Method for producing manganese-based alloy and production apparatus therefor

Abstract

[Problem] The present invention addresses the problem of providing: a method for producing a CO2 emission reducing-manganese alloy that enables reduction of CO2 emission in the production of manganese alloys; and a production device for the method. [Solution] This method is for producing a CO2 emission-reducing manganese alloy and comprises a step (1) for heating a manganese ore to cause same to undergo hydrogen reduction to obtain a reduced manganese ore.

Description

Technical Field

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

Background Art

[0002] Manganese-based alloys, such as ferromanganese, are produced by charging manganese ore and a reducing agent such as coke into a blast furnace or an electric furnace and heating them to reduce manganese and iron in the ore. In the blast furnace method, coke is used as a heat source and a reducing agent, while in the electric furnace method, the heat source is electric power and coke is used as a reducing agent. This is the basic concept.

[0003] Conventionally, technological development has been carried out from the perspective of how to efficiently produce manganese-based alloys. For example, techniques of charging a reducing agent such as alloy iron containing silicon or metallic aluminum to further reduce and extract manganese remaining in the slag are disclosed in Patent Document 1 and Patent Document 2. In addition, instead of directly charging manganese ore into a blast furnace or an electric furnace, techniques of pre-reducing manganese ore with carbon monoxide CO gas or coke generated in the blast furnace method or the electric furnace method and then charging it into the blast furnace or the electric furnace are disclosed in Patent Documents 3 to 6.

[0004] In addition, Non-Patent Document 1 mentions pre-treatment of preheating and pre-reduction in the background of using inexpensive coal instead of expensive electric power in the production of ferromanganese, and discloses a series of basic studies on each reduction reaction process using carbon monoxide or hydrogen gas as part of research on the reduction of manganese ore by carbon.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] [Non-Patent Document 1] Kiyoshi Terayama et al., Thermal Measurement 18(3), 164(1991) [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] As described above, in the production of manganese-based alloys, although technological development has been carried out to produce them efficiently so far, it has been found that attempts to reduce CO2 have not been made on the premise of using carbonaceous materials such as coke as reducing agents when reducing manganese ore.

[0008] In fact, looking at Patent Documents 1 to 6 and other prior art documents related to the production of manganese-based alloys, no technological development has been carried out for the purpose of reducing CO2 emissions, and there is no description or suggestion regarding it. In the conventional technological development related to the production of manganese-based alloys, although some reduction of CO2 emissions has been indirectly achieved by improving efficiency, no attempt has been made to reduce or eliminate the use of carbonaceous materials, which are the sources of CO2 generation, from the perspective of reducing CO2 generation.

[0009] For example, as in Non-Patent Document 1, there is basic research on the reduction behavior of manganese ore using reducing agents such as carbon monoxide and hydrogen other than carbon, but in the process of reducing to metallic manganese to produce manganese-based alloys, it has only reached the proposal of using natural gas containing methane CH4 for reduction, and there is no disclosure or suggestion regarding its use from the perspective of reducing CO2 generation.

[0010] In addition, in the description of FIG. 4 in Patent Document 4, surplus gas (derived from coke) from a ferromanganese furnace and Si and Mn furnaces is used to produce preliminary reduced pellets, so the CO2 reduction effect of the present invention is not achieved. Although Patent Document 4 seems to have the effect of reducing the power unit, it has no effect of reducing the carbonaceous material.

[0011] Therefore, the inventors have found that it is necessary to actively develop a technology for reducing CO2 emissions in the production of manganese-based alloys.

[0012] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a manganese-based alloy that enables reduction of CO2 emissions in the production of manganese-based alloys.

Means for Solving the Problems

[0013] Preferred embodiments 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 a step (1) of heating manganese ore and subjecting it to hydrogen reduction to produce reduced manganese ore.

[0015] 2. The method for producing a manganese-based alloy according to 1., further comprising a step (2) of charging the reduced manganese ore into an electric furnace together with a carbonaceous material, performing refining, and then performing slag-metal separation.

[0016] 3. The method for producing a manganese-based alloy according to 1. or 2., further comprising a step (3) of refining a part or all of the reduced manganese ore by molten oxide electrolysis and then performing 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 claim 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 claims 1 to 5, wherein the proportion of hydrogen in the gas of the reducing material in the hydrogen reduction is more than 70 mol%.

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

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

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

[0023] 10. The method for producing a manganese-based alloy according to any one of claims 2 to 9, including a step (4) of reducing at least a part of the manganese oxide contained in the molten slag with a reducing material containing ferroalloy containing silicon or metallic aluminum, or a reducing material containing ferroalloy containing silicon and metallic aluminum.

