Blast furnace operation method

Abstract

An operation method of a blast furnace includes: heating a hydrogen-based reducing gas supplied from outside a blast furnace system; blowing the heated hydrogen-based reducing gas into the blast furnace; separating a reducing gas from a top gas; heating the separated reducing gas; and blowing the heated reducing gas into the blast furnace.

Description

TECHNICAL FIELD

[0001] The present invention relates to an operation method of a blast furnace.

[0002] Priority is claimed on Japanese Patent Application No. 2023-101584, filed on June 21, 2023, the content of which is incorporated herein by reference.BACKGROUND ART

[0003] In the steel industry, a blast furnace method is the mainstream process in the production of pig iron. In the blast furnace method, while an iron-based raw material (a raw material containing an iron oxide, mainly sintered ore, hereinafter, also simply referred to as "iron-based raw material") and coke are alternately charged in layers into a blast furnace from the top of the blast furnace, hot blast is blown into the blast furnace from a tuyere provided in a lower portion of the blast furnace below a bosh portion. The hot blast reacts with pulverized coal blown together with the hot blast and the coke in the blast furnace so that a high-temperature reducing gas (here, mainly CO gas) is produced. That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace and reduces the iron-based raw material while heating the iron-based raw material. The iron-based raw material is heated and reduced by the reducing gas while falling in the blast furnace. Next, the iron-based raw material is melted and dropped in the blast furnace while being further reduced by the coke. Finally, the iron-based raw material is accumulated in a hearth portion as hot metal (pig iron) including just under 5 mass% of carbon. The hot metal in the hearth portion is extracted from a tap-hole and is provided for the next steelmaking process. Accordingly, in the blast furnace method, a carbon material such as coke or pulverized coal is used as a reducing material.

[0004] Meanwhile, in recent years, there has been a growing demand to reduce of global warming, and the reduction of carbon dioxide (CO 2 gas) emissions, which is one of the greenhouse gases, has become a social issue. As described above, in the blast furnace method, a carbon material is used as a reducing material, and thus a large amount of CO 2 gas is generated. Accordingly, the steel industry is a major industry regarding CO 2 gas emissions and needs to meet the demand of society. Specifically, it is imperative to further reduce a reducing material ratio (the amount of a reducing material used per ton of hot metal) in the blast furnace operation.

[0005] The reducing material has a function of heating charges inside the furnace as a heat source and a function of reducing the iron-based raw material in the furnace and needs to increase the reduction efficiency in the furnace to reduce the reducing material ratio. Reduction reactions in the furnace can be represented by various reaction formulae. Among these reduction reactions, a direct reduction reaction (reaction formula: FeO + C → Fe + Co) by coke is an endothermic reaction accompanied by large heat absorption. Accordingly, in order to reduce the reducing material ratio, it is important to suppress the occurrence of this reaction as much as possible. The direct reduction reaction occurs in a lower portion of the blast furnace. Therefore, as long as the iron-based raw material can be sufficiently reduced by a reducing gas such as CO or H 2 until the iron-based raw material reaches the lower portion of the furnace, the iron-based raw material to be subjected to the direct reduction reaction can be reduced.

[0006] As techniques in the related art for solving the above-described problem, for example, as disclosed in Patent Document 1, a technique of improving the reducing gas potential in a furnace by blowing hydrogen gas together with hot blast from a tuyere is known. In this technique, the reducing material ratio is reduced by using the hydrogen gas as a reducing gas for an iron-based raw material.Citation ListPatent Document

[0007] Patent Document 1: PCT International Publication No. WO2021 / 107091SUMMARY OF INVENTIONTechnical Problem

[0008] As disclosed in Patent Document 1, the present inventors defined, as a parameter serving as an index for reducing the reducing material ratio, a reduction percentage (Input ΔC) of carbon consumption intensity. The "carbon consumption intensity (Input C)" indicates the carbon required to produce 1 ton of hot metal (that is, the amount of carbon consumed per ton of hot metal). The "reduction percentage Input ΔC of carbon consumption intensity" means a reduction percentage of carbon consumption intensity with respect to a base operation that is an operation in which no hydrogen gas is blown. Assuming that the Input C in the base operation in kg / t is A and the Input C during a certain operation in kg / t is B, the Input ΔC is expressed by the following formula. Input ΔC = A − B / A × 100 %

[0009] The larger the reduction percentage Input ΔC of the carbon consumption intensity, the smaller the reducing material ratio, and the more CO 2 emissions are reduced.

[0010] The present inventors have conducted intensive studies on the technique described in Patent Document 1, and found that a large amount of hydrogen gas needs to be heated to a high temperature and blown into a blast furnace to increase the Input ΔC by the technique described in Patent Document 1. For example, it was necessary to adjust the gas volume of the hydrogen gas to 650 Nm 3< / t or more and the temperature of the hydrogen gas to 1,200°C or higher to adjust the Input ΔC to 40% or more. In this case, it was necessary to prepare a large amount of hydrogen gas, and it was necessary to prepare a heating apparatus that heats the hydrogen gas to a high temperature. Moreover, the blast furnace equipment needed to be constructed from materials capable of withstanding a high-temperature hydrogen gas.

[0011] As described above, the technique disclosed in Patent Document 1 has a problem in that a great deal of effort is required to increase the Input ΔC.

[0012] Therefore, the present invention has been made in view of the above problem, and an object of the present invention is to provide an operation method of a blast furnace in which it is possible to increase an Input AC even in a case where the gas volume of a hydrogen-based reducing gas (details of the hydrogen-based reducing gas will be described later) is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.Solution to Problem

[0013] The present inventors have conducted intensive studies on the technique described in Patent Document 1, and found that a large amount of hydrogen gas is discharged as a top gas during the operation of the blast furnace. Therefore, the present inventors attempted to separate a reducing gas (the reducing gas contains a hydrogen gas and a CO gas) from the top gas and blow the separated reducing gas into the blast furnace. As a result, it was found that the same level of Input ΔC as in the technique described in Patent Document 1 can be obtained even in a case where the gas volume of the hydrogen gas is reduced and the heating temperature of the hydrogen gas is lowered compared to those in the technique described in Patent Document 1. The present invention has been made based on these findings.

