Method for producing carbon composite agglomerate and method for producing molten iron

Abstract

Proposed are a method for manufacturing a carbonaceous material-containing agglomerate ore and a method for manufacturing molten pig iron, with which a highly reducible source material can be obtained and the quantity of reducing material that is used in the manufacture of molten pig iron in a countercurrent moving bed can be reduced. A method for manufacturing a carbonaceous material-containing agglomerate ore according to the present invention includes a step in which carbon-including gas that includes carbon monoxide is brought into contact with a porous material to recover carbon, and an agglomeration step in which a carbon-including source material that includes said carbon is mixed with an iron-including source material and the result is agglomerated.

Description

[Technical field]

[0001] The present invention relates to a method for producing carbon composite agglomerated ore and a method for producing molten iron in the steelmaking industry. [Background technology]

[0002] In the production of molten iron in a countercurrent moving bed, highly reducible raw materials are required to reduce the amount of reducing material used in the reduction of iron-containing raw materials. As one of the highly reducible raw materials, by including carbonaceous material in the agglomerated raw materials, Direct reduction with carbonaceous materials: C+FeO X →CO2+FeO X-2 and, Indirect reduction from the inside by CO generated by solution loss reaction: C+CO2→2CO CO+FeO X →CO2+FeO X-1 Examples of such agglomerated ore include carbonaceous composite agglomerated ore with improved reducibility.

[0003] For example, as shown in the following Patent Documents 1 to 4, numerous research and development projects have been conducted on carbon composite agglomerates.

[0004] Patent Document 1 discloses a method for producing carbonaceous sintered ore by charging carbonaceous granulated particles with 3 mm or larger coke particles as nuclei into a sintering machine together with normal raw materials and firing them. Patent Document 2 discloses carbonaceous sintered ore containing iron-containing raw materials, carbonaceous material, and binder, with the condition that pores of 0.5 μm or larger are 10% or less. Patent Document 3 discloses carbonaceous sintered ore in which porous ore with a pore size of nanometer level is covered with carbonaceous material so that the carbon content is 18% or more. Patent Document 4 discloses a method for agglomerating iron-containing raw materials, carbonaceous material, hydraulic binder, and water by pressurizing and molding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-129353 A [Patent Document 2] JP 2019-157253 A [Patent Document 3] JP 2019-007036 A [Patent Document 4] JP 2014-025135 A Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 to 4, which disclose carbonaceous iron ore agglomerates, have the following problems. In Patent Document 1, coke particles of 3 mm or more are used, so the contact area between the coke and the iron oxide and the contact area with the atmosphere are limited, and the effect of improving reducibility is limited. In Patent Document 2, the carbonaceous material is a raw material containing a carbon source of 0 to 10 mm, and is not necessarily intended to have a highly reducible particle size condition. In Patent Document 3, the material is limited to porous ore, and the freedom of the raw material is reduced. Furthermore, in Patent Document 4, the particle size of the carbonaceous material is not specified, and the particle size condition with a high reducibility is not intended.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for producing carbonaceous iron ore agglomerates and a method for producing molten iron, which can obtain raw materials with high reducibility and reduce the amount of reducing agent used in the molten iron production in the countercurrent moving bed. [Means for solving the problem]

[0008] The present invention includes a step of contacting a carbon-containing gas containing carbon monoxide with a porous material to recover carbon; and agglomerating the carbon-containing raw material containing the carbon with an iron-containing raw material to form an agglomerate.

[0009] In the method for producing carbon composite agglomerated ore according to the present invention configured as described above, (1) The carbon recovery step is carried out using a carbon deposition reaction; (2) The iron-containing raw materials include iron ore and / or dust generated in a steel mill; (3) the carbon-containing raw material comprises iron carbide; (4) in the agglomeration step, biomass is further mixed into the carbon-containing raw material; (5) The carbon content per particle in the carbonaceous composite agglomerate is 15% by mass or less; (6) in the agglomeration step, a binder is further mixed with the carbon-containing raw material, and in the agglomeration step, the binder is hardened by cold working; (7) in the agglomeration step, a cement-based solidification material is further mixed into the carbon-containing raw material, and the cement-based solidification material is solidified in the agglomeration step; This is believed to be a more preferable solution.

[0010] The present invention also relates to a method for producing molten iron using carbonaceous composite agglomerates produced by the method for producing carbonaceous composite agglomerates described above, which comprises charging iron-containing lump raw materials containing the carbonaceous composite agglomerates from above and flowing a reducing gas upward from below, thereby producing molten iron by reducing and melting the iron-containing lump raw materials in a countercurrent moving bed.

