Method for determining blast furnace operating conditions and method for operating a blast furnace

Abstract

The present invention aims to provide a method for determining the operating conditions of a blast furnace and a method for operating a blast furnace, which determine the amount of hydrogen-based reducing gas injected into the blast furnace, enabling stable blast furnace operation and efficient CO2 reduction. [Solution] A method for determining the operating conditions of a blast furnace according to one aspect of the present invention includes: a first step of determining a first relationship, which is the relationship between the amount of sensible heat input into the blast furnace by hydrogen-based reducing gas and hot air, and the reduction ratio of carbon consumption per unit compared to operation without the injection of hydrogen-based reducing gas, and a second relationship, which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace; and a second step of determining the amount of sensible heat input so that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas injected so that the direct reduction rate of ore by carbon in the blast furnace is 5% or less based on the second relationship.

Description

[Technical Field]

[0001] The present invention relates to a method for determining the operating conditions of a blast furnace and a method for operating a blast furnace. [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. High-temperature reducing gas (mainly CO gas in this case) is generated by the reaction of pulverized coal blown in with the hot air and the coke in the blast furnace. 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 a reservoir at the bottom of the furnace as molten pig iron (pig iron) containing slightly less than 5% by mass of carbon. The molten pig iron in the reservoir 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, global warming has become a social problem in recent years, and as a countermeasure, there is a demand to reduce emissions of carbon dioxide, one of the greenhouse gases. In the blast furnace method described above, carbon is used as a reducing agent to produce large quantities of pig iron, so a large amount of CO2 is generated. Therefore, the steel industry is one of the major industries in terms of CO2 emissions, and it must respond to this social demand. Specifically, in order to reduce CO2 emissions, it is important to further reduce the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operation.

[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, minimizing the occurrence of the direct reduction reaction by coke (reaction equation: FeO + C ⇒ Fe + CO) 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. Note that the direct reduction reaction by coke is an endothermic reaction that involves a large amount of endothermic heat.

[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 blown in 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] As disclosed in Patent Document 1, the inventors have defined a parameter called the reduction rate of carbon consumption per unit (Input △C) as an indicator parameter for reducing the reducing agent ratio. "Carbon consumption per unit (Input C)" is the amount of carbon required to produce 1 ton of molten iron (i.e., the amount of carbon consumed per ton of molten iron). "The reduction rate of carbon consumption per unit (Input △C)" means the reduction rate of carbon consumption per unit compared to base operation, which is operation without blowing in a hydrogen-based reducing gas. If the Input C for base operation in units of kg / t_pig is A, and the Input C for a certain operation in units of kg / t_pig is B, then Input △C is expressed by the following formula. Input △C = (AB) / A × 100 (%) The larger the reduction rate of carbon consumption per unit (Input △C), the lower the reducing agent ratio, and consequently, the lower the CO2 emissions. Note that " / t_pig" means per ton of molten iron.

[0008] In the blast furnace process, the combustion of coke and pulverized coal in front of the tuyeres is one of the heat sources in the blast furnace. When the amount of carbon (input carbon) introduced into the blast furnace decreases due to the injection of hydrogen-based reducing gases such as hydrogen gas, the amount of air blown in to burn the input carbon and the amount of enriched oxygen supplied to the blast furnace are reduced accordingly. As a result, the amount of sensible heat introduced into the blast furnace decreases. However, a sufficient amount of sensible heat is necessary to produce molten iron, including ensuring reactivity. Therefore, simply increasing the amount of hydrogen-based reducing gas supplied to the blast furnace may not allow for stable operation of the blast furnace or may not yield the desired Input ΔC.

[0009] The present invention has been made in view of the above problems, and aims to provide a method for determining the operating conditions of a blast furnace and a method for operating a blast furnace, which determine the amount of hydrogen-based reducing gas injected into the blast furnace, enabling stable operation of the blast furnace and efficiently reducing CO2. [Means for solving the problem]

[0010] As will be explained in detail later, the inventors have found that when the amount of hydrogen-based reducing gas injected is small relative to the amount of sensible heat injected, the direct reduction reaction by carbon is promoted, making it difficult to improve Input ΔC. For example, if the amount of hydrogen-based reducing gas injected is kept constant and the amount of sensible heat injected is increased by raising the air temperature (hot air temperature) and the temperature of the hydrogen-based reducing gas, the amount of hydrogen-based reducing gas injected relative to the amount of sensible heat injected becomes small. In such a case, the amount of carbon injected decreases due to the injection of hydrogen-based reducing gas, but because the amount of hydrogen-based reducing gas injected is insufficient, the indirect reduction by CO cannot be adequately replaced by the hydrogen-based reducing gas, and the deficiency is compensated for by direct reduction by carbon. Based on this finding, the inventors conceived of adjusting the amount of hydrogen-based reducing gas injected relative to the amount of sensible heat injected to efficiently obtain the desired Input ΔC, and thus came to present invention.

