Method for producing clean reducing gas for low-carbon blast furnace ironmaking

Abstract

To provide a new decarbonization technology utilized in a blast furnace ironmaking process.SOLUTION: A method for producing a reducing gas used for ironmaking in a blast furnace comprises a step (1) in which reduced iron and carbon dioxide are supplied to an oxidant reactor, and a step (2) in which the reduced iron is oxidized with carbon dioxide at a high temperature in the oxidant reactor to produce a carbon monoxide-enriched reducing gas.

Description

[Technical field]

[0001] The present invention relates to a method for producing a reducing gas for use in iron making in a blast furnace, and also to a method for producing pig iron in a blast furnace using the reducing gas obtained by said method. [Background technology]

[0002] In recent years, against the backdrop of global environmental issues and the depletion of fossil fuels, there has been a great deal of interest in energy conservation and the reduction of carbon dioxide (CO 2 There is a strong demand to reduce CO2 emissions. In particular, the steel industry accounts for approximately 40% of Japan's total industrial emissions. Meanwhile, demand for steel production continues to increase around the world, and the blast furnace steelmaking process remains the most effective and efficient way to produce molten iron.

[0003] Therefore, in order to reduce greenhouse gas emissions by more than 30% by 2030 compared to fiscal 2013 levels and achieve carbon neutrality by 2050, the steel industry’s CO 2 There is an urgent need to propose and develop decarbonization technologies for the blast furnace steelmaking process, which accounts for more than 70% of emissions.

[0004] To date, various decarbonization technologies have been proposed and developed to reduce carbon consumption (coke and pulverized coal) in blast furnaces. For example, (1) direct charging of direct reduced iron (DRI) / hot briquette iron (HBI) into the blast furnace (Non-Patent Documents 1 and 2); (2) technology of injecting hydrogen-rich gas (COG) into the blast furnace (Patent Document 1 and Non-Patent Document 3); and (3) top gas recycle (TGR) blast furnace technology (Patent Document 2 and Non-Patent Document 4) are the three main decarbonization technologies currently under development. However, each of the above technologies has operational constraints, making the operating conditions of the blast furnace ironmaking process complex and difficult. In particular, relying solely on the above technologies will result in a large amount of CO 2 The potential for reducing emissions is very limited (around 20-25%). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] EP2719777A1 [Patent Document 2] U.S. Patent No. 10106863 [Non-patent literature]

[0006] [Non-Patent Document 1] Yu Ujizawa, Kohei Sunahara, Yoshinori Matsukura, Kaoru Nakano, Takafumi Yamamoto, "Study on the effect of increasing blast furnace production by using HBl", Iron and Steel, Vol. 92 (2016) No. 10 [Non-Patent Document 2] A. Griesser and Th. Buergler Berg Huettenmaenn Monatsh (2019) Vol. 164 (7): 267-273 [Non-Patent Document 3] Kenichi HIGUCHI, Shinroku MATSUZAKI, Koji SAITO and Seiji NOMURA, Improvement in Reduction Behavior of Sintered Ores in a Blast Furnace through Injection of Reformed Coke Oven Gas. ISIJ International, Vol. 60 (2020), No. 10, pp. 2218-2227 [Non-Patent Document 4] Wei Zhang, Juhua Zhang, Zhengliang Xue, Exergy analyzes of the oxygen blast furnace with top gas recycling process. Energy 121, 15, Pages 135-146 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0007] The present invention aims to develop a new decarbonization technology for use in the blast furnace steelmaking process. [Means for solving the problem]

[0008] The inventors have demonstrated that CO 2 After extensive research into how to reduce emissions as much as possible, they came up with the idea that clean reducing gas (CO-based) could be obtained by using reduced iron as a raw material in a chemical looping process. They found that this could provide an innovative low-carbon process for producing pig iron from blast furnace steelmaking, and thus completed the present invention.

