JP6967776B2 - Microwave heating device and chemical reaction method - Google Patents

Description

The present invention relates to a microwave heating device and a chemical reaction method.

The use of microwaves has spread from household use such as microwave ovens, and since then, practical development and use as an industrial heating system has been studied. Microwave irradiation has the advantages that the object to be heated directly generates heat and can be heated in a short time, and that temperature unevenness due to heat conduction can be reduced. In addition to this, there are advantages such as non-contact heating and selective heating of only those with good microwave absorption.
In the industrial field, continuous heat treatment leads to automation of heat treatment and labor saving, leading to improvement of production cost and quality. Therefore, various methods have been proposed for the continuation of microwave heat treatment methods (see, for example, Patent Document 1).

On the other hand, microwaves, which are electromagnetic waves, tend to cause uneven heating because their energy intensities change with wavelength periods. For this reason, measures such as diffuse reflection of electromagnetic waves are often taken by moving the position of the object to be heated in time.
As a technique for dealing with this problem, for example, Patent Document 2 describes a microwave heating device using an empty body resonator. In this technique, an axially targeted microwave electric field parallel to the central axis is generated in a cylindrical cavity resonator, and a chemical reaction is allowed to proceed in a circular tube arranged in a portion where the electric field strength is concentrated. Further, in Patent Document 3, a flow tube is arranged along a portion where the electric field strength of the single-mode standing wave formed in the cavity resonator is maximum, and the fluid is circulated in the flow tube to provide the fluid. A distribution type microwave-based chemical resonator to be heated is described. Further, Patent Document 4 describes that a feedback control means for controlling the oscillation frequency of the microwave generator to match the current resonance frequency of the cavity resonator is used. As a result, it is said that _{the resonance state of TM 010} is always maintained and high-precision heat treatment is possible.
By using the cavity resonator in this way, it is said that a standing wave can be formed inside to heat the object to be heated uniformly and with high efficiency.

Japanese Unexamined Patent Publication No. 62-159883 Japanese Unexamined Patent Publication No. 2005-322582 Japanese Unexamined Patent Publication No. 2010-207735 Japanese Unexamined Patent Publication No. 2009-80997

As a result of repeated studies by the present inventors, we have found a means for realizing uniform and highly efficient heating of the object to be heated using a standing wave. That is, it was found that a form in which a plurality of cavity resonators are connected in series and microwaves are individually supplied from the microwave generator to each cavity resonator is effective. However, in this form, microwaves may leak from each cavity resonator and propagate to adjacent cavity resonators. The leaked microwaves disturb the state of the standing wave in the adjacent cavity resonator or affect the detector arranged in the resonator, so that the standing wave in the cavity resonator is fixed. It may interfere with the stable formation of standing waves. In addition, the microwave leaking into the adjacent cavity resonator may directly heat the object to be heated in the resonator. Furthermore, if microwaves leak, the efficiency of microwave energy utilization will decrease accordingly. That is, in order to efficiently use the microwave energy and stably form a standing wave in the cavity resonator, the leakage of the microwave into the adjacent cavity resonator is sufficiently suppressed. I came up with the idea that it is important.

The present invention is effective in leaking microwaves from each cavity resonator to an adjacent cavity resonator when a plurality of cavity resonators are connected in series to form a standing wave in each resonator. An object of the present invention is to provide a microwave heating device that can be effectively suppressed. More specifically, it is possible to efficiently and uniformly heat the object to be heated penetrating the cavity resonators connected in series, and the heating mechanism (state of formation of standing waves in each resonator). An object of the present invention is to provide a microwave heating device that can be stably maintained.

The present inventors have made extensive studies in view of the above problems. As a result, a plurality of cavity resonators are connected in series, an object to be heated is arranged through each cavity resonator, and a standing wave is formed in each resonator to be heated. We have found the following in a device that microwaves an object. That is, it has been found that providing a mechanism for preventing microwave leakage between adjacent cavity resonators is effective for stable and uniform heating of an object to be heated by a standing wave.
The present invention has been further studied based on these findings and has been completed.

That is, the above problem of the present invention is solved by the following means.
[1]
Multiple cavity resonators arranged in series to form a standing wave,
Through the plurality of cavity resonators in the series connection direction of the plurality of cavity resonators and along the portion where the energy of the standing wave formed in the plurality of cavity resonators is maximized. The arranged object to be heated and
It has a microwave generator that separately supplies microwaves to each of the plurality of cavity resonators.
A microwave heating device having a mechanism for preventing microwave leakage between adjacent cavity resonators.
[2]
The standing wave to be formed in the cavity resonator is TM _0n0 mode or TE _n0 mode, [1] Microwave heating apparatus according. However, n is a positive integer.
[3]
The microwave heating device according to [1] or [2], wherein the mechanism for preventing the leakage of microwaves is at least one mechanism selected from the following (A) to (C).
(A) A mechanism in which the relationship between the thickness of the partition wall partitioning between the air bodies of adjacent air body resonators and the size of the through hole through which the object to be heated is passed is adjusted.
(B) A mechanism in which a microwave absorption structure is provided between adjacent cavity resonators.
(C) The frequency of the microwave for forming a standing wave in one cavity resonator and the microwave for forming a standing wave in the cavity resonator adjacent to the cavity resonator. A mechanism that makes the frequencies different from each other.
[4]
The microwave heating device according to [3], wherein the above (C) is realized by any one or both of the following (c-1) and (c-2).
(C-1) A dielectric or a metal piece is placed in the cavity resonator.
(C-2) In the cavity resonators adjacent to each other, the cross sections perpendicular to the series connection direction have different shapes.
[5]
In the above (C), the frequency of the microwave for forming a standing wave supplied in one empty body resonator and the standing state supplied in the empty body resonator adjacent to the empty body resonator. The microwave heating device according to [3] or [4], wherein the absolute value of the difference from the frequency of the microwave for forming a wave is 3 MHz or more.
[6]
The microwave heating device according to [3], wherein the microwave absorbing mechanism of (B) has a choke structure or an electromagnetic wave absorber.
[7]
The energy of the microwave supplied to form a stationary wave in one cavity resonator is Px _-in , and the cavity resonator is transferred to the cavity resonator adjacent to the cavity resonator. The microwave heating device according to any one of [1] to [6], which satisfies P _y-x ≤ P _{x-in x 0.25, where P y-x} is the energy of the propagating microwave.
[8]
The microwave heating device according to any one of [1] to [7], wherein the microwave heating device is a chemical reaction device that heats the object to be heated by microwaves to cause a chemical reaction.
[9]
A chemical reaction method using the microwave heating device according to any one of [1] to [8], which comprises heating the object to be heated to cause a chemical reaction. ..

The microwave heating device of the present invention has a structure in which a plurality of cavity resonators are connected in series, and when a standing wave is formed in each resonator, the cavity resonances adjacent to each other from each cavity resonator. It is possible to effectively suppress the leakage of microwaves to the vessel. As a result, the object to be heated in the flow tube arranged in the cavity resonator can be efficiently and uniformly heated, and this heating mechanism can be stably maintained.

