Processing method and apparatus for manufacturing ferroalloys

Abstract

To provide a processing method that can produce high-purity ferroalloys through a simple process, and to provide a ferroalloy manufacturing apparatus that can produce high-purity ferroalloys through a simple process. [Solution] The present invention provides a processing method in which a ferrite containing iron and a metal other than iron is reduced by magnetic heating by irradiating it with microwaves in the presence of a reducing agent, thereby producing a ferroalloy. It is preferable that the ferrite be placed in a position with a relatively strong magnetic field. Furthermore, it is preferable that the ferrite is produced and dissolved by magnetic heating by irradiating the processing material with steady-state microwaves.

Description

[Technical Field]

[0001] The present invention relates to a processing method and an apparatus for manufacturing ferroalloys. [Background technology]

[0002] Conventionally, metal smelting has involved high-temperature and long-duration reduction reactions. For example, in the reduction of nickel ferrite to ferronickel, the reaction is carried out under high-temperature conditions, mainly using gas. For example, Non-Patent Literature 1 discloses that when hydrogen gas is used, a reduction reaction at 700°C produces Fe3O4, FeO, Ni, α-Fe, and Fe-Ni alloys in coexistence. Furthermore, Non-Patent Literature 2 discloses that a reduction reaction at an even higher temperature of 800°C to 1100°C produces Fe (0.7-0.64) Ni (0.3-0.36) It has been disclosed that an alloy is formed. Furthermore, Non-Patent Document 3 discloses that when a mixed gas of carbon monoxide and carbon dioxide is used, (Fe,Ni)O and Fe-Ni alloy are formed in coexistence. [Prior art documents] [Patent Documents]

[0003] [Non-Patent Document 1] Kazunori Shimakage et al., Journal of the Japan Institute of Metals 33, 1969, 1188. [Non-Patent Document 2] M. Bahgat et al., Mater. Trans. 48, 2007, 3132. [Non-Patent Document 3] GH La et al., Miner. Eng. 164, 2021, 106829. [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a processing method that can produce high-purity ferroalloys through a simple process, and to provide a ferroalloy manufacturing apparatus that can produce high-purity ferroalloys through a simple process. [Means for solving the problem]

[0005] These objectives are achieved by the present invention as described below. The present invention relates to a processing method in which ferrite containing iron and other metals is reduced by magnetic heating by irradiating it with microwaves in the presence of a reducing agent, thereby producing a ferroalloy.

[0006] In the processing method of the present invention, it is preferable that the ferrite be placed in a position with a relatively strong magnetic field.

[0007] In the processing method of the present invention, it is preferable that the ferrite is generated and dissolved by magnetic heating by irradiating the workpiece with steady-state microwaves.

[0008] In the processing method of the present invention, the ferrite is preferably nickel ferrite.

[0009] In the processing method of the present invention, the reducing agent preferably contains solid carbon.

[0010] In the processing method of the present invention, the molar ratio of the solid carbon to the ferrite is preferably 1.94 or more and 4.00 or less.

[0011] In the processing method of the present invention, it is preferable that the reducing agent contains at least one of hydrogen gas and carbon monoxide gas.

[0012] In the processing method of the present invention, it is preferable that the temperature of the magnetic heating is 730°C or higher and 1300°C or lower.

[0013] In the processing method of the present invention, it is preferable that the microwave is a steady-state microwave.

[0014] In the processing method of the present invention, it is preferable that the frequency of the microwave is 0.9 GHz or more and 30 GHz or less.

[0015] The ferroalloy manufacturing apparatus of the present invention comprises a processing chamber in which ferrite containing iron and a metal other than iron is placed, and a microwave irradiation means for irradiating the ferrite placed in the processing chamber with microwaves to magnetically heat the ferrite.

[0016] The ferroalloy manufacturing apparatus of the present invention preferably includes a movable metal shorting plate arranged in the processing chamber, and by moving the movable shorting plate, the phase of the incident wave incident into the processing chamber from the microwave irradiation means and the phase of the reflected wave reflected by the movable shorting plate are adjusted. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a processing method that can produce high-purity ferroalloys through a simple process, and a ferroalloy manufacturing apparatus that can produce high-purity ferroalloys through a simple process. [Brief explanation of the drawing]

[0018] [Figure 1] This diagram schematically shows one example configuration of a ferrite manufacturing apparatus using microwave irradiation extraction. [Figure 2] Figure 1 schematically illustrates the relationship between the external magnetic field and the electric and magnetic field components of the microwaves in the manufacturing apparatus shown. [Figure 3] This diagram schematically shows the relationship between microwave irradiation time and temperature when the object to be treated is subjected to a heat treatment as a pretreatment before microwave irradiation. [Figure 4]This diagram schematically shows the relationship between microwave irradiation time and temperature when a magnetic field is applied to the object being treated as a pretreatment before microwave irradiation. [Figure 5] This diagram schematically shows the relationship between microwave irradiation time and temperature when an external magnetic field is applied and the magnetic field strength is swept while irradiating the object with microwaves. [Figure 6] This diagram schematically shows the relationship between microwave irradiation time and temperature when a material is irradiated with microwaves, and a steady magnetic field is applied perpendicular to the magnetic field component of the microwaves, while maintaining a constant magnetic field strength. [Figure 7] This figure shows the relationship between microwave irradiation time and temperature when nickel ferrite and solid carbon are irradiated with microwaves at maximum magnetic field. [Figure 8] These are the XRD patterns for ferronickel obtained in Examples 1-4. [Figure 9] These are the XRD patterns for ferronickel obtained in Example 3 and the Comparative Example. [Figure 10] This is an XRD pattern of ferronickel obtained when nickel ferrite was placed in a position with a relatively strong electric field and irradiated with microwaves. [Figure 11] This is an XRD pattern showing the results when the maximum temperature achievable by microwave magnetic heating is changed. [Figure 12] This is an XRD pattern obtained when nickel ferrite is placed in a location with a relatively strong magnetic field and the heating time by microwave irradiation is changed. [Figure 13] This is an XRD pattern obtained when nickel ferrite is placed in a position with a relatively strong electric field intensity and the heating time by microwave irradiation is changed. [Modes for carrying out the invention]

[0019] Preferred embodiments of the present invention will be described in detail below. [1] Method of processing ferrite First, the ferrite processing method of the present invention will be described. The present invention relates to a processing method in which ferrite containing iron and other metals is reduced by magnetic heating by irradiating it with microwaves in the presence of a reducing agent, thereby producing a ferroalloy. This allows for the production of high-purity ferroalloy through a simple process.

[0020] More specifically, when microwaves are irradiated onto ferrite containing iron and other metals in the presence of a reducing agent, the ferrite, which absorbs microwaves more readily than the reducing agent, is selectively heated by magnetic heating. Therefore, the energy used to raise the temperature of the reducing agent can be reduced. In addition, the consumption of the reducing agent can be suppressed, and the generation of undesirable reactants from the reducing agent can be prevented, making it possible to produce ferroalloys with high purity.

[0021] In this invention, "ferrite" refers to a magnetic oxide mainly composed of iron oxide. Examples of ferrites include those having structures such as spinel type, magnetoprumbite type, and ferroxprauner type, but are not particularly limited.

[0022] Furthermore, in this invention, "steady state" refers to a state in which microwaves, which are electromagnetic waves, are in a standing wave state. In a standing wave state, the incident wave and the reflected wave overlap, and therefore the wave energy is amplified.

[0023] Furthermore, in this invention, "magnetic heating" refers to a heating mechanism that occurs when a magnetic material such as ferrite interacts with microwaves. Specifically, "magnetic heating" refers to magnetic hysteresis heating, eddy current heating, or heating that utilizes resonance phenomena (resonant heating), and in the following explanation, these types of heating may also be referred to as "magnetic heating."

[0024] [1-1] Ferrite First, the ferrite used in the processing method of the present invention will be described.

[0025] Examples of ferrites used in the processing method of the present invention include nickel ferrite (NiFe2O4, Ni2FeO4), chromium ferrite (CrFe2O4, Cr2FeO4), manganese ferrite (MnFe2O4, Mn2FeO4), cobalt ferrite (CoFe2O4, Co2FeO4), magnesium ferrite (MgFe2O4, Co2FeO4), copper ferrite (CuFe2O4, Cu2FeO4), and the like.

[0026] The ferrite used in the processing method of the present invention may be obtained by any means, but it is preferable to use ferrite that is generated and dissolved by magnetic heating by irradiating the processing material described later with steady-state microwaves. Hereinafter, this method will be referred to as the "microwave irradiation extraction method".

[0027] By using ferrite obtained by microwave irradiation extraction in the processing method of the present invention, it becomes possible to produce ferroalloy from ferrite using microwave heating as the next step, after producing ferrite by microwave heating. Therefore, ferroalloy can be produced through a simpler process.

