Blast furnace operation method and blast furnace auxiliary facility

Abstract

Provided is a blast furnace operation method capable of further reducing the amount of carbon dioxide discharged from a blast furnace under a stable operation. A first reducing gas containing carbon monoxide and a second reducing gas containing at least one among hydrocarbon and hydrogen are used as blowing reduction materials, and the first reducing gas is heated before blowing into the inside of the blast furnace.

Description

Blast furnace operation methods and auxiliary equipment

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

[0002] In recent years, against the backdrop of global environmental issues, carbon dioxide (CO ２ Therefore, it is required to operate blast furnaces in steel works at low reducing agent ratios (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) and hydrogen (H ２ ) are produced. These carbon monoxide and hydrogen reduce the iron ore charged inside the blast furnace. Carbon dioxide is also produced during the reduction reaction of this iron ore. Blast gas is the gas blown into the blast furnace from the tuyere. Blast gas also plays a role in gasifying pulverized coal and coke inside the blast furnace.

[0004] As a technology for reducing carbon dioxide emissions in blast furnace operation, for example, technologies such as those disclosed in Patent Documents 1 and 2 have been proposed. In these technologies, carbon monoxide and carbon dioxide contained in by-product gas discharged from a blast furnace are reformed to produce hydrocarbons such as methane, and the produced hydrocarbons are then introduced back into the blast furnace as reducing agents.

[0005] WO 2021 / 106578 German Patent Application Publication No. 102017006067 (A1) Specification

[0006] However, the techniques of Patent Documents 1 and 2 have limitations in their effectiveness in reducing carbon dioxide emissions, and currently cannot fully meet the demand for further reductions in carbon dioxide emissions.

[0007] The present invention was developed in consideration of the above-mentioned current situation, and aims to provide a blast furnace operation method that enables further reduction in carbon dioxide emissions from the blast furnace under stable operation. Another aim of the present invention is to provide blast furnace auxiliary equipment to be used in the above-mentioned blast furnace operation method. In this disclosure, all numerical ranges expressed using "to" mean ranges that include the numerical values ​​written before and after "to" as the lower and upper limits, respectively, except when written as "greater than" or "less than."

[0008] The inventors have conducted extensive research to achieve the above-mentioned object. As a result, the inventors have found that the desired object can be achieved by simultaneously satisfying the following points: - A first reducing gas containing carbon monoxide and a second reducing gas containing at least one of a hydrocarbon and hydrogen are used as the reducing agents to be injected; - The first reducing gas is heated before being injected into the blast furnace.

[0009] Furthermore, the inventors conducted further intensive research and discovered the following: When the first reducing gas and the second reducing gas are used as the injection reducing agent, if fluctuations over time (hereinafter also referred to as operational fluctuations) occur in the component composition and particle size of the charged raw materials, such as sintered ore, lump ore, and pellets (hereinafter also referred to as raw ore), as well as coke, the progress of the reduction reaction of the raw ore inside the blast furnace will fluctuate significantly. That is, if operational fluctuations occur, for example, a temporary delay in the progress of the reduction reaction of the raw ore inside the blast furnace may occur, causing the raw ore to descend to the lower part of the blast furnace without being reduced. As a result, the unreduced raw ore undergoes an endothermic reaction in the lower part of the blast furnace, resulting in a heat shortage in the lower part of the blast furnace and causing operational problems such as increased pressure drop and poor slag discharge. In order to prevent such operational problems, it is effective to set the ratio of the first reducing gas to the second reducing gas in the injected reducing material using an indicator of the blast furnace operation status, in particular at least one of the molten iron temperature and the tuyere temperature. This makes it possible to further reduce carbon dioxide emissions from the blast furnace under stable operation, even when operational fluctuations occur.

[0010] The present invention has been completed based on the above findings and further investigations. That is, the gist and configuration of the present invention are as follows.

[0011] 1. A method for operating a blast furnace, comprising: a first heating step of heating a first reducing gas; and an injection step of injecting a blast gas and an injection reducing material into the blast furnace from tuyere ports of the blast furnace, wherein the injection reducing material contains the first reducing gas and a second reducing gas, and the first reducing gas contains carbon monoxide, and the second reducing gas contains at least one of a hydrocarbon and hydrogen.

[0012] 2. The method for operating a blast furnace according to 1 above, wherein the injection amounts of the first reducing gas and the second reducing gas in the injection step are set based on an index of a blast furnace operation state.

[0013] 3. The method for operating a blast furnace according to 2 above, wherein the indicators of the blast furnace operation status are the molten iron temperature and the tuyere temperature.

[0014] 4. The method for operating a blast furnace according to any one of 1 to 3 above, wherein the first reducing gas has a carbon monoxide concentration of 30% by volume or more, and the second reducing gas has a total concentration of hydrocarbons and hydrogen of more than 70% by volume.

[0015] 5. The method for operating a blast furnace according to any one of 1 to 4 above, further comprising a second heating step of heating the second reducing gas.

[0016] 6. The method for operating a blast furnace according to any one of 1 to 5 above, wherein the second reducing gas contains methane as the hydrocarbon.

[0017] 7. The method for operating a blast furnace according to any one of 1 to 6 above, wherein the oxygen concentration of the blast gas is 80% by volume or more.

[0018] 8. The method for operating a blast furnace according to any one of 1 to 7 above, wherein the raw material gas for at least one of the first reducing gas and the second reducing gas is a by-product gas from a steelworks.

[0019] 9. The method for operating a blast furnace according to 8, wherein carbon dioxide is separated from the steelworks by-product gas to obtain a carbon dioxide-containing gas and a remaining gas, and the first reducing gas uses the remaining gas as a raw material gas, and the second reducing gas uses the carbon dioxide-containing gas as a raw material gas.

[0020] 10. The method for operating a blast furnace according to 8 or 9 above, wherein an excess of at least one of the first reducing gas and the second reducing gas is supplied into a steelworks.

[0021] 11. The method for operating a blast furnace according to any one of 1 to 10, wherein at least a portion of the second reducing gas is generated from a steelworks by-product gas and hydrogen gas, and the amount of the second reducing gas to be injected in the injection step is set based on the supplyable amount of the hydrogen gas.

[0022] 12. A blast furnace auxiliary facility comprising: a first reducing gas generation device that generates a first reducing gas; a second reducing gas generation device that generates a second reducing gas; a first heating device that heats the first reducing gas; and a gas injection device having a reducing gas supply unit that introduces the first reducing gas and the second reducing gas into tuyere of a blast furnace, and a blast gas supply unit that introduces a blast gas into the tuyere of the blast furnace, wherein the first reducing gas contains carbon monoxide, and the second reducing gas contains at least one of a hydrocarbon and hydrogen.

[0023] According to the present invention, carbon dioxide (CO ) emitted from a blast furnace to the outside under stable operation can be prevented. ２ ) emissions can be further reduced.

