TW202336238A - Method for producing hot metal - Google Patents

Abstract

The present invention provides a method for producing a hot metal, the method being capable of producing a hot metal by charging a recovered C source, as a carbonaceous material-containing agglomerated ore, through the throat of a shaft furnace, while circulating a C source in a process. The present invention provides a method for producing a hot metal, the method comprising: a first step in which a carbonaceous material-containing agglomerated ore is produced from an iron-containing starting material and a carbon-containing starting material; a second step in which a hot metal is produced by reducing and melting the carbonaceous material-containing agglomerated ore by blowing an oxygen-containing gas thereinto; and a third step in which carbon is recovered by bringing a carbon-containing gas, which is generated as a by-product by the reduction and contains carbon monoxide and carbon dioxide, into contact with a porous material. With respect to this method for producing a hot metal, the carbon recovered in the third step is used as a part or the entirety of the carbon-containing starting material in the first step. Instead of the second step, this method for producing a hot metal may have: a reduction step in which reduced iron is obtained by heating the carbonaceous material-containing agglomerated ore to 1160-1450 DEG C for reducing and melting the carbonaceous material-containing agglomerated ore, and subsequently cooling the carbonaceous material-containing agglomerated ore; and a melting step in which a hot metal is produced by melting the reduced iron.

Description

How to make molten iron

The invention relates to a method for manufacturing molten iron in the iron-making industry.

All industries are required to reduce carbon dioxide (CO ₂ ) emissions, including the United Nations Sustainable Development Goals (SDGs) and the Paris Agreement. In the manufacturing industry, the demand for CO ₂ reduction is particularly high in the iron and steel industry, which has high CO ₂ emissions. In this iron-making industry, more than 60% of CO ₂ is emitted during the iron-making process. In this process, iron ore is reduced and melted using carbon sources to produce molten iron. The main reason for the extremely high _CO2 emissions in the ironmaking process is thought to be the use of coke or coal for the reduction and melting. It is necessary to develop a molten iron manufacturing process that does not discharge CO ₂ out of the system.

A zero-carbon iron-making process is being studied. Non-patent Document 1 reviews technology prospects for achieving the long-term goal of reducing carbon dioxide in steel. For example, a method will be introduced to reduce CO ₂ emissions to the outside by separating CO ₂ from the exhaust gas generated during the reduction reaction and isolating it for storage (Caron dioxide Capture and Storage (CCS)). Furthermore, a technology is known in which CO ₂ from the exhaust gas is used _for synthesis among other methods (Carbon dioxide Capture and Utilization (CCU)). CH ₄ , the synthesized CH ₄ is blown from the tuyere of the blast furnace and used again for the reduction reaction. [Prior art documents] [Non-patent documents]

[Non-patent document 1] Tatsuro Ariyama, Technology Outlook for Achieving Long-term Goals of Carbon Dioxide Reduction in Steel, Iron and Steel, Vol. 105, 2019, No. 6, pp. 567-586 [Non-patent document 2] "Materials Transactions", Vol.58, No.12 (2017) pp. 1742～1748 "Developed by carbothermal reduction of a composite of hematite and biochar Development of Manufacturing Principle of Porous Iron by Carbothermic Reduction of Composite of Hematite and Biomass Char"

[Problems to be Solved by the Invention] However, the above-described prior art has the following problems. That is, even if the CCS method helps reduce _CO2 emissions, the process itself consumes energy, and there are problems of moving the carbon source outside the system and problems of storage capacity. Furthermore, there is a problem that when CH ₄ is synthesized from CO ₂ and the CH ₄ is blown from the tuyere of the blast furnace, a pipeline for blowing CH ₄ to the tuyere is required.

The present invention was completed in view of this situation, and its purpose is to provide a method for manufacturing molten iron that can circulate the carbon source within the process and load the recovered carbon source as carbonaceous material briquettes from the furnace mouth of the shaft furnace. And make molten iron. [Means to solve problems]

The manufacturing method of molten iron of the present invention that advantageously solves the above-mentioned problems is characterized by including: a first step of producing carbonaceous material pellets from iron-containing raw materials and carbonaceous raw materials; and a second step of preparing the carbonaceous material briquettes. The mine blows oxygen-containing gas for reduction and melting to produce molten iron; and the third step is to make the carbon-containing gas including carbon monoxide and carbon dioxide by-products due to the reduction contact the porous material to recover carbon. In the first step , the carbon recovered in the third step is used for part or all of the carbon-containing raw materials.