[0028] Furthermore, in the microwave irradiation extraction method, the generated ferrite is heated selectively and from within, allowing for high-purity refining at lower temperatures, in a shorter time, and more easily compared to external heating that does not use microwaves. In addition, since there is no need to use autoclaves or other devices using acid solvents, heating can be done at atmospheric pressure without requiring high pressure.

[0029] Therefore, by using ferrite obtained by microwave irradiation extraction in the processing method of the present invention, it is possible to produce ferroalloys of higher purity with less environmental impact.

[0030] [1-1-1] Microwave Irradiation Extraction Method In the microwave irradiation extraction method, ferrite is generated within the material by magnetic heating through the irradiation of a steady-state microwave.

[0031] [1-1-1-1] Processed items In microwave irradiation extraction, selective extraction is achieved by providing the energy necessary to reach the Curie temperature of the component to be extracted (in other words, the target ferrite generated by magnetic heating via microwave irradiation) through magnetic heating caused by microwave irradiation.

[0032] Therefore, microwave irradiation extraction can be applied to processed materials from which ferrite having a Curie temperature is obtained as an extract. The Curie temperature Tc is the transition temperature at which a ferromagnetic material changes to a paramagnetic material.

[0033] The material to be treated is not particularly limited as long as it generates ferrite by magnetic heating with microwave irradiation, but for example, a material containing iron and a metal element other than iron can be used. Examples of metal elements other than iron include Cr, Mn, Co, Ni, Mg, Cu, and rare earth elements (Sc, Y, and lanthanides). Among the above, a material containing Cr, Mn, Co, Ni, Mg or Cu and iron can be preferably used as the material to be treated, and a material containing Ni and iron, or Mn and iron can be more preferably used.

[0034] Furthermore, the treated material is preferably nickel-containing ore. This makes the effects of the present invention even more pronounced.

[0035] In this specification, nickel-containing ore refers to ore containing nickel and iron. From such nickel-containing ore, for example, NiFe2O4 can be extracted as ferrite.

[0036] Nickel-containing ore only needs to contain nickel and iron, but it may also contain other elements. Examples of these other elements include rare earth elements. While the amount of rare earth elements in nickel-containing ore is usually very small, microwave irradiation extraction allows for the extraction of a solid solution containing ferrite (NiFe2O4), the main target material, along with RFe2O4 (R: rare earth element) as a by-product. In particular, rare earth elements contained in nickel-containing ore can be recovered in the extract with a high recovery rate. Therefore, by further purification of the extract, high-purity NiFe2O4 (or Fe and Ni as elemental metals) and high-purity rare earth elements can be obtained.

[0037] As described above, nickel-containing ore, as a processed material, generates ferrite when irradiated with steady-state microwaves. Examples of components that serve as raw materials for ferrite contained in nickel-containing ore include oxides such as (Ni,Mg)3Si2O5(OH)4(Serpentine), FeOOH(Goethite), and (Fe,Mg)3Si2O5(OH)4(Lizardite).

[0038] Furthermore, nickel-containing ore may also contain oxides other than those mentioned above. Examples of such oxides include ferrite (NiFe2O4), silicon dioxide (alpha-SiO2, etc.), and aluminum oxide. This ferrite can be dissolved and extracted by magnetic heating.

[0039] In addition to nickel-containing ore, other materials that can be used for processing include, for example, chromium-containing ore containing chromium and iron, manganese-containing ore containing manganese and iron, cobalt-containing ore containing cobalt and iron, magnesium-containing ore containing magnesium and iron, and copper-containing ore containing copper and iron.

[0040] Specifically, chromium-containing ores containing chromium and iron can be used to extract ferrites such as CrFe2O4 and Cr2FeO4. Manganese-containing ores containing manganese and iron can be used to extract ferrites such as MnFe2O4 and Mn2FeO4. Cobalt-containing ores containing cobalt and iron can be used to extract ferrites such as CoFe2O4 and Co2FeO4. Magnesium-containing ores containing magnesium and iron can be used to extract ferrites such as MgFe2O4 and Mg2FeO4. Copper-containing ores containing copper and iron can be used to extract ferrites such as CuFe2O4 and Cu2FeO4.

[0041] Similar to nickel-containing ores, these ores have traditionally undergone smelting processes that have a significant environmental impact. However, with microwave irradiation extraction, it is possible to extract ferrite containing these metals at low temperatures, in a short time, and at atmospheric pressure using a simple process with minimal environmental impact.

[0042] Furthermore, these ores, like the nickel-containing ores mentioned above, usually contain trace amounts of rare earth elements. Using microwave irradiation extraction, rare earth elements can be efficiently extracted from these ores, and subsequent processing can yield high-purity CrFe2O4, Cr2FeO4, MnFe2O4, Mn2FeO4, CoFe2O4, Co2FeO4, MgFe2O4, Mg2FeO4, CuFe2O4, Cu2FeO4 (or Fe, Cr, Mn, Co, Mg, Cu as elemental metals) and high-purity rare earth elements with high recovery rates. In particular, when extracting ferrite represented by the general formula: M2FeO4 (where M is a metallic element other than Fe), it is generally advantageous in that it is possible to efficiently obtain metals that are more expensive than iron.

[0043] The shape of the processed material is not particularly limited, but it is preferably particulate (powdered). This allows the processed material to absorb microwaves more effectively, and thus more effectively promote the generation of the target ferrite, the magnetic heating of the target ferrite, and its elution.

[0044] The following explanation will primarily focus on the case where the treated material is a nickel-containing ore containing nickel and iron, and NiFe2O4 is extracted from this material as ferrite. NiFe2O4 is a ferrite with a typical spinel-type crystal structure.

[0045] [1-1-1-2] Ferrite manufacturing apparatus in microwave irradiation extraction method The following describes the ferrite manufacturing equipment used in microwave irradiation extraction.

[0046] Figure 1 is a schematic diagram showing one example of the configuration of a ferrite manufacturing apparatus using microwave irradiation extraction.

[0047] The ferrite manufacturing apparatus 1 comprises a processing chamber 10 in which the workpiece 20 is placed, a microwave irradiation means 11 that irradiates the workpiece 20 placed in the processing chamber 10 with steady-state microwaves to magnetically heat the workpiece 20, and an external magnetic field application means 14 that applies an external magnetic field to the workpiece 20.

[0048] In the ferrite manufacturing apparatus 1, ferrite is generated in the workpiece 20 by magnetic heating through steady-state microwave irradiation, and the ferrite generated in the workpiece 20 is selectively dissolved by heating from within, thereby selectively extracting the desired ferrite.

[0049] Thus, the microwave irradiation extraction method provides a ferrite manufacturing apparatus 1 that has a simple structure with minimal environmental impact, and enables extraction at low temperature, in a short time, and at atmospheric pressure.

[0050] Furthermore, the ferrite manufacturing apparatus 1 makes it possible to efficiently and inexpensively obtain ferrite containing the target metal element (metal element other than iron) as a constituent element, even from processed materials with a relatively low content of the target metal element. Therefore, it is possible to suitably obtain ferrite containing the target metal element from processed materials with a low content of the target metal element, which have not been used conventionally. Consequently, it is expected that the amount of metal resources available to humankind will increase significantly in the future.

[0051] In the following explanation, we will mainly describe the case where the ferrite manufacturing apparatus 1 is a single-mode type that irradiates with microwaves in a single mode. However, the ferrite manufacturing apparatus 1 for the microwave irradiation extraction method may also be a multi-mode type apparatus that irradiates with microwaves in a multi-mode.

[0052] The processing chamber 10 has a hollow, box-like shape. The object to be processed 20 is placed inside the processing chamber 10. The outer wall of the processing chamber 10 is made of a material such as copper or aluminum, and the inner surface is plated with silver, gold, etc., and has microwave reflectivity. The shape and size of the processing chamber 10 are determined, for example, according to the distribution of microwaves irradiated onto the object to be processed 20.

[0053] Furthermore, it is preferable that the processing chamber 10 is closed in such a way as to prevent microwave leakage, except for areas where openings are necessary, such as the entrance and exit for the processed material 20. The processing chamber 10 may also be provided with an observation window (not shown) for observing the interior, and ventilation openings or fans (not shown) for supplying and exhausting air.

[0054] The microwave irradiation means 11 is equipped with a microwave oscillator and irradiates microwaves into the processing chamber 10.

[0055] A microwave oscillator oscillates microwaves at a predetermined frequency. The microwave oscillator may, for example, include a variable frequency oscillator and a variable amplifier (not shown). The variable frequency oscillator is configured to output microwaves of variable frequency. The variable amplifier amplifies the power of the microwaves output from the variable frequency oscillator.

