Blast furnace operation methods

Abstract

To provide a blast furnace operation method for blowing hydrogen gas, capable of achieving a reduction target of carbon consumption without increasing the blowing amount of hydrogen gas even when the temperature of the hydrogen gas is within a temperature range capable of warming.SOLUTION: A blast furnace operation method comprises: a first step of determining a predetermined sensible heat quantity based on a sensible heat quantity input to a blast furnace by hydrogen gas and hot air in a hydrogen blowing base dimension of a predetermined carbon consumption, where the carbon consumption quantity is reduced from the basic operation dimension by blowing hydrogen gas; a second step of generating a hydrogen gas temperature-hot air temperature correlation based on the relation between the temperature of hydrogen gas and hot air at which the sensible heat quantity input by hydrogen gas and hot air becomes a predetermined sensible heat quantity; a third step of determining a first temperature of hydrogen gas and a second temperature of hot air based on the generated hydrogen gas temperature-hot air temperature correlation; and a fourth step of blowing hydrogen gas at the determined first temperature through a tuyere and blowing hot air at the second temperature through the tuyere.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In the steel industry, the blast furnace method is the mainstream of the pig iron manufacturing process. In the blast furnace method, while charging iron-based raw materials for blast furnace (raw materials containing iron oxide. Mainly sintered ore. Hereinafter, also simply referred to as "iron-based raw materials") and coke into the blast furnace alternately and in layers from the top of the blast furnace, hot air is blown into the blast furnace from tuyeres at the lower part of the blast furnace. The hot air reacts with pulverized coal blown in together with the hot air and coke in the blast furnace to generate high-temperature reducing gas (here mainly CO gas). That is, the hot air gasifies coke and pulverized coal. The reducing gas rises in the blast furnace and reduces the iron-based raw materials while heating them. The iron-based raw materials descend in the blast furnace while being heated and reduced by the reducing gas. Then, the iron-based raw materials melt and drip in the blast furnace while being further reduced by coke. The iron-based raw materials are finally stored as hot metal (pig iron) containing less than 5% by mass of carbon in the hearth part. The hot metal in the hearth part is taken out from the hot metal tapping hole and supplied to the next steelmaking process. Therefore, in the blast furnace method, carbonaceous materials such as coke and pulverized coal are used as reducing agents.

[0003] By the way, in recent years, prevention of global warming has been called for, and reduction of the emission amount of carbon dioxide (CO2 gas), which is one of the greenhouse gas, has become a social problem. As described above, since carbonaceous materials are used as reducing agents in the blast furnace method, a large amount of CO2 gas is generated. Therefore, the steel industry has become one of the major industries in terms of CO2 gas emissions and must respond to the social demands. Specifically, it is urgent to further reduce the reducing agent ratio (amount of reducing agent used per ton of hot metal) 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, the direct reduction reaction with coke (reaction equation: FeO + C ⇒ Fe + CO) is an endothermic reaction that involves a large amount of heat absorption. Therefore, minimizing the occurrence of this reaction is important in reducing the reducing agent ratio. Since this direct reduction reaction occurs in the lower part of the blast furnace, if the iron-based raw materials can be sufficiently reduced by reducing gases such as CO and H2 before reaching the lower part of the furnace, the amount of iron-based raw materials subject to direct reduction can be reduced.

[0005] Patent Document 1 describes a method for operating a blast furnace by injecting hydrogen gas (H2 gas), which is a reducing gas, after heating the hydrogen gas. Specifically, it describes heating the hydrogen gas to an appropriate temperature according to the amount of hydrogen gas injected, taking into account the decrease in furnace temperature due to the endothermic reduction reaction of iron-based raw materials by hydrogen gas. According to the method in Patent Document 1, it is possible to reduce CO2 emissions while maintaining stable blast furnace operation. [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] However, in the case of the method disclosed in Patent Document 1, existing equipment can only raise the temperature of hydrogen gas to about 1000°C, so under certain conditions, it may be difficult to achieve the carbon consumption reduction target.

[0008] Therefore, the present invention has been made in view of the above problems, and aims to provide a method for operating a blast furnace that injects hydrogen gas, which makes it possible to achieve the carbon consumption reduction target without increasing the amount of hydrogen gas injected, even when the temperature of the hydrogen gas is within the temperature range that can be raised. [Means for solving the problem]

[0009] This invention was made to solve the above-mentioned problems, and the gist of the invention is as follows.

