JP5268047B2 - Microwave chemical reactor - Google Patents

Abstract

[PROBLEMS] To provide novel means for introducing a microwave having an extremely wide frequency band and an extremely high output level efficiently with respect to the resonance load. [MEANS FOR SOLVING PROBLEMS] A microwave device comprises a voltage-controlled solid-state oscillator (1) for generating a microwave, a microwave amplifier (3) for amplifying the output of the oscillator (1), a TM010-mode cylindrical cavity resonator (2) which the output of the amplifier (3) is made to enter, a sensing element (7) coupled to the cavity resonator (2) and adapted for sensing the electromagnetic field inside the cavity resonator (2), a feedback control means (8) for controlling the oscillator (1) according to the output signal from the sensing element (7) so that the oscillation frequency of the oscillator (1) may match the present resonance frequency of the cavity resonator (2), and a subject-holding tubular member which is permeable to a microwave, is disposed inside the cavity resonator (2) generally coaxially with the central axis of the cavity resonator (2), and holds therein a subject (S) to be irradiated with a microwave.

Description

The present invention irradiates the irradiated object installed in the cavity resonator with the microwave output having a narrow spectral width generated by the voltage controlled oscillator and amplified by the amplifier, thereby heating the irradiated object, BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus that promotes a chemical reaction of an object to be irradiated, and relates to a microwave chemical reaction apparatus in which the oscillation frequency of a voltage-controlled oscillator is controlled so that the microwave output frequency matches the resonance frequency of a cavity resonator. .

Microwaves are widely used as heating devices for industrial heating furnaces such as microwave ovens, and in recent years, they have been attracting attention as a medium that has the ability to cause chemical reactions more rapidly. In the following, the effects of microwaves, including chemical reaction effects, will be described using the word “microwave heating” or “heating” as a representative.
When a single-mode cavity resonator is used for microwave heating, an extremely strong electromagnetic field can be generated in a resonated state, and an inherent electromagnetic field distribution can be obtained. Therefore, there is a possibility that a sample that cannot be heated by other microwave means can be heated efficiently and uniformly.
In particular, when this single mode resonator is a cylindrical cavity resonator and this resonator is resonated in TM010 mode, a constant strong electric field is obtained in the circumferential direction and the axial direction. It becomes possible to heat a cylindrical or columnar object disposed inside the chamber substantially uniformly. Hereinafter, a cylindrical cavity resonator that resonates in the TM010 mode is simply referred to as a cavity resonator or a resonator. An example of a microwave device using TM010 is disclosed in Patent Document 1.
As will be described later, since the cavity resonator has extremely strict requirements for microwaves, it has not yet been generally used. If this difficulty can be solved, it is considered that the cavity resonator can establish and maintain a high position as an effective tool because of its excellent characteristics.
As a device for generating a microwave, a magnetron oscillator (hereinafter simply referred to as a magnetron) is the most inexpensive device. However, the magnetron has a drawback that the oscillation frequency changes when the output is changed or the magnitude or phase of the reflected wave from the load is changed. Further, there is a problem that the output of the magnetron is not a single frequency but spreads with a certain width. On the other hand, the cavity resonator can only enter microwaves with frequency components that are close to or close to the resonance frequency, and most microwaves with other frequency components are reflected at the entrance of the cavity. There is a problem that. Especially for irradiated objects with low microwave absorption (hereinafter also referred to as “cavity load”) placed in a cavity resonator, the smaller the microwave absorption, the narrower the frequency range that can be incident. There is. Because of this drawback, it is impossible to efficiently microwave heat the cavity load with a magnetron.
As a method for removing the disadvantages of the magnetron, Patent Document 2 describes a means for injecting a signal from an oscillator having excellent spectral characteristics into the magnetron to stabilize the oscillation frequency and improve the spectral characteristics. This improved magnetron device will be referred to as a controlled magnetron. The control type magnetron can increase the heating efficiency of the cavity load by about 3 to 5 times or more.
When heating a cavity load, it is necessary to match the oscillation frequency with the resonance frequency of the cavity, that is, to tune. There are several issues regarding tuning.
First, the resonant frequency of the cavity varies greatly depending on the dielectric constant, amount, shape, etc. of the irradiated object. For this reason, first, it is necessary to determine an optimum structural dimension in accordance with the irradiated object at the design stage. In many cases, the cavity design must be renewed as the irradiated object changes.
Another problem arises after the object to be irradiated is determined and the optimum dimensions of the cavity are determined. That is, the dielectric property of the irradiated object changes with the progress of heating, and the resonance frequency changes accordingly. Accordingly, it is necessary to correct the resonance frequency of the cavity resonator.
Changing the resonance frequency of the cavity resonator usually requires a mechanical method, so it is impossible to desire a fast correction. In the mechanical method, the variable range is limited to some extent.
On the other hand, since the method of changing the oscillation frequency is an electronic means, there is an advantage that a quick correction can be made. In the case of a control type magnetron, first, the injection frequency into the magnetron is changed by a voltage control type oscillator, and the magnetron can be oscillated at that frequency. The spectral characteristics are good oscillations. A strong electromagnetic field is generated in the cavity resonator. Therefore, to pick up the electromagnetic field, the electromagnetic field is fed back to the detection signal so as to maximize, automatically how to turn the oscillation frequency of the magnetron, the present applicant in Japanese Patent Application 2006-463 4 No. 9 Proposed.
Such an improvement makes it possible to automatically maintain synchronization. However, since the magnetron itself is a resonator, there is a difficulty that tuning cannot be maintained over a wide range. The frequency variable width is quite narrow. For example, when the microwave frequency is 2,450 MHz, it is about several MHz.
In addition to the problem related to tuning, the magnetron has a problem that the operation becomes unstable when the microwave output is lowered to about 1/10 of the prescribed output, and the oscillation stops when the frequency is further lowered. Controlled magnetrons cannot escape this problem.
JP 2005-322582 A Japanese Patent Application No. 2002-43848

