JP7849593B2 - Blast furnace operation methods - Google Patents

Description

This invention relates to a method for operating a blast furnace.

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% carbon by mass. The molten pig iron from the hearth is removed through 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.

Incidentally, in recent years, with calls for preventing global warming, reducing emissions of carbon dioxide ( _CO2 gas), one of the greenhouse gases, has become a social issue. As mentioned above, the blast furnace method uses carbon as a reducing agent, which generates a large amount of _CO2 gas. Therefore, the steel industry is one of the major industries in terms of _CO2 gas emissions, and it must respond to this social demand. Specifically, further reduction of the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operation is urgently needed.

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. Reduction reactions in the furnace can be expressed by various reaction equations. Of these reduction reactions, the direct reduction reaction by coke (reaction equation: FeO + C ⇒ Fe + CO) is an endothermic reaction that involves significant 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.

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.

International Publication No. 2021/107091

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.

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 enables the achievement of carbon consumption reduction targets 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.

This invention was made to solve the above-mentioned problems, and the gist of the invention is as follows:

(1) A blast furnace operation method comprising: a first step of determining a predetermined sensible heat amount based on the amount of sensible heat input to the blast furnace by hydrogen gas and hot air, in a hydrogen injection base specification with a predetermined carbon consumption, where carbon consumption is reduced compared to the basic operating specifications 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 sensible heat amount 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.

(2) The blast furnace operation method according to (1) above, characterized in that the second step involves changing the hydrogen gas temperature and hot air temperature while keeping the hydrogen gas injection rate and hot air injection rate unchanged with respect to the hydrogen injection base parameters, and determining the hydrogen gas temperature-hot air temperature correlation based on the hydrogen gas temperature and hot air temperature at which the input sensible heat amount from the hydrogen gas and hot air becomes the predetermined sensible heat amount.

(3) The blast furnace operation method 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, 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.

(4) A blast furnace operation method according to any one of (1) to (3) above, characterized in that the second step is performed for each carbon consumption amount 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 carbon consumption amount in the operation.

(5) The fourth step is 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, as described in any one of (1) to (4) above.

According to the present invention, in a blast furnace operation method that injects hydrogen gas, it is possible to provide a method that can 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.

This diagram shows the configuration of the blast furnace and hot blast furnace, etc., according to this embodiment. This graph shows an example of the hydrogen gas temperature-hot air temperature correlation in this embodiment. 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. 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.

The embodiments will be described below with reference to the drawings. The operation method of the blast furnace 1 in this embodiment involves blowing hydrogen gas, as a reducing agent, into the furnace along with hot air from the tuyeres. Figure 1 shows the configuration of the blast furnace 1 and hot air furnace, etc., according to this embodiment. The blast furnace 1 is equipped with tuyeres 2, annular pipes 3, blower pipes 4, lances 6, plasma heating devices 8, etc., for blowing hot air and hydrogen gas into the blast furnace 1.

The tuyeres 2 are inlets for blowing hot air into the blast furnace. The hot air blown in from tuyeres 2 is generated, for example, in a hot blast furnace and supplied to tuyeres 2 via the annular pipe 3 and the blower pipe 4. The hot blast furnace is, for example, a furnace with a heat storage chamber inside, constructed by arranging silica bricks in a grid pattern. The temperature of the hot air is measured, and based on this measurement data, the amount of heat stored in the hot blast furnace 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. Furthermore, a lance for blowing pulverized coal, used as a reducing agent, may be inserted through tuyeres 2 or the blower pipe 4 to blow pulverized coal into the blast furnace through tuyeres 2.

Lance 6 is an injection lance for blowing hydrogen gas. Lance 6 is inserted into the tuyere 2, and hydrogen gas supplied from the gas tank is blown into the tuyere 2 through lance 6. While hydrogen gas is usually injected into the blast furnace 1 through tuyere 2, this is not limited to this; lance 6 may also be installed in locations other than tuyere 2 to inject hydrogen gas. The hydrogen gas injected from lance 6 is heated to the desired temperature by a heating device and then supplied.

The hydrogen gas injected from lance 6 is not limited to being composed solely of hydrogen gas; it may also be a hydrogen-based gas with hydrogen as its main component. Preferably, it is a hydrogen-based gas containing 80 mol% or more of hydrogen (mol% of hydrogen gas relative to the total amount of all gases constituting the gas injected from lance).

The plasma heating device 8 is 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 using a plasma torch within the air supply pipe 4 or 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, where the hydrogen gas confluence occurs, 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.

Furthermore, as a method and apparatus for heating hot air using plasma heating, methods such as those described in "Shinichi Inaba, Junichiro Yagi, Iron and Steel, 78 (1992), pp. 1187-1197," "D. S. 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.

