Method for producing manganese-based alloy and apparatus for producing the same

Abstract

An object of the present invention is 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 an apparatus for producing the same. 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. Fig. 1

Description

Manganese alloy manufacturing method and manufacturing device

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

[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] Conventionally, 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 techniques for adding a reducing agent such as a silicon-containing ferroalloy or metallic aluminum to further reduce and extract manganese remaining in the slag. Patent Documents 3 to 6 also disclose techniques for pre-reducing manganese ore with carbon monoxide (CO) gas or coke generated in the blast furnace or electric furnace process before adding it to the blast furnace or electric furnace, rather than directly adding the manganese ore 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 inexpensive 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.

[0005] Japanese Patent Application Laid-Open No. 2006-161079 Japanese Patent Application Laid-Open No. 59-222552 Japanese Patent Application Laid-Open No. 63-195244 Japanese Patent Application Laid-Open No. 59-215458 Japanese Patent Application Laid-Open No. 38-4456 Japanese Patent Application Laid-Open No. 38-12811

[0006] Terayama, Kiyoshi et al., Thermal Measurement 18(3), 164(1991)

[0007] As mentioned above, technological developments have been made to efficiently manufacture manganese alloys. However, these have been based on the premise that carbonaceous materials such as coke are used as reducing agents when reducing manganese ore, and CO ２found that no attempt had been made to reduce

[0008] In fact, even when Patent Documents 1 to 6 and other prior art documents relating to the production of manganese-based alloys are examined, CO ２ No technological development has been carried out with the aim of reducing emissions, and there is no mention or suggestion of this. Conventional technological developments related to the production of manganese alloys have indirectly reduced some CO emissions by increasing efficiency. ２ Emissions reductions have been made, but CO ２ From the perspective of reducing CO emissions ２ No effort has been made to reduce or eliminate the use of carbonaceous materials, which are the source of carbon emissions.

[0009] Furthermore, 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 in the process of producing manganese alloys by reducing it to metallic manganese, methane CH ４ The only proposal has been to reduce CO using natural gas. ２ There is no disclosure or suggestion of its use in terms of reducing emissions.

[0010] In addition, in the explanation of FIG. 4 of Patent Document 4, surplus gas (coke-derived) from the ferromanganese furnace and the Si, Mn furnace is used to prepare pre-reduced pellets. ２ Patent Document 4 is thought to have the effect of reducing the power consumption rate, but does not have the effect of reducing carbonaceous materials.

[0011] Therefore, in the production of manganese-based alloys, CO ２ The present inventors have found that there is a need for technological development to proactively reduce emissions.

[0012] The present invention has been made in view of the above problems, and provides a method for producing a manganese-based alloy by using CO ２ The present invention aims to provide a method for producing manganese-based alloys that enables emissions reduction.

[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 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, 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., characterized in that 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 14., further comprising means (2) for charging 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 a part or all of the reduced manganese ore by molten oxide electrolysis, followed by slag / metal separation.

[0030] 17. The apparatus for producing a manganese-based alloy according to any one of 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.

[0031] According to the method of the present invention, the manganese ions contained in manganese ore are reduced with hydrogen, thereby reducing CO2 in the production of manganese-based alloys. ２Furthermore, the manufacturing apparatus of the present invention has the effect of significantly reducing CO emissions in the production of manganese-based alloys. ２ It can significantly reduce CO emissions ２ This has the effect of reducing emissions to almost zero.

[0032] Temperature dependence of Gibbs free energy ΔG (chemical potential) of each reaction ２ ) and CO when hydrogen reduction is introduced in the production of manganese-based alloys. ２ Reduction effect When manganese ore is reduced by carbon, the Mn content in the slag is reduced to zero, increasing the Mn yield. This figure explains the production of a manganese alloy. 40% of the Mn content is produced as metallic manganese (manganese alloy) from manganese ore containing 50% Mn, and 30% Mn-containing slag (30% Mn in the slag) is discharged. ２ As a result of calculating the reduction effect, assuming 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, the CO ２ Calculation result of reduction effect (when each is combined into one reaction formula) CO ２ Effect of Mn content of manganese ore and Mn content in slag on CO reduction effect ２ Effect of manganese alloy production volume and Mn content in slag on CO reduction effect ２ The influence of the degree of reduction of manganese ore by hydrogen reduction (the degree of Mn oxidation of reduced Mn ore) on the reduction effect. Configuration flow of a conventional manganese alloy manufacturing device. Configuration flow of the manganese alloy manufacturing device of the present invention. Confirmation of hydrogen reduction by thermogravimetric changes of manganese ore.

