Method for operating blast furnace

Abstract

This method for operating a blast furnace comprises: a step for heating a hydrogen-based reducing gas supplied from outside the blast furnace system; a step for blowing the heated hydrogen-based reducing gas into a blast furnace; a step for separating the reducing gas from the furnace top exhaust gas; a step for heating the separated reducing gas; and a step for blowing the reducing gas into the blast furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for operating a blast furnace.

[0002] This application claims priority based on Japanese Application No. 2023-101584 filed on June 21, 2023, the contents of which are incorporated herein. BACKGROUND

[0003] In the steel industry, the blast furnace method assumes the mainstream of the pig iron manufacturing process. In the blast furnace method, an iron-based raw material (a raw material containing iron oxide, mainly sintered ore, hereinafter also referred to as "iron-based raw material") and coke for a blast furnace are alternately and layer-wise charged into a blast furnace from the top of the blast furnace, on the other hand, hot air is blown into the blast furnace from a tuyere provided in the lower part of the blast furnace below the bosh. A reducing gas (here, mainly CO gas) of high temperature is generated by the reaction of the hot air 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 the pulverized coal. The reducing gas rises in the blast furnace, heating and reducing the iron-based raw material. The iron-based raw material descends in the blast furnace, on the other hand, is heated and reduced by the reducing gas. Then, the iron-based raw material is melted, further reduced by the coke and dripped in the blast furnace. The iron-based raw material is finally accumulated as molten iron (pig iron) containing less than 5% by mass of carbon in the hearth. The molten iron in the hearth is taken out from the tap hole and supplied to the subsequent steelmaking process. Therefore, in the blast furnace method, carbon materials such as coke and pulverized coal are used as reducing materials.

[0004] However, in recent years, there has been a call for prevention of global warming, and reduction of the amount of carbon dioxide (CO2 gas), which is one of greenhouse gases, has become a social problem. As described above, in the blast furnace method, since carbon materials are used as reducing materials, a large amount of CO2 gas is generated. Therefore, the steel industry has become one of the major industries in terms of CO2 gas emissions, and must respond to this social demand. Specifically, it is imperative to further reduce the reducing material ratio (amount of reducing material used per 1 ton of molten iron) in blast furnace operation.

[0005] The reducing material has the effect of becoming thermal energy in the furnace to warm up the charged material, and the effect of reducing the iron-based raw material in the furnace, and in order to reduce the reducing material ratio, it is necessary to improve the reduction efficiency in the furnace. The reduction reaction in the furnace can be represented by various reaction equations. Among these reduction reactions, the direct reduction reaction by coke (reaction equation: FeO + C => Fe + CO) is an endothermic reaction accompanied by a large amount of heat absorption. Therefore, it is important to prevent this reaction from occurring as much as possible for the reduction of the reducing material ratio. This direct reduction reaction occurs in the lower part of the blast furnace, and therefore, if the iron-based raw material can be sufficiently reduced by CO, H2, or the like before it reaches the lower part of the furnace, the iron-based raw material that becomes the target of the direct reduction reaction can be reduced.

[0006] As a prior art for solving the above problem, for example, as disclosed in Patent Literature 1, a technique of improving the reduction gas potential in the furnace by blowing hydrogen together with hot air from a tuyere is known. In this technique, the reduction material ratio is reduced by using hydrogen as the reduction gas of the iron-based raw material.

[0007] Prior Art Documents Patent Literature Patent Literature 1: International Publication No. 2021 / 107091 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION Although disclosed in Patent Literature 1, the present inventors defined a parameter of the reduction ratio of the carbon consumption basic unit (Input ΔC) as a parameter of an index for reducing the reduction material ratio. The "carbon consumption basic unit (Input C)" is the carbon required for manufacturing 1 ton of molten iron (i.e., the carbon consumption amount per 1 ton of molten iron). The "reduction ratio of the carbon consumption basic unit Input ΔC" refers to the reduction ratio of the carbon consumption basic unit with respect to the operation without blowing hydrogen, i.e., the base operation. If the Input C of the base operation in unit kg / t is set to A, and the Input C at a certain operation in unit kg / t is set to B, the Input ΔC is represented by the following mathematical expression.

[0009] Input ΔC = (A - B) / A x 100 (%), the greater the reduction ratio of the carbon consumption basic unit Input ΔC, the more the reduction material ratio is reduced, and further, the CO2 emission amount is reduced.

[0010] The present inventors have conducted detailed research on the technique described in Patent Literature 1, and as a result, it has been found that, in the case where it is intended to improve the Input ΔC by the technique described in Patent Literature 1, a large amount of hydrogen needs to be heated to a high temperature and blown into the blast furnace. For example, in the case where the Input ΔC is to be 40% or more, the amount of hydrogen to be blown in needs to be 650 Nm 3 / t or more, and the temperature of the hydrogen needs to be 1200°C or more. In this case, in addition to the need for a large amount of hydrogen, a heating device for heating the hydrogen to a high temperature is also required, and further, the blast furnace equipment needs to be composed of a material capable of withstanding high-temperature hydrogen.

[0011] Thus, in the technique disclosed in Patent Literature 1, there is a problem that much effort is required to improve the Input ΔC.

[0012] Therefore, the present application was made in view of the above problem, and an object of the present application is to provide a blast furnace operation method capable of improving Input ΔC even when the amount of blowing 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.

[0013] Means for solving the problem The present inventors have made a detailed study of the technology described in Patent Literature 1, and as a result, found that a large amount of hydrogen gas is discharged as top gas in the operation of a blast furnace. Therefore, the present inventors have attempted to separate a reducing gas (the reducing gas contains hydrogen gas and CO gas) from the top gas, and blow the separated reducing gas into the blast furnace. As a result, it has been shown that, compared with the technology described in Patent Literature 1, the same degree of Input ΔC as that of the technology described in Patent Literature 1 can be obtained even when the amount of blowing of hydrogen gas is reduced and the heating temperature of the hydrogen gas is lowered. The present application was made on the basis of this insight.

[0014] The gist of the present application is as follows.

[0015] (1) A blast furnace operation method characterized by comprising: a step of heating a hydrogen-based reducing gas supplied from outside a blast furnace system; a step of blowing the heated hydrogen-based reducing gas into a blast furnace; a step of separating a reducing gas from top gas; a step of heating the separated reducing gas; and a step of blowing the reducing gas into the blast furnace.

[0016] (2) The blast furnace operation method according to (1), characterized in that the reducing gas is blown into the blast furnace from a tuyere provided at a lower portion of the blast furnace.

[0017] (3) The blast furnace operation method according to (1) or (2), characterized in that the reducing gas is blown into a shaft portion of the blast furnace.

[0018] (4) The blast furnace operation method according to any one of (1) to (3), characterized in that an operation condition is adjusted on the basis of a pre-tuyere combustion temperature and a top gas temperature.

[0019] (5) The blast furnace operation method according to (4), characterized in that the operation condition includes the amount of blowing of the reducing gas, the amount of supply of hot blast, and the amount of oxygen contained in the hot blast.

[0020] (6) The operation method of the blast furnace according to any one of (1) to (5), characterized by further comprising: a process of heating a hydrogen-based reducing gas supplied from outside the blast furnace system; a process of blowing the heated hydrogen-based reducing gas into the blast furnace from at least one of a general tuyere and a shaft portion tuyere provided at a position higher than the general tuyere; a process of separating a reducing gas from a top gas; a process of heating the separated reducing gas; and a process of blowing the heated reducing gas into the blast furnace from at least one of the general tuyere and the shaft portion tuyere, at least one of a timing when the heated hydrogen-based reducing gas is blown into the blast furnace from at least one of the general tuyere and the shaft portion tuyere and a timing when the heated reducing gas is blown into the blast furnace from at least one of the general tuyere and the shaft portion tuyere, at least one of the blowing amount of the reducing gas, the supply amount of hot blast, and the amount of oxygen contained in the hot blast is adjusted based on a pre-tuyere combustion temperature and a top gas temperature.

