Method for producing metal oxides

Abstract

A manufacturing apparatus (1A) includes a first gas introduction portion (20) provided on one end portion (10a) side of a calcination furnace (10) to introduce a gas into the calcination furnace (10), a gas discharge portion (30) provided on the other end portion (10b) side of the calcination furnace (10) to discharge the gas in the calcination furnace (10) to the outside, and a conveying apparatus (40) to convey a metal compound and a flux from the gas discharge portion (30) side to the first gas introduction portion (20) side. The calcination furnace (10) has a temperature increasing region (12A), a cooling region (14A), and a reaction region (13A) provided between the temperature increasing region (12A) and the cooling region (14A) and causing the metal compound and the flux to react. In the manufacturing apparatus (1A), a gas flow (AF1) generated by the gas introduced from the first gas introduction portion (20) causes the flux gasified in the reaction region (13A) to be powdered in the cooling region (14A), and the gas containing the powdered flux is sent to the gas discharge portion (30).

Description

Technical Field

[0001] This invention relates to an apparatus for manufacturing metal oxides and a method for manufacturing metal oxides.

[0002] This application claims priority based on Japanese Patent Application No. 2021-183370 filed on November 10, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, research on the synthesis of inorganic materials learned from nature and biology has been actively conducted. Among them, the flux method, developed based on the idea of ​​creating crystals (minerals) in nature, is a method of precipitating crystals from molten inorganic compounds or metals at high temperatures. The advantages of this flux method include the ability to cultivate crystals at temperatures far below the melting point of the target crystal, the growth of crystals with very few defects, and the development of euhedral crystals.

[0004] As methods for producing metal oxides using a fluxing process, known methods include: a fluxing slow cooling method, in which a metal compound, as a precursor of the metal oxide, is calcined at high temperature in the presence of a suitable oxide or salt as a flux, followed by (1) slow cooling; and a fluxing evaporation method, in which the flux is evaporated. In the fluxing slow cooling method, a supersaturated state is formed while the flux is slowly cooled, promoting crystal growth of the metal oxide. In contrast, the fluxing evaporation method promotes crystal growth of the metal oxide by using the evaporation of the flux as a driving force. It should be noted that in the fluxing evaporation method, the flux escapes from the calcination vessel through evaporation, thus having the advantage of not requiring the cumbersome operation of cleaning to remove the flux, as is present in the fluxing slow cooling method.

[0005] Flux evaporation is widely used in the manufacture of metal oxides because it does not require complicated operations. For example, Patent Document 1 describes an invention for manufacturing artificial corundum crystals, characterized by manufacturing artificial corundum crystals with a hexagonal bipyramidal basic shape by heating a sample containing raw materials and flux, and using the evaporation of flux as the driving force to precipitate and grow crystals.

[0006] In the manufacture of metal oxides based on flux evaporation, the nature of the process, which is driven by flux evaporation and releases the evaporated flux outside the system / environment, results in a significant environmental burden and high manufacturing costs.

[0007] To eliminate this problem, the applicant discloses a manufacturing apparatus comprising: a calcining furnace for calcining a metal compound in the presence of a flux; cooling piping connected to the calcining furnace and pulverizing the flux vaporized during calcination; and a recovery unit for recovering the pulverized flux in the cooling piping (Patent Document 2). In this manufacturing apparatus, the flux evaporated from the calcining furnace is primarily pulverized in the cooling piping and can be recovered in a dust collector. The recovered flux can be recycled in the manufacture of metal oxides, thus achieving a reduction in environmental burden and manufacturing costs.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2005 / 054550

[0011] Patent Document 2: Japanese Patent No. 6455747 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In the aforementioned conventional manufacturing apparatus, the cooling pipe comprises: a longitudinal pipe that discharges gas from the calcining furnace; a transverse pipe having a gas inlet at one end and the other end connected to a recovery unit; and a connecting section that cross-connects the longitudinal and transverse pipes. When using this manufacturing apparatus to manufacture metal oxides such as molybdenum oxide (MoO3), powdered flux (molybdenum compound) adheres to the inner wall of the connecting section, particularly the inner wall of the longitudinal pipe. This flux adhesion causes the inner diameter of the connecting section to narrow, making it sometimes difficult to maintain a proper flow path. As a countermeasure, methods exist for periodically removing the flux adhesion by placing a scraper or similar fixture on the cooling pipe; however, since the gas discharged from the calcining furnace contains molybdenum oxide, there is a problem of corrosion of the fixture due to molybdenum oxide. Additionally, methods exist for providing an insulating sleeve inside the longitudinal pipe to prevent the reaction between the vaporized flux from the calcining furnace and the longitudinal pipe; however, even in this case, the insulating sleeve is exposed to the gas containing molybdenum oxide, and therefore corrodes due to molybdenum oxide.

[0014] The purpose of this invention is to provide an apparatus and a method for manufacturing metal oxides. According to the apparatus and method, flux can be stably recovered. In addition, there is no need to install jigs or components for maintenance, which can significantly reduce the maintenance burden.

[0015] Solution for solving the problem

[0016] To achieve the above objectives, the present invention provides the following technical solutions.

[0017] [1] An apparatus for manufacturing a metal oxide, which is an apparatus for manufacturing a metal oxide based on a flux evaporation method, wherein the apparatus comprises: a calcining furnace for calcining a metal compound in the presence of a flux; a first gas inlet provided at one end of the calcining furnace for introducing gas into the calcining furnace; a gas outlet provided at the other end of the calcining furnace for discharging the gas in the calcining furnace to the outside; and a conveying device disposed in the calcining furnace for conveying the metal compound and the flux, or the metal oxide obtained by their reaction, from one side of the first gas inlet and the gas outlet to the other side. The calcining furnace includes: a heating zone located on one side of the gas discharge section and the first gas inlet section; a cooling zone located on the other side of the gas discharge section and the first gas inlet section; and a reaction zone located between the heating zone and the cooling zone, wherein the temperature in the reaction zone is higher than that in both the heating zone and the cooling zone, and the metal compound and the flux react. A gas flow generated by the gas introduced from the first gas inlet section pulverizes the flux vaporized in the reaction zone in the heating zone or the cooling zone, and the gas containing the pulverized flux is discharged to the gas discharge section.

[0018] [2] In the metal oxide manufacturing apparatus described in [1] above, the heating zone is provided on the gas discharge section side and the cooling zone is provided on the first gas inlet section side. The gas flow is countercurrent relative to the conveying direction of the conveying device and passes through the cooling zone, the reaction zone and the heating zone in sequence. In the heating zone, the flux vaporized in the reaction zone is pulverized.

[0019] [3] According to the metal oxide manufacturing apparatus described in [1] above, the heating zone is provided on the side of the first gas inlet and the cooling zone is provided on the side of the gas outlet. The gas flow is parallel to the conveying direction of the conveying device and passes through the heating zone, the reaction zone and the cooling zone in sequence. In the cooling zone, the flux vaporized in the reaction zone is pulverized.

[0020] [4] In the metal oxide manufacturing apparatus described in [3] above, a vaporized metal oxide obtained from the metal compound and flux in the conveying direction located upstream of the reaction zone is supplied to the metal compound and flux located downstream of the reaction zone.

[0021] [5] The metal oxide manufacturing apparatus according to [3] or [4] above, wherein the manufacturing apparatus further comprises a second gas inlet, which is provided in the cooling zone of the calcining furnace and supplies gas to the gas flow passing through the cooling zone.

[0022] [6] The apparatus for manufacturing metal oxides according to any one of [1] to [5] above, wherein the gas discharge section has: a main flow path that discharges gas from the calcining furnace to the outside of the furnace; and a third gas inlet section provided in the main flow path that supplies gas from the outside to the gas containing powdered flux flowing in the main flow path.