An object of the present invention is to provide a microwave chemical reaction device capable of generating a microwave having a relatively narrow spectral width in synchronization with a changing resonance frequency of a cavity resonator and having a wide output dynamic range. It is.

In the present invention, in order to solve the above problems, a voltage-controlled solid-state oscillator 1 (hereinafter also referred to as “VCO”) that generates a microwave and a microwave amplifier 3 (hereinafter referred to as “VCO”) that amplifies the output of the oscillator 1. Also referred to as “HPA”), the TM010 mode cylindrical cavity resonator 2 into which the output of the amplifier 3 is incident, the detection element 7 coupled to the cavity resonator 2 to detect the internal electromagnetic field, and the detection Feedback control means 8 for controlling the oscillation frequency of the oscillator 1 to coincide with the current resonance frequency of the cavity resonator 2 according to the output signal of the element 7, and the center axis of the cavity resonator 2 substantially concentrically with it. The microwave chemical reaction apparatus is configured to include a microwave transmissive cylindrical tubular irradiator holding member that is disposed in the inside and holds the microwave irradiator S.
If necessary, a temperature detector for detecting the temperature of the irradiated body in the cavity resonator, the output from the amplifier by an output signal of the temperature detector, control the output to maintain the irradiation object the appropriate temperature The temperature of the irradiated object is kept constant by adding the output control means.