[0010] (1) A method for operating a blast furnace, comprising: a first step of determining a predetermined amount of sensible heat based on the amount of sensible heat input to the blast furnace by hydrogen gas and hot air in hydrogen injection base parameters with a predetermined carbon consumption, in which the carbon consumption is reduced from the basic operating parameters by injecting hydrogen gas; a second step of creating a hydrogen gas temperature-hot air temperature correlation based on the relationship between the temperature of the hydrogen gas and the temperature of the hot air so that the amount of sensible heat input by hydrogen gas and hot air becomes the predetermined amount of sensible heat determined in the first step; a third step of determining a first temperature, which is the temperature of the hydrogen gas, and a second temperature, which is the temperature of the hot air, based on the hydrogen gas temperature-hot air temperature correlation created in the second step; and a fourth step of injecting hydrogen gas from the tuyere at the first temperature determined in the third step and injecting hot air from the tuyere at the second temperature.

[0011] (2) The method for operating a blast furnace as described in (1) above, characterized in that the second step involves changing the hydrogen gas temperature and the hot air temperature with respect to the hydrogen injection base parameters, without changing the hydrogen gas injection rate and the hot air injection rate, and determining the hydrogen gas temperature-hot air temperature correlation based on the hydrogen gas temperature and hot air temperature at which the amount of sensible heat input by the hydrogen gas and hot air becomes the predetermined amount of sensible heat.

[0012] (3) The method for operating a blast furnace according to (1) or (2) above, characterized in that the hydrogen gas temperature-hot air temperature correlation is an approximate formula showing the relationship between the hydrogen gas temperature and the hot air temperature, which is obtained based on a set of data consisting of combinations of hydrogen gas temperatures and hot air temperatures that result in a predetermined sensible heat amount.

[0013] (4) A method for operating a blast furnace according to any one of (1) to (3) above, characterized in that a second step is performed for each amount of carbon consumed in the operation of the blast furnace to derive the hydrogen gas temperature-hot air temperature correlation, and the first temperature and the second temperature are determined based on the hydrogen gas temperature-hot air temperature correlation corresponding to the target amount of carbon consumed in the operation.

[0014] (5) The method for operating a blast furnace according to any one of (1) to (4) above, characterized in that the fourth step is to heat the hot air to the second temperature using a plasma heating device upstream of the tuyere in the hot air flow path. [Effects of the Invention]

[0015] According to the present invention, in a method for operating a blast furnace that injects hydrogen gas, it is possible to provide a method for operating a blast furnace that can achieve the target of reducing carbon consumption without increasing the amount of hydrogen gas injected, even when the temperature of the hydrogen gas is within the temperature range that can be raised. [Brief explanation of the drawing]

[0016] [Figure 1] This diagram shows the configuration of the blast furnace and hot blast furnace, etc., according to this embodiment. [Figure 2] This graph shows an example of the hydrogen gas temperature-hot air temperature correlation in this embodiment. [Figure 3] This graph shows the results of hydrogen gas injection for examples and comparative examples of operations that achieved a 20% reduction in carbon consumption per unit of production. [Figure 4] This graph shows the results of hydrogen gas injection for examples and comparative examples of operations that achieved a 40% reduction in carbon consumption per unit of production. [Modes for carrying out the invention]

[0017] Hereinafter, embodiments will be described with reference to the drawings. The operation method of the blast furnace 1 in this embodiment is to blow hydrogen gas as a reducing material from the tuyere together with hot air. FIG. 1 is a diagram showing the configuration of the blast furnace 1 and a hot blast stove according to the embodiment. The blast furnace 1 includes a tuyere 2, an annular pipe 3, a blower pipe 4, a lance 6, a plasma heating device 8, etc. for blowing hot air, hydrogen gas, etc. into the blast furnace 1.