It is schematic cross-sectional view which showed the example of the basic form of the microwave heating apparatus of this invention schematically. It is a schematic sectional drawing schematically showing an example of a preferable embodiment (first embodiment) of the microwave heating apparatus of the present invention. It is a schematic sectional drawing schematically showing an example of another preferable embodiment (second embodiment) of the microwave heating apparatus of the present invention. It is a schematic cross-sectional view cut in the direction perpendicular to the central axis which shows the modification of the 2nd Embodiment of the microwave heating apparatus of this invention schematically. It is a schematic sectional drawing schematically showing an example of another preferable embodiment (third embodiment) of the microwave heating apparatus of the present invention. It is a schematic sectional drawing schematically showing an example of still another preferable embodiment (fourth embodiment) of the microwave heating apparatus of this invention. It is a schematic sectional drawing schematically showing an example of still another preferable embodiment (fifth embodiment) of the microwave heating apparatus of this invention. It is the schematic sectional drawing which shows typically the microwave heating apparatus for demonstrating Examples 1-7. It is a drawing which showed the thermal image of the alumina tube heated by the microwave in Example 1 and Example 7. It is the schematic sectional drawing which shows typically the microwave heating apparatus for demonstrating Examples 21-25. It is the schematic sectional drawing which shows typically the microwave heating apparatus for demonstrating Example 31. It is a graph which showed the temperature distribution measured by the radiation temperature diameter of the flow tube heated by the microwave in Example 31. It is the schematic sectional drawing which shows typically the microwave heating apparatus for demonstrating Examples 61-67. It is explanatory drawing which shows typically the structure of the hydrogen production apparatus used in Examples 68 and 69.

Hereinafter, preferred embodiments of the microwave heating apparatus of the present invention will be described with reference to the drawings.

[Microwave heating device]
First, an example of the basic form of the microwave heating device will be described with reference to FIG.
As shown in FIG. 1, the microwave heating device 1 is a stack of microwave irradiation devices 10 in a plurality of stages, and is arranged in series in a state where a plurality of cavity resonators 2 are stacked. In the drawing, as an example, three cavity resonators 2A, 2B, and 2C are shown in which they are stacked in order in the vertical direction. The number of cavity resonators 2 is not limited to three. The number of cavity resonators 2 can be two or more and several thousand. In the plurality of cavity resonators 2, the energy of the standing wave formed in each cavity resonator 2 in the series connection direction is maximized, and the circulation pipe 6 penetrates the portion that becomes uniform in the axial direction. Is arranged. In this case, the object to be heated is arranged in the distribution pipe. For example, in _{the case of a cylindrical cavity resonator 2 in which a standing wave in TM 0n0} mode (n is an integer of 1 or more) is generated, the electric field strength of the cylindrical central axis becomes maximum and the electric field strength is along the central axis C. It has the characteristic of being uniform, and it is preferable that the flow pipe 6 is arranged on the cylindrical central axis C.
A microwave generator 5 is arranged in each cavity resonator 2, and microwaves are individually supplied to each cavity resonator 2. Generally, the microwave frequency uses an S band centered on 2.45 GHz.
Further, a mechanism for preventing leakage due to microwaves leaking from the inside of the cavity resonator 2 is arranged between the cavity resonators 2 and 2 or in the cavity resonator 2. The mechanism for preventing this microwave leakage will be described in detail in each embodiment described later.

In the microwave heating device 1 described above, a microwave is generated for an empty cavity resonator 2 in which an object to be heated (not shown) exists inside or a distribution pipe 6 through which the object to be heated flows is arranged. Microwaves are supplied from the vessel 5 to form a standing wave in the cavity resonator 2. The object to be heated in the flow pipe 6 is heated by the portion where the electric field strength of the standing wave is maximized. In the microwave heating device 1, microwaves forming a standing wave are supplied into the cavity resonator 2 from the microwave supply port 3 provided in the cavity resonator 2.

In the microwave heating device 1, the microwave supplied from the microwave generator 5 is supplied by adjusting the frequency. By adjusting the frequency, the electric field intensity distribution of the standing wave formed in the cavity resonator 2 can be controlled to a desired distribution state, and the intensity of the standing wave can be adjusted by the output of the microwave. That is, it becomes possible to control the heating state of the object to be heated.
The frequency of the microwave supplied from the microwave supply port 3 can form a specific single-mode standing wave in the cavity resonator 2. The type (mode) of the standing wave formed in each resonator may be different, but it is preferable that the type (mode) of the standing wave formed in each resonator is the same.
The configuration of the microwave heating device 1 of the present invention will be described in order.

<Aircraft resonator>
The shape of the cavity resonator (cavity) 2 used in the microwave heating device has one microwave supply port 3 and a single mode standing wave is formed when the microwave is supplied. There are no particular restrictions. For example, a cylindrical or square tubular cavity resonator can be used. In the present specification, the cylindrical cavity resonator includes one having a circular inner cross-sectional shape perpendicular to the central axis C of the void resonator, and one having an elliptical or oval cross-sectional shape. Used for meaning. Further, the square tubular cavity resonator means that the inner cross-sectional shape perpendicular to the central axis C is polygonal, and the cross-sectional shape is preferably 4 to 10 decagonal. Further, the corners of the polygon may have a rounded shape.
The size of the empty body resonator 2 can also be appropriately designed according to the purpose. It is desirable that the cavity resonator 2 has a small electrical resistivity, and is usually made of metal. As an example, aluminum, copper, iron, magnesium, brass, stainless steel, alloys thereof, or the like can be used. Alternatively, the surface of resin, ceramic, or metal may be coated with a substance having a low electrical resistivity by plating, vapor deposition, or the like. Materials containing silver, copper, gold, tin and rhodium can be used for the coating.

<Supplying microwaves>
[Microwave irradiation device]
The microwave irradiation device 10 used in the microwave heating device 1 of the present invention is a device suitable for carrying out the above-mentioned heating control. The microwave irradiation device 10 supplies the microwave resonator 2 having the microwave supply port 3 and the microwave having a frequency capable of forming a standing wave in the cavity resonator 2 to the cavity resonator 2. It has a microwave generator 5 and the like. The microwave generator may be composed of a microwave generator (not shown) and a microwave amplifier (not shown).
The configuration of the cavity resonator 2 constituting the microwave heating device 1 of the present invention is the same as that described in the above-mentioned cavity resonator.

As the microwave generator 5, for example, a microwave generator such as a magnetron or a microwave generator using a semiconductor solid-state element can be used. From the viewpoint of finely adjusting the microwave frequency, it is preferable to use a microwave generator using a semiconductor solid-state element.

As shown in FIG. 1, in the microwave irradiation device 10, a cylindrical cavity resonator is used as the cavity resonator 2. A microwave supply port 3 is provided on or near the wall surface (inner surface of the cylinder) parallel to the central axis C of the cavity resonator 2. In one embodiment, the microwave supply port 3 has an antenna 3A capable of applying a high frequency. As the antenna 3A, it is preferable to use a magnetic field excitation antenna, for example, a loop antenna. Hereinafter, the antenna 3A is also referred to as a loop antenna 3A. The loop antenna 3A is connected to the microwave generator 5 via a cable 4. For the cable 4, for example, a coaxial cable is used. In this configuration, the microwave emitted from the microwave generator 5 is supplied into the cavity resonator 2 from the loop antenna 3A via the cable 4. A matching device (not shown) for suppressing reflected waves or an isolator (not shown) for protecting the microwave generator may be installed between the microwave generator 5 and the antenna 3.
The end face of the loop antenna 3A is connected to a ground potential such as a wall surface of a cavity resonator. By applying a microwave (high frequency) to the loop antenna 3A, a magnetic field is excited in the loop to form a standing wave in the cavity resonator.
_{For example, when a single-mode standing wave of TM 010} is formed in the above-mentioned cylindrical cavity resonator, the electric field strength becomes maximum at the central axis C, and the electric field strength becomes uniform in the central axis C direction. Therefore, in the flow pipe 6, the object to be heated existing or circulating inside the flow pipe 6 can be uniformly and highly efficiently heated by microwaves.
In addition, the microwave may be supplied from the microwave generator 5 to the microwave supply port 3 by using a waveguide.

