Method for operating blast furnace

Abstract

A method for operating a blast furnace having a plurality of blowing devices for a hydrogen-based reducing gas is provided, the method being characterized in that the blowing devices have been disposed along the circumferential direction of the blast furnace and the blowing devices include blowing lances and are equipped with a flow rate regulation system for the hydrogen-based reducing gas and a tank for the hydrogen-based reducing gas, the blowing lances each having been disposed on a tuyere of the blast furnace at a position which, when the diameter of the opening of the tuyere is expressed by D, is 0.4D or less in terms of distance from the inner wall at the tuyere opening toward the outside of the tuyere, and that the hydrogen gas distribution inside the blast furnace is controlled by regulating the flow rate of the hydrogen-based reducing gas and / or the angles of the blowing lances.

Description

Blast furnace operation methods

[0001] This disclosure relates to a method for operating a blast furnace. This application claims priority based on Japanese Patent Application No. 2025-019034, filed in Japan on February 7, 2025, the contents of which are incorporated herein by reference.

[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] By the way, in recent years, there has been much talk about preventing global warming, and carbon dioxide (CO2), one of the greenhouse gases, is being addressed. ２ Reducing CO2 emissions has become a social issue. As mentioned above, the blast furnace method uses carbon as a reducing agent, so a large amount of CO2 is emitted. ２ It generates gas. Therefore, the steel industry is CO2 ２ As one of the major industries in terms of gas emissions, we must respond to this societal demand. Specifically, there is an urgent need to further reduce the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operations.

[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 by coke (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, the iron-based raw materials must absorb CO and H before reaching the lower part of the furnace. ２ If iron-based raw materials can be sufficiently reduced with reducing gases such as those mentioned above, the amount of iron-based raw materials that are directly subject to reduction can be reduced.

[0005] When a large amount of hydrogen-based reducing gas is injected into the blast furnace from the tuyeres, the upper and lower parts of the furnace (the lower part here refers to the Sol Roth reaction (C + CO)) ２ →2CO) This is the region where the furnace temperature is higher than the starting temperature. The upper part of the furnace is the region above the lower part of the furnace. The thermal balance of the upper and lower parts changes significantly. Therefore, it is necessary to appropriately control the operating parameters so that the thermal balance of the upper and lower parts of the furnace is maintained. In other words, if a large amount of hydrogen-based reducing gas is blown into the blast furnace from the tuyere in order to enjoy a significant carbon reduction effect, the tuyere combustion temperature will decrease. If the oxygen enrichment rate is increased to suppress this decrease in tuyere combustion temperature, the heat flow ratio will increase. As a result, the furnace top gas temperature will decrease, falling below the lower limit of the furnace top gas temperature as an operational management standard, and there is a concern that this may lead to a significant delay in the heating of the charges in the upper part of the furnace and a deterioration of ventilation due to insufficient discharge of dust to the outside of the furnace.

[0006] Furthermore, if the reducing agent is replaced with a hydrogen-based reducing gas, resulting in a decrease in the reducing agent ratio and thus a reduction in the amount of expensive coke charged, the thickness of the ore layer will increase compared to the thickness of the coke layer in the blast furnace. Therefore, there are concerns about a decrease in reaction efficiency due to a decrease in the reducing gas concentration within the ore layer, as well as an increase in aeration resistance.

[0007] Here, Patent Document 1 describes a method for injecting reducing agents into a blast furnace. In this method, when injecting at least two types of reducing agents, namely solid reducing agents, liquid reducing agents, and gaseous reducing agents, into the blast furnace through a lance provided penetrating the blast pipe of the blast furnace, a plurality of lances are arranged at the same tuyere, different types of reducing agents are injected from each lance, and the lances are arranged such that the extension lines of the injection directions of the plurality of lances do not intersect each other.

[0008] Further, Patent Document 2 describes a method for operating a blast furnace in which a flammable reducing agent and a solid reducing agent are injected from a tuyere through a lance. In this method, the flammable reducing agent and the solid reducing agent are injected using a double-pipe lance, the outlet flow rate of the outer pipe of the double-pipe lance is set to 20 to 120 m / sec, and the oxygen excess ratio of the air blowing into the tuyere is set to 0.7 to 1.3.

[0009] Furthermore, Patent Document 3 discloses an apparatus for adding a hydrogen-containing raw material into a blast furnace. The apparatus has an end tip with injection holes for the raw material at the tip of an injection pipe for the hydrogen-containing raw material that is partially inserted into a tuyere or a blow pipe for feeding hot air into the furnace. The end tip has a plurality of injection holes arranged in a vertical row with a spacing in the vertical direction of the furnace across the approximate center of the tuyere or the blow pipe, each injection hole is equipped with a flow control valve, and the injection pipe has a heat insulation layer on the outer periphery of the portion exposed in the tuyere or the blow pipe.

