Cylindrical member for microwave heating device

Abstract

To provide a cylindrical member for a microwave heating device that can be reduced in the number of components and can efficiently exhaust gas generated by decomposition or vaporization during carbonization.SOLUTION: A cylindrical member for a microwave heating device includes a porous ceramic cylindrical body having air permeability and microwave permeability, and coatings located at least at parts of an outer peripheral surface and an inner peripheral surface of the cylindrical body and having a lower microwave permeability than the cylindrical body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cylindrical member for a microwave heating device.

Background Art

[0002] Conventionally, carbon fibers have been manufactured using a carbon fiber manufacturing apparatus employing a microwave dielectric heating method. Such a carbon fiber manufacturing apparatus has a structure in which an organic fiber serving as a precursor is supplied from one end of a cylindrical body that transmits microwaves, dielectrically heated, and the carbon fiber is taken out from the other end. If the cylindrical body has heat insulation properties, the heating efficiency can be improved and the power consumption can be reduced. In recent years, carbon fiber manufacturing apparatuses have been required to control the temperature profile in the axial direction (heating rate and holding temperature). In order to control the temperature profile, the intensity of microwaves irradiated on the organic fiber has been controlled by the cylindrical body.

[0003] For example, in the carbon fiber manufacturing apparatus described in Patent Document 1, a microwave absorption / transmission member is used as the cylindrical body. It is described in Cited Document 1 that the intensity of microwaves irradiated on the organic fiber is changed by joining a plurality of cylindrical bodies having different microwave transmittance rates. Patent Document 2 describes that the intensity of microwaves irradiated on the organic fiber is changed by arranging a cylindrical body that partially absorbs microwaves so as to partially cover the organic fiber along the movement path of the organic fiber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] However, conventional microwave dielectric heating carbon fiber manufacturing equipment requires the arrangement of multiple components. This can lead to misalignment and an increased number of parts. Furthermore, gases generated during the decomposition or vaporization of organic fibers tend to adhere to the inner wall of the cylindrical body. This can cause sparks to occur inside the cylindrical body, making it prone to damage.

[0006] The object of this disclosure is to provide a cylindrical member for a microwave heating device that can reduce the number of parts and efficiently discharge gases generated by decomposition or vaporization during carbonization. [Means for solving the problem]

[0007] (1) The cylindrical member for a microwave heating apparatus according to the present disclosure includes a cylindrical body made of porous ceramic having air permeability and microwave permeability, and a coating located on at least a portion of the outer and inner surfaces of the cylindrical body, having a lower microwave transmittance than the cylindrical body. Furthermore, the outer surface of the cylindrical body has a region where the coating is located and a region where the coating is not located. .

[0008] (2) In the cylindrical member described in (1) above, the coating has a thickness smaller than the average pore diameter of the cylindrical body. (3) In the cylindrical member described in (1) or (2) above, the coating is located at at least one end of the cylindrical body. (4) In the cylindrical member described in any of (1) to (3) above, the coating is located on both the outer and inner surfaces of the cylindrical body. (5) In the cylindrical member described in any of (1) to (4) above, coatings with different microwave transmittances are located at multiple locations in the axial direction of the cylindrical body. (6) In the cylindrical member described in any of (1) to (5) above, the coating is a DLC film. (7) In the cylindrical member described in (6) above, the DLC film has a ratio of SP3 bonds of 10% or more and 40% or less. (8) In the cylindrical member described in (6) or (7) above, the DLC film is located on the inner circumferential surface of the cylindrical body. (9) In the cylindrical member described in (6) or (7) above, the DLC film is located on the inner and outer surfaces of the cylindrical body, and the ratio of SP3 bonds in the DLC film on the inner surface is higher than the ratio of SP3 bonds in the DLC film on the outer surface.

