Manufacturing method of very low carbon ferromanganese and its manufacturing apparatus as well as manufacturing method of manganese-based alloy and its manufacturing apparatus

Abstract

To provide a manufacturing method of very low carbon ferromanganese that makes it possible to reduce CO2 exhaust in manufacture of ferromanganese and its manufacturing apparatus.SOLUTION: A method for producing an extremely low carbon manganese-based alloy, comprises: a step (1) of carbon-reducing manganese ore or reduced manganese ore; a step (2) of performing molten slag-metal separation; and a step (3) of reducing the separated molten slag with a non-carbon reductant to perform refining, followed by slag-metal separation.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing ultra-low carbon ferromanganese and an apparatus therefor. Further, the present invention relates to a method for producing a manganese-based alloy and an apparatus therefor.

Background Art

[0002] First, the background art regarding manganese-based alloys will be described.

[0003] Manganese-based alloys, such as ferromanganese, are produced by reducing manganese and iron in ore by charging manganese ore and a reducing agent such as coke into a blast furnace or an electric furnace and heating them. In the blast furnace method, coke is used as a heat source and a reducing agent, while in the electric furnace method, the basic concept is to use electric power as the heat source and coke as the reducing agent.

[0004] Conventionally, technological development has been carried out from the perspective of how to efficiently produce manganese-based alloys. For example, techniques of charging a reducing agent such as alloy iron containing silicon or metallic aluminum to further reduce and extract manganese remaining in the slag are disclosed in Patent Document 1 and Patent Document 2. In addition, instead of directly charging manganese ore into a blast furnace or an electric furnace, techniques of pre-reducing manganese ore with carbon monoxide CO gas or coke generated in the blast furnace method or the electric furnace method and then charging it into the blast furnace or the electric furnace are disclosed in Patent Documents 3 to 6.

[0005] Further, Non-Patent Document 1 mentions preheating and pre-reduction pretreatment in the background of using inexpensive coal instead of expensive electric power in the production of ferromanganese, and discloses a series of basic studies on each reduction reaction process using carbon monoxide or hydrogen gas as part of research on the reduction of manganese ore by carbon.

[0006] In the production of manganese-based alloys as described above, heretofore, technological development has been carried out from the perspective of how to efficiently produce manganese-based alloys.

[0007] The background art related to ultra-low carbon ferromanganese is described below.

[0008] Ferromanganese is produced by charging manganese ore and a reducing agent such as coke into a blast furnace or an electric furnace and heating them to reduce manganese and iron in the ore. In the blast furnace method, coke is used as a heat source and a reducing agent, while in the electric furnace method, the basic idea is to use electric power as the heat source and coke as the reducing agent. The ferromanganese obtained by these production methods contains a large amount of carbon derived from carbonaceous materials such as coke as a reducing agent, and is sometimes called high-carbon ferromanganese. Medium-carbon ferromanganese and low-carbon ferromanganese are produced by decarburization refining of the high-carbon ferromanganese. As a technique for the decarburization refining, for example, there is a method of blowing oxygen gas into the molten metal of high-carbon ferromanganese to oxidize and remove carbon in the molten metal (Patent Document 7).

[0009] In addition, Patent Documents 2 to 5 disclose that ferromanganese with a low carbon content can be produced by adding and reducing any one of metallic silicon, ferrosilicon, silicon manganese, calcium silicon, and metallic aluminum to molten slag containing manganese, for example, the slag obtained when producing the high-carbon ferromanganese.

[0010] In addition, as another production method for producing ferromanganese with a low carbon content, there is an electrolysis method (Non-Patent Document 2). After reducing and roasting manganese ore together with a carbonaceous material, it is dissolved in sulfuric acid, and the purified solution is electrolyzed in an electrolytic cell to electrodeposit metallic manganese on the cathode for production. Since no carbonaceous material is used when reducing to metallic manganese, metallic manganese basically free of carbon can be produced.

[0011] In the production of ferromanganese as described above, heretofore, technological development has been carried out from the perspective of how to efficiently produce ferromanganese. For example, instead of directly charging manganese ore into a blast furnace or an electric furnace, technologies for pre-reducing manganese ore with carbon monoxide CO gas or coke generated by the blast furnace method or the electric furnace method and then charging it into the blast furnace or the electric furnace are disclosed in Patent Documents 3 to 6.

[0012] In addition, Non-Patent Document 1 mentions a pretreatment of preheating and pre-reduction in the background of using inexpensive coal instead of expensive electricity in the production of ferromanganese. As part of research on the reduction of manganese ore by carbon, a series of basic studies on each reduction reaction process by carbon monoxide or hydrogen gas are disclosed.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Non-Patent Documents

[0014]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0015] The problems to be solved by the invention related to manganese-based alloys are described below.

[0016] As described above, in the production of manganese-based alloys, although technological development for efficient production has been carried out so far, it has been found that attempts to reduce CO2 have not been made on the premise of using carbonaceous materials such as coke as reducing agents when reducing manganese ore.

[0017] In fact, looking at Patent Documents 1 to 6 and other prior art documents related to the production of manganese-based alloys, no technological development has been carried out for the purpose of reducing CO2 emissions, nor is there any description or suggestion regarding it. In the technological development related to the production of conventional manganese-based alloys, some indirect reduction of CO2 emissions has been achieved by improving efficiency, but no attempt has been made to reduce or eliminate the use of carbonaceous materials, which are the sources of CO2 generation, from the perspective of reducing CO2 generation.

[0018] Also, for example, as in Non-Patent Document 1, there is basic research on the reduction behavior of manganese ore using reducing agents such as carbon monoxide and hydrogen other than carbon, but in the process of reducing to metallic manganese to produce manganese-based alloys, only the proposal of using natural gas containing methane CH4 for reduction has been made, and there is no disclosure or suggestion regarding its utilization from the perspective of reducing CO2 generation. There is no disclosure or suggestion.

[0019] In addition, in the description of FIG. 4 in Patent Document 4, surplus gas (derived from coke) from a ferromanganese furnace and Si and Mn furnaces is used to produce pre-reduced pellets, so the CO2 reduction effect of the present invention is not achieved. Although Patent Document 4 seems to have the effect of reducing the power unit, it has no effect of reducing the carbonaceous material.

[0020] Therefore, the present inventors have found that it is necessary to actively develop a technology for reducing CO2 emissions in the production of manganese-based alloys.

[0021] The problems to be solved by the invention related to extra-low carbon ferromanganese will be described below.

[0022] As described above, in the conventional production of ferromanganese, it is premised that carbonaceous materials such as coke are used as reducing materials for reducing manganese ore to ferromanganese, resulting in ferromanganese containing carbon. Therefore, decarburization treatment is required to obtain extra-low carbon ferromanganese. Also, from the perspective of a manufacturing method considering the global environment, since a reducing material that generates CO2 is used, it is not a manufacturing method that takes into account CO2 emission reduction.

[0023] In fact, looking at Patent Documents 1 to 9, Non-Patent Documents 1 to 2, and other prior art documents related to the production of ferromanganese, no technical development has been carried out for the purpose of reducing CO2 emissions, and there is no description or suggestion regarding this. In the technical development related to the conventional production of ferromanganese, some indirect CO2 emission reduction has been achieved by increasing efficiency, but no effort has been made to reduce or eliminate the amount of carbonaceous material that is the source of CO2 generation from the perspective of reducing CO2 generation.

[0024] For example, as in Non-Patent Document 1, there is basic research on the reduction behavior of manganese ore using reducing materials such as carbon monoxide and hydrogen other than carbon, but it only reaches the proposal of using natural gas containing methane CH4 for reduction in the process of producing ferromanganese by reducing to metallic manganese, and there is no disclosure or suggestion regarding its use from the perspective of reducing CO2 generation.

[0025] In the conventional technology, a large amount of CO2 is emitted in the manufacturing process of high-carbon ferromanganese that by-produces slag. That is, CO2 is emitted in the production of extra-low-carbon ferromanganese.

[0026] On the other hand, when producing metallic manganese by electrolyzing manganese ions dissolved in an aqueous solution, it seems to be a manufacturing method of extra-low-carbon ferromanganese that does not emit CO2 at first glance because it is reduction by electricity (which can also be said to be a non-carbon reducing material). However, since manganese ore cannot be directly dissolved in sulfuric acid, the manganese ore needs to be subjected to reduction roasting together with a carbon material. That is, CO2 is emitted when looking at the whole process.

[0027] Therefore, the inventors have found that it is necessary to actively develop technologies for reducing CO2 emissions in the production of extra-low-carbon ferromanganese.

[0028] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a manganese-based alloy that enables reduction of CO2 emissions in the production of a manganese-based alloy. Further, the present invention has been made in view of the above problems, and an object thereof is to provide a method for producing extra-low-carbon ferromanganese that enables reduction of CO2 emissions in the production of ferromanganese and a production apparatus therefor.

Means for Solving the Problems

[0029] Preferred embodiments of the present invention for solving at least one of the above problems will be described below.

[0030] 1. A method for producing a manganese-based alloy, comprising a step (1) of heating manganese ore and subjecting it to hydrogen reduction to produce reduced manganese ore.

[0031] 2. A process for producing reduced manganese ore by heating and hydrogen-reducing manganese ore (step (1)), and a process for melting the reduced manganese ore by heating (step (2)), or a process for heating and hydrogen-reducing manganese ore to obtain a melt (step (3)), characterized in that the method for producing ultra-low carbon ferromanganese comprises these steps.

[0032] 3. The method for producing ultra-low carbon ferromanganese according to 2., further comprising a step (4) of reducing the melt with a non-carbon reducing agent for refining, and then performing slag-metal separation.

[0033] 4. The method for producing ultra-low carbon ferromanganese according to 3., characterized in that the non-carbon reducing agent is a reducing agent containing ferrosilicon or metallic aluminum, or a reducing agent containing ferrosilicon and metallic aluminum.

[0034] 5. The method for producing ultra-low carbon ferromanganese according to any one of 2. to 4., further comprising a step (5) of refining the melt by molten oxide electrolysis, and then performing slag-metal separation.

[0035] 6. The method for producing ultra-low carbon ferromanganese according to any one of 2. to 5., characterized in that in step (1), the manganese oxidation degree is reduced to 1.1 or less.

[0036] 7. The method for producing ultra-low carbon ferromanganese according to any one of 2. to 6., characterized in that the heating in at least one step selected from the group consisting of step (1), step (2) and step (3) includes heating by hydrogen combustion.

[0037] 8. An apparatus for producing ultra-low carbon ferromanganese, comprising means (1) for heating and hydrogen-reducing manganese ore to produce reduced manganese ore, means (2) for heating the reduced manganese ore to obtain a melt, or means (3) for heating and hydrogen-reducing manganese ore to obtain a melt.

[0038] 9. Further, means (4) for reducing the melt with a non-carbon reducing agent for refining and then performing slag-metal separation is included, and the manufacturing apparatus for ultra-low carbon ferromanganese according to 8. is characterized by this.