[0011] Based on the above findings, the gist of the present invention is as follows: [1] A method for determining the operating conditions of a blast furnace according to one aspect of the present invention is a method for determining the operating conditions of a blast furnace into which at least a hydrogen-based reducing gas and hot air are blown, and includes a first step of determining a first relationship which is the relationship between the amount of sensible heat input into the blast furnace by the hydrogen-based reducing gas and the hot air and the reduction ratio of carbon consumption per unit compared to operation without the hydrogen-based reducing gas, and a second relationship which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace, and a second step of determining the amount of sensible heat input such that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas to be blown in such that the direct reduction rate of ore by carbon in the blast furnace is below a threshold based on the second relationship. [2] In the method for determining the operating conditions of the blast furnace described in [1] above, the first and second relationships may be determined according to the amount of iron produced, the molten iron temperature, and the top gas temperature. [3] In the method for determining the operating conditions of the blast furnace described in [1] or [2] above, the first and second relationships may be determined according to the amount of hydrogen-based reducing gas injected. [4] In the method for determining the operating conditions of a blast furnace described in any of [1] to [3] above, the first and second relationships may be determined according to the hydrogen concentration of the hydrogen-based reducing gas.

[0012] [5] Another embodiment of the present invention provides a method for determining the operating conditions of a blast furnace, in which at least a hydrogen-based reducing gas and hot air are injected, comprising: a first step of determining a first relationship, which is the relationship between the amount of sensible heat injected into the blast furnace by the hydrogen-based reducing gas and the hot air, and the reduction ratio of carbon consumption per unit of operation compared to operation without the injection of the hydrogen-based reducing gas; and a third relationship, which is the relationship between the amount of sensible heat injected and the amount of solution loss carbon per ton of molten iron; and a second step of determining the amount of sensible heat injected so that it corresponds to the reduction ratio of carbon consumption per unit of operation based on the first relationship, and determining the amount of hydrogen-based reducing gas injected so that the amount of solution loss carbon is 30 kg / t_pig or less based on the third relationship.

[0013] [6] A further embodiment of the present invention relates to a blast furnace operation method in which at least a hydrogen-based reducing gas and hot air are blown into the blast furnace, and includes a first step of determining a first relationship which is the relationship between the amount of sensible heat input into the blast furnace by the hydrogen-based reducing gas and the hot air and the reduction ratio of carbon consumption per unit compared to operation without the hydrogen-based reducing gas, and a second relationship which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace, and a second step of determining the amount of sensible heat input such that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas to be blown in such that the direct reduction rate of ore by carbon in the blast furnace is below a threshold based on the second relationship. [Effects of the Invention]

[0014] According to the present invention, stable operation of a blast furnace is possible, and CO2 emissions can be reduced efficiently. [Brief explanation of the drawing]

[0015] [Figure 1] It is a schematic diagram showing an example of a hot metal production facility including a blast furnace to which an operation method of a blast furnace according to an embodiment of the present invention can be applied. [Figure 2] It is a schematic diagram showing an example of a hot metal production facility to which the operation method of a blast furnace according to the embodiment can be applied. [Figure 3] It is a graph showing Input ΔC with respect to the amount of H2 gas blown when the blast temperature and the amount of H2 gas blown are changed. [Figure 4] It is a graph showing Input ΔC with respect to the sensible heat input amount when the blast temperature and the amount of H2 gas blown are changed. [Figure 5] It is a graph showing Input ΔC with respect to the sensible heat input amount when the blast temperature and the amount of H2 gas blown are changed. [Figure 6] It is a graph showing the reduction rate of ore by CO (CO reduction rate) with respect to the sensible heat input amount for each amount of H2 gas blown. [Figure 7] It is a graph showing the reduction rate of ore by H2 (H2 reduction rate) with respect to the sensible heat input amount for each amount of H2 gas blown. [Figure 8] It is a graph showing the reduction rate of ore by carbon (direct reduction rate) with respect to the sensible heat input amount for each amount of H2 gas blown. [Figure 9] It is a graph showing the relationship (first relationship) between the sensible heat input amount for each amount of H2 gas blown and Input ΔC in Example 1. [Figure 10] It is a graph showing the relationship (second relationship) between the sensible heat input amount for each amount of H2 gas blown and the direct reduction rate in Example 1. [Figure 11] It is a graph showing the relationship (third relationship) between the sensible heat input amount for each amount of H2 gas blown and the SLC amount in Example 1. [Figure 12] It is a graph showing the relationship (first relationship) between the sensible heat input amount for each amount of COG gas blown and Input ΔC in Example 2. [Figure 13] It is a graph showing the relationship (second relationship) between the sensible heat input amount for each amount of COG gas blown and the direct reduction rate in Example 2. [Figure 14]This graph shows the relationship (third relationship) between the amount of sensible heat input and the amount of SLC for each COG injection rate in Example 2. [Modes for carrying out the invention]

[0016] The embodiments of the present invention will be described below with reference to the drawings. The dimensions and proportions of each component shown in the drawings do not represent the actual dimensions and proportions of each component.

[0017] <Outline configuration of molten iron production equipment> First, before describing the method for determining the operating conditions of a blast furnace and the method for operating a blast furnace according to the embodiment of the present invention, an example of a molten iron production facility will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing an example of a molten iron production facility equipped with a blast furnace. Figure 2 is a schematic diagram showing an example of a blast furnace.

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

[0019] [Blast furnace 1] Blast furnace 1 is equipment that produces molten iron by reducing iron-based raw materials. As shown in Figure 2, blast furnace 1 comprises a furnace body 10, tuyeres 11, main air supply pipe 12, branch air supply pipes 13, pulverized coal injection lance 14, reducing gas injection lance 15, tapping port 16, and a swirling chute 17.

