Blast furnace auxiliary equipment and blast furnace operation method

Abstract

In a blast furnace operation method according to the present invention, a blowing gas and a reducing material are blown from a tuyere. The reducing material contains a hydrocarbon-hydrogen mixed gas. The method includes: a step of preheating the hydrocarbon-hydrogen mixed gas to generate a high-temperature hydrocarbon-hydrogen mixed gas; and a step of blowing the high-temperature hydrocarbon-hydrogen mixed gas from the tuyere of the blast furnace. Blast furnace auxiliary equipment according to the present invention comprises: a preheating device that preheats the hydrocarbon-hydrogen mixed gas to generate high-temperature hydrocarbon-hydrogen mixed gas; and a blowing device that has a hydrocarbon-hydrogen mixed gas supply unit which introduces the high-temperature hydrocarbon-hydrogen mixed gas into the tuyere.

Description

Blast furnace auxiliary equipment and blast furnace operation method

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

[0002] In recent years, against the backdrop of global environmental issues, carbon dioxide (CO ２ Therefore, it is required to operate blast furnaces installed in steelworks at a low reducing agent ratio (low RAR).

[0003] In a typical blast furnace, hot air (air heated to about 1200°C) is blown into the furnace from the tuyere as a blast gas. This causes the oxygen in the hot air to react with the coke and pulverized coal that act as reducing agents, producing carbon monoxide (CO) gas and hydrogen (H ２ ) gases are produced. These carbon monoxide and hydrogen gases reduce the iron ore charged into the blast furnace. Carbon dioxide is also produced during the reduction reaction of the iron ore. Blast gas is the gas blown into the blast furnace from the tuyere. Blast gas plays a role in gasifying pulverized coal and coke inside the blast furnace.

[0004] As a technology for reducing carbon dioxide emissions in the operation of such blast furnaces, a technology has been proposed in which the carbon monoxide and carbon dioxide contained in the by-product gases emitted from blast furnaces and the like are reformed to produce hydrocarbons such as methane and ethanol, and the produced hydrocarbons are then reintroduced into the blast furnace as reducing agents.

[0005] For example, Patent Document 1 states, ２ and / or CO from a CO-containing gas mixture ２ and / or a step (A) of separating and recovering CO, and the CO separated and recovered in the step (A). ２ and / or adding hydrogen to CO ２ and / or CO to CH ４ and a step (B) of converting the gas that has undergone the step (B) into H. ２ The document discloses a method for operating a blast furnace, comprising: a step (C) of separating and removing O; and a step (D) of injecting the gas that has been subjected to the step (C) into the blast furnace.

[0006] Patent Document 2 states that "CO is extracted from the exhaust gas of a combustion furnace that uses blast furnace gas as a part or all of the fuel. ２ and the separated CO ２ "A method for operating a blast furnace, characterized in that reducing gas obtained by reforming sulphur dioxide into methane is injected into the blast furnace."

[0007] Patent Document 3 discloses "a method for operating a blast furnace, comprising the steps of generating recycled methane gas from a by-product gas discharged from the blast furnace, and injecting a blast gas and a reducing agent into the blast furnace through a tuyere of the blast furnace, wherein oxygen gas is used as the blast gas and the recycled methane gas is used as at least a part of the reducing agent."

[0008] Patent Document 4 discloses "a method of operating a blast furnace, comprising the steps of generating regenerated methane gas using a by-product gas discharged from the blast furnace, and injecting a blast gas and a reducing material into the blast furnace through tuyeres of the blast furnace, wherein oxygen gas is used as the blast gas and the regenerated methane gas is used as at least a part of the reducing material, and the oxygen gas and / or the regenerated methane gas is preheated before being blown into the blast furnace through the tuyeres of the blast furnace."

[0009] Non-Patent Document 1 discloses the configuration of a blast furnace simulation model that can reproduce the operating state of a blast furnace.

[0010] Japanese Patent Publication No. 2011-225969 Japanese Patent Publication No. 2014-005510 International Publication No. 2021 / 106578 Pamphlet International Publication No. 2021 / 131866 Pamphlet

[0011] Sato et al., Kawasaki Steel Technical Report, Vol. 29 (1997), pp. 30-36

[0012] In the techniques of Patent Documents 1 and 2, when the amount of methane injected into the blast furnace as a reducing agent exceeds a certain level, operational problems such as insufficient heat transfer in the lower part of the blast furnace, increased pressure loss, poor slag discharge, etc. Therefore, in order to ensure stable operation, it is necessary to limit the amount of methane injected, which limits the effect of reducing carbon dioxide emissions.

[0013] The technology of Patent Document 3 uses oxygen as the blast gas instead of heated air (hot air). Hereinafter, a typical blast furnace that uses hot air as the blast gas will be referred to as a hot air blast furnace, and a blast furnace that uses oxygen as the blast gas will be referred to as an oxygen blast furnace. The technology of Patent Document 3 claims that by using an oxygen blast furnace instead of a hot air blast furnace, it becomes possible to appropriately control the tuyere temperature even when a large amount of methane is blown in, thereby significantly reducing carbon dioxide emissions. However, the demand for reducing carbon dioxide emissions is increasing significantly, and it is difficult to achieve a carbon dioxide reduction effect that meets this demand.

[0014] Furthermore, the technology of Patent Document 4 uses oxygen instead of heated air (hot air) as the blast gas, and preheats oxygen gas and / or regenerated methane gas before blowing it into the blast furnace through the tuyere. In the technology of Patent Document 4, by preheating oxygen gas and / or regenerated methane gas, the heat required in the blast furnace, which would have been provided by burning carbon such as coke, is replaced by the sensible heat of oxygen gas and / or regenerated methane gas. This reduces the amount of carbon such as coke burned, and is said to further reduce carbon dioxide emissions. However, when methane is heated to high temperatures, thermal decomposition occurs, causing carbon to precipitate and adhere to the piping, resulting in piping blockage and unstable operation. Therefore, to achieve stable operation, it is difficult to preheat regenerated methane gas to a high temperature, and the amount of heat that can be provided as sensible heat of methane gas is also limited. As a result, it is difficult to achieve a carbon dioxide reduction effect sufficient to meet societal demands.