[0056] The ferrite manufacturing apparatus 1 shown in Figure 1 is equipped with a movable metal shorting plate 13 located inside the processing chamber 10. By moving the movable shorting plate 13 in the x-axis direction within the processing chamber 10, the phase of the incident wave that enters the processing chamber 10 from the microwave irradiation means 11 and the phase of the reflected wave reflected by the movable shorting plate 13 can be adjusted.

[0057] Specifically, for example, the phase of the incident wave that enters the processing chamber 10 from the microwave irradiation means 11 is aligned with the phase of the reflected wave reflected by the movable short-circuit plate 13.

[0058] An iris 12 may be provided as an opening in the side wall of the processing chamber 10, which serves as the microwave inlet from the microwave irradiation means 11 to the processing chamber 10. This iris 12 has the function of allowing incident waves that enter the processing chamber 10 from the microwave irradiation means 11 to pass through, and returning the reflected waves reflected by the movable shorting plate 13 back into the processing chamber 10.

[0059] Figure 1 also shows an image of the standing microwave wave in the ferrite manufacturing apparatus 1.

[0060] Note that the electric field component of microwaves (E mw The direction of the magnetic field and the magnetic field component (H mw The direction of the microwaves is perpendicular to the direction of the electric field component (E). That is, in Figure 1 and Figure 2 shown later, the electric field component of the microwaves (E) mw The direction of the microwaves is parallel to the plane of the paper (in-plane direction), and the magnetic field component of the microwaves (H mw The orientation of the ) is perpendicular to the paper surface (in the depth direction).

[0061] In this specification, "perpendicular" does not mean strictly perpendicular in a mathematical sense, but rather allows for some degree of deviation.

[0062] Furthermore, in this specification, "parallel" does not mean strictly parallel in a mathematical sense, but rather allows for a slight deviation.

[0063] The microwave (wavelength) incident from the microwave irradiation means 11 is blocked at the movable short-circuit plate 13 (x = L) at the microwave outlet, reflects the microwave that has not been irradiated to the object to be irradiated, the processed object 20, and the reflected wave is re-irradiated to the processed object 20, passes through, and returns to the microwave irradiation means 11.

[0064] Here, an iris 12 that allows the incident wave to pass through and returns the reflected wave is provided between the processed object 20 and the microwave irradiation means 11, so that the incident wave is confined in this space in a resonant state (L = nλ / 2; n = 1, 2, 3,...), in other words, the phases of the incident wave and the reflected wave are aligned, and a standing wave (stationary wave) with amplified energy is generated.

[0065] By using this standing wave, by arranging the processed object 20 at a position where the microwave energy is relatively large, it becomes possible to irradiate the processed object 20 with microwaves having energy greater than the energy of the incident wave, and the processed object 20 can be efficiently magnetically heated.

[0066] The external magnetic field applying means 14 applies an external magnetic field to the processed object 20 arranged in the processing chamber 10. The external magnetic field applying means 14 includes, for example, an electromagnet. The external magnetic field by the electromagnet becomes a direct current magnetic field.

[0067] Prior to irradiating the processed object 20 with microwaves, by applying an external magnetic field by the external magnetic field applying means 14, pre-treatment can be performed on the processed object 20. Also, when magnetically heating the processed object 20, by applying an external magnetic field by the external magnetic field applying means 14, the magnetic heating of the processed object 20 can be performed more efficiently.

[0068] The installation location x of the external magnetic field applying means 14 a is, for example, the position where the electric field is maximum as E max. and the position where the magnetic field is maximum as H max. such that, taking E max. -λ / 2 ≤ x a ≤ H max. +λ / 2 is satisfied.

[0069] In this specification, "maximum" does not refer to the exact mathematical maximum, but rather allows for some degree of deviation.

[0070] The ferrite manufacturing apparatus 1 shown in Figure 1 is further equipped with an external heating means 15 for heating the workpiece 20 in addition to magnetic heating.

[0071] The external heating means 15 is equipped with a heating element, which heats the workpiece 20 from the outside. The heating element provided by the external heating means 15 is, for example, an electric heater.

[0072] Prior to microwave heating of the workpiece 20, pretreatment can be performed on the workpiece 20 by external heating using the external heating means 15. This provides the effects described later.

[0073] Installation location x of the external heating means 15 b For example, E max. -λ / 2≦x b ≤H max. This position satisfies the condition +λ / 2.

[0074] The ferrite manufacturing apparatus 1 shown in Figure 1 further includes a radiation thermometer 16 for measuring the temperature of the irradiated object and a gaussmeter 17 for measuring the magnitude of the external magnetic field.

[0075] The radiation thermometer 16 measures the temperature of the object being irradiated, which is the object being processed 20. The Gaussmeter 17 has a hose element positioned at the center of the pole piece of the electromagnet provided by the external magnetic field application means 14, and measures the magnitude of the external magnetic field.

[0076] Furthermore, the ferrite manufacturing apparatus 1 is equipped with a control unit 18 that controls the operation of the external magnetic field application means 14, the external heating means 15, and the movable short-circuit plate 13 according to the measurement results from the radiation thermometer 16 and the gauss meter 17.

[0077] In such a single-mode device, the electric field component (E) that constitutes the microwave mw ) and magnetic field component (H mw By utilizing the different properties of reflection at the metal plate (movable short-circuit plate 13) compared to ), the position of the maximum energy of each standing wave, in other words, the position of the maximum electric field (E max. ) and the location of the strongest magnetic field (H max. ) and λ / 4(=|E max. -H max. A key characteristic is that they are generated with a shift of only |) units.

[0078] The object to be processed 20 is primarily placed at a location with a relatively strong magnetic field, as indicated by g in Figure 1. As will be described in more detail later, in this specification, "a location with a relatively strong magnetic field" refers to the location where the magnetic field strength is maximum (H max. It is located at a position of ±λ / 8 from ).

[0079] [1-1-1-3] Pre-treatment It is preferable to perform pretreatment on the object to be treated before irradiating it with microwaves. This allows for more efficient magnetic heating using microwave irradiation.

[0080] Pretreatments include heat treatment and / or magnetic field application treatment, which involves applying an external magnetic field.

[0081] By performing a heat treatment as a pretreatment, functional groups, such as hydroxyl groups, contained in the material are removed, facilitating magnetic heating by microwave irradiation. Furthermore, magnetic heating by microwave irradiation in the subsequent process is performed more efficiently, the temperature of the material rises more rapidly, and the target temperature (e.g., Curie temperature Tc) can be reached more quickly.

[0082] Furthermore, by applying a magnetic field as a pretreatment, the magnetic hysteresis of the ferrite contained in the material is increased, facilitating magnetic heating by microwave irradiation. In addition, magnetic heating by microwave irradiation in the subsequent process is performed more efficiently, the temperature of the material rises more rapidly, and the target temperature (e.g., Curie temperature Tc) can be reached more quickly.

[0083] When a magnetic field application process is performed as a pretreatment, the direction of the external magnetic field is not particularly limited and may be perpendicular or parallel to the magnetic field component of the microwave.

[0084] Here, Figure 2 shows the manufacturing apparatus shown in Figure 1, with an external magnetic field (H ex. ) and the electric field component of microwaves (E mw ) and magnetic field component (H mw This diagram schematically shows the relationship between ( ).

[0085] The pretreatments, namely heat treatment and magnetic field application treatment, may be performed individually or in combination. When both heat treatment and magnetic field application treatment are performed, they may be performed simultaneously or sequentially. Furthermore, when the treatments are performed sequentially, the order is not particularly limited.

[0086] [1-1-1-3-1] Heat treatment as a pretreatment The heat treatment as a pretreatment for the workpiece 20 is not particularly limited, but for example, external heating by external heating means 15, and the electric field component (E) of microwaves irradiated from microwave irradiation means 11. mw Examples of heating methods include dielectric heating and Joule heating.

[0087] Figure 3 schematically shows the relationship between microwave irradiation time and temperature when the object to be treated is subjected to heat treatment as a pretreatment before microwave irradiation. The temperature T of the object 20 was measured using a radiation thermometer 16.

[0088] The magnetic field component of the microwave in the subsequent process (H) depends on the temperature T of the material being processed in the pre-processing stage. mw The time it takes to reach the target temperature (e.g., Curie temperature Tc) by magnetic heating using microwave irradiation differs. In other words, the higher the temperature of the material treated by pretreatment (T2 > T1 > RT), the shorter the time it takes to reach the target temperature by magnetic heating using microwave irradiation in the subsequent process. This allows for more efficient magnetic heating.

[0089] However, once the Curie temperature Tc is reached, the ferrite stops absorbing microwave energy due to changes in magnetism, so no further temperature increase of the processed material is observed.

