Production method of reduced iron

Abstract

To provide a method for producing reduced iron substantially without using coke and suppressing CO2 emission from a reaction system as much as possible.SOLUTION: Disclosed is a method for producing reduced iron, which includes the steps of: successively carrying out reactions shown in formulae (1) and (2) in a substantially anhydrous environment to produce carbon monoxide and hydrogen; using the carbon monoxide obtained by the reaction shown in the formula (2) for a reduction reaction of an iron oxide raw material containing Fe2O3 shown in formula (3); adjusting a molar amount of CH4 to be used in the formula (1) according to a molar amount of carbon dioxide produced in the reduction reaction; and using the carbon dioxide produced in the reduction reaction shown in the formula (3) for the reaction shown in the formula (2). CH4→C+2H2...(1) C+CO2→2CO...(2) Fe2O3+3CO→2Fe+3CO2...(3)SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for producing reduced iron. [Background technology]

[0002] The amount of carbon dioxide emitted during steel production is equivalent to 14.6% of Japan's total GHG emissions (Non-Patent Document 1). In particular, in blast furnaces, a large amount of carbon dioxide is generated because iron ore is reduced with coke produced by high-temperature carbonization of coal. In order to reduce this emission, efforts are being made to reduce the amount of coke used in blast furnaces, including using hydrogen produced in coke production as an alternative reducing agent (Patent Document 1), producing synthetic gas from methane produced in coke production and using it as an alternative reducing agent (COURSE50, Patent Document 2), and separating and capturing CO2, methanating it, and reusing it as a reducing agent (Patent Document 3). In addition, a method of burying it underground (CCS, Non-Patent Document 1) is also being considered.

[0003] Apart from the efforts in blast furnaces, several processes have been put into practical use to obtain direct reduced iron (DRI) by using synthetic gas, which is made by reforming natural gas, as the reducing gas for iron oxide raw materials (for example, Patent Document 4). The DRI production process is characterized by low CO2 emissions because it does not use coke at all, and by converting DRI into blast furnace raw material, it is possible to reduce the amount of coke used for blast furnaces (Non-Patent Document 1).

[0004] Whether the reduction is performed using a blast furnace or a DRI manufacturing process, as long as the reduction is performed using a hydrogen-based reducing gas species, it is an endothermic reaction, and the temperature inside the furnace will drop and iron will not melt (Non-Patent Document 2). In addition, a large amount of hydrogen is required to achieve carbon neutrality in a blast furnace, but there is a major problem that the supply of clean hydrogen is insufficient. In addition, as long as the reduction is performed using a carbon-based reducing gas species, there is a problem that the generation and emission of CO2 is unavoidable in the end. Therefore, it has been proposed to utilize the high-temperature sensible heat and waste heat in a steelworks to convert CO2 in the furnace gas into CO by reacting it with C and reusing it as a reducing gas for iron ore (Patent Document 5), but this is merely a conversion of a part of the CO2 emitted from a blast furnace based on the use of coke into CO. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-221549 A [Patent Document 2] JP 2011-213545 A [Patent Document 3] JP 2011-225969 A [Patent Document 4] U.S. Patent No. 5,437,708 [Patent Document 5] Special Publication No. 2023-503296 [Non-patent literature]

[0006] [Non-Patent Document 1] Shinichi Hara, "The Road to Zero Carbon Steelmaking," presentation material from the SCE·Net Energy Research Group of the Society of Chemical Engineers, January 18, 2021 [Non-Patent Document 2] NEDO Green Innovation Fund feature article: "Realizing an innovative steelmaking process using hydrogen with virtually zero CO2 emissions," August 2023, (URL: https: / / green-innovation.nedo.go.jp / feature / iron-steelmaking / ) Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, whether coke or synthetic gas is used to reduce iron ore, CO2 will eventually be emitted from the system.