[0009] (10) The microwave heating apparatus relating to this disclosure includes a cylindrical member as described in any of (1) to (9) above and an irradiation unit for irradiating microwaves. [Effects of the Invention]

[0010] The cylindrical member for microwave heating apparatus according to this disclosure, having the above-described configuration, can reduce the number of parts and efficiently discharge gases generated by decomposition or vaporization during carbonization. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram showing a cylindrical member for a microwave heating apparatus according to one embodiment of the present disclosure. [Figure 2] Figure 1 is an explanatory diagram showing a cross-section when the garment is cut along the XX line. [Figure 3] This is a schematic diagram showing a microwave heating apparatus according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0012] Hereinafter, the cylindrical member for a microwave heating apparatus according to the present disclosure will be described based on the drawings. Figure 1 is an explanatory diagram showing a cylindrical member for a microwave heating apparatus according to one embodiment of the present disclosure (hereinafter sometimes simply referred to as "cylindrical member"). As shown in Figure 1, the cylindrical member 1 for a microwave heating apparatus according to one embodiment includes a cylindrical body 11 and a coating 12.

[0013] In one embodiment of the cylindrical member 1, the cylindrical body 11 is made of porous ceramic and has air permeability and microwave permeability. Specifically, the cylindrical body 11 has air permeability and microwave permeability between its outer and inner surfaces.

[0014] The porous ceramic is not limited as long as it has a porous structure. In this specification, "porous ceramic" means a ceramic having a porosity exceeding 10% by volume. The porosity of the porous ceramic may be, for example, 25% by volume or more and 35% by volume or less.

[0015] Examples of the ceramic forming the cylindrical body 11 include ceramics mainly composed of aluminum oxide, zirconium oxide, yttrium oxide, yttrium aluminum composite oxide, magnesium oxide, silicon carbide, silicon nitride, titanium oxide, sialon, etc. Among these ceramics, it is preferably a ceramic mainly composed of aluminum oxide. By using a ceramic mainly composed of aluminum oxide, the cylindrical member 1 can be made inexpensive. When the ceramic is a ceramic mainly composed of aluminum oxide, it may further contain oxides such as magnesium, calcium, silicon, sodium, etc.

[0016] In this specification, "main component" means a component contained at a ratio of 80% by mass or more when the total of the components constituting the ceramic is 100% by mass. The identification of each component contained in the ceramic is performed by an X-ray diffractometer using CuKα rays, and the content of each component may be determined by, for example, an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or a fluorescent X-ray analyzer.

[0017] The size of the cylindrical body 11 is appropriately set according to the size of the microwave heating device, etc. The cylindrical body 11 may have, for example, a length of 100 mm or more and 2500 mm or less, an outer diameter of 20 mm or more and 60 mm or less, and an inner diameter of 15 mm or more and 55 mm or less. As long as the cylindrical body 11 is cylindrical, it may have a cylindrical shape, an elliptical cylindrical shape, or a rectangular cylindrical shape. In the case of an elliptical cylindrical shape and a rectangular cylindrical shape, the outer diameter and the inner diameter mean the diameter of the longest part.

[0018] In the cylindrical member 1 according to one embodiment, the coating 12 is located at least in part on the outer peripheral surface and the inner peripheral surface of the cylindrical body 11. The coating 12 has a lower microwave transmittance than the cylindrical body 11. Since the coating 12 has a lower microwave transmittance than the cylindrical body 11 and is located at least in part on the outer peripheral surface and the inner peripheral surface of the cylindrical body 11, different microwave transmittance portions can be provided in one cylindrical body 11. As a result, the number of parts can be reduced, and the accuracy when attaching to the microwave heating device can be improved. Further, when carbonized by microwaves inside the cylindrical body 11, the gas generated by decomposition or vaporization during carbonization can be efficiently discharged from the entire cylindrical body 11.

[0019] Examples of the coating 12 include a film formed of a conductor, a magnetic material, a dielectric, or a combination thereof that reflects or absorbs microwaves. In particular, a film formed of a conductor is preferably used. Specifically, examples of the coating 12 include a film formed of DLC (diamond-like carbon), graphite, metal, ferrite, or the like.

[0020] In the region where the coating 12 is located, the microwave is reflected or absorbed by the coating 12. As a result, the intensity of the microwave irradiated inside the cylindrical body 11 is reduced, and the temperature of the object to be heated can be reduced. The object to be heated is appropriately determined according to the application of the microwave heating device. For example, when the microwave heating device is a carbon fiber manufacturing device, the object to be heated is an organic fiber that is a precursor of carbon fiber.