[0021] (7) The operation method of the blast furnace according to any one of (1) to (6), characterized in that the reducing gas contains CO gas and hydrogen gas separated from the top gas.

[0022] Effects of Invention According to the present invention, even when the blowing amount of the hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered, it is possible to increase Input ΔC. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flowchart showing the overall structure of a blast furnace system used in the present embodiment.

[0024] Figure 2 is a graph for verifying the effect of the first embodiment.

[0025] Figure 3 is a graph for verifying the effect of the first embodiment.

[0026] Figure 4 is a graph for verifying the effect of the second embodiment.

[0027] Figure 5 is a graph for verifying the effect of the second embodiment.

[0028] Figure 6 is a graph for verifying the effect of the second embodiment.

[0029] Figure 7 is a graph for verifying the effect of the second embodiment. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same function and structure are denoted with the same reference numerals, and thus repeated explanation will be omitted.

[0031] <Overall structure of blast furnace system> First, the overall structure of the blast furnace system 1 of the present embodiment and the hydrogen-based reducing gas supply system 2 connected to the blast furnace system 1 will be described based on Figure 1 The blast furnace system 1 is provided with a blast furnace 10, a CO2 separation and recovery device 20, a buffer tank 30, a compressor 40, a heater 50, and flow meters 61 and 62.

[0032] The blast furnace 10 is provided with a blast furnace main body 10a, a general tuyere 11, and a shaft portion tuyere 12. Inside the blast furnace main body 10a, a reduction reaction of an iron-based raw material based on the blast furnace method occurs. Specifically, an iron-based raw material and coke are alternately and layer-wise charged into the blast furnace 10 from the top of the blast furnace 10, and on the other hand, hot air, pulverized coal, and oxygen-enriched gas are blown into the blast furnace 10 from the general tuyere 11. Further, in the following description, the "tuyere front end combustion temperature" refers to the temperature at the gas injection port of the general tuyere 11. By the reaction of the hot air with the pulverized coal blown in together with the hot air and the coke inside the blast furnace 10, a high-temperature reducing gas (mainly CO gas here) is generated. That is, the hot air gasifies the coke and the pulverized coal. Further, details will be described later, but sometimes the pulverized coal is not blown into the blast furnace 10 either. The reducing gas rises inside the blast furnace 10, heating and reducing the iron-based raw material. The iron-based raw material descends inside the blast furnace 10, on the other hand, is heated and reduced by the reducing gas. Then, the iron-based raw material is melted, further reduced by the coke, and dripped inside the blast furnace 10. The iron-based raw material is finally accumulated as molten iron (pig iron) containing less than 5% by mass of carbon in the hearth portion. The molten iron in the hearth portion is taken out from the tap hole and supplied to the subsequent steelmaking process.

[0033] The general tuyere 11 is provided at a position lower than the bosh portion of the blast furnace 10, and in addition to the above-mentioned hot air, as will be described later, heated hydrogen-based reducing gas and reducing gas separated from the top gas (blast furnace off-gas) is blown into the blast furnace 10. Further, in Figure 1 In the present embodiment, the general tuyere 11 is depicted at two places on the left and right of the blast furnace 10, but it can also be that the general tuyere 11 is installed three or more separated at regular intervals on the entire circumference of the blast furnace 10.

[0034] The shaft portion tuyere 12 is provided at a position higher than the general tuyere 11 of the blast furnace 10, and blows the reducing gas separated from the top gas into the shaft portion 10b of the blast furnace 10. Further, in Figure 1In the present embodiment, tuyeres 12 are depicted at both left and right of the shaft portion 10b, but three or more tuyeres 12 can be installed separately at a prescribed interval on the entire circumference of the blast furnace 10. Also, in the present embodiment, the tuyere 12 is depicted at the shaft portion 10b, but as long as the reducing gas separated from the top gas can be blown into the shaft portion 10b and is at a position higher than the position of the general tuyere 11, it can also be installed at a position lower than the shaft portion 10b, i.e., the belly portion, the bosh portion, or a position lower than these. Figure 1

[0035] The CO2 separation and recovery device 20 is a device that recovers the top gas and separates it into reducing gas (CO gas and hydrogen gas) and nitrogen gas, and CO2 gas and H2O gas. The method of separation is not particularly limited, and for example, chemical adsorption and physical adsorption (PSA) can be cited. In the following description, the reducing gas and nitrogen gas separated from the top gas will also be referred to as RBFG (Returned Blast Furnace Gas). The CO2 gas and H2O gas are discharged to the outside of the system. Also, the CO2 separation and recovery device 20 can not necessarily recover the entire amount of the top gas. For example, the CO2 separation and recovery device 20 can recover an amount of the top gas corresponding to the flow rate of the RBFG blown into the blast furnace.

[0036] The buffer tank 30 is a tank that temporarily stores the RBFG. The desired amount of RBFG is introduced from the buffer tank 30 to the compressor 40. The remaining RBFG is used, for example, as a heat source in the ironworks.

[0037] The compressor 40 pressurizes the RBFG. Here, the compressor 40 pressurizes the RBFG to, for example, approximately the internal pressure of the blast furnace 10 (approximately 4.5 atm). The pressurized RBFG is introduced to the heater 50.

[0038] The heater 50 heats the RBFG. The heating temperature is arbitrarily set according to the operating conditions of the blast furnace 10, and for example, in the case where the RBFG is blown into the shaft portion 10b of the blast furnace 10 from the shaft portion tuyere 12, it is preferably set to 800°C or higher. The heater 50 can be sufficiently implemented by an electric heater or the like. The RBFG heated by the heater 50 is blown into the blast furnace 10, for example, from the general tuyere 11 or from the shaft portion tuyere 12 into the shaft portion 10b of the blast furnace 10. Figure 1 In the present embodiment, the RBFG is blown into the blast furnace 10 from the general tuyere 11 and the shaft portion tuyere 12 on the left side, but the RBFG can also be blown into the blast furnace 10 from the general tuyere 11 and the shaft portion tuyere 12 on the right side. The RBFG can also be blown into the blast furnace 10 from both the general tuyere 11 and the shaft portion tuyere 12.

[0039] ​The flow meter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the general tuyere 11. The flow meter 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 surge tank 30 into the compressor 40, the flow rate of the RBFG blown into the blast furnace 10 from the general 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 can be arbitrarily adjusted.

[0040] The hydrogen-based reducing gas supply system 2 is provided with a hydrogen-based reducing gas tank 70, a heater 71, and a flow meter 72. The hydrogen-based reducing gas supply system 2 is a system that supplies the hydrogen-based reducing gas to the blast furnace system 1 from outside the system.

[0041] The hydrogen-based reducing gas tank 70 is a tank that stores the hydrogen-based reducing gas. Here, the hydrogen-based reducing gas is a concept of a mixed gas that includes hydrogen gas and other gas (for example, nitrogen gas) other than hydrogen gas (without impairing 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 implemented by an electric heater or the like. The heater 71 is connected to the general tuyere 11, and the heated hydrogen-based reducing gas is blown into the blast furnace 10 from the general tuyere 11. The heater 71 can also be used in conjunction with the heater 50. The flow meter 72 measures the flow rate of the hydrogen-based reducing gas blown into the blast furnace 10 from the general tuyere 11. In addition, as described later, even in a case where the amount of blowing of the hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered, Input ΔC can be increased. In addition, in the present embodiment, the hydrogen-based reducing gas is blown from the general tuyere 11, but the hydrogen-based reducing gas can also be blown into the blast furnace 10 from the shaft portion tuyere 12.