[0014] The gist of the present invention is as follows. (1) An operation method of a blast furnace, including: heating a hydrogen-based reducing gas supplied from outside a blast furnace system; blowing the heated hydrogen-based reducing gas into the blast furnace; separating a reducing gas from a top gas; heating the separated reducing gas; and blowing the heated reducing gas into the blast furnace. (2) The operation method of a blast furnace according to (1), in which the reducing gas is blown into the blast furnace from a normal tuyere provided in a lower portion of the blast furnace. (3) The operation method of a blast furnace according to (1) or (2), in which the reducing gas is blown into a shaft portion of the blast furnace. (4) The operation method of a blast furnace according to any one of (1) to (3), in which operation conditions are adjusted based on a flame temperature and a top gas temperature. (5) The operation method of a blast furnace according to (4), in which the operation conditions include a gas volume of the reducing gas, a blast volume of hot blast, and an amount of oxygen contained in the hot blast. (6) The operation method of a blast furnace according to any one of (1) to (5), further including: heating a hydrogen-based reducing gas supplied from outside a blast furnace system; blowing the heated hydrogen-based reducing gas into the blast furnace from at least one of a normal tuyere and a shaft portion tuyere provided at a position higher than at least the normal tuyere; separating a reducing gas from a top gas; heating the separated reducing gas; and blowing the heated reducing gas into the blast furnace from at least one of the normal tuyere and the shaft portion tuyere, in which at at least one of a time when the heated hydrogen-based reducing gas is blown into the blast furnace from at least one of the normal tuyere and the shaft portion tuyere and a time when the heated reducing gas is blown into the blast furnace from at least one of the normal tuyere and the shaft portion tuyere, at least one of operation conditions including a gas volume of the reducing gas, a blast volume of hot blast, and an amount of oxygen contained in the hot blast is adjusted based on a flame temperature and a top gas temperature. (7) The operation method of a blast furnace according to any one of (1) to (6), in which the reducing gas contains a CO gas and a hydrogen gas that are separated from the top gas. Advantageous Effects of Invention

[0015] According to the present invention, it is possible to increase an Input ΔC even in a case where the gas volume of a hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.BRIEF DESCRIPTION OF DRAWINGS

[0016] [FIG. 1] A flowchart showing an overall configuration of a blast furnace system used in the present embodiment. [FIG. 2] A graph for verifying the effects of a first embodiment. [FIG. 3] A graph for verifying the effects of the first embodiment. [FIG. 4] A graph for verifying the effects of a second embodiment. [FIG. 5] A graph for verifying the effects of the second embodiment. [FIG. 6] A graph for verifying the effects of the second embodiment. [FIG. 7] A graph for verifying the effects of the second embodiment. DESCRIPTION OF EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, like constituent elements having substantially the same function and configuration are denoted by like reference numerals, and redundant description will be omitted.<1. Overall Configuration of Blast Furnace System>

[0018] First, an overall configuration of a blast furnace system 1 according to the present embodiment and a hydrogen-based reducing gas supply system 2 connected to the blast furnace system 1 will be described with reference to FIG. 1. The blast furnace system 1 includes a blast furnace 10, a CO 2 separation and recovery device 20, a buffer tank 30, a compressor 40, a heater 50, and flowmeters 61 and 62.

[0019] The blast furnace 10 includes a blast furnace body 10a, a normal tuyere 11, and a shaft portion tuyere 12. In the blast furnace body 10a, a reduction reaction of an iron-based raw material occurs by a blast furnace method. Specifically, while the iron-based raw material and coke are alternately charged in layers into the blast furnace 10 from the top of the blast furnace 10, hot blast, pulverized coal, and an enriched oxygen gas are blown into the blast furnace 10 from the normal tuyere 11. In the following description, the term "flame temperature" is assumed to mean a temperature at a gas jetting port of the normal tuyere 11. The hot blast reacts with the pulverized coal blown together with the hot blast and the coke in the blast furnace 10, and a high-temperature reducing gas (here, mainly CO gas) is thus generated. That is, the hot blast gasifies the coke and the pulverized coal. The pulverized coal may not be blown into the blast furnace 10, which will be described in detail later. The reducing gas rises in the blast furnace 10 and reduces the iron-based raw material while heating the iron-based raw material. The iron-based raw material is heated and reduced by the reducing gas while falling in the blast furnace 10. Next, the iron-based raw material is melted and dropped in the blast furnace 10 while being further reduced by the coke. Finally, the iron-based raw material is accumulated in a hearth portion as hot metal (pig iron) including just under 5 mass% of carbon. The hot metal in the hearth portion is extracted from a tap-hole and is provided for the next steelmaking process.

[0020] The normal tuyere 11 is provided below a bosh portion of the blast furnace 10 to blow, in addition to the hot blast described above, a heated hydrogen-based reducing gas and a reducing gas separated from a top gas (blast furnace exhaust gas) into the blast furnace 10. In FIG. 1, two normal tuyeres 11 are shown on the left and right sides of the blast furnace 10, but three or more normal tuyeres 11 may be attached at a predetermined pitch over the whole circumference of the blast furnace 10.

[0021] The shaft portion tuyere 12 is positioned higher than the normal tuyere 11 of the blast furnace 10 to blow the reducing gas separated from the top gas into a shaft portion 10b of the blast furnace 10. In FIG. 1, two shaft portion tuyeres 12 are shown on the left and right sides of the shaft portion 10b, but three or more shaft portion tuyeres 12 may be attached at a predetermined pitch over the whole circumference of the blast furnace 10. In addition, in FIG. 1, the shaft portion tuyere 12 is shown in the shaft portion 10b, but the shaft portion tuyere 12 may be attached to a portion lower than the shaft portion 10b, including a belly portion, a bosh portion, and lower portions, as long as the reducing gas separated from the top gas can be blown into the shaft portion 10b and the shaft portion tuyere 12 is positioned higher than the position where the normal tuyere 11 is installed.

[0022] The CO 2 separation and recovery device 20 is a device that recovers a top gas and separates the gas into a reducing gas (CO gas and hydrogen gas) and a nitrogen gas, and a CO 2 gas and a H 2 O gas. The separation method is not particularly limited, and examples thereof include a chemical adsorption method and a physical adsorption method (PSA). In the following description, the reducing gas and the nitrogen gas separated from the top gas are also referred to as a returned blast furnace gas (RBFG). The CO 2 gas and the H 2 O gas are discharged outside the system. The CO 2 separation and recovery device 20 does not necessarily recover the entire amount of the top gas. For example, the CO 2 separation and recovery device 20 may recover only an amount of the top gas corresponding to the flow rate of the RBFG blown into the blast furnace.

[0023] The buffer tank 30 is a tank that temporarily stores the RBFG. A desired amount of the RBFG is introduced into the compressor 40 from the buffer tank 30. The remaining RBFG is used as, for example, a heat source of a steel plant.

[0024] The compressor 40 pressurizes the RBFG. Here, the compressor 40 pressurizes the RBFG to, for example, an internal pressure (about 4.5 atm) of the blast furnace 10. The pressurized RBFG is introduced into the heater 50.

[0025] The heater 50 heats the RBFG. The heating temperature is optionally set according to operation conditions of the blast furnace 10. However, for example, in a case where the RBFG is blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, the heating temperature is preferably set to 800°C or higher. The heater 50 can be sufficiently realized by an electric heater or the like. The RBFG heated by the heater 50 is blown into the blast furnace 10 from the normal tuyere 11, or blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, for example. In FIG. 1, the RBFG is blown into the blast furnace 10 from the normal tuyere 11 and the shaft portion tuyere 12 on the left side, but the RBFG may be blown into the blast furnace 10 from the normal tuyere 11 and the shaft portion tuyere 12 on the right side. The RBFG may be blown into the blast furnace 10 from both of the normal tuyere 11 and the shaft portion tuyere 12.

[0026] The flowmeter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the normal tuyere 11. The flowmeter 62 measures the flow rate of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12. In the present embodiment, by adjusting the flow rate of the RBFG introduced from the buffer tank 30 to the compressor 40, it is possible to optionally adjust the flow rate of the RBFG blown into the blast furnace 10 from the normal tuyere 11 and the flow rate of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12.