[0018] The tuyere 2 is an injection port for blowing hot air into the blast furnace. The hot air blown from the tuyere 2 is generated, for example, in a hot blast stove, and is supplied from the hot blast stove to the tuyere 2 via the annular pipe 3 and the blower pipe 4. The hot blast stove is, for example, a furnace having a regenerator in which silica bricks are arranged in a lattice shape inside. The temperature of the hot air is measured, and based on the measurement data, the heat storage amount in the hot blast stove and the amount of air supplied are controlled to adjust the temperature of the hot air, which is then sent to the annular pipe 3. Also, a lance for blowing pulverized coal as a reducing material into the blast furnace through the tuyere 2 may be inserted and arranged in the tuyere 2 or the blower pipe 4.

[0019] The lance 6 is an injection lance for blowing hydrogen gas. The lance 6 is inserted into the tuyere 2, and the hydrogen gas supplied from the gas tank is blown into the tuyere 2 through the lance 6. The blowing of hydrogen gas into the blast furnace 1 is usually performed through the tuyere 2, but is not limited thereto, and the lance 6 may be installed at a location other than the tuyere 2 and hydrogen gas may be blown. The hydrogen gas blown from the lance 6 is heated to a desired temperature by a heating device that heats the hydrogen gas and then supplied.

[0020] The hydrogen gas blown from the lance 6 is not limited to being composed only of hydrogen gas, and may be a hydrogen-based gas having hydrogen as a main component. It is preferably a hydrogen-based gas containing 80 mol% or more of hydrogen (mol% of hydrogen gas with respect to the total amount of all gases constituting the gas blown from the lance).

[0021] The plasma heating device 8 is a heating device used to heat the hot air to a temperature higher than that under normal operating conditions (basic operating parameters). The plasma heating device 8 is positioned, for example, upstream of the tuyere 2, and heats the hot air with a plasma torch inside the air supply pipe 4 or inside the tuyere 2. However, the heating location of the hot air by the plasma heating device 8 is not limited to this; it can be anywhere between the hot air furnace and the tip of the lance 6, which is the hydrogen gas confluence point, as long as the hot air can be heated. By heating the hot air with the plasma heating device 8 before the tuyere 2, the temperature of the hot air can be appropriately increased from the temperature under basic operating conditions without changing the heating conditions or equipment in the existing hot air furnace.

[0022] For the heating method and apparatus for hot air using plasma heating, methods such as those described in "Shinichi Inaba, Junichiro Yagi, Iron and Steel, 78 (1992), pp. 1187-1197", "DS Gathergood: Applied Energy Research Conf., Swansea (September 1989), Session I", and "https: / / abmproceedings.com.br / en / article / download-pdf / the-use-of-plasma-torches-in-blast-furnace-ironmaking" may be adopted.

[0023] Furthermore, in this embodiment, the temperature of the hot air and the temperature of the hydrogen gas refer to the temperature at which they are blown in from the tuyere, and it is preferable that these temperatures be measured by a temperature sensor or the like at a position that allows for a more accurate evaluation of the amount of sensible heat injected into the blast furnace 1, as described later. Specifically, the temperatures of the hot air and hydrogen gas should be measured upstream of the point where the hydrogen gas mixes with the hot air, and as close to the tuyere 2 as possible. For example, if hydrogen gas is blown in from the lance 6 at the position shown in Figure 1, the temperature of the hot air should be measured upstream of the tip of the lance 6 inside the tuyere 2 (or blower pipe 4). The temperature of the hydrogen gas should be measured inside the lance 6 at the tip of the lance.

[0024] Furthermore, the temperature at which the hot air decreases by the time it is supplied from the hot air furnace to the vicinity of the tuyere 2 may be confirmed in advance through actual operation or simulation, and the set temperatures of the hot air furnace and plasma heating device 8 may be set to a temperature that takes this temperature decrease into account so that the temperature near the tuyere 2 reaches the desired temperature. Similarly, for hydrogen gas, the set temperature of the hydrogen gas heater may be set considering the temperature decrease up to the tip of the lance 6.

