JPH0443399B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to the heating or melting of a processed material using microwaves, and more specifically, to the heating or melting of a processed material using microwaves, and more specifically, to the heating or melting of a processed material using microwaves. This invention relates to preventing dust fumes contained in the decomposed gas from entering or accumulating in the microwave transmission waveguide.

(Prior art) Heaters using microwaves are shown in Figures 4 and 5.
There is one shown in the figure. In either heater, the object to be processed is continuously fed into the heater and heated or melted by microwave irradiation.

In the melting furnace shown in FIG. 4, a workpiece is melted in a cylindrical metal crucible 2 provided under a cylindrical melting furnace main body 1. The object to be processed is
From the hopper 3 to the feeder 4, the melting furnace body 1
is fed into the metal crucible 2 through a hole in the cylindrical side of the crucible. The waveguide 5 is connected to the melting furnace main body 1
connected at right angles to the top of the The microwave is transmitted through the waveguide 5 into the melting furnace main body 1 and the crucible 2, and the object to be processed absorbs the microwave and generates heat.
melt. Adjustment of the microwave within the melting furnace main body 1 is performed by moving the matching box 6 up and down. Decomposition gas, dust, and fume generated in the furnace are removed through an exhaust pipe 7 provided on the side of the melting furnace body 1.
It is smoothly discharged to the outside through. Arrow 8 indicates the discharge direction. Here, the decomposed gas is water vapor, sulfur dioxide gas, etc. generated by heating and melting the material, although it varies depending on the properties or chemical composition of the material to be processed.
Consists of chlorine gas or commonly known as smoke. Dust is fine powder etc. that are scattered when the object to be processed is supplied. Huyum refers to a component that has been vaporized by heating and melting and reacts with cold air, changing into a fine solid component (for example, zinc oxide).

The heater shown in FIG. 5 differs from the heater shown in FIG. 4 in the way the waveguide 5 is connected. The waveguide 5 is vertically connected to the top of the rectangular crucible 2 . In this melting furnace, similarly to the melting furnace shown in FIG. It is heated and melted.
The molten material flows out through an outflow hole 9 provided on the side surface of the metal crucible 2.

(Problems to be Solved by the Invention) As shown by arrow 8 in these two types of melting furnaces, the problem with the microwave heater is that foreign matter (generated cracked gas and dust and fume accompanying this cracked gas) A part of the waveguide 5 penetrates into the waveguide 5. The inside of the waveguide 5 is where the microwave electric field is strongest, and at the internal end of the waveguide 5 there are magnetron tubes and cryostron tubes that oscillate microwaves (not shown). . Therefore, within the waveguide 5 there is a decomposed gas,
Intrusion of dust or fume causes frequent occurrence of discharge and also causes failure of the microwave oscillator tube.

Therefore, countermeasures as shown in FIGS. 6A and 6B are generally taken. (The melting furnace shown in FIG. 4 is illustrated as an example.) That is, a plate-like material called a spacer 11 is placed inside the waveguide 5 near the connection point of the waveguide 5 with the melting furnace main body 1. The pipes will be placed in such a way as to block the pipes. The spacer 11 is made of Teflon, quartz, or the like, which has good microwave transparency. Further, a blower 12 such as a blower is provided on the front side of the spacer 11 of the waveguide 5, that is, on the side of the melting furnace main body 1, and compressed air or inert gas is blown into the melting furnace (arrow 13 indicates the flow direction). A positive pressure is applied to the internal pressure of the main body 1 to prevent decomposition gas, dust, or fume from entering.

Currently, the frequency of microwaves generally used industrially for purposes such as heating is 2450MHz.
It is 915MHz. The wavelength is 12.2 for 2450MHz
cm, and 33 cm for 915MHz.
Considering the transmission efficiency, the inner diameter dimensions of the waveguide for transmitting these microwaves are approximately 109 x 55 mm for 2450 MHz, and approximately 109 x 55 mm for 915 MHz.
In the case of , it is approximately 248 x 124 mm.

When using the prevention mechanism shown in Figure 6a and b for waveguides of these sizes, especially when the internal dimensions are large,
In the case of a waveguide for 915MHz, the internal dimensions are large, so
If the airflow is small, the wind pressure will be weak and it will not be useful for preventing decomposition gas etc. from entering. On the other hand, if you increase the air volume,
Although it is possible to prevent the intrusion of decomposition gas, etc., there are many problems from a practical point of view, such as the increased air flow into the heater, which causes the supplied processed material to scatter further and the amount of exhaust gas to increase. . Furthermore, if the decomposed gas contains radioactive substances, retention and accumulation of radioactive substances in the waveguide should be avoided in order to reduce radiation exposure.

