JP6572517B1 - Heating device and hot air generator - Google Patents

Abstract

A heating device capable of high-temperature heating and rapid heating, capable of sustaining for a long time and capable of repeated heating, and a hot air generator using the heating device are provided. A heating apparatus including a heating element 20 containing fine particles mainly composed of silica and microwave generation means 12 for irradiating the heating element 20 with microwaves, wherein the fine particles are incinerated in rice husks. It is a heating device characterized in that it is a residue and fine particles contain carbon. Moreover, it is a hot air generator provided with the heating apparatus and the ventilation means 4 for blowing air to a heating apparatus. [Selection] Figure 1

Description

  The present invention relates to a heating device using microwaves and a hot air generator using the heating device.

  Conventionally, as a heat source of a heating device, an electric heater using a nichrome wire, an infrared lamp, a burner using a combustible gas or combustible oil, and the like have been used. Each of these heat sources has advantages and disadvantages. For example, a burner is capable of rapid heating, but increases carbon monoxide and carbon dioxide and pollutes the air. It also has fire, and has problems in terms of environmental health and safety. It was a thing.

  As a heating device using a heat source other than the above, a heating device using a microwave is known. For example, Patent Document 1 includes a heating element made of carbon powder as a main material and sintered in a honeycomb shape, electromagnetic microwave generation means for irradiating the heating element with electromagnetic microwaves, and a blower. A heating device using microwaves is disclosed.

JP-A-6-231880

  However, the heating device of Patent Document 1 uses carbon powder as a main material, and when the carbon powder is oxidized, an oxide film is formed, and there is a concern that durability is lowered.

  Generally, a heating device is required to be able to be heated to a high temperature in a short time, to be excellent in energy efficiency, and to be excellent in durability of the device.

  The present invention has been made in view of such a situation. That is, an object of the present invention is to provide a heating device that can perform high-temperature heating and rapid heating, can be sustained for a long time, and can be repeatedly heated, and a hot-air generator using the heating device.

  The inventors of the present invention have repeatedly studied a method for effectively using rice husk, which is one of biomass produced in large quantities every year. When the rice husk is self-combusted at a high temperature for a long time, almost all of the organic combustibles are incinerated, leaving a residue. We focused on the effective use of this residue.

  The main component of the incineration residue of rice husk is silica. Moreover, as components other than silica, metal, carbon, etc. are contained in trace amounts. The present inventors have surprisingly found that when the incineration residue of rice husk is irradiated with microwaves, heat is rapidly generated up to several hundred degrees Celsius in a short time. Furthermore, it has been found that the exothermic phenomenon repeats every time the microwave irradiation is repeated many times. The present invention has been made based on such findings. That is, the present invention has the following configuration.

(1) A heating device comprising a heating element containing fine particles mainly composed of silica and microwave generation means for irradiating the heating element with microwaves, wherein the fine particles are incineration residue of rice husks. A heating device, wherein the fine particles contain carbon.

(2) The heating device according to (1), wherein the fine particles contain a metal.

(3) The heating apparatus according to (1) or (2), wherein the fine particles have a carbon content of 30% by mass or less.

(4) The heating device according to any one of (1) to (3), wherein the heating element is a sintered body including the fine particles and ceramic particles.

(5) The heating device according to any one of (1) to (3), wherein the heating element is a molded body in which the fine particles are wrapped with ceramics.

(6) A hot air generator comprising the heating device according to any one of (1) to (5) and a blowing unit for blowing air to the heating device.

  The heating device and hot air generator of the present invention can be heated at high temperature and rapidly, can be sustained for a long time, and can be repeatedly heated.

It is a typical sectional view of a hot air generating device using a heating device of this embodiment.

  Hereinafter, the present invention will be specifically described. The following embodiments are merely examples, and the present invention should not be construed as being limited to these embodiments.

  The heating device of the present embodiment includes a heating element containing fine particles mainly composed of silica, and a microwave generation means for irradiating the heating element with microwaves. Hereinafter, each means which comprises a heating apparatus is demonstrated.