[0023] [7] The apparatus for manufacturing metal oxides according to any one of [1] to [6] above, wherein the calcining furnace has a corrosion-resistant heat-insulating part installed on the inner surface of the calcining furnace.

[0024] [8] The metal oxide manufacturing apparatus according to [1] above, wherein the manufacturing apparatus includes a recycling device connected to the gas discharge section, which recycles the powdered flux contained in the gas.

[0025] [9] The metal oxide manufacturing apparatus according to [8] above, wherein the recycling apparatus has a dust collector for collecting dust from the powdered flux.

[0026]

[10] According to the metal oxide manufacturing apparatus described above [9], the recycling apparatus further includes a classifier disposed between the gas discharge section and the dust collector to classify the powdered flux.

[0027]

[11] A method for manufacturing a metal oxide, which is a method for manufacturing a metal oxide based on a flux evaporation method, wherein gas is introduced into a calcining furnace from a gas inlet located at one end of a calcining furnace in the presence of a flux, and the gas in the calcining furnace is discharged to the outside from a gas outlet located at the other end of the calcining furnace. Inside the calcining furnace, the metal compound and the flux, or the metal oxide obtained by their reaction, are transported from one side of the gas inlet and the gas outlet to the other side. Inside the calcining furnace, the metal compound and the flux, or the metal oxide obtained by their reaction, are transported from one side of the gas inlet and the gas outlet to the other side. A heating zone is provided on one side of the gas discharge section and the gas inlet section, and a cooling zone is provided on the other side of the gas discharge section and the gas inlet section. A reaction zone is provided between the heating zone and the cooling zone. In the reaction zone, the temperature is higher than that of both the heating zone and the cooling zone, causing the metal compound and the flux to react. The flux vaporized in the reaction zone is pulverized in the heating zone or the cooling zone by an airflow generated by the gas introduced from the gas inlet section. The gas containing the pulverized flux is then sent to the gas discharge section.

[0028] The effects of the invention

[0029] According to the present invention, an apparatus for manufacturing metal oxides and a method for manufacturing metal oxides are provided. According to the apparatus and method for manufacturing metal oxides, flux can be stably recovered. In addition, there is no need to install jigs or components for maintenance, which can significantly reduce the maintenance burden. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating an example of a metal oxide manufacturing apparatus according to this embodiment.

[0031] Figure 2 It means Figure 1 A schematic diagram of the area inside the roasting furnace.

[0032] Figure 3 This is a schematic diagram illustrating a modified example of the metal oxide manufacturing apparatus of this embodiment.

[0033] Figure 4 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment.

[0034] Figure 5 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment.

[0035] Figure 6 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0037] It should be noted that in the accompanying drawings used in the following description, the scale of the dimensions is sometimes different depending on the component to facilitate observation of each component, and the size ratios of each component may not be the same as the actual dimensions. Furthermore, the structures and materials illustrated in the following description are examples, and the present invention is not necessarily limited to them; it can be implemented with appropriate modifications without changing its essence.

[0038] <Apparatus for Manufacturing Metal Oxides>

[0039] Figure 1 This is a schematic diagram illustrating an example of a metal oxide manufacturing apparatus according to this embodiment. Figure 1 The manufacturing apparatus is a metal oxide manufacturing apparatus based on the flux evaporation method. The flux evaporation method is a method for manufacturing metal oxides by calcining a metal compound in the presence of a flux. It should be noted that during the calcination process, the flux evaporates, and the crystal growth of the metal oxide is driven by the evaporation of the flux.

[0040] like Figure 1 As shown, the metal oxide manufacturing apparatus 1A includes: a calcining furnace 10, which calcines a metal compound in the presence of a flux; a first gas inlet 20, which is provided at one end 10a of the calcining furnace 10 to introduce gas into the calcining furnace 10; a gas outlet 30, which is provided at the other end 10b of the calcining furnace 10 to discharge the gas inside the calcining furnace 10 to the outside; and a conveying device 40, which is disposed inside the calcining furnace 10 to convey the metal compound and the flux, or the metal oxide obtained by their reaction, from the gas outlet 30 side to the first gas inlet 20 side.

[0041] From the viewpoint of easily creating high-temperature and low-temperature zones within the furnace, and from the viewpoint of continuously supplying raw materials to the roasting furnace and enabling mass production, the roasting furnace 10 of this embodiment is typically a continuous roasting furnace. There are no particular limitations on the type of continuous roasting furnace; examples include continuous rotary kilns, roller hearth kilns, pusher furnaces, conveyor furnaces, net conveyor furnaces, shaft kilns, and fluidized kilns. Among these, roller hearth furnaces, pusher furnaces, conveyor furnaces, and net conveyor furnaces are more preferred, and roller hearth furnaces and pusher furnaces are even more preferred.

[0042] There are no particular limitations on the heating method for the roasting furnace 10, and examples include electricity, gas, microwave, and infrared radiation. Among these, from the viewpoint of ease of industrialization and control, electric heating is preferred. In this embodiment, a heater 11 is provided inside the roasting furnace 10, and the heater 11 is disposed on the upper wall and the bottom wall of the roasting furnace 10. The heater 11 may also be disposed on either the upper wall or the bottom wall of the roasting furnace 10.

[0043] The roasting furnace 10, when viewed from above, has, for example, a conveying direction along the conveying device 40 ( Figure 1 The direction of the long side (the direction of the arrow in the diagram) and the direction orthogonal to the long side (also called the short side direction or the transverse direction). In this embodiment, one end 10a of the roasting furnace 10 is one end of the aforementioned long direction, and the other end 10b of the roasting furnace 10 is the other end of the aforementioned long direction.

[0044] From the viewpoint of efficiently removing powdered flux from the calcining furnace, the first gas inlet 20 is preferably positioned on the side opposite to the location of the gas outlet 30. In this embodiment, the first gas inlet 20 is positioned on the opposite end 10a side of the calcining furnace, opposite to the end 10b side where the gas outlet 30 is located.

[0045] Furthermore, from the viewpoint of efficiently forming an airflow from the first gas inlet 20 toward the gas outlet 30 throughout the entire roasting furnace 10, the first gas inlet 20 is preferably provided in the lower part of the bottom wall or side wall of the roasting furnace 10. One or more first gas inlets 20 may be provided in the roasting furnace 10.

[0046] In addition, when the roasting furnace 10 is provided with two or more first gas inlet sections 20, the first gas inlet section 20 may have: one or more main inlet sections for generating the airflow AF1 described later in the roasting furnace 10; and a plurality of secondary inlet sections, which are provided at certain intervals at the bottom of the roasting furnace 10 for forming an airflow from the bottom to the top in the roasting furnace 10.

[0047] The gas introduced from the first gas inlet 20 is not particularly limited as long as it does not react with flux vapor, and examples include air (in this case, the gas inlet is also referred to as the "external gas inlet"), oxygen, nitrogen, argon, water vapor, etc. Among these, air is preferred as a gas from a cost point of view.

[0048] The first gas inlet 20 may also include a first air supply device (not shown) forcibly introducing gas into the calcining furnace 10. This allows for sufficient airflow from the reaction zone (described later) towards the heating zone within the calcining furnace 10, and enables the appropriate discharge of the pulverized flux from the calcining furnace 10 to the outside. Specifically, when gas is forcibly introduced into the calcining furnace 10, a unidirectional airflow is generated within the furnace, and compared to the case where gas is not forcibly introduced into the furnace, the gas (containing the pulverized flux) within the calcining furnace 10 moves more easily towards the gas outlet 30. Therefore, the pulverized flux can be recovered quickly and efficiently. Furthermore, since flux evaporation becomes the driving force for crystal growth in the flux evaporation method, the flux evaporation method can be appropriately performed when the vaporized flux easily moves from the reaction zone (described later) to the heating zone. As a result, the obtained metal oxide can undergo appropriate crystal growth.