<Heating of the object to be heated>
In the microwave heating device of the present invention, the object to be heated (for example, the flow tube 6 in which the object to be heated exists or circulates) is arranged inside the cavity resonator 2 in accordance with the electric field strength. .. In particular, if the standing wave formed in the cavity resonator 2 is arranged along the portion where the electric field strength becomes maximum, more efficient heating becomes possible.

In the microwave heating device as shown in FIG. 1, the object to be heated arranged in the flow pipe 6 is not particularly limited, and examples thereof include liquids, solids, powders, and mixtures thereof. Alternatively, a honeycomb structure, a catalyst, etc. installed in advance in the distribution pipe can be mentioned.
When the object to be heated is a liquid, a solid, or a powder, the temperature of the object to be heated can be continuously controlled by transporting the object to be heated by a pump or the like. Since many chemical reactions can control the progress of the reaction by temperature, the microwave heating device of the present invention may be used for controlling the chemical reaction.
The object to be heated does not need to be placed in the distribution pipe as long as it can maintain its shape by itself. For example, if the object to be heated is a fibrous solid, it can be continuously transported from the inside of one resonator to the adjacent resonator without the support of a flow pipe or the like.
When the object to be heated is a honeycomb structure, the microwave heating device can be used, for example, to control the temperature of the gaseous substance passing through the honeycomb structure. Further, when the object to be heated is used as a catalyst, it can be used to cause a chemical reaction due to the action of the catalyst, as will be described later. It is also preferable that the catalyst is supported on a honeycomb structure.
The chemical reactions include transfer reaction, substitution reaction, addition reaction, cyclization reaction, reduction reaction, oxidation reaction, selective catalytic reduction reaction, selective oxidation reaction, lasemilation reaction, cleavage reaction, catalytic decomposition reaction (cracking) and the like. However, various chemical reactions are not limited to these, and examples thereof include various chemical reactions.
Specific examples of chemical reactions include reactions that oxidatively decompose volatile organic substances, reactions that reduce nitrogen oxides to nitrogen and oxygen, reactions that fix sulfur oxides to calcium, and reactions that lighten heavy oils. Can be mentioned.

In the chemical reaction method of the present invention, conditions such as reaction time, reaction temperature, reaction substrate, reaction medium and the like may be appropriately set according to the desired chemical reaction. For example, Chemistry Handbook (edited by Shuichi Suzuki and Mitsuaki Mukaiyama, Asakura Shoten, 2005), Microwave Chemical Process Technology II (supervised by Kazuhiko Takeuchi and Yuji Wada, CMC Publishing, 2013), JP-A-2010-215677, etc. With reference, the chemical reaction conditions can be set as appropriate.

In the form shown in FIG. 1, the frequency of the standing wave is not particularly limited as long as the standing wave can be formed in the cavity resonator 2. For example, it can be a frequency in the case of supplying the microwaves from the microwave supply port 3, the standing wave of the TM _0n0 mode or TE _n0 mode described above into the cavity in the resonator 2 is formed.
Examples of the standing wave in the _{TM 0n0 mode include the modes of TM 010} , TM ₀₂₀ , and TM ₀₃₀ , and the standing wave of _{TM 010 is preferable.}

Hereinafter, various preferred embodiments of the microwave heating device 1 will be described in more detail with reference to the drawings. It should be noted that the present invention is not construed as being limited to these except as specified in the present invention.

First, as a preferred embodiment (first embodiment) of the microwave heating device, it will be described below with reference to FIG.
As shown in FIG. 2, the microwave heating device 1 (1A) has the same basic configuration as the microwave heating device 1 described with reference to FIG. That is, a plurality of cavity resonators 2 are stacked in series in the central axis C direction with the central axis C aligned. In the illustrated example, three cavity resonators 2A, 2B, and 2C are connected in series, and a partition wall 8 for partitioning between the cavity resonators 2 and 2 is provided. In FIG. 2, the bottom wall 8B of the upper empty body resonator (for example, 2A) and the upper surface wall 8U of the lower empty body resonator (for example, 2B) are individually shown, but a single partition wall may be used. No. The partition wall 8 is provided with a through hole 9 so that the hole axis coincides with the central axis C. Further, a through hole 9 is also arranged on the upper surface wall 8U of the uppermost air body resonator 2A, and a through hole 9 is also arranged on the bottom wall 8B of the lowermost air body resonator 2C. By appropriately designing the hole diameter φ of the through hole 9 and the thickness t of the partition wall 8, it is possible to effectively prevent the leakage of microwaves. For the purpose of preventing leakage of microwaves, it is desirable that the pore diameter φ is smaller than the wavelength of the microwave to be irradiated, and the thickness t of the partition wall is preferably thick. On the other hand, since the hole diameter φ is limited by the size of the object to be heated, it is desirable that the larger the hole diameter φ is, the wider the applicable range is. Further, since the portion of the partition wall 8 is insufficiently irradiated with microwaves, it is desirable that the partition wall thickness t is thin from the viewpoint that it becomes difficult to control the temperature of the object to be heated located in the partition wall 8. As described above, the hole diameter φ and the partition wall thickness t must satisfy two contradictory factors, and an appropriate design is required.

Therefore, the conditions of the hole diameter φ and the partition wall thickness t provided to prevent the leakage of microwaves were examined in detail, and the following design formula was derived. However, λ is the wavelength, ρ _0n is the root of the Bessel function J ₀ (x) = 0, _{ρ 01} = 2.405 _{in TM 010} mode, _{ρ 02} = 5.52 _{in TM 020} mode, _{and TM 030} mode. Then, ρ ₀₃ = 8.651. Further, Decay_dB is a value in which the amount of leakage between the cavity resonators is expressed in decibels, and when 10% of the amount leaks, Decay_dB = -10 dB. However, when the term in the square root of the denominator in Equation 1 becomes negative, the electromagnetic wave is transmitted through the partition hole without attenuation, so that the function of preventing leakage cannot be achieved.
The following equations 1 and 2 are merely guidelines for design, and the relationship between the hole diameter φ and the partition wall thickness t does not necessarily have to satisfy the following equations. For example, based on the following equations 1 and 2, the approximate relationship between the hole diameter φ and the partition wall thickness t is derived, and microwave leakage is detected within the range of ordinary experiments conducted by those skilled in the art with reference to this. It is possible to determine the form of suppression to the desired level.

It should be noted that this formula is a condition in which nothing is installed in the through hole portion. In reality, a distribution pipe and an object to be heated are arranged in this part. As a correction formula in this case, it was possible to design by substituting _{λ m derived in Equation 2 instead of λ in Equation 1.}

However, ε _eff and μ _eff are the relative permittivity and the relative magnetic permeability of the substance arranged in the through hole 9 of the partition wall 8. Since many materials are non-magnetic, it does not matter if _{μ eff = 1.} When the substance arranged in the through hole 9 is composed of a plurality of substances such as the flow pipe 6 and the object to be heated (not shown), and the air layer of the gap portion 9A between the flow pipe 6 and the through hole 9. The effective permittivity, which is the weighted average of the volume of the substance, will be used instead.
In the design formula, the through hole 9 is circular and its diameter φ is used, but the through hole 9 is not limited to a circular shape. In that case, the maximum opening length of the through hole 9 may be used instead of the hole diameter φ for designing.
If the partition wall thickness t is not uniform, the thickness of the thinnest portion of the partition wall 8 may be used instead of the partition wall thickness t.

