratio in Table 1 is the amount of pulverized coal used to produce 1 ton of molten iron. The blast volume in Table 1 is the flow rate of air in the hot blast, and the enriched oxygen volume is the flow rate of enriched oxygen. The blast temperature in Table 1 is the temperature of the hot blast.

[0044] [Table 1]

[0045] When reducing gas was injected, the blast rate and the amount of enriched oxygen were adjusted so that the pig iron production rate and the molten iron temperature were constant throughout the entire operation. In addition, the pulverized coal ratio, blast rate, and the amount of enriched oxygen were adjusted under a constant coke rate condition so that the pig iron production rate, molten iron temperature, and top gas temperature were constant.

[0046] The relationship between the amount of reducing gas injected and the reduction rate of carbon consumption per unit of production (Input ΔC) obtained by blast furnace operation simulation using a blast furnace mathematical model under the above-mentioned conditions, with hydrogen gas, COG, or natural gas as the reducing gas, is shown in Figure 3. The oxygen enrichment rate at this time is shown in Figure 4, and the temperature before the tuyere is shown in Figure 5.

[0047] As shown in Fig. 3, the blowing amount was 450Nm 3 In the range of 10000 / t or less, when the reducing gas is hydrogen gas, the reduction rate Input ΔC of the carbon consumption intensity increases as the reducing gas injection rate increases. On the other hand, when the reducing gas is natural gas or COG, under the condition that the injection rate is relatively small, the reduction rate Input ΔC of the carbon consumption intensity increases as the reducing gas injection rate increases. It was found that as the injection rate increases further, the increase rate of the reduction rate Input ΔC of the carbon consumption intensity decreases, and when the injection rate increases to a certain extent, the increase rate of the reduction rate Input ΔC of the carbon consumption intensity starts to decrease. This is because, as shown in Figure 4, the oxygen enrichment rate increases with the increase in the injection rate of each reducing gas, but as shown in Figure 5, the temperature in front of the tuyere decreases with the increase in the injection rate of the reducing gas. As a result, when the injection rate of the reducing gas exceeds a certain amount, the amount of input sensible heat supplied to the furnace decreases significantly, and even if the injection rate of the reducing gas is increased, the hydrogen reduction efficiency decreases, so the increase rate of the reduction rate Input ΔC of the carbon consumption intensity decreases.

[0048] When the reducing gas is a hydrogen-based gas containing hydrocarbons, the gas injected into the furnace through the tuyere decomposes to produce hydrogen and CO. FIG. 6 shows the correlation between the total input hydrogen amount, which is the amount of hydrogen generated by the decomposition of the reducing gas, pulverized coal, and moisture in the hot blast, and the reduction rate Input ΔC of the carbon consumption intensity. When the reducing gas is COG and natural gas and the amount of hydrogen generated by their decomposition is equal, the reduction rate Input ΔC of the carbon consumption intensity is almost the same, and the reduction rate Input ΔC of the carbon consumption intensity is at most about 5 to 6%. Thus, the present inventors have found, by a simulation model, that when a hydrogen-based gas containing hydrocarbons is used as the reducing gas, there is an appropriate range for the injection amount to reduce CO2 emissions.

