Blast furnace operation method, and blast furnace auxiliary equipment

Abstract

This blast furnace operation method includes a step of preheating a hydrocarbon-based gas, and a step of blowing the preheated hydrocarbon-based gas into a tuyere of the blast furnace. The preheating step involves: setting the preheating temperature of the hydrocarbon-based gas to a predetermined temperature in accordance with the preheating time period of the hydrocarbon-based gas; and setting the predetermined temperature to be equal to or higher than a predetermined temperature threshold.

Description

Blast furnace operating methods and blast furnace ancillary equipment

[0001] This disclosure relates to a blast furnace operating method and blast furnace ancillary equipment.

[0002] A blast furnace is a facility for heat-treating and reducing iron ore. Iron ore and coke are charged into the top of the furnace, and hot air and pulverized coal are blown in from tuyeres on the lower sides, burning the coke and pulverized coal. As a result, the oxygen in the hot air reacts with the reducing agents, coke and pulverized coal, to produce carbon monoxide (CO) gas and hydrogen (H2). ２ ) gas is generated. These carbon monoxide and hydrogen gases reduce the iron ore charged into the blast furnace. In addition, carbon dioxide (CO2) is produced in this reduction reaction of iron ore. ２ ) and water vapor (H ２ O) is generated. Blast furnaces account for the majority of carbon dioxide emissions at steel mills.

[0003] In recent years, global warming has become a major social issue, and reducing carbon dioxide emissions is a matter of urgency. Therefore, it is necessary to operate blast furnaces within steel mills using a low reducing agent ratio.

[0004] As a technology for reducing carbon dioxide emissions in blast furnace operation, a technique is known in which hydrogen and hydrocarbon gases, including hydrocarbons, are injected from the tuyeres along with hot air and pulverized coal. This technique reduces carbon usage by having hydrogen take on part of the reducing agent function, which is one of the roles of carbon in blast furnace operation. There are many inventions related to such operating methods, but for example, Patent Document 1 discloses a blast furnace operation method characterized in that, in a blast furnace in which iron ore and coke are charged from the top and pulverized coal is normally injected from the tuyeres, coke oven gas and / or natural gas are injected together with the pulverized coal from the normal tuyeres.

[0005] Furthermore, as a means of further increasing the reduction rate of carbon dioxide emissions, it is effective to preheat the hydrocarbon gas before injecting it into the blast furnace from the tuyeres. Preheating the hydrocarbon gas increases the sensible heat of the blown air, which reduces the amount of coke consumed and thus reduces carbon dioxide emissions. For example, Patent Document 2 discloses a method of operating a blast furnace in which a hydrogen-based gas containing hydrocarbons is injected from the tuyeres at an injection temperature higher than room temperature and at a predetermined injection rate, wherein the injection temperature is set according to the injection rate, or the injection rate is set according to the injection temperature.

[0006] Non-patent document 1 discloses the configuration of a blast furnace simulation model that can reproduce the operating conditions of a blast furnace.

[0007] Japanese Patent Publication No. 2015-129325 Japanese Patent Publication No. 2022-182422

[0008] Sato et al., Kawasaki Steel Technical Report, vol. 29 (1997), pp. 30-36.

[0009] However, it is known that when hydrocarbon gases are heated to high temperatures, the hydrocarbons contained in the hydrocarbon gases undergo thermal decomposition, producing sooty solid carbon. If sooty solid carbon accumulates in piping, it can lead to an increase in the reducing agent ratio and operational problems due to pipe blockage.

[0010] Therefore, there is a need to develop blast furnace operating methods that enable further reductions in carbon dioxide emissions from blast furnaces while maintaining stable operation.

[0011] This disclosure was developed in view of the above-mentioned circumstances and aims to provide a blast furnace operating method that enables further reduction of carbon dioxide emissions from the blast furnace under stable operation.

[0012] [1] A method for operating a blast furnace, comprising the steps of: preheating a hydrocarbon gas; and blowing the preheated hydrocarbon gas into the tuyeres of the blast furnace, wherein the preheating step sets the preheating temperature of the hydrocarbon gas to a predetermined temperature according to the preheating time of the hydrocarbon gas, and the predetermined temperature is set to be equal to or greater than a predetermined temperature threshold.