[0010] However, in the technologies disclosed in Patent Documents 1 and 2, operations from the perspective of controlling the hydrogen gas concentration distribution are not assumed in the operation of the blast furnace. Also, in the technology disclosed in Patent Document 3, although the control of the hydrogen gas concentration distribution is performed, it is an operation of injecting water, and an operation of injecting a hydrogen-based reducing gas is not assumed. Therefore, in the operation of the blast furnace, there was room for further stabilization of the operation and reduction of the reducing agent ratio.

[0011] Japanese Patent Application Laid-Open No. 2006-291251, Japanese Patent Application Laid-Open No. 2013-019007, Japanese Patent Application Laid-Open No. 60-092410

[0012] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an operating method for a blast furnace capable of reducing the reducing agent ratio.

[0013] In order to solve the above problems, the present disclosure adopts the following configuration. (1) An operating method for a blast furnace having a hydrogen-based reducing gas blowing device, wherein a plurality of the blowing devices are provided in the circumferential direction of the blast furnace, the blowing device includes a tuyere and a hydrogen-based reducing gas blowing lance, and when the diameter of the opening of the tuyere of the blast furnace is D, the blowing lance is disposed at a position within 0.4D from the inner wall of the opening of the tuyere toward the outside of the tuyere, and the hydrogen gas distribution in the blast furnace is controlled by adjusting at least one of the flow velocity of the hydrogen-based reducing gas and the angle of the blowing lance. (2) A measurement step of measuring the radial distribution of the hydrogen gas utilization rate defined by formula (A) in the blast furnace, a target setting step of setting a target value to a representative value of the hydrogen gas utilization rate in the blast furnace or a pattern of the radial distribution of the hydrogen gas utilization rate in the blast furnace, and based on the measured value of the hydrogen gas utilization rate and the target value, while keeping the flow rate of the hydrogen-based reducing gas supplied to the blowing lance constant, adjusting the flow velocity of the hydrogen-based reducing gas or adjusting the angle of the blowing lance to make the difference between the measured value and the target value smaller. The operating method for a blast furnace according to (1) is characterized by having the above steps. y = H ２ O / (H ２ +H ２ O) (A) However, in formula (A), y is the hydrogen gas utilization rate, H ２ , H ２ O are H ２ and H ２The concentration of O. (3) The method for operating a blast furnace according to (1), wherein the blowing device further comprises a blowing lance, and for each tuyere, there is at least one set of two blowing lances, one of the set of blowing lances is positioned above the top of the opening of the tuyere, and the other of the set of blowing lances is positioned below the center of the opening of the tuyere, and the hydrogen gas distribution in the blast furnace is controlled by adjusting at least one of the following: the flow rate ratio of the set of blowing lances, the flow velocity of the hydrogen-based reducing gas in at least one of the set of blowing lances, and the angle of at least one of the set of blowing lances. (4) A method for operating a blast furnace as described in (3), comprising: a measurement step of measuring the radial distribution of the hydrogen gas utilization rate defined by formula (A) in the blast furnace; a target setting step of setting a target value, with a representative value of the hydrogen gas utilization rate in the blast furnace or a pattern of the radial distribution of the hydrogen gas utilization rate in the blast furnace as the target value; and an adjustment step of adjusting the flow rate ratio while keeping the flow rate of the hydrogen-based reducing gas supplied to the pair of injection lances constant, or adjusting the flow velocity of the hydrogen-based reducing gas in at least one of the pair of injection lances, or adjusting the angle of at least one of the pair of injection lances, so that the difference between the measured value and the target value becomes small. ２ O / (H ２ +H ２ O) (A) However, in equation (A), y is the hydrogen gas utilization rate, H ２ , H ２ O is H ２ and H ２ This is the concentration of O.

[0014] This disclosure provides a method for operating a blast furnace that can further reduce the reducing agent ratio.

[0015] This is a schematic diagram showing the overall configuration of the blast furnace system used in this embodiment. This is a schematic diagram showing the overall configuration of the blast furnace system used in this embodiment. This is a cross-sectional view of the tuyere with the blowing lance used in this embodiment, as shown in Figure 1. This is a view taken along the line V-V in Figure 3, showing the positional relationship between the mounting position of the blowing lance used in this embodiment and the opening of the tuyere. This is a cross-sectional view of the tuyere with the blowing lance used in this embodiment, as shown in Figure 2. This is a view taken along the line X-X in Figure 5, showing the positional relationship between the mounting position of the blowing lance used in this embodiment and the opening of the tuyere. This is a cross-sectional view of the tuyere to explain the mounting angle of the blowing lance used in this embodiment. This is a diagram explaining the operation caused by the mounting of the blowing lance used in this embodiment. This is a diagram explaining the operation caused by the mounting of the blowing lance used in this embodiment. This is a diagram showing the results of operation caused by the mounting of the blowing lance according to this embodiment. This is a diagram showing the results of operation caused by the mounting of the blowing lance according to this embodiment. This is a diagram showing the results of operation caused by the mounting of the blowing lance according to this embodiment. This is a diagram showing the results of operation caused by the mounting of the blowing lance according to this embodiment. This is a diagram showing the results of operation caused by the mounting of the blowing lance according to this embodiment.