Further, an object to be heated is arranged inside along the central axis C of each cavity resonator 2, or a flow pipe 6 through which the object to be heated flows is arranged through the through hole 9. ..

The cavity resonator 2 is provided with a microwave generator 5 that generates a standing wave in the cavity resonator. One end of a cable 4 for guiding the generated microwave is connected to the microwave generator 5. Further, an antenna 3A for receiving microwaves is arranged on the side wall of the cavity resonator 2, and the other end of the cable 4 is connected to the antenna 3A. The antenna 3A serves as a microwave supply port 3, and is, for example, a magnetic field excitation type loop antenna. The cable 4 is not limited as long as it transmits microwaves, and for example, a coaxial cable is used.

Further, the energy of the microwave supplied to one cavity resonator 2 (for example, 2A) is _{defined as Px-in} , and the void resonator 2A is adjacent to the cavity resonator 2A (for example, the cavity resonator 2A). _{For example, let Py-x} be the energy of the microwave propagating to 2B). In this case, it is preferable to satisfy the equation 3 of Py _−x ≦ _{Px−in × 0.25.} By satisfying the above equation 3, it is possible to suppress the temperature rise of the object to be heated due to the action of the electromagnetic wave leaked to the adjacent cavity resonator. At the same time, it is possible to suppress the malfunction of the detector used for control. The notation that the value is 0.25 times or less has the same meaning as the value of -10 dB or less.

Next, as another preferred embodiment (second embodiment) of the microwave heating device, it will be described below with reference to FIG.
As shown in FIG. 3, in the microwave heating device 1 (1B) shown in FIG. 1, each cavity resonator 2 is connected in the central axis C direction with the central axes aligned. It is arranged in the state. Further, a dielectric 51 or a metal piece (not shown) is arranged in the cavity resonator 2, and the frequency of the microwave supplied to the adjacent cavity resonator 2 is different. Other configurations are the same as those of the microwave heating device 1 described with reference to FIG.

The microwave heating device 1B reduces the influence of the leakage of the microwave supplied to the one-body resonator 2. This prevents the influence of microwave leakage on the detector 11 installed in the cavity resonator 2 adjacent to the cavity resonator 2. From this point of view, it is preferable that the difference from the frequency of the microwave supplied to the adjacent cavity resonators 2 and 2 is 3 MHz or more in the 2.45 GHz band. And more preferably 6 MHz or more, still more preferably 10 MHz or more. Further, from the viewpoint that the industrially usable ISM band has a width of only 100 MHz in the 2.45 GHz band, for example, 70 MHz or less is preferable, 50 MHz or less is more preferable, and 30 MHz or less is further preferable. This is because it is necessary to design the resonance frequency of all the cavity resonators to be within the ISM band. Further, since the resonance frequency fluctuates due to the temperature change and the composition change of the object to be heated, it is necessary to fit in the ISM band after considering the fluctuation range. "ISM" is an abbreviation for Industry Science Medical, and the ISM band is a band of frequencies allocated for general use in the industrial, scientific, and medical fields.
When the frequencies of the two microwaves to be irradiated are f1 and f2 in order to extend the preferable frequency band to the entire microwave, and Δf = 2 (f1-f2) / (f1 + f2) is defined, Δf> 0. It is preferable to satisfy 1%.
Therefore, the frequencies of the microwave generators 5 and 5 are set so that the frequencies of the microwaves supplied to the adjacent cavity resonators 2 and 2 are different. Further, although the frequencies of the microwaves supplied to the adjacent cavity resonators 2 and 2 are different, the types of standing waves formed in the resonators are usually the same. In order to realize the formation of the same type of standing wave at different frequencies, it is preferable to arrange the above-mentioned dielectric 51 or metal piece (not shown) in the resonator. It is more preferably a dielectric, and specific examples thereof include an embodiment in which a resin, ceramic, glass, or the like is arranged.

When a dielectric is used, one with a small dielectric loss must be used. When a dielectric having a large dielectric loss is used, microwaves are absorbed by the dielectric and generate heat. As a result, the heating efficiency of the object to be heated is lowered. In addition, there is a risk of inducing troubles such as thermal transformation and ignition of the dielectric.
When the dielectric 51 is inserted into the cavity resonator, the wavelength of the microwave is shortened in the portion of the dielectric 51. Therefore, a standing wave having a longer wavelength is formed in the entire cavity resonator 2, and the resonance frequency is adjusted to a lower frequency side than when the dielectric 51 is not inserted.

On the other hand, as shown in FIG. 4, the resonance frequency can be increased by inserting the metal piece 53 into the cavity resonator 2. For the metal piece 53, it is preferable to use the metal constituting the cavity resonator 2, and it is more preferable to use copper or aluminum. The shape of the metal piece 53 is not particularly specified, but it is preferably a rectangular parallelepiped having the same height as the cavity resonator, and the edge portion is preferably processed into a curved surface, and the width and thickness thereof are the cavity. It is appropriately determined by the size of 22. The metal piece 53 is arranged so that it can be inserted and removed in the direction of the arrow with respect to the side wall 24 of the cavity resonator 2, and it is preferable to install the metal piece 53 in a place where the electric field strength is small, such as near the side wall 24 of the cavity resonator. It is desirable to ground the device so that it has the same potential as the device 2. When the metal piece 53 is inserted into the empty body 22, the volume of the empty body 22 of the empty body resonator 2 becomes small, so that a standing wave having a shorter wavelength than before the metal piece 53 is inserted is formed. Become. The resonance frequency has the effect of being adjusted to the higher frequency side as compared with the case where the metal piece 53 is not inserted.
In this way, by arranging the metal piece 53 on the side wall 24 of the cavity resonator 2 so that the metal piece 53 can be inserted and removed, in a configuration in which a plurality of cavity resonators are laminated, the resonance frequency is the same for each cavity resonator 2. It will be possible to adjust to.
Although not shown, the metal pieces 53 may be arranged at a plurality of locations on the side wall 24 of the cavity resonator 2. In this case, by arranging them diagonally with respect to the central axis C so as to maintain symmetry with respect to the central axis C, the disturbance of the electromagnetic field strength distribution in the cavity resonator 2 is reduced. can do.

Since the industrial microwave frequency uses, for example, the ISM band, the microwave frequencies supplied to the cavity resonators 2A, 2B, and 2C are set to different values within the range of the ISM band. As an example, the frequency of the microwave supplied to the cavity resonator 2A in which no dielectric is installed is set to 2.42 GHz. Further, as a dielectric, a Teflon (registered trademark) tube (dielectric constant 2.1) is supplied to a microwave resonator 2B installed so that the center axis C of the body in the body and the center axis of the dielectric coincide with each other. The frequency of the wave is 2.45 GHz. Further, the frequency of the microwave supplied to the cavity resonator 2C in which a quartz tube (dielectric constant 4) is installed as a dielectric so that the center axis C of the cavity in the cavity coincides with the center axis of the dielectric is 2.48 GHz. And. By installing the tubular dielectric material so as to coincide with the center axis C of the cavity, the symmetry of the electric field distribution is maintained, so that the disturbance of the electric field strength around the object to be heated is reduced, which is desirable.
Since the microwave leaked from the cavity resonator 2 has a different frequency from the microwave supplied to the adjacent cavity resonator 2, the detector is arranged outside the side wall 24 of the adjacent cavity resonator 2. 11 will no longer be affected.