[0027] The hydrogen-based reducing gas supply system 2 includes a hydrogen-based reducing gas tank 70, a heater 71, and a flowmeter 72. The hydrogen-based reducing gas supply system 2 is a system that supplies a hydrogen-based reducing gas to the blast furnace system 1 from outside the blast furnace system 1.

[0028] The hydrogen-based reducing gas tank 70 is a tank that stores a hydrogen-based reducing gas. Here, the hydrogen-based reducing gas is a concept that includes not only a hydrogen gas but also a mixed gas of a hydrogen gas and other gases (for example, nitrogen gas) which does not impair the effects of the present embodiment. The heater 71 heats the hydrogen-based reducing gas supplied from the hydrogen-based reducing gas tank 70. The heater 71 can be sufficiently realized by an electric heater or the like. The heater 71 is connected to the normal tuyere 11, and the heated hydrogen-based reducing gas is blown into the blast furnace 10 from the normal tuyere 11. The heater 71 may be used in combination with the heater 50. The flowmeter 72 measures the flow rate of the hydrogen-based reducing gas blown into the blast furnace 10 from the normal tuyere 11. In addition, as will be described later, even in a case where the gas volume of the hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered, an Input ΔC can be increased. In addition, in the present embodiment, the hydrogen-based reducing gas is blown in from the normal tuyere 11, but the hydrogen-based reducing gas may be blown into the blast furnace 10 from the shaft portion tuyere 12.<2. First Embodiment>(2-1. Operation Method of Blast Furnace According to First Embodiment)

[0029] Next, a first embodiment of the present invention will be described. In the first embodiment, an RBFG is blown into the blast furnace 10 from the normal tuyere 11. In the first embodiment, the shaft portion tuyere 12 and the flowmeter 62 may be omitted.

[0030] An operation method of the blast furnace 10 according to the first embodiment is generally as follows. That is, while an iron-based raw material and coke are alternately charged in layers into the blast furnace 10 from the top of the blast furnace 10, a heated hydrogen-based reducing gas is supplied from the hydrogen-based reducing gas supply system 2 to the normal tuyere 11. Then, hot blast, pulverized coal, an enriched oxygen gas, a heated hydrogen-based reducing gas, and a heated RBFG containing CO and H 2 are blown into the blast furnace 10 from the normal tuyere 11. The hot blast reacts with the pulverized coal blown together with the hot blast and the coke in the blast furnace 10, and a high-temperature reducing gas (here, mainly CO gas) is thus generated. That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace 10 and reduces the iron-based raw material while heating the iron-based raw material. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10 and reduce the iron-based raw material while heating the iron-based raw material. The iron-based raw material is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG while falling in the blast furnace 10. Next, the iron-based raw material is melted and dropped in the blast furnace 10 while being further reduced by the coke. Finally, the iron-based raw material is accumulated in a hearth portion as hot metal (pig iron) including just under 5 mass% of carbon. The hot metal in the hearth portion is extracted from a tap-hole and is provided for the next steelmaking process.

[0031] Meanwhile, the top gas of the blast furnace 10 is discharged. The CO 2 separation and recovery device 20 recovers the top gas and separates the gas into a reducing gas (CO gas and hydrogen gas) and a nitrogen gas (that is, RBFG), and a CO 2 gas and a H 2 O gas. The CO 2 gas and the H 2 O gas are discharged outside the system.

[0032] The RBFG is temporarily stored in the buffer tank 30. A desired amount of the RBFG is introduced into the compressor 40 from the buffer tank 30. The remaining RBFG is discharged outside the system and is used as, for example, a heat source of a steel plant.

[0033] The RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, an internal pressure (about 4.5 atm) of the blast furnace 10. The pressurized RBFG is introduced into the heater 50.

[0034] Then, the RBFG is heated by the heater 50. The heating temperature is optionally set according to operation conditions of the blast furnace 10. The RBFG heated by the heater 50 is blown into the blast furnace 10 from the normal tuyere 11. The flowmeter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the normal tuyere 11. The RBFG is mainly blown into the blast furnace 10 from the normal tuyere 11, but may also be blown into the blast furnace 10 from the shaft portion tuyere 12 supplementarily. Details thereof will be described later.

[0035] Here, in the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are preferably maintained within predetermined ranges for reasons such as performing a stable operation. For example, the flame temperature is preferably maintained at about 2,000°C to 2300°C, the top gas temperature is preferably maintained at about 105°C or higher, and the hot metal temperature is preferably maintained at about 1,520°C or higher. The upper limit of the flame temperature is an upper limit assumed for a normal operation (operation in which no hydrogen-based reducing gas is blown and no RBFG is blown). In a case where the flame temperature is higher than the upper limit, it is preferable to take measures such as enhancing the cooling capacity of the tuyere equipment or using a material having higher heat resistance performance to prevent wear of the tuyere equipment. It is preferable that the specifications of the blast furnace operation be determined so that the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the specifications of the blast furnace operation can be freely designed as long as the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the flame temperature may be higher than the upper limit as a result of the design, but it is preferable to take the above-described measures separately.

[0036] For example, the blowing temperature of the hydrogen-based reducing gas (the temperature of the hydrogen-based reducing gas blown from the normal tuyere 11) is preferably adjusted to about 800°C to 1,000°C, and the gas volume of the hydrogen gas in the hydrogen-based reducing gas is preferably adjusted to about 300 to 600 Nm 3< / t. All the ranges are lower than those in Patent Document 1. The blowing temperature of the RBFG (the temperature of the RBFG blown from the normal tuyere 11, that is, the heating temperature by the heater 50) is preferably adjusted to about 800°C to 1,000°C, and the gas volume of the RBFG is preferably adjusted to about 400 to 800 Nm 3< / t. The gas volume of the RBFG is particularly preferably 600 Nm 3< / t or more. This is because the Input ΔC exceeds 40% in this case as will be described later. Other adjustable specifications include the gas volume of hot blast and the amount of oxygen contained in the hot blast (gas volume of oxygen). In addition, the hot metal temperature can also be adjusted by the gas volume of the pulverized coal blown into the blast furnace 10 or the coke ratio (the amount of coke used per ton of hot metal). For example, it is possible to perform control in which, first, the hot metal temperature is adjusted by the gas volume of the pulverized coal, and in a case where the gas volume of the pulverized coal becomes zero but the hot metal temperature exceeds a predetermined range, the coke ratio is adjusted. The hot metal temperature is a value reflecting the total heat amount (furnace heat) in the blast furnace 10. During the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are monitored periodically (preferably, constantly). In a case where the value of any of the flame temperature, the top gas temperature, or the hot metal temperature is outside the above-described range, the operation conditions (for example, at least one of the blowing temperature of the hydrogen-based reducing gas, the gas volume of hydrogen gas in the hydrogen-based reducing gas, the blowing temperature of the RBFG, the gas volume of the RBFG, the gas volume of the hot blast, and the amount of oxygen contained in the hot blast (the gas volume of the enriched oxygen gas) as described above) may be adjusted. Since the flame temperature, the top gas temperature, and the hot metal temperature are likely to fluctuate during blowing of the hydrogen-based reducing gas or the RBFG, the flame temperature, the top gas temperature, and the hot metal temperature are preferably monitored during blowing of these gases.(2-2. Specific Examples of Operation Method)