(Rice husk)
Rice husk is about 70 to 90% by mass of organic components mainly composed of cellulose, and the remaining about 10 to 30% by mass is inorganic components. The inorganic component is mainly silica and contains a trace amount of mineral components. Silica has the potential to be used in a variety of applications, so we tried to almost completely remove organic combustibles by burning rice husks in the atmosphere under atmospheric pressure.

(Incineration residue of rice husk)
A continuous firing furnace was created to burn a large amount of rice husk continuously. When the rice husk is continuously introduced into the continuous firing furnace together with air, an external ignition source is required at the start of combustion, but after ignition, self-combustion causes continuous combustion in the atmosphere under atmospheric pressure. Started. The combustion temperature was in the range of 1000-1900 ° C. by appropriately adjusting the rice husk and air input speed. The average combustion time was in the range of 5 to 15 hours.

  The obtained incineration residue was fine particles containing silica as a main component and containing carbon, metal and the like. Here, having silica as the main component means that the content of silica with respect to the fine particles exceeds 50% by mass. The content of silica varies depending on the rice production area and variety of rice husk, but is substantially in the range of 60 to 96 mass%. Hereinafter, the incineration residue fine particles of the rice husk will be referred to as silica-based fine particles.

  The inventors of the present invention conducted an experiment in which 10 g of silica-based fine particles were put into a ceramic container, covered with a ceramic lid, and irradiated with microwaves (2.45 GHz) in a 700 W microwave oven for 1 minute. It was found that the system fine particles rapidly generated heat up to about 900 ° C. Further, the present inventors have found that the exothermic phenomenon is repeatedly manifested every time microwave irradiation is repeated. It is presumed that the silica-based fine particles exhibit such a unique exothermic phenomenon because a small amount of components such as carbon and metal contained in the silica-based fine particles cause induction heating, dielectric heating, and the like by microwave irradiation. Therefore, using this unique heat generation phenomenon of silica-based fine particles, the use of silica-based fine particles as a heating element of a heating device was examined.

(Heating element)
In order for the silica-based fine particles to exhibit an exothermic phenomenon, the silica-based fine particles need to contain carbon. 30 mass% or less is preferable, as for content of the carbon which a silica type fine particle contains, 1-29 mass% is more preferable, and 3-28 mass% is further more preferable.

  In order for the silica-based fine particles to exhibit an exothermic phenomenon, the silica-based fine particles preferably contain a metal. The total content of the metals contained in the silica-based fine particles is preferably 10% by mass or less, more preferably 0.1 to 8% by mass, and further preferably 0.3 to 7% by mass. Examples of the metal include potassium, magnesium, calcium, iron, aluminum, sodium, manganese, and zinc. These metals may be a single metal, an alloy, a metal oxide, or a composite oxide.

  Silica-based fine particles used as a heating element have an average particle size of about 10 to 300 μm. The shape of the silica-based fine particles is not particularly limited. Silica may be amorphous or crystalline and is not limited.

  In order to make the heating element containing silica-based fine particles into a form excellent in heat transfer efficiency and handleability, it is preferable to form a sintered body composed of silica-based fine particles and ceramic particles. Ceramic particles are melted at the time of sintering, and silica-based fine particles are bonded together. When the silica-based fine particles and the ceramic particles are mixed and bonded to each other, a stable form can be obtained as the sintered body. Specifically, particles such as soda lime glass, borosilicate glass, lead glass, and quartz glass can be used as the ceramic particles. The kind of ceramic particles, the average particle diameter, and the mixing ratio between the silica-based fine particles and the ceramic particles can be appropriately adjusted as necessary.

  Silica-based fine particles can be coated and protected so that components such as carbon and metal contained in the silica-based fine particles are not directly exposed to the outside world by forming a sintered body composed of ceramic particles. it can. As a result, when carbon, metal, etc. in silica-based fine particles are repeatedly heated and cooled by microwave irradiation, they can be prevented from being oxidized and deteriorated by oxygen, and durability can be improved. .