[0024] 11. The method for producing a manganese-based alloy according to any one of claims 1 to 10, including a step (5) of reducing and refining part or all of the reduced manganese ore with a reducing material containing ferroalloy containing silicon or metallic aluminum, or a reducing material containing ferroalloy containing silicon and metallic aluminum, and then performing slag-metal separation.

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

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

[0027] 14. A manufacturing apparatus for a manganese-based alloy, characterized by comprising means (1) for heating a manganese ore and subjecting it to hydrogen reduction.

[0028] 15. The manufacturing apparatus for a manganese-based alloy according to 14., further comprising means (2) for charging the reduced manganese ore into an electric furnace together with a carbonaceous material for refining, and then performing slag-metal separation.

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

[0030] 17. The manufacturing apparatus for a manganese-based alloy according to any one of 14. to 16., comprising means (4) for reducing at least a part of the manganese oxide contained in the molten slag by a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum, in the molten slag by-produced by the means (2).

Effect of the Invention

[0031] By the method of the present invention, by hydrogen-reducing manganese ions contained in a manganese ore, there is an effect that the amount of CO2 emissions in the production of a manganese-based alloy can be significantly reduced. Further, according to the manufacturing apparatus of the present invention, there is an effect that the amount of CO2 emissions in the production of a manganese-based alloy can be significantly reduced, or the amount of CO2 emissions can be made almost zero.

Brief Description of the Drawings

[0032]

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Embodiments for Carrying Out the Invention

[0033] The present invention will be described below. Note that the present invention is not limited only to the following embodiments. Also, in this specification, "X to Y" indicating a range means "X or more and Y or less". Further, unless otherwise specified, measurements such as operations and physical properties are measured under the conditions of room temperature (20 to 25 ° C) / relative humidity 40 to 50% RH. Note that "%" described in this specification is, in all cases except for specific cases (for example, "mol% (volume%)"), mass% (weight%).

[0034] In an embodiment of the present invention, there is provided a method for producing a manganese-based alloy with reduced CO2 emissions, which includes a step (1) of heating a manganese ore and subjecting it to hydrogen reduction to produce a reduced manganese ore.

[0035] The raw material of the manganese-based alloy, for example, manganese ore, is usually tetravalent manganese (equivalent to MnO2). Even if the reduction reaction theoretically occurs efficiently when a carbonaceous material such as coke is charged into an electric furnace together with manganese ore as a reducing agent and reduced from tetravalent manganese (ore) to zero-valent metallic manganese (manganese-based alloy), a considerable amount of carbon dioxide will be emitted.

[0036] Here, the inventors examined the reduction of manganese ore from a thermodynamic point of view and determined that reducing agents capable of reducing tetravalent manganese (equivalent to MnO2) to divalent manganese (equivalent to MnO) are carbon C, carbon monoxide CO, hydrogen H2, etc. (Fig. 1). The only reducing agent capable of reducing divalent manganese (equivalent to MnO) to zero-valent manganese (metallic Mn) is carbon C (Fig. 1). Carbon C can also reduce to metallic manganese under conditions of 1450 ° C or higher.

[0037] Next, in the process of producing a manganese-based alloy by simplifying manganese ore to MnO₂, consider the CO₂ reduction effect when hydrogen-reducing manganese ore (Fig. 2). Even if hydrogen, a reducing agent that does not generate CO₂, is used to reduce tetravalent manganese (equivalent to MnO₂) to divalent manganese (equivalent to MnO), as described above, only carbon C can reduce divalent manganese (equivalent to MnO) to zero-valent manganese (metallic Mn). Therefore, 1 mole of carbon C is required to produce 1 mole of metallic Mn of manganese Mn, and the CO₂ reduction effect is zero.

[0038] Thus, even if manganese ore is hydrogen-reduced, the CO₂ reduction effect is considered to be zero in the first place, and demerits such as the need for new devices and facilities are also assumed. Therefore, those skilled in the art would not come up with the idea of using hydrogen for preliminary reduction.

[0039] In contrast, the present inventors have found that if the manganese-based alloy (especially ferromanganese) is produced by setting the Mn content in the slag discharged from the manganese ore to be around 30% for example, a CO₂ reduction effect can be achieved by pre-hydrogen-reducing the manganese ore. In this way, the inventors came up with the idea that positive CO₂ emission reduction can be achieved by hydrogen-reducing manganese to less than tetravalent, leading to the present invention. The existing form of Mn in the slag is considered to be dissolved as Mn 2+ ions, and / or dispersed as MnO oxides. The existing form can be observed with an electron microscope.

