Method for operating steelworks and steelworks

Abstract

Provided is a method for operating a steelworks, characterized by circulating, within the steelworks, external ethylene introduced from outside the steelworks, self-generated ethylene generated inside the steelworks, by-product gas generated in the steelworks, and electric power generated by using the by-product gas in the steelworks, and supplying the steelworks with electric power generated by renewable energy or a nuclear power plant.

Description

Operating methods of steel mills and steel mills

[0001] This disclosure relates to the operating methods of a steel mill. This application claims priority based on Japanese Patent Application No. 2024-179526, filed in Japan on October 15, 2024, the contents of which are incorporated herein by reference.

[0002] Current steel mills use sintered ore, produced by solidifying powdered ore in a sintering furnace, as raw material for charging into blast furnaces. They also use coke and pulverized coal obtained by the carbonization of coal in coke ovens as reducing agents for the sintered ore. Pig iron is then produced by blowing high-temperature air heated in a hot blast furnace through tuyeres. The gases discharged from the coke ovens and blast furnaces are recovered as by-product gases and effectively utilized as fuel within the steel mill.

[0003] In the blast furnace process, pig iron is produced by alternately charging iron raw materials and coke in layers from the top of the furnace while blowing hot air together with pulverized coal from the tuyeres. ２ From the perspective of reducing emissions, there is a need to reduce the use of carbon materials (coke and pulverized coal).

[0004] In conventional methods, 45% of the heat input from coal is effectively utilized for steel production throughout the entire steelworks, while the remaining 55% is released into the atmosphere as waste heat. Therefore, CO2 emissions from the entire steelworks are high. ２ To reduce emissions, waste heat from the process can be reduced, and the reducing agent in the ore can be replaced with renewable energy. One such method is disclosed in Patent Document 1, which describes a blast furnace operation method in which hydrogen is injected into the furnace.

[0005] Japanese Patent Application Publication No. 2023-67695

[0006] Kazuhisa Murata, Textiles and Industry Vol. 66, No. 5 (2010) Successful development of fuel cell catalyst using hydrogen and carbon monoxide as fuel (Kyushu University) https: / / www.kyushu-u.ac.jp / ja / researches / view / 132 Chungseok Choi et al., Nature Catalysis, 804(3), 804-812 (2020) https: / / doi.org / 10.1038 / s41929-020-00504-x Kouji Takatani, Takanobu Inada, Yutaka Ujisawa, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, pp. 15-22, Nakagawa, Futoshihiko, Transactions of the Japan Society of Energy and Resources, Vol. 32 (2011), No. 4, pp. 1-8

[0007] Using hydrogen reduces waste heat from sintering and coke ovens and allows for the replacement of ore reducing agents with renewable energy. However, hydrogen-based reduction reactions are endothermic, requiring the addition of sensible heat (such as heat dissipation) to the furnace. This leads to a decrease in exergy loss, and the latent heat of water vapor in the by-product gas generated after ore reduction becomes waste heat, reducing the heat content of the by-product gas within the steelworks. Consequently, fuel and electricity must be purchased separately. Therefore, the overall energy reduction for the steelworks is diminished. In contrast, by-product gas emitted from conventional blast furnaces contains a moderate amount of carbon (CO gas) even after ore reduction and can be used as fuel within the steelworks. Therefore, steelworks can use renewable energy containing carbon to reduce the overall CO content of the steelworks. ２ Reducing emissions was the challenge.

[0008] According to this disclosure, the entire steelworks CO2 reduction will be achieved while using renewable energy that includes carbon. ２ Emissions can be reduced.

[0009] To solve the above problems, this disclosure adopts the following configuration: (1) A method for operating a steelworks, characterized in that external ethylene introduced from outside the steelworks, self-generated ethylene produced inside the steelworks, by-product gas generated at the steelworks, and electricity generated using the by-product gas at the steelworks are circulated within the steelworks, and electricity generated from renewable energy or a nuclear power plant is supplied to the steelworks.

[0010] (2) The method of operating the steelworks described in (1) above, characterized in that the steelworks is equipped with a molten iron production facility that combines a pre-reduction furnace and a blast furnace, the external ethylene and the self-produced ethylene are blown into the blast furnace, and the by-product gas of the blast furnace is used as the reducing gas of the pre-reduction furnace.

[0011] (3) The method for operating a steelworks according to (2) above, characterized in that at least one of the external ethylene and the self-produced ethylene is blown into the pre-reduction furnace of the steelworks.

[0012] (4) The method of operating a steelworks according to (2) or (3) above, characterized in that the steelworks has a power generation facility, and in this power generation facility, it generates electricity using the by-product gas of the pre-reduction furnace and supplies the generated electricity to the steelworks.

[0013] (5) The method of operating the steelworks described in (4) above, characterized in that the steelworks has a steel heating furnace and uses the by-product gas of the pre-reduction furnace as fuel gas in the steel heating furnace.

[0014] (6) The blast furnace is supplied with air mixed with oxygen to increase the oxygen concentration to 21% by volume or more, and carbon dioxide is separated from the by-product gas of the pre-reduction furnace to obtain 1000 kcal / Nm³ ３ The method for operating a steel mill according to (5) above, characterized in that the above-mentioned high-calorie gas is used as the fuel gas.

[0015] (7) The blast furnace is supplied with oxygen-enriched air, which is air mixed with oxygen to increase the oxygen concentration to 21% by volume or more, and carbon dioxide is separated from the by-product gas of the pre-reduction furnace to obtain 1000 kcal / Nm³３ The operation method of the steelworks according to the above (4), characterized by using the above high-calorie gas in the power generation facility.

