Blast furnace operation methods

Abstract

This blast furnace operation method is characterized in that a hydrogen-based reducing gas is blown into a blast furnace, a CO2 gas and a H2O gas are separated and removed from a furnace top exhaust gas to generate a reformed furnace top circulating gas, and the reformed furnace top circulating gas is blown into the blast furnace, the method including a step of acquiring a target range of the iron tapping ratio during operation on the basis of the previously acquired relationship between the blowing amount of hydrogen based reducing gas and the total pressure loss, the operating condition being adjusted so that the range of the iron tapping ratio during operation is within the target range of the iron tapping ratio.

Description

[Technical Field]

[0001] This invention relates to a method for operating a blast furnace. This application claims priority based on Japanese Patent Application No. 2024-035001, filed in Japan on March 7, 2024, the contents of which are incorporated herein by reference. [Background technology]

[0002] In the iron and steel industry, the blast furnace method is the dominant process for producing pig iron. In the blast furnace method, blast furnace iron-based raw materials (raw materials containing iron oxide, mainly sintered ore; hereinafter simply referred to as "iron-based raw materials") and coke are alternately and layered into the blast furnace from the top, while hot air is blown into the blast furnace from tuyeres at the bottom. The hot air reacts with the pulverized coal blown in with the hot air and the coke in the blast furnace to generate high-temperature reducing gas (mainly CO gas in this case). In other words, the hot air gasifies the coke and pulverized coal. The reducing gas rises inside the blast furnace, heating and reducing the iron-based raw materials. The iron-based raw materials descend inside the blast furnace, being heated and reduced by the reducing gas. Subsequently, the iron-based raw materials melt and drip down the blast furnace while being further reduced by the coke. Iron-based raw materials are ultimately stored in the hearth as molten pig iron (pig iron) containing slightly less than 5% by mass of carbon. The molten pig iron in the hearth is removed from the tap and used in the next steelmaking process. Therefore, in the blast furnace method, carbon materials such as coke and pulverized coal are used as reducing agents.

[0003] Incidentally, in recent years, with calls for preventing global warming, reducing emissions of carbon dioxide (CO2 gas), one of the greenhouse gases, has become a social issue. As mentioned above, the blast furnace method uses carbon as a reducing agent, thus generating a large amount of CO2 gas. Therefore, the steel industry is one of the major industries in terms of CO2 gas emissions, and it must respond to this social demand. Specifically, further reduction of the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operation is urgently needed.

[0004] Reducing agents play two roles in the furnace: generating heat to raise the temperature of the charge and reducing the iron-based raw materials. To reduce the reducing agent ratio, it is necessary to increase the reduction efficiency in the furnace. The reduction reactions in the furnace can be expressed by various reaction equations. Of these reduction reactions, the direct reduction reaction with coke (reaction equation: FeO + C → Fe + CO) is an endothermic reaction that involves a large amount of heat absorption. Therefore, minimizing the occurrence of this reaction is important in reducing the reducing agent ratio. Since this direct reduction reaction occurs in the lower part of the blast furnace, if the iron-based raw materials can be sufficiently reduced by reducing gases such as CO and H2 before reaching the lower part of the furnace, the amount of iron-based raw materials subject to direct reduction can be reduced.

[0005] As a conventional technology to solve the above problems, for example, as disclosed in Patent Document 1, a technique is known in which hydrogen gas is injected along with hot air from a tuyer to improve the reducing gas potential in the furnace. In this technique, hydrogen gas is used as a reducing gas for iron-based raw materials to reduce the reducing agent ratio. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2021 / 107091 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, in order to further reduce the reducing agent ratio, it was necessary to increase the tapping ratio to improve efficiency, that is, to further improve the efficiency of molten iron production. However, achieving stable high tapping ratio operation presented challenges such as ensuring proper ventilation within the furnace and stabilizing the combustion temperature of the tuyeres.

[0008] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to provide a method for operating a blast furnace that can further improve the efficiency of molten iron production.