[0090] Thus, by changing the temperature of the workpiece during the pretreatment heat treatment, it is possible to control the temperature and time in magnetic heating by microwave irradiation.

[0091] For example, in the ferrite manufacturing apparatus 1 shown in Figure 1, the heating process, which includes a pretreatment heat treatment and magnetic heating by microwave irradiation, allows for easy heating of the workpiece 20 by selecting and using the microwave electric field space and magnetic field space depending on the purpose.

[0092] In other words, first, the object to be processed 20 is placed in a position f with a relatively strong electric field intensity within the processing chamber 10, and microwaves are irradiated from the microwave irradiation means 11 to perform a pre-treatment heating treatment (electric field component E of the microwaves). mw Dielectric heating or Joule heating is performed. After that, the workpiece 20 is moved from a position f with a relatively strong electric field to a position g with a relatively strong magnetic field (H max. By moving the object to the processing chamber and irradiating it with microwaves to perform magnetic heating in an alternating magnetic field space, a series of heating processes for the object 20 can be easily carried out within the same processing chamber.

[0093] As mentioned above, the electric field is at its maximum position E. max. And, the position of maximum magnetic field H max.This means that the displacement is λ / 4. Therefore, when moving from a position f with a relatively strong electric field to a position g with a relatively strong magnetic field, the object 20 only needs to be moved by λ / 4.

[0094] [1-1-1-3-2] Magnetic field application as a pretreatment As a pretreatment, applying an external magnetic field to the material induces the expansion of magnetic hysteresis originating from the nickel content. This allows the material's temperature to reach the target temperature (e.g., Curie temperature Tc) in a shorter time during subsequent magnetic heating by microwave irradiation. ex. ) is, for example, a DC magnetic field provided by an electromagnet in the external magnetic field application means 14.

[0095] Figure 4 schematically shows the relationship between microwave irradiation time and temperature when a magnetic field is applied to the object as a pretreatment before microwave irradiation.

[0096] As a pretreatment, a magnetic field is applied to the workpiece 20 using an external magnetic field application means 14. The magnitude of the magnetic field applied to the workpiece 20 is H. ex. (>0) represents the value measured using a Gauss meter 17. The temperature T of the processed material 20 is the value measured using a radiation thermometer 16.

[0097] In a later process, the magnetic field component of microwaves (H mw By performing magnetic heating by irradiation with ) the magnitude of the external magnetic field H in the pretreatment, ex. The time it takes to reach the target temperature (e.g., Curie temperature Tc) varies depending on the external magnetic field H applied to the material during pretreatment. ex The higher the H2 > H1 ratio, the shorter the time required to reach the target temperature through magnetic heating by microwave irradiation in the subsequent process.

[0098] In pretreatment using an external magnetic field, the temperature of the workpiece itself does not change substantially, but magnetic heating by microwave irradiation is performed efficiently, and the temperature change gradient is equal to the magnitude of the external magnetic field H ex.The higher the value, the greater the increase. However, once the Curie temperature Tc is reached, no further temperature increase of the processed material is observed.

[0099] Thus, by changing the magnetic field strength during the application of an external magnetic field as a pretreatment, it is possible to control the temperature and time in magnetic heating by microwave irradiation.

[0100] In the pretreatment by heat treatment and / or magnetic field application treatment described above, when the target ferrite's Curie temperature is Tc[°C], it is preferable to heat the material to a temperature of less than 0.9×Tc[°C], more preferably to a temperature of less than 0.8×Tc[°C], and even more preferably to a temperature of less than 0.7×Tc[°C].

[0101] This allows for more efficient magnetic heating by microwave irradiation in subsequent processes, enabling the temperature of the processed material to reach the target temperature (e.g., Curie temperature Tc) in an even shorter time.

[0102] For example, if the target ferrite is NiFe2O4, the Curie temperature Tc is 585°C, so it is preferable to heat the material to a temperature of less than 410°C during pretreatment.

[0103] Furthermore, the pretreatment only needs to raise the temperature of the material to above its original temperature; there is no particular lower limit to the temperature, but for example, it should be above room temperature.

[0104] Furthermore, the Curie temperatures of ferrite compounds other than NiFe2O4 are, for example, MnFe2O4(T C :300℃~327℃), CoFe2O4(T C :520℃), CuFe2O4(T C :490℃), MgFe2O4(T C The temperature is 440°C, and the heating temperature for pretreatment can be set appropriately depending on the target ferrite.

[0105] Furthermore, in the pretreatment by heat treatment and / or magnetic field application treatment as described above, the pretreatment time is not particularly limited, as long as it is sufficient to raise the workpiece to the temperature described above, but for example, it can be between 1 second and 3600 seconds.

[0106] This allows for more favorable pretreatment of the material to be processed, and enables more efficient extraction of ferrite by microwave irradiation extraction.

[0107] [1-1-1-4] Magnetic heating by microwave irradiation The material is irradiated with steady-state microwaves to magnetically heat it. This generates ferrite in the material. Furthermore, the ferrite generated in the material can be selectively heated and dissolved by magnetic heating via microwave irradiation.

[0108] Specifically, for example, if the material to be treated is a nickel-containing ore containing nickel and iron, microwave irradiation causes the components in the nickel-containing ore to react, generating NiFe2O4 as ferrite, and a solid solution containing this ferrite is obtained.

[0109] Microwaves can be multimode or single-mode. In multimode, microwaves are irradiated onto the material being processed in random directions and phases, whereas in single-mode, a resonator is used to separate the electric field and magnetic field components of the microwave, which are electromagnetic waves, and selectively irradiate the material with either one of them.

[0110] The following explanation will primarily focus on the case where microwaves are irradiated in single mode.

[0111] First, the object to be processed 20 is placed inside the processing chamber 10, and then the movable short-circuit plate 13 is moved to adjust the phase so that the incident wave that enters the processing chamber 10 from the microwave irradiation means 11 and the reflected wave reflected by the movable short-circuit plate 13 are in phase.

[0112] This results in a single-mode "steady state" that has a standing wave with energy greater than that of the incident wave.

[0113] As a result, the processed material 20 is heated in the microwave alternating magnetic field space, mainly by magnetic hysteresis heating, causing its temperature to rise. The temperature of the processed material 20 during microwave heating is measured by a radiation thermometer 16. Furthermore, since the magnetic loss (μ') of the processed material 20 (nickel-containing ore) changes as the temperature rises, it is necessary to readjust it using the movable shorting plate 13.

[0114] It is preferable to position the workpiece 20 in the processing chamber 10 at a location with a relatively strong magnetic field. This allows for irradiation with microwave energy greater than the energy of the incident wave, enabling more effective magnetic heating of the workpiece 20. Therefore, additives such as microwave absorbers and catalysts can be eliminated.

[0115] In this specification, "a location with a relatively strong magnetic field" refers to the location where the magnetic field strength is maximum (H max. From ) to the position where the electric field strength is maximum (E max. ) and the position where the magnetic field strength is maximum (H max. This is defined as the range up to 1 / 2 of λ / 4, which is the difference between λ and λ.

[0116] In other words, as shown by g in Figure 1, a "position with relatively strong magnetic field strength" is the position where the magnetic field strength is maximum (H max. ) is at a position of ±λ / 8 = ±(λ / 4) / 2 from H max. -λ / 8≦x g ≤H max. It is expressed as +λ / 8.

[0117] For example, if the microwave frequency is 2.45 GHz, the microwave wavelength λ = 122 mm, so λ / 8 = approximately 15 mm, and the position g with relatively strong magnetic field strength is the position of maximum magnetic field strength (H max.The range is ±15mm from ). Also, when the frequency is 5.8GHz, the wavelength λ = 52mm, so λ / 8 = approximately 6.5mm, and the position g with relatively strong magnetic field strength is the position of maximum magnetic field (H max. This ranges from ±6.5mm.

[0118] Furthermore, the object being processed 20 may be placed in a position with a relatively strong electric field intensity. This allows the electric field component E of the microwaves to be controlled. mw It is heated by dielectric heating or Joule heating.

[0119] In this specification, "positions with relatively strong electric field strength" refers, for example, to the position where the electric field strength is maximum (E max. From ) to the position of maximum electric field (E max. ) and the position of maximum magnetic field (H max. This is defined as the range up to half of the difference λ / 4 between )

[0120] In other words, as shown by f in Figure 1, the "position with relatively strong electric field strength" is the position where the electric field strength is maximum (E max. ) is at a position of ±λ / 8 = ±(λ / 4) / 2 from E max. -λ / 8≦x f ≤E max. It is expressed as +λ / 8.