[0024] FIG. 1 is a diagram schematically showing an example of a blast furnace and blast furnace ancillary equipment used in a method for operating a blast furnace according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing an example of a gas injection device used in a method for operating a blast furnace according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing an example of a gas injection device used in a method for operating a blast furnace according to an embodiment of the present invention. FIG. 4 is a diagram schematically showing a blast furnace and blast furnace ancillary equipment used in Reference Examples 1 and 3. FIG. 5 is a diagram schematically showing an example of a blast furnace and blast furnace ancillary equipment used in a method for operating a blast furnace according to an embodiment of the present invention. FIG. 6 is a diagram schematically showing a blast furnace and blast furnace ancillary equipment used in Reference Example 2. FIG. 7 is a diagram schematically showing a blast furnace and blast furnace ancillary equipment used in Comparative Example 2.

[0025] The present invention will be described based on the following embodiments. A method for operating a blast furnace according to one embodiment of the present invention includes a first heating step of heating a first reducing gas, and an injection step of injecting a blast gas and an injection reducing agent into the blast furnace through the tuyere of the blast furnace, wherein the injection reducing agent contains the first reducing gas and a second reducing gas, and the first reducing gas contains carbon monoxide, and the second reducing gas contains at least one of a hydrocarbon and hydrogen.

[0026] In blast furnace operation, for example, raw ore and coke are charged into the blast furnace from its top. Blast gas and a reducing agent are injected into the blast furnace through tuyere holes located at the bottom. The reducing agent injected into the blast furnace through the tuyere is also called an injected reducing agent to distinguish it from coke. The raw ore charged into the blast furnace is reduced by carbon monoxide and hydrogen produced by the reaction between the blast gas and the reducing agent. This reduction reaction of the raw ore generates carbon dioxide. This carbon dioxide, along with the carbon monoxide and hydrogen that did not react with the raw ore, is then discharged from the blast furnace top as a by-product gas. The blast furnace top is under high-pressure conditions of approximately 2.5 atmospheres. Therefore, the by-product gas (hereinafter also referred to as blast furnace gas) discharged from the blast furnace top expands and cools as it returns to atmospheric pressure, condensing the water vapor. The condensed water is then removed in a dehydrator.

[0027] The first reducing gas and second reducing gas, as well as each step of the method for operating a blast furnace according to one embodiment of the present invention, will be described below, taking as an example a case where the method is applied to a blast furnace and blast furnace auxiliary facilities as schematically shown in Fig. 1. In the figure, reference numeral 1 denotes a blast furnace, 2 denotes a tuyere, 3 denotes a second reducing gas generator, 4 denotes a gas injection device, 5 denotes a first dehydration device, 6 denotes a second dehydration device, 7 denotes a burner, 8 denotes a first reducing gas generator, 9-1 denotes a first heating device, 9-2 denotes a second heating device, and 9-3 denotes a third heating device. Note that the blast furnace referred to here also includes a shaft-type reducing furnace and the like.

[0028] [First reducing gas] The first reducing gas contains carbon monoxide. The remainder of the first reducing gas other than carbon monoxide is, for example, hydrogen (H ２ ), nitrogen (N ２ ), carbon dioxide (CO ２ ), water vapor (H ２ O) and hydrogen sulfide (H ２ S). Here, the higher the concentrations of carbon monoxide and hydrogen in the first reducing gas, the more the reduction reaction of the ore raw material is promoted. Therefore, in the first reducing gas, it is preferable that the concentrations of carbon monoxide and hydrogen contributing to the reduction reaction are high. The concentration of carbon monoxide in the first reducing gas is preferably 30 vol% or more, more preferably 40 vol% or more, even more preferably 45 vol% or more, and still more preferably 47.5 vol% or more. The concentration of carbon monoxide in the first reducing gas may be 100 vol%. Furthermore, the concentration of hydrogen in the first reducing gas is preferably 40 vol% or more, more preferably 45 vol% or more, and even more preferably 47.5 vol% or more. Furthermore, the total concentration of carbon monoxide and hydrogen in the first reducing gas is preferably 80 vol% or more, more preferably 90 vol% or more, and even more preferably 95 vol% or more. The total concentration of carbon monoxide and hydrogen in the first reducing gas may be 100 vol%. In order to prevent clogging of the flow passages due to carbon deposition during heating, the hydrocarbon concentration in the first reducing gas is preferably 5% by volume or less.

[0029] The first reducing gas is a gas component having carbon atoms (CO, CO ２ , C.H. ４The reducing gas can be produced from a gas containing hydrocarbons such as benzene, toluene ...

[0030] For example, when blast furnace gas is used as a steelworks by-product gas, the blast furnace gas is introduced into a first reducing gas generator as shown in FIG. 1 . Then, the first regenerated reducing gas can be generated by removing carbon dioxide from the blast furnace gas using a carbon dioxide separation method such as a pressure swing method or an amine absorption method. The method for generating the first regenerated reducing gas is not particularly limited. For example, the first regenerated reducing gas can be generated by reforming a gas containing a hydrocarbon such as methane and carbon dioxide as a feed gas, or by partially combusting the hydrocarbons from a hydrocarbon-containing gas as a feed gas. Alternatively, a portion of the steelworks by-product gas may be extracted with its original composition and used as the first regenerated reducing gas.

[0031] In addition, the first reducing gas may be a gas supplied from outside the steelworks in accordance with the operation of the steelworks (hereinafter also referred to as the first external reducing gas), or a mixture of the first regenerated reducing gas and the first external reducing gas. The first external reducing gas can be produced, for example, by reforming a hydrocarbon gas such as natural gas.

[0032] The preferred compositions and concentrations of the first regenerative reducing gas and the first external reducing gas are the same as the preferred composition and concentration of the first reducing gas described above.

[0033] The ratio of the first regenerative reducing gas and the first external reducing gas in the first reducing gas is not particularly limited, and may be appropriately changed depending on the operating conditions of the steelworks. In addition, taking into consideration the amount of by-product gas generated in the steelworks, the amount of the first regenerative reducing gas used is preferably 700 Nm3, for example. ３ / t or less, more preferably 600 Nm ３ / t or less. ３ The unit " / t" is the amount (Nm3) of each gas used (injected into the blast furnace) to produce 1 ton of molten iron. ３ ) The same applies to the unit "kg / t" described below.

[0034] The excess of the steelworks by-product gas (other than the raw material gas for the first regenerated reducing gas) may be supplied, for example, to (another facility within) the steelworks. The excess of the first reducing gas (other than that injected into the blast furnace) may also be supplied, for example, to (another facility within) the steelworks. The same applies to the excess of the second reducing gas described below.