[0049] On the other hand, as shown in Fig. 6, when hydrogen gas is used as the reducing gas, the reduction rate of carbon consumption per unit of production, Input ΔC, increases as the amount of hydrogen gas increases and the total amount of hydrogen input increases. 3At 1000 / t, the reduction rate Input ΔC of the carbon consumption intensity is about 16%. As shown in FIG. 6, when the injection temperature is normal temperature, the reduction rate Input ΔC of the carbon consumption intensity when natural gas or COG, which is a hydrogen-based gas containing hydrocarbon, is used as the reducing gas is significantly smaller than the reduction rate Input ΔC of the carbon consumption intensity equivalent to that when hydrogen gas is used. The present inventors have come up with the idea of ​​increasing the injection temperature of the reducing gas in order to achieve a reduction rate Input ΔC of the carbon consumption intensity equivalent to or greater than that when hydrogen gas is used as the reducing gas, even when a hydrogen-based gas containing hydrocarbon is used as the reducing gas. It is very difficult to accurately grasp the reaction rates in the furnace when a large amount of hydrogen-based gas containing hydrocarbon is injected as the reducing gas, and detailed studies on these have not been conducted so far. The present inventors have conducted detailed studies on the above matters for the first time. That is, a test blast furnace operation was carried out under conditions of injection of a large amount of hydrogen-based gas, and the accuracy of the simulation model was improved using the operation results, and a scale-up evaluation to actual blast furnace conditions was performed. The present inventors carried out an investigation using the above simulation model, and as a result, found that there exists an appropriate range of the injection amount for each injection temperature of the hydrogen-based gas containing a hydrocarbon.

[0050] <Blast furnace operation method> Next, the blast furnace operation method according to the present embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a graph showing the correlation between the amount of natural gas injected as the reducing gas and the reduction rate Input ΔC of the carbon consumption intensity for each reducing gas injection temperature. Fig. 8 is a graph showing the correlation between the amount of COG injected as the reducing gas and the reduction rate Input ΔC of the carbon consumption intensity for each reducing gas injection temperature. Figs. 7 and 8 also show the reduction rate Input ΔC of the carbon consumption intensity when hydrogen gas is injected at an injection temperature of 25°C.

[0051] In the method for operating a blast furnace according to the present embodiment, a hydrogen-based gas containing a hydrocarbon is injected from a tuyere at a temperature higher than room temperature and at a predetermined injection rate. This will be described in detail below.

[0052] In the blast furnace operation method according to the present embodiment, a hydrogen-based gas containing a hydrocarbon is used as a reducing gas. The hydrogen-based gas containing a hydrocarbon contains 30 mol% or more of a hydrocarbon. The content of the hydrocarbon in the hydrogen-based gas containing a hydrocarbon may be 90 mol% or more. The content of the hydrocarbon in the hydrogen-based gas containing a hydrocarbon may be 30 mol% or less. Examples of hydrogen-based gases containing hydrocarbons include COG, natural gas, and LPG. LPG is a gas containing hydrocarbons with a carbon number of 3 or 4. LPG is, for example, propane, butane, propylene, butylene, or a gas mainly containing these. COG is a gas obtained when coal is dry distilled in a coke oven, and mainly contains hydrogen and methane, as well as oxygen, carbon monoxide, water vapor, ethylene, and other hydrocarbons. Natural gas mainly contains methane, as well as ethane, propane, butane, and other hydrocarbons. Hydrogen-based gases containing hydrocarbons may contain hydrogen gas, carbon monoxide gas, carbon dioxide gas, water vapor, nitrogen gas, and the like.

[0053] In the blast furnace operation method according to the present embodiment, the injection temperature is set to a temperature higher than room temperature, and the injection amount is set to a predetermined amount. The graphs shown in Figs. 7 and 8 were obtained by performing a blast furnace operation simulation using the same method as described in the above-mentioned section "Knowledge of the Inventors". As shown in Figs. 7 and 8, the reduction ratio Input ΔC of the carbon consumption intensity for the same injection amount increases as the injection temperature of the reducing gas increases. In addition, the higher the injection temperature of the reducing gas, the more the amount of reducing gas required to achieve the same reduction ratio Input ΔC of the carbon consumption intensity can be reduced. The reason for this is that the higher the injection temperature of the reducing gas, the greater the amount of sensible heat shared from the bosh gas (mixture of nitrogen gas, hydrogen gas, and CO gas) generated in the blast furnace, and therefore the efficiency of hydrogen reduction is considered to be higher. Therefore, it is considered that the higher the injection temperature of the reducing gas, the greater the reduction ratio Input ΔC of the carbon consumption intensity. Therefore, in the blast furnace operation method according to the present embodiment, the injection temperature is set to a temperature higher than room temperature, and the injection amount is set to a predetermined amount. In the blast furnace operation method according to the present embodiment, the blowing temperature is set according to the blowing amount, or the blowing amount is set according to the blowing temperature.