[0015] The present disclosure has been developed in view of the above-described current situation, and aims to provide a method for operating a blast furnace and blast furnace ancillary equipment that can further reduce carbon dioxide emissions from the blast furnace while suppressing thermal decomposition of hydrocarbons.

[0016] The present inventors have conducted extensive research to achieve the above object, and as a result have found that by preheating a mixed gas of hydrocarbons and hydrogen and then injecting it from a tuyere, it is possible to preheat the reducing agent to be injected from the tuyere to a high temperature while also suppressing the thermal decomposition of hydrocarbons such as methane.

[0017] The gist of the present invention is as follows: (1) A method for operating a blast furnace by injecting a blast gas and a reducing agent through a tuyere, wherein the reducing agent contains a hydrocarbon-hydrogen mixed gas, the method comprising the steps of: preheating the hydrocarbon-hydrogen mixed gas to generate a high-temperature hydrocarbon-hydrogen mixed gas; and injecting the high-temperature hydrocarbon-hydrogen mixed gas through the tuyere of the blast furnace.

[0018] (2) The method for operating a blast furnace according to (1), wherein the hydrocarbon-hydrogen mixed gas is a methane-hydrogen mixed gas.

[0019] (3) The method for operating a blast furnace according to (1) or (2), wherein the ratio of the amount of hydrogen to the total amount of hydrocarbons and hydrogen contained in the hydrocarbon-hydrogen mixed gas is 10% by volume or more and 80% by volume or less.

[0020] (4) The method for operating a blast furnace according to any one of (1) to (3), wherein at least a part of the hydrocarbon-hydrogen mixed gas is a recycled hydrocarbon gas synthesized using blast furnace gas discharged from the blast furnace as a raw material.

[0021] (5) The method for operating a blast furnace according to any one of (1) to (4), wherein the ratio of hydrocarbons derived from the regenerated hydrocarbon gas to the hydrocarbons contained in the hydrocarbon-hydrogen mixed gas is 80% by volume or more.

[0022] (6) The method for operating a blast furnace according to any one of (1) to (5), wherein 90% by volume or more of the hydrocarbon-hydrogen mixed gas is preheated before being injected into the blast furnace through the tuyere.

[0023] (7) The method for operating a blast furnace according to claim 1 or 2, wherein the hydrocarbon-hydrogen mixed gas is preheated to a temperature of 500° C. or higher. The method for operating a blast furnace according to any one of (1) to (6).

[0024] (8) The method for operating a blast furnace according to any one of (1) to (7), wherein the blast gas is oxygen gas having an oxygen concentration of 80% by volume or more.

[0025] (9) The method for operating a blast furnace according to any one of (1) to (8), wherein the ratio of the amount of the hydrocarbon-hydrogen mixed gas injected to the amount of the reducing agent injected is 90 wt % or more.

[0026] (10) A blast furnace auxiliary facility comprising: a preheating device that preheats the hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas; and an injection device having a hydrocarbon-hydrogen mixed gas supply section that introduces the high-temperature hydrocarbon-hydrogen mixed gas into a tuyere. (11) The blast furnace auxiliary facility according to (10), further comprising a mixing device that mixes hydrocarbon gas and hydrogen gas to produce a hydrocarbon-hydrogen mixed gas.

[0027] According to the present invention, it is possible to provide a method for operating a blast furnace and blast furnace ancillary equipment that can further reduce the amount of carbon dioxide emitted from the blast furnace while suppressing the thermal decomposition of hydrocarbons.

[0028] It is a schematic diagram showing the configuration of a blast furnace equipped with blast furnace ancillary equipment according to one embodiment of the present invention. It is a schematic diagram showing the configuration of a blast furnace equipped with blast furnace ancillary equipment of a modified example. It is a schematic diagram showing an example of an injection device. It is a schematic diagram showing another example of an injection device.

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. For convenience, an embodiment of a blast furnace auxiliary facility will be described first.

[0030] <Blast Furnace Ancillary Equipment> Fig. 1A is a schematic diagram showing the configuration of a blast furnace equipped with blast furnace ancillary equipment according to one embodiment of the present invention. As shown in Fig. 1A, a blast furnace 1 is equipped with tuyere 2 and blast furnace ancillary equipment. The blast furnace ancillary equipment of this embodiment is equipped with a mixing device 10, a preheating device 11, and an injection device 3. In this example, the blast furnace ancillary equipment further includes a first dehydration device 4, a shaft preheat gas production device 5, a shaft preheat gas injection device 6, a CO ２ A separation unit 7, a regenerated hydrocarbon gas synthesis unit 8, and a second dehydration unit 9 are also provided.

[0031] A typical blast furnace 1 can be used. In this example, the blast furnace 1 includes a furnace body into which raw materials are charged and a tuyere 2 through which blast gas and reducing agent are injected into the furnace body. Raw materials such as sintered ore, iron ore, coke, and pellets (hereinafter also referred to as raw ore materials) are charged into the furnace body from the top (not shown). In this disclosure, the blast furnace 1 is preferably an oxygen blast furnace, as in this example. In other words, oxygen gas is preferably used as the blast gas. When hot air (air heated to approximately 1200°C) is used as the blast gas, the combustion gas contains approximately 50% by volume of nitrogen, which does not contribute to the combustion reaction, making it difficult for the flame temperature in the raceway to reach a high temperature. Therefore, injecting a large amount of reducing agent containing hydrocarbons such as methane may lower the flame temperature in the raceway formed at the tuyere tip (hereinafter also referred to as tuyere tip temperature), potentially resulting in operational problems. On the other hand, by using oxygen gas as the blast gas, it is possible to suppress the inclusion of nitrogen gas, which does not contribute to the combustion reaction, and therefore the tuyere tip temperature can be made higher than when hot air is used. Furthermore, as will be described later, the effect of increasing the tuyere tip temperature can also be obtained by preheating the reducing material containing hydrocarbons such as methane to a high temperature. These two effects make it possible to maintain the tuyere tip temperature at an appropriate range of 2000°C or higher, enabling stable operation. However, in the present disclosure, the blast furnace is not limited to an oxygen blast furnace and may also be a hot air blast furnace.