[0037] Hereinafter, several specific examples of the operation method will be described. Specific examples to be listed below can also be applied to a second embodiment to be described later.(2-2-1. In a Case Where Hot Metal Temperature Decreases)

[0038] The gas volume of the RBFG blown into the blast furnace 10 from the normal tuyere 11 is increased. At the same time, the gas volume of the enriched oxygen gas is increased, and the gas volume of the hot blast (blast volume) is decreased to maintain the flame temperature. As a result, in a case where the top gas temperature is lower than a predetermined range, the gas volume of the RBFG blown from the shaft portion tuyere 12 is further increased.(2-2-2. In a Case Where Flame Temperature Decreases)

[0039] The gas volume of the hot metal enriched oxygen gas is increased, and the gas volume of the hot blast is decreased to increase the flame temperature. Therefore, there is a concern that the amount of bosh gas may decrease and the top gas temperature falls below a predetermined range. In order to handle that case, the gas volume of the RBFG blown from the shaft portion tuyere 12 is increased at the same time.(2-2-3. In a Case Where Top Gas Temperature Decreases)

[0040] The gas volume of the RBFG blown from the shaft portion tuyere 12 is increased.(2-2-4. In a Case Where Both Flame Temperature and Top Gas Temperature Decrease)

[0041] While the gas volume of the enriched oxygen gas is increased and the gas volume of the hot blast is decreased to increase the flame temperature, the gas volume of the RBFG blown from the shaft portion tuyere 12 is increased at the same time.(2-2-5. In a Case Where Flame Temperature Decreases and Top Gas Temperature Increases)

[0042] In a case where the top gas temperature is too high, the gas flow rate in the furnace increases and the possibility of causing operational fluctuations increases. Therefore, an excessive increase in top gas temperature is not preferable.

[0043] The gas volume of the enriched oxygen gas is increased, and the gas volume of the hot blast is decreased. Therefore, the flame temperature tends to increase, and the top gas temperature tends to decrease. In a case where the top gas temperature is lower than a predetermined range, the gas volume of the RBFG blown from the shaft portion tuyere 12 is increased at the same time to control the top gas temperature.(2-2-6. In a Case Where Flame Temperature Increases and Top Gas Temperature Decreases)

[0044] The gas volume of the enriched oxygen gas is decreased, and the gas volume of the hot blast is increased. Therefore, the flame temperature tends to decrease, and the top gas temperature tends to increase. In a case where the top gas temperature is higher than a predetermined range, the gas volume of the RBFG blown from the shaft portion tuyere 12 is decreased at the same time to control the top gas temperature.(2-2-7. In a Case Where Both Flame Temperature and Top Gas Temperature Increase)

[0045] The gas volume of the enriched oxygen gas is decreased, the gas volume of the hot blast is increased, and the gas volume of the RBFG blown from the shaft portion tuyere 12 is decreased.(2-3. Verification of Effects)

[0046] Next, verification of the effects performed by the present inventors will be described. In this verification, a blast furnace operation was simulated to verify the effects of the operation method of the blast furnace according to the first embodiment. As a simulation model, a so-called "Blast Furnace Mathematical Model" Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No.1, p.15 to 22 was used. In summary, in this blast furnace mathematical model, an internal region of the blast furnace is divided in a height direction, a radial direction, and a circumferential direction to define a plurality of meshes (small regions), and the behavior of each of the meshes is simulated. Prerequisites for the simulation are as follows. · A hydrogen gas is used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The iron tapping quantity and the hot metal temperature are constant (12,350 t / d, 1,535°C) at all levels. · The top gas temperature is near the lower limit (105°C). · Furnace heat adjustment (adjustment of the hot metal temperature) is performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal is zero but the hot metal temperature is higher than 1,535°C, the coke ratio is adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied.

[0047] Under the above-described prerequisites, simulation was performed in association with each of the following levels. A level 1-5 corresponds to the first embodiment. (Level 1-1) No hydrogen gas blowing, hot blast blowing temperature of 1,200°C, and RBFG blowing operation (blowing temperature: 1,200°C) (H2-0 BT 1,200°C in FIGS. 2 and 3. H2-0 BT 1,200°C indicates that no hydrogen gas is blown and a blowing temperature of hot blast is 1,200°C) (Level 1-2) Hydrogen gas blowing (blowing temperature: 1,200°C, gas volume: 650 Nm 3< / t), hot blast blowing temperature of 1,200°C, and RBFG blowing operation (blowing temperature: 1,000°C) (H2-650 1,200°C, BT 1,200°C in FIGS. 2 and 3. H2-650 1,200°C indicates that a gas volume of a hydrogen gas is 650 Nm 3< / t and a blowing temperature of the hydrogen gas is 1,200°C, and BT 1,200°C indicates that a blowing temperature of hot blast is 1,200°C) (Level 1-3) Hydrogen gas blowing (blowing temperature: 1,000°C, gas volume: 650 Nm 3< / t), hot blast blowing temperature of 1,200°C, and RBFG blowing operation (blowing temperature: 1,000°C) (H2-650 1,000°C, BT 1,200°C in FIGS. 2 and 3. H2-650 1,000°C indicates that a gas volume of a hydrogen gas is 650 Nm 3< / t and a blowing temperature of the hydrogen gas is 1,000°C, and BT 1,200°C indicates that a blowing temperature of hot blast is 1,200°C) (Level 1-4) Hydrogen gas blowing (blowing temperature: 1,000°C, gas volume: 650 Nm 3< / t), hot blast blowing temperature of 1,300°C, and RBFG blowing operation (blowing temperature: 1,000°C) (H2-650 1,000°C, BT 1,300°C in FIGS. 2 and 3. H2-650 1,000°C indicates that a gas volume of a hydrogen gas is 650 Nm 3< / t and a blowing temperature of the hydrogen gas is 1,000°C, and BT 1,300°C indicates that a blowing temperature of hot blast is 1,300°C) (Level 1-5) Hydrogen gas blowing (blowing temperature: 1,000°C, gas volume: 325 Nm 3< / t), hot blast blowing temperature of 1,300°C, and RBFG blowing operation (blowing temperature: 1,000°C) (H2-325 1,000°C, BT 1,300°C in FIGS. 2 and 3. H2-325 1,000°C indicates that a gas volume of a hydrogen gas is 325 Nm 3< / t and a blowing temperature of the hydrogen gas is 1,000°C, and BT 1,300°C indicates that a blowing temperature of hot blast is 1,300°C)

[0048] The results are shown in FIGS. 2 and 3. In FIG. 2, the horizontal axis (RBFG tuyere gas volume) indicates a gas volume (Nm 3< / t) of the RBFG blown into the blast furnace 10 from the normal tuyere 11, and the vertical axis indicates an Input ΔC (%). In FIG. 3, the horizontal axis (RBFG tuyere gas volume) indicates a gas volume (Nm 3< / t) of the RBFG blown into the blast furnace 10 from the normal tuyere 11, and the vertical axis (whole-system hydrogen gas utilization rate) indicates a hydrogen gas utilization rate (%) of the whole system. Here, the hydrogen gas utilization rate of the whole system is represented by the following expression. n H 2 * = 100 × a / a + b n H2 *: Hydrogen gas utilization rate (%) a: Amount (Nm 3< / t) of the H 2 O gas discharged outside the system from the CO 2 separation and recovery device 20 b: Amount (Nm 3< / t) of the hydrogen gas discharged outside the system from the buffer tank 30