Furthermore, in the manufacturing method of molten iron of the present invention, (a) includes the following steps in place of the second step: a reduction step by heating the carbonaceous material briquettes to 1160°C to 1450°C to reduce them; Cooling after melting to obtain reduced iron; and a melting step to produce molten iron by melting the reduced iron; (b) In the third step, the carbon-containing gas further contains a refining step including molten iron. The by-product carbon monoxide and carbon dioxide gases; (c) Before contacting the porous material in the third step, supply hydrogen to the carbon-containing gas and heat it to 800°C to 1200°C to make the carbon-containing gas The carbon dioxide contained in the gas becomes carbon monoxide; (d) After the heating in the third step and before contacting the porous material, remove the water contained in the carbon-containing gas; (e) Satisfy The following formula (1) (in the formula, [H ₂ O] represents the moisture concentration (volume %) contained in the reorganized mixed gas, and [H ₂ ] represents the hydrogen concentration (volume %) contained in the reorganized mixed gas. %)), remove the moisture contained in the carbon-containing gas and the moisture generated due to the recombination reaction of the carbon-containing gas; (f) In the third step, the porous material is iron , part of the recovered carbon is iron carbide; (g) the particle size of the carbon-containing raw material is below 100 μm; (h) in the first step, the carbon-containing raw material further includes biomass; (i) ) The iron-containing raw material is iron ore, and the manufacturing method of molten iron further includes: a pretreatment step, before the first step, the iron ore is heat treated at a temperature above 300°C and below 1000°C, etc. , can become a better solution. [H ₂ O]/([H ₂ O]+[H ₂ ])＜0.1…(1) [Effects of the Invention]

According to the present invention, since the carbonaceous material briquettes using the recovered carbon can be loaded from the furnace mouth of the shaft furnace to produce molten iron, there is no need to modify the shaft furnace and the recovered carbon can be circulated in the process.

Hereinafter, the method of producing molten iron according to this embodiment will be described based on the drawings. The following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and do not limit these structures to the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

FIG. 1 is a schematic diagram showing an example of a method for producing molten iron according to this embodiment. FIG. 2 is a schematic diagram showing an example of a manufacturing process of carbonaceous material briquettes. FIG. 3 is a schematic diagram showing an example of equipment using a convective reduction layer. In this embodiment, the molten iron 36 is produced by reducing the iron-containing raw material 4 contained in the carbon-containing material agglomerate 26 in a convective reduction layer. In manufacturing the molten iron 36, it is preferable to use a vertical shaft furnace, for example. In the following embodiment, the manufacturing method of molten iron of this invention is demonstrated using the example of using the blast furnace 32 as a shaft type shaft furnace. Furthermore, there is no vertical shaft furnace that can produce molten iron without using coke.

In the first step, the iron-containing raw material 4 and the carbon-containing raw material 6 are mixed to produce the carbon-containing material pellet 26 . The iron-containing raw material 4 is mainly pulverized iron ore, but may also include dust generated in an iron smelting plant. In the second step, the obtained carbonaceous material briquettes 26 are charged into the blast furnace 32, and the blast gas 34 is blown into the furnace to perform a reduction reaction to produce molten iron 36. In the third step, the waste gas 38 produced by the reduction reaction in the second step is recovered, and the carbon monoxide contained in the waste gas 38 is contacted with the porous material to precipitate and recover solid carbon. The waste gas 38 to be treated preferably contains the waste gas 40 produced by the refining process of molten iron.

Part or all of the carbonaceous raw material 6 used in the first step is the solid carbon recovered in the third step. Furthermore, when the amount of carbon is insufficient due to only the recovered solid carbon, the deficiency can be supplemented by a carbon source such as biomass. In this case, the carbon-containing raw material 6 includes a carbon source such as biomass. Furthermore, the particle size is preferably 100 μm or less. When the iron-containing raw material 4 used in the first step is pulverized iron ore and contains a large amount of crystallization water, it is preferable to perform a heat treatment step before the first step, that is, in the range of 300°C or more and 1000°C or less. Perform heat treatment.

Each step is explained in detail below. [First step] The first step is to mix iron-containing raw materials and carbon-containing raw materials to produce carbon-containing material briquettes. In the example shown in FIG. 2 , first, the iron-containing raw material 4 stored in the storage tank 2 and the carbon-containing raw material 6 containing solid carbon recovered from the carbon monoxide contained in the exhaust gas 38 , and the iron-containing raw material 4 stored in the storage tank 8 are The cement powder 10 is divided into predetermined amounts from the respective storage tanks 2 and 8 to the conveyor 12 . The iron-containing raw material 4, the carbon-containing raw material 6 and the cement powder 10 are transported to the kneading machine 14 by the conveyor 12. The transported iron-containing raw material 4, carbon-containing raw material 6 and cement powder 10 are mixed together with an appropriate amount of water 16 inside the kneader 14 to become mixed powder 20. Thereafter, the mixed powder 20 is transported to the granulator 24 by the conveyor 22, and is granulated inside the granulator 24 together with an appropriate amount of water 16 to become the carbonaceous material briquettes 26.