[0016] In conventional blast furnace operation methods, simply increasing the oxygen enrichment rate makes it difficult to simultaneously maintain the tuyere combustion temperature and the furnace top gas temperature within the appropriate range. This is because the blast furnace process utilizes the exhaust gas (exhaust gas after the completion of the Solroth reaction in the lower furnace) after the heat balance in the lower furnace, where the reduction and thermal load are greatest, is established to establish the reduction reaction and thermal balance in the upper furnace. In normal operation without the use of hydrogen-based reducing gas, the operation is carried out with appropriate parameters so that the heat balance in the upper and lower furnaces is simultaneously satisfied. On the other hand, in operation in which a large amount of hydrogen-based reducing gas is injected into the blast furnace, the ore reduction rate becomes almost 100% at the fusion zone level, and the amount of molten reduction becomes almost zero, so the reduction and thermal load in the lower furnace are greatly alleviated. Consequently, carbon consumption is reduced. However, since the temperature of the exhaust gas generated from the lower furnace decreases, establishing the heat balance in the upper furnace becomes the rate-limiting factor in blast furnace operation. Therefore, it is important to control the reducing gas concentration distribution inside the furnace and to efficiently carry out heat exchange and reactions between the rising gas and the descending coke and ore inside the furnace, thereby maintaining appropriate heat levels, air permeability, and liquid permeability.

[0017] However, the technologies disclosed in Patent Documents 1 to 3 involve installing an injection lance inside the tuyer. As a result, the hydrogen injected from the injection lance burns due to the hot air, making it difficult to control the radial distribution of hydrogen gas concentration inside the furnace.

[0018] The present inventors have conducted a detailed study on a technique for injecting hydrogen-based reducing gas into a blast furnace from an injection lance attached around the tuyer. They found a correlation between the installation position and angle of the injection lance and the charge distribution ((radial) hydrogen utilization rate), and succeeded in quantitatively demonstrating a control method. Below, an embodiment of the blast furnace operation method described in this disclosure will be explained.

[0019] The blast furnace operation method of this embodiment is a blast furnace operation method having a hydrogen-based reducing gas injection device, wherein a plurality of injection devices are provided in the circumferential direction of the blast furnace, and each injection device has a tuyeres and an injection lance 4 for injecting hydrogen-based reducing gas, and the injection lance is positioned within 0.4D from the inner wall of the tuyeres opening toward the outside of the tuyeres when the diameter of the tuyeres opening of the blast furnace is D, and the hydrogen gas distribution inside the blast furnace is controlled by adjusting at least one of the flow velocity of the hydrogen-based reducing gas and the angle of the injection lance.

[0020] Furthermore, the blast furnace operation of this embodiment may also be a blast furnace operation method characterized by the blowing device further having blowing lances, with at least one set of two blowing lances provided for each tuyere, one of the set of blowing lances positioned above the top of the tuyere opening, and the other of the set of blowing lances positioned below the other blowing lance and below the center of the tuyere opening, and controlling the hydrogen gas distribution in the blast furnace by adjusting at least one of the following: the flow rate ratio of the set of blowing lances, the flow velocity of the hydrogen-based reducing gas of at least one of the set of blowing lances, and the angle of at least one of the set of blowing lances. In the following description, "a set of two blowing lances" refers to the blowing lances installed for each tuyere. Furthermore, in some cases, the lance positioned higher than one of the two blowing lances in a pair may be referred to as the "upper blowing lance 4a," and the other blowing lance as the "lower blowing lance 4b." In addition, the "blowing lance 4," "upper blowing lance 4a," and "lower blowing lance 4b" may be collectively referred to as the "lance." Moreover, the blowing device may be equipped with a pair of blowing lances at every tuyere.

