JP7416340B1 - Method for producing hot metal - Google Patents

Abstract

To provide a method for producing hot metal in which hot metal can be produced by circulating a C source within a process and charging the recovered C source as carbonaceous agglomerate from the furnace mouth of a shaft furnace. a first step of producing a carbonaceous agglomerate ore from an iron-containing raw material and a carbon-containing raw material; a second step of blowing an oxygen-containing gas into the carbonaceous agglomerate ore to reduce and melt it to produce hot metal; a third step of recovering carbon by bringing a carbon-containing gas containing carbon monoxide and carbon dioxide by-produced by the reduction into contact with a porous material, and in the first step, the carbon is recovered in the third step. This is a method for producing hot metal, in which carbon is used as part or all of the carbon-containing raw material. Instead of the second step, a reduction step is performed in which reduced iron is obtained by heating the carbonaceous material-incorporated agglomerate to 1160 to 1450 ° C. to reduce and melt it, and then cooling it, and a reduction step in which reduced iron is obtained by melting the reduced iron. It can also have a melting step of producing hot metal.

Description

The present invention relates to a method for producing hot metal in the steel industry.

All industries are required to reduce carbon dioxide (CO ₂ ) emissions, including the SDGs and the Paris Agreement. Among manufacturing industries, the steel industry, which produces high CO ₂ emissions, has a particularly strong need for CO ₂ reduction. In the steel industry, more than 60% of CO ₂ is emitted during the pig iron making process, in which iron ore is reduced and melted using a carbon source to produce hot metal. The reason why CO ₂ emissions are so high in the ironmaking process is thought to be that coke and coal are used for reduction and melting. There is a need to develop a hot metal production process that does not emit CO ₂ outside the system.

Steel manufacturing processes aimed at zero carbon have been devised.
Non-Patent Document 1 reviews the technological prospects for achieving the long-term goal of reducing carbon dioxide in steel. For example, a carbon dioxide capture and storage (CCS) method has been introduced in which CO ₂ in the exhaust gas generated in the reduction reaction is separated, isolated and stored, and the amount of CO ₂ released to the outside is reduced. Another known method is carbon dioxide capture and utilization (CCU) technology, which separates and reuses CO ₂ in exhaust gas. In this technology, CH ₄ is synthesized using CO ₂ in exhaust gas. The synthesized CH ₄ is then blown into the blast furnace through the tuyere and used again for the reduction reaction.

Tatsuro Ariyama, Technology prospects for achieving long-term carbon dioxide reduction goals in steel, Tetsu to Hagane, Vol. 105, 2019, No. 6, pp. 567-586 Materials Transactions, Vol.58, No.12(2017)pp.1742 to 1748 “Development of Manufacturing Principle of Porous Iron by Carbothermic Reduction of Composite of Hematite and Biomass Char”

However, the above conventional technology has the following problems. That is, although the adoption of the CCS method can contribute to reducing CO ₂ emissions, the process itself consumes energy, and there are problems with moving the C source outside the system and storage capacity. Furthermore, when synthesizing CH ₄ from CO ₂ and blowing the CH ₄ into the tuyere of a blast furnace, a line for blowing CH ₄ into the tuyere is required.

The present invention has been made in view of the above circumstances, and involves circulating the C source within the process and charging the recovered C source as agglomerated ore with carbonaceous material through the furnace mouth of a shaft furnace to produce hot metal. The purpose of the present invention is to provide a method for producing hot metal that can produce molten pig iron.

The method for producing hot metal according to the present invention, which advantageously solves the above problems, includes a first step of producing a carbonaceous agglomerate from an iron-containing raw material and a carbon-containing raw material, and an oxygen-containing gas applied to the carbonaceous agglomerate. A second step in which the carbon-containing gas containing carbon monoxide and carbon dioxide by-produced by the reduction is brought into contact with a porous material to recover carbon. and, in the first step, the carbon recovered in the third step is used as part or all of the carbon-containing raw material.

