Method for producing manganese carbide and method for producing manganese-containing steel

Abstract

Disclosed is a method for producing a manganese carbide, which is capable of reducing the emission of CO2. Manganese ore is heated to a treatment temperature at which the manganese ore is not molten, and the manganese ore is brought into contact with a mixed gas of hydrogen gas and hydrocarbon gas at atmospheric pressure to perform reduction treatment of the manganese ore. It is preferable that the partial pressure of the hydrocarbon gas in the mixed gas is 10.0 kPa or more, the number of hydrogen atoms in the mixed gas is 12 times or more of the number of carbon atoms, and the processing temperature is 800 DEG C or more and less than the melting temperature Tm. It is preferable that the manganese ore has a particle diameter of 3-100 mm inclusive, is treated with a rotary kiln, and is supplied with the hydrocarbon gas or the like from a position at which the temperature inside the rotary kiln is 700 DEG C or higher. Also disclosed is a method for producing manganese-containing steel, which comprises a step in which the obtained manganese carbide is added to molten steel.

Description

Technical Field

[0001] This invention relates to a method for producing manganese carbides by reducing and carbonizing manganese ore, and to a method for manufacturing manganese-containing steel using the produced manganese carbides.

[0002] [definition]

[0003] In this specification, when referred to by letters such as "Mn" or "MnO2", the chemical formula indicates the substance. When referred to by "manganese" and in non-abbreviated form, the amount of manganese contained in the substance is indicated regardless of its morphology.

[0004] Additionally, in this specification, the unit of volume "L" represents 10 -3 m 3 The symbol "N" preceding the unit of volume for a gas indicates its standard state. Standard state refers to a temperature of 0°C and an atmospheric pressure of 1 atm. Additionally, the unit of pressure, 1 atm, is 1.01325 × 10⁻⁶. 5 Pa. Furthermore, T.Mn (total Mn) in a substance represents the total amount of manganese contained in that substance, regardless of its form. Background Technology

[0005] Manganese is added to molten steel during the steelmaking process to improve its toughness and wear resistance. Manganese-containing substances added during steelmaking include metallic manganese, ferromanganese, and ferrosilicon. Ferromanganese is generally produced by charging manganese ore, iron ore, and a reducing agent into a melting furnace, where the manganese and iron ore are melted and reduced. This method requires a conveying container to hold and transport the molten material, and a casting device to cool and solidify it. Therefore, there are concerns about the increasing size of the equipment and the deterioration of the processability of ferromanganese products. Furthermore, there are concerns about the reduction yield due to the scattering of molten material during the reduction process and its residue in the melting furnace.

[0006] Regarding methods for reducing manganese ore in a solid state, for example, as shown in Patent Documents 1 to 4, a method has been proposed that uses a reducing gas instead of a solid carbonaceous substance for heat treatment.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 50-070202

[0010] Patent Document 2: Japanese Patent Application Publication No. 56-072150

[0011] Patent Document 3: Japanese Patent Application Publication No. 08-253308

[0012] Patent Document 4: Japanese Patent Application Publication No. 2023-140706 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, the aforementioned prior art presents the following problems that must be addressed.

[0015] That is, in the methods disclosed in Patent Documents 1 and 2, the highly oxidized manganese oxides (MnO2, Mn2O3, etc.) contained in the manganese ore are partially reduced to obtain only the less oxidized manganese oxides (MnO). In order to obtain manganese alloy products, the reduced products need to be further melted and reduced.

[0016] On the other hand, in the smelting and reduction process of manganese ore, solid carbonaceous materials such as coke are used as reducing agents, resulting in the emission of large amounts of CO2. From the perspective of recent efforts to reduce greenhouse gas emissions for global environmental protection, it is also necessary to reduce the amount of solid carbonaceous materials used in manganese alloy manufacturing to lower CO2 emissions.

[0017] However, the methods disclosed in Patent Documents 1 and 2 cannot obtain manganese alloy products using only reducing gas; it is necessary to supply solid carbonaceous materials during the further melting and reduction of the reduced products. Therefore, the overall reduction in CO2 emissions during the ore reduction process is limited.

[0018] Furthermore, the methods disclosed in Patent Documents 3 and 4 reduce manganese oxides with high oxidation levels contained in manganese ore to obtain manganese carbides (Mn7C3, Mn3C, etc.). However, the method disclosed in Patent Document 3 requires a step of micro-grinding the manganese ore to below 1 mm. With such fine granules or powder, there are concerns about deterioration in processability and a decrease in the yield of the resulting manganese carbides. Additionally, the method disclosed in Patent Document 4 does not disclose an appropriate range for the particle size of the manganese ore. Again, with fine granules or powder, there are concerns about deterioration in processability and a decrease in the yield of the resulting manganese carbides. On the other hand, if the particle size is too large, there are concerns that the reaction efficiency of the reduction-carbonization treatment will decrease.

[0019] Furthermore, the reduction-carbonization reaction of manganese ore proceeds faster at higher temperatures, but the method disclosed in Patent Document 3 requires maintaining the manganese ore at 250–520°C. Therefore, the reduction-carbonization treatment of manganese ore requires 48 hours, resulting in reduced production efficiency of manganese carbides.