Means for Solving the Problem

[0009] The gist of the present invention is as follows. (1) Inject a hydrogen-based reducing gas into the blast furnace, separate and remove CO2 gas and H2O gas from the top gas to produce a reformed top circulating gas, and a method for operating a blast furnace in which the reformed top circulating gas is injected into the blast furnace, including a step of obtaining a target range of the tapping ratio during operation from the relationship between the injection amount of the hydrogen-based reducing gas and the total pressure loss obtained in advance, A method for operating a blast furnace, characterized in that the operating conditions are adjusted so that the range of the tapping ratio during operation falls within the target range of the tapping ratio. " (2) The range of the tapping ratio is 2.7 t / d / m

[0011] , <00,00098>exceeding 3.7 t / d / m 3 The method for operating a blast furnace according to (1), characterized in that it is as follows. " (3) The range of the tapping ratio is 3.0 t / d / m 3 The method for operating a blast furnace according to (2), characterized in that it is as follows. " (4) The method for operating a blast furnace according to any one of (1) to (3), characterized in that the tuyere tip combustion temperature is maintained at 2100 °C or higher. "

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a method for operating a blast furnace capable of further increasing the production efficiency of hot metal. "

Brief Description of the Drawings

[0011] [Figure 1] It is a flowchart showing the overall configuration of the blast furnace system used in the present embodiment. [Figure 2] It is a graph for verifying the effect of the present embodiment. [Figure 3] It is a graph for verifying the effect of the present embodiment. [Figure 4]This graph verifies the effects of this embodiment. [Figure 5] This graph verifies the effects of this embodiment. [Figure 6] This graph verifies the effects of this embodiment. [Figure 7] This graph verifies the effects of this embodiment. [Figure 8] This graph verifies the effects of this embodiment. [Modes for carrying out the invention]

[0012] The inventors conducted simulations of hydrogen gas injection operations and performed a detailed analysis of the internal state of the blast furnace. The results revealed that the pressure loss (total pressure loss) inside the blast furnace was significantly reduced compared to base operation (operation without hydrogen gas injection).

[0013] As will be explained in detail in the examples, increasing the tapping ratio (the amount of molten iron produced per unit volume and unit time (day) of the blast furnace) in hydrogen gas injection operation increases the total pressure drop, while decreasing the amount of carbon fed into the blast furnace (carbon consumption per ton of molten iron). Therefore, increasing the tapping ratio not only increases the efficiency of molten iron production but also decreases carbon consumption. Furthermore, the tapping ratio can be increased to at least near the total pressure drop of base operation.

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0015] <1. Overall configuration of the blast furnace system> First, the overall configuration of the blast furnace system 1 and the hydrogen-based reducing gas supply system 2 connected to the blast furnace system 1 according to this embodiment will be described based on Figure 1. The blast furnace system 1 comprises a blast furnace 10, a CO2 separation and recovery device 20, a buffer tank 30, a compressor 40, and a heater 50.

[0016] The blast furnace 10 comprises a blast furnace body 10a, a conventional tuyere 11, and a shaft tuyere 12. Inside the blast furnace body 10a, a reduction reaction of iron-based raw materials is carried out by the blast furnace method. Specifically, iron-based raw materials and coke are charged into the blast furnace 10 alternately and in layers from the top of the blast furnace 10, while hot air, pulverized coal, and enriched oxygen gas are blown into the blast furnace 10 from the conventional tuyere 11. Furthermore, as will be described later, hydrogen-based reducing gas is also blown into the blast furnace 10 from the conventional tuyere 11 or the shaft tuyere 12. In the following description, "tuyere tip combustion temperature" refers to the temperature at the gas outlet of the conventional tuyere 11. From the viewpoint of stable operation of the blast furnace, it is preferable that the tuyere tip combustion temperature is high and constant. In this regard, as shown in the embodiment described later, the tuyere tip combustion temperature can be maintained at 2100°C or higher in this embodiment. The hot air reacts with the pulverized coal blown in with it and the coke inside the blast furnace 10 to generate high-temperature reducing gas (primarily CO gas in this case). In other words, the hot air gasifies the coke and pulverized coal. As will be described in more detail later, there are cases where pulverized coal is not blown into the blast furnace 10. In this case, the hot air becomes Bosch gas, mainly composed of hydrogen gas, CO gas, and nitrogen gas. The Bosch gas and hydrogen-based reducing gas rise inside the blast furnace 10, heating and reducing the iron-based raw materials. More specifically, the hydrogen gas and CO gas in the Bosch gas and hydrogen-based reducing gas reduce the iron-based raw materials. Subsequently, these gases are discharged from the top of the blast furnace as top exhaust gas. The top exhaust gas contains unreacted hydrogen gas, CO gas, as well as CO2 gas, H2O gas, and nitrogen gas. The iron-based raw materials descend inside the blast furnace 10, while being heated and reduced by the Bosch gas and hydrogen-based reducing gas. Subsequently, the iron-based raw materials melt and are further reduced by coke as they drip through the blast furnace 10. The iron-based raw materials are ultimately accumulated in the hearth as molten pig iron (pig iron) containing slightly less than 5% by mass of carbon. The molten pig iron in the hearth is removed from the tap and used for the next steelmaking process. The tap ratio in this embodiment is (t / d / m 3 ) refers to the amount of molten iron produced per unit volume and per unit time (day) of the blast furnace 10.