[0008] In view of the above-mentioned current situation, an object of the present invention is to provide a method for producing reduced iron in which coke is not substantially used and CO2 emissions from the reaction system are suppressed as much as possible. [Means for solving the problem]

[0009] One aspect of the present invention made to achieve the above-mentioned object is a method for producing reduced iron, comprising the steps of: producing carbon monoxide and hydrogen by sequentially performing the reactions shown in the following formulas (1) and (2) in a substantially anhydrous environment (sequential dry reforming method, SDRM method); using the carbon monoxide obtained in the reaction shown in the following formula (2) in a reduction reaction of an iron oxide raw material containing Fe2O3 shown in the following formula (3); adjusting the molar amount of CH4 to be provided to the following formula (1) in accordance with the molar amount of carbon dioxide produced in the reduction reaction; and using the carbon dioxide produced in the reduction reaction shown in the following formula (3) in the reaction shown in the following formula (2). CH4 → C + 2H2 (1) C + CO2 → 2CO (2) Fe2O3+3CO→2Fe+3CO2···(3) According to this method, the reactions (1) and (2) are carried out successively, and therefore the following reverse water gas shift reaction is generated from the reaction system. CO2+H2→CO+H2O (5) As a result, it is possible to provide a method for producing reduced iron that uses only CO as a reducing agent and is suitable for use in blast furnaces. In addition, by adjusting the molar amount of CH4 to be used in the above formula (1) according to the molar amount of carbon dioxide produced in the reduction reaction (stoichiometrically, when the molar ratio of carbon dioxide:CH4 is 1:1, Fe:CO:H2 is discharged at a ratio of 2:3:6, so adjustment is made in this manner), it is possible to recycle and reuse the entire amount of carbon dioxide produced in the reaction shown in the above formula (2), and it is possible to suppress CO2 emissions from the reaction system as much as possible.

[0010] The method for producing reduced iron may further include a step of using combustion heat obtained by burning the hydrogen obtained in the reaction shown in the above formula (1) for the reaction shown in the above formula (1) or (2). With this configuration, the endothermic reaction shown in the above formula (1) or (2) can be smoothly promoted by the high combustion heat of hydrogen.

[0011] Another aspect of the present invention is a method for producing a synthesis gas or a chemical product using the same, which comprises mixing hydrogen obtained by the above-mentioned method for producing reduced iron and carbon monoxide at a constant ratio by adjusting the molar flow rates. The above-mentioned method for producing a synthesis gas or a chemical product using the same may further comprise adjusting the H2 / CO ratio by adding hydrogen derived from renewable energy. This makes it possible to adjust the H2 / CO ratio from around 1, which is obtained by the SDRM method, to any level exceeding 2.

[0012] Another aspect of the present invention is a reduced iron production apparatus including a reduction module for an oxidized iron raw material such as a blast furnace or a direct reduction furnace, a reactor containing a structure catalyst having a catalytic effect for a methane pyrolysis reaction, and a sequential dry reforming (SDRM) reaction module having a CO detector on a flow path connected to a gas outlet of the reactor. With such a configuration, a reduced iron production apparatus is obtained by combining a small reaction module suitable for implementing the SDRM method of generating carbon monoxide by utilizing carbon generated by the catalytic effect of a methane pyrolysis reaction. In particular, when the reduction module for the oxidized iron raw material is a blast furnace, the SDRM reaction module replaces the coke oven, and when the reduction module for the oxidized iron raw material is a direct reduction furnace, the CO outlet of the SDRM reaction module is connected to a natural gas supply port. In addition, since a structure catalyst is used, the amount of generated carbon (filamentous carbon, carbon nanotubes, etc.) temporarily stored due to clogging of the reactor by generated carbon as in the case of a catalyst using a support is reduced, and the risk of an increase in the energy required to send reaction gas, etc. is also reduced.

[0013] The reduced iron manufacturing apparatus is preferably one in which the reactor includes one gas supply port and one gas exhaust port, and further includes a supply-side three-way valve for switching the supply path to the gas supply port and a discharge-side three-way valve for switching the exhaust path from the gas exhaust port. With such a configuration, the number of pipes directly connected to the apparatus is reduced, and when the supply-side three-way valve is open in the CH4 supply direction and the discharge-side three-way valve is open in the H2 exhaust direction, the valves are automatically closed in the CO2 supply direction and the CO exhaust direction, and when the supply-side three-way valve is open in the CO2 supply direction and the discharge-side three-way valve is open in the CO2 exhaust direction, the valves are automatically closed in the CH4 supply direction and the H2 exhaust direction, making the apparatus even more suitable for implementing the SDRM method.

