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

Abstract

Provided is a method for producing a manganese carbide with which it is possible to reduce the discharge amount of CO2. The present invention is a method in which manganese ore is heated to a treatment temperature corresponding to an unmelted state and brought into contact with a mixed gas of a hydrogen gas and a hydrocarbon gas under atmospheric pressure to perform a reduction treatment on the manganese ore. It is preferable that the partial pressure of the hydrocarbon gas in the mixed gas is 10.0 kPa or higher, the number of hydrogen atoms in the mixed gas is at least 12 times the number of carbon atoms, and the treatment temperature is within the range from equal to or higher than 800°C to less than the melting temperature Tm. It is preferable to adjust the grain diameter of the manganese ore to 3-100 mm, to treat the manganese ore in a rotary kiln, and to supply the hydrocarbon gas from a position where the temperature inside the rotary kiln is 700°C or higher. The present invention is also a method for producing manganese-containing steel, the method including a step for adding the obtained manganese carbide to molten steel.

Description

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

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

[0002] [Definitions] In this specification, "Mn", "MnO" ２ When written in alphabets, such as "," it refers to the substance with that chemical formula, and when written in katakana as "manganese," it refers to the manganese contained in that substance regardless of its form.

[0003] In this specification, the unit of volume "L" is 10 －３ m ３ The symbol "N" before the unit of gas volume represents the standard state of the gas. The standard state is when the temperature is 0°C and the atmospheric pressure is 1 atm. The pressure unit 1 atm is 1.01325 x 10 ５ Pa. The total manganese content (T.Mn) in a substance indicates the total amount of manganese contained in the substance, regardless of its form.

[0004] Manganese is added to molten steel during the steelmaking process to improve its toughness and wear resistance. Manganese-containing substances added during the steelmaking process include metallic manganese, ferromanganese, and silicon manganese. Ferromanganese is generally produced by charging manganese ore, iron ore, and a reducing agent into a melting furnace and melting and reducing the manganese ore and iron ore. This method requires handling high-temperature molten material, and therefore requires a transport vessel for containing and transporting the molten material and a casting device for cooling and solidifying the molten material. This raises concerns about the increased size of the equipment and the deterioration of the handleability of ferromanganese products. Furthermore, there are concerns about reduced product yield due to the molten material scattering during the reduction process or remaining in the melting furnace.

[0005] As a method for reducing manganese ore in a solid state, methods have been proposed in which a heat treatment is carried out using a reducing gas instead of a solid carbon-containing substance, as shown in Patent Documents 1 to 4, for example.

[0006] JP-A-50-070202 JP-A-56-072150 JP-A-08-253308 JP-A 2023-140706

[0007] However, the above-mentioned conventional techniques have the following problems to be solved. That is, the methods disclosed in Patent Documents 1 and 2 are unable to remove manganese oxide (MnO) with a high degree of oxidation contained in manganese ore. ２ and Mn ２ O ３ In this method, manganese oxide (MnO) is only obtained by partially reducing manganese oxide (MnO) with a low degree of oxidation. To obtain a manganese alloy product, the reduced product must be further melted and reduced.

[0008] On the other hand, in the smelting reduction process of manganese ore, a solid carbon-containing substance such as coke is used as a reducing agent, and a large amount of CO ２ In light of the recent trend toward reducing greenhouse gas emissions in order to protect the global environment, the amount of solid carbon-containing substances used in manganese alloy manufacturing has also been reduced, resulting in CO ２ Emissions need to be reduced.

[0009] However, in the methods disclosed in Patent Documents 1 and 2, it is not possible to obtain a manganese alloy product using only a reducing gas, and it is necessary to supply a solid carbon-containing substance when the reduced product is further melted and reduced. ２ There are limits to how much emissions can be reduced.

[0010] In addition, the methods disclosed in Patent Documents 3 and 4 involve reducing highly oxidized manganese oxide contained in manganese ore to produce manganese carbide (Mn ７ C ３ and Mn ３C, etc.) can be obtained. However, the method disclosed in Patent Document 3 requires a step of pulverizing the manganese ore to 1 mm or less. With such fine granular or powdered forms, there are concerns that handling may be impaired and the yield of manganese carbide obtained after treatment may decrease. Furthermore, the method disclosed in Patent Document 4 does not disclose a suitable range for the particle size of the manganese ore, and similarly, when the manganese ore is in a fine granular or powdered form, there are concerns that handling may be impaired and the yield of manganese carbide obtained after treatment may decrease. On the other hand, there is a concern that if the particle size is too large, the reaction efficiency of the reduction and carbonization treatment may decrease.

[0011] Furthermore, although the reduction and carbonization reaction of manganese ore proceeds more rapidly at higher temperatures, the method disclosed in Patent Document 3 requires that the manganese ore be maintained at a temperature of 250 to 520° C. Therefore, the reduction and carbonization treatment of the manganese ore takes as long as 48 hours, which reduces the production efficiency of manganese carbide.

