JP2013076562A - Microwave dryer and microwave drying method - Google Patents

Abstract

An object of the present invention is to selectively heat a lower layer portion of an agglomerate charged into a drying furnace using a microwave.
A microwave drying apparatus according to the present invention is a hot air type that reduces moisture contained in a material to be dried by blowing the hot air to the material to be dried when the material to be dried is conveyed by a conveyor. A microwave oscillator that is installed in a drying furnace and oscillates the microwave used to dry the object to be dried, and a heating range in which microwaves can be heated inside the object layer to be dried A plurality of waveguides inserted to a depth including the lowest layer of the layer, and at least two of the plurality of waveguides are arranged at different positions in the furnace width direction of the drying furnace, The positions of the waveguides adjacent to each other in the transport direction are different from each other.
[Selection] Figure 7

Description

  The present invention relates to a microwave drying apparatus and a microwave drying method.

  As the production of steel materials by electric furnaces becomes popular, the demand for scrap, which is the main raw material, is tightened, and the demand for reduced iron is increasing due to the demand for high-grade steel production in electric furnaces.

  As one of the methods for producing reduced iron, iron oxide raw materials such as powdered iron ore and iron-making dust are mixed with carbonaceous materials such as powdered coal and coke, for example, a lump such as pellets and briquettes. There is a method in which an agglomerated material is obtained, and this agglomerated material is charged into a reduction furnace such as a rotary hearth furnace and heated to a high temperature to reduce the iron oxide raw material to obtain solid metallic iron. In such a method, it is important to adjust the moisture content of the agglomerated material containing the iron oxide raw material and the carbonaceous material in order to increase the reduction rate of the agglomerated material.

  In the manufacturing process of reduced iron as described above, as a device for adjusting the moisture content of agglomerates, etc., a tunnel-shaped furnace for drying the material to be dried placed on a wire mesh conveyor by hot air (For example, refer to Patent Document 1 below.) Such a drying furnace dries the material to be dried by passing hot air from the top to the bottom of the furnace.

  Since the drying furnace as disclosed in Patent Document 1 is hot air drying by supplying hot air upward, the lower layer portion of the raw material to be dried (portion close to the wire mesh conveyor) Drying is delayed, and drying of the small block raw material located in the lower layer portion becomes insufficient. If the drying of the small block material is insufficient, the strength of the small block material is insufficient, and in the next step, the small block material is pulverized, resulting in a reduction in production yield. In addition, in order to prevent such a reduction in production yield, it is necessary to add various binders to be mixed with the small mass raw material, resulting in an increase in manufacturing cost.

  In addition, since the small lump material contains carbonaceous materials such as coal and coke, if the small lump material is heated too much, there is a risk of ignition, and it is difficult to improve the drying efficiency by raising the temperature of the hot air. is there. Therefore, from the viewpoint of preventing ignition, it is required to selectively heat the lower layer portion where moisture remains rather than the upper layer portion that is sufficiently dried.

  In addition to the drying furnace using hot air as described above, there has been proposed a drying furnace that irradiates microwaves into the free space of the drying chamber from the outside of the workpiece in order to assist drying by the heater ( For example, see the following Patent Document 2.)

JP-A-2005-113197 JP-A-6-347165

  In the manufacturing process of reduced iron as described above, the layer thickness of the agglomerated material to be dried in the drying furnace is as thick as about 200 mm or more. Therefore, as described in Patent Document 2, when microwaves are applied to the free space in the furnace, it is possible to cause the microwaves to act on the upper layer portion of the agglomerate layer. As will be described in detail, as a result of investigations by the present inventors, it has become clear that microwaves cannot be applied to the lower layer portion of the agglomerated material.

  In addition, since the conveyor for transporting the heavy agglomerate is a metal wire mesh, even if microwaves are irradiated from the back surface of the conveyor to the lower part of the agglomerate, the microwave is transmitted by the metal conveyor. Is reflected, and microwaves cannot be applied to the lower layer portion of the agglomerated material.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to selectively select a lower layer portion of an object to be dried charged in a drying furnace using a microwave. An object of the present invention is to provide a microwave drying apparatus and a microwave drying method that can be heated.

  In order to solve the above-described problem, according to a certain aspect of the present invention, when the object to be dried is transported by a conveyor, moisture contained in the object to be dried is reduced by blowing hot air against the object to be dried. A microwave drying apparatus installed in a hot-air drying furnace, comprising: a microwave oscillator that oscillates a microwave used for drying the object to be dried; and the object to be dried being conveyed. A heating range in which the microwave can be heated is inserted to a depth including the lowest layer of the object layer to be dried, and a plurality of guides for irradiating the object with the microwave. A wave tube, and at least two of the plurality of waveguides are arranged at different positions in the furnace width direction of the drying furnace, and the waveguides adjacent to each other in the furnace width direction The position in the transport direction is Microwave drying apparatus which differs provided to.

  The plurality of waveguides are arranged in the furnace width direction at intervals such that the heating range of each of the waveguides covers the entire furnace width direction of the drying furnace as the whole of the plurality of waveguides. It is preferable.

  The plurality of waveguides may have an opening at an end facing the conveyor when the waveguide is inserted into the layer to be dried.

  The plurality of waveguides are formed on the layer to be dried so that a separation distance between a front end portion of the waveguide and the conveyor is equal to or more than a quarter of a wavelength of the microwave in free space. It is preferably inserted.

  The plurality of waveguides are provided with a notch on at least a side surface that is parallel to the drying object layer transport direction of the drying furnace when the waveguide is inserted into the drying object layer. The microwave may be irradiated from the notch.

  The plurality of waveguides are preferably inserted into the material to be dried such that an upper end in the height direction of the material layer to be dried is not more than a height of the material layer to be dried. .

  In the plurality of waveguides, a distance between an upper end in a height direction of the layer to be dried of the notch and the conveyor is equal to or more than a quarter of the wavelength of the microwave in free space. It is preferable to be inserted into the dried material layer.

  The waveguide has a rectangular cross-sectional shape perpendicular to the traveling direction of the microwave, the short side of the rectangular cut surface is orthogonal to the transport direction, and the rectangular cut The long side of the surface may be parallel to the transport direction.

  A ceramic cover made of an inorganic material ceramic having a dielectric loss coefficient of less than 0.02 is provided at the tip or notch of the waveguide, and the microwave is irradiated from the outer periphery of the ceramic cover. It is preferable.

  It is preferable to provide a vibration mitigating mechanism for mitigating vibrations generated along with the conveyance of the object to be dried.

  As the vibration relaxation mechanism, a slide waveguide having a slide mechanism that enables axial sliding between the waveguide and the microwave oscillator, or a flexible waveguide having a metal bellows portion. It is preferable to dispose at least one of the tubes.

  As the vibration relaxation mechanism, it is preferable to provide an elastic member on a part of the support that supports the waveguide.

  The waveguides may be arranged side by side in the transport direction so that the heating range continues in the transport direction.

  The waveguide may be branched so that the heating range is continuous in the transport direction.

  It is preferable that a dustproof gas is introduced into the waveguide, and a positive pressure is applied to the inside of the waveguide.

  A tapered portion may be provided at an end of the waveguide on the upstream side in the transport direction so that an area of a cross section perpendicular to the transport direction becomes smaller toward the upstream side in the transport direction.

  The microwave drying device includes an impedance of the microwave oscillated from the microwave oscillator and the microwave reflected between the microwave oscillator and the plurality of waveguides in the drying furnace. It is preferable to further include an automatic matching device that performs matching with the impedance of the microwave toward the oscillator.