[0054] When natural gas is used as the reducing gas, as shown in Figure 7, by increasing the injection temperature to 300°C or higher, the carbon consumption reduction effect per unit of natural gas injection is improved, and the reduction rate of carbon consumption Input ΔC can be made 5% or more. A reduction rate of carbon consumption Input ΔC of 5% or more is a value that could not be achieved when natural gas is injected at an injection temperature of 25°C. In addition, when the injection temperature of natural gas is 25°C, the reduction rate of carbon consumption Input ΔC can be made 5% or more when the injection temperature of hydrogen gas is room temperature and the injection rate is 100 Nm 3 It is not possible to achieve the reduction rate of carbon consumption per unit of production (Input ΔC) when the natural gas injection temperature is increased to 300°C or higher, but if the hydrogen gas injection temperature is normal temperature and the injection amount is 100 Nm 3 / t, the reduction rate of carbon consumption intensity Input ΔC or more is achieved.

[0055] Even when COG is used as the reducing gas, as shown in Fig. 8, by increasing the injection temperature to 300°C or higher, the carbon consumption reduction effect per COG injection amount is improved, and the reduction rate of carbon consumption input △C can be made 6% or more. In addition, when the COG injection temperature is 25°C, the hydrogen gas injection temperature is room temperature and the injection amount is 100 Nm 3 It is not possible to achieve the reduction rate of carbon consumption per unit of production (Input ΔC) when the COG injection temperature is increased to 300°C or higher, but the hydrogen gas injection temperature is normal and the injection amount is 100 Nm 3 / t, the reduction rate of carbon consumption intensity Input ΔC or more is achieved.

[0056] As described above, when the amount of reducing gas containing hydrocarbons injected is constant, the reduction rate Input ΔC of the carbon consumption intensity can be significantly increased by injecting the reducing gas from the tuyere at an injection temperature higher than room temperature. In addition, when the reduction rate Input ΔC of the carbon consumption intensity is constant, the amount of reducing gas injected can be reduced.

[0057] Also, for example, as shown in Figures 7 and 8, there is a certain correlation between the injection amount of the hydrogen-based gas containing hydrocarbons and the reduction rate Input ΔC of the carbon consumption intensity. Therefore, in the blast furnace operation method according to the present embodiment, it is preferable to obtain a correlation between the injection amount according to the injection temperature of the hydrogen-based gas containing hydrocarbons and the reduction rate Input ΔC of the carbon consumption intensity, and to determine the injection temperature and injection amount based on the correlation.

[0058] The correlation between the injection amount according to the injection temperature of the hydrogen-based gas containing hydrocarbons and the reduction rate Input ΔC of the carbon consumption intensity may be obtained by the following method. For example, the reduction rate Input ΔC of the carbon consumption intensity for each of several injection amounts is obtained by a blast furnace operation simulation that reflects the current blast furnace operation including the injection temperature of the reducing gas. The blast furnace operation simulation may be performed by the above-mentioned method.

[0059] Next, the horizontal axis is in units of Nm3 The values ​​obtained by the above method are plotted on a plane with the injection amount of hydrogen-based gas containing hydrocarbons as / t and the reduction rate of carbon consumption intensity Input ΔC (%) as the vertical axis. Next, an approximation curve of these plots is obtained, for example, by the least squares method, and the correlation equation showing the approximation curve is set as the correlation equation of injection amount - reduction rate of carbon consumption intensity Input ΔC.

[0060] The amount and temperature of the reducing gas to be injected may be determined based on the correlation equation of the injection amount-reduction rate of the carbon consumption intensity obtained above, so that the injection amount that will result in a larger reduction rate of the carbon consumption intensity Input ΔC than the current operation is determined. The reducing gas is then injected from the tuyere at the determined injection amount. This makes it possible to more reliably increase the reduction rate of the carbon consumption intensity Input ΔC.