[0021] Figure 1 is a schematic diagram showing the overall configuration of a blast furnace 1 and a system connected to the blast furnace 1 according to this embodiment. The blast furnace 1 comprises a hot blast furnace 2, tuyeres 3, a blowing lance 4, a hydrogen-based reducing gas flow rate adjustment system 5, a hydrogen-based reducing gas tank 6, and a top sonde 7. In this disclosure, the series of devices including the blowing lance 4, the hydrogen-based reducing gas flow rate adjustment system 5, and the hydrogen-based reducing gas tank 6 may be described collectively as the "blowing device". Regarding the hydrogen-based reducing gas tank 6, each tuyere 3 may be connected to its own hydrogen-based reducing gas tank 6. Alternatively, the tuyeres 3 may be connected together to one hydrogen-based reducing gas tank 6 in groups of, for example, 10 tuyeres. Furthermore, all tuyeres 3 attached to the blast furnace may be connected together to one hydrogen-based reducing gas tank 6. Figure 2 is a schematic diagram showing a modified example of a blast furnace 1 and a system connected to the blast furnace 1 according to this embodiment. In this embodiment, the blast furnace 1 may be equipped with two blowing lances 4 as a pair, as shown in Figure 2, namely an upper blowing lance 4a and a lower blowing lance 4b. Inside the blast furnace 1, the 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 1 alternately and in layers from the top of the blast furnace 1, while hot air, pulverized coal, and enriched oxygen gas are blown into the blast furnace 1 from the tuyeres 3. In the following description, "tuyere tip combustion temperature" refers to the temperature at the gas outlet of the tuyeres 3. The hot air reacts with the pulverized coal blown in with the hot air and the coke inside the blast furnace 1 to generate high-temperature reducing gas (in this case, for example, CO gas). The hot air gasifies the coke and pulverized coal. Note that pulverized coal does not necessarily have to be included in the hot air. The flow rate of the hydrogen-based reducing gas can be calculated, for example, from the amount of gas injected from the injection lance and the lance diameter set during operation. The reducing gas rises within the blast furnace 1, heating and reducing the iron-based raw materials. The iron-based raw materials descend within the blast furnace 1, being heated and reduced by the reducing gas. Subsequently, the iron-based raw materials melt and are further reduced by coke as they drip down within the blast furnace 1. The iron-based raw materials are ultimately accumulated in the hearth as molten 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.

[0022] The tuyeres 3 are located below the Bosch section of the blast furnace 1 and blow the aforementioned hot air into the blast furnace 1. The blowing lances 4 are attached above and below the tuyeres 3 and blow hydrogen-based reducing gas into the blast furnace 1. In Figure 1, the tuyeres 3 and blowing lances 4 are depicted only at both ends of the blast furnace 1, but two or more blowing devices may be provided along the circumference of the blast furnace at equal intervals. The ends of the blast furnace 1 refer to the positions corresponding to the ends of the diameter of the cross-sectional circle when considering the circumferential cross-section of the blast furnace 1. In this case, it is preferable to adjust the flow rate of each blowing lance 4 provided in the circumferential direction of the blast furnace, or the sum of the flow rates of each pair of upper blowing lances 4a and lower blowing lances 4b, so that they are the same in the circumferential direction of the blast furnace. The number of tuyeres may vary depending on the size of the blast furnace. For example, in the case of a blast furnace with a diameter of 10 m, it is preferable to have 30 to 40 tuyeres installed. The relationship between the tuyeres 3 and the mounting positions of the lances will be described later. In this disclosure, the circumferential direction of the blast furnace 1 is defined as the direction parallel to the blast furnace wall with respect to a plane cut out from the blast furnace perpendicular to the vertical direction, and the radial direction R of the blast furnace 1 is defined as the radial direction from the center of the blast furnace 1 on a plane cut out from the blast furnace 1 perpendicular to the vertical direction.

[0023] Hydrogen-based reducing gases are gases that contain 30 mol% or more of H as an elemental component and exist as gases under standard conditions (0°C, 1 atm). For example, H ２ Gas, unsaturated hydrocarbon gas (C ２ H ４ , C ２ H ２ , C ３ H ６ (etc.), saturated hydrocarbon gases (CH ４ , C ２ H ６ , etc.), NH ３ This includes gas, coke oven gas, city gas, natural gas, etc., and mixtures thereof. 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 contain other gases (e.g., N) (without impairing the effects of this embodiment). ２ A mixed gas with (or other gas) is also acceptable.

[0024] The hydrogen-based reducing gas is branched off from the hydrogen-based reducing gas tank 6, its flow rate is adjusted by the flow rate adjustment system 5, and it is then injected into the blast furnace 1 through the injection lance 4. The hydrogen-based reducing gas tank 6 is a tank for storing the hydrogen-based reducing gas. The flow rate adjustment system 5 may be, for example, a mass flow meter.

