Blast furnace operation method

Abstract

A blast furnace operation method is characterized in having a blowing-in step for blowing in, from a tuyere, a hydrocarbon that has an unsaturated bond and is generated in accordance with a carbon-neutral method. The hydrocarbon is derived from biomass or renewable energy.

Description

Blast furnace operation method

[0001] This disclosure relates to a method for operating a blast furnace in which reducing gas is injected through a tuyere. This application claims priority to Japanese Patent Application No. 2024-144052, filed on August 26, 2024, the contents of which are incorporated herein by reference.

[0002] In the pig iron making process for producing pig iron, raw ore and coke are charged into a blast furnace in alternating layers, and hot air is blown into the furnace through the tuyeres together with pulverized coal, etc., to reduce the raw ore.

[0003] Patent Document 1 discloses a technology in which a blast furnace tuyere is configured with a main flow hole and a side flow hole, and a gaseous reducing agent blown through the side flow hole is merged with an oxygen-containing gas at the tip of the tuyere of the main flow hole, so that the gaseous reducing agent and the oxygen-containing gas are discharged into the furnace from the tip of the tuyere and then combusted. It also discloses that at least one of blast furnace gas, COG, ammonia, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butene, butyne, methanol, ethanol, and dimethyl ether can be used as the gaseous reducing agent.

[0004] Japanese Patent Application Publication No. 2023-3125 International Publication No. 2021 / 107091

[0005] Kazuhisa Murata, Textiles and Industry, Vol. 66, No. 5 (2010) Kouji Takatani, Takanobu Inada, Yutaka Ujisawa, "Three-dimensional Dynamic Simulator for Blast Furnace," ISIJ International, Vol. 39 (1999), No. 1, pp. 15-22

[0006] Patent Document 1 only selectively lists hydrogen-based reducing gases such as methane, COG, ethylene, propylene, and acetylene as examples, and does not consider the relationship between the type of gas and the blast furnace carbon consumption unit.

[0007] The method for operating a blast furnace according to the present disclosure is: (1) a method for operating a blast furnace, comprising an injection step of injecting hydrocarbons having unsaturated bonds produced according to a carbon-neutral method through a tuyere.

[0008] (2) The method for operating a blast furnace according to (1) above, further comprising a step of producing hydrocarbons having unsaturated bonds according to the carbon-neutral method.

[0009] (3) The method for operating a blast furnace according to (1) or (2) above, wherein the hydrocarbons are derived from biomass.

[0010] (4) The method for operating a blast furnace according to any one of (1) to (3) above, wherein the hydrocarbon is ethylene derived from bioethanol.

[0011] (5) The hydrocarbons are hydrogen derived from renewable energy or hydrogen generated using surplus electricity from a steel mill, and CO generated in the steel mill. ２ The method for operating a blast furnace according to any one of (1) to (4) above, wherein the raw material is slag.

[0012] (6) In the injection step, an action to reduce carbonaceous material derived from fossil fuels is carried out when the injection amount of the hydrocarbon is increased, and the degree of reduction of the carbonaceous material in the action is, on a carbon basis, 1 Nm of the hydrocarbon. ３ The method for operating a blast furnace according to any one of (1) to (5), wherein the sintering rate is 1.5 kg / t or more and 1.8 kg / t or less per sintering rate / t.

[0013] (7) A method for operating a blast furnace according to any one of (1) to (6) above, wherein in the injection step, at least one of the injection amount of the hydrocarbon and the blast temperature is controlled according to the supply and demand situation of blast furnace gas in the entire steelworks.

[0014] (8) A method for operating a blast furnace according to any one of (1) to (7) above, comprising an acquisition step of acquiring in advance for each blast temperature the relationship between the differential heat quantity, which is the difference between the calorie and sensible heat of the blast furnace gas, and the amount of hydrocarbon blown in, and in the blowing process, controlling at least one of the amount of hydrocarbon blown in and the blast temperature based on the information acquired in the acquisition step.

[0015] (9) CO from furnace top gas ２ and H ２ O removed gas at 50 Nm ３ The method for operating a blast furnace according to any one of (1) to (8), wherein the furnace top gas temperature is maintained at the target temperature by blowing from the shaft tuyere under a blowing condition of 1000 W / t or more.

[0016] (10) The method for operating a blast furnace according to any one of (1) to (9) above, wherein saturated hydrocarbons are injected from the tuyere together with the hydrocarbons.

