Manganese-based alloy production method and production device therefor

Abstract

To provide a method for producing a CO2 emission-reducing manganese-based alloy that enables CO2 emission reduction in the production of a manganese-based alloy, and a device for producing the same.SOLUTION: Provided is a method for producing a CO2 emission-reducing manganese-based alloy, including a step (1) of subjecting manganese ore to hydrogen reduction by heating to produce reduced manganese ore.

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing a manganese-based alloy. [Background technology]

[0002] 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.

[0003] 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.

[0004] 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]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-161079 [Patent Document 2] Japanese Patent Application 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 [Non-patent literature]

[0006] [Non-Patent Document 1] Terayama Kiyoshi et al., Calorimetry 18(3), 164(1991) Summary of the Invention [Problem to be solved by the invention]

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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. [Means for solving the problem]

[0013] A preferred embodiment of the present invention for solving at least one of the above problems will be described below.

[0014] 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.

[0015] 2. The method for producing a manganese-based alloy according to 1., further comprising the step (2) 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.

[0016] 3. A method for producing a manganese-based alloy according to 1. or 2., further comprising the step (3) of refining a part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag-metal separation.

[0017] 4. The method for producing a manganese-based alloy according to any one of 1. to 3., wherein the manganese oxidation degree of the reduced manganese ore is 1.6 or less.

[0018] 5. The method for producing a manganese-based alloy according to 4., wherein the manganese oxidation degree of the reduced manganese ore is 1.1 or less.

[0019] 6. The method for producing a manganese-based alloy according to any one of 1. to 5., wherein the proportion of hydrogen in the reducing agent gas in the hydrogen reduction is more than 70 mol %.

[0020] 7. The method for producing a manganese-based alloy according to any one of 2. to 6., wherein the amount of Mn in the slag is 10% to 29%.

[0021] 8. The method for producing a manganese-based alloy according to any one of 1. to 7., wherein the heating includes electric heating.

[0022] 9. The method for producing a manganese-based alloy according to any one of 1. to 8., wherein the heating includes heating by hydrogen combustion.

[0023] 10. A method for producing a manganese-based alloy according to any one of 2. to 9., characterized in that it comprises a step (4) of reducing at least a portion of the manganese oxide contained in the molten slag by-produced in the step (2) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum.

[0024] 11. A method for producing a manganese-based alloy according to any one of 1. to 10., characterized in that it comprises a step (5) 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.

[0025] 12. The method for producing a manganese-based alloy according to any one of 2. to 11., wherein a part or all of the carbonaceous material is green carbon.

[0026] 13. The method for producing a manganese-based alloy according to any one of 2. to 12., wherein a slag former is added in step (2).

[0027] 14. An apparatus for producing a manganese-based alloy, comprising means (1) for heating manganese ore and reducing it with hydrogen.

[0028] 15. The apparatus for producing a manganese-based alloy according to claim 14, further comprising means (2) for feeding the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, followed by slag / metal separation.

[0029] 16. The apparatus for producing a manganese-based alloy according to 14. or 15., further comprising means (3) for refining part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag-metal separation.

[0030] 17. An apparatus for producing a manganese-based alloy according to any one of items 14 to 16, further comprising means (4) for reducing at least a portion of the manganese oxide contained in the molten slag by-produced in means (2) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum. [Effects of the Invention]

[0031] The method of the present invention has the effect of significantly reducing CO2 emissions in the production of manganese-based alloys 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 in the production of manganese-based alloys, or even reducing CO2 emissions to almost zero. [Brief explanation of the drawings]

[0032] [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 that when manganese ore is reduced with carbon, the Mn content in the slag is reduced to zero, and a manganese alloy with an increased Mn yield is not produced. [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] Confirmation of hydrogen reduction of manganese ore by thermogravimetric changes. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described below. However, 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 under conditions of room temperature (20 to 25°C) and a relative humidity of 40 to 50% RH. In this specification, "%" means mass % (weight %) except in specific cases (for example, "mol % (volume %)."

[0034] In an embodiment of the present invention, there is provided a method for producing a CO2 emission reducing manganese alloy, comprising the step (1) of heating manganese ore and reducing it with hydrogen to produce reduced manganese ore.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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) obtained 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 similar to that shown in the graph of Mn in the slag and Si in the manganese-based alloy (Si in FMn). 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 Mn content in the slag to, for example, around 30%.

[0041] 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-based 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) used here 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 produced for every mole of MnO2.

[0042] 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. Of the manganese in the hydrogen-reduced manganese ore, 40% 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 (2) of refining the reduced manganese ore together with a carbonaceous material in an electric furnace, followed by slag-metal separation. Steps (1) and (2) may be performed in the same reactor or in separate reactors. The separate reactors may be connected or not directly connected.

[0047] Furthermore, what is generated in the step (2) 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).

[0048] The CO2 reduction effect of the present invention is due to the above-mentioned CO2 reduction mechanism, and thus 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 content in the slag. That is, with regard to the Mn grade (Mn content) of 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 slag, the higher the CO2 reduction effect. In other words, the lower the Mn content in the slag, the lower the CO2 reduction effect. The process (1) of heating manganese ore to produce reduced manganese ore by hydrogen reduction 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 content 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.

[0049] In some embodiments, 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, 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.

[0050] 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%.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Reducing agents can be divided into gaseous and solid forms.

[0055] 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%.

[0056] 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 weight. 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.

[0057] 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.