Note that the method for producing hot metal according to the present invention is as follows:
(a) Instead of the second step, a reduction step in which reduced iron is obtained by heating the carbonaceous material-incorporated agglomerated ore to 1160 to 1450° C. to reduce and melt it, and then cooling it, and melting the reduced iron. and a melting process for producing hot metal by
(b) in the third step, the carbon-containing gas further includes a gas containing carbon monoxide and carbon dioxide, which are by-produced in the hot metal refining process;
(c) Before contacting the porous material in the third step, hydrogen is supplied to the carbon-containing gas and heated to 800 to 1200°C to convert carbon dioxide contained in the carbon-containing gas to carbon monoxide. to do,
(d) removing water contained in the carbon-containing gas after the heating in the third step and before contacting the porous material;
(e) The following formula (1) (in the formula, [H ₂ O] represents the water concentration (volume %) contained in the mixed gas after reforming, and [H ₂ ] represents the water concentration (volume %) contained in the mixed gas after reforming. The moisture contained in the carbon-containing gas and the moisture generated by the reforming reaction of the carbon-containing gas are removed so as to satisfy the hydrogen concentration (volume %) contained in the carbon-containing gas. in the step, the porous material is iron and a portion of the recovered carbon is iron carbide;
(g) the particle size of the carbon-containing raw material is 100 μm or less;
(h) in the first step, the carbon-containing raw material further includes biomass;
(i) the iron-containing raw material is iron ore, further comprising a pretreatment step of heat-treating the iron ore at 300° C. or higher and 1000° C. or lower before the first step;
etc. may be a more preferable solution.

According to the present invention, hot metal can be produced by charging carbon-filled agglomerate using recovered carbon from the furnace mouth of a shaft furnace, so the recovered carbon can be used in the process without modifying the shaft furnace. can be circulated.

FIG. 1 is a schematic diagram showing an example of a method for producing hot metal according to the present invention. FIG. 1 is a schematic diagram showing an example of a process for manufacturing a carbonaceous material-incorporated agglomerate according to the first step of the present invention. It is a schematic diagram which shows an example of the equipment using the countercurrent reduction layer concerning the 2nd process of this invention. (a) is a schematic diagram showing an example of carbonization equipment according to the third step of the present invention, and (b) is an enlarged photograph of a porous material used in the carbonization equipment. It is a graph showing the influence of carbon species on the reducibility of iron ore. (a) is a SEM photographic image of recovered carbon used in the present invention, and (b) is an enlarged photographic image of the broken line area in (a). This is a SEM photographic image of carbon black used in a comparative example.

Hereinafter, a method for manufacturing hot metal according to the present 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 their configurations are not limited to those described below. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

FIG. 1 is a schematic diagram showing an example of the method for producing hot metal according to the present embodiment. FIG. 2 is a schematic diagram showing an example of the manufacturing process of agglomerated ore with carbonaceous materials. FIG. 3 is a schematic diagram showing an example of equipment using a countercurrent reduction layer. In this embodiment, the hot metal 36 is produced by reducing the iron-containing raw material 4 contained in the carbonaceous agglomerated ore 26 in a countercurrent reduction layer. For example, it is preferable to use a vertical shaft furnace for producing the hot metal 36. In the following embodiments, a method for producing hot metal according to the present invention will be explained using an example in which a blast furnace 32 is used as a vertical shaft furnace. Note that, up to now, there has been no vertical shaft furnace that produces hot metal without using coke.

In the first step, the iron-containing raw material 4 and the carbon-containing raw material 6 are mixed to produce a carbonaceous material-incorporated agglomerate 26. The iron-containing raw material 4 is mainly pulverized iron ore, and may also contain dust generated in a steel mill. In the second step, the obtained carbonaceous agglomerated ore 26 is charged into a blast furnace 32, and blowing gas 34 is blown into the furnace to advance a reduction reaction to produce hot metal 36. In the third step, the exhaust gas 38 by-produced by the reduction reaction in the second step is recovered, and the carbon monoxide contained in the exhaust gas 38 is brought into contact with a porous material to precipitate and recover solid carbon. It is preferable that the exhaust gas 38 to be treated includes exhaust gas 40 that is by-produced by the refining process of hot metal .

A part or all of the carbon-containing raw material 6 used in the first step is solid carbon recovered in the third step. In addition, if the amount of carbon is insufficient with only the recovered solid carbon, the shortage may be supplemented with a carbon source such as biomass. In this case, a carbon source such as biomass may be used as the carbon-containing raw material 6. include. Furthermore, it is preferable that the particle size is 100 μm or less. If the iron-containing raw material 4 used in the first step is crushed iron ore and contains a large amount of water of crystallization, a heat treatment step of heat treatment at a temperature of 300° C. or higher and 1000° C. or lower is performed before the first step. is preferred.