  The inorganic material ceramics may be selected from the group consisting of alumina, silicon nitride, sialon, aluminum nitride, boron nitride, and mixtures thereof.

  Moreover, in order to solve the said subject, according to another viewpoint of this invention, when conveying a to-be-dried object with a conveyor, the moisture contained in the to-be-dried object by spraying a hot air with respect to the to-be-dried object A microwave drying method implemented for a hot-air drying furnace for reducing the temperature of the object to be dried, the microwave being used for drying the object to be dried being oscillated and transported from the object to be dried The microwave is heated from the plurality of waveguides inserted to the depth including the lowermost layer of the object layer, and the microwave is heated with respect to the object layer. And at least two of the plurality of waveguides are arranged at different positions in the furnace width direction of the drying furnace, and the waveguides adjacent to each other in the furnace width direction are arranged. The position in the transport direction is Microwave drying method different are provided together.

  As described above, according to the present invention, the microwave irradiation member is inserted from above the layer to be dried to a predetermined position and irradiated with microwaves, so that the object to be dried charged in the drying furnace can be obtained. It becomes possible to selectively heat the lower layer portion.

It is explanatory drawing shown about the flow of the manufacturing method of a general reduced iron. It is explanatory drawing for demonstrating the state of the agglomerate in a drying furnace. It is explanatory drawing which showed the outline of the microwave drying method which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the examination result regarding the heating method using a microwave. It is explanatory drawing for demonstrating the examination result regarding the heating method using a microwave. It is explanatory drawing which showed the structure of the microwave drying apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment. It is explanatory drawing shown about the modification of the microwave irradiation member which concerns on the same embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(About manufacturing process of reduced iron)
Prior to describing the microwave drying apparatus and the microwave drying method according to the embodiment of the present invention, first, the manufacturing process of reduced iron will be described in detail with reference to FIG. Drawing 1 is an explanatory view for explaining the manufacturing process of reduced iron.

  First, iron oxide raw materials such as iron dust (iron oxide powder), iron ore, and powder ore, and reducing materials such as coal, coke, and fine carbon are stored in the hopper 1 and the like in advance. The iron oxide raw material and the reducing material are blended so as to have a preset blending ratio and charged into the pulverizer 2.

  A crusher 2 typified by a vibration mill such as a ball mill crushes the charged iron oxide raw material and the reducing material to a predetermined particle size while mixing them. The particle diameters of the iron oxide raw material and the reducing material after pulverization can be set to values suitable for a solid reduction furnace such as a rotary hearth furnace, a fluidized bed furnace, and a shaft furnace used for producing reduced iron. The mixture of the pulverized iron oxide raw material and the reducing material is conveyed to the kneader 3.

  The kneader 3 kneads the mixture pulverized to a predetermined particle size by the pulverizer 2. Moreover, the kneading machine 3 may perform a humidity control process for adding water to the mixture until the water content is suitable for a solid reduction furnace used for producing reduced iron. As an example of the kneading machine 3, for example, a mix muller can be cited. The mixture kneaded by the kneader 3 is conveyed to the molding machine 4.

  A molding machine 4 such as a pan pelletizer (dish granulator), a double roll compressor (briquette making machine), and an extrusion molding machine molds a mixture containing an iron oxide raw material and a reducing material, and agglomerates such as pellets. It is a chemical. Here, the agglomerated material refers to pellets, briquettes, extruded products that have been cut by extrusion molding, and granular materials / agglomerated materials such as mass-adjusted agglomerated materials. When the molding machine 4 is dried and heat-reduced, which will be described later, for example, when charged into the melting furnace 7 in the hot state, the above mixture is adjusted so as to have a size larger than the particle size so as not to be scattered by the rising gas flow in the furnace. Agglomerates. The produced agglomerated material is charged into the drying furnace 5.

  The drying furnace 5 dries the agglomerated material and has a moisture content suitable for the heating and reducing process described later (in other words, a moisture content suitable for each solid reduction furnace used for producing reduced iron: for example, 1% And so on. The agglomerated product having a predetermined moisture content is conveyed to a solid reduction furnace 6 to be described later.

  For example, the solid reduction furnace 6 such as a rotary hearth furnace (RHF), a fluidized bed furnace, a shaft furnace, etc., heats the agglomerate charged in a heating atmosphere such as an LNG burner or a COG burner. Reduce to iron reduced. The solid reduction furnace heats the agglomerate to, for example, about 1000 to 1300 ° C. to reduce the agglomerate and produce reduced iron. The manufactured reduced iron is conveyed to the melting furnace 7. In the melting furnace 7, the reduced iron produced in the solid reduction furnace 6 is melted to produce hot metal. The produced hot metal is processed into various steel products through a desulfurization / decarburization process, a secondary refining process, a continuous casting process, a rolling process, and the like.

(Outline of drying method using microwaves)
In the manufacturing process of reduced iron as described above, the drying furnace 5 is usually a tunnel-shaped furnace that dries the agglomerated material using hot air. Inside the drying furnace 5, normally, agglomerates such as briquettes are charged until the height reaches, for example, about 250 mm, and the inside of the furnace is conveyed by a mesh-like metal conveyor. Each agglomerated material to be conveyed has various sizes depending on the type of the reduction furnace or melting furnace, for example, a roughly spherical shape of about 10φ to 20φ, or 30φ to 50φ × thickness of about 25 mm. The load is about 300 kg / m ^{2 on} the mesh conveyor by being stacked up to about 250 mm in height. In the course of this conveyance, the moisture in the agglomerated material is removed by hot air, and the moisture content of the agglomerated material is controlled to a desired value. In addition, as described above, in order to prevent ignition of coal components contained in the agglomerated material, there is a restriction that the hot air used is about 200 ° C. or less.

  However, as a result of investigating the remaining state of moisture in the drying furnace by the present inventors, as schematically shown in FIG. 2, in the drying with hot air from above, the upper layer part of the agglomerate layer is dried. In the lower layer portion (portion close to the mesh conveyor), it was revealed that the residual amount of water is large, and the agglomerated material in the lower layer portion is often poorly dried. Due to such factors, the yield of the average drying rate of the agglomerated material decreases, and the drying time must be lengthened to increase the degree of drying.

  Therefore, the present inventors have intensively studied a method for selectively heating the lower layer portion of the agglomerate layer. For example, the following are the events that have become a concern in this study.

In other words, the floor surface of the drying furnace is a mesh-like conveyor using metal, so if microwaves are simply irradiated from below the conveyor, the irradiated microwaves are reflected by the conveyor and agglomerated. The chemical cannot be heated. It is also conceivable to change the material of the conveyor to a material that absorbs less microwaves, such as Teflon (registered trademark) or nylon, but such a material is more expensive than a metal mesh belt, The cost is high and the load of about 300 kg / m ² cannot be withstood. In addition, even when microwaves are irradiated from above, the agglomerate previously located in the lower layer may be heated by inverting the agglomerate layer in the drying furnace. However, if such an upside down is carried out, the agglomerated product may be crushed by colliding with each other, and the agglomerated product may be pulverized.

  Therefore, in order to sufficiently dry the agglomerated material under the condition that the material to be dried such as agglomerated material is moving in the furnace (that is, the material to be dried is not stationary). In addition, it is necessary to study a method that can efficiently irradiate the lower part of the agglomerate with high-power microwave of kW class, for example, while maintaining the wear resistance of the microwave irradiation member. It was.

  As a result, as schematically shown in FIG. 3, the agglomerate located in the lower layer by microwave heating is supplied to the lower layer part of the agglomerate layer without passing through the mesh conveyor. The inventors have conceived four types of methods capable of selectively heating the above.