[0039] 10. The manufacturing apparatus for ultra-low carbon ferromanganese according to 9., wherein the non-carbon reducing agent is a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum.

[0040] 11. Further, means (5) for refining the melt by molten oxide electrolysis and then performing slag-metal separation is provided, and the manufacturing apparatus for ultra-low carbon ferromanganese according to any one of 8. to 10. is characterized by this.

[0041] 12. Further, a step (6) of charging the reduced manganese ore into an electric furnace together with a carbonaceous material for refining and then performing slag-metal separation is included, and the manufacturing method of the manganese-based alloy according to 1. is characterized by this. alloy

[0042] 13. Further, a step (5) of refining part or all of the reduced manganese ore by molten oxide electrolysis and then performing slag-metal separation is included, and the manufacturing method of the manganese-based alloy according to 1. or 12. is characterized by this.

[0043] 14. The manufacturing method of the manganese-based alloy according to any one of 1., 12., 13., wherein the manganese oxidation degree of the reduced manganese ore is 1.6 or less.

[0044] 15. The manufacturing method of the manganese-based alloy according to 14., wherein the manganese oxidation degree of the reduced manganese ore is 1.1 or less.

[0045] 16. The manufacturing method of the manganese-based alloy according to any one of 1., 12. to 15., wherein the proportion of hydrogen in the gas of the reducing agent in the hydrogen reduction is more than 70 mol%.

[0046] 17. The method for producing a manganese-based alloy according to any one of 12. to 16., wherein the amount of Mn in the slag is 10% to 29%.

[0047] 18. The method for producing a manganese-based alloy according to any one of 1., 12. to 17., wherein the heating includes heating by electric heating or hydrogen combustion.

[0048] 19. The method for producing a manganese-based alloy according to any one of 12. to 18., further comprising a step (7) of reducing at least a part of the manganese oxide contained in the molten slag with a reducing agent containing ferrosilicon or metallic aluminum, or a reducing agent containing ferrosilicon and metallic aluminum, which is by-produced in the step (6).

[0049] 20. The method for producing a manganese-based alloy according to any one of 1., 12. to 19., further comprising a step (8) of reducing and refining a part or all of the reduced manganese ore with a reducing agent containing ferrosilicon or metallic aluminum, or a reducing agent containing ferrosilicon and metallic aluminum, and then performing slag-metal separation.

[0050] 21. The method for producing a manganese-based alloy according to any one of 12. to 20., wherein a part or all of the carbon material is green carbon.

[0051] 22. A manufacturing apparatus for a manganese-based alloy, comprising means (1) for heating a manganese ore and subjecting it to hydrogen reduction.

Advantages of the Invention

[0052] By the method for producing a manganese-based alloy of the present invention, by hydrogen-reducing manganese ions contained in a manganese ore, it is possible to significantly reduce the amount of CO2 emissions in the production of a manganese-based alloy. Further, according to the manufacturing apparatus of the present invention, it is possible to significantly reduce the amount of CO2 emissions in the production of a manganese-based alloy, or to make the amount of CO2 emissions almost zero.

[0053] By the method for producing ultra-low-carbon ferromanganese of the present invention, by hydrogen-reducing manganese ions contained in manganese ore, the effect of significantly reducing the CO2 emission amount in the production of ultra-low-carbon ferromanganese can be achieved. Further, according to the production apparatus of the present invention, the effect of significantly reducing the CO2 emission amount in the production of ultra-low-carbon ferromanganese or making the CO2 emission amount almost zero can be achieved.

Brief Description of the Drawings

[0054]

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Figure 20

Embodiments for Carrying Out the Invention

[0055] Hereinafter, the method for manufacturing a manganese-based alloy of the present invention will be described.

[0056] Note that the present invention is not limited only to the following embodiments. Also, in this specification, "X to Y" indicating a range means "X or more and Y or less". Further, unless otherwise specified, measurements of operations and physical properties are made under the conditions of room temperature (20 to 25°C) / relative humidity 40 to 50%RH. Note that "%" described in this specification is, in all cases except for specific cases (for example, "mol% (volume%)"), mass% (weight%). Note that the embodiments of the method for producing a manganese-based alloy and the embodiments of the production of extra-low carbon ferromanganese described below are mutually applicable.

[0057] In one aspect of the present invention, there is provided a method for producing a CO2 emission-reducing manganese-based alloy, which includes a step (1) of heating manganese ore and subjecting it to hydrogen reduction to produce reduced manganese ore.

[0058] The raw material of the manganese-based alloy, for example, manganese ore, is usually tetravalent manganese (equivalent to MnO2). Even if the reduction reaction theoretically occurs efficiently when a carbonaceous material such as coke is charged into an electric furnace together with manganese ore as a reducing agent and the tetravalent manganese (ore) is reduced to zero-valent metallic manganese (manganese-based alloy), a considerable amount of carbon dioxide will be emitted.

[0059] Here, the inventors considered the reduction of manganese ore from a thermodynamic perspective and determined that reducing agents capable of reducing tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO) are carbon C, carbon monoxide CO, hydrogen H2, etc. (Figure 1). The only reducing agent capable of reducing divalent manganese (equivalent to MnO) to zero-valent manganese (metallic Mn) is carbon C (Figure 1). Carbon C can also reduce to metallic manganese under conditions of 1450°C or higher.

[0060] Subsequently, in the process of producing a manganese-based alloy by simplifying manganese ore to MnO2, the CO2 reduction effect when hydrogen-reducing manganese ore is considered (Figure 2). Even if the reduction of tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO) is carried out using a reducing agent that does not generate CO2, such as hydrogen, as described above, only carbon C can reduce divalent manganese (equivalent to MnO) to zero-valent manganese (metallic Mn). Therefore, 1 mole of carbon C is required to produce 1 mole of metallic Mn of manganese Mn, and the CO2 reduction effect is zero.

[0061] Thus, it is considered that the CO2 reduction effect is zero even when hydrogen-reducing manganese ore, and furthermore, demerits such as the need for new devices and facilities are assumed. Therefore, those skilled in the art will not come up with the idea of using hydrogen for preliminary reduction.

[0062] In contrast, the inventors of the present invention have found that if the Mn content in the slag discharged from manganese ore is set to be around 30% or so to produce a manganese-based alloy (especially ferromanganese), a CO2 reduction effect can be achieved by preliminarily hydrogen-reducing the manganese ore. In this way, the inventors have come up with the idea that positive CO2 emission reduction can be achieved by hydrogen-reducing manganese to less than tetravalent, leading to the present invention. The existence form of Mn in the slag is considered to be dissolved as Mn 2+ ions and / or dispersed as MnO oxides. The existence form can be observed with an electron microscope.

[0063] In a preferred embodiment, when carbon-reducing reduced manganese ore, it is set not to reduce the Mn content in the slag to zero%. The reasons are as follows. That is, manganese ore contains slag components (silica SiO2, silicate), that is, in the coexistence of MnO-SiO2. Therefore, reaction formulas (1) and (2) in Figure 3 occur. From the equilibrium formula of reaction formula (3) obtained by (formula (1)×2 - formula (2)), the relationship of formula (4) is derived. Formula (4) means that to lower the [MnO] concentration, that is, to increase the Mn yield, the [Si] concentration needs to be increased. Then, it will be in a relationship like a graph of the amount of Mn in the slag and Si in the manganese-based alloy (Si in FMn). If the amount of Mn in the slag is lowered too much and the Mn yield is increased too much, the Si content in the obtained manganese-based alloy will increase. Therefore, in order to manufacture a manganese-based alloy from manganese ore so that the Si content in the manganese-based alloy does not increase too much, it is advisable to set the amount of Mn in the slag to about 30% or so.

[0064] By making such a contrivance, the inventors have found that when manganese ore is pre-reduced with hydrogen, a CO2 reduction effect appears (Figures 4 and 5). In Figure 4, as an example, the CO2 reduction effect is calculated based on the assumption (model) of producing 40% of the Mn content as metallic manganese (manganese-based alloy) from manganese ore containing 50% Mn (Mn grade) and discharging slag containing 30% Mn (Mn amount in the slag 30%). First, all the manganese (50%) contained in the manganese ore is reduced to MnO. According to the current coke (carbon) reduction method using an electric furnace, carbon C (coke) and carbon monoxide CO are used in a ratio of 0.3:0.4 as the reducing agent. Here, the carbon monoxide CO is the carbon monoxide CO generated by the reaction of the carbon C required to produce 50% of metallic manganese (manganese-based alloy) from MnO. Therefore, 0.7 moles of CO2 are generated per mole of MnO2.

[0065] In contrast, preferably for the reduction to MnO, when hydrogen reduction is utilized, the manganese (50%) contained in the manganese ore does not generate CO2 at that time. In other words, when hydrogen reduction is used for the reduction from MnO2 to MnO, all the manganese contained in the manganese ore is reduced to MnO, but CO2 is not generated at that time. Of the manganese in the hydrogen-reduced manganese ore, 40% of it is reduced by coke (carbon) to metallic manganese (manganese-based alloy), and carbon monoxide CO corresponding to the amount of the carbon is generated here. The generated carbon monoxide CO is burned (reacted with oxygen O2) and discharged as carbon dioxide CO2. Therefore, 0.4 mol of CO2 is generated per 1 mol of MnO2.

[0066] Therefore, according to the above model, when hydrogen reduction is carried out until MnO, a 43% CO2 reduction effect can be obtained with respect to the amount of CO2 generated in the current electric furnace reaction. Note that FIG. 5 is represented by one reaction formula respectively.

[0067] That is, the mechanism for obtaining the CO2 reduction effect is, as explained in FIG. 3, not to deliberately produce a manganese-based alloy by reducing all the manganese contained in the manganese ore to metallic manganese, but to hydrogen-reduce all the manganese in the manganese ore to manganese with a valence of less than 4, hydrogen-reduce divalent manganese (manganese oxidation degree 1.0), or hydrogen-reduce it to near divalent and then use it as a reduced manganese ore, and then reduce part or all of it to metallic manganese to produce a manganese-based alloy.

[0068] Therefore, by including the step (1) of heating the manganese ore to obtain a hydrogen-reduced manganese ore, ultimately, a method for producing a manganese-based alloy capable of reducing CO2 emissions compared to the carbon dioxide CO2 generated by the conventional method for producing a manganese-based alloy can be achieved.

[0069] According to an embodiment of the present invention, a step (1) of heating manganese ore to produce reduced manganese ore by hydrogen reduction and a step (6) of charging the reduced manganese ore into an electric furnace together with a carbonaceous material for refining and then performing slag-metal separation are combined. Note that the step (1) and the step (6) may be performed in the same reaction vessel or in separate reaction vessels that are separated from each other. The separated reaction vessels may or may not be connected to each other. As described above, this embodiment is also applicable to an embodiment of the production of extra-low carbon ferromanganese.