[0016] (8) The operation method of the steelworks according to the above (6), characterized by using a mixed by-product gas obtained by mixing coke oven gas and converter gas with the above high-calorie gas as the fuel gas.

[0017] (9) The power generation facility is at least one of a gas turbine combined cycle type power generation facility and a fuel cell type power generation facility, and a mixed by-product gas obtained by mixing coke oven gas and converter gas with the above high-calorie gas is used in the power generation facility. The operation method of the steelworks according to the above (7), characterized by this.

[0018] (10) The steelworks includes an electric furnace for melting scrap to produce molten steel, and by supplying the electric power generated by the power generation facility to the electric furnace, molten steel is produced by a hybrid method using the blast furnace and the electric furnace. The operation method of the steelworks according to the above (9), characterized by this.

[0019] (11) The operation method of the steelworks according to the above (7), characterized by producing the self-generated ethylene by synthesizing the separated carbon dioxide and hydrogen generated using the surplus power of the power generation facility.

[0020] (12) The steelworks includes an external ethylene production facility for dehydrating ethanol or dimethyl ether introduced from outside the steelworks to produce the external ethylene, and waste heat of the steelworks is supplied to the external ethylene production facility as a heat source for performing the dehydration. The operation method of the steelworks according to the above (2) or (3), characterized by this.

[0021] (13) The steelworks includes a carbon dioxide separation facility for separating carbon dioxide from the by-product gas of the preliminary reduction furnace, and the carbon dioxide separation facility separates carbon dioxide by the amine method. The operation method of the steelworks according to the above (4), characterized by this.

[0022] (14) A steelworks comprising: a carbon dioxide separation facility for separating carbon dioxide from by-product gas generated within the steelworks; a power generation facility for generating electricity using the by-product gas; a hydrogen production apparatus for synthesizing hydrogen using the electricity generated by the power generation facility; an ethylene synthesis facility for synthesizing self-produced ethylene using the carbon dioxide obtained by the carbon dioxide separation facility and the hydrogen obtained by the hydrogen production apparatus; and a blast furnace capable of supplying the self-produced ethylene and at least one external ethylene.

[0023] (15) The steelworks according to (14), comprising: a blast furnace; a pre-reduction furnace capable of supplying by-product gas from the blast furnace; a carbon dioxide separation facility capable of separating carbon dioxide from the by-product gas of the pre-reduction furnace; a steel heating furnace capable of receiving by-product gas of the steelworks, including at least the by-product gas after carbon dioxide has been separated by the carbon dioxide separation facility; a hydrogen production facility capable of producing hydrogen using electricity generated by the by-product gas of the steelworks; an ethylene synthesis facility capable of synthesizing the self-generated ethylene to be blown into the blast furnace using the carbon dioxide separated by the carbon dioxide separation facility and the hydrogen produced by the hydrogen production facility; and a tank capable of storing the self-generated ethylene synthesized by the ethylene synthesis facility.

[0024] (16) The steel mill according to (14) or (15) above, further having an electric furnace capable of producing molten steel using electricity generated by the power generation equipment.

[0025] This is the equipment configuration of a steelworks for effectively implementing the steelworks operation method of this disclosure (without electric furnace). This is the equipment configuration of a steelworks for effectively implementing the steelworks operation method of this disclosure (with electric furnace). This shows the overall energy balance of the steelworks (Comparative Example 1). This shows the overall energy balance of the steelworks (Comparative Example 2). This shows the overall energy balance of the steelworks (Example 1). This shows the overall energy balance of the steelworks (Example 2). This shows the overall energy balance of the steelworks (Example 3). This shows the overall energy balance of the steelworks (Example 4).

[0026] This disclosure is based on the technical concept of "a method for operating a steelworks characterized by circulating external ethylene introduced from outside the steelworks, self-generated ethylene produced inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases at the steelworks within the steelworks, and supplying electricity generated from renewable energy sources or nuclear power plants to the steelworks."

[0027] The steelworks of this embodiment is an integrated steelworks where the energy necessary for steel production is shared and operational control is implemented uniformly. Therefore, the steelworks of this embodiment differs from conventional integrated steelworks. As is clear from this definition, it is not necessary whether the equipment is gathered in one place or not. For example, power may be supplied from a distant steelworks using the grid's power distribution network. In other words, the equipment systems connected as a system may be considered as the interior of the steelworks.

[0028] The energy required for steel production can be supplied by renewable energy sources or electricity generated from nuclear power plants. "Energy required for steel production" includes electricity, fuel, and heat. In this embodiment, fuel includes by-product gases, ethylene, etc. Heat includes steam, hot air, etc. Hot air includes preheating air for blast furnaces and steel heating furnaces. Furthermore, "supplying the necessary energy" does not necessarily mean that all the energy required for steel production is covered by renewable energy sources. For example, as will be described later, the steelworks in this embodiment is configured to supply by-product gases (fuel gases) to the steel heating furnaces, and the operation method of the steelworks in this disclosure may also include supplementing the fuel gas shortage with liquid natural gas (LNG). According to the operation method of the steelworks in this embodiment, sensible heat conversion in the ironmaking process, such as lowering the temperature of blast furnace airflow to room temperature, can be eliminated, and waste heat in the steelworks can be reduced. As a result, the amount of energy that must be replaced by renewable energy can be significantly reduced. Furthermore, CO2 emissions can be reduced. ２ By converting CO into a reducing agent and carrying out the carbon cycle, ２ This can further expand the effect of reducing emissions.