[0121] Similarly, for example, if the microwave frequency is 2.45 GHz, the position f with the relatively strong electric field strength is the position with the maximum electric field strength (E). max. ) will be within a range of ±15 mm. Also, when the frequency is 5.8 GHz, the position f with relatively strong electric field strength is the position of maximum electric field strength (E max. This ranges from ±6.5mm.

[0122] When the Curie temperature of the ferrite is Tc[°C], it is preferable to heat the treated material by microwave irradiation to 0.7×Tc[°C] or more and 1.3×Tc[°C] or less, more preferably to 0.8×Tc[°C] or more and 1.2×Tc[°C] or less, and even more preferably to 0.9×Tc[°C] or more and 1.1×Tc[°C] or less.

[0123] This allows for more efficient generation of the target ferrite in the processed material, and more efficient elution of the target ferrite generated in the processed material.

[0124] For example, if the target ferrite is NiFe2O4(T C If the temperature is 585°C, it is preferable to heat the processed material to 410°C or higher and 760°C or lower, more preferably to 468°C or higher and 702°C or lower, and even more preferably to 523°C or higher and 644°C or lower.

[0125] The microwave frequency is not particularly limited, but is preferably between 0.9 GHz and 30 GHz, more preferably between 0.9 GHz and 6.0 GHz, and even more preferably between 0.9 GHz and 3.0 GHz.

[0126] By reducing the microwave frequency, the magnetic heating space—in other words, the region of "relatively strong magnetic field" mentioned above—expands compared to the case of high frequencies, making it possible to heat a larger number of objects by microwave irradiation.

[0127] When microwaves are used for industrial, scientific, or medical purposes, they are subject to regulations under the Radio Law. Currently, the frequencies legally permitted for microwave heating under the Radio Law are 0.915 GHz, 2.45 GHz, 5.8 GHz, and 24.125 GHz.

[0128] As mentioned above, when the microwave frequency is 5.8 GHz, the position g with the relatively strong magnetic field is the position with the strongest magnetic field (H). max. Although it is within a range of ±6.5 mm from ), by lowering the frequency to 2.45 GHz, the position g with relatively strong magnetic field strength is the position with the strongest magnetic field (H max. The range expands from ±15mm, and theoretically, it is possible to heat the processed material approximately 13 times more than at 5.8GHz.

[0129] The microwave irradiation time is not particularly limited, as long as it is sufficient to magnetically heat and dissolve the target ferrite, but for example, it can be between 1 second and 3600 seconds.

[0130] This allows for more efficient generation of the target ferrite in the processed material and more efficient elution of the target ferrite generated in the processed material.

[0131] [1-1-1-4-1] External magnetic field sweep process When irradiating the object to be processed with microwaves, a magnetic field application process may be performed in which an external magnetic field perpendicular to the magnetic field component of the microwaves is swept.

[0132] When irradiating with microwaves, if an external magnetic field is applied while sweeping perpendicular to the magnetic field component of the microwaves, and resonance conditions are met, the absorption of microwaves by the material being treated becomes stronger, the temperature of the material rises more rapidly, and the target temperature (e.g., Curie temperature) can be reached in a shorter time (resonant heating).

[0133] The resonance condition is generally given by "hν = g·μ". B ·H ex. It is expressed as '', where h is Planck's constant, ν is the microwave frequency, and μ is the frequency of the microwave. B H is the magnetic moment due to electron spin. ex. This represents the strength of the external magnetic field.

[0134] Furthermore, the resonance condition is met when the magnetic field component of microwaves (H mw ) direction and external magnetic field (H) applied from external magnetic field application means 14 ex. The direction of ) is perpendicular (H mw ⊥H ex. ) and the magnetic field component of microwaves (H mw ) direction and external magnetic field (H ex. If the direction is not perpendicular to the direction, for example, parallel (H mw / / H ex.In this case, the resonance conditions are not satisfied even by sweeping the external magnetic field, and the temperature of the workpiece treated by resonant heating hardly rises.

[0135] Figure 5 schematically shows the relationship between microwave irradiation time and temperature when an external magnetic field is applied and the magnetic field strength is swept while irradiating the object with microwaves.

[0136] Note that the external magnetic field (H ex. The magnitude of the ) was measured using a Gauss meter 17, and the temperature of the processed material 20 was measured using a radiation thermometer 16.

[0137] The magnetic field component (H) of the microwaves irradiated from the microwave irradiation means 11 mw The direction of the external magnetic field (H) applied from the external magnetic field application means 14. ex. ) is perpendicular to the direction (H mw ⊥H ex. In the case of ), an external magnetic field (critical magnetic field: H) that satisfies the resonance condition is obtained by sweeping the external magnetic field. ex. =H C In this process, the workpiece 20 is heated by absorbing microwaves, causing the temperature of the workpiece 20 to rise (resonant heating).

[0138] As the temperature of the workpiece at the start of microwave irradiation (T=T2>T1>RT) increases due to pretreatment, the temperature reached by resonant heating also increases. However, once the temperature reached reaches the Curie temperature (T C Once it reaches ), no further temperature changes are observed, regardless of the magnetic field sweep.

[0139] Note that the magnetic field component of microwaves (H mw The direction of the external magnetic field (H) applied from the external magnetic field application means 14. ex. ) is parallel to the direction (H mw / / H ex. In this case, the temperature of the processed material 20 remains virtually unchanged.

[0140] [1-1-1-4-2] Steady-state magnetic field application process When irradiating with microwaves, a magnetic field application process may be further performed to apply a stationary magnetic field with a constant magnetic field strength as an external magnetic field and perpendicular to the magnetic field component of the microwaves.

[0141] When irradiating with microwaves, by applying a stationary external magnetic field with the direction of the magnetic field component of the microwaves perpendicular to the direction of the external magnetic field, the absorption of microwaves by the processed object becomes stronger, the temperature of the processed object rises more rapidly, and it can reach the target temperature (e.g., Curie temperature Tc) in a shorter time (resonance heating).

[0142] The magnetic field strength at this time is fixed at the magnetic field strength at which resonance conditions are satisfied by sweeping the external magnetic field strength in a state where the direction of the magnetic field component of the microwaves is perpendicular to the direction of the external magnetic field.

[0143] FIG. 6 is a diagram schematically showing the relationship between the microwave irradiation time and the temperature when irradiating a processed object with microwaves and further applying a stationary magnetic field with a constant magnetic field strength and perpendicular to the magnetic field component of the microwaves.

[0144] Note that the magnitude of the external magnetic field is a value measured using a gaussmeter 17, and the temperature of the processed object 20 is a value measured using a radiation thermometer 16.

[0145] The direction of the magnetic field component (H mw ) of the microwaves oscillated from the microwave irradiation means 11 and the direction of the external magnetic field (H ex. ) applied from the external magnetic field application means 14 are perpendicular (H mw ⊥H ex. ). Before irradiating with the magnetic field component (H ex. ) of the microwaves, the magnitude of the external magnetic field (H ex. ) is fixed at a magnetic field (critical magnetic field: H ex. = H C ) that satisfies the resonance conditions. When irradiating with the magnetic field component (H mw ) of the microwaves, the processed object 20 is heated by absorbing the microwaves. At this time, at the critical magnetic field, resonance occurs, the absorption of microwaves becomes stronger, and the time until reaching the target temperature becomes shorter (resonance heating).

[0146] In addition, when an external magnetic field is fixed to a magnetic field (H ex. =H2≠H C 、H ex. =H1≠H C ) that does not satisfy the resonance condition and the magnetic field component (H mw ) of the microwave oscillated from the microwave irradiation means 11 is irradiated, the temperature of the processed object 20 shows the same temperature rise as when an external magnetic field is applied as a pretreatment as shown in FIG. 4.

[0147] For example, as shown in FIG. 4, when an external magnetic field is applied only in the pretreatment (H ex. =H1, H2), the direction of the magnetic field hardly affects the subsequent heating by microwave irradiation.

[0148] However, when an external magnetic field is applied as a pretreatment (H ex. =H1, H2, H C ) and the microwave is continuously irradiated in the state where the external magnetic field is applied, as shown in FIG. 6, due to the difference in the arrangement between the direction of the external magnetic field applied when irradiating the microwave and the direction of the magnetic field component (H mw ) of the microwave, the effects, for example, the resonance heating effect, are greatly different. That is, when an external magnetic field is applied as a pretreatment and then the microwave is irradiated in the state where the external magnetic field is applied, the external magnetic field applied when irradiating the microwave is preferably perpendicular to the magnetic field component of the microwave.

[0149] When an external magnetic field is applied as a pretreatment and the microwave is continuously irradiated in the state where the external magnetic field is applied, the direction of the external magnetic field applied as a pretreatment and the direction of the external magnetic field applied when irradiating the microwave may be the same direction (parallel direction) or different directions (for example, perpendicular direction).