[0017] According to the present disclosure, the effect of reducing the blast furnace carbon consumption intensity can be enhanced.

[0018] 7 is a schematic diagram of a blast furnace in this embodiment. FIG. 7 is a graph showing the relationship between the amount of hydrogen-based reducing gas (ethylene, methane, hydrogen) injected and the blast furnace carbon consumption reduction rate. FIG. 7 corresponds to FIG. 2 and is a graph when the reducing gas is carbon-neutral derived. FIG. 7 is a graph showing the relationship between the primary combustion heat of the reducing gas and the blast furnace carbon consumption reduction rate for each reducing gas injection amount. FIG. 7 is a graph showing the relationship between the reducing gas combustion heat index and the blast furnace carbon consumption reduction rate for each reducing gas injection amount. FIG. 7 is a graph showing the relationship between the reducing gas injection amount and the blast furnace carbon consumption reduction rate for each reducing gas type. FIG. 7 is a graph showing the relationship between the amount of ethylene injected from carbon-neutral origin and the blast furnace carbon consumption intensity for each blast temperature. FIG. 7 is a graph in which the vertical axis of FIG. 7 is changed to the blast furnace carbon consumption reduction rate. FIG. 7 is a graph showing the relationship between the amount of ethylene injected from carbon-neutral origin and the blast sensible heat for each blast temperature. FIG. 7 is a graph showing the relationship between the amount of ethylene injected from carbon-neutral origin and BFG calories for each blast temperature. 1 is a graph showing the relationship between the ethylene injection rate and the difference in BFG calories and sensible blast heat for each blast temperature. 2 is an analysis result of the relationship between the reduction in fossil-derived carbon supply / ethylene injection rate and the change in molten iron temperature. 3 is an analysis result of the relationship between the furnace top gas circulation rate and the increment in furnace top gas temperature.

[0019] 1 is a schematic diagram of a blast furnace according to the present embodiment. The blast furnace 1 is a bell-less type blast furnace located in a steelworks, and includes a tuyere 2, an annular pipe 3, a blowpipe 4, an auxiliary reducing agent injection lance 5, a pulverized coal injection lance 6, a swivel chute 7, and a tap hole 8. The present disclosure can also be applied to a bell-type blast furnace that does not have a swivel chute.

[0020] The tuyere 2 is an inlet for blowing hot air generated in a hot stove (not shown) into the blast furnace 1, and a plurality of tuyere 2 are provided along the circumferential direction of the blast furnace 1. From the tuyere 2, pulverized coal and hydrocarbons with unsaturated bonds, which will be described in detail later, can be blown in together with the hot air.

[0021] The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. A plurality of blowpipes 4 are provided at predetermined intervals in the circumferential direction of the annular pipe 3. The annular pipe 3 supplies hot air sent from the hot stove to the blowpipes 4.

[0022] Each blowpipe 4 is connected to the annular pipe 3 and is also connected to a different tuyere 2. The blowpipe 4 blows the hot air sent from the annular pipe 3 into the blast furnace 1 through the tuyere 2.

[0023] The auxiliary reducing agent injection lance 5 is provided for injecting unsaturated hydrocarbons from the tuyere 2. The pulverized coal injection lance 6 is provided for injecting pulverized coal from the tuyere 2. The auxiliary reducing agent injection lance 5 and the pulverized coal injection lance 6 penetrate the wall surface of each blowpipe 4 and extend into the interior of each blowpipe 4. The unsaturated hydrocarbons and pulverized coal injected into the blowpipe 4 from the auxiliary reducing agent injection lance 5 and the pulverized coal injection lance 6 are injected into the furnace together with hot air through the tuyere 2.

[0024] The rotating chute 7 rotates around an axis extending in the vertical direction and charges the raw ore and coke alternately in layers. The raw ore may be lump ore, sintered ore, pellets, uncalcined carbon-containing agglomerated ore, or the like. The raw ore may also contain a reduction aid such as small coke. The coke may also contain ferro coke. The raw ore and coke can be charged at desired positions by controlling the drive method (forward tilting / reverse tilting), tilting angle, and rotation speed of the rotating chute 7. Forward tilting refers to a drive method in which the rotating chute 7 is driven from the furnace wall side toward the furnace center, and reverse tilting refers to a drive method in which the rotating chute 7 is driven from the furnace center side toward the furnace wall side.