[0011] In the method for producing molten iron according to the present invention configured as described above, it is considered that a more preferable solution is to produce the molten iron in a shaft furnace.

[0012] The present invention also relates to a method for producing molten iron using the carbonaceous iron agglomerates produced by the method for producing carbonaceous iron agglomerates described above, which comprises heating the carbonaceous iron agglomerates to 1160 to 1450°C to reduce and melt them, and then cooling them to form reduced iron, and melting the reduced iron to produce molten iron. Effect of the Invention

[0013] According to the method for producing carbonaceous iron agglomerates of the present invention, the carbon used in the carbonaceous iron agglomerates is very small because carbon recovered from a carbon-containing gas including carbon monoxide is used, and the contact area with the iron-containing raw material and the gas is large, so that carbonaceous iron agglomerates having higher reducibility than conventional agglomerates can be obtained. [Brief description of the drawings]

[0014] [Figure 1] 2 is a flowchart for explaining an example of a method for producing carbon composite agglomerated ore according to the present embodiment. [Diagram 2] FIG. 2 is a diagram for explaining processes from step S1 to step S3 in the method for producing carbon composite agglomerated ore. [Diagram 3] FIG. 2 is a diagram for explaining the processes from step S3 to step S5 in the manufacturing method of carbon composite agglomerated ore. [Figure 4] FIG. 1 is a diagram for explaining one embodiment of a method for producing molten iron according to the present invention. [Diagram 5] 1 is a graph showing the effect of carbon species on the reducibility of iron ore. [Figure 6] (a) SEM image of the recovered carbon used in the present invention. (b) An enlarged image of the dashed line area in (a). [Figure 7] 1 is a SEM photograph of carbon black used in a comparative example. [Figure 8] FIG. 2 is a diagram showing the reduction rate of iron ore. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present invention will be described in detail. Note that the following embodiments are merely examples of devices and methods for embodying the technical ideas of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical ideas of the present invention can be modified in various ways within the technical scope described in the claims.

[0016] <Regarding the method for producing carbon composite agglomerates according to the present invention> FIG. 1 is a flow chart for explaining an example of the method for producing carbonaceous agglomerates according to the present embodiment. In the example of the method for producing carbonaceous agglomerates according to the present invention, a carbon-containing gas containing carbon monoxide is prepared in step S1. Next, carbon is recovered from the carbon-containing gas containing carbon monoxide in step S2. Next, a carbon-containing raw material containing the recovered carbon is prepared in step S3. At the same time, an iron-containing raw material is prepared in step S4. Finally, in step S5, the carbon-containing raw material containing the recovered carbon is mixed with the prepared iron-containing raw material, preferably with a solidifying material such as a binder or cement, and biomass, and agglomerated to produce carbonaceous agglomerates. Note that the step of preparing the carbon-containing raw material containing recovered carbon in step S3 may be omitted, and the carbon recovered in step S2 may be used in step S5 as it is.

[0017] Here, the carbon-containing gas containing carbon monoxide in step S1 can be blast furnace gas, converter gas, or a synthesis gas of these, or a reformed gas in which part of the carbon dioxide contained in these gases is reformed into carbon monoxide by the water-gas shift reaction, etc.

[0018] As a method for recovering carbon from the carbon-containing gas containing carbon monoxide in step S2, a carbon deposition reaction can be used in which the carbon-containing gas is brought into contact with a porous material to cause a bimolecular decomposition reaction (I) of carbon monoxide or a unimolecular decomposition reaction (II) of carbon monoxide, as shown in the following chemical reaction formulas (I) to (II), to proceed, and carbon is deposited on the porous material.

[0019] 2CO → C + CO2 (I) CO+H2→ C+H2O (II)

[0020] In the carbon deposition reaction, for example, when a porous material such as platinum or Ni is used, solid carbon is precipitated on the surface of the porous material, and the solid carbon is recovered. On the other hand, when a porous material made of iron is used, a part or all of the precipitated solid carbon carburizes the iron, and solid carbon and iron carbide, or carbon is recovered as iron carbide.

[0021] When an iron porous material is used as the porous material, it is preferable to use solid carbon and iron carbide as the carbon-containing raw material and the iron porous material as the iron-containing raw material. This allows the porous material and carbon to be used together as the iron-containing raw material and the carbon-containing raw material without separating them. Note that the carbon recovered when an iron porous material is used includes solid carbon precipitated on the surface of the porous material and iron carbide carburized into the iron.

