Manufacturing method and apparatus for ultra-low carbon ferromanganese, and manufacturing method and apparatus for manganese alloy

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 manufacturing method of extremely low carbon ferromanganese comprises a step (1) of heating and hydrogen-reducing a manganese ore to produce a reduced manganese ore, and a step (2) of heating the reduced manganese ore to form a melt, or a step (3) of heating and hydrogen-reducing the manganese ore to form a melt.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] Manganese alloys, such as ferromanganese, are produced by heating manganese ore and a reducing agent such as coke in a blast furnace or electric furnace to reduce the manganese and iron in the ore. The blast furnace method uses coke as both the heat source and the reducing agent, while the electric furnace method basically uses electricity as the heat source and coke as the reducing agent.

[0004] Traditionally, technological developments in the production of manganese-based alloys have focused on how to produce them as efficiently as possible. For example, Patent Documents 1 and 2 disclose technologies in which a reducing agent such as a silicon-containing ferroalloy or metallic aluminum is added to further reduce and extract the manganese remaining in the slag. Patent Documents 3 to 6 also disclose technologies in which, rather than directly adding manganese ore to a blast furnace or electric furnace, manganese ore is pre-reduced with carbon monoxide (CO) gas or coke generated in the blast furnace or electric furnace process and then added to the blast furnace or electric furnace.

[0005] Furthermore, Non-Patent Document 1 mentions pre-treatments such as preheating and pre-reduction, which are being carried out against the backdrop of a shift from expensive electricity to cheap coal in the production of ferromanganese, and discloses a series of basic studies on each reduction reaction process using carbon monoxide and hydrogen gas as part of research on the reduction of manganese ore with carbon.

[0006] In the production of the above-mentioned manganese-based alloys, technological development has been carried out up to now from the viewpoint of how to produce manganese-based alloys as efficiently as possible.

[0007] The background art regarding 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, heating the mixture, and thereby reducing the manganese and iron in the ore. While the blast furnace method uses coke as both the heat source and the reducing agent, the electric furnace method basically uses electricity 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 the carbonaceous material such as coke used as the reducing agent, and is sometimes referred to as high-carbon ferromanganese. Medium-carbon ferromanganese and low-carbon ferromanganese are produced by decarburization and refining the high-carbon ferromanganese. One example of a decarburization and refining technique is a method in which oxygen gas is blown into molten high-carbon ferromanganese to oxidize and remove carbon from the molten metal (Patent Document 7).

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

[0010] Another method for producing ferromanganese with a low carbon content is the electrolytic method (Non-Patent Document 2). Manganese ore is reduced and roasted together with a carbonaceous material, and then the resulting solution is dissolved in sulfuric acid and purified, and then metallic manganese is electrodeposited onto the cathode in an electrolytic cell. Because no carbonaceous material is used in the reduction to produce metallic manganese, it is possible to produce metallic manganese that basically does not contain carbon.

[0011] In the production of ferromanganese as described above, technological development has been carried out up to now from the viewpoint of how to produce ferromanganese as efficiently as possible. For example, Patent Documents 3 to 6 disclose technologies in which, instead of directly charging manganese ore into a blast furnace or electric furnace, manganese ore is pre-reduced in advance with carbon monoxide (CO) gas or coke generated in the blast furnace process or electric furnace process, and then charged into the blast furnace or electric furnace.

[0012] Furthermore, Non-Patent Document 1 mentions pre-treatments such as preheating and pre-reduction, which are being carried out against the backdrop of a shift from expensive electricity to cheap coal in the production of ferromanganese, and discloses a series of basic studies on each reduction reaction process using carbon monoxide and hydrogen gas as part of research on the reduction of manganese ore with carbon. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-161079 [Patent Document 2] Japanese Patent Publication No. 59-222552 [Patent Document 3] Japanese Unexamined Patent Publication No. 63-195244 [Patent Document 4] Japanese Patent Application Publication No. 59-215458 [Patent Document 5] Special Publication No. 38-4456 [Patent Document 6] Special Publication No. 38-12811 [Patent Document 7] Japanese Patent Application Publication No. 11-293332 [Patent Document 8] Japanese Patent Application Publication No. 55-62141 [Patent Document 9] International Publication No. 2009-136684 [Non-patent literature]

[0014] [Non-Patent Document 1] Terayama Kiyoshi et al., Calorimetry 18(3), 164(1991) [Non-patent document 2] Yutaka Chikuta, Resources and Materials 109, 1091 (1993) Summary of the Invention [Problem to be solved by the invention]

[0015] The problems that the invention relating to manganese-based alloys aims to solve are described below.

[0016] As mentioned above, technological developments have been made to efficiently manufacture manganese-based alloys, but it was discovered that no attempts had been made to reduce CO2 emissions, assuming the use of carbonaceous materials such as coke as a reducing agent when reducing manganese ore.

[0017] In fact, Patent Documents 1 to 6 and other prior art documents related to the production of manganese-based alloys do not mention or suggest that technological development has been carried out with the aim of reducing CO2 emissions. Conventional technological developments related to the production of manganese-based alloys have indirectly reduced CO2 emissions to some extent by increasing efficiency, but no efforts have been made to reduce or eliminate the use of carbonaceous materials, which are a source of CO2, from the perspective of reducing CO2 emissions.

[0018] Furthermore, as shown in Non-Patent Document 1, for example, there has been basic research into the reduction behavior of manganese ore using reducing agents other than carbon, such as carbon monoxide and hydrogen, but in the process of reducing manganese metal to produce a manganese-based alloy, the only proposal has been to use natural gas for reduction using methane (CH4), and there has been no disclosure or suggestion regarding its use from the perspective of reducing CO2 emissions.

[0019] In addition, in the explanation of Figure 4 of Patent Document 4, surplus gas (coke-derived) from the ferromanganese furnace and the Si, Mn furnace is used to produce pre-reduced pellets, so the CO2 reduction effect of the present invention is not achieved. Patent Document 4 is thought to be effective in reducing the electricity consumption rate, but is not effective in reducing carbonaceous materials.

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

[0021] The problems that the invention relating to ultra-low carbon ferromanganese aims to solve are described below.

[0022] As mentioned above, conventional ferromanganese production is premised on the use of carbonaceous materials such as coke as a reducing agent to reduce manganese ore to produce ferromanganese, which results in ferromanganese that contains carbon, so decarburization is required to produce ultra-low carbon ferromanganese.Furthermore, from the perspective of being an environmentally friendly production method, the use of a reducing agent that generates CO2 means that it is not a production method that takes into consideration the reduction of CO2 emissions.

[0023] Furthermore, even when Patent Documents 1 to 9, Non-Patent Documents 1 and 2, and other prior art documents relating to the production of ferromanganese are examined, no technological development has been carried out with the aim of reducing CO2 emissions, and there is no mention or suggestion of such a goal. Conventional technological developments relating to the production of ferromanganese have indirectly reduced CO2 emissions to some extent by increasing efficiency, but no efforts have been made to reduce or eliminate the use of carbonaceous materials, which are a source of CO2, from the perspective of reducing CO2 emissions.

[0024] For example, as in Non-Patent Document 1, there has been basic research into the reduction behavior of manganese ore using reducing agents other than carbon, such as carbon monoxide and hydrogen, but this research has only led to a proposal to use natural gas (methane CH4) for reduction in the process of reducing manganese metal to produce ferromanganese, and there has been no disclosure or suggestion regarding its use from the perspective of reducing CO2 emissions.

[0025] Furthermore, with conventional technology, a large amount of CO2 is emitted in the process of producing high-carbon ferromanganese, which produces slag as a by-product. In other words, CO2 is emitted in the production of ultra-low-carbon ferromanganese.

[0026] On the other hand, when producing metallic manganese by electrolyzing manganese ions dissolved in an aqueous solution, reduction is done by electricity (it can also be said to be a non-carbon reducing agent), so at first glance it seems like a method of producing ultra-low carbon ferromanganese that does not emit CO2, but since manganese ore cannot be dissolved directly in sulfuric acid, the manganese ore must be reduced and roasted together with carbon material. In other words, when looking at the entire process, CO2 is emitted.

[0027] Therefore, the present inventors have found that it is necessary to develop technology that actively reduces CO2 emissions in the production of ultra-low carbon ferromanganese.

[0028] The present invention has been made in view of the above problems, and has an object to provide a method for producing a manganese-based alloy that enables a reduction in CO2 emissions in the production of the manganese-based alloy. Furthermore, the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a method and an apparatus for producing ultra-low carbon ferromanganese that enable a reduction in CO2 emissions in the production of ferromanganese. [Means for solving the problem]

[0029] A preferred embodiment 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 the step (1) of heating manganese ore and reducing it with hydrogen to produce reduced manganese ore.