[0040] In a preferred embodiment, when carbon-reducing reduced manganese ore, it is set not to reduce the Mn content in the slag to zero%. The reasons are as follows. That is, manganese ore contains slag components (silica SiO2, silicate), that is, in the coexistence of MnO-SiO2, so the reaction formulas (1) and (2) in Figure 3 occur, and the relationship of formula (4) is derived from the equilibrium formula of reaction formula (3) which is formula (1)×2 - formula (2). Formula (4) means that to lower the [MnO] concentration, that is, to increase the Mn yield, the [Si] concentration needs to be increased. Then, it will be in a relationship like the graph of Mn in the slag and Si in the manganese-based alloy (Si in FMn). If the Mn amount in the slag is lowered too much and the Mn yield is increased too much, the Si content in the obtained manganese-based alloy will increase. Therefore, in order to manufacture a manganese-based alloy from manganese ore so that the Si content in the manganese-based alloy does not increase too much, it is advisable to set the Mn amount in the slag to about 30% or so.

[0041] By making such a contrivance, the inventors have found that when manganese ore is pre-reduced with hydrogen, a CO2 reduction effect appears (Figures 4 and 5). In Figure 4, as an example, the CO2 reduction effect is calculated based on a hypothesis (model) of manufacturing 40% of the Mn content as metallic manganese (manganese-based alloy) from manganese ore containing 50% Mn (Mn grade) and discharging slag containing 30% Mn (30% Mn in the slag). First, all the manganese (50%) contained in the manganese ore is reduced to MnO. According to the current coke (carbon) reduction method using an electric furnace, carbon C (coke) and carbon monoxide CO are used in a ratio of 0.3:0.4 as the reducing agent. Here, the carbon monoxide CO is the carbon monoxide CO generated by the reaction of the carbon C required to manufacture 50% of metallic manganese (manganese-based alloy) from MnO. Therefore, 0.7 moles of CO2 are generated per 1 mole of MnO2.

[0042] In contrast, preferably for the reduction to MnO, when hydrogen reduction is used, the manganese (50%) contained in the manganese ore does not generate CO2 at that time. In other words, when hydrogen reduction is used for the reduction from MnO2 to MnO, all the manganese contained in the manganese ore is reduced to MnO, but CO2 is not generated at that time. Of the manganese in the hydrogen-reduced manganese ore, 40% of it is reduced by coke (carbon) to metallic manganese (manganese-based alloy), and carbon monoxide CO corresponding to the amount of carbon is generated here. The generated carbon monoxide CO is burned (reacted with oxygen O2) and discharged as carbon dioxide CO2. Therefore, 0.4 mol of CO2 is generated per 1 mol of MnO2.

[0043] Therefore, in the case of the above model, when hydrogen reduction is carried out to MnO with respect to the amount of CO2 generated in the current electric furnace reaction, a CO2 reduction effect of 43% can be obtained. Incidentally, Fig. 5 is expressed by one reaction formula respectively.

[0044] That is, the mechanism for obtaining the CO2 reduction effect is, as explained in Fig. 3, not to dare to produce a manganese-based alloy by reducing all the manganese contained in the manganese ore to metallic manganese, and to hydrogen-reduce all the manganese in the manganese ore to manganese with a valence of less than 4, hydrogen-reduce divalent manganese (manganese oxidation degree 1.0), or hydrogen-reduce it to near divalent to obtain a reduced manganese ore, and then a part or all of it is reduced to metallic manganese to produce a manganese-based alloy.

[0045] Therefore, by including the step (1) of heating the manganese ore to obtain a hydrogen-reduced manganese ore, ultimately, a method for producing a manganese-based alloy capable of reducing CO2 emissions compared to the carbon dioxide CO2 generated by the conventional method for producing a manganese-based alloy can be obtained.

[0046] According to an embodiment of the present invention, a step (1) of heating manganese ore to obtain reduced manganese ore by hydrogen reduction and a step (2) of putting the reduced manganese ore into an electric furnace together with a carbonaceous material for refining and then performing slag-metal separation are combined. Note that the step (1) and the step (2) may be carried out in the same reaction vessel or in separate reaction vessels that are separated from each other. The separated reaction vessels may or may not be connected to each other.