[0042] <2. First Embodiment> (2-1. Method of operating the blast furnace according to the first embodiment) Next, the first embodiment of the present application will be described. In the first embodiment, the RBFG is blown into the blast furnace 10 from the general tuyere 11. In the first embodiment, the shaft portion tuyere 12 and the flow meter 62 can also be omitted.

[0043] The operation method of the blast furnace 10 of the first embodiment is roughly described as follows. That is, the iron-based raw material and the coke are alternately and layerwisely charged into the blast furnace 10 from the top of the blast furnace 10, on the other hand, the heated hydrogen-based reducing gas is supplied to the common tuyere 11 from the hydrogen-based reducing gas supply system 2. Then, the hot blast, the pulverized coal, the oxygen-enriched gas, the heated hydrogen-based reducing gas, and the RBFG containing the heated CO and H2 are blown into the blast furnace 10 from the common tuyere 11. The hot blast reacts with the pulverized coal blown together with the hot blast and the coke in the blast furnace 10, thereby generating a high-temperature reducing gas (here, mainly CO gas). That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace 10, heating and reducing the iron-based raw material. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10, heating and reducing the iron-based raw material. The iron-based raw material descends in the blast furnace 10, on the other hand, is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG. Then, the iron-based raw material is melted, further reduced by the coke, and dripped in the blast furnace 10. The iron-based raw material is finally accumulated as molten iron (pig iron) containing less than 5% by mass of carbon in the hearth portion. The molten iron in the hearth portion is taken out from the tap hole, and supplied to the subsequent steelmaking process.

[0044] On the other hand, the top gas of the blast furnace 10 is discharged. The CO2 separation and recovery device 20 recovers the top gas, separates it into the reducing gas (CO gas and hydrogen gas) and nitrogen gas (i.e., RBFG), and CO2 gas and H2O gas. The CO2 gas and H2O gas are discharged to the outside of the system.

[0045] The RBFG is temporarily stored in the buffer tank 30. The desired amount of the RBFG is introduced from the buffer tank 30 to the compressor 40. The remaining RBFG is discharged to the outside of the system, for example, used as a heat source of the ironworks.

[0046] Next, the RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, the internal pressure of the blast furnace 10 (about 4.5 atm). The pressurized RBFG is introduced to the heater 50.

[0047] Next, the RBFG is heated by the heater 50. The heating temperature is arbitrarily set according to the operation conditions of the blast furnace 10. The RBFG heated by the heater 50 is blown into the blast furnace 10 from the common tuyere 11. The flow meter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the common tuyere 11. The RBFG is mainly blown into the blast furnace 10 from the common tuyere 11, but can be additionally blown into the blast furnace 10 from the shaft portion tuyere 12. Details will be described later.

[0048] Here, in the blast furnace operation, for the reason of performing stable operation and the like, it is preferable to maintain the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature within a prescribed range. For example, the raceway front end combustion temperature is preferably maintained at around 2000 to 2300°C, the top gas temperature is preferably maintained at around 105°C or higher, and the molten iron temperature is preferably maintained at around 1520°C or higher. Further, the upper limit value of the raceway front end combustion temperature is a value that is assumed when the usual operation (operation without blowing in the hydrogen-based reducing gas and blowing in the RBFG) is performed. In the case where the raceway front end combustion temperature exceeds the upper limit value, in order to prevent the raceway equipment from being damaged, it is preferable to perform a countermeasure such as reinforcing the cooling capacity of the raceway equipment, using a material having a higher heat resistance, and the like. The parameter specifications of the blast furnace operation are preferably determined in a manner such that the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature are maintained within the prescribed range. In addition, as long as the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature are maintained within the prescribed range, the parameter specifications of the blast furnace operation can be freely designed. In addition, the raceway front end combustion temperature can exceed the upper limit value as a result of the design, but it is preferable to additionally perform the countermeasure described above.

[0049] For example, the blowing-in temperature of the hydrogen-based reducing gas (temperature of the hydrogen-based reducing gas blown in from the general raceway 11) is preferably around 800 to 1000°C, and the blowing-in amount of hydrogen gas in the hydrogen-based reducing gas is preferably around 300 to 600 Nm 3 / t. All are ranges lower than Patent Document 1. The blowing-in temperature of the RBFG (temperature of the RBFG blown in from the general raceway 11, that is, the heating temperature of the heater 50) is preferably around 800 to 1000°C, and the blowing-in amount of the RBFG is preferably around 400 to 800 Nm 3 / t. In particular, the blowing-in amount of the RBFG is preferably around 600 Nm 3or more of the above-mentioned adjustable parameter specifications. In addition, the molten iron temperature can be adjusted by the amount of pulverized coal blown into the blast furnace 10 or the coke ratio (the amount of coke used per 1 ton of molten iron). For example, the molten iron temperature is first adjusted by the amount of pulverized coal blown in, and even if the amount of pulverized coal blown in becomes zero and the molten iron temperature exceeds the prescribed range, control of the coke ratio can be performed. In addition, the molten iron temperature is a value reflecting the total heat (furnace heat) in the blast furnace 10. In addition, in the blast furnace operation, the raceway front combustion temperature, the top gas temperature, and the molten iron temperature are periodically (preferably always) monitored, and in the case where any of the raceway front combustion temperature, the top gas temperature, and the molten iron temperature becomes a value outside the above-mentioned range, at least one or more of the above-mentioned adjustable parameter specifications can be adjusted. In addition, when the hydrogen-based reducing gas or the RBFG is blown in, the raceway front combustion temperature, the top gas temperature, and the molten iron temperature easily fluctuate, and therefore, it is preferable to monitor the raceway front combustion temperature, the top gas temperature, and the molten iron temperature when these gases are blown in.

[0050] (2-2. Specific examples of the operation method) Hereinafter, specific examples of the operation method will be described. In addition, the specific examples listed below can also be applied to the second embodiment described later.

[0051] (2-2-1. Case where the molten iron temperature decreases) The amount of RBFG blown into the blast furnace 10 from the general tuyere 11 is increased. At the same time, the amount of oxygen-rich gas blown in is increased, and the amount of hot blast blown in (blast volume) is decreased, thereby maintaining the raceway front combustion temperature. In addition, in the case where the top gas temperature is lower than the prescribed range, the amount of RBFG blown in from the shaft tuyere 12 is further increased.

[0052] (2-2-2. Case where the raceway front combustion temperature decreases) The amount of oxygen-rich gas blown in is increased, and the amount of hot blast blown in is decreased, thereby increasing the raceway front combustion temperature. As a result, there is a concern that the amount of bosh gas decreases and the top gas temperature becomes lower than the prescribed range, but at this time, the amount of RBFG blown in from the shaft tuyere 12 can be simultaneously increased to cope with this.

[0053] (2-2-3. Case where the top gas temperature decreases) The amount of RBFG blown in from the shaft tuyere 12 is increased.

[0054] (2-2-4. Case where both of the combustion temperature at the front end of the tuyere and the top gas temperature are decreased) The amount of the oxygen-enriched gas is increased, and the amount of the hot blast is decreased, so that the combustion temperature at the front end of the tuyere is increased, and the amount of the RBFG blown from the tuyere 12 of the shaft portion is simultaneously increased.

[0055] (2-2-5. Case where the combustion temperature at the front end of the tuyere is decreased and the top gas temperature is increased) If the top gas temperature is excessively high, the gas flow rate in the furnace is increased, and the possibility of the operation variation is increased, so that the excessive increase of the top gas temperature is not preferable.

[0056] The amount of the oxygen-enriched gas is increased, and the amount of the hot blast is decreased. Thereby, the combustion temperature at the front end of the tuyere tends to be increased, and the top gas temperature tends to be decreased. In the case where the top gas temperature is lower than the prescribed range, the amount of the RBFG blown from the tuyere 12 of the shaft portion is simultaneously increased to control the top gas temperature.