[0031] 2. A method for producing ultra-low carbon ferromanganese, comprising the steps of: (1) heating manganese ore and reducing it with hydrogen to produce reduced manganese ore; and (2) heating the reduced manganese ore to form a molten material; or (3) heating manganese ore and reducing it with hydrogen to form a molten material.

[0032] 3. The method for producing ultra-low carbon ferromanganese according to 2., further comprising the step (4) of reducing the molten material with a non-carbon reducing agent to carry out refining, followed by slag-metal separation.

[0033] 4. The method for producing ultra-low carbon ferromanganese according to 3, wherein the non-carbon reducing material is a reducing material containing a silicon-containing ferroalloy or metallic aluminum, or a reducing material containing a silicon-containing ferroalloy 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 molten product by molten oxide electrolysis, followed by slag-metal separation.

[0035] 6. The method for producing ultra-low carbon ferromanganese according to any one of 2. to 5., wherein in the 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., wherein 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 manganese ore and reducing it with hydrogen to produce reduced manganese ore; and means (2) for heating the reduced manganese ore to form a molten material; or means (3) for heating manganese ore and reducing it with hydrogen to form a molten material.

[0038] 9. The apparatus for producing ultra-low carbon ferromanganese according to 8., further comprising means (4) for reducing the molten material with a non-carbon reducing agent to perform refining, followed by slag / metal separation.

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

[0040] 11. The apparatus for producing ultra-low carbon ferromanganese according to any one of items 8 to 10, further comprising means (5) for refining the molten material by molten oxide electrolysis and then separating the slag from the metal.

[0041] 12. The method for producing a manganese-based alloy according to claim 1, further comprising the step (6) of charging the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, followed by separating the slag from the metal.

[0042] 13. A method for producing a manganese-based alloy according to 1. or 12., further comprising step (5) of refining a part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag-metal separation.

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

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

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

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

[0047] 18. A method for producing a manganese-based alloy according to any one of 1. and 12. to 17., characterized in that the heating includes electrical heating or heating by hydrogen combustion.

[0048] 19. A method for producing a manganese-based alloy according to any one of items 12 to 18, characterized in that it comprises step (7) of reducing at least a portion of the manganese oxide contained in the molten slag by-produced in step (6) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum.

[0049] 20. A method for producing a manganese-based alloy according to any one of 1. and 12. to 19., characterized in that it comprises a step (8) of reducing a part or all of the reduced manganese ore with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum, to carry out refining, followed by slag-metal separation.

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

[0051] 22. An apparatus for producing manganese-based alloys, comprising means (1) for heating manganese ore and reducing it with hydrogen. [Effects of the Invention]

[0052] The method for producing a manganese-based alloy of the present invention has the effect of significantly reducing CO2 emissions during the production of a manganese-based alloy by hydrogen reduction of manganese ions contained in manganese ore.Furthermore, the production apparatus of the present invention has the effect of significantly reducing CO2 emissions during the production of a manganese-based alloy, or even reducing CO2 emissions to almost zero.

[0053] The method for producing ultra-low carbon ferromanganese of the present invention has the effect of significantly reducing CO2 emissions during the production of ultra-low carbon ferromanganese by hydrogen reduction of manganese ions contained in manganese ore. Furthermore, the production apparatus of the present invention has the effect of significantly reducing CO2 emissions during the production of ultra-low carbon ferromanganese, or even reducing CO2 emissions to almost zero. [Brief explanation of the drawings]

[0054] [Figure 1] Temperature dependence of Gibbs free energy ΔG (chemical potential) of each reaction [Figure 2] CO2 reduction effect when hydrogen reduction is introduced in the production of manganese ore (MnO2) and simplified manganese alloys [Figure 3] This diagram explains why, when manganese ore is reduced with carbon, it is not possible to produce a manganese alloy with an increased Mn yield by reducing the Mn content in the slag to zero. [Figure 4] The CO2 reduction effect was calculated based on the assumption that 40% of the Mn content of manganese ore containing 50% Mn is produced as metallic manganese (manganese alloy), and 30% Mn-containing slag (30% Mn in the slag) is discharged. [Figure 5] The CO2 reduction effect was calculated based on the assumption that 40% of the Mn content is produced as metallic manganese (manganese alloy) from manganese ore containing 50% Mn, and slag containing 30% Mn (30% Mn in the slag) is discharged (each step is combined into one reaction formula). [Figure 6] Effect of Mn grade of manganese ore and Mn content in slag on CO2 reduction effect [Figure 7] Effect of manganese alloy production volume and Mn content in slag on CO2 reduction effect [Figure 8] Effect of the degree of manganese ore reduction by hydrogen reduction (Mn oxidation degree of reduced Mn ore) on CO2 reduction effect [Figure 9] Conventional manganese alloy manufacturing equipment configuration flow [Figure 10]Configuration flow of the manganese-based alloy manufacturing apparatus of the present invention [Figure 11] Calculation example of CO2 reduction effect when manganese ore with 50% Mn content is hydrogen-reduced and melted in an electric furnace to produce high-carbon ferromanganese and ultra-low-carbon ferromanganese. [Figure 12] Effect of Mn grade of manganese ore and Mn content in slag on CO2 reduction effect [Figure 13] Effect of Mn grade of manganese ore and Mn content in slag on the production rate of ultra-low carbon ferromanganese [Figure 14] Relationship between CO2 reduction effect and ultra-low carbon ferromanganese production rate [Figure 15] Example 1 of the configuration flow of the ultra-low carbon ferromanganese manufacturing apparatus of the present invention [Figure 16] Example 2 of the configuration flow of the ultra-low carbon ferromanganese manufacturing apparatus of the present invention [Figure 17] Example 3 of the configuration flow of the ultra-low carbon ferromanganese manufacturing apparatus of the present invention [Figure 18] Confirmation of hydrogen reduction of manganese ore by thermogravimetric changes. DETAILED DESCRIPTION OF THE INVENTION

[0055] The method for producing the manganese-based alloy of the present invention will be described below.

[0056] The present invention is not limited to the following embodiments. In this specification, the range "X to Y" means "X or more and Y or less." Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20 to 25°C) and a relative humidity of 40 to 50%RH. In this specification, "%" refers to mass % (weight %) except in specific cases (for example, "mol % (volume %)." The embodiments of the method for producing a manganese-based alloy and the embodiment of the method for producing ultra-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, comprising the step (1) of heating manganese ore and reducing it with hydrogen to produce reduced manganese ore.

[0058] The raw material for manganese alloys, for example, manganese ore, is usually tetravalent manganese (equivalent to MnO2). When a carbonaceous material such as coke is used as a reducing agent together with manganese ore and the tetravalent manganese (ore) is reduced to zerovalent metallic manganese (manganese alloy) by charging it into an electric furnace, a considerable amount of carbon dioxide is emitted, even if the reduction reaction occurs theoretically efficiently.

[0059] Here, the inventors looked at the reduction of manganese ore from a thermodynamic perspective and determined that the reducing agents that can reduce tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO) are carbon (C), carbon monoxide (CO), hydrogen (H2), etc. (Figure 1). Only carbon (C) can reduce divalent manganese (equivalent to MnO) to zerovalent manganese (metallic Mn) (Figure 1). Even carbon (C) can be reduced to metallic manganese only at temperatures of 1450°C or higher.

[0060] Next, let's consider the CO2 reduction effect when manganese ore is reduced with hydrogen in the process of producing manganese-based alloys, simplifying manganese ore to MnO2 (Figure 2). Even if a reducing agent that does not generate CO2, such as hydrogen, is used to reduce tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO), as mentioned above, only carbon (C) can reduce divalent manganese (equivalent to MnO) to zerovalent manganese (metallic Mn), so one mole of carbon (C) is required to produce one mole of metallic Mn from manganese (Mn), and the CO2 reduction effect is zero.

[0061] As such, even if manganese ore is reduced using hydrogen, the CO2 reduction effect is considered to be zero in the first place, and furthermore, there are expected disadvantages such as the possibility that new devices and facilities may be required, so those skilled in the art have not thought of using hydrogen for pre-reduction.

[0062] In response to this, the present inventors discovered that if the Mn content in the slag discharged from manganese ore is set to, for example, around 30% and manganese-based alloys (particularly ferromanganese) are produced, the effect of reducing CO2 emissions by preliminarily reducing the manganese ore with hydrogen can be achieved. In this way, the inventors came up with the idea that CO2 emissions can be actively reduced by reducing manganese to less than tetravalent manganese with hydrogen, leading to the present invention. Note that the form of Mn in the slag is Mn 2+ It is believed that Mn is dispersed as a solid solution of ions and / or as MnO oxide. The form of existence can be observed using an electron microscope.