[0025] Next, the operation method of the blast furnace according to this embodiment will be described. The operation method of the blast furnace according to this embodiment has the following first to fourth steps. (First step) By injecting hydrogen gas, carbon consumption is reduced compared to the basic operating parameters. Based on the hydrogen injection base parameters with a predetermined carbon consumption, the predetermined sensible heat amount is determined based on the amount of sensible heat injected into the blast furnace by hydrogen gas and hot air. (Step 2) Create a hydrogen gas temperature-hot air temperature correlation based on the relationship between the hydrogen gas temperature and the hot air temperature such that the amount of sensible heat input by hydrogen gas and hot air is the predetermined sensible heat amount determined in Step 1. (Step 3) Based on the hydrogen gas temperature-hot air temperature correlation created in Step 2, set the hydrogen gas temperature (first temperature) and the hot air temperature (second temperature). (Fourth stage) In the third stage, hydrogen gas and hot air are blown in from the tuyeres at the respective temperatures set during operation.

[0026] The following describes each process. In this specification, "carbon consumption per unit" refers to the carbon required to produce 1 ton of molten iron (i.e., the amount of carbon consumed per ton of molten iron). "Carbon consumption reduction rate" means the ratio of the carbon consumption rate reduced in operation under different operating conditions to the carbon consumption rate under the basic operating conditions. If the carbon consumption rate under the basic conditions is A (kg / t) and the carbon consumption rate under a different operating condition is B (kg / t), then the carbon consumption reduction rate ΔC is given by the following formula. △C = (AB) / A × 100 (%) The greater the reduction rate ΔC in carbon consumption intensity, the lower the ratio of reducing agents, and consequently, the lower the CO2 emissions.

[0027] Furthermore, the "basic operating parameters" are the parameters used as a basis for setting targets for reducing carbon consumption, and as described above, the carbon consumption reduction rate is calculated based on the carbon consumption under the basic operating parameters. In this embodiment, operations without hydrogen gas injection are described as the basic operating parameters, but the embodiment is not limited to this, and any parameters that can be set as standard operating conditions are acceptable. Alternatively, the operating parameters with hydrogen gas injection may be used as the basic operating parameters and the carbon consumption reduction target may be set based on those operating conditions using the method of this embodiment.

[0028] Furthermore, when determining the hydrogen gas temperature-hot air temperature correlation in the above process, or when evaluating the carbon consumption reduction effect under the determined operating conditions, a blast furnace operation simulation using a blast furnace mathematical model may be used. Any mathematical model that can simulate the overall operating state of the blast furnace can be used as the blast furnace mathematical model. In this embodiment, as an example, 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, p.15-22" was used. This blast furnace mathematical model basically defines multiple meshes (small regions) by dividing the internal region of the blast furnace in the height, radial, and circumferential directions, and simulates the behavior of each mesh.

[0029] Let's explain the first step. First, we set a reduction rate for carbon consumption per unit of production as the target carbon consumption. For example, for the basic operating conditions shown in Table 1 below, we set a target of achieving an overall reduction rate of 20% by injecting hydrogen gas and reducing the amount of pulverized coal injected as a reducing agent.

[0030] [Table 1]

[0031] Next, operating conditions are set to reduce carbon consumption per unit area by 20% by injecting hydrogen gas under the conditions that keep the furnace top temperature, molten iron temperature, and iron tapping volume constant, relative to the basic operating parameters. Specifically, these operating conditions are determined by reducing the amount of pulverized coal injected, adjusting the amount of hot air injected (airflow rate), and oxygen enrichment, and setting the hydrogen gas injection conditions (injection rate and temperature), so that the furnace top temperature, molten iron temperature, and iron tapping volume remain constant.

[0032] The hydrogen gas injection conditions can be determined by the method described in Patent Document 1. Specifically, the amount of hot air injected (airflow rate), oxygen enrichment rate, and pulverized coal injected are adjusted so that the furnace top temperature, tapping ratio, and molten iron temperature remain constant relative to the basic operating parameters. While making these adjustments, the reduction rate of carbon consumption per unit is determined when the amount of hydrogen gas injected is changed at a certain hydrogen gas temperature.

[0033] Then, the reduction rate is repeatedly calculated by changing the hydrogen gas temperature and similarly changing the injection rate, thereby determining the relationship between the hydrogen gas injection rate and the reduction rate for each temperature range. From the calculated relationships, the hydrogen gas temperature and injection rate that result in the desired reduction rate of carbon consumption per unit area should be selected. Since there may be multiple combinations of hydrogen gas temperature and injection rate that result in the desired reduction rate, the appropriate conditions should be selected according to other operating conditions and circumstances.