[0049] The first gas inlet 20 may also have an opening adjustment damper (not shown) for adjusting the amount and speed of gas introduced into the roasting furnace. There are no particular limitations on the opening adjustment damper; known opening adjustment dampers can be used. The opening adjustment damper may have a motor, a backflow prevention mechanism, or a slit. Furthermore, depending on the structure of the roasting furnace, there may be one opening adjustment damper or two or more.

[0050] The gas discharge section 30 discharges gas containing powdered flux to the outside of the calcining furnace 10. The gas discharge section 30 includes, for example, a main flow path 31 that discharges gas from inside the calcining furnace 10 to the outside; and a third gas inlet section 32 located in the main flow path 31, supplying gas from the outside to the gas flowing in the main flow path 31. The gas discharge section 30 has, for example, a T-shaped pipe, with the main flow path 31 formed by an L-shaped portion, and the third gas inlet section 32 formed by an I-shaped portion communicating with the L-shaped portion. By shaping the gas discharge section 30 as described above, the introduced external gas travels linearly and is conveyed to the dust collector described later, thus allowing for a short transfer to the recycling process. This enables the recovery of flux with large particle size and minimal particle aggregation.

[0051] There are no particular restrictions on the material of the piping that constitutes the gas exhaust section 30; known metals and alloys can be used.

[0052] The gas introduced from the third gas inlet 32 ​​is not particularly limited as long as it is a gas that does not react with flux vapor. Examples include air (in this case, the gas inlet is sometimes specifically referred to as the "external gas inlet"), oxygen, nitrogen, argon, and water vapor. Among these, air is preferred from a cost point of view.

[0053] The gas discharge section 30 may also have a second air supply device (not shown) provided at the third gas inlet section 32 and forcibly supplying air into the gas discharge section 30. Due to the negative pressure generated by the gas introduced from the third gas inlet section, the gas containing powdered flux within the calcining furnace 10 moves more easily towards the gas discharge section 30. Furthermore, considering the flux temperature during downstream recovery, the flux-containing gas can be further cooled outside the calcining furnace 10. This allows for the recovery of flux with uniform particle size and minimal or suppressed particle aggregation.

[0054] The third gas inlet 32 ​​may also have an opening adjustment damper (not shown) for adjusting the amount and speed of gas introduced into the roasting furnace. There are no particular limitations on the opening adjustment damper; known opening adjustment dampers can be used. The opening adjustment damper may have a motor, a backflow prevention mechanism, or a slit. Furthermore, depending on the structure of the roasting furnace, there may be one opening adjustment damper or two or more.

[0055] The conveying device 40, for example, has a conveying section and a drive section that drives the conveying section. The container 41 is placed in the conveying section, and the drive section drives the conveying section, thereby conveying the container 41 within the roasting furnace 10. There are no particular limitations on the conveying section; rollers, platforms, trolleys, etc., can be used. The container 41 placed in the conveying section is, for example, a roasting container called a sagger. In the conveying direction of the conveying device 40, upstream of the reaction zone (described later), the container 41 contains reactants (metal compounds and flux), and downstream of the reaction zone, it contains products (metal oxides obtained through the reaction of metal compounds and flux).

[0056] In this embodiment, a first gas inlet 20 is provided at one end 10a of the calcining furnace 10, and a gas outlet 30 is provided at the other end 10b. Furthermore, the conveying device 40 feeds a container 41 containing reactants into the calcining furnace 10 from one end 10b and discharges a container 41 containing products from one end 10a of the calcining furnace 10.

[0057] Figure 2 It means Figure 1 A schematic diagram of the area inside the roasting furnace 10.

[0058] like Figure 2 As shown, the calcining furnace 10 includes: a heating zone 12A located on the gas exhaust section 30 side; a cooling zone 14A located on the first gas inlet section 20 side; and a reaction zone 13A located between the heating zone 12A and the cooling zone 14A, wherein the temperature in the reaction zone 13A is higher than that in both the heating zone 12A and the cooling zone 14A, and the metal compound reacts with the flux.

[0059] Heating zone 12A is the area where the container 41 and the reactants inside the container 41 are heated and fed into the calcination furnace 10. Heating zone 12A has a temperature gradient in the conveying direction that increases as it approaches reaction zone 13A. A heater 11 is provided in heating zone 12A, and the heater 11 is controlled to maintain the aforementioned concentration gradient in heating zone 12A.

[0060] The heating zone 12A is, for example, disposed downstream of the gas discharge section 30 in the conveying direction of the conveying device 40. In other words, the heating zone 12A is disposed upstream of the gas discharge section 30 in the flow direction of the gas flow AF1, which will be described later.

[0061] Reaction zone 13A is the zone where the reactants in container 41, which is conveyed from heating zone 12A, react. There are no particular limitations on reaction zone 13A, as long as its temperature is higher than that of heating zone 12A and cooling zone 14A. For example, reaction zone 13A may not have a substantial temperature gradient in the conveying direction, but rather a substantially constant temperature. Furthermore, provided that the temperature of reaction zone 13A is higher than that of heating zone 12A and cooling zone 14A, reaction zone 13A may have a stepped or continuous temperature gradient in the conveying direction. A heater 11 is provided in reaction zone 13A, and the heater 11 is controlled to maintain the aforementioned constant temperature in reaction zone 13A.

[0062] Cooling zone 14A is a region for cooling the container 41 and the products contained in the container 41, which are conveyed from reaction zone 13A. Heating zone 12A has a temperature gradient that decreases in temperature along the conveying direction as it moves away from reaction zone 13A. A heater 11 is provided locally in reaction zone 13A, and the heater 11 is controlled to maintain the aforementioned concentration gradient. In cooling zone 14A, the heater 11 may or may not be provided locally.

[0063] The boundaries between the heating zone 12A and the reaction zone 13A, and between the reaction zone 13A and the cooling zone 14A, are not explicitly defined. However, for example, within the regions of the calcining furnace 10, in the conveying direction, the region maintaining the temperature for the decomposition of the intermediate obtained through the reaction between the flux and the metal compound can be designated as the reaction zone 13A, the upstream side (inlet side of container 41) of the reaction zone 13A can be designated as the heating zone 12A, and the downstream side (outlet side of container 41) of the reaction zone 13A can be designated as the cooling zone 14A. For example, the temperature distribution of each of the heating zone 12A, the reaction zone 13A, and the cooling zone 14A can be measured, and the average temperature of each temperature distribution can be determined. Alternatively, the temperature of the center of each of the heating zone 12A, the reaction zone 13A, and the cooling zone 14A can be measured in the conveying direction. Examples of temperature measurements for each zone include, for example, the temperature of the heater itself in each zone, and the ambient temperature near the thermocouple-based heater.

[0064] In this embodiment, the heating zone 12A is located at the other end 10b of the calcining furnace 10, and the cooling zone 14A is located at one end 10a of the calcining furnace 10. The container 41 is conveyed sequentially through the cooling zone 14A, the reaction zone 13A, and the heating zone 12A within the calcining furnace 10.

[0065] In the metal oxide manufacturing apparatus 1A configured as described above, the flux vaporized in the reaction zone 13A is pulverized in the cooling zone 14A by a gas flow AF1 formed by gas introduced from the first gas inlet 20, and the gas containing the pulverized flux is discharged to the gas outlet 30. Thus, in this embodiment, the vaporized flux is pulverized in the calcining furnace 10 by slow cooling inside the furnace.

[0066] Furthermore, in this embodiment, the airflow AF1 flows counter-currently to the aforementioned conveying direction and sequentially passes through the cooling zone 14A, the reaction zone 13A, and the heating zone 12A. Then, in the heating zone 12A, the flux vaporized in the reaction zone 13A is pulverized. That is, in this embodiment, the heating zone 12A functions as a zone that heats the metal compound and flux as reactants and cools the gas containing the vaporized flux to pulverize the flux. Figure 2 In the example, at position P1 above the airflow AF1 and above the conveying device 40 (above the heating zone 12A), the vaporized flux is pulverized.