  By using the drying method schematically shown in FIG. 3, the drying progress of the lower layer portion of the agglomerated layer is improved, the average drying rate of the agglomerated material is improved, and the drying time is shortened. As a result, productivity of the drying process can be improved.

  Prior to describing the microwave drying apparatus and the microwave drying method according to the embodiment of the present invention, various examination results on the method for drying an agglomerate using microwave heating by the present inventors will be described with reference to FIGS. This will be specifically described with reference to FIG.

<Examination of the range covered by microwave heating>
The present inventors conducted the following experiment in order to examine the range covered by microwave heating. FIG. 4 schematically shows an experimental apparatus for verifying the range covered by microwave heating when the agglomerate (briquette) is irradiated with microwaves from above.

  As shown in FIG. 4, the present inventors laminated an undried briquette (used in actual operation) of about 40φ × 20 mm on a metal container and placed it in the chamber. At this time, a thermocouple is inserted into a briquette located at a substantially central portion of the metal container, and between each layer (for example, between layer A and layer B, between layer B and layer C in the lower diagram of FIG. 4). ... etc.) was also equipped with a thermocouple to monitor the temperature rise. In addition, a 3.0 kW microwave oscillator capable of radiating a 2.45 GHz microwave, a power monitor capable of measuring the incident microwave output and reflected microwave output to the chamber, and reducing the reflected microwave For this purpose, a microwave output from the automatic aligner was irradiated from above the chamber through the waveguide. In this experiment, the microwave incident power was 600 W, and the microwave irradiation time was 60 seconds.

  As a result, in the thermocouple inserted in the briquette located in the layer A shown in the lower diagram of FIG. 4 and the thermocouple inserted between the layers A and B, a clear temperature rise was confirmed, and the briquette located in the layer B was confirmed. However, although it was not as high as the briquette located in the layer A, an increase in temperature was confirmed. However, in the briquettes located below the layer C, no temperature increase could be confirmed. This experimental result indicates that when microwaves are irradiated from above the agglomerated material, the range of heating by microwaves is at most from the outermost layer to the second layer.

By the way, the microwave energy P _abs per unit volume absorbed by the substance is expressed as the following Expression 11. As can be seen by referring to Equation 11 below, the microwave energy P _abs per unit volume absorbed by the substance to be heated (substance to be heated) depends on the conductivity, dielectric constant and permeability of the substance to be heated. You can see that Therefore, it can be said that P _abs represented by the following formula 11 is an amount related to the microwave absorption efficiency of the heated material.

Here, in Equation 11 above,
σ: Conductivity of heated material [S / m]
f: Microwave frequency [Hz]
ε ₀ : dielectric constant in vacuum [F / m]
ε ″: Imaginary part of relative permittivity of heated material μ ₀ : Permeability in vacuum [H / m]
μ ”: Imaginary part of relative permeability of heated material E: Electric field strength formed by microwave [V / m]
H: intensity of magnetic field formed by microwave [A / m]
π: Pi ratio.

  The values of the imaginary part ε ″ of the relative dielectric constant are collectively shown below for the iron oxide and carbon material (reducing material) that are the raw materials of the agglomerated material and the refractory furnace materials that are generally used.

Imaginary part of dielectric constant ε ”
Alumina, which is a typical refractory furnace material: 0.004 to 0.01
・ Powdered carbon powder: 10-50
・ Iron oxide: 0.1-10

  As is clear from the above, the iron oxide and carbon material used as the raw material for the agglomerate have a large value of the imaginary part ε ″ of the relative dielectric constant relative to the refractory furnace material generally used in a drying furnace or the like, The oxide and carbon material (reducing material) can absorb more microwave energy, and the value of alumina, which is a typical refractory furnace material, compared to the values of iron oxide and carbon powder, The value is about 1/1000, and it can be seen that the refractory furnace material does not absorb much microwave energy, so when the microwave is irradiated in the furnace in which the agglomerates are inserted, There is little energy supply to the furnace wall etc. which are coat | covered with the furnace material, and it becomes possible to raise only the temperature of the agglomerate which is a raw material efficiently, suppressing the raise in furnace temperature.

  However, in the experimental situation where the microwave as shown in FIG. 4 is irradiated to the free space in the furnace due to the characteristics as described above, the microwave irradiated from above is agglomerated in the upper layer region. It is considered that the microwave does not penetrate into the lower layer portion that needs to be supplied with heat to promote drying and is absorbed by the chemicals very well. Therefore, the present inventors, as in the prior art, heat the agglomerate located in the lower layer part when microwaves are irradiated from the furnace ceiling, side walls, or furnace bottom toward the space in the furnace. Judged that it is not possible.

  By the way, when the microwave is absorbed by the material due to dielectric loss, the energy of the microwave is converted into heat, and as a result, the material that has absorbed the microwave is heated. At this time, how much the microwave penetrates into the substance can be calculated by the following equation 12.

Here, in the above equation 12,
δ: microwave penetration depth [cm]
λ: wavelength of microwave in free space [cm]
ε ': relative permittivity of the substance (real part)
tan δ: the dielectric loss tangent of the substance.
Further, tan δ can be calculated by (ε _r ′ / ε _r ″) using the dielectric constant ε _r ′ and the dielectric loss coefficient ε _r ″ of the substance.

As a result of further experiments by the present inventors, the briquette is a lump of 30φ to 50φ × thickness 25 mm, and there is a gap between each briquette, and in the briquette being transported, the gap between each briquette Since the state changes, the microwave heating range is expanded, and the range up to 10 times the penetration depth δ obtained by Equation 12 is an effective heating range (hereinafter also referred to as δ _eff ). It became clear. When the penetration depth δ is calculated from the physical property values of the briquette, the magnitude is about 1 cm, so the effective heating range δ _eff by microwave heating is about 10 cm. Therefore, it was also clarified that microwave irradiation from the side face cannot heat the entire lower layer of the drying furnace having a width of about 2 to 2.5 m and a transport distance of about 20 to 30 m used in the operation.

  Therefore, as a result of further studies based on the knowledge obtained by the experiments as described above, the present inventors have come up with a microwave irradiation method capable of heating the entire lower layer portion of the drying furnace. The inventors have arrived at a microwave drying apparatus and a microwave drying method as described below.

  FIG. 5 is a graph schematically showing the relationship between the moisture content (%) after drying the agglomerated material and the crushing strength of the agglomerated material. In producing the agglomerated material, starch-based paste such as corn starch is used as a binder to achieve the required strength. The starch-based paste increases in strength as it is dried as illustrated in FIG. . Therefore, the crushing strength of the agglomerated product can be increased without changing the binder amount by improving the drying rate of the entire agglomerated product by the method described below. As a result, it is possible to reduce the amount of agglomerated material that cannot be used by being crushed during transportation, and the yield can be improved. Further, by improving the drying rate, it is possible to reduce the amount of the binder to be added in order to obtain the same strength, and thus it is possible to reduce the manufacturing cost.

(About the microwave used)
Next, a microwave used in the microwave drying apparatus and the microwave drying method according to the embodiment of the present invention will be briefly described.

  The microwave generally refers to an electromagnetic wave having a wavelength of 1 mm to 1 m and a frequency of 300 MHz to 300 GHz. However, as noted in the method for heating an agglomerate according to the present embodiment, when microwaves are used as heating means (so-called microwave heating is performed), microwaves are so-called ISM (Industry- Science-Medical) refers to an electromagnetic wave in a frequency band belonging to the band.