[0013] [2] The method for operating a blast furnace as described in [1] above, wherein the predetermined temperature threshold is 500°C.

[0014] [3] The method for operating a blast furnace according to [1] or [2] above, wherein the hydrocarbon gas is coke oven gas or natural gas, and the predetermined temperature is further set so that the decomposition rate of methane contained in the coke oven gas or natural gas during the preheating time is less than or equal to a predetermined percentage.

[0015] [4] The method of operating a blast furnace as described in [3] above, wherein the predetermined percentage is 5%.

[0016] [5] The hydrocarbon gas is coke oven gas, and the condition for the predetermined temperature threshold T (°C) at which the decomposition rate during the preheating time t (seconds) is less than or equal to the predetermined percentage is: The method of operating a blast furnace as described in [3] or [4] above.

[0017] [6] The hydrocarbon gas is natural gas, and the condition for the predetermined temperature threshold T (°C) at which the decomposition rate during the preheating time t (seconds) is less than or equal to the predetermined percentage is: The method of operating a blast furnace as described in [3] or [4] above.

[0018] [7] Blast furnace ancillary equipment attached to a blast furnace, comprising: a gas preheating device for preheating a hydrocarbon gas; and a blowing device for blowing the preheated hydrocarbon gas into the tuyere of the blast furnace, wherein the gas preheating device sets the preheating temperature of the hydrocarbon gas to a predetermined temperature according to the preheating time of the hydrocarbon gas.

[0019] According to this disclosure, it will be possible to further reduce carbon dioxide emissions from blast furnaces under stable operation. Furthermore, by using hydrocarbon gases, it will be possible to reduce the amount of coke and pulverized coal used. In addition, by preheating the hydrocarbon gases, the reducing agent ratio will be reduced, making it possible to reduce the amount of coke used as well. In other words, it will be possible to reduce the amount of coal used, which is a finite fossil fuel. Moreover, by appropriately setting the preheating temperature and preheating time, the thermal decomposition of hydrocarbons contained in the hydrocarbon gases will be suppressed, reducing the risk of increased reducing agent ratio due to the generation of sooty solid carbon and operational troubles due to pipe blockage, thereby enabling stable operation.

[0020] This diagram schematically shows the configuration of a blast furnace and its ancillary equipment to which the blast furnace operating method described in this disclosure is applied. This is a schematic diagram showing an example of a blowing device. This is a graph showing the change in gas composition over time when coke oven gas is preheated to 1200°C. This is a graph showing the change in gas composition over time when coke oven gas is preheated to 950°C. Preheating time t (seconds) and maximum preheating temperature T of coke oven gas. ｍａｘ This graph shows the relationship between (°C). This graph shows the time change in gas composition when natural gas is preheated to 1050°C. This graph shows the time change in gas composition when natural gas is preheated to 650°C. The graph also shows the relationship between the preheating time t (seconds) and the maximum preheating temperature T of natural gas. ｍａｘ This graph shows the relationship between (°C) and temperature.

[0021] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, parts having the same configuration or function are denoted by the same reference numerals. In the description of this embodiment, redundant descriptions of the same parts may be omitted or simplified as appropriate.

[0022] Figure 1 is a schematic diagram showing the configuration of blast furnace 1 and blast furnace auxiliary equipment 2 to which the blast furnace operating method described herein is applied.

[0023] The blast furnace 1 comprises a furnace body 11 and a tuyeres 12. In one embodiment of the present disclosure, a general-purpose blast furnace can be used.

[0024] Raw materials including ore raw materials are charged into the furnace body 11 from the furnace top (not shown). The ore raw materials include sintered ore, iron ore, coke, or pellets, etc.

[0025] The tuyere 12 includes a blow pipe, a small tuyere, a large tuyere, a bent pipe, etc. The tuyere 12 blows blowing gas and a reducing agent into the furnace body 11. When the blowing gas and the reducing agent are blown from the tuyere 12, a raceway is formed in front of the tuyere 12.

[0026] The blowing gas is the gas blown into the furnace body 11 from the tuyere 12, and plays a role in gasifying the reducing agent and coke in the furnace body 11. The ore raw materials charged into the furnace body 11 are reduced by carbon monoxide gas or hydrogen gas generated by the reaction of the blowing gas with the reducing agent or coke, and hot metal is produced.