[0032] The tuyere 2 is used to inject blast gas and reducing material into the furnace body. The tuyere 2 is arranged on the lower side wall of the blast furnace body. When the blast gas and reducing material are injected through the tuyere 2, a raceway is formed in front of the tuyere 2. The blast gas is a gas injected into the blast furnace 1 from the tuyere, and serves to gasify the injected reducing material and coke within the blast furnace 1. The ore raw material charged into the blast furnace 1 is reduced by carbon monoxide gas or hydrogen gas produced by reaction of the blast gas with the reducing material or coke, and molten iron is produced. The tuyere 2 can be configured to include a blowpipe, a small tuyere, a large tuyere, a curved pipe, or the like.

[0033] The injection device 3 is a device for introducing at least a reducing agent (in this example, a reducing agent and oxygen gas as a blast gas) into the tuyere 2 of the blast furnace 1. In this embodiment, the reducing agent contains a hydrocarbon-hydrogen mixed gas. The injection device 3 has a hydrocarbon-hydrogen mixed gas supply unit that introduces a high-temperature hydrocarbon-hydrogen mixed gas (described below) as a reducing agent (for example, a preheated methane-hydrogen mixed gas) into the tuyere 2. In this example, the injection device 3 also has a blast gas supply unit that is configured to introduce a blast gas (oxygen gas in this example) into the tuyere 2.

[0034] 2A is a schematic diagram showing an example of the blowing device 3. In the example shown in FIG. 2A, the blowing device 3 has a coaxial multi-tube configuration having a central tube 31 and an outer tube 33. The inner path of the central tube 31 serves as a hydrocarbon-hydrogen mixed gas supply section (path), into which a high-temperature hydrocarbon-hydrogen mixed gas (for example, a preheated methane-hydrogen mixed gas) is introduced. The annular path between the central tube 31 and the outer tube 33 serves as a blast gas supply section (path), into which a blast gas (oxygen gas in this example) is introduced.

[0035] FIG. 2B is a schematic diagram showing another example of the blowing device 3. In the example shown in FIG. 2B, the blowing device 3 has a coaxial multi-tube configuration including a central tube 31, an outer tube 33, and an inner tube 32 disposed between the central tube 31 and the outer tube 33. The inner path of the central tube 31 serves as a solid supply section (path), into which other blown reducing materials such as pulverized coal and waste plastics are introduced. The annular path between the central tube 31 and the outer tube 33 serves as a hydrocarbon-hydrogen mixed gas supply section (path), into which a high-temperature hydrocarbon-hydrogen mixed gas (e.g., preheated methane-hydrogen mixed gas) is introduced. The annular path between the inner tube 32 and the outer tube 33 serves as a blast gas supply section (path), into which a blast gas (oxygen gas in this example) is introduced.

[0036] In addition, when room temperature oxygen gas is used as the blast gas, ignition properties become poor, so it is preferable to make the discharge section of the outer tube that constitutes the oxygen blast gas supply section (path) of the blowing device 3 a porous structure to promote mixing of the oxygen blast gas and the blown reducing material.

[0037] The first dehydration device 4 is a device for removing condensed water. Specifically, carbon dioxide is generated during the reduction process of the ore raw material. This carbon dioxide, along with carbon monoxide and hydrogen that did not react with the ore raw material, is discharged from the top of the blast furnace as a by-product gas. The top of the blast furnace is under high-pressure conditions of approximately 2 to 4 atmospheres. Therefore, when the blast furnace gas, which is a by-product gas discharged from the top of the blast furnace, returns to normal pressure, it expands and cools, causing the water vapor to condense, generating condensed water. The first dehydration device 4 can remove such condensed water.

[0038] The shaft preheating gas production device 5 is a device for producing preheating gas (hereinafter simply referred to as "shaft preheating gas") to be blown into the shaft of the blast furnace 1. Note that an increase in the oxygen concentration in the blast gas reduces the amount of gas in the furnace, potentially resulting in insufficient heating of the charge material in the upper part of the blast furnace. In this case, blowing preheating gas into the shaft of the blast furnace 1 can promote heating inside the furnace. Therefore, in this embodiment, for example, a portion of the blast furnace gas downstream of the first dehydration device 4 is heated by the shaft preheating gas production device 5 to, but not limited to, a temperature of, for example, 800°C to 1000°C, and then blown into the shaft of the blast furnace using a shaft preheating gas blowing device, thereby promoting heating inside the furnace. Here, the preheating method of the shaft preheating gas production device 5 is not particularly limited, but may include partially burning a portion of the blast furnace gas using a burner or indirectly heating by heat exchange using an electric heater. The shaft preheating gas is not necessarily limited to gas obtained by heating blast furnace gas, and can also be produced by preheating externally supplied hydrogen gas, carbon monoxide gas, nitrogen gas, etc. Meanwhile, in the present disclosure, the blast furnace is not limited to an oxygen-blowing blast furnace, and may be a hot-air blast furnace with a low blast oxygen concentration, and therefore does not necessarily need to have a shaft preheating gas blowing device.

[0039] The shaft preheating gas injection device 6 is a device that injects the shaft preheating gas into the blast furnace 1. For example, it may be configured so that a portion of the blast furnace gas downstream of the first dehydration device 4, which has been preheated as described above, is injected into the shaft of the blast furnace 1. The injection height of the shaft preheating gas is preferably 0.5 or less, where the lower end of the belly of the blast furnace 1 is 0 and the height from the lower end of the belly to the stock line is 1. If the injection position is higher than this, the distance over which heat is exchanged between the shaft preheating gas and the raw materials in the furnace is short, and the temperature-raising effect of the shaft preheating gas cannot be sufficiently obtained.