[0009] That is, the present invention has the following configuration. [1] A method for producing reducing gas for use in ironmaking in a blast furnace, comprising the steps of: (1) providing reduced iron and carbon dioxide to an oxidizer reactor; and (2) oxidizing the reduced iron with carbon dioxide in the oxidizer reactor at elevated temperature to produce a carbon monoxide-rich reducing gas; The manufacturing method includes: [2] (3) sending the partially oxidized reduced iron produced in the oxidant reactor to an air reactor; and (4) completely oxidizing the partially oxidized reduced iron with air in the air reactor; The method for producing a semiconductor device according to [1], further comprising: [3] The method according to [2], further comprising a step of recovering completely oxidized reduced iron. [4] The method according to any one of [1] to [3], wherein the carbon dioxide is concentrated carbon dioxide. [5] The method according to any one of [1] to [4], wherein the carbon dioxide is carbon dioxide separated and recovered from any process in a steel plant, or carbon dioxide of biogenic origin. [6] The method according to any one of [1] to [5], wherein the reduced iron is direct reduced iron (DRI) and / or hot briquette iron (HBI). [7] The method according to any one of [2] to [6], wherein the completely oxidized reduced iron is reused as iron oxide to be charged into a blast furnace, or as iron oxide to be sintered before being charged into a blast furnace. [8] A method for producing pig iron in a blast furnace, comprising injecting a reducing gas obtained by the production method according to any one of [1] to [7] into the blast furnace. [9] A method for producing pig iron in a blast furnace, comprising the steps of: (a) supplying reduced iron and carbon dioxide to an oxidant reactor; (b) oxidizing the reduced iron with carbon dioxide in the reactor at elevated temperature to produce a carbon monoxide rich reducing gas; (c) A step of supplying the reducing gas obtained in the step (b) into a blast furnace. The manufacturing method includes:

[10] (d) A step of sending the partially oxidized reduced iron produced in the oxidizer reactor in the step (b) to an air reactor; and (e) completely oxidizing the partially oxidized reduced iron with air in the air reactor; The method for producing a semiconductor device according to [9], further comprising:

[11] The method according to

[10] , further comprising a step of recovering the completely oxidized reduced iron.

[12] The method according to any one of [9] to

[11] , wherein the carbon dioxide is carbon dioxide recovered from any process in a steel plant or carbon dioxide of biogenic origin.

[13] The method according to any one of [9] to

[12] , wherein the reduced iron is direct reduced iron (DRI) and / or hot briquette iron (HBI).

[14] The method according to any one of

[10] to

[13] , wherein the completely oxidized reduced iron is reused as iron oxide to be charged into a blast furnace, or as iron oxide to be sintered before being charged into a blast furnace. Effect of the Invention

[0010] The present invention can reduce carbon usage by 35% or more without major blast furnace renovation. Thus, the present invention can significantly reduce the consumption of coke and pulverized coal compared to the conventional blast furnace steelmaking process, and therefore CO 2 Emissions can be significantly reduced. [Brief description of the drawings]

[0011] [Figure 1] 1 shows a schematic diagram of a non-limiting example of a method for producing a reducing gas of the present invention. [Diagram 2] 1 shows a schematic diagram of a non-limiting example of a method for producing pig iron of the present invention. [Diagram 3] 1 shows another schematic diagram of a non-limiting example of a method for producing pig iron of the present invention. [Figure 4] FIG. 1 is a schematic diagram showing one embodiment of the method for producing pig iron of the present invention. [Diagram 5] FIG. 2 shows a schematic diagram of a process simulation of a method for producing a reducing gas according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention provides an innovative low carbon process for pig iron production from Blast Furnace (BF) steelmaking. The process of the present invention allows clean reducing gas (CO based) to be obtained by utilizing reduced iron, e.g. direct reduced iron (DRI) / hot briquetted iron (HBI), as feedstock for the chemical looping process.

[0013] 1. A method for producing reducing gas for use in blast furnace iron making One embodiment of the present invention is a method for producing reducing gas for use in making iron in a blast furnace, comprising the steps of: (1) providing reduced iron and carbon dioxide to an oxidizer reactor; and (2) oxidizing the reduced iron with carbon dioxide in the oxidizer reactor at elevated temperature to produce a carbon monoxide-rich reducing gas; (hereinafter, also referred to as "the method for producing a reducing gas of the present invention").

[0014] In the present invention, it is important that the reduced iron is not directly charged into the blast furnace but is loaded into an oxidizer reactor provided outside the blast furnace and the reduced iron is oxidized in the oxidizer reactor to generate a reducing gas rich in carbon monoxide.

[0015] In the method for producing a reducing gas of the present invention, the reduced iron is preferably direct reduced iron (DRI) and / or hot briquetted iron (HBI). Direct reduced iron (DRI) is produced by a steelmaking process in which iron ore (lump or pellets) is directly reduced at a lower temperature than in a blast furnace using reducing gas produced from natural gas or other reducing agents such as coal. Hot briquetted iron (HBI) is obtained by compressing and molding (briquetting) direct reduced iron (DRI) at around 700°C for large-volume, long-distance transportation such as by sea, or for long-term outdoor storage.