[0047] Also, since 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 description of the oxidation (combustion) of carbon monoxide CO is omitted), the carbon monoxide CO generated here may be used together with hydrogen for reduction in the step (1).

[0048] The CO2 reduction effect in the present invention is due to the above-described CO2 reduction mechanism, and thus has the relationship as shown in FIG. 6. Note that FIG. 6 was derived by deforming the reaction formula described in FIG. 4 so that the Mn grade in the desired ore and the amount of Mn in the desired slag are obtained, and plotting the corresponding percentage of the reduction effect. That is, regarding the Mn grade (Mn content) of the manganese ore, the lower the Mn grade, the higher the CO2 reduction effect. In other words, as the Mn grade increases, the CO2 reduction effect tends to decrease. Also, regarding the amount of Mn remaining in the slag, the higher the amount of Mn in the slag, the higher the CO2 reduction effect. In other words, as the amount of Mn in the slag decreases, the CO2 reduction effect tends to decrease. By having the step (1) of heating the manganese ore to obtain a reduced manganese ore by hydrogen reduction, the CO2 reduction effect can be exerted. However, as described above, the CO2 reduction effect varies depending on the Mn grade of the manganese ore and the amount of Mn in the slag. Generally speaking, the more efficiently a large amount of manganese-based alloys are produced from the manganese ore, the lower the CO2 reduction effect will be. Therefore, from the viewpoint of ensuring a certain level of productivity and obtaining the CO2 reduction effect, preferably, for example, the Mn grade of the manganese ore is set to be 40 to 60%. Within this range, a CO2 reduction effect of about 20 to 70% can be obtained. According to an embodiment, the Mn grade of the manganese ore is 20% or more, 25% or more, 31% or more, 32% or more, 35% or more, 38% or more, 40% or more, 45% or more, or 46% or more. According to an embodiment, the Mn grade of the manganese ore is 80% or less, 68% or less, 60% or less, 55% or less, 54% or less, 50% or less, 49% or less, or 48% or less.

[0049] Also, according to an embodiment, the amount of Mn in the slag is 0.1% or more, 1% or more, 5% or more, 10% or more, 20% or more, 25% or more, or 26% or more. According to an embodiment, the amount of Mn in the slag is 35% or less, 31% or less, 30% or less, or 29% or less.

[0050] Figure 7 shows the influence of the production amount of manganese-based alloy (the ratio of producing manganese-based alloy (ferromanganese) from manganese ore, Mn / Mn ore - %) on the CO₂ reduction effect. This Figure 7 is derived by transforming the reaction formula described in Figure 4 so that the amount of Mn in the desired slag and the desired manganese production amount (manganese production ratio) are obtained, and plotting the corresponding percentage of the reduction effect. It can be read from Figure 7 that there is a similar tendency to that in Figure 6. According to a preferred embodiment, the production amount of manganese-based alloy is 5 - 50%, 5 - 40%, or 10 - 30%.

[0051] Here, the manganese oxidation degree (Mn oxidation degree) will be described. When represented by the composition formula MnO x the value of x is the manganese oxidation degree. For example, when the manganese oxidation degree x = 2, it is MnO₂, and when the manganese oxidation degree x = 1, it is MnO. Therefore, the manganese oxidation degree of manganese ore or reduced manganese ore is obtained by calculating x of MnO from the value of the total manganese amount (Mn%, JIS M8232 2005 Manganese ore - Manganese quantification method) and the value of the effective oxygen of manganese oxide (MnO₂%, JIS M8233 1995 Manganese ore - Active oxygen quantification method), and is taken as the manganese oxidation degree. x

[0052] ​Figure 8 shows the influence of the degree of reduction by hydrogen reduction of manganese ore, i.e., the manganese oxidation degree of the reduced manganese ore, on the CO2 reduction effect. This Figure 8 was derived by transforming the reaction formula described in Figure 4 so as to obtain a desired oxidation degree, a desired Mn grade, and a desired amount of Mn in the slag, and then plotting the corresponding percentage of the reduction effect. Although it is premised that the manganese oxidation degree in the reduced manganese ore is less than 2, as shown in Figure 8, the greater the manganese oxidation degree, the smaller the CO2 reduction effect. In other words, the smaller the manganese oxidation degree and the closer it is to 1.0, the greater the CO2 reduction effect. In order to ensure the production volume of the manganese-based alloy and obtain a more effective CO2 reduction effect, in step (1), it is preferable to use a reduced manganese ore with a manganese oxidation degree of 1.6 or less, more preferably 1.5 or less, still more preferably 1.2 or less, and even more preferably 1.1 or less. In addition, when the manganese oxidation degree of the manganese ore to be hydrogen-reduced is already less than 2.0, the manganese oxidation degree of the reduced manganese ore should be less than the manganese oxidation degree of the raw material manganese ore. According to a preferred embodiment, when the manganese oxidation degree of the manganese ore is 100%, the manganese ore is reduced so that the manganese oxidation degree becomes 80% or less, 75% or less, or 70% or less. Also, regardless of the manganese oxidation degree of the raw material manganese ore, it is preferable to make the manganese oxidation degree of the reduced manganese ore 1.6 or less, 1.5 or less, 1.2 or less, 1.15 or less, or 1.1 or less.