[0029] (First Embodiment) Figure 1 shows the equipment configuration of the integrated steelworks described above (hereinafter also referred to as steelworks 100). Steelworks 100 includes a blast furnace 1 and a pre-reduction furnace 2 combined to produce molten iron, a coke oven 3, a converter 4, a carbon dioxide separation facility 5, a steel heating furnace 6, a power generation facility 7, a hydrogen production facility 8, an ethylene synthesis facility 9, an ethylene storage tank 10, and an external ethylene production facility 11. Although Figure 1 shows steelworks 100, these facilities do not necessarily have to be located within the same facility. The area where the systems are connected may be considered the interior of steelworks 100, and the area where the systems are not connected may be considered the exterior of steelworks 100. For example, if a steelworks has a configuration in which fuel such as bioethanol is supplied from an external source, it is first placed in a supply tank and then supplied from the supply tank to each system. In this case, the source of the bioethanol is outside the steelworks, but the supply tank may not be located within the steelworks premises. However, if the system is connected to the supply tank, it may be considered the interior of the steelworks.

[0030] The preliminary reduction furnace 2 can be supplied with the off-gas from the blast furnace 1. The carbon dioxide separation facility 5 is a facility capable of separating carbon dioxide from the off-gas of the preliminary reduction furnace 2. The steel heating furnace 6 can accept the off-gas of the steelworks as fuel gas. Such off-gas of the steelworks includes at least the off-gas after carbon dioxide is separated by the carbon dioxide separation facility 5 (that is, the off-gas of the preliminary reduction furnace 2), and further may include the off-gas of the coke oven 3 (hereinafter also referred to as coke oven gas (COG)) and the off-gas of the converter 4 (hereinafter also referred to as converter gas (LDG)). The hydrogen production facility 8 is a facility for producing hydrogen by electrolyzing water, and the electric power generated by using the off-gas of the steelworks may be used as the operating power. However, the hydrogen production facility 8 may be a facility for separating hydrogen from the off-gas of the steelworks (for example, coke oven gas) (not shown). The operating power of the hydrogen production facility 8 may include surplus power generated by surplus energy outside the steelworks. The ethylene synthesis facility 9 is a facility for synthesizing ethylene (self-generated ethylene) blown into the blast furnace 1 by using the carbon dioxide separated by the carbon dioxide separation facility 5 and the hydrogen produced by the hydrogen production facility 8. The ethylene storage tank 10 is a facility capable of storing the self-generated ethylene synthesized by the ethylene synthesis facility 9. The external ethylene production facility 11 is a facility for producing ethylene from ethanol (including bioethanol) introduced from outside the steelworks. However, the external ethylene production facility 11 may be a facility for producing ethylene from dimethyl ether (CH ３ OCH ３ ). Dimethyl ether has a higher fuel value (for example, cetane number, etc.) than ethanol.

[0031] In this embodiment, it is assumed that an operation of 100% hot metal (in other words, 0% electric furnace steel) is required according to the requirements on the steel quality side. External ethylene and self-generated ethylene are blown into the blast furnace 1, and the off-gas of the blast furnace 1 (hereinafter also referred to as blast furnace gas (BFG)) is used as the reducing gas of the preliminary reduction furnace 2. By blowing in ethylene, the coke ratio can be reduced, so that the generation of sensible heat in the coke oven 3 can be reduced.

[0032] (Regarding external ethylene) External ethylene is ethylene derived from ethanol or dimethyl ether introduced from outside the steelworks 100. Ethylene can be produced, for example, by dehydrating ethanol or dimethyl ether using a catalyst (see Non-Patent Literature 1). Ethanol may be bioethanol. Waste heat generated at the steelworks can be used as the heat source for the dehydration reaction. Since the temperature required for the dehydration reaction is 160 to 170°C or higher, low-temperature waste heat from the steelworks (for example, waste heat from the coke oven 3, waste heat from the steel heating furnace 6) can be suitably used as the heat source for the dehydration reaction. As the spread of electric vehicles progresses, a decrease in ethanol use in the vehicle sector is expected, so a sufficient supply of bioethanol can be secured. In Figure 1, the injection direction of external ethylene is indicated by arrow A. Arrow B indicates the injection direction of coal (PCI is used in this disclosure), and arrow C indicates the tapping direction of the blast furnace 1.

[0033] (Regarding self-generated ethylene) In short, self-generated ethylene is ethylene produced within a steel mill using surplus energy generated both inside and outside the steel mill. The specific method for producing self-generated ethylene will be described later.

[0034] When injecting external ethylene and self-generated ethylene into the blast furnace 1, hydrogen-based gas may also be injected from the shaft. This allows for appropriate control of the heat flow ratio (temperature in front of the tuyere) of the blast furnace 1.