Each step will be explained in detail below.
[First step]
The first step is a step of mixing an iron-containing raw material and a carbon-containing raw material to produce a carbonaceous material-incorporated agglomerate ore. 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 carbon monoxide contained in the exhaust gas 38 and the carbon-containing raw material 6 stored in the storage tank 8 A predetermined amount of cement powder 10 is cut out from the respective storage tanks 2 and 8 to a conveyor 12. The iron-containing raw material 4, the carbon-containing raw material 6, and the cement powder 10 are conveyed to a kneading machine 14 by a 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 a kneader 14 to form a mixed powder 20. Thereafter, the mixed powder 20 is conveyed 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 a carbonaceous material-incorporated agglomerate 26.

In the first step, if the amount of carbon in the obtained carbonaceous agglomerate 26 does not reach the target carbon mass ratio, biomass etc. are included in the carbon-containing raw material 6 to reach the target carbon mass ratio. It is preferable. Moreover, since it is necessary to avoid combustion and gasification of carbon, it is preferable that the carbonaceous material-incorporated agglomerated ore 26 be formed in a cold manner. Examples of the cold molding method include a method in which a cement-based solidifying agent is blended and then granulated using a pelletizer or a drum mixer, or a method in which compression molding is performed using a briquette machine or the like. Further, in order to maintain the strength after reduction, it is preferable that the carbon mass ratio of one particle of the carbonaceous material-incorporated agglomerate is 15% by mass or less. Here, if the carbon mass ratio of one particle of the carbonaceous agglomerate exceeds 15% by mass, the crushing strength of the granules measured by autograph (1 mm/min) will fall below the threshold (2.5 MPa). This is not desirable because it causes

[Second step]
The second step is a process of reducing and melting the iron-containing raw material 4 contained in the carbon material-incorporated agglomerate 26 produced in the first step using a countercurrent reduction layer to produce hot metal. In the example shown in FIG. 3, the iron-containing lumpy raw material 30 containing the carbonaceous material-incorporated agglomerate 26 and other raw materials 28 produced by the above-described method for producing carbonaceous material-incorporated agglomerate ore is introduced from the furnace mouth of the blast furnace 32. The reducing gas is flowed upward from the bottom. By doing so, the iron-containing lumpy raw material 30 can be reduced and melted as a countercurrent moving bed to the reducing gas, and the hot metal 36 can be manufactured. Oxygen-containing gas is blown into the blast furnace 32 as the blowing gas 34, and indirect reduction is performed using carbon monoxide gas generated by the reaction between the carbon source in the furnace and oxygen, and a solid carbon source placed close to the iron-containing raw material 4 direct reduction is progressing. Note that the blast gas 34 may contain hydrogen, and when hydrogen is contained, direct reduction of the iron-containing raw material 4 by hydrogen proceeds. When blowing hydrogen, the hydrogen is preferably derived from renewable energy. As described above, in the method for producing hot metal according to the present embodiment, since hot metal can be produced by charging agglomerated ore embedded in carbonaceous materials from the furnace mouth of the blast furnace 32 using carbon recovered from the exhaust gas 38, it is possible to produce hot metal using the carbon recovered from the exhaust gas 38. The conventional blast furnace 32 can be used as is without performing the above steps.

[Third step]
The third step is a step in which solid carbon is precipitated and recovered from exhaust gas etc. produced as a by-product by the reduction reaction in the second step. The exhaust gas 38 produced by the reduction reaction and the exhaust gas 40 produced by the refining process of hot metal contain carbon monoxide, carbon dioxide, hydrogen, and water, but in the method for producing hot metal according to the present embodiment, , the exhaust gases 38 and 40 only need to contain at least carbon monoxide and carbon dioxide. In the third step of this embodiment, as shown in FIG. 1, the exhaust gases 38 and 40 are treated in a carbonization facility 100, a gas reforming furnace 110, and a water removal device 120. In addition to the above, the exhaust gas may be exhaust gas discharged from automobiles, gas turbines, incinerators, thermal power plants, and factories. Further, the volume ratio of each gas component present in the exhaust gas can be adjusted by the combustion conditions of the fuel that is the raw material of the exhaust gas. For example, when the exhaust gas is blast furnace gas, the blast furnace gas contains 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% of nitrogen gas. The volume ratio is preferably % by volume. Incidentally, such blast furnace gas is produced by the partial combustion of coke, heavy oil, and pulverized coal fed into the blast furnace by air, resulting in a reducing gas whose main components are carbon monoxide and nitrogen, which is produced by reducing iron ore. It is something.