[0014] The above-mentioned reduced iron manufacturing apparatus preferably includes a discharge-side valve for controlling the discharge of hydrogen and / or CO from the reactor, and a main valve capable of releasing gas remaining in the reactor into the atmosphere, or a main valve capable of releasing the gas to a flow path separate from the flow paths of hydrogen and CO, is provided at a position closer to the gas outlet of the reactor than the discharge-side valve. With such a main valve, the purity of the generated gas controlled by the discharge-side valve located downstream of the main valve can be improved by a purging operation using the raw material gas at the main valve. Effect of the Invention

[0015] According to the production method of the present invention, high-quality H and CO are separately produced without producing water as a by-product from the reaction system. Therefore, the method can be used as a production method for reduced iron that selectively uses CO alone as a reducing agent and can be used in blast furnaces. In addition, when producing synthesis gas, the H / CO ratio can be freely adjusted depending on the target product. The production method of the present invention has the following advantages: (a) molten iron can be extracted without releasing CO2 into the reaction system; (b) molten iron can be produced in a blast furnace without using hydrogen derived from renewable energy, which is in absolute short supply; and (c) useful H2 and CO can be obtained as by-products. In addition, since the reaction shown in formula (3) is an exothermic reaction, the energy efficiency is better than that of direct reduction methods using hydrogen or synthetic gas. [Brief description of the drawings]

[0016] [Figure 1] 2A and 2B are cross-sectional views taken along the line AA of the SDRM reaction module of Experimental Example 1. FIG. [Diagram 2] 4 is a graph showing the change in hydrogen concentration over time in Experimental Example 1. [Diagram 3] SEM image and EDS measurement results of the catalyst with the product attached. [Figure 4] A graph showing the relationship between furnace temperature and equilibrium concentration levels of CO and CO2. [Diagram 5] A graph showing the change in CO and CO2 concentration levels over time after switching from N2 gas to CO2. [Figure 6]Schematic diagram showing the reaction scheme for turquoise steel. [Figure 7] Schematic diagram of a turquoise steel production equipment. [Figure 8] An overview of the SDRM process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The following defines the terms used in this specification. In this specification, "in a substantially anhydrous environment" means an environment in which water or water vapor (steam) is not artificially added to or introduced into the raw materials for the purpose of involving them in the reaction. Therefore, while "in a substantially anhydrous environment," the accidental or unavoidable inclusion of water due to reactions between the raw materials and impurities, reactions between multiple impurities, etc. is permitted, it is preferable to reduce the moisture and humidity of the raw materials by contacting them with a desiccant, etc. As used herein, the term "conducting reactions sequentially" means conducting a plurality of reactions in one reactor in a desired order and / or alternating manner, and in the case of reversible reactions, in a desired direction. In this specification, the term "structure catalyst" refers to a catalyst in which the structure itself functions as a catalyst, or a catalyst based on the structure. A structure-based catalyst generally refers to a catalyst obtained by impregnating a substrate having a shape such as a honeycomb with a slurry containing a catalyst component, but it may also be a catalyst in which an exposed non-supported catalyst layer (plated layer, sprayed layer) is formed on a structure by spraying, plating, or the like. In this specification, the term "structure" refers to an object that has a certain shape even if there is no mold to maintain the shape. The shape of the structure is not particularly limited, and examples thereof include a plate (not only a flat plate, but also a flat plate that has been subjected to any processing such as bending, folding, punching, notching, embossing, etc.), a rod, a cylinder, a porous body, a honeycomb (monolith type), a felt, a mesh, a fabric, and an expanded metal. In this specification, "renewable energy" refers to non-fossil energy sources that are recognized as being able to be used permanently as energy sources (Article 2, Paragraph 3 of the Law Concerning the Promotion of Environmentally Friendly Use of Energy Sources and Effective Use of Fossil Energy Resources by Energy Suppliers). For example, there are seven types of energy: (a) solar power, (b) wind power, (c) hydroelectric power, (d) geothermal power, (e) solar heat, (f) heat in the atmosphere and other heat present in nature, and (g) biomass (organic matter derived from plants and animals) (Article 4 of the Enforcement Order of the Law). In this specification, the term "chemical products" refers to any product produced in the chemical industry using synthetic gas. Examples include industrial chemicals such as methacrylic acid, methanol, acetic acid, and aldehydes, synthetic fuels, chemical fertilizers, synthetic fibers, rubber, synthetic resins such as polycarbonate and urethane, pharmaceuticals, dyes, soaps, and cosmetics.