[0021] The thickness of the coating 12 is not limited; for example, it may be smaller than the average pore diameter of the pores formed in the cylindrical body 11. By having a thickness of the coating 12 smaller than the average pore diameter of the pores formed in the cylindrical body 11, the pores of the cylindrical body 11 are less likely to be blocked. As a result, the air permeability can be further improved. The average pore diameter of the pores formed in the cylindrical body 11 may be, for example, 0.5 μm or more and 5.0 μm or less. The coating 12 may have a thickness of, for example, less than 1 μm, or a thickness of 1 / 3 or more the average pore diameter of the cylindrical body 11.

[0022] The coating 12 is not limited as long as it is located on at least a portion of the outer and inner surfaces of the cylindrical body 11, as described above. Specifically, the coating 12 may be located on the entire outer surface, the entire inner surface, or on both the outer and inner surfaces, and may be formed intermittently, with regions where the coating 12 is located and regions where it is not located. When microwaves are irradiated from the side of the cylindrical body 11, the coating 12 is located on at least the surface on which the microwaves are irradiated.

[0023] The coating 12 may be located, for example, at least one end of the cylindrical body 11. By having the coating 12 located at at least one end of the cylindrical body 11, the temperature change when the object to be heated by microwaves enters the cylindrical body 11 or exits the cylindrical body 11 can be slowed down. As a result, the distortion of the object to be heated can be reduced and the quality can be improved.

[0024] The coating 12 may be located only on the outer circumferential surface of the cylindrical body 11, only on the inner circumferential surface, or on both the outer and inner circumferential surfaces. When the coating 12 is located on both the outer and inner circumferential surfaces of the cylindrical body 11, the temperature difference between the outside and inside of the cylindrical body 11 is reduced. As a result, the possibility of cracks or fractures occurring in the cylindrical body 11 can be reduced.

[0025] The coating 12 may be of only one type, or two or more types of coatings 12 with different microwave transmittances may be used in combination. Specifically, coatings 12 with different microwave transmittances may be located at multiple points along the axial direction of the cylindrical body 11. By using coatings 12 with different microwave transmittances, the temperature distribution can be easily adjusted.

[0026] The coating 12 is preferably a DLC film among the examples given above. Since DLC films have a lower thermal conductivity than graphite, metals, etc., using a DLC film can further improve heat retention. Furthermore, because DLC films are conductive, they can remove the electric charge that accumulates on the inner wall surface of the cylindrical body 11. DLC films allow for control of various physical properties through composition control, and the composition of the DLC film can be easily changed depending on the application of the microwave heating device and the object being heated.

[0027] DLC films are materials primarily composed of carbon and possess both SP3 bonds (diamond skeleton structure) and SP2 bonds (graphite skeleton structure) of carbon-carbon bonding. A higher proportion of SP3 bonds results in properties similar to diamond, while a higher proportion of SP2 bonds results in properties similar to graphite. DLC films have lower thermal conductivity than highly crystalline diamond and graphite. For example, DLC films with a high proportion of SP2 bonds have lower thermal conductivity and superior heat retention. On the other hand, DLC films with a high proportion of SP3 bonds have excellent heat resistance and thermal shock resistance. Various properties can also be adjusted by adding elements other than carbon (C) (e.g., hydrogen (H), fluorine (Fe), silicon (Si), etc.).

[0028] Examples of DLC films used as coating 12 include DLC films containing 10% to 90% SP3 bonds, or DLC films containing 10% to 40% SP3 bonds. If the ratio of SP3 bonds is 40% or less, the film will have relatively low thermal conductivity and high heat retention. The ratio of SP2 bonds to SP3 bonds in the DLC film can be determined by methods such as Raman spectroscopy, X-ray photoelectron spectroscopy, or nuclear magnetic resonance spectroscopy.

[0029] The DLC film may be positioned as a coating 12 on the inner circumferential surface of the cylindrical body 11. When the DLC film is positioned as a coating 12 on the inner circumferential surface of the cylindrical body 11, the conductivity on the inner circumferential surface of the cylindrical body 11 can be lowered, and the generation of sparks inside the cylindrical body 11 can be further reduced. In the DLC film used as the coating 12 on the inner circumferential surface, the ratio of SP3 bonds may be 10% or more, or it may be 40% or more. If the ratio of SP3 bonds is 40% or more, the film will have relatively low conductivity and will be less prone to sparking.