[0025] <Relationship between Tuyere 3 and Lance Mounting Position> Next, the blowing device in the blast furnace 1 shown in Figure 1 according to this embodiment will be described. Figures 3 and 4 are schematic diagrams of the blowing device attached to the blast furnace 1 shown in Figure 1. As shown in Figures 3 and 4, the blowing lance 4 may be provided below the tuyere 3. Also, although the blowing lance 4 is attached below the tuyere 3 in Figures 3 and 4, the blowing lance 4 may be installed above the opening of the tuyere 3. Next, the blowing device in the blast furnace 1 shown in Figure 2 according to this embodiment will be described. Figures 5 and 6 are schematic diagrams of the blowing device attached to the blast furnace 1 shown in Figure 2. As shown in Figures 5 and 6, an upper blowing lance 4a and a lower blowing lance 4b may be provided as a set at the upper and lower parts of the tuyere 3, at positions that are roughly coincidental in the vertical direction.

[0026] Furthermore, the blowing lance 4 is installed within a range α of 0.4D from the inner wall of the tuyere toward the outside of the tuyere 3, where D is the opening diameter of the tuyere furnace opening 8. Note that the mounting positions of the specified blowing lance 4, upper blowing lance 4a, and lower blowing lance 4b are limited only to the vertical direction, such as above and below the center of the tuyere, and are not limited to the horizontal direction. However, if the mounting position of the lance is more than 0.4D from the inner wall of the tuyere hardware toward the outside of the tuyere 3, the influence of the gas flow around the raceway will weaken, and there is a risk that it will exceed the gas flow control range of this disclosure (hydrogen will not be carried by the gas flow). Note that "outside" above refers to the radial direction from the center of the tuyere opening in the front view of the tuyere 3. Also, if the mounting position of the lance is inside the inner wall of the tuyere hardware, the influence of the gas flow around the raceway will weaken. That is, it is preferable that the mounting position of the blowing lance 4 be installed within a range of 0.4D from the inner wall of the tuyere hardware toward the outside. The lower limit of the mounting position of the blowing lance 4 is not particularly limited, but for example, it may be in a position greater than 0D when viewed from the inner wall of the tuyere hardware outward.

[0027] <Inventors' Study> Next, the inventors' study will be described. The inventors studied blast furnace operation using the blast furnace system described above, and after going through the measurement step, target setting step, and adjustment step described later, they optimized the mounting position and lance angle of the injection lance 4 and found conditions for reducing the reducing agent ratio. The steps according to this embodiment will be described below.

[0028] <Measurement Step> Using the top sonde 7, the hydrogen concentration and water vapor concentration are measured at n locations selected at regular intervals in the radial direction at the top of the furnace. n is preferably 6 to 20. When determining the hydrogen gas utilization rate y from the obtained hydrogen and water vapor concentrations, it is defined by the following formula (A).

[0029] y = H ２ O / (H ２ +H ２ O) (A)

[0030] In equation (A), H ２ , H ２ O is H ２ and H２ These are the concentrations of each element.

[0031] The representative value used as the target value for the hydrogen gas utilization rate y can be, for example, the average value. The average value may be, for example, an area-weighted average A. The area-weighted average A is calculated using the following formula (B).

[0032] A = Σ(x) i ×y i ) i=1~n (B)

[0033] In equation (B), x i is the area ratio of the radial position i of blast furnace 1, y i These are measured values.

[0034] Furthermore, a representative value to be used as the target value for hydrogen gas utilization rate is, for example, the radial position i shown in the following formula (C). ｍａｘ You may also use the value that maximizes the hydrogen gas utilization rate P.

[0035] P = i ｍａｘ (C)

[0036] The target pattern A' of the radial distribution of hydrogen gas utilization rate can be expressed as an n-dimensional vector, as shown in equation (D) below: A' = (y １ , y ２ , , y ｉ , , y ｎ ) (D)

[0037] In equation (D), y i This is the measured value of the hydrogen gas utilization rate at radial position i.

[0038] <Target Setting Step> Based on the definition above, the obtained measured values ​​are used to set target values ​​for the hydrogen gas concentration distribution, i.e., the area-weighted average A of the hydrogen gas utilization rate, the hydrogen gas utilization rate P at radial locations, or the target radial pattern A' of the hydrogen gas utilization rate, as follows: - Extract the operating conditions from operational records that yielded the most stable operation, a low reducing agent ratio, or a high pig production ratio. - Extract the conditions from numerical simulations that yielded the lowest reducing agent ratio or a high pig production ratio. The difference between the extracted target values ​​and the measured values ​​(ΔA, ΔP, ΔA') is quantified as shown in the following equations (E) to (G).

[0039] ΔA = A ａｉｍ -A ｏｂｓ (E) ΔP = i ｍａｘ ａｉｍ -i ｍａｘ ｏｂｓ (F) ΔA' = |A' ａｉｍ - A' ｏｂｓ | (G)

[0040] In equations (E) through (G), the subscript 'aim' represents the target value, and the subscript 'obs' represents the measured value.