[0017] Typically, the tuyeres 11 are located at the bottom of the blast furnace 10 and, in addition to the hot air mentioned above, heated hydrogen-based reducing gas is blown into the blast furnace 10, as will be described later. In this embodiment, the pressure loss from the gas outlet (tuyeres tip) of the tuyeres 11 to the top of the furnace is defined as the "pressure loss inside the blast furnace" (in the following explanation, the "pressure loss inside the blast furnace" will be referred to as the "total pressure loss"). In Figure 1, tuyeres 11 are depicted only at both ends of the blast furnace 10, but three or more may be provided at regular intervals along the circumferential direction. Furthermore, reformed furnace top circulating gas may be blown into the blast furnace 10 from the tuyeres 11.

[0018] The shaft tuyeres 12 are provided on the shaft section 10b of the blast furnace 10, and reformed top-circulating gas (RBFG), which is obtained by reforming the top-circulating exhaust gas, is blown into the shaft section 10b of the blast furnace 10. In Figure 1, the shaft tuyeres 12 are depicted only on the left side of the shaft section 10b, but shaft tuyeres 12 may also be provided on the right side of the shaft section 10b, and three or more may be provided at regular intervals along the circumferential direction. Furthermore, hydrogen-based reducing gas may be blown into the blast furnace 10 from the shaft tuyeres 12.

[0019] The CO2 separation and recovery device 20 recovers the furnace top exhaust gas and separates CO2 gas and H2O gas from it to produce reformed furnace top circulating gas (RBFG). The reformed furnace top circulating gas is a gas containing 20% ​​or more CO gas by volume fraction. The reformed furnace top circulating gas can be, for example, gas recovered and separated from the furnace top exhaust gas, or gas containing CO gas and H2 gas obtained by reforming hydrocarbon gases by general methods such as partial oxidation. It is preferable that the CO2 gas and H2O gas content in the reformed furnace top circulating gas be low. For example, the H2O gas is preferably 10% or less by volume fraction, more preferably 5% or less. Also, the CO2 gas is preferably 5% or less by volume fraction, more preferably 3% or less. Keeping these values ​​below the limit suppresses the influence of the gasification reaction, which is an endothermic reaction. Here, the CO2 separation and recovery device 20 does not necessarily have to recover the entire amount of furnace top exhaust gas. For example, the CO2 separation and recovery unit 20 may recover only the amount of top flue gas corresponding to the flow rate of the reformed top circulating gas (RBFG) injected into the blast furnace. The remaining top flue gas is used as a heat source for the steelworks. The separation method is not particularly limited, but examples include chemical adsorption and physical adsorption (PSA). The separated CO2 gas and H2O gas are discharged outside the system. In the following description, the reformed top circulating gas may also be referred to as "RBFG".

[0020] The buffer tank 30 is a tank for temporarily storing RBFG. The desired amount of RBFG is introduced from the buffer tank 30 to the compressor 40.

[0021] The compressor 40 pressurizes the RBFG. Here, the compressor 40 pressurizes the RBFG to approximately the internal pressure of the blast furnace 10 (about 4.5 atmospheres). The pressurized RBFG is then introduced into the heater 50.

[0022] The heater 50 heats the RBFG. The heating temperature can be set arbitrarily according to the operating conditions of the blast furnace 10, but for example, when the RBFG is blown from the shaft tuyere 12 into the shaft portion 10b of the blast furnace 10, it is preferable to set it to 800°C or higher. The heater 50 can be adequately realized with an electric heater or the like. The RBFG heated by the heater 50 is blown from the shaft tuyere 12 into the shaft portion 10b of the blast furnace 10. In Figure 1, the RBFG is blown into the blast furnace 10 from the left shaft tuyere 12, but the RBFG may also be blown into the blast furnace 10 from the right shaft tuyere 12 (not shown). The RBFG may normally be blown into the blast furnace 10 from both the tuyere 11 and the shaft tuyere 12, or normally from the tuyere 11.