[0034] In this description, the operating conditions that result in a predetermined carbon consumption, achieved by adjusting the hydrogen gas conditions (temperature and injection rate) using the method described above, will also be referred to as the hydrogen injection base specifications.

[0035] For example, with a hydrogen gas temperature of 1200°C and a hydrogen injection rate of approximately 270 Nm³, 3 Table 2 shows the hydrogen injection base specifications that result in a 20% reduction in carbon consumption per unit of production, set at / t.

[0036] [Table 2]

[0037] Next, the amount of sensible heat injected from tuyere 2 in the hydrogen injection base specifications is derived. The amount of sensible heat injected can be determined by the product of the injection temperature, specific heat, and injection rate. In this embodiment, the sensible heat amount derived is the sum of the sensible heat amount injected by hot air and the sensible heat amount injected by hydrogen gas in the hydrogen injection base specifications. This derived sum of the sensible heat amounts injected by hydrogen gas and hot air is used as a predetermined sensible heat amount when creating the hydrogen gas temperature-hot air temperature correlation in the next second step.

[0038] Next, the second step will be explained. Based on the hydrogen injection base specifications, the hydrogen gas injection rate and the hot air injection rate (airflow rate) are kept constant, and the hydrogen gas temperature and hot air temperature are adjusted to plot the hydrogen gas temperature and hot air temperature at which the input sensible heat amount becomes the predetermined sensible heat amount derived above. As mentioned above, the sensible heat amount is obtained by the product of the injection temperature, specific heat, and injection rate, and the total input sensible heat amount of hot air and hydrogen gas remains constant at the predetermined sensible heat amount derived. Therefore, by setting the hydrogen gas temperature to a certain temperature, the hot air temperature at which the input sensible heat amount becomes constant can be derived.

[0039] Using the method described above, several combinations of hydrogen gas temperature and hot air temperature are derived that result in a predetermined sensible heat amount, which is the same as the hydrogen injection base specifications for a 20% reduction shown in Table 2. The approximate straight line obtained from these plots represents the hydrogen gas temperature-hot air temperature correlation, which shows the relationship between the hot air temperature and the hydrogen gas temperature in this embodiment. In other words, a set of data consisting of combinations of hydrogen gas temperature and hot air temperature that result in the same predetermined sensible heat amount as the hydrogen injection base specifications is created, and the approximate formula identified based on this set is the hydrogen gas temperature-hot air temperature correlation. The approximate straight line (approximate formula) can be obtained, for example, by the least squares method. Furthermore, the approximate straight line (approximate formula) which is the hydrogen gas temperature-hot air temperature correlation in this embodiment is an equation that shows the relationship between the hot air temperature and the hydrogen gas temperature as a linear function.

[0040] Figure 2 shows a graph representing the hydrogen gas temperature-hot air temperature correlation for a 20% reduction rate, as calculated in the example above. Figure 2 also shows the hydrogen gas temperature-hot air temperature correlation calculated using the same method from the hydrogen injection base parameters (shown in Table 3 below) that result in a 40% reduction in carbon consumption per unit of operation relative to the basic operating parameters.

[0041] The hydrogen injection base parameters for a 40% reduction rate shown in Table 3 were determined by finding the relationship between the hydrogen injection amount and the reduction rate for each hydrogen gas temperature range using the method described in Patent Document 1, similar to the case for a 20% reduction rate. From these relationships, the operating conditions that can achieve a 40% reduction rate were determined. For the sake of clarity, these are the hydrogen injection base parameters for a 40% reduction rate when the hot air temperature and hydrogen gas temperature are set to 1200°C, the same as in the case for a 20% reduction rate.

[0042] [Table 3]

[0043] In the hydrogen gas temperature-hot air temperature correlation shown in Figure 2, for the 20% reduction rate, the hydrogen gas temperature of 1200°C and the hot air temperature of 1200°C at the right end of the graph correspond to the hydrogen injection base specifications for a 20% reduction rate shown in Table 2. If the relationship between the hydrogen gas temperature and the hot air temperature satisfies the hydrogen gas temperature-hot air temperature correlation for a 20% reduction rate, then even when the hydrogen gas temperature is lowered from 1200°C, the amount of sensible heat input to blast furnace 1 remains constant at a predetermined amount, and a 20% reduction rate can be achieved. Note that the hydrogen gas temperature-hot air temperature correlation for a 20% reduction rate is a correlation under operating conditions where only the hydrogen gas temperature and hot air temperature change relative to the hydrogen injection base specifications in Table 2, while the amount of hydrogen gas and hot air injected remain constant.