  In the embodiment of the present invention described below, there is no particular limitation as long as the electromagnetic wave has a frequency belonging to the IMS band. For example, a 2.45 GHz band (2.40 GHz to 2.50 GHz), a 5.8 GHz band (5. 725 GHz to 5.875 GHz) and frequencies belonging to the 24 GHz band (24.0 GHz to 24.25 GHz) can be selected as appropriate. However, since the penetration of microwaves into the object to be heated is proportional to the wavelength of the microwaves as represented by the above equation 12, the penetration depth δ in the 2.45 GHz band is one for the microwaves in the ISM band. The raw material briquette can be heated over the entire number of coaxial antennas or waveguides and the entire width of the drying furnace. In addition, 2.45 GHz is widely used for microwave ovens and other microwave heating applications, and the device is inexpensive, and it is possible to radiate high power up to several tens of kW with one oscillator. Also, the equipment cost of the present invention that requires a large output of kW class can be introduced at a lower cost than the other two frequency devices. For this reason, the ISM band microwave device used in the present invention is preferably capable of oscillating 2.45 GHz microwave.

(First embodiment)
Subsequently, the microwave drying apparatus and the microwave drying method according to the first embodiment of the present invention will be described in detail with reference to FIGS.

<About the configuration of the microwave dryer>
First, the configuration of the microwave drying apparatus according to the present embodiment will be described in detail with reference to FIG. FIG. 6 is an explanatory diagram for explaining the configuration of the microwave drying apparatus according to the present embodiment.

  The microwave drying apparatus 10 according to the present embodiment blows hot air from above the raw material and passes the hot air from the upper side to the lower side of the raw material in the process of conveying the powder or small block raw material by a mesh conveyor. Thus, it is used for a hot-air type tunnel drying furnace that reduces moisture contained in the raw material.

  As shown in FIG. 6, the microwave drying apparatus 10 according to the present embodiment mainly includes a microwave oscillator 101, a circulator 103, an automatic matching unit 107, and a microwave irradiation member 109. Are connected by a waveguide 111. In FIG. 6, a support mechanism for supporting each member such as the microwave guiding member 109 and the waveguide 111 is not shown.

  The microwave oscillator 101 is a device that oscillates a microwave having a frequency belonging to, for example, an ISM band. The microwave oscillator 101 is preferably a device capable of oscillating microwaves having a kW class output. For example, a microwave having a frequency belonging to a 2.45 GHz band is output to the circulator 103 described later by the microwave oscillator 101. As this microwave oscillator 101, a publicly known one can be appropriately selected and used.

  The circulator 103 performs a microwave progress control using, for example, a magnet, so that the microwave input to the circulator 103 is changed from the incident wave output from the microwave oscillator 101 to the automatic matching unit 107 described later. It separates into the reflected wave that has returned. The circulator 103 guides the separated incident microwave toward the automatic matching unit 107 described later, and guides the reflected microwave toward the isolator 105 side. Thereby, the reflected microwave can be absorbed by a dummy load (for example, water) provided in the isolator 105 and can be prevented from returning to the microwave oscillator 101 side. By providing such a circulator 103, the microwave drying apparatus 10 according to the present embodiment can output a stable microwave. As this circulator 103, a known circulator can be appropriately selected and used.

  The automatic matching unit 107 reduces the reflected wave from the load side by matching the impedance on the incident side with the impedance on the load side (that is, the raw material layer side made of agglomerated material), and the reflected wave is almost zero. It is a device. The automatic matching unit 107 measures the phase and intensity of the reflected electric field and automatically performs impedance matching, thereby realizing the reduction of the reflected wave as described above.

  The object to be dried by the microwave drying apparatus 10 according to the present embodiment is a small lump raw material such as an agglomerated material being conveyed in the drying furnace 5. Therefore, the contact state between the moving small lump material and the microwave irradiation member 109 to be described later constantly changes, and the impedance on the load side changes, so that the microwave irradiation efficiency changes. By providing an automatic matching unit 107 and realizing automatic matching processing according to the impedance on the load side, it is possible to stably and efficiently irradiate the raw material layer with microwave energy from the microwave irradiation member 109 described later. It becomes.

  The microwave irradiation member 109 is a member that irradiates the microwave to the lower layer portion of the raw material layer in order to selectively heat the lower layer portion of the raw material layer made of agglomerated material in the hot air drying furnace 5. The configuration of the microwave irradiation member 109 will be described in detail later.

  The waveguide 111 is a tube that guides a microwave to a desired location. The shape of the waveguide 111 may be appropriately determined in consideration of the waveguide characteristics of the microwave, etc., and the waveguide 111 itself also depends on the frequency and output intensity of the microwave to be used. A well-known thing can be selected suitably.

<Configuration of microwave irradiation member>
Then, the structure of the microwave irradiation member which concerns on this embodiment is demonstrated in detail, referring FIGS. 7-12. 7-12 is explanatory drawing shown about the microwave irradiation member which concerns on this embodiment.

  As illustrated in FIG. 7, in this embodiment, the waveguide 111 that is a hollow metal tube is used as the microwave irradiation member 109 and is formed of an agglomerated material that is conveyed in the depth direction of the paper in FIG. 7. A waveguide 111 is inserted into the raw material layer from above the drying furnace 5. In FIG. 7, only one of the waveguides 111 inserted into the drying furnace 5 is shown for easy understanding, but the drying furnace 5 includes a plurality of waveguides. 111 is inserted from above. The waveguide 111 is inserted so as to be substantially perpendicular to the bottom surface of the drying furnace 5 formed of a mesh conveyor.

  The cross-sectional shape of the waveguide 111 used as the microwave irradiation member 109 (cross-sectional shape in a direction parallel to the conveying direction of the raw material layer) and the size of the cross-section guide microwaves having a desired frequency and intensity. For example, the cross-sectional shape is preferably rectangular (rectangular waveguide) or circular (circular waveguide).

  In particular, in a rectangular waveguide, when the wavelength in a free space of a microwave that can be transmitted is λ and the length of the long side of the rectangular waveguide is a, the relationship expressed by the following Expression 13 is satisfied. For example, transmission in the TE10 mode, which is a fundamental wave of microwaves, is possible. At this time, the short side b of the rectangular waveguide has no restriction on microwave transmission, and the short side b is reduced under the condition that the electric field strength in the waveguide does not exceed the dielectric breakdown voltage of the internal medium (internal gas). can do. Therefore, in the rectangular waveguide, it is possible to make the width of the waveguide corresponding to the short side installed substantially perpendicular to the conveying direction when inserted into the drying furnace sufficiently smaller than that of the cylindrical waveguide. . That is, in the rectangular waveguide, the influence on the conveyance of briquettes due to the waveguide insertion can be reduced. In this embodiment, it is preferable to use the rectangular waveguide rather than the cylindrical waveguide. .

    λ / 2 <a <λ (Formula 13)

  Since the agglomerated material is moving in the transport direction inside the drying furnace 5, the waveguide 111 is not resistant to the agglomerated material flow (i.e., the agglomerated material flow is not corrected). Inserted in the raw material layer (so that the area with respect to it is reduced). For example, when the cross-sectional shape of the waveguide 111 is rectangular, the long side of the rectangular shape is substantially parallel to the transport direction, and the short side of the rectangular shape is substantially orthogonal to the transport direction. Inserted into the raw material layer. Moreover, in order to reduce the conveyance resistance of the agglomerated material, the waveguide 111 may be inclined so that the lower end faces the downstream side in the conveyance direction of the raw material layer.

  In addition, the waveguide 111 takes into consideration the load per unit surface that is received from the agglomerated material being transferred, so that the cross-sectional shape has a strength that prevents buckling deformation due to the load. Manufactured using various metals such as aluminum (Al), nonmagnetic austenitic stainless steel (SUS), and alloys containing these. Further, when the waveguide 111 itself is fixed to the upper part (for example, the ceiling) of the place where the drying furnace 5 is installed, the waveguide itself receives a load from the agglomerated material and buckles and deforms. However, it is preferable to have strength that does not bend in the transport direction.