[0023] Amount of RBFG injected into blast furnace 10 (Nm 3 / t) can be set arbitrarily according to the operating conditions of the blast furnace 10.

[0024] The hydrogen-based reducing gas supply system 2 comprises a hydrogen-based reducing gas tank 70 and a heater 71. The hydrogen-based reducing gas tank 70 stores hydrogen-based reducing gas. Here, hydrogen-based reducing gas refers to a gas in which H is present in an elemental composition ratio of 30 mol% or more and which exists as a gas under standard conditions (0°C, 1 atm). For example, H2 gas, unsaturated hydrocarbon gases (C2H4, C2H2, C3H6, etc.), saturated hydrocarbon gases (CH4, C2H6, etc.), NH3 gas, coke oven gas, city gas, natural gas, etc. and mixtures thereof. Particularly preferred are H2 gas and unsaturated hydrocarbon gases (C2H4, C2H2, C3H6, etc.). H2 gas is preferable from the viewpoint of reducing carbon consumption per unit because it does not contain carbon and does not cause a thermal decomposition reaction at the tuyeres. It is also preferable from the viewpoint of permeability in the blast furnace because the viscosity and density of the gas are low. Furthermore, while the hydrogen-based reducing gas may be injected into the blast furnace at room temperature, it is preferable that it be injected in a heated state in order to supply heat to the blast furnace. The heating temperature of the hydrogen-based reducing gas is, for example, 500°C or higher, 1000°C or higher, or 1200°C or higher. It is more preferable that the elemental composition ratio of H in the hydrogen-based reducing gas is 50 mol% or higher. The hydrogen-based reducing gas may also be a mixed gas with other gases (e.g., N2 gas) (without impairing the effects of this embodiment). The hydrogen-based reducing gas tank 70 supplies the hydrogen-based reducing gas to the heater 71.

[0025] The heater 71 heats the hydrogen-based reducing gas. The hydrogen-based reducing gas heated in the heater 71 is blown into the blast furnace 10. Therefore, in this embodiment, hydrogen gas injection operation is performed. The heater 71 can be adequately implemented with an electric heater or the like. Heating temperature and injection amount (Nm³) of the hydrogen-based reducing gas. 3 / t) can be set arbitrarily according to the operating conditions of the blast furnace 10. In Figure 1, the heater 71 is shown as being normally connected to the tuyere 11, but the heater 71 may also be connected to the shaft tuyere 12.

[0026] As will be described later, when a hydrogen-based reducing gas is blown into the blast furnace 10, the total pressure loss significantly decreases compared to the base operation (operation without blowing a hydrogen-based reducing gas into the blast furnace 10) (see Fig. 2). On the other hand, when the tapping ratio is increased, the total pressure loss tends to increase (see Fig. 3). Furthermore, when the tapping ratio is increased, the amount of carbon per ton of hot metal charged into the blast furnace 10 (hereinafter also referred to as carbon consumption) decreases. Therefore, increasing the tapping ratio not only increases the production efficiency of hot metal but also reduces the carbon consumption. Furthermore, the tapping ratio can be increased at least up to near the total pressure loss of the base operation. Specifically, the tapping ratio can be set to be more than 2.7 t / d / m 3 exceeding 3.7 t / d / m 3 as follows. The tapping ratio of 2.7 t / d / m 3 or less can be achieved even in the base operation. When the tapping ratio exceeds 3.7 t / d / m 3 the total pressure loss deteriorates compared to the base operation. The tapping ratio is preferably 3.0 t / d / m 3 or less. In this case, the total pressure loss becomes particularly low.

[0027] As a method for increasing the tapping ratio, for example, increasing the blowing amount of hot air, increasing the blowing amount of a hydrogen-based reducing gas, increasing the blowing amount of RBFG, etc. can be considered. Furthermore, since the total pressure loss decreases, fine iron-based raw materials and coke that could not be used in the base operation due to an increase in pressure loss can be used. Thereby, resources can be effectively utilized.