[0057] (2-2-6. Case where the combustion temperature at the front end of the tuyere is increased and the top gas temperature is decreased) The amount of the oxygen-enriched gas is decreased, and the amount of the hot blast is increased. Thereby, the combustion temperature at the front end of the tuyere is decreased, and the top gas temperature tends to be increased. In the case where the top gas temperature exceeds the prescribed range, the amount of the RBFG blown from the tuyere 12 of the shaft portion is simultaneously decreased to control the top gas temperature.

[0058] (2-2-7. Case where both of the combustion temperature at the front end of the tuyere and the top gas temperature are increased) The amount of the oxygen-enriched gas is decreased, and the amount of the hot blast is increased, and the amount of the RBFG blown from the tuyere 12 of the shaft portion is decreased.

[0059] (2-3. Verification of effects) Next, the verification of the effects performed by the present inventors will be described. In this verification, the simulation of the blast furnace operation was performed, and the effects of the operation method of the blast furnace of the first embodiment were verified. The simulation model used a 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, and the like. This blast furnace mathematical model simulates the behavior of each grid by roughly dividing the internal region of the blast furnace in the height direction, the radial direction, and the circumferential direction to define a plurality of grids (small regions). The simulation premise conditions are as follows.

[0060] • Hydrogen gas is used as a hydrogen-based reducing gas.

[0061] • The CO2 separation and recovery device 20 separates and removes 100% of the CO2 gas and H2O gas contained in the top gas.

[0062] • The tapping amount and the molten iron temperature are constant at all levels (12350 t / d, 1535°C).

[0063] • The top gas temperature is near the lower limit value (105°C).

[0064] • Furnace heat adjustment (adjustment of the molten iron temperature) is performed by adjusting the pulverized coal injection amount. In the case where the molten iron temperature exceeds 1535°C even if the pulverized coal injection amount is zero, the coke ratio is adjusted.

[0065] • The hot blast injection amount and the oxygen injection amount are adjusted to satisfy the above-mentioned prerequisite conditions.

[0066] Under the above-mentioned prerequisite conditions, each of the following levels was simulated. Levels 1-5 correspond to the first embodiment.

[0067] (Level 1-1) No hydrogen injection, hot blast injection temperature is 1200°C, RBFG injection operation (injection temperature is 1200°C) Figure 2 , 3 H2-0 BT1200°C. In addition, H2-0 BT1200°C indicates no hydrogen injection, and the hot blast injection temperature is 1200°C.

[0068] (Level 1-2) Hydrogen injection (injection temperature is 1200°C, injection amount is 650 Nm 3 / t), hot blast injection temperature is 1200°C, RBFG injection operation (injection temperature is 1000°C) Figure 2 , 3 H2-650 1200°C, BT1200°C. In addition, H2-650 1200°C indicates that the hydrogen injection amount is 650 Nm 3 / t, and the injection temperature is 1200°C, and BT1200°C indicates that the hot blast injection temperature is 1200°C.

[0069] (Level 1-3) Hydrogen injection (injection temperature is 1000°C, injection amount is 650 Nm 3 / t), hot blast injection temperature is 1200°C, RBFG injection operation (injection temperature is 1000°C) Figure 2 , 3 H2-650 1000°C, BT1200°C. In addition, H2-650 1000°C indicates that the hydrogen injection amount is 650 Nm 3 / t, the blowing temperature is 1000℃, BT1200℃ indicates that the blowing temperature of the hot air is 1200℃).

[0070] (Level 1-4) Hydrogen gas is blown in (blowing temperature is 1000℃, blowing rate is 650 Nm). 3 / t), the hot air inlet temperature is 1300℃, RBFG inlet operation (inlet temperature is 1000℃) ( Figure 2 , 3 The specifications are: H2-650 1000℃, BT1300℃. Additionally, H2-650 1000℃ indicates a hydrogen injection rate of 650 Nm³. 3 / t, the blowing temperature is 1000℃, BT1300℃ indicates that the blowing temperature of the hot air is 1300℃).

[0071] (Level 1-5) Hydrogen gas is blown in (blowing temperature 1000℃, blowing rate 325 Nm). 3 / t), the hot air inlet temperature is 1300℃, RBFG inlet operation (inlet temperature 1000℃) ( Figure 2 , 3 The specifications are H2-325 1000℃ and BT1 300℃. Additionally, H2-325 1000℃ indicates a hydrogen blowing rate of 325 Nm³. 3 / t, the blowing temperature is 1000℃, BT1300℃ indicates that the blowing temperature of the hot air is 1300℃).

[0072] The results are expressed in Figure 2 and Figure 3 . Figure 2 The horizontal axis (RBFG tuyere injection rate) represents the injection rate (Nm³) of RBFG into the blast furnace 10 from the general tuyere 11. 3 / t), with the vertical axis representing Input ΔC (%). Figure 3 The horizontal axis (RBFG tuyere injection rate) represents the injection rate (Nm³) of RBFG into the blast furnace 10 from the general tuyere 11. 3 / t), the vertical axis (overall hydrogen utilization rate of the system) represents the overall hydrogen utilization rate of the system (%). Here, the overall hydrogen utilization rate of the system is expressed by the following mathematical formula.

[0073] n H2 (a+b) n H2 Hydrogen utilization rate (%) a: The amount of H2O gas discharged from the CO2 separation and recovery unit 20 to the outside of the system (Nm³) 3 / t); b: The amount of hydrogen gas discharged from buffer tank 30 to the outside of the system (Nm³)3 / t).

[0074] according to Figure 2 and Figure 3 The following insights were obtained.

[0075] The greater the amount of hydrogen blown in from the hydrogen-based reducing gas supply system 2 (i.e., not included in the RBFG), the larger the Input ΔC will be. However, this problem arises because a large amount of hydrogen needs to be prepared.

[0076] The greater the RBFG injection rate, the larger the Input ΔC. In levels 1-5, the RBFG injection rate is set to 600 Nm. 3 / t, thus the Input ΔC exceeds 40% (43.2%). Figure 2 (The point enclosed by the dashed circle in the diagram). This value is comparable to levels 1-2 to 1-4 where a large amount of hydrogen is blown in. Moreover, the hydrogen blowing rate at level 1-5 is 325 Nm³. 3 / t, which is 50% less than levels 1-2 to 1-4, and the hydrogen blowing temperature is also as low as 1000℃. Furthermore, the hydrogen utilization rate of level 1-5 at this point is 77% (a=253Nm). 3 / t, b=76Nm 3 / t)( Figure 3 (The point enclosed by the dashed circle in the middle).

[0077] As described above, according to the first embodiment, even when the amount of hydrogen reducing gas blown in from the hydrogen reducing gas supply system 2 is reduced and the heating temperature of the hydrogen reducing gas is lowered, the Input ΔC can still be increased.

[0078] <3. Second Implementation Method> (3-1. Operation method of the blast furnace in the second embodiment) Next, a second embodiment of the present invention will be described. In the second embodiment, RBFG is blown into the blast furnace 10 from the tuyeres 12 in the furnace body. In the second embodiment, the flow meter 61 may also be omitted.