[0041] <Adjustment Step> In the adjustment step, one or more of the following adjustment means are performed so that the difference between the measured value obtained by equations (E) to (G) in the target setting step and the target value becomes small. If the blowing lance 4 is installed only at the bottom of the tuyere 3, one or both of the following means A1 and A2 are performed. [Method A1] Adjust the flow velocity while keeping the flow rate of the hydrogen-based reducing gas supplied to the blowing lance 4 constant. [Method A2] Adjust the angle of the blowing lance 4. The above means A1 and means A2 can be controlled separately. For example, the angle of the blowing lance 4 can be changed according to the flow velocity of the hydrogen-based reducing gas, or the flow velocity of the hydrogen-based reducing gas can be adjusted according to the angle of the blowing lance 4. The flow rate is the total flow rate, and when adjusting the flow velocity while keeping the flow rate constant, tuyeres with different lance diameters can be installed. By installing a blowing device with blowing lances of different lance diameters, the ratio of reducing gas flowing to each tuyere can be changed, but the total flow rate can be kept constant. Note that "keeping the flow rate constant" includes temporarily stopping the gas injection and means that there is no change in the flow rate before and after the equipment modification. If the injection lances are installed as a pair, one at the top (upper injection lance 4a) and bottom (lower injection lance 4b) of the tuyere 3, one or more of the following means B1, B2, and B3 are performed. Note that the angle of the injection lances is adjusted within a range of ±90° from the center line TC of the tuyere, which faces the furnace of the blast furnace 1 from the tuyere 3, with counterclockwise rotation being positive, in the range of +θ and -θ. [Method B1] Adjust the flow rate ratio of the upper injection lance 4a and the lower injection lance 4b while keeping the flow rate of the hydrogen-based reducing gas supplied to the pair of injection lances constant. [Method B2] Adjust the flow velocity of the hydrogen-based reducing gas in at least one of the pair of injection lances. More preferably, it is effective to change the flow velocity of the lower injection lance 4b installed at the bottom of the tuyere 3. [Method B3] Adjust the angle of at least one of the pair of blowing lances. More preferably, it is effective to change the angle of the lower blowing lance 4b installed at the bottom of the tuyere 3. Means B1, B2, and B3 described above can each be controlled separately. For example, the flow rate ratio of the blowing lances can be adjusted according to the flow velocity of the hydrogen-based reducing gas and the angles of the pair of blowing lances.Alternatively, the flow velocity of the hydrogen-based reducing gas injected from at least one of the injection lances may be adjusted according to the flow rate ratio and angle of the injection lances. Or, while keeping the flow rate ratio and flow rate of the injection lances constant, injection lances with different lance diameters may be installed to adjust the flux of the hydrogen-based reducing gas from the injection lances.

[0042] The specific adjustment methods for the target values ​​mentioned above are shown below. ｍａｘ ｏｂｓ ga i ｍａｘ ａｉｍ If it is located towards the center of the furnace, the hydrogen-based reducing gas is adjusted to flow further towards the center of the furnace. On the other hand, i ｍａｘ ｏｂｓ ga i ｍａｘ ａｉｍ If the gas source is located on the furnace wall side, the system should be adjusted so that the hydrogen-based reducing gas flows more towards the furnace wall.

[0043] ΔA is the i ｍａｘ ａｉｍ This can be done through trial and error while using the adjustment methods mentioned above.

[0044] In ΔA', if the hydrogen gas utilization rate in the surrounding area is higher than the target, hydrogen is flowed towards the furnace wall. If the hydrogen gas utilization rate in the surrounding area is lower than the target, hydrogen is flowed towards the center of the furnace. If the hydrogen gas utilization rate in the center is higher than the target, hydrogen is flowed towards the center of the furnace. If the hydrogen gas utilization rate in the center is lower than the target, hydrogen is flowed towards the furnace wall.

[0045] (Effect of injecting hydrogen-based reducing gas from injection lance 4) As shown in Figure 8, when hydrogen-based reducing gas is injected from the upper injection lance 4a attached to the top of the tuyeres 3, its low density and low momentum cause it to enter the furnace while drawing a separate streamline from the main flow shown by the dashed arrow within the swirling flow. That is, when hydrogen-based reducing gas is injected from the top of the raceway, it is repelled by the swirling gas in the raceway and flows to the periphery of the furnace. Note that arrow A represents the condition where the lance angle of the upper injection lance 4a is small, and arrow a represents the condition where the lance angle is large, and these are simplified representations of the flow path of hydrogen-based reducing gas. Also, as shown in Figure 9, when hydrogen-based reducing gas is injected into the blast furnace 1 from the lower injection lance 4b via the bottom of the raceway, it cannot follow the swirling gas in the raceway in the same way as above and flows towards the center of the furnace. Note that arrow B represents the condition where the lance angle of the lower injection lance 4b is small, and arrow b represents the condition where the lance angle is large, both showing a simplified flow path for the hydrogen-based reducing gas.