[0035] The pre-reduction furnace 2 reduces the iron raw material using by-product gas blown in from the blast furnace 1. The reduction rate in the pre-reduction furnace 2 is, for example, over 80%. In Figure 1, arrow D indicates the direction of injection of the blast furnace by-product gas into the pre-reduction furnace 2, and arrow E indicates the direction of charging the reduced iron obtained in the pre-reduction furnace 2 into the blast furnace 1. This reduces the proportion of sintered ore produced in the sintering machine, thereby reducing the generation of sensible heat in the sintering machine. Since this method involves blowing the high-temperature by-product gas from the blast furnace into the pre-reduction furnace 2, there is no need to heat the gas injected into the pre-reduction furnace 2, thus reducing the generation of sensible heat for the pre-reduction furnace 2. Here, it is advantageous to use a hydrogen-based gas with a high C / H ratio as the gas injected into the blast furnace 1, and methane (CH4), which has a low C / H ratio, is preferable. ４ ) and other fuels cause CO2 throughout the entire steel mill ２ It becomes difficult to sufficiently reduce emissions. In other words, C is used as the hydrogen-based gas injected into the blast furnace 1. ｎ H ｍ It is not possible to use all of these; the operation requires that ethylene with a C / H ratio of at least 0.33 be injected into the blast furnace.

[0036] The by-product gas from the pre-reduction furnace 2 is sent to the carbon dioxide separation facility 5, as indicated by arrow G. Arrow F indicates the waste heat (such as reduction heat) from the pre-reduction furnace 2. In the carbon dioxide separation facility 5, the carbon dioxide contained in the by-product gas from the pre-reduction furnace 2 is separated. The carbon dioxide separation method may be the pressure swing method or other methods, but the amine method is preferred. The amine method is a chemical absorption method, which is one of the carbon dioxide separation and recovery technologies, and uses an amine-based absorbent such as an alkanolamine aqueous solution as the absorbent, resulting in a high carbon dioxide recovery rate.

[0037] The by-product gas after carbon dioxide has been separated is sent to the steel heating furnace 6 and the power generation equipment 7 (see arrow H). However, there may be an operating period in which the by-product gas is injected into only one of the steel heating furnace 6 or the power generation equipment 7. A portion of the separated carbon dioxide is sent to the ethylene synthesis equipment 9 (arrow L), and the remainder is exhausted (see arrow K). Alternatively, the by-product gas from the pre-reduction furnace 2, which has not separated carbon dioxide, may be sent to the steel heating furnace 6 and / or the power generation equipment 7.

[0038] By using the by-product gas from the preliminary reduction furnace 2 as fuel for the steel heating furnace 6 and the power generation equipment (for example, the GTCC described later) 7, the CO2 in the steelworks can be reduced. ２ Emissions can be reduced. For example, with hydrogen, the calorific value of the gas emitted from the top of the pre-reduction furnace 2 is low and it cannot be used as fuel, so the electricity required to operate the steel manufacturing equipment within the steelworks and the fuel for the steel heating furnace 6 must be purchased from outside, and CO2 emissions from the blast furnace ２ The effect of reducing emissions will diminish (externally purchased electricity is CO2 ２ (Emissions factor > 0, and fuel in circulation is assumed to be derived from fossil fuels such as LNG).

[0039] By injecting ethylene into the blast furnace 1, the carbon monoxide concentration of the by-product gas in the pre-reduction furnace 2 is increased. By supplying the by-product gas, after carbon dioxide has been separated, as fuel gas to the steel heating furnace 6, the carbon monoxide is burned to obtain a gas containing a large amount of carbon dioxide. Since gas containing carbon dioxide has excellent radiance, steel can be heated using a gas with high heating capacity. The carbon monoxide concentration of the by-product gas in the pre-reduction furnace 2 is preferably 15% by volume or more. However, if hydrogen is injected into the blast furnace 1, the carbon dioxide concentration in the steel heating furnace 6 decreases, and the heating efficiency by radiant heat transfer decreases. Furthermore, using hydrogen for steel heating generates a large amount of water vapor, and it is necessary to verify the impact on steel quality and combustion equipment (a large amount of wastewater is generated in the regenerative burner). In order to ensure quality and heating capacity, a significant upgrade of the combustion equipment may be necessary.

[0040] The electricity generated by the power generation equipment 7 is used for steel production within the steelworks 100. Thus, the electricity generated by the combustion heat of excess by-product gases generated within the steelworks is called surplus electricity. Of the electricity generated by the power generation equipment 7, the electricity supplied to the hydrogen production equipment 8 is indicated by arrow N, and the electricity used for other purposes is indicated by arrow M. Both arrows N and M are included in "used for steel production within the steelworks 100". The energy originating from the power generation equipment 7, indicated by arrow M, is not sufficient as "energy for steel production", so the deficit is supplemented by renewable energy or electricity generated by a nuclear power plant (see arrow O). Renewable energy includes that produced by solar power, wind power, geothermal power, hydroelectric power, etc. A nuclear power plant only needs to have the function of rotating a steam turbine with the energy generated by nuclear fission, and the power generation method, such as a boiling water reactor or pressurized water reactor, is not particularly limited.

[0041] The power generation equipment 7 may be a GTCC (Gas Turbine Combined Cycle) type or a fuel cell type power generation equipment. GTCC generates electricity by combining a gas turbine and a steam turbine. It can generate electricity using the gas turbine with by-product gas, and also generate steam using the heat from the exhaust gas discharged from the gas turbine, thereby generating electricity using the steam turbine. This can increase the power generation efficiency of the power generation equipment 7 to 50% or more. The fuel cell type power generation equipment may be a power generation equipment using a fuel cell catalyst that uses hydrogen and carbon monoxide as fuel (see, for example, Non-Patent Document 2).

[0042] Here, it is preferable to blow oxygen-enriched air, which is air mixed with oxygen to increase the oxygen concentration to 21% by volume or more, into the tuyeres of the blast furnace 1. This increases the calorific value of the by-product gas in the pre-reduction furnace 2, supplying 1000 kcal / Nm³ to the steel heating furnace 6 and the power generation equipment 7. ３ The above-mentioned fuel gas (hereinafter also referred to as "high-calorie gas") can be supplied. In addition, oxygen enrichment ensures the tuyer temperature in ambient temperature air supply and reduces waste heat by reducing the amount of nitrogen emitted from the blast furnace gas.