<Gas reforming process>
The exhaust gases 38 and 40 used in this embodiment contain carbon monoxide, carbon dioxide, hydrogen, and water. The exhaust gases 38 and 40 are charged into a gas reforming furnace 110. Next, hydrogen gas supplied from the hydrogen supply unit is added to the gas reforming furnace 110 to form a mixed gas. Thereafter, the inside of the gas reforming furnace 110 filled with the mixed gas is heated to 800 to 1200°C. When the system of the gas reformer is heated within the above temperature range, carbon dioxide in the mixed gas existing in the system of the gas reformer is mixed with hydrogen and water according to the following chemical reaction formula (I). A gas shift reaction produces carbon monoxide and water.

The water gas shift reaction between carbon dioxide and hydrogen is a reversible reaction, and in a region where the reaction temperature exceeds 500° C., the chemical equilibrium of the water gas shift reaction is biased toward the production of carbon monoxide. Therefore, in the hot metal manufacturing method of the present embodiment, by setting the temperature in the system of the gas reforming furnace 110 to 800 to 1200°C, carbon dioxide is efficiently converted to carbon monoxide, and solid carbon is efficiently converted. Carbon monoxide can be produced as a raw material. That is, in the gas reforming step, by setting the temperature within the system of the gas reforming furnace 110 to 800 to 1200° C., the mixed gas can be efficiently reformed.

The water gas shift reaction that progresses within 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 section. Here, it is preferable to supply hydrogen from the hydrogen supply unit so that the hydrogen concentration contained in the mixed gas (based on the gas composition excluding nitrogen gas and inert gas) is 58% by volume or more. It is preferable that the hydrogen concentration contained in the mixed gas is 58% by volume or more, since solid carbon can be recovered in the subsequent carbon separation step while increasing the ratio of carbon monoxide in the water gas shift reaction. The fact that the hydrogen concentration contained in the mixed gas is 58% by volume or more is determined by taking into consideration the condition that carbon monoxide gas increases in the water gas shift reaction in the temperature range of 800 to 1200°C. The conditions under which carbon monoxide gas increases can be determined from the relationship between the temperature of the water gas shift reaction and the equilibrium constant. Note that 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 according to the carbon dioxide concentration.

Furthermore, it is preferable that the hydrogen gas supplied from the hydrogen supply unit installed outside the gas reforming furnace 110 be hydrogen gas derived from renewable energy. This is preferable because the amount of carbon dioxide emissions can be further suppressed. Note that the amount of hydrogen gas supplied from the hydrogen supply section can be set in consideration of the amount of hydrogen contained in the exhaust gases 38 and 40.

<Step of removing moisture from carbon-containing gas>
The reformed gas after the water gas shift reaction of the mixed gas is supplied to the water removal device 120. The reformed gas contains moisture (water vapor) generated by the water gas shift reaction. The moisture contained in this reformed gas is removed by passing through the moisture removal device 120. Moisture can be removed by a method such as passing a reformed gas containing moisture through an adsorbent packed bed included in the water removal device 120, or passing a reformed gas through a separation membrane. It is preferable that moisture contained in the reformed gas is removed so that the relationship of formula (1) below is satisfied. By removing moisture from the reformed gas so as to satisfy the relationship of formula (1), the carbon recovery efficiency in the carbon recovery process is increased. In the following formula (1), [H ₂ O] represents the water concentration (volume %) in the reformed gas, and [H ₂ ] represents the hydrogen concentration (volume %) in the reformed gas.

To remove moisture from the reformed gas, an adsorbent or a separation membrane can be used as described above. As the adsorbent, oxides such as silica, zeolite, alumina, calcium chloride, magnesium sulfate, etc. can be used. Examples of membranes for separating moisture in gas include carbon membranes, resin membranes, and inorganic membranes. These membranes have pores of subnanometer diameter. The moisture in the gas is recovered by the moisture removal device 120 as liquid water at room temperature.

The dehumidified gas from which water has been removed becomes a raw material for solid carbon. A bimolecular decomposition reaction (II) resulting from the decomposition of two molecules of carbon monoxide shown by the following chemical reaction formulas (II) to (III), or a single molecule decomposition reaction resulting from the reaction of one molecule of carbon monoxide with hydrogen. According to (III), solid carbon is separated from carbon monoxide in the carbonization equipment 100.