[0020] The furnace body 10 is a vertical reaction vessel with an open top. The furnace body 10 is formed of a hollow iron shell, a refractory material lined to the inner surface of the iron shell, and staves. The furnace body 10 comprises a shaft section 10a, a belly section 10b, a Bosch section 10c, and a hearth section 10d. The shaft section 10a, belly section 10b, Bosch section 10c, and hearth section 10d are arranged in this order from the top 10e to the bottom 10f. The bottom 10f is provided with a reservoir section 101 for storing molten iron produced by the reduction of iron-based raw materials inside the furnace body 10. Iron-based raw materials and coke are charged into the furnace body 10 from the top 10e by various known methods, and molten iron is produced by the reduction of iron-based raw materials inside the furnace body 10.

[0021] The shaft portion 10a has a tapered cylindrical shape that widens towards the bottom. The shaft portion 10a has a flared shape, with the diameter increasing towards the bottom.

[0022] The belly section 10b is cylindrical. The belly section 10b has a straight body shape, and its diameter is constant at each position in the vertical direction.

[0023] The Bosch section 10c has a tapered cylindrical shape that decreases in diameter towards the bottom. The Bosch section 10c has a tapered shape, with its diameter decreasing towards the bottom.

[0024] The hearth section 10d is located at the lower end of the furnace body 10. The hearth section 10d is approximately cylindrical in shape. In the illustrated example, the inner diameter of the hearth section 10d decreases in stages towards the bottom. A tap port 16 is provided in the hearth section 10d. Molten iron produced by the reduction of iron-based raw materials is stored in the hearth section 10d. The molten iron stored in the hearth section 10d is removed from the furnace through the tap port 16.

[0025] Multiple tuyeres 11 are provided on the furnace wall of the hearth section 10d at intervals from each other in the circumferential direction of the furnace. Hot air and hydrogen-based reducing gas are blown into the furnace of the furnace body 10 from the tuyeres 11. Pulverized coal may also be blown in from the tuyeres 11. The hot air contains enriched oxygen gas. 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). Examples of hydrogen-based reducing gases include 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 hydrogen-based reducing gases are H2 gas and unsaturated hydrocarbon gases (C2H4, C2H2, C3H6, etc.). H2 gas is preferable from the viewpoint of reducing carbon consumption per unit area because it does not contain carbon and does not undergo thermal decomposition reactions at the tuyeres. It is also preferable from the viewpoint of permeability within the blast furnace because of its low viscosity and density. Unsaturated hydrocarbon gases are preferable because they contain double and triple bonds in their gas molecules, resulting in a relatively large heat of combustion per mole of oxygen, and they also act as a heat source at the tuyeres. Hydrogen-based reducing gases (excluding unsaturated hydrocarbon gases) may be blown into the blast furnace at room temperature, but it is preferable that they be blown in after being heated in order to supply heat to the blast furnace. The temperature of the hydrogen-based reducing gas is, for example, 500°C or higher, 1000°C or higher, or 1200°C or higher. Furthermore, it is more preferable that the elemental composition ratio of H in the hydrogen-based reducing gas is 50 mol% or more. Furthermore, the hydrogen-based reducing gas may be a mixed gas with another gas (for example, N2 gas) (as long as it does not impair the effects of this embodiment). Although not specifically illustrated, a cavity (combustion space) called a raceway is formed by the hot air blown in from the tuyeres 11.

[0026] Bosch gas, generated from hydrogen-based reducing gases injected into the blast furnace, rises within the furnace, heating and reducing the iron-based raw materials. The iron-based raw materials descend within the furnace, being heated and reduced by the hydrogen-based reducing gases. Subsequently, the iron-based raw materials melt and are further reduced by coke as they drip down the furnace. The iron-based raw materials are ultimately stored in the hearth section 5 as molten iron (pig iron) containing, for example, slightly less than 5% by mass of carbon. The molten iron from the hearth section 5 is removed from the tap and used in the next steelmaking process.

[0027] The main air supply pipe 12 is an annular pipe installed so as to surround the furnace body 10, and a branch air supply pipe 13 is connected to the main air supply pipe 12. The main air supply pipe 12 supplies hot air sent from the hot blast furnace 4 to the branch air supply pipe 13.

[0028] The vent pipe 13 is connected to the main vent pipe 12 and the tuyere 11. The vent pipe 13 supplies hot air sent from the main vent pipe 12 into the furnace through the tuyere 11.

[0029] The pulverized coal blowing lance 14 has a tubular shape and supplies pulverized coal into the furnace body 10 through the tuyeres 11. The pulverized coal blowing lance 14 is inserted into the blower branch pipe 13 from the wall surface of the blower branch pipe 13, for example. The pulverized coal blowing lance 14 is not particularly limited as long as a predetermined amount of pulverized coal is blown into the furnace, and for example, a circular pipe, a square pipe, or a multi-tube with pipes of different diameters arranged concentrically can be used.

[0030] The reducing gas injection lance 15 has a tubular shape and supplies hydrogen-based reducing gas into the furnace body 10 through the tuyere 11. The reducing gas injection lance 15 is inserted into the blower pipe 13 from the wall surface of the blower pipe 13, for example. In Figure 2, the pulverized coal injection lance 14 is inserted into the blower pipe 13 closer to the tuyere 11 than the reducing gas injection lance 15, but the reducing gas injection lance 15 may also be inserted into the blower pipe 13 closer to the tuyere 11 than the pulverized coal injection lance 14.