[0020] Therefore, in order to solve the above-mentioned problems existing in the prior art, the object of the present invention is to provide a method for manufacturing manganese carbides, which does not use more than two reduction treatment devices and does not require the micro-pulverization of manganese ore, and can efficiently carry out the reduction-carbonization treatment of manganese ore in a short time, thereby reducing CO2 emissions. Furthermore, a method for manufacturing manganese-containing steel using the obtained manganese carbides is proposed.

[0021] Methods for solving problems

[0022] In the process of researching the above-mentioned problems existing in the prior art, the inventors contacted manganese ore with hydrogen and hydrocarbon gases at a processing temperature in an unmelted state to carry out the reduction-carbonization treatment of manganese ore, thus completing the present invention.

[0023] That is, the method for manufacturing manganese carbides according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that manganese ore is heated to a processing temperature in an unmelted state and contacted with a mixture of hydrogen and hydrocarbon gases under atmospheric pressure to perform the reduction-carbonization treatment of the manganese ore.

[0024] It should be noted that the method for manufacturing manganese carbides of the present invention can be implemented in a more preferred manner, such as the following: a. The partial pressure of the hydrocarbon gas in the above-mentioned mixed gas is 10.0 kPa or more, and the number of hydrogen atoms in the above-mentioned mixed gas is 12 times or more the number of carbon atoms; b. The above processing temperature is above 800°C but below the melting temperature T. m Scope; c. The particle size of the aforementioned manganese ore is also pre-adjusted to be above 3mm and below 100mm; d. Perform the above reduction-carbonization treatment using a rotary kiln; e. The mixed gas is supplied from a location inside the rotary kiln where the temperature is above 700°C; f. At the location where the above-mentioned mixed gas is supplied, the partial pressure of the hydrocarbon gas in the above-mentioned mixed gas is 10.0 kPa or more, and the number of hydrogen atoms in the above-mentioned mixed gas is 12 times or more the number of carbon atoms; g. Ensure that the highest internal temperature of the rotary kiln is above 800°C but below the melting temperature T. m The range.

[0025] In addition, the above-mentioned melting temperature T m The temperature at which the solid sample changes into a liquid is determined by any of the first to third methods described below, which is simple and therefore preferred, but not limited to these methods.

[0026] The first method is as follows: a solid sample is placed in a container such as a crucible, and the sample in the container is continuously observed while being heated at 5°C per minute, preferably less than 1°C per minute, using a resistance furnace or the like under the gas atmosphere to be targeted. The melting point is the temperature at which the gaps between the particles of the solid sample disappear and a smooth surface is formed.

[0027] The second method is as follows: Under the gas atmosphere to be tested, the temperature is increased by 5°C per minute, preferably less than 1°C per minute, using differential calorimetry, and the temperature at which the endothermic peak minimum occurs is taken as the melting point. Here, the method is as follows: When two or more endothermic peaks are generated, the measurement is stopped at the temperature at which each endothermic peak occurs, the appearance of the sample is observed, and the temperature at which the minimum of the lowest endothermic peak occurs when the gaps between the particles of the solid sample disappear and a smooth surface is formed is taken as the melting point.

[0028] The third method is as follows: using thermodynamic calculation software on a computer, inputting the sample composition and changing the temperature to calculate the liquidus fraction, and taking the temperature at which the calculated liquidus fraction exceeds 95% as the melting point.

[0029] Furthermore, the method for manufacturing manganese-containing steel according to the present invention, which advantageously solves the above-mentioned problems, is characterized by including a step of adding manganese carbides manufactured by any of the above-mentioned manufacturing methods to molten steel.

[0030] Invention Effects

[0031] According to the present invention, when performing reduction-carbonization treatment on manganese ore, no more than two reduction treatment devices are used, micronization of the manganese ore is unnecessary, and the manganese ore is not melted, enabling efficient reduction-carbonization treatment of manganese ore in a shorter time. Furthermore, it reduces CO2 emissions during the reduction-carbonization process. Detailed Implementation

[0032] In developing this invention, the inventors loaded manganese ore into a reaction vessel for reduction-carbonization treatment, and while supplying a reducing agent, maintained the reaction vessel at a predetermined temperature to perform the reduction-carbonization treatment, thereby producing manganese carbides. Here, manganese carbides refer to manganese compounds in which the oxygen concentration in the manganese compound decreases to below a predetermined value after the manganese ore is reduced, and the carbon concentration is within a predetermined range. For example, manganese compounds with an oxygen (O) concentration of 6.0% by mass or less and a carbon (C) concentration of 4.0% by mass or more are preferably used as manganese carbides.

[0033] In this manufacturing process, various changes were made to conditions such as the type of reducing agent, the amount of reducing agent supplied, and the method of supplying the reducing agent to investigate the reduction behavior of manganese ore. The results showed that by using hydrogen and hydrocarbon gases as reducing agents and performing reduction-carbonization treatment without melting the manganese ore, the reduction-carbonization treatment could be performed easily without using more than two reduction treatment units. Furthermore, it was found that CO2 emissions during the reduction-carbonization treatment could be reduced. Details are as follows.