[0028] <2. Operating Method of Blast Furnace> Next, the operating method of the blast furnace will be described. First, while charging iron-based raw materials and coke into the blast furnace 10 alternately and in layers from the top of the blast furnace 10, hot air, pulverized coal, and enriched oxygen gas are blown into the blast furnace 10 from the normal tuyere 11. Here, in the operating method of the blast furnace according to the present embodiment, since the total pressure loss decreases, fine iron-based raw materials and coke that could not be used in the base operation due to an increase in pressure loss can be used. Thereby, resources can be effectively utilized.

[0029] Meanwhile, the hydrogen-based reducing gas tank 70 supplies hydrogen-based reducing gas to the heater 71. The heater 71 heats the hydrogen-based reducing gas. Here, the heating temperature is set arbitrarily according to the operating conditions of the blast furnace 10, but it may be set to a temperature similar to that of hot air (for example, around 1200°C). Next, the heated hydrogen-based reducing gas is blown into the blast furnace 10. By blowing hydrogen-based reducing gas into the blast furnace 10, the total pressure drop can be reduced. Furthermore, by increasing the amount of hydrogen-based reducing gas injected, the tapping ratio can be increased to near the total pressure drop in base operation. The amount of hydrogen-based reducing gas injected into the blast furnace can be set arbitrarily according to the operating conditions of the blast furnace 10 based on the range of the tapping ratio obtained from the process of obtaining the target range of the tapping ratio, which will be described later.

[0030] (Process for obtaining the target range of the pig iron production ratio) In this embodiment, it is desirable to obtain in advance the relationship between the amount of hydrogen-based reducing gas injected and the total pressure drop, for example, by simulation. The range of the feasible tapping ratio can be obtained from the difference between the total pressure drop value corresponding to the amount of hydrogen-based reducing gas injected and the total pressure drop value in base operation. Specifically, the tapping ratio is 2.7 t / d / m 3 Ultra-high 3.7 t / d / m 3 The following can be achieved. Note that the "operable tapping ratio range" refers to the range of operating conditions in which stable operation is possible without the tuyere combustion temperature rising too high. In this embodiment, the above-mentioned operable tapping ratio range is set as the "target range of tapping ratio during operation," and the blast furnace is operated by adjusting the operating conditions. This makes it possible to further increase the efficiency of molten iron production.

[0031] The hot air reacts with the pulverized coal blown in with it and the coke inside the blast furnace 10 to generate high-temperature reducing gas (primarily CO gas in this case). In other words, the hot air gasifies the coke and pulverized coal. As a result, the hot air becomes Bosch gas, mainly composed of hydrogen gas, CO gas, and nitrogen gas. The Bosch gas and hydrogen-based reducing gas rise inside the blast furnace 10, heating and reducing the iron-based raw materials. More specifically, the hydrogen gas and CO gas in the Bosch gas and hydrogen-based reducing gas reduce the iron-based raw materials. Subsequently, these gases are discharged from the top of the blast furnace as top exhaust gas. The top exhaust gas contains unreacted hydrogen gas, CO gas, as well as CO2 gas, H2O gas, and nitrogen gas. The iron-based raw materials descend inside the blast furnace 10, while being heated and reduced by the Bosch gas and hydrogen-based reducing gas. Subsequently, the iron-based raw materials melt and are further reduced by the coke as they drip down inside the blast furnace 10. The iron-based raw materials are ultimately stored in the hearth as molten pig iron (pig iron) containing slightly less than 5% carbon by mass. The molten pig iron from the hearth is removed from the tap and used in the next steelmaking process.

[0032] The top exhaust gas is introduced into the CO2 separation and recovery unit 20. The CO2 separation and recovery unit 20 recovers the top exhaust gas and separates and removes CO2 gas and H2O gas from the top exhaust gas to produce RBFG. The buffer tank 30 temporarily stores the RBFG. The desired amount of RBFG is introduced from the buffer tank 30 into the compressor 40.

[0033] The compressor 40 pressurizes the RBFG. Here, the compressor 40 pressurizes the RBFG to approximately the internal pressure of the blast furnace 10 (about 4.5 atmospheres). The pressurized RBFG is then introduced into the heater 50.