[0027] The auxiliary equipment 2 of the blast furnace includes a blowing device 21 and a gas preheating device 22.

[0028] The blowing device 21 is at least a device for introducing a reducing agent into the tuyere 12. In the present embodiment, the blowing device 21 introduces hot air, which is a reducing agent and a blowing gas, into the tuyere 12. In the present embodiment, the reducing agent contains a hydrocarbon-based gas.

[0029] FIG. 2 is a schematic diagram showing an example of the blowing device 21. In the example shown in FIG. 2, the blowing device 21 has a first lance 211, a second lance 212, and a blow pipe 213.

[0030] The first lance 211 serves as a hydrocarbon-based gas supply part (hydrocarbon-based gas supply path) and introduces a high-temperature hydrocarbon-based gas into the tuyere 12. The high-temperature hydrocarbon-based gas may be, for example, preheated coke oven gas.

[0031] The second lance 212 serves as a pulverized coal supply part (pulverized coal supply path) and introduces pulverized coal and a pulverized coal carrier gas into the tuyere 12. The pulverized coal carrier gas may be, for example, normal-temperature nitrogen gas.

[0032] The blow pipe 213 serves as a blowing gas supply part (blowing gas supply path) and introduces a blowing gas into the tuyere 12. In an embodiment according to the present disclosure, the blowing gas is hot air.

[0033] The gas preheating device 22 is a device that preheats a hydrocarbon gas at normal temperature to generate a high-temperature hydrocarbon gas. In one embodiment according to the present disclosure, the hydrocarbon gas is coke oven gas or natural gas. The gas preheating device 22 is not particularly limited, but a device that heats without changing the gas composition is desirable. For example, an electric heater that heats a heating element electrically and preheats the hydrocarbon gas by indirect heat exchange between the heating element and the hydrocarbon gas, a gas heating furnace that burns fuel to generate high-temperature combustion gas and preheats the hydrocarbon gas by indirect heat exchange between the combustion gas and the hydrocarbon gas, etc. can be mentioned. Further, in order to suppress thermal decomposition of hydrocarbons contained in the hydrocarbon gas, it is desirable to use piping made of a material with little catalytic action. Examples of materials with little catalytic action include silica and alumina.

[0034] Hereinafter, an operation method of the blast furnace 1 according to one embodiment of the present disclosure will be described.

[0035] The operation method of the blast furnace 1 in one embodiment of the present disclosure is an operation method of the blast furnace 1 in which blowing gas and a reducing agent are blown from the tuyere 12. In one embodiment according to the present disclosure, an ore raw material is charged into the blast furnace 1 from the top of the furnace body 11. Further, blowing gas and a reducing agent are blown into the furnace body 11 from the tuyere 12 provided at the lower part. The reducing agent contains a hydrocarbon gas. The blowing gas is a gas blown into the blast furnace 1 from the tuyere, and plays a role of gasifying the reducing agent and coke in the furnace body 11. The ore raw material charged into the furnace body 11 is reduced by carbon monoxide or hydrogen generated by the reaction of the blowing gas with the blown reducing agent or coke, and hot metal is produced.

[0036] The method of this embodiment includes a step of preheating a hydrocarbon gas to generate a high-temperature hydrocarbon gas, and a step of blowing the high-temperature hydrocarbon gas from the tuyere 12 of the blast furnace 1. Hereinafter, each step will be described.

[0037] First, a hydrocarbon gas is prepared. In this example, the hydrocarbon gas is coke oven gas or natural gas.

[0038] Next, the gas preheating device 22 is used to preheat the hydrocarbon gas to generate a high-temperature hydrocarbon gas.

[0039] When hydrocarbon gases are directly partially combusted, some of the hydrocarbons are converted into CO ２ and H ２ It is undesirable because it changes to oxygen (O) and reacts with coke after being blown into the blast furnace, resulting in the consumption of extra coke. Also, the energy input during heating includes CO during energy generation and heating. ２ A method that does not generate waste is desirable. For electric heaters, it is desirable to use renewable electricity obtained from solar power generation, and for gas heating furnaces, it is desirable to use non-fossil fuels such as hydrogen produced by water electrolysis.