[0049] According to FIGS. 2 and 3, the following findings can be obtained. · The larger the gas volume of the hydrogen gas from the hydrogen-based reducing gas supply system 2 (that is, not included in the RBFG), the larger the Input ΔC. However, since it is necessary to prepare a large amount of hydrogen gas, the above-described problem occurs. · The larger the gas volume of the RBFG, the larger the Input ΔC. At the level 1-5, by adjusting the gas volume of the RBFG to 600 Nm 3< / t, the Input ΔC exceeds 40% (43.2%, point enclosed by the broken line circle in FIG. 2). This value is comparable to those at the levels 1-2 to 1-4 at which a large amount of hydrogen gas is blown. Furthermore, the gas volume of the hydrogen gas at the level 1-5 is 325 Nm 3< / t, which is 50% less than those at the levels 1-2 to 1-4, and the blowing temperature of the hydrogen gas is also low at 1,000°C. In this case, the hydrogen gas utilization rate at the level 1-5 is 77% (a = 253 nm 3< / t, b = 76 Nm 3< / t) (point enclosed by the broken line circle in FIG. 3).

[0050] As described above, according to the first embodiment, it is possible to increase an Input ΔC even in a case where the gas volume of a hydrogen-based reducing gas from the hydrogen-based reducing gas supply system 2 is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.<3. Second Embodiment>(3-1. Operation Method of Blast Furnace According to Second Embodiment)

[0051] Next, a second embodiment of the present invention will be described. In the second embodiment, an RBFG is blown into the blast furnace 10 from the shaft portion tuyere 12. In the second embodiment, the flowmeter 61 may be omitted.

[0052] An operation method of the blast furnace 10 according to the second embodiment is generally as follows. That is, while an iron-based raw material and coke are alternately charged in layers into the blast furnace 10 from the top of the blast furnace 10, a heated hydrogen-based reducing gas is supplied from the hydrogen-based reducing gas supply system 2 to the normal tuyere 11. Then, hot blast, pulverized coal, an enriched oxygen gas, and a heated hydrogen-based reducing gas are blown into the blast furnace 10 from the normal tuyere 11. Meanwhile, an RBFG is blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuycre 12. The hot blast reacts with the pulverized coal blown together with the hot blast and the coke in the blast furnace 10, and a high-temperature reducing gas (here, mainly CO gas) is thus generated. That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace 10 and reduces the iron-based raw material while heating the iron-based raw material. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10 and reduce the iron-based raw material while heating the iron-based raw material. The iron-based raw material is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG while falling in the blast furnace 10. Next, the iron-based raw material is melted and dropped in the blast furnace 10 while being further reduced by the coke. Finally, the iron-based raw material is accumulated in a hearth portion as hot metal (pig iron) including just under 5 mass% of carbon. The hot metal in the hearth portion is extracted from a tap-hole and is provided for the next steelmaking process.

[0053] Meanwhile, the top gas of the blast furnace 10 is discharged. The CO 2 separation and recovery device 20 recovers the top gas and separates the gas into a reducing gas (CO gas and hydrogen gas) and a nitrogen gas (that is, RBFG), and a CO 2 gas and a H 2 O gas. The CO 2 gas and the H 2 O gas are discharged outside the system.

[0054] The RBFG is temporarily stored in the buffer tank 30. A desired amount of the RBFG is introduced into the compressor 40 from the buffer tank 30. The remaining RBFG is discharged outside the system and is used as, for example, a heat source of a steel plant.

[0055] The RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, an internal pressure (about 4.5 atm) of the blast furnace 10. The pressurized RBFG is introduced into the heater 50.

[0056] Then, the RBFG is heated by the heater 50. The heating temperature is optionally set according to operation conditions of the blast furnace 10. The RBFG heated by the heater 50 is blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12. The flowmeter 62 measures the flow rate of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12. The RBFG is mainly blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, but may also be blown into the blast furnace 10 from the normal tuyere 11 supplementarily. Specific examples of the operation method are as described in the first embodiment.

[0057] Here, in the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are preferably maintained within predetermined ranges for reasons such as performing a stable operation. For example, the flame temperature is preferably maintained at about 2,000°C to 2300°C, the top gas temperature is preferably maintained at about 105°C or higher, and the hot metal temperature is preferably maintained at about 1,520°C or higher. The upper limit of the flame temperature is an upper limit assumed for a normal operation (operation in which no hydrogen-based reducing gas is blown and no RBFG is blown). In a case where the flame temperature is higher than the upper limit, it is preferable to take measures such as enhancing the cooling capacity of the tuyere equipment or using a material having higher heat resistance performance to prevent wear of the tuyere equipment. The specifications of the blast furnace operation are determined so that the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the specifications of the blast furnace operation can be freely designed as long as the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the flame temperature may be higher than the upper limit as a result of the design, but it is preferable to take the above-described measures separately.

[0058] For example, the blowing temperature of the hydrogen-based reducing gas (the temperature of the hydrogen-based reducing gas blown from the normal tuyere 11) is preferably adjusted to about 600°C to 1,000°C, and the gas volume of the hydrogen gas in the hydrogen-based reducing gas is preferably adjusted to about 400 to 600 Nm 3< / t. All the ranges are lower than those in Patent Document 1. The blowing temperature of the RBFG (the temperature of the RBFG blown from the shaft portion tuyere 12, that is, the heating temperature by the heater 50) is preferably adjusted to about 800°C to 1,000°C, and the gas volume of the RBFG is preferably adjusted to about 200 to 600 Nm 3< / t. This is because the Input ΔC exceeds 40% in this case as will be described later. Other adjustable specifications include the gas volume of hot blast and the amount of oxygen contained in the hot blast (gas volume of oxygen). In addition, the hot metal temperature can also be adjusted by the gas volume of the pulverized coal blown into the blast furnace 10 or the coke ratio (the amount of coke used per ton of hot metal) . For example, it is possible to perform control in which, first, the hot metal temperature is adjusted by the gas volume of the pulverized coal, and in a case where the gas volume of the pulverized coal becomes zero but the hot metal temperature exceeds a predetermined range, the coke ratio is adjusted. The hot metal temperature is a value reflecting the total heat amount (furnace heat) in the blast furnace 10. During the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are monitored periodically (preferably, constantly). In a case where the value of any of the flame temperature, the top gas temperature, or the hot metal temperature is outside the above-described range, the operation conditions (for example, at least one of the blowing temperature of the hydrogen-based reducing gas, the gas volume of hydrogen gas in the hydrogen-based reducing gas, the blowing temperature of the RBFG, the gas volume of the RBFG, the gas volume of the hot blast, and the amount of oxygen contained in the hot blast (the gas volume of the enriched oxygen gas) as described above) may be adjusted. Since the flame temperature, the top gas temperature, and the hot metal temperature are likely to fluctuate during blowing of the hydrogen-based reducing gas or the RBFG, the flame temperature, the top gas temperature, and the hot metal temperature are preferably monitored during blowing of these gases.(3-2. Verification of Effects)