[0150] As explained above, the microwave irradiation extraction method involves irradiating the material with steady-state microwaves to generate ferrite through magnetic heating, and then extracting the material by eluting the ferrite. The eluted ferrite is obtained as a solid solution.

[0151] Although the above-described embodiment mainly focused on the case where microwaves are irradiated in single mode, the microwave irradiation extraction method is not limited to this, and for example, microwaves may be irradiated in multi-mode.

[0152] For example, even when irradiating with microwaves using multimode technology, the object to be processed can be magnetically heated in the same way as with single-mode technology by using microwaves in a "steady state" due to local resonance caused by the installation of a metal antenna or metal plate, or by using microwaves in a "steady state" where the standing wave is in a resonant state due to focusing using a metal mirror.

[0153] In this case, when using multimode, compared to single-mode, heating due to the contribution of the electric field component may result in the presence of non-magnetic contaminants eluted into the extract due to the heating of the electric field component. In such cases, since the target extract is a ferrite with a Curie temperature, the magnetic and non-magnetic components can be separated by additionally using a known external magnetic field separation method (magnetic separation), and the target substance can be extracted.

[0154] [1-1-1-5] By-products Next, we will explain the by-products obtained in addition to ferrite, the main product, in the microwave irradiation extraction method.

[0155] By irradiating the material with microwaves, a solid solution containing the target substance, ferrite, and a residue powder remaining after the solid solution has been extracted are obtained.

[0156] Since the ferrite contained in the solid solution, such as NiFe2O4, reacts to magnets, while the residual powder does not, the solid solution and the residual powder can be separated using a magnetic separation method.

[0157] For example, if the nickel-containing ore being processed contains trace amounts of rare earth elements, the ferrite NiFe2O4 extracted by microwave irradiation extraction will contain these rare earth elements as by-products.

[0158] In other words, the microwave irradiation extraction method yields a solid solution containing ferrite (NiFe2O4) and, as a byproduct, RFe2O4 (R: rare earth element) from nickel-containing ore that contains trace amounts of rare earth elements as the processed material.

[0159] RFe2O4 (R: rare earth element), obtained as a byproduct, is a group of materials that are attracting attention from both magnetic and dielectric perspectives. In particular, a multiferroic state is realized at low temperatures in which both ferrimagnetism (possessing ferromagnetic properties) and ferroelectricity coexist, and it is attracting attention from an applied perspective as "green ferrite (GF)" which has polar charge order due to strong correlation effects.

[0160] Furthermore, in conventional high-temperature metallurgy smelting using a rotary kiln, coal (carbon) is added as a reducing agent, high-temperature heat treatment is carried out, and finally, magnetic separation is used to separate the product into magnetic and non-magnetic materials.

[0161] However, because the Curie temperature of RFe2O4 is below room temperature, it is usually disposed of together with non-magnetic carbon-containing residues. Therefore, conventional technology has not been able to recover the "rare earth elements" contained in trace amounts in the processed material.

[0162] In contrast, microwave irradiation extraction allows for the recovery of trace amounts of "rare earth elements" contained in the processed material as a solid solution together with ferrite, making effective utilization possible. From the obtained solid solution, the target ferrite and the rare earth elements as by-products can be separated by known methods. With the processing method of the present invention, ferroalloys can also be produced from RFe2O4 (R: rare earth element) obtained as a by-product.

[0163] Furthermore, for example, if the material being processed contains nickel and iron, iron oxide slag is obtained as the residue after extracting ferrite from the material. This residue is in the same powdery state as before the extraction process, and its form is considered to be a porous material similar to the residue after removing nickel when performing the "method for determining nickel in ore" specified in the Japanese Industrial Standard (JIS M8126-1994).

[0164] Therefore, the by-products, as residues, have functions such as accumulating substances inside the pores, adsorbing substances on their surfaces, or selecting substances and objects that can pass through based on their size. By utilizing these functions, the by-products obtained from ferrite extraction can be applied to a wide range of uses, such as deodorizers, desiccants, and industrially, for substance separation.

[0165] [1-1-2] Ferrite obtained by methods other than microwave irradiation extraction The ferrite used in this invention is not limited to ferrite obtained by microwave irradiation extraction, but can also be obtained by conventional methods or commercially available ferrite. Conventional methods include, for example, dry and wet processes used in the smelting of Cr, Mn, Co, Ni, Mg, or Cu. Dry processes include, for example, smelting by adding a reducing agent such as coal (carbon) to a treated material containing Cr, Mn, Co, Ni, Mg, or Cu and iron (for example, industrial waste, soil, ore, etc.) and melting it for a long time at high temperatures in an electric furnace (for example, a rotary kiln, etc.) at 900°C to 1400°C (high-temperature metallurgy). Wet processes include, for example, leaching using high-concentration acid or long-term reaction at high temperatures and pressures of 200°C or higher and 3 MPa or higher in an autoclave charged with high-concentration acid (high-pressure acid leaching).

[0166] Furthermore, even if the ferrite used in this invention is not obtained by microwave irradiation extraction, it is preferable that the ferrite used is nickel ferrite. This makes the effects of the present invention even more pronounced.

[0167] [1-2] Reducing agent By irradiating ferrite with microwaves in the presence of a reducing agent, the ferrite can be reduced, making it possible to selectively produce ferroalloys.

[0168] The reducing agent is not particularly limited, but examples include solid carbon, hydrogen gas, carbon monoxide gas, etc.

[0169] In particular, it is preferable that the reducing agent contains solid carbon. This allows for reduction in a simpler process compared to when a gas is used as the reducing agent. Furthermore, reducing agents and ferrite have different microwave absorption characteristics, with ferrite absorbing microwaves more readily than the reducing agent. That is, ferrite reaches a higher temperature when irradiated with microwaves, and in particular, the temperature reached by solid carbon is lower than that reached by ferrite. Therefore, by including solid carbon in the reducing agent, the energy used to raise the temperature of the solid carbon can be reduced more effectively. In addition, the consumption of solid carbon can be more effectively suppressed, and the generation of undesirable reactants from solid carbon can be more effectively prevented, thereby reducing the environmental burden and enabling the production of ferroalloys with higher purity.

[0170] Furthermore, when using nickel ferrite as the ferrite, the maximum magnetic field (H max. Because the temperatures reached by ferronickel and solid carbon are significantly different in this process, the aforementioned effects can be made more pronounced.

[0171] Figure 7 shows the maximum magnetic field (H max. This figure shows the relationship between microwave irradiation time and temperature when nickel ferrite (NiFe2O4) and solid carbon (Carbon) are irradiated with microwaves.

[0172] The molar ratio of solid carbon to ferrite is preferably 1.94 to 4.00, more preferably 1.98 to 3.50, and even more preferably 2.00 to 3.00. This makes the effects of the solid carbon more pronounced.

[0173] Furthermore, the reducing agent preferably contains at least one of hydrogen gas and carbon monoxide gas. This makes it possible to produce a ferroalloy with higher purity, as the gas used for reduction is less likely to remain in the resulting ferroalloy compared to when a solid is used as the reducing agent.

[0174] Examples of hydrogen gas include crude hydrogen. Crude hydrogen may contain carbon monoxide gas. This can reduce the cost of purifying hydrogen gas. Alternatively, crude hydrogen may be obtained by irradiating a mixture containing raw materials such as rubber, plastic, and cellulose with microwaves, selectively heating and activating the iron-based catalyst, and decomposing the raw materials in the presence of the iron-based catalyst. This allows for the effective utilization of waste materials such as rubber, plastic, and cellulose to obtain useful materials, and the crude hydrogen generated as a byproduct can be effectively utilized to produce ferrite.

[0175] [1-3] Ferroalloy manufacturing equipment For example, a device similar to the one used for producing ferrite using the microwave irradiation extraction method described above can be used as the manufacturing apparatus for ferroalloy.

[0176] In other words, the ferroalloy manufacturing apparatus comprises a processing chamber in which ferrite containing iron and other metals is placed, and a microwave irradiation means that irradiates the ferrite placed in the processing chamber with microwaves to magnetically heat the ferrite.

[0177] In the ferroalloy manufacturing apparatus, ferrite containing iron and other metals is reduced by magnetic heating through microwave irradiation in the presence of a reducing agent, thereby producing a ferroalloy. This allows for the production of high-purity ferroalloys through a simple process.

[0178] Furthermore, it is preferable that the ferroalloy manufacturing apparatus, like the ferrite manufacturing apparatus, is equipped with a movable metal shorting plate located in the processing chamber, and that by moving the movable shorting plate, the phase of the incident wave incident from the microwave irradiation means into the processing chamber and the phase of the reflected wave reflected by the movable shorting plate can be adjusted.