[0079] The operation method of the blast furnace 10 of the second embodiment is roughly described as follows. That is, the iron-based raw material and the coke are alternately and layerwisely charged into the blast furnace 10 from the top of the blast furnace 10, on the other hand, the heated hydrogen-based reducing gas is supplied to the general tuyere 11 from the hydrogen-based reducing gas supply system 2. Then, the hot blast, the pulverized coal, the oxygen-enriched gas, and the heated hydrogen-based reducing gas are blown into the blast furnace 10 from the general tuyere 11. On the other hand, the RBFG is blown into the shaft portion 10b of the blast furnace 10 from 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, thereby generating a high-temperature reducing gas (here, mainly CO gas). That is, the hot blast gasifies the coke and the pulverized coal. The reducing gas rises in the blast furnace 10, heating and reducing the iron-based raw material. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10, heating and reducing the iron-based raw material. The iron-based raw material descends in the blast furnace 10, on the other hand, is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG. Then, the iron-based raw material is melted, further reduced by the coke, and dripped in the blast furnace 10. The iron-based raw material is finally accumulated as molten iron (pig iron) containing less than 5% by mass of carbon in the hearth portion. The molten iron in the hearth portion is taken out from the tap hole and supplied to the next steelmaking process.

[0080] On the other hand, the top gas of the blast furnace 10 is discharged. The CO2 separation and recovery device 20 recovers the top gas, separates it into a reducing gas (CO gas and hydrogen) and nitrogen (i.e., RBFG) and CO2 gas and H2O gas, and recovers the reducing gas and the nitrogen. The CO2 gas and the H2O gas are discharged to the outside of the system.

[0081] The RBFG is temporarily stored in the buffer tank 30. The desired amount of the RBFG is introduced to the compressor 40 from the buffer tank 30. The remaining RBFG is discharged to the outside of the system, for example, used as a heat source of the ironworks.

[0082] Next, the RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, the internal pressure (about 4.5 atm) of the blast furnace 10. The pressurized RBFG is introduced to the heater 50.

[0083] Next, the RBFG is heated by the heater 50. The heating temperature is arbitrarily set according to the 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 flow meter 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 can be additionally blown into the blast furnace 10 from the general tuyere 11. Specific examples of the operation method are described in the first embodiment.

[0084] Here, in the blast furnace operation, for the reason of performing stable operation and the like, it is preferable to maintain the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature within a prescribed range. For example, the raceway front end combustion temperature is preferably maintained at around 2000 to 2300°C, the top gas temperature is preferably maintained at around 105°C or higher, and the molten iron temperature is preferably maintained at around 1520°C or higher. Further, the upper limit value of the raceway front end combustion temperature is a value that is assumed when the usual operation (operation without blowing in the hydrogen-based reducing gas and the RBFG) is performed. In the case where the raceway front end combustion temperature exceeds the upper limit value, in order to prevent the raceway equipment from being damaged, it is preferable to perform a countermeasure such as reinforcing the cooling capacity of the raceway equipment, using a material having a higher heat resistance, and the like. The parameter specifications of the blast furnace operation are determined in a manner such that the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature are maintained within the prescribed range. In addition, as long as the raceway front end combustion temperature, the top gas temperature, and the molten iron temperature are maintained within the prescribed range, the parameter specifications of the blast furnace operation can be freely designed. In addition, the raceway front end combustion temperature can exceed the upper limit value as a result of the design, but it is preferable to additionally perform the countermeasure described above.

[0085] For example, the blowing-in temperature of the hydrogen-based reducing gas (the temperature of the hydrogen-based reducing gas blown in from the general raceway 11) is preferably around 600 to 1000°C, and the blowing-in amount of hydrogen gas in the hydrogen-based reducing gas is preferably around 400 to 600 Nm 3 The blowing-in temperature of the RBFG (the temperature of the RBFG blown in from the shaft raceway 12, that is, the heating temperature of the heater 50) is preferably around 800 to 1000°C, and the blowing-in amount of the RBFG is preferably around 200 to 600 Nm 3left and right. This is because, as described later, in this case, Input ΔC exceeds 40%. As other adjustable parameter specifications, the amount of hot blast blown in, the amount of oxygen contained in the hot blast (the amount of oxygen blown in), and the like can be cited. In addition, the molten iron temperature can also be adjusted by the amount of pulverized coal blown in to the blast furnace 10 or the coke ratio (the amount of coke used per 1 ton of molten iron). For example, the molten iron temperature is first adjusted by the amount of pulverized coal blown in, and even in the case where the amount of pulverized coal blown in is zero and the molten iron temperature exceeds the prescribed range, control of the coke ratio can be performed. Furthermore, the molten iron temperature is a value reflecting the total heat (furnace heat) in the blast furnace 10. Furthermore, in the blast furnace operation, the raceway front combustion temperature, the top gas temperature, and the molten iron temperature are periodically (preferably always) monitored, and in the case where any of the raceway front combustion temperature, the top gas temperature, and the molten iron temperature is a value outside the above-described range, at least one or more of the operation conditions (for example, as described above, the blowing-in temperature of the hydrogen-based reducing gas, the amount of hydrogen gas in the hydrogen-based reducing gas blown in, the blowing-in temperature of the RBFG, the amount of RBFG blown in, the amount of hot blast blown in, and the amount of oxygen contained in the hot blast (the amount of oxygen-rich gas blown in)) can be adjusted. Furthermore, when the hydrogen-based reducing gas or the RBFG is blown in, the raceway front combustion temperature, the top gas temperature, and the molten iron temperature easily fluctuate, and therefore, when these gases are blown in, it is preferable to monitor the raceway front combustion temperature, the top gas temperature, and the molten iron temperature.

[0086] (3-2. Verification of effects) Next, verification of effects performed by the present inventors will be described. In this verification, simulation of the blast furnace operation was performed, and the effects of the operation method of the blast furnace of the second embodiment were verified. The simulation model was the same as that of the first embodiment. The simulation premise conditions were as follows.

[0087] • Hydrogen gas was used as the hydrogen-based reducing gas.

[0088] • The CO2 separation and recovery device 20 separated and removed 100% of the CO2 gas and H2O gas contained in the top gas.

[0089] • The blowing-in temperature of the hydrogen gas and the blowing-in temperature of the RBFG were both 800°C at any level. Among them, the blowing-in temperature of the hydrogen gas at level 2-1 was 1200°C.

[0090] • The blowing-in temperature (blast temperature) of the hot blast was 1200°C at any level.

[0091] • The amount of molten iron tapped and the molten iron temperature were set to be constant at all levels (12350 t / d, 1535°C).

[0092] • The top gas temperature was 135°C at any level.

[0093] • Furnace heat adjustment (adjustment of the molten iron temperature) is performed by adjusting the amount of pulverized coal blown in. In the case where the molten iron temperature exceeds 1535°C even if the amount of pulverized coal blown in is zero, the coke ratio is adjusted.

[0094] • The amount of hot blast blown in and the amount of oxygen blown in are adjusted so as to satisfy the above-mentioned prerequisite conditions.

[0095] Under the above-mentioned prerequisite conditions, the following levels were simulated. Levels 2-2 to 2-4 correspond to the second embodiment.

[0096] (Level 2-1) Hydrogen blown-in amount 650 Nm 3 / t, hot blast blown-in temperature 1200°C, no RBFG blown in (H2: 650 Nm 3 / t, BT 1200°C).

[0097] (Level 2-2) Hydrogen blown-in amount 600 Nm 3 / t, hot blast blown-in temperature 1200°C, RBFG blown-in operation (H2: 600 Nm 3 / t, BT 1200°C).

[0098] (Level 2-3) Hydrogen blown-in amount 500 Nm 3 / t, hot blast blown-in temperature 1200°C, RBFG blown-in operation (H2: 500 Nm 3 / t, BT 1200°C).

[0099] (Level 2-4) Hydrogen blown-in amount 400 Nm 3 / t, hot blast blown-in temperature 1200°C, RBFG blown-in operation (H2: 400 Nm 3 / t, BT 1200°C).