[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, a method for producing a reduced manganese ore by heating and hydrogen-reducing manganese ore is provided. ２ A method for producing reduced emission manganese-based alloys is provided.

[0035] The raw material for manganese-based alloys, for example, manganese ore, usually contains tetravalent manganese (MnO ２ When manganese ore is mixed with coke or other carbonaceous material as a reducing agent and put into an electric furnace to reduce tetravalent manganese (ore) to zerovalent metallic manganese (manganese alloy), a considerable amount of carbon dioxide is emitted, even if the reduction reaction occurs theoretically efficiently.

[0036] Here, the inventors have considered the reduction of manganese ore from a thermodynamic point of view and have found that tetravalent manganese (MnO ２ The reducing agents that can reduce manganese dioxide (equivalent to MnO) to divalent manganese (equivalent to MnO) are carbon C, carbon monoxide CO, and hydrogen H. ２ , etc. (Figure 1). Only carbon (C) can reduce divalent manganese (equivalent to MnO) to zerovalent manganese (metallic Mn) (Figure 1). Carbon (C) can also be reduced to metallic manganese only at temperatures above 1450°C.

[0037] Next, manganese ore was treated as MnO ２ In the process of producing manganese alloys, the CO generated during hydrogen reduction of manganese ore is ２ Consider the reduction effect (Figure 2). Tetravalent manganese (MnO ２ (equivalent to MnO) with CO. ２ Even if a reducing agent that does not generate CO, such as hydrogen, is used, only carbon (C) can reduce divalent manganese (equivalent to MnO) to zerovalent manganese (metallic Mn), as mentioned above. Therefore, 1 mole of carbon C is required to produce 1 mole of metallic Mn from manganese (Mn). ２ The reduction effect is zero.

[0038] Thus, even if manganese ore is reduced with hydrogen, CO ２The reduction effect is considered to be zero in the first place, and there are also expected disadvantages such as the need for new devices and equipment, so those skilled in the art would not consider using hydrogen for pre-reduction.

[0039] In response to this, the present inventors have found that if a manganese alloy (particularly ferromanganese) is produced by setting the Mn content in the slag discharged from manganese ore to, for example, around 30%, the CO ２ In this way, we found that the reduction of manganese to less than tetravalent manganese with hydrogen has an active CO ２ The present invention was based on the idea that Mn can be emitted from slag in the form of 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 with 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: manganese ore contains slag components (silica SiO ２ , silicates), i.e., MnO—SiO ２ Since they coexist, reaction equations (1) and (2) in Figure 3 occur, and the relationship shown in equation (4) can be derived from the equilibrium equation of reaction equation (3) obtained by subtracting equation (1) x 2 from equation (2). Equation (4) indicates that to lower the [MnO] concentration, i.e., to increase the Mn yield, the [Si] concentration must be increased. 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 best to set the Mn content in the slag to around 30%, for example.

[0041] By using this method, manganese ore can be reduced with hydrogen in advance, and CO ２The inventors have found that a reduction effect is observed (Figs. 4 and 5). Fig. 4 shows, as an example, a CO reduction model in which 40% of the Mn content is produced as metallic manganese (manganese alloy) from manganese ore containing 50% Mn (Mn grade), and 30% Mn-containing slag (30% Mn in the slag) is discharged. ２ First, all of the manganese (50%) contained in manganese ore is reduced to MnO. According to the current coke (carbon) reduction method using an electric furnace, carbon (C) and carbon monoxide (CO) are used as reducing agents in a ratio of 0.3:0.4. Here, the carbon monoxide (CO) is generated by the reaction of carbon (C) required to produce 50% of metallic manganese (manganese alloy) from MnO. Therefore, 1 mole of MnO ２ 0.7 moles of CO ２ will be generated.