[0030] The DLC film may be located not only on the inner circumferential surface of the cylindrical body 11 but also on the outer circumferential surface. In this case, the DLC film located on the inner circumferential surface of the cylindrical body 11 may have a higher proportion of SP3 bonds than the DLC film located on the outer circumferential surface of the cylindrical body 11. With this configuration, the DLC film located on the inner circumferential surface of the cylindrical body 11 has a lower conductivity than the DLC film located on the outer circumferential surface of the cylindrical body 11. As a result, the generation of sparks inside the cylindrical body 11 can be further reduced. Furthermore, the DLC film located on the outer circumferential surface of the cylindrical body 11 has a lower thermal conductivity than the DLC film located on the inner circumferential surface of the cylindrical body 11. As a result, the heat retention can be further improved.

[0031] The method for manufacturing the cylindrical member 1 according to one embodiment is not limited, and for example, it may be manufactured by the following procedure. First, one embodiment of the method for manufacturing the cylindrical body 11 will be described. When the main component of the ceramic forming the cylindrical body 11 is aluminum oxide, aluminum oxide powder having an average particle size of 0.4 μm or more and 0.6 μm or less (aluminum oxide powder A), and aluminum oxide powder having an average particle size of 1.2 μm or more and 1.8 μm or less (aluminum oxide powder B) are prepared. Furthermore, silicon oxide powder having an average particle size of 0.5 μm or less is prepared as a Si source, and calcium carbonate powder is prepared as a Ca source. Magnesium hydroxide powder may also be used as a Mg source. Powders other than the main components aluminum oxide powder A and aluminum oxide powder B are collectively referred to as "auxiliary component powders".

[0032] Next, aluminum oxide powder A and aluminum oxide powder B were weighed in a mass ratio of 40:60 to 60:40, and the resulting ceramic component contained 99.4% or more by mass of Al (in terms of aluminum oxide), thereby obtaining an aluminum oxide blended powder. The auxiliary component powders were weighed as follows: First, the amount of sodium contained in the aluminum oxide blended powder was confirmed and converted to sodium oxide from the amount of sodium in the ceramic. The weight was then measured so that the ratio (sodium / auxiliary component) between the obtained converted value and the converted value obtained by converting the components of the auxiliary component powder to oxides was 1.1 or less. In this way, the auxiliary component powders were weighed in predetermined amounts.

[0033] Next, the aluminum oxide powder, auxiliary component powder, binder, solvent, and dispersant are placed in a stirring device and mixed and stirred to obtain a slurry. When the total amount of aluminum oxide powder and auxiliary component powder is 100 parts by mass, the binder is used in proportions of 1 to 1.5 parts by mass, the solvent in proportions of 50 to 200 parts by mass, and the dispersant in proportions of 0.1 to 0.5 parts by mass. Examples of binders include polyvinyl alcohol. Examples of solvents include water.

[0034] Next, the obtained slurry is spray-granulated to obtain granules. The obtained granules are molded using a hydrostatic pressurizer or a uniaxial pressurizer, and if necessary, subjected to machining to obtain a cylindrical molded body. Alternatively, the cylindrical molded body may be formed by extrusion molding.

[0035] Next, the obtained cylindrical molded body is held at a temperature of 1200°C to 1500°C for 1 hour to 3 hours to obtain a cylindrical ceramic (cylindrical body 11).

[0036] Next, a method for forming a coating 12 on at least a portion of the outer and inner surfaces of the obtained cylindrical body 11 will be described. An example using a DLC film as the coating 12 will be described. DLC films are formed using PVD methods such as vacuum arc deposition and sputtering, as well as plasma CVD methods using hydrocarbon gases as raw materials. Film properties such as the ratio of SP2 bonds to SP3 bonds and hydrogen content vary depending on the film formation method and conditions. For example, in the case of plasma CVD, desired properties are obtained by adjusting the plasma irradiation dose, acceleration voltage, processing temperature, and gas supply ratio.