[0063] In a preferred embodiment, when reducing manganese ore with carbon, the reduction is not performed until the Mn content in the slag reaches zero. The reason for this is as follows: Since manganese ore contains slag components (silica SiO2, silicates), i.e., in the presence of MnO-SiO2, reactions (1) and (2) in Figure 3 occur. Therefore, the relationship shown in Equation (4) can be derived from the equilibrium equation of Equation (3), which is calculated by multiplying Equation (1) by Equation (2) and subtracting Equation (1) from Equation (2). Equation (4) indicates that to decrease the [MnO] concentration, i.e., to increase the Mn yield, increase the [Si] concentration. This results in a relationship between the amount of Mn in the slag and the Si content in the manganese-based alloy (Si in FMn), as shown in the graph. If the Mn content in the slag is reduced to increase the Mn yield too much, the resulting manganese-based alloy will contain too much Si. Therefore, to produce a manganese-based alloy from manganese ore without increasing the Si content too much, it is recommended to set the amount of Mn in the slag to, for example, around 30%.

[0064] The inventors have found that by employing these techniques, prior hydrogen reduction of manganese ore can reduce CO2 emissions (Figures 4 and 5). Figure 4 shows an example of a model in which 40% of the Mn content of manganese ore (with a Mn content of 50%) is converted into metallic manganese (manganese alloy) and 30% Mn-containing slag (30% Mn in the slag) is discharged. First, all of the manganese (50%) contained in the manganese ore is reduced to MnO. Current coke reduction methods using electric furnaces use a mixture of carbon (C) and carbon monoxide (CO) in a ratio of 0.3:0.4 as reducing agents. The carbon monoxide (CO) is generated by the reaction of the carbon (C) required to produce 50% of metallic manganese (manganese alloy) from MnO. Therefore, 0.7 moles of CO2 are produced for every mole of MnO2.

[0065] In contrast, when hydrogen reduction is used to reduce manganese ore to MnO, the manganese (50%) contained in the manganese ore does not generate CO2 during the process. In other words, when hydrogen reduction is used to reduce MnO2 to MnO, all of the manganese contained in the manganese ore is reduced to MnO, but no CO2 is generated during the process. 40% of the manganese in the hydrogen-reduced manganese ore is reduced to metallic manganese (manganese alloy) using coke (carbon), generating carbon monoxide (CO) in an amount commensurate with the carbon content. The generated carbon monoxide (CO) is combusted (reacted with oxygen (O2)) and emitted as carbon dioxide (CO2). Therefore, 0.4 moles of CO2 are generated for every mole of MnO2.

[0066] Therefore, in the above model, hydrogen reduction to MnO will result in a 43% CO2 reduction compared to the amount of CO2 generated in the current electric furnace reaction. Note that Figure 5 shows each reaction as a single reaction formula.

[0067] In other words, as explained in Figure 3, the mechanism by which the CO2 reduction effect is achieved is to reduce all of the manganese contained in manganese ore to metallic manganese so as not to produce a manganese-based alloy, but to reduce all of the manganese in the manganese ore with hydrogen to manganese less than tetravalent, or to divalent manganese (manganese oxidation degree 1.0), or to reduce manganese ore with hydrogen to nearly divalent manganese, and then reduce some or all of that to metallic manganese to produce a manganese-based alloy.

[0068] Therefore, by including the step (1) of heating manganese ore to convert it into reduced manganese ore by hydrogen reduction, it is possible to provide a method for producing a manganese-based alloy that can reduce CO2 emissions compared to the carbon dioxide CO2 generated in conventional methods for producing manganese-based alloys.

[0069] According to an embodiment of the present invention, a process (1) of heating manganese ore to reduce it with hydrogen to form reduced manganese ore is combined with a process (6) of refining the reduced manganese ore together with a carbonaceous material in an electric furnace, followed by slag-metal separation. Steps (1) and (6) may be performed in the same reactor or in separate reactors. The separate reactors may be connected or not directly connected. As mentioned above, this embodiment is also applicable to an embodiment of producing ultra-low carbon ferromanganese.

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

[0071] The CO2 reduction effect in the embodiment of the present invention is due to the above-mentioned CO2 reduction mechanism, and therefore has the relationship shown in Figure 6. Figure 6 was derived by plotting the corresponding percentage reduction effect by modifying the reaction equation shown in Figure 4 to achieve the desired Mn grade in the ore and the desired Mn amount in the slag. That is, with regard to the Mn grade (Mn content) of the manganese ore, the lower the Mn grade, the higher the CO2 reduction effect. In other words, the higher the Mn grade, the lower the CO2 reduction effect. Furthermore, with respect to the amount of Mn remaining in the discharged slag, the higher the CO2 reduction effect. In other words, the lower the Mn amount in the slag, the lower the CO2 reduction effect. The process (1) of heating manganese ore to hydrogen-reduce it into reduced manganese ore can achieve a CO2 reduction effect. However, as described above, the CO2 reduction effect varies depending on the Mn grade of the manganese ore and the Mn amount in the slag. Generally speaking, the more efficiently a manganese-based alloy is produced from manganese ore, the lower the CO2 reduction effect. Therefore, from the viewpoint of ensuring a certain level of productivity and achieving a CO2 reduction effect, it is preferable to set the Mn content of the manganese ore to, for example, 40 to 60%. Within this range, a CO2 reduction effect of approximately 20 to 70% can be achieved. According to one embodiment, the Mn content 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 one embodiment, the Mn content 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] In some embodiments, the Mn content in the discharged 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. In some embodiments, the Mn content in the slag is 35% or less, 31% or less, 30% or less, or 29% or less.

[0073] FIG. 7 shows the influence of the manganese alloy production amount (the ratio of manganese ore to manganese alloy (ferromanganese), Mn / Mn ore-%) on the CO2 reduction effect. FIG. 7 was derived by plotting the corresponding reduction effect percentages while modifying the reaction formula shown in FIG. 4 to achieve the desired Mn content in the slag and the desired manganese production amount (manganese production ratio). A similar trend to that shown in FIG. 6 can be seen in FIG. 7. According to a preferred embodiment, the manganese alloy production amount is 5 to 50%, 5 to 40%, or 10 to 30%.

[0074] Here, the manganese oxidation degree (Mn oxidation degree) will be explained. x The value of x is the manganese oxidation degree, for example, manganese oxidation degree x=2 is MnO2, and manganese oxidation degree x=1 is MnO. Therefore, the manganese oxidation degree of manganese ore or reduced manganese ore can be calculated from the total manganese content (Mn%, JIS M8232 2005 Manganese ore - Manganese determination method) and the available oxygen content of manganese oxide (MnO2%, JIS M8233 1995 Manganese ore - Active oxygen determination method) to obtain MnO. x Calculate x and use this as the degree of manganese oxidation.

[0075] Figure 8 shows the effect of the degree of reduction of manganese ore by hydrogen reduction, i.e., the manganese oxidation degree of reduced manganese ore, on the CO2 reduction effect. Figure 8 was derived by plotting the corresponding percentage reduction effect as a percentage, while modifying the reaction equation shown in Figure 4 to achieve the desired oxidation degree, desired Mn content, and desired Mn content in the slag. While the manganese oxidation degree in reduced manganese ore is assumed to be less than 2, as shown in Figure 8, the higher the manganese oxidation degree, the smaller the CO2 reduction effect. In other words, the lower the manganese oxidation degree (approaching 1.0), the greater the CO2 reduction effect. To ensure the production volume of manganese-based alloys and achieve more effective CO2 reduction effects, it is preferable to reduce the manganese ore in step (1) to a manganese oxidation degree of 1.6 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and even more preferably 1.1 or less. If the manganese oxidation degree of the manganese ore to be reduced with hydrogen is already less than 2.0, the manganese oxidation degree of the reduced manganese ore is set to be less than that of the raw manganese ore. According to a preferred embodiment, the manganese ore is reduced so that the manganese oxidation degree is 80% or less, 75% or less, or 70% or less, when the manganese oxidation degree of the manganese ore is taken as 100%. Furthermore, regardless of the manganese oxidation degree of the raw manganese ore, it is preferable to set the manganese oxidation degree 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.

[0076] Regarding hydrogen reduction of manganese ore, as long as the conditions are hydrogen-containing, reducing materials that are CO2 generating sources, such as CO or carbonaceous materials, may be included within the range in which CO2 reduction effects can be achieved.