It is preferable that CO/(CO+CO ₂ ) of carbon monoxide contained in the dehumidified gas is 0.5 or more, and more preferably 0.7 or more. Thereby, solid carbon can be efficiently recovered from carbon monoxide.

The dehumidified gas is supplied at a predetermined supply rate to the carbon separation section of the carbonization facility 100 comprising porous material.

<Step of bringing carbon-containing gas into contact with porous material and separating solid carbon>
The method for recovering carbon from dehumidified gas includes contacting the dehumidified gas with a porous material and separating solid carbon. Contact of the dehumidified gas with the porous material and separation of carbon from the dehumidified gas are performed within the system of the carbon separation section of the carbonization equipment 100. In the system of the carbon separation section of the carbonization equipment 100, a packed bed filled with a porous material 102 is provided as illustrated in FIG.

As shown in FIG. 1, carbon constituting carbon monoxide contained in the dehumidified gas is separated from the carbon monoxide gas within the carbonization equipment 100 system. Carbon monoxide contained in the dehumidified gas is produced by the two-molecule decomposition reaction (II) of carbon monoxide or the one-molecule decomposition reaction (III) of carbon monoxide shown by the above chemical reaction formulas (II) to (III). , separated from carbon monoxide as solid carbon. Solid carbon separated from carbon monoxide is adsorbed onto the surface of the porous material 102 and precipitated. The dehumidified gas and the porous material 102 come into contact, and the off-gas from which carbon has been separated is discharged from the carbonization equipment 100. Since the off-gas contains carbon dioxide, it is preferable that some or all of the off-gas be mixed into the mixed gas.

In the step of bringing the dehumidifying gas into contact with the porous material 102 to separate solid carbon, the contact between the dehumidifying gas and the porous material 102 is preferably performed in an atmosphere of 500 to 800° C. or lower. If the temperature at which the reformed gas and porous material 102 are brought into contact is 500°C or higher, the decomposition reaction of carbon monoxide is promoted, so it is preferable, and if it is 800°C or lower, carbon monoxide is generated due to the decomposition reaction. This is preferable because thermal energy can be used effectively. The temperature at which the reformed gas and the porous material 102 are brought into contact includes 500 to 800° C., which is the temperature condition employed in the direct reduction ironmaking reaction. Note that the dehumidifying gas may be brought into contact with the porous material by passing the dehumidifying gas through a packed bed of the porous material 102 provided within the system of the carbon separation section. As a result, the decomposition reaction of carbon monoxide shown by the above chemical reaction formula proceeds. As the decomposition reaction of carbon monoxide progresses, solid carbon constituting carbon monoxide is deposited on the surface of the porous material 102. Furthermore, when a porous iron material is used, part or all of the solid carbon deposited on the surface is carburized to produce iron carbide.

In the step of bringing the dehumidifying gas into contact with the porous material 102 to separate solid carbon, the contact between the dehumidifying gas and the porous material 102 is preferably performed in an atmosphere where the pressure of the dehumidifying gas is 1.0 to 10 atm. If the pressure at which the dehumidified gas and the porous material 102 are brought into contact is 1.0 atm or higher, the pressure is increased, and the equilibrium of the carbon monoxide decomposition reaction shifts to the right, promoting the carbon monoxide decomposition reaction. 10 atm or less is preferable because the safety of the carbon separation section of the carbonization equipment 100 can be ensured from the viewpoint of laws and regulations.

The porous material 102 with which the dehumidifying gas is brought into contact preferably has an open porosity of 50 to 99%, more preferably 80 to 95%, as measured by the Archimedes method. If the open porosity of the porous material is 50% or more, the dehumidifying gas passes through the pores of the porous material, promoting the decomposition reaction of carbon monoxide and adsorbing the decomposed carbon. This is preferable because it allows for On the other hand, it is preferable for the open porosity of the porous material 102 to be 99% or less, since the thermal shock resistance caused by the dehumidifying gas supplied to the porous material 102 can be maintained. The diameter of the pores of the porous material 102 is preferably 10 μm or more. The open porosity of the porous material 102 is measured by the Archimedes method, and specifically, the open porosity of the porous material is measured by the measurement method specified in the Japanese Industrial Standards (JIS R2205; 1992). It can be used as porosity.