[0179] More specifically, it is preferable to align the phase of the incident wave that enters the processing chamber from the microwave irradiation means with the phase of the reflected wave reflected by the movable shorting plate. This makes it possible to magnetically heat the workpiece more efficiently and to produce ferroalloys more efficiently.

[0180] Furthermore, it is preferable that the microwaves irradiated onto the ferrite are steady-state microwaves. Steady-state microwaves are standing waves in which the incident wave and the reflected wave overlap. Therefore, it is possible to irradiate the ferrite with microwaves having greater energy than the energy of the incident wave. Thus, the ferrite can be magnetically heated more efficiently, and ferroalloys can be produced more efficiently.

[0181] Furthermore, it is preferable to position the ferrite in a location with a relatively strong magnetic field. This allows for irradiation with microwave energy greater than the energy of the incident wave, enabling more effective magnetic heating of the workpiece. As a result, additives such as microwave absorbers and catalysts can be eliminated.

[0182] Furthermore, by positioning the ferrite in a location with a relatively strong magnetic field, the difference in microwave absorption characteristics between the reducing agent and the ferrite can be made more pronounced, allowing for a more effective reduction in the energy used to raise the temperature of the reducing agent. This also more effectively suppresses the consumption of the reducing agent and more effectively prevents the formation of undesirable reactants from solid carbon, making it possible to produce ferroalloys of higher purity.

[0183] Furthermore, by positioning the ferrite in a location with a relatively strong magnetic field, the ferrite can be reduced in a shorter time, allowing for more efficient production of ferroalloys.

[0184] Furthermore, the temperature of the magnetic heating when irradiating the ferrite with microwaves is preferably between 730°C and 1300°C, more preferably between 750°C and 1200°C, and even more preferably between 800°C and 1000°C. This makes it possible to reduce the ferrite more efficiently and produce a ferroalloy with higher purity.

[0185] Furthermore, the frequency of the microwaves used when irradiating the ferrite is preferably between 0.9 GHz and 30 GHz, more preferably between 0.9 GHz and 20.0 GHz, and even more preferably between 0.9 GHz and 10.0 GHz.

[0186] By reducing the microwave frequency, the magnetic heating space—in other words, the region of "relatively strong magnetic field" mentioned earlier—expands compared to the case of high frequencies, making it possible to heat more ferrite by microwave irradiation.

[0187] Furthermore, the microwave irradiation time is not particularly limited, as long as it is sufficient to magnetically heat and reduce the target ferrite, but for example, it can be between 1 second and 3600 seconds.

[0188] This allows for more efficient generation of the target ferrite in the processed material and more efficient elution of the target ferrite generated in the processed material.

[0189] Furthermore, if the ferroalloy manufacturing apparatus is equipped with means for applying an external magnetic field and means for external heating, then, similar to the manufacturing of ferrite, external magnetic field application treatment and external heating treatment may also be performed in the manufacturing of ferroalloy.

[0190] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

[0191] For example, the ferrite processing method of the present invention is not limited to being carried out using the ferroalloy manufacturing apparatus described above, but may also be carried out using an apparatus with other configurations.

[0192] Furthermore, the ferrite processing method of the present invention may include steps other than those described above (for example, a pre-treatment step, an intermediate treatment step, a post-treatment step, etc.).

[0193] Furthermore, while the embodiments described above primarily focused on cases where external heating of the workpiece is performed using a heating element, in the present invention, external heating of the workpiece may be performed by means other than a heating element.

[0194] Furthermore, while the embodiments described above primarily focused on the case where an external magnetic field is applied to the workpiece using an electromagnet, in the present invention, the external magnetic field applied to the workpiece may be provided by means other than an electromagnet. [Examples]

[0195] The present invention will be described in detail below based on specific examples, but the present invention is not limited thereto.

[0196] In the following explanation, unless otherwise specified, the processes were performed at room temperature (23°C), atmospheric pressure (101325 Pa), and relative humidity of 50%. Similarly, unless otherwise specified, the measurement conditions are also based on room temperature (23°C), atmospheric pressure (101325 Pa), and relative humidity of 50%.

[0197] (Example 1) First, nickel-containing ore (laterite ore) mined in Indonesia was prepared as the material to be processed. This nickel-containing ore contains nickel and iron, as well as trace amounts of rare earth elements. The nickel-containing ore was powdered, and 200 mg of it was packed and sealed into a quartz test tube.

[0198] Next, in the processing chamber of the ferrite manufacturing apparatus shown in Figure 1, a quartz test tube filled with nickel-containing ore was placed at a position (g) where the magnetic field strength was relatively strong. Then, the movable short-circuit plate was moved to adjust the phase between the incident wave that entered the processing chamber from the microwave irradiation means and the reflected wave reflected by the movable short-circuit plate.

[0199] Nickel-containing ore was irradiated with a steady-state microwave at a frequency of 5.8 GHz in air at atmospheric pressure. The microwave was single-mode. The nickel-containing ore was heated to 700°C by magnetic heating due to microwave irradiation. A portion of the nickel-containing ore was dissolved by microwave irradiation, yielding a solid solution and residual powder. Rare earth elements were separated from the obtained solid solution by a known method to obtain nickel ferrite.

[0200] After crushing the obtained nickel ferrite, 170 mg of nickel ferrite and 30 mg of solid carbon (molar ratio of 3.45 to nickel ferrite) were packed into a quartz test tube. Then, in the processing chamber of the ferrite manufacturing apparatus shown in Figure 1, the quartz test tube was placed at a position (g) where the magnetic field strength was relatively strong. The movable short-circuit plate was then moved to adjust the phase so that the incident wave incident into the processing chamber from the microwave irradiation means and the reflected wave reflected by the movable short-circuit plate were aligned.

[0201] Nickel ferrite was irradiated with a steady-state microwave at a frequency of 5.8 GHz in air at atmospheric pressure. The microwave was single-mode. The nickel ferrite was heated to 950°C by magnetic heating due to microwave irradiation. The microwave irradiation time was 10 minutes. By microwave irradiation, the nickel ferrite was reduced to obtain ferronickel.

[0202] (Example 2) Ferronickel was obtained in the same manner as in Example 1, except that the amounts of nickel ferrite and solid carbon used during microwave irradiation were 176 mg of nickel ferrite and 24 mg of solid carbon (molar ratio to nickel ferrite: 2.66).

[0203] (Example 3) Ferronickel was obtained in the same manner as in Example 1, except that the amounts of nickel ferrite and solid carbon used during microwave irradiation were 182 mg of nickel ferrite and 18 mg of solid carbon (molar ratio to nickel ferrite: 1.93).

[0204] (Example 4) Ferronickel was obtained in the same manner as in Example 1, except that the amounts of nickel ferrite and solid carbon used during microwave irradiation were 186 mg of nickel ferrite and 14 mg of solid carbon (molar ratio to nickel ferrite: 1.47).

[0205] (Comparative example) The nickel ferrite obtained in the same manner as in Example 1 was externally heated at 1000°C for 10 minutes using an electron furnace, instead of being irradiated with microwaves.

[0206] The ferronickel samples obtained in each of the above examples and comparative examples were measured using a powder X-ray diffractometer (XRD: X-ray diffraction) to determine their X-ray diffraction patterns (XRD patterns). The results are shown in Figures 8 and 9.

[0207] Figure 8 shows, from top to bottom, the results for Example 1 (molar ratio 3.45), Example 2 (molar ratio 2.66), Example 3 (molar ratio 1.93), Example 4 (molar ratio 1.47), simulations for NiFe, simulations for FeO, solid carbon as the raw material, and nickel ferrite as the raw material.

[0208] In all of the above Examples 1 to 4, peaks originating from ferronickel (NiFe) were clearly observed. That is, nickel ferrite was reduced by microwave irradiation, and ferronickel was obtained.

[0209] In particular, when the amounts of nickel ferrite and solid carbon during microwave irradiation were set to Example 1 (molar ratio 3.45) and Example 2 (molar ratio 2.66), no peaks originating from substances other than ferronickel were observed, and high-purity ferronickel was obtained. On the other hand, when the amounts of nickel ferrite and solid carbon during microwave irradiation were set to Example 3 (molar ratio 1.93) and Example 4 (molar ratio 1.47), peaks originating from substances other than ferronickel were observed, although they were lower than the peaks originating from ferronickel. Therefore, it is preferable to use a molar ratio of solid carbon to nickel ferrite of 1.94 or higher.

[0210] Figure 9 shows, from top to bottom, the results for Example 3 (molar ratio 1.93), Comparative Example (Conventional heating), NiFe simulation, FeO simulation, solid carbon raw material, and nickel ferrite raw material, respectively.

[0211] In Example 3, a peak originating from ferronickel (NiFe) was observed, and ferronickel was obtained. On the other hand, in the comparative example, no peak originating from ferronickel (NiFe) was observed, and ferronickel was not obtained.