[0053] Regarding the hydrogen reduction of manganese ore, as long as it is a condition containing hydrogen, a reducing agent that becomes a CO2 generation source within the range where a CO2 reduction effect can be obtained, for example, a reducing agent containing CO or a carbonaceous material, may be included.

[0054] The reducing agent can be divided into a gas (gaseous) form and a solid form.

[0055] According to a preferred embodiment, the proportion of hydrogen in the gas of the reducing agent is 50 mol% or more, more preferably 70 mol% or more, even more preferably more than 70 mol%, even more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 99 mol% or more, and even more preferably 100 mol%. The proportion of CO in the gas of the reducing agent is 30 mol% or less, less than 30 mol%, 10 mol% or less, 5 mol% or less, 1 mol% or less, or 0 mol%.

[0056] According to a preferred embodiment, the amount (proportion) of the solid reducing agent (the reducing agent that becomes a CO2 source (for example, carbonaceous material (coke))) with respect to the manganese ore is 20 wt% or less, 10 wt% or less, 8 wt% or less, the impurity level, or 0 wt%. According to a preferred embodiment, the impurity level means that the amount of the reducing agent that becomes a CO2 source is 1000 wtppm or less. As described above, according to a preferred embodiment, the reducing agent does not contain CO or carbonaceous material.

[0057] In addition, as the gas other than the reducing agent in hydrogen reduction, nitrogen, water vapor, CO2, argon, helium, oxygen, nitrogen oxides, etc. may be included. The hydrogen content in hydrogen reduction is sufficient as long as it can reduce the manganese ore to the target degree of oxidation. However, considering the supply amount of the hydrogen-containing gas corresponding to the treatment amount of the manganese ore, for example, in all gases (that is, the gas of the reducing agent and the gas other than the reducing agent), it is 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more. From the viewpoint of more efficient reduction, it may be set to more than 4 mol%. According to a preferred embodiment, it is 10 mol% or less, 9 mol% or less, 8 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, 3 mol% or less, or 2 mol% or less.

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

[0059] According to a preferred embodiment, the introduction amount of the hydrogen-containing gas with respect to the amount of manganese ore is, as a guideline, 1.0 to 3.1 times, 1.05 to 1.9 times, or 1.1 to 1.4 times the amount of hydrogen required to reduce to a desired manganese oxidation degree.

[0060] According to an embodiment, the manganese oxidation degree of the reduced manganese ore is 1.0 to 1.5, the Mn grade of the manganese ore is 40 to 60%, and the amount of Mn in the slag is 20 to 31%. According to an embodiment, the manganese oxidation degree of the reduced manganese ore is 1.0 to 1.2, the Mn grade of the manganese ore is 40 to 55%, and the amount of Mn in the slag is 25 to 31%. According to an embodiment, the manganese oxidation degree of the reduced manganese ore is 1.0 to 1.15, the Mn grade of the manganese ore is 45 to 54%, and the amount of Mn in the slag is 25 to 30%. According to an embodiment, the manganese oxidation degree of the reduced manganese ore is 1.0 to 1.1, the Mn grade of the manganese ore is 46 to 54%, and the amount of Mn in the slag is 26 to 29%.

[0061] According to a preferred embodiment, when hydrogen reduction is carried out to MnO with respect to the amount of CO2 generated in the current electric furnace reaction shown in FIG. 4, a CO2 reduction effect of preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more can be obtained.