[0022] The iron-containing raw material in step S4 preferably includes iron ore and / or steel mill dust.

[0023] Fig. 2 is a diagram for explaining the processes from step S1 to step S4 in the manufacturing method of carbon composite agglomerated ore. Fig. 2 shows an example in which an iron porous material (iron whiskers) is used as the porous material, solid carbon and iron carbide are used as the carbon-containing raw material, and iron whiskers are used as the iron-containing raw material.

[0024] The left side of FIG. 2 is the porous material formation zone, the center is the reforming zone, and the right side is the carbonization zone. In the porous material formation zone, for example, 1000°C gas is sucked from below through a carbonaceous material composite raw material made by mixing iron powder with carbonaceous material, and the carbonaceous material composite raw material is subjected to carbon-thermal reduction to obtain porous acicular iron (iron whiskers). In the reforming zone, the gas sucked in during the carbon-thermal reduction is used to heat the raw material to 800°C or higher, while various exhaust gases containing carbon dioxide are passed through the iron whiskers to proceed with the water-gas shift reaction, which reforms carbon dioxide into carbon monoxide, to obtain carbon monoxide-rich gas. In the carbonization zone, the carbon monoxide-rich gas is passed through the iron whiskers as a carbon-containing gas in an environment of 500 to 800°C by utilizing the atmospheric temperature in the water-gas shift reaction, and solid carbon is precipitated on the surface of the iron whiskers by the carbon deposit reaction (carbonization), thereby obtaining solid carbon and iron carbide. The obtained solid carbon and iron carbide are then subjected to the agglomeration process and reduction process. This process corresponds to steps S1 to S4 in the method for producing carbon composite agglomerated ore shown in FIG.

[0025] Fig. 3 is a diagram for explaining the process from step S3 to step S5 in the manufacturing method of carbon composite agglomerated ore. In Fig. 3, an example is explained in which iron whiskers containing solid carbon and iron carbide are used as the carbon-containing raw material and the iron-containing raw material, and cement powder is used as the solidification material. Note that the solidification material is not limited to cement powder, and a binder that can be hardened in cold may also be used.

[0026] In the example shown in FIG. 3, first, a predetermined amount of the iron porous material 4 (iron-containing raw material) stored in the storage bin 2, solid carbon and / or iron carbide 6 (carbon-containing raw material) recovered from the carbon-containing gas containing carbon monoxide, and cement powder 10 stored in the storage bin 8 are cut out from each storage bin and transferred to a conveyor 12. The iron-containing raw material, the carbon-containing raw material, and the cement powder 10 are conveyed to a kneader 14 by the conveyor 12. The conveyed iron-containing raw material, the carbon-containing raw material, and the cement powder 10 are mixed in the kneader 14 together with an appropriate amount of water 16 to become a mixed powder 20. Thereafter, the mixed powder 20 is conveyed to a granulator 24 by the conveyor 22, and granulated in the granulator 24 together with an appropriate amount of water 16. The cement powder is cured for a predetermined period of time to solidify, thereby becoming carbonaceous agglomerated ore 26. The crushing strength of the carbonaceous agglomerated ore 26 increases if the amount of cement powder 10 is increased. Therefore, the amount of cement powder 10 mixed with the carbon-containing raw material may be determined according to the desired crushing strength of the carbonaceous composite agglomerated ore 26. The crushing strength of the carbonaceous composite agglomerated ore 26 can be measured by an autograph (1 mm / min).

[0027] In the above-mentioned method for producing carbon composite agglomerates, if the carbon content of the carbon composite agglomerates obtained does not reach the predetermined carbon mass ratio, it is preferable to add biomass or the like to the carbon-containing raw material to make the predetermined carbon mass ratio. Similarly, if the iron-containing raw material does not reach the predetermined iron mass ratio, iron ore or dust generated in the steelworks may be added. In addition, when forming the carbon composite agglomerates, it is necessary to avoid combustion and gasification of the contained carbon, so cold forming is preferable. Examples of the cold forming method include a method of granulating the carbon composite agglomerates using a pelletizer or drum mixer after mixing a cement-based solidifying agent, or a method of compression forming using a briquette machine or the like. In addition, in order to maintain the strength after reduction, it is preferable that the carbon content per particle of the carbon composite agglomerates is 15 mass% or less. Here, if the carbon content per particle of the carbon composite agglomerates exceeds 15 mass%, it is not preferable because the crushing strength of the carbon composite agglomerates measured by autograph (1 mm / min) falls below the threshold value (2.5 MPa).