  The inside of the raw material layer of the drying furnace 5 has a temperature of about 80 ° C. or higher at the lower layer portion and is in a high temperature and high humidity state having a humidity close to about 100%, and the agglomerated material is moving under such conditions. . Therefore, in order to prevent the occurrence of arcing due to moisture entering the inside of the waveguide 111 and to prevent the intrusion of dust into the inside of the waveguide 111, dry air, dry nitrogen, dry argon, etc. It is preferable to introduce dustproof gas into the hollow waveguide so that a positive pressure is applied to the waveguide 111.

Further, a ceramic cover 113 is provided at the tip of the waveguide 111 used as the microwave irradiation member 109, and microwaves are radiated from the periphery of the ceramic cover, thereby widening the heating range around the waveguide. It is preferable to do so.
Here, as shown in FIG. 7, the shape of the ceramic cover 113 is a rectangular parallelepiped when the cross-sectional shape of the waveguide 109 is rectangular, and is cylindrical when the cross-sectional shape of the waveguide 109 is circular. It is preferable to do.

The ceramic cover 113 is made of an inorganic material ceramic that has a low absorption of microwaves as a heating source, can be used even in a high temperature and high humidity state, and has strength, wear resistance, and workability that can withstand contact with an agglomerated material. It is formed. The inorganic material ceramic used for the ceramic cover 113 preferably has a dielectric loss coefficient ε _r ″ related to microwave absorption characteristics of less than 0.02. The dielectric loss coefficient ε _r ″ is less than 0.02. This makes it possible to suppress self-heating of the inorganic material ceramics due to microwave absorption.

Examples of such inorganic material ceramics include alumina (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), sialon (SiAlON, chemical formula: Si ₃ N ₄ · Al ₂ O ₃ ), aluminum nitride (AlN), Examples include boron nitride (BN). The ceramic cover 113 may be manufactured by using these inorganic material ceramics alone, or the ceramic cover 113 may be manufactured by mixing these inorganic material ceramics.

  In this embodiment, the waveguide 111 is inserted from above the drying furnace 5 to such a depth that the heating range of the waveguide 111 reaches the lowest layer of the raw material layer. By inserting the waveguide 111 into the raw material layer in this way, it is possible to selectively heat the agglomerate located in the lower layer portion of the raw material layer by the microwave energy irradiated from the tip of the waveguide 111. It becomes.

  That is, in this embodiment, the microwave is radiated inside the raw material layer (lower layer part), so that most of the radiated microwave energy is absorbed by the raw material around the radiation point and used for heating the raw material. It is a heating method with high energy efficiency of heating.

At this time, if the separation distance between the tip of the waveguide 111 and the mesh conveyor becomes too small, microwave radiation from the tip of the waveguide cannot be performed. Therefore, as shown in FIG. 8 for example, it is preferable that the distance L ₁ between the waveguide tip and reticulated conveyor, more than a quarter of the wavelength of the microwaves λ utilized as a heat source .

Result of studies by the present inventors, by setting the distance L ₁ lambda / 4 or more, the proportion of the microwave radiated from the waveguide tip can be 70% excess, from reticulated conveyor It has been found that the proportion of reflected microwaves can be less than 30%. When the ratio of the reflected microwaves is large, the oscillation wavelength of the microwaves is disturbed due to interference, so that the operation of the automatic matching unit 107 may become unstable. On the other hand, if the ratio of the reflected microwave is about 30%, the reflected microwave can be made almost zero by phase matching using the automatic matching unit 107. In addition, when the ratio of reflected microwaves is large, microwaves are radiated by pushing back a large reflected power, which may cause abnormal heating in parts that are not normally heated, such as the joints of waveguides. There is a possibility that the operational stability of the microwave drying apparatus 10 may be reduced.

Even when the ceramic cover 113 is provided at the tip of the waveguide 111, the separation distance L1 is preferably λ / 4 or more. Furthermore, if the tip of the waveguide 111 providing a ceramic cover 113, as shown in FIG. 9, the distance L ₂ between the tip and the mesh-like conveyor ceramic cover 113, the degree of agglomerate does not enter It is preferable to set it as the magnitude | size (For example, magnitude | size about the average height of an agglomerate).

  In this embodiment, when a plurality of waveguides 111 that are the microwave irradiation members 109 are arranged in the width direction of the drying furnace 5, the agglomerated material is removed from the furnace of the drying furnace 5 by the plurality of arranged waveguides 111. In order to heat uniformly in the width direction, at least two of the plurality of waveguides 111 are arranged at different positions in the furnace width direction of the drying furnace.

  In addition, in order to prevent the arranged plurality of waveguides 111 from resisting the flow of the agglomerated material, for example, as shown in FIG. 10, in the projection view shown in FIG. The conveyance direction position of the waveguide should not be the same. That is, in the view of the drying furnace 5 shown in FIG. 10, the width direction of the drying furnace 5 is divided into five regions A to E for convenience, the conveying direction of the raw material layer is the X direction, and the drying furnace. The width direction is defined as the Y direction. In this case, in the present embodiment, the waveguides 111 are distributed and arranged so that the X-direction positions of the waveguides 111 belonging to adjacent regions (for example, the region A and the region B) are not the same. .

  Further, for example, as shown in the projection view shown in FIG. 11, when the drying furnace 5 is viewed in the conveyance direction, the range heated by each waveguide 111 (heating range) is the width direction of the drying furnace 5. It is preferable to arrange the waveguides 111 at intervals so as to cover substantially the whole. At this time, it is preferable to determine the arrangement interval of the waveguides 111 so that the heating ranges of the respective waveguides 111 overlap each other. In other words, the maximum width of the heating range by the single waveguide 111 is L, the width of the drying furnace 5 is W, and the number of waveguides in the width direction of the drying furnace 5 in the projection view shown in FIG. When N is N, it is preferable to determine the maximum number of waveguides in the width direction of the drying furnace 5 so as to satisfy L × N ≧ W.

Specifically, when 10 times the microwave penetration depth δ shown in Equation 12 is considered as the effective heating range δ _eff , the maximum width L of the heating range by the single waveguide 111 is 2 × [delta] _eff becomes, so that the width direction distance between the respective waveguides adjacent in the width direction is less than L, and preferably to determine the arrangement interval in the width direction of the waveguide 111. By arranging the waveguides 111 at such intervals, the agglomerated material for the entire width of the drying furnace can be heated without unevenness.

  When the interval between the plurality of waveguides is larger than the above L, the heating range by the microwave does not reach the entire width of the furnace, and uneven heating of the agglomerated raw material can be performed in the width direction of the furnace. It is not preferable to lead to. However, since the drying of the raw material is improved in the portion heated by the microwave, the drying as the average value of the entire raw material is improved according to the number of inserted waveguides.

  Also, if the efficiency of hot air drying in the furnace width direction is different as a characteristic of the drying furnace, a waveguide is inserted only in the part where drying efficiency is inferior and drying of the agglomerated raw material is delayed, and microwave irradiation is performed It is also effective to do.

  Further, how to arrange each waveguide 111 is not particularly limited. For example, based on knowledge about the uneven state of residual moisture in the drying furnace 5, the unevenness can be eliminated. What is necessary is just to determine the arrangement position of a waveguide. Therefore, for example, in FIG. 11, a plurality of waveguides 111 may be disposed in the same region.