[0042] In contrast, when hydrogen reduction is used, preferably for reduction to MnO, the manganese contained in the manganese ore (50%) is reduced by CO ２ In other words, MnO ２ When hydrogen reduction is used to reduce manganese ore to MnO, all of the manganese contained in the manganese ore is reduced to MnO. ２ Of the manganese in the hydrogen-reduced manganese ore, 40% is reduced to metallic manganese (manganese alloy) with coke (carbon), and carbon monoxide (CO) is generated in an amount corresponding to the amount of carbon. The generated carbon monoxide (CO) is then burned (oxygen O ２ (by reacting with carbon dioxide CO ２ Therefore, 1 mole of MnO ２ 0.4 moles of CO ２ will be generated.

[0043] Therefore, in the above model, CO generated in the current electric furnace reaction ２ When hydrogen reduction to MnO is performed, 43% CO ２ In addition, in FIG. 5, each reaction is expressed by a single reaction formula.

[0044] In other words, CO ２ As explained in FIG. 3 , the mechanism by which the reduction effect is obtained is such that all of the manganese contained in the manganese ore is reduced to metallic manganese so as not to produce a manganese-based alloy, but rather all of the manganese in the manganese ore is reduced with hydrogen to manganese with a valence of less than 4, or to divalent manganese (manganese oxidation degree 1.0), or reduced with hydrogen to a valence close to 2 to produce reduced manganese ore, and then part or all of this is reduced 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, the carbon dioxide CO generated in the conventional manganese alloy production method can be reduced. ２ Compared to CO ２ The method for producing a manganese-based alloy can reduce emissions.

[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. The processes (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] In addition, since what is generated in the step (2) is basically carbon monoxide (CO), the final form of emission is carbon dioxide (CO) (see FIG. 10). ２ and omits the description of the oxidation (combustion) of carbon monoxide (CO), and the carbon monoxide (CO) generated here may be used together with hydrogen for the reduction in the step (1).

[0048] CO in the present invention ２ The reduction effect is the above-mentioned CO ２Since this depends on the reduction mechanism, the relationship shown in Figure 6 is obtained. Note that Figure 6 was derived by plotting the percentage of the corresponding reduction effect by modifying the reaction formula shown in Figure 4 so as to obtain the desired Mn grade in the ore and the desired Mn amount in the slag. In other words, in terms of the Mn grade (Mn content) of manganese ore, the lower the Mn grade, the greater the reduction in CO ２ In other words, the higher the Mn grade, the greater the CO reduction effect. ２ In addition, the amount of Mn remaining in the slag increases as the amount of Mn in the slag increases. ２ In other words, the reduction effect of CO ２ By including the step (1) of heating manganese ore to reduce it with hydrogen, the CO ２ However, as mentioned above, the Mn content of the manganese ore and the Mn content of the slag affect the CO reduction effect. ２ Generally speaking, the more manganese alloys can be produced efficiently from manganese ore, the greater the reduction effect. ２ Therefore, it is necessary to secure a certain level of productivity and reduce CO ２ From the viewpoint of obtaining a reduction effect, it is preferable to set the Mn content of the manganese ore to, for example, 40 to 60%. ２ A 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 CO ２ FIG. 7 shows the influence of the manganese-based alloy production rate (the ratio of manganese ore to manganese alloy (ferromanganese), Mn / Mn ore-%) on the reduction effect. This FIG. 7 was derived by plotting the corresponding reduction effect percentages while modifying the reaction formula shown in FIG. 4 to obtain the desired Mn content in the slag and the desired manganese production rate (manganese production ratio). A similar trend to that shown in FIG. 6 can be seen from FIG. 7. According to a preferred embodiment, the manganese-based alloy production rate is 5 to 50%, 5 to 40%, or 10 to 30%.