[0061] Here, it is preferable to obtain in advance a correlation equation of the injection amount and the reduction rate Input ΔC of the carbon consumption intensity for each injection temperature of the hydrogen-based gas containing hydrocarbon. This makes it possible to easily determine a desired injection amount of the reducing gas even when the injection temperature varies. In other words, it is possible to easily determine an injection amount of the reducing gas that increases the reduction rate Input ΔC of the carbon consumption intensity even when the injection temperature varies.

[0062] More specifically, when the hydrogen-based gas containing hydrocarbons is natural gas, the injection temperature is 300°C, and the injection amount of natural gas is 140 Nm 3 / t or more, 160Nm 3 When the injection temperature is set to 600°C, the injection amount of natural gas is set to 90Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 900°C, the injection amount of natural gas is set to 70Nm 3 / t or more, 200Nm 3 When the injection temperature is set to 1200°C, the injection amount of natural gas is set to 50 Nm 3 / t or more, 200Nm 3In particular, when the hydrogen-based gas containing hydrocarbons is natural gas, by controlling the injection amount and injection temperature as described above, a high reduction rate Input ΔC of the carbon consumption intensity can be obtained more reliably.

[0063] The lower and upper limits of the blowing amount at each blowing temperature may be calculated by creating an approximation formula based on the plotted data, and using the created approximation line or curve and the threshold value of Input ΔC, Input ΔC=6.3%. The lower and upper limits of the blowing amount at each blowing temperature may be calculated by a numerical simulation at each blowing temperature for the blowing amount at which Input ΔC is 6.3% or more. In this embodiment, a linear approximation formula is created based on the plotted data, and the range of the blowing amount at which Input ΔC is 6.3% or more at each blowing temperature is estimated based on the created linear approximation formula. As a result, at 300°C, the blowing amount is about 140 Nm 3 / t or more, approximately 160Nm 3 When the injection temperature was 600°C, 900°C, and 1200°C, the range of the injection amount of natural gas was also determined by the above method.

[0064] Furthermore, in the blast furnace operation method according to this embodiment, it is preferable to obtain a correlation between the injection amount according to the injection temperature and the reduction rate Input ΔC of the carbon consumption intensity at a desired injection temperature of 100°C or higher for each injection amount based on the obtained correlation, derive a reduction rate Input ΔC of the carbon consumption intensity at a desired injection temperature of 100°C or higher by linear interpolation, and determine a range of the injection amount using the injection temperature, injection amount, and reduction rate Input ΔC of the carbon consumption intensity within a range in which the reduction rate Input ΔC of the carbon consumption reduction rate is equal to or greater than the maximum value of the reduction rate Input ΔC of the carbon consumption intensity when the injection temperature is room temperature, and inject hydrogen-based gas from the tuyere at the desired injection temperature and the determined injection amount.

[0065] The above description has been given for the cases where the injection temperatures are 300°C, 600°C, 900°C, and 1200°C. When the injection temperature is other than the above temperatures, the Input ΔC at the corresponding injection temperature may be calculated by linear interpolation from the Input ΔC at room temperature (25°C), 300°C, 600°C, 900°C, and 1200°C for each injection amount, and the relationship between the Input ΔC and the injection amount may be derived from the relationship between the injection temperature and the calculated Input ΔC, and the range of the injection amount may be determined based on this relationship. A method for determining the injection amount when natural gas is used as the hydrogen-based gas and the injection temperature is 100°C will be described below.