[0031] The reducing gas injection lance 15 can be, for example, a circular tube, a square tube, or a multi-tube system with tubes of different diameters arranged concentrically. Furthermore, if the reducing gas injection lance 15 is a multi-tube lance, multiple types of hydrogen-based reducing gases can be injected into the furnace simultaneously by supplying different hydrogen-based reducing gases to each of the multiple spaces formed inside the reducing gas injection lance 15.

[0032] The tapping port 16 is provided in the reservoir 101 and discharges molten iron and molten iron slag, a by-product, generated by the reduction of iron-based raw materials. Multiple tapping ports 16 are provided, allowing for continuous or intermittent tapping of molten iron slag.

[0033] The rotating chute 17 is installed at the top 10e of the furnace and charges iron-based raw materials and coke into the furnace body 10. The iron-based raw materials and coke are charged to desired positions inside the furnace by controlling the tilt angle and rotation speed of the rotating chute 17.

[0034] Up to this point, the general configuration of blast furnace 1 has been described. In blast furnace 1 during operation, iron-based raw materials and coke are charged into the furnace body 10 from the top, and hot air, pulverized coal, and hydrogen-based reducing gas are blown in from the tuyeres 11. The oxygen in the hot air burns the coke, pulverized coal, and hydrogen-based reducing gas to produce CO and H2. Bosch gas is produced, which includes the CO and H2 generated, as well as the nitrogen gas contained in the hot air. The generated Bosch gas reduces Fe2O3, Fe3O4, etc., contained in the iron-based raw materials. Inside the furnace body 10, where molten iron is produced in this way, a blob zone 20, a fusion zone 30 formed below the blob zone 20, and a drip zone 40 formed below the fusion zone 30 are formed.

[0035] As shown in Figure 2, the massive zone 20 is a region formed by the alternating stacking of an ore layer 201 composed of iron-based raw materials and a coke layer 202 composed of coke. The massive zone 20 is formed, for example, by alternatingly charging iron-based raw materials and coke from the top of the furnace body 10 via a swirling chute 17. As shown in Figure 2, the massive zone 20 is formed in the upper part of the furnace. In the massive zone 20, indirect reduction occurs in which the iron-based raw materials are reduced by CO and H2 contained in the Bosch gas rising from below the furnace body 10, gasification of coke (C+CO2→2CO and C+H2O→CO+H2), and CO and H2 produced by the water-gas shift reaction (CO+H2O→CO2+H2). The temperature of the massive zone 20 is approximately 400-1000°C.

[0036] The fusion zone 30 is a region located below the lumpy zone 20 where the reduction and heating of the iron-based raw materials progress, resulting in a semi-molten state of the iron-based raw materials. In the fusion zone 30, the FeO and slag components generated during the reduction of the iron-based raw materials are in a semi-molten state. The fusion zone 30 contains a coke layer (coke slit 50), which is a channel for gas to move from the dripping zone 40 to the lumpy zone 20. Bosch gas from the bottom of the furnace moves to the lumpy zone 20 through the coke slit 50. The temperature of the fusion zone 30 is approximately 1000-1200°C.

[0037] The dropping zone 40 is mainly formed by coke, and is the region where molten iron and molten iron slag drip downward through the voids between the coke. In the dropping zone 40, direct reduction by solid carbon occurs (FeO(liquid) + C → Fe(liquid) + CO). Also, in the dropping zone 40, the coke changes to the liquid phase (C → C ), Si in iron-based raw materials changes to the liquid phase (SiO + C → Si A reaction involving the addition of CO also occurs. The molten iron and molten iron slag are stored in the reservoir 101. The temperature of the dripping zone 40 is approximately 1200-1400°C, and the combustion space (raceway) in front of the tuyeres 11 is approximately 2200°C.

[0038] [Gas Tank 2] Gas tank 2 is a facility for storing hydrogen-based reducing gas. The temperature of the hydrogen-based reducing gas stored in gas tank 2 is regulated by a heater (heat exchanger) 3 installed in gas tank 2. The hydrogen-based reducing gas whose temperature has been regulated by the heater (heat exchanger) 3 is sent to tuyeres 11. The hydrogen-based reducing gas sent to tuyeres 11 is mixed with hot air and blown into the furnace body 10 from tuyeres 11.

[0039] [Hot stove 4] The hot blast furnace 4 is equipment that produces the hot air blown into the furnace. The hot air is produced by heating air, or a gas mixture of air and enriched oxygen. Enriched oxygen is oxygen used to adjust the oxygen enrichment rate of the hot air. The temperature of the hot air produced in the hot blast furnace 4 is adjusted by controlling the amount of heat stored and the amount of hot air supplied.

[0040] Up to this point, an example of a molten iron production facility has been described with reference to Figures 1 and 2, but it goes without saying that the molten iron production facility to which the blast furnace operation method according to the embodiment of the present invention is applied is not limited to the one described above. The blast furnace operation method according to the embodiment may be applied to a molten iron production facility in which some of the components described above are omitted or other components are added. Furthermore, the blast furnace operation method according to the embodiment may be applied to a blast furnace 1 in which some of the components are omitted or other components are added.

[0041] <Our findings> Next, with reference to Figures 3 to 8, the inventors will explain the findings obtained in developing the method for determining the operating conditions of a blast furnace according to the present invention.

[0042] The inventors conducted a blast furnace operation simulation using a blast furnace mathematical model. The blast furnace operation simulation used the blast furnace mathematical model described 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.