  For example, as shown in FIG. 12, a tapered portion 115 whose width becomes narrower toward the upstream side in the transport direction may be provided on the upstream side in the transport direction of the short side of the waveguide 111. By providing such a tapered portion 115, it is possible to further reduce the agglomerated material transport resistance by the waveguide 111. Further, the tapered portion 115 may be provided not only on the upstream side in the transport direction of the short side of the waveguide 111 but also on the downstream side in the transport direction.

  The microwave drying apparatus 10 and the microwave drying method according to the first embodiment of the present invention have been described in detail above with reference to FIGS.

<Modification of First Embodiment>
Next, a modification of the microwave irradiation member according to the first embodiment of the present invention will be described with reference to FIGS. 13A to 18B. FIG. 13A to FIG. 18B are explanatory views for explaining a modification of the microwave irradiation member according to the first embodiment of the present invention.

[Microwave irradiation from the side of the waveguide]
The waveguide 111 in the above description has an opening at the end (that is, the bottom surface of the waveguide 111 in FIG. 7 or the like) facing the mesh conveyor when the waveguide 111 is inserted into the raw material layer. The microwave was irradiated from this bottom surface. When an opening is provided in the bottom surface of the waveguide 111, the waveguide 111 is formed in order to prevent the agglomerates and the like from entering the waveguide 111 while expanding the heating range around the waveguide 111. It was preferable to provide a ceramic cover 113 made of an inorganic material ceramic at the tip of the ceramic.

  Since such inorganic material ceramics has a hardness that can withstand the friction of the agglomerated material, it takes time to process the ceramic cover 113. Therefore, for example, as shown in FIG. 12, when performing shape processing into a tapered shape or the like for reducing resistance so as not to hinder the transportation of the agglomerated material, the manufacturing costs of the waveguide and the ceramic cover increase. End up.

  Therefore, in this modification, not the bottom surface of the waveguide 111 but the side surface of the waveguide 111 (more specifically, when the waveguide 111 is inserted into the material layer, it becomes parallel to the material layer transport direction. A method of forming a notch on the side surface and irradiating microwaves from the side surface will be described.

  FIG. 13A schematically shows the distal end portion of the waveguide 111 according to this modification. In the waveguide 111 shown in FIG. 13A, a tapered portion 115 is provided on the upstream side in the transport direction of the raw material layer. Further, as shown in the diagram on the left side of FIG. 13A, when the waveguide 111 is inserted into the raw material layer, the side surface that is parallel to the raw material layer transport direction of the drying furnace (that is, parallel to the paper surface of FIG. 13A). On the side surface, a notch 151 is formed.

  By forming such a notch 151 on the side surface of the waveguide 111, the notch 151 becomes a microwave radiation window, and the microwave is irradiated from the notch 151 to the raw material layer. Become.

  In order to prevent the agglomerate from entering the inside of the waveguide 111 from the notch 151, as shown in the diagram on the right side of FIG. 13A, a plate-like ceramic formed of the inorganic material ceramic as described above It is preferable to cover the notch 151 with the cover 153.

  In the drying furnace 5, since the agglomerated material constituting the raw material layer is dried by supplying hot air from above the raw material layer, more moisture remains as it goes to the lower layer of the laminated agglomerated material. Become. Therefore, in order to further improve the drying effect by microwave irradiation, it is preferable to irradiate the raw material layer with microwaves as much as possible, and the cutout portion 151 is guided near the lower layer portion as shown in FIG. 13B. It is desirable to provide up to the tip of the tube. Further, since the metal portion 111a on the bottom surface of the waveguide 111 is a microwave reflector, the distribution of the emitted microwaves is changed by changing the width A of the metal portion 111a on the bottom surface shown in FIG. 13C. Will be.

  More specifically, by reducing the width A of the bottom surface portion of the waveguide 111 as shown in FIG. 13D, compared to the case shown in FIG. It is also possible to do so. However, since the width of the bottom metal portion 111a affects the impedance of the microwave radiating portion, it is desirable that the width of the metal portion 111a be an appropriate width so that the reflection of the microwave to the waveguide does not become so large. It is desirable to design the width A so that the amount of reflected microwaves is reduced according to the electromagnetic property values (dielectric constant, magnetic permeability, conductivity, etc.) of the chemicalizing raw material, the size of the agglomerated raw material, the packing density, etc. .

  Note that a member made of a material that does not absorb microwaves may be present on the bottom surface of the waveguide 111. Therefore, as shown in FIGS. 13C and 13D, a ceramic cover 153a may be provided for dust prevention. Further, as shown in FIG. 13D, when the width A of the metal portion 111a on the bottom surface is narrowed, it is preferable to provide a ceramic cover 153a on the bottom surface of the waveguide 111.

  Further, as shown in the schematic cross-sectional view taken along the line BB shown in FIG. 13E, the ceramic cover 153 is formed in the notch 151 with a jig using a known material that can be used even inside the drying furnace. Fix it.

  The width W of the cutout portion 151 in the raw material layer conveyance direction is not particularly limited, and may be determined as appropriate according to the size of the waveguide 111, the frequency of the microwave used, the output intensity, and the like. .

  Next, a method for inserting the waveguide 111 according to the present modification into the raw material layer will be described with reference to FIG. FIG. 14 is an explanatory view schematically showing a state in which the waveguide 111 according to this modification is inserted from above the drying furnace 5 when viewed from the side of the drying furnace 5. In FIG. 14, for convenience, the plate-like ceramic cover 153 is omitted.

  When the notch 151 is provided on the side surface of the waveguide 111, the radiation of the notch 151 close to the microwave oscillator 101 (that is, the upper end of the notch 151 in the height direction of the raw material layer). Strength increases. On the other hand, in the drying furnace 5, since the agglomerated material constituting the raw material layer is dried by supplying hot air from above the raw material layer, more moisture remains as it goes to the lower layer of the laminated agglomerated material. It will be. Therefore, in order to further improve the drying effect by the microwave irradiation, it is preferable to irradiate the raw material layer with the microwave as much as possible.

Therefore, in this modification, the thickness of the raw material layer to be heated by the microwave is represented by L, and the position of the upper end of the cutout portion 151 in the raw material layer height direction (that is, the mesh conveyor and the cutout portion 151 in FIG. When the separation distance from the upper end is expressed as L ₃ , it is preferable to insert the waveguide 111 so as to satisfy the relationship L ₃ ≦ L. By setting the thickness L of the raw material layer to be heated by the microwave to a thickness corresponding to the lowermost layer of the raw material layer, the lowermost layer of the raw material layer can be effectively heated by the microwave.

  The method for selecting the thickness L is not particularly limited, and may be appropriately selected based on knowledge obtained from past operation results.

Also, increasing the proportion of the microwave radiated from the cutout portion 151, and, in order to reduce the proportion of the reflected microwaves from the reticulated conveyor, the wavelength of the microwaves utilizing distance L _3, as a heat source ( It is preferable that the wavelength is equal to or more than a quarter of the wavelength (λ) in free space.

On the other hand, in order to prevent an agglomerate from entering between the distal end portion of the waveguide 111 and the mesh container, the separation distance between the distal end portion of the waveguide and the mesh container shown in FIG. L ₄ is preferably set to such a size that the agglomerated material does not enter (for example, the size of the average height of the agglomerated material).

The configuration of the waveguide 111 according to this modification has been described in detail above with reference to FIGS. 13A to 14.
The notch 151 may be formed only on one of the side surfaces parallel to the material layer transport direction of the drying furnace when the waveguide 111 is inserted into the material layer. It is preferable to form both. In addition to the side surface parallel to the material layer conveyance direction of the drying furnace, a notch 151 may be formed on the side surface of the waveguide 111 on the downstream side in the material layer conveyance direction.