The porous material 102 with which the dehumidifying gas is brought into contact preferably contains at least one selected from iron, platinum, nickel, cobalt, rhodium, and palladium. That is, the porous material may be composed of 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 as a carbide, oxide, carbonate, sulfate, or the like.

Among these metals employed as the porous material 102 with which the dehumidifying gas is brought into contact, iron, platinum, and nickel are preferable. When platinum or nickel is used as the porous material, it is preferable because the platinum or nickel acts as a catalyst for the decomposition reaction of carbon monoxide and is less likely to deteriorate as a catalyst. Further, it is preferable to use platinum or nickel as the porous material 102 because solid carbon produced by a decomposition reaction of carbon monoxide is precipitated as a single graphite.

More preferably, the porous material 102 with which the dehumidifying gas is brought into contact is iron. By using iron as the porous material 102, carbon generated by the decomposition reaction of carbon monoxide carburizes the porous material 102, and austenite (γ iron) in which the carbon is dissolved can be obtained, which is preferable. Further, by using iron as the porous material 102, carbon generated by the decomposition reaction of carbon monoxide carburizes the porous material 102, and the carbon and iron react to form cementite (iron carbide (Fe ₃ C). )) is preferable. Austenite and cementite, which are produced by carburizing the porous material 102 with carbon produced by the decomposition reaction of carbon monoxide, have a hardness comparable to that of hardened steel, and can be used as raw materials for steelmaking as they are. Further, the porous material 102 with which the dehumidifying gas is brought into contact is preferably made of one or two types of iron selected from iron oxide and reduced iron.

It is particularly preferred that the porous material 102 with which the dehumidifying gas is contacted is an iron whisker. Iron whiskers are crystals that grow outward from the crystal surface in the form of whiskers. Iron whiskers are formed when compressive stress occurs near the surface of the crystal, and new crystals grow outward from the original crystal in an attempt to relieve the stress. Iron whiskers have a small starting point for crystal growth and tend to continue to grow continuously. For this reason, iron whiskers are formed as very elongated whisker-like single crystals, and have a diameter of about 1 μm and a length of 1 mm or more. When iron whiskers are used as the porous material with which the dehumidifying gas is brought into contact, the carbon produced by the decomposition reaction of carbon monoxide carburizes the iron whiskers, creating whiskers made of austenite or cementite. Obtainable.

Iron whiskers, which are the porous material 102 that is brought into contact with dehumidified gas, can be manufactured by, for example, the iron whisker manufacturing method described in Non-Patent Document 2. According to this method for producing iron whiskers, it is possible to obtain iron whiskers in which the open porosity of the porous material is 90% or more and the pore diameter is 10 μm or more. Since the iron whiskers obtained by this iron whisker manufacturing method also have a high open porosity, they can be suitably used as the porous material 102 used in the carbon recovery method. Note that even if a metal other than iron is used as the metal constituting the porous material 102 with which the dehumidifying gas is brought into contact, the porous material 102 can be manufactured in the same manner.

<Process of recovering carbon adsorbed on porous material>
Recovery of carbon adsorbed on the porous material 102 is performed within the system of the carbon recovery unit 130. Here, recovering the carbon adsorbed on the porous material means recovering solid carbon precipitated on the surface of the porous material 102, or recovering carbon that has been carburized inside the porous material. This includes recovery as a solid solution with metal elements contained in the material or as a metal carbide compound.

Carbon decomposed by the decomposition reaction of carbon monoxide contained in the dehumidified gas is deposited on the surface of the porous material 102. Further, carbon decomposed by the decomposition reaction of carbon monoxide contained in the dehumidified gas carburizes inside the porous material 102 and reacts with the metal elements constituting the porous material, thereby forming a carbon solid solution or a metal carbide compound. form. Furthermore, carbon decomposed by the decomposition reaction of carbon monoxide contained in the dehumidified gas is deposited on the surface of the carbon solid solution or metal carbide compound.

The carbon precipitated on the surface of the porous material 102 can be recovered by separating the particles of the porous material 102 containing carbon using a sieve or the like. Furthermore, after carburizing the inside of the porous material 102, the carbon that has become a carbon solid solution or a metal carbide compound by reacting with a metal element constituting the porous material can be recovered by removing the carbon solid solution or metal carbide compound itself. This can be done by collecting it as is. In addition, when using the recovered carbon as a raw material for iron manufacturing, by using iron as the porous material 102, the recovered carbon can be used as a raw material for iron manufacturing all at once without having to separate the recovered carbon from the porous material 102. More preferred.