Furthermore, in this embodiment, the temperature of the hot air and the hydrogen gas refer to the temperature at the time 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 within the tuyere 2 (or air supply pipe 4). The temperature of the hydrogen gas should be measured at the tip of the lance within the lance 6.

Furthermore, the temperature drop that occurs when hot air 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 drop into consideration 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 drop up to the tip of the lance 6.

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.
(Step 1) Determine a predetermined sensible heat amount based on the amount of sensible heat input to the blast furnace by hydrogen gas and hot air, using hydrogen gas injection as the base hydrogen injection parameters, which reduce carbon consumption compared to the basic operating parameters by injecting hydrogen gas. (Step 2) Create 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 sensible heat amount determined in Step 1. (Step 3) Set the temperature of the hydrogen gas (first temperature) and the temperature of the hot air (second temperature) based on the hydrogen gas temperature-hot air temperature correlation created in Step 2. (Step 4) Inject hydrogen gas and hot air from the tuyeres at the temperatures set in Step 3 and begin operation.

The following describes each process. In this specification, "carbon consumption per unit" refers to the carbon required to produce one ton of molten iron (i.e., the amount of carbon consumed per ton of molten iron). "Reduction rate of carbon consumption per unit" means the ratio of the reduction in carbon consumption per unit in operation under different operating conditions to the carbon consumption per unit in operation under the basic operating conditions. If the carbon consumption per unit under the basic conditions is A (kg/t) and the carbon consumption per unit in operation under a different set of conditions is B (kg/t), then the reduction rate of carbon consumption per unit ΔC is given by the following formula.
△C=(A-B)/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.

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, operation without hydrogen gas injection is described as the basic operating parameters, but it is not limited to this; 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, the carbon consumption reduction target may be set as the basis, and carbon consumption may be reduced using the method of this embodiment based on those operating conditions.

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 "Koji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, pp. 15-22" was used. This blast furnace mathematical model, in essence, defines multiple meshes (small regions) by dividing the internal region of the blast furnace in the height, radial, and circumferential directions, and then simulates the behavior of each mesh.

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

Next, operating conditions are set to reduce carbon consumption per unit area by 20% by injecting hydrogen gas, under conditions where the furnace top temperature, molten iron temperature, and iron tapping volume remain 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 rate, 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.

The hydrogen gas injection conditions can be determined by the method described in Patent Document 1. Specifically, the hot air injection rate (airflow rate), oxygen enrichment rate, and pulverized coal injection rate 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 of production is determined when the hydrogen gas injection rate is varied at a given hydrogen gas temperature.

Then, by repeatedly changing the hydrogen gas temperature and similarly changing the injection rate, the reduction rate is determined, and the relationship between the hydrogen gas injection rate and the reduction rate for each temperature range is established. From the relationships obtained, 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.

In this description of the embodiment, 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.

As an example, Table 2 shows the hydrogen injection base specifications that result in a 20% reduction in carbon consumption per unit of production, with the hydrogen gas temperature set to 1200°C and the hydrogen injection rate set to approximately 270 ^Nm³ /t.

Next, the amount of sensible heat input from tuyere 2 in the hydrogen injection base specifications is derived. The amount of sensible heat input can be determined by the product of the injection temperature, specific heat, and injection rate. In this embodiment, the total sensible heat input from the hot air and the hydrogen gas is derived in the hydrogen injection base specifications. This derived sum of sensible heat input from 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.

Next, we will explain the second step. Using the hydrogen injection base specifications, the hydrogen gas injection rate and the hot air injection rate (airflow rate) are kept constant. The hydrogen gas temperature and hot air temperature are adjusted, and the hydrogen gas temperature and hot air temperature are plotted so that the input sensible heat amount becomes the predetermined sensible heat amount derived above. As mentioned above, the sensible heat amount is calculated as the product of the injection temperature, specific heat, and injection rate. Since the total input sensible heat amount of hot air and hydrogen gas remains constant at the predetermined sensible heat amount derived, setting the hydrogen gas temperature to a certain temperature allows us to derive the hot air temperature at which the input sensible heat amount becomes constant.

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 expresses the relationship between hot air temperature and hydrogen gas temperature in this embodiment. In other words, a set of data consisting of hydrogen gas temperature and hot air temperature combinations 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) representing the hydrogen gas temperature-hot air temperature correlation in this embodiment is an equation that shows the relationship between hot air temperature and hydrogen gas temperature as a linear function.

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 displays 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 output relative to the basic operating parameters.

The hydrogen injection base specifications for a 40% reduction rate shown in Table 3 were determined by calculating 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. The operating conditions that achieve a 40% reduction rate were then selected from these relationships. For clarity, these are the hydrogen injection base specifications 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.

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, achieving a 20% reduction rate. 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 hydrogen gas injection rate and hot air injection rate remain constant.