[0051] Here, the manganese oxidation degree (Mn oxidation degree) will be explained. ｘ where x is the manganese oxidation degree. For example, manganese oxidation degree x = 2 is MnO ２ and the manganese oxidation degree x=1 is MnO. Therefore, the manganese oxidation degree of manganese ore or reduced manganese ore is calculated by the total manganese content (Mn%, JIS M8232 2005 Manganese ore - Manganese determination method) and the available oxygen content of manganese oxide (MnO ２ %, JIS M8233 1995 Manganese ore - Active oxygen determination method) ｘ Calculate x and use this as the manganese oxidation degree.

[0052] FIG. 8 shows the CO ２Fig. 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 CO reduction effect. This Fig. 8 was derived by plotting the corresponding percentage of reduction effect while modifying the reaction formula shown in Fig. 4 to achieve the desired oxidation degree, desired Mn content, and desired Mn amount in the slag. It is assumed that the manganese oxidation degree in reduced manganese ore is less than 2. However, as shown in Fig. 8, the higher the manganese oxidation degree, the greater the CO reduction effect. ２ In other words, the smaller the manganese oxidation degree becomes and the closer it is to 1.0, the smaller the CO reduction effect becomes. ２ The reduction effect will be greater. By securing the production volume of manganese alloys, more effective CO ２ To achieve this reduction effect, in step (1), the reduced manganese ore is preferably reduced 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. When 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 lower 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, where the manganese oxidation degree of the manganese ore is taken as 100%. Regardless of the manganese oxidation degree of the raw manganese ore, the manganese oxidation degree of the reduced manganese ore is preferably 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, under conditions containing hydrogen, CO ２ Within the range where CO reduction effects can be achieved ２ It may contain reducing materials that are sources of generation, such as CO and carbonaceous materials.

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

[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, a solid reducing agent (CO ２ The amount (proportion) of the reducing material (e.g., carbonaceous material (coke)) to be generated 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 is CO ２ The amount of the reducing material that becomes a source of generation is 1000 ppm by weight or less. As described above, according to a preferred embodiment, the reducing material does not include CO or carbonaceous materials.

[0057] In addition, gases other than the reducing agent in hydrogen reduction include nitrogen, water vapor, and CO ２ , 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, taking into consideration 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 in all gases (i.e., reducing agent gas and gas 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, CO generated in the current electric furnace reaction shown in FIG. ２ When hydrogen reduction is performed to MnO, the amount of CO is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. ２ This will result in a reduction effect.

[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 specific gravity between them, the molten manganese-based alloy is positioned at the bottom of the furnace and the molten slag is positioned above it. Therefore, depending on the timing of tapping, the height of the tap opening, and other factors, 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 yield ferromanganese or metallic manganese with almost no carbon content. This embodiment is schematically illustrated in the middle flow chart of Figure 10.

[0064] The heating in the step (1) may be performed by any heating method as long as it is possible to heat the manganese ore to a temperature at which it can be reduced with hydrogen. ２ For example, the heating method in the step (1) is more preferable because it can reduce the amount of carbon dioxide CO ２In addition, the heating in the step (1) by hydrogen combustion is preferable from the viewpoint of reducing carbon dioxide CO ２ This is preferable from the viewpoint of reducing emissions and being able to supply hydrogen at the same time.

[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 the 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] The carbonaceous material in the step (2) may be conventional coke, but by using green carbon as part or all of it, it is possible to obtain a carbon dioxide (CO ２ The green carbon includes biocarbon (biologically derived carbon materials such as charcoal and bamboo charcoal), coke made from waste plastics, fuel-derived carbon materials obtained from hydrogen and carbon dioxide synthesized 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 contained in 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 more efficiently as a reducing agent.

[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 the step (2), a slag forming agent (slag adjusting agent) can be added to the electric furnace. The slag forming agent can control the properties of the slag, such as viscosity, oxygen potential, and basicity. For example, lime, slaked lime, Na ２ CO ３ , CaCl ２ , MgCO ２ , etc.