[0034] First, in the reduction method of manganese ore conforming to the present invention, a mixture of hydrogen and hydrocarbon gases is required as a reducing agent. Mn in manganese ore mainly exists in the form of MnO2. Therefore, when only hydrogen is used, as shown in formulas (1) to (3) of Chemical Formula 1 below, MnO2 is reduced only to MnO. Reduction to metallic manganese using only hydrogen is thermodynamically difficult.

[0035] [Chemical Formula 1]

[0036] On the other hand, when using hydrocarbon gases such as methane and propane, a portion of the hydrocarbon gas decomposes at high temperatures to produce highly reactive carbon and hydrogen. Therefore, in addition to the reactions described in formulas (1) to (3) above, for example, a carbonization reaction from MnO to manganese carbides such as Mn7C3 can be carried out as shown in formula (4) of chemical formula 2 below.

[0037] [Chemical Formula 2]

[0038] However, when the highly reactive carbon generated by the decomposition of hydrocarbon gases is consumed in the reduction reaction from MnO2 to MnO, a large amount of CO2 is emitted, similar to conventional melt reduction processes using solid carbonaceous materials. Furthermore, the carbon supply required for the carbonization reaction from MnO to Mn7C3 is insufficient, necessitating an excessive supply of hydrocarbon gases. This can potentially lead to a decrease in reduction efficiency and an increase in the cost of the reducing agent. Therefore, it is proposed that by using a mixture of hydrogen and hydrocarbon gases as the reducing agent, the reduction process from MnO2 to MnO can be performed primarily using hydrogen, while simultaneously carrying out the carbonization process of MnO with a minimal supply of hydrocarbon gases.

[0039] Furthermore, in the reduction-carbonation process, the manganese ore needs to be reacted at a processing temperature in its unmelted state. As mentioned above, in the molten reduction of manganese ore, issues such as the large size of the reduction processing equipment and the deterioration of processability have become problems. On the other hand, by ensuring permeability without melting the manganese ore and using a gaseous reducing agent for reduction-carbonation processing, it is possible to simplify the reduction processing equipment and improve processability.

[0040] Regarding the composition of the mixture of hydrogen and hydrocarbon gases in contact with manganese ore, the following ranges are preferred. First, the partial pressure of the hydrocarbon gas in the mixture is 10.0 kPa or higher. Furthermore, reducing the partial pressure of oxygen in the atmosphere is effective in promoting the carbonization reaction of MnO. For example, when the temperature of the manganese ore is 1100°C, and the partial pressure of the hydrocarbon gas in the supplied mixture is less than 10.0 kPa, the oxygen partial pressure required to promote the carbonization reaction of MnO is 1.0 × 10⁻⁶ kPa. -17 Below kPa. This makes it difficult to maintain a very low oxygen partial pressure in the atmosphere. There is no upper limit to the partial pressure of hydrocarbon gases in the supplied mixed gas. However, as mentioned above, the higher this value, the more likely it is to result in an excess of hydrocarbon gases being supplied; therefore, it is more preferable to set it to below 50.0 kPa. Furthermore, the number of hydrogen atoms in the mixed gas should be more than 12 times the number of carbon atoms. If the number of hydrogen atoms in the mixed gas contacting the manganese ore is less than 12 times the number of carbon atoms, the hydrogen concentration in the mixed gas may be too low. Therefore, as mentioned above, an increase in the proportion of hydrocarbon gases consumed in the reduction reaction from MnO2 to MnO may lead to an increase in CO2 emissions. There is no upper limit to the ratio of hydrogen atoms to carbon atoms in the mixed gas, but the higher this value, the lower the proportion of hydrocarbon gases in the mixed gas, and the more difficult the carbonization reaction of MnO may be to proceed. Therefore, it is more preferable to set the number of hydrogen atoms in the mixed gas to be less than 22 times the number of carbon atoms.

[0041] Regarding the processing temperature for reduction-carbonization, it is preferable to heat the manganese ore to above 800°C but below the melting temperature T. m Regarding the melting temperature T m The definition of MnO is preferably achieved using the first to third methods described above. Patent Document 3 discloses a carbonization initiation temperature of 1870°C for MnO using a mixture of hydrogen and methane gas. However, through repeated implementation of reduction-carbonization treatment of manganese ore using hydrogen and hydrocarbon gases, the inventors found that manganese carbides can be obtained even at temperatures below 1870°C. In the reduction method for manganese ore conforming to the present invention, the carbonization reaction of MnO using hydrocarbon gas begins at approximately 750°C. The higher the processing temperature, the more it promotes the reduction reaction of MnO2 and the carbonization reaction of MnO. Therefore, a temperature of 1100°C or higher is more preferable. The processing temperature is the melting temperature T of the manganese ore. m At the above temperatures, due to melting, air permeability decreases, which may hinder the reduction-carbonization reaction. From an energy-saving perspective, the processing temperature for reduction-carbonization is more preferably set below 1200°C.