The present invention has the following effects.
(1) Since the VCO is controlled and oscillated by the signal detected by the cavity resonator, the oscillation frequency of the VCO and the amplification frequency of the HPA always coincide with the current resonance frequency of the cavity resonator.
(2) Since the output spectrum of the VCO and HPA is narrow, microwaves can be introduced efficiently to loads that absorb only narrow-band microwaves, such as cavity loads.
(3) The VCO itself has the disadvantage that the frequency drifts under the influence of environmental temperature, etc., but it is automatically corrected to the resonance frequency at the current load of the cavity resonator by the action of the feedback control means. . For this reason, it is not necessary to use an expensive PLL-type oscillator that requires frequency control.
(4) The output can be changed over a wide range by the amplifier. If the output is controlled by the output control means that receives the feedback signal, the irradiated object can be maintained at a prescribed temperature.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a basic configuration diagram of a microwave chemical reaction apparatus (hereinafter simply referred to as a microwave apparatus) according to the present invention, and FIG. 2 is a structural cross section for explaining an outline of the structure and operation of the microwave irradiation section of the present invention. FIG. 3 and FIG. 3 are characteristic diagrams showing changes in resonance frequency when a cylindrical dielectric irradiated body is inserted into a TM010 cavity resonator.

  In FIG. 1, the feedback-controlled VCO 1 oscillates a microwave having a frequency characteristic that matches the resonance frequency of the cavity resonator 2 and that has a narrow frequency spectrum width and good frequency characteristics. This output is amplified by the HPA 3 and enters the cavity resonator 2 through the circulator 4, the power monitor 5, and the stub tuner 6. An extremely strong microwave electromagnetic field is generated in the cavity resonator 2. By this action, the microwave irradiation object S placed in the cavity resonator 2 is efficiently heated, or the chemical reaction progresses efficiently. Since a very strong electromagnetic field is generated in the cavity resonator 2, even a sample that cannot be heated by ordinary means can be sufficiently heated. Note that a mechanism for changing the output level of the microwave is omitted in FIG. 1 because there is no particular confusion.

  A part of the electromagnetic field generated in the cavity resonator 2 is taken out by the detection element 7. The feedback controller 8 operates to control the oscillation frequency of the VCO 1 so that the detection signal becomes maximum or very close to the maximum value. The oscillation frequency of the VCO 1 usually tends to drift under the influence of the environmental temperature, but always oscillates at a frequency that matches the resonance frequency of the cavity resonator 2 by the action of the feedback controller 8. The cavity resonator 2 is always kept tuned and generates a maximum electromagnetic field. The irradiated object S receives the maximum microwave action.

  The reflected wave reflected from the cavity resonator 2 is first suppressed to be as small as possible by the stub tuner 6 and guided to the non-reflecting terminator 9 through the circulator 4. For this reason, the microwave returning to the HPA 3 is suppressed to a sufficiently low level, and the HPA 3 is not damaged. The microwave (traveling wave) and the reflected wave incident on the cavity resonator 2 are measured by the power monitor 5.

  The output of the HPA 3 can be freely changed from almost zero to a specified total power range by changing the attenuation of the input through an attenuator (not shown) or by the output control means 11 for changing the gain by a gain control circuit. Can do. The magnetron has an unstable operation at a level of about 1/10 of the total power, and has a problem that oscillation stops when the output is further reduced. However, when HPA3 is used, it can be applied to a wider range of irradiated objects. The irradiated object S may have to be a very weak output microwave, and conversely, a certain chemical reaction requires a considerably large output, so that the wide dynamic range is important.

  The single system has been described above. For example, the output of the VCO is branched, guided to a plurality of HPAs, amplified, and combined so that these outputs are added in phase, and then led to the cavity resonator. be able to.

  In FIG. 1, a temperature detector 10 such as a radiation thermometer detects the temperature of the irradiated object S in the cavity resonator 2. This detection signal is fed back, the output control means 11 controls the output of the HPA 3, and the temperature of the irradiated object S is maintained at a temperature specified in advance.