[0012] Therefore, in order to solve the above-mentioned problems of the prior art, the present invention provides a method for producing manganese carbide by efficiently reducing and carbonizing manganese ore in a relatively short time without using a plurality of reduction treatment devices or needing to pulverize the manganese ore, and by using CO ２ The present invention aims to propose a method for producing manganese carbide that can reduce emissions, and a method for producing manganese-containing steel using the obtained manganese carbide.

[0013] The inventors have studied the above-mentioned problems of the conventional techniques, and have completed the present invention by bringing manganese ore into contact with hydrogen gas or hydrocarbon gas at a treatment temperature at which the manganese ore is in an unmolten state, thereby carrying out a reduction and carbonization treatment of the manganese ore.

[0014] That is, the method for producing manganese carbide according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that manganese ore is heated to a treatment temperature at which it remains in an unmolten state, and is brought into contact with a mixed gas of hydrogen gas and hydrocarbon gas under atmospheric pressure, thereby carrying out a reduction and carbonization treatment of the manganese ore.

[0015] The method for producing manganese carbide according to the present invention includes the steps of: a) setting the partial pressure of the hydrocarbon gas in the mixed gas to 10.0 kPa or more, and setting the number of hydrogen atoms in the mixed gas to 12 times or more the number of carbon atoms; b) setting the treatment temperature to 800°C or more and the melting temperature T ｍ a temperature range of 100°C or more and a melting temperature T 100°C or more; a temperature range of 100°C or more and a melting temperature T 200°C or more; a temperature range of 100°C or more and a melting temperature T 300°C or more; a temperature range of 100°C or more and a melting temperature T 400°C or more; a temperature range of 100°C or more and a melting temperature T 500°C or more; a temperature range of 100°C or more and a melting temperature T 600°C or more; ｍ A more preferred embodiment may be one in which the range is less than .

[0016] Furthermore, the melting temperature T ｍ The melting point is the temperature at which a solid sample changes into a liquid. It is easy and preferable to determine this temperature by one of the following three methods, but it is not limited to these. The first method involves placing a solid sample in a container such as a crucible, and continuously observing the sample in the container while heating it in an electric resistance furnace or the like under a target gas atmosphere at a rate of 5°C per minute, preferably 1°C per minute or less. The melting point is determined as the temperature at which the gaps between the particles of the solid sample disappear and a smooth surface appears on the surface. The second method involves measuring the melting point by differential thermal analysis under a target gas atmosphere while heating it in an electric resistance furnace or the like at a rate of 5°C per minute, preferably 1°C per minute or less. If multiple endothermic peaks appear, the measurement is stopped at the temperature at each endothermic peak, the appearance of the sample is observed, and the melting point is determined as the temperature at the lowest endothermic peak at which the gaps between the particles of the solid sample disappear and a smooth surface appears on the surface. The third method is to use a thermodynamic calculation software on a computer, input the sample composition, change the temperature, calculate the liquid phase ratio, and define the temperature at which the calculated liquid phase ratio exceeds 95% as the melting point.

[0017] Furthermore, a method for producing a manganese-containing steel according to the present invention, which advantageously solves the above-mentioned problems, is characterized by including a step of adding manganese carbide produced by any of the above-mentioned production methods to molten steel.

[0018] According to the present invention, when manganese ore is reduced and carbonized, it is possible to efficiently reduce and carbonize the manganese ore in a relatively short time without using a plurality of reduction treatment devices, without the need to finely grind the manganese ore, and without melting the manganese ore. ２ Emissions can be reduced.

[0019] In developing the present invention, the inventors charged manganese ore into a reaction vessel for reduction and carbonization treatment, and then performed the reduction and carbonization treatment while supplying a reducing agent and maintaining the reaction vessel at a predetermined temperature to produce manganese carbide. Here, manganese carbide refers to a manganese compound obtained by reducing manganese ore, in which the oxygen concentration in the manganese compound is reduced to a predetermined value or less and the carbon concentration is within a predetermined range. For example, it is preferable to use a manganese compound having an oxygen (O) concentration of 6.0 mass% or less and a carbon (C) concentration of 4.0 mass% or more as the manganese carbide.

[0020] In this manufacturing process, the reduction behavior of manganese ore was investigated by changing various conditions, such as the type of reducing agent, the supply amount of reducing agent, and the supply method of reducing agent. As a result, it was found that by using hydrogen gas and hydrocarbon gas as reducing agents and performing reduction and carbonization treatment without melting the manganese ore, reduction and carbonization treatment can be easily performed without using multiple reduction treatment devices. Furthermore, CO ２ It was found that emissions can be reduced by the following methods.

[0021] First, in the method for reducing manganese ore that is suitable for the present invention, it is necessary to use a mixed gas of hydrogen gas and hydrocarbon gas as a reducing agent. Mn in manganese ore is mainly present as MnO ２ Therefore, when only hydrogen gas is used, MnO ２is reduced only to MnO. It is thermodynamically difficult to reduce manganese metal using only hydrogen gas.