[0042] Furthermore, it is preferable to add the manganese carbide obtained by the above method to the molten steel in any step of the steelmaking process. As described above, ferromanganese is used in the steelmaking process of molten steel. Ferromanganese is classified according to carbon content into high-carbon ferromanganese, medium-carbon ferromanganese, low-carbon ferromanganese, and very low-carbon ferromanganese, and is used separately according to the steel composition standards and manufacturing processes. Among them, high-carbon ferromanganese contains about 7% by mass of C, and the C in ferromanganese exists in the form of manganese carbides such as Mn7C3 and Mn5C2. The manganese carbide obtained by the manganese carbide manufacturing method according to the present invention mainly contains Mn7C3 and Mn5C2. The manganese carbide according to the present invention, like high-carbon ferromanganese, can be used as a manganese source in the primary and secondary refining of molten steel. On the other hand, in the manganese carbide manufacturing method according to the present invention, it is difficult to separate and remove the gangue components (oxides of Si, Al, etc.) contained in the manganese ore. Therefore, the obtained manganese carbide contains the above-mentioned gangue components. However, if the manganese carbides obtained by the above method are added to molten steel, Mn7C3 and Mn5C2 will quickly melt into the molten steel, and the gangue components will be transferred to the steelmaking slag. Therefore, the Mn concentration can be increased without increasing the impurity elements in the molten steel.

[0043] Next, an example of reducing-carbonizing manganese ore based on the method for manufacturing manganese carbides according to the present invention will be specifically described. It should be noted that examples of the composition of the manganese ore used are shown in Table 1.

[0044] [Table 1]

[0045] Manganese ore, used as raw material, is loaded into a reaction vessel for reduction-carbonization treatment. The form of the reaction vessel is not limited; continuous reaction vessels such as blast furnaces and batch reaction vessels such as rotary kilns can be used. The particle size of the manganese ore is not limited, but the addition of fine granules or powder raises concerns about reduced yield and deterioration of processability; therefore, a particle size of 3 mm or larger is preferred. Excessively large particle sizes may reduce the reaction efficiency of the reduction-carbonization treatment; therefore, a particle size of 100 mm or smaller is preferred.

[0046] Furthermore, there are no restrictions on the properties of the manganese ore. Hydrogen and hydrocarbon gases, acting as reducing gases, are supplied to the reaction vessel, with the supply of each gas controlled to achieve a predetermined gas composition within the vessel. The method of gas supply is not limited; a mixture of hydrogen and hydrocarbon gases can be used, or hydrogen and hydrocarbon gases can be supplied from separate, independent inlets. Alternatively, reducing gases can be introduced through vents located on the bottom or side of the reaction vessel, or by blowing reducing gases from above the manganese ore layer filled within the reaction vessel using a spray gun. Next, the reaction vessel is heated to a predetermined processing temperature within a range where the manganese ore does not melt. The heating method for the manganese ore and the reaction vessel is not limited; burner heating, resistance heating, induction heating, etc., can be used. The manganese ore that has undergone reduction-carbonization treatment in the above process becomes a manganese carbide product. The uses of manganese carbide products are not limited; for example, they can be added to molten steel as a manganese source in steelmaking processes.

[0047] In methods for manufacturing manganese-containing steel, the Mn concentration in the molten steel can be adjusted, for example, by adding manganese carbides during ladle refining after converter tapping, or during processes such as arc heating or vacuum degassing. In this case, it is preferable to supply oxygen during vacuum degassing to perform decarburization, thereby adjusting the carbon concentration that increases due to the addition of manganese carbides. The molten steel with adjusted composition can then be formed into steel sheets through continuous casting or similar methods, and surface treatments such as hot rolling, heat treatment, cold rolling, annealing, and plating can be performed as needed to manufacture manganese-containing steel.

[0048] Example

[0049] <Example 1>

[0050] An example of reduction-carbonization treatment of manganese ore A (Table 1) using a 10 kg resistance furnace is described. After adjusting the output of the resistance furnace and heating it to the specified temperature, 10 kg of a sample of manganese ore A with a particle size of 1–5 mm was loaded into the furnace. Various conditions are shown in Table 2. The T.Mn concentration in the manganese ore A before reduction-carbonization treatment was 51.2–55.8% by mass. It should be noted that the T.Mn concentration refers to the total manganese concentration in the manganese ore. Next, at treatment levels No.1–No.10 and No.16, a mixed gas of hydrogen (H2) and methane (CH4) was supplied from two or more vents located on the side of the reaction vessel at a flow rate of 30 NL / min using a sample of manganese ore A with a particle size of 5 mm. Then, the reduction-carbonization treatment was carried out for a specified time. During this process, various changes were made to the composition of the supplied gas and the temperature inside the resistance furnace to implement the reduction-carbonization treatment. In addition, at levels No. 11 and No. 12, samples of manganese ore A with particle sizes of 1 mm and 3 mm, respectively, were subjected to the same reduction-carbonization treatment. Here, as a pretreatment, samples of manganese ore A with a particle size of 5 mm were crushed using a roller crusher to produce samples of manganese ore A with particle sizes of 1 mm and 3 mm. At some levels, as a comparative example, manganese ore samples with a particle size of 5 mm were used, with only hydrogen gas supplied (treatment No. 13) and only methane gas supplied (treatment No. 14). In treatment No. 15, coke was used as the solid carbonaceous material for the reduction-carbonization treatment. It should be noted that when using coke, the coke loading was set to 5 kg, and Ar gas was supplied from a vent located on the side of the reaction vessel at a flow rate of 30 NL / min. In addition, in treatment No. 16, as a comparative example, a sample of manganese ore A with a particle size of 5 mm was used. A mixture of hydrogen and methane gas was used, and the temperature inside the resistance furnace was maintained at 1300°C to perform a reduction-carbonization treatment. A gas chromatograph was installed in part of the gas exhaust system of the resistance furnace to measure the CO and CO2 concentrations in the gas emitted outside the resistance furnace.