[0018] The method for producing reduced iron according to the present invention includes a step of producing carbon monoxide and hydrogen by successively carrying out a methane pyrolysis reaction represented by the following formula (1) and a Boudouard reaction represented by the following formula (2) in a substantially anhydrous environment. CH4 → C + 2H2 (1) C + CO2 → 2CO (2)

[0019] The reaction temperature of reaction formula (1) requires a high temperature of 1200° C. or more in the absence of a catalyst, but when a catalyst is used, it is usually set to 800° C. or more. In this specification, the reaction temperature is a value obtained by measurement using a thermocouple. When a catalyst is used, the reaction temperature of reaction formula (2) is usually set to 400°C or higher. In order to cause the reaction to proceed in a manner that favors CO production, however, the reaction temperature is preferably 650°C or higher, and more preferably 800°C or higher.

[0020] The reactions represented by the above formulas (1) and (2) may or may not require the use of a catalyst, but when the reactions are carried out at the above reaction temperatures, it is preferable to use a catalyst.

[0021] The reaction of formula (1) above is usually carried out using a catalyst that has catalytic activity for the thermal decomposition of methane. As the catalyst "that has catalytic activity for the thermal decomposition of methane", a catalyst having an exposed nickel-containing layer with a thickness of about 1 μm to 200 μm and a layer made of iron, copper, nickel, steel, cast iron, an iron-nickel alloy, or a copper alloy with a thickness of about 0.5 mm to 10 mm as a support layer is preferably used, and a catalyst having an intermediate layer containing copper with a thickness of about 1 to 1000 μm between the support layer and the nickel-containing layer is more preferably used. Here, "exposed" means that methane molecules can come into contact with the nickel-containing layer, and is not limited to being exposed to the naked eye. The nickel-containing layer may be an unsupported nickel-containing layer. "Unsupported" means that the nickel-containing component as the catalyst component is not present as particles dispersed on a porous carrier such as activated carbon or a porous oxide, but is present in an organized state. "Organized" may mean that the particles are fused together in some areas, may be fused together in the entire area, or may be melted as a whole and then cooled and solidified. The catalyst used in carrying out the production method according to the present invention is not limited to a structure catalyst, but may be a powder catalyst that cannot maintain a constant shape without a mold to maintain the shape.

[0022] The catalyst preferably has a layer of iron, copper, nickel, steel, cast iron, an iron-nickel alloy, or a copper alloy having a thickness of about 0.5 mm to 10 mm as a support layer for the nickel-containing layer, and more preferably has an intermediate layer containing copper having a thickness of about 1 to 1000 μm between the support layer and the nickel-containing layer. The support layer may be the structure itself before the nickel-containing layer is laminated, or may be a layer laminated on the structure.

[0023] The reaction of formula (2) above is usually carried out in the presence of the carbon produced in the reaction of formula (1) above. It is sufficient that some of the carbon generated here remains, and some of it may be removed. The carbon generated here tends to be observed mainly in the form of nanofibers (tip-growth form with nickel nanoparticles attached, which are shown as white dots at the tip as shown in the SEM image in Figure 3). The generated carbon containing these catalytic fine particles may have a catalytic effect in addition to serving as a raw material, but regardless of the form or role it has, it is sufficient that it exists in order to carry out the manufacturing method of the present invention. In other words, what has the catalytic effect does not in any way restrict the technical scope of the manufacturing method of the present invention.

[0024] The methane (CH4) used in the above formula (1) is preferably derived from natural gas. Natural gas contains methane (CH4) at high concentrations, and is abundant in supply. Furthermore, city gas, which is also derived from natural gas, can easily become a source containing high concentrations of methane if it is passed through a desulfurizer. Examples of natural gas include city gas, non-associated gas produced from gas fields, associated gas produced together with crude oil from oil fields, shale gas, methane hydrate, etc. In view of the global trend toward carbon negativity, methane derived from biogas, that is, methane obtained by separating CO2 from biogas, may be used, but there is a limit to the amount that can be supplied. Methane derived from coal gas may be used, but there is a drawback in that coal gas is essentially a mixed gas, and methane and CO2 cannot be supplied separately.

[0025] The carbon monoxide obtained by the reaction shown in the above formula (2) is used in the reduction reaction of the iron oxide raw material containing Fe2O3 shown in the following formula (3). Fe2O3+3CO→2Fe+3CO2···(3) The iron oxide raw material is not particularly limited as long as it mainly contains Fe2O3. For example, the form of the iron oxide raw material that can be suitably used is lump iron ore (lump ore), sintered ore obtained by agglomerating powdered iron ore (including iron-containing dusts), and pellets obtained by agglomerating powdered iron ore (including iron-containing dusts).