[0043] In addition to this high-calorie gas, a mixed by-product gas obtained by mixing coke oven gas (see arrow I) generated in the coke oven 3 and converter gas (see arrow J) generated in the converter 4 may be used as fuel gas for the steel heating furnace 6 and the power generation equipment 7. In an operating configuration that supplies such a mixed by-product gas, the oxygen concentration of the oxygen-enriched air blown into the blast furnace 1 is more preferably 60% by volume or more. As a result, the calorific value of the by-product gas (by-product gas after carbon dioxide has been removed) from the pre-reduction furnace 2 is 1500 kcal / Nm³. ３ As a result of this improvement, it becomes possible to operate the steel heating furnace 6 without procuring fuel from external sources. Furthermore, the power generation efficiency of the GTCC power generation equipment can be increased to 57% or more. This promotes carbon cycling within the steelworks.

[0044] These coke oven gases and converter gases have large fluctuations in calorific value, but this can be adjusted by the by-product gas of the pre-reduction furnace 2. In contrast, in Comparative Example 2 (operation involving the injection of hydrogen into the pre-reduction furnace), which will be described later, it is difficult to adjust the calorific value using the by-product gas of the pre-reduction furnace 2.

[0045] In this embodiment, in order to self-generate and recycle ethylene, electricity and CO2 are required. ２ Hydrogen (electricity from electrolysis) is required, and in order to procure it independently, it is necessary to generate surplus electricity required for ethylene production (surplus electricity other than that used in the steel manufacturing process (blast furnace, converter, rolling)) through high-efficiency power generation using by-product gas. The power generation efficiency of a by-product gas-fired gas turbine combined cycle (GTCC) power generation facility can be increased as the calorific value of the fuel gas increases, so the calorific value of the by-product gas used as fuel for power generation is 7,000 kJ / Nm³. ３ The use of ethylene that can be produced as described above is desirable.

[0046] Preferably, the hydrogen production facility 8 produces hydrogen by electrolyzing water using the surplus electricity described above. The ethylene synthesis facility 9 synthesizes ethylene using the hydrogen produced in the hydrogen production facility 8 (see arrow T) and the carbon dioxide separated in the carbon dioxide separation facility 5 (see arrow L). For example, the method described in Non-Patent Document 3 can be used for synthesizing ethylene. In this specification, such ethylene is defined as self-produced ethylene. However, as described above, ethylene synthesized using hydrogen separated from the by-product gas of the steelworks and carbon dioxide separated in the carbon dioxide separation facility 5 (see arrow L) may also be considered self-produced ethylene. In the above description, the electricity required to produce self-produced ethylene is supplied by surplus energy, including surplus electricity generated within the steelworks, but self-produced ethylene may also be produced using surplus energy from outside the steelworks.

[0047] When water is electrolyzed in the hydrogen production facility 8, oxygen is obtained. This oxygen can be used to adjust the oxygen concentration of the air blown into the blast furnace 1 (see arrow P). Therefore, there is no need to produce oxygen separately.

[0048] The self-generated ethylene produced is stored in the ethylene storage tank 10 (see arrow Q) and then injected into the blast furnace 1 (see arrow R). This allows for the recycling of the reducing agent (carbon cycle in the steelworks).

[0049] (Second Embodiment) Figure 2 shows the equipment configuration of the steelworks of this embodiment. In addition to the equipment configuration of Figure 1, the steelworks of this embodiment is equipped with an electric furnace 21. The electric furnace 21 melts scrap to produce molten steel. In other words, in the steelworks of this embodiment, molten steel is produced using a hybrid method with the blast furnace 1 and the electric furnace 21. The hybrid method means that the blast furnace 1 and the electric furnace 21 produce molten steel in a predetermined ratio. The "predetermined ratio" cannot be uniquely defined as it differs depending on the required steel quality and energy, etc.

[0050] The electric furnace 21 is powered by electricity generated by the power generation equipment 7. As described in the first embodiment, the power generation equipment 7 efficiently generates electricity using high-calorie gas. Furthermore, in the steelworks of this embodiment, the amount of blast furnace steel can be reduced by the amount of electric furnace steel.

[0051] Therefore, more of the electricity generated by the power generation facility 7 can be allocated to purposes other than hydrogen production, namely, the production of electric furnace steel. In addition to the electricity generated by the power generation facility 7, at least a portion of the electricity generated by renewable energy or a nuclear power plant may be supplied to the electric furnace 21.

[0052] It is desirable to operate blast furnace 1 and electric furnace 21 so that the ratio of molten steel to the steelworks' crude steel, as defined by the following formula (1), is 50% or less. Electric furnace steel / (blast furnace steel + electric furnace steel) × 100 ... Formula (1) By operating blast furnace 1 and electric furnace 21 with this steelworks crude steel ratio, carbon dioxide emissions at the steelworks can be effectively reduced. By increasing the ratio of electric furnace 21, heat input is reduced, and carbon dioxide emissions during molten steel production can be further reduced. However, if the ratio of electric furnace 21 becomes excessively high, the amount of energy that must be procured from outside the steelworks will increase. Also, there are cases where more blast furnace steel is required due to quality requirements. Therefore, it is desirable to adjust the steelworks' crude steel ratio within the range of 35% to 45%.