[0035] [Second reducing gas] The second reducing gas is a hydrocarbon (C ｉ H ｊ The second reducing gas contains at least one of hydrocarbons and hydrogen. The hydrocarbons and hydrogen may be one kind or a mixture of two or more kinds. The remainder of the second reducing gas other than the hydrocarbons and hydrogen may be, for example, nitrogen (N ２ ), carbon monoxide (CO) and carbon dioxide (CO ２) Furthermore, if the hydrocarbon concentration and hydrogen concentration of the second reducing gas decrease, the amount of gas injected into the blast furnace and, consequently, the pressure loss in the blast furnace increase, which may result in a decrease in productivity. Furthermore, the hydrocarbon concentration and hydrogen concentration of the second reducing gas decrease relatively during repeated gas circulation. Therefore, the hydrocarbon and hydrogen concentrations in the second reducing gas are preferably greater than 70 vol%, more preferably 80 vol% or more, even more preferably 90 vol% or more, and still more preferably 95 vol% or more. The hydrocarbon and hydrogen concentrations in the second reducing gas may each be 100 vol%. Furthermore, the total concentration of the hydrocarbon and hydrogen in the second reducing gas is preferably 80 vol% or more, more preferably 90 vol% or more, and even more preferably 95 vol% or more. The total concentration of the hydrocarbon and hydrogen in the second reducing gas may be 100 vol%. The concentration of the remainder other than hydrocarbons and hydrogen in the second reducing gas is preferably less than 30% by volume, more preferably 20% by volume or less, even more preferably 10% by volume or less, and even more preferably 5% by volume or less. The concentration of the remainder other than hydrocarbons and hydrogen in the second reducing gas may be 0% by volume.

[0036] Furthermore, the hydrocarbon preferably has four or fewer carbon atoms in the molecule. If a hydrocarbon with five or more carbon atoms in the molecule is used, soot may be generated at the tuyere, which may reduce the conversion efficiency when the hydrocarbon is converted into carbon monoxide and hydrogen inside the blast furnace. Examples of preferred hydrocarbons include methane, ethylene, and propane.

[0037] The second reducing gas can be generated using a gas containing at least one of carbon monoxide and carbon dioxide, such as a steelworks by-product gas, as a feed gas. Examples of steelworks by-product gases include blast furnace gas, converter gas, and a mixture thereof. Steelworks by-product gases also include the gas remaining after introducing a steelworks by-product gas, such as blast furnace gas, into a first reducing gas generator to generate the first reducing gas (hereinafter also referred to as "post-product gas"), as shown in FIG. 1 , and a gas extracted by separating only a portion of the components from a steelworks by-product gas, such as blast furnace gas, using a carbon dioxide separator or the like. Among these, the post-product gas is preferred. By using the post-product gas as a feed gas, carbon dioxide generated and remaining during the generation of the first reducing gas can be reused as the second reducing gas without being discharged to the outside, thereby further reducing carbon dioxide emissions. Hereinafter, the second reducing gas generated from the steelworks by-product gas is also referred to as a second regenerated reducing gas.

[0038] For example, when a produced gas is used as the feed gas, the produced gas is introduced into a second reducing gas generator as shown in Figure 1. In the second reducing gas generator, carbon monoxide and carbon dioxide contained in the feed gas are reacted with hydrogen contained in a separately supplied hydrogen gas to form hydrocarbons, thereby generating the second regenerated reducing gas. The second regenerated reducing gas may optionally be dehydrated to remove water vapor. For example, the second regenerated reducing gas is cooled to near room temperature to condense the water vapor, and the condensed water is removed in a second dehydrator as shown in Figure 1.

[0039] The hydrogen gas used to generate the second regenerated reducing gas may be supplied from an external source, or may be a by-product gas from a steelworks, such as coke oven gas (a by-product gas discharged from a coke oven) containing hydrogen as a main component, or blast furnace gas containing a certain amount of hydrogen. Since coke oven gas and blast furnace gas contain carbon monoxide in addition to hydrogen, the hydrogen may be separated from these gases by PSA or the like and extracted for use. Since coke oven gas has a high hydrogen concentration, it may be used as hydrogen gas without separation. When hydrogen gas is supplied from an external source, the method for producing the hydrogen gas is not particularly limited. A method for producing hydrogen gas that generates as little carbon dioxide as possible, such as electrolysis of water, is preferred. To increase the concentration of hydrocarbons or hydrogen in the second regenerated reducing gas, the hydrogen concentration of the hydrogen gas is preferably 80% by volume or more, more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrogen concentration of the hydrogen gas may be 100% by volume. The remainder of the hydrogen gas other than hydrogen may be, for example, nitrogen (N ２ ), carbon monoxide (CO), carbon dioxide (CO ２ ), hydrogen sulfide (H ２ S) and methane (CH ４ ) etc. Such hydrogen gas may be used as the second reducing gas.

[0040] In addition, the second reducing gas may be a gas supplied from outside the steelworks in accordance with the operation of the steelworks (hereinafter also referred to as the second external reducing gas), or a mixture of the second regenerated reducing gas and the second external reducing gas may be used as shown in Figure 1. Examples of the second external reducing gas include gases containing hydrocarbons or hydrogen produced outside the steelworks, such as methane gas, natural gas, city gas, ethylene gas, propane gas, and hydrogen gas. Note that steelworks by-product gas may be supplied to an outside steelworks, and a gas containing hydrocarbons such as methane may be produced outside the steelworks, and the gas may be brought back into the steelworks.

[0041] The preferred compositions and concentrations of the second regenerating reducing gas and the second external reducing gas are the same as the preferred composition and concentration of the second reducing gas described above.

[0042] The proportions of the second regenerative reducing gas and the second external reducing gas in the second reducing gas are not particularly limited and may be changed as appropriate depending on the operating conditions of the steelworks. Furthermore, from the viewpoint of reducing carbon dioxide emissions, the greater the amount of the second regenerative reducing gas used in the second reducing gas, the more preferable. For example, the proportion of the second regenerative reducing gas in the second reducing gas is preferably 80% by volume or more, and more preferably 90% by volume or more. The proportion of the second regenerative reducing gas in the second reducing gas may be 100% by volume. Note that, when the hydrocarbon and hydrogen concentrations in the second reducing gas decrease, the proportion of the second regenerative reducing gas is reduced while the proportion of the second external reducing gas, which has high hydrocarbon and hydrogen concentrations, is increased, thereby making it possible to maintain the hydrocarbon and hydrogen concentrations in the second reducing gas at a certain level or higher.

[0043] In addition to the first reducing gas and the second reducing gas, other reducing materials, such as pulverized coal and waste plastics, may be used together as the reducing material. The total amount of the other reducing materials injected into the blast furnace is preferably 150 kg / t or less, more preferably 100 kg / t or less, and even more preferably 50 kg / t or less. The total amount of the other reducing materials injected into the blast furnace may be 0 kg / t.