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

[0078] According to a preferred embodiment, the proportion of hydrogen in the reducing agent gas 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 reducing agent gas 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 (ratio) of the solid reducing material (reducing material that serves as a CO2 generation source (e.g., carbonaceous material (coke)) relative to the manganese ore) is 20% by weight or less, 10% by weight or less, 8% by weight or less, impurity level, or 0% by mass. According to a preferred embodiment, the impurity level means that the amount of the reducing material that serves as a CO2 generation source is 1000 ppm by weight or less. As described above, according to a preferred embodiment, the reducing material does not contain CO or carbonaceous material.

[0080] Gases other than the reducing agent used in hydrogen reduction may include nitrogen, water vapor, CO2, argon, helium, oxygen, nitrogen oxides, etc. The hydrogen content in hydrogen reduction is sufficient as long as it can reduce manganese ore to the desired oxidation level. However, considering the supply amount of hydrogen-containing gas corresponding to the amount of manganese ore to be processed, the hydrogen content is, for example, 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more of all gases (i.e., reducing agent gas and gases other than reducing agent). From the viewpoint of more efficient reduction, it may be set to more than 4 mol%. According to a preferred embodiment, the hydrogen content 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 the 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. Furthermore, according to a preferred embodiment, the temperature in the hydrogen reduction is 1200°C or lower, 1100°C or lower, 1000°C or lower, 900°C or lower, or lower than 800°C. According to a preferred embodiment, the time for the hydrogen reduction is 0.5 hours or longer, 1.0 hour or longer, or 2.0 hours or longer. According to a preferred embodiment, the time for the hydrogen reduction is 10 hours or shorter, 5 hours or shorter, or 3 hours or shorter.

[0082] According to a preferred embodiment, the amount of the hydrogen-containing gas introduced relative 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 manganese to a desired oxidation level.

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

[0084] According to a preferred embodiment, when hydrogen reduction is performed to MnO, a CO2 reduction effect of preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more can be achieved relative to the amount of CO2 generated in the current electric furnace reaction shown in FIG.

[0085] According to a preferred embodiment, as described above, the reduced manganese ore prepared in step (1) is introduced into an electric furnace together with a carbonaceous material for refining, followed by step (6) of slag-metal separation to produce a manganese-based alloy. The electric furnace may be a conventional submerged arc furnace or an equivalent. It is heated primarily by electricity and is used primarily by a carbonaceous material to reduce the reduced manganese ore to metallic manganese (manganese-based alloy). As refining progresses 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 positioned at the bottom of the furnace and the molten slag is positioned above it. Depending on the timing of tapping and the height of the tap opening, the slag and metal are separated and discharged from the electric furnace. The manganese-based alloy produced using the carbonaceous material in this way yields carbon-containing ferromanganese, which may then be decarburized depending on the intended use. This embodiment is schematically illustrated in the upper flow chart of Figure 10.

[0086] According to a preferred embodiment, a step (5) may be provided in which a portion or all of the reduced manganese ore produced in step (1) is refined by molten oxide electrolysis, followed by slag-metal separation. The molten oxide electrolysis involves melting the reduced manganese ore, placing two electrodes (an anode and a cathode) in contact with the molten material, and applying a voltage sufficient to reduce divalent manganese to zerovalent manganese (metallic manganese), thereby producing molten metallic manganese (manganese-based alloy). The heat source for melting the reduced manganese ore can be electric heating, utilizing Joule heat generated by the current flowing between the electrodes, or a separate heat source. Manganese-based alloys produced in this way without using carbonaceous materials can be ferromanganese or metallic manganese with almost no carbon content. This embodiment is schematically illustrated in the middle flow chart of Figure 10.

[0087] The heating in step (1) may be performed by any heating method as long as it can heat the manganese ore to a temperature at which it can be reduced with hydrogen, but a heating method that can reduce carbon dioxide (CO2) emissions is more preferable. For example, electric heating is preferable from the viewpoint of reducing carbon dioxide (CO2) emissions. Furthermore, heating by hydrogen combustion in step (1) is preferable from the viewpoint of reducing carbon dioxide (CO2) emissions and from the viewpoint of being able to perform heating simultaneously with hydrogen supply.

[0088] Furthermore, if the process includes a step (7) of producing a manganese-based ferroalloy by reducing at least a portion of the manganese oxide contained in the molten slag by-produced in step (6) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or with a reducing agent containing both a silicon-containing ferroalloy and metallic aluminum, the manganese remaining in the slag can be recovered, thereby improving productivity. In this way, manganese-based alloys produced from Mn-containing slag without using a carbonaceous material can be obtained, such as ferromanganese or metallic manganese, which contain almost no carbon. This embodiment is schematically shown in the lower flow chart of Figure 10.

[0089] The carbonaceous material in step (6) may be conventional coke, but using green carbon for part or all of it will improve the carbon dioxide reduction effect. Examples of green carbon include biocarbon (biologically derived carbonaceous materials such as charcoal and bamboo charcoal), coke made from waste plastics, fuel-derived carbonaceous materials obtained from hydrogen and carbon dioxide synthesized using renewable energy, and green coke synthesized using renewable energy.

[0090] In addition, a part or all of the carbonaceous material in the step (6) may be granulated together with the reduced manganese ore prepared in the step (1) to form carbonaceous material-containing pellets, which are then charged into an electric furnace. By forming such carbonaceous material-containing pellets, the reduction reaction and gas release in the electric furnace may be improved, which may facilitate stable operation and improve the carbonaceous material consumption rate.

[0091] The dust and the carbonaceous material generated in the step (1) may be granulated together to form carbonaceous material-containing pellets, which are then charged into an electric furnace. Furthermore, crushed manganese alloy products and manganese ore fines may be added to the carbonaceous material-containing pellets.

[0092] The above-mentioned carbonaceous material-containing pellets are more effective when green carbon is used, and when the carbonaceous material used in the carbonaceous material-containing pellets is green carbon, the green carbon can act as a reducing agent more efficiently.

[0093] As a method for granulating the carbonaceous material into pellets, a conventional method can be used, such as a pellet method, a briquette method, an extrusion molding method, etc.

[0094] In step (6), a slag former (slag conditioner) can be added to the electric furnace. The slag former controls the viscosity, oxygen potential, basicity, and other properties of the slag. Examples of such slag formers include lime, slaked lime, Na2CO3, CaCl2, and MgCO2.

[0095] It is also possible to produce manganese-based ferroalloys by reducing part or all of the reduced manganese ore produced in step (1) with a reducing agent containing silicon-containing ferroalloys or metallic aluminum, or with both a reducing agent containing silicon-containing ferroalloys and metallic aluminum, followed by slag-metal separation in step (8).Manganese-based alloys produced from Mn-containing slag without using a carbonaceous material in this way yield ferromanganese or metallic manganese that contains almost no carbon.

[0096] An apparatus for producing a manganese-based alloy that achieves the above-described method for producing a manganese-based alloy comprises means (1) for heating manganese ore and reducing it with hydrogen to produce reduced manganese ore, and means (6) for feeding the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, followed by separating the slag from the metal.

[0097] Furthermore, it is more preferable that the apparatus for producing a manganese-based alloy is provided with a means (5) for refining a part or all of the reduced manganese ore produced in the step (1) by molten oxide electrolysis, followed by slag-metal separation.

[0098] Furthermore, it is more preferable that the apparatus for producing a manganese-based alloy comprises means (7) for producing a manganese-based ferroalloy by reducing at least a portion of the manganese oxide contained in the molten slag by-produced in the means (6) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or with both a silicon-containing ferroalloy and a reducing agent containing metallic aluminum.

[0099] A method for producing ultra-low carbon ferromanganese according to one embodiment of the present invention will now be described.

[0100] In one aspect of the present invention, there is provided a method for producing ultra-low carbon ferromanganese, comprising: a step (1) of heating manganese ore and reducing it with hydrogen to produce reduced manganese ore; and a step (2) of heating the reduced manganese ore to form a molten material.

[0101] The raw material for ferromanganese, for example manganese ore, is usually tetravalent manganese (equivalent to MnO2). When manganese ore is fed into an electric furnace together with a carbonaceous material such as coke as a reducing agent to reduce the tetravalent manganese (ore) to zerovalent metallic manganese (ferromanganese), a considerable amount of carbon dioxide is emitted, even if the reduction reaction occurs theoretically efficiently.

[0102] Here, the inventors looked at the reduction of manganese ore from a thermodynamic perspective and determined that the reducing agents that can reduce tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO) are carbon (C), carbon monoxide (CO), hydrogen (H2), etc. (Figure 1). Only carbon (C) can reduce divalent manganese (equivalent to MnO) to zerovalent manganese (metallic Mn) (Figure 1). Furthermore, carbon (C) can only be reduced to metallic manganese at temperatures above 1450°C.