[0040] The regenerated hydrocarbon gas synthesis apparatus 8 is an apparatus that synthesizes regenerated hydrocarbon gas using at least a portion of the blast furnace gas. In this embodiment, the regenerated hydrocarbon gas synthesis apparatus 8 is configured to generate regenerated hydrocarbon gas (regenerated methane gas in this example). In this example, when at least a portion of the blast furnace gas is introduced into the regenerated hydrocarbon gas synthesis apparatus 8, the regenerated hydrocarbon gas synthesis apparatus 8 reacts carbon dioxide and carbon monoxide contained in the blast furnace gas with hydrogen to generate regenerated hydrocarbon gas (regenerated methane gas in this example). On the other hand, in the present disclosure, the hydrocarbon gas (methane gas in this example) may be external hydrocarbon gas (external methane gas in this example) prepared from the outside, and therefore the blast furnace auxiliary equipment of the present disclosure does not necessarily have to have the regenerated hydrocarbon gas synthesis apparatus 8.

[0041] The hydrogen gas used to generate the recycled hydrocarbon gas (e.g., recycled methane gas) may be supplied from an external source, but the hydrogen gas is preferably generated by a method that generates as little carbon dioxide as possible, such as electrolysis of water. In addition, examples of hydrogen gas supplied from an external source include hydrogen gas produced by reforming hydrocarbons such as natural gas using steam reforming, hydrogen gas obtained by vaporizing liquefied hydrogen, and hydrogen gas produced by dehydrogenating organic hydrides.

[0042] Furthermore, the hydrogen gas used to generate regenerated hydrocarbon gas (e.g., regenerated methane gas) does not need to have a hydrogen concentration of 100% by volume. However, in order to increase the purity of the hydrocarbons in the regenerated hydrocarbon gas to be generated, it is preferable to use a gas with a high hydrogen concentration, specifically, hydrogen gas with a hydrogen concentration of 80% by volume or more. The hydrogen concentration is more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrogen concentration may be 100% by volume. Examples of the remaining gas other than hydrogen include CO and CO. ２ , H ２ S, CH ４ , N ２ Examples include:

[0043] FIG. 1B is a schematic diagram showing the configuration of a blast furnace equipped with a modified example of blast furnace auxiliary equipment. ２ The separation device 7 is a device that separates only carbon dioxide gas from the blast furnace gas. ２ Only the carbon dioxide gas separated from the blast furnace gas by the separator 7 is introduced into the regenerated hydrocarbon gas synthesizer 8. This reduces the volume of gas fed to the regenerated hydrocarbon gas synthesizer 8, allowing the regenerated hydrocarbon gas synthesizer 8 to be made more compact. In this case, the gas remaining after separating the carbon dioxide gas from the blast furnace gas (hereinafter also referred to as "residual gas after separation") may be merged into the supply line for blast furnace gas to the steelworks, for example, as shown in FIG. 1B. The residual gas after separation is mainly composed of carbon monoxide and hydrogen, and may also contain nitrogen, argon, etc.

[0044] The second dehydration device 9 is a device for removing condensed water from the regenerated hydrocarbon gas (in this example, regenerated methane gas). The regenerated hydrocarbon gas (in this example, regenerated methane gas) produced in the regenerated hydrocarbon gas synthesis device 8 is cooled to a temperature below the boiling point of water, thereby condensing water vapor from the regenerated hydrocarbon gas. The second dehydration device 9 makes it possible to remove condensed water from such regenerated hydrocarbon gas.

[0045] In the present disclosure, CO ２The separation device 7, the regenerated hydrocarbon gas synthesis device 8, and the second dehydration device 9 do not necessarily have to be adjacent to the blast furnace 1. For example, the separation device 7, the regenerated hydrocarbon gas synthesis device 8, and the second dehydration device 9 may be provided adjacent to the blast furnace 1. ２ Carbon dioxide is separated from the blast furnace gas in a separator 7, and then the carbon dioxide is reacted with hydrogen supplied from an external source in an external regenerated hydrocarbon gas synthesis unit 8 to produce regenerated hydrocarbon gas, which can also be used.

[0046] The mixing device 10 is a device that mixes a hydrocarbon gas with hydrogen gas to produce a hydrocarbon-hydrogen mixed gas. The hydrocarbon gas can be, for example, methane gas. In this example, it is regenerated methane gas that is produced by the regenerated hydrocarbon gas synthesis device 8 and dehydrated by the second dehydration device 9. The hydrocarbon gas is not limited to methane gas; for example, ethane gas, propane gas, butane gas, ethylene gas, propylene gas, etc. can also be used. Furthermore, the hydrocarbon gas does not need to contain one type of hydrocarbon, and may be a mixed gas of two or more types of hydrocarbons. In this example, the hydrocarbon gas is methane gas, and therefore the hydrocarbon-hydrogen mixed gas is a mixed gas of methane gas and hydrogen gas (hereinafter also referred to as a "methane-hydrogen mixed gas").

[0047] Here, the hydrocarbon gas (e.g., methane gas) used to mix with hydrogen gas may be a hydrocarbon gas (e.g., methane gas) supplied from a separate line in accordance with the operation of the steelworks (hereinafter also referred to as "external hydrocarbon gas" (in the case of methane gas, "external methane gas")), but if a recycled hydrocarbon gas produced using steelworks by-product gas (blast furnace gas, etc.) as the raw material gas is used, the carbon dioxide reduction effect can be further enhanced. Examples of external hydrocarbon gases include hydrocarbon gas derived from fossil fuels.

[0048] In the present disclosure, it is preferable that at least a portion of the hydrocarbon-hydrogen mixed gas (in this example, methane-hydrogen mixed gas) is a recycled hydrocarbon gas (in this example, recycled methane gas) synthesized using blast furnace gas discharged from a blast furnace as a raw material. Therefore, as in this embodiment, the blast furnace auxiliary equipment is preferably equipped with a recycled hydrocarbon gas synthesis unit 8.