The same principles apply 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, the amount of sensible heat input to blast furnace 1 remains constant, and a 40% reduction can be achieved.

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 to achieve a 40% reduction rate will be 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, requiring the hot air temperature to be raised higher to maintain the same input sensible heat.

The hydrogen gas temperature-hot air temperature correlation can be calculated based on a predetermined carbon consumption intensity reduction target. Alternatively, multiple correlations can be calculated in advance for each reduction rate. The achievable reduction rate can then be determined based on feasible operating conditions, and the final operating conditions can be determined using the correlations of these reduction rates.

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.

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."

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 based on that reduction rate.

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 prioritized; for example, depending on the equipment conditions, the temperature with the more stringent requirements may be determined first, and the corresponding temperature of the other may be determined from the hydrogen gas temperature-hot air temperature correlation. Alternatively, an appropriate temperature combination may be determined by considering both temperatures based on the correlation.

For example, in the case of a 20% reduction rate, 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 shown in Figure 2, the hot air temperature for a hydrogen gas temperature of 600°C can be determined to be approximately 1400°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, remain constant compared to the hydrogen injection base parameters in Table 2, where both the hydrogen gas and hot air temperatures are 1200°C, with no change in the input sensible heat. Furthermore, in the injection temperature adjustment parameters, the injection volume of hydrogen gas and hot air are kept constant, the same as in the hydrogen injection base parameters, and other operating conditions such as oxygen levels are also kept the same as in the hydrogen injection base parameters.

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.

Next, the fourth step is to operate the system using the 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 using the injection temperature adjustment parameters determined by the method of this embodiment, it becomes possible to achieve 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 hydrogen injection rate.

In this embodiment, the hydrogen injection base parameters were set such that the hydrogen gas injection rate and hydrogen gas temperature would result in a predetermined reduction in carbon consumption, while keeping the hot air temperature the same as 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 capable of achieving 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 corresponding hydrogen gas temperature-hot air temperature correlation can be determined. Consequently, this embodiment allows for stable operation at the same tapping ratio as the basic operating parameters while determining hydrogen gas temperatures and hot air temperatures to accommodate various conditions.

Regarding the injection temperature adjustment parameters determined by the method of this embodiment, typically, the hydrogen temperature is lowered compared to the hydrogen injection base parameters, while the hot air temperature is increased so that the total input sensible heat 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 hydrogen gas temperature are adjusted based on the hydrogen gas temperature-hot air temperature correlation.

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

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

The present invention will be described in further detail below with reference to examples. Using the hydrogen gas temperature-hot air temperature correlation previously determined 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 of production was confirmed.

The basic operating parameters were those shown in Table 1. 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, and assuming a hydrogen temperature of 900°C, 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. 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 20% and 40% reduction rates 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.

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

First, regarding a 20% reduction rate, the operating results for 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 under the operating specifications for hydrogen injection base specification 1, comparative example 1, and example 1, which result in a 20% reduction rate. In Figure 3, BT represents the hot air temperature.

As shown in Table 2, hydrogen injection base specification 1, which achieved a 20% reduction, required a hydrogen injection rate of approximately 270 ^Nm³ /t. 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 shown in Table 2, a hydrogen injection rate of 300 ^Nm³ /t was required to achieve a 20% reduction. In other words, comparative example 1 required a larger amount of hydrogen injection to achieve the same 20% reduction rate.

On the other hand, in Example 1, even with a hydrogen temperature of 900°C, by raising the hot air temperature to 1302°C using a plasma heating device and blowing the air, a reduction rate of 20% was achieved with a hydrogen gas injection rate of approximately 270 ^Nm³ /t, which is the same as the injection rate specified in the hydrogen injection base specifications.

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

In the hydrogen injection base specifications 2, which achieved a 40% reduction, a hydrogen injection rate of approximately 650 ^Nm³ /t was required, as shown in Table 3. In comparative example 2, where the hydrogen temperature was lowered to 900°C and the hot air temperature remained at 1200°C as in Table 3, a hydrogen injection rate of 900 ^Nm³ /t was required to achieve a 40% reduction, indicating that a larger amount of hydrogen injection was necessary.

On the other hand, in Example 2, even with a hydrogen temperature of 900°C, by raising the hot air temperature to 1510°C using a plasma heating device and blowing the air, a reduction rate of 40% was achieved with a hydrogen gas injection rate of approximately 650 ^Nm³ /t, which is the same as the injection rate specified in the hydrogen injection base specifications.

1. Blast furnace 2. Tuyer 4. Air blower 6. Lance 8. Plasma heating device

Claims (3)

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 reduce 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: 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 characterized in that the first temperature and the second temperature are determined based on the hydrogen gas temperature-hot air temperature correlation corresponding to the target carbon consumption in operation, as described in claim 1 . The fourth step is 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, as described in claim 1 or 2 .