[0059] Next, verification of the effects performed by the present inventors will be described. In this verification, a blast furnace operation was simulated to verify the effects of the operation method of the blast furnace according to the second embodiment. The same simulation model as that in the first embodiment is used. Prerequisites for the simulation are as follows. · A hydrogen gas is used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The blowing temperature of the hydrogen gas and the blowing temperature of an RBFG arc 800°C at any level. However, the blowing temperature of the hydrogen gas at a level 2-1 is 1,200°C. · The blowing temperature (blast temperature) of hot blast is 1,200°C at any level. · The iron tapping quantity and the hot metal temperature are constant (12,350 t / d, 1,535°C) at all levels. · The top gas temperature is 135°C at any level. · Furnace heat adjustment (adjustment of the hot metal temperature) is performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal is zero but the hot metal temperature is higher than 1,535°C, the coke ratio is adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied.

[0060] Under the above-described prerequisites, simulation was performed in association with each of the following levels. Levels 2-2 to 2-4 correspond to the second embodiment. (Level 2-1) Gas volume of hydrogen gas of 650 Nm 3< / t, hot blast blowing temperature of 1,200°C, and no RBFG blowing (H2: 650 Nm 3< / t, BT 1200°C) (Level 2-2) Gas volume of hydrogen gas of 600 Nm 3< / t, hot blast blowing temperature of 1,200°C, and RBFG blowing operation (H2: 600 Nm 3< / t, BT 1200°C) (Level 2-3) Gas volume of hydrogen gas of 500 Nm 3< / t, hot blast blowing temperature of 1,200°C, and RBFG blowing operation (H2: 500 Nm 3< / t, BT 1200°C) (Level 2-4) Gas volume of hydrogen gas of 400 Nm 3< / t, hot blast blowing temperature of 1,200°C, and RBFG blowing operation (H2: 400 Nm 3< / t, BT 1200°C)

[0061] The results are shown in FIGS. 4 and 5. In FIG. 4, the horizontal axis (shaft tuyere RBFG gas volume) indicates a gas volume (Nm 3< / t) of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, and the vertical axis indicates an Input ΔC (%). In FIG. 5, the horizontal axis (shaft tuyere RBFG gas volume) indicates a gas volume (Nm 3< / t) of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, and the vertical axis (whole-system hydrogen gas utilization rate) indicates a hydrogen gas utilization rate (%) of the whole system. The method of calculating the hydrogen gas utilization rate of the whole system is as described above.

[0062] According to FIGS. 4 and 5, the following findings can be obtained. · The larger the gas volume of the hydrogen gas from the hydrogen-based reducing gas supply system 2 (that is, not included in the RBFG), the larger the Input ΔC. · The larger the gas volume of the RBFG, the larger the Input ΔC. At the level 2-4, by adjusting the gas volume of the RBFG to 600 Nm 3< / t, the Input ΔC exceeds 40% (40.5%, point enclosed by the broken line circle in FIG. 4). This value is comparable to those at the level 2-1 at which a large amount of hydrogen gas is blown and the levels 2-2 and 2-3 at which the gas volume of the hydrogen gas is slightly increased. Furthermore, the gas volume of the hydrogen gas at the level 2-4 is 400 Nm 3< / t, which is less than those at the levels 2-1 to 2-3, and the blowing temperature of the hydrogen gas is also low at 800°C. In this case, the hydrogen gas utilization rate at the level 2-4 is 63% (a = 260 nm 3< / t, b = 151 Nm 3< / t) (point enclosed by the broken line circle in FIG. 5).

[0063] As described above, according to the second embodiment, it is possible to increase an Input ΔC even in a case where the gas volume of a hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.

[0064] Furthermore, the present inventors also conducted studies on the degree of freedom in the operation. The results are shown in FIGS. 6 and 7. In FIG. 6, the horizontal axis (shaft tuyere RBFG gas volume) indicates a gas volume (Nm 3< / t) of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, and the vertical axis indicates a flame temperature (°C). AC indicates an Input ΔC. In FIG. 6, a group of points at which the Input ΔC was 29% or more and less than 33%, a group of points at which the Input ΔC was 33% or more and less than 38%, and a group of points at which the Input ΔC was more than 40% are enclosed by broken lines. In FIG. 6, the "normal upper limit" (= 2,300°C) of the flame temperature is an upper limit assumed for a normal operation (operation in which no hydrogen-based reducing gas is blown and no RBFG is blown). In FIG. 7, the horizontal axis indicates a flame temperature (°C), and the vertical axis indicates a top gas temperature (°C). FIGS. 6 and 7 also show a reference example in which the blast temperature is 1,300°C (BT 1,300°C) and the blowing temperature of the hydrogen gas is 1,000°C at the level 2-4.

[0065] According to FIGS. 6 and 7, the following findings can be obtained. ·By reducing the gas volume of the hydrogen-based reducing gas from the hydrogen-based reducing gas supply system 2 (that is, not included in the RBFG) or increasing the gas volume of the RBFG, the flame temperature is increased.

[0066] In the blast furnace operation, it is necessary to perform the operation so that both of the top gas temperature and the flame temperature are within appropriate ranges. The top gas temperature largely depends on the flow rate of the gas supplied to the inside of the blast furnace, and the higher the gas flow rate per iron tapping quantity, the higher the top gas temperature. Meanwhile, the flame temperature largely depends on the oxygen enriching ratio, which is a combustion condition at the tuyere tip, and the higher the oxygen enriching ratio, the higher the flame temperature. In the blast furnace operation, increasing an oxygen enriching ratio leads to a decrease in blast volume of hot blast and a decrease in flow rate of the gas supplied from the tuyere. Therefore, in a case where the flame temperature is increased by increasing the oxygen enriching ratio, the flow rate of the gas supplied into the furnace is decreased and the top gas temperature thus decreases. Therefore, assuming that the operation involves blowing the gas from the normal tuyere 11, it is difficult to independently control the top gas temperature and the flame temperature (because trying to move one of them will cause the other to move in the opposite direction). In a case where the RBFG is blown into the normal tuyere as in the first embodiment, it is possible to adjust the gas volume of the gas supplied into the furnace by adjusting the gas volume of the RBFG. However, since a gas having a lower temperature than the flame temperature is supplied into the blast furnace, increasing the gas volume of the RBFG leads to a decrease in flame temperature, and thus it is not possible to independently control the top gas temperature and the flame temperature.

[0067] In the second embodiment, a gas at a lower temperature than the flame temperature is supplied into the furnace as in the first embodiment. However, since the RBFG is blown from the shaft portion 10b instead of the tuyere portion (tip of the normal tuyere 11) where coke is burning, operating the gas volume of the RBFG does not result in a decrease in flame temperature. Therefore, while the top gas temperature is adjusted by increasing the gas volume of the RBFG, the flame temperature can be set to an appropriate value by separately adjusting the oxygen enriching ratio at the tuycrc portion. This is one of the strengths of the second embodiment (the gas is blown into a portion different from the normal tuyere 11).