[0034] The heater 50 heats the RBFG. The heating temperature is set arbitrarily according to the operating conditions of the blast furnace 10, but for example, when the RBFG is blown from the shaft tuyere 12 into the shaft portion 10b of the blast furnace 10, it is preferable to set it to 800°C or higher. The RBFG heated in the heater 50 is blown from the shaft tuyere 12 into the shaft portion 10b of the blast furnace 10.

[0035] Amount of RBFG injected into blast furnace 10 (Nm 3 The t) can be set arbitrarily according to the operating conditions of the blast furnace 10. The tapping ratio can be increased by increasing the amount of RBFG injected into the blast furnace 10.

[0036] As explained above, according to this embodiment, since hydrogen-based reducing gas is injected into the blast furnace 10, the total pressure drop can be reduced. Furthermore, increasing the tapping ratio increases the total pressure drop, but reduces carbon consumption. For this reason, the tapping ratio can be increased until the total pressure drop is about the same as that of base operation. In this way, it becomes possible to obtain a target range for the tapping ratio during operation from the relationship between the amount of hydrogen-based reducing gas injected and the total pressure drop obtained in advance, and to adjust the operating conditions so that the tapping ratio during operation falls within the target range. Specifically, in this embodiment, the tapping ratio is 2.7 t / d / m 3 Ultra-high 3.7 t / d / m 3 It can be increased to the following level. This will further improve the efficiency of molten iron production. Also, the tapping ratio is 3.0 t / d / m 3 The following is preferable. Furthermore, by reducing the total pressure drop, it becomes possible to use iron-based raw materials and coke with particle sizes that could not be used in base operation. In addition, in this embodiment, the tuyere combustion temperature can be maintained at 2100°C or higher. Furthermore, the operating conditions are adjusted, for example, by the airflow rate, oxygen enrichment rate, coke ratio, and the amount of pulverized coal blown in. [Examples]

[0037] Next, an embodiment of this design will be described. In this design, a simulation of blast furnace operation was performed to verify the effectiveness of this design. Here, the simulation model used was the so-called "blast furnace mathematical model" shown in Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace," ISIJ International, Vol.39 (1999), No.1, pp.15-22, etc. This blast furnace mathematical model basically defines multiple meshes (small regions) by dividing the internal region of the blast furnace in the height, radial, and circumferential directions, and simulates the behavior of each mesh.

[0038] For blast furnace operation, we considered base operation (operation without hydrogen gas injection) and hydrogen injection operation (example) in which hydrogen gas is normally injected into the blast furnace 10 from tuyere 11 while RBFG is injected into the blast furnace 10 from shaft tuyere 12. The specifications common to each operation are as follows.

[0039] The distribution of iron-based raw materials and coke charged from the top of the furnace was kept constant. The CO2 separation and recovery device 20 is designed to completely separate and remove CO2 gas and H2O gas contained in the furnace top exhaust gas. The molten iron temperature was set to 1535°C. Furnace temperature adjustment (molten iron temperature adjustment) was performed by adjusting the pulverized coal ratio and coke ratio. Other specifications are shown in Table 1 below.

[0040] [Table 1]

[0041] The results are shown in Figures 2 to 8. Figure 2 shows a production ratio of 2.75 t / d / m 3 This graph shows the relationship between the total pressure loss and the hydrogen injection rate, assuming a constant pressure. The horizontal axis represents the hydrogen injection rate (Nm³). 3The graph shows the pressure drop (kPa) on the vertical axis. Base operation (hydrogen injection rate: 0 Nm³) 3 At t), the total pressure drop was 90 kPa. However, it can be seen that the total pressure drop decreases by increasing the hydrogen injection rate. In particular, when the hydrogen injection rate is 700 Nm³ 3 During operation at / t, the total pressure drop is reduced to approximately 46kPa. This is mainly due to two effects: (1) the low density and low viscosity of the hydrogen-based reducing gas reduces gas resistance, and (2) the direct reduction reaction by the hydrogen-based reducing gas improves the melting properties of the ore in the fusion zone. Due to these effects, the total pressure drop can be reduced by injecting hydrogen-based reducing gas into the blast furnace. This study provides a relationship between the amount of hydrogen-based reducing gas injected and the total pressure drop.