[0026] The molar amount of CH4 to be provided to the above formula (1) is adjusted according to the molar amount of carbon dioxide generated in the reduction reaction. The adjustment of the molar amount here refers to an adjustment based on the molar amount of carbon dioxide and CH4, taking into consideration the stoichiometric ratio in the subsequent reaction using Fe2O3 and carbon monoxide shown in the above (3). The adjustment ratio is adjusted so that, in a stoichiometric manner, when the molar ratio of carbon dioxide:CH4 is 1:1, no CO2 is discharged from the reaction system, that is, only Fe:CO:H2 is discharged in a ratio of 2:3:6, so that the CH4 to be provided to the above formula (1) is usually 3 moles for every 3 moles of carbon dioxide generated in the reduction reaction, but it does not have to be strictly equal to the stoichiometric ratio, and in reality, it is acceptable to make it higher or lower than the stoichiometric ratio based on the conversion rate of the reaction shown in the above formula (2), the control state of the plant, the amount of carbon dioxide generated from impurities contained in the raw material, etc. The adjustment ratio can be set to, for example, ±50%, ±20%, ±5%, etc., compared to the stoichiometric ratio.

[0027] The carbon dioxide produced by the reduction of the iron oxide raw material shown in formula (3) above is used in the Boudouard reaction shown in formula (2) above. Of the six moles of CO produced in this reaction, three moles are used to reduce iron ore in the reduction module as shown in Figure 6. The remaining three moles are discharged and can be used to produce synthesis gas, which will be described later, or chemical products using the synthesis gas.

[0028] A part of the 6 moles of hydrogen obtained by the reaction shown in formula (1) above can be used together with the 3 moles of CO to produce a synthesis gas or chemical products using the synthesis gas, which will be described later, or to be mixed with city gas, or used as turbine fuel or as a raw material for fuel cells. Alternatively, the combustion heat obtained by combustion, as shown in FIG. 7, can be used for the reaction shown in formula (1) or formula (2) above. H2(g)+1 / 2O2(g)→H2O(l) ΔH=-286kJ / mol Here, "using the combustion heat for the reaction" means using it to preheat the raw materials, or using it as heat to overcome the activation energy barrier, or using it to move the equilibrium to the right (forward reaction side).

[0029] Another aspect of the present invention is a method for producing a synthesis gas or a chemical product using the same, which comprises mixing hydrogen obtained by the above-mentioned method for producing reduced iron and carbon monoxide at a constant ratio by adjusting the molar flow rates. The molar flow rate adjustment is based on the molar ratio of carbon monoxide to hydrogen, taking into consideration the stoichiometric ratio of hydrogen to carbon monoxide in the subsequent reaction using synthesis gas, which is a mixture of hydrogen and carbon monoxide. The constant ratio here does not have to be strictly equal to the stoichiometric ratio, and can be higher or lower than the stoichiometric ratio based on established knowledge about the subsequent reaction using synthesis gas. The constant ratio can be set to, for example, ±50%, ±20%, ±5%, etc., compared to the stoichiometric ratio of the subsequent reaction.

[0030] The above-mentioned synthesis gas or the method for producing a chemical product using the synthesis gas may further include adding hydrogen derived from renewable energy to adjust the H2 / CO ratio. The hydrogen derived from renewable energy is not particularly limited, but examples thereof include hydrogen generated by water electrolysis using surplus electricity from solar power generation or wind power generation.

[0031] The turquoise steel manufacturing apparatus 51 of this embodiment shown in FIG. 7 includes a sequential dry reforming (SDRM) reaction module 1 having a methane gas supply port 12, a CO2 supply port 14, a hydrogen gas exhaust port 16, and a CO gas exhaust port 18, a blast furnace 52 having an iron oxide raw material inlet 53, a furnace top gas outlet 54, a molten iron / slag exhaust port 55, and a tuyere 56, a blower pipe 57 connecting the tuyere 56 and the CO gas exhaust port 18, and a CO2 recovery pipe 58 connecting the furnace top gas outlet 54 and the CO2 supply port 14.

[0032] The SDRM reaction module 1 of this embodiment shown in FIG. 8 includes a reactor 3 having a methane gas supply port 12, a CO2 supply port 14, a hydrogen gas exhaust port 16, and a CO gas exhaust port 18, a heating device 5 inserted and fixed into the reactor 3 from the top, a structural catalyst 7 having a catalytic effect for a methane thermal decomposition reaction and arranged to surround the heating device 5 inside the reactor 3, a first on-off valve 9 for controlling the supply of CH4 to the methane gas supply port 12, a second on-off valve 11 for controlling the supply of CO2 to the CO2 supply port 14, a third on-off valve 13 for controlling the discharge of hydrogen from the hydrogen gas exhaust port 16, and a fourth on-off valve 15 for controlling the discharge of CO from the CO gas exhaust port 18.