[0022]

[0023] On the other hand, when hydrocarbon gases such as methane and propane are used, a part of the hydrocarbon gas decomposes at high temperatures to generate highly reactive carbon and hydrogen gas. Therefore, in addition to the reactions of the above formulas (1) to (3), for example, the reaction of MnO with Mn as shown in formula (4) in the following chemical formula 2 can be performed. ７ C ３ The carbonization reaction to manganese carbide proceeds.

[0024]

[0025] However, the highly reactive carbon produced by the decomposition of hydrocarbon gases is converted into MnO ２ When consumed in the reduction reaction from MnO to MnO, a large amount of CO is generated, which is equivalent to that of a conventional smelting reduction process using a solid carbon-containing material. ２ Furthermore, MnO is extracted from Mn ７ C ３ Since the supply of carbon necessary for the carbonization reaction to the carbon dioxide particles is insufficient, an excess supply of hydrocarbon gas is required. This may result in a decrease in the reduction efficiency and an increase in the cost of the reducing material. Therefore, by using a mixed gas of hydrogen gas and hydrocarbon gas as the reducing material, it is possible to produce MnO mainly using hydrogen gas. ２ It was thought that it would be possible to carry out the reduction treatment from SiO to MnO and to carry out the carbonization treatment of MnO while minimizing the supply amount of hydrocarbon gas.

[0026] Furthermore, in the reduction and carbonization treatment, it is necessary to react the manganese ore at a treatment temperature where the manganese ore is in an unmolten state. As mentioned above, the melting and reduction of manganese ore poses challenges such as an increase in the size of the reduction treatment device and poor handling. On the other hand, by performing the reduction and carbonization treatment using a gaseous reducing agent while ensuring gas permeability without melting the manganese ore, it is possible to simplify the reduction treatment device and improve its handling.

[0027] The composition of the mixed gas of hydrogen gas and hydrocarbon gas to be brought into contact with the manganese ore is preferably within the following range. First, the partial pressure of the hydrocarbon gas in the mixed gas is set to 10.0 kPa or more. In addition, in order to promote the carbonization reaction of MnO, it is effective to reduce the partial pressure of oxygen in the atmosphere. For example, when the temperature of the manganese ore is 1100°C, if the partial pressure of the hydrocarbon gas in the mixed gas supplied is less than 10.0 kPa, the partial pressure of oxygen required to promote the carbonization reaction of MnO is 1.0 x 10 －１７ kPa or less. It is difficult to maintain the oxygen partial pressure in the atmosphere at such a low level. There is no upper limit on the partial pressure of the hydrocarbon gas in the mixed gas supplied. However, as mentioned above, the higher this value, the more likely it is that the hydrocarbon gas will be supplied in excess, so it is more preferable to set it at 50.0 kPa or less. Furthermore, the number of hydrogen atoms in the mixed gas is set to 12 times or more the number of carbon atoms. If the number of hydrogen atoms in the mixed gas to be contacted with the manganese ore is set to less than 12 times the number of carbon atoms, the hydrogen gas concentration in the mixed gas may be too low. Therefore, as mentioned above, MnO ２ The proportion of hydrocarbon gas consumed in the reduction reaction from CO to MnO increases, ２ There is no upper limit to the ratio of the number of hydrogen atoms to the number of carbon atoms in the mixed gas, but the larger this value is, the lower the proportion of hydrocarbon gas in the mixed gas, which may make it difficult for the carbonization reaction of MnO to proceed. Therefore, it is more preferable to set the number of hydrogen atoms in the mixed gas to 22 times or less the number of carbon atoms.

[0028] The processing temperature for the reduction and carbonization process is 800°C or higher, the melting point T ｍ It is preferable to heat the mixture to a temperature below the melting temperature T ｍThe definition of is preferably based on the first to third methods described above. Patent Document 3 discloses that the carbonization start temperature of MnO using a mixed gas of hydrogen gas and methane gas is 1870°C. However, the inventors have repeatedly performed reduction and carbonization treatment of manganese ore using hydrogen gas and hydrocarbon gas, and have found that manganese carbide can be obtained even at temperatures lower than 1870°C. In the manganese ore reduction method suitable for the present invention, the carbonization reaction of MnO using hydrocarbon gas begins at approximately 750°C. The higher the treatment temperature, the faster the carbonization of MnO. ２ Therefore, it is more preferable to set the treatment temperature at 1100°C or higher. ｍ If the temperature exceeds this, the permeability will be deteriorated due to melting, which may inhibit the reduction and carbonization reaction. From the viewpoint of energy saving, it is more preferable that the treatment temperature for the reduction and carbonization treatment is 1200°C or less.