[0025] The tap hole 8 is provided at the hearth of the blast furnace 1, and taps the molten iron produced by reducing the raw ore. A plurality of tap holes 8 are provided around the periphery of the furnace, and the molten iron can be tapped continuously or intermittently.

[0026] 1, the blast furnace 1 may be provided with a plurality of shaft tuyere openings along the circumferential direction of the blast furnace 1. The shaft tuyere openings are provided at a position higher than the tuyere 2 of the blast furnace 1, and are injection openings for injecting gas into the shaft portion of the blast furnace 1.

[0027] The method for operating a blast furnace according to this embodiment is characterized by including an injection step of injecting hydrocarbons having unsaturated bonds (hereinafter referred to as "hydrocarbons (unsaturated bonds)") produced according to a carbon-neutral method from a tuyere.

[0028] The inventors have discovered that the carbon reduction effect of a blast furnace can be effectively enhanced by injecting hydrocarbons (unsaturated bonds) into the blast furnace as a reducing gas. The carbon reduction effect of a blast furnace can be evaluated by the blast furnace carbon consumption intensity and the blast furnace carbon consumption reduction rate. The blast furnace carbon consumption intensity is the carbon consumption per ton of molten iron and refers to the total carbon amount contained in the coke, pulverized coal, and reducing gas required to produce one ton of molten iron. "Producing hydrocarbons having unsaturated bonds produced according to a carbon-neutral method" means, for example, hydrogen produced using renewable energy (e.g., solar power generation, wind power generation) or surplus electricity generated in a steelworks, and CO2 generated in a steelworks. ２ This includes producing hydrocarbons with unsaturated bonds from raw materials, and producing hydrocarbons from biomass-derived raw materials procured from outside the steelworks. The blast furnace carbon consumption reduction rate is the difference between the blast furnace carbon consumption intensity in standard operation and the blast furnace carbon consumption intensity in operation in which hydrocarbons (unsaturated bonds) are injected as reducing gas, divided by the blast furnace carbon consumption intensity in standard operation, and expressed as a percentage. Standard operation is an operation format in which only pulverized coal is injected as a reducing agent from the tuyere. An example of standard operation will be described later.

[0029] Table 1 below shows the decomposition reactions (hydrocarbon + oxygen → aCO + bH) occurring before the tuyere of a blast furnace for ethylene, propylene, acetylene, methane, natural gas (NG; example composition), and COG (example composition). ２ ) These gases are all hydrogen-based reducing gases.

[0030] Methane, NG, and COG have positive heat of decomposition (in other words, endothermic reactions), so their temperatures before the tuyere decrease. The same applies to hydrogen. According to Patent Document 2 and other documents, increasing the sensible heat of blast of these gases can reduce the carbon consumption intensity of a blast furnace, but this has the following problems. Specifically, since the hydrogen reduction of iron ore is an endothermic reaction, heat equivalent to this endothermic heat must be supplied. However, since hydrogen itself does not produce heat, heat must be supplied as sensible heat. To supply sensible heat, the process gas must be heated or heating equipment must be installed, which results in increased exergy loss and a significant decrease in energy efficiency. Note that "increasing the sensible heat of blast" is synonymous with "raising the blast temperature."

[0031] In contrast, hydrocarbons (unsaturated bonds) such as ethylene, propylene, and acetylene have a negative heat of decomposition (in other words, an exothermic reaction), and therefore can supply heat to the furnace. Although details will be made clear in the examples below, by blowing hydrocarbons (unsaturated bonds) as reducing gas, the effect of reducing the carbon consumption intensity of the blast furnace can be increased compared to standard operation, even without increasing the blast temperature.

[0032] It was found that the higher the C / H (molar ratio) of the constituent molecules of the hydrocarbon, the better. When the C / H (molar ratio) of the molecules constituting the hydrocarbon becomes low, the H per unit heat quantity of the hydrocarbon becomes low. ２ The amount of O (water vapor) generated increases, and H ２ This is because the loss of latent heat and sensible heat of O (water vapor) increases.

[0033] The hydrocarbons (unsaturated bonds) produced according to the carbon-neutral process may be biomass-derived hydrocarbons.