[0040] The preheating time and preheating temperature are set within a range where the hydrocarbons contained in the hydrocarbon gas do not undergo thermal decomposition. The preheating time is the time required from when the hydrocarbon gas is preheated until it is injected into the blast furnace, and is determined by dividing the volume in the piping by the flow rate of the hydrocarbon gas. For a predetermined preheating time determined in this way, the preheating temperature is set so that the decomposition rate of methane in the hydrocarbon gas is below a predetermined percentage. The predetermined percentage may be, for example, 5%. More preferably, the predetermined percentage may be, for example, 1%. As the thermal decomposition rate of methane increases with increasing preheating temperature, the allowable preheating temperature increases as the preheating time decreases.

[0041] Elementary reaction analysis is used to set the preheating temperature. It has been confirmed that elementary reaction analysis can accurately reproduce the actual thermal decomposition behavior of hydrocarbons, and it can be assumed that similar results will be obtained when hydrocarbon gases are preheated in an injection reducing agent preheating device. The thermal decomposition behavior of the preheated hydrocarbon gas is predicted by elementary reaction analysis, and the amount of methane thermally decomposed is determined.

[0042] Figure 3A is a graph showing the time change of the gas composition when the coke oven gas is preheated to 1200°C. Since the methane has decreased from the initial methane concentration of 27% in the coke oven gas to 17% at the 1-second point, it can be seen that it is difficult to preheat the coke oven gas to 1200°C. Figure 3B is a graph showing the time change of the gas composition when the coke oven gas is preheated to 950°C. Since no decrease in the methane concentration is observed even after 1000 seconds, it can be seen that it is possible to preheat to 950°C even with a preheating time of 1000 seconds.

[0043] Figure 4 is a graph showing the relationship between the preheating time t (seconds) of the coke oven gas and the maximum preheating temperature T ｍａｘ (°C). The maximum preheating temperature is the maximum value of the temperature at which the thermal decomposition rate of methane is 1% or less. The preheating time t (seconds) and the maximum preheating temperature T ｍａｘ (°C) satisfy the following relationship (1). That is, in order to make the thermal decomposition rate of methane 1% or less, the preheating time t (seconds) and the preheating temperature T (°C) of the natural gas are controlled so as to satisfy the following inequality (2).

[0044] Figure 5A is a graph showing the time change of the gas composition when the natural gas is preheated to 1050°C. Since the methane has decreased from the initial methane concentration of 90% in the natural gas to 68% or less at the 1-second point, it can be seen that it is difficult to preheat the natural gas to 1050°C. Figure 5B is a graph showing the time change of the gas composition when the natural gas is preheated to 650°C. The decrease in methane is slower compared to Figure 5A, and if the preheating time is 21 seconds or less, the thermal decomposition rate of methane becomes 1% or less.

[0045] Figure 6 is a graph showing the relationship between the preheating time t (seconds) of the natural gas and the maximum preheating temperature T ｍａｘ (°C). The maximum preheating temperature is the maximum value of the temperature at which the thermal decomposition rate of methane is 1% or less. The preheating time t (seconds) and the maximum preheating temperature T ｍａｘ (°C) satisfy the following relationship (3). That is, in order to make the thermal decomposition rate of methane 1% or less, the preheating time t (seconds) and the preheating temperature T (°C) of the natural gas are controlled so as to satisfy the following inequality (4).

[0046] The minimum preheating temperature is not particularly limited, but can be, for example, 500°C or higher. This is because a temperature of 500°C or higher can further reduce carbon dioxide emissions. For similar reasons, a preheating temperature of 600°C or higher is more preferable, and 700°C or higher is even more preferable. Accordingly, the gas preheating device 22 is capable of raising the temperature of hydrocarbon gas to preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 700°C or higher.

[0047] With the above configuration, the gas preheating device 22 preheats the hydrocarbon gas to a high temperature. The temperature at which the hydrocarbon gas is preheated is set according to the preheating time. Specifically, the preheating temperature is set so that the decomposition rate of methane contained in the hydrocarbon gas during preheating is below a predetermined percentage and above a predetermined temperature threshold. The blowing device 21 then blows the high-temperature hydrocarbon gas into the furnace body 11 through the tuyeres 12.