[0029] It is also preferable to add the manganese carbide obtained by the above method to molten steel in any step in the molten steel production process. As mentioned above, ferromanganese is used in the steelmaking process in the molten steel production process. Ferromanganese is classified according to its carbon content, such as high-carbon, medium-carbon, low-carbon, and very-low-carbon ferromanganese, and is used according to the steel composition specifications and production process. Of these, high-carbon ferromanganese contains about 7 mass% C, and the C in ferromanganese is Mn ７ C ３ and Mn ５ C ２ The manganese carbide obtained by the manganese carbide manufacturing method according to the present invention mainly contains Mn ７ C ３ and Mn ５ C ２The manganese carbide suitable for the present invention can be used as a manganese source in the primary and secondary refining of molten steel, similar to high-carbon ferromanganese. However, in the method for producing manganese carbide suitable for the present invention, it is difficult to separate and remove gangue components (oxides of Si, Al, etc.) contained in manganese ore. Therefore, the obtained manganese carbide contains the gangue components. However, when the manganese carbide obtained by the above method is added to molten steel, Mn ７ C ３ and Mn ５ C ２ Since the iron quickly dissolves in the molten steel and the gangue components migrate into the steelmaking slag, it is possible to increase the Mn concentration without increasing the impurity elements in the molten steel.

[0030] Next, an example of reduction and carbonization of manganese ore will be described in detail based on the method for producing manganese carbide according to the present invention. Table 1 shows an example of the composition of the manganese ore used.

[0031]

[0032] Manganese ore as a raw material is charged into a reaction vessel for reduction and carbonization treatment. The type of reaction vessel is not limited, and a continuous reaction vessel such as a blast furnace or a batch reaction vessel such as a rotary kiln can be used. There are no limitations on the particle size of the manganese ore, but since fine granular or powdered manganese ore may reduce the addition yield and make handling difficult, a particle size of 3 mm or more is preferable. If the particle size is too large, there is a concern that the reaction efficiency of the reduction and carbonization treatment may decrease, so a particle size of 100 mm or less is preferable.

[0033] The properties of the manganese ore are not limited. Hydrogen gas and hydrocarbon gas are supplied as reducing gases into the reactor, and the supply amounts of each gas are controlled to achieve a predetermined gas composition within the reactor. The gas supply method is not limited; a mixed gas of hydrogen gas and hydrocarbon gas may be used, or hydrogen gas and hydrocarbon gas may be supplied from separate inlets. Other methods include injecting the reducing gas through tuyeres installed on the bottom or side of the reactor, or spraying the reducing gas using a lance from above the manganese ore layer packed within the reactor. The reactor is then heated to a predetermined treatment temperature within a range that does not melt the manganese ore. The heating method for the manganese ore and the reactor is not limited; burner heating, electrical resistance heating, induction heating, and other methods are applicable. The manganese ore reduced and carbonized in the above process becomes a manganese carbide product. The uses of the manganese carbide product are not limited; for example, it can be added to molten steel as a manganese source in the molten steel production process.

[0034] In a method for producing manganese-containing steel, the Mn concentration in molten steel can be adjusted, for example, by adding manganese carbide during ladle refining after steel is tapped from a converter, such as during arc heating or vacuum degassing. In this case, it is preferable to adjust the C concentration, which has increased due to the addition of manganese carbide, by supplying oxygen during vacuum degassing to perform decarburization. The molten steel with the adjusted composition can be formed into a slab by continuous casting or the like, and can be subjected to surface treatments such as hot rolling, heat treatment, cold rolling, annealing, and plating as necessary to produce manganese-containing steel.

[0035] Example 1 This example describes the reduction and carbonization treatment of manganese ore A in Table 1 using a 10 kg electric resistance furnace. After adjusting the output of the electric resistance furnace to raise the temperature inside the electric resistance furnace to a predetermined level, 10 kg of a sample of manganese ore A with a particle size of 1 to 5 mm was charged into the electric resistance furnace. Various conditions are shown in Table 2. The total manganese (T.Mn) concentration in manganese ore A before reduction and carbonization treatment was 51.2 to 55.8 mass %. The total manganese (T.Mn) concentration is the total manganese concentration in the manganese ore. Next, in the levels of Treatment Nos. 1 to 10 and 16, a sample of manganese ore A with a particle size of 5 mm was used, and hydrogen gas (H２ ) and methane gas (CH ４ ) was supplied at a flow rate of 30 NL / min. The reduction and carbonization treatment was then carried out by holding the furnace for a predetermined time. The reduction and carbonization treatment was carried out by varying the composition of the supplied gas and the temperature inside the electric resistance furnace. In addition, in the levels of Treatment Nos. 11 and 12, similar reduction and carbonization treatment was carried out using manganese ore A samples with particle sizes of 1 mm and 3 mm, respectively. Here, as a pretreatment, manganese ore A samples with particle sizes of 1 mm and 3 mm were prepared by crushing a manganese ore A sample with particle sizes of 5 mm using a roll crusher. In some levels, as comparative examples, a manganese ore sample with particle size 5 mm was used, and only hydrogen gas (Treatment No. 13) or only methane gas (Treatment No. 14) was supplied. In Treatment No. 15, reduction and carbonization treatment was carried out using coke as the solid carbon-containing material. When coke was used, the amount of coke charged was 5 kg, and Ar gas was supplied at a flow rate of 30 NL / min from a tuyere installed on the side of the reaction vessel. In Treatment No. 16, as a comparative example, a sample of manganese ore A with a particle size of 5 mm was used, and reduction and carbonization treatment was carried out using a mixed gas of hydrogen gas and methane gas, while the temperature inside the electric resistance furnace was maintained at 1300°C. A gas chromatograph analyzer was installed in part of the gas exhaust system of the electric resistance furnace, and the CO concentration and CO ２ The concentration was measured.