[0028] <Regarding the manufacturing method of molten iron using carbon composite agglomerated ore obtained by the above manufacturing method> FIG. 4 is a diagram for explaining an embodiment of the method for producing molten pig iron according to the present invention. As shown in FIG. 4, the method for producing molten pig iron according to the present embodiment will be explained using an example in which a blast furnace 32 is used as a vertical shaft furnace. Note that there is no vertical shaft furnace for producing molten pig iron without using coke. In the blast furnace 32, iron-containing lumpy raw materials 30 including carbonaceous agglomerates 26 produced by the above-mentioned method for producing carbonaceous agglomerates and other raw materials 28 are charged from the top of the blast furnace 32, and a reducing gas 34 is made to flow upward from the bottom, so that the iron-containing lumpy raw materials 30 are reduced and melted as a countercurrent moving layer to produce molten pig iron 36. In addition, the exhaust gas 38 discharged from the top of the blast furnace 32 by reduction may be included in the carbon-containing gas containing carbon monoxide used in the method for producing carbonaceous agglomerates according to the present embodiment, and gas obtained by reforming carbon dioxide contained in the exhaust gas into carbon monoxide by the water-gas shift reaction may be included in the carbon-containing gas containing carbon monoxide. By including the exhaust gas 38 in the carbon-containing gas containing carbon monoxide, the blast furnace exhaust gas can be effectively utilized and carbon recycling can be realized in the molten iron production process, which is preferable. In the above, the blast furnace 32 is used to produce molten iron, but the present invention is not limited to this. For example, instead of the blast furnace 32, a rotary hearth furnace may be used to produce molten iron by carrying out a reduction step in which carbonaceous iron composite agglomerates are heated to 1160 to 1450°C, reduced and melted, and then cooled to obtain reduced iron, and a melting step in which the reduced iron is melted to obtain molten iron. Even when a rotary hearth furnace is used, an existing rotary hearth furnace can be used as it is as long as the carbonaceous iron composite agglomerates are made using recovered carbon. EXAMPLES

[0029] The effect of the recovered carbon on the reducibility of iron ore was investigated. The composition of the iron ore used is shown in Table 1. In Table 1, T.Fe represents the total iron content. Also, LOI is the loss on ignition when heated at 1000°C for 60 min, and in the case of iron ore, most of it is water of crystallization. The recovered carbon consisted of cementite (iron carbide) and solid carbon, with C: 38.35 mass% and the remainder Fe. Of the total carbon, C present as cementite was 18.7 mol% and C present as solid carbon, respectively, and 81.3 mol%.

[0030] [Table 1]

[0031] The particle size of iron ore A was adjusted to -105μm. -105μm means the undersize of a sieve with 105μm mesh. 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 was obtained without changing the powder particle size during mixing. The sample was mixed by adding 0.8 times the molar amount of oxygen in the iron oxide, and then adding 0.2 times the molar amount of iron in the iron oxide and iron carbide. By adding 0.8 times the molar amount of oxygen in the iron oxide, carbon was used as a reducing agent, and by adding 0.2 times the molar amount of iron in the iron oxide and iron carbide, carbon was given the dual role of reducing agent and carburizing agent, aiming for the effect of carburizing metallic iron.

[0032] The homogeneously mixed sample was press-molded for 30 seconds under a pressure of 98 MPa to form a cylinder 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 where 5% by volume N2-Ar mixed gas was supplied at a flow rate of 0.5 NL / min. The generated gas was analyzed by an infrared spectrophotometer, and the reduction rate of the iron ore was calculated. 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 also shown in Figure 5. As is clear from Figure 5, the recovered carbon (solid line) improves the reducibility of iron ore A compared to carbon black (dashed line).

[0033] The recovered solid carbon was fibrous with a size of several nm as shown in Figure 6(a)(b), whereas the carbon black was particles with a particle size of several tens of μm as shown in Figure 7. In this way, the solid carbon recovered from carbon monoxide is very small, so by using this carbon for carbon composite agglomerates, the contact area with the iron-containing raw materials and gas is increased, which is thought to result in the production of carbon composite agglomerates with high reducibility.