[0068] Therefore, the flame temperature at the level 2-4 is higher than the flame temperatures at the levels 2-1 to 2-3. The flame temperature at the level 2-4 is sufficiently higher than the lower limit (2,000°C). Furthermore, the top gas temperature at the level 2-4 is also sufficiently higher than the lower limit (105°C).

[0069] Therefore, in the second embodiment, the degree of freedom in the operation is increased (the design width of the operation specifications is large). In a case where the Input ΔC at the level 2-4 is more than 40%, the flame temperature is higher than the upper limit (2,300°C) ((point indicated by the broken line circle A in FIG. 6). However, the operation can be continued by performing the above-described measures.<4. Third Embodiment>(4-1. Operation Method of Blast Furnace According to Third Embodiment)

[0070] Next, a third embodiment of the present invention will be described. In the third embodiment, an RBFG is blown into the blast furnace 10 from both of the normal tuyere 11 and the shaft portion tuyere 12.

[0071] An operation method of the blast furnace 10 according to the third embodiment is generally as follows. That is, while an iron-based raw material and coke arc alternately charged in layers into the blast furnace 10 from the top of the blast furnace 10, a heated hydrogen-based reducing gas is supplied from the hydrogen-based reducing gas supply system 2 to the normal tuyere 11. Then, hot blast, pulverized coal, an enriched oxygen gas, and a heated hydrogen-based reducing gas arc blown into the blast furnace 10 from the normal tuyere 11. Meanwhile, an RBFG is blown into the blast furnace 10 from the normal tuyere 11 and the shaft portion tuyere 12. The hot blast reacts with the pulverized coal blown together with the hot blast and the coke in the blast furnace 10, and a high-temperature reducing gas (here, mainly CO gas) is thus generated. That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace 10 and reduces the iron-based raw material while heating the iron-based raw material. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10 and reduce the iron-based raw material while heating the iron-based raw material. The iron-based raw material is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG while falling in the blast furnace 10. Next, the iron-based raw material is melted and dropped in the blast furnace 10 while being further reduced by the coke. Finally, the iron-based raw material is accumulated in a hearth portion as hot metal (pig iron) including just under 5 mass% of carbon. The hot metal in the hearth portion is extracted from a tap-hole and is provided for the next steelmaking process.

[0072] Meanwhile, the top gas of the blast furnace 10 is discharged. The CO 2 separation and recovery device 20 recovers the top gas and separates the gas into a reducing gas (CO gas and hydrogen gas) and a nitrogen gas (that is, RBFG), and a CO 2 gas and a H 2 O gas. The CO 2 gas and the H 2 O gas are discharged outside the system.

[0073] The RBFG is temporarily stored in the buffer tank 30. A desired amount of the RBFG is introduced into the compressor 40 from the buffer tank 30. The remaining RBFG is discharged outside the system and is used as, for example, a heat source of a steel plant.

[0074] The RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, an internal pressure (about 4.5 atm) of the blast furnace 10. The pressurized RBFG is introduced into the heater 50.

[0075] Then, the RBFG is heated by the heater 50. The heating temperature is optionally set according to operation conditions of the blast furnace 10. The RBFG heated by the heater 50 is blown into the blast furnace 10 from the normal tuyere 11 and the shaft portion tuyere 12. The flowmeter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the normal tuyere 11. The flowmeter 62 measures the flow rate of the RBFG blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12. Specific examples of the operation method are as described in the first embodiment.

[0076] Here, in the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are preferably maintained within predetermined ranges for reasons such as performing a stable operation. For example, the flame temperature is preferably maintained at about 2,000°C to 2300°C, the top gas temperature is preferably maintained at about 105°C or higher, and the hot metal temperature is preferably maintained at about 1,520°C or higher. The upper limit of the flame temperature is an upper limit assumed for a normal operation (operation in which no hydrogen-based reducing gas is blown and no RBFG is blown). In a case where the flame temperature is higher than the upper limit, it is preferable to take measures such as enhancing the cooling capacity of the tuyere equipment or using a material having higher heat resistance performance to prevent wear of the tuyere equipment. The specifications of the blast furnace operation are determined so that the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the specifications of the blast furnace operation can be freely designed as long as the flame temperature, the top gas temperature, and the hot metal temperature are maintained within predetermined ranges. In addition, the flame temperature may be higher than the upper limit as a result of the design, but it is preferable to take the above-described measures separately.

[0077] For example, the blowing temperature of the hydrogen-based reducing gas (the temperature of the hydrogen-based reducing gas blown from the normal tuyere 11) is preferably adjusted to about 800°C to 1,000°C, and the gas volume of the hydrogen gas in the hydrogen-based reducing gas is preferably adjusted to about 300 to 600 Nm 3< / t. All the ranges are lower than those in Patent Document 1. The normal tuyere blowing temperature of the RBFG (the temperature of the RBFG blown from the normal tuyere 11, that is, the heating temperature by the heater 50) is preferably about 800°C to 1,000°C, and the normal tuyere gas volume of the RBFG is preferably adjusted to about 100 to 300 Nm 3< / t. The shaft portion tuyere blowing temperature of the RBFG (the temperature of the RBFG blown from the shaft portion tuyere 12, that is, the heating temperature by the heater 50) is preferably the same as the normal tuyere blowing temperature, and the shaft portion tuyere gas volume of the RBFG is preferably adjusted to about 200 to 600 Nm 3< / t. In particular, the gas volume of the RBFG is preferably 600 Nm 3< / t or more in total of the normal tuyere gas volume and the shaft portion tuyere gas volume. This is because the Input ΔC exceeds 40% in this case as will be described later. Other adjustable specifications include the gas volume of hot blast and the amount of oxygen contained in the hot blast (gas volume of oxygen). In addition, the hot metal temperature can also be adjusted by the gas volume of the pulverized coal blown into the blast furnace 10 or the coke ratio (the amount of coke used per ton of hot metal) . For example, it is possible to perform control in which, first, the hot metal temperature is adjusted by the gas volume of the pulverized coal, and in a case where the gas volume of the pulverized coal becomes zero but the hot metal temperature exceeds a predetermined range, the coke ratio is adjusted. The hot metal temperature is a value reflecting the total heat amount (furnace heat) in the blast furnace 10. During the blast furnace operation, the flame temperature, the top gas temperature, and the hot metal temperature are monitored periodically (preferably, constantly). In a case where the value of any of the flame temperature, the top gas temperature, or the hot metal temperature is outside the above-described range, the operation conditions (for example, at least one of the blowing temperature of the hydrogen-based reducing gas, the gas volume of hydrogen gas in the hydrogen-based reducing gas, the blowing temperature of the RBFG, the gas volume of the RBFG, the gas volume of the hot blast, and the amount of oxygen contained in the hot blast (the gas volume of the enriched oxygen gas) as described above) may be adjusted. Since the flame temperature, the top gas temperature, and the hot metal temperature are likely to fluctuate during blowing of the hydrogen-based reducing gas or the RBFG, the flame temperature, the top gas temperature, and the hot metal temperature are preferably monitored during blowing of these gases.(3-2. Verification of Effects)

[0078] Next, verification of the effects performed by the present inventors will be described. In this verification, a blast furnace operation was simulated to verify the effects of the operation method of the blast furnace according to the third embodiment. The same simulation model as that in the first embodiment is used. Prerequisites for the simulation arc as follows. · A hydrogen gas is used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The blowing temperature of the hydrogen gas and the blowing temperature of an RBFG are 800°C. · The blowing temperature (blast temperature) of hot blast is 1,200°C. · The iron tapping quantity is 12,350 t / d and the hot metal temperature is 1,535°C. · The top gas temperature is 132°C and the flame temperature is 2,196°C. · Furnace heat adjustment (adjustment of the hot metal temperature) is performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal is zero but the hot metal temperature is higher than 1,535°C, the coke ratio is adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied.