Next, as another preferred embodiment (third embodiment) of the microwave heating device, it will be described below with reference to FIG.
As shown in FIG. 5, in the microwave heating device 1 (1C) of the third embodiment, in the microwave heating device 1 described with reference to FIG. 1, each cavity resonator 2 coincides with the central axis C. It is arranged in a state of being connected in the direction of the central axis C. Further, the inner diameters D1 to D3 of the body 22 of each body resonator 2 are different as a mechanism for preventing the leakage of microwaves. Other configurations are the same as those of the microwave heating device 1 shown in FIG. Each cavity resonator 2 is a cylindrical cavity resonator and may have a square cylinder shape. As an example, if the cross section of the fuselage is circular, change its diameter. If the cross section of the fuselage is oval or oval, change the major axis. If the cross section of the fuselage is rectangular, change the length of the diagonal line.

The microwave heating device 1 (1C) is prevented from being affected by the cavity resonator 2 adjacent to the detector 11 installed in the cavity resonator 2. Therefore, the inner diameter of the cavity 22 of each cavity resonator 2 is set so that the frequency of the standing wave generated in each cavity resonator 2 is constant and the frequency of the supplied microwave is different from each other. D is changing. The constant frequency means that the frequencies of the standing waves formed in each cavity resonator 2 match. For example, in the 2.45 GHz band, the difference in the frequencies of the microwaves supplied into the adjacent cavity resonator 2 is preferably 3 MHz or more, more preferably 6 MHz or more, still more preferably 10 MHz or more. In order to obtain such a difference in microwave frequency, in the case of a cylindrical cavity, as an example, the difference in the inner diameter D of the cavity 22 of the adjacent cavity resonator 2 is preferably 0.1 mm or more. .. It is more preferably 0.2 mm or more, still more preferably 0.5 mm or more. Then, from the viewpoint of keeping within the ISM band of 2.4 GHz to 2.5 GHz, the difference in the inner diameter of the cavity 22 is preferably 1.5 mm or less, and more preferably 1 mm or less.
In this way, the inner diameter of the cavity 22 is set so that the frequency of the standing wave generated in each cavity resonator 2 is constant and the frequency of the microwave supplied to each cavity resonator 2 is different. NS.
Therefore, the microwave leaked from the cavity resonator 2 (leakage microwave) can be different from the frequency of the microwave (supplied microwave) supplied to the adjacent cavity resonator 2. Therefore, the leaking microwave and the supply microwave are not synchronized, and the propagation of the leaking microwave into the adjacent resonator is suppressed. Further, it is possible to prevent the detector 11 arranged outside the side wall 24 of the adjacent cavity resonator 2 from being affected.

Next, as yet another preferred embodiment (fourth embodiment) of the microwave heating device, it will be described below with reference to FIG.
As shown in FIG. 6, in the microwave heating device 1 (1D) of the fourth embodiment, in the microwave heating device 1A shown in FIG. It is arranged in a state of being connected in the C direction. Further, a choke structure 31 is arranged between the partition walls 8 and 8 of the cavity resonators 2 and 2 as a mechanism for preventing microwave leakage. Other configurations are the same as those of the microwave heating device 1A shown in FIG.

The choke structure 31 is an annular body 32 having a thickness of Lt arranged between the partition walls 8 and 8 of the cavity resonators 2 and 2, and is arranged above and below the space of the inner portion thereof and the space of the inner portion thereof. It is composed of a space 33 having a choke length Lc and a choke thickness Lt surrounded by the partition walls 8 and 8. The choke length Lc is the radial length of the annular body 32 from the side portion of the partition wall 8 on the through hole 9 side to the inside of the annular body 32. The space 33 may be directly formed on the partition wall 8. The space 33 cancels the incident wave of the microwave entering the space 33 by the reflected wave reflected in the space 33, thereby preventing the microwave from leaking to the outside of the cavity resonator 2. Therefore, it is preferable that the choke length Lc has a length that cancels microwaves. That is, it is preferably 1/4 of the wavelength of the microwave. Since the wavelength is 1/4 of that of the microwave in this way, the incident wave and the reflected wave are shifted by 1/2 wavelength, and the phase is reversed. Therefore, the incident wave and the reflected wave can cancel each other out.
For example, when the wavelength of the microwave is 120 mm, the choke length Lc is preferably 25 mm to 35 mm as a range in which the incident wave and the reflected wave can cancel each other out. More preferably, it is 30 mm, which is a quarter wavelength. In the case of inserting a dielectric having a relative dielectric constant epsilon in the space 33 portion of the choke length Lc, the wavelength lambda _epsilon propagating dielectric material, the wavelength propagating in air as λ _a, λ _{a /} √ε Just get shorter. Therefore, by arranging the dielectric in the space 33, the choke length Lc in the state where there is nothing in the space 33 can be further shortened, and the volume required for forming the choke structure can be reduced.

Since the choke structure 31 is arranged between the partition walls 8 and 8 of the cavity resonators 2 and 2, the microwave leaked from the cavity resonator 2 is canceled by the choke structure 31.
Therefore, microwaves are less likely to leak from the inside of each cavity resonator 2, and the leaking microwaves do not affect the detector 11 arranged on the outer surface of the side wall 24 of the adjacent cavity resonator 2.

Next, as yet yet another preferred embodiment (fifth embodiment) of the microwave heating device, it will be described below with reference to FIG. 7.
As shown in FIG. 7, in the microwave heating device 1 (1E) of the fifth embodiment, in the microwave heating device 1 shown in FIG. It is arranged in a state of being connected in the C direction. Further, an absorber 41 that absorbs microwaves is arranged between the cavity resonators 2 and 2 as a microwave absorbing structure. The absorber 41 is preferably arranged so as to embed the inside of the space 43 provided in the partition wall 8 between the cavity resonators 2 and 2. From the viewpoint of preventing microwave leakage, the size of the absorber 41 (space 43) should be larger in the direction perpendicular to the central axis C, that is, in the radial direction of the cavity resonator 2. Other configurations are the same as those of the microwave heating device 1 shown in FIG.

The absorber 41 is preferably a filler that fills the space 43 as an electromagnetic wave absorbing structure, and more preferably a filler that fills the entire space 43. Examples of such a material include styrofoam, urethane foam, rubber, and ceramic mixed with carbon powder, which utilize the dielectric loss caused by the polarization reaction of the molecule. Further, iron, nickel, ferrite and the like can be mentioned as ones that absorb electromagnetic waves due to the magnetic loss of the magnetic material. These may be such as foaming agents, rubbery bodies, powders or pastes as fillers. Further, textiles made of conductive fibers can also be mentioned. Since the absorber generates heat due to microwave absorption, it is also preferable to allow the absorber to be cooled.
The thickness of the absorber 41 depends on the material, but for example, in the absorber 41 made of ceramic mixed with carbon powder, the thickness is 0.5 mm or more, preferably 2 mm or more, from the viewpoint of absorbing electromagnetic waves. It is preferably 3 mm or more. Further, from the viewpoint of uniformly heating the object to be heated in the flow tube 6 between the cavity resonators 2 and 2, the thickness is set to 10 mm or less, preferably 5 mm or less, and more preferably 3 mm or less.