[0049] The hydrogen gas used for mixing may be supplied from an external source, but is preferably produced by a method that generates as little carbon dioxide as possible, such as electrolysis of water. Examples of hydrogen gas supplied from an external source include hydrogen gas produced by reforming hydrocarbons such as natural gas using steam reforming, hydrogen gas obtained by vaporizing liquefied hydrogen, and hydrogen gas produced by dehydrogenating organic hydrides. While the hydrogen gas does not need to have a hydrogen concentration of 100% by volume, it is preferable to use a gas with a high hydrogen concentration, specifically, hydrogen gas with a hydrogen concentration of 80% by volume or more. The hydrogen concentration is more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrogen concentration may be 100% by volume. Examples of the remaining gas other than hydrogen include CO and CO. ２ , H ２ S, CH ４ , N ２ Examples include:

[0050] The preheating device 11 is a device that preheats a hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas. In this example, the hydrocarbon-hydrogen mixed gas is a methane-hydrogen mixed gas. There are no particular limitations on the preheating device 11, but it is desirable to use a type that heats without changing the gas composition. For example, there are electric heaters that electrically heat a heating element and preheat the hydrocarbon-hydrogen mixed gas through indirect heat exchange between the heating element and the hydrocarbon-hydrogen mixed gas, and gas heating furnaces that combust fuel to generate high-temperature combustion gas and preheat the hydrocarbon-hydrogen mixed gas through indirect heat exchange between the combustion gas and the hydrocarbon-hydrogen mixed gas.

[0051] When a hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is directly partially combusted, a part of the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is converted into CO ２ and H ２ This is undesirable because the carbon dioxide is converted to CO2 when it is injected into the blast furnace and reacts with the coke, resulting in excessive coke consumption. ２It is desirable to use a method that does not generate CO2, and it is desirable to use renewable electricity obtained from solar power generation or other non-fossil fuels such as hydrogen produced by water electrolysis in the case of an electric heater, or in the case of a gas heating furnace.

[0052] The 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 the same reason, the preheating temperature is more preferably 600°C or higher, and even more preferably 800°C or higher. Therefore, the preheating device 11 is capable of raising the temperature of the hydrocarbon-hydrogen mixed gas to preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 800°C or higher.

[0053] The effects of the blast furnace ancillary equipment of this embodiment will be described below. As described above, the blast furnace ancillary equipment of this embodiment includes a mixing device 10 that mixes hydrocarbon gas and hydrogen gas to produce a hydrocarbon-hydrogen mixed gas, a preheating device 11 that preheats the hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas, and an injection device 3 having a hydrocarbon-hydrogen mixed gas supply unit that introduces the high-temperature hydrocarbon-hydrogen mixed gas into the tuyere. With this configuration, first, a hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) can be obtained by the mixing device 10. Then, the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) can be preheated by the preheating device 11 to produce a high-temperature hydrocarbon-hydrogen mixed gas (in this example, a preheated methane-hydrogen mixed gas). Then, using the injection device 3, this high-temperature hydrocarbon-hydrogen mixed gas (in this example, a preheated methane-hydrogen mixed gas) can be injected into the blast furnace 1 through the tuyere 2. In the blast furnace auxiliary equipment of this embodiment, the hydrocarbon-hydrogen mixed gas (in this example, methane-hydrogen mixed gas) is preheated, and therefore, of the heat amount required in the blast furnace 1, the amount supplied by burning carbon such as coke is replaced by the sensible heat of the hydrocarbon-hydrogen mixed gas (in this example, methane-hydrogen mixed gas). This reduces the amount of carbon such as coke burned, and makes it possible to reduce carbon dioxide emissions. Here, to explain an example in which the hydrocarbon-hydrogen mixed gas is a methane-hydrogen mixed gas, the thermal decomposition reaction of methane produces CH ４ ⇔C+2H ２ This reaction occurs by moving to the right. ２ When a certain amount of is added, according to Le Chatelier's principle, the above reaction tends to proceed to the left and the reaction to the right is suppressed, so CH ４The thermal decomposition of hydrocarbons is suppressed. Therefore, it is also possible to suppress carbon deposition. This principle is similar even when the hydrocarbon is other than methane, for example, ethylene or propane. As described above, the blast furnace ancillary equipment of this embodiment can further reduce carbon dioxide emissions from the blast furnace while suppressing the thermal decomposition of hydrocarbons. Note that, since a gas mixture of hydrocarbon gas such as coke oven gas and hydrogen gas can also be used, the blast furnace ancillary equipment of the present disclosure does not necessarily have to include the mixing device 10.

[0054] <Blast Furnace Operation Method> Next, a blast furnace operation method according to one embodiment of the present invention will be described by way of example. Although not particularly limited, the blast furnace operation method according to this embodiment can be an operation method for a blast furnace equipped with the blast furnace ancillary equipment according to the above-described embodiment. Since such blast furnace ancillary equipment has already been described in the above-described embodiment, it will be used in the description of the embodiment of the blast furnace operation method, and a repeated description will be omitted.

[0055] The blast furnace operating method of this embodiment is a method of operating a blast furnace in which a blast gas and a reducing agent are injected through the tuyere 2. In the blast furnace operating method of this embodiment, raw materials such as sintered ore, lump ore, pellets, coke, etc. are charged into the blast furnace 1 from the top of the blast furnace 1 (not shown). Furthermore, a blast gas (oxygen gas in this example) and a reducing agent are injected into the blast furnace 1 through the tuyere 2 installed at the bottom. The reducing agent contains a hydrocarbon-hydrogen mixed gas. Furthermore, the blast gas is a gas injected into the blast furnace 1 through the tuyere, and serves to gasify the injected reducing agent and coke within the blast furnace 1. The ore raw material charged into the blast furnace 1 is reduced by carbon monoxide or hydrogen produced by reaction of the blast gas with the injected reducing agent or coke, and molten iron is produced.