[0053] The present disclosure will be explained in more detail with reference to examples. The energy balance of a steelworks operating with a crude steel production of 8.5 million tons / year was evaluated for each of the four examples, Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4, each with different operating methods. Comparative Example 1 is a steelworks without a pre-reduction furnace and uses a conventional operating method without ethylene injection. Comparative Example 2 is a steelworks operating method in which molten iron is produced by charging 100% reduced iron, obtained by injecting hydrogen into a pre-reduction furnace, into a blast furnace. Example 1 corresponds to an "integrated steelworks operating method" in which the steelworks operates with a crude steel ratio of 100% blast furnace steel and 0% electric furnace steel while injecting ethylene into the blast furnace. Example 2 corresponds to an "integrated hybrid steelworks operating method" in which the steelworks operates with a crude steel ratio of 60% blast furnace steel and 40% electric furnace steel while injecting ethylene into the blast furnace. Example 3 corresponds to an "integrated steelworks operation method" in which the steelworks operates with a crude steel ratio of 100% blast furnace steel and 0% electric furnace steel while injecting ethylene into the blast furnace and pre-reduction furnace. Example 4 corresponds to an "integrated hybrid steelworks operation method" in which the steelworks operates with a crude steel ratio of 76% blast furnace steel and 24% electric furnace steel while injecting ethylene into the blast furnace and pre-reduction furnace. Table 1 shows the operating specifications of the blast furnaces for Comparative Example 1, Example 1, Example 2, Example 3 and Example 4. Note that the percentages in Tables 1 and 2 are volume percentages (however, the metallization rate in Table 2 represents the percentage of iron element that is metallic iron). The power generation equipment in Examples 1 and 2 is a gas turbine combined cycle alone, which is the least expensive option, and the power generation efficiency is 57%. Note that at least one of either external ethylene or self-produced ethylene may be used as the ethylene injected into blast furnace 1 and pre-reduction furnace 2. If sufficient surplus energy can be obtained from outside the steelworks, it is more preferable from a cost standpoint to use only self-produced ethylene and not external ethylene. On the other hand, depending on the operating conditions, the amount of surplus by-product gas may be small. In that case, the amount of ethylene used in blast furnace 1 and pre-reduction furnace 2 will be insufficient if self-produced ethylene alone is used, so external ethylene will be used.

[0054]

[0055] In Comparative Example 2, the by-product gas from the pre-reduction furnace is cooled to remove moisture, then enriched with hydrogen and blown back into the pre-reduction furnace. Therefore, the by-product gas from the pre-reduction furnace is independent of the by-product gas within the steelworks. In Examples 1 and 2, in addition to the pre-reduction ore from the pre-reduction furnace, reduced iron was introduced from an external source, and the sintering furnace was omitted. In Examples 3 and 4, the entire iron source used in the blast furnace was the pre-reduction ore from the pre-reduction furnace, and the sintering furnace was omitted. Table 2 shows the specifications of the pre-reduction furnace in Comparative Example 2, Examples 1 and 2, Examples 3 and 4.

[0056]

[0057] Here, the specifications of the blast furnace and pre-reduction furnace were evaluated based on the description in Non-Patent Document 4. The overall energy balance of the steelworks was evaluated based on the description in Non-Patent Document 5. Figure 3 shows the overall energy balance of the steelworks corresponding to Comparative Example 1, Figure 4 shows the overall energy balance of the steelworks corresponding to Comparative Example 2, Figure 5 shows the overall energy balance of the steelworks corresponding to Example 1, Figure 6 shows the overall energy balance of the steelworks corresponding to Example 2, Figure 7 shows the overall energy balance of the steelworks corresponding to Example 3, and Figure 8 shows the overall energy balance of the steelworks corresponding to Example 4. In these figures, the blast furnace, pre-reduction furnace, coke oven, converter, CO ２ Separation, steel heating furnace self-consumption, GTCC power generation equipment, H ２ manufacturing, C ２ H ４ Synthesis, Tank, C ２ H ５ OH dehydration and electric furnace correspond to the blast furnace 1, pre-reduction furnace 2, coke oven 3, converter 4, carbon dioxide separation equipment 5, steel heating furnace 6, power generation equipment 7, hydrogen production equipment 8, ethylene synthesis equipment 9, ethylene storage tank 10, external ethylene production equipment 11, and electric furnace 21 described in the embodiment, respectively.

[0058] Referring to Figure 3, which corresponds to Comparative Example 1, CO2 emissions from a steel mill ２ CO2 is calculated by subtracting the amount of carbon derived from valuable chemical products from the amount of carbon derived from coal flowing in with the steel mill as the boundary (coal for coke production and coal for blowing pulverized coal into blast furnaces).２ It is possible to evaluate it by converting it to this. As a result, the annual CO2 in Comparative Example 1 ２ The emissions totaled 11.24 million tons + 4.99 million tons - 0.56 million tons = 15.67 million tons.