[0044] The same applies to the 40% reduction in carbon consumption per unit of production as to the 20% reduction. The hydrogen injection base specifications in Table 3 correspond to the conditions at the far right of the graph, where the hydrogen gas temperature is 1200°C and the hot air temperature is 1200°C. If the hydrogen gas temperature and hot air temperature satisfy the hydrogen gas temperature-hot air temperature correlation for a 40% reduction, then even if the hydrogen gas temperature is lowered from 1200°C during operation, the amount of sensible heat input to blast furnace 1 will remain constant, and a 40% reduction can be achieved.

[0045] Furthermore, assuming the hot air and hydrogen gas temperatures are both 1200°C in the hydrogen injection base specifications, the amount of hydrogen gas injected required to achieve a 40% reduction rate is greater than that required for a 20% reduction rate. As shown in the graph in Figure 2, for a 40% reduction rate, the hot air needs to be heated to a higher temperature to compensate for the decrease in hydrogen gas temperature compared to the 20% reduction rate. In other words, as the carbon consumption reduction rate increases, the amount of hydrogen injected increases, and therefore, the hot air temperature needs to be raised to a higher temperature to maintain the same input sensible heat.

[0046] The hydrogen gas temperature-hot air temperature correlation can be calculated by determining the correlation corresponding to the reduction rate of carbon consumption per unit of energy when a reduction rate target has been determined. Alternatively, multiple correlations can be calculated in advance for each reduction rate, the reduction rate to be achieved can be determined according to feasible operating conditions, and the final operating conditions can be determined using the correlation of that reduction rate.

[0047] Next, we will explain the third step. The third step is to determine the hydrogen gas temperature (first temperature) and the hot air temperature (second temperature) based on the hydrogen gas temperature-hot air temperature correlation obtained in the second step.

[0048] In the following description, the operating conditions under which the hydrogen gas temperature and hot air temperature are set based on the hydrogen gas temperature-hot air temperature correlation using the method of this embodiment will also be referred to as "injection temperature adjustment parameters".

[0049] First, the reduction rate for carbon consumption per unit of operation, which is the amount of carbon consumption to be achieved during operation, is set. Then, based on the hydrogen gas temperature-hot air temperature correlation determined in the second step, the hydrogen gas temperature and hot air temperature are determined for that reduction rate.

[0050] The hydrogen gas temperature should be determined within the temperature range that the hydrogen gas heating equipment can achieve. The hot air temperature should be determined within a temperature range that does not affect the blast furnace refractories or other equipment. Either the hydrogen gas temperature or the hot air temperature can be determined in any order; for example, depending on the equipment conditions, the temperature with the more stringent conditions may be determined first, and the corresponding temperature of the other may be determined from the hydrogen gas temperature-hot air temperature correlation, or an appropriate combination of temperatures may be determined by considering both temperatures based on the correlation.

[0051] For example, if the reduction rate is 20%, the hydrogen gas temperature is set to 600°C due to reasons such as the hydrogen gas heating equipment only being able to heat up to 600°C. Then, from the hydrogen gas temperature-hot air temperature correlation for a 20% reduction rate in Figure 2, the hot air temperature can be determined to be approximately 1400°C when the hydrogen gas temperature is 600°C. In this case, the injection temperature adjustment parameters with a hydrogen gas temperature of 600°C and a hot air temperature of 1400°C are constant compared to the hydrogen injection base parameters in Table 2 where the hydrogen gas temperature and hot air temperature are 1200°C, with no change in the amount of sensible heat input. Furthermore, in the injection temperature adjustment parameters, the amount of hydrogen gas and hot air injected are kept constant at the same injection rates as the hydrogen injection base parameters, and other operating conditions such as the amount of oxygen are also kept the same as the hydrogen injection base parameters.