In the first step, when the carbon content of the obtained carbonaceous material pellet 26 does not reach the target carbon mass ratio, it is preferable to make the carbonaceous raw material 6 contain biomass or the like and set it to the target carbon mass ratio. Furthermore, the carbonaceous material agglomerate 26 needs to avoid combustion and gasification of carbon, so it is preferably cold formed. Examples of cold forming methods include a method of preparing a cement-based curing agent and the like and then granulating the mixture using a granulator or a drum mixer, or a method of performing compression molding using a briquetting machine or the like. Furthermore, in order to maintain the strength after reduction, the carbon mass ratio per particle of the carbon-containing material agglomerate is preferably 15 mass % or less. Here, if the carbon mass ratio per particle of the carbonaceous material briquettes exceeds 15% by mass, the compressive strength of the granulated material measured by an automatic stereogrammeter (1 mm/min) will fall below the critical limit. value (2.5 MPa), so it is not optimal.

[Second step] The second step is a process of using a convective reduction layer to reduce and melt the iron-containing raw material 4 contained in the carbonaceous material briquette 26 produced in the first step to produce molten iron. In the example shown in FIG. 3 , the iron-containing massive raw material 30 including the carbonaceous material briquettes 26 produced in the method for producing carbonaceous material briquettes and other raw materials 28 is charged from the furnace mouth of the blast furnace 32 , The reducing gas flows from bottom to top. In this way, the iron-containing lump raw material 30 can be reduced and melted as a convection moving layer with respect to the reducing gas, thereby producing molten iron 36 . Oxygen-containing gas is blown into the blast furnace 32 as the air supply gas 34 to perform indirect reduction and direct reduction. The indirect reduction is performed using carbon monoxide gas generated by the reaction of the carbon source and oxygen in the furnace. The direct reduction is performed using The solid carbon source is arranged adjacent to the iron-containing raw material 4. In addition, the air blowing gas 34 may contain hydrogen. If hydrogen is contained, the iron-containing raw material 4 is directly reduced using hydrogen. When hydrogen is blown, the hydrogen is preferably derived from renewable energy sources. As described above, in the method of producing molten iron according to the present embodiment, the carbonaceous material pellets using the carbon recovered from the exhaust gas 38 can be charged from the furnace mouth of the blast furnace 32 to produce molten iron. Therefore, the blast furnace 32 does not need to be modified. Instead, the existing blast furnace 32 is used directly.

[Step 3] The third step is a step of precipitating and recovering solid carbon from the waste gas and the like produced by the reduction reaction in the second step. The waste gas 38 produced by the reduction reaction or the waste gas 40 produced by the refining process of the molten iron contains carbon monoxide, carbon dioxide, hydrogen, and water. However, in the method for producing molten iron according to this embodiment, the waste gas 38 and the waste gas 40 It only needs to contain at least carbon monoxide and carbon dioxide. In the third step of this embodiment, as shown in FIG. 1 , the waste gas 38 and the waste gas 40 are processed using the carbonization equipment 100, the gas reforming furnace 110 and the moisture removal device 120. In addition to the above, exhaust gas discharged from automobiles, gas turbines, incinerators, thermal power plants, and factories can also be used as the exhaust gas. Furthermore, the volume ratio of each gas component present in the exhaust gas can be adjusted according to the combustion conditions of the fuel as the exhaust gas raw material. For example, when the exhaust gas is blast furnace gas, the volume ratio of the blast furnace gas is 21% to 23% by volume of carbon monoxide gas, 19% to 22% by volume of carbon dioxide gas, 2% to 3% by volume of hydrogen, and 53% to 56% by volume of nitrogen. Volume %, so it is better. Furthermore, the blast furnace gas is produced by reducing iron ore by partially burning the coke, heavy oil, and pulverized coal fed into the blast furnace with air to become a reducing gas containing carbon monoxide and nitrogen as the main components.

＜Gas recombination step＞ The exhaust gas 38 and the exhaust gas 40 used in this embodiment contain carbon monoxide, carbon dioxide, hydrogen, and water. The exhaust gas 38 and the exhaust gas 40 are filled in the gas reforming furnace 110 . Next, hydrogen gas supplied from the hydrogen supply unit is added to the gas reforming furnace 110 to prepare a mixed gas. Thereafter, the system of the gas reforming furnace 110 filled with the mixed gas is heated to 800°C to 1200°C. Within the above temperature range, when the system of the gas reforming furnace is heated, the carbon dioxide in the mixed gas existing in the system of the gas reforming furnace undergoes a water gas conversion reaction with hydrogen according to the following chemical reaction formula (I) to generate carbon monoxide and water.