[Method of disposing the waveguide in the material layer transport direction]
Next, with reference to FIGS. 15 to 17B, a method of arranging the waveguide according to this modification in the raw material layer transport direction will be described.

  The time t during which the agglomerated material transported inside the drying furnace 5 is heated by the microwave irradiated from one waveguide 111 according to this modification is the notch 151 of the waveguide 111. When the width in the raw material layer transport direction is W [mm] and the transport speed of the agglomerated material is V [mm / sec], it is approximately (W / V) seconds.

  On the other hand, when a microwave is guided using a waveguide, the width of the waveguide is guided in order to prevent a plurality of propagation modes from occurring inside the waveguide and to maintain the transmission efficiency of the microwave. It is often less than the microwave wavelength. For example, when a 2.45 GHz microwave is used, the maximum width of the waveguide in the conveyance direction is about 120 mm. Therefore, when the maximum width of one waveguide is about 120 mm, the time t is extremely short considering the transport speed of a normal mesh conveyor.

  In order to sufficiently dry the agglomerate with microwaves in such a short time, it is conceivable to use microwaves with high output intensity as one of the measures. However, the agglomerates that exist around the waveguide and are heated by microwaves are not necessarily heated uniformly because of differences in heating depending on the position of the agglomerates. In addition, when trying to obtain drying in a short time using a high-power microwave, some agglomerates may be overheated and the volatile components contained in the agglomerates may ignite. is there. Therefore, in order to sufficiently dry the agglomerate by microwave, the microwave is used so that the agglomerate does not overheat, and the microwave action time is lengthened to promote drying. It is important to plan.

  Therefore, in this modification, for example, as shown in FIG. 15, the waveguides 111 are arranged side by side in the material layer conveyance direction so that the heating range of the waveguide 111 is continuous in the material layer conveyance direction. . By adopting such a waveguide arrangement method, it is possible to lengthen the section where the microwave is irradiated, and in turn, it is possible to lengthen the action time of the microwave on the agglomerated material. Become.

  Here, the arrangement method of the waveguides 111 in the transport direction is not particularly limited as long as the heating ranges of the waveguides 111 adjacent to each other in the transport direction are continuous. 111 may be in contact with each other or may be separated from each other. When the adjacent waveguides 111 are arranged apart from each other, it is preferable to provide a cover or the like so that the agglomerated material is not clogged in the space between the adjacent waveguides 111.

  Further, FIG. 15 illustrates the case where two waveguides 111 are continuously arranged in the carrying direction, but three or more waveguides 111 may be arranged continuously in the carrying direction. Needless to say, it is good.

  When arranging the plurality of waveguides 111 in contact with each other, for example, as shown in FIG. 16A and FIG. 16B which is a schematic cross-sectional view taken along the line AA of FIG. The notch 151 may be provided continuously so as to extend over the wave tube 111. In this case, the thickness of the partition d shown in FIG. 16B can be reduced as long as the microwave can be guided.

  Note that the waveguide arrangement method as shown in FIG. 15 is not limited to the waveguide 111 according to the present modification, but also to the waveguide 111 according to the first reference embodiment illustrated in FIG. It goes without saying that it is also possible to apply.

  Moreover, in order to lengthen the action time of the microwave, for example, as shown in FIGS. 17A and 17B, the end of the waveguide is branched to widen the waveguide and the microwave is irradiated. The area may be increased. In this case, a known microwave branching technique such as providing a matching pin 155 and a branch plate 157 for impedance matching inside the waveguide 111 can be applied. In this case, since the microwave guided through one waveguide is guided to each of the two waveguides, the waveguide is guided while satisfying the condition that the width of the waveguide is less than the wavelength of the microwave. It becomes possible to lengthen the heating range of the tube 111. In addition, since the number of the waveguides 111 protruding above the drying furnace 5 can be reduced while expanding the microwave heating range, it is possible to save the space for the equipment.

[Vibration relaxation mechanism]
Next, with reference to FIGS. 18A and 18B, a technique for mitigating vibrations that occur in the waveguide 111 as the agglomerated material is conveyed will be described.

  In the microwave drying apparatus 10 according to the first embodiment of the present invention and the modification thereof, the agglomerated material is stacked on a mesh conveyor to form a raw material layer, and then conveyed from the upper part to the lower part of the raw material layer. Corresponding by inserting the waveguide 111 from above the drying furnace and irradiating the raw material layer lower layer with the microwave to the drying furnace that dries the agglomerate by passing hot air toward it. It is a device that promotes drying of the part.

  At this time, a stress that fluctuates with the transport of the agglomerated material acts on the waveguide 111 inserted from above the drying furnace 5. The stress acting on the waveguide fluctuates because the conveyance speed by the mesh conveyor is not constant but slightly fluctuates, and the density of the agglomerates is not strictly uniform, so it contacts the waveguide. It is conceivable that the state of the agglomerated material changes from moment to moment with the conveyance. When such a fluctuating stress acts on the waveguide 111, the waveguide 111 is vibrated in the direction in which the raw material layer is conveyed. When considering long-term use of the waveguide under such circumstances, there is a concern that such vibration may cause fatigue fracture of the waveguide.

  Therefore, in the microwave drying apparatus 10 according to the present modification, a vibration mitigation mechanism that mitigates vibrations generated along with the transportation of the agglomerated material is installed in the waveguide 111. Examples of such a vibration relaxation mechanism include the following two types of mechanisms.

  As a first vibration mitigating mechanism, a waveguide having a mechanism for mitigating vibration is provided in a portion of the waveguide 111 that guides the microwave generated by the microwave oscillator 101 as close as possible to the vibration generating portion. Is mentioned.

  As a waveguide including a mechanism for reducing vibration, for example, a waveguide having a slide mechanism that enables sliding in the central axis direction of the waveguide (hereinafter referred to as a slide waveguide), or a microwave. For example, a waveguide having a bellows portion formed of a metal material capable of being guided (more preferably, a metal material similar to the waveguide) (hereinafter referred to as a flexible waveguide).

  Since the slide waveguide has a slide mechanism, it can expand and contract in the central axis direction of the waveguide, so that vibration substantially parallel to the central axis direction of the waveguide can be mitigated. In addition, since the flexible waveguide has a metal bellows portion, it can be bent in a direction substantially orthogonal to the central axis direction of the waveguide. On the other hand, it is possible to mitigate vibrations in a direction substantially perpendicular to the direction.

  Further, as the second vibration relaxation mechanism, an elastic member may be provided on a part of the support that supports the waveguide 111 that is a microwave irradiation member. By providing an elastic member such as a spring mechanism or a rubber member in a part of the support, vibration generated in the waveguide 111 supported by the support can be reduced by the elastic member.

  By providing the vibration mitigating mechanism as described above, it is possible to mitigate vibrations that occur with the transportation of the agglomerated material, and it is possible to prevent the waveguide 111 from being fatigued.

  In FIG. 18A, a flexible waveguide 161 is installed as a first vibration relaxation mechanism with respect to the waveguide 111, and an elastic member made of, for example, a spring mechanism as a second vibration relaxation mechanism is formed on a part of the support 163. An example in which 165 is provided is shown.

  In the example shown in FIG. 18A, among the waveguides 111 extending from the microwave oscillation mechanism such as the microwave oscillator 101, the circulator 103, and the automatic matching unit 107, a part of the waveguide extending in the vertical direction is used. A flexible waveguide 161 is installed. As described above, the flexible waveguide 161 relieves vibration in a direction substantially orthogonal to the axial direction of the waveguide, and therefore is inserted into the drying furnace 5 as shown in FIG. 18A. Therefore, it is preferable to be installed in a part of the waveguide 111 provided in a substantially vertical direction.