[0044] Furthermore, in a blast furnace operating method according to one embodiment of the present invention, it is important to simultaneously use the first reducing gas and the second reducing gas as the injected reducing agent (injected into the blast furnace). In this case, it is preferable to appropriately control the ratio of the first reducing gas to the second reducing gas in the injected reducing agent. If only the first reducing gas is used as the injected reducing agent, for example, if the hydrogen concentration in the blast furnace decreases due to operational fluctuations, causing a temporary delay in the progress of the reduction reaction of the ore raw material inside the blast furnace, the delay in the progress of the reduction reaction may not be recovered, and the ore raw material may descend to the lower part of the blast furnace without being reduced. As a result, the unreduced ore raw material may undergo an endothermic reaction in the lower part of the blast furnace, resulting in a heat shortage in the lower part of the blast furnace, which may cause operational problems such as a decrease in the molten iron temperature, an increase in pressure drop, and poor slag discharge. Furthermore, if only the second reducing gas is used as the injected reducing agent, the effect of reducing carbon dioxide emissions may not be sufficient. In this regard, the first reducing gas and the second reducing gas are simultaneously used as the blown reducing material, and preferably the ratio of the first reducing gas to the second reducing gas in the blown reducing material is appropriately controlled, for example, in the manner described below. This makes it possible to further reduce the amount of carbon dioxide emitted from the blast furnace under stable operation, even when operational fluctuations occur.

[0045] [Blast gas] The blast gas is a gas blown into the inside of the blast furnace from the tuyere, and serves to gasify the coke and pulverized coal. The type of blast gas is not particularly limited. Examples of the blast gas include gases having an oxygen concentration of 21% to 100% by volume (air, oxygen-enriched air, oxygen gas, etc.). In particular, from the viewpoint of increasing the effect of reducing carbon dioxide emissions by blowing a large amount of the first reducing gas and the second reducing gas from the tuyere, the oxygen concentration of the blast gas is preferably 80% by volume or more, more preferably 90% by volume or more, and even more preferably 95% by volume or more. The oxygen concentration of the blast gas may be 100% by volume. The remainder of the blast gas other than oxygen is, for example, nitrogen (N ２ ), carbon dioxide (CO ２ ) and argon (Ar).

[0046] In particular, if the oxygen concentration of the blast gas is 90% by volume or higher, the concentration of impurity gases (such as nitrogen) in the blast furnace gas decreases. Therefore, when a second regenerated reducing gas is generated using blast furnace gas as the feed gas, the hydrocarbon concentration of the second reducing gas can be maintained at a high concentration (approximately 90% by volume) without the need for the supply of a second external reducing gas, which is extremely advantageous. Furthermore, when a first regenerated reducing gas is generated using blast furnace gas as the feed gas, it is possible to prevent impurity gases (such as nitrogen) from accumulating in the first reducing gas during repeated gas circulation, which would result in a relative decrease in the carbon monoxide and hydrogen concentrations of the first reducing gas. For the same reason, when a second regenerated reducing gas is generated using blast furnace gas as the feed gas, it is also possible to prevent a relative decrease in the hydrocarbon concentration of the second reducing gas. Furthermore, since the volume of gas flowing through each facility, such as a blast furnace and various reducing gas generation devices, is reduced, this is extremely advantageous from the perspective of reducing the facility scale and improving productivity by reducing pressure loss in the blast furnace.

[0047] If the tuyere temperature drops excessively, there is an increased risk of operational problems, such as insufficient heat transfer in the lower part of the blast furnace, increased pressure loss, and poor slag discharge. In this regard, if the oxygen concentration of the blast gas is increased, the tuyere temperature can be controlled within an appropriate range of 1900°C to 2500°C, preferably 2000°C to 2400°C, even when large amounts of the first reducing gas and the second reducing gas are used. Therefore, it is possible to prevent the occurrence of operational problems such as those described above and ensure stable operation, while significantly reducing the amount of reducing materials other than the first reducing gas and the second reducing gas, such as coke, and thus further reducing carbon dioxide emissions.

[0048] [First heating step] In the first heating step, the first reducing gas is heated. Of the heat required for blast furnace operation, the first reducing gas blown through the tuyere is heated and supplied to the blast furnace as sensible heat, instead of the heat supplied as reaction heat when gasifying carbon contained in coke with oxygen. This makes it possible to further reduce the amount of carbon used as a reducing agent such as coke, and therefore the amount of carbon dioxide emitted from the blast furnace.

[0049] Here, the heating temperature (supply temperature) of the first reducing gas is preferably 700°C or higher. That is, the carbon monoxide contained in the first reducing gas is stable even at high temperatures. Furthermore, the effect of reducing carbon dioxide emissions improves as the heating temperature of the first reducing gas increases. In addition, when the heating temperature of the first reducing gas is less than 700°C, the carbon monoxide contained in the first reducing gas undergoes the following reaction: 2CO → C + CO ２

[0050] This may result in the precipitation of solid carbon, which may lead to deterioration or clogging of the piping, hindering the operation of the equipment. On the other hand, if the heating temperature of the first reducing gas is 700°C or higher, the precipitation of solid carbon is suppressed. Therefore, the heating temperature of the first reducing gas is preferably 700°C or higher. The heating temperature of the first reducing gas is more preferably 800°C or higher, and even more preferably 1000°C or higher. Furthermore, there is no particular limitation on the upper limit of the heating temperature of the first reducing gas. The heating temperature of the first reducing gas is preferably, for example, 1300°C or lower, since this can reduce the rate of equipment deterioration.

[0051] The heating in the first heating step may be performed, for example, by a first heating device described later. The heating in the second heating step and the third heating step may be performed, for example, by a second heating device and a third heating device described later, respectively.

[0052] [Second Heating Step] In the optional second heating step, the second reducing gas is heated. By heating the second reducing gas together with the first reducing gas, the effect of reducing carbon dioxide emissions is further enhanced.

[0053] Here, from the viewpoint of sufficiently enhancing the effect of reducing carbon dioxide emissions and preventing problems such as pipe clogging due to liquefaction of higher hydrocarbons in particular, the heating temperature (supply temperature) of the second reducing gas is preferably equal to or higher than the boiling point of the hydrocarbons contained in the second reducing gas, more preferably equal to or higher than 100°C, and even more preferably equal to or higher than 200°C. However, if the heating temperature of the second reducing gas exceeds 450°C, the hydrocarbons contained in the second reducing gas may be thermally decomposed (e.g., CH ４ →C+2H ２ , C ３ H８ →3C+4H ２ ) may occur, resulting in the generation of solid carbon, which may cause problems such as pipe clogging. Therefore, the heating temperature of the second reducing gas is preferably 600°C or lower, and more preferably 450°C or lower. If the second reducing gas does not contain hydrocarbons, there is no risk of thermal decomposition, so the heating temperature of the second reducing gas may be set to 1300°C or lower, the same as the heating temperature of the first reducing gas.

[0054] [Third Heating Step] In the optional third heating step, the blast gas is heated. By heating the blast gas as well as the first reducing gas, the effect of reducing carbon dioxide emissions is further enhanced.

[0055] Here, from the viewpoint of enhancing the effect of reducing carbon dioxide emissions, the heating temperature (supply temperature) of the blown gas is preferably 300°C to 1300°C, and more preferably in the range of 1000°C to 1300°C.