CO ₂ +H ₂ →CO+H ₂ O…(I)

The water-gas conversion reaction using carbon dioxide and hydrogen is a reversible reaction. In the region where the reaction temperature exceeds 500°C, the chemical balance of the water-gas conversion reaction is biased toward the production of carbon monoxide. Therefore, in the manufacturing method of molten iron of this embodiment, by setting the temperature in the system of the gas reforming furnace 110 to 800°C to 1200°C, carbon dioxide can be efficiently converted into carbon monoxide to generate a raw material as solid carbon. of carbon monoxide. That is, in the gas reforming step, by setting the temperature in the system of the gas reforming furnace 110 to 800°C to 1200°C, the mixed gas can be reformed efficiently.

The water gas reforming reaction performed in the system of the gas reforming furnace 110 is a reaction between carbon dioxide contained in the mixed gas, hydrogen contained in the mixed gas, and hydrogen in the hydrogen gas supplied from the hydrogen supply unit. Here, it is preferable that hydrogen is supplied from the hydrogen supply unit so that the hydrogen concentration contained in the mixed gas (based on a gas composition other than nitrogen or an inert gas) becomes 58 volume % or more. If the hydrogen concentration contained in the mixed gas is 58 volume % or more, it is preferable because the ratio of carbon monoxide can be increased in the water gas reforming reaction and solid carbon can be recovered in the subsequent carbon separation step. The hydrogen concentration contained in the mixed gas is 58 volume % or more and is determined by considering the conditions of adding carbon monoxide gas in the water gas conversion reaction in the temperature range of 800°C to 1200°C. The conditions for adding carbon monoxide gas can be determined based on the relationship between the temperature of the water gas conversion reaction and the equilibrium constant. Furthermore, the upper limit of the hydrogen concentration in the mixed gas may be less than 100% by volume, and the upper limit of the hydrogen concentration in the mixed gas may be determined based on the carbon dioxide concentration.

Furthermore, it is preferable that the hydrogen supplied from the hydrogen supply unit provided outside the gas reforming furnace 110 is hydrogen derived from renewable energy. This is preferable since the amount of carbon dioxide discharge can be further suppressed. Furthermore, the supply amount of hydrogen gas supplied from the hydrogen supply unit can be set taking into account the amount of hydrogen contained in the exhaust gas 38 and the exhaust gas 40 .

<Step of removing moisture from carbon-containing gas> The recombinant gas after the water-gas conversion reaction of the mixed gas is supplied to the moisture removal device 120 . The reformed gas contains moisture (water vapor) produced by the water-to-gas conversion reaction. The moisture contained in the recombinant gas is removed by passing through the moisture removal device 120 . Moisture can be removed by passing the recombinant gas containing moisture into the adsorbent packed layer provided in the moisture removal device 120, by passing the recombinant gas into a separation membrane, or the like. It is preferable that the moisture contained in the recombined gas is removed so that the relationship of the following formula (1) is satisfied. By removing moisture from the recombinant gas in a manner that satisfies the relationship of equation (1), the carbon recovery efficiency in the carbon recovery step is improved. In the following formula (1), [H ₂ O] represents the moisture concentration (volume %) in the recombinant gas, and [H ₂ ] represents the hydrogen concentration (volume %) in the recombinant gas.

[H ₂ O]/（[H ₂ O]+[H ₂ ])＜0.1…(1)

Moisture in the recombinant gas can be removed as described above, using adsorbents or separation membranes. As the adsorbent, oxides such as silica, zeolite, and alumina, calcium chloride, magnesium sulfate, etc. can be used. Examples of moisture separation membranes in gas include carbon membranes, resin membranes, and inorganic membranes. These membranes have sub-nanometer pores. The moisture in the gas is recovered by the moisture removal device 120 in the form of liquid water at normal temperature.

The dehumidified gas after removing the moisture becomes the raw material for solid carbon. The bimolecular decomposition reaction (II) by the decomposition of two molecules of carbon monoxide represented by the following chemical reaction formulas (II) to chemical reaction formulas (III), or the one-molecule decomposition by the reaction of one molecule of carbon monoxide and hydrogen Reaction (III), in the carbonization device 100, solid carbon is separated from carbon monoxide.

2CO→C+CO ₂ …(II)

CO+H ₂ →C+H ₂ O…(III)

The carbon monoxide contained in the dehumidified gas is preferably CO/(CO+CO ₂ ) of 0.5 or more, more preferably 0.7 or more. Thereby, solid carbon can be recovered from carbon monoxide with high efficiency.

The dehumidified gas is supplied to the carbon separation part of the carbonization equipment 100 including the porous material at a predetermined supply rate.