[0067] In this embodiment, the gas introduced from the first gas inlet 20 cools the container 41 in the cooling zone 14A, and the gas passing through the cooling zone 14A and the reaction zone 13A heats the container 41 in the heating zone 12A. Thus, the container 41 and the products within it are efficiently cooled in the cooling zone 14A, and the container 41 and the reactants within it are efficiently heated in the heating zone 12A.

[0068] <Methods for Manufacturing Metal Oxides>

[0069] The method for manufacturing metal oxides in this embodiment is a method for manufacturing metal oxides based on flux evaporation, and includes the following steps (1) to (3). The order of steps (1) to (3) is not particularly limited and can be changed without departing from the spirit of the present invention. Alternatively, one or more other steps may be included before step (1), after step (3), or between two steps.

[0070] The following is for reference Figure 2 This embodiment uses an apparatus for manufacturing metal oxides as an example to illustrate the method for manufacturing metal oxides. The method for manufacturing metal oxides according to this embodiment is not limited to... Figure 2 The apparatus for manufacturing metal oxides can also be used to manufacture other metal oxides.

[0071] (Process (1))

[0072] In step (1), gas is introduced into the calcining furnace from a first gas inlet located at one end of the furnace where the metal compound is calcined in the presence of a flux, and the gas in the calcining furnace is discharged to the outside from a gas outlet located at the other end of the calcining furnace. For example, in Figure 2 In the example, gas is introduced into the roasting furnace 10 from the first gas inlet 20 located at one end 10a side of the roasting furnace 10, and the gas in the roasting furnace 10 is discharged to the outside from the gas outlet 30 located at the other end 10b side of the roasting furnace 10.

[0073] Examples of gases introduced from the first gas inlet section include air, oxygen, nitrogen, argon, and water vapor. From a cost perspective, air is preferred.

[0074] When gas is supplied to the roasting furnace from the first gas inlet section, the temperature of the supplied gas is preferably 5°C or higher, and more preferably 10°C or higher.

[0075] In addition, relative to the effective volume of the roasting furnace of 100L, the gas supply speed is preferably 1~500L / min, more preferably 10~200L / min.

[0076] There are no particular limitations on the internal pressure inside the calcining furnace; it can be positive or reduced pressure, and can be set to -5000 to +1000 Pa. Furthermore, from the viewpoint of properly discharging the flux from the calcining furnace to the cooling pipes, calcination is preferably carried out under reduced pressure. Specific pressure reduction levels can be set to -5000 to -10 Pa, -2000 to -20 Pa, or -1000 to -50 Pa.

[0077] (Fluoride)

[0078] There are no particular limitations on fluxes, and examples include molybdenum compounds, tungsten compounds, vanadium compounds, chlorine compounds, fluorine compounds, boron compounds, sulfates, nitrates, and carbonates.

[0079] There are no particular limitations on the molybdenum compound mentioned above, and examples include metallic molybdenum, molybdenum trioxide, molybdenum dioxide, molybdenum sulfide, ammonium molybdate, and H3PMo. 12 O 40 H3SiMo 12 O 40 K2Mo n O 3n＋1 (n=1~3), Na2Mo n O 3n＋1 (n=1~3), Li2Mo n O 3n＋1 (n=1~3), MgMo n O 3n＋1 (n=1~3), aluminum molybdate, silicon molybdate, magnesium molybdate, sodium molybdate, titanium molybdate, iron molybdate, potassium molybdate, zinc molybdate, boron molybdate, lithium molybdate, cobalt molybdate, nickel molybdate, manganese molybdate, chromium molybdate, cesium molybdate, barium molybdate, strontium molybdate, yttrium molybdate, zirconium molybdate, copper molybdate, etc.

[0080] There are no particular limitations on the tungsten compounds mentioned, and examples include tungsten trioxide, tungsten sulfide, tungstic acid, tungsten chloride, calcium tungstate, potassium tungstate, lithium tungstate, aluminum tungstate, sodium tungstate, ammonium paratungstate, ammonium metatungstate, phosphotungstic acid, and silicotungstic acid.

[0081] There are no particular limitations on the vanadium compounds mentioned, and examples include vanadium oxide, ammonium metavanadate, potassium vanadate, sodium metavanadate, sodium vanadate, vanadium trichloride, vanadium oxysulfate, and vanadium chloride.

[0082] There are no particular limitations on the chlorine compounds mentioned, and examples include potassium chloride, sodium chloride, lithium chloride, magnesium chloride, barium chloride, and ammonium chloride.

[0083] There are no particular limitations on the fluorine compounds mentioned, and examples include aluminum fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, cryolite, and lead fluoride.

[0084] There are no particular limitations on the boron compounds mentioned, and examples include boric acid, boron oxide, sodium borate, and boron fluoride.

[0085] There are no particular limitations on the sulfates mentioned, and examples include sodium sulfate, potassium sulfate, calcium sulfate, and lithium sulfate.

[0086] There are no particular limitations on the nitrates mentioned, and examples include sodium nitrate, potassium nitrate, calcium nitrate, and lithium nitrate.

[0087] There are no particular limitations on the carbonates mentioned, and examples include sodium carbonate, potassium carbonate, calcium carbonate, and lithium carbonate.

[0088] These fluxes can be used alone or in combination of two or more.

[0089] It should be noted that, among these, from the viewpoint that the obtained metal oxide can be easily controlled in terms of single crystal structure and / or shape, it is preferable to include a molybdenum compound, and from the viewpoint that it can be efficiently recovered when the gasified flux is pulverized, it is more preferable to include molybdenum trioxide.

[0090] There are no particular limitations on the amount of flux used, and it can be appropriately selected according to the desired metal oxide. For example, when manufacturing metal oxides with large particle sizes (1 mm or more), the molar ratio (flux metal / metal element) of the fluxing metal constituting the flux to the metal element constituting the metal compound described later is preferably greater than 3.0. On the other hand, when manufacturing metal oxides with small particle sizes (less than 1 mm), the molar ratio (flux metal / metal element) of the fluxing metal constituting the flux to the metal element constituting the metal compound described later is preferably 0.001 to 3.0 moles, more preferably 0.03 to 3.0 moles, and even more preferably 0.08 to 0.7 moles.

[0091] (Metal compounds)

[0092] There are no particular limitations on the metal compounds used; examples include aluminum compounds, silicon compounds, titanium compounds, magnesium compounds, sodium compounds, potassium compounds, zirconium compounds, yttrium compounds, zinc compounds, copper compounds, and iron compounds. Among these, aluminum compounds, silicon compounds, titanium compounds, and magnesium compounds are preferred.

[0093] Examples of aluminum compounds include aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, transitional alumina (γ-alumina, δ-alumina, θ-alumina, etc.), α-alumina, and mixed alumina having two or more crystal phases.

[0094] Examples of silicon compounds include crystalline silica, silica gel, silica nanoparticles, mesoporous silica, artificially synthesized amorphous silica, silicon-containing organosilicon compounds, and biomineralized silica.

[0095] There are no particular limitations on the titanium compounds mentioned, and examples include titanium chloride, titanium sulfate, metatitanic acid, amorphous titanium oxide, anatase titanium oxide, rutile titanium oxide, and mixed anatase and rutile titanium oxide.

[0096] There are no particular limitations on the magnesium compounds mentioned, and examples include magnesium oxide, magnesium hydroxide, magnesium acetate tetrahydrate, magnesium carbonate, magnesium sulfate, magnesium chloride, magnesium nitride, magnesium hydride, magnesium fluoride, magnesium iodide, magnesium bromide, magnesium acrylate, magnesium dimethacrylate, magnesium ethanol, magnesium gluconate, magnesium naphthenate, magnesium salicylate tetrahydrate, magnesium stearate, magnesium molybdate, magnesium lactate trihydrate, potassium magnesium chloride, magnesium nitrate hexahydrate, magnesium bromide hexahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, magnesium oxalate dihydrate, magnesium benzoate tetrahydrate, magnesium citrate n-hydrate, magnesium dicitrate trihydrate, and magnesium monoperoxyphthalate, etc.