As described above, in the third step according to the present embodiment, carbon monoxide contained in the dehumidified gas is brought into contact with the porous material 102 to promote the decomposition reaction of carbon monoxide, separate the solid carbon, and Carbon can be recovered as solid carbon, or as a carbon solid solution or metal carbide compound containing the carbon. In addition, hot metal can be produced using carbonaceous agglomerate containing recovered carbon as a raw material, so the recovered carbon can be circulated within the process, thereby reducing _CO2 emissions outside the system. realizable. The exhaust gases 38, 40, mixed gas, and dehumidified gas in this embodiment are examples of carbon-containing gases containing carbon monoxide and carbon dioxide.

In addition, in this embodiment, although the example which implements a 2nd process using the blast furnace 32 was shown, it is not restricted to this. For example, a reduction step in which a rotary hearth furnace is used in place of the blast furnace 32 to heat the coal-filled agglomerate to 1160 to 1450°C to reduce and melt it, and then cool it to obtain reduced iron; For example, hot metal may be manufactured by performing a melting process of manufacturing hot metal by melting it in an electric furnace or the like. Even when a rotary hearth furnace is used, an existing rotary hearth furnace can be used as is if the agglomerated ore with carbonaceous material is produced using recovered carbon.

An example of carbonization equipment according to this embodiment is shown in FIG. 4(a). As illustrated in FIG. 4(a), the carbonization equipment 100 includes a tubular reaction tower 101 in which carbon separation reaction from carbon monoxide contained in the carbon-containing gas occurs, and a carbon-containing gas supplied from the lower part of the reaction tower 101. A supply pipe 104 for discharging the carbon separation reaction, a layer of porous material 102 provided inside the reaction tower, and an exhaust gas pipe 105 for discharging the off-gas generated after the carbon separation reaction are provided. The inside of the reaction column 101 is equipped with a quartz tube 101a and a sample holder 101b. As the porous material 102 included in the carbonization equipment 100, it is preferable to use a plurality of tablet-shaped iron whiskers having an open porosity of 97.7%, as shown in FIG. 4(b). Porous material 102 is placed on a layer of granular alumina balls 103 (particle size 10 mm). Note that the porous material 102 is manufactured according to the iron whisker manufacturing method described in Non-Patent Document 2.

The influence of carbon recovered by the apparatus shown in FIG. 4(a) on the reducibility of iron ore was investigated. Table 1 shows the composition of the iron ore used. T. in Table 1. Fe represents the total amount of iron. Further, LOI is the loss on ignition when heated at 1000° C. for 60 minutes, and in the case of iron ore, most of it is crystal water. The recovered carbon contained 38.35% by mass of C and the balance was Fe as cementite and solid carbon. Furthermore, of the total carbon, 18.7 mol% of C existed as cementite and 81.3 mol% of C existed as solid carbon.

The particle sizes of iron ore A and the recovered carbon were adjusted to -105 μm. -105 μm represents the bottom of a sieve with a mesh size of 105 μm. The sample was prepared by mixing weighed powders of iron ore A and recovered carbon in a mortar by stirring for 3 minutes without pressing with a pestle. A uniform mixed powder could be obtained without changing the powder particle size during mixing. The sample was mixed by adding carbon in an amount 0.8 times the molar amount of oxygen in iron oxide, and further adding carbon in an amount 0.2 times the molar amount of iron in iron oxide or iron carbide. By adding carbon in an amount 0.8 times the molar amount of oxygen in iron oxide, carbon is used as a reducing agent, and by adding carbon in an amount 0.2 times the molar amount of iron in iron oxide or iron carbide, metallic iron can be produced. Aiming for the effect of carburizing on carbon, we gave carbon the dual role of reducing agent and carburizing agent.

The uniformly mixed sample was press-molded for 30 seconds under a pressure of 98 MPa to form a cylindrical shape with a diameter of 10 mm and a height of 10 mm. The molded sample was heated to 1300° C. at a heating rate of 10° C./min in an atmosphere in which a 5% by volume N ₂ -Ar mixed gas was supplied at a flow rate of 0.5 NL/min. The generated gas was analyzed using an infrared spectrophotometer, and the reduction rate of iron ore was calculated. The results are shown in FIG. As a comparative example, a similar test was conducted using carbon black instead of the recovered carbon, and the results are also shown in FIG. As is clear from FIG. 5, the recovered carbon (solid line) improves the reducibility of iron ore A compared to carbon black (dashed line).