[0051] After a specified time, the manganese ore sample was removed from the resistance furnace and cooled in air. The oxygen and carbon concentrations in the sample were analyzed by combustion, and the concentrations of elements other than oxygen and carbon were analyzed by fluorescence X-ray diffraction. The reduction state of the sample was investigated. The reduction-carbonization treatment conditions and reduction rate of the manganese ore are shown in Table 2. Here, the reduction rate of the manganese ore in Table 2 is expressed as a percentage relative to the oxygen concentration of manganese oxides in the manganese ore before reduction-carbonization treatment, representing the difference between the oxygen concentration of manganese oxides in the manganese ore before reduction-carbonization treatment and the oxygen concentration of manganese oxides in the manganese compounds after reduction-carbonization treatment. It should be noted that the oxygen concentration of manganese oxides in the manganese ore is the difference between the analytical value of the overall oxygen concentration of the manganese ore sample and the calculated sum of the oxygen concentrations of oxides other than manganese in the manganese ore. Furthermore, the CO2 concentration in the exhaust gas in Table 2 is the sum of the average CO2 concentration measured during the reduction-carbonization treatment and the average value of the CO concentration measured during the reduction-carbonization treatment converted to CO2 concentration. In Table 2, "H2" in the "Supply Gas" column represents the hydrogen concentration, "CH4" represents the hydrocarbon gas concentration, and "P" represents the hydrocarbon gas concentration. CH4 "H / C" indicates the partial pressure of the hydrocarbon gas, and "H / C" indicates the ratio of hydrogen atoms to carbon atoms in the gas mixture. Additionally, in the "Mn compound composition before treatment" and "Mn compound composition after treatment" columns, "T.Mn" indicates the total manganese concentration, "O" indicates the oxygen concentration, and "C" indicates the carbon concentration. Furthermore, "Tr" indicates the treatment temperature of the reduction-carbonization treatment, and "tr" indicates the treatment time. Additionally, "d" indicates the particle size of the manganese ore sample, and "tb" indicates the pretreatment time for the manganese ore sample, i.e., the treatment time required to prepare manganese ore samples with particle sizes of 1 mm and 3 mm.

[0052]

[0053] The results shown in Table 2 confirm that in processes No. 1 to No. 12, where manganese ore was subjected to reduction-carbonation treatment according to the method of the present invention, manganese carbides with a reduction rate of over 80% were obtained. On the other hand, it is confirmed that in reduction treatments using only hydrogen (process No. 13), only hydrocarbon gas (process No. 14), and reduction-carbonation treatments using coke (process No. 15), the reduction rate of manganese ore was less than 60%. Furthermore, it is confirmed that the CO2 concentration in the exhaust gas from the reduction-carbonation treatments of processes No. 1 to No. 12 was lower than that of processes No. 14 to No. 15. Additionally, in process No. 16, where the temperature inside the electric resistance furnace was maintained at 1300°C, partial melting of the manganese ore sample was observed during the reduction-carbonation treatment, confirming a lower reduction rate of manganese ore compared to processes No. 1 to No. 12. This is believed to be due to deterioration in permeability.

[0054] The results shown in Table 2 confirm that, under the conditions of a manganese ore sample particle size of 5 mm and a treatment temperature of 900℃, the reduction rate of manganese ore in treatments No. 3 and No. 4 is higher than 87% compared to treatments No. 1, No. 2, and No. 5. In treatments No. 3 and No. 4, the partial pressure of hydrocarbon gases in the mixed gas is higher than 10.0 kPa, and the number of hydrogen atoms in the mixed gas is more than 12 times the number of carbon atoms. Treatments No. 1, No. 2, and No. 5 do not meet one of these conditions. Furthermore, it can be confirmed that, compared to treatments No. 3 and No. 4, in treatment No. 5, the ratio of hydrogen atoms to carbon atoms in the mixed gas is too small, resulting in an increase in the CO2 concentration of the exhaust gas.

[0055] The results shown in Table 2 confirm that in treatments No. 4 and No. 6 to No. 10, where the manganese ore sample particle size was 5 mm and the hydrocarbon partial pressure was the same, the higher the reduction-carbonation treatment temperature, the higher the reduction rate of the manganese ore. When the reduction-carbonation treatment temperature was above 800℃, the reduction rate of the manganese ore was above 86%, and when the reduction-carbonation treatment temperature was above 1100℃, the reduction rate of the manganese ore was above 94%.