[0097] These metal compounds can be used alone or in combination of two or more.

[0098] It should be noted that composite oxides can be manufactured by using two or more metal compounds in combination. For example, by using aluminum and magnesium compounds in combination, spinel composite oxides with the basic composition of MgAl2O4 can be manufactured.

[0099] Among these, aluminum compounds, aluminum compounds, and magnesium compounds are preferred.

[0100] (Process (2))

[0101] In process (2), within the calcining furnace, reactants (metal compounds and fluxes) or products (metal oxides obtained from the reaction of metal compounds and fluxes) are conveyed from one side of the first gas inlet (gas inlet) and the gas outlet to the other side. For example, in Figure 2 In this example, within the calcining furnace 10, the reactants or products are conveyed from the gas discharge section 30 side to the first gas inlet section 20 side. The conveying method is not particularly limited as long as it allows for continuous conveying of the reactants or products along a predetermined direction within the calcining furnace. For example, the reactants or products can be stored in multiple containers and moved sequentially within the furnace, thereby conveying the reactants or products. Furthermore, the conveying speed of the reactants or products is not particularly limited as long as it ensures sufficient time for the metal compound and flux to react within the calcining furnace.

[0102] (Process (3))

[0103] In step (3), in the calcining furnace, a heating zone is provided on one side of the gas exhaust section and the first gas inlet section (gas inlet section), and a cooling zone is provided on the other side of the gas exhaust section and the first gas inlet section. A reaction zone is provided between the heating zone and the cooling zone, in which the temperature is higher than that of both the heating zone and the cooling zone, causing the metal compound and the flux to react. The flux vaporized in the reaction zone is pulverized in the heating zone or the cooling zone by a gas flow generated by the gas introduced from the first gas inlet section, and the gas containing the pulverized flux is sent to the gas exhaust section. For example, in Figure 2 In this example, a heating zone 12A is provided on the gas discharge section 30 side, a cooling zone 14A is provided on the first gas inlet section 20 side, and a reaction zone 13A is provided between the heating zone 12A and the cooling zone 14A. In this reaction zone 13A, the temperature is higher than that of both the heating zone 12A and the cooling zone 14A, causing the metal compound and the flux to react. Then, by a gas flow AF1 generated by the gas introduced from the first gas inlet section 20, the flux vaporized in the reaction zone 13A is pulverized in the heating zone 12A, and the gas containing the pulverized flux is sent to the gas discharge section 30.

[0104] In the heating zone, the metal compound is heated in the presence of flux, and the flux readily evaporates in the downstream reaction zone. Additionally, in... Figure 2 In the example, in the heating region 12A, the metal compound and flux are heated, and the gas containing the vaporized flux is cooled to pulverize the flux.

[0105] There are no particular limitations on the temperature of the heating zone, but it is preferably 20~2000℃, and more preferably 40~1500℃.

[0106] In the heating zone, the heating rate of the metal compound and flux varies depending on the flux, metal compound, and desired metal oxide used. From the viewpoint of manufacturing efficiency, it is preferably 0.5 to 100 °C / min, more preferably 1 to 50 °C / min, and even more preferably 2 to 10 °C / min. Specifically, by setting the temperature gradient ( °C / m) and conveying speed (m / s) in the heating zone within the calcining furnace, the heating rate within the above range can be achieved by setting the temperature gradient and conveying speed.

[0107] (Cooling of vaporized flux)

[0108] The vaporized flux is cooled by the temperature difference between the heating zone and the reaction zone.

[0109] There is no particular limitation on the cooling rate of the vaporized flux, but it is preferably 100~100000℃ / second, more preferably 1000~50000℃ / second. It should be noted that the faster the cooling rate of the flux, the more likely it is to obtain flux powder with small particle size and large specific surface area.

[0110] The discharge rate of the powdered flux from the calcining furnace to the gas exhaust section can be controlled by using the flux dosage, the temperature of the calcining furnace, the air supply to the calcining furnace, and the diameter of the calcining furnace exhaust port. The discharge rate of the powdered flux from the calcining furnace to the gas exhaust section is preferably 0.001 to 100 g / min, more preferably 0.1 to 50 g / min, relative to 1 kg of the metal compound used as raw material.

[0111] Alternatively, the gas containing powdered flux can be discharged from the furnace by supplying gas to the gas exhaust section from the outside. For example, in Figure 2 In the example, the main flow path 31 of the gas discharge section 30 discharges the gas containing powdered flux inside the roasting furnace 10 to the outside of the furnace, and the third gas inlet section 32 provided in the main flow path 31 supplies gas from the outside to the gas flowing in the main flow path 31.

[0112] It should be noted that the air supply speed and the flow velocity inside the gas exhaust pipe can be appropriately controlled by adjusting the opening of the damper (not shown).

[0113] In the reaction zone, the metal compound is calcined at high temperature in the presence of a flux and the flux is evaporated, thereby producing a metal oxide (flux evaporation method).

[0114] In the flux evaporation method, the flux typically first reacts with a metal compound to form an intermediate. This intermediate is then decomposed to allow crystal growth, thereby producing a metal oxide. In this process, the evaporation of the flux drives the crystal growth of the metal oxide.

[0115] It should be noted that, for example, when using molybdenum compounds as flux, a metal molybdate salt is formed as an intermediate, which decomposes to produce a metal oxide. In this case, molybdenum trioxide evaporates through vaporization, which serves as a driving force to promote the crystal growth of the metal oxide.

[0116] There are no particular limitations on the mixing state of the flux and the metal compound; they can coexist in the same space. For example, a flux reaction can occur even when the two are immiscible. When the two are mixed, simple mixing of powders, mechanical mixing using a pulverizer, or mixing using a mortar and pestle are possible, and the resulting mixture can be in either a dry or wet state. When the two are immiscible, a gas-solid reaction can occur by setting the calcination temperature above the flux's sublimation temperature, thereby allowing the vaporized flux to contact the metal oxide.

[0117] The calcination temperature varies depending on the flux, metal compound, and desired metal oxide used, and is generally preferably set to a temperature at which the intermediate can decompose. For example, when using a molybdenum compound as a flux and an aluminum compound as a metal compound, aluminum molybdate can be formed as an intermediate. Therefore, the calcination temperature is preferably 500°C to 900°C, more preferably 600°C to 900°C, and even more preferably 700°C to 900°C.

[0118] There are no particular limitations on the reaction time; for example, it can be set from 1 minute to 30 hours.

[0119] (Gasified flux)

[0120] The flux used for vaporization varies depending on the flux used, but is typically a metal oxide constituting the flux. For example, when ammonium molybdate is used as the flux, it is converted into thermodynamically stable molybdenum trioxide by calcination, and thus the vaporized flux becomes the molybdenum trioxide. It should be noted that, sometimes the flux and metal compound form an intermediate through flux evaporation, but even in this case, the intermediate decomposes upon calcination, leading to crystal growth; therefore, the flux vaporizes in a thermodynamically stable form.

[0121] The temperature of the vaporized flux varies depending on the type of flux used, preferably 200~2000℃, more preferably 400~1500℃. It should be noted that when the temperature of the vaporized flux is below 2000℃, it tends to be easily pulverized in the cooling zone.

[0122] In the cooling zone, metal oxides obtained through the reaction of metal compounds and fluxes are cooled. Additionally, in... Figure 2 In the example, the obtained metal oxide is cooled in the cooling zone 14A, and the gas introduced from the first gas inlet 20 is heated.