[0070] In addition, since basically carbon monoxide CO is generated in the step (6) (in FIG. 10, carbon dioxide CO2 is shown as the final discharge form, and the description of the oxidation (combustion) of carbon monoxide CO is omitted), the carbon monoxide CO generated here may be used together with hydrogen for reduction in the step (1).

[0071] The CO2 reduction effect in the embodiment of the present invention is in the relationship as shown in FIG. 6 due to the above-described CO2 reduction mechanism. Note that FIG. 6 is derived by transforming the reaction formula described in FIG. 4 so that the Mn grade in the desired ore and the amount of Mn in the desired slag are obtained, and plotting the corresponding percentage of the reduction effect. That is, regarding the Mn grade (Mn content) of manganese ore, the lower the Mn grade, the higher the CO2 reduction effect. In other words, as the Mn grade increases, the CO2 reduction effect tends to decrease. Also, regarding the amount of Mn remaining in the discharged slag, the more the amount of Mn in the slag, the higher the CO2 reduction effect. In other words, when the amount of Mn in the slag is small, the CO2 reduction effect tends to decrease. By having the step (1) of heating manganese ore to produce reduced manganese ore by hydrogen reduction, the CO2 reduction effect can be exerted. However, as described above, the CO2 reduction effect varies depending on the Mn grade of manganese ore and the amount of Mn in the slag. Generally speaking, the more efficiently a large amount of manganese-based alloys are produced from manganese ore, The CO2 reduction effect will be low. Therefore, from the perspective of ensuring a certain level of productivity and obtaining a CO2 reduction effect, preferably, for example, the Mn grade of the manganese ore is set to be 40-60%. Within this range, a CO2 reduction effect of about 20-70% can be obtained. According to an embodiment, the Mn grade of the manganese ore is 20% or more, 25% or more, 31% or more, 32% or more, 35% or more, 38% or more, 40% or more, 45% or more, or 46% or more. According to an embodiment, the Mn grade of the manganese ore is 80% or less, 68% or less, 60% or less, 55% or less, 54% or less, 50% or less, 49% or less, or 48% or less.

[0072] Also, according to an embodiment, the amount of Mn in the slag discharged is 0.1% or more, 1% or more, 5% or more, 10% or more, 20% or more, 25% or more, or 26% or more. According to an embodiment, the amount of Mn in the slag is 35% or less, 31% or less, 30% or less, or 29% or less.

[0073] Figure 7 shows the influence of the production amount of manganese-based alloy (the ratio of producing manganese-based alloy (ferromanganese) from manganese ore, Mn / Mn ore-%) on the CO2 reduction effect. This Figure 7 is derived by transforming the reaction formula described in Figure 4 so that the amount of Mn in the desired slag and the desired production amount of manganese (manganese production ratio) are obtained, and then plotting the corresponding percentage of the reduction effect. It can be read from Figure 7 that there is a similar trend to that in Figure 6. According to a preferred embodiment, the production amount of manganese-based alloy is 5-50%, 5-40%, or 10-30%.

[0074] Here, the manganese oxidation degree (Mn oxidation degree) will be described. The composition formula is MnO xWhen expressed by [formula], the value of x is the manganese oxidation state. For example, a manganese oxidation state of x = 2 is MnO₂, and a manganese oxidation state of x = 1 is MnO. Therefore, the manganese oxidation state of manganese ore or reduced manganese ore is determined from the value of the total manganese content (Mn%, JIS M8232 2005 Manganese Ore - Method for Determination of Manganese) and the value of the available oxygen of the manganese oxide (MnO₂%, JIS M8233 1995 Manganese Ore - Method for Determination of Active Oxygen) to obtain x of MnO x and use it as the manganese oxidation state.

[0075] Figure 8 shows the influence of the degree of reduction by hydrogen reduction of manganese ore, that is, the manganese oxidation state of reduced manganese ore, on the CO₂ reduction effect. This Figure 8 was derived by modifying the reaction formula described in Figure 4 so as to obtain a desired oxidation state, a desired Mn grade, and a desired amount of Mn in the slag, and then plotting the corresponding percentage of the reduction effect. Although it is assumed that the manganese oxidation state in the reduced manganese ore is less than 2, as shown in Figure 8, the greater the manganese oxidation state, the smaller the CO₂ reduction effect. In other words, the smaller the manganese oxidation state and the closer it is to 1.0, the greater the CO₂ reduction effect. In order to ensure the production volume of manganese-based alloys and obtain a more effective CO₂ reduction effect, in step (1), it is preferable to use reduced manganese ore with a manganese oxidation state of 1.6 or less, more preferably 1.5 or less, still more preferably 1.2 or less, and even more preferably 1.1 or less. In addition, when the manganese oxidation state of the manganese ore to be hydrogen-reduced is already less than 2.0, the manganese oxidation state of the reduced manganese ore should be less than the manganese oxidation state of the raw material manganese ore. According to a preferred embodiment, when the manganese oxidation state of the manganese ore is 100%, the manganese ore is reduced so that the manganese oxidation state becomes 80% or less, 75% or less, or 70% or less. Also, regardless of the manganese oxidation state of the raw material manganese ore, it is preferable to make the manganese oxidation state of the reduced manganese ore 1.6 or less, 1.5 or less, 1.2 or less, 1.15 or less, or 1.1 or less.

[0076] Regarding the hydrogen reduction of manganese ore, as long as the condition contains hydrogen, a reducing agent that becomes a CO2 generation source within the range where a CO2 reduction effect can be obtained, for example, may contain CO or a carbon material.

[0077] Here, the reducing agent can be divided into a gas (gaseous) form and a solid form.

[0078] According to a preferred embodiment, the proportion of hydrogen in the gas of the reducing agent is 50 mol% or more, more preferably 70 mol% or more, even more preferably more than 70 mol%, even more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 99 mol% or more, and even more preferably 100 mol%. The proportion of CO in the gas of the reducing agent is 30 mol% or less, less than 30 mol%, 10 mol% or less, 5 mol% or less, 1 mol% or less, or 0 mol%.

[0079] According to a preferred embodiment, the amount (proportion) of the solid reducing agent (the reducing agent that becomes a CO2 generation source (for example, a carbon material (coke))) relative to the manganese ore is 20 wt% or less, 10 wt% or less, 8 wt% or less, the impurity level, or 0 mass%. According to a preferred embodiment, the impurity level means that the amount of the reducing agent that becomes a CO2 generation source is 1000 wt ppm or less. As described above, according to a preferred embodiment, the reducing agent does not contain CO or a carbon material.

[0080] In addition, as gases other than the reducing agent in hydrogen reduction, nitrogen, water vapor, CO2, argon, helium, oxygen, nitrogen oxides, etc. may be included. The hydrogen content in hydrogen reduction is sufficient as long as it can reduce the manganese ore to the desired degree of oxidation. However, considering the supply amount of the hydrogen-containing gas corresponding to the treatment amount of the manganese ore, for example, in all gases (that is, the gas of the reducing agent and the gas other than the reducing agent), it is 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more. From the perspective of more efficient reduction, it may be set above 4 mol%. According to a preferred embodiment, it is 10 mol% or less, 9 mol% or less, 8 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, 3 mol% or less, or 2 mol% or less.

[0081] As will be described later, according to a preferred embodiment, the temperature in hydrogen reduction is 200°C or higher, 300°C or higher, 400°C or higher, 500°C or higher, 600°C or higher, 700°C or higher, 800°C or higher, or 900°C or higher. Also, according to a preferred embodiment, the temperature in hydrogen reduction is 1200°C or lower, 1100°C or lower, 1000°C or lower, 900°C or lower, or less than 800°C. According to a preferred embodiment, the time of hydrogen reduction is 0.5 hours or more, 1.0 hour or more, or 2.0 hours or more. According to a preferred embodiment, the time of hydrogen reduction is 10 hours or less, 5 hours or less, or 3 hours or less.

[0082] According to a preferred embodiment, the introduction amount of the hydrogen-containing gas with respect to the amount of manganese ore is, as a guideline, 1.0 to 3.1 times, 1.05 to 1.9 times, or 1.1 to 1.4 times the amount of hydrogen required to reduce to the desired manganese oxidation degree.

[0083] According to an embodiment, the degree of manganese oxidation of the reduced manganese ore is 1.0 to 1.5, the Mn grade of the manganese ore is 40 to 60%, and the Mn in the slag is 20 to 31%. According to an embodiment, the degree of manganese oxidation of the reduced manganese ore is 1.0 to 1.2, the Mn grade of the manganese ore is 40 to 55%, and the Mn in the slag is 25 to 31%. According to an embodiment, the degree of manganese oxidation of the reduced manganese ore is 1.0 to 1.15, the Mn grade of the manganese ore is 45 to 54%, and the Mn in the slag is 25 to 30%. According to an embodiment, the degree of manganese oxidation of the reduced manganese ore is 1.0 to 1.1, the Mn grade of the manganese ore is 46 to 54%, and the Mn in the slag is 26 to 29%.

[0084] According to a preferred embodiment, when hydrogen reduction is carried out up to MnO with respect to the amount of CO2 generated in the current electric furnace reaction shown in FIG. 4, preferably 10% or more, more preferably 20% or more, Further preferably, a CO2 reduction effect of 30% or more can be obtained.

[0085] According to a preferred embodiment, as described above, the reduced manganese ore produced in the step (1) is charged into an electric furnace together with a carbonaceous material for refining, and then through a step (6) of performing slag-metal separation, a manganese-based alloy is produced. The electric furnace may be a conventional submerged arc furnace or an equivalent electric furnace, which mainly heats the inside of the furnace by electric power and is mainly used for reducing reduced manganese ore to metallic manganese (manganese-based alloy) by a carbonaceous material. As refining proceeds in the electric furnace, molten slag and molten manganese-based alloy are formed. Due to the difference in their specific gravities, the molten manganese-based alloy is placed at the bottom of the furnace and the molten slag is placed on it. Therefore, depending on the tapping timing, the height of the tapping port, etc., the slag and metal are separated and discharged from the electric furnace. The manganese-based alloy produced using a carbonaceous material in this way obtains ferromanganese containing carbon, and may be decarburized later according to the application. This embodiment is schematically shown by the upper flow in FIG. 10.

[0086] According to a preferred embodiment, a step (5) may be provided in which part or all of the reduced manganese ore produced in the step (1) is refined by molten oxide electrolysis, and then slag-metal separation is performed. The molten oxide electrolysis is a method of melting a reduced manganese ore, applying a voltage capable of reducing divalent manganese to zero-valent manganese (metallic manganese) by bringing two electrodes, an anode and a cathode, into contact with the melt, and electrolytically producing molten metallic manganese (manganese-based alloy). Here, the heat source for melting the reduced manganese ore can also be electric heating, using the Joule heat generated from the current flowing between the electrodes, or a separate heat source can be prepared. The manganese-based alloy produced without using a carbon material in this way can obtain ferromanganese or metallic manganese that contains almost no carbon. This embodiment is schematically shown by the flow in the middle stage of FIG. 10.