[0016] Direct reduced iron (DRI) is usually produced by using reducing gas (H 2 The reduced iron, such as direct reduced iron, is preferably produced using a carbon-free source in order to reduce carbon dioxide emissions from the iron-making process. Examples of carbon-free sources include green hydrogen and biosyngas. As such reduced iron, for example, one produced by the MIDREX process or the ENERGIRON process is preferable, but it is not limited thereto. For the MIDREX process, see https: / / www.midrex.com / technology / midrex-process / and U.S. Pat. No. 11499201. For the ENERGIRON process, see https: / / www.energiron.com / technology / and German Patent Application Publication No. 102016122083.

[0017] The carbon dioxide used in the method for producing a reducing gas of the present invention is preferably concentrated carbon dioxide.

[0018] The carbon dioxide used in the method for producing a reducing gas of the present invention is carbon dioxide separated and recovered from any process in a steel plant, or carbon dioxide of biological origin. Steel plants emit off-gases (gases used as raw materials and fuels, gases released without being used other than those shipped as products; also called steel-off gas) from various processes, some of which contain carbon dioxide. Examples of steel-off gases that contain carbon dioxide include blast furnace gas (BFG; mainly containing carbon dioxide, carbon monoxide, and hydrogen) produced as a by-product from blast furnaces, and coke oven gas (COG) produced in coke ovens where coke is obtained by carbonizing coal. In addition, BFG and COG can be combusted to generate heat and electricity for downstream steel production, and the gas discharged from the combustion system also contains carbon dioxide. Converter furnace gas (LDG (Linz-Donawitz converter gas) or BOSG (basic oxygen steelmaking gas)) is also a steel off-gas containing carbon dioxide that can be used in the present invention. Converter furnace gas, like BFG and COG, is one of the most important by-products generated during steelmaking, since it has a high calorific value and can be used as an energy source in the steel industry. After combustion of converter furnace gas, the carbon dioxide generated can also be recovered as a source for use in the oxidizer reactor. Carbon dioxide separated and recovered from gases discharged from any process in such steel plants (steel off-gas) can be used in the present invention.

[0019] Carbon dioxide can be captured from any of the steel plant process emissions using carbon dioxide capture systems, such as pressure swing adsorption (PSA), monoethanolamine adsorption, membrane separation, or oxyfuel combustion processes.

[0020] In addition, the method for producing a reducing gas of the present invention can also use carbon dioxide of biological origin, for example, carbon dioxide obtained from a gas obtained from a bioenergy system (e.g., biofuel obtained using biomass) or biogas (gas generated by fermentation or anaerobic digestion of biological waste, organic fertilizer, biodegradable material, sludge, sewage, garbage, energy crops, etc.). Biogenic carbon dioxide sources can also be recovered from biomass power plants (e.g., biomass-fired boiler plants), biomass integrated gasification combined cycle (IGCC) plants, waste-to-energy power plants (e.g., incineration plants from municipal solid waste), and the like. To separate and capture these biogenic carbon dioxide, the above-mentioned carbon dioxide capture system can be used, similar to that used to separate and capture carbon dioxide from gases emitted from any process in a steel plant.

[0021] In the method for producing a reducing gas of the present invention, the reduced iron and carbon dioxide may be supplied to the oxidant reactor together, or may be supplied to the oxidant reactor separately. The cases where reduced iron and carbon dioxide are supplied together to the oxidant reactor include a case where reduced iron is preliminarily charged into a carbon dioxide stream and then these are supplied together to the oxidant reactor, and a case where reduced iron and carbon dioxide stream are simultaneously charged into the oxidant reactor from different supply ports. In addition, when the reduced iron and the carbon dioxide are supplied separately to the oxidant reactor, this includes a case where the reduced iron and the carbon dioxide flow are each fed into the oxidant reactor from different feed ports, and a case where the reduced iron and the carbon dioxide flow are fed into the oxidant reactor in that order (either one can be fed first) using a single pipe or the like.

[0022] The oxidizer reactor is a reactor that oxidizes reduced iron with supplied carbon dioxide to generate carbon monoxide-rich reducing gas, and is also called an oxidizer. Any oxidizer reactor that can withstand high temperatures and high pressures can be used. Examples of materials for the reactor include steel (or alloy steel) and wrought iron, and high-temperature firebricks can also be used if necessary.

[0023] In the method for producing a reducing gas of the present invention, reduced iron is oxidized with carbon dioxide at a high temperature in an oxidizer reactor to produce a reducing gas rich in carbon monoxide. The chemical reaction that produces carbon monoxide-rich reducing gas in the oxidizer reactor can occur at 700 to 1200°C. From the viewpoint of energy saving, it is preferable to operate at 1000°C or less, but it is preferable to select the reaction temperature taking into consideration the yield of carbon monoxide-rich reducing gas. Therefore, the preferred operating temperature is in the range of 800 to 1000°C.