[0056] However, if the oxygen concentration of the blast gas exceeds 35% by volume, the heating temperature of the blast gas may be set to a range of 300°C to 800°C from the viewpoint of suppressing deterioration of the blast gas heating equipment and extending its life.

[0057] [Injection Step] Next, the blast gas and the first reducing gas and the second reducing gas, which are the reducing agents to be injected, are injected into the interior of the blast furnace through the tuyere of the blast furnace.

[0058] Here, the blowing amount of the blast gas is 200 Nm ３ / t~1300Nm ３ / t. The blowing amount of the first reducing gas is preferably 100 Nm ３ / t~220Nm ３ The amount of the second reducing gas blown is preferably 70 Nm ３ / t~500Nm ３ / t is preferable. In addition, the blowing amount of the first reducing gas (Nm ３ / t): Amount of second reducing gas injected (Nm ３ / t) = 1:0.3 to 2.5 is preferred. In particular, when the second reducing gas is mainly methane, the blowing amount of the second reducing gas is 110 Nm ３ / t~220Nm ３ / t, and the injection amount of the first reducing gas (Nm ３ / t): Amount of second reducing gas injected (Nm ３ / t)=1:0.5 to 2.0 is more preferable.

[0059] Furthermore, as described above, when the first reducing gas and the second reducing gas are used as the blown reducing agent, if an operational fluctuation occurs, for example, a temporary delay occurs in the progress of the reduction reaction of the ore raw material inside the blast furnace, and the ore raw material may descend to the lower part of the blast furnace without being reduced. As a result, the unreduced ore raw material may undergo an endothermic reaction in the lower part of the blast furnace, causing a heat shortage in the lower part of the blast furnace, which may cause operational problems such as an increase in pressure drop and poor slag discharge. Furthermore, if the reduction reaction of the ore raw material progresses excessively quickly, an excessive supply of reducing agent may occur, resulting in CO ２ This is a problem as emissions are increasing unnecessarily.

[0060] The progress of the reduction reaction of the ore raw material and the heat supply state in the lower part of the blast furnace can be grasped from indicators of the blast furnace operation status, such as the molten iron temperature and the tuyere temperature. For example, if the reduction reaction is delayed and unreduced ore raw material descends to the lower part of the blast furnace, the molten iron temperature will decrease. Conversely, if the reduction reaction is accelerated, the molten iron temperature will increase.

[0061] Furthermore, the higher the ratio of the first reducing gas among the injected reducing materials, the greater the effect of reducing carbon dioxide. However, the hydrogen concentration inside the blast furnace decreases, slowing the reduction rate of the ore raw material. On the other hand, the higher the ratio of the second reducing gas, the higher the hydrogen concentration inside the blast furnace, speeding up the reduction rate of the ore raw material.

[0062] Therefore, by setting the injection amounts of the first reducing gas and the second reducing gas using an index of the blast furnace operation status, it is possible to further reduce the amount of carbon dioxide emissions from the blast furnace under stable operation, even when operational fluctuations occur.

[0063] For example, when the molten pig iron temperature and the tuyere temperature are used as indicators of the blast furnace operation status, if the molten pig iron temperature is below a reference temperature range, at least one of the following is performed: reducing the injection rate of the first reducing gas and increasing the injection rate of the second reducing gas. On the other hand, if the molten pig iron temperature exceeds the reference temperature range, at least one of the following is performed: increasing the injection rate of the first reducing gas and decreasing the injection rate of the second reducing gas. The reference temperature range for the molten pig iron temperature may be set, for example, preferably from 1500°C to 1550°C.

[0064] Furthermore, when the tuyere tip temperature is below the reference temperature range, at least one of the first reducing gas injection rate and the second reducing gas injection rate is reduced. On the other hand, when the tuyere tip temperature exceeds the reference temperature range, at least one of the first reducing gas injection rate and the second reducing gas injection rate is increased. The reference temperature range for the tuyere tip temperature may be set, for example, preferably from 1900°C to 2500°C, more preferably from 2000°C to 2400°C.

[0065] Furthermore, when increasing or decreasing the injection rates of the first reducing gas and the second reducing gas (hereinafter also referred to as injection rate adjustment), the amounts by which the injection rates of the first reducing gas and the second reducing gas are increased or decreased (hereinafter also referred to as adjustment amounts of the first reducing gas and the second reducing gas) may be selected depending on the deviations of the molten iron temperature and the tuyere temperature from the reference temperature ranges. For example, the adjustment amounts of the first reducing gas and the second reducing gas may be set to 5 Nm ３ / t ~ 30Nm ３ / t range can be selected.

[0066] If the molten iron temperature and tuyere temperature do not fall within the reference temperature range even after a single injection rate adjustment, the injection rate adjustment may be performed multiple times. As a result of the injection rate adjustment, the injection rate of the first reducing gas may temporarily become 0 (a state in which only the second reducing gas is injected). Similarly, as a result of the injection rate adjustment, the injection rate of the second reducing gas may temporarily become 0 (a state in which only the first reducing gas is injected).

[0067] In addition, since it is preferable to simultaneously set the molten iron temperature and the tuyere temperature within the appropriate range, it is more preferable to use both the molten iron temperature and the tuyere temperature as indicators of the blast furnace operating conditions.

[0068] Furthermore, other indicators corresponding to the reduction or heat transfer state of the blast furnace may be used as indicators of the blast furnace operation status. For example, the gas utilization rate calculated from the composition of the blast furnace gas using the following formula can be used. The slower the progress of the reduction reaction, the lower the gas utilization rate. [Gas utilization rate (%)] = [CO of blast furnace gas] ２ concentration (volume %) / ([CO concentration (volume %) in blast furnace gas] + [CO ２ Concentration (volume %) × 100

[0069] In addition, when generating a second reducing gas (second regenerated reducing gas) using steelworks by-product gas as a raw material gas, it may be necessary to use a large amount of hydrogen gas supplied from outside the steelworks. It is expected that hydrogen gas will be produced by an electrolytic production method using renewable energy sources such as solar power generation and hydroelectric power generation in the future. However, renewable energy sources have significant fluctuations in power generation due to weather and other factors, making stable supply difficult. Therefore, the available supply of hydrogen gas also fluctuates significantly from day to day, which may result in an insufficient supply of the second reducing gas. Therefore, it is preferable to set the injection amount of the second reducing gas based on the available supply of hydrogen gas (the amount of hydrogen gas that can be used to generate the second regenerated reducing gas). When the hydrogen supply is unstable, the injection amount of the second reducing gas may be temporarily set to zero (a state in which only the first reducing gas is injected). Furthermore, the injection amount of the first reducing gas may be simultaneously adjusted in accordance with the injection amount of the second reducing gas.

[0070] The operating conditions other than those mentioned above are not particularly limited and may be in accordance with conventional methods depending on the capacity of the blast furnace, etc. The injection of each gas may be carried out, for example, by a gas injection device described later.