[0043] The furnace body volume is 12 m³ 3 Assuming the above, the output values ​​of tapping rate, molten iron temperature, and furnace top gas temperature were set as follows: tapping rate (daily molten iron production (t / day)) was 34 t / day, molten iron temperature (temperature of molten iron immediately after leaving the furnace) was 1450°C, and furnace top temperature (furnace top gas temperature) was 110°C.

[0044] As base operating conditions for calculating the reduction rate of carbon consumption per unit (Input △C), no hydrogen-based reducing gas was injected, the blowing temperature was set to 900°C, and the PCR (pulverized coal ratio; amount of pulverized coal required to produce 1 ton of molten iron) was set to 176 kg / t_pig. The carbon content was adjusted by adjusting the coke ratio (amount of coke required to produce 1 ton of molten iron). When injecting hydrogen-based reducing gas from a tuyer, the input conditions (ore / coke ratio, airflow rate required to produce 1 ton of molten iron, airflow temperature, oxygen enrichment amount, hydrogen-based reducing gas injection rate required to produce 1 ton of molten iron, injection temperature) were changed within a range where each output value remained constant, under the condition of a constant pulverized coal ratio (PCR) (70 kg / t_pig). As an example of hydrogen-based reducing gas, H2 gas (pure hydrogen) was assumed, and the H2 gas injection rate required to produce 1 ton of molten iron was set to 500-800 Nm³. 3 Assuming / t_pig, an H2 gas temperature of 800~1000°C, and a fan temperature of 900~1200°C, the calculation results were summarized in terms of the H2 gas injection rate and the sensible heat amount due to the input gas. Here, the sensible heat amount due to the input gas is adjusted by the fan rate, fan temperature, H2 gas injection rate, and H2 gas temperature.

[0045] Figure 3 is a graph showing the Input ΔC as a function of H2 gas injection rate when the airflow temperature and H2 gas injection rate are changed. As shown in Figure 3, it was found that as the H2 gas injection rate increases, the Input ΔC also increases. However, in the range of high H2 gas injection rates, a tendency was observed for the increase in Input ΔC to be smaller in proportion to the increase in H2 gas injection rate.

[0046] Figure 4 is a graph showing the Input ΔC as a function of the input sensible heat when the airflow temperature and H2 gas injection rate are changed. As shown in Figure 4, it was found that under the condition of a constant H2 gas injection rate, Input ΔC increases linearly as the input sensible heat increases.

[0047] Figure 5 is a graph showing the Input ΔC with respect to the input sensible heat when the airflow temperature and H2 gas injection rate are changed, and the calculation results are for input sensible heat amounts even larger than the range shown in Figure 4. As shown in Figure 5, it was found that under the condition of a constant H2 gas injection rate, even at higher input sensible heat amounts, Input ΔC increases linearly as the input sensible heat amount increases. Also, as shown in Figure 5, when the H2 gas injection rate is 500 Nm³ 3 / t_pig and 800Nm 3Compared to / t_pig, the H2 gas injection amount is 800 Nm³. 3 It was found that the slope of the line is steeper when / t_pig is used.

[0048] Figure 6 is a graph showing the reduction rate of ore by CO (CO reduction rate) relative to the input sensible heat for each H2 gas injection rate. Figure 7 is a graph showing the reduction rate of ore by H2 (H2 reduction rate) relative to the input sensible heat for each H2 gas injection rate. Figure 8 is a graph showing the reduction rate of ore by carbon (direct reduction rate) relative to the input sensible heat for each H2 gas injection rate. The direct reduction rate is the reduction rate of ore by solid carbon, and more specifically, it is the reduction rate of ore by carbon contained in solid raw materials (e.g., coke or biomass coal) charged from inlets including the furnace top.

[0049] As shown in Figure 6, the CO reduction rate decreased with increasing input sensible heat. This is because the amount of carbon input for reducing and securing furnace heat decreased as the ore was reduced by H2 gas. Furthermore, the rate of decrease in the CO reduction rate (the slope of the line at the same H2 gas injection rate) remained almost constant regardless of the H2 gas injection rate.

[0050] As shown in Figure 7, the H2 reduction rate increased with increasing sensible heat input. This is due to a decrease in CO in the furnace. Figures 6 and 7 show that H2 reduction compensates for the decrease in the CO reduction rate.

[0051] On the other hand, as shown in Figure 8, the H2 gas injection rate is 800 Nm³. 3 In the case of / t_pig, the direct reduction rate based on the input sensible heat was approximately constant, but when the H2 gas injection amount was 500 Nm³ 3In the case of / t_pig, the direct reduction rate increased with increasing input sensible heat. It was found that when the input sensible heat was increased while the H2 gas injection rate remained low, the proportion by which direct reduction compensated for the decrease in the CO reduction rate increased. In other words, it was found that there is an input sensible heat amount at which Input ΔC efficiently increases depending on the H2 gas injection rate. Therefore, by adjusting the injection rate of hydrogen-based reducing gas relative to the input sensible heat, the desired Input ΔC can be efficiently obtained.