[0087] The heating in the step (1) only needs to be able to heat the manganese ore to a temperature at which it can be hydrogen-reduced, and any heating method can be used, but a heating method that can reduce the carbon dioxide CO2 emission is more preferable. For example, from the viewpoint that the heating in the step (1) being electric heating can reduce the carbon dioxide CO2 emission, it is preferable. Also, from the viewpoints that the heating in the step (1) being heating by hydrogen combustion can reduce the carbon dioxide CO2 emission and that it can be carried out simultaneously with hydrogen supply, it is preferable.

[0088] Furthermore, if a step (7) of producing a manganese-based alloy iron by reducing at least a part of the manganese oxide contained in the molten slag by using a reducing material containing alloy iron containing silicon or metallic aluminum, or both a reducing material containing alloy iron containing silicon and metallic aluminum, is included in the molten slag by-produced in the step (6), the manganese remaining in the slag can be recovered, so the productivity is improved. The manganese-based alloy produced from the Mn-containing slag without using a carbon material in this way can obtain ferromanganese or metallic manganese that contains almost no carbon. This embodiment is schematically shown by the flow in the lower stage of FIG. 10.

[0089] According to a modified example of this embodiment, for example, instead of the reduced manganese ore obtained by hydrogen-reducing manganese ore, manganese ore (Mn ore) or reduced manganese ore obtained by a reduction treatment such as hydrogen reduction is used. For example, carbon reduction is performed with coke or the like (step (1)), then a step (2) of performing molten slag-metal separation, and the separated molten slag is reduced with a non-carbon reducing material (for example, an alloy iron containing silicon or a reducing material containing metallic aluminum, or a reducing material containing alloy iron containing silicon and metallic aluminum) for refining, and then slag-metal separation (step (3)) is performed. By doing so, manganese remaining in the slag can be recovered, so productivity is improved. A manganese-based alloy produced from Mn-containing slag without using a carbon material in this way can obtain ferromanganese or metallic manganese that hardly contains carbon. Such an embodiment is schematically shown by the upper flow in FIG. 19. As shown in the lower flow of FIG. 19, a mixture of Mn ore and a carbon material such as coke may be preheated by a preheating means before being charged into an electric furnace together with the carbon material such as coke.

[0090] Also, according to the modified example of the flow shown in the middle part of FIG. 10, for example, instead of the reduced manganese ore obtained by hydrogen-reducing manganese ore, manganese ore (Mn ore) or reduced manganese ore obtained by a reduction treatment such as hydrogen reduction is used, and carbon reduction is performed with coke or the like (step (1)). Next, a step (2) of performing molten slag-metal separation, and refining by reducing the separated molten slag with a non-carbon reducing material. Here, the method of refining by reducing with the non-carbon reducing material is refining by molten oxide electrolysis. Next, slag-metal separation (step (3)) is performed. By doing so, manganese remaining in the slag can be recovered, so productivity is improved. In addition, since the separated molten slag can be used for molten oxide electrolysis in a molten state, more efficient production can be realized. Thus, manganese-based alloys produced from Mn-containing slag without using a carbon material can obtain ferromanganese and metallic manganese that contain almost no carbon. Such an embodiment is schematically shown by the flow in the upper part of FIG. 20. As shown in the lower flow of FIG. 20, a mixture of Mn ore and a carbon material such as coke may be preheated by a preheating means before being charged into an electric furnace together with the carbon material such as coke.

[0091] Note that in these embodiments, the slag separated by the step (2) of performing molten slag-metal separation contains a certain amount of Mn (for example, around 30%). According to an embodiment, the amount of Mn in the slag is 0.1% or more, 1% or more, 5% or more, 10% or more, 20% or more, 25% or more, or 26% or more. According to an embodiment, the amount of Mn in the slag is 35% or less, 31% or less, 30% or less, or 29% or less. According to an embodiment, the amount of Mn in the slag is 10% - 29%.

[0092] Figure 13 arranges the production ratio of ultra-low-carbon ferromanganese to the total amount of ferromanganese based on the reaction formula in Figure 11 in terms of the Mn grade of the manganese ore and Mn in the slag. That is, the reaction formula described in Figure 11 is deformed so as to have a desired Mn grade and a desired amount of Mn in the discharged slag, and the percentage of the production ratio of ultra-low-carbon ferromanganese to the total amount of ferromanganese corresponding thereto is derived by plotting. The production ratio of ultra-low-carbon ferromanganese increases as the Mn grade of the manganese ore is lower and increases as the amount of Mn in the slag is higher. As long as it is within the range where ultra-low-carbon ferromanganese can be produced, any conditions are acceptable, but it is preferable that the production ratio of ultra-low-carbon ferromanganese is higher. For example, the production ratio of ultra-low-carbon ferromanganese is preferably 20% or more, more preferably 40% or more, and still more preferably 50% or more. Also, the preferable upper and lower limit values of the Mn grade of the manganese ore and the amount of Mn in the slag are applicable to the description of Figure 12.

[0093] From Figures 12 and 13, it can be seen that the greater the production ratio of ultra-low-carbon ferromanganese, the greater the CO2 reduction effect (Figure 14). As can be seen from Figure 14, a production ratio of ultra-low-carbon ferromanganese of 35% or more is preferable for the CO2 reduction effect to be 20% or more, a production ratio of ultra-low-carbon ferromanganese of 45% or more is more preferable for the CO2 reduction effect to be 30% or more, and a production ratio of ultra-low-carbon ferromanganese of 50% or more is still more preferable for the CO2 reduction effect to be 24% or more.

[0094] As the carbon material in the step (6), conventional coke may be used, but the CO2 reduction effect can be further improved by using a part or all of it as green carbon. The green carbon includes bio-carbon (biomass-derived carbon materials such as charcoal and bamboo charcoal), coke made from waste plastics, fuel-derived carbon materials obtained from hydrogen and carbon dioxide synthesized by renewable energy, green coke synthesized using renewable energy, and the like.

[0095] Further, part or all of the carbon material in step (6) may be granulated together with the reduced manganese ore produced in step (1) and charged into an electric furnace as pellets with an internal carbon material. By using pellets with an internal carbon material as described above, the reduction reaction and gas escape in the electric furnace may be improved, making stable operation easier and potentially reducing the carbon material consumption per unit.

[0096] Alternatively, the dust generated in step (1) and the carbon material may be granulated together and charged into the electric furnace as pellets with an internal carbon material. Further, product crushing scraps of manganese-based alloys or ore fines of raw material manganese ore may be included in the pellets with an internal carbon material.

[0097] The above-mentioned pellets with an internal carbon material are more effective when using green carbon, and the carbon material used for the pellets with an internal carbon material is preferably green carbon, which can make green carbon act more efficiently as a reducing agent.

[0098] As the granulation method for making pellets with an internal carbon material, ordinary methods can be adopted, such as the pellet method, the briquette method, the extrusion molding method, etc.

[0099] In step (6), a slag-making agent (slag conditioner) can be charged into the electric furnace. The slag-making agent can control properties such as the viscosity, oxygen potential, and basicity of the slag. Examples include lime, slaked lime, Na2CO3, CaCl2, MgCO2, etc.

[0100] Part or all of the reduced manganese ore produced in step (1) can be reduced and refined using a reducing material containing alloy iron with silicon or metallic aluminum, or both a reducing material containing alloy iron with silicon and metallic aluminum, and then manganese-based alloy iron can be produced in step (8) where slag-metal separation is performed. In this way, manganese-based alloys produced from Mn-containing slag without using carbon material can obtain ferromanganese or metallic manganese that contains almost no carbon.

[0101] As a manufacturing apparatus for manganese-based alloys that achieves the method for manufacturing manganese-based alloys as described above, there is provided a means (1) for heating manganese ore and subjecting it to hydrogen reduction to obtain reduced manganese ore, and a means (6) for charging the reduced manganese ore into an electric furnace together with a carbonaceous material, performing refining, and then performing slag-metal separation.

[0102] Furthermore, it is more preferable to provide a manufacturing apparatus for manganese-based alloys that includes a means (5) for refining a part or all of the reduced manganese ore generated in the step (1) by molten oxide electrolysis and then performing slag-metal separation.

[0103] Furthermore, it is more preferable to provide a manufacturing apparatus for manganese-based alloys that includes a means (7) for reducing at least a part of the manganese oxide contained in the molten slag by using a reducing material containing alloy iron containing silicon or metallic aluminum, or both a reducing material containing alloy iron containing silicon and metallic aluminum, to produce manganese-based alloy iron.

[0104] Hereinafter, a method for manufacturing ultra-low carbon ferromanganese according to one embodiment of the present invention will be described.

[0105] In one embodiment of the present invention, there is provided a method for manufacturing ultra-low carbon ferromanganese, characterized by including a step (1) of heating and subjecting manganese ore to hydrogen reduction to produce reduced manganese ore, and a step (2) of heating the reduced manganese ore to obtain a melt.

[0106] The raw material for ferromanganese, for example, manganese ore, is usually tetravalent manganese (equivalent to MnO2). When a carbonaceous material such as coke is used as a reducing material and charged into an electric furnace together with manganese ore to reduce tetravalent manganese (ore) to zero-valent metallic manganese (ferromanganese), a considerable amount of carbon dioxide will be emitted even if the reduction reaction occurs efficiently theoretically.

[0107] Here, the inventors have considered the reduction of manganese ore from a thermodynamic perspective, and tetravalent manganese Reducing agents that can reduce (MnO2 equivalent) to divalent manganese (equivalent to MnO) were determined to be carbon C, carbon monoxide CO, hydrogen H2, etc. (Fig. 1). Only carbon C can reduce divalent manganese (equivalent to MnO) to zero-valent manganese (metallic Mn) (Fig. 1). Note that carbon C can also reduce to metallic manganese under conditions of 1450 °C or higher.

[0108] Therefore, in common sense, to produce ferromanganese by reducing manganese ore to metallic manganese, it is natural to use a carbon reducing agent such as coke as the reducing agent. It is also assumed that one more step is added for hydrogen reduction, and the idea of using hydrogen that cannot reduce to metallic manganese has never occurred before.

[0109] However, in the method for producing ultra-low-carbon ferromanganese, the inventors found a new problem of considering the CO2 reduction effect, and came up with the idea of reducing manganese ore by hydrogen as much as possible.