[0066] Step S1: First, the injection amount is set to 100 Nm by numerical simulation. 3 / t, and the blowing temperature is room temperature (25°C), and the input ΔC and blowing amount are 100 Nm 3 / t and the blowing temperature is 300℃, calculate the input ΔC. 3 / t, and the input ΔC is about 4.5% when the blowing temperature is room temperature (25°C). 3 / t and the input ΔC when the blowing temperature is 300°C is about 5.5%. Step S2: Next, in order to create a linear approximation equation for the relationship between Input ΔC and the blowing temperature, α and β are calculated as Input ΔC = α × (Blowing temperature / °C) + β. Specifically, (Input ΔC, blowing temperature) = (4.5, 25), (5.5, 300) are substituted to calculate α and β. In this case, α ≒ 0.0036, β ≒ 4.41. Therefore, the above equation becomes Input ΔC = 0.0036 × (Blowing temperature / °C) + 4.41. This equation is used when the blowing amount is 100 Nm 3 / t, this is an approximate formula for Input ΔC and blowing temperature. Step S3: From the above approximation formula, the blowing amount is 100 Nm 3 / t and the blowing temperature is 100°C, calculate Input ΔC. In this case, Input ΔC = 0.0036 × 100 + 4.41 = 4.77%. Step S4: Blowing volume is 0 Nm 3 / t, 50Nm 3 / t, 150Nm 3 / t, and 200Nm 3 For the case of / t, steps S1 to S3 are carried out to derive an approximate formula for Input ΔC and the blowing temperature, and from each approximate formula, Input ΔC for each of the above blowing amounts when the blowing temperature is 100° C. is calculated. Step S5: From each calculated Input ΔC, an approximation formula between Input ΔC and blowing amount when the blowing temperature is 100° C. is created. The approximation formula between Input ΔC and blowing amount may be obtained by, for example, the least squares method. Step S6: In the created approximation formula, calculate the range of the injection amount where Input ΔC is 6.3% or more. When the injection temperature is 100°C, natural gas is injected within this injection amount range. Note that the above 6.3% is calculated when the injection temperature is room temperature and the injection amount is 0 Nm 3 / t, 50Nm 3 / t, 150Nm 3 / t, and 200Nm 3 / t is the maximum value of Input ΔC.

[0067] In addition, when the hydrogen-based gas containing hydrocarbons is COG, the injection temperature is 300°C, and the injection amount of COG is 200 Nm 3 / t, and when the blowing temperature is 600℃, the COG blowing amount is 140Nm 3 / t or more, 200Nm 3 When the blowing temperature is set to 900°C or less, the COG blowing amount is set to 100 Nm 3 / t or more, 200Nm 3 When the blowing temperature is set to 1200°C or less, the COG blowing amount is set to 80Nm 3 / t or more, 200Nm 3When the hydrogen-based gas containing hydrocarbons is COG, by controlling the injection amount and injection temperature as described above, a high reduction rate of carbon consumption intensity, Input ΔC, can be obtained more reliably.

[0068] As in the case of using natural gas as the hydrogen-based gas, in the case of COG, the lower and upper limits of the blowing amount at each blowing temperature may be determined by creating an approximation formula based on the plotted data, and based on the created approximation line or approximation curve and the threshold value of Input ΔC, Input ΔC=6.3%. Also, the blowing amount at which Input ΔC is 6.3% or more may be determined by numerical simulation at each blowing temperature. In this embodiment, a linear approximation formula was created based on the plotted data, and the blowing amount at which Input ΔC is 6.3% or more at each blowing temperature was estimated based on the created linear approximation formula. As a result, at 300°C, the blowing amount was about 200 Nm 3 When the injection temperature was 600°C, 900°C, and 1200°C, the range of the COG injection amount was also determined by the above method.

[0069] When the hydrogen-based gas is COG, similar to the case of natural gas, the relationship between the Input ΔC and the injection amount at a desired temperature may be derived by linear interpolation, and the range of the injection amount at the desired temperature may be determined. EXAMPLES

[0070] Next, examples of the present invention will be shown, but the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the conditions used in the following examples. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0071] In this example, by performing a blast furnace operation simulation, it was confirmed that the reduction rate Input ΔC of the carbon consumption intensity is increased by the blast furnace operation method according to this embodiment, that is, the CO2 emissions are reduced.

[0072] For the blast furnace operation simulation, the so-called "blast furnace mathematical model" shown in Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, pp. 15-22, etc. was used.