[0062] According to a preferred embodiment, the reduced manganese ore produced in the step (1) is charged into an electric furnace together with a carbonaceous material for refining, and then, through a step (2) of performing slag-metal separation, a manganese-based alloy is produced. The electric furnace may be a conventional submerged arc furnace or an equivalent electric furnace, which mainly heats the inside of the furnace by electric power and is mainly used for reducing reduced manganese ore to metallic manganese (manganese-based alloy) by a carbonaceous material. As refining proceeds in the electric furnace, molten slag and molten manganese-based alloy are formed. Due to the difference in their specific gravities, the molten manganese-based alloy is placed at the bottom of the furnace and the molten slag is placed thereon. Therefore, depending on the tapping timing, the height of the tapping port, etc., slag and metal are separated and discharged from the electric furnace. The manganese-based alloy produced using a carbonaceous material in this way results in ferromanganese containing carbon, and may be decarburized thereafter according to the application. This embodiment is schematically shown by the upper flow in FIG. 10.

[0063] According to a preferred embodiment, a step (3) may be provided in which part or all of the reduced manganese ore produced in the step (1) is refined by molten oxide electrolysis and then slag-metal separation is performed. The molten oxide electrolysis is a method of electrolytically producing molten metallic manganese (manganese-based alloy) by melting reduced manganese ore, applying a voltage capable of reducing divalent manganese to zero-valent manganese (metallic manganese) by bringing two electrodes, an anode and a cathode, into contact with the melt. Here, the heat source for melting the reduced manganese ore can also be electric heating, using the Joule heat generated from the current flowing between the electrodes, or a separate heat source can be prepared. The manganese-based alloy produced in this way without using a carbonaceous material results in ferromanganese or metallic manganese containing almost no carbon. This embodiment is schematically shown by the middle flow in FIG. 10.

[0064] The heating in the step (1) only needs to heat the manganese ore to a temperature at which it can be hydrogen-reduced, and any heating method may be used, but a heating method that can reduce the carbon dioxide (CO2) emission is more preferable. For example, from the perspective that electric heating in the step (1) can reduce the carbon dioxide (CO2) emission, it is preferable. Also, from the perspectives that heating by hydrogen combustion in the step (1) can reduce the carbon dioxide (CO2) emission and can be carried out simultaneously with hydrogen supply, it is preferable.

[0065] Furthermore, if a step (4) of producing a manganese-based alloy iron by reducing at least a part of the manganese oxide contained in the molten slag by using a reducing material containing alloy iron containing silicon or metallic aluminum, or both a reducing material containing alloy iron containing silicon and metallic aluminum, is included in the molten slag by-produced in the step (2), manganese remaining in the slag can be recovered, so that the productivity is further improved. Thus, a manganese-based alloy produced from Mn-containing slag without using a carbon material can obtain ferromanganese or metallic manganese that hardly contains carbon. The said embodiment is schematically shown by the flow in the lower part of FIG. 10.

[0066] As the carbon material in the step (2), conventional coke may be used, but by partially or entirely using green carbon, the carbon dioxide (CO2) reduction effect is further improved. The green carbon includes bio-carbon (bio-derived carbon materials such as charcoal and bamboo charcoal), coke made from waste plastic, fuel-derived carbon materials obtained from hydrogen and carbon dioxide synthesized by renewable energy, green coke synthesized using renewable energy, and the like.

[0067] Also, a part or all of the carbon material in the step (2) may be granulated together with the reduced manganese ore produced in the step (1) to form a carbon material-embedded pellet and charged into an electric furnace. By using the carbon material-embedded pellet as described above, the reduction reaction and gas escape in the electric furnace may be better, and it may be easier to operate stably and the carbon material unit consumption may be improved.

[0068] Alternatively, the dust generated in the step (1) and the carbonaceous material may be granulated together and charged into the electric furnace as carbonaceous material-lined pellets. Further, product crushing scraps of manganese-based alloys or ore fines of raw manganese ore may be included in the carbonaceous material-lined pellets.

[0069] The above-mentioned carbonaceous material-lined pellets are more effective when using green carbon, and the carbonaceous material used for the carbonaceous material-lined pellets is preferably green carbon, which can make green carbon act as a reducing agent more efficiently.

[0070] As the granulation method for making carbonaceous material-lined pellets, ordinary methods can be adopted, for example, pellet method, briquet method, extrusion molding method, etc.

[0071] In the step (2), a slag-forming agent (slag regulator) can be charged into the electric furnace. The slag-forming agent can control properties such as the viscosity, oxygen potential, basicity, etc. of the slag. For example, it is lime, slaked lime, Na2CO3, CaCl2, MgCO2, etc.