[0056] The results shown in Table 2 confirm that in treatments No. 4, No. 11, and No. 12, where the partial pressure of hydrocarbons is the same and the treatment temperature is 900℃, the smaller the particle size of the manganese ore sample, the higher the reduction rate of the manganese ore. However, the smaller the particle size of the manganese ore sample, the longer the pretreatment time for the manganese ore. Furthermore, in treatment No. 4, 10 kg of manganese ore sample with a particle size of 5 mm can be prepared and directly added. On the other hand, in treatments No. 11 and No. 12, when the manganese ore sample is crushed, powder smaller than the specified particle size is generated. Therefore, to ensure the recovery rate, 15 kg and 13 kg of manganese ore sample with a particle size of 5 mm are prepared, respectively.

[0057] <Example 2>

[0058] An example of manufacturing manganese-containing steel in a 50 kg induction melting furnace using manganese carbides obtained at the levels of Processes No. 1 to No. 12 of Example 1 described above is described. 50 kg of high-purity electrolytic iron was loaded into the induction melting furnace, and the output of the furnace was adjusted to melt the high-purity electrolytic iron. While maintaining the temperature of the molten steel in the furnace at 1600–1620 °C, manganese carbides obtained at the levels of Processes No. 1 to No. 12 of Example 1 were added to the molten steel to manufacture manganese-containing steel. As a reference example, high-carbon ferromanganese (Process No. 17) was added to manufacture manganese-containing steel. Here, the amounts of manganese carbides and high-carbon ferromanganese added were determined such that the Mn concentration in the molten steel was 1.00% by mass. The compositions of the manganese carbides and high-carbon ferromanganese are shown in Table 3. Furthermore, the compositions of the molten steel before and after the addition of manganese carbides or high-carbon ferromanganese are shown in Table 3.

[0059] Manganese carbide or high-carbon ferromanganese is added to molten steel. After about 3 minutes, the molten steel is collected from the induction melting furnace, water-cooled, and a steel sample is prepared. The carbon concentration in the sample is analyzed by combustion analysis, and the concentrations of elements other than carbon are analyzed by ICP-N (Inductively Coupled Phosphorus) spectroscopy to investigate the composition of the sample.

[0060]

[0061] As shown in Table 3, in processes No. 1 to No. 12, manganese ore was subjected to reduction-carburization treatment according to the method of the present invention, and the resulting manganese carbides were used to manufacture manganese-containing steel. The results confirmed that in processes No. 1 to No. 12, the Mn concentration in the steel was 0.92–0.97% by mass, and the C concentration was 0.060–0.092% by mass. Furthermore, in processes No. 1 to No. 12, the Si concentration and sol.Al concentration in the steel were both below 0.01% by mass, confirming that the Si and Al contained in the manganese carbides could be separated and removed as slag without entering the steel. On the other hand, in process No. 17, which uses high-carbon ferromanganese to manufacture manganese-containing steel, the Mn concentration in the steel was 0.95% by mass, the C concentration was 0.095% by mass, and the Si concentration and sol.Al concentration were both below 0.01% by mass. Therefore, it can be confirmed that the composition is similar to that of the manganese-containing steel manufactured by the method of the present invention.

[0062] <Example 3>

[0063] An example of reduction-carbonization treatment of manganese ore B (Table 1) using a rotary kiln with a processing capacity of 100 kg / h is described. After heating to the specified maximum temperature within the rotary kiln using a propane gas burner, 100 kg of a sample of manganese ore B with a particle size of 1–120 mm was charged into the rotary kiln. Various conditions are shown in Table 4-1. It should be noted that the propane gas flow rate for the burner was set to 20 NL / min, and the oxygen flow rate for the burner was set to 100 NL / min. The T.Mn concentration in the manganese ore B before reduction-carbonization treatment was 50.3–54.7% by mass. It should be noted that the T.Mn concentration refers to the total manganese concentration in the manganese ore. Next, at the treatment levels No. 21–No. 31 and No. 35–No. 37, a spray gun was inserted at a specified position within the rotary kiln, and a mixture of hydrogen (H2) and methane (CH4) gas was supplied using the spray gun at a flow rate of 2000 NL / min. Then, a reduction-carbonization treatment was performed for a specified time. During this process, various changes were made to the particle size of the manganese ore, the insertion position of the spray gun, the composition of the supplied gas, and the maximum temperature inside the rotary kiln. As a comparative example, at some levels, a manganese ore sample with a particle size of 10 mm was used. The spray gun was inserted at a temperature of 650°C inside the rotary kiln, and only hydrogen gas was supplied (treatment No. 32) or only methane gas was supplied (treatment No. 33). In treatment No. 34, coke was used as the solid carbonaceous material for the reduction-carbonization treatment. It should be noted that when using coke, the coke charge was set to 25 kg, the spray gun was inserted at a temperature of 650°C inside the rotary kiln, and Ar gas was supplied using the spray gun at a flow rate of 2000 NL / min. Furthermore, in treatment No. 37, as a comparative example, a manganese ore sample with a particle size of 10 mm was used. A spray gun was inserted at a temperature of 650°C inside a rotary kiln, and a mixture of hydrogen and methane gas was used. The maximum temperature inside the rotary kiln was maintained at 1300°C to perform a reduction-carbonization treatment. A gas chromatograph was installed at the spray gun insertion point and part of the gas exhaust system in the rotary kiln to measure the H2 and CH4 concentrations at the spray gun insertion point within the treatment equipment, as well as the CO and CO2 concentrations in the gas emitted outside the treatment equipment.