[0071] In addition, if the oxygen concentration in the blast gas increases, the amount of gas in the furnace decreases, and the temperature rise of the charge material in the upper part of the blast furnace may be insufficient. In this case, as shown in Figure 1, it is preferable to perform preheated gas injection, in which gas preheated to about 800 °C to 1000 °C is injected into the blast furnace shaft. As the preheated gas, for example, gas obtained by partially burning a portion of the blast furnace gas downstream of the first dehydration device or gas heated by electrical heating may be used.

[0072] In addition, the coke charged into the blast furnace from the top promotes the progress of the reduction reaction of the ore and enhances the effect of reducing carbon dioxide emissions. １５０ １５ Preferably, the drum strength index DI is 82.0 or more. １５０ １５ is an index representing the strength of coke by the drum method specified in JIS K 2151:2004, and is the percentage (%) of a sample remaining on a 15 mm sieve after 150 rotations by a drum testing machine.

[0073] [Blast Furnace Ancillary Equipment] The blast furnace ancillary equipment according to one embodiment of the present invention is an ancillary equipment of a blast furnace that can be suitably used in the above-described blast furnace operating method. That is, the blast furnace ancillary equipment according to one embodiment of the present invention comprises: a first reducing gas generation device that generates a first reducing gas; a second reducing gas generation device that generates a second reducing gas; a first heating device that heats the first reducing gas; and a gas injection device that has a reducing gas supply unit that introduces the first reducing gas and the second reducing gas into the tuyere of the blast furnace and a blast gas supply unit that introduces a blast gas into the tuyere of the blast furnace, wherein the first reducing gas contains carbon monoxide and the second reducing gas contains at least one of a hydrocarbon and hydrogen. An example of the blast furnace ancillary equipment according to one embodiment of the present invention is the blast furnace ancillary equipment as shown in FIG. 1.

[0074] Here, the first reducing gas generator has, for example, a raw material gas intake section and a carbon dioxide separation section. The carbon dioxide separation section may be configured in any manner as long as it can perform carbon dioxide separation by, for example, a pressure swing method or an amine absorption method. When carbon dioxide separation is performed by a pressure swing method, the carbon dioxide separation section has, for example, an adsorption tower filled with an adsorbent such as zeolite or activated carbon and a compressor. When carbon dioxide separation is performed by an amine absorption method, the carbon dioxide separation section has, for example, an absorption tower that brings carbon dioxide into contact with an absorption liquid (aqueous amine solution), and a regeneration tower that heats the absorption liquid that has absorbed carbon dioxide to recover carbon dioxide. An example of the raw material gas for the first reducing gas is the steelworks by-product gas described above.

[0075] Here, the second reducing gas generator has, for example, a raw material gas intake section, a hydrogen gas intake section, and a reaction section. In the reaction section, the raw material gas taken in through the raw material gas intake section reacts with the hydrogen gas taken in through the hydrogen gas intake section to produce a second reducing gas containing hydrocarbons. Since the hydrocarbon production reaction generates heat, the reaction section is preferably equipped with a cooling mechanism. An example of the raw material gas for the second reducing gas is the above-mentioned steelworks by-product gas.

[0076] The first heating device heats the first reducing gas, for example, by an electric heater or a heat exchanger (such as a heat exchanger using high-temperature gas as a medium).

[0077] The electricity used for electric heating is not particularly limited, but it is preferable to use electricity derived from renewable energy or electricity generated by power generation equipment within the steelworks. Using electricity derived from renewable energy enables further reduction of carbon dioxide emissions. Here, renewable energy refers to energy that is constantly present in nature, such as solar, wind, hydroelectric, geothermal, and biomass. Using electricity generated by power generation equipment within the steelworks enables the construction of a more efficient resource circulation system. Examples of power generation equipment within the steelworks include blast furnace top pressure power generation equipment and power generation equipment that uses blast furnace gas as fuel (heat source). Note that power generation equipment that uses blast furnace gas as fuel (heat source) can also use coke oven gas, converter gas, and city gas as fuel, depending on the operating status of the blast furnace.

[0078] Furthermore, as a medium for heat exchange (heat source), it is possible to use exhaust heat from blast furnace gas, heat generated from the second reducing gas (exhaust heat from the second reduction device), heat generated from the hydrogen produced by the electrolysis of water, or the like.

[0079] The first heating device may be located downstream of the confluence of the supply lines for the first regenerated reducing gas and the first external reducing gas, as shown in Figure 1. Alternatively, a first heating device may be located on each of the supply lines for the first regenerated reducing gas and the first external reducing gas, and after heating the first regenerated reducing gas and the first external reducing gas, these gases may be supplied to the reducing gas supply section of the gas blowing device directly or after being joined. The same applies to the second reducing gas. When the second regenerated reducing gas and the second external reducing gas are joined and then supplied to the reducing gas supply section of the gas blowing device, for example, as shown in Figure 1, the second external reducing gas supply line may be connected to the second regenerated reducing gas flow passage between the second dehydration device and the second heating device.

[0080] The optional second heating device heats the second reducing gas. The aspect of the device is the same as that of the first heating device described above. It is preferable that the first heating device and the second heating device are provided individually to suit the preferred heating temperatures of the first reducing gas and the second reducing gas described above. However, when miniaturization of the equipment is required, the first reducing gas, the second reducing gas, and other reducing materials to be blown may be mixed, and then the first heating device may simultaneously heat the first reducing gas, the second reducing gas, and other reducing materials to be blown.

[0081] In addition, an optional third heating device heats the blast gas. The configuration of the device is the same as that of the first heating device described above. When the oxygen concentration of the blast gas is less than 30% by volume, a regenerative heat exchanger such as a hot stove used in a general blast furnace may be used. Alternatively, air may be heated by a regenerative heat exchanger, and then oxygen may be mixed therein to increase the oxygen concentration of the blast gas.

[0082] The gas injection device has a reducing gas supply unit that introduces the first reducing gas and the second reducing gas into the tuyere of the blast furnace, and a blast gas supply unit that introduces the blast gas into the tuyere of the blast furnace. The gas injection device is, for example, configured with a coaxial multi-tube structure including a central tube, an outer tube, and an inner tube between the central tube and the outer tube, as shown in Figures 2A and 2B. In the figures, reference numeral 2 denotes the tuyere, 4 denotes the gas injection device, 4-1 denotes the central tube, 4-2 denotes the inner tube, 4-3 denotes the outer tube, and 11 denotes the raceway.

[0083] 2A, the central pipe inner passage and the annular pipe between the central pipe and the inner pipe serve as reducing gas supply sections, with the second reducing gas being introduced through the central pipe inner passage and the first reducing gas being introduced through the annular pipe between the central pipe and the inner pipe. The annular pipe between the inner pipe and the outer pipe serves as a blast gas supply section, with the blast gas being introduced through the annular pipe between the inner pipe and the outer pipe. While a simple multi-pipe configuration may be used, it is preferable to provide a strongly agitating flow path, such as a porous or swirling structure, that promotes gas mixing.