[0052] Conversely, if there is a condition that the upper limit of the hot air temperature is 1400°C, the hot air temperature may be set to 1400°C, and the corresponding hydrogen temperature (approximately 600°C if the reduction rate is 20% in Figure 2) may be determined based on the hydrogen gas temperature-hot air temperature correlation.

[0053] Next, the fourth step is to operate the system using injection temperature adjustment parameters, which are determined in the third step by adjusting the hydrogen gas temperature and hot air temperature to the desired temperatures. By operating with the injection temperature adjustment parameters determined by the method of this embodiment, it becomes possible to operate the system while achieving the carbon consumption intensity reduction target. This allows for stable operation that achieves the reduction target within a range where the hydrogen gas temperature can be adjusted, without increasing the amount of hydrogen injected.

[0054] In this embodiment, the hydrogen injection base parameters were set such that the amount of hydrogen gas injected and the hydrogen gas temperature would result in a predetermined reduction in carbon consumption, without changing the temperature of the hot air from that of the basic operating parameters. The hydrogen gas temperature-hot air temperature correlation was then determined based on these hydrogen injection base parameters, but this is not the only method. As described above, hydrogen injection base parameters that can achieve the same reduction rate can be arbitrarily set within a range where the basic operating parameters such as the tapping ratio and molten iron temperature remain unchanged. Therefore, the hydrogen injection base parameters can be appropriately set according to other conditions, and the hydrogen gas temperature-hot air temperature correlation corresponding to those parameters can be determined. Accordingly, according to this embodiment, it is possible to determine hydrogen gas temperatures and hot air temperatures that correspond to various conditions while achieving stable operation with the same tapping ratio as the basic operating parameters.

[0055] The injection temperature adjustment parameters determined by the method of this embodiment are typically such that the hydrogen temperature is lowered from the hydrogen injection base parameters while the hot air temperature is increased so that the total amount of sensible heat input remains constant. However, this is not necessarily the only condition. For example, depending on the equipment and other conditions, the hydrogen temperature may be increased from the temperature of the hydrogen injection base parameters, and the hot air temperature may be lowered based on the hydrogen gas temperature-hot air temperature correlation. In other words, the injection temperature adjustment parameters only need to be parameters in which both the hot air temperature and the hydrogen gas temperature are adjusted based on the hydrogen gas temperature-hot air temperature correlation.

[0056] In this embodiment, the reduction rate of carbon consumption per unit was used as a parameter to evaluate the reduction in carbon consumption, but it is not limited to this. Any parameter can be used as long as it can evaluate the change in carbon consumption due to hydrogen gas injection, such as carbon consumption per unit, reducing agent ratio, reduction rate of reducing agent ratio (reduction rate of reducing agent ratio relative to base operation; the method of calculation is the same as the reduction rate of carbon consumption per unit).

[0057] Furthermore, while a plasma heating device is shown as a means for further heating the temperature of the hot air in this embodiment, the invention is not limited to this, and other means capable of heating to the required temperature may be used as appropriate. [Examples]

[0058] The present invention will be described in more detail below with reference to examples. Using the hydrogen gas temperature-hot air temperature correlation obtained in advance by the method of this embodiment, a simulation of blast furnace operation was performed using the blast furnace mathematical model described above, and the effect of reducing carbon consumption per unit was confirmed.

[0059] The basic operating parameters were those shown in Table 1, while the hydrogen injection base parameters for achieving reduction rates of 20% and 40% by heating only hydrogen gas were those shown in Tables 2 and 3. Based on the parameters in Tables 2 and 3, the hot air temperature required to achieve the target reduction rate was determined based on the previously calculated hydrogen gas temperature-hot air temperature correlation, assuming a hydrogen temperature of 900°C. Other operating conditions were the same as those for the hydrogen injection base parameters in Tables 2 and 3. The hydrogen gas temperature-hot air temperature correlations for reduction rates of 20% and 40% were determined using the relationship shown in the graph in Figure 2. The blast furnace operation was simulated using the injection temperature adjustment parameters determined as described above.

[0060] Furthermore, as a comparative example, we simulated the operating conditions required to achieve reduction rates of 20% and 40% by changing the hydrogen temperature and hydrogen injection rate while keeping the hot air temperature constant.