[0037] The cylindrical member for microwave heating apparatus according to this disclosure is used as a component of a microwave heating apparatus. Specifically, as shown in Figure 3, the microwave heating apparatus 10 according to one embodiment includes the cylindrical member 1 according to one embodiment and an irradiation unit (microwave irradiation unit 20) for irradiating microwaves. Figure 3 is a schematic diagram showing the microwave heating apparatus 10 according to one embodiment of this disclosure. Hereinafter, the microwave heating apparatus 10 according to one embodiment will be described using a microwave dielectric heating method carbon fiber manufacturing apparatus as an example.

[0038] As shown in Figure 3, the microwave heating apparatus 10 according to one embodiment is equipped with a microwave irradiation unit 20 so as to irradiate microwaves 20a from the side surface of the cylindrical member 1. At least one microwave irradiation unit 20 is sufficient. As shown in Figure 3, multiple microwave irradiation units 20 may be provided so as to irradiate microwaves 20a from two, four, or eight directions on the side surface of the cylindrical member 1.

[0039] In the case of a carbon fiber manufacturing apparatus, organic fibers 30a, which are precursors to the heated material (carbon fiber 30b), are continuously supplied from one end (inlet) of a cylindrical member 1. Irradiation with microwaves 20a causes the organic fibers 30a passing through the inside of the cylindrical member 1 to be dielectrically heated and carbonized. An inert gas (e.g., nitrogen, argon, etc.) is supplied inside the cylindrical member 1. The carbonized organic fibers 30a are removed as carbon fibers 30b from the other end (outlet) of the cylindrical member 1.

[0040] When the object being heated is heated, it decomposes or vaporizes, generating gas. If the gas generated inside the cylindrical member 1 accumulates, it may adhere to the inner surface of the cylindrical member 1, the object being heated, etc., and solidify. When the gas adheres to the inner surface of the cylindrical member 1, the object being heated, etc., and solidifies, it can cause a decrease in the quality of the resulting product and equipment malfunctions.

[0041] A microwave heating apparatus 10 according to one embodiment includes a cylindrical member 1 according to one embodiment. The cylindrical member 1 according to one embodiment is permeable as described above. Therefore, gas generated inside the cylindrical member 1 is discharged to the outside of the cylindrical member 1. As a result, it is less likely to cause a deterioration in the quality of the resulting product, and the occurrence of equipment troubles can also be suppressed.

[0042] In one embodiment, the cylindrical member 1 may be used as a single cylindrical member, or multiple cylindrical members 1 may be connected to form a relatively long cylindrical member. When multiple cylindrical members 1 are connected, for example, a connecting member having an annular shape corresponding to the outer diameter of the cylindrical members 1 may be used. [Explanation of Symbols]

[0043] 1. Cylindrical member for microwave heating device 10 Microwave heating device 11. Cylindrical body 12 Coating 20 Microwave irradiation section 20a microwave 30a Organic Fibers 30b carbon fiber

Claims

1. A cylindrical body made of porous ceramic having breathability and microwave permeability, A coating located on at least a portion of the outer and inner circumferential surfaces of the cylindrical body, having a microwave transmittance lower than that of the cylindrical body, Includes, The outer surface of the cylindrical body has a region where the coating is located and a region where the coating is not located. A cylindrical component for microwave heating equipment.

2. The cylindrical member according to claim 1, wherein the coating has a thickness smaller than the average pore diameter of the cylindrical body.

3. The cylindrical member according to claim 1 or 2, wherein the coating is located at at least one end of the cylindrical body.

4. The cylindrical member according to claim 1 or 2, wherein the coating is located on both the outer and inner surfaces of the cylindrical body.

5. The cylindrical member according to claim 1 or 2, wherein the coatings having different microwave transmittances are located at multiple locations in the axial direction of the cylindrical body.

6. The cylindrical member according to claim 1 or 2, wherein the coating is a DLC film.

7. The cylindrical member according to claim 6, wherein the DLC film has a SP3 bond ratio of 10% or more and 40% or less.

8. The cylindrical member according to claim 6, wherein the DLC film is located on the inner circumferential surface of the cylindrical body.

9. The microwave heating apparatus according to claim 6, wherein the DLC film is located on the inner and outer surfaces of the cylindrical body, and the ratio of SP3 bonds in the DLC film on the inner surface is higher than the ratio of SP3 bonds in the DLC film on the outer surface.

10. A microwave heating apparatus comprising a cylindrical member according to claim 1 or 2 and an irradiation unit for irradiating microwaves.

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