[0110] In one aspect of the present invention, in the step (2) of heating the reduced manganese ore to form a melt, one method of forming the melt includes arc melting using an electric furnace (for example, a single-phase arc furnace, a submerged arc furnace, submerged arc furnace). Manganese ions (Mn in the melt 2+) reduces [substance] to produce ultra-low carbon ferromanganese. However, carbonaceous materials such as coke (e.g., bio-coke) may be charged into the electric furnace to obtain a part of high-carbon ferromanganese. An example is shown in Fig. 11. After reducing manganese ore with 50% Mn grade to reduced manganese ore (manganese oxidation degree = 1.0) in step (1), carbonaceous materials are charged into the electric furnace to produce 50% high-carbon ferromanganese, and ultra-low carbon ferromanganese is produced from the melt (molten slag) with 47% Mn content in the slag. Under these conditions, the same amount of high-carbon ferromanganese and ultra-low carbon ferromanganese can be produced from manganese ore, and the CO2 reduction effect at this time is 33%. This CO2 reduction effect is based on the case of reducing manganese ore with 50% Mn grade to 47% Mn content in the slag in the current electric furnace without hydrogen reduction. However, when the Mn content in the slag is 30% (when the Mn content in the slag is minimized as much as possible), the CO2 reduction effect is 44%. More specifically about Fig. 11, in Fig. 11, first, all the manganese (50%) contained in the manganese ore is reduced to MnO. According to the current coke (carbon) reduction method using an electric furnace, 0.75 mol of carbon C (coke) is used as the reducing agent for 1 mol of MnO2. Here, carbon monoxide CO is the carbon monoxide CO generated by the reaction of the carbon C required to produce 50% of metallic manganese (ferromanganese) from MnO. Therefore, 0.75 mol of CO2 is generated for 1 mol of MnO2, and 2+ (equivalent to MnO) remains at 0.50 mol in the slag. Ultra-low carbon ferromanganese can be produced from this Mn in the slag, but 0.75 mol of CO2 will be generated.

[0111] In contrast, preferably, for the reduction to MnO, when hydrogen reduction is used, the manganese (50%) contained in the manganese ore does not generate CO2 at that time. In other words, if both hydrogen reduction for the reduction from MnO2 to MnO and CO reduction generated during carbon reduction from Mn to Mn are utilized, all the manganese contained in the manganese ore is reduced to MnO, but no CO2 is generated at that time. Of the manganese in the hydrogen-reduced manganese ore, 25% of it is reduced by coke (carbon) to metallic manganese (ferromanganese), and carbon monoxide CO corresponding to the amount of carbon is generated here. The generated carbon monoxide CO is utilized for the reduction from MnO2 to MnO as described above and is discharged as carbon dioxide CO2. Therefore, 0.5 mol of CO2 is generated per 1 mol of MnO2.

[0112] Therefore, when compared under the same conditions as above, a 33% CO2 reduction effect can be obtained by hydrogen-reducing the manganese ore with respect to the amount of CO2 generated in the current electric furnace reaction.

[0113] That is, the mechanism for obtaining the CO2 reduction effect is, as explained in Fig. 11, not to dare to produce a manganese-based alloy (ferromanganese) by reducing all the manganese contained in the manganese ore to metallic manganese only with sufficient carbon C (coke) in one step, but to hydrogen-reduce all the manganese in the manganese ore to manganese with a valence of less than 4, hydrogen-reduce to divalent manganese (manganese oxidation degree 1.0), or hydrogen-reduce to near divalent and then use part or all of it to reduce to metallic manganese to produce high-carbon ferromanganese and ultra-low-carbon ferromanganese. Therefore, by including the step (1) of heating and hydrogen-reducing the manganese ore to produce a reduced manganese ore and the step (2) of heating the reduced manganese ore to make a melt, ultimately, a method for producing ultra-low-carbon ferromanganese capable of reducing CO2 emissions compared to the carbon dioxide CO2 generated by the conventional ferromanganese production method can be achieved.

[0114] Figure 12 arranges the CO2 reduction effect based on the reaction formula in Figure 11 from the Mn grade of the manganese ore and the amount of Mn in the slag. That is, the reaction formula described in Figure 11 is transformed so as to obtain the desired Mn grade and the amount of Mn in the desired slag to be discharged, and the percentage of the corresponding reduction effect is derived by plotting. The CO2 reduction effect becomes larger when the Mn grade of the manganese ore is lower, and becomes larger as the amount of Mn in the slag is higher. Here, the condition that the CO2 reduction effect is 20% or more is preferable, more preferably 40% or more, still more preferably 50% or more, and most preferably 55% or more. According to an embodiment, the Mn grade of the manganese ore is 20% or more, 25% or more, 31% or more, 32% or more, 35% or more, 38% or more, 40% or more, 45% or more, or 46% or more. According to an embodiment, the Mn grade of the manganese ore is 80% or less, 68% or less, 60% or less, 55% or less, 54% or less, 50% or less, 49% or less, or 48% or less. According to an embodiment, the amount of Mn in the slag is 0.1% or more, 1% or more, 5% or more, 10% or more, 20% or more, 25% or more, 26% or more, 32% or more, 37% or more, 42% or more, or 47% or more. Thus, increasing the amount of manganese in the discharged slag (that is, reducing the production of high-carbon ferromanganese) increases the yield of extra-low-carbon ferromanganese and makes the carbon dioxide reduction effect more remarkable. According to an embodiment, the amount of Mn in the slag is 70% or less, 60% or less, 55% or less, 43% or less, 38% or less, 35% or less, 31% or less, 30% or less, or 29% or less.

[0115] Figure 13 arranges the production ratio of ultra-low carbon ferromanganese with respect to the total amount of ferromanganese based on the reaction formula in Figure 11 in terms of the Mn grade of the manganese ore and Mn in the slag. That is, the reaction formula described in Figure 11 is deformed so as to have a desired Mn grade and the amount of Mn in the desired slag to be discharged, and the percentage of the production ratio of ultra-low carbon ferromanganese with respect to the total amount of ferromanganese corresponding thereto is derived by plotting. The production ratio of ultra-low carbon ferromanganese increases as the Mn grade of the manganese ore is lower and increases as the amount of Mn in the slag is higher. As long as it is within the range where ultra-low carbon ferromanganese can be produced, any conditions are acceptable, but it is preferable that the production ratio of ultra-low carbon ferromanganese is higher. For example, the production ratio of ultra-low carbon ferromanganese is preferably 20% or more, more preferably 40% or more, and still more preferably 50% or more. Also, the preferable upper and lower limit values of the Mn grade of the manganese ore and the amount of Mn in the slag are applicable to the description in Figure 12.

[0116] From Figures 12 and 13, it can be seen that the greater the production ratio of ultra-low carbon ferromanganese, the greater the CO2 reduction effect (Figure 14). As can be seen from Figure 14, a production ratio of ultra-low carbon ferromanganese of 35% or more where the CO2 reduction effect is 20% or more is preferable, a production ratio of ultra-low carbon ferromanganese of 45% or more where the CO2 reduction effect is 30% or more is more preferable, and a production ratio of ultra-low carbon ferromanganese of 50% or more where the CO2 reduction effect is 24% or more is still more preferable.

[0117] In the above step (2) of heating the reduced manganese ore to form a melt, the case of using a conventional electric furnace has been described, but it may also be made into a melt by other methods. For example, electric heating by a tubular furnace, an arc furnace, etc., induction heating, various burner heating, heating by hydrogen combustion, etc., but a heating method that does not generate CO2 is preferred. That is, in electric heating and induction heating, it is preferable to use green power, and for the fuel of various burner heating, it is preferable to use hydrogen or green fuel. When specifically explaining the case of using a conventional electric furnace, a conventional submerged arc furnace or an equivalent electric furnace may be used. The inside of the furnace is mainly heated by electricity and is mainly used for the reduction of some reduced manganese ore to high-carbon ferromanganese by carbonaceous materials. As refining progresses in the electric furnace, molten slag and molten high-carbon ferromanganese are formed. Due to the difference in their specific gravities, the molten high-carbon ferromanganese is placed at the bottom of the furnace and the molten slag is placed on it. Therefore, depending on the tapping timing, the height of the tapping hole, etc., the slag and metal are separated and discharged from the electric furnace. The ferromanganese produced using carbonaceous materials in this way is high-carbon ferromanganese containing carbon, and in some cases, decarburization may be carried out using known methods according to the application.

[0118] As the temperature of step (2), 1200 °C or higher, 1300 °C or higher, or 1400 °C or higher is preferable. As the temperature of step (2), 1700 °C or lower, 1600 °C or lower, or 1550 °C or lower is preferable. As the time of step (2), any time sufficient to form a melt may be used. For example, 0.5 hours or more, 1.0 hours or more, or 2.0 hours or more. Also, as the time of step (2), 10 hours or less, 5 hours or less, or 3 hours or less. Regarding the conditions of hydrogen reduction in step (1), the embodiments of the manufacturing method of manganese-based alloys described above may be applied.

[0119] According to another aspect of the present invention, there is provided a method for producing ultra-low carbon ferromanganese, characterized by including a step (3) of heating and hydrogen-reducing manganese ore to form a melt. As the method for forming the melt in step (3), any method may be used. For example, it may be electric heating by a tubular furnace, an arc furnace, etc., induction heating, various burner heating, etc. However, a heating method that does not generate CO2 is preferred. That is, in electric heating and induction heating, it is preferable to use green power, and for the fuel of various burner heating, it is preferable to use hydrogen or green fuel. More preferably, it is a method of heating and hydrogen-reducing manganese ore using a hydrogen burner to form a melt.

[0120] Here, the manganese oxidation degree (Mn oxidation degree) will be described. When represented by the composition formula MnO x the value of x is the manganese oxidation degree. For example, when the manganese oxidation degree x = 2, it is MnO2, and when the manganese oxidation degree x = 1, it is MnO. Therefore, the manganese oxidation degree of manganese ore and reduced manganese ore is determined from the value of the total manganese amount (Mn%, JIS M8232 2005 Manganese Ore - Manganese Quantification Method) and the value of the available oxygen of manganese oxide (MnO2%, JIS M8233 1995 Manganese Ore - Active Oxygen Quantification Method) to MnO xDetermine x and use it as the manganese oxidation state. It is assumed that the manganese oxidation state in the reduced manganese ore is less than 2. However, the higher the manganese oxidation state, the smaller the CO2 reduction effect. In other words, the closer the manganese oxidation state is to 1.0, the greater the CO2 reduction effect. In order to ensure the production volume of the manganese-based alloy and obtain a more effective CO2 reduction effect, in step (1), it is preferable to use a reduced manganese ore with a manganese oxidation state of 1.5 or less, more preferably 1.5 or less, still more preferably 1.2 or less, and even more preferably 1.1 or less. When the manganese oxidation state of the manganese ore to be hydrogen-reduced is already less than 2.0, the manganese oxidation state of the reduced manganese ore should be less than that of the raw material manganese ore. According to a preferred embodiment, when the manganese oxidation state of the manganese ore is 100%, the manganese ore is reduced so that the manganese oxidation state is 80% or less, 75% or less, or 70% or less. Also, regardless of the manganese oxidation state of the raw material manganese ore, it is preferable to set the manganese oxidation state of the reduced manganese ore to 1.6 or less, 1.5 or less, 1.2 or less, 1.15 or less, or 1.1 or less. Regardless of the manganese oxidation state of the raw material manganese ore, it is preferable to set the manganese oxidation state of the reduced manganese ore to 1.6 or less, 1.5 or less, 1.2 or less, 1.15 or less, or 1.1 or less.