[0034] Biomass-derived hydrocarbons (unsaturated bonds) refer to the production of hydrocarbons (unsaturated bonds) using biomass raw materials. The biomass raw materials may be from agriculture, forestry, livestock, fisheries, or waste. For example, biomass such as sugarcane, corn, or wood can be fermented to produce bioethanol as a biomass raw material, and ethylene can be produced from the bioethanol. While the method for producing ethylene from bioethanol is not particularly limited, for example, the method described in Non-Patent Document 1 can be used to produce ethylene with a high yield. Non-Patent Document 1 also discloses a method for easily producing ethylene by dehydrating bioethanol at a temperature of 200°C or less using a catalyst (e.g., a zeolite-based catalyst). Propylene can also be produced using the method described in Non-Patent Document 1. Acetylene can be produced from biomass using the carbide method.

[0035] The hydrocarbons (unsaturated bonds) may be produced outside the steelworks or may be produced inside the steelworks. When produced inside the steelworks, carbon neutrality can be achieved, for example, by using waste heat or renewable energy (e.g., solar power generation, wind power generation) inside the steelworks as the heat source for the dehydration reaction. That is, a production step of producing hydrocarbons (unsaturated bonds) according to a carbon-neutral method may be included. When procuring hydrocarbons (unsaturated bonds) from outside the steelworks, hydrocarbons (unsaturated bonds) produced according to a carbon-neutral method may be transported to the steelworks and injected into the tuyere of the blast furnace.

[0036] In addition, hydrocarbons (unsaturated bonds) produced according to carbon-neutral methods are hydrogen produced using renewable energy (e.g., solar power generation, wind power generation) or hydrogen produced using surplus electricity generated in steelworks, and CO generated in steelworks. ２The hydrocarbons (unsaturated bonds) produced by the carbon-neutral method may be hydrocarbons (unsaturated bonds) produced from biomass-derived raw materials procured from outside the steelworks. Patent Document 1 (paragraph 0004) describes a method of injecting gases such as ethylene, propylene, and acetylene from blast furnace gas into a blast furnace, but does not describe a method of producing hydrocarbons derived from renewable energy. Surplus electricity refers to electricity generated within the steelworks that is not used in sintering, coke ovens, blast furnace blowers, oxygen production, rolling, plating, and other steelworks processes.

[0037] Here, when a reducing material derived from a fossil fuel (such as pulverized coal) is injected into a blast furnace, the carbon contained in the reducing material cannot be deducted from the blast furnace carbon consumption when evaluating the carbon reduction effect of the blast furnace. In contrast, if the reducing material is produced according to a carbon-neutral method, the carbon contained in the reducing material can be deducted from the blast furnace carbon consumption to evaluate the carbon reduction effect of the blast furnace. Therefore, the reduction effect of the blast furnace carbon consumption intensity can be further improved.

[0038] The present inventors obtained the above-mentioned knowledge from the results of analysis using a blast furnace mathematical model (see Non-Patent Document 2). Non-Patent Document 2 describes a method for dividing the internal region of a blast furnace into a plurality of small regions, substituting preset blast furnace operating conditions and raw material properties into calculation formulas for material balance, momentum balance, and energy balance in each small region to perform calculation processing, thereby determining the ratio of solids (raw ore, etc.) and furnace gases (CO gas, H ２A mathematical model has been disclosed that calculates state variables such as the reduction reaction rate with the furnace gas (e.g., gas), the furnace gas flow, the furnace gas temperature, and the furnace gas composition, and comprehensively simulates the furnace state. For example, in the case of a three-dimensional blast furnace mathematical model, the internal region of the blast furnace can be divided in the height, radial, and circumferential directions of the blast furnace to define multiple meshes (small regions), and the furnace state can be comprehensively simulated. Furthermore, in the case of a two-dimensional blast furnace mathematical model, the internal region of the blast furnace can be divided in the height and radial directions of the blast furnace to define multiple meshes, and the furnace state can be comprehensively simulated. Note that the blast furnace mathematical model described below refers to the blast furnace mathematical model in Non-Patent Document 2, unless otherwise specified.

[0039] The carbon reduction effect of the blast furnace when room-temperature hydrogen-based reducing gas is injected through the tuyere was analyzed using a blast furnace mathematical model, assuming that the operation is thermally balanced, relative to the standard operation of the blast furnace shown in Table 2 (operation in which only pulverized coal is injected through the tuyere). The iron production rate, molten iron temperature, furnace top gas temperature, and coke rate were constant. The blast furnace process is a process in which room-temperature iron raw materials are reduced to molten iron, and the amount of heat required to achieve this process is thermodynamically determined. "Thermal balance of operation" means that the operation is performed so that this amount of heat is obtained. In the following explanation, "standard operation" may be referred to as "base operation."