[0064] After a specified time, the manganese ore sample was removed from the processing equipment and cooled in air. The oxygen and carbon concentrations in the sample were analyzed by combustion, and the concentrations of elements other than oxygen and carbon were analyzed by fluorescence X-ray diffraction. The reduction state of the sample was investigated. The reduction-carbonization treatment conditions and reduction rate of the manganese ore are shown in Table 4-2. Here, the reduction rate of the manganese ore in Table 4-2 is expressed as a percentage relative to the oxygen concentration of manganese oxides in the manganese ore before reduction-carbonization treatment, representing the difference between the oxygen concentration of manganese oxides in the manganese ore before reduction-carbonization treatment and the oxygen concentration of manganese oxides in the manganese compounds after reduction-carbonization treatment. It should be noted that the oxygen concentration of manganese oxides in the manganese ore is the difference between the analytical value of the overall oxygen concentration of the manganese ore sample and the calculated sum of the oxygen concentrations of oxides other than manganese in the manganese ore. Additionally, the "Y" in Table 4-2... Mn "" indicates the total manganese yield, and "" indicates the percentage of the product of the weight of the manganese ore sample after reduction-carbonization treatment and the total manganese concentration relative to the product of the weight of the manganese ore sample before reduction-carbonization treatment and the total manganese concentration. Additionally, the CO2 concentration in the exhaust gas in Table 4-2 is the sum of the average CO2 concentration measured during the reduction-carbonization treatment and the average of the CO concentration measured during the reduction-carbonization treatment converted to CO2 concentration. In Table 4-1, "H2" in the "Gas Flow Rate for Reduction" column indicates hydrogen flow rate, "CH4" indicates hydrocarbon gas concentration, and "H2" in the "Gas Composition at the Spray Gun Insertion Position" column indicates hydrogen concentration, "CH4" indicates hydrocarbon gas concentration, and "P" indicates hydrogen concentration. CH4 "H / C" indicates the partial pressure of the hydrocarbon gas, and "H / C" indicates the ratio of hydrogen atoms to carbon atoms in the gas mixture. Additionally, in Table 4-2, under the columns "Mn compound composition before treatment" and "Mn compound composition after treatment," "T.Mn" indicates the total manganese concentration, "O" indicates the oxygen concentration, and "C" indicates the carbon concentration. Furthermore, "Tg" indicates the temperature at the location where the reducing gas or Ar gas is supplied, "Tr" indicates the highest temperature during the reduction-carbonization treatment, and "tr" indicates the treatment time for the reduction-carbonization treatment. Finally, "d" indicates the particle size of the manganese ore sample.

[0065]

[0066] The results shown in Tables 4-1 and 4-2 confirm that in processes No. 21 to No. 31, where manganese ore was subjected to reduction-carbonation treatment using the method conforming to the present invention, manganese carbides with a reduction rate of over 80% could be obtained. On the other hand, it can be confirmed that in reduction treatments using only hydrogen (process No. 32), reduction-carbonation treatments using only hydrocarbon gas (process No. 33), and reduction-carbonation treatments using coke (process No. 34), the reduction rate of manganese ore was less than 60%. Furthermore, it can be confirmed that the CO2 concentration in the exhaust gas during reduction-carbonation treatments in processes No. 21 to No. 31 was lower than that in processes No. 33 and No. 34. The smaller the particle size of the manganese ore, the higher the reduction rate; however, it can be confirmed that in the reduction-carbonation treatment using manganese ore with a particle size of 1 mm (process No. 35), the total manganese yield decreased to 86%. On the other hand, it can be confirmed that in the reduction-carbonation treatment (treatment No. 36) using manganese ore with a particle size of 120 mm, the reduction rate of manganese ore decreased to below 75%. Furthermore, in treatment No. 38, where the maximum temperature inside the rotary kiln was maintained at 1300°C, partial melting of the manganese ore sample was observed during the reduction-carbonation treatment. Therefore, it can be confirmed that the reduction rate of manganese ore in treatment No. 38 is lower than that in treatments No. 21 to No. 31. This is believed to be due to deterioration in permeability.

[0067] The results shown in Tables 4-1 and 4-2 confirm that, under the conditions of a manganese ore sample particle size of 10 mm and a maximum temperature of 750 °C in the rotary kiln, the reduction rate of manganese ore was increased in treatments No. 25 and No. 26 compared to treatment No. 22. In treatments No. 25 and No. 26, the mixed gas was supplied from a position in the rotary kiln where the temperature was above 700 °C.