Although the reason for this is not clear, the inventors believe that it is a difference in particle size of the carbon-containing substances. The recovered carbon was in the form of fibers of several nanometers as shown in Figures 6(a) and (b), whereas the carbon black was particles with a particle size of several tens of micrometers as shown in Figure 7. . In this way, the solid carbon recovered from carbon monoxide becomes very small, so by using the carbon in the carbon-filled agglomerate ore, the contact area with the iron-containing raw material and gas becomes larger, and as a result, It is thought that agglomerated ore containing carbonaceous material with high reducibility was obtained.

In addition to the effect of reducing CO ₂ emissions outside the system, the method for producing hot metal according to the present invention recovers CO ₂ in the exhaust gas as solid carbon and combines it with iron-containing raw materials to produce carbonaceous agglomerates. By doing so, it is possible to improve the reducibility of the agglomerate ore, and it becomes possible to reduce the carbon consumption required for reduction, which contributes to reducing the environmental load in the steel industry and is extremely useful industrially.

2,8 Storage tank
4 Iron-containing raw material 6 Carbon-containing raw material (solid carbon and/or iron carbide)
10 Cement powder 12, 22 Conveyor 14 Kneading machine 16 Water 20 Mixed powder 24 Granulator 26 Carbonaceous agglomerate 28 Other raw materials 30 Iron-containing lump raw material 32 Blast furnace 34 Blast gas 36 Hot metal 38 Blast furnace exhaust gas 40 Refining treatment Exhaust gas 100% Carbonization equipment (carbon separation section)
101 Reaction tower 101a Quartz tube 101b Sample holder 102 Porous material (iron whisker)
103 Alumina ball 104 Supply pipe (for carbon-containing gas)
105 Exhaust gas pipe 110 Gas reforming furnace (gas reforming section)
120 Moisture removal device (moisture removal section)
130 Carbon recovery department 140 Carbonaceous material-incorporated agglomerate production equipment

Claims (8)

A first step of producing a carbonaceous agglomerate from an iron-containing raw material and a carbon-containing raw material, or from an iron-containing raw material and a carbon-containing raw material containing biomass;
A second step of blowing oxygen-containing gas into the carbonaceous agglomerate ore to reduce and melt it to produce hot metal, or heating the carbonaceous agglomerate ore to 1160 to 1450°C to reduce and melt it. a second step consisting of a reduction step of obtaining reduced iron by subsequent cooling and a melting step of producing hot metal by melting the reduced iron;
Supply hydrogen to the carbon-containing gas containing carbon monoxide and carbon dioxide by-produced by the reduction, heat it to 800 to 1200 ° C. to convert the carbon dioxide contained in the carbon-containing gas to carbon monoxide, and A third step of recovering carbon by bringing it into contact with a porous material,
In the first step, the carbon recovered in the third step is used as a part of the carbon-containing raw material and all or all of the remaining material other than biomass. The method for producing hot metal according to claim 1, wherein in the third step, the carbon-containing gas further includes a gas containing carbon monoxide and carbon dioxide that are by-produced in a hot metal refining process. Furthermore, in the case where the iron-containing raw material is iron ore and contains a large amount of crystallization water, the iron ore further comprises a pretreatment step of heat-treating the iron ore at a temperature of 300° C. or more and 1000° C. or less before the first step. Item 1. The method for producing hot metal according to item 1. The method for producing hot metal according to claim 1, 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 producing hot metal according to claim 4 , wherein moisture contained in the carbon-containing gas and moisture generated by a reforming reaction of the carbon-containing gas are removed so as to satisfy the following formula (1).

In the above formula (1), [H ₂ O] represents the water concentration (volume %) contained in the mixed gas after reforming, and [H ₂ ] represents the hydrogen concentration (volume %) contained in the mixed gas after reforming. % by volume). The method for producing hot metal according to any one of claims 1 to 5 , wherein in the third step, the porous material is iron, and a part of the recovered carbon is iron carbide. The method for producing hot metal according to any one of claims 1 to 5 , wherein the carbon-containing raw material has a particle size of 100 μm or less. The method for producing hot metal according to claim 6 , wherein the carbon-containing raw material has a particle size of 100 μm or less.

Images