[0024] Without intending to be bound by theory, it is believed that the following reactions occur in the oxidant reactor: Oxidation step 1: TIFF2024175931000001.tif10144 Oxidation step 2: TIFF2024175931000002.tif11144

[0025] In this manner, in the method for producing a reducing gas of the present invention, a carbon monoxide-rich reducing gas is produced, and at the same time, partially oxidized reduced iron (i.e., FeO, Fe 3 O 4 ) The partially oxidized reduced iron (FeO, Fe 3 O 4 ) is sent to the air reactor and 2 O 3 and heat, which is used as the heat source for the oxidant reactor. In addition, partially oxidized reduced iron (FeO, Fe 3 O 4) can be split directly into the sintering process for utilization in the sintering plant.

[0026] The carbon monoxide-rich reducing gas thus produced can be sent to the blast furnace as clean CO as a reducing gas. By supplying this reducing gas, the carbon monoxide-rich reducing gas can be used as the reducing gas for the blast furnace, and the amount of coke and pulverized coal fed to the blast furnace can be significantly reduced. As a result, it is possible to reduce the amount of carbon dioxide emitted from steelmaking in the blast furnace.

[0027] In the method for producing a reducing gas according to the present invention, water vapor can be supplied to the oxidizing agent reactor together with carbon dioxide, if necessary. By supplying water vapor, unreacted iron and iron oxide are oxidized to produce partially oxidized reduced iron, Fe, according to the following reaction formula: 3 O 4 and small amounts of hydrogen can be produced in the carbon monoxide-rich reducing gas. TIFF2024175931000003.tif11157If desired, this process can be used to approximate (similarize) the gas composition of the carbon monoxide-rich reducing gas produced to that of conventional operating techniques (i.e., pulverized coal and coke-based operations).

[0028] In one preferred embodiment of the method for producing a reducing gas of the present invention, (3) sending the partially oxidized reduced iron produced in the oxidant reactor to an air reactor; and (4) completely oxidizing the partially oxidized reduced iron with air in the air reactor; Further includes.

[0029] Any air reactor can be used as long as it is resistant to high temperature and high pressure. The reactor material can be, for example, steel (or alloy steel) or wrought iron, and high-temperature refractory bricks can also be used if necessary.

[0030] In the air reactor, partially oxidized reduced iron (FeO, Fe 3 O 4 ) is completely oxidized by air, Without intending to be bound by theory, it is believed that Fe 3 O 4 is completely oxidized to Fe by the following reaction: 2 O 3 is thought to be generated. TIFF2024175931000004.tif10144

[0031] The temperature in the air reactor is preferably 800-1200°C.

[0032] In addition, the heat released by the exothermic reaction of formula (4) may be utilized by transferring it to the oxidant reactor by heat exchange or the like.

[0033] One preferred embodiment of the method for producing a reducing gas of the present invention includes a step of recovering completely oxidized reduced iron. The fully oxidized reduced iron can be reused as iron oxide charged to the blast furnace or as iron oxide sintered before being charged to the blast furnace.

[0034] A schematic diagram of a non-limiting example of the method for producing a reducing gas of the present invention is shown in FIG. The carbon monoxide-rich reducing gas (CO-rich reducing gas in FIG. 1) obtained by the reducing gas production method of the present invention can be used to produce pig iron in a blast furnace by injecting it into the blast furnace. That is, another embodiment of the present invention is a method for producing pig iron in a blast furnace, characterized in that a reducing gas obtained by the method for producing a reducing gas of the present invention is injected into the blast furnace.

[0035] 2. How pig iron is produced in a blast furnace Another embodiment of the present invention is a method for producing pig iron in a blast furnace, comprising the steps of: (a) supplying reduced iron and carbon dioxide to an oxidant reactor; (b) oxidizing the reduced iron with carbon dioxide in the reactor at elevated temperature to produce a carbon monoxide rich reducing gas; (c) A step of supplying the reducing gas obtained in the step (b) into a blast furnace. (hereinafter also referred to as the "method for producing pig iron of the present invention").

[0036] The above steps (a) and (b) of the method for producing pig iron of the present invention correspond to steps (1) and (2) of the method for producing a reducing gas of the present invention, respectively, and their details (reduced iron, carbon dioxide, oxidant reactor, etc.) are as described in detail for steps (1) and (2) of the method for producing a reducing gas of the present invention.