[0040]

[0041] Figure 2 shows the relationship between the amount of reducing gas (ethylene, methane, hydrogen) injected and the blast furnace carbon consumption reduction rate. Here, the blast furnace carbon consumption reduction rate on the vertical axis was evaluated by regarding the carbon in the reducing gas as being derived from fossil fuels and as the carbon consumed in the blast furnace. The "blast furnace carbon consumption reduction rate" will not be explained again.

[0042] With methane, the carbon reduction effect due to hydrogen reduction increases with increasing injection rate, but the thermal compensation carbon due to the endothermic reaction at the tuyere tip also increases, so the injection rate is 100 to 150 Nm ３The carbon consumption reduction rate of the blast furnace peaked at around 1 / t. In contrast, in the case of ethylene, the carbon reduction effect was greater due to the exothermic reaction at the tuyere tip.

[0043] FIG. 3 corresponds to FIG. 2, and shows the reduction gas as hydrogen generated using renewable energy (e.g., solar power generation, wind power generation) or surplus electricity generated in the steelworks, and CO generated in the steelworks. ２ The results are based on the assumption that ethylene was produced using raw materials derived from biomass or procured from outside the steelworks, i.e., produced according to a carbon-neutral method. Here, the blast furnace carbon consumption reduction rate on the vertical axis was evaluated by subtracting the carbon in the reducing gas from the carbon consumed in the blast furnace. It was found that ethylene has about twice the carbon reduction effect of methane.

[0044] FIG. 4 shows the relationship between the primary combustion heat of an arbitrary hydrocarbon gas (reducing gas) and the blast furnace carbon consumption reduction rate. As shown in FIG. 4, it can be seen that there is no correlation between the primary combustion heat of the reducing gas and the blast furnace carbon consumption reduction rate. On the other hand, FIG. 5 shows the relationship between the combustion heat index defined above, i.e., H ２ The relationship between the primary combustion heat per mole, i.e., the combustion heat index of the reducing gas, and the blast furnace carbon consumption reduction rate is shown in Figure 5. As shown in Figure 5, it was found that there is a good correlation between the reduction gas combustion heat index and the blast furnace carbon consumption reduction rate. ２ It was found that a gas with a high primary heat of combustion per mole amount can increase the carbon reduction rate.

[0045] Figure 6 shows the relationship between the injection amount of each hydrocarbon gas (reducing gas) and the blast furnace carbon consumption reduction rate. As shown in Figure 6, the blast furnace carbon consumption reduction rate can be increased by injecting unsaturated hydrocarbons such as ethylene, propylene, and butene. Furthermore, among unsaturated hydrocarbons, ethylene can more effectively increase the blast furnace carbon consumption reduction rate when the injection amount into the blast furnace is the same.

[0046] Figure 7 shows the relationship between the ethylene injection rate and the blast furnace carbon consumption rate for each blast temperature. The blast furnace carbon consumption rate on the vertical axis is evaluated by subtracting the carbon contained in the reducing gas (ethylene) from the carbon consumed in the blast furnace. "Base" in this figure is an abbreviation for base operation (Base) (the same applies to Figures 8 to 11). The analysis results in Figures 7 to 12 were obtained using a blast furnace mathematical model.

[0047] It was found that the relationship between the ethylene injection rate and the blast furnace carbon consumption rate is a linear equation with the same slope (but different intercepts) regardless of the blast temperature. ３ / t, the carbon supply in carbonaceous materials derived from fossil fuels is approximately 1.6 kg / Nm ３ - It was discovered that the heat balance could be achieved by reducing the ethylene injection rate. In other words, the ethylene injection rate was reduced to 1 Nm ３ It was found that when the blast furnace carbon consumption rate is increased by approximately 1.6 kg / t, heat balance can be achieved by reducing the amount of fossil fuel-derived carbonaceous material by approximately 1.6 kg / t on a carbon basis. It was also found that the blast furnace carbon consumption intensity can be reduced by up to approximately 40% compared to standard operation (Base). Figure 8 shows Figure 7 with the vertical axis changed to the blast furnace carbon consumption reduction rate. The blast furnace carbon consumption reduction rate will not be explained again. It was found that in the operation method in which ethylene is injected, the carbon reduction effect of the blast furnace is higher than that of standard operation (Base) even when the blast temperature is lowered to 700°C.