<The step of contacting the carbon-containing gas with the porous material to separate the solid carbon> The method of recovering carbon from dehumidified gas includes the step of contacting the dehumidified gas with a porous material to separate solid carbon. The contact between the dehumidified gas and the porous material and the separation of carbon from the dehumidified gas are performed within the system of the carbon separation part of the carbonization equipment 100 . In the system of the carbon separation part of the carbonization equipment 100, as illustrated in FIGS. 4(a) and 4(b), a filling layer filled with the porous material 102 is provided.

As shown in FIG. 1 , carbon constituting carbon monoxide contained in the dehumidified gas is separated from the carbon monoxide gas in the system of the carbonization equipment 100 . The carbon monoxide contained in the dehumidified gas is generated by the decomposition reaction (II) of two molecules of carbon monoxide or the decomposition reaction (III) of one molecule of carbon monoxide represented by the chemical reaction formula (II) to the chemical reaction formula (III). Carbon monoxide separates as solid carbon. The solid carbon separated from the carbon monoxide is adsorbed on the surface of the porous material 102 and precipitated. The dehumidified gas contacts the porous material 102, and the off gas after carbon separation is discharged from the carbonization equipment 100. Since the exhaust gas contains carbon dioxide, it is preferable that part or all of the exhaust gas is mixed with the mixed gas.

In the step of contacting the dehumidified gas with the porous material 102 to separate the solid carbon, the contact between the dehumidified gas and the porous material 102 is preferably performed in an environment of 500°C to 800°C or lower. The temperature at which the recombinant gas is brought into contact with the porous material 102 is preferably 500° C. or higher because the decomposition reaction of carbon monoxide is accelerated. The temperature at which the recombinant gas is brought into contact with the porous material 102 is 800° C. or lower because the heat energy generated by the decomposition reaction of carbon monoxide can be effectively utilized. Better. The temperature at which the recombinant gas is brought into contact with the porous material 102 includes the temperature conditions used in the direct reduction iron production reaction, that is, 500°C to 800°C. In addition, regarding the contact between the dehumidification gas and the porous material, the dehumidification gas may be passed into the filling layer of the porous material 102 provided in the system of the carbon separation unit. Thereby, the decomposition reaction of carbon monoxide represented by the chemical reaction formula proceeds. As the decomposition reaction of carbon monoxide proceeds, solid carbon constituting carbon monoxide is precipitated on the surface of the porous material 102 . Furthermore, when a porous material of iron is used, part or all of the solid carbon precipitated on the surface is carburized to generate iron carbide.

In the step of contacting the dehumidifying gas with the porous material 102 to separate the solid carbon, the contact between the dehumidifying gas and the porous material 102 is preferably performed in an environment where the pressure of the dehumidifying gas is 1.0 atm to 10 atm. If the pressure at which the dehumidification gas is brought into contact with the porous material 102 is 1.0 atm or more, it becomes a pressurized condition, and the balance of the carbon monoxide decomposition reaction shifts to the right to promote the carbon monoxide decomposition reaction. Therefore, it is preferable if it is 10 atm or less. , then from the viewpoint of legal constraints, the safety of the carbon separation unit of the carbonization equipment 100 can be ensured, so it is preferable.

The porous material 102 in contact with the dehumidifying gas preferably has an opening rate measured by Archimedes' method of 50% to 99%, and more preferably 80% to 95%. It is preferable if the porosity of the porous material is 50% or more because the dehumidification gas can pass through the pores (pores) of the porous material to promote the decomposition reaction of carbon monoxide and adsorb the decomposed carbon. On the other hand, it is preferable that the porosity of the porous material 102 is 99% or less because the dehumidification gas supplied to the porous material 102 can maintain thermal shock resistance. The size of the pores (pores) of the porous material 102 is preferably 10 μm or more in diameter. In addition, the porosity of the porous material 102 is measured by the Archimedean method. Specifically, the value measured by the measurement method specified in Japanese Industrial Standards (JIS R2205; 1992) can be used as the porosity. The porosity of the material.

The porous material 102 in contact with the dehumidification gas preferably contains at least one selected from iron, platinum, nickel, cobalt, rhodium and palladium. That is, the porous material may contain one metal element selected from iron, platinum, nickel, cobalt, rhodium, and palladium, or may be composed of a combination of two or more metal elements. Furthermore, the porous material may be a metal compound containing one metal element selected from iron, platinum, nickel, cobalt, rhodium and palladium in the form of carbide, oxide, carbonate, sulfate, etc.

Among the metals used as the porous material 102 in contact with the dehumidification gas, iron, platinum, and nickel are preferred. When platinum or nickel is used as the porous material, it is preferable because the platinum and nickel function as a catalyst for the decomposition reaction of carbon monoxide and cause less deterioration as a catalyst. Furthermore, it is preferable to use platinum or nickel as the porous material 102 because solid carbon generated by the decomposition reaction of carbon monoxide is precipitated in the form of simple graphite.