[0100] The results are shown in Figure 4 and Figure 5 . Figure 4 The horizontal axis (amount of RBFG blown in from the tuyere 12 of the shaft portion 10b of the blast furnace 10) indicates the amount of RBFG blown in (Nm 3 / t) from the tuyere 12 of the shaft portion 10b of the blast furnace 10, and the vertical axis indicates Input ΔC (%). Figure 5 The horizontal axis (amount of RBFG blown in from the tuyere 12 of the shaft portion 10b of the blast furnace 10) indicates the amount of RBFG blown in (Nm 3 / t) from the tuyere 12 of the shaft portion 10b of the blast furnace 10, and the vertical axis (overall system hydrogen utilization rate) indicates the utilization rate of hydrogen (%). The calculation method of the overall system hydrogen utilization rate is as described above.

[0101] From Figure 4 and Figure 5 the following insights were obtained.

[0102] The greater the amount of hydrogen blown in from the hydrogen-based reducing gas supply system 2 (i.e., not included in the RBFG), the greater the Input ΔC.

[0103] The greater the RBFG injection rate, the larger the Input ΔC. In level 2-4, the RBFG injection rate is set to 600 Nm. 3 / t, thus the Input ΔC exceeds 40% (40.5%). Figure 4 (The point enclosed by the dashed circle in the diagram). This value is comparable to that of level 2-1, where a large amount of hydrogen is blown in, and levels 2-2 to 2-3, where the amount of hydrogen blown in is slightly larger. Furthermore, the amount of hydrogen blown in level 2-4 is 400 Nm³. 3 / t, less than levels 2-1 to 2-3, and the hydrogen blowing temperature is also lower than 800℃. Furthermore, the hydrogen utilization rate of level 2-4 at this point is 63% (a=260Nm). 3 / t, b=151Nm 3 / t)( Figure 5 (The point enclosed by the dashed circle in the middle).

[0104] As described above, according to the second embodiment, even when the amount of hydrogen-based reducing gas blown in is reduced and the heating temperature of the hydrogen-based reducing gas is lowered, the Input ΔC can still be increased.

[0105] The inventors of this application further investigated the degrees of freedom of operation. The results are displayed... Figure 6 and Figure 7 . Figure 6 The horizontal axis (RBFG injection rate at the tuyeres) represents the injection rate (Nm³) of RBFG from the tuyeres 12 in the blast furnace to the furnace body 10b of the blast furnace 10. 3 / t), the vertical axis represents the combustion temperature at the air outlet (°C). ΔC represents the input ΔC. Figure 6 In the diagram, groups of points with an Input ΔC of 29% or higher but less than 33% are enclosed by dashed lines; groups with an Input ΔC of 33% or higher but less than 38% are enclosed by dashed lines; and groups with an Input ΔC of more than 40% are enclosed by dashed lines. Figure 6 The “normal upper limit” (=2300℃) of the combustion temperature at the front end of the air inlet is the upper limit assumed for normal operation (without the blowing of hydrogen-based reducing gas and RBFG). Figure 7 The horizontal axis represents the combustion temperature at the tuyeres (°C), and the vertical axis represents the exhaust gas temperature at the furnace top (°C). Figure 6 , Figure 7 As a reference example, an example is also shown in level 2-4 where the supply air temperature is 1300°C (BT1300°C) and the hydrogen blowing temperature is 1000°C.

[0106] According to Figure 6 and Figure 7 , the following insights are obtained.

[0107] • By reducing the amount of hydrogen-based reducing gas (i.e., not included in the RBFG) blown from the hydrogen-based reducing gas supply system 2, or increasing the amount of RBFG blown, the raceway front combustion temperature rises.

[0108] In blast furnace operation, it is necessary to operate in such a manner that both the top gas temperature and the raceway front combustion temperature are within appropriate ranges. The top gas temperature depends largely on the flow rate of gas supplied to the blast furnace, and the greater the flow rate of gas per amount of iron produced, the higher the top gas temperature. On the other hand, the raceway front combustion temperature depends largely on the combustion conditions at the raceway front, i.e., the oxygen enrichment rate, and the greater the oxygen enrichment rate, the higher the raceway front combustion temperature. In blast furnace operation, increasing the oxygen enrichment rate = reducing the amount of hot blast blown and reducing the flow rate of gas supplied from the tuyere, so if the oxygen enrichment rate is increased to increase the raceway front combustion temperature, the flow rate of gas supplied to the furnace is reduced and the top gas temperature is reduced. Therefore, if the operation of blowing gas from the general tuyere 11 is assumed, it is difficult to independently control the top gas temperature and the raceway front combustion temperature (since if one side is changed, the other side changes in the opposite direction). In addition, in the case of blowing RBFG to the general tuyere as in the first embodiment, the amount of gas supplied to the furnace can be adjusted by adjusting the amount of RBFG blown, but since gas at a lower temperature than the raceway front combustion temperature is supplied to the blast furnace, increasing the amount of RBFG blown = reducing the raceway front combustion temperature, and it is not possible to independently control the top gas temperature and the raceway front combustion temperature.

[0109] In the case of the second embodiment, the point that gas at a lower temperature than the raceway front combustion temperature is supplied to the furnace is the same as in the first embodiment, but since RBFG is blown from the shaft portion 10b, not from the tuyere portion (the front end of the general tuyere 11) where coke is burned, even if the amount of RBFG blown is operated, the raceway front combustion temperature does not decrease. Therefore, it is possible to increase the amount of RBFG blown to adjust the top gas temperature, and to adjust the oxygen enrichment rate at the tuyere to make the raceway front combustion temperature an appropriate value. This is one of the strong points of the second embodiment (it is good to blow gas at a different place from the general tuyere 11).

[0110] Therefore, the raceway front combustion temperature of the level 2-4 is higher than the raceway front combustion temperature of the levels 2-1 to 2-3. The raceway front combustion temperature of the level 2-4 is sufficiently higher than the lower limit value (2000°C). Also, the top gas temperature of the level 2-4 is also sufficiently higher than the lower limit value (105°C).

[0111] Therefore, in the second embodiment, the degree of freedom of the operation is increased (the range of the parameter specifications of the operation can be designed to be large). Further, if the Input ΔC of levels 2 to 4 exceeds 40%, the combustion temperature at the front end of the tuyere exceeds the upper limit value (2300°C) (the point indicated by the dotted circle A), but the operation can be continued if the countermeasure described above is taken. Figure 6

[0112] <4. Third Embodiment> (4-1. Method of operating the blast furnace according to the third embodiment) Next, the third embodiment of the present application will be described. In the third embodiment, the RBFG is blown into the blast furnace 10 from both the general tuyere 11 and the shaft tuyere 12.

[0113] The method of operating the blast furnace 10 according to the third embodiment is roughly as follows. That is, the iron-based raw material and the coke are alternately and layerwise charged into the blast furnace 10 from the top of the blast furnace 10, and on the other hand, the heated hydrogen-based reducing gas is supplied to the general tuyere 11 from the hydrogen-based reducing gas supply system 2. Further, the hot blast, the pulverized coal, the oxygen-enriched gas, and the heated hydrogen-based reducing gas are blown into the blast furnace 10 from the general tuyere 11. On the other hand, the RBFG is blown into the blast furnace 10 from the general tuyere 11 and the shaft tuyere 12. The hot blast gasifies the pulverized coal and the coke blown together with the hot blast, and a high-temperature reducing gas (mainly CO gas in this case) is 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 it. The hydrogen-based reducing gas and the RBFG rise in the blast furnace 10, and reduce the iron-based raw material while heating it. The iron-based raw material descends in the blast furnace 10, and on the other hand, is heated and reduced by the reducing gas, the hydrogen-based reducing gas, and the RBFG. Further, the iron-based raw material is melted, and drips down in the blast furnace 10 while being further reduced by the coke. The iron-based raw material is finally accumulated in the hearth portion as molten iron (pig iron) containing less than 5% by mass of carbon. The molten iron in the hearth portion is taken out from the tap hole, and supplied to the subsequent steelmaking process.