[0058] As will be described later, according to a preferred embodiment, the temperature in the hydrogen reduction is 600°C or higher, 800°C or higher, or 900°C or higher. Also, according to a preferred embodiment, the temperature in the hydrogen reduction is 1200°C or lower, 1100°C or lower, or 1000°C or lower. According to a preferred embodiment, the time for the hydrogen reduction is 0.5 hours or higher, 1.0 hour or higher, or 2.0 hours or higher. According to a preferred embodiment, the time for the hydrogen reduction is 10 hours or lower, 5 hours or lower, or 3 hours or lower.

[0059] 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.

[0060] 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%.

[0061] 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.

[0062] According to a preferred embodiment, the reduced manganese ore prepared in step (1) is introduced into an electric furnace together with a carbonaceous material for refining, followed by step (2) 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 ferromanganese containing carbon, which may then be decarburized depending on the intended use. This embodiment is schematically illustrated in the upper flow chart of Figure 10.

[0063] According to a preferred embodiment, a step (3) 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, which contain almost no carbon. This embodiment is schematically illustrated in the middle flow chart of Figure 10.

[0064] 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.

[0065] Furthermore, if the process includes a step (4) 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 (2) 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.

[0066] Conventional coke may be used as the carbonaceous material in step (2), 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 wood 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.

[0067] In addition, a part or all of the carbonaceous material in the step (2) 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] In step (2), 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.

[0072] 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 (5).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.

[0073] 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 (2) 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.

[0074] Furthermore, it is more preferable that the manganese-based alloy production apparatus be equipped with a means (3) 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.

[0075] Furthermore, it is more preferable that the apparatus for producing a manganese-based alloy comprises means (4) 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 (2) 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. [Example]

[0076] 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.

[0077] Furthermore, when thermogravimetric analysis was performed on the manganese ore while flowing a 4 mol% hydrogen / nitrogen mixed gas, a mass loss due to the reduction of manganese could be confirmed, as shown in Figure 11. It was found that hydrogen reduction was possible if the ore was heated to approximately 800°C or higher. Increasing the hydrogen reduction temperature makes it easier to reduce the manganese ore, and for example, shortens the reduction treatment time for the manganese ore. However, 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 above reasons, the hydrogen reduction temperature is preferably 1200°C or lower, and more preferably 1100°C or lower.

[0078] As described above, a hydrogen concentration of 4 mol% is sufficient for hydrogen reduction, but it may be increased to more than 4 mol% 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 amount of manganese ore to be processed, a concentration of 1 mol% or more is preferable.

[0079] 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.

[0080] In this embodiment, the amount of Mn in the slag may be 20 to 33%, and the amount of manganese-based alloy produced may be 10 to 40%.

[0081] 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.

[0082] 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.

[0083] 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. [Industrial Applicability]

[0084] The present invention makes it possible to reduce CO2 emissions in the production of manganese-based alloys, contributes to the prevention of global warming, and meets the demands for carbon neutrality and zero CO2 emissions.

Claims

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.

2. 2. The method for producing a manganese alloy according to claim 1, further comprising the step (2) 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.

3. 3. The method for producing a manganese-based alloy according to claim 1, further comprising the step (3) of refining a part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag-metal separation.

4. 4. The method for producing a manganese-based alloy according to claim 1, wherein the manganese oxidation degree of the reduced manganese ore is 1.6 or less.

5. 5. The method for producing a manganese alloy according to claim 4, wherein the manganese oxidation degree of the reduced manganese ore is 1.1 or less.

6. The method for producing a manganese-based alloy according to any one of claims 1 to 5, wherein the proportion of hydrogen in the reducing agent gas in the hydrogen reduction is more than 70 mol %.

7. The method for producing a manganese-based alloy according to any one of claims 2 to 6, wherein the amount of Mn in the slag is 10% to 29%.

8. The method for producing a manganese-based alloy according to any one of claims 1 to 7, characterized in that the heating includes electric heating.

9. The method for producing a manganese-based alloy according to any one of claims 1 to 8, characterized in that the heating includes heating by hydrogen combustion.

10. 10. The method for producing a manganese-based alloy according to any one of claims 2 to 9, further comprising a step (4) of reducing at least a portion of the manganese oxide contained in the molten slag by-produced in the step (2) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum.

11. 11. The method for producing a manganese-based alloy according to any one of claims 1 to 10, further comprising a step (5) of reducing a part or all of the reduced manganese ore with a reducing material containing a silicon-containing ferroalloy or metallic aluminum, or a reducing material containing a silicon-containing ferroalloy and metallic aluminum to perform refining, followed by slag-metal separation.

12. The method for producing a manganese-based alloy according to any one of claims 2 to 11, characterized in that a part or all of the carbonaceous material is green carbon.

13. 13. The method for producing a manganese-based alloy according to claim 2, wherein a slag former is added in the step (2).

14. An apparatus for producing a manganese-based alloy, comprising a means (1) for heating and hydrogen-reducing manganese ore.

15. 15. The apparatus for producing a manganese-based alloy according to claim 14, further comprising means (2) for introducing the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, followed by slag / metal separation.

16. 16. The apparatus for producing a manganese-based alloy according to claim 14 or 15, further comprising means (3) for refining a part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag / metal separation.

17. 17. The apparatus for producing a manganese-based alloy according to any one of claims 14 to 16, further comprising means (4) for reducing at least a portion of the manganese oxide contained in the molten slag by-produced in the means (2) with a reducing agent containing a silicon-containing ferroalloy or metallic aluminum, or a reducing agent containing a silicon-containing ferroalloy and metallic aluminum.

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