[0052] <Method for determining blast furnace operating conditions> A method for determining the operating conditions of a blast furnace according to one embodiment of the present invention is based on the above findings. More specifically, the method for determining the operating conditions of a blast furnace according to this embodiment is a method for determining the operating conditions of a blast furnace in which at least hydrogen-based reducing gas and hot air are blown in. The method for determining the operating conditions of a blast furnace according to this embodiment includes a first step of determining a first relationship, which is the relationship between the amount of sensible heat input into the blast furnace by hydrogen-based reducing gas and hot air and the reduction ratio of carbon consumption per unit compared to operation without blowing in hydrogen-based reducing gas, and a second relationship, which is the relationship between the amount of sensible heat and the direct reduction rate of ore by carbon in the blast furnace; and a second step of determining the amount of sensible heat input so that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas to be blown in so that the direct reduction rate of ore by carbon in the blast furnace is below a threshold based on the second relationship.

[0053] [1st step] In the first step, a first relationship is determined, which is the relationship between the amount of sensible heat introduced into the blast furnace by hydrogen-based reducing gas and hot air, and the reduction ratio of carbon consumption per unit compared to operation without the injection of hydrogen-based reducing gas. A second relationship is also determined, which is the relationship between the amount of sensible heat and the direct reduction rate of ore by carbon in the blast furnace. Preferably, the first and second relationships are determined according to the amount of hydrogen-based reducing gas injected. For example, when an arbitrary amount of H2 input (total hydrogen input) is determined, and data on multiple input sensible heat amounts are collected, an appropriate region where the order is 1 is selected using an information criterion (AIC or BIC). Alternatively, if the relationship is obvious, especially if the observation range clearly shows linear behavior, the range may be determined visually. A general method such as the least squares method can be used for linear approximation.

[0054] Sensible heat is the sum of the sensible heat contained in the hydrogen-based reducing gas and hot air blown into the blast furnace from the tuyeres, which is required to produce 1 ton of molten iron. The sensible heat of the hydrogen-based reducing gas and the sensible heat of the hot air are the products of the injection rate and temperature, respectively, and the sum of these is the sensible heat introduced into the blast furnace by the hydrogen-based reducing gas and hot air.

[0055] The reduction in carbon consumption per unit of operation compared to operation without injecting hydrogen-based reducing gas is the Input ΔC mentioned above. In this process, we determine the relationship between the above sensible heat and Input ΔC. The first and second relationships can be obtained, for example, by blast furnace operation simulation using a blast furnace mathematical model as described above.

[0056] In the first step, the relationship (the third relationship) between the input sensible heat amount and the solution loss carbon amount (SLC amount) per ton of hot metal produced may be obtained. The solution loss carbon amount per ton of hot metal produced is calculated by calculating the difference between the C content (mol) in the top gas and the C content (mol) in the bosh gas and converting it to the mass per ton of hot metal. The SLC amount may be calculated, for example, by the method described in Nakano et al., “Development of Low Carbon Blast Furnace Operation Technology by using Experimental Blast Furnace”, ISIJ International, Vol. 62 (2022), No. 12, pp. 2424-2432. Also, the third relationship may be used in the second step described later.

[0057] [Second Step] In the second step, the input sensible heat amount is determined so as to be the sensible heat amount corresponding to the reduction rate (Input ΔC) of the carbon consumption per unit based on the first relationship, and the blowing amount of the hydrogen-based reducing gas is determined so that the direct reduction rate of the ore by carbon (coke and pulverized coal) in the blast furnace is below the threshold based on the second relationship. The threshold is an arbitrarily determined value, preferably 10% or less, more preferably 5% or less. In this embodiment, when reducing Input ΔC, at least one of the coke and pulverized coal ratios is changed.

[0058] For example, referring to FIG. 5, when it is desired to obtain an Input ΔC of about 40%, the input sensible heat amount may be set to 1550 MJ / t_pig, 1650 MJ / t_pig, or 1950 MJ / t_pig. Here, the condition of the input sensible heat amount of 1550 MJ / t_pig is that the temperature of the H2 gas is 1000°C, the temperature of the hot blast is 1000°C, and the blowing amount of the H2 gas is 800 Nm 3 / t_pig. The condition of the input sensible heat amount of 1650 MJ / t_pig is that the temperature of the H2 gas is 1000°C, the temperature of the hot blast is 1100°C, and the blowing amount of the H2 gas is 700 Nm 3The value is / t_pig. The conditions for an input sensible heat rate of 1950 MJ / t_pig are: the temperature of the H2 gas is 1200°C, the temperature of the hot air is 1200°C, and the amount of H2 gas blown in is 500 Nm³. 3 It is / t_pig. Referring to Figure 8, for the direct reduction rate to be 5% or less, the amount of H2 gas injected must be 600 Nm³. 3 It should be set to / t_pig or greater. Therefore, to obtain an Input ΔC of approximately 40%, the input sensible heat rate should be 1550 MJ / t_pig, the H2 gas temperature 1000°C, the hot air temperature 1000°C, and the H2 gas injection rate 800 Nm³. 3 The conditions are / t_pig, or the input sensible heat amount is 1650 MJ / t_pig, the H2 gas temperature is 1000°C, the hot air temperature is 1100°C, and the H2 gas injection rate is 700 Nm³. 3 The condition should be / t_pig. If you want to suppress the amount of H2 gas injected, you should select the latter condition from among these options.