[0042] Next, we will examine Figures 3 and 4. Figure 3 shows the amount of hydrogen-based reducing gas injected at 600 Nm³. 3 This figure shows the relationship between the total pressure loss and the tapping ratio when operating at a constant rate of t / d / m. The horizontal axis of Figure 3 represents the tapping ratio (t / d / m). 3 The graph shows the relationship between the tapping ratio and the total pressure loss (kPa) on the vertical axis. Point P1 shows the relationship between the tapping ratio and the total pressure loss in the example, and graph L1 is the approximate straight line of point P1. Graph L2 shows the total pressure loss in base operation. In base operation, the tapping ratio (Po) is 2.7 t / d / m 3 The total pressure drop was 90 kPa. As shown in graph L1, in this embodiment, increasing the tapping ratio also increases the total pressure drop, but there is a region where the total pressure drop is lower than that of base operation. Specifically, when the tapping ratio is 3.7 t / d / m 3 In the region below the intersection of graphs L1 and L2, the total pressure drop in the example is lower than the total pressure drop in base operation. Therefore, in the example, the tapping ratio is 2.7 t / d / m 3 Ultra-high 3.7 t / d / m 3 It can be increased to the following levels. In this way, the target range of the pig iron production ratio during operation is obtained from the relationship between the amount of hydrogen-based reducing gas injected and the total pressure drop, which was acquired in advance.

[0043] Figure 4 shows the amount of hydrogen-based reducing gas injected at 600 Nm³. 3This figure shows the relationship between carbon consumption and the tapping ratio when operating at a constant rate of t / d / m. The horizontal axis of Figure 4 is the tapping ratio (t / d / m). 3 The graph shows the relationship between the tapping ratio and carbon consumption in the example, with the vertical axis representing carbon consumption per ton of molten iron (carbon input to the blast furnace) (kg / t). Point P3 shows the relationship between the tapping ratio and carbon consumption in the example, and graph L3 is the approximate straight line of point P3. As graph L3 shows, increasing the tapping ratio reduces carbon consumption. Therefore, 2.7 t / d / m 3 Ultra-high 3.7 t / d / m 3 The following is the target range for the tapping ratio. By increasing the tapping ratio to this target range, the efficiency of molten iron production can be further increased, and carbon consumption can be reduced. In this way, carbon consumption can be reduced by adjusting the blast furnace operating conditions to fall within the obtained target range for the tapping ratio.

[0044] Figures 5-7 show the amount of hydrogen-based reducing gas injected at 600 Nm³. 3 This figure shows the results of an investigation into why carbon consumption decreased with increasing the tapping ratio when operating at a constant rate of / t. The horizontal axis of Figure 5 is the tapping ratio (t / d / m). 3 The graph shows the relationship between the tapping ratio and the reduction ratio of hydrogen gas in the example, and the vertical axis shows the various reduction ratios (the proportion of the reduction reaction of each gas in the total reduction reaction) (%). Point P4 shows the relationship between the tapping ratio and the reduction ratio of hydrogen gas in the example, and graph L4 is the approximate curve for point P4. Point P5 shows the relationship between the tapping ratio and the reduction ratio of CO gas in the example, and graph L5 is the approximate curve for point P5. Point P6 shows the relationship between the tapping ratio and the reduction ratio of carbon (reduction ratio of direct reduction) in the example, and graph L6 is the approximate curve for point P6. Table 2 shows the relationship between the tapping ratio of 2.7 t / d / m 3 The total heat required for the reduction reaction (MJ / t) is shown based on the value obtained when the following condition is met. The values ​​in the upper row of Table 2 represent the pig iron production ratio.

[0045] [Table 2]

[0046] As shown in Figure 5 and Table 2, as the pig extraction ratio increases, the ratio of hydrogen gas and carbon reduction reactions (i.e., the ratio of endothermic reactions) increases, and the ratio of CO gas reduction reactions (i.e., the ratio of exothermic reactions) decreases. Therefore, as the pig extraction ratio increases, the amount of heat required increases. In other words, carbon consumption increases.

[0047] The horizontal axis in Figure 6 represents the tapping ratio (t / d / m). 3 The graph shows the relationship between the tapping ratio and the Si content in the molten iron (mass%) on the vertical axis. Point P7 shows the relationship between the tapping ratio and the Si content in the molten iron in the example, and graph L7 is the approximation curve for point P7. Table 3 shows the relationship when the tapping ratio is 2.7 t / d / m 3 The required heat (MJ / t) for the reduction reaction of SiO2 is shown based on the following condition. Note that the SiO2 here refers to the SiO2 in the iron-based raw material. The values ​​in the upper row of Table 3 are the pig production ratio.