[0103] Therefore, in order to produce ferromanganese by reducing manganese ore to metallic manganese, it is common sense to think of using a carbon reducing agent such as coke as the reducing agent, and it is expected that an additional process will be required for hydrogen reduction, so the idea of using hydrogen, which cannot be used to reduce manganese to metallic manganese, has not been thought of until now.

[0104] However, in the production method of ultra-low carbon ferromanganese, the inventors discovered a new problem of considering the effect of reducing CO2 emissions, and came up with the idea of reducing manganese ore with hydrogen as much as possible.

[0105] In one embodiment of the present invention, one method for producing a melt in the step (2) of heating the reduced manganese ore is arc melting in an electric furnace (e.g., a single-phase arc furnace, a submerged arc furnace, or a submerged arc furnace). 2+) to produce ultra-low carbon ferromanganese, but it is also possible to convert some of the manganese ore into high carbon ferromanganese by adding a carbonaceous material such as coke (e.g., bio-coke) to the electric furnace. An example is shown in FIG. 11. Manganese ore with a manganese content of 50% is reduced to manganese ore (manganese oxidation degree = 1.0) in step (1), and then carbonaceous material is added to the electric furnace to produce 50% high carbon ferromanganese. Ultra-low carbon ferromanganese is then produced from the molten material (molten slag) with a slag manganese content of 47%. Under these conditions, the same amounts of high carbon ferromanganese and ultra-low carbon ferromanganese can be produced from manganese ore, and the CO2 reduction effect during this process is 33%. This CO2 reduction effect is based on the assumption that no hydrogen reduction is performed and that the slag contains 47% Mn from manganese ore with a Mn content of 50% in a current electric furnace. However, if the slag contains 30% Mn (minimizing the amount of Mn in the slag), the CO2 reduction effect is 44%. To explain Figure 11 in more detail, in Figure 11, first, all of 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 moles of carbon (C) (coke) are used as the reducing agent for 1 mole of MnO2. Here, carbon monoxide (CO) is generated by the reaction of carbon (C), which is necessary to produce 50% of metallic manganese (ferromanganese) from MnO. Therefore, 0.75 moles of CO2 are generated for 1 mole of MnO2, and the slag contains Mn. 2+ 0.50 moles of MnO remain. Ultra-low carbon ferromanganese can be produced from the Mn in this slag, but 0.75 moles of CO2 will be generated.

[0106] In contrast, if hydrogen reduction is preferably used to reduce MnO, the manganese (50%) contained in manganese ore does not generate CO2 during the process. In other words, if both hydrogen reduction and CO2 reduction, which are generated during the carbon reduction of MnO to Mn, are used to reduce MnO2 to MnO, all of the manganese contained in the manganese ore is reduced to MnO, but no CO2 is generated during the process. Of the manganese in the hydrogen-reduced manganese ore, 25% is reduced to metallic manganese (ferromanganese) using coke (carbon), generating carbon monoxide (CO) in an amount commensurate with the carbon content. As mentioned above, the generated carbon monoxide (CO2) is used to reduce MnO2 to MnO and is emitted as carbon dioxide (CO2). Therefore, 0.5 moles of CO2 are generated for every mole of MnO2.

[0107] Therefore, when compared under the same conditions as above, hydrogen reduction of manganese ore will result in a 33% reduction in CO2 emissions compared to the amount of CO2 generated by reactions in current electric furnaces.

[0108] In other words, the mechanism for achieving the CO2 reduction effect is that, as explained in Figure 11, the reduction of all the manganese contained in manganese ore to metallic manganese is intentionally avoided by producing a manganese alloy (ferromanganese) by reducing all of the manganese in the manganese ore to manganese with hydrogen to less than tetravalent manganese, or to divalent manganese (manganese oxidation degree 1.0), or by reducing manganese ore to nearly divalent manganese to produce reduced manganese ore, and then reducing some or all of that to metallic manganese to produce high-carbon ferromanganese and ultra-low-carbon ferromanganese. Therefore, by including step (1) of heating and hydrogen-reducing manganese ore to produce reduced manganese ore and step (2) of heating the reduced manganese ore to form a molten material, a method for producing ultra-low-carbon ferromanganese can be achieved that reduces CO2 emissions compared to the carbon dioxide CO2 generated by conventional ferromanganese production methods.

[0109] FIG. 12 shows the CO2 reduction effect calculated from the Mn content of the manganese ore and the Mn content of the slag based on the reaction equation in FIG. 11. Specifically, the reaction equation in FIG. 11 was modified to accommodate the desired Mn content and the desired Mn content of the discharged slag, and the corresponding percentage of reduction effect was plotted. The CO2 reduction effect increases as the Mn content of the manganese ore decreases and increases as the Mn content of the slag increases. Here, conditions under which the CO2 reduction effect is 20% or more are preferred, more preferably 40% or more, even more preferably 50% or more, and most preferably 55% or more. According to one embodiment, the Mn content 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 one embodiment, the Mn content 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 another embodiment, the Mn content 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. Increasing the manganese content in the discharged slag (i.e., reducing the production of high-carbon ferromanganese) in this manner increases the yield of ultra-low-carbon ferromanganese and more significantly reduces carbon dioxide emissions. According to one embodiment, the Mn content 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.

[0110] FIG. 13 shows the production ratio of ultra-low carbon ferromanganese relative to the total amount of ferromanganese, based on the reaction formula in FIG. 11, organized in terms of the Mn content of the manganese ore and the Mn content in the slag. Specifically, the reaction formula in FIG. 11 was modified to accommodate the desired Mn content and the desired Mn content in the discharged slag, and the corresponding percentage of the production ratio of ultra-low carbon ferromanganese relative to the total amount of ferromanganese was plotted. The production ratio of ultra-low carbon ferromanganese increases as the Mn content of the manganese ore decreases and as the Mn content in the slag increases. While any conditions are acceptable as long as ultra-low carbon ferromanganese can be produced, a higher production ratio of ultra-low carbon ferromanganese is preferred. For example, the production ratio of ultra-low carbon ferromanganese is preferably 20% or more, more preferably 40% or more, and even more preferably 50% or more. In addition, the explanation of FIG. 12 applies to the preferable upper and lower limits of the Mn grade of the manganese ore and the Mn amount in the slag.

[0111] 12 and 13, it can be seen that the higher the production ratio of ultra-low carbon ferromanganese, the greater the CO2 reduction effect (FIG. 14). As can be seen from FIG. 14, an ultra-low carbon ferromanganese production ratio of 35% or more is preferable, at which the CO2 reduction effect is 20% or more, an ultra-low carbon ferromanganese production ratio of 45% or more is more preferable, at which the CO2 reduction effect is 30% or more, and an ultra-low carbon ferromanganese production ratio of 50% or more is even more preferable, at which the CO2 reduction effect is 24% or more.

[0112] The above describes the use of a conventional electric furnace in step (2) of heating the reduced manganese ore to form a melt. However, other methods are also acceptable. For example, electric heating using a tubular furnace or arc furnace, induction heating, various burner heating methods, and heating by hydrogen combustion are possible, but heating methods that do not generate CO2 are preferred. For electric heating and induction heating, green electricity is preferred, and hydrogen or other green fuels are preferred for various burner heating methods. To explain in detail the use of a conventional electric furnace, a conventional submerged arc furnace or equivalent may be used. The furnace interior is primarily heated by electricity, and a carbonaceous material is primarily used to reduce a portion of the reduced manganese ore to high-carbon ferromanganese. 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 located at the bottom of the furnace, while the molten slag is located above it. Therefore, the slag and metal are separated and discharged from the electric furnace depending on the timing of tapping and the height of the tap opening. Ferromanganese produced using carbonaceous materials in this way is high-carbon ferromanganese that contains carbon, and may then be decarburized using a known method depending on the intended use.

[0113] The temperature in step (2) is preferably 1200°C or higher, 1300°C or higher, or 1400°C or higher. The temperature in step (2) is preferably 1700°C or lower, 1600°C or lower, or 1550°C or lower. The time for step (2) may be any time sufficient to form a molten material, for example, 0.5 hours or higher, 1.0 hours or higher, or 2.0 hours or higher. The time for step (2) is also preferably 10 hours or shorter, 5 hours or shorter, or 3 hours or shorter. The conditions for hydrogen reduction in step (1) may be the same as those in the embodiment of the method for producing a manganese-based alloy, as described above.