[0046] As described above, according to the blast furnace operation method of this embodiment, the radial reduction gas composition distribution within the blast furnace can be adjusted by adjusting the amount of air blown in from the blowing lance 4 located below the tuyere 3, or from the upper blowing lance 4a and lower blowing lance 4b located above and below the tuyere 3. As a result, the reduction efficiency within the furnace is improved, and improvements in hydrogen and carbon intensity can be expected.

[0047] The present disclosure will be specifically described below with reference to examples. In this example, 12m ３ We conducted operations using a small blast furnace. The operating conditions for the small blast furnace were within the range described in Table 1. Note that the unit in Table 1 is "t / m". ３ " / d" represents the weight of molten iron (t) per unit volume of blast furnace 1 per day. Also, the unit in Table 1 is "Nm". ３ " / t" represents the amount of iron blown in per ton of molten iron (Nm³). ３The radial hydrogen gas concentration distribution of the blast furnace 1 was monitored using a top sonde 7 attached to the blast furnace 1. Below is an example of actual measurements when the injection lances are provided as a set, one above and one below the tuyere 3. In the following embodiment, the amount of hydrogen-based reducing gas injected from the upper injection lance 4a may be referred to as the "upper injection amount," and the amount of hydrogen-based reducing gas injected from the lower injection lance 4b may be referred to as the "lower injection amount."

[0048]

[0049] Figure 10 shows the hydrogen concentration distribution in the radial direction of the blast furnace for each ratio of hydrogen injected from the upper injection lance 4a (upper injection rate): upper injection amount / (upper injection amount + lower injection amount) (the vertical axis shows the multiplier of the concentration in each part when the average radial concentration of the blast furnace is set to 1.0). When hydrogen-based gas is injected only from the upper injection lance 4a (upper injection rate = 1.0), the hydrogen flows skewed to about 6 times the average in the flow around the furnace, and as the injection amount from the lower injection lance 4b is gradually increased (or the injection ratio from the upper injection lance 4a is decreased), the hydrogen concentration distribution gradually becomes flatter. When the flow rate ratio of the upper injection lance 4a and the lower injection lance 4b is equal (upper injection rate = 0.5), there is a lot of flow around the furnace, but the hydrogen concentration distribution is almost uniform in the radial direction. Also, when injection is made only from the lower injection lance 4b (upper injection rate = 0), the hydrogen flows to the center, and the concentration in the center is about 3 times the average.

[0050] Figure 11 shows an example of the ratio of hydrogen injected from the upper injection lance 4a (upper injection rate): upper injection amount / (upper injection amount + lower injection amount), and the degree of high hydrogen concentration in the surrounding flow: surrounding flow ratio at the furnace top = surrounding flow / (surrounding flow + central flow). Here, the surrounding flow is the hydrogen concentration in the region closest to the furnace wall when the radial direction is divided into 10 parts, and the central flow is the hydrogen concentration in the central region. When the upper injection rate is between 0 and around 0.1 (when there is a lot of injection from the lower injection lance 4b), the hydrogen concentration in the center is zero, and when the upper injection rate is 0.9 or higher (1.0, where all is injected from the upper injection lance 4a), the hydrogen concentration in the center is zero, so the vertical axis is 1.0.

[0051] Figure 12 shows the hydrogen concentration distribution in the blast furnace radial direction when the angles of both the upper and lower lances are tilted downward by 10°, and the ratio of hydrogen injected from the upper injection lance 4a (upper injection rate): upper injection amount / (upper injection amount + lower injection amount) is 0.25 and 0.80, respectively. For comparison, the curve for the case where the injection lance angle is horizontal (lance angle: 0°) (Figure 10) is also shown in the figure. It can be seen that even when the injection amount ratio of the upper injection lance 4a and the lower injection lance 4b differs due to the downward lance angle, hydrogen wraps around to the center of the furnace more effectively.

[0052] Figure 13 shows the hydrogen concentration distribution in the blast furnace radial direction when the diameters of both the upper and lower lances are enlarged to 15 mm, and the ratio of hydrogen injected from the upper injection lance 4a (upper injection rate): upper injection amount / (upper injection amount + lower injection amount) is 0.25 and 0.80, respectively. For comparison, the curve for the case where the lance diameter is 10 mm is also shown in the figure, as in Figure 10. It can be seen that as the lance diameter is enlarged, the inlet flow velocity of the hydrogen-based reducing gas decreases, and even when the injection amount ratio of the upper injection lance 4a and the lower injection lance 4b is different, hydrogen flows more towards the periphery of the furnace.