[0056] The method of this embodiment includes the steps of preheating a hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas, and injecting the high-temperature hydrocarbon-hydrogen mixed gas through the tuyeres of the blast furnace. The method of this embodiment also includes the step of preparing the hydrocarbon-hydrogen mixed gas prior to preheating the hydrocarbon-hydrogen mixed gas. Each step will be described below.

[0057] In the method of this embodiment, first, a hydrocarbon-hydrogen mixed gas is prepared. The hydrocarbon-hydrogen mixed gas contains hydrocarbon and hydrogen. As in the previous embodiment, the hydrocarbon-hydrogen mixed gas is preferably a methane-hydrogen mixed gas.

[0058] The hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is preferably prepared by generating a recycled hydrocarbon gas and mixing it with hydrogen gas, as in the above-described embodiment. That is, at least a portion of the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is preferably a recycled hydrocarbon gas (in this example, a recycled methane gas) synthesized using blast furnace gas discharged from a blast furnace as a raw material. When recycled hydrocarbon gas is used as at least a portion of the hydrocarbon-hydrogen mixed gas, the step of mixing the hydrocarbon gas with hydrogen gas is not essential. By supplying blast furnace gas, synthesis hydrogen gas, and mixing hydrogen gas in advance as raw gases for the recycled hydrocarbon gas production step, the hydrocarbon-hydrogen mixed gas can be produced directly in the recycled hydrocarbon gas production step. Alternatively, the hydrocarbon-hydrogen mixed gas can also be prepared by, for example, feeding it from an external source. In this case, a blast furnace ancillary equipment different from the blast furnace ancillary equipment of the above-described embodiment (one that does not include the first dehydration device 4, the recycled hydrocarbon gas synthesis device 8, the second dehydration device 9, and the mixing device 10) can be used. Hereinafter, a case will be described in which a hydrocarbon-hydrogen mixed gas is prepared by producing a regenerated hydrocarbon gas and mixing it with hydrogen gas as in the above-described embodiment.

[0059] The generation of a hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) has already been described in the above embodiment. The ratio of hydrocarbons derived from the regenerated hydrocarbon gas (in this example, a regenerated methane gas) among the hydrocarbons contained in the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is preferably 80% by volume or more, more preferably 90% by volume or more, and even more preferably 95% by volume or more. By increasing the ratio of hydrocarbons derived from the regenerated hydrocarbon gas, a high CO ２This is because a reduction effect can be obtained. In addition, the ratio of hydrocarbons derived from the regenerated hydrocarbon gas to the hydrocarbons contained in the hydrocarbon gas for mixing is preferably 80% by volume or more, more preferably 90% by volume or more, and even more preferably 95% by volume or more. The entire amount of the hydrocarbon gas may be regenerated hydrocarbon gas, and external hydrocarbon gas may not be included. This is because as the external hydrocarbon gas increases, the amount of CO emitted from the furnace top decreases. ２ The amount of CO emitted to the outside is reduced by converting it into regenerated hydrocarbon gas and reusing it. ２ By reducing the ratio of external hydrocarbon gas in the hydrocarbon-hydrogen mixture and increasing the ratio of regenerated hydrocarbon gas, high CO ２ This can achieve a reduction effect.

[0060] The hydrocarbon concentration (methane concentration) of the hydrocarbon gas (e.g., methane gas) containing at least one of a regenerated hydrocarbon gas (e.g., regenerated methane gas) and an external hydrocarbon gas (e.g., external methane gas) is preferably 80% by volume or more. That is, if the hydrocarbon concentration of the hydrocarbon gas is low, the amount of gas injected into the blast furnace increases, which may increase the pressure loss in the blast furnace and reduce productivity. Furthermore, if the hydrocarbon concentration of the hydrocarbon gas is low, the reduction efficiency of the iron ore in the blast furnace may deteriorate, which may cause operational problems. Therefore, the hydrocarbon concentration of the hydrocarbon gas is preferably 80% by volume or more. The hydrocarbon concentration of the hydrocarbon gas is more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrocarbon concentration of the hydrocarbon gas may be 100% by volume. For the same reason, the hydrocarbon concentrations of the regenerated hydrocarbon gas and the external hydrocarbon gas are each preferably 80% by volume or more. The hydrocarbon concentrations of the regenerated hydrocarbon gas and the external hydrocarbon gas are each more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrocarbon concentrations of the regenerated hydrocarbon gas and the external hydrocarbon gas may each be 100% by volume. The remaining gases other than the hydrocarbon gas in the hydrocarbon gas, regenerated hydrocarbon gas, and external hydrocarbon gas may include, for example, carbon monoxide, carbon dioxide, hydrogen, hydrocarbons, and impurity gases such as nitrogen. Furthermore, if the hydrocarbon concentration of the regenerated hydrocarbon gas decreases, it is possible to maintain a high hydrocarbon concentration in the hydrocarbon gas by, for example, decreasing the proportion of the regenerated hydrocarbon gas in the hydrocarbon gas while increasing the proportion of the external hydrocarbon gas with a higher hydrocarbon concentration.

[0061] The ratio of the amount of hydrogen to the total amount of hydrocarbon (methane in this example) and hydrogen contained in the hydrocarbon-hydrogen mixed gas (methane-hydrogen mixed gas in this example) is preferably 10% by volume or more and 80% by volume or less. By making it 10% by volume or more, it is possible to sufficiently suppress the thermal decomposition of the hydrocarbon (methane in this example) when preheated to a high temperature. Furthermore, by making it 80% by volume or less, it is possible to ensure the amount of hydrocarbon (methane in this example) contained in the hydrocarbon-hydrogen mixed gas, and to obtain a sufficient amount of CO, particularly when a regenerated hydrocarbon gas (regenerated methane gas in this example) is used. ２ For the same reason, it is more preferable that the ratio of the amount of hydrogen to the total amount of hydrocarbon (methane in this example) and hydrogen contained in the hydrocarbon-hydrogen mixed gas (methane-hydrogen mixed gas in this example) be 20% by volume or more and 70% by volume or less.