[0048] 7 and 8, the carbon reduction effect of the blast furnace can be improved by increasing the blast temperature. In other words, by increasing the blast temperature, the blast furnace carbon consumption intensity can be reduced, and the blast furnace carbon consumption reduction rate can be increased.

[0049] However, increasing the blast temperature reduces the calorific value of the blast furnace gas supplied to other equipment, so it cannot necessarily be said that carbon consumption has been reduced when viewed from the perspective of the steelworks as a whole. The inventors also clarified this point through analysis using a blast furnace mathematical model. Figures 9 to 11 show the analysis results. Figure 9 shows the relationship between the ethylene injection rate and the blast sensible heat for each blast temperature. Figure 10 shows the relationship between the ethylene injection rate and BFG calories for each blast temperature. Figure 11 shows the relationship between the difference between the BFG calories and the blast sensible heat and the ethylene injection rate for each blast temperature. Note that BFG refers to blast furnace gas (the same applies hereinafter).

[0050] 9 and 10, the lower the blast temperature, the smaller the blast sensible heat and the higher the BFG calories. The sensible heat of the hot air blown from the tuyere of the blast furnace is the blast sensible heat. When BFG is used as fuel for the hot stove, the amount of heat obtained by subtracting the blast sensible heat from the BFG calories is the amount of heat supplied to equipment other than the blast furnace in the steelworks (hereinafter also referred to as the "difference heat"). This difference heat can be increased by lowering the blast temperature.

[0051] Referring to FIG. 11 , in the operation method of blowing ethylene, the differential heat quantity can be increased compared to the standard operation (Base) by lowering the blast temperature compared to the standard operation (Base). That is, in the operation method of blowing ethylene, the differential heat quantity can be increased compared to the standard operation (Base) by setting the blast temperature to 1000°C or less. Furthermore, even if the blast temperature is the same as the standard operation (Base), 1200°C (or 1100°C), the differential heat quantity can be increased compared to the standard operation (Base) by increasing the ethylene blowing rate. As is clear from FIG. 11 , the operation method of this embodiment allows the differential heat quantity to be controlled over an extremely wide range by controlling the blast temperature.

[0052] If information corresponding to FIG. 11 is acquired in advance based on the analysis results of the blast furnace mathematical model, a desired differential heat quantity can be obtained by controlling at least one of the hydrocarbon (unsaturated bond) injection rate and the blast temperature. That is, an acquisition step may be performed in which the relationship between the hydrocarbon injection rate, which is the difference between the blast furnace gas calories and the blast sensible heat, and the hydrocarbon injection rate is acquired in advance for each blast temperature. Furthermore, the blast oxygen concentration may be included in such control targets. That is, the blast oxygen concentration may be controlled in conjunction with the control of the hydrocarbon (unsaturated bond) injection rate and the blast temperature.

[0053] Here, if the oxygen enrichment rate is improved and the blast temperature is reduced while blowing in hydrocarbons (unsaturated bonds), the waste heat in the ironmaking process is reduced, allowing for a reduction in the energy input.

[0054] Here, as shown in Fig. 7, the blast furnace carbon consumption rate can be reduced by increasing the blast temperature from 1200°C to 1300°C in standard operation (Base). However, when an operational action of increasing the blast temperature is carried out, the differential heat quantity decreases as shown in Fig. 11. In other words, the heat quantity available for use by other facilities decreases.