[0059] Figure 4 corresponds to Comparative Example 2, in which hydrogen is introduced as a reducing agent into the pre-reduction furnace, thereby reducing the amount of coal introduced into the steelworks. However, in order to satisfy the energy demands within the steelworks, LNG is introduced from outside the steelworks. CO2 emissions from the steelworks ２ CO2 is calculated by subtracting the amount of carbon derived from valuable chemical products from the amount of carbon derived from coal flowing in with the steelworks as the boundary (coal for coke production) and LNG introduced to satisfy the energy demand within the steelworks. ２ Converted to CO2, this represents the CO2 derived from electricity purchased from external sources to meet the power demand within the railway plant. ２ (Japan's electricity CO2 in 2023) ２ The evaluation is performed by adding up the emission factors (0.441 kg / kWh). As a result, the annual CO2 emissions in Comparative Example 2 ２ The total emissions were 5.33 million tons + 1.15 million tons - 270,000 tons + 2.43 million tons = 8.64 million tons. From this, the CO emissions from the steel mill in Comparative Example 2 ２ This is 55% compared to Comparative Example 1, and 45% CO ２ Emission reduction is possible.

[0060] Figure 5 (corresponding to Example 1) shows the energy flow of an integrated steelworks where external ethylene (1.377 million tons) introduced from outside the steelworks, self-generated ethylene (174,000 tons (11% of external ethylene)) produced inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases at the steelworks are circulated within the steelworks, and the energy required for steel production at the steelworks is supplied by electricity generated from renewable energy. CO2 emissions from the steelworks ２ Regarding this, it is possible to evaluate it in the same way as in Comparative Example 1, and the CO of Example 1 ２ The emissions amounted to 4.01 million tons + 1.05 million tons - 200,000 tons = 4.86 million tons. Compared to Comparative Example 1, the CO2 emissions were approximately 69% lower. ２A reduction is possible, and compared to Comparative Example 2, an additional 24% of CO2 can be reduced. ２ This indicates that it is possible to reduce emissions.

[0061] Figure 6 (corresponding to Example 2) shows the energy flow of an integrated hybrid steelworks in which external ethylene (912,000 tons) introduced from outside the steelworks, self-produced ethylene (20,000 tons (2% of external ethylene)) generated inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases at the steelworks are circulated within the steelworks, and the energy required for steel production at the steelworks is supplied by electricity generated from renewable energy. CO2 emissions from the steelworks ２ Regarding this, it is possible to evaluate it in the same way as in Comparative Example 1, and the CO of Example 2 ２ The emissions amounted to 2.53 million tons + 0.63 million tons - 0.13 million tons = 3.03 million tons. Compared to Comparative Example 1, the CO emissions were approximately 81% of the original amount. ２ A reduction is possible, and compared to Comparative Example 2, an additional 36% of CO2 can be reduced. ２ This indicates that it is possible to reduce emissions.

[0062] Figure 7 (corresponding to Example 3) shows the energy flow of an integrated steelworks, where the energy required for steel production is supplied by external ethylene (1.691 million tons) introduced from outside the steelworks, self-generated ethylene (65,000 tons (4% of external ethylene)) produced inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases and renewable energy. CO2 emissions from the steelworks ２ Regarding this, it is possible to evaluate it in the same way as in Comparative Example 1, and the CO of Example 3 ２ The emissions amounted to 2.99 million tons + 1.65 million tons - 150,000 tons = 4.49 million tons. Compared to Comparative Example 1, the CO emissions were approximately 71% lower. ２ A reduction is possible, and compared to Comparative Example 2, an additional 26% of CO2 can be reduced. ２ This indicates that it is possible to reduce emissions.

[0063] Figure 8 (corresponding to Example 4) shows the energy flow of an integrated hybrid steelworks in which external ethylene (1.29 million tons) introduced from outside the steelworks, self-generated ethylene (0 tons (0% of external ethylene)) produced inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases at the steelworks are circulated within the steelworks, and the energy required for steel production at the steelworks is supplied by electricity generated from renewable energy. CO2 emissions from the steelworks ２ Regarding this, it is possible to evaluate it in the same way as in Comparative Example 1, and the CO of Example 4 ２ The emissions were 2.27 million tons - 110,000 tons = 2.16 million tons. And, compared to Comparative Example 1, the CO2 emissions were approximately 86% of the original amount. ２ A reduction is possible, and compared to Comparative Example 2, an additional 41% of CO2 can be reduced. ２ This shows that it is possible to reduce emissions. Here, the example shown in Table 1 is when biomass charcoal material is used as pulverized coal, so CO ２ It is deducted from emissions.

[0064] For Examples 1, 2, 3, and 4, CO ２ To achieve a significant reduction in emissions economically, we will not purchase electricity from external sources (purchased electricity will be used by the power company's CO2 emissions). ２ CO2 emissions depend on the emission factor and are the responsibility of the steel company. ２ (Because the reduction amount could not be committed), it was assumed that the electricity would be covered by power generated by the power generation facilities within the steelworks. If the production of blast furnace steel is reduced and the production of electric furnace steel is increased, the amount of electricity required will increase, while the amount of by-product gas from the pre-reduction furnace will decrease, thus reducing the amount of electricity generated within the steelworks. For this reason, there is a lower limit to the ratio of blast furnace steel to steelworks crude steel, and the 60% shown in Example 2 is approximately that lower limit.

[0065] The reason why the effects shown in Examples 1, 2, 3, and 4 are obtained can first be explained by the amount of heat required for steel production at the steelworks. The amount of heat required at the steelworks is 180 trillion kJ / year for Comparative Example 1, 156 trillion kJ / year for Comparative Example 2, 121 trillion kJ / year for Example 1, 78 trillion kJ / year for Example 2, 131 trillion kJ / year for Example 3, and 100 trillion kJ / year for Example 4. By using ethylene, the amount of heat required at the steelworks is greatly reduced. The reason why the amount of heat required at the steelworks is reduced is that, with the use of ethylene, each process within the steelworks is optimized and waste heat is reduced. By using renewable energy for this reduced amount of heat required, a significant and economical reduction in CO2 emissions can be achieved. ２ Reductions can be achieved. This aligns with the approach to climate change countermeasures outlined by the IEA (International Energy Agency).