[0036] After a predetermined time had elapsed, the manganese ore sample was removed from the electric 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 in the sample were analyzed by X-ray fluorescence analysis to investigate the reduction state of the sample. Table 2 shows the manganese ore reduction and carbonization treatment conditions and the reduction rate of the manganese ore. Here, the reduction rate of the manganese ore in Table 2 is the difference between the oxygen concentration of manganese oxide in the manganese ore before reduction and carbonization and the oxygen concentration of manganese oxide in the manganese compound after reduction and carbonization, expressed as a percentage of the ratio to the oxygen concentration of manganese oxide in the manganese ore before reduction and carbonization. The oxygen concentration of manganese oxide in the manganese ore is the difference between the analytical value of the oxygen concentration of the entire manganese ore sample and the calculated total oxygen concentration of oxides other than manganese in the manganese ore. In addition, the CO in the exhaust gas in Table 2 ２ The CO concentration was measured during the reduction and carbonization process. ２ The average CO concentration and the CO concentration measured during the reduction and carbonization treatment were used as the CO ２ In Table 2, the "H" in the "Supply gas" column is the sum of the average values ​​of the concentrations. ２ " represents the hydrogen gas concentration, and "CH ４ " represents the hydrocarbon gas concentration, and "P ＣＨ４ " represents the partial pressure of the hydrocarbon gas, and "H / C" represents the ratio of the number of hydrogen atoms to the number of carbon atoms in the mixed gas. In the columns "Mn compound composition before treatment" and "Mn compound composition after treatment," "T.Mn" represents the total manganese concentration, "O" represents the oxygen concentration, and "C" represents the carbon concentration. In addition, "Tr" represents the treatment temperature of the reduction and carbonization treatment, and "tr" represents the treatment time of the reduction and carbonization treatment. In addition, "d" represents the particle size of the manganese ore sample, and "tb" represents the treatment time of the pretreatment of the manganese ore sample, i.e., the treatment time required to prepare manganese ore samples with particle sizes of 1 mm and 3 mm.

[0037]

[0038] The results shown in Table 2 confirm that in Processes No. 1 to 12, in which manganese ore was reduced and carbonized using a method consistent with the present invention, manganese carbide was obtained with a reduction rate of 80% or more. On the other hand, in the case of reduction using only hydrogen gas (Process No. 13), only hydrocarbon gas (Process No. 14), or coke (Process No. 15), the reduction rate of manganese ore was confirmed to be less than 60%. Furthermore, compared to Processes Nos. 14 to 15, Processes Nos. 1 to 12 had a lower CO content in the exhaust gas from the reduction and carbonization process. ２ It was confirmed that the manganese ore concentration was low. Furthermore, in Process No. 16, in which the temperature inside the electric resistance furnace was maintained at 1,300°C, it was observed that part of the manganese ore sample melted during the reduction and carbonization process, and it was confirmed that the reduction rate of the manganese ore was lower than in Process Nos. 1 to 12. This is thought to be due to a deterioration in air permeability.

[0039] From the results shown in Table 2, it was confirmed that when the particle size of the manganese ore sample was 5 mm and the treatment temperature was the same at 900°C, the reduction rate of the manganese ore was improved in Treatments Nos. 3 and 4, reaching 87% or more, compared to Treatments Nos. 1, 2, and 5. In Treatments Nos. 3 and 4, the partial pressure of the hydrocarbon gas in the mixed gas was 10.0 kPa or more, and the number of hydrogen atoms in the mixed gas was 12 times or more the number of carbon atoms. Treatments Nos. 1, 2, and 5 did not satisfy either of these conditions. Furthermore, compared to Treatments Nos. 3 and 4, in Treatment No. 5, the ratio of the number of hydrogen atoms to the number of carbon atoms in the mixed gas was too small, resulting in a high CO2 content in the exhaust gas. ２ It was confirmed that the concentration increased.

[0040] The results shown in Table 2 confirm that in Processes Nos. 4 and 6 to 10, in which the particle size of the manganese ore samples was 5 mm and the hydrocarbon partial pressure was the same, the higher the reduction and carbonization treatment temperature, the more improved the reduction rate of the manganese ore. At reduction and carbonization temperatures of 800°C or higher, the reduction rate of the manganese ore was 86% or higher, and at temperatures of 1100°C or higher, the reduction rate of the manganese ore was 94% or higher.