[0123] There are no particular limitations on the temperature of the cooling zone, but it is preferably 20~2000℃, and more preferably 40~1500℃.

[0124] In the cooling zone, the cooling rate of the metal oxide varies depending on the flux, metal compound, and desired metal oxide used. From the viewpoint of manufacturing efficiency, it is preferably 0.1 to 100°C / min, more preferably 1 to 50°C / min, and even more preferably 2 to 20°C / min.

[0125] (Metal oxides)

[0126] The metal oxide varies depending on the metal compound used. From the viewpoint of the functionality of the metal oxide, the preferred options are aluminum oxide, silicon oxide, titanium oxide, magnesium oxide, sodium oxide, potassium oxide, zirconium oxide, yttrium oxide, zinc oxide, copper oxide, iron oxide, and spinel composite oxides of aluminum and magnesium. More preferred options are aluminum oxide, silicon oxide, titanium oxide, and spinel composite oxides of aluminum and magnesium. Even more preferred options are aluminum oxide and spinel composite oxides of aluminum and magnesium.

[0127] Regarding the crystal structure of metal oxides, those manufactured via flux evaporation typically exhibit dense single-crystal structures. Metal oxides with such dense single-crystal structures can possess high functionality. For example, alumina and spinel composite oxides of aluminum and magnesium naturally tend to have low density and polycrystalline structures, thus easily causing phonon scattering and making it difficult to achieve high thermal conductivity. However, alumina and spinel composite oxides of aluminum and magnesium obtained via flux evaporation have dense, highly regular crystal structures, thus suppressing phonon scattering and achieving high thermal conductivity. This crystal structure can be appropriately controlled by the type and amount of flux used in the flux evaporation process, the type and amount of metal compound added, and the calcination conditions.

[0128] It should be noted that metal oxides can contain fluxes. For example, when molybdenum compounds are used as fluxes, as mentioned above, most of them evaporate in the form of molybdenum trioxide, but some of the molybdenum compounds enter the metal oxide. As a result, alumina containing molybdenum can become a colored substance.

[0129] There is no particular limitation on the content of flux in the metal oxide. From the viewpoint of manufacturing metal oxides at low cost and high efficiency, it is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3 to 0.01% by mass. It should be noted that when metal oxides manufactured by the flux method contain flux, there is a tendency for the content of metal elements (usually around 100 ppm) to be higher than that contained as unavoidable impurities.

[0130] The average particle size of the metal oxide is not particularly limited, but is preferably 0.1 to 1000 μm, more preferably 0.2 to 100 μm, even more preferably 0.3 to 80 μm, and particularly preferably 0.4 to 60 μm. It should be noted that, in this specification, "average particle size" refers to the value calculated by measuring the particle size of any 100 particles from an image obtained by scanning electron microscopy (SEM). In this case, "particle size" refers to the maximum distance between two points on the particle's outline.

[0131] The shape of metal oxides can be controlled by appropriately changing the manufacturing conditions according to the desired purpose. For example, if one wants to use molybdenum oxide as a flux and aluminum oxide as a metal compound to manufacture α-crystalline alumina, the amount of flux added and the calcination conditions can be appropriately changed to manufacture α-crystalline alumina.

[0132] In one embodiment, hexagonal bipyramidal alpha-crystalline alumina can be manufactured by using a large amount of molybdenum oxide and undergoing slow crystal growth over a long period. This alpha-crystalline alumina can be used in applications such as laser oscillation materials, high-hardness bearing materials, standard materials for physical property measurement, and jewelry.

[0133] In another embodiment, by using a small amount of molybdenum oxide and performing crystal growth in a short time, it is possible to produce α-crystalline alumina with a narrow particle size distribution and a single-crystal structure. This α-crystalline alumina can be used in applications such as resin fillers, abrasives, and raw materials for fine ceramics.

[0134] It should be noted that, in any of the above cases, molybdenum oxide can also selectively adsorb onto the

[113] facet of the alumina crystal. As a result, it becomes difficult to supply crystal components to the

[001] facet, and the appearance of the

[001] facet can be suppressed. As a result, it is possible to manufacture α-crystal alumina with faces other than the

[001] facet as the main crystal plane. Unlike the plate-shaped α-alumina obtained by conventional calcination, which is a polyhedron with the

[001] facet as the main crystal plane, the growth of the

[001] facet is effectively suppressed, and particles with a uniform and nearly spherical polyhedral shape can be formed. It should be noted that, in this specification, "faces other than the

[001] facet as the main crystal plane" means that the area of ​​the

[001] facet is less than 20% of the total area of ​​the metal oxide.

[0135] It should be noted that when the metal oxide is a spinel composite oxide with the basic composition of MgAl2O4, it is possible to manufacture polyhedral particles with a single-crystal structure. These spinel particles can be used as resin fillers, catalysts, optical materials, substrate raw materials, abrasives, and other applications.

[0136] Furthermore, when the metal oxide is rutile titanium dioxide, it exhibits excellent concealment and high infrared scattering ability, thus making it suitable for applications in coatings, inks, cosmetics, etc. Additionally, when the metal oxide is silicon oxide, a two-phase co-continuous structure composed of Q4 bonds that are virtually devoid of silanol groups can be fabricated, enabling applications in life sciences as a support, resin filler, catalyst, cosmetics, etc.

[0137] After the above process (3), there may also be a process (4) to recover the powdered flux.

[0138] In step (4), for example, a dust collector is used to collect dust from the powdered flux contained in the gas discharged from the gas exhaust section. Alternatively, for example, a classifier can be used to classify the powdered flux contained in the gas discharged from the gas exhaust section and collect the classified flux.

[0139] There are no particular restrictions on the recycling method; it can be either batch recycling or continuous recycling.

[0140] In a batch process, the powdered flux is recovered from the recovery unit in each reaction. In this case, when the recovered flux is used to manufacture metal oxides, the shape of the metal oxides can be appropriately controlled by adjusting the amount added, particle size, etc. in advance.

[0141] Furthermore, in the continuous reaction process, the powdered flux is recovered sequentially during the reaction. In this case, the flux can be continuously mixed directly with the metal compound and fed into the calcining furnace, resulting in an increase in the amount of metal oxide produced per unit time.

[0142] In addition, after the above-mentioned process (4), there may be a further process (4) for reusing the flux recovered in process (3).

[0143] The flux recovered in process (4) is obtained by pulverizing the vaporized flux, and tends to have high purity. Therefore, it can be reused in the manufacture of metal oxides. This reduces the environmental burden and lowers manufacturing costs.

[0144] As described above, according to this embodiment, the flux vaporized in the reaction zone 13A is pulverized in the heating zone 12A, which is at a lower temperature than the reaction zone 13A, by the gas flow AF1 generated from the gas introduced from the first gas inlet 20. The gas containing the pulverized flux is then discharged to the gas outlet 30. Therefore, in the heating zone 12A within the calcining furnace 10, the flux in the gas flow AF1 changes from gas to solid, and there is essentially no situation where vaporized flux is discharged to the gas outlet 30. Therefore, flux can be stably recovered. In addition, it is possible to prevent flux from adhering to the gas outlet 30, eliminating the need for fixtures for removing flux deposits and insulating sleeves for preventing the reaction between the gas outlet 30 and the flux, thus significantly reducing the maintenance burden.

[0145] Furthermore, the gas flow AF1 flows counter-currently relative to the conveying device 40, passing sequentially through the cooling zone 14A, the reaction zone 13A, and the heating zone 12A. In the heating zone 12A, the flux vaporized in the reaction zone 13A is pulverized. Therefore, the container 41 and the products inside the container 41 can be efficiently cooled using the lower-temperature gas flow AF1 in the cooling zone 14A. Conversely, the container 41 and the reactants inside the container 41 can be efficiently heated using the higher-temperature gas flow AF1 in the heating zone 12A. Thus, through heat exchange between the gas constituting the gas flow AF1 and the container 41 and the reactants or products inside the container 41, thermal energy can be effectively utilized, flux can be stably recovered, and energy saving can be achieved.