[0066] 1. Blast furnace 2. Pre-reduction furnace 3. Coke oven 4. Converter 5. Carbon dioxide separation equipment 6. Steel heating furnace 7. Power generation equipment 8. Hydrogen production equipment 9. Ethylene synthesis equipment 10. Ethylene storage tank 11. External ethylene production equipment 21. Electric arc furnace 100. Steelworks

Claims

1. A method for operating a steelworks, characterized by circulating external ethylene introduced from outside the steelworks, self-generated ethylene produced inside the steelworks, by-product gases generated at the steelworks, and electricity generated using the by-product gases at the steelworks within the steelworks, and supplying electricity generated from renewable energy sources or nuclear power plants to the steelworks.

2. The method for operating a steelworks according to claim 1, characterized in that the steelworks is equipped with a molten iron production facility combining a pre-reduction furnace and a blast furnace, the external ethylene and the self-produced ethylene are blown into the blast furnace, and the by-product gas of the blast furnace is used as the reducing gas for the pre-reduction furnace.

3. The method for operating a steel mill according to claim 2, characterized in that at least one of the external ethylene and the self-produced ethylene is blown into the pre-reduction furnace of the steel mill.

4. The method for operating a steelworks according to claim 2 or 3, characterized in that the steelworks has a power generation facility, and in this power generation facility, it generates electricity using the by-product gas of the pre-reduction furnace and supplies the generated electricity to the steelworks.

5. The method for operating a steelworks according to claim 4, characterized in that the steelworks has a steel heating furnace and uses the by-product gas of the pre-reduction furnace as fuel gas in the steel heating furnace.

6. Air is mixed with oxygen to increase the oxygen concentration to 21% by volume or more and blown into the blast furnace, and carbon dioxide is separated from the by-product gas of the pre-reduction furnace to obtain 1000 kcal / Nm³ ３ The method for operating a steel mill according to claim 5, characterized in that the above-mentioned high-calorie gas is used as the fuel gas.

7. The blast furnace is supplied with oxygen-enriched air, which is air mixed with oxygen to increase the oxygen concentration to 21% by volume or more, and carbon dioxide is separated from the by-product gas of the pre-reduction furnace to obtain 1000 kcal / Nm³. ３ The method for operating a steel mill according to claim 4, characterized in that the above-mentioned high-calorie gas is used in the power generation equipment.

8. The method for operating a steel mill according to claim 6, characterized in that a mixed by-product gas obtained by mixing the high-calorie gas with coke oven gas and converter gas is used as the fuel gas.

9. The method for operating a steel mill according to claim 7, characterized in that the power generation equipment is at least one of a gas turbine combined cycle type power generation equipment and a fuel cell type power generation equipment, and a mixed by-product gas obtained by mixing the high-calorie gas with coke oven gas and converter gas is used in the power generation equipment.

10. The method for operating a steelworks according to claim 9, characterized in that the steelworks is equipped with an electric furnace for melting scrap and producing molten steel, and by supplying electricity generated by the power generation equipment to the electric furnace, molten steel is produced in a hybrid manner using the blast furnace and the electric furnace.

11. The method for operating a steel mill according to claim 7, characterized in that the self-generated ethylene is produced by synthesizing the separated carbon dioxide with hydrogen produced using surplus electricity from the power generation equipment.

12. The method for operating a steelworks according to claim 2 or 3, wherein the steelworks is equipped with an external ethylene production facility that dehydrates ethanol or dimethyl ether introduced from outside the steelworks to produce external ethylene, and the waste heat of the steelworks is supplied to the external ethylene production facility as a heat source for the dehydration.

13. The method for operating a steelworks according to claim 4, wherein the steelworks is equipped with a carbon dioxide separation facility for separating carbon dioxide from the by-product gas of the pre-reduction furnace, and the carbon dioxide separation facility separates carbon dioxide by an amine method.

14. A steelworks comprising: a carbon dioxide separation facility for separating carbon dioxide from by-product gases generated within the steelworks; a power generation facility for generating electricity using the by-product gases; a hydrogen production facility for synthesizing hydrogen using the electricity generated by the power generation facility; an ethylene synthesis facility for synthesizing self-produced ethylene using the carbon dioxide obtained by the carbon dioxide separation facility and the hydrogen obtained by the hydrogen production facility; and a blast furnace capable of supplying the self-produced ethylene and at least one external ethylene.

15. The steelworks according to claim 14, comprising: a blast furnace; a pre-reduction furnace capable of supplying by-product gas from the blast furnace; a carbon dioxide separation facility capable of separating carbon dioxide from the by-product gas of the pre-reduction furnace; a steel heating furnace capable of receiving by-product gas of the steelworks, including at least the by-product gas after carbon dioxide has been separated by the carbon dioxide separation facility; a hydrogen production facility capable of producing hydrogen using electricity generated by the by-product gas of the steelworks; an ethylene synthesis facility capable of synthesizing self-generated ethylene to be blown into the blast furnace using carbon dioxide separated by the carbon dioxide separation facility and hydrogen produced by the hydrogen production facility; and a tank capable of storing the self-generated ethylene synthesized by the ethylene synthesis facility.

16. The steel mill according to claim 14 or 15, further comprising an electric furnace capable of producing molten steel using electricity generated by the power generation equipment.

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