  As apparent from the above description, according to the present invention, the most inexpensive VCO 1 among the microwave oscillators capable of controlling the frequency is used so that the oscillation frequency is always tuned to the resonance frequency of the cavity resonator 2. It is controlled and operated, and has an advantage that a microwave having an optimum frequency can be efficiently introduced into the irradiated object even if the load condition changes. The frequency of the cavity resonator 2 is affected by the type, amount, size, and shape of the irradiated object inserted therein, and the resonance frequency changes with a considerable width. In addition, the resonance frequency changes even when the irradiated object is heated or the amount or state changes due to the microwave irradiation. If the oscillation frequency of VCO 1 is not controlled, it drifts under the influence of the surrounding temperature. In response to such changes, the feedback controller 8 has a function of always tuning the oscillation frequency of the VCO 1 to the resonance frequency of the cavity resonator 2. The spectral characteristics of the VCO 1 are good, and the HPA 3 simply amplifies it, so that it can sufficiently meet the spectral characteristics required by the cavity load. Compared to a normal magnetron, the efficiency is improved and the HPA with a relatively small output can meet the requirements. A known feedback control type magnetron device is inexpensive, but has a drawback that the frequency variable width is narrow. Since the microwave device of the present invention does not have this problem at all, it can always ensure a wide application range. Since the price of solid HPA is also on the decline, it is expected that the position as an increasingly promising tool will be maintained in the future. From the standpoint of energy saving effect and ease of use, it is possible to provide a microwave device that is extremely advantageous.

  Next, the operation outline of the microwave irradiation unit of the present apparatus will be described with reference to FIG. In FIG. 2, 2 is a cavity resonator, 12 is an inner dielectric tube, and 13 is an outer dielectric tube. The dielectric circular tubes 12 and 13 are both arranged substantially concentrically with the cylindrical cavity resonator 2. Two types of fluids A and B flow through the dielectric tubes 12 and 13. The inner dielectric tube 12 allows the fluid to permeate to the outside at the center, and the two fluids A and B are mixed. The catalyst 14 promotes the chemical reaction of both fluids A and B, and is supported on the inner dielectric tube 13. Although not shown in the figure, a microwave is introduced into the cavity resonator 2 from the outside. In the cavity resonator 2, an electromagnetic field substantially close to TM010 is excited in a resonance state. This electromagnetic field is substantially uniform in the axial direction and the circumferential direction. The catalyst 14 is mainly heated by receiving the microwave irradiation. The resonance state is extracted as a signal to the outside by the detection element 7 (FIG. 1) coupled to the cavity resonator 2. The oscillation frequency of VCO 1 is controlled so that this signal is maximized. In addition, when the present invention is applied to an experimental apparatus, it is possible to provide a simple test apparatus in which the frequency is manually changed by visually observing the detection signal.

  FIG. 3 shows how the resonance frequency changes when an irradiated object having a different relative dielectric constant is inserted into a specific TM010 mode resonance cavity. When a metal piece is inserted into the cavity resonator, the resonance frequency can be increased, but the tuning range cannot be increased so much. That is, it is impossible to correct the large frequency drop as shown in FIG. For this reason, it is necessary to prepare a plurality of cavity resonators, which is considered to be a considerable burden for users who want to perform microwave irradiation on samples having different relative permittivity over a considerable width. . If the microwave frequency can be changed widely, the burden can be avoided. The VCO and HPA in the present invention can sufficiently meet this requirement.

Comparing the device of the present applicant proposed feedback-controlled magnetron apparatus and the present invention in Japanese Patent Application No. 2006-463 4 No. 9, the reference signal NOTE ON has been controlled output frequency magnetron, the VCO and HPA It was just replaced. However, as a result, (1) the dynamic range of the output spreads over a very wide range from almost zero to the maximum output, and (2) the output frequency becomes extremely wide, for example exceeding ± 50% of the operating center frequency. . When the present invention is applied to a research experimental apparatus, a single apparatus can deal with a variety of irradiated samples, and the effect is extremely large.