[0059] In the second step, the amount of hydrogen-based reducing gas injected may be determined such that the amount of solution loss carbon per ton of molten iron produced based on the third relationship is 30 kg / t_pig or less. That is, the method for determining the operating conditions of a blast furnace according to one embodiment of the present invention is a method for determining the operating conditions of a blast furnace into which at least hydrogen-based reducing gas and hot air are injected, and includes: a first step of determining a first relationship which is the relationship between the amount of sensible heat injected into the blast furnace by the hydrogen-based reducing gas and the hot air and the reduction ratio of carbon consumption per unit compared to operation without the injection of the hydrogen-based reducing gas, and a third relationship which is the relationship between the amount of sensible heat injected and the amount of solution loss carbon per ton of molten iron; and a second step of determining the amount of sensible heat injected so that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas injected based on the third relationship so that the amount of solution loss carbon is 30 kg / t_pig or less.

[0060] [Blast furnace operation methods] By operating the blast furnace according to the operating conditions determined by the method for determining the operating conditions of the blast furnace according to the embodiment described above, the blast furnace can be operated stably even when hydrogen-based reducing gas is blown in from the tuyeres, and the desired Input ΔC can be efficiently obtained. Therefore, another aspect of the present invention is a method for operating a blast furnace in which at least hydrogen-based reducing gas and hot air are blown in, comprising: a first step of determining a first relationship which is the relationship between the amount of sensible heat input into the blast furnace by hydrogen-based reducing gas and hot air and the reduction ratio of carbon consumption per unit compared to operation without the injection of hydrogen-based reducing gas, and a second relationship which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace; and a second step of determining the amount of sensible heat input so that it corresponds to the reduction ratio of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas to be blown in so that the direct reduction rate of ore by carbon in the blast furnace is 5% or less based on the second relationship.

[0061] The present invention has been described with reference to these embodiments. However, the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0062] Although the embodiments of the present invention were described using H2 gas as an example of a hydrogen-based reducing gas, as mentioned above, a hydrogen-based reducing gas is a gas whose main component is H2 gas. Therefore, it is preferable that the first and second relationships described above be determined according to the hydrogen concentration of the hydrogen-based reducing gas.

[0063] In addition, reformed top-circulating gas (equivalent to RBFG), which is obtained by reforming the top-circulating gas, may be injected from the tuyeres in addition to reducing gas from outside the blast furnace system. The reformed top-circulating gas contains CO, H2, H2O, and N2.

[0064] Furthermore, although the above embodiment described an example in which the hydrogen-based reducing gas is blown in only from the tuyere 11 provided in the hearth section 10d, the hydrogen-based reducing gas may also be blown in from, for example, the shaft tuyere provided in the shaft section 10a. [Examples]

[0065] The following are examples of the present invention. The conditions in these examples are merely examples of conditions adopted to confirm the feasibility and effectiveness of the present invention, and the present invention is not limited to the conditions used in the following examples. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention.

[0066] [Example 1] In this example, a blast furnace operation simulation was performed. For the blast furnace operation simulation, the blast furnace mathematical model shown in Kouji TAKATANI, Takanobu INADA, and Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace," ISIJ International, Vol.39 (1999), No.1, pp.15-22, was used.

[0067] The base operating conditions (operating conditions without the injection of hydrogen-based reducing gas) were as follows: iron production rate of 10,200 t / day, molten iron temperature of 1,535°C, top gas temperature of 125°C, coke ratio (CR) of 296 kg / t_pig, pulverized coal ratio of 200 kg / t_pig, hot air temperature of 1,200°C, and sensible heat input of 1,550 MJ / t_pig. The temperature in front of the tuyeres was set at 2,200°C. Pulverized coal and hot air were injected through tuyeres located in the hearth section. To ensure that the tapping rate, molten iron temperature, and furnace top gas temperature were equivalent to the base operating conditions, the H2 gas injection rate, injection temperature, blown air temperature, hot air rate, oxygen enrichment rate, and pulverized coal injection rate (PCI) were changed to alter the input sensible heat. From the calculation results for each condition, the relationship between the input sensible heat and Input ΔC, the relationship between the input sensible heat and the direct reduction rate, and the relationship between the input sensible heat and the SLC amount were determined. Furnace heat adjustment was assumed to be achieved by adjusting the pulverized coal injection rate. If the molten iron temperature exceeded 1535°C even when the pulverized coal injection rate was zero, the coke ratio (CR) was adjusted. The tuyeres temperature was set to 1900-2250°C.

[0068] Figure 9 is a graph showing the relationship between the input sensible heat and Input ΔC for each H2 gas injection rate. Figure 10 is a graph showing the relationship between the input sensible heat and the direct reduction rate for each H2 gas injection rate. Figure 11 is a graph showing the relationship between the input sensible heat and the SLC amount for each H2 gas injection rate.

[0069] Based on the relationship between the input sensible heat and Input ΔC shown in Figure 9, the input sensible heat is determined to obtain the desired Input ΔC. Based on the relationship between the input sensible heat and the direct reduction rate shown in Figure 10, the amount of H2 gas injected is determined so that the direct reduction rate is below a predetermined threshold, for example, 5%. This allows for stable blast furnace operation and efficient acquisition of the desired Input ΔC. For example, if the desired Input ΔC is 40%, the conditions for a direct reduction rate of 5% or less are selected from the combinations of input sensible heat and H2 gas injection rate that result in an Input ΔC of 40% in Figure 9, based on Figure 10. This allows for the determination of blast furnace operating conditions that efficiently achieve Input ΔC = 40%. Furthermore, by selecting the condition with the minimum H2 gas injection rate from among the conditions with a direct reduction rate of 5% or less, the amount of hydrogen input can be suppressed.