[0073] In the blast furnace mathematical model, the reducing gas injection rate was set as the amount of reducing gas injected from the tuyere. The reducing gas injection temperature was set as the temperature of the reducing gas when it was injected from the tuyere. The top gas temperature was calculated by subtracting the heat loss from the gas temperature at the top layer of the furnace contents to the top gas temperature measurement point. The temperature before the tuyere was calculated by taking into account the combustion heat of various gases, the sensible heat of the blast, the temperature of the coke flowing into the tuyere, the heat of various reactions, etc.

[0074] The iron-based raw materials were assumed to be a mixture of sintered ore, pellets, and lump ore. The average composition of these iron-based raw materials was assumed to be T-Fe: 59.48 mass%, FeO: 6.10 mass%, and the remainder was other components. The coke was assumed to be C: 85.61 mass%, Ash: 11.5 mass%, and the remainder was other components.

[0075] Natural gas and COG were assumed to be used as reducing gas. The amount of natural gas and COG injected was 0 to 200 Nm 3 / t, and the injection temperature was 25 to 1200°C. The calculation results assuming that natural gas was used as the reducing gas are shown in Figure 7, and the calculation results assuming that COG was used as the reducing gas are shown in Figure 8.

[0076] Assuming that natural gas is used as the reducing gas, a correlation was obtained between the injection amount according to the injection temperature of natural gas and the reduction rate of carbon consumption intensity (Input ΔC) as shown in Fig. 7. Also, as shown in Fig. 7, when the injection temperature is 300°C, the injection amount of natural gas corresponding to an Input ΔC of 6.3% or more is 140 Nm 3 / t or more, 160Nm 3 The lower limit of the injection amount (140 Nm 3 / t) and upper limit (160Nm 3 / t) is the data plotted in Figure 7 (blowing temperature: 300°C, blowing rate: 0 Nm 3 / t, 50Nm 3 / t, 100Nm 3 / t, 150Nm 3 / t, and 200Nm 3 The approximate formula created by the input ΔC obtained under the condition of / t and the reference data (blowing temperature: normal temperature, blowing amount: 0 Nm 3 / t, 50Nm 3 / t, 100Nm 3 / t, 150Nm 3 / t, and 200Nm 3 The calculation was based on the maximum value (Input ΔC = 6.3%) obtained by the approximation curve created using the Input ΔC obtained under the condition of / t.

[0077] Similarly, when the injection temperature is 600°C, the injection rate of natural gas corresponding to an Input ΔC of 6.3% or more is 90Nm 3 / t or more, 200Nm 3 The lower limit of the injection amount (90 Nm 3 / t) is the data plotted in Fig. 7 (blowing temperature: 600°C, blowing rate: 0 Nm 3 / t, 50Nm 3 / t, 100Nm 3 / t, 150Nm 3 / t, and 200Nm 3 The approximate formula created by the input ΔC obtained under the condition of / t and the reference data (blowing temperature: normal temperature, blowing amount: 0 Nm 3 / t, 50Nm 3 / t, 100Nm3 / t, 150Nm 3 / t, and 200Nm 3 The calculation was based on the maximum value (Input ΔC = 6.3%) obtained by the approximation curve created by the Input ΔC obtained under the condition of 100 Nm / t. 3 / t) was set based on the maximum injection amount expected in actual operation.

[0078] Similarly, when the injection temperature is 900°C, the injection rate of natural gas corresponding to an Input ΔC of 6.3% or more is 70Nm 3 / t or more, 200Nm 3 When the injection temperature was 1200°C, the injection amount of natural gas corresponding to an Input ΔC of 6.3% or more was 50 Nm 3 / t or more, 200Nm 3 The range was below / t.