[0114] Another aspect of the present invention is a method for producing ultra-low carbon ferromanganese, characterized by comprising step (3) of heating and hydrogen-reducing manganese ore to form a molten material. Any method may be used to form the molten material in step (3), including, for example, electric heating using a tubular furnace or arc furnace, induction heating, or various burner heating methods, but a heating method that does not generate CO2 is preferred. That is, green electricity is preferably used for electric heating or induction heating, and hydrogen or other green fuels are preferably used as fuel for various burner heating methods. A more preferred method is to use a hydrogen burner to heat and hydrogen-reducing manganese ore to form a molten material.

[0115] Here, the manganese oxidation degree (Mn oxidation degree) will be explained. x The value of x is the manganese oxidation degree, for example, manganese oxidation degree x=2 is MnO2, and manganese oxidation degree x=1 is MnO. Therefore, the manganese oxidation degree of manganese ore or reduced manganese ore can be calculated from the total manganese content (Mn%, JIS M8232 2005 Manganese ore - Manganese determination method) and the available oxygen content of manganese oxide (MnO2%, JIS M8233 1995 Manganese ore - Active oxygen determination method) to obtain MnO. xThe manganese oxidation degree is calculated by calculating x. The manganese oxidation degree in the reduced manganese ore is assumed to be less than 2, but the higher the manganese oxidation degree, the smaller the CO2 reduction effect. In other words, the lower the manganese oxidation degree (approaching 1.0), the greater the CO2 reduction effect. To ensure the production volume of manganese-based alloys and achieve a more effective CO2 reduction effect, it is preferable to reduce the manganese ore in step (1) to a manganese oxidation degree of 1.5 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and even more preferably 1.1 or less. If the manganese oxidation degree of the manganese ore to be reduced with hydrogen is already less than 2.0, the manganese oxidation degree of the reduced manganese ore is set to be less than that of the raw manganese ore. According to a preferred embodiment, the manganese ore is reduced so that the manganese oxidation degree is 80% or less, 75% or less, or 70% or less, when the manganese oxidation degree of the manganese ore is 100%. Regardless of the manganese oxidation degree of the raw manganese ore, it is preferable to set the manganese oxidation degree 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.

[0116] In the hydrogen reduction of manganese ore, as long as the conditions include hydrogen, a reducing agent that serves as a CO2 generating source, such as CO or carbonaceous material, may be included within the range in which a CO2 reduction effect can be obtained. Of course, as mentioned above, when reduced manganese ore is heated and melted in an electric furnace, for example, and high-carbon ferromanganese is also partially produced using a carbonaceous material such as coke (e.g., bio-coke), the carbon monoxide (CO) generated can be recovered and used simultaneously with the hydrogen reduction, and a CO2 reduction effect can also be obtained.

[0117] Here, the reducing agent can be divided into a gaseous form and a solid form.

[0118] According to a preferred embodiment, the proportion of hydrogen in the reducing agent gas 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 reducing agent gas is 30 mol% or less, less than 30 mol%, 10 mol% or less, 5 mol% or less, 1 mol% or less, or 0 mol%.

[0119] According to a preferred embodiment, the amount (proportion) of the solid reducing material (reducing material that serves as a CO2 generation source (e.g., carbonaceous material (coke))) relative to the manganese ore is 20% by weight or less, 10% by weight or less, 8% by weight or less, impurity level, or 0% by mass. According to a preferred embodiment, the impurity level means that the amount of the reducing material that serves as a CO2 generation source is 1000 ppm by weight or less. As described above, according to a preferred embodiment, the reducing material does not contain CO or carbonaceous material.

[0120] Gases other than the reducing agent used in hydrogen reduction may include nitrogen, water vapor, CO2, argon, helium, oxygen, nitrogen oxides, etc. The hydrogen content in hydrogen reduction is sufficient as long as it can reduce manganese ore to the desired oxidation level. However, considering the supply amount of hydrogen-containing gas corresponding to the amount of manganese ore to be processed, the hydrogen content is, for example, 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more of all gases (i.e., reducing agent gas and gases other than reducing agent). From the viewpoint of more efficient reduction, it may be set to more than 4 mol%. According to a preferred embodiment, the hydrogen content 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 the 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. Furthermore, according to a preferred embodiment, the temperature in the hydrogen reduction is 1200°C or lower, 1100°C or lower, 1000°C or lower, 900°C or lower, or lower than 800°C. According to a preferred embodiment, the time for the hydrogen reduction is 0.5 hours or longer, 1.0 hour or longer, or 2.0 hours or longer. According to a preferred embodiment, the time for the hydrogen reduction is 10 hours or shorter, 5 hours or shorter, or 3 hours or shorter.

[0121] According to a preferred embodiment, the amount of the hydrogen-containing gas introduced relative 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 manganese to a desired oxidation level.

[0122] When manganese ore is heated and reduced with hydrogen to form a melt, the temperature is preferably 1200°C or higher, more than 1200°C, 1300°C or higher, 1400°C or higher, or 1500°C or higher. When manganese ore is heated and reduced with hydrogen to form a melt, the temperature is preferably 1700°C or lower, 1650°C or lower, or 1600°C or lower.

[0123] The manganese ions (Mn 2+Ultra-low carbon ferromanganese is produced by reducing manganese ore (equivalent to MnO), and any reduction method may be used, but a reduction method that minimizes the carbon content of the ferromanganese is preferred. For example, the heating in this embodiment is preferably heating by hydrogen combustion. For example, one embodiment of the present invention is a method for producing ultra-low carbon ferromanganese, characterized by including step (4) of reducing the molten material with a non-carbon reducing agent to perform refining, and then performing slag / metal separation. In this case, the reduced manganese ore and a reducing agent (e.g., bio-coke, a non-carbon reducing agent) may be mixed to form the molten material. In other words, steps (2) and (4) may be carried out simultaneously. The non-carbon reducing agent is MnO (Mn 2+ ) to metallic Mn (MnO), without allowing carbon to be mixed (form a solid solution) in the reduced ferromanganese. Examples of the non-carbon reducing material include metallic silicon (metal 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 materials may be combined to control the amount of heat generated by the thermite reaction, thereby simultaneously carrying out the reduction reaction and forming a molten material.

[0124] From the viewpoint of productivity, it is preferable that the non-carbon reducing material is a reducing material containing silicon-containing ferroalloy or metallic aluminum, or a reducing material containing silicon-containing ferroalloy and metallic aluminum.

[0125] The heating in step (1) may be any method capable of heating the manganese ore to a temperature at which it can be reduced by hydrogen, but a heating method capable of reducing carbon dioxide (CO2) emissions is more preferable. For example, electric heating is preferable for the heating in step (1) from the viewpoint of reducing carbon dioxide (CO2) emissions. Furthermore, heating by hydrogen combustion in step (A) is preferable from the viewpoint of reducing carbon dioxide (CO2) emissions and from the viewpoint of being able to supply hydrogen simultaneously.

[0126] In step (2), when the molten material is simultaneously molten in an electric furnace and a portion of the molten material is reduced with a carbonaceous material to form high-carbon ferromanganese, conventional coke may be used. However, using green carbon for some or all of the coke results in a more effective reduction of carbon dioxide (CO2). Examples of green carbon include biocarbon (biologically derived carbonaceous materials such as charcoal and bamboo charcoal), coke made from waste plastics, fuel-derived carbonaceous materials obtained from hydrogen and carbon dioxide synthesized using renewable energy, and green coke synthesized using renewable energy. Furthermore, some or all of the carbonaceous material may be granulated together with reduced manganese ore to form carbonaceous material composite pellets and then charged into the electric furnace. The use of such carbonaceous material composite pellets may improve the reduction reaction and gas release in the electric furnace, leading to stable operation and improved carbonaceous material consumption.

[0127] Alternatively, the dust and the carbonaceous material generated in the step (1) may be granulated together to form carbonaceous material-containing pellets, which are then charged into an electric furnace. Furthermore, crushed manganese alloy product chips or manganese ore powder may be added to the carbonaceous material-containing pellets. The above-mentioned carbonaceous material-containing pellets are more effective when green carbon is used, and using green carbon as the carbonaceous material in the carbonaceous material-containing pellets allows the green carbon to act as a reducing agent more efficiently.

[0128] As a method for granulating the carbonaceous material into pellets, a conventional method can be used, such as a pellet method, a briquette method, an extrusion molding method, etc.

[0129] When forming the molten material in step (2), a slag former (slag control agent) can be added. The slag former controls the viscosity, oxygen potential, basicity, and other properties of the slag. Examples of such slag formers include lime, slaked lime, Na2CO3, CaCl2, MgCO2, and silica SiO2.