[0041] The results shown in Table 2 confirm that in Processes Nos. 4, 11, and 12, which had the same hydrocarbon partial pressure and the same treatment temperature of 900°C, 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 treatment time for manganese ore pretreatment. Furthermore, in Process No. 4, 10 kg of manganese ore sample with a particle size of 5 mm could be prepared and charged as is. On the other hand, in Processes Nos. 11 and 12, powder smaller than the specified particle size was generated when the manganese ore sample was crushed. Therefore, to ensure the recovery amount, 15 kg and 13 kg of manganese ore sample with a particle size of 5 mm were prepared, respectively.

[0042] Example 2: This example describes the production of manganese-containing molten steel in a 50 kg induction melting furnace using manganese carbide obtained in Process Nos. 1 to 12 of Example 1. 50 kg of high-purity electrolytic iron was charged into the induction melting furnace, and the output of the induction melting furnace was adjusted to melt the high-purity electrolytic iron. While the temperature of the molten steel in the induction melting furnace was maintained at 1600 to 1620°C, manganese-containing molten steel was produced by adding the manganese carbide obtained in Process Nos. 1 to 12 of Example 1 to the molten steel. As a reference example, manganese-containing molten steel was produced by adding high-carbon ferromanganese (Process No. 17). The amounts of manganese carbide and high-carbon ferromanganese added were determined so that the Mn concentration in the molten steel was 1.00% by mass. The compositions of the manganese carbide and high-carbon ferromanganese are shown in Table 3. Table 3 shows the compositions of the molten steel before and after the addition of manganese carbide or high carbon ferromanganese.

[0043] Approximately three minutes after adding manganese carbide or high-carbon ferromanganese to molten steel, the molten steel was sampled from the induction melting furnace and water-cooled to prepare steel samples. The carbon concentration in the samples was analyzed by a combustion method, and the concentrations of elements other than carbon were analyzed by ICP atomic emission spectrometry to investigate the composition of the samples.

[0044]

[0045] As shown in Table 3, in Process Nos. 1 to 12, manganese ore was reduced and carbonized using a method consistent with the present invention, and manganese-containing molten steel was produced using the resulting manganese carbide. As a result, it was confirmed that in Process Nos. 1 to 12, the Mn concentration in the molten steel was 0.92 to 0.97 mass%, and the C concentration was 0.060 to 0.092 mass%. Furthermore, in Process Nos. 1 to 12, the Si and sol. Al concentrations in the molten steel were both less than 0.01 mass%, confirming that the Si and Al contained in the manganese carbide could be separated and removed as slag without being picked up in the molten steel. On the other hand, in Process No. 17, in which manganese-containing molten steel was produced using high-carbon ferromanganese, the Mn concentration in the molten steel was 0.95 mass%, the C concentration was 0.095 mass%, and the Si and sol. Al concentrations were both less than 0.01 mass%. Therefore, it was confirmed that the composition was comparable to that of manganese-containing molten steel produced by a method conforming to the present invention.

[0046] Example 3 This example describes the reduction and carbonization of manganese ore B in Table 1 using a rotary kiln with a throughput of 100 kg / hr. After the maximum temperature inside the rotary kiln was raised to a predetermined temperature using a propane gas burner, 100 kg of a sample of manganese ore B with particle sizes of 1 to 120 mm was charged into the rotary kiln. The various conditions are shown in Table 4-1. The flow rate of propane gas for the burner was 20 NL / min, and the flow rate of oxygen gas for the burner was 100 NL / min. The total manganese (T.Mn) concentration in manganese ore B before reduction and carbonization was 50.3 to 54.7 mass%. The total manganese (T.Mn) concentration is the total manganese concentration in the manganese ore. Next, for treatments Nos. 21 to 31 and 35 to 37, a lance was inserted into a predetermined position in the rotary kiln, and hydrogen gas (H ２ ) and methane gas (CH ４) mixed gas was supplied at a flow rate of 2000 NL / min. The mixture was then held for a predetermined time, and reduction and carbonization treatment was performed. The reduction and carbonization treatment was performed by varying the particle size of the manganese ore, the insertion position of the lance, the composition of the supplied gas, and the maximum temperature inside the rotary kiln. At some levels, as comparative examples, a manganese ore sample with a particle size of 10 mm was used, and the lance was inserted at a position where the temperature inside the rotary kiln was 650°C, and only hydrogen gas (Process No. 32) or only methane gas (Process No. 33) was supplied. In Process No. 34, reduction and carbonization treatment was performed using coke as the solid carbon-containing material. When coke was used, the coke charge amount was 25 kg, and the lance was inserted at a position where the temperature inside the rotary kiln was 650°C, and Ar gas was supplied using the lance at a flow rate of 2000 NL / min. Furthermore, in Process No. In No. 37, as a comparative example, a manganese ore sample with a particle size of 10 mm was used, and a lance was inserted into the rotary kiln at a position where the temperature inside the rotary kiln was 650°C. A mixed gas of hydrogen gas and methane gas was used, and the maximum temperature inside the rotary kiln was maintained at 1300°C, and reduction and carbonization treatment was carried out. Gas chromatograph analyzers were installed at the lance insertion position of the rotary kiln and in a part of the gas exhaust system, and H at the lance insertion position inside the treatment facility was measured. ２ Concentration and CH ４ concentration, and CO concentration and CO in the gas discharged outside the treatment facility ２ The concentration was measured.