[0055] The findings obtained from Figures 7, 8, and 11 can be summarized as follows (1) to (3): (1) By injecting hydrocarbons (unsaturated bonds) produced according to a carbon-neutral method as a reducing gas, the carbon intensity of the blast furnace can be reduced compared to standard operation (Base) without being affected by the blast temperature. (2) The carbon reduction effect of the blast furnace can be controlled by adjusting at least one of the blast temperature and the amount of hydrocarbons (unsaturated bonds) injected. (3) By controlling at least one of the blast temperature and the amount of hydrocarbons (unsaturated bonds) injected according to the supply and demand situation of blast furnace gas throughout the steelworks, it is possible to satisfy supply and demand without procuring fuel from outside the steelworks. Within steelworks, by-product gases generated from coke ovens and converters, including blast furnace gas, are combusted and used as a heat source for each process or as fuel for power generation. Because by-product gases are generated in the ironmaking and steelmaking processes, their supply fluctuates due to operational issues with blast furnaces, shutdowns for scheduled maintenance, and fluctuations in production due to economic conditions. Meanwhile, by-product gas consumption fluctuates not only in the ironmaking and steelmaking processes but also in other processes consuming by-product gases throughout the steelworks, such as rolling, surface treatment, and power generation, due to operational issues and fluctuations in product mix due to economic conditions. Steelworks operate by procuring fuel from external sources or supplying electricity to external sources in response to such supply and demand fluctuations. In order to promote carbon reduction throughout the steelworks, it is necessary to reduce the amount of by-product gas generated while reducing the demand in each by-product gas consuming process. For example, if the calorific value of blast furnace gas supplied to facilities other than the blast furnace falls below demand, the calorific value (calorific value difference) of the blast furnace gas supplied to those facilities can be increased by implementing at least one of the following actions: lowering the blast temperature and increasing the amount of hydrocarbon (unsaturated bond) injection. This eliminates the need to supplement energy needs by supplying city gas, coal, etc. from outside the steelworks to other facilities, and therefore makes it possible to maintain the carbon reduction effect obtained from each blast furnace alone at a higher level than that of standard operation (Base), while also increasing the carbon reduction effect when evaluated for the steelworks as a whole.The more hydrocarbon injection amount is increased, the greater the carbon reduction effect of the blast furnace can be, but this comes at the expense of increased costs, which makes it difficult to consider cost-effectiveness and social CO2 reduction. ２ It may vary depending on the reduction pressure. Even when the blast furnace gas supply and demand situation of the entire steelworks is satisfied, the calorific value (calorific value difference) of the blast furnace gas may be increased by performing at least one of the actions of lowering the blast temperature and increasing the amount of hydrocarbon (unsaturated bond) injected. In this case, for example, the differential calorific value can be used to generate electricity and sell it.

[0056] According to conventional thinking, if hydrogen is injected into the blast furnace to reduce the amount of carbon input, the amount of blast furnace gas will decrease and the energy that can be used in the steel heating furnace will also decrease, but it is possible to avoid using energy derived from fossil fuels and reduce CO ２ To reduce emissions, ２ At this time, since there is little carbon in the fuel, CO ２ The concentration decreases, and the heating efficiency by radiant heat transfer decreases. Furthermore, when hydrogen is used to heat steel, a large amount of water vapor is generated, 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, it may be necessary to significantly update the combustion equipment. The blast furnace in this embodiment can supply blast furnace gas that is suitable for heating steel in, for example, the rolling and annealing processes. In other words, by reducing the amount of blast furnace gas, blast furnace gas with superior heating capacity can be supplied to downstream processes compared to an operating method in which hydrogen is injected into a steel heating furnace.

[0057] Using a blast furnace mathematical model, we analyzed how much fossil-derived carbon could be replaced with ethylene. Specifically, the blast temperature was 1200°C, and the ethylene injection rate was 50 Nm ３The relationship between the reduction in pulverized coal supply and the change in hot metal temperature was analyzed for the ethylene injection rate when the productivity rate, coke rate, and top gas temperature were kept constant at a 1000 MPa / t furnace. Figure 12 shows the analysis results. When increasing the ethylene injection rate and reducing the amount of pulverized coal, the basic principle is to replace ethylene and pulverized coal so that the change in hot metal temperature (Δhot metal temperature) is zero. However, in actual operation, it is not always easy to achieve Δhot metal temperature = 0 due to the influence of fluctuations in raw material properties, etc.

[0058] Considering that a fluctuation of about ±20°C in Δhot metal temperature is generally allowed, the analysis results in Fig. 12 show that the appropriate range of the reduction in the supply of fossil-derived carbon relative to the injection rate of hydrocarbons (unsaturated bonds) is 1.5 to 1.8 kg / Nm ３ -ethylene. In other words, when increasing the amount of hydrocarbon (unsaturated bond) injected and taking action to reduce carbonaceous material derived from fossil fuels, the degree of reduction in carbonaceous material is, on a carbon basis, 1 Nm of hydrocarbon. ３ The "action to reduce carbonaceous materials derived from fossil fuels" includes actions to reduce only pulverized coal, actions to reduce only coke charged from the furnace top, and actions to reduce both pulverized coal and coke. When operation is performed within the above-mentioned appropriate range, fluctuations in the molten iron temperature are within the allowable range, and therefore no operational action is required.