[0084] 2B, the central pipe inner passage and the annular pipe between the central pipe and the inner pipe serve as reducing gas supply sections, through which other reducing materials are introduced and through which a mixed gas of the first reducing gas and the second reducing gas is introduced. Also, the annular pipe between the inner pipe and the outer pipe serves as a blast gas supply section, through which a blast gas is introduced.

[0085] Furthermore, the flow paths for the first reducing gas, the second reducing gas, and the other reducing materials to be injected may be independent of each other. In particular, when a solid reducing material such as pulverized coal or waste plastic is used as the other reducing material to be injected, it is preferable to provide a separate reducing material supply unit (path) for circulating the solid reducing material, separate from the supply units for the first reducing gas and the second reducing gas.

[0086] In addition, in order to promote combustion and gasification of the reducing material, it is preferable that the discharge portion of the outer tube constituting the blast gas supply portion has a porous structure, which can promote mixing of the blast gas and the blown reducing material.

[0087] 2A and 2B, the reducing agent and blast gas introduced from the gas injection device are mixed in the tuyere. This mixed gas is rapidly ignited and combusted immediately after being injected into the blast furnace through the tuyere. A raceway is then formed in the blast furnace beyond the tuyere, where the reducing agent and coke react with oxygen gas.

[0088] The other components are not particularly limited and may be prepared in the usual manner.

[0089] Example 1 A numerical analysis simulating blast furnace operation under the conditions shown in Table 1 was performed by a heat and mass balance analysis of a blast furnace that reproduced the blast furnace and blast furnace auxiliary equipment schematically shown in FIG. 1 (Invention Examples 1 to 4, Comparative Example 1 (Comparative Example 1 does not have a first heating device), and Comparative Example 2 (Comparative Example 2 does not have injection of a second reducing gas)) or FIG. 3 (Reference Example 1), and the amount of carbon dioxide emissions from the blast furnace was evaluated. For comparison, the specifications of the blast furnaces were standardized as much as possible, and the heat loss was set to 150,000 kcal / t. The first regenerated reducing gas was used in its entirety as the first reducing gas. The second regenerated reducing gas was used in its entirety as the second reducing gas. Heating by each heating device was performed electrically.

[0090] Here, the unit "kcal / t" means the amount of heat loss (kcal) that occurs when producing 1 ton of molten pig iron. The unit "kg / t" used in the coke ratio, etc. means the amount of coke (kg) used when producing 1 ton of molten pig iron. The unit "Nm ３ The unit " / t" also refers to the amount of each gas (Nm3) injected into the blast furnace when producing 1 ton of molten iron. ３ ) etc. In addition, "Input C" in the table means the mass (kg) of externally derived carbon atoms (specifically, carbon atoms contained in coke, other reducing materials (pulverized coal), the first external reducing gas, and the second external reducing gas) used in producing 1 ton of molten iron.

[0091] The effect of reducing carbon dioxide emissions under stable operation (hereinafter also referred to as carbon dioxide reduction effect under stable operation) was evaluated according to the following criteria. The evaluation results are also shown in Table 1. Note that Comparative Example 1 corresponds to the operation of Patent Document 2. Pass: The molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C (preferably 2000°C to 2400°C), and the carbon dioxide emissions were less than those of Reference Example 1 (corresponding to the operation of Patent Document 1) (in which only the second reducing gas was used as the injected reducing agent). Fail: At least one of the following conditions was not met: the molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C, and the carbon dioxide emissions were less than those of Reference Example 1.

[0092]

[0093] As shown in Table 1, all of Invention Examples 1 to 4 had an excellent carbon dioxide reduction effect under stable operation. In particular, Invention Example 3, in which the first reducing gas and the second reducing gas were used as the blown reducing materials and the first reducing gas, the second reducing gas, and the blast gas were all heated before being blown into the blast furnace, had an even better carbon dioxide reduction effect under stable operation than Invention Example 1.

[0094] On the other hand, in Comparative Examples 1 and 2, the carbon dioxide reduction effect under stable operation was not sufficient.

[0095] Example 2 A numerical analysis was performed simulating blast furnace operation under the conditions shown in Table 2 using a heat and mass balance analysis of a blast furnace that reproduced the blast furnace and blast furnace auxiliary equipment shown schematically in Figure 4 (Invention Examples 5 to 7) or Figure 5 (Reference Example 2), and the amount of carbon dioxide emissions from the blast furnace was evaluated. For comparison, the specifications of the blast furnace were standardized as much as possible, and the heat loss was set to 150,000 kcal / t. The first regenerated reducing gas was used in its entirety as the first reducing gas. The second external reducing gas was used in its entirety as the second reducing gas. Heating by each heating device was performed electrically.

[0096] The carbon dioxide reduction effect under stable operation was evaluated according to the following criteria. The evaluation results are also shown in Table 2. Pass: The molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C (preferably 2000°C to 2400°C), and the carbon dioxide emission was less than that of Reference Example 2 (in which only the second reducing gas was used as the injected reducing agent). Fail: At least one of the following conditions was not met: the molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C, and the carbon dioxide emission was less than that of Reference Example 2.

[0097]

[0098] As shown in Table 2, all of Examples 5 to 7 exhibited excellent carbon dioxide reduction effects under stable operation.

[0099] Example 3 A numerical analysis was performed simulating blast furnace operation under the conditions shown in Table 3 using a heat and mass balance analysis of a blast furnace that reproduced the blast furnace and blast furnace auxiliary equipment schematically shown in Figure 1 (Invention Example 8), Figure 3 (Reference Example 3), or Figure 6 (Comparative Example 3), to evaluate the amount of carbon dioxide emissions from the blast furnace. In Figure 6, reference numeral 10 denotes a hot stove. For comparison, the specifications of the blast furnace were standardized as much as possible, and the heat loss was set to 150,000 kcal / t. The first regenerated reducing gas was used in its entirety as the first reducing gas. The second regenerated reducing gas was used in its entirety as the second reducing gas. Electric heating was used for the first heating device. A hot stove was used to heat the blast gas.

[0100] The carbon dioxide reduction effect under stable operation was evaluated according to the following criteria. The evaluation results are also shown in Table 3. Pass: The molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C (preferably 2000°C to 2400°C), and the carbon dioxide emission was less than that of Reference Example 3 (in which only the second reducing gas was used as the injected reducing agent). Fail: At least one of the following conditions was not met: the molten iron temperature was 1500°C to 1550°C, the tuyere temperature was 1900°C to 2500°C, and the carbon dioxide emission was less than that of Reference Example 3.

[0101]

[0102] As shown in Table 3, Example 8 of the present invention exhibited an excellent effect of reducing carbon dioxide emissions under stable operation.

[0103] On the other hand, in Comparative Example 3, the carbon dioxide reduction effect under stable operation was not sufficient.