[0047] After a predetermined time had elapsed, the manganese ore samples were removed from the treatment facility and cooled in air. The oxygen and carbon concentrations in the samples were analyzed by combustion, and the concentrations of elements other than oxygen and carbon in the samples were analyzed by X-ray fluorescence analysis to investigate the reduction state of the samples. Table 4-2 shows the manganese ore reduction and carbonization treatment conditions and the reduction rate of the manganese ore. Here, the reduction rate of the manganese ore in Table 4-2 is the difference between the oxygen concentration of manganese oxide in the manganese ore before reduction and carbonization and the oxygen concentration of manganese oxide in the manganese compound after reduction and carbonization, expressed as a percentage of the ratio to the oxygen concentration of manganese oxide in the manganese ore before reduction and carbonization. The oxygen concentration of manganese oxide in the manganese ore is the difference between the analytical value of the oxygen concentration of the entire manganese ore sample and the calculated total oxygen concentration of oxides other than manganese in the manganese ore. Also, "Y" in Table 4-2 Ｍｎ " represents the total manganese yield, and is the percentage of the ratio of the product of the weight of the manganese ore sample after reduction and carbonization treatment and the total manganese concentration to the product of the weight of the manganese ore sample before reduction and carbonization treatment and the total manganese concentration. ２ The CO concentration was measured during the reduction and carbonization process. ２ The average CO concentration and the CO concentration measured during the reduction and carbonization treatment were used as the CO ２ In Table 4-1, the "H" in the "reducing gas flow rate" column is the sum of the average values ​​of the concentrations. ２ " represents the hydrogen gas flow rate, and "CH ４ " indicates the hydrocarbon gas concentration, and "H ２ " represents the hydrogen gas concentration, and "CH ４ " represents the hydrocarbon gas concentration, and "P ＣＨ４" represents the partial pressure of the hydrocarbon gas, and "H / C" represents the ratio of the number of hydrogen atoms to the number of carbon atoms in the mixed gas. In addition, in the columns "Mn compound composition before treatment" and "Mn compound composition after treatment" in Table 4-2, "T.Mn" represents the total manganese concentration, "O" represents the oxygen concentration, and "C" represents the carbon concentration. Furthermore, "Tg" represents the temperature at the position where the reducing gas or Ar gas is supplied, "Tr" represents the maximum temperature in the reduction and carbonization treatment, and "tr" represents the treatment time of the reduction and carbonization treatment. Furthermore, "d" represents the particle size of the manganese ore sample.

[0048]

[0049]

[0050] The results shown in Tables 4-1 and 4-2 confirm that in Processes No. 21 to 31, in which manganese ore was reduced and carbonized using a method consistent with the present invention, manganese carbide was obtained with a reduction rate of 80% or more. On the other hand, in the case of reduction using only hydrogen gas (Process No. 32), only hydrocarbon gas (Process No. 33), or coke (Process No. 34), the reduction rate of manganese ore was confirmed to be less than 60%. Furthermore, compared with Processes Nos. 33 and 34, Processes Nos. 21 to 31 had lower CO in the exhaust gas from the reduction and carbonization process. ２ It was confirmed that the manganese ore concentration was low. The smaller the particle size of the manganese ore, the higher the reduction rate of the manganese ore. However, in the reduction and carbonization process using manganese ore with a particle size of 1 mm (Process No. 35), the total manganese yield was confirmed to be reduced to 86%. On the other hand, in the reduction and carbonization process using manganese ore with a particle size of 120 mm (Process No. 36), the reduction rate of the manganese ore was confirmed to be reduced to less than 75%. Furthermore, in Process No. 38, in which the maximum temperature inside the rotary kiln was maintained at 1300°C, it was observed that part of the manganese ore sample melted during the reduction and carbonization process. Therefore, it was confirmed that Process No. 38 had a lower reduction rate of the manganese ore than Processes Nos. 21 to 31. This is thought to be due to the deterioration of air permeability.

[0051] From the results shown in Tables 4-1 and 4-2, it was confirmed that under the conditions where the particle size of the manganese ore sample was 10 mm and the maximum temperature inside the rotary kiln was the same as 750°C, the reduction rate of the manganese ore was improved in Processes 25 and 26 compared to Process 22. In Processes 25 and 26, the mixed gas was supplied from a position inside the rotary kiln where the temperature was 700°C or higher.