[0146] Figure 3 This is a schematic diagram illustrating a modified example of the metal oxide manufacturing apparatus of this embodiment.

[0147] like Figure 3 As shown, the metal oxide manufacturing apparatus 1B includes: a calcining furnace 10, which calcines a metal compound in the presence of a flux; a first gas inlet 20, which is provided at one end 10b of the calcining furnace 10 to introduce gas into the calcining furnace 10; a gas outlet 30, which is provided at the other end 10a of the calcining furnace 10 to discharge the gas inside the calcining furnace 10 to the outside; and a conveying device 40, which is disposed inside the calcining furnace 10 to convey the metal compound and the flux, or the metal oxide obtained by their reaction, from the first gas inlet 20 to the gas outlet 30.

[0148] The calcining furnace 10 includes: a heating zone 12B located on the side of the first gas inlet 20; a cooling zone 14B located on the side of the gas outlet 30; and a reaction zone 13B located between the heating zone 12B and the cooling zone 14B, wherein the temperature in the reaction zone 13B is higher than that in both the heating zone 12B and the cooling zone 14B, and the metal compound reacts with the flux.

[0149] In this modified example, the heating zone 12B is located at one end 10b of the calcining furnace 10, and the cooling zone 14B is located at the other end 10a of the calcining furnace 10. Furthermore, the container 41 is conveyed sequentially through the heating zone 12B, the reaction zone 13B, and the cooling zone 14B within the calcining furnace 10.

[0150] In the metal oxide manufacturing apparatus 1B, a conveying device 40 is disposed in a calcining furnace 10 to convey metal compounds and fluxes, or metal oxides obtained by their reaction, from the first gas inlet 20 side to the gas outlet 30 side.

[0151] In the metal oxide manufacturing apparatus 1B, a gas flow AF2 generated by gas introduced from the first gas inlet 20 is used to pulverize the flux vaporized in the reaction zone 13A in the cooling zone 14A, and the gas containing the pulverized flux is then discharged to the gas outlet 30. In this modified example, the gas flow AF2 flows parallel to the conveying direction of the conveying device 40 and passes sequentially through the heating zone 12B, the reaction zone 13B, and the cooling zone 14B. Then, the flux vaporized in the reaction zone 13B is pulverized in the cooling zone 14B. That is, in this embodiment, the cooling zone 14B functions as a zone for cooling the metal oxide as a product and cooling the gas containing the vaporized flux to pulverize the flux. Figure 3 In the example, at position P2 above the airflow AF2 and above the conveying device 40 (above the cooling area 14B), the vaporized flux is pulverized.

[0152] Furthermore, since the airflow AF2 flows parallel to the conveying direction of the conveying device 40, the vaporized flux obtained from the metal compound and flux in the upstream portion 13Ba of the reaction zone 13B, which are conveyed by the conveying device 40, can be supplied to the metal compound in the downstream portion 13Bb of the reaction zone 13B. Therefore, even if the flux in the downstream portion 13Bb is insufficient and the reaction between the metal compound and the flux is inadequate, flux can still be supplied to the metal compound in the downstream portion 13Bb to ensure a sufficient reaction between the metal compound and the flux, and to increase the reaction rate between the metal compound and the flux.

[0153] According to this modified example, the flux vaporized in the reaction zone 13A is pulverized in the cooling zone 14B, which is at a lower temperature than the reaction zone 13B, by the airflow AF2 generated from the gas introduced from the first gas inlet 20. The gas containing the pulverized flux is then discharged to the gas outlet 30. Therefore, in the cooling zone 14B within the calcining furnace 10, the flux in the airflow AF2 changes from gas to solid, and there is essentially no situation where vaporized flux is discharged to the gas outlet 30. Thus, flux can be stably recovered, and it is possible to prevent flux from adhering to the gas outlet 30. There is no need to install fixtures for removing flux deposits or insulating sleeves for preventing the reaction between the gas outlet 30 and the flux, which significantly reduces the maintenance burden.

[0154] Furthermore, since the vaporized flux obtained from the metal compound and flux located in the upstream portion 13Ba of the reaction region 13B is supplied to the metal compound located in the downstream portion 13Bb of the reaction region 13B, the metal compound and flux can react sufficiently, and the particles of metal oxides such as alumina obtained as reactants are easily plated, which can promote the plated formation of the particles.

[0155] Figure 4 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment. For example... Figure 4 As shown, the metal oxide manufacturing apparatus 1C also includes a second gas inlet 50, which is provided in the cooling zone 14B of the calcining furnace 10 and supplies gas to the gas flow AF2 passing through the cooling zone 14B.

[0156] The second gas inlet 50 is provided, for example, on the upper wall of the calcining furnace 10. From the viewpoint of further cooling the gas flow AF2, the second gas inlet 50 is preferably positioned directly above the cooling zone 14B, and more preferably directly above the position P2 where the flux is pulverized. In addition, in this modified example, the gas from the second gas inlet 50 is supplied from above the gas flow AF2 and impacts it at a right angle relative to the gas flow AF2, but it can also impact at other angles, such as acute angles, within the range that does not affect the flow direction of the gas flow AF2.

[0157] If the airflow AF2 can be cooled in the cooling zone 14B, the second gas inlet 50 can be provided in a part other than the upper wall of the roasting furnace 10, for example, in the bottom or side of the roasting furnace 10.

[0158] The gas introduced from the second gas inlet 50 is not particularly limited as long as it does not react with flux vapor, and examples include air (in this case, the gas inlet is specifically referred to as the "external gas inlet"), oxygen, nitrogen, argon, water vapor, etc. Among these, air is preferred from a cost point of view.

[0159] The temperature of the gas introduced from the second gas inlet 50 is preferably 5 to 100°C, more preferably 5 to 40°C.

[0160] There is no particular limitation on the air supply speed of the gas introduced from the second gas inlet 50. It is preferably 1 to 500 L / min, more preferably 10 to 200 L / min, relative to the effective volume of the roasting furnace 10 of 100 L.

[0161] The second gas inlet 50 may also include a second air supply device (not shown) forcibly introducing air into the roasting furnace 10, and a cooling device (not shown) for cooling the air introduced into the roasting furnace 10. This allows for further cooling of the airflow AF2. Additionally, the second gas inlet 50 may also include an opening adjustment damper (not shown) for adjusting the amount and speed of gas introduced into the roasting furnace.

[0162] According to this modified example, since gas is supplied to the gas flow AF2 passing through the cooling zone 14B via the second gas inlet 50, the cooling of the gas flow AF2 is promoted in the cooling zone 14B, enabling more stable recovery of flux with uniform particle size and less or suppressed particle aggregation. Furthermore, by setting the temperature of the gas introduced from the second gas inlet 50 to a lower temperature, flux with large and uniform particle size and less particle aggregation can be recovered.

[0163] Figure 5 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment.

[0164] like Figure 5 As shown, the roasting furnace 10 may also have a corrosion-resistant heat insulation part 15 installed on the inner surface of the roasting furnace 10. The heat insulation part 15 is provided on at least a portion of the inner surface of the bottom wall, side wall, and top wall of the roasting furnace 10, but preferably installed on the inner surface of the bottom wall, side wall, and top wall.

[0165] There are no particular limitations on the material of the insulation part 15, which not only possesses the prerequisites of insulation and heat resistance but also corrosion resistance; examples include glass wool. From the viewpoint of corrosion resistance to fluxes such as molybdenum oxide, alumina fibers, clay bricks, and high-alumina bricks are preferred.

[0166] According to this modified example, since the corrosion-resistant heat insulation part 15 is installed on the inner surface of the roasting furnace 10, the heat dissipation of the roasting furnace 10 can be suppressed to improve the thermal efficiency, and the deterioration of the roasting furnace 10 caused by corrosion can be suppressed, thereby further reducing the maintenance burden.