[0062] In the present disclosure, the hydrocarbon gas (methane gas in this example) does not necessarily contain recycled hydrocarbon gas (recycled methane gas in this example), and the entire amount can be external hydrocarbon gas. In this case, a blast furnace ancillary equipment different from the blast furnace ancillary equipment of the above-described embodiment (one that does not have the first dehydration unit 4, recycled hydrocarbon gas synthesis unit 8, and second dehydration unit 9) can be used. Furthermore, the step of mixing hydrocarbon gas and hydrogen gas is not essential, and the effects of the present invention can be obtained even if a gas containing hydrocarbon and hydrogen is supplied from the outside and used as a hydrocarbon-hydrogen mixed gas.

[0063] In the method of the present embodiment, the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is then preheated using the preheating device 11 to generate a high-temperature hydrocarbon-hydrogen mixed gas (in this example, a preheated methane-hydrogen mixed gas).

[0064] It is also preferable that 90% by volume or more of the hydrocarbon-hydrogen mixed gas be preheated before being injected into the blast furnace through the tuyere 2. This is because by preheating the amount to 90% by volume or more, the amount of carbon dioxide emissions can be further reduced.

[0065] As mentioned above, the 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 the same reason, the preheating temperature is more preferably 600°C or higher, and even more preferably 800°C or higher. Furthermore, the preheating temperature is preferably 1200°C or lower, which can suppress thermal decomposition of hydrocarbons.

[0066] Here, it is preferable to sufficiently insulate the transport piping between the preheating device 11 and the blowing device 3 to minimize heat loss. If heat loss in the transport piping is unavoidable, the preheating temperature in the preheating device 11 should be set higher than the temperature reached when the hydrocarbons are introduced into the blowing device 3, taking the heat loss into consideration. In addition, the preheating temperature is preferably 1200°C or lower in order to suppress thermal decomposition of hydrocarbons.

[0067] In the method of this embodiment, the hot hydrocarbon-hydrogen mixed gas is then injected into the blast furnace through the tuyere.

[0068] Here, it is preferable that the ratio of the blowing amount of hydrocarbon-hydrogen mixed gas (methane-hydrogen mixed gas in this example) to the blowing amount of reducing agent is 90 wt % or more. By making it 90 wt % or more, high CO ２ The amount of the other reducing materials to be injected into the blast furnace is preferably 10 wt % or less of the total amount of the reducing materials to be injected including the hydrocarbon gas (methane gas in this example) and hydrogen gas.

[0069] The oxygen concentration of the blast gas is not particularly limited, and the effects of the present invention can be obtained even with the hot blast gas (oxygen concentration 21 to 30%) used in ordinary blast furnaces. However, from the viewpoint of reducing carbon dioxide emissions by blowing a large amount of hydrocarbon-hydrogen mixed gas, it is preferable for the blast gas to have an oxygen concentration of 50% by volume or more. The blast gas is preferably oxygen gas, and the oxygen concentration of the oxygen gas is preferably 80% by volume or more, more preferably 90% by volume or more, even more preferably 95% by volume or more, and particularly preferably 100% by volume. This is because by sufficiently increasing the oxygen concentration in the oxygen gas, a sufficient tuyere tip temperature can be ensured when blowing a large amount of reducing material containing hydrocarbons, and operational problems can be prevented.

[0070] The effects of the method for operating a blast furnace according to this embodiment will be described below. The method for operating a blast furnace according to this embodiment includes the steps of preheating a hydrocarbon-hydrogen mixed gas to generate a high-temperature hydrocarbon-hydrogen mixed gas, and injecting the high-temperature hydrocarbon-hydrogen mixed gas from the tuyere of the blast furnace. According to the method for operating a blast furnace according to this embodiment, the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas) is preheated, and therefore the amount of heat required in the blast furnace 1 that would otherwise be supplied by burning carbon such as coke is replaced by the sensible heat of the hydrocarbon-hydrogen mixed gas (in this example, a methane-hydrogen mixed gas). This reduces the amount of carbon such as coke that is burned, making it possible to reduce carbon dioxide emissions. Here, to explain by way of example the case where the hydrocarbon-hydrogen mixed gas is a methane-hydrogen mixed gas, the thermal decomposition reaction of methane produces CH ４ ⇔C+2H ２ This reaction occurs by moving to the right. ２ When a certain amount of is added, according to Le Chatelier's principle, the above reaction tends to proceed to the left and the reaction to the right is suppressed, so CH ４ Therefore, it is possible to suppress the deposition of carbon. This principle is also applicable to hydrocarbons other than methane, such as ethylene and propane. As described above, according to the blast furnace operation method of this embodiment, it is possible to further reduce the amount of carbon dioxide emitted from the blast furnace while suppressing the thermal decomposition of hydrocarbons.

[0071] Examples of the present invention will be described below, but the present invention is not limited to the following examples in any way.

[0072] The invention examples and comparative examples of this embodiment are shown in Tables 1 to 4. The invention examples and comparative examples were prepared using a furnace with a volume of 4,300 m ３ The operational parameters for a blast furnace of this type, operating to achieve a production rate of approximately 8,700 t / d, are predicted using a blast furnace simulation model and elementary reaction analysis of hydrocarbon-hydrogen mixed gas. Comparative Example 1 is an example of a conventional blast furnace in which hot air and pulverized coal are injected through the tuyere. Comparative Example 2 is an example in which methane is injected through the tuyere at room temperature (25°C) without being heated. In Examples 1 (Table 1), 2 (Table 2), and 3 (Table 3), excluding Comparative Examples 1 and 2, the hydrocarbon gas is regenerated methane gas with a methane concentration of 100%, and the hydrogen gas is hydrogen gas with a hydrogen concentration of 100%. A methane-hydrogen mixed gas is used as the hydrocarbon-hydrogen mixed gas, and no other reducing agent is used. The entire methane-hydrogen mixed gas is preheated, with preheating temperatures of 500°C, 800°C, and 1200°C, respectively. Only a methane-hydrogen mixed gas is used as the reducing agent. In Example 4 (Table 4), the hydrocarbon gas is regenerated ethane gas with an ethane concentration of 100%, and the hydrogen gas is hydrogen gas with a hydrogen concentration of 100%. An ethane-hydrogen mixed gas is used as the hydrocarbon-hydrogen mixed gas, and no other reducing agent is used for injection. The entire amount of the ethane-hydrogen mixed gas is preheated to a preheating temperature of 500°C. Only an ethane-hydrogen mixed gas is used as the reducing agent for injection.