[0033] The heating device 5 is an internal heating type that is inserted into the reactor 3 and heats from the inside. Specifically, a recuperative burner that uses hydrogen as fuel is used, but biogas may be used as fuel instead. Also, a heater that heats the reactor 3 from the outside (external heating type) can be used.

[0034] The structural catalyst 7 having catalytic activity for the methane thermal decomposition reaction is formed by electrolytically plating, in that order, a copper layer as a copper-containing intermediate layer and a nickel layer as a nickel-containing layer on a nickel plate catalyst as a support layer (structure).

[0035] As the first to fourth on-off valves 9, 11, 13, and 15, gate valves that can be switched between fully open and fully closed are used, but any other valves such as ball valves can be used instead. When flow rate adjustment is particularly required, butterfly valves and globe valves can also be used. Although the on-off valves are switched manually, they may be automatically performed using solenoid valves or the like.

[0036] A desulfurizer 4 for removing trace amounts of sulfur-based compounds contained in the city gas is provided between the CH4 supply source 17 and the first on-off valve 9. As the desulfurizer 4, a conventionally known solid catalyst or adsorbent can be used.

[0037] In this embodiment, the pressure swing adsorption (PSA) method is used as the H2 purification device 6, but instead of this, a purification method based on permeation through a palladium alloy membrane can also be used.

[0038] In this embodiment, a replaceable solid absorbent having a property of absorbing CO2, in which amine is supported on a porous support, is used as the CO purification device 8. However, instead of this, a liquid absorbent, a membrane separation method, or a PSA method can also be used. When the required purity is low, the refining devices 6 and 8 do not need to be provided.

[0039] In this embodiment, a CO detector (not shown) is provided on a flow path connecting the gas exhaust port of the reactor and the fourth on-off valve 15, or on a flow path connecting the fourth on-off valve 15 and the CO purification device 8. The CO detector is an instrument capable of specifically detecting the carbon monoxide concentration or an indicator reflecting the change therein (for example, a change in potential or a change in absorbance). In this embodiment, an NDIR gas sensor is used as the CO detector, but the measurement method is not particularly limited. Also, a detector capable of simultaneously measuring the concentration of gases other than carbon monoxide may be used.

[0040] Compressors 10a and 10b are provided downstream of the refining devices 6 and 8, respectively.

[0041] In actual operation, when the first on-off valve 9 and the third on-off valve 13 are open, the second on-off valve 11 and the fourth on-off valve 15 are closed, and when the second on-off valve 11 and the fourth on-off valve 15 are closed, the first on-off valve 9 and the third on-off valve 13 are closed. The procedure for opening and closing each valve is as follows: close the second on-off valve 11 → close the fourth on-off valve 15 → open the first on-off valve 9 → open the third on-off valve 13 to perform the methane direct decomposition process shown in formula (1), and close the first on-off valve 9 → close the third on-off valve 13 → open the second on-off valve 11 → open the fourth on-off valve 15 to perform the CO2 reduction process shown in formula (2).