Since the present invention produces advantages such as improved efficiency, expanded application range and ease of use, low price maintenance, and improved energy saving, it can be used effectively as a microwave heating device, plasma processing device, or research experimental device. it can.
The present invention has a great potential for use in chemical reaction promoting devices, exhaust gas purifying devices, air purifiers, sterilizing / sterilizing devices, bio equipment and the like.

It is a block diagram which shows the basic composition of the microwave apparatus which concerns on this invention. It is structure sectional drawing for demonstrating the outline | summary of the structure and operation | movement of a microwave irradiation part of this invention. FIG. 6 is a characteristic diagram showing a change in resonance frequency when a cylindrical dielectric object is inserted into a TM010 cavity resonator.

Explanation of symbols

1 VCO
2 Cavity resonator 3 HPA
Reference Signs List 4 Circulator 5 Power monitor 6 Stub tuner 7 Detection element 8 Feedback controller 9 Non-reflective terminal 10 Temperature detector 11 Output control means 12 Inner dielectric tube (illuminated object holding member)
13 Outer dielectric tube (emitter holding member)
14 Catalyst (Subject to be irradiated)
A Fluid (Subject to be irradiated)
B Fluid (Subject to be irradiated)
S Subject to be irradiated

Claims (8)

A microwave chemical reaction apparatus using a TM010 mode cylindrical cavity resonator having an irradiated body holding member for holding a chemical reaction target fluid, a voltage-controlled solid-state oscillator for generating a microwave, and A microwave amplifier that amplifies the output of the oscillator, a TM010 mode cylindrical cavity resonator to which the output of the amplifier is incident, and a detection element that is coupled to the cavity resonator and detects an internal TM010 mode electromagnetic field receives the output signal of the detection element, an oscillation frequency before Symbol oscillator, to match the TM010 mode resonant frequency of the TM010 mode cylindrical cavity resonator, the output signal is controlled to be near the maximum value at all times, holding the feedback control means to said oscillator output signal of the detection element, a substantially concentrically arranged inside the chemical reaction subject fluid and that of the central shaft to the cavity resonator Microwave reaction device characterized by comprising a target ITerukarada holding member of the cylindrical tubular in microwave permeable. A temperature detector for detecting the temperature of the irradiated body in said cavity resonator, the output from the amplifier by an output signal of the temperature detector, and controls the output to maintain the irradiation object to a proper temperature The microwave chemical reaction device according to claim 1, further comprising an output control means.   The irradiated body holding member is a cylindrical tube channel that circulates the irradiated body that is a fluid inside, and the cylindrical tube channel contains a microwave absorber that is heated by receiving microwave irradiation. The microwave chemical reaction apparatus according to claim 1, wherein the microwave chemical reaction apparatus is supported on the microwave reaction apparatus. The output control means includes an attenuator that is interposed between the oscillator and the amplifier and controls an attenuation amount of microwave power input from the oscillator to the amplifier by an output signal of the temperature detector. Microwave chemical reactor according to any one of claims 1 to 3, wherein. It said output control means, a microwave chemical reaction apparatus according to any one of claims 1 to 3, characterized in that it comprises a gain controller for controlling a gain of the amplifier by an output signal of said temperature detector. Between the amplifier and the cavity resonator, according to claim 1, characterized in that the circulator for guiding the microwaves reflected towards the amplifier from the cavity resonator to non-reflective terminator is provided - Microwave chemical reactor according to any one of 5.   The microwave chemical reaction device according to claim 6, wherein a power monitor and a stub tuner are provided between the circulator and the cavity resonator. The voltage-controlled solid-state oscillator is automatically controlled and oscillated by the signal detected by the cavity resonator, and the oscillation frequency of the voltage-controlled solid-state oscillator and the amplification frequency of the microwave amplifier that amplifies the output of this oscillator are The microwave chemical reaction device according to any one of claims 1 to 7, wherein the microwave chemical reaction device always matches a current resonance frequency of a cavity resonator including an irradiated body holding member that holds a reaction target fluid. .

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