[0053] Figure 14 shows the degree of peripheral flow with high hydrogen concentration relative to the upper injection rate when the lance angle is horizontal (lance angle: 0°) and the diameter is 10 mm, and when both the upper injection lance 4a and the lower injection lance 4b are tilted downwards by 10° and when the lance diameter is increased from 10 mm to 15 mm. It can be seen that when the proportion from the upper injection lance 4a is large in a pair of injection lances, the hydrogen-based reducing gas shifts to the periphery of the furnace, when the lance angle is tilted downwards, the hydrogen-based reducing gas moves more towards the center, and the larger the lance diameter, the more it flows to the periphery.

[0054] Based on the above results, by charging ore with good hydrogen reducibility to the periphery in the charge distribution from the top of the furnace, and using upper injection for the hydrogen injection lance, it is possible to maintain a high hydrogen reaction efficiency in the furnace and keep the reducing agent ratio low.

[0055] While preferred embodiments of the present disclosure have been described in detail above with reference to the attached drawings, the present disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art to which the present disclosure pertains that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure.

[0056] 1. Blast furnace 2. Hot blast furnace 3. Tuyeres 4. Blowing lance 4a. Upper blowing lance 4b. Lower blowing lance 5. Hydrogen-based reducing gas flow rate adjustment system 6. Hydrogen-based reducing gas tank 7. Top sonde 8. Opening FC: Centerline of the blast furnace R: Radial direction of the blast furnace TC: Centerline of the tuyeres

Claims

A method for operating a blast furnace having a hydrogen-based reducing gas injection device, Multiple blowing devices are provided in the circumferential direction of the blast furnace. The blowing device comprises a tuyere and a blowing lance for the hydrogen-based reducing gas. The blowing lance is positioned within 0.4D from the inner wall of the tuyere opening toward the outside of the tuyere, where D is the diameter of the tuyere opening of the blast furnace. By adjusting at least one of the flow velocity of the hydrogen-based reducing gas and the angle of the injection lance, A method for operating a blast furnace, characterized by controlling the distribution of hydrogen gas within the blast furnace. 　 A measurement step of measuring the radial distribution of the hydrogen gas utilization rate defined by formula (A) in the blast furnace, A target setting step in which a representative value of the hydrogen gas utilization rate in the blast furnace or the pattern of the radial distribution of the hydrogen gas utilization rate in the blast furnace is set as the target value, Based on the measured value of the hydrogen gas utilization rate and the target value, the difference between the measured value and the target value is reduced. While maintaining a constant flow rate of the hydrogen-based reducing gas supplied to the injection lance, adjust the flow velocity of the hydrogen-based reducing gas. Adjust the angle of the blowing lance, A method for operating a blast furnace according to claim 1, characterized by comprising an adjustment step of performing at least one of the following. y=H ２ O / (H ２ +H ２ O) (A) However, in equation (A), y is the hydrogen gas utilization rate, H ２ , H ２ O is H ２ and H ２ This is the concentration of O. 　 The blowing device further includes the blowing lance, so that each tuyere is provided with at least one set of two blowing lances. One of the aforementioned pair of blowing lances is positioned above the top of the opening of the tuyere. The other of the aforementioned pair of blowing lances is positioned below the center of the opening of the tuyere. The flow rate ratio of the aforementioned set of injection lances, The flow velocity of the hydrogen-based reducing gas in at least one of the aforementioned pair of blowing lances, The angle of at least one of the aforementioned pair of blowing lances, By adjusting at least one of the following, A method for operating a blast furnace according to claim 1, characterized by controlling the distribution of hydrogen gas within the blast furnace. 　 A measurement step of measuring the radial distribution of the hydrogen gas utilization rate defined by formula (A) in the blast furnace, A target setting step in which a representative value of the hydrogen gas utilization rate in the blast furnace or the pattern of the radial distribution of the hydrogen gas utilization rate in the blast furnace is set as the target value, Based on the measured value of the hydrogen gas utilization rate and the target value, the difference between the measured value and the target value is reduced. While maintaining a constant flow rate of the hydrogen-based reducing gas supplied to the set of blowing lances, the flow rate ratio can be adjusted. Adjust the flow rate of the hydrogen-based reducing gas in at least one of the set of blowing lances, Adjust the angle of at least one of the aforementioned pair of blowing lances, A method for operating a blast furnace according to claim 3, characterized by comprising an adjustment step of performing at least one of the following. y=H ２ O / (H ２ +H ２ O) (A) However, in equation (A), y is the hydrogen gas utilization rate, H ２ , H ２ O is H ２ and H ２ This is the concentration of O.

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