The porous material 102 in contact with the dehumidified gas is preferably iron. By using iron as the porous material 102 , carbon generated by the decomposition reaction of carbon monoxide is carburized into the porous material 102 to obtain Worthfield iron (γ iron) in which the carbon is solidly dissolved. Furthermore, by using iron as the porous material 102, the carbon generated by the decomposition reaction of carbon monoxide is carburized into the porous material 102, and the carbon reacts with the iron, whereby snow carbon iron (iron carbide (Fe ₃ C)), therefore better. The carbon produced by the decomposition reaction of carbon monoxide is carburized into the porous material 102, and the Vostian iron and snow carbon iron produced have the same level of hardness as quenched steel and can be directly used as raw materials for iron production. Furthermore, the porous material 102 in contact with the dehumidification gas is preferably one or two types of iron selected from iron oxide and reduced iron.

The porous material 102 in contact with the dehumidification gas is preferably iron whiskers. Iron whiskers are crystals that grow in the shape of whiskers from the crystal surface to the outside. Iron whiskers are formed when compressive stress occurs near the surface of the crystal. In order to relieve the stress, new crystals grow toward the outside of the original crystal. Iron whiskers tend to have a small starting point for crystal growth and continue to grow continuously. Therefore, iron whiskers are formed into very elongated whisker-shaped single crystals with a length of more than 1 mm relative to a diameter of about 1 μm. When iron whiskers are used as porous materials in contact with dehumidification gas, the carbon generated due to the decomposition reaction of carbon monoxide is carburized into the iron whiskers, and iron whiskers containing Worthfield iron or snow carbon iron can be obtained. Iron whiskers.

The iron whiskers as the porous material 102 that contacts the dehumidified gas can be produced by the iron whisker production method described in Non-Patent Document 2, for example. According to this method of producing iron whiskers, it is possible to obtain iron whiskers with a porous material having an opening ratio of 90% or more and a pore diameter of 10 μm or more. The iron whiskers obtained by this method of producing iron whiskers also have a high porosity, and therefore can be suitably used as the porous material 102 used in the carbon recovery method. Furthermore, even if a metal other than iron is used as the metal constituting the porous material 102 that contacts the dehumidified gas, the porous material 102 can be manufactured in the same manner.

＜Steps to recover carbon adsorbed on porous materials＞ The carbon adsorbed on the porous material 102 is recovered within the system of the carbon recovery unit 130 . Here, recovering the carbon adsorbed on the porous material includes recovering the solid carbon precipitated on the surface of the porous material 102 or combining the carbon carburized inside the porous material with the metal contained in the porous material. The elements are recovered in the form of solid solutions or carbide metal compounds.

Carbon decomposed by the decomposition reaction of carbon monoxide contained in the dehumidified gas is precipitated on the surface of the porous material 102 . Furthermore, the carbon decomposed due to the decomposition reaction of carbon monoxide contained in the dehumidified gas is carburized into the inside of the porous material 102 and reacts with the metal elements constituting the porous material to form a carbon solid solution or a carbide metal compound. . Furthermore, carbon decomposed by the decomposition reaction of carbon monoxide contained in the dehumidified gas is precipitated on the surface of the carbon solid solution or the carbide metal compound.

The carbon precipitated on the surface of the porous material 102 can be recovered by performing a separation operation of powder and granules of the porous material 102 containing carbon using a screen or the like. Furthermore, the carbon that, after being carburized into the interior of the porous material 102, reacts with the metal elements constituting the porous material to become a carbon solid solution or a carbide metal compound can be recovered by directly recovering the carbon. Carbon solid solution or carbide metal compound itself. Furthermore, when the recovered carbon is used as a raw material for iron production, by using iron as the porous material 102, the recovered carbon and the porous material 102 can be used together without separating the recovered carbon and the porous material 102. Raw materials, therefore better.

In this way, in the third step of this embodiment, by bringing the carbon monoxide contained in the dehumidified gas into contact with the porous material 102, the decomposition reaction of the carbon monoxide can be promoted, the solid carbon can be separated, and the carbon can be separated into solid carbon, or the carbon monoxide can be separated into solid carbon or the porous material 102. Carbon is recovered in the form of a carbon solid solution or a carbon metal compound. In addition, since the carbonaceous material briquettes using the recovered carbon can be used as raw materials to produce molten iron, the recovered carbon can be circulated within the process, thereby reducing the amount of CO ₂ emissions outside the system. The exhaust gas 38, the exhaust gas 40, the mixed gas, and the dehumidified gas in this embodiment are examples of carbon-containing gases including carbon monoxide and carbon dioxide.