[0167] Figure 6 This is a schematic diagram illustrating other variations of the metal oxide manufacturing apparatus of this embodiment. For example... Figure 6 As shown, the metal oxide manufacturing apparatus 1C includes a recovery device 80 connected to a gas discharge section 30 to recover powdered flux contained in the gas. The recovery device 80 includes a dust collector 81 for collecting dust from the powdered flux, and a classifier 82 disposed between the gas discharge section 30 and the dust collector 81 for classifying the powdered flux. In this modified example, the recovery device 80 includes both the dust collector 81 and the classifier 82, but it is not limited to this and may also omit the classifier 82. In this case, the dust collector 81 is directly connected to the gas discharge section 30 of the calcining furnace 10.

[0168] The dust collector 81 recovers the powdered flux in the cooling zone 14B within the calcining furnace 10. There are no particular limitations on the type of dust collector 81; examples include cyclone dust collectors, bag filter dust collectors, inertial dust collectors, moving layer dust collectors, wet dust collectors, filter dust collectors, and electrostatic precipitators.

[0169] The classifier 82 sieves the flux powdered in the cooling zone 14B within the calcining furnace 10 according to the size (particle diameter) of the particles. The flux of a specified size (particle diameter) is then fed to the dust collector 81. The classifier 82 is not particularly limited; for example, it can be a dry classifier. As a dry classifier, centrifugal gravimetric classifiers such as cyclones, gravity classifiers, and inertial classifiers can be used.

[0170] The recycling unit 80 is connected to an exhaust device 90, which serves as a third air supply device. Exhaust is performed through the exhaust device 90, thereby drawing air from the dust collector 81, the classifier 82, and the gas discharge section 30. External air is supplied to the gas discharge section 30 from the third gas inlet 32. In other words, air supply is passively generated in the gas discharge section 30 by the suction of the exhaust device 90.

[0171] According to this modified example, since the dust collector 81 recovers the pulverized flux in the cooling zone 14B within the calcining furnace 10, the recovered flux can be recycled in the manufacture of metal oxides. As a result, the environmental burden is reduced, and manufacturing costs are lowered. Furthermore, the classifier 82 classifies the pulverized flux, thus allowing the dust collector 81, located downstream, to recover flux of a specified size range (e.g., relatively large particle size). As a result, the recovered flux can be directly reused for recycling, while flux of sizes outside the specified range (e.g., relatively small particle size) can be recovered separately for other uses. Additionally, by ensuring uniform flux particle size, control over the plate-like formation of metal oxides can be easily achieved.

[0172] The above describes this embodiment, but the present invention is not necessarily limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0173] Explanation of reference numerals in the attached figures

[0174] 1A. Manufacturing apparatus; 1B. Manufacturing apparatus; 1C. Manufacturing apparatus; 10. Calcination furnace; 10a. One end (the other end); 10b. The other end (one end); 11. Heater; 12A. Heating zone; 12B. Heating zone; 13A. Reaction zone; 13B. Reaction zone; 13Ba. Upstream section; 13Bb. Downstream section; 14A. Cooling zone; 14B. Cooling zone; 15. Insulation section; 20. First gas inlet; 30. Gas outlet; 31. Main flow path; 32. Third gas inlet; 40. Conveying device; 41. Container; 50. Second gas inlet; 80. Recovery device; 81. Dust collector; 82. Classifier; 90. Exhaust system.

Claims

1. A method for manufacturing a metal oxide, which is a method for manufacturing a metal oxide based on a flux evaporation method, wherein, Gas is introduced into the calcining furnace from a gas inlet located at one end of the furnace where a metal compound is calcined in the presence of a flux, and the gas inside the calcining furnace is discharged to the outside from a gas outlet located at the other end of the furnace. Within the calcining furnace, the metal compound and the flux, or the metal oxide obtained through their reaction, are conveyed from one side of the gas inlet and the gas outlet to the other side. In the calcining furnace, a heating zone is provided on one side of the gas exhaust section and the gas inlet section, and a cooling zone is provided on the other side of the gas exhaust section and the gas inlet section. A reaction zone is provided between the heating zone and the cooling zone. In the reaction zone, the temperature is higher than that of both the heating zone and the cooling zone, causing the metal compound and the flux to react. The flux vaporized in the reaction zone is pulverized in the heating zone or the cooling zone by an airflow generated by the gas introduced from the gas inlet section. The gas containing the pulverized flux is then sent to the gas exhaust section.

2. The method for manufacturing a metal oxide according to claim 1, wherein, The apparatus for manufacturing the metal oxide used in the method for manufacturing the metal oxide includes: A roasting furnace, which roasts metal compounds in the presence of flux; The first gas inlet is located at one end of the roasting furnace and introduces gas into the roasting furnace. A gas exhaust section, located at the other end of the roasting furnace, exhausts the gas inside the roasting furnace to the outside; and A conveying device, disposed within the calcining furnace, conveys the metal compound and the flux, or the metal oxide obtained through their reaction, from one side of the first gas inlet and the gas outlet to the other side. The calcining furnace includes: a heating zone located on one side of the gas exhaust section and the first gas inlet section; a cooling zone located on the other side of the gas exhaust section and the first gas inlet section; and a reaction zone located between the heating zone and the cooling zone, wherein the temperature in the reaction zone is higher than that in both the heating zone and the cooling zone, and the metal compound and the flux react. The flux vaporized in the reaction zone is pulverized in the heating zone or the cooling zone by an airflow generated by the gas introduced from the first gas inlet, and the gas containing the pulverized flux is sent to the gas outlet.

3. The method for manufacturing a metal oxide according to claim 2, wherein, The heating zone is located on the gas discharge side, and the cooling zone is located on the first gas inlet side. The airflow is counter-current to the conveying direction of the conveying device, and passes sequentially through the cooling zone, the reaction zone, and the heating zone. In the heating zone, the flux that has been vaporized in the reaction zone is pulverized.

4. The method for manufacturing a metal oxide according to claim 2, wherein, The heating zone is located on the side of the first gas inlet, and the cooling zone is located on the side of the gas outlet. The airflow is parallel to the conveying direction of the conveying device, and passes sequentially through the heating zone, the reaction zone, and the cooling zone. In the cooling zone, the flux that has vaporized in the reaction zone is pulverized.

5. The method for manufacturing a metal oxide according to claim 4, wherein, Vaporized metal oxides obtained from the metal compounds and fluxes transported by the conveying device, located upstream of the reaction zone in the conveying direction, are supplied to the metal compounds and fluxes located downstream of the reaction zone.

6. The method for manufacturing a metal oxide according to claim 4 or 5, wherein, The manufacturing apparatus also includes a second gas inlet located in the cooling zone of the roasting furnace, which supplies gas to the gas flow passing through the cooling zone.

7. The method for manufacturing a metal oxide according to any one of claims 2 to 5, wherein, The gas discharge section has: The main path discharges the gas inside the roasting furnace to the outside of the furnace; as well as The third gas inlet is located in the main flow path and supplies gas from the outside to the gas containing powdered flux flowing in the main flow path.

8. The method for manufacturing a metal oxide according to claim 2 or 3, wherein, The roasting furnace has a corrosion-resistant heat-insulating part installed on the inner surface of the roasting furnace.

9. The method for manufacturing a metal oxide according to claim 2, wherein, The manufacturing apparatus includes a recovery device connected to the gas discharge section, which recovers the powdered flux contained in the gas.

10. The method for manufacturing a metal oxide according to claim 9, wherein, The recycling device includes a dust collector for collecting dust from the powdered flux.

11. The method for manufacturing a metal oxide according to claim 10, wherein, The recycling device also includes a classifier located between the gas discharge section and the dust collector to classify the powdered flux.

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