Since the absorber 41 is arranged between the cavity resonators 2 and 2, the microwave leaked from the cavity resonator 2 is absorbed by the absorber 41, so that it is transferred to the adjacent cavity resonator 2. It is less likely to affect you. Further, it does not affect the detector 11 arranged on the outside of the side wall 24 of the adjacent cavity resonator 2.

In each of the above embodiments, the detector 11 suppresses the leakage of microwaves from each cavity resonator 2 to the adjacent cavity resonator or to the detector 11 of the adjacent cavity resonator. The frequency of the standing wave can be detected accurately. Therefore, the frequency of the detected standing wave can be fed back to the microwave generator 5 to precisely control the frequency of the microwave supplied from the microwave generator 5. In this way, a standing wave can be stably generated in the cavity resonator 2. Therefore, the object to be heated in the flow tube 6 can be efficiently and uniformly heated by the standing wave, and this heating mechanism (the state in which the standing wave is formed in each resonator) is stably maintained. can do.
Further, the microwave heating device of each of the above embodiments has the following advantages.
(1) It becomes possible to heat-treat a large amount of fluid, and it becomes possible to use it for synthesis of chemical materials.
(2) Since a relatively inexpensive low-power microwave generator can be used, the initial investment in equipment can be suppressed.
(3) Since the microwave generator and the cavity resonator can be increased or decreased in stages according to the increase or decrease in the production scale, it is possible to quickly respond to changes in the market.
(4) Since the propagation of electromagnetic waves to the adjacent cavity resonator is suppressed to a certain level or less, the protection circuit of the microwave generator does not need excessive performance.
(5) Since it is possible to detect the standing wave by the detector and adjust the microwave frequency by the microwave generator, the electromagnetic wave irradiation condition and the heating condition by each cavity resonator can be used. It can be controlled individually. As a result, it becomes possible to finely control the temperature of the object to be heated in the distribution pipe.
(6) Since the detector can monitor the reflected wave intensity, resonance frequency, and impedance of each cavity resonator, it is possible to detect the heat treatment status and the abnormal state of each cavity resonator.
(7) Even if a problem occurs in some of the cavity resonators and microwave generators and the heat treatment in that portion becomes insufficient, it becomes possible to supplement the capacity with other cavity resonator parts. It is possible to construct a process that is highly resistant to abnormal occurrences and has high robustness.
(8) Since different temperature control is possible for each cavity resonator, it is easy to adapt to a multi-stage reaction consisting of a plurality of reaction temperatures.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Examples 1 to 7]
The microwave heating device 1 of Examples 1 to 7 having the configuration shown in FIG. 8 was produced.
As the body resonator 2, two metal (aluminum) waveguide-coupled cylindrical body resonators 2A and 2B having a body length LA of 100 mm and a body diameter D of 90 mm were used. The respective cavity resonators 2A and 2B were superposed in the central axis C direction. The thickness t of the partition wall 8 in Examples 1 to 7 is as shown in Table 1, and the hole diameter φ of the through hole 9 arranged in the range of 1 mm to 5 mm and arranged along the central axis C is also shown in Table 1. As shown in the above, the setting was made within the range of 3.2 mm to 40 mm. Under these conditions, Examples 1 to 7 were prepared. Comparative Example 1 was produced in the same configuration as in Example 1 except that the partition wall and the through hole were not provided in Example 1.

For each of Examples 1 to 7 and Comparative Example 1, the other cavity resonator is used with respect to the microwave energy supplied from the waveguide (not shown) of the upper cavity resonator 2A (referred to as the supply side). The microwave energy detected in the 2B (passive side) waveguide (not shown) was measured.
A network analyzer (E5071C (trade name) manufactured by Agilent) was used for the measurement. The port 1 of the network analyzer is connected to the waveguide of the cavity resonator 2A on the supply side via the coaxial waveguide converter (coaxial waveguide conversion flange), and the waveguide of the cavity resonator 2B on the passive side is made. Port 2 of the network analyzer was connected to the tube via a coaxial waveguide conversion flange. From the S21 signal of the S parameter obtained by the network analyzer, it is possible to know how much the microwave energy on the supply side leaks to the passive side.

When the S21 signal is 0, it indicates that all the energy of the microwave on the supply side is detected in the waveguide on the passive side. When the S21 signal is -10 dB, 10% of the microwave energy is transmitted to the passive side. The larger the absolute value of S21, the less microwave leakage.
Table 1 shows the results when the actual measurement was performed by changing the thickness t of the partition wall and the hole diameter φ. The resonance frequency of the TM ₀₁₀ mode at this time was in the range of 2.5 to 2.6 GHz.

[Examples 8 and 9]
In Example 8, the microwave heating device 1 of the above-mentioned Example 1 was used, and in Example 9, the microwave heating device 1 of the above-mentioned Example 7 was used. In Examples 8 and 9, the alumina tube (outer diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm, inner diameter 1 mm 0.5 mm) (carbon coated on the surface) was installed with its central axis aligned. Then, microwave heating was performed with the cavity resonator 2A side as the microwave supply side and the cavity resonator 2B side as the passive side of the microwave. The side walls 24 of the cavity resonators 2A and 2B are provided with slits (not shown) having a width of 5 mm along the central axis C so that the inside thereof can be observed.
From the slit, a thermal image of an alumina tube was acquired by thermography (868 manufactured by testo).
FIG. 9 shows the result of a thermal image when a microwave corresponding to the resonance frequency of _{TM 010} mode is supplied from the cavity resonator 2A (supply side) at an output of 50 W for 30 seconds.
Under the conditions of Example 1 shown in Table 1, the temperature rise of the alumina tube in the cavity resonator 2B on the passive side was not confirmed, but under the conditions of Example 7 shown in Table 1, the alumina on the passive side It has been confirmed that the temperature of the tube has risen. From the above results, it can be said that it is desirable to suppress the electromagnetic wave leakage between the cavity resonators 2A and 2B to -3.17 dB or less.

[Examples 10 to 13]
Examples 10 to 11 are the same as the microwave heating device 1 of the above-mentioned Example 2 except that the inner diameter D of the cavity 22 of the cavity resonator 2B on the microwave passive side is different. Further, Examples 12 to 13 are the same as those of the microwave heating device 1 of the above-mentioned Example 8 except that the inner diameter D of the cavity 22 of the cavity resonator 2B on the microwave passive side is different. Table 2 also shows Examples 2 and 8 in which the inner diameters of the air bodies 22 on the microwave supply side and the microwave passive side are the same.
In Examples 10 to 13, the inner diameter of the cavity 22 of the cavity resonator 2A on the microwave supply side is 90 mm, and in Examples 10 and 12, the inner diameter of the cavity 22 of the cavity resonator 2B on the passive side is 90.5 mm. In 10 and 12, the inner diameter of the cavity 22 of the cavity resonator 2B on the passive side was set to 91.5 mm. As described above, the configuration is the same as that of the second or eighth embodiment except that the inner diameter of the empty body on the passive side is different.
At this time, _{the resonance frequency of the TM 010} mode was 2.5507 GHz for an inner diameter of 90 mm, 2.5366 GHz for an inner diameter of 90.5 mm, and 2.5089 GHz for an inner diameter of 91.5 mm when nothing was installed in the fuselage. With the supply side as a reference, there was a difference Δf between the resonance frequencies of 14 MHz and 42 MHz. This difference Δf was 0.55% and 1.64% in terms of the ratio to the supply frequency f, Δf / f.
The S21 signal is transmitted under two conditions: when these two cavity resonators 2 and 2 are connected by a partition wall having a thickness of 1 mm and a hole diameter of 3.2 mm, and when they are connected by a partition wall having a thickness of 5 mm and a hole diameter of 40 mm. It was measured. The results are shown in Table 2. When the hole diameter is 3.2 mm, the S21 signal of Example 11 having different inner diameters is −69 dB, and No. 1 having the same inner diameters of the two cavity resonators. It was found that it was significantly smaller than -15.6 dB of the S21 signal of 2. Similarly, when the inner diameter of the partition wall was 40 mm, it was found that the inner diameter was significantly smaller than -3.16 dB of Example 8 having the same inner diameter to -31.6 dB of Example 13 having a different inner diameter.
Further, when an attempt was made to heat the alumina tube under the conditions of Example 12 in the same manner as in Examples 8 and 9, the alumina tube located in the cavity resonator on the microwave supply side was heated to 60 to 70 ° C. The alumina tube located in the cavity resonator on the passive side did not change from 17 ° C. at room temperature.
As described above, it was shown that the leakage of electromagnetic waves affecting heating can be significantly reduced by changing the resonance frequency by adjusting the inner diameter of the cavity resonator.
It was also shown that the amount of electromagnetic wave leakage is preferably at least -3 dB, more preferably less than -6 dB, and even more preferably less than -10 dB.