Furthermore, in this embodiment, the example in which the second step is performed using the blast furnace 32 is shown, but the invention is not limited to this. For example, a reduction step and a melting step may be performed by using a rotary hearth furnace instead of the blast furnace 32 to heat the carbonaceous material briquettes to 1160°C to 1450°C, reduce and melt them, and then cool them. A step of obtaining reduced iron, and the melting step is a step of producing molten iron by melting the reduced iron in, for example, an electric furnace or the like. Even when a rotary hearth furnace is used, the existing rotary hearth furnace can be used as it is as long as the carbonaceous material briquettes using the recovered carbon are used.

An example of the carbonization equipment of this embodiment is shown in (a) of FIG. 4 . As illustrated in (a) of FIG. 4 , the carbonization equipment 100 includes a tubular reaction tower 101 in which carbon is separated from carbon monoxide contained in the carbon-containing gas; and a supply pipe 104 for supplying water from the lower part of the reaction tower 101 Carbon-containing gas; the layer of porous material 102 is provided inside the reaction tower; and the exhaust gas pipe 105 is used to discharge the exhaust gas generated after the carbon separation reaction. The interior of the reaction tower 101 includes a quartz tube 101a and a sample holder 101b. As the porous material 102 provided in the carbonization equipment 100, as shown in FIG. 4(b), it is preferable to use a material obtained by molding a plurality of iron whiskers with a porosity of 97.7% into a tablet shape. The porous material 102 is provided on a layer containing granular alumina balls 103 (particle diameter: 10 mm). In addition, the porous material 102 is manufactured according to the iron whisker manufacturing method described in Non-Patent Document 2. [Example]

The effect of carbon recovered by the device shown in FIG. 4(a) on the reducibility of iron ore was investigated. Table 1 shows the composition of the iron ore used. T.Fe in Table 1 represents the total iron content. Moreover, the loss on ignition (LOI) is the strong heat loss during heating at 1000°C for 60 minutes. In the case of iron ore, most of it is crystal water. The recovered carbon is C: 38.35% by mass based on snow carbon iron and solid carbon, and the remainder is Fe. Moreover, among the total carbon, C in the form of snow carbon iron was 18.7 mol%, and C in the form of solid carbon was 81.3 mol%.

[Table 1] Ingredient composition [mass %] LOI T.Fe SiO ₂ Al ₂ O ₃ mass % Iron Ore A 57.16 5.51 2.54 10.13

The particle diameters of the iron ore A and the recovered carbon were unified to -105 μm. The so-called -105 μm means the bottom of the sieve with a mesh opening of 105 μm. The sample was mixed by stirring the weighed powder of iron ore A and the recovered carbon in a mortar for 3 minutes without pressing the pestle. A uniform mixed powder can be produced without changing the particle size of the powder during mixing. To the sample, carbon 0.8 times the molar amount of oxygen in the iron oxide was added, and carbon 0.2 times the molar amount of iron in the iron oxide or iron carbide was added and mixed. By adding carbon 0.8 times the molar amount of oxygen in iron oxide, and using carbon as a reducing material, by adding carbon 0.2 times the molar amount of iron in iron oxide or iron carbide, the resistance to metallic iron can be obtained The effect of carburizing has two functions: reducing material and carburizing material.

The uniformly mixed sample was punched at a pressure of 98 MPa for 30 s and formed into a cylindrical shape with a diameter of 10 mm and a height of 10 mm. In an environment where 5% by volume N ₂ -Ar mixed gas is supplied at a flow rate of 0.5 NL/min, the formed sample is heated to 1300°C at a heating rate of 10°C/min. The generated gas is analyzed using an infrared spectrophotometer to calculate the reduction rate of the iron ore. The results are shown in Figure 5. As a comparative example, the same test was performed using carbon black instead of the recovered carbon, and the results are shown in Figure 5 . It is clear from Figure 5 that the recovered carbon (solid line) improves the reduceability of iron ore A compared with carbon black (dashed line).

The reason for this is not clear, but the inventors believe that it is due to the difference in particle size of the carbon-containing material. As shown in Figure 6(a) and Figure 6(b) , the recovered carbon is in the form of fibers with a diameter of approximately several nm. In contrast, as shown in Figure 7 , the carbon black has a particle size of approximately several tens of μm. particle of. In this way, it is considered that the solid carbon recovered from carbon monoxide becomes very small. Therefore, by using this carbon in the carbonaceous material pellet, the contact area with the iron-containing raw material or gas becomes larger, thereby obtaining a highly reducible material. Carbonaceous material agglomerates. [Industrial availability]

In addition to the effect of reducing the amount of CO ₂ discharged outside the system, the manufacturing method of molten iron of the present invention also recovers CO ₂ in the waste gas in the form of solid carbon, and combines it with iron-containing raw materials to produce carbonaceous material briquettes. This can improve the reducibility of briquettes and reduce the number of carbon units required for reduction, which can help reduce the environmental load in the steelmaking industry and is very useful for industry.