  As a method for producing a sintered body composed of silica-based fine particles and ceramic particles, a known method can be used. That is, after mixing silica-based fine particles and ceramic particles, they are put into a mold, the inside of the mold is heated to a temperature equal to or higher than the melting point of the ceramic particles, cooled, and sintered with silica-based fine particles and ceramic particles. Assume a body. The shape of the sintered body can be freely designed. In order to increase the efficiency of conduction heating of air, it is preferable to increase the surface area of the sintered body as much as possible. Examples of the shape of the sintered body having a large surface area include a structure in which a large number of cylindrical or prismatic holes are arranged in parallel along the air flow path. The cross-sectional area of the holes, the number of holes, the length of the holes, and the like can be appropriately determined according to the air flow rate.

  Moreover, in order to make the heating element containing silica-based fine particles into a form excellent in heat transfer efficiency and handleability, it is preferable to form a molded body in which the silica-based fine particles are wrapped with ceramics. By holding the aggregate of silica-based fine particles in a ceramic container, it becomes easy to handle or install in an apparatus without directly touching the silica-based fine particles. Further, by enclosing the silica-based fine particles in a ceramic container, the silica-based fine particles can be prevented from coming into direct contact with the atmosphere. As a result, when carbon, metal, and the like in the silica-based fine particles are repeatedly heated and cooled by microwave irradiation, they can be prevented from being oxidized and deteriorated by oxygen, and durability can be improved.

  The method for producing the ceramic molded body is not particularly limited, such as an integrally molded ceramic product, a combination of ceramic plates, a sintered body of ceramic particles, or a combination thereof. The type and shape of the ceramics constituting the formed body are not particularly limited, and can be freely designed by appropriately selecting an appropriate type and shape as necessary. The shape of the molded body is preferably as large as possible in order to increase the efficiency of conduction heating of air.

(Microwave generation means)
As the microwave generating means for irradiating the heating element with microwaves, there are microwave oscillators such as a magnetron, a klystron, a gyrotron, and a traveling wave tube. Among these, magnetron is common. The frequency of the microwave is in the range of 0.3 to 30 GHz, but usually a microwave with a frequency of 2.45 GHz is used. By changing the oscillation output (W) of the microwave oscillator, the heat generation energy fluctuates, and the heat generation temperature of the heat generator can be controlled.

(Heating device)
The heating device of this embodiment includes a heating element and a microwave generation means. In order to prevent the irradiated microwave from leaking to the outside, the heating element is installed in a metal casing. A part of the wall plate of the casing is made of a metal mesh plate or a punching metal plate in order to allow air to flow and to prevent leakage of microwaves. In addition, a waveguide made of metal is used to convey the microwave generated by the microwave oscillator into the housing.

(Hot air generator)
FIG. 1 is a schematic cross-sectional view of a hot air generator using the heating device of the present embodiment. The hot air generator 1 includes a metal (SUS) external housing 2, a metal (SUS) internal housing 7, a blower (fan) 4, a blower cylinder 5, a heat storage rectifying plate 14, a blower cylinder 6, a magnetron 12, A waveguide 13 is provided. Inside the metallic inner housing 7, a heating element 20 including an aggregate 9 of silica-based fine particles, a ceramic particle sintered body 10, and a ceramic molding plate 11 is installed.

  In the metal outer casing 2, the air introduction side and discharge side wall plates are metal plates 3 having a large number of circular holes. In addition, in the metal inner housing 7, the air introduction side and discharge side wall plates are punched metal plates 8 so that microwaves do not leak. In addition, on the air discharge side in the external housing 2, a copper heat storage rectifier having a large number of circular holes is provided in order to reduce the temperature unevenness of the heated air and to make the air flow steady. A plurality of plates 14 are installed.

  The blowing means is for blowing air to the heating device, and is a blower. The blower includes a fan and a blower, and can be appropriately selected and used as necessary.

  In FIG. 1, air to be heated is introduced into a hot air generator 1 by a blower (fan) 4. The introduced air enters the outer casing 2 through the blower cylinder 5. Furthermore, it passes through the punching metal plate 8 and enters the internal housing 7. A heating element 20 containing an aggregate 9 of silica-based fine particles is installed in the inner casing 7. Microwaves are irradiated from the magnetron 12 through the waveguide 13 into the inner casing 7. As a result, the aggregate 9 of silica-based fine particles generates heat, and the surface temperature of the heating element 20 increases. The air that has entered the internal housing 7 is heated by the heating element 20. The heated air passes through the punching metal plate 8, passes through the plurality of heat storage rectifying plates 14, and is discharged from the external housing 2 to the outside. Then, it passes through the blower cylinder 6 and is discharged as heated air.