[0130] According to a preferred embodiment, a step (5) may be provided in which a portion or all of the molten material from step (2) or (3) is refined by molten oxide electrolysis, followed by slag-metal separation. The molten oxide electrolysis is a method for electrolytically producing molten metallic manganese (ferromanganese) by placing two electrodes, an anode and a cathode, in contact with the molten material and applying a voltage sufficient to reduce divalent manganese to zerovalent manganese (metallic manganese). The heat source for melting the reduced manganese ore can be electric heating, or Joule heat generated by the current flowing between the electrodes can be utilized. Alternatively, a separate heat source can be provided. Ferromanganese produced in this way without using carbonaceous materials is obtained as ultra-low-carbon ferromanganese containing almost no carbon.

[0131] An apparatus for producing ultra-low carbon ferromanganese that achieves the above-described method for producing ultra-low carbon ferromanganese comprises 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 molten material. Alternatively, it comprises means (3) for heating and hydrogen-reducing manganese ore to form a molten material. It is more preferable that the apparatus for producing ultra-low carbon ferromanganese further comprises means (4) for reducing the molten material produced in steps (2) or (3) with a non-carbon reducing agent to perform refining, followed by slag-metal separation. It is also more preferable that the non-carbon reducing agent is a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum.

[0132] Furthermore, it is more preferable that the apparatus for producing ultra-low carbon ferromanganese is provided with a means (5) for refining the molten material by molten oxide electrolysis and then separating the slag and metal.

[0133] 15 and 16 show an example of a configuration flow of a method and apparatus for producing ultra-low carbon ferromanganese according to one embodiment of the present invention. FIG. 15 shows a method including a step (1) or means (1) of reducing manganese ore (Mn ore) with manganese ore and hydrogen to produce reduced manganese ore (reduced Mn ore), and a step (2) or means (2) of heating the reduced manganese ore to produce a molten material. In one embodiment of the present invention, ultra-low carbon ferromanganese is produced from the molten material. As described above, melting the reduced manganese ore can also include partially reducing it using a carbonaceous material to produce high carbon ferromanganese. FIG. 15 shows an example of a method for producing ultra-low carbon ferromanganese from the molten material, in which a non-carbon reducing material is used to reduce manganese ions (Mn 2+ , equivalent to MnO) to metallic manganese (MnO) to produce ultra-low carbon ferromanganese; and 2+ , equivalent to MnO) to metallic manganese (MnO) (Si,Al-reduction) to produce ultra-low carbon ferromanganese.

[0134] FIG. 16 shows a structural flow diagram in which the description of producing high-carbon ferromanganese by partial reduction using a carbonaceous material is omitted from FIG.

[0135] FIG. 17 shows a method and an apparatus for producing ultra-low carbon ferromanganese, which includes a step (3) or means (3) of reducing manganese ore (Mn ore) with hydrogen to produce a molten material. As an example of producing ultra-low carbon ferromanganese from the molten material, a non-carbon reducing agent is used to reduce the manganese ions (Mn 2+ , equivalent to MnO) to metallic manganese (MnO) (Si,Al-reduction) to produce ultra-low carbon ferromanganese, and 2+ , equivalent to MnO) to metallic manganese (MnO), thereby producing ultra-low carbon ferromanganese. [Example]

[0136] The production of manganese-based ferroalloy will be described below.

[0137] The following describes an example of producing reduced manganese ore by heating and hydrogen reduction of manganese ores, such as Gabonese manganese ore (Comilog) (manganese grade 52%) and South African manganese ore (Assoman) (manganese grade 47%). While industrial furnaces capable of heating and hydrogen reduction, such as fluidized bed furnaces, shaft furnaces, and rotary kilns, are used, the manganese ore is experimentally reduced in a tubular furnace by heating and supplying hydrogen-containing gas. As an example, Gabonese manganese ore (containing MnO) is placed in an alumina boat and loaded into a tubular furnace. It is heated at 900°C for 1 hour in a 4 mol% hydrogen / nitrogen gas flow to produce reduced manganese ore. The manganese oxidation degree of the resulting reduced manganese ore is measured and calculated according to the above-mentioned measurement methods (JIS M8232, JIS M8233), resulting in a manganese oxidation degree of 1.0. Similar results were obtained when South African manganese ore (Assoman) was used.

[0138] Furthermore, when thermogravimetric analysis of the manganese ore was performed while flowing a 4 mol% hydrogen / nitrogen mixed gas, a mass loss due to the reduction of manganese was confirmed, as shown in Figure 18. Significant weight loss began above 200°C, but it is believed that the manganese ore begins to be reduced by heating to 500-600°C or higher. According to one embodiment, the ore may be heated to approximately 800°C or higher and reduced by hydrogen. Increasing the hydrogen reduction temperature facilitates the reduction of manganese ore, for example, shortening the reduction treatment time. However, if the hydrogen reduction temperature is too high, the reduced manganese ore may stick together (sintering or fusion solidification) and solidify, making it difficult to handle. For these reasons, the hydrogen reduction temperature is preferably 1200°C or lower, more preferably 1100°C or lower. According to one embodiment, the hydrogen reduction temperature may be lower than 800°C.

[0139] As described above, a hydrogen concentration of 4 mol% is sufficient for hydrogen reduction, but it may be set to more than 4% for more efficient reduction. Conversely, a hydrogen concentration of about 1 mol% is sufficient for reduction, but considering the supply amount of hydrogen-containing gas corresponding to the processing amount of manganese ore, a hydrogen concentration of 1% or more is preferable.

[0140] A more industrial-scale experimental example of hydrogen reduction is an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln. A 4 mol% hydrogen / nitrogen mixed gas was introduced into the test kiln, and the manganese ore was heated and reduced in the test kiln to obtain reduced manganese ore. For example, reduced manganese ore with a manganese oxidation degree of 1.1 was obtained by treating the ore at 900°C for one hour. The manganese oxidation degree of the reduced manganese ore can be varied by adjusting the amount of hydrogen-containing gas introduced, the heating temperature, and the heating time relative to the amount of manganese ore. A higher manganese oxidation degree of the reduced manganese ore shortens the hydrogen reduction process and reduces the amount of hydrogen required, but reduces the CO2 reduction effect. Conversely, the lower the manganese oxidation degree of the reduced manganese ore, approaching 1.0 or closer to 1.0, the greater the CO2 reduction effect.

[0141] Next, an experiment will be described in which reduced manganese ore is reduced with a carbonaceous material to produce a manganese-based alloy. In industrial practice, reduced manganese ore is reduced with a carbonaceous material using a submerged arc furnace or an electric furnace with equivalent functions, but here, the following experiment will be described.

[0142] The reduced manganese ore and coke used as the carbonaceous material are refined in a 100 kVA Giraud furnace (single-phase arc furnace), and the molten manganese alloy (ferromanganese) is separated and removed using a tap to produce a manganese alloy (ferromanganese). Because the Giraud furnace is an open furnace, the amount of carbon monoxide (CO) (carbon dioxide (CO2)) generated cannot be measured. However, the ability to produce a manganese alloy by reducing reduced manganese ore with carbonaceous material and the low oxygen content (manganese oxidation degree) of the reduced manganese ore used as the raw material means that only a small amount of carbonaceous material is required, confirming the CO2 reduction effect. The resulting manganese alloy (ferromanganese) satisfies JIS G 2301.

[0143] In addition, reduced manganese ore and coke as a carbonaceous material are mixed and placed in a refractory container, which is then electrically heated to 1450°C or higher in a vertical tubular furnace while an inert carrier gas (nitrogen N2 or argon Ar) is circulated. The amount of CO2 generated by the reaction between reduced manganese ore and coke can be determined by measuring the carbon monoxide (CO) concentration. Meanwhile, ordinary manganese ore and coke are reacted under the same conditions as above, and the amount of CO2 generated is compared with this. These experimental results demonstrate the CO2 reduction effect of the present invention.

[0144] In this embodiment, the Mn content in the slag may be 20 to 33%, and the manganese alloy production amount may be 10 to 40%.

[0145] Next, the production of ultra-low carbon ferromanganese will be described.

[0146] Below is an example of producing reduced manganese ore by heating and hydrogen reduction manganese ore such as Gabonese manganese ore (Comilog) (manganese grade 52%) and South African manganese ore (Assoman) (manganese grade 47%).

[0147] 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 Figure 18, the mass loss due to the reduction of manganese can be confirmed. Significant weight loss begins above 200°C, but it is believed that the manganese ore begins to be reduced by heating to 500-600°C or higher. In one embodiment, the ore may be heated to approximately 800°C or higher and reduced with hydrogen. Increasing the hydrogen reduction temperature makes it easier to reduce the manganese ore, thereby shortening the reduction treatment time for the manganese ore. In one embodiment, the hydrogen reduction temperature may be less than 800°C.