[0042] (Experimental Example 1 - Fabrication of SDRM reaction module and pyrolysis of methane) In the SDRM reaction module 21 shown in FIG. 1, a metal plate catalyst 27 (size: width 30 mm × length 300 mm × thickness 0.6 mm) obtained by electrolytic plating of Cu to a thickness of about 1 μm on both sides of a Ni plate, and then electrolytic plating of Ni to a thickness of about 10 μm was housed in a reaction furnace 23 (capacity Φ30 * 300 mm, 0.2 L) in a state of being suspended from a catalyst suspension stay 24. While flowing room temperature methane from a methane supply port 32 provided at the upper part of the peripheral wall of the furnace 23 from top to bottom at 10 mL / min, the furnace was heated with a heater (not shown) provided on the outer periphery of the furnace 23 until the temperature inside the furnace reached 800 ° C., and the temperature was maintained for 8 hours a day, and the transition of the hydrogen concentration discharged from the hydrogen gas exhaust port 36 was observed. For safety, after 8 hours of continuous operation each day, the core was cooled and heated again from room temperature to 800 ° C. the next day. Figure 2 shows the time course of hydrogen concentration, and Figure 3 shows an SEM image of the catalyst with the product attached and the EDS measurement results. The temperature inside the furnace was measured using a thermocouple 25 inserted through the top cover of the furnace to reach the center. The hydrogen concentration was measured using a Wheatstone bridge type gas thermal conductivity gas analyzer (zero gas: city gas 13A, span gas: 100% hydrogen, gas flow rate: 0.2L / min, Chino) attached to the generated gas exhaust pipe at the bottom of the furnace peripheral wall. SEM images and EDS were obtained by secondary electron detection using a scanning electron microscope (model number: JCM-7000, JEOL Ltd.) (incident voltage 15.0kV, WD 12.5mm, magnification x5,000, probe current mode Std.-PC, vacuum mode HighVac.). As can be seen from Figure 2, the hydrogen concentration (conversion rate) due to the direct decomposition reaction of methane continued to increase from the first day to the second day, and at the end of the second day the hydrogen concentration reached the theoretical equilibrium concentration of 80%, and thereafter remained stable at around 80% even from the sixth day onwards. From Figure 3, it was found that the product was fibrous and consisted mainly of C and Ni. Furthermore, a separate elemental mapping study revealed that the white dots seen at the tip or in the middle of the fiber were Ni particles.

[0043] (Experimental Example 2 - Demonstration of the Boudouard reaction with residual carbon produced and examination of the implementation temperature) After the experiment of Example 1, the supply of methane was stopped and the weight of the carbon produced in the reactor was measured. After measuring the weight of the carbon produced, the metal catalyst plate with the carbon produced and the carbon produced were returned to the reactor. At that time, in order to remove the air that had entered the reactor, room temperature nitrogen gas was filled into the reactor at a flow rate of 0.4 L / min for 30 minutes to purge the air remaining in the reactor. Next, instead of stopping the nitrogen gas supply, room temperature CO2 was supplied at a flow rate of 0.4 L / min while heating until the temperature inside the furnace reached a constant heater temperature, and the CO and CO2 concentration levels were measured until they reached equilibrium. The relationship between the furnace temperature and the equilibrium concentration levels of CO and CO2 is shown in Figure 4. The concentrations of CO and CO2 at this time were measured by sampling the generated gas from the exhaust pipe that releases into the atmosphere, installed at the bottom end of the peripheral wall of the furnace, and using an NDIR gas sensor (gas flow rate: 0.5 L / min, manufactured by AWIT). As can be seen from Figure 4, as the heater temperature increased from 400°C to 800°C, CO increased from 0% to nearly 85%, while CO2 decreased from 100% to 15%. The equilibrium concentration at 800°C is C + CO2⇔2CO The theoretical concentration is 87% (RTlnK = -ΔG°, ΔG° = -17.5 kJ mol -1 This is close to the fundamental characteristics of a molten carbonate direct carbon fuel cell using a cylindrical cell, and suggests that the Boudouard reaction occurs, in which the carbon produced on the catalyst reacts with CO2 to produce CO.

[0044] (Experimental Example 3 - Changes in Boudouard reaction over time) In Example 1, the supply of methane was stopped, and the reaction furnace with the metal catalyst plate to which the produced carbon was attached still in place was filled with room temperature nitrogen gas at a flow rate of 0.4 L / min for 30 minutes to purge the methane and hydrogen remaining in the furnace. Next, the supply of nitrogen gas was stopped and room temperature CO2 was supplied into the furnace at a flow rate of 0.4 L / min. The moment when nitrogen was switched to CO2 was set as 0 seconds, and the time-dependent changes in the CO and CO2 concentration levels were observed in seconds. The results are shown in Figure 5. As can be seen from Figure 5, reduction began 22 seconds after switching from nitrogen to CO2, and the CO concentration stabilized at 83% 1 minute 41 seconds later. From this, it is believed that although there was a drop in temperature when CO2 was first introduced, the temperature inside the furnace soon returned to around 800°C, causing CO reduction to progress rapidly, and the concentration of the supplied CO2 was converted to CO with almost no increase. In this state, it is believed that there was still enough carbon produced in the furnace to reduce the CO2.

[0045] The present invention is not limited to the above-described embodiment, and not all of the configurations described in the above-described embodiment are essential requirements for the present invention. The present invention may be modified in various ways within the scope of the technical concept of the present invention.