  The heating device and hot air generator of the present embodiment can heat the heating element to a high temperature and rapidly by irradiating the heating element with microwaves. The surface temperature of the heating element can be changed over a wide range from several tens of degrees Celsius to about 1000 degrees Celsius by changing the microwave oscillation output and irradiation time.

  The heating device and hot air generator of the present embodiment can be used for various purposes for the purpose of heating, drying, temperature control, reaction, and the like. Further, the heating device and hot air generating device of the present embodiment can be used for various industrial applications in various technical fields such as food, chemistry, rubber, wood, casting, ceramics, paper, printing, painting, textiles, and medical. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these.

  Using a continuous firing furnace, the rice husk was burned at a combustion temperature of about 1800 ° C. and a combustion time of about 10 hours, and almost all of the organic combustibles were burned off to obtain an incineration residue of rice husk. As rice husks, rice husks from Saitama Prefecture were used. The amount of the obtained incineration residue was about 20% by mass with respect to the rice husk of the raw material. The incineration residue was a black powder, and the average particle size was about 38 μm. When the incineration residue was analyzed, it was 77% by mass of silica, 8.5% by mass of carbon, and 4.9% by mass of metal. As metals, potassium, magnesium, calcium, iron, aluminum, sodium, manganese, zinc and the like were included. As a metal analyzer, a wavelength dispersive X-ray fluorescence analyzer was used.

  About 10 g of the obtained incineration residue (silica-based fine particles) is sealed in a spherical sintered body having a diameter of 15 cm made of fine particles of soda-lime glass, and is further enclosed in a ceramic spherical container having a thickness of 2 mm. Encapsulated to form a heating element.

  An experiment was conducted using the hot air generator 1 shown in FIG. The heating element 20 obtained in the hot-air generator 1 was installed and irradiated with 2.45 GHz microwaves using a 700 W magnetron 12. The surface temperature of the heating element 20 was raised to about 400 ° C. by irradiation for about 25 minutes, and air at 25 ° C. was introduced into the hot air generator 1 by the blower 4. While the surface of the heating element 20 was heated to about 400 ° C., the heated air at about 70 ° C. could be discharged. Each temperature was measured using a thermocouple.

  Next, while air of 25 ° C. is introduced into the hot air generator 1 by the blower 4, microwave irradiation is continued for about 5 hours, and then the surface temperature of the heating element 20 is lowered to about 30 ° C. after the irradiation is stopped. The operation of allowing the mixture to stand for about 2 hours and then continuing the irradiation again for about 5 hours was repeated for about 8 days. As a result, every time irradiation is performed, the surface temperature of the heating element 20 is heated to about 400 ° C., the temperature is maintained during irradiation, and the surface temperature decreases repeatedly when irradiation is stopped. It was.

DESCRIPTION OF SYMBOLS 1 Hot-air generator 2 External housing 3 Metal plate 4 Blower 5, 6 Blower 7 Internal housing 8 Punching metal plate 9 Silica-based fine particle aggregate 10 Ceramic particle sintered body 11 Ceramic molded plate 12 Magnetron 13 Waveguide 14 Heat storage current plate 20 Heating element

Claims (5)

A heating element containing fine particles mainly composed of silica;
A heating device comprising a microwave generating means for irradiating the heating element with microwaves,
The fine particles are incineration residue of rice husks,
The fine particles contain 3 to 28% by mass of carbon and 0.3 to 7% by mass of metal,
The heating apparatus, wherein the fine particles repeatedly generate heat when irradiated with microwaves . The heating apparatus according to claim 1, wherein the metal is any one selected from potassium, magnesium, calcium, iron, aluminum, sodium, manganese, and zinc . The heating device according to claim 1 or 2 , wherein the heating element is a sintered body made of the fine particles and ceramic particles. The heating element is a heating device according to claim 1 or claim 2 wherein the particulate is characterized in that a molded body wrapped in ceramic. A hot air generator comprising the heating device according to any one of claims 1 to 4 and a blowing means for blowing air to the heating device.