[0037] The carbon monoxide-rich reducing gas is preferably supplied into the blast furnace from either (1) the tuyere of the blast furnace, (2) the blast furnace shaft, or (3) both the tuyere and the blast furnace shaft of the blast furnace (see FIG. 3).

[0038] In one preferred embodiment of the method for producing pig iron of the present invention, (d) sending the partially oxidized reduced iron produced in the oxidant reactor in the step (b) to an air reactor; and (e) completely oxidizing the partially oxidized reduced iron with air in the air reactor; Further includes.

[0039] The above steps (d) and (e) of the method for producing pig iron of the present invention correspond to steps (3) and (4) of the method for producing reducing gas of the present invention, respectively, and their details (partial oxidation, air reactor, etc.) are as described in detail for steps (3) and (4) of the method for producing reducing gas of the present invention.

[0040] In one preferred embodiment of the method for producing pig iron of the present invention, the method includes a step of recovering fully oxidized reduced iron. The fully oxidized reduced iron can be reused as iron oxide charged to the blast furnace or as iron oxide sintered before being charged to the blast furnace.

[0041] The general method of producing pig iron in a blast furnace is to put metal raw materials such as iron ore, reducing materials such as coke, which also serves as fuel, and limestone to remove impurities into the top of the furnace, and then blow heated air (hot blast) into the bottom side to burn the coke. The raw materials put in from the top are usually burned briefly in advance and processed into a solid block, ensuring the upward flow of high-temperature gas in the furnace and the fluidity of the raw materials. Inside the blast furnace, the carbon in the coke removes oxygen from the iron, producing heat, carbon monoxide, and carbon dioxide. This reaction serves as a heat source to melt the iron ore, and the necessary reactions occur continuously as the ore settles from the top to the bottom of the furnace, and by the time it reaches the bottom, the combustion temperature reaches its maximum, and hot liquid pig iron is obtained at the bottom of the furnace. Hot liquid slag containing many impurities accumulates in a layer on top of the pig iron. The pig iron and slag are removed from the bottom side at the appropriate time by natural flow.

[0042] The method for producing pig iron of the present invention includes the above-mentioned steps (a) to (c) in addition to the general method for producing pig iron in such a blast furnace. A schematic diagram of a non-limiting example of the method for producing pig iron of the present invention is shown in FIG.

[0043] In Fig. 2, carbon dioxide obtained from blast furnace gas generated from a blast furnace using a carbon dioxide capture system is supplied to the oxidant reactor, but in the pig iron production method of the present invention, carbon dioxide separated and recovered from any process in a steel plant, or carbon dioxide of biogenic origin can be used. Details of the carbon dioxide separated and recovered from any process in a steel plant and carbon dioxide of biogenic origin are as described in detail in the reducing gas production method of the present invention. In addition, the provision of a carbon dioxide capture system is optional, and the case where carbon dioxide is supplied to the oxidant reactor without using a carbon dioxide capture system is also included in the scope of the present invention. As shown in FIG. 2, a carbon dioxide capture system is used to separate and capture carbon dioxide from the blast furnace gas to produce carbon dioxide (preferably concentrated carbon dioxide) and also produce nitrogen-rich gas.

[0044] As shown in FIG. 2, in the pig iron production method of the present invention, carbon dioxide separated and recovered from blast furnace gas (as described above, the carbon dioxide that can be used in the pig iron production method of the present invention is not limited to this) is reduced in an oxidizer reactor to generate a carbon monoxide-rich reducing gas, which is sent to a blast furnace, and the carbon monoxide in this reducing gas is used for the reduction of iron (Fe in iron ore). 2 O 3 Therefore, depending on the amount of carbon monoxide fed into the blast furnace in step (c), it is possible to reduce the amount of coke fed to generate carbon monoxide. Furthermore, the carbon dioxide separated and recovered from the blast furnace gas becomes carbon monoxide, a reducing gas, and is supplied back into the blast furnace. These reactions and processes form a chemical loop, making it possible to reduce the amount of carbon dioxide emitted from the blast furnace.

[0045] Another schematic diagram of a non-limiting example of the method for producing pig iron of the present invention is shown in Figure 3. In Figure 3, the supply of reduced iron, the supply of steam (if necessary), and the steps in the air reactor shown in Figure 2 are omitted, but the tuyere (3) and the blast furnace shaft (7) of the blast furnace are shown as the places where carbon monoxide-rich reducing gas is supplied to the blast furnace.