[0046] In an alternative embodiment, a pipe may be provided between the purification device 6 and the compressor 10a for returning the raw gas methane separated in the purification device 6 to the reactor 3 or the methane supply port 12, and a pipe may be provided between the purification device 8 and the compressor 10b for returning the raw gas CO2 separated in the purification device 8 to the reactor 3 or the CO2 supply port 14.

[0047] In an alternative embodiment, a compressor may also be provided upstream of the purification devices 6, 8 (closer to the gas outlet).

[0048] In an alternative embodiment, a main valve capable of releasing the gas remaining in the reactor into the atmosphere or a main valve for releasing the gas into a flow path separate from each flow path of the generated gas may be provided at a position closer to the gas outlet of the reactor than the third and fourth on-off valves. Purging the main valve using the raw material gas can improve the purity of the generated gas managed by the third and fourth on-off valves downstream of the main valve.

[0049] In another alternative embodiment, the number of gas supply inlets and gas exhaust outlets may be reduced to one each, and the flow paths from the gas supply inlets to the supply sources of each raw material gas and the flow paths from the gas exhaust outlet to the third and fourth on-off valves may be unified partway through. A configuration may also be adopted in which one supply-side three-way valve is used in place of the first and second on-off valves at each branch point, and one exhaust-side three-way valve is used in place of the third and fourth on-off valves.

[0050] In an alternative embodiment, it is conceivable to prepare a plurality of apparatuses (e.g., two apparatuses, apparatus A and apparatus B) shown in FIG. 8, and first perform the reaction of formula (1) in apparatus A and the reaction of formula (2) in apparatus B for a while, and when solid carbon accumulates in apparatus A, switch to perform the reaction of formula (2) in apparatus A and the reaction of formula (1) in apparatus B. With such an apparatus and method, carbon monoxide and hydrogen can be produced simultaneously and continuously. Furthermore, by preparing at least three apparatuses, it is possible to prevent operation stoppage even if one of the apparatus has some equipment or piping trouble. [Industrial Applicability]

[0051] The present invention is suitable for use in DRI and blast furnaces because it can significantly suppress the generation of CO2 in the production of reduced iron. In addition, there is little concern that the carbon monoxide or synthesis gas produced will contain water, making it suitable for the production of useful chemicals, and therefore has great industrial applicability. In particular, the present invention is suitable for the production of useful chemicals such as acetic acid (CH3COOH), acrylic acid (C3H4O2), benzoic acid (C7H6O2), and polycarbonate (C 16 H 14 O3) n The present invention is also preferably applicable to on-site production and supply of highly toxic carbon monoxide. [Explanation of symbols]

[0052] 1, 21 SDRM reaction module 3. 23 Reactor 4 Desulfurizer 5 Heating device 6 H2 purification equipment 7, 27 Structure catalyst 8. CO purification equipment 9 First opening and closing valve 10a, 10b Compressor 11 Second opening and closing valve 12, 32 Methane supply port 13 Third opening and closing valve 14, 34 CO2 supply port 15 Fourth opening and closing valve 16, 36 Hydrogen gas outlet 17 CH4 source 18, 38 CO gas outlet 19 CO2 source 24 Catalyst suspension stay 25 Thermocouple 51 Turquoise Steel Manufacturing Equipment 52 Blast Furnace 53 Iron oxide raw material inlet 54 Top gas outlet 55 Molten iron and slag discharge port 56 Tuyere 57 Air pipe 58 CO2 capture tube

Claims

1. The method comprises the steps of: producing carbon monoxide and hydrogen by sequentially carrying out reactions represented by the following formulas (1) and (2) in a substantially anhydrous environment; and reacting the carbon monoxide obtained by the reaction represented by the following formula (2) with Fe ２ O ３ and a step of using the resulting iron oxide raw material in a reduction reaction containing the iron oxide raw material. ４ and using carbon dioxide generated in the reduction reaction shown in the following formula (3) for a reaction shown in the following formula (2). <h2 style=";text-align:left;direction:ltr">CH<h2 style=";text-align:left;direction:ltr"> ４ <h2 style=";text-align:left;direction:ltr"> →C+2H<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr">・・・・(1) C+CO ２ →2CO・・・・(2) Fe ２ O ３ +3CO→2Fe+3CO ２ ・・・・(3)

2. and using combustion heat obtained by burning the hydrogen obtained in the reaction represented by the formula (1) for the reaction represented by the formula (1) or (2).

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