[Examples 21 to 25]
The microwave heating device 1 of Examples 21 to 25 having the configuration shown in FIG. 10 was produced. In Examples 21 to 25, the choke structure 31 is provided between the partition walls 8A and 8B of the two cavity resonators 2 (2A) and 2 (2B), and the hole diameter φ of the through hole 9 is set to 24 mm. Other than that, it was produced in the same manner as in Example 1 described above. Therefore, in Examples 21 to 25, the partition walls 8A and 8B of the cavity resonators 2A and 2B are connected to each other via the region having the choke structure 31. The thickness of each of the partition walls 8A and 8B was 1 mm, the choke thickness Lt of the choke structure 31 was 3 mm, and the choke length Lc was set as shown in Table 3.
The cavity resonator 2A side is the microwave supply side, and the cavity resonator 2B side is the passive side of the microwave.
The S21 signal was calculated by simulation for each choke length Lc. At that time, the microwave is introduced into the cavity resonator 2 by a waveguide (not shown) via a coaxial waveguide converter so that it can be detected by the waveguide of the cavity resonator on the passive side. I set it.
As a result, as shown in Table 3, it was found that the S21 signal became smaller at a specific frequency, and the influence on the adjacent cavity resonator could be reduced.

[Example 31]
The microwave heating device 1 of Example 31 having the configuration shown in FIG. 11 was produced. Specifically, eight cavity resonators 2 (2A to 2H) were laminated so that the central axes of the respective cylindrical cavity 22s were aligned. The central axis C is an axis in which the central axes of the cavities 22 are aligned. The inner diameter D of the empty body 22 was varied in the range of 90.5 mm to 92 mm as shown in Table 4. In the figure, the expression of the difference in the inner diameter D is omitted. The length L in the central axis direction of the cavity 22 of each cavity resonator 2 in the central axis C direction was set to 15 mm. The thickness t of the partition wall 8 of each cavity resonator 2 that partitions the cavity 22 between the cavity resonators 2 and 2 was set to 5 mm. Further, a through hole 9 having a hole diameter φ of 3.2 mm was provided at the center of each partition wall 8 viewed in a plan view.
A distribution pipe 6 was installed in the portion of the through hole 9 by penetrating all the cavity resonators 2 and aligning the central axis of the flow tube 6 with the central axis C of the cavity resonator 2. For the distribution pipe 6, a tube made of polytetrafluoroethylene (for example, Teflon (registered trademark)) having an outer diameter of 3 mm and an inner diameter of 2 mm was used. Then, ethylene glycol was supplied as a simulated reaction solution into the flow tube 6 by the gear pump 61 from the lower side of the flow tube 6 (the lower side of the empty body resonator 2).
The cavity resonators 2A to 2H are referred to as the first stage and the second stage from the simulated reaction solution supply side, and the outlet side is referred to as the eighth stage. On each side wall 24 of the cavity resonators 2A to 2H of each stage, a window (not shown) that can measure the outer wall temperature of the distribution pipe 6 in a non-contact manner with a radiation thermometer 71 (TMHX (trade name) manufactured by Japan Sensor). Was provided. The standing wave formation state in each cavity resonator 2 was monitored by a detector (not shown). A half-wave rectifier circuit using a high-frequency diode was used as the detector.

Each cavity resonator 2 is independently supplied to the cavity resonator 2 for each stage so that the indicated value of the radiation thermometer 71 arranged in the stage reaches a predetermined temperature. Was feedback controlled. In addition to power control, the _{microwave oscillation frequency is also adjusted to match the resonance frequency of TM 010} mode based on the monitor signal of the detector (not shown) by adjusting the microwave generator (not shown) at the same time. Controlled. The microwave was supplied from the loop antenna 3A connected to the side wall 24 of the cavity resonator.
Under the above conditions, ethylene glycol 30 mL / min was sent into the flow tube 6 as a simulated reaction solution by a gear pump 61, and the temperature was controlled so that the solution temperature at the outlet of the flow tube 6 was 160 ° C. The upper limit of the microwave power of each stage of the cavity resonator was set to 50 W.

The measurement result of the radiation thermometer 71 is shown in FIG. Table 4 shows the frequencies of the microwaves controlled by each stage of the cavity resonator 2 at that time _{to maintain the standing wave in the TM 010 mode.}
As is clear from FIG. 12, the temperature of the solution increased toward 160 ° C. from the first stage to the third stage of the cavity resonator 2. Then, it was found that the target temperature of 160 ° C. could be stably maintained after the fourth stage. Further, the control frequencies of the microwaves supplied to the adjacent cavity resonators 2 and 2 are separated by 3.4 MHz or more, and electromagnetic wave leakage occurs in the adjacent cavity resonators 2 and 2 even through the through hole 9. Even so, it turned out that it was able to operate so as not to affect the control.

Next, Examples 41 to 50 of the method for adjusting the microwave resonance frequency in the cavity resonator 2 will be described below.
[Examples 41 to 50]
In Examples 41 to 50, the cavity resonator 2 shown in FIG. 4 was manufactured as a method for adjusting the resonance frequency of the cavity resonator 2. The height of the cavity resonator 2 is 100 mm, the inner diameter is 95 mm, and the metal piece 53 is arranged in the cavity 22 so as to be removable. The width of the metal piece 53 was 10 mm and the height was 98 mm. By inserting this metal piece 53 from the side wall 24 parallel to the central axis C, the resonance frequency of the microwave forming the standing wave _{of the TM 010 mode in the cavity resonator 2 was adjusted.}
Table 5 shows the results of measuring how the resonance frequency of _{TM 010} changes with respect to the insertion length Lm of the metal piece 53. Example 41 was the resonance frequency before inserting the metal piece 53, which was 2.416 GHz. On the other hand, it was found that the resonance frequency was increased by increasing the insertion length Lm of the metal piece. The insertion length Lm is a length that goes out from the inner surface of the side wall 24 of the cavity resonator 2 into the cavity 22. That is, it was found that a desired resonance frequency can be obtained by changing the insertion length Lm of the metal piece 53.
The metal pieces 53 may be arranged at a plurality of places. In that case, it was found that the electromagnetic field intensity distribution in the cavity resonator 2 is less disturbed when the symmetry is maintained, such as by arranging them diagonally.