[0061] First, regarding a 20% reduction rate, the operating results in the example and comparative example are shown in the graph in Figure 3. Figure 3 is a graph showing the hydrogen gas injection amount when operating with the hydrogen injection base specifications 1, comparative example 1, and example 1, which result in a 20% reduction rate. In Figure 3, BT represents the hot air temperature.

[0062] As shown in Table 2, the hydrogen injection base specification 1, which achieves a 20% reduction, uses approximately 270 Nm³. 3 A hydrogen injection rate of / t was required. In Comparative Example 1, where the hydrogen temperature was lowered to 900°C and the hot air temperature remained at 1200°C under the conditions in Table 2, 300 Nm was required to achieve a 20% reduction. 3 A hydrogen injection rate of / t was required. In other words, in Comparative Example 1, a larger amount of hydrogen injection was needed to achieve the same reduction rate of 20%.

[0063] On the other hand, in Example 1, even though the hydrogen temperature was 900°C, the hot air temperature was raised to 1302°C by a plasma heating device and blown in, resulting in the same injection volume of 270 Nm³ as specified by the hydrogen injection base specifications. 3 We were able to achieve a 20% reduction rate by injecting hydrogen gas at a rate of approximately / t.

[0064] Next, regarding a reduction rate of 40%, the operating results in the example and comparative example are shown in the graph in Figure 4. Figure 4 is a graph showing the amount of hydrogen gas injected when operating with the operating specifications for hydrogen injection base specifications 2, comparative example 2, and example 2, which result in a reduction rate of 40%. In Figure 4, BT represents the hot air temperature.

[0065] As shown in Table 3, the hydrogen injection base specification 2, which achieves a 40% reduction, uses approximately 650 Nm³. 3 A hydrogen injection rate of / t was required. In Comparative Example 2, where the hydrogen temperature was lowered to 900°C and the hot air temperature remained at 1200°C under the conditions in Table 3, 900 Nm was required to achieve a 40% reduction. 3 A blowing rate of / t was required, necessitating the injection of a larger quantity of hydrogen.

[0066] On the other hand, in Example 2, even though the hydrogen temperature was 900°C, the hot air temperature was raised to 1510°C by a plasma heating device and blown in, resulting in the same injection volume of 650 Nm³ as specified by the hydrogen injection base specifications. 3 We were able to achieve a 40% reduction rate by injecting hydrogen gas at a rate of approximately / t. [Explanation of Symbols]

[0067] 1 blast furnace 2 Tuyere 4 Air pipe 6 Lance 8. Plasma heating device

Claims

1. The first step involves determining a predetermined sensible heat amount based on the amount of sensible heat input to the blast furnace by hydrogen gas and hot air, under hydrogen-injected base specifications with a predetermined carbon consumption, which reduces carbon consumption compared to basic operating specifications without hydrogen gas injection. A second step involves creating a hydrogen gas temperature-hot air temperature correlation based on the relationship between the hydrogen gas temperature and the hot air temperature such that the amount of sensible heat input by the hydrogen gas and hot air is the predetermined sensible heat amount determined in the first step, when the hydrogen gas injection rate and the amount of hot air injection rate are kept constant with respect to the hydrogen injection base specifications, while the hydrogen gas temperature and the hot air temperature are changed. A third step involves determining a first temperature, which is the temperature of the hydrogen gas at 1000°C or less, and a second temperature, which is the temperature of the hot air, based on the hydrogen gas temperature-hot air temperature correlation created in the second step. A fourth step involves blowing hydrogen gas from the tuyere at the first temperature determined in the third step, and blowing hot air from the tuyere at the second temperature, A method for operating a blast furnace, characterized by comprising the following:

2. The second step is performed for each carbon consumption during the operation of the blast furnace to derive the hydrogen gas temperature-hot air temperature correlation. The third step is to determine the first temperature and the second temperature based on the hydrogen gas temperature-hot air temperature correlation corresponding to the target carbon consumption in operation, as described in claim 1.

3. The fourth step is the method for operating a blast furnace according to claim 1 or 2, characterized in that the hot air is heated to the second temperature by a plasma heating device upstream of the tuyere in the hot air flow path.

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