[0046] In the pig iron production method of the present invention, the oxidizer reactor can be installed at any location outside the blast furnace. For example, when the carbon dioxide used in the step (a) is carbon dioxide separated and recovered from the blast furnace gas, the oxidizer reactor can be installed around the blast furnace. In addition, the carbon monoxide-rich reducing gas generated in the oxidizer reactor may be directly injected into the blast furnace, or the reducing gas may be temporarily supplied and stored in a gas storage vessel (storage tank) or the like, and then injected into the blast furnace from there as required. In addition, in the pig iron manufacturing method of the present invention, when the carbon dioxide used in step (a) is carbon dioxide of biogenic origin, steps (a) to (b) can be carried out outside the steel plant, and the resulting carbon monoxide-rich reducing gas can be prepared and injected into a blast furnace for use.

[0047] Here, the three main decarbonization technologies considered in the blast furnace ironmaking process described as the prior art will be compared with the pig iron manufacturing method of the present invention.

[0048] First, the pig iron manufacturing method of the present invention is superior to the technology of directly feeding direct reduced iron (DRI) / hot briquette iron (HBI) into a blast furnace in the following points.

[0049] Direct reduced iron (DRI) / hot briquetted iron (HBI) materials can be produced using green hydrogen as fuel, so DRI / HBI are essentially considered clean and green raw materials for use in the steel industry. When charging DRI / HBI directly into the blast furnace, the amount of coke and pulverized coal (injected through the tuyere) can be reduced, since DRI / HBI has a high iron content and is a premium ore-based metal raw material. This therefore means that the charging of DRI / HBI aims to avoid the reduction process that would be required, leading to a reduction in the consumption of coke and pulverized coal. This behavior is due to the fact that the consumption of carbon-based fuels (coke and coal) can be reduced, since part of the raw material (iron ore) charged into the blast furnace is already reduced in the form of DRI / HBI.

[0050] However, this technology has some drawbacks. First, the maximum charging rate of DRI / HBI is approximately 400 kg / tHM (based on theoretical calculations), and exceeding this rate may cause problems with the energy balance of the blast furnace, which may seriously damage the blast furnace. On the other hand, directly charging a large amount of DRI / HBI into the blast furnace changes the phenomena inside the blast furnace both physically and chemically, so it is necessary to explore new process operating conditions for the blast furnace in order to control the reaction behavior inside the blast furnace. In contrast, the production method of the present invention does not require charging reduced iron such as DRI / HBI material into the blast furnace, but instead uses an oxidizer reactor to produce clean CO2-rich gas as a reducing agent for operating the blast furnace, allowing the reduced iron such as DRI / HBI material to be used externally, so that the reaction behavior inside the blast furnace is almost the same as that of conventional operating techniques, i.e., pulverized coal or coke-based operation.

[0051] In addition, among the three main decarbonization technologies mentioned above, there is a technology in which hydrogen-rich gas (COG) is injected into a blast furnace, but the pig iron manufacturing method of the present invention is superior to this technology in the following ways.

[0052] There are strict limitations on the maximum injection rate of hydrogen-rich gas (COG) in a blast furnace. On the other hand, injecting high content hydrogen, such as pure hydrogen, into a blast furnace remains problematic due to changes in internal blast furnace phenomena, both physical and chemical, such as indirect reduction reaction behavior (i.e., endothermic reactions dominate in hydrogen-rich injection technology compared to exothermic reactions in the case of conventional CO reduction gas-based operation) and the pattern and location of the cohesive zone inside the blast furnace. Safety concerns (i.e., how to safely inject large amounts of hydrogen into a blast furnace) are also a major issue. These operational limitations complicate reactor design, make operation unpredictable, and difficult to qualify. On the other hand, hydrogen gas needs to be preheated to at least 1000-1200 °C before injection into the blast furnace, otherwise the energy balance of the blast furnace becomes problematic and may cause serious damage to the blast furnace. As a result, for this purpose, only hydrogen-rich gas (COG) has been successfully injected into a blast furnace to produce pig iron, but as mentioned above, many operational factors affect the performance of the blast furnace.

[0053] In contrast, in the present invention, a CO-based reducing gas is used as a raw material to carry out a reduction reaction with the raw material (iron ore raw material) charged into the blast furnace. As a result, the reaction behavior and the pattern and location of the cohesive zone inside the blast furnace may be the same as in conventional blast furnace ironmaking operations (using coke and coal-based fuels). In other words, in the present invention, the changes in the behavior and phenomenon of the internal BF are not significant compared to the technology of charging DRI / HBI directly into the blast furnace technology and the technology of injecting hydrogen-rich gas (COG) into the blast furnace technology.