[0068] As shown in Tables 4-1 and 4-2, treatments No. 22, No. 27, and No. 28 were compared under the following conditions: the temperature at the nozzle insertion point was 650°C, the manganese ore sample particle size was 10 mm, and the highest temperature inside the rotary kiln was 750°C. It was confirmed that, compared to treatments No. 22 and No. 28, the reduction rate of manganese ore was increased to over 89% in treatment No. 27. The partial pressure of hydrocarbon gases in the mixed gas of treatment No. 27 was over 10.0 kPa, and the number of hydrogen atoms in the mixed gas was more than 12 times the number of carbon atoms. Furthermore, it was confirmed that, compared to treatments No. 22 and No. 27, the ratio of hydrogen atoms to carbon atoms in the mixed gas was too small in treatment No. 28, resulting in an increase in the CO2 concentration of the exhaust gas.

[0069] As shown in Tables 4-1 and 4-2, treatments No. 22 and No. 29 to No. 31 were compared, where the temperature at the nozzle insertion point was 650℃, the particle size of the manganese ore sample was 10mm, and the partial pressure of hydrocarbons was the same. It can be confirmed that in treatments No. 22 and No. 29 to No. 31, the higher the maximum temperature inside the rotary kiln, the higher the reduction rate of manganese ore; above 800℃, the reduction rate of manganese ore exceeded 87%.

[0070] <Example 4>

[0071] An example of manufacturing manganese-containing steel in a 50 kg induction melting furnace using manganese carbides obtained at the levels of Processes No. 21 to No. 31 of Example 3 described above is described. 50 kg of high-purity electrolytic iron was loaded into the induction melting furnace, and the output of the furnace was adjusted to melt the high-purity electrolytic iron. While maintaining the temperature of the molten steel in the furnace at 1600–1620 °C, manganese carbides obtained at the levels of Processes No. 21 to No. 31 of Example 3 were added to the molten steel to manufacture manganese-containing steel. As a reference example, high-carbon ferromanganese (Process No. 38) was added to manufacture manganese-containing steel. Here, the amounts of manganese carbides and high-carbon ferromanganese added were determined such that the Mn concentration in the molten steel was 1.00% by mass. The compositions of the manganese carbides and high-carbon ferromanganese are shown in Table 5. Furthermore, the compositions of the molten steel before and after the addition of manganese carbides or high-carbon ferromanganese are shown in Table 5.

[0072] Manganese carbide or high-carbon ferromanganese is added to molten steel. After about 3 minutes, the molten steel is collected from the induction melting furnace, water-cooled, and a steel sample is prepared. The carbon concentration in the sample is analyzed by combustion analysis, and the concentrations of elements other than carbon are analyzed by ICP-N (Inductively Coupled Phosphorus) spectroscopy to investigate the composition of the sample.

[0073]

[0074] As shown in Table 5, in Processes No. 21 to No. 31, which involved reducing and carbonizing manganese ore using the method of the present invention and producing manganese-containing steel from the resulting manganese carbides, the Mn concentration in the molten steel was 0.90–0.99% by mass, and the C concentration was 0.047–0.095% by mass. Furthermore, the Si and sol.Al concentrations in the molten steel were both below 0.01% by mass, confirming that the Si and Al contained in the manganese carbides could be separated and removed as slag without entering the molten steel. On the other hand, in Process No. 38, which involved producing manganese-containing steel using high-carbon ferromanganese, the Mn concentration in the molten steel was 0.97% by mass, the C concentration was 0.091% by mass, and the Si and sol.Al concentrations were both below 0.01% by mass, confirming that the composition was similar to that of the manganese-containing steel produced by the method of the present invention.

[0075] Industrial availability

[0076] The technology disclosed in this invention can easily manufacture manganese carbides and can also be applied to the manufacture of high-carbon ferromanganese.

Claims

1. A method for manufacturing manganese carbide, wherein, The manganese ore is heated to a processing temperature that is not in a molten state, and then contacted with a mixture of hydrogen and hydrocarbon gases under atmospheric pressure to carry out the reduction-carbonization treatment of the manganese ore.

2. The method for manufacturing manganese carbide according to claim 1, wherein, The partial pressure of the hydrocarbon gas in the mixed gas is made to be 10.0 kPa or higher, and the number of hydrogen atoms in the mixed gas is more than 12 times the number of carbon atoms.

3. The method for manufacturing manganese carbide according to claim 1 or 2, wherein, The processing temperature is set to above 800°C but below the melting temperature T. m The range.

4. The method for manufacturing manganese carbide according to any one of claims 1 to 3, wherein, The particle size of the manganese ore is also pre-adjusted to be above 3mm and below 100mm.

5. The method for manufacturing manganese carbide according to claim 4, wherein, The reduction-carbonization treatment is carried out using a rotary kiln.

6. The method for manufacturing manganese carbide according to claim 5, wherein, The mixed gas is supplied from a location inside the rotary kiln where the temperature is above 700°C.

7. The method for manufacturing manganese carbide according to claim 6, wherein, At the location where the mixed gas is supplied, the partial pressure of the hydrocarbon gas in the mixed gas is made to be 10.0 kPa or more, and the number of hydrogen atoms in the mixed gas is more than 12 times the number of carbon atoms.

8. The method for producing manganese carbide according to any one of claims 5 to 7, wherein, The highest internal temperature of the rotary kiln is set to be above 800°C but below the melting temperature T. m The range.

9. A method for manufacturing manganese-containing steel, comprising the step of adding a manganese carbide manufactured by any one of claims 1 to 8 to molten steel.

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