[0048] Furthermore, in the blast furnace auxiliary equipment 2 of this embodiment, since hydrocarbon gas is preheated, the portion of the heat required by the blast furnace 1 that was previously supplied by burning carbon such as coke is replaced by the sensible heat of the hydrocarbon gas. As a result, the amount of carbon such as coke burned is reduced, and carbon dioxide emissions can be reduced.

[0049] To illustrate with an example where the hydrocarbon gas is a mixed gas containing methane, the thermal decomposition reaction of methane is CH ４ ⇔C+2H ２ This reaction proceeds to the right. However, by appropriately setting the preheating time and temperature, the above rightward reaction is suppressed, so CH ４ This prevents thermal decomposition. Therefore, it is also possible to suppress carbon precipitation. This principle is the same even if the hydrocarbon is not methane, for example, ethane, ethylene, propane, or butane.

[0050] As described above, the blast furnace auxiliary equipment 2 of this embodiment can further reduce carbon dioxide emissions from the blast furnace while suppressing the thermal decomposition of hydrocarbons.

[0051] The embodiments of this disclosure are described below. However, the embodiments of this disclosure are not limited to the embodiments described below and can be modified at will without departing from the gist of this disclosure.

[0052] Table 1 shows the results of the first example when the injected hydrocarbon gas was coke oven gas.

[0053] The first embodiment is a furnace with a volume of 5000 m³. ３ This study predicts the operating parameters for a blast furnace with a daily production capacity of approximately 10,000 tons using a blast furnace simulation model and elementary reaction analysis of hydrocarbon gases. Comparative Example 1 is an example of a normal blast furnace in which hot air and pulverized coal are blown in from a tuyeres. Comparative Example 2 is an example in which the coke oven gas is not heated and is blown in from a tuyeres at room temperature (25°C). Comparative Example 3 is an example in which the coke oven gas is heated to 1200°C for 10 seconds and then blown in from a tuyeres. Comparative Example 4 is an example in which the coke oven gas is heated to 450°C for 1 second and then blown in from a tuyeres. Invention Example 1 is an example in which the coke oven gas is heated to 950°C for 10 seconds and then blown in from a tuyeres. Invention Example 2 is an example in which the coke oven gas is heated to 1000°C for 1 second and then blown in from a tuyeres.

[0054] The blast furnace simulation model used was the same as that described in Non-Patent Document 1. This blast furnace simulation model has been confirmed to accurately reproduce the actual operating conditions of a blast furnace, and it can be assumed that similar results will be obtained when an actual blast furnace is operated. In addition, detailed chemical reaction calculation software capable of elementary reaction analysis was used for the elementary reaction analysis of hydrocarbon gases. It has been confirmed that the actual thermal decomposition behavior of hydrocarbons can be well reproduced through elementary reaction analysis, and it can be assumed that similar results will be obtained when hydrocarbon gases are actually preheated in a blown reducing agent preheating device.

[0055] In the first embodiment, a process configuration as shown in Figure 1 is assumed, and a preheated hydrocarbon gas is blown in from the tuyer 12. The hydrocarbon gas is preheated using an electric heater. It is assumed that there is sufficient insulation between the gas preheating device 22 and the blowing device 21, and that the preheating temperature and the blowing temperature are the same. The thermal decomposition behavior of the preheated hydrocarbon gas after 10 seconds at this temperature is predicted by elementary reaction analysis, and the amount of methane that has been thermally decomposed is compared. The smaller the amount of thermal decomposition during preheating, the more suppressed carbon deposition is during preheating.

[0056] The simulation results showed that CO ２ If the emissions are 1499 kg / t or less, ２ The reduction effect is rated as "good," and if it is 1500 kg / t or more, it is rated as "poor." In addition, the thermal decomposition rate of methane after 10 seconds at each preheating temperature is evaluated, and if the decomposition rate is 5% or less, the suppression of methane thermal decomposition is rated as "good," and if it is 6% or more, the suppression of methane thermal decomposition is rated as "poor."