[0054] Among the three major decarbonization technologies mentioned above, the top gas recycle (TGR) blast furnace technology uses CO as a reducing gas for molten iron production. 2 However, the TGR-BF technology has several drawbacks. First, reducing gas (CO+H) separated from the blast furnace gas (BFG) stream must be removed before being reinjected into the blast furnace (BF). 2 ) must be reheated from ambient temperature to at least 900°C (depending on the injection point in the blast furnace). Also, the recycle gas (CO 2 Free BFG) has N 2 The gas may be high, resulting in N 2 Usually, the oxygen content of the blast air is N 2 The oxygen content must be increased from 21% up to 90% or more (i.e. full oxygen conditions) to avoid the build-up of oxygen. However, full oxygen operation is difficult in blast furnaces because the flame temperatures can be very high. Another concern would be the tuyere and refractory materials used in blast furnaces. Such high temperature flames can cause severe damage to machinery and heat-resistant materials.

[0055] Second, separated CO 2 The separated high-purity CO may need to be transported underground for storage or shipped to a chemical plant for reuse in the synthesis of various chemicals. 2 The captured CO needs to be further processed somewhere outside the steel industry. 2 How to deal with this efficiently is an important issue. Third, BFG is typically combusted and used to generate heat and electricity further downstream in the steelmaking process. Nevertheless, if BFG is always used and recycled to the blast furnace for the production of molten iron, it is necessary to find another heating and power source to replace BFG for downstream steelmaking. Similarly, coke oven gas (COG) has a higher heating value than BFG. It is also originally used to generate heat and electricity for downstream steelmaking. Therefore, if COG is used to inject into the blast furnace (Hydrogen-rich gas (COG) injection into the blast furnace technology), it is still necessary to find another heating and power source to replace COG for downstream steelmaking.

[0056] In contrast, one of the advantages of the production method of the present invention is that it uses a chemical loop cycle to produce CO 2 Only 10% of the BFG and COG can be reused. This means that the BFG and COG can still be burned to generate heat and power for downstream steelmaking. In addition, CO is removed from the combustion system. 2 If you capture the CO 2 is circulated to the oxidant reactor in a chemical loop cycle, enabling the continuous generation of clean CO reduction gas. On the other hand, the partially oxidized reduced iron (e.g., FeO, Fe 3 O 4 ) can be fed to the air reactor to generate heat energy for the oxidizer reactor or other units. After passing through the oxidizer reactor, the fully oxidized iron can be reused in the sinter plant or blast furnace depending on its physical and chemical quality. This reduces the CO emissions of the steelmaking process itself. 2 This closes the loop. 2 There is no need to transport it to a chemical plant or store it underground. On the other hand, BFG to CO 2 It is also possible to recover and reuse it directly in the oxidizer reactor. This depends on the energy flow allocation and energy allocation in the steelmaking process. However, our design facilitates flexible allocation of the energy flow in the steelmaking process without purchasing additional electricity from the market.

[0057] A schematic diagram of one embodiment of the pig iron manufacturing method of the present invention is shown in Fig. 4. In the pig iron manufacturing method shown in Fig. 4, the following steps are added to the pig iron manufacturing method shown in Fig. 2. (i) The process of feeding coke from a coke plant to a blast furnace. (ii) A process for the combustion of coke oven gas and blast furnace gas to feed the power generation cycle, and a system for capturing the carbon dioxide produced therefrom. (iii) A step of supplying the carbon dioxide separated and recovered in (ii) to an oxidant reactor. (iv) Supplying the heat and electricity produced in the combustion and power generation cycle of (ii) to the hot stove and downstream steelmaking process.

[0058] In the pig iron manufacturing method shown in Figure 4, blast furnace gas is converted into any CO 2 The carbon dioxide may be separated and captured through a capture system and fed to an oxidizer reactor, or the coke oven gas and blast furnace gas in (ii) above may be fed to a combustion and power generation cycle in addition to or without the carbon dioxide derived from the blast furnace gas, and the carbon dioxide produced therein may be converted to CO 2 It can be separated and captured in a capture system and the separated and captured carbon dioxide can be fed to the oxidant reactor. EXAMPLES

[0059] The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0060] A process simulation of the reducing gas of the present invention was carried out based on the schematic diagram shown in FIG.