[0114] On the other hand, the top gas of the blast furnace 10 is discharged. The CO2 separation and recovery device 20 recovers the top gas, and separates it into the reducing gas (CO gas and hydrogen gas) and nitrogen gas (i.e., the RBFG) and the CO2 gas and H2O gas. The CO2 gas and the H2O gas are discharged to the outside of the system.

[0115] The RBFG is temporarily stored in the buffer tank 30. The desired amount of the RBFG is introduced from the buffer tank 30 to the compressor 40. The remaining RBFG is discharged to the outside of the system, and used as a heat source of the ironworks, for example.

[0116] ​Next, the RBFG is pressurized by the compressor 40. Here, the compressor 40 pressurizes the RBFG to, for example, the internal pressure of the blast furnace 10 (around 4.5 atm). The pressurized RBFG is introduced into the heater 50.

[0117] Next, the RBFG is heated by the heater 50. The heating temperature is arbitrarily set according to the operation conditions of the blast furnace 10. The RBFG heated by the heater 50 is blown into the blast furnace 10 from the general tuyere 11 and the shaft tuyere 12. The flowmeter 61 measures the flow rate of the RBFG blown into the blast furnace 10 from the general tuyere 11. The flowmeter 62 measures the flow rate of the RBFG blown into the shaft 10b of the blast furnace 10 from the shaft tuyere 12. Specific examples of the operation method are as described in the first embodiment.

[0118] Here, in the blast furnace operation, for reasons such as performing stable operation, it is preferable to maintain the front-end combustion temperature of the tuyere, the top gas temperature, and the molten iron temperature within a prescribed range. For example, the front-end combustion temperature of the tuyere is preferably maintained at around 2000 to 2300°C, the top gas temperature is preferably maintained at around 105°C or higher, and the molten iron temperature is preferably maintained at around 1520°C or higher. In addition, the upper limit value of the front-end combustion temperature of the tuyere is a value when the usual operation (operation without blowing in the hydrogen-based reducing gas and the RBFG) is assumed. In the case where the front-end combustion temperature of the tuyere exceeds the upper limit value, in order to prevent damage to the tuyere equipment, it is preferable to take measures such as increasing the cooling capacity of the tuyere equipment and using a material with higher heat resistance. The parameter specifications of the blast furnace operation are determined in such a manner that the front-end combustion temperature of the tuyere, the top gas temperature, and the molten iron temperature are maintained within a prescribed range. In addition, as long as the front-end combustion temperature of the tuyere, the top gas temperature, and the molten iron temperature are maintained within a prescribed range, the parameter specifications of the blast furnace operation can be freely designed. In addition, the front-end combustion temperature of the tuyere can exceed the upper limit value as a result of the design, but it is preferable to take the above measures in addition.

[0119] For example, the blowing-in temperature of the hydrogen-based reducing gas (the temperature of the hydrogen-based reducing gas blown in from the general tuyere 11) is preferably around 800 to 1000°C, and the blowing-in amount of hydrogen gas in the hydrogen-based reducing gas is preferably around 300 to 600 Nm 3 / t. Both are ranges lower than those of Patent Document 1. The general tuyere blowing-in temperature of the RBFG (the temperature of the RBFG blown in from the general tuyere 11, that is, the heating temperature of the heater 50) is preferably around 800 to 1000°C, and the general tuyere blowing-in amount of the RBFG is preferably around 100 to 300 Nm 3 / t. Both are ranges lower than those of Patent Document 1. The general tuyere blowing-in temperature of the RBFG (the temperature of the RBFG blown in from the general tuyere 11, that is, the heating temperature of the heater 50) is preferably around 800 to 1000°C, and the general tuyere blowing-in amount of the RBFG is preferably around 100 to 300 Nm 3Approximately / t. In particular, the preferred RBFG injection rate is a combined value of 600 Nm³ for both the general tuyeres and the furnace body tuyeres. 3 / t or more. This is because, as will be explained later, in this case, the Input ΔC exceeds 40%. Other adjustable parameters include the amount of hot blast injected, the amount of oxygen in the hot blast (oxygen injection rate), etc. Additionally, the molten iron temperature can also be adjusted by the amount of pulverized coal injected into the blast furnace 10 or the coke ratio (the amount of coke used per ton of molten iron). For example, the molten iron temperature can be adjusted first by the amount of pulverized coal injected, and even if the amount of pulverized coal injected becomes zero and the molten iron temperature exceeds the specified range, control such as adjusting the coke ratio can be performed. Furthermore, the molten iron temperature is a value reflecting the total heat (furnace heat) within the blast furnace 10. Furthermore, during blast furnace operation, the tuyere tip combustion temperature, furnace top exhaust gas temperature, and molten iron temperature should be monitored periodically (preferably continuously). If any of these temperatures falls outside the aforementioned range, adjustments to the operating conditions (e.g., as described above, at least one of the following: the hydrogen-based reducing gas injection temperature, the amount of hydrogen injected into the hydrogen-based reducing gas, the RBFG injection temperature, the RBFG injection amount, the hot blast injection amount, and the oxygen content in the hot blast (the amount of oxygen-enriched gas injected)) are sufficient. Additionally, the tuyere tip combustion temperature, furnace top exhaust gas temperature, and molten iron temperature are prone to fluctuation when hydrogen-based reducing gas or RBFG is injected; therefore, it is preferable to monitor these temperatures when injecting these gases.

[0120] (3-2. Verification of the effect) Next, the inventors of this application will describe the verification of the effect. In this verification, a blast furnace operation simulation was conducted to verify the effectiveness of the blast furnace operation method of the third embodiment. The simulation model is the same as that of the first embodiment. The prerequisites for the simulation are as follows.

[0121] • Use hydrogen as a hydrogen-based reducing gas.

[0122] The CO2 separation and recovery device 20 separates and removes 100% of the CO2 and H2O gases contained in the exhaust gas from the furnace top.

[0123] • The hydrogen blowing temperature and the RBFG blowing temperature are 800℃.

[0124] • The inlet temperature of the hot air (supply air temperature) is 1200℃.

[0125] • The iron output and molten iron temperature are 12350t / d and 1535℃.

[0126] The exhaust gas temperature at the top of the furnace is 132℃, and the combustion temperature at the front end of the tuyeres is 2196℃.

[0127] • Furnace heat adjustment (adjustment of molten iron temperature) is achieved by adjusting the amount of pulverized coal blown in. Even if the amount of pulverized coal blown in is zero and the molten iron temperature exceeds 1535°C, the coke ratio is adjusted.

[0128] • The amount of hot air and oxygen blown in was adjusted to meet the above prerequisites.

[0129] Under the aforementioned conditions, the following level was simulated. In this level, the hydrogen injection rate was set to 400 Nm³. 3 / t, set the tuyeres blowing into the furnace body of the RBFG to 400 Nm 3 / t, set the general air inlet volume to 200Nm 3 The result is that the Input ΔC is 42.2%.

[0130] As described above, according to the third embodiment, even when the amount of hydrogen injected is reduced and the heating temperature of the hydrogen is lowered, the Input ΔC can still be increased.

[0131] Example Next, embodiments of this implementation will be described. In this embodiment, a blast furnace operation simulation using a blast furnace mathematical model was performed, and the effects of the first to third implementations were confirmed. Embodiment 1 corresponds to the first implementation, Embodiment 2 corresponds to the second implementation, and Embodiment 3 corresponds to the third implementation.

[0132] <1. Example 1> (1-1. Main parameters and specifications) • Use hydrogen as a hydrogen-based reducing gas.

[0133] The CO2 separation and recovery device 20 separates and removes 100% of the CO2 and H2O gases contained in the exhaust gas from the furnace top.