An example of a configuration in which a dielectric is inserted as a method for adjusting the resonance frequency will be described below.
[Examples 61-67]
In Examples 61 to 67, as an empty body resonator 2 for adjusting the resonance frequency, a cylindrical empty body resonator 2 in which the dielectric 51 is arranged in the empty body 22 shown in FIG. 13 was manufactured. As the dielectric 51, a cylindrical Teflon (registered trademark) (relative permittivity 2.1) or alumina (relative permittivity 9) having a diameter d of 10 mm and a height of 19.5 mm was used. .. It is preferable to use a dielectric 51 to be inserted having a small dielectric loss. This is because if the dielectric loss is too large, the dielectric absorbs microwaves and generates heat. In short, microwave energy is taken by the dielectric 51, which may result in insufficient heating of the object to be heated. Therefore, by suppressing the heat generation of the dielectric 51, microwaves can be effectively used for heating the object to be heated. In the illustrated example, one to four dielectrics 51 are arranged at positions close to the side wall 24 of the cavity resonator 2. The resonance frequencies of the TM ₀₁₀ mode are shown in Table 6. By inserting the dielectric 51 into the cavity 22, the resonance frequency could be reduced. By increasing the number of dielectrics 51 and using a dielectric having a large relative permittivity, it was possible to increase the amount of change in the resonance frequency.
It was found that it is also effective to continuously move the dielectric piece in and out from the side wall as in Examples 41 to 50 in order to continuously change the resonance frequency.

[Example 68]
Example 68 attempted to synthesize silver nanoparticles under the conditions shown in Example 31 above. As a reaction raw material, 10 mM of silver nitrate was dissolved in ethylene glycol, and 300 mM of polyvinylpyrrolidone (molecular weight 10,000) was added as a protective agent. A microwave heating device 1 in which eight cavity resonators 2 shown in FIG. 11 were connected was used. Other conditions were the same as in Example 31. The reaction raw material was sent into the flow tube 6 by the gear pump 61 at a flow rate of 30 mL / min, and the temperature was controlled so that the solution temperature at the outlet of the flow tube 6 was 160 ° C. The upper limit of the microwave power of each stage of the cavity resonator 2 is set to 50 W. The residence time at this time was 1 second. As a result of observing the dried nanoparticles by TEM (TECNA Ig2 manufactured by FEI), it was confirmed that silver nanoparticles having a diameter of 10 nm could be synthesized.

[Example 69]
In Example 69, hydrogen production was carried out by a selective partial oxidation reaction of ethanol as a reaction example by a catalyst filling reaction. As shown in FIG. 14, among the five connected cavity resonators 2, four microwave irradiation devices 10 located on the raw material gas supply side were used. A microwave heating device 1 arranged so that the central axes C coincide with each other was used. The inner diameter of the cavity resonator 2 is 90.5 mm to 92 mm (the difference in diameter is omitted in FIG. 14), and the thickness of the partition wall 8 between the cylindrical cavity resonators 2 and 2 (adjacent cavity 22). , The distance between 22) was 6 mm, and the hole diameter of the through hole 9 through which the reaction tube 16 (flow tube 6) passed was 10.5 mm. Each cylindrical resonator 2 was made of aluminum.
As the reaction tube 16, a quartz reaction tube having an outer diameter of 10 mm and an inner diameter of 8 mm was used. The quartz reaction tube was filled with 3.0 g of a hydrogen production catalyst so that the length of the catalyst filling portion CT was 6.7 cm. As a catalyst for hydrogen production, Ni-supported alumina supported on porous γ-alumina so that nickel (Ni) was 5% by mass by an impregnation method was used. Silicon carbide (SiC) having good microwave absorption was added to this catalyst so that nickel-supported alumina: SiC = 10: 1. Before the reaction experiment, the reduction treatment was carried out in an electric furnace at 600 ° C. for 1 hour in a hydrogen atmosphere.
Table 7 shows the resonance frequencies when microwaves are applied to each cavity resonator 2 so that a standing wave in TM010 mode is formed.

Under the above conditions, a liquid raw material prepared at ethanol: water = 1: 2 is supplied to a vaporizer preheated to 150 ° C. by a syringe pump, and the whole amount is evaporated to form a gas, and then a mixture of oxygen and nitrogen is used as the raw material. It was gas. The composition was ethanol: water: oxygen = 1: 2: 0.5 (volume ratio), and nitrogen was adjusted as a carrier gas so that the ethanol concentration was 5%, and the total flow rate was 100 ml / min. The temperature was controlled within the range of the maximum output of 100 W of the microwave generator of each stage so that the temperature of each cavity resonator was 700 ° C., and the composition of the outlet gas was measured by gas chromatography. As a result, an ethanol conversion rate of 98%, a hydrogen selectivity of 92%, and a hydrogen yield of 90% were obtained.

1, 1A, 1B, 1C Microwave heating device 2 Air body resonator 3 Microwave supply port 3A Antenna 4 Cable 5 Microwave generator 6 Flow tube 10 Microwave irradiation device 11 Detector 16 Reaction tube 22 Air body 24 Side wall 31 Chalk structure 41 Absorber 51 Dielectric 53 Metal piece C Central axis, Cavity center axis D1, D2, D3 Cylinder diameter (inner diameter)
φ Hole diameter L Length of empty body

Claims (7)

Multiple cavity resonators arranged in series to form a standing wave,
Through the plurality of cavity resonators in the series connection direction of the plurality of cavity resonators and along the portion where the energy of the standing wave formed in the plurality of cavity resonators is maximized. The arranged object to be heated and
It has a microwave generator that separately supplies microwaves to each of the plurality of cavity resonators.
Have a mechanism to prevent leakage of microwaves between adjacent cavity resonator,
The mechanism has a microwave frequency for forming a standing wave in one cavity resonator and a microwave for forming a standing wave in the cavity resonator adjacent to the cavity resonator. A microwave heating device that is a mechanism that makes the frequencies of the above different from each other. The standing wave to be formed in the cavity resonator is a TM _0n0 mode or TE _n0 mode, microwave heating apparatus according to claim 1. However, n is a positive integer. The microwave heating device according to claim 1 or 2 , wherein the mechanism is realized by any one or both of the following (c-1) and (c-2).
(C-1) A dielectric or a metal piece is placed in the cavity resonator.
(C-2) In the cavity resonators adjacent to each other, the cross sections perpendicular to the series connection direction have different shapes. In the mechanism , the frequency of the microwave for forming the standing wave supplied in one empty body resonator and the standing wave supplied to the empty body resonator adjacent to the empty body resonator are formed. The microwave heating device according to any one of claims 1 to 3, wherein the absolute value of the difference from the frequency of the macro wave for the purpose is 3 MHz or more. The energy of the microwave supplied to form a stationary wave in one cavity resonator is Px _-in , and the cavity resonator is transferred to the cavity resonator adjacent to the cavity resonator. The microwave heating device according to any one of claims 1 to 4 , which satisfies P _y-x ≤ P _{x-in x 0.25, where P y-x} is the energy of the propagating microwave. The microwave heating device according to any one of claims 1 to 5 , wherein the microwave heating device is a chemical reaction device that heats the object to be heated by microwaves to cause a chemical reaction. The chemical reaction method using the microwave heating device according to any one of claims 1 to 6 , wherein a chemical reaction is caused by heating the object to be heated.

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