[0121] Regarding the hydrogen reduction of manganese ore, as long as it is a condition containing hydrogen, a reducing agent that becomes a CO2 generation source within the range where a CO2 reduction effect can be obtained, for example, CO or a carbon material, may be included. Of course, as described above, for example, when producing a part of high-carbon ferromanganese using a carbon material such as coke (for example, bio-coke) by heating the reduced manganese ore in an electric furnace to form a melt, the carbon monoxide CO generated can be recovered and used simultaneously with the hydrogen reduction to obtain a CO2 reduction effect.

[0122] Here, the reducing agent can be divided into a gas (gaseous) form and a solid form.

[0123] According to a preferred embodiment, the proportion of hydrogen in the gas of the reducing agent is 50 mol% or more, more preferably 70 mol% or more, even more preferably more than 70 mol%, even more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 99 mol% or more, and even more preferably 100 mol%. The proportion of CO in the gas of the reducing agent is 30 mol% or less, less than 30 mol%, 10 mol% or less, 5 mol% or less, 1 mol% or less, or 0 mol%.

[0124] According to a preferred embodiment, the amount (proportion) of the solid reducing agent (the reducing agent that becomes a CO2 source (for example, carbon material (coke))) relative to the manganese ore is 20 wt% or less, 10 wt% or less, 8 wt% or less, the impurity level, or 0 mass%. According to a preferred embodiment, the impurity level means that the amount of the reducing agent that becomes a CO2 source is 1000 wtppm or less. As described above, according to a preferred embodiment, the reducing agent does not contain CO or carbon material.

[0125] In addition, as gases other than the reducing agent in hydrogen reduction, nitrogen, water vapor, CO2, argon, helium, oxygen, nitrogen oxides, etc. may be included. The hydrogen content in hydrogen reduction is sufficient as long as it can reduce the manganese ore to the target oxidation degree. However, considering the supply amount of the hydrogen-containing gas corresponding to the treatment amount of the manganese ore, for example, in all gases (that is, the gas of the reducing agent and the gas other than the reducing agent), it is 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more. From the perspective of more efficient reduction, it may be set above 4 mol%. According to a preferred embodiment, it is 10 mol% or less, 9 mol% or less, 8 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, 3 mol% or less, or 2 mol% or less. As will be described later, according to a preferred embodiment, the temperature in hydrogen reduction is 200°C or higher, 300°C or higher, 400°C or higher, 500°C or higher, 600°C or higher, 700°C or higher, 800°C or higher, or 900°C or higher. Also, according to a preferred embodiment, the temperature in hydrogen reduction is 1200°C or lower, 1100°C or lower, 1000°C or lower, 900°C or lower, or less than 800°C. According to a preferred embodiment, the time of hydrogen reduction is 0.5 hours or more, 1.0 hour or more, or 2.0 hours or more. According to a preferred embodiment, the time of hydrogen reduction is 10 hours or less, 5 hours or less, or 3 hours or less.

[0126] According to a preferred embodiment, the introduction amount of the hydrogen-containing gas with respect to the amount of manganese ore is, as a guideline, 1.0 to 3.1 times, 1.05 to 1.9 times, or 1.1 to 1.4 times the amount of hydrogen required to reduce to the desired manganese oxidation degree.

[0127] When heating and hydrogen-reducing the manganese ore to form a melt, 1200°C or higher, above 1200°C, 1300°C or higher, 1400°C or higher, or 1500°C or higher is preferable. When heating and hydrogen-reducing the manganese ore to form a melt, 1700°C or lower, 1650°C or lower, or 1600°C or lower is preferable.

[0128] Manganese ions (Mn in the melt 2+, it produces ultra-low carbon ferromanganese by reducing (equivalent to MnO), and the reduction method can be any method, but a reduction method that minimizes carbon content in ferromanganese is preferred. For example, the heating in this embodiment is preferably heating by hydrogen combustion. For example, as one embodiment of the present invention, there is provided a method for producing ultra-low carbon ferromanganese, characterized by including a step (4) of reducing the melt with a non-carbon reducing agent for refining and then performing slag-metal separation. At this time, the reduced manganese ore and the reducing agent (e.g., bio-coke, non-carbon reducing agent) may be mixed to form a melt. That is, step (2) and step (4) may be performed simultaneously. The non-carbon reducing agent can reduce MnO (Mn 2+ ) to metallic Mn (Mn0) and does not mix (dissolve) carbon into the reduced ferromanganese. For example, examples of the non-carbon reducing agent include metallic silicon (metallic silicon) or its alloy, metallic aluminum or its alloy, metallic vanadium or its alloy, metallic titanium or its alloy, metallic magnesium or its alloy, metallic lithium or its alloy, etc. These non-carbon reducing agents may be combined to control the calorific value of the thermite reaction and simultaneously perform the reduction reaction and the formation of the melt.

[0129] From the perspective of productivity, it is preferred that the non-carbon reducing agent is a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum.

[0130] For the heating in step (1), any heating method is acceptable as long as it can heat the manganese ore to a temperature at which hydrogen reduction is possible, but a heating method that can reduce the carbon dioxide CO2 emission is more preferred. For example, from the perspective that electric heating in step (1) can reduce the carbon dioxide CO2 emission, it is preferred. Also, from the perspective that heating by hydrogen combustion in step (A) can reduce the carbon dioxide CO2 emission and the perspective that it can be performed simultaneously with hydrogen supply, it is preferred.

[0131] In the step (2), when making the melt in an electric furnace and simultaneously reducing a part of it with a carbonaceous material to form high-carbon ferromanganese, conventional coke may be used. However, by using green carbon for part or all of it, the effect of reducing carbon dioxide (CO2) can be further improved. The green carbon includes bio-carbon (carbonaceous materials derived from organisms such as charcoal and bamboo charcoal), coke made from waste plastics, carbonaceous materials derived from fuels obtained from hydrogen and carbon dioxide synthesized with renewable energy, green coke synthesized using renewable energy, and the like. Also, part or all of the carbonaceous material may be granulated together with reduced manganese ore and charged into the electric furnace as pellets with an internal carbonaceous material. By using pellets with an internal carbonaceous material as described above, the reduction reaction and gas escape in the electric furnace may become better, making stable operation easier and the carbonaceous material unit consumption may improve.

[0132] Also, the dust generated in the step (1) and the carbonaceous material may be granulated together and charged into the electric furnace as pellets with an internal carbonaceous material. Further, product crushing scraps of manganese-based alloys and ore fines of raw material manganese ore may be included in the pellets with an internal carbonaceous material. The above-mentioned pellets with an internal carbonaceous material are more effective when using green carbon, and the carbonaceous material used for the pellets with an internal carbonaceous material is preferably green carbon, which can make green carbon act more efficiently as a reducing agent.

[0133] As the granulation method for making pellets with an internal carbonaceous material, ordinary methods can be adopted, such as the pellet method, briquette method, extrusion molding method, and the like.

[0134] When forming the melt in the step (2), a slag-forming agent (slag conditioner) can be added. The slag-forming agent can control properties such as the viscosity, oxygen potential, and basicity of the slag. For example, it includes lime, slaked lime, Na2CO3, CaCl2, MgCO2, silica SiO2, and the like.

[0135] According to a preferred embodiment, a step (5) of refining a part or all of the melt in the step (2) or (3) by molten oxide electrolysis and then performing slag-metal separation may be provided. The molten oxide electrolysis is a method of electrolytically producing molten metal manganese (ferromanganese) by applying a voltage capable of reducing divalent manganese to zero-valent manganese (metallic manganese) by bringing two electrodes, an anode and a cathode, into contact with the melt. Here, the heat source for melting the reduced manganese ore can also be electric heating, using the Joule heat generated from the current flowing between the electrodes, or a separate heat source can be prepared. The ferromanganese produced without using a carbon material in this way can be obtained as ultra-low carbon ferromanganese containing almost no carbon.

[0136] As a manufacturing apparatus for ultra-low carbon ferromanganese that achieves the method for manufacturing ultra-low carbon ferromanganese as described above, it is provided with means (1) for heating and hydrogen-reducing manganese ore to produce reduced manganese ore, and means (2) for heating the reduced manganese ore to form a melt. Or, it is provided with means (3) for heating and hydrogen-reducing manganese ore to form a melt. Further, it is more preferable to use an ultra-low carbon ferromanganese manufacturing apparatus provided with means (4) for refining the melt produced in the step (2) or (3) by reduction with a non-carbon reducing agent and then performing slag-metal separation. Also, it is more preferable that the non-carbon reducing agent is a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum.

[0137] Furthermore, it is more preferable to use an ultra-low carbon ferromanganese manufacturing apparatus provided with means (5) for refining the melt by molten oxide electrolysis and then performing slag-metal separation.

[0138] The examples of the manufacturing method and the configuration flow of the manufacturing apparatus of the ultra-low carbon ferromanganese according to one aspect of the present invention are shown in FIGS. 15 to 16. FIG. 15 includes a step (1) or means (1) of reducing manganese ore (Mn ore) with hydrogen to obtain reduced manganese ore (reduced Mn ore), and a step (2) or means (2) of heating the reduced manganese ore to obtain a melt. In one aspect of the present invention, ultra-low carbon ferromanganese is produced from the melt. As described above, when melting the reduced manganese ore, it is also possible to include the production of high-carbon ferromanganese by partially reducing it using a carbonaceous material. In FIG. 15, as an example of the method for producing ultra-low carbon ferromanganese from the melt, a step (D) or means (D) of reducing manganese ions (Mn 2+ corresponding to MnO) in the melt to metallic manganese (Mn0) using a non-carbon reducing agent to produce ultra-low carbon ferromanganese, and a step (E) or means (E) of reducing manganese ions (Mn 2+ corresponding to MnO) in the melt to metallic manganese (Mn0) by molten oxide electrolysis to produce (Si,Al-reduced) ultra-low carbon ferromanganese are shown.

[0139] FIG. 16 is a configuration flow excluding the description of producing high-carbon ferromanganese by partially reducing it using a carbonaceous material from FIG. 15.

[0140] FIG. 17 shows a manufacturing method and a manufacturing apparatus of ultra-low carbon ferromanganese including a step (3) or means (3) of reducing manganese ore (Mn ore) with hydrogen to obtain a melt. As an example of obtaining ultra-low carbon ferromanganese from the melt, a step (4) or means (4) of reducing manganese ions (Mn 2+ corresponding to MnO) in the melt to metallic manganese (Mn0) using a non-carbon reducing agent to produce (Si,Al-reduced) ultra-low carbon ferromanganese, and a step (5) or means (5) of reducing manganese ions (Mn 2+ corresponding to MnO) in the melt to metallic manganese (Mn0) by molten oxide electrolysis to produce ultra-low carbon ferromanganese are shown.