[0057]

[0058] As shown in Table 1, if the preheating temperature exceeds a predetermined temperature threshold (500°C), CO ２ A reduction effect is observed. Furthermore, when the relationship between preheating temperature and preheating time satisfies inequality (2), the thermal decomposition of methane contained in coke oven gas is suppressed. Invention examples 1 and 2 satisfy all of the above conditions and are CO ２ It can be seen that both reduction effects and suppression of methane thermal decomposition can be achieved. In contrast, in comparative examples 2 and 4, the preheating temperature is below the predetermined temperature threshold (500°C), so sufficient CO ２ No reduction effect was observed. In Comparative Example 3, the relationship between preheating temperature and preheating time does not satisfy inequality (2), so methane is thermally decomposed beyond the acceptable range.

[0059] Table 2 shows the results of the second example when natural gas was used as the injected hydrocarbon gas. The simulation conditions and evaluation of the effects were the same as in the first example, except that the injected hydrocarbon gas was changed from coke oven gas to natural gas.

[0060] Comparative Example 1 is an example of a normal blast furnace in which hot air and pulverized coal are blown in from the tuyere. Comparative Example 5 is an example in which natural gas is not heated and is blown in from the tuyere at room temperature (25°C). Comparative Example 6 is an example in which natural gas is heated to 1050°C for 13 seconds and then blown in from the tuyere. Comparative Example 7 is an example in which natural gas is heated to 450°C for 1.3 seconds and then blown in from the tuyere. Invention Example 3 is an example in which natural gas is heated to 650°C for 13 seconds and then blown in from the tuyere. Invention Example 4 is an example in which natural gas is heated to 700°C for 1.3 seconds and then blown in from the tuyere.

[0061]

[0062] As shown in Table 2, if the preheating temperature exceeds a predetermined temperature threshold (500°C), CO ２ A reduction effect is observed. Furthermore, when the relationship between preheating temperature and preheating time satisfies inequality (4), the thermal decomposition of methane contained in natural gas is suppressed. Invention examples 3 and 4 satisfy all of the above conditions and are CO ２ It is clear that both reduction effects and suppression of methane thermal decomposition can be achieved. In contrast, in Comparative Examples 5 and 7, the preheating temperature is below the predetermined temperature threshold (500°C), so sufficient CO ２ No reduction effect was observed. In Comparative Example 6, the relationship between preheating temperature and preheating time does not satisfy inequality (4), so methane is thermally decomposed beyond the acceptable range.

[0063] According to the blast furnace operating method described herein, it will be possible to further reduce carbon dioxide emissions from the blast furnace under stable operation.

[0064] 1. Blast furnace 11. Furnace body 12. Tuyeres 2. Blast furnace ancillary equipment 21. Blowing device 211. First lance (hydrocarbon gas supply section) 212. Second lance (pulverized coal supply section) 213. Blowpipe 22. Gas preheating device

Claims

1. A method for operating a blast furnace, comprising the steps of: preheating a hydrocarbon gas; and blowing the preheated hydrocarbon gas into the tuyeres of the blast furnace, wherein the preheating step sets the preheating temperature of the hydrocarbon gas to a predetermined temperature according to the preheating time of the hydrocarbon gas, and the predetermined temperature is set to be equal to or greater than a predetermined temperature threshold.

2. The method for operating a blast furnace according to claim 1, wherein the predetermined temperature threshold is 500°C.

3. The method for operating a blast furnace according to claim 1 or 2, wherein the hydrocarbon gas is coke oven gas or natural gas, and the predetermined temperature is further set so that the decomposition rate of methane contained in the coke oven gas or natural gas during the preheating time is less than or equal to a predetermined percentage.

4. The method for operating a blast furnace according to claim 3, wherein the predetermined percentage is 5%.

5. The hydrocarbon-based gas is coke oven gas, and the condition of the temperature T (°C) at which the decomposition rate during the preheating time t (seconds) is equal to or less than the predetermined ratio is This is the operation method of the blast furnace according to claim 3 or 4.

6. The hydrocarbon gas is natural gas, and the temperature T (°C) condition under which the decomposition rate during the preheating time t (seconds) is less than or equal to the predetermined rate is: The method for operating a blast furnace according to claim 3 or 4.

7. Blast furnace ancillary equipment attached to a blast furnace, comprising: a gas preheating device for preheating a hydrocarbon gas; and a blowing device for blowing the preheated hydrocarbon gas into the tuyere of the blast furnace, wherein the gas preheating device sets the preheating temperature of the hydrocarbon gas to a predetermined temperature according to the preheating time of the hydrocarbon gas.

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