[0104] Example 4 Using Invention Example 1 of Example 1 as the base condition, a numerical analysis was performed simulating blast furnace operation under the conditions shown in Table 4, with the injection rates of the first reducing gas and the second reducing gas in the injection step set based on an index of the blast furnace operation status, and the amount of carbon dioxide emitted from the blast furnace was evaluated. In this case, the numerical analysis was performed simulating operational fluctuations due to fluctuations in the properties of the ore raw material.

[0105] Here, the molten iron temperature and tuyere temperature were used as indicators of the blast furnace operation status, and the injection rates of the first reducing gas and the second reducing gas were controlled so that both the molten iron temperature and the tuyere temperature were within the reference temperature ranges shown in Table 4. For example, when the reduction reaction was delayed due to a fluctuation in the properties of the ore raw material and the molten iron temperature fell below the reference temperature range, the injection rate of the first reducing gas was reduced and the injection rate of the second reducing gas was increased to ensure operational stability. When the reduction reaction was excessively promoted due to a fluctuation in the properties of the ore raw material and the molten iron temperature exceeded the reference temperature range, the injection rate of the first reducing gas was increased and the injection rate of the second reducing gas was reduced to ensure CO ２ The discharge amount was further reduced. When the tuyere temperature was below the reference temperature range, the injection rates of both the first reducing gas and the second reducing gas were reduced. When the tuyere temperature exceeded the reference temperature range, the injection rates of both the first reducing gas and the second reducing gas were increased. By combining these, the injection rates of the first reducing gas and the second reducing gas were controlled so that the molten iron temperature and the tuyere temperature were both within the reference temperature ranges shown in Table 4.

[0106] The carbon dioxide reduction effect under stable operation was evaluated according to the following criteria. The evaluation results are also shown in Table 4. Pass: The carbon dioxide emission amount was less than that of Reference Example 1. Fail: The carbon dioxide emission amount was the same as or greater than that of Reference Example 1.

[0107]

[0108] As shown in Table 4, in Example 9, the carbon dioxide reduction effect under stable operation was excellent even when operational fluctuations occurred. Note that when operational fluctuations occurred, if the injection rates of the first reducing gas and the second reducing gas in the injection process were not set based on the index of the blast furnace operation status (operation was carried out with the injection rates of the first reducing gas and the second reducing gas kept constant), the state in which the molten iron temperature was below the reference temperature range could not be resolved, resulting in unstable operation.

[0109] Example 5 Using Example 1 of Example 1 as the base condition, a numerical analysis was performed simulating blast furnace operation under the conditions shown in Table 5, where the injection rates of the first reducing gas and the second reducing gas in the injection process were set based on the available hydrogen gas supply, and the amount of carbon dioxide emitted from the blast furnace was evaluated. Fluctuations in the available hydrogen supply rate were simulated, and a constraint was imposed so that the amount of hydrogen gas used in generating the second regenerated reducing gas would not exceed the available hydrogen supply rate. When the available hydrogen supply rate decreased and became equal to or less than the amount of hydrogen gas used in generating the second regenerated reducing gas, the injection rate of the second reducing gas was reduced. In the same manner as in Example 4, the molten iron temperature and tuyere temperature were used as indicators of the blast furnace operation status, and the injection rates of the first reducing gas and the second reducing gas were controlled so that both the molten iron temperature and the tuyere temperature were within the reference temperature ranges shown in Table 5.

[0110] The carbon dioxide reduction effect under stable operation was evaluated according to the following criteria. The evaluation results are also shown in Table 5. Pass: The carbon dioxide emission amount was less than that of Reference Example 1. Fail: The carbon dioxide emission amount was the same as or greater than that of Reference Example 1.

[0111]

[0112] As shown in Table 5, Example 10 exhibited an excellent carbon dioxide reduction effect under stable operation.

[0113] 1: Blast furnace 2: Tuyere 3: Second reducing gas generator 4: Gas injection device 4-1: Center tube 4-2: Inner tube 4-3: Outer tube 5: First dehydration device 6: Second dehydration device 7: Burner 8: First reducing gas generator 9-1: First heating device 9-2: Second heating device 9-3: Third heating device 10: Hot stove 11: Raceway

Claims

1. A method of operating a blast furnace, comprising: a first heating step of heating a first reducing gas; an injection step of injecting a blast gas and an injection reducing material into the blast furnace through a tuyere of the blast furnace; the blown reducing material contains the first reducing gas and a second reducing gas, A method for operating a blast furnace, wherein the first reducing gas contains carbon monoxide and the second reducing gas contains at least one of a hydrocarbon and hydrogen.

2. 2. The method for operating a blast furnace according to claim 1, wherein the amounts of the first reducing gas and the second reducing gas to be injected in the injection step are set based on an index of a blast furnace operation state.

3. 3. The method for operating a blast furnace according to claim 2, wherein the indicators of the blast furnace operation status are the molten iron temperature and the tuyere temperature.

4. 4. The method for operating a blast furnace according to any one of claims 1 to 3, wherein the first reducing gas has a carbon monoxide concentration of 30% by volume or more, and the second reducing gas has a total concentration of hydrocarbons and hydrogen of more than 70% by volume.

5. The method for operating a blast furnace according to any one of claims 1 to 3, further comprising a second heating step of heating the second reducing gas.

6. The method for operating a blast furnace according to any one of claims 1 to 3, wherein the second reducing gas contains methane as the hydrocarbon.

7. The method for operating a blast furnace according to any one of claims 1 to 3, wherein the oxygen concentration of the blast gas is 80% by volume or more.

8. The method for operating a blast furnace according to any one of claims 1 to 3, wherein at least one raw material gas of the first reducing gas and the second reducing gas is a steelworks by-product gas.

9. Carbon dioxide is separated from the steelworks by-product gas to obtain a carbon dioxide-containing gas and a remaining gas, 9. The method for operating a blast furnace according to claim 8, wherein the first reducing gas uses the remaining gas as a raw material gas, and the second reducing gas uses the carbon dioxide-containing gas as a raw material gas.

10. The method for operating a blast furnace according to claim 8, further comprising supplying an excess of at least one of the first reducing gas and the second reducing gas into a steelworks.

11. 4. The method for operating a blast furnace according to claim 1, wherein at least a part of the second reducing gas is generated from a steelworks by-product gas and hydrogen gas, and the amount of the second reducing gas to be injected in the injection step is set based on a supplyable amount of the hydrogen gas.

12. a first reducing gas generator that generates a first reducing gas; a second reducing gas generator that generates a second reducing gas; a first heating device that heats the first reducing gas; a gas injection device having a reducing gas supply unit that introduces the first reducing gas and the second reducing gas into a tuyere of a blast furnace, and a blast gas supply unit that introduces a blast gas into the tuyere of the blast furnace; With A blast furnace auxiliary facility, wherein the first reducing gas contains carbon monoxide, and the second reducing gas contains at least one of a hydrocarbon and hydrogen.