[0034] Next, the effect of iron carbide in the recovered carbon was investigated. Recovered carbon containing iron carbide, which was precipitated by contacting carbon-containing gas containing carbon monoxide with porous acicular iron, and recovered carbon not containing iron carbide, which was precipitated by contacting with porous alumina as a comparative example, were prepared. The molar ratio of carbon in the iron carbide in the total carbon of each was 30.9 mol% for recovered carbon containing iron carbide and 0 mol% for recovered carbon not containing iron carbide.

[0035] After uniformly mixing each recovered carbon and hematite reagent, the sample was press-molded at a pressure of 98 MPa for 30 s to form a cylindrical shape with a diameter of 10 mm and a height of 10 mm. The mixture ratio of recovered carbon and hematite reagent was mixed so that the molar ratio of C (derived from recovered carbon) and O (derived from hematite reagent) in the mixed sample was C / O = 1.0. The molded sample was heated to 1300 ° C at a heating rate of 10 ° C / min in an atmosphere where 5 vol % N2-Ar mixed gas was supplied at a flow rate of 0.5 NL / min. The generated gas was analyzed with an infrared spectrophotometer, and the reduction rate of the iron ore was calculated. The results are shown in Figure 8. Compared to the comparative example, the reduction progressed faster in the example containing iron carbide. [Industrial Applicability]

[0036] According to the method for producing carbonaceous iron ore agglomerates of the present invention, in the production of molten iron in a countercurrent moving bed, highly reducible raw materials can be obtained, which can reduce the amount of reducing agent used in the reduction of iron-containing raw materials. This method is industrially useful, together with the method for producing molten iron using these raw materials. [Explanation of symbols]

[0037] 2, 8 Storage tank 4 Porous materials 6. Solid carbon and / or iron carbide 10 Cement Powder 12, 22 Conveyor 14 Mixer 16 water 20 Mixed powder 24 Granulator 26 Carbonaceous agglomerate ore 28 Other ingredients 30 Iron-containing lump materials 32 Blast Furnace 34 Reducing Gas 36 Molten Iron 38 Exhaust Gas

Claims

1. A process for passing a gas containing carbon dioxide at 800°C to 1000°C through iron whiskers to reform the carbon dioxide into carbon monoxide and obtain a carbon monoxide-rich gas; a step of passing the carbon monoxide-rich gas through iron whiskers in an environment of 500°C to 800°C to recover carbon from the carbon monoxide; an agglomeration step of mixing the carbon-containing raw material containing carbon with an iron-containing raw material and agglomerating the mixture; The method for producing carbon composite agglomerated ore comprises:

2. 2. The method for producing carbon composite agglomerated ore according to claim 1, wherein the carbon recovery step is carried out using a carbon deposition reaction.

3. The method for producing carbonaceous iron agglomerate according to claim 1 , wherein the iron-containing raw material includes iron ore and / or dust generated in a steelworks.

4. The method for producing carbon composite agglomerates according to claim 1 , wherein the carbon-containing raw material contains iron carbide.

5. The method for producing carbonaceous composite agglomerates according to claim 1 , wherein in the agglomeration step, biomass is further mixed with the carbon-containing raw material.

6. 2. The method for producing carbonaceous composite agglomerates according to claim 1, wherein the carbon content per particle in the carbonaceous composite agglomerates is 15 mass % or less.

7. 2. The method for producing carbonaceous composite agglomerates according to claim 1, wherein in the agglomerating step, a binder is further mixed with the carbon-containing raw material, and in the agglomerating step, the binder is hardened under cold working conditions.

8. 2. The method for producing carbonaceous composite agglomerated ore according to claim 1, wherein in the agglomerating step, a cement-based solidification material is further mixed with the carbon-containing raw material, and in the agglomerating step, the cement-based solidification material is solidified.

9. A method for producing molten iron using the carbonaceous composite agglomerated ore produced by the method for producing carbonaceous composite agglomerated ore according to any one of claims 1 to 8, The method for producing molten iron comprises charging iron-containing lump raw materials containing the carbonaceous composite agglomerated ore from above and flowing a reducing gas upward from below, thereby reducing and melting the iron-containing lump raw materials in a countercurrent moving bed to produce molten iron.

10. The method for producing molten iron according to claim 9, wherein the molten iron is produced in a shaft furnace.

11. A method for producing molten iron using the carbonaceous composite agglomerated ore produced by the method for producing carbonaceous composite agglomerated ore according to any one of claims 1 to 8, The carbonaceous composite agglomerated ore is heated to 1160 to 1450° C. to be reduced and melted, and then cooled to form reduced iron, and the reduced iron is melted to produce molten iron.

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