[0072] Part or all of the reduced manganese ore produced in the step (1) is reduced and refined with a reducing agent containing alloy iron containing silicon or metallic aluminum, or both a reducing agent containing alloy iron containing silicon and metallic aluminum, and then manganese-based alloy iron is produced in the step (5) of performing slag-metal separation. In this way, manganese-based alloys produced from Mn-containing slag without using carbonaceous material can obtain ferromanganese and metallic manganese that contain almost no carbon.

[0073] As a manufacturing apparatus for manganese-based alloys that achieves the method for manufacturing manganese-based alloys as described above, it includes means (1) for heating manganese ore and subjecting it to hydrogen reduction to obtain reduced manganese ore, and means (2) for charging the reduced manganese ore into an electric furnace together with a carbonaceous material for refining, and then performing slag-metal separation.

[0074] Furthermore, it is more preferable to provide a manufacturing apparatus for a manganese-based alloy, which includes means (3) for refining some or all of the reduced manganese ore produced in the step (1) by molten oxide electrolysis and then separating slag and metal.

[0075] Furthermore, it is more preferable to provide a manufacturing apparatus for a manganese-based alloy, which includes means (4) for producing a manganese-based alloy iron by reducing at least a part of the manganese oxide contained in the molten slag by using a reducing agent containing alloy iron containing silicon or metallic aluminum, or both a reducing agent containing alloy iron containing silicon and metallic aluminum, in the molten slag by-product in the means (2).

Example

[0076] Examples of producing reduced manganese ore by heating manganese ore such as Gabon-produced manganese ore (Comilog) (manganese grade 52%) and South Africa-produced manganese ore (Assmang) (manganese grade 47%) and subjecting it to hydrogen reduction are shown below. Although industrial furnaces such as a fluidized bed furnace, a shaft furnace, and a rotary kiln furnace that can be heated and subjected to hydrogen reduction are applied, experimentally, the manganese ore is reduced by heating in a tubular furnace and supplying a hydrogen-containing gas to obtain reduced manganese ore. As an example, Gabon-produced manganese ore (containing MnO2) is placed in an alumina boat, charged into a tubular furnace, and heated at 900°C for 1 hour while flowing 4 mol% hydrogen / nitrogen gas to obtain reduced manganese ore. When the manganese oxidation degree of the obtained reduced manganese ore is measured and calculated based on the above-described measurement methods (JIS M8232, JIS M8233), the manganese oxidation degree becomes 1.0. The same result is obtained when using South Africa-produced manganese ore (Assmang).

[0077] In addition, when performing thermogravimetric analysis of the manganese ore while flowing a 4 mol% hydrogen / nitrogen mixed gas, a mass loss due to the reduction of manganese can be confirmed as shown in FIG. 11. It can be seen that hydrogen reduction is possible when heated to about 800°C or higher. Increasing the temperature of hydrogen reduction makes it easier to reduce the manganese ore. For example, the reduction treatment time of the manganese ore is shortened. However, if the temperature of hydrogen reduction is too high, the reduced manganese ores stick to each other (sintering or fusion solidification) and solidify, which may make it difficult to handle. From the above, the temperature of hydrogen reduction is preferably 1200°C or lower, more preferably 1100°C or lower.

[0078] As described above, a hydrogen concentration of 4 mol% for hydrogen reduction is sufficient, but it may be further increased to more than 4 mol% for more efficient reduction. On the contrary, even a hydrogen concentration of about 1 mol% can sufficiently reduce, but considering the supply amount of the hydrogen-containing gas corresponding to the processing amount of the manganese ore, 1 mol% or more is preferable.

[0079] As a more industrial experimental example of hydrogen reduction, there is an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln. By introducing a 4 mol% hydrogen / nitrogen mixed gas and heating the manganese ore in the test kiln for hydrogen reduction, reduced manganese ore can be obtained. For example, by treating at 900°C for 1 hour, reduced manganese ore with a manganese oxidation degree of 1.1 can be obtained. By adjusting the introduction amount of the hydrogen-containing gas, the heating temperature, and the heating time with respect to the amount of the manganese ore, the manganese oxidation degree of the reduced manganese ore can be varied. The higher the manganese oxidation degree of the reduced manganese ore, the shorter the hydrogen reduction treatment time and the less hydrogen consumption required. However, the CO2 reduction effect becomes smaller. On the contrary, the lower the manganese oxidation degree of the reduced manganese ore and the closer it is to 1.0, the greater the CO2 reduction effect.

[0080] In addition, in this example, the Mn amount in the slag can be 20 - 33%. Also, the production amount of the manganese-based alloy can be 10 - 40%.