[0048] [Table 3]

[0049] As shown in Figure 6 and Table 3, the Si content in the molten iron decreases as the tapping ratio increases, and therefore the amount of heat required to reduce SiO2 decreases as the tapping ratio increases. In other words, carbon consumption decreases.

[0050] The horizontal axis in Figure 7 represents the tapping ratio (t / d / m). 3 The graph shows the relationship between the tapping ratio and heat loss, with the vertical axis representing the heat loss of the blast furnace (value per ton of molten iron) (MJ / t). Here, heat loss is the amount of heat removed from the blast furnace. Point P8 shows the relationship between the tapping ratio and heat loss in the example, and graph L8 is the approximation curve for point P8. Graph L9 shows the heat loss in base operation (tapping ratio of 2.7). Table 4 shows the relationship between the tapping ratio of 2.7t / d / m 3 The heat loss (MJ / t) is shown based on the value at which this occurs. The values ​​in the upper row of Table 4 are the pig iron production ratios.

[0051] [Table 4]

[0052] As shown in Figure 7 and Table 4, heat loss decreases as the pig iron extraction ratio increases. In other words, carbon consumption decreases.

[0053] In summary, Figures 5-7 and Tables 2-4 suggest that carbon consumption decreases as the pig iron production ratio increases. Therefore, the results shown in Figure 3 are likely to be obtained.

[0054] Figure 8 shows the results of the investigation into the combustion temperature at the tuyere tip. The horizontal axis of Figure 8 is the tapping ratio (t / d / m). 3 The graph shows the tuyere combustion temperature (°C) on the vertical axis. Point P10 shows the relationship between the tapping ratio and the tuyere combustion temperature in the example, and graph L11 shows the tuyere combustion temperature in base operation (tapping ratio 2.7). As shown in Figure 8, the tuyere combustion temperature can be maintained at 2100°C or higher in the example.

[0055] As explained above, according to this embodiment, since hydrogen-based reducing gas is injected into the blast furnace 10, the total pressure drop can be reduced. Furthermore, increasing the tapping ratio increases the total pressure drop, but reduces carbon consumption. For this reason, the tapping ratio can be increased until the total pressure drop is about the same as that of base operation. Specifically, the tapping ratio is 2.7 t / d / m 3 Ultra-high 3.7 t / d / m 3 It can be increased to the following level. This will further improve the efficiency of molten iron production. The tapping ratio is 3.0 t / d / m 3 The following is preferable. Furthermore, by reducing the total pressure drop, it becomes possible to use iron-based raw materials and coke with particle sizes that could not be used in base operation. In addition, in this embodiment, the tuyere combustion temperature can be maintained at 2100°C or higher.

[0056] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Explanation of Symbols]

[0057] 1. Blast furnace system 2. Hydrogen-based reducing gas supply system 10 blast furnace 10a Blast furnace body 10b Shaft section 11 Normal tuyere 12 Shaft section tuyere 20 CO2 Separation and Recovery Device 30 buffer tanks 40 Compressors 50, 71 heater 70 Hydrogen-based reduction gas tank

Claims

1. A hydrogen-based reducing gas is injected into the blast furnace. CO2 from the top exhaust gas of the furnace ２ Gas and H ２ O gas is separated and removed to generate a reformed furnace top circulation gas. A method for operating a blast furnace, comprising injecting the reformed top circulating gas into the blast furnace, In advance, The relationship between the amount of hydrogen-based reducing gas injected and the total pressure loss, The relationship between the total pressure loss and the tapping ratio, The process includes obtaining the target range of the pig iron production ratio during operation, A method for operating a blast furnace, characterized by adjusting the operating conditions so that the range of the pig iron production ratio during operation falls within the target range of the pig iron production ratio.

2. The aforementioned tapping ratio range is 2.7 t / d / m ３ Ultra-high 3.7 t / d / m ３ The method for operating a blast furnace according to claim 1, characterized in that it is as follows.

3. The aforementioned tapping ratio range is 3.0 t / d / m ３ The method for operating a blast furnace according to claim 2, characterized in that it is as follows.

4. A method for operating a blast furnace according to any one of claims 1 to 3, characterized in that the combustion temperature of the tuyere tip is maintained at 2100°C or higher.

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