[0134] • The iron output and molten iron temperature are 12350t / d and 1535℃.

[0135] • To maximize carbon reduction benefits, the exhaust gas temperature at the furnace top is set near the lower limit (105°C).

[0136] • Furnace heat adjustment (adjustment of molten iron temperature) is achieved by adjusting the amount of pulverized coal blown in. Even if the amount of pulverized coal blown in is zero and the molten iron temperature exceeds 1535°C, the coke ratio is adjusted.

[0137] • The amount of hot air and oxygen blown in was adjusted to meet the above prerequisites.

[0138] • Hydrogen gas is blown in (blowing temperature 1000℃, blowing rate 325 Nm). 3 / t, the blowing temperature of the hot blast 1300°C, the blowing temperature of the RBFG 1000°C, the blowing amount 600 Nm 3 / t.

[0139] (1-2. Results of simulation) The results of simulation, in Example 1, Input ΔC was 43.2%.

[0140] <2. Example 2> (2-1. Main parameter specifications) • Hydrogen gas was used as the hydrogen-based reducing gas.

[0141] • The CO2 separation and recovery device 20 separates and removes 100% of the CO2 gas and H2O gas contained in the top gas.

[0142] • The blowing temperature of the hydrogen gas and the blowing temperature of the RBFG were 800°C.

[0143] • The blowing temperature (blast temperature) of the hot blast was 1200°C.

[0144] • The tapping amount and the molten iron temperature were 12350 t / d and 1535°C.

[0145] • The top gas temperature was set to 135°C.

[0146] • The furnace heat adjustment (adjustment of the molten iron temperature) was performed by adjusting the blowing amount of the pulverized coal. In the case where the molten iron temperature exceeds 1535°C even if the blowing amount of the pulverized coal is zero, the coke ratio was adjusted.

[0147] • The blowing amount of the hot blast and the blowing amount of oxygen were adjusted to satisfy the above-mentioned prerequisite conditions.

[0148] • The blowing amount of the hydrogen gas was 400 Nm 3 / t, the blowing amount of the RBFG 600 Nm 3 / t.

[0149] (2-2. Results of simulation) The results of simulation, in Example 2, Input ΔC was 40.5%.

[0150] <3. Example 3> (3-1. Main parameter specifications) • Hydrogen gas was used as the hydrogen-based reducing gas.

[0151] • The CO2 separation and recovery device 20 separates and removes 100% of the CO2 gas and H2O gas contained in the top gas.

[0152] • The blowing temperature of the hydrogen gas and the blowing temperature of the RBFG were 800°C.

[0153] • the blowing temperature of the hot blast (blast temperature) is 1200°C.

[0154] • the tapping amount and the temperature of the molten iron are 12350 t / d and 1535°C, respectively.

[0155] • the temperature of the top gas is 132°C, and the combustion temperature at the front end of the tuyere is 2196°C.

[0156] • the furnace heat adjustment (adjustment of the temperature of the molten iron) is performed by adjusting the blowing amount of the pulverized coal. In the case where the temperature of the molten iron exceeds 1535°C even if the blowing amount of the pulverized coal is zero, the coke ratio is adjusted.

[0157] • the blowing amount of the hot blast and the blowing amount of oxygen are adjusted so as to satisfy the above-mentioned prerequisite.

[0158] • the blowing amount of hydrogen is 400 Nm 3 / t, the blowing amount of the shaft portion tuyere of the RBFG is 400 Nm 3 / t, and the general tuyere blowing amount is 200 Nm 3 / t.

[0159] (3-2. Results of the simulation) The results of the simulation are that the Input ΔC in Example 3 is 42.2%.

[0160] Therefore, according to the first to third embodiments, it is possible to improve the Input ΔC even in the case where the blowing amount of the hydrogen-based reducing gas is reduced and the heating temperature of the hydrogen-based reducing gas is lowered.

[0161] The preferred embodiments of the present application have been described in detail with reference to the accompanying drawings. However, the present application is not limited to the above-described examples. Various modifications or changes can be obvious to those skilled in the art to which the present application pertains, provided that they fall within the technical scope recited in the claims. Such modifications or changes naturally belong to the technical scope of the present application.

[0162] Explanation of Reference Numerals 1 blast furnace system; 2 hydrogen-based reducing gas supply system; 10 blast furnace; 10a blast furnace main body; 10b shaft portion; 11 general tuyere; 12 shaft portion tuyere; 20 CO2 separation and recovery device; 30 buffer tank; 40 compressor; 50, 71 heater; 61, 62, 72 flow meter; 70 hydrogen-based reducing gas tank.

Claims

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

2. The method of operating a blast furnace according to claim 1, characterized in that the reducing gas is blown into the blast furnace from a common tuyere provided at a lower portion of the blast furnace.

3. The method of operating a blast furnace according to claim 1 or 2, characterized in that the reducing gas is blown into a shaft portion of the blast furnace.

4. The method of operating a blast furnace according to claim 1, characterized in that an operating condition is adjusted based on a pre-tuyere combustion temperature and a top gas temperature.

5. The method of operating a blast furnace according to claim 4, characterized in that the operating condition includes a blowing amount of the reducing gas, a blowing amount of hot blast, and an oxygen amount contained in the hot blast.

6. The method of operating a blast furnace according to claim 1 or 2, characterized in that the method of operating a blast furnace comprises: a step of heating a hydrogen-based reducing gas supplied from outside a blast furnace system; a step of blowing the heated hydrogen-based reducing gas into a blast furnace from at least one of a common tuyere and a shaft portion tuyere provided at a position higher than the common tuyere; a step of separating a reducing gas from a top gas; a step of heating the separated reducing gas; and a step of blowing the heated reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere, at least one of a timing of blowing the heated hydrogen-based reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere and a timing of blowing the heated reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere, an operating condition of at least one or more of a blowing amount of the reducing gas, a blowing amount of hot blast, and an oxygen amount contained in the hot blast is adjusted based on a pre-tuyere combustion temperature and a top gas temperature.

7. The method of operating a blast furnace according to claim 1 or 2, characterized in that the reducing gas contains CO gas and hydrogen gas separated from the top gas.

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

2. The method of operating a blast furnace according to claim 1, characterized in that the reducing gas is blown into the blast furnace from a common tuyere provided at a lower portion of the blast furnace.

3. The method of operating a blast furnace according to claim 1 or 2, characterized in that the reducing gas is blown into a shaft portion of the blast furnace.

4. The method of operating a blast furnace according to claim 1, characterized in that an operating condition is adjusted based on a pre-tuyere combustion temperature and a top gas temperature.

5. The method of operating a blast furnace according to claim 4, characterized in that the operating condition includes a blowing amount of the reducing gas, a blowing amount of hot blast, and an oxygen amount contained in the hot blast.

6. The method of operating a blast furnace according to claim 1 or 2, characterized in that the method of operating a blast furnace comprises: a step of heating a hydrogen-based reducing gas supplied from outside a blast furnace system; a step of blowing the heated hydrogen-based reducing gas into a blast furnace from at least one of a common tuyere and a shaft portion tuyere provided at a position higher than the common tuyere; a step of separating a reducing gas from a top gas; a step of heating the separated reducing gas; and a step of blowing the heated reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere, at least one of a timing of blowing the heated hydrogen-based reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere and a timing of blowing the heated reducing gas into the blast furnace from at least one of the common tuyere and the shaft portion tuyere, an operating condition of at least one or more of a blowing amount of the reducing gas, a blowing amount of hot blast, and an oxygen amount contained in the hot blast is adjusted based on a pre-tuyere combustion temperature and a top gas temperature.

7. The method of operating a blast furnace according to claim 1 or 2, characterized in that the reducing gas contains CO gas and hydrogen gas separated from the top gas. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images