[0052] As shown in Tables 4-1 and 4-2, Processes No. 22, 27, and 28 were compared, under the same conditions as Processes No. 22, 27, and 28, in which the temperature at the lance insertion position was 650°C, the particle size of the manganese ore sample was 10 mm, and the maximum temperature in the rotary kiln was 750°C. It was confirmed that Process No. 27 had an improved reduction rate of the manganese ore, reaching 89% or more, compared to Processes No. 22 and 28. In Process No. 27, the partial pressure of the hydrocarbon gas in the mixed gas was 10.0 kPa or more, and the number of hydrogen atoms in the mixed gas was 12 times or more the number of carbon atoms. Furthermore, compared to Processes No. 22 and 27, Process No. 28 had an excessively small ratio of the number of hydrogen atoms to the number of carbon atoms in the mixed gas, resulting in a high CO2 content in the exhaust gas. ２ It was confirmed that the concentration increased.

[0053] As shown in Tables 4-1 and 4-2, comparison was made between Processes No. 22 and 29 to 31, in which the temperature at the lance insertion position was 650°C, the particle size of the manganese ore sample was 10 mm, and the hydrocarbon partial pressure was the same. In Processes No. 22 and 29 to 31, it was confirmed that the higher the maximum temperature inside the rotary kiln, the more improved the reduction rate of the manganese ore, and that at temperatures of 800°C or higher, the reduction rate of the manganese ore was 87% or higher.

[0054] Example 4 This example describes the production of manganese-containing molten steel in a 50 kg induction melting furnace using manganese carbide obtained in Process Nos. 21 to 31 of Example 3. 50 kg of high-purity electrolytic iron was charged into the induction melting furnace, and the output of the induction melting furnace was adjusted to melt the high-purity electrolytic iron. While the temperature of the molten steel in the induction melting furnace was maintained at 1600 to 1620°C, manganese-containing molten steel was produced by adding the manganese carbide obtained in Process Nos. 21 to 31 of Example 3 to the molten steel. As a reference example, manganese-containing molten steel was produced by adding high-carbon ferromanganese (Process No. 38). The amounts of manganese carbide and high-carbon ferromanganese added were determined so that the Mn concentration in the molten steel was 1.00% by mass. The compositions of the manganese carbide and high-carbon ferromanganese are shown in Table 5. Table 5 also shows the compositions of the molten steel before and after the addition of manganese carbide or high carbon ferromanganese.

[0055] Approximately three minutes after adding manganese carbide or high-carbon ferromanganese to molten steel, the molten steel was sampled from the induction melting furnace and water-cooled to prepare steel samples. The carbon concentration in the samples was analyzed by a combustion method, and the concentrations of elements other than carbon were analyzed by ICP atomic emission spectrometry to investigate the composition of the samples.

[0056]

[0057] The results shown in Table 5 confirm that in Processes No. 21 to 31, in which manganese ore was reduced and carbonized by a method consistent with the present invention and the resulting manganese carbide was used to produce manganese-containing molten steel, the Mn concentration in the molten steel was 0.90 to 0.99 mass% and the C concentration was 0.047 to 0.095 mass%. Furthermore, the Si and sol. Al concentrations in the molten steel were both less than 0.01 mass%, confirming that the Si and Al contained in the manganese carbide could be separated and removed as slag without being picked up in the molten steel. On the other hand, in Process No. 38, in which manganese-containing molten steel was produced using high-carbon ferromanganese, the Mn concentration in the molten steel was 0.97 mass%, the C concentration was 0.091 mass%, and the Si and sol. Al concentrations were both less than 0.01 mass%, confirming that these concentrations were similar to those of manganese-containing molten steel produced by a method consistent with the present invention.

[0058] The technology disclosed in the present invention can easily produce manganese carbide and can also be applied to the production of high-carbon ferromanganese.

Claims

1. A method for producing manganese carbide, comprising heating manganese ore to a processing temperature in an unmolten state and contacting the manganese ore with a mixed gas of hydrogen gas and a hydrocarbon gas under atmospheric pressure to reduce and carbonize the manganese ore.

2. A method for producing manganese carbide as described in claim 1, wherein the partial pressure of the hydrocarbon gas in the mixed gas is 10.0 kPa or more, and the number of hydrogen atoms in the mixed gas is 12 times or more the number of carbon atoms.

3. The treatment temperature is set to 800°C or higher. ｍ The method for producing manganese carbide according to claim 1 or 2, wherein the range is less than 10 ...

4. A method for producing manganese carbide according to any one of claims 1 to 3, further comprising adjusting the particle size of the manganese ore in advance to 3 mm or more and 100 mm or less.

5. The method for producing manganese carbide according to claim 4, wherein the reduction and carbonization treatment is carried out in a rotary kiln.

6. A method for producing manganese carbide according to claim 5, wherein the mixed gas is supplied from a position inside the rotary kiln where the temperature therein is 700°C or higher.

7. A method for producing manganese carbide as described in claim 6, wherein the partial pressure of the hydrocarbon gas in the mixed gas at the position where the mixed gas is supplied is 10.0 kPa or more, and the number of hydrogen atoms in the mixed gas is 12 times or more the number of carbon atoms.

8. The maximum temperature inside the rotary kiln is set to 800°C or higher (melting temperature T ｍ The method for producing manganese carbide according to any one of claims 5 to 7, wherein the range is less than 100%.

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

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