  In FIG. 18A, an elastic member 165 including a spring mechanism is provided on a part of a support 163 that supports the waveguide 111 and extends in the horizontal direction. The spring mechanism is a mechanism that relieves stress by expanding and contracting the spring in the direction of the central axis of the spring.

  As shown in FIG. 18A, the ends of the microwave oscillation mechanism and the support 163 are fixed to a strong member such as a wall. In addition, by installing the flexible waveguide 161 and the elastic member 165 as described above, the waveguide 111 positioned downstream of the flexible waveguide 161 and ahead of the elastic member 165 is structurally separated. It is possible to move freely to some extent. In addition, it is preferable to provide an embedding material 167 for maintaining the hermeticity of the drying furnace 5 while allowing the waveguide 111 to move to some extent while inserting the waveguide 111 into the drying furnace 5. .

  FIG. 18B shows an example in which a slide waveguide 169 is installed instead of the flexible waveguide 161 shown in FIG. 18A. As described above, the slide waveguide 169 relaxes vibrations in the axial direction of the waveguide. Therefore, as shown in FIG. 18B, one of the waveguides 111 extending in the substantially horizontal direction. It is preferable to be installed in the section.

  18A and 18B illustrate the case where one of the flexible waveguide 161 and the slide waveguide 169 is provided for one waveguide 111, the flexible waveguide 161 and the slide are illustrated. A waveguide 169 may be used in combination. 18A and 18B illustrate the case where one flexible waveguide 161, elastic member 165, and slide waveguide 169 are used, a plurality of these members are provided for one waveguide 111. May be installed.

  18A and 18B illustrate the case where the flexible waveguide 161 or the slide waveguide 169 and the elastic member 165 are used together, but depending on the transport speed of the agglomerated material, the elastic member Instead of using 165, only the flexible waveguide 161 or the slide waveguide 169 may be provided.

  18A and 18B, the mechanism for structurally separating the waveguide subjected to fluctuating stress has been described. However, the entire waveguide 111 including the microwave oscillation mechanism is made movable so that vibration can be generated. It may be possible to relax.

  In the above, the modification of the microwave irradiation member which concerns on the 1st Embodiment of this invention was demonstrated, referring FIG. 13A-FIG. 18B.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Microwave dryer 101 Microwave oscillator 103 Circulator 105 Isolator 107 Automatic aligner 109 Microwave irradiation member 111 Waveguide 113,153 Ceramics cover 115 Tapered part 151 Notch part 155 Alignment pin 157 Branch plate 161 Flexible waveguide 163 Support 165 Elastic member 167 Embedding material 169 Slide waveguide

Claims (19)

A microwave drying apparatus installed in a hot-air drying furnace that reduces moisture contained in the material to be dried by transporting the material to be dried by hot air when the material is conveyed by a conveyor. And
A microwave oscillator that oscillates a microwave used to dry the object to be dried;
A heating range in which the microwave can be heated is inserted to a depth including the lowermost layer of the object to be dried, with respect to the inside of the object layer to be dried that is conveyed, A plurality of waveguides for irradiating the microwave;
With
At least two of the plurality of waveguides are disposed at different positions in the furnace width direction of the drying furnace,
The microwave drying apparatus according to claim 1, wherein positions of the waveguides adjacent to each other in the furnace width direction are different from each other in the transport direction. The plurality of waveguides are arranged in the furnace width direction at intervals such that the heating range of each of the waveguides covers the entire furnace width direction of the drying furnace as the whole of the plurality of waveguides. The microwave drying apparatus according to claim 1, wherein: The plurality of waveguides have openings at opposite ends to the conveyor when the waveguides are inserted into the material layer to be dried. Microwave drying equipment. The plurality of waveguides are formed on the layer to be dried so that a separation distance between a front end portion of the waveguide and the conveyor is equal to or more than a quarter of a wavelength of the microwave in free space. The microwave drying apparatus according to claim 3, wherein the microwave drying apparatus is inserted. The plurality of waveguides are provided with a notch on at least a side surface that is parallel to the drying object layer transport direction of the drying furnace when the waveguide is inserted into the drying object layer. The microwave drying apparatus according to claim 1, wherein the microwave is irradiated from the cutout portion. The plurality of waveguides are inserted into the material layer to be dried so that an upper end of the cutout portion in a height direction of the material layer to be dried is equal to or less than a height of the material layer to be dried. The microwave drying apparatus according to claim 5. In the plurality of waveguides, a distance between an upper end in a height direction of the layer to be dried of the notch and the conveyor is equal to or more than a quarter of the wavelength of the microwave in free space. The microwave drying apparatus according to claim 5, wherein the microwave drying apparatus is inserted into the layer to be dried. The waveguide has a rectangular cross-sectional shape perpendicular to the traveling direction of the microwave,
The short side of the rectangular cut surface is orthogonal to the transport direction, and the long side of the rectangular cut surface is parallel to the transport direction. The microwave drying apparatus of any one of Claims. A ceramics cover formed of an inorganic material ceramic having a dielectric loss coefficient of less than 0.02 is provided at the tip or notch of the waveguide,
The microwave drying apparatus according to any one of claims 1 to 8, wherein the microwave is irradiated from an outer periphery of the ceramic cover. The microwave drying according to any one of claims 1 to 9, wherein a vibration mitigation mechanism for mitigating vibration generated along with the conveyance of the object to be dried is provided for the waveguide. apparatus. As the vibration relaxation mechanism, a slide waveguide having a slide mechanism that enables axial sliding between the waveguide and the microwave oscillator, or a flexible waveguide having a metal bellows portion. The microwave drying apparatus according to claim 10, wherein at least one of the tubes is disposed. The microwave drying apparatus according to claim 10 or 11, wherein an elastic member is provided as a part of a support that supports the waveguide as the vibration relaxation mechanism. The microwave drying apparatus according to any one of claims 1 to 12, wherein the waveguides are arranged side by side in the transport direction so that the heating range is continuous in the transport direction. The microwave drying apparatus according to claim 1, wherein the waveguide is branched so that the heating range is continuous in the transport direction. The dust-proof gas is introduced into the inside of the waveguide, and a positive pressure is applied to the inside of the waveguide. The microwave drying apparatus as described. The taper portion in which an area of a cross section perpendicular to the transport direction decreases toward an upstream side in the transport direction is provided at an end portion of the waveguide on the upstream side in the transport direction. The microwave drying apparatus according to any one of 15. Between the microwave oscillator and the plurality of waveguides, impedance of the microwave oscillated from the microwave oscillator, and the microwave reflected in the drying furnace and heading toward the microwave oscillator The microwave drying apparatus according to any one of claims 1 to 16, further comprising an automatic matching unit that performs matching with the impedance of the microwave. The microwave drying apparatus according to claim 9, wherein the inorganic material ceramics is selected from the group consisting of alumina, silicon nitride, sialon, aluminum nitride, boron nitride, and a mixture thereof. This is a microwave drying method implemented in a hot-air drying furnace that reduces moisture contained in the material to be dried by conveying the material to be dried with hot air when the material to be dried is conveyed by a conveyor. And
Oscillates a microwave used to dry the object to be dried;
From each of the plurality of waveguides in which the heating range in which the microwave can be heated is inserted to the depth including the lowermost layer of the object to be dried, with respect to the inside of the object layer to be dried that is transported Irradiating the microwave to the layer to be dried;
At least two of the plurality of waveguides are disposed at different positions in the furnace width direction of the drying furnace,
The microwave drying method, wherein positions of the waveguides adjacent in the furnace width direction are different from each other.

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