[0079] Under the above-described prerequisites, simulation was performed in association with the following level. At this level, the gas volume of the hydrogen gas was set to 400 Nm 3< / t, the shaft portion tuyere gas volume of the RBFG was set to 400 Nm 3< / t, and the normal tuyere gas volume was set to 200 Nm 3< / t. As a result, the Input ΔC was 42.2%.

[0080] As described above, according to the third embodiment, it is possible to increase an Input ΔC even in a case where the gas volume of a hydrogen gas is reduced and the heating temperature of the hydrogen gas is lowered.Examples

[0081] Next, examples of the present embodiment will be described. In the examples, a blast furnace operation was simulated using a blast furnace mathematical model to confirm the effects of the first to third embodiments. Example 1 corresponds to the first embodiment, Example 2 corresponds to the second embodiment, and Example 3 corresponds to the third embodiment.<1. Example 1>(1-1. Main Specifications)

[0082] · A hydrogen gas was used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The iron tapping quantity is 12,350 t / d and the hot metal temperature was 1,535°C. · The top gas temperature was near the lower limit (105°C) to maximize a carbon reduction effect. · Furnace heat adjustment (adjustment of the hot metal temperature) was performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal was zero but the hot metal temperature was higher than 1,535°C, the coke ratio was adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied. · Hydrogen gas blowing (blowing temperature: 1,000°C, gas volume: 325 Nm 3< / t), hot blast blowing temperature of 1,300°C, RBFG blowing temperature of 1,000°C, and gas volume of 600 Nm 3< / t (1-2. Simulation Result)

[0083] As a result of the simulation, the Input ΔC was 43.2% in Example 1.<2. Example 2>(2-1. Main Specifications)

[0084] · A hydrogen gas was used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The blowing temperature of the hydrogen gas and the blowing temperature of an RBFG were 800°C. · The blowing temperature (blast temperature) of hot blast was 1,200°C. · The iron tapping quantity was 12,350 t / d and the hot metal temperature was 1,535°C. · The top gas temperature was 135°C. · Furnace heat adjustment (adjustment of the hot metal temperature) was performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal was zero but the hot metal temperature was higher than 1,535°C, the coke ratio was adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied. · Gas volume of hydrogen gas was 400 Nm 3< / t and gas volume of RBFG was 600 Nm 3< / t (2-2. Simulation Result)

[0085] As a result of the simulation, the Input AC was 40.5% in Example 2.<3. Example 3>(3-1. Main Specifications)

[0086] · A hydrogen gas was used as a hydrogen-based reducing gas. · The CO 2 separation and recovery device 20 separates and removes 100% of a CO 2 gas and an H 2 O gas contained in a top gas. · The blowing temperature of the hydrogen gas and the blowing temperature of an RBFG were 800°C. · The blowing temperature (blast temperature) of hot blast was 1,200°C. · The iron tapping quantity is 12,350 t / d and the hot metal temperature was 1,535°C. · The top gas temperature was 132°C and the flame temperature was 2,196°C. · Furnace heat adjustment (adjustment of the hot metal temperature) was performed by adjusting the gas volume of pulverized coal. In a case where the gas volume of the pulverized coal was zero but the hot metal temperature was higher than 1,535°C, the coke ratio was adjusted. · The gas volume of the hot blast and the gas volume of the oxygen were adjusted so that the above-described prerequisites were satisfied. · The gas volume of the hydrogen gas was set to 400 Nm 3< / t, the shaft portion tuyere gas volume of the RBFG was set to 400 Nm 3< / t, and the normal tuyere gas volume was set to 200 Nm 3< / t. (3-2. Simulation Result)

[0087] As a result of the simulation, the Input ΔC was 42.2% in Example 3.

[0088] Therefore, according to the first to third embodiments, it is possible to increase an Input ΔC even in a case where the gas volume of a hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.

[0089] Although the preferable embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is apparent that a person having common knowledge in the technical field to which the present invention belongs is able to devise various changes or modifications within the scope of the technical idea described in the claims, and it should be understood that such examples belong to the technical scope of the present invention as a matter of course.REFERENCE SIGNS LIST

[0090] 1 Blast furnace system 2 Hydrogen-based reducing gas supply system 10 Blast furnace 10a Blast furnace body 10b Shaft portion 11 Normal tuyere 12 Shaft portion tuyere 20 CO 2 separation and recovery device 30 Buffer tank 40 Compressor 50, 71 Heater 61, 62, 72 Flowmeter 70 Hydrogen-based reducing gas tank

Claims

1. An operation method of a blast furnace, comprising: heating a hydrogen-based reducing gas supplied from outside a blast furnace system; blowing the heated hydrogen-based reducing gas into the blast furnace; separating a reducing gas from a top gas; heating the separated reducing gas; and blowing the heated reducing gas into the blast furnace.

2. The operation method of a blast furnace according to Claim 1, wherein the reducing gas is blown into the blast furnace from a normal tuyere provided in a lower portion of the blast furnace.

3. The operation method of a blast furnace according to Claim 1 or 2, wherein the reducing gas is blown into a shaft portion of the blast furnace.

4. The operation method of a blast furnace according to Claim 1, wherein operation conditions are adjusted based on a flame temperature and a top gas temperature.

5. The operation method of a blast furnace according to Claim 4, wherein the operation conditions include a gas volume of the reducing gas, a blast volume of hot blast, and an amount of oxygen contained in the hot blast.

6. The operation method of a blast furnace according to Claim 1 or 2, further comprising: heating a hydrogen-based reducing gas supplied from outside a blast furnace system; blowing the heated hydrogen-based reducing gas into the blast furnace from at least one of a normal tuyere and a shaft portion tuyere installed at a position higher than at least the normal tuyere; separating a reducing gas from a top gas; heating the separated reducing gas; and blowing the heated reducing gas into the blast furnace from at least one of the normal tuyere and the shaft portion tuyere, wherein at at least one of a time when the heated hydrogen-based reducing gas is blown into the blast furnace from at least one of the normal tuyere and the shaft portion tuyere and a time when the heated reducing gas is blown into the blast furnace from at least one of the normal tuycre and the shaft portion tuyere, at least one of operation conditions including a gas volume of the reducing gas, a blast volume of hot blast, and an amount of oxygen contained in the hot blast is adjusted based on a flame temperature and a top gas temperature.

7. The operation method of a blast furnace according to Claim 1 or 2, wherein the reducing gas contains a CO gas and a hydrogen gas that are separated from the top gas.

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