[0141] The present invention includes the following aspects and forms.

[0142] 1. A method for producing an extra-low carbon manganese-based alloy, comprising a step (1) of carbon-reducing manganese ore or reduced manganese ore, then a step (2) of performing molten slag-metal separation, and a step (3) of reducing and refining the separated molten slag with a non-carbon reducing agent and then performing slag-metal separation.

[0143] 2. The method for producing an extra-low carbon manganese-based alloy according to 1., wherein the non-carbon reducing agent is a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum.

[0144] 3. The method for producing an extra-low carbon manganese-based alloy according to 1. or 2., wherein the method of reducing and refining with the non-carbon reducing agent is a method of refining by molten oxide electrolysis.

[0145] 4. The method for producing an extra-low carbon manganese-based alloy according to any one of 1. to 3., wherein the Mn amount in the separated slag is 10% to 29%.

[0146] 5. The method for producing an extra-low carbon manganese-based alloy according to any one of 1. to 4., wherein the production ratio of extra-low carbon ferromanganese to the total amount of ferromanganese production is 20% or more.

[0147] 6. The method for producing an extra-low carbon manganese-based alloy according to any one of 1. to 5., wherein the carbon used for the carbon reduction contains green carbon.

[0148] 7. An apparatus for producing an extra-low carbon manganese-based alloy, comprising means (1) for carbon-reducing manganese ore or reduced manganese ore, then means (2) for performing molten slag-metal separation, and means (3) for reducing and refining the separated molten slag with a non-carbon reducing agent and then performing slag-metal separation.

[0149] 8. The manufacturing apparatus of the extra-low carbon manganese-based alloy according to 7., wherein the non-carbon reducing material is a reducing material containing ferrosilicon alloy or metallic aluminum, or a reducing material containing ferrosilicon alloy and metallic aluminum.

[0150] 9. The manufacturing apparatus of the extra-low carbon manganese-based alloy according to 7. or 8., wherein the method of refining by reducing with the non-carbon reducing material is a method of refining by molten oxide electrolysis.

[0151] 10. The manufacturing apparatus of the extra-low carbon manganese-based alloy according to any one of 7. to 9., wherein the Mn content in the separated slag is 10% to 29%.

[0152] 11. The manufacturing apparatus of the extra-low carbon manganese-based alloy according to any one of 7. to 10., wherein the production ratio of the extra-low carbon ferromanganese to the total production amount of ferromanganese is 20% or more.

[0153] 12. The manufacturing apparatus of the extra-low carbon manganese-based alloy according to any one of 7. to 11., wherein the carbon used for the carbon reduction contains green carbon.

[0154] 13. A method for manufacturing a manganese-based alloy, comprising a step (1) of heating a manganese ore and subjecting it to hydrogen reduction to produce a reduced manganese ore.

[0155] 14. A method for manufacturing extra-low carbon ferromanganese, comprising a step (1) of heating and hydrogen-reducing a manganese ore to produce a reduced manganese ore, a step (2) of heating the reduced manganese ore to form a melt, or a step (3) of heating and hydrogen-reducing a manganese ore to form a melt.

[0156] 15. The method for manufacturing extra-low carbon ferromanganese according to 14., further comprising a step (4) of reducing and refining the melt with a non-carbon reducing material and then performing slag-metal separation.

[0157] 16. The method for producing ultra-low carbon ferromanganese according to 15., wherein the non-carbon reducing material is a reducing material containing ferrosilicon or metallic aluminum, or a reducing material containing ferrosilicon and metallic aluminum.

[0158] 17. The method for producing ultra-low carbon ferromanganese according to any one of 14. to 16., further comprising a step (5) of refining the melt by molten oxide electrolysis and then performing slag-metal separation.

[0159] 18. The method for producing ultra-low carbon ferromanganese according to any one of 14. to 17., wherein in the step (1), the manganese oxidation degree is reduced to 1.1 or less.

[0160] 19. The method for producing ultra-low carbon ferromanganese according to any one of 14. to 18., wherein the heating in at least one step selected from the group consisting of the step (1), the step (2), and the step (3) includes heating by hydrogen combustion.

[0161] 20. An apparatus for producing ultra-low carbon ferromanganese, comprising means (1) for heating and hydrogen-reducing manganese ore to produce reduced manganese ore, and means (2) for heating the reduced manganese ore to form a melt, or means (3) for heating and hydrogen-reducing manganese ore to form a melt.

[0162] 21. The apparatus for producing ultra-low carbon ferromanganese according to 20., further comprising means (4) for reducing and refining the melt with a non-carbon reducing material and then performing slag-metal separation.

[0163] 22. The apparatus for producing ultra-low carbon ferromanganese according to 21., wherein the non-carbon reducing material is a reducing material containing ferrosilicon or metallic aluminum, or a reducing material containing ferrosilicon and metallic aluminum.

[0164] 23. Further, the apparatus for producing ultra-low carbon ferromanganese according to any one of 20. to 22. is characterized by comprising means (5) for refining the melt by molten oxide electrolysis and then performing slag-metal separation.

[0165] 24. The method for producing a manganese-based alloy according to 13. is characterized by further including a step (6) of charging the reduced manganese ore into an electric furnace together with a carbonaceous material for refining and then performing slag-metal separation.

[0166] 25. The method for producing a manganese-based alloy according to 13. or 24. is characterized by further including a step (5) of refining part or all of the reduced manganese ore by molten oxide electrolysis and then performing slag-metal separation.

[0167] 26. The method for producing a manganese-based alloy according to any one of claims 13., 24., and 25. is characterized in that the manganese oxidation degree of the reduced manganese ore is 1.6 or less.

[0168] 27. The method for producing a manganese-based alloy according to 26. is characterized in that the manganese oxidation degree of the reduced manganese ore is 1.1 or less.

[0169] 28. The method for producing a manganese-based alloy according to any one of 13., 24. to 27. is characterized in that the proportion of hydrogen in the gas of the reducing agent in the hydrogen reduction exceeds 70 mol%.

[0170] 29. The method for producing a manganese-based alloy according to any one of 24. to 28. is characterized in that the Mn amount in the slag is 10% to 29%.

[0171] 30. The method for producing a manganese-based alloy according to any one of claims 1, 24. to 29. is characterized in that the heating includes electric heating or heating by hydrogen combustion.

[0172] 31. In the molten slag by-produced in the step (6), a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum is used to reduce at least a part of the manganese oxide contained in the molten slag in a step (7), and the method for producing a manganese-based alloy according to any one of 24. to 30. is characterized by including this.

[0173] 32. A part or all of the reduced manganese ore is reduced and refined with a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum, and then a step (8) of performing slag-metal separation is included, and the method for producing a manganese-based alloy according to any one of 13., 24. to 31. is characterized by including this.

[0174] 33. The method for producing a manganese-based alloy according to any one of 24. to 32., characterized in that a part or all of the carbon material is green carbon.

[0175] 34. A manufacturing apparatus for a manganese-based alloy, characterized by comprising means (1) for heating a manganese ore and subjecting it to hydrogen reduction.

Example

[0176] The production of manganese-based alloy iron will be described below.

[0177] The following shows an example of producing reduced manganese ore by heating manganese ores such as Gabon-produced manganese ore (Comilog) (manganese grade 52%) and South African-produced manganese ore (Assmang) (manganese grade 47%) and subjecting them to hydrogen reduction. Although industrial furnaces such as fluidized bed furnaces, shaft furnaces, and rotary kiln furnaces that can be heated and hydrogen-reduced are applied, experimentally, the manganese ore is reduced by heating in a tubular furnace and supplying a hydrogen-containing gas to obtain reduced manganese ore. As an example, Gabon-produced manganese ore (containing MnO₂) is placed in an alumina boat, charged into a tubular furnace, and heated at 900 °C for 1 hour while flowing 4 mol% hydrogen / nitrogen gas to obtain reduced manganese ore. When the manganese oxidation degree of the obtained reduced manganese ore is measured and calculated based on the above measurement methods (JIS M8232, JIS M8233), the manganese oxidation degree becomes 1.0. The same result is obtained when using South African-produced manganese ore (Assmang).

[0178] Also, when performing thermogravimetric analysis of the manganese ore while flowing a 4 mol% hydrogen / nitrogen mixed gas, a mass loss due to the reduction of manganese can be confirmed as shown in Fig. 18. A large weight loss starts from 200 °C or higher, but if heated to 500 - 600 °C or higher, it is considered that the manganese ore has started to be reduced. According to an embodiment, it may be heated to about 800 °C or higher and hydrogen-reduced. Increasing the temperature of hydrogen reduction makes it easier to reduce the manganese ore. For example, the reduction treatment time of the manganese ore is shortened, but if the temperature of hydrogen reduction is too high, the reduced manganese ores stick to each other (sintering or fusion solidification) and solidify, which may make it difficult to handle. From the above, the temperature of hydrogen reduction is preferably 1200 °C or lower, and more preferably 1100 °C or lower. According to an embodiment, the temperature of hydrogen reduction may be less than 800 °C.

[0179] As described above, a hydrogen concentration of 4 mol% is sufficient for hydrogen reduction, but it may be further increased to more than 4% for more efficient reduction. On the contrary, a hydrogen concentration of about 1 mol% can also sufficiently reduce, but considering the supply amount of the hydrogen-containing gas corresponding to the treatment amount of the manganese ore, 1% or more is preferred.

[0180] As an experimental example of more industrial hydrogen reduction, there is an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln. By introducing a mixed gas of 4 mol% hydrogen / nitrogen and heating the manganese ore in the test kiln for hydrogen reduction, reduced manganese ore can be obtained. For example, by treating at 900 °C for 1 hour, reduced manganese ore with a manganese oxidation degree of 1.1 can be obtained. By adjusting the introduction amount of the hydrogen-containing gas, the heating temperature, and the heating time with respect to the amount of the manganese ore, the manganese oxidation degree of the reduced manganese ore can be varied. The higher the manganese oxidation degree of the reduced manganese ore, the shorter the hydrogen reduction treatment time or the less hydrogen consumption is required, but the CO2 reduction effect becomes smaller. On the contrary, the closer the manganese oxidation degree of the reduced manganese ore is to 1.0 or 1.0, the greater the CO2 reduction effect becomes.

[0181] Next, an experiment of producing a manganese-based alloy by reducing the reduced manganese ore with a carbon material will be described. Industrially, the reduced manganese ore will be reduced with a carbon material using a submerged arc furnace or an electric furnace having an equivalent function, but here, the following experiment will be described.

[0182] The above reduced manganese ore and coke as the carbon material are refined in a 100 kVA Jiro furnace (single-phase arc furnace), tapped, and the molten metal and slag of the manganese-based alloy (ferromanganese) are separated and taken out to obtain the manganese-based alloy. Since the Jiro furnace is an open furnace, the amount of carbon monoxide CO (carbon dioxide CO2) generated cannot be measured, but it can be confirmed that a manganese-based alloy can be produced by reducing the reduced manganese ore with a carbon material, and since the oxygen content (manganese oxidation degree) of the reduced manganese ore as a raw material is small, the amount of carbon material required is small, so the CO2 reduction effect can be confirmed. The obtained manganese-based alloy (ferromanganese) satisfies JIS G 2301.