[0059] CO from furnace top gas ２ and H ２ A specified gas from which O has been removed is ３ The furnace top gas temperature may be maintained at the target temperature by injecting the gas from the shaft tuyere into the shaft section under an injection condition of 1 / t or more. It is expected that it will be difficult to maintain the furnace top gas temperature if the carbon input amount into the blast furnace is reduced, but it is necessary to maintain a lower limit temperature of preferably about 100°C. When it is expected that it will be difficult to maintain the furnace top gas temperature at the target temperature due to fluctuations in the raw fuel such as sintered ore or coke, the furnace top gas temperature can be maintained at the target temperature by injecting the above-mentioned specified gas from the shaft tuyere into the shaft section.

[0060] An example corresponding to this embodiment is shown in Figure 13. Figure 13 is an analysis result using a blast furnace mathematical model, and shows the relationship between the above-mentioned predetermined gas (simply referred to as the furnace top gas circulation amount) and the increment in furnace top gas temperature. ３ By circulating the furnace gas at a rate of 1 / t or more, it is possible to raise the furnace gas temperature by 20°C or more.

[0061] Saturated hydrocarbons (such as methane) may be injected into the tuyere together with hydrocarbons (unsaturated bonds). If injecting hydrocarbons (unsaturated bonds) increases the target pre-tuyere combustion temperature or increases the heat load of the equipment due to combustion rate control, the pre-tuyere combustion temperature and heat load can be controlled within an appropriate range by replacing some of the hydrocarbons (unsaturated bonds) with saturated hydrocarbons (such as methane).

[0062] REFERENCE SIGNS LIST 1 blast furnace 2 tuyere 3 annular pipe 4 blowpipe 5 auxiliary reducing agent injection lance 6 pulverized coal injection lance 7 swivel chute 8 taphole

Claims

1. A method for operating a blast furnace, comprising: an injection step of injecting hydrocarbons having unsaturated bonds produced according to a carbon-neutral method through the tuyere.

2. The method for operating a blast furnace according to claim 1, further comprising a step of producing the hydrocarbons having unsaturated bonds according to the carbon-neutral method.

3. The method for operating a blast furnace according to claim 1 or 2, wherein the hydrocarbons are derived from biomass.

4. The method for operating a blast furnace according to claim 1 or 2, wherein the hydrocarbon is ethylene derived from bioethanol.

5. The hydrocarbons are hydrogen derived from renewable energy or hydrogen generated using surplus electricity from steelworks, and CO generated within the steelworks. ２ The method for operating a blast furnace according to claim 1, wherein the raw materials are sintered steel and sintered steel.

6. In the injection step, an action is taken to reduce carbonaceous material derived from fossil fuels when increasing the amount of hydrocarbon injection, and the degree of reduction in carbonaceous material in the action is such that, on a carbon basis, the amount of hydrocarbon 1 Nm ３ 3. The method for operating a blast furnace according to claim 1 or 2, wherein the carbon dioxide is 1.5 kg / t or more and 1.8 kg / t or less per sintered material.

7. A method for operating a blast furnace according to claim 1 or 2, wherein in the injection step, at least one of the amount of hydrocarbon injection and the blast temperature is controlled according to the supply and demand situation of blast furnace gas throughout the steelworks.

8. A method for operating a blast furnace as set forth in claim 7, further comprising an acquisition step of acquiring in advance for each blast temperature the relationship between the differential heat quantity, which is the difference between the calorie of the blast furnace gas and the sensible heat of the blast, and the amount of hydrocarbon injection, and in the injection process, controlling at least one of the amount of hydrocarbon injection and the blast temperature based on the information acquired in the acquisition step.

9. CO from furnace top gas ２ and H ２ O removed gas at 50 Nm ３ 3. The method for operating a blast furnace according to claim 1 or 2, wherein the furnace top gas temperature is maintained at the target temperature by injecting the gas from the shaft tuyere under an injection condition of 1 / t or more.

10. A method for operating a blast furnace according to claim 1 or 2, wherein saturated hydrocarbons are injected from the tuyere together with the hydrocarbons.