[0079] When COG is assumed as the reducing gas, a correlation was obtained between the injection amount according to the COG injection temperature and the reduction rate of carbon consumption intensity (Input ΔC) as shown in Fig. 8. Also, as shown in Fig. 8, when the injection temperature is 300°C, the COG injection amount is 200 Nm 3 Similarly, when the blowing temperature is 600°C, the range of the COG blowing amount is 140 Nm 3 / t or more, 200Nm 3 Similarly, when the injection temperature is 900°C, the range of COG injection amount is 100 Nm 3 / t or more, 200Nm 3 Similarly, when the blowing temperature is 1200°C, the range of the COG blowing amount is 80 Nm 3 / t or more, 200Nm 3 It was set to / t or less.

[0080] As described above, by injecting a hydrogen-based gas containing a hydrocarbon into a blast furnace according to the blast furnace operation method according to this embodiment, the reduction rate Input ΔC of the carbon consumption intensity can be increased, and thus CO2 emissions can be significantly reduced.

[0081] Although the embodiment of the present invention has been described above, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0082] 1 blast furnace 2 Gas Tank 3. Heater 4 hot stove 10 Furnace body 11 Tuyere 12 Air main 13 Air branch pipe 14 Pulverized coal injection lance 15 Reducing gas injection lance 16 Taphole 17 Swivel Shot 20 Lumpy Zone 30 Cohesive Zone 40 Dripping Zone 50 Coke Slit 101 Reservoir 201 Ore Layer 202 Coke layer

Claims

1. A hydrogen-based gas, which is a gas containing hydrocarbons, is blown from a tuyere at a blowing temperature higher than room temperature and at a predetermined blowing amount, The blowing temperature is a temperature set according to the blowing amount, or the blowing amount is a blowing amount set according to the blowing temperature, A correlation between the injection amount corresponding to the injection temperature and a reduction rate of carbon consumption intensity is obtained, A method for operating a blast furnace, comprising injecting the hydrogen-based gas from the tuyere at the injection temperature and the injection amount determined based on the correlation.

2. A correlation between the blowing amount according to the blowing temperature and a reduction rate of a carbon consumption unit is obtained, and a reduction rate of the carbon consumption unit at a desired blowing temperature that is 100° C. or more is derived by linear interpolation for each blowing amount based on the obtained correlation, Using the blowing temperature, the blowing amount, and the reduction rate of the carbon consumption unit, a range of the blowing amount is determined so that the reduction rate of the carbon consumption unit is equal to or greater than a maximum value of the reduction rate of the carbon consumption unit when the blowing temperature is room temperature; The method for operating a blast furnace according to claim 1 , wherein the hydrogen-based gas is injected from the tuyere at the desired injection temperature and at the determined injection amount.

3. The hydrogen-based gas is natural gas, When the injection temperature is 300°C, the injection amount of the natural gas is 140 Nm ３ / t or more, 160Nm ３ / t or less, When the injection temperature is 600°C, the injection amount of the natural gas is 90 Nm ３ / t or more, 200Nm ３ / t or less, When the injection temperature is 900°C, the injection amount of the natural gas is 70 Nm ３ / t or more, 200Nm ３ / t or less, When the injection temperature is 1200°C, the injection amount of the natural gas is 50 Nm ３ / t or more, 200Nm ３ The method for operating a blast furnace according to claim 1 or 2, wherein the range of 0.1 to 1.5 μm is set to 0.1 to 0.2 μm.

4. The hydrogen-based gas is coke oven gas, When the blowing temperature is 300°C, the blowing amount of the coke oven gas is 200 Nm ３ Set it to / t, When the blowing temperature is 600°C, the blowing amount of the coke oven gas is 140 Nm ３ / t or more, 200Nm ３ Set it to / t or less, When the blowing temperature is 900°C, the blowing amount of the coke oven gas is 100 Nm ３ / t or more, 200Nm ３ Set it to / t or less, When the blowing temperature is 1200°C, the blowing amount of the coke oven gas is 80 Nm ３ / t or more, 200Nm ３ The method for operating a blast furnace according to claim 1 or 2, wherein the blast furnace pressure is set to 0.05 ... MPa or less.

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