[0183] Further, a coke made of reduced manganese ore and a carbonaceous material is mixed, placed in a refractory container, and electrically heated to 1450 °C or higher while an inert carrier gas (nitrogen N2 or argon Ar) is circulated in a vertical tubular furnace. By measuring the concentration of carbon monoxide CO generated, the amount of CO2 generated by the reaction of the reduced manganese ore and the coke can be known. On the other hand, ordinary manganese ore and coke are reacted under the same conditions as above, and the amount of CO2 generated is compared. By these, the CO2 reduction effect of the present invention is experimentally clear.

[0184] In addition, in this example, Mn in the slag can be 20 to 33%. Also, the production amount of the manganese-based alloy can be 10 to 40%.

[0185] Next, the production of ultra-low-carbon ferromanganese will be described.

[0186] Examples of producing reduced manganese ore by heating and hydrogen-reducing manganese ores such as Gabon-produced manganese ore (Comilog) (manganese grade 52%) and South Africa-produced manganese ore (Assmang) (manganese grade 47%) are shown below.

[0187] The production of reduced manganese ore can be confirmed by thermogravimetric analysis of the manganese ore while flowing a 4 mol% hydrogen / nitrogen mixed gas. As shown in FIG. 18, a mass loss due to the reduction of manganese can be confirmed. A large weight loss has started from 200 °C or higher, but if it is heated to 500 to 600 °C or higher, it is considered that the manganese ore has started to be reduced. According to an embodiment, it may be heated to about 800 °C or higher and hydrogen-reduced. If the temperature of hydrogen reduction is increased, it becomes easier to reduce the manganese ore, and the reduction treatment time of the manganese ore can be shortened. According to an embodiment, the temperature of hydrogen reduction may be less than 800 °C.

[0188] It applies industrial furnaces such as fluidized bed furnaces, shaft furnaces, and rotary kiln furnaces that can be heated and hydrogen-reduced. Experimentally, a tubular furnace is used for heating and a hydrogen-containing gas is supplied to reduce manganese ore to reduced manganese ore. As an example, Gabon-produced manganese ore (containing MnO2) is placed in an alumina boat and charged into a tubular furnace, and heated at 700 to 1100 °C for 0.5 to 10 hours while flowing 4 mol% hydrogen / nitrogen gas to obtain reduced manganese ore. When the manganese oxidation degree of the obtained reduced manganese ore is measured and calculated based on the above-mentioned measurement methods (JIS M8232, JIS M8233), the manganese oxidation degree is 1.0 to 1.5 in the above temperature and time ranges. The same result is obtained when using South African-produced manganese ore (Assmang). The manganese oxidation degree becomes 1.1 or less when the temperature is 800 °C or higher for 1 hour or more.

[0189] When obtaining reduced manganese ore, if the temperature of hydrogen reduction is too high, the reduced manganese ores may stick to each other (sintering, fusion solidification) and solidify, which may make them difficult to handle. From the above, the temperature of hydrogen reduction is preferably 1200 °C or lower, more preferably 1100 °C or lower. The hydrogen concentration of hydrogen reduction is sufficient at 4 mol% as described above, but it may be more efficiently reduced at more than 4 mol%. On the contrary, sufficient reduction can also be achieved with a hydrogen concentration of about 1 mol%, but considering the supply amount of the hydrogen-containing gas corresponding to the treatment amount of manganese ore, 1 mol% or more is preferable.

[0190] As a more industrial experimental example of hydrogen reduction, an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln can be conducted. By introducing a 4 mol% hydrogen / nitrogen mixed gas and heating the manganese ore in the test kiln for hydrogen reduction, reduced manganese ore can be obtained. For example, when treated at 900 °C for 1 hour, reduced manganese ore with a manganese oxidation degree of 1.1 can be obtained. Regarding the introduction amount of the hydrogen-containing gas, heating temperature, and heating time with respect to the amount of the manganese ore By adjustment, the manganese oxidation degree of the reduced manganese ore can be made variable. The larger the manganese oxidation degree of the reduced manganese ore, the shorter the hydrogen reduction treatment time and the less hydrogen consumption are required, but the CO2 reduction effect becomes smaller. On the contrary, the smaller the manganese oxidation degree of the reduced manganese ore and the closer it is to 1.0, the greater the CO2 reduction effect becomes.

[0191] Next, an experiment of heating the reduced manganese ore to form a melt and an experiment of producing extra-low carbon ferromanganese from the melt will be described.

[0192] Industrially, one method is to arc-melt the reduced manganese ore using a submerged arc furnace or an electric furnace having an equivalent function. As other methods, there are methods of melting in a shaft furnace, a plasma melting furnace, a thermite melting furnace, a burner melting furnace, etc.

[0193] Here, the following experiments will be described.

[0194] Mix the reduced manganese ore and ferrosilicon as a non-carbon reducing material, put them into a refractory container, and electrically heat them to 1200°C to 1500°C while flowing an inert carrier gas (nitrogen N2 or argon Ar) in a vertical tubular furnace, and reduce them while forming a melt to obtain extra-low carbon ferromanganese. The obtained extra-low carbon ferromanganese has a carbon content with a low level of inevitable impurities because it is non-contact with carbon in the above process. When measuring the carbon content in the produced extra-low carbon ferromanganese with a carbon and sulfur analyzer (combustion-infrared absorption method), it is 0.2 mass% or less.

[0195] Also, mix the reduced manganese ore and ferrosilicon as a non-carbon reducing material, put them into a refractory container, heat them to 1200°C to 1500°C by induction heating, and reduce them while forming a melt to obtain extra-low carbon ferromanganese. The obtained extra-low carbon ferromanganese has a carbon content with a low level of inevitable impurities because it is non-contact with carbon in the above process. When measuring the carbon content in the produced extra-low carbon ferromanganese with a carbon and sulfur analyzer (combustion-infrared absorption method), it is 0.2 mass% or less.

[0196] Further, reduced manganese ore and charcoal as bio-coke are charged into a 100 kVA Jiro furnace (single-phase arc furnace) for smelting. After tapping, the molten high-carbon ferromanganese and slag (melt) are separated and taken out. Metal aluminum chips are added to the molten slag for reduction to obtain extra-low-carbon ferromanganese. When the carbon content of the obtained extra-low-carbon ferromanganese is measured in the same manner as the above method, it is 0.2 mass% or less.

[0197] Also, reduced manganese ore and ferrosilicon as a non-carbon reducing material are reduced while being arc-melted in a 100 kVA Jiro furnace (single-phase arc furnace). After tapping, the molten extra-low-carbon ferromanganese and slag are separated and taken out to obtain extra-low-carbon ferromanganese. When the carbon content of the obtained extra-low-carbon ferromanganese is measured in the same manner as the above method, it is 0.2 mass% or less.

[0198] When hydrogen reduction is carried out to directly obtain a melt, the temperature usually needs to be further increased compared with the above. For example, in a vertical tubular furnace, Gabon manganese ore is placed in a magnesia crucible and heated for reduction and melting while maintaining the temperature above the melting temperature while flowing a mixed gas of 4 mol% hydrogen / nitrogen. Specifically, a melt can be obtained by setting the temperature at 1200 °C or higher (or exceeding 1200 °C). Even when the maximum temperature of the vertical tubular furnace is set at 1500 °C, a melt can be obtained. When the manganese oxidation degree of the cooled and solidified melt is measured in the same manner as above, it is 1.1 or less. Also, when using manganese ore produced in South Africa (Assmang), the same result is obtained. The obtained melt is reduced in the same manner as the above method to obtain extra-low-carbon ferromanganese. When the carbon content of the obtained extra-low-carbon ferromanganese is measured in the same manner as the above method, it is 0.2 mass% or less.

Industrial Applicability

[0199] According to the present invention, it is possible to achieve a CO2 reduction effect in the production of manganese-based alloys, contribute to the suppression of global warming, and meet the requirements of carbon neutrality and zero CO2 emissions. Further, according to the present invention, it is possible to achieve a CO2 reduction effect in the production of extra-low carbon ferromanganese, contribute to the suppression of global warming, and meet the requirements of carbon neutrality and zero CO2 emissions.

Claims

1. A step (1) of carbon-reducing manganese ore or reduced manganese ore, subsequently a step (2) of performing molten slag-metal separation, and a step (3) of reducing and refining the separated molten slag with a non-carbon reducing agent and then performing slag-metal separation A method for producing an extra-low carbon manganese-based alloy, characterized by including the above steps.

2. The method for producing an extra-low carbon manganese-based alloy according to claim 1, wherein the non-carbon reducing agent is a reducing agent containing ferrosilicon or metallic aluminum, or a reducing agent containing ferrosilicon and metallic aluminum.

3. The method for producing an extra-low carbon manganese-based alloy according to claim 1 or 2, wherein the method of reducing and refining with the non-carbon reducing agent is a method of refining by molten oxide electrolysis.

4. The method for producing an extra-low carbon manganese-based alloy according to claim 1 or 2, wherein the Mn content in the separated slag is 10% to 29%.

5. The method for producing an extra-low carbon manganese-based alloy according to claim 1 or 2, wherein the production ratio of extra-low carbon ferromanganese to the total amount of ferromanganese production is 20% or more.

6. The method for producing an extra-low carbon manganese-based alloy according to claim 1 or 2, wherein the carbon used for the carbon reduction contains green carbon.

7. Means (1) for carbon-reducing manganese ore or reduced manganese ore, subsequently means (2) for performing molten slag-metal separation, and means (3) for reducing and refining the separated molten slag with a non-carbon reducing agent and then performing slag-metal separation An apparatus for producing an extra-low carbon manganese-based alloy, characterized by including the above means.

8. The apparatus for producing an extra-low carbon manganese-based alloy according to claim 7, wherein the non-carbon reducing agent is a reducing agent containing ferrosilicon or metallic aluminum, or a reducing agent containing ferrosilicon and metallic aluminum.

9. The apparatus for producing an extra-low carbon manganese-based alloy according to claim 7 or 8, wherein the method of reducing and refining with the non-carbon reducing agent is a method of refining by molten oxide electrolysis.

10. The apparatus for producing an extra-low carbon manganese-based alloy according to claim 7 or 8, wherein the Mn content in the separated slag is 10% to 29%.

11. The manufacturing apparatus of an extra-low carbon manganese-based alloy according to claim 7 or 8, characterized in that the production ratio of the extra-low carbon ferromanganese to the total amount of ferromanganese production is 20% or more.

12. The manufacturing apparatus of an extra-low carbon manganese-based alloy according to claim 7 or 8, characterized in that the carbon used for the carbon reduction contains green carbon.

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