2. 8: Storage tank 4: Iron-containing raw materials 6: Carbon-containing raw materials (solid carbon and/or iron carbide) 10:cement powder 12, 22: Conveyor 14:Kneading machine 16:water 20:Mixed powder 24:Pelletizer 26: Carbonaceous material briquettes 28:Other raw materials 30: Iron-containing lump raw materials 32: Blast furnace 34: Supply air gas 36:Molten iron 38: Blast furnace exhaust gas 40: Refining waste gas 100: Carbonization equipment (carbon separation department) 101:Reaction tower 101a: Quartz tube 101b: Sample holder 102: Porous materials (iron whiskers) 103:Alumina ball 104: Supply pipe (for carbon-containing gas) 105:Exhaust gas pipe 110: Gas reforming furnace (gas reforming department) 120: Moisture removal device (moisture removal section) 130:Carbon Recycling Department 140: Carbonaceous material pellet manufacturing equipment

FIG. 1 is a schematic diagram showing an example of the method for producing molten iron according to the present invention. FIG. 2 is a schematic diagram showing an example of the manufacturing process of the carbonaceous material briquettes in the first step of the present invention. 3 is a schematic diagram showing an example of equipment using a convection reduction layer in the second step of the present invention. FIG. 4(a) is a schematic diagram showing an example of the carbonization equipment in the third step of the present invention, and FIG. 4(b) is an enlarged photograph of the porous material used in the carbonization equipment. FIG. 5 is a diagram showing the influence of carbon type on the reducibility of iron ore. Fig. 6(a) is a scanning electron microscope (SEM) photograph of the recovered carbon used in the present invention, and Fig. 6(b) is an enlarged photographic image of the dotted line portion in Fig. 6(a). Fig. 7 is an SEM photograph image of the carbon black used in the comparative example.

6: Carbon-containing raw materials (solid carbon and/or iron carbide)

26: Carbonaceous material briquettes

32: Blast furnace

34: Supply air gas

36:Molten iron

38: Blast furnace exhaust gas

40: Refining waste gas

100: Carbonization equipment (carbon separation department)

110: Gas reforming furnace (gas reforming department)

120: Moisture removal device (moisture removal section)

130:Carbon Recycling Department

140: Carbonaceous material pellet manufacturing equipment

Claims (10)

A method for manufacturing molten iron, including: The first step is to manufacture carbonaceous material briquettes from iron-containing raw materials and carbonaceous raw materials; The second step is to blow oxygen-containing gas into the carbonaceous material briquettes for reduction and melting to produce molten iron; and The third step is to make carbon-containing gas including carbon monoxide and carbon dioxide by-produced by the reduction contact the porous material to recover carbon, In the first step, the carbon recovered in the third step is used for part or all of the carbonaceous feedstock. The manufacturing method of molten iron as described in claim 1, wherein The following steps are included in place of the second step: The reduction step is to obtain reduced iron by heating the carbonaceous material briquettes to 1160°C to 1450°C to reduce and melt them and then cool them; and In the melting step, molten iron is produced by melting the reduced iron. The method for producing molten iron according to claim 1 or 2, wherein in the third step, the carbon-containing gas further contains gas containing carbon monoxide and carbon dioxide that are by-products in the refining step of molten iron. The method for producing molten iron according to any one of claims 1 to 3, wherein before contacting the porous material in the third step, hydrogen is supplied to the carbon-containing gas and heated to 800°C. ~1200°C turns the carbon dioxide contained in the carbon-containing gas into carbon monoxide. The method for producing molten iron according to claim 4, wherein water contained in the carbon-containing gas is removed after the heating in the third step and before contacting the porous material. The method for recovering carbon from carbon-containing gas as described in claim 5, wherein the moisture contained in the carbon-containing gas and the recombination of the carbon-containing gas are removed in a manner that satisfies the following formula (1). Moisture generated by the reaction, [H ₂ O]/([H ₂ O] + [H ₂ ]) < 0.1 ... (1) In the formula (1), [H ₂ O] represents the recombined mixed gas The moisture concentration (volume %) contained in , [H ₂ ] represents the hydrogen concentration (volume %) contained in the reorganized mixed gas. The method for producing molten iron according to any one of claims 1 to 6, wherein in the third step, the porous material is iron, and part of the recovered carbon is iron carbide. The method for producing molten iron according to any one of claims 1 to 7, wherein the particle size of the carbon-containing raw material is 100 μm or less. The method for producing molten iron according to any one of claims 1 to 8, wherein in the first step, the carbonaceous raw material further includes biomass. The manufacturing method of molten iron according to any one of claims 1 to 9, wherein the iron-containing raw material is iron ore, and the manufacturing method of molten iron further includes: a pretreatment step. Before the first step, the iron ore is heat-treated at a temperature above 300°C and below 1000°C.

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