[0148] This method utilizes industrial furnaces capable of heating and hydrogen reduction, such as fluidized bed furnaces, shaft furnaces, and rotary kilns. Experimentally, manganese ore was reduced to produce reduced manganese ore by heating in a tubular furnace and supplying hydrogen-containing gas. As an example, Gabonese manganese ore (containing MnO) was placed in an alumina boat and charged into a tubular furnace. It was then heated at 700–1100°C for 0.5–10 hours in a 4 mol% hydrogen / nitrogen gas flow to produce reduced manganese ore. The manganese oxidation degree of the resulting reduced manganese ore was measured and calculated according to the aforementioned measurement methods (JIS M8232 and JIS M8233), resulting in a manganese oxidation degree of 1.0–1.5 within the temperature and time ranges. Similar results were obtained using South African manganese ore (Assoman). The manganese oxidation degree reached 1.1 or less at 800°C or higher for 1 hour or more.

[0149] When reducing manganese ore, if the hydrogen reduction temperature is too high, the reduced manganese ore may stick together (sintering or fusion solidification) and harden, making it difficult to handle. For the reasons mentioned above, the hydrogen reduction temperature is preferably 1200°C or lower, and more preferably 1100°C or lower. As mentioned above, a hydrogen concentration of 4 mol% is sufficient for hydrogen reduction, but it may be higher than 4 mol% for more efficient reduction. Conversely, a hydrogen concentration of around 1 mol% is sufficient for reduction, but considering the supply amount of hydrogen-containing gas corresponding to the amount of manganese ore to be processed, 1 mol% or higher is preferred.

[0150] As a more industrial-scale experimental example of hydrogen reduction, an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln can be conducted. A 4 mol% hydrogen / nitrogen mixed gas is introduced into the manganese ore, and the manganese ore is heated in the test kiln and hydrogen-reduced to obtain reduced manganese ore. For example, reduced manganese ore with a manganese oxidation degree of 1.1 is obtained by treating it at 900°C for 1 hour. The manganese oxidation degree of the reduced manganese ore can be varied by adjusting the amount of hydrogen-containing gas introduced, the heating temperature, and the heating time relative to the amount of manganese ore. A higher manganese oxidation degree of the reduced manganese ore shortens the hydrogen reduction process and reduces the amount of hydrogen required, but reduces the CO2 reduction effect. Conversely, the lower the manganese oxidation degree of the reduced manganese ore, approaching 1.0 or closer to 1.0, the greater the CO2 reduction effect.

[0151] Next, an experiment will be described in which reduced manganese ore is heated to form a melt, and an experiment in which ultra-low carbon ferromanganese is produced from the melt.

[0152] One industrial method is to melt reduced manganese ore using a submerged arc furnace or an electric furnace with equivalent functionality, while other methods include melting in a shaft furnace, plasma melting furnace, thermite melting furnace, burner melting furnace, etc.

[0153] Here, the following experiments are described.

[0154] Reduced manganese ore is mixed with ferrosilicon as a non-carbon reducing agent and placed in a refractory container. The mixture is then electrically heated to 1200-1500°C in a vertical tubular furnace while an inert carrier gas (nitrogen N2 or argon Ar) is circulated, and the mixture is reduced while molten to obtain ultra-low carbon ferromanganese. The obtained ultra-low carbon ferromanganese has a low carbon content, the same as unavoidable impurities, because it has not come into contact with carbon in the previous process. The carbon content of the produced ultra-low carbon ferromanganese is measured using a carbon / sulfur analyzer (combustion-infrared absorption method), and is found to be less than 0.2% by mass.

[0155] Alternatively, reduced manganese ore can be mixed with ferrosilicon as a non-carbon reducing agent, placed in a refractory container, and reduced while molten by induction heating at 1200-1500°C to obtain ultra-low carbon ferromanganese. The obtained ultra-low carbon ferromanganese has a low carbon content, the same as unavoidable impurities, because it has not come into contact with carbon in the above process. The carbon content of the produced ultra-low carbon ferromanganese was measured using a carbon / sulfur analyzer (combustion-infrared absorption method) and was found to be 0.2 mass% or less.

[0156] Alternatively, reduced manganese ore and charcoal as bio-coke can be added and refined in a 100 kVA Giro furnace (single-phase arc furnace), tapped to separate and remove the high-carbon ferromanganese molten metal and slag (molten material), and aluminum metal chips can be added to the molten slag and reduced to obtain ultra-low-carbon ferromanganese. The carbon content of the resulting ultra-low-carbon ferromanganese, measured in the same manner as above, is 0.2% by mass or less.

[0157] Furthermore, reduced manganese ore and ferrosilicon as a non-carbon reducing agent are arc-melted and reduced in a 100 kVA Giro furnace (single-phase arc furnace), and then tapped to separate and remove the molten ultra-low carbon ferromanganese from the slag, thereby obtaining ultra-low carbon ferromanganese. The carbon content of the obtained ultra-low carbon ferromanganese is measured in the same manner as above, and is found to be 0.2 mass% or less.

[0158] When directly reducing the ore with hydrogen to a melt, the temperature is usually higher than that described above. For example, Gabonese manganese ore is placed in a magnesia crucible in a vertical tubular furnace, and heated, reduced, and melted while a 4 mol% hydrogen / nitrogen mixed gas is passed through it, maintaining the temperature above the melting point. Specifically, a melt can be obtained by heating the ore to 1200°C or higher (or even higher). A melt can also be obtained even when the maximum temperature of the vertical tubular furnace is 1500°C. The manganese oxidation degree of the cooled and solidified melt is measured in the same manner as above, and is found to be 1.1 or less. Similar results are obtained when South African manganese ore (Assoman) is used. The resulting melt is reduced in the same manner as described above to obtain ultra-low carbon ferromanganese. The carbon content of the resulting ultra-low carbon ferromanganese is measured in the same manner as described above, and is found to be 0.2 mass% or less. [Industrial Applicability]

[0159] The present invention can reduce CO2 emissions in the production of manganese-based alloys, contribute to the prevention of global warming, and meet the demands for carbon neutrality and zero CO2 emissions. Furthermore, the present invention can reduce CO2 emissions in the production of ultra-low carbon ferromanganese, contribute to the prevention of global warming, and meet the demands for carbon neutrality and zero CO2 emissions.

Claims

1. a step (1) of heating and hydrogen-reducing manganese ore to produce reduced manganese ore, and a step (2) of heating the reduced manganese ore to form a molten material; or, (3) heating and hydrogen reducing manganese ore to form a melt; Including, Further, a step (4) of reducing the molten material with a non-carbon reducing agent to perform refining, followed by slag-metal separation; or, The method for producing ultra-low carbon ferromanganese having a carbon content of 0.2 mass % or less further comprises a step (5) of refining the molten product by molten oxide electrolysis, followed by slag-metal separation.

2. 2. The method for producing ultra-low carbon ferromanganese according to claim 1, wherein the non-carbon reducing material is a reducing material containing a silicon-containing ferroalloy or metallic aluminum, or a reducing material containing a silicon-containing ferroalloy and metallic aluminum.

3. CO ２ 3. The method for producing ultra-low carbon ferromanganese according to claim 1, wherein the manganese grade of the manganese ore, the Mn amount in the slag, and the oxidation degree of the reduced manganese ore are set so as to obtain a reduction effect of 20% or more.

4. 4. The method for producing ultra-low carbon ferromanganese according to claim 1, wherein in the step (1), the manganese oxidation degree is reduced to 1.1 or less.

5. The method for producing an ultra-low carbon manganese alloy according to any one of claims 1 to 4, wherein the amount of Mn in the slag is 10% to 29%.

6. 6. The method for producing ultra-low carbon ferromanganese according to any one of claims 1 to 5, wherein the heating in at least one step selected from the group consisting of steps (1), (2), and (3) includes heating by hydrogen combustion.

7. A means (1) for heating and hydrogen-reducing manganese ore to produce reduced manganese ore, and a means (2) for heating the reduced manganese ore to form a molten material; or, (3) A method for heating manganese ore and reducing it with hydrogen to form a melt. Including, Further, a means (4) for reducing the molten material with a non-carbon reducing agent to perform refining, followed by slag / metal separation. or, Further, means (5) for refining the molten material by molten oxide electrolysis and then separating the slag and metal; An apparatus for producing ultra-low carbon ferromanganese having a carbon content of 0.2 mass % or less, comprising:

8. 8. The apparatus for producing ultra-low carbon ferromanganese according to claim 7, wherein the non-carbon reducing material is a reducing material containing a silicon-containing ferroalloy or metallic aluminum, or a reducing material containing a silicon-containing ferroalloy and metallic aluminum.

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