[0081] Next, an experiment of reducing reduced manganese ore with a carbonaceous material to produce a manganese-based alloy will be described. Industrially, the reduced manganese ore will be reduced with a carbonaceous material using a submerged arc furnace or an electric furnace having an equivalent function. Here, the following experiment will be described.

[0082] The above reduced manganese ore and coke as the carbonaceous material are refined in a 100 kVA Jiro furnace (single-phase arc furnace), tapped, and the molten metal of the manganese-based alloy (ferromanganese) and slag are separated and taken out to obtain the manganese-based alloy. Since the Jiro furnace is an open furnace, the amount of carbon monoxide CO (carbon dioxide CO2) generated cannot be measured. However, it can be confirmed that a manganese-based alloy can be produced by reducing the reduced manganese ore with a carbonaceous material, and since the oxygen content (manganese oxidation degree) of the raw material reduced manganese ore is small, less carbonaceous material is required, resulting in a CO2 reduction effect. The obtained manganese-based alloy (ferromanganese) satisfies JIS G 2301.

[0083] Also, the reduced manganese ore and coke as the carbonaceous material are mixed, put into a refractory container, and electrically heated to 1450 °C or higher while flowing an inert carrier gas (nitrogen N2 or argon Ar) through a vertical tubular furnace. By measuring the concentration of the generated carbon monoxide CO, the amount of CO2 generated by the reaction between the reduced manganese ore and coke can be known. On the other hand, ordinary manganese ore and coke are reacted under the same conditions as above, and the amount of generated CO2 is compared. Through these, the CO2 reduction effect of the present invention is experimentally clear.

Industrial Applicability

[0084] According to the present invention, it is possible to achieve a CO2 reduction effect in the production of manganese-based alloys, contribute to the suppression of global warming, and meet the requirements of carbon neutrality and zero CO2 emissions.

Claims

1. A step (1) of heating manganese ore and subjecting it to hydrogen reduction to produce reduced manganese ore; Furthermore, a step (2) of charging the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, and then performing slag-metal separation; including CO ２ The operation is carried out with the manganese grade of the manganese ore, the amount of Mn in the slag, and the degree of oxidation of the reduced manganese ore such that a reduction effect of 20% or more is obtained. A method for producing a manganese-based alloy, characterized by this.

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

3. The method for producing a manganese-based alloy according to claim 1 or 2, wherein the manganese oxidation degree of the reduced manganese ore is 1.6 or less.

4. The method for producing a manganese-based alloy according to claim 3, wherein the manganese oxidation degree of the reduced manganese ore is 1.1 or less.

5. The method for producing a manganese-based alloy according to any one of claims 1 to 4, wherein the proportion of hydrogen in the gas of the reducing agent in the hydrogen reduction exceeds 70 mol%.

6. The method for producing a manganese-based alloy according to any one of claims 1 to 5, wherein the Mn content in the slag is 10% to 29%.

7. The method for producing a manganese-based alloy according to any one of claims 1 to 6, wherein the heating includes electric heating.

8. The method for producing a manganese-based alloy according to any one of claims 1 to 7, wherein the heating includes heating by hydrogen combustion.

9. The method for producing a manganese-based alloy according to any one of claims 1 to 8, further comprising a step (4) of reducing at least a part of the manganese oxide contained in the molten slag with a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum, in the molten slag produced as a by-product in the step (2).

10. The method for producing a manganese-based alloy according to any one of claims 1 to 9, further comprising a step (5) of reducing and refining a part or all of the reduced manganese ore with a reducing agent containing alloy iron containing silicon or metallic aluminum, or a reducing agent containing alloy iron containing silicon and metallic aluminum, and then performing slag-metal separation.

11. The method for producing a manganese-based alloy according to any one of claims 1 to 10, wherein a part or all of the carbonaceous material is green carbon.

12. The method for producing a manganese-based alloy according to any one of claims 1 to 11, characterized in that a slag-forming agent is added in the step (2).

13. The operation is at least one of the following: The manganese grade of the manganese ore is 60% or less, The manganese oxidation degree of the reduced manganese ore is 1.6 or less, The Mn content in the slag is 10% or more, The method for producing a manganese-based alloy according to claim 1, wherein the method is carried out by satisfying the above conditions.

14. The operation is all of the following: The manganese grade of the manganese ore is 48% or less, The manganese oxidation degree of the reduced manganese ore is 1.1 or less, The Mn content in the slag is 26% or more, The method for producing a manganese-based alloy according to claim 13, wherein the method is carried out by satisfying the above conditions.

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