[0073] The configuration of the blast furnace simulation model used is the same as that described in Non-Patent Document 1. It has been confirmed that this blast furnace simulation model can accurately reproduce the operating conditions of an actual blast furnace, and it is believed that similar results to this simulation model will be obtained when an actual blast furnace is operated. In addition, the elementary reaction analysis of methane-hydrogen mixed gas and ethane-hydrogen mixed gas uses Cantera, a detailed chemical reaction calculation software capable of elementary reaction analysis. It has been confirmed that elementary reaction analysis can accurately reproduce the actual thermal decomposition behavior of methane and ethane, and it is believed that similar results will be obtained when a methane-hydrogen mixed gas is actually preheated in an injection reducing agent preheater.

[0074] In this example, the process configuration shown in FIG. 1B is assumed, and CO is extracted from the blast furnace gas discharged from the top of the blast furnace. ２ After separating CO ２ The methane-hydrogen mixture is reacted with hydrogen to generate regenerated methane or ethane gas, which is then mixed with hydrogen gas, preheated, and injected through the tuyere. The methane-hydrogen mixture is preheated using an electric heater. Preheat gas for the shaft is generated by recovering and dehydrating blast furnace gas from the top of the blast furnace, combusting a portion of it with oxygen, and then mixing it with the uncombusted blast furnace gas. The preheating device and the injection device are assumed to be sufficiently insulated, and the preheating temperature and injection temperature are the same. The thermal decomposition behavior of the preheated methane-hydrogen or ethane-hydrogen mixture after four seconds at this temperature is predicted using elementary reaction analysis, and the amount of methane or ethane thermally decomposed is compared. A lower amount of thermal decomposition during preheating indicates less carbon deposition during preheating.

[0075] As a result of the simulation, CO ２ If the emission is less than 1100 kg / t, CO ２The reduction effect was rated as "good," and if it was 1100 kg / t or more, it was rated as "poor." Furthermore, the thermal decomposition rate of methane or ethane after 4 seconds at each preheating temperature of 500°C, 800°C, and 1200°C was evaluated as a ratio to a reference example (conditions in which only methane or only ethane was preheated without mixing with hydrogen), and if the decomposition rate was less than 1, the suppression of the thermal decomposition of methane or ethane was rated as "good," and if it was 1 or more, the suppression of the thermal decomposition of methane or ethane was rated as "poor."

[0076]

[0077]

[0078]

[0079]

[0080] As shown in Tables 1 to 4, in the invention examples, CO ２ It is possible to achieve both a reduction effect and suppression of the thermal decomposition of methane or ethane, but it is clear that in the comparative example, one of these effects is insufficient.

[0081] 1: blast furnace, 2: tuyere, 3: blowing device, 31: central tube, 32: inner tube, 33: outer tube, 4: first dehydration device, 5: shaft preheating gas production device, 6: shaft preheating gas blowing device, 7: CO ２ Separation device, 8: Regenerated hydrocarbon gas synthesis device, 9: Second dehydration device, 10: Mixing device, 11: Preheating device

Claims

1. A method of operating a blast furnace in which a blast gas and a reducing agent are injected through a tuyere, wherein the reducing agent contains a hydrocarbon-hydrogen mixed gas, the method comprising the steps of: preheating the hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas; and injecting the high-temperature hydrocarbon-hydrogen mixed gas through the tuyere of the blast furnace.

2. The method for operating a blast furnace according to claim 1, wherein the hydrocarbon-hydrogen mixed gas is a methane-hydrogen mixed gas.

3. The method for operating a blast furnace according to claim 1 or 2, wherein the ratio of the amount of hydrogen to the total amount of hydrocarbons and hydrogen contained in the hydrocarbon-hydrogen mixed gas is 10% by volume or more and 80% by volume or less.

4. A method for operating a blast furnace according to any one of claims 1 to 3, wherein at least a portion of the hydrocarbon-hydrogen mixed gas is a recycled hydrocarbon gas synthesized using blast furnace gas discharged from the blast furnace as a raw material.

5. A method for operating a blast furnace according to any one of claims 1 to 4, wherein the ratio of hydrocarbons derived from the regenerated hydrocarbon gas to the hydrocarbons contained in the hydrocarbon-hydrogen mixed gas is 80% by volume or more.

6. A method for operating a blast furnace according to any one of claims 1 to 5, wherein 90% by volume or more of the hydrocarbon-hydrogen mixed gas is preheated before being injected into the blast furnace through the tuyere.

7. The method for operating a blast furnace according to any one of claims 1 to 6, wherein the hydrocarbon-hydrogen mixed gas is preheated to a temperature of 500°C or higher.

8. A method for operating a blast furnace according to any one of claims 1 to 7, wherein the blast gas is oxygen gas having an oxygen concentration of 80% by volume or more.

9. A method for operating a blast furnace according to any one of claims 1 to 8, wherein the ratio of the amount of the hydrocarbon-hydrogen mixed gas injected to the amount of the reducing agent injected is 90 wt % or more.

10. A blast furnace auxiliary facility comprising: a preheating device that preheats the hydrocarbon-hydrogen mixed gas to produce a high-temperature hydrocarbon-hydrogen mixed gas; and an injection device having a hydrocarbon-hydrogen mixed gas supply section that introduces the high-temperature hydrocarbon-hydrogen mixed gas into a tuyere.

11. The blast furnace auxiliary facility according to claim 10, further comprising a mixing device for mixing hydrocarbon gas and hydrogen gas to produce a hydrocarbon-hydrogen mixed gas.

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