[0070] Furthermore, by determining the amount of sensible heat input and Input ΔC based on the relationship between the input sensible heat and Input ΔC shown in Figure 9, and by determining the amount of H2 gas injected so that the SLC amount is 30 kg / t_pig or less based on the relationship between the input sensible heat and the direct reduction rate shown in Figure 11, stable blast furnace operation is possible, and the desired Input ΔC can be obtained efficiently. For example, if you want Input ΔC to be 40%, you select the condition in Figure 11 where the direct reduction rate is 30 kg / t_pig or less from the combinations of input sensible heat and H2 gas injection rate that result in Input ΔC of 40%. This allows you to determine the operating conditions for the blast furnace that can efficiently achieve Input ΔC = 40%. In addition, by selecting the condition in which the H2 gas injection rate is minimized from the conditions where the SLC amount is 30 kg / t_pig or less, the amount of hydrogen input can be suppressed.

[0071] [Example 2] Assuming COG is the hydrogen-based reducing gas to be injected, a blast furnace operation simulation was performed in the same manner as in Example 1. Figure 12 is a graph showing the relationship between the input sensible heat and Input ΔC for each COG injection rate. Figure 13 is a graph showing the relationship between the input sensible heat and the direct reduction rate for each COG injection rate. Figure 14 is a graph showing the relationship between the input sensible heat and the SLC amount for each COG injection rate. Based on Figures 12 and 13, by determining the COG injection rate in the same manner as in Example 1 so that the direct reduction rate is below a predetermined threshold, for example, 5%, stable blast furnace operation can be achieved, and the desired Input ΔC can be efficiently obtained. Furthermore, based on Figures 13 and 14, by determining the H2 gas injection rate so that the SLC amount is below 30 kg / t_pig, stable blast furnace operation can be achieved, and the desired Input ΔC can be efficiently obtained.

[0072] As described above, the method for determining the operating conditions of a blast furnace according to this embodiment can efficiently increase the reduction rate of carbon consumption per unit, Input △C, and consequently, significantly reduce CO2 emissions. [Explanation of Symbols]

[0073] 1 blast furnace 2 gas tanks 3 Heater 4 hot stove 10 Furnace body 10a Shaft section 10b Belly section 10c Bosch section 10d Hearth Department 10e hearth top 10f hearth bottom 11 Tuyere 12 Main air supply pipe 13 Air branch pipe 14. Fine coal blowing lance 15. Reducing gas injection lance 16 Taphead 17. Swinging Shot 20. Massive zone 30 Fusion zone 40 Dropping Zone 50 Coke Slits 101 Gathering area 201 Ore layer 202 Coke layer

Claims

1. A method for determining the operating conditions of a blast furnace into which at least a hydrogen-based reducing gas and hot air are injected, A first step to determine a first relationship, which is the relationship between the amount of sensible heat input into the blast furnace by the hydrogen-based reducing gas and the hot air, and the reduction ratio of carbon consumption per unit compared to operation without the injection of the hydrogen-based reducing gas, and a second relationship, which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace. A method for determining the operating conditions of a blast furnace, comprising: a second step of determining the input sensible heat amount such that it corresponds to the reduction rate of the carbon consumption unit based on the first relationship, and determining the amount of hydrogen-based reducing gas injected such that the direct reduction rate of the ore by carbon in the blast furnace is below a threshold based on the second relationship.

2. The method for determining the operating conditions of a blast furnace according to claim 1, wherein the first and second relationships are determined according to the amount of iron tapped, the molten iron temperature, and the top gas temperature of the furnace.

3. The method for determining the operating conditions of a blast furnace according to claim 1 or 2, wherein the first and second relationships are determined according to the amount of hydrogen-based reducing gas injected.

4. The method for determining the operating conditions of a blast furnace according to claim 1 or 2, wherein the first and second relationships are determined according to the hydrogen concentration of the hydrogen-based reducing gas.

5. A method for determining the operating conditions of a blast furnace into which at least a hydrogen-based reducing gas and hot air are injected, A first step is to determine a first relationship, which is the relationship between the amount of sensible heat input into the blast furnace by the hydrogen-based reducing gas and the hot air, and the reduction ratio of carbon consumption per unit compared to operation without the injection of the hydrogen-based reducing gas, and a third relationship, which is the relationship between the amount of sensible heat input and the amount per ton of molten iron. A method for determining the operating conditions of a blast furnace, comprising: a second step of determining the input sensible heat amount such that it corresponds to the reduction rate of carbon consumption per unit based on the first relationship, and determining the amount of hydrogen-based reducing gas injected such that the solution loss carbon amount is 30 kg / t or less based on the third relationship.

6. A method for operating a blast furnace that blows in at least a hydrogen-based reducing gas and hot air, A first step to determine a first relationship, which is the relationship between the amount of sensible heat input into the blast furnace by the hydrogen-based reducing gas and the hot air, and the reduction ratio of carbon consumption per unit compared to operation without the injection of the hydrogen-based reducing gas, and a second relationship, which is the relationship between the amount of sensible heat input and the direct reduction rate of ore by carbon in the blast furnace. A method for operating a blast furnace, comprising: a second step of determining the amount of sensible heat input so that it corresponds to the reduction rate of the carbon consumption unit based on the first relationship, and determining the amount of hydrogen-based reducing gas injected so that the direct reduction rate of the ore by carbon in the blast furnace is 5% or less, based on the second relationship.

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