[0212] Comparing the X-ray diffraction patterns of the raw material solid carbon and raw material nickel ferrite with those of the comparative example, it can be seen that in the comparative example, the peak originating from solid carbon has disappeared, but the peak originating from nickel ferrite has not. This suggests that the solid carbon did not reduce the nickel ferrite during the reaction. Therefore, it is clear that in order to obtain nickel ferrite, magnetic heating by irradiating with microwaves, as in the processing method of the present invention, is necessary, rather than external heating using an electron furnace.

[0213] Furthermore, when the composition of the ferronickel in Example 1 was confirmed by energy-dispersive X-ray spectroscopy (EDX), the molar ratio of Fe to Ni was found to be 2.07:1.

[0214] Furthermore, nickel ferrite was magnetically heated in the same manner as in Examples 1 to 4, except that the nickel ferrite was placed in a position (f) with a relatively strong electric field intensity within the processing chamber during microwave irradiation. The X-ray diffraction pattern (XRD pattern) of the obtained ferronickel was measured using a powder X-ray diffractometer (XRD). The results are shown in Figure 10.

[0215] Figure 10 shows, from top to bottom, the results for molar ratios of 3.45, 2.66, 1.93, and 1.47, simulations for NiFe, simulations for FeO, solid carbon as the raw material, and nickel ferrite as the raw material.

[0216] When nickel ferrite was placed in a position with a relatively strong electric field (f) within the processing chamber during microwave irradiation, and also when placed in a position with a relatively strong magnetic field (g), a peak originating from ferronickel (NiFe) was clearly observed in both cases. In other words, microwave irradiation reduced the nickel ferrite, yielding ferronickel.

[0217] <Considerations on the effects of magnetic heating temperature by microwaves> We investigated the effect of the temperature of magnetic heating by microwave irradiation on the purity of the resulting ferronickel.

[0218] Nickel ferrite was magnetically heated in the same manner as in Example 3, except that the maximum temperature reached during microwave irradiation was varied to 750°C, 800°C, 850°C, and 950°C. The X-ray diffraction pattern (XRD pattern) of the obtained ferronickel was measured using a powder X-ray diffractometer (XRD). The results are shown in Figure 11.

[0219] Figure 11 shows, from top to bottom, the simulation results for 950°C, 850°C, 800°C, 750°C, NiFe, FeO, solid carbon as the raw material, and nickel ferrite as the raw material.

[0220] Even when the maximum temperature reached by nickel ferrite was varied between 750°C and 950°C, a peak originating from ferronickel (NiFe) was clearly observed. In other words, microwave irradiation reduced nickel ferrite, yielding ferronickel.

[0221] More specifically, as the maximum temperature reached increased, peaks of fixed carbon and other components derived from sources other than ferronickel decreased, allowing for the acquisition of higher-purity ferronickel. In particular, when the heating temperature was 800°C or higher, the peaks derived from fixed carbon disappeared. Therefore, to obtain high-purity ferronickel, a heating temperature of 800°C or higher is preferable.

[0222] <Considerations on the effect of magnetic heating time by microwaves> We investigated the effect of the duration of magnetic heating by microwave irradiation on the purity of the resulting ferronickel.

[0223] Nickel ferrite was placed in a position with a relatively strong magnetic field (g) or a position with a strong electric field (f) within the processing chamber of the manufacturing apparatus, and the nickel ferrite was magnetically heated in the same manner as in Example 3, except that the heating time during microwave irradiation was changed between 1 minute and 10 minutes. The X-ray diffraction pattern (XRD pattern) of the obtained ferronickel was measured using a powder X-ray diffractometer (XRD). The results are shown in Figures 12 and 13.

[0224] Figure 12 shows the results when nickel ferrite is placed in a relatively strong magnetic field location (g) within the processing chamber. From top to bottom, the results are shown for 10 minutes, 6 minutes, 3 minutes, 1.5 minutes, 1 minute, simulations for NiFe, raw material nickel ferrite, and raw material solid carbon, respectively.

[0225] Figure 13 shows the results when nickel ferrite is placed at a relatively strong electric field location (f) within the processing chamber. From top to bottom, the results are shown for 10 minutes, 6 minutes, 3 minutes, 1.5 minutes, FeO simulation, NiFe simulation, raw material nickel ferrite, and raw material solid carbon, respectively.

[0226] When nickel ferrite was placed in a location with a relatively strong magnetic field (g) or a location with a strong electric field (f) within the processing chamber, a peak originating from ferronickel (NiFe) was clearly observed at both heating times. In other words, microwave irradiation reduced the nickel ferrite, yielding ferronickel.

[0227] In particular, when nickel ferrite was placed in a location with a relatively strong magnetic field (g) within the processing chamber, high-purity ferronickel was obtained more efficiently and in a shorter time compared to when nickel ferrite was placed in a location with a strong electric field (f).

[0228] More specifically, when nickel ferrite was placed in a location (g) with a relatively strong magnetic field within the processing chamber, high-purity ferronickel could be obtained with heating for a short time of 1 minute. Therefore, it is preferable to place nickel ferrite in a location (g) with a stronger magnetic field than in a location (f) with a relatively strong electric field within the processing chamber of the manufacturing apparatus.

[0229] From the above results, it was found that, according to the method of the present invention, ferrite containing iron and other metals can be reduced by magnetic heating by irradiating it with microwaves in the presence of a reducing agent, thereby producing a high-purity ferroalloy.

[0230] Except for using a ferrite containing Mn, Co, Mg, or Cu and iron instead of nickel ferrite, microwave heating was performed in the same manner as described above, and it was confirmed that the corresponding ferroalloy could be efficiently extracted. [Industrial applicability]

[0231] The processing method of the present invention reduces ferrite containing iron and metals other than iron by magnetic heating by irradiating the ferrite with microwaves in the presence of a reducing agent, thereby producing a ferroalloy. Therefore, a high-purity ferroalloy can be produced by a simple working process.

[0232] Further, the ferroalloy production apparatus includes a processing chamber in which ferrite containing iron and metals other than iron is disposed, and microwave irradiation means for irradiating the ferrite disposed in the processing chamber with microwaves to magnetically heat the ferrite. Therefore, it is possible to provide a ferroalloy production apparatus capable of producing a high-purity ferroalloy by a simple working process.

[0233] Therefore, the ferrite processing method and the ferroalloy production apparatus of the present invention have industrial applicability.

Explanation of Signs

[0234] 1: Ferrite production apparatus 10: Processing chamber 11: Microwave irradiation means 12: Iris 13: Movable short-circuit plate 14: External magnetic field application means 15: External heating means 16: Radiation thermometer 17: Gaussmeter 18: Control unit 20: Workpiece E mw : Electric field component of microwave H mw : Magnetic field component of microwave H ex. : External magnetic field E max. : Electric field maximum position H max. : Magnetic field maximum position f: Position where electric field intensity is relatively strong g: Position where magnetic field intensity is relatively strong

Claims

1. A method for producing a ferroalloy by reducing ferrite containing iron and other metals by magnetic heating, which is achieved by irradiating the ferrite with microwaves in the presence of a reducing agent.

2. The processing method according to claim 1, wherein the ferrite is placed in a position where the magnetic field strength is relatively strong.

3. The processing method according to claim 1 or 2, wherein the ferrite is generated and dissolved by magnetic heating by irradiating the processed material with steady-state microwaves.

4. The processing method according to claim 1 or 2, wherein the ferrite is nickel ferrite.

5. The treatment method according to claim 1 or 2, wherein the reducing agent contains solid carbon.

6. The processing method according to claim 5, wherein the molar ratio of the solid carbon to the ferrite is 1.94 or more and 4.00 or less.

7. The treatment method according to claim 1 or 2, wherein the reducing agent comprises at least one of hydrogen gas and carbon monoxide gas.

8. The processing method according to claim 1 or 2, wherein the temperature of the magnetic heating is 730°C or higher and 1300°C or lower.

9. The processing method according to claim 1 or 2, wherein the microwave is a steady-state microwave.

10. The processing method according to claim 1 or 2, wherein the frequency of the microwave is 0.9 GHz or more and 30 GHz or less.

11. A processing chamber in which ferrite containing iron and other metals is placed, A microwave irradiation means for irradiating the ferrite placed in the processing chamber with microwaves to magnetically heat the ferrite, A ferroalloy manufacturing apparatus equipped with the following features.

12. The ferroalloy manufacturing apparatus according to claim 11, further comprising a movable metal shorting plate disposed in the processing chamber, wherein the phase of the incident wave incident from the microwave irradiation means into the processing chamber and the phase of the reflected wave reflected by the movable shorting plate are adjusted by moving the movable shorting plate.

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