[0061] About the process in simulation A thermodynamic approach was used to model the complex chemical reactions that occur in a blast furnace (BF). As shown in Figure 5, carbon monoxide-rich reducing gas is produced from the oxidizer reactor. In the oxidizer reactor, the direct reduced iron material is heated to 1000°C, which is then cooled to 100°C. 2The reduced iron is oxidized with concentrated CO separated and recovered from the oxidizer reactor (source). The operating temperature of the oxidizer reactor is 800-1200 °C depending on the required blast furnace operating conditions. The product from the oxidizer reactor (partially oxidized reduced iron) is fed to the air reactor, where the partially oxidized reduced iron is completely oxidized with air by a combustion reaction. The heat released from the air reactor is also fed to the oxidizer reactor to improve the energy efficiency of the process. The resulting high temperature and pressurized carbon monoxide-rich reducing gas is injected into the BF through the tuyere as a reducing agent. In a BF, iron-based charge material, coke, and flux move downwards from the top of the BF, while hot carbon monoxide-rich reducing gas moves upwards. Solid material is initially fed into the top of the BF, known as the heated zone (HZ), where countercurrent solid-gas contact is simulated. In the HZ, the solid material is preheated by hot reducing gas. To model the main body of the BF, the descending solid material and the ascending reducing gas are then fed into a series of equilibrium reactors (GZs). 1 , , G n ), in which the chemical equilibrium for multiple reactions in each reactor is calculated based on the Gibbs free energy minimization method. At the bottom of the BF, hot blast is introduced through the tuyere. In particular, the hot blast and carbon monoxide rich reducing gas conditions can be adjusted to maintain a reasonable theoretical raceway adiabatic flame temperature (RAFT) and bosh gas volumetric flow rate. In time, the hot stove gases leave the top of the BF, while the molten pig iron and molten slag are poured out of the bottom of the BF.

[0062] It should be noted that various simulation constraints regarding top gas temperature, RAFT, molten metal temperature, and slag basicity are considered while solving the mass and energy balance of BF to reflect the realistic operation constraints of BF.

[0063] The results of a simulation using the above process are shown below.

[0064] [Table 1]

[0065] The prior art in Table 1 (Comparative Examples 1 and 2) was obtained from data described in Reference 1 (ISIJ International, Vol. 45 (2005), No. 10) and Reference 2 (ISIJ International, Vol. 62 (2022), No. 12), respectively (see Table 1 in Reference 1 and Table 3 in Reference 2).

[0066] By running a blast furnace ironmaking model, simulation results from the low carbon ironmaking BF process of the present invention showed that it is achievable to save approximately 35% or more of carbon usage in the blast furnace compared to conventional operation.

Claims

1. 1. A method for producing reducing gas for use in steelmaking in a blast furnace, comprising: (1) supplying reduced iron and carbon dioxide to an oxidant reactor; and (2) oxidizing the reduced iron with carbon dioxide in the oxidizer reactor at elevated temperature to produce a carbon monoxide-rich reducing gas; The manufacturing method includes:

2. (3) sending the partially oxidized reduced iron produced in the oxidant reactor to an air reactor; and (4) completely oxidizing the partially oxidized reduced iron with air in the air reactor; The method of claim 1 further comprising:

3. The method of claim 2, further comprising recovering the fully oxidized reduced iron.

4. The process of claim 1 , wherein the carbon dioxide is concentrated carbon dioxide.

5. The method according to claim 4, wherein the carbon dioxide is carbon dioxide separated and recovered from any process in a steel plant, or carbon dioxide of biological origin.

6. The method according to claim 1 , wherein the reduced iron is direct reduced iron (DRI) and / or hot briquetted iron (HBI).

7. 3. The method according to claim 2, wherein the fully oxidized reduced iron is recycled as iron oxide charged to a blast furnace or as iron oxide sintered before being charged to a blast furnace.

8. A method for producing pig iron in a blast furnace, comprising injecting a reducing gas obtained by the method according to any one of claims 1 to 7 into the blast furnace.

9. 1. A method for producing pig iron in a blast furnace, comprising the steps of: (a) supplying reduced iron and carbon dioxide to an oxidant reactor; (b) oxidizing the reduced iron with carbon dioxide in the reactor at elevated temperature to produce a carbon monoxide-rich reducing gas; (c) A step of supplying the reducing gas obtained in the step (b) into a blast furnace. The manufacturing method includes:

10. (d) sending the partially oxidized reduced iron produced in the oxidant reactor in the step (b) to an air reactor; and (e) completely oxidizing the partially oxidized reduced iron with air in the air reactor; The method of claim 9 further comprising:

11. The method of claim 10, further comprising recovering the fully oxidized reduced iron.

12. The method according to claim 9, wherein the carbon dioxide is carbon dioxide recovered from any process in a steel plant or carbon dioxide of biogenic origin.

13. The method according to claim 9, wherein the reduced iron is direct reduced iron (DRI) and / or hot briquetted iron (HBI).

14. The method according to claim 10, wherein the fully oxidized reduced iron is recycled as iron oxide charged to a blast furnace or as iron oxide sintered before being charged to a blast furnace.

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