[0072] A manganese-based ferroalloy can also be produced by reducing a part or all of the reduced manganese ore produced in step (1) 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, 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 a means (1) for heating manganese ore and subjecting it to hydrogen reduction to produce reduced manganese ore, and a means (2) for introducing the reduced manganese ore together with a carbonaceous material into an electric furnace for refining, followed by slag / metal separation.

[0074] Furthermore, it is more preferable that the apparatus for producing a manganese-based alloy further comprises 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.

[0076] 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%). While industrial furnaces capable of heating and hydrogen reduction, such as fluidized bed furnaces, shaft furnaces, and rotary kilns, are used, experimentally the manganese ore is heated in a tubular furnace and supplied with a hydrogen-containing gas to reduce it and produce reduced manganese ore. As an example, Gabonese manganese ore (MnO ２ The resulting reduced manganese ore was placed in an alumina boat, which was then charged into a tubular furnace and heated at 900°C for 1 hour in a flow of 4 mol% hydrogen / nitrogen gas to produce reduced manganese ore. The manganese oxidation degree of the resulting reduced manganese ore was 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 was 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 the hydrogen reduction, but it may be set 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 processing amount of manganese ore, a hydrogen concentration of 1 mol% or more is preferable.

[0079] An example of a more industrial-scale hydrogen reduction experiment is an experiment on hydrogen reduction of manganese ore using an externally heated rotary kiln. Reduced manganese ore is obtained by introducing a 4 mol% hydrogen / nitrogen mixed gas and heating the manganese ore in the test kiln for hydrogen reduction. For example, reduced manganese ore with a manganese oxidation degree of 1.1 is obtained by treating 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. The higher the manganese oxidation degree of the reduced manganese ore, the shorter the hydrogen reduction treatment time and the less hydrogen required, but the CO ２ On the other hand, the lower the manganese oxidation degree of the reduced manganese ore becomes, the closer it is to 1.0 or 1.0, the smaller the CO reduction effect becomes. ２ The reduction effect will be greater.

[0080] In this embodiment, the Mn content in the slag may be 20 to 33%, and the manganese-based alloy production rate 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 as a carbonaceous material are refined in a 100 kVA Giraud furnace (single-phase arc furnace), and the manganese alloy (ferromanganese) molten metal and slag are separated and removed by tapping, thereby obtaining a manganese alloy. Since the Giraud furnace is an open furnace, the carbon monoxide (CO) (carbon dioxide (CO)) generated is removed. ２Although the amount of CO2 cannot be measured, it is possible to produce manganese alloys by reducing reduced manganese ore with carbonaceous material, and the oxygen content of the reduced manganese ore used as the raw material (manganese oxidation degree) is low, so only a small amount of carbonaceous material is required. ２ The reduction effect can be confirmed. The obtained 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, and then heated in a vertical tubular furnace with an inert carrier gas (nitrogen N ２ By electrically heating the furnace to over 1450°C while circulating gas (or argon Ar) and measuring the concentration of carbon monoxide (CO), the CO concentration due to the reaction between reduced manganese ore and coke can be determined. ２ On the other hand, when ordinary manganese ore and coke are reacted under the same conditions as above, the amount of CO generated can be seen. ２ These results indicate that the CO ２ The reduction effect is clearly demonstrated experimentally.

[0084] According to the present invention, the CO ２ This can contribute to the prevention of global warming and contribute to carbon neutrality and CO ２ This meets the demand for zero 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. 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. A method for producing a manganese alloy according to claim 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.

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

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 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 electrical heating.

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.

10. A 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 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. A method for producing a manganese-based alloy as set forth in any one of claims 1 to 10, further comprising a step (5) of reducing all or part 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 perform refining, followed by slag-metal separation.

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

13. A method for producing a manganese-based alloy according to any one of claims 2 to 12, characterized in that a slag former is added in step (2).

14. An apparatus for producing manganese alloys, comprising means (1) for heating manganese ore and reducing it with hydrogen.

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

16. The apparatus for producing manganese alloys according to claim 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.

17. An apparatus for producing a manganese-based alloy as set forth in any one of claims 14 to 16, characterized in that it comprises 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.