An object of the present invention is to prevent decomposition gas and the like from entering a waveguide in a microwave heater.

(Means for Solving the Problems) The microwave heater according to the present invention includes a heating part that heats or melts a processed object using microwaves, and a waveguide part that transmits microwaves to this heating part. In the microwave heater, the gas ejection means is made of a material that absorbs little microwaves and has a large number of gas ejection openings for ejecting gas toward the heating section. The present invention is characterized in that a gas supply means is provided above the heating section and supplies gas to the gas ejection means.

(Function and Effects of the Invention) During heating and melting by the microwave heater, the gas supplied from the gas supply means is jetted toward the heating section from the jet opening provided in the gas jetting means. This can prevent foreign matter (decomposition gas, dust, fume) generated in the heating section from entering the waveguide section or a specific location within the heating section.

(Example) Hereinafter, an example of the present invention will be described using the accompanying drawings.

In the first embodiment shown in FIGS. 1A and 1B, a planar gas ejection body 21 is placed inside the waveguide 5 between the melting furnace body 1 and the spacer 11.
The waveguide 5 is provided on the side over the entire surface of the waveguide 5. The gas ejecting body 21 consists of four pipes 23 each having a large number of ejection holes 22, 22, .
4, . . . are integrally connected in a planar manner.
The opening direction of the ejection holes 22, 22, . . . is directed toward the melting furnace main body 1 side. Outside the waveguide 5,
The gas jet 21 is connected to a compressed air container 26 via a pipe 25. In addition, the gas ejecting body 21
is made from a material (Teflon, polystyrene, etc.) that has good microwave transparency and is easy to process.

When heating and melting the object to be processed, compressed air is uniformly ejected from the ejection holes 22, 22, . . Intrusion of decomposition gas, dust, fume, etc. into a specific location within the waveguide 5 can be efficiently prevented by using an extremely small amount of ejected gas.

In the second embodiment shown in FIGS. 2A and 2B, a gas ejection plate 31 that also serves as a spacer is provided with a structure for ejecting compressed air or inert gas. That is, a cavity 33 is formed on the side surface of the plate 32 on the melting furnace main body 1 side.
are provided, and the ejection holes 34, 34, . . . are provided over the entire end face.
... will be established. Gas from a gas container (not shown) placed outside the waveguide 5 enters the cavity 33 through the pipe 35 and is ejected from the ejection holes 34, 34, . etc. to prevent intrusion.

In the third embodiment shown in FIG. 3, a gas ejection plate 41 having the same structure as the second embodiment shown in FIGS. 2A and B is connected to the feeder 4 of the melting furnace main body 1 and the exhaust pipe. and the part to which the waveguide 5 is connected. This blowout plate 41 is connected to a gas container 43 via a pipe 42 outside the melting furnace main body.
connected to. By ejecting compressed air or inert gas from the ejection plate 41, it is possible to prevent decomposed gas and the like from entering the waveguide 5.

In addition, these intrusion prevention mechanisms 21, 31, 4
The material used for 1 is preferably a material that absorbs as little microwave as possible. The value of the dielectric loss angle (tan δ), which is an index representing this, measured at normal temperature and normal pressure using a frequency of 2450 MHz is preferably a value of 4×10 ^-3 or less.

[Brief explanation of drawings]

1A and 1B are a sectional view and a perspective view, respectively, of a first embodiment of the present invention. Figure 2 A and B are
FIG. 7 is a sectional view and a perspective view, respectively, of a second embodiment according to the present invention. FIG. 3 is a perspective view of a third embodiment of the present invention. 4 and 5 are perspective views of the microheater. FIGS. 6A and 6B are a perspective view and a sectional view, respectively, of a foreign matter intrusion prevention mechanism in a conventional microwave heater. 1... Melting furnace main body, 2... Crucible, 3... Hopper,
4... feeder, 5... waveguide, 6... matching box, 7... exhaust pipe, 11... spacer, 12... blower, 21...
Gas ejection body, 22, 22... ...Ejection hole, 25...
Pipe, 26... Gas container, 31... Gas ejection plate, 3
4, 34,......Blowout hole, 35...Pipe, 41
...Gas ejection plate, 42...Pipe, 43...Gas container.

Claims (1)

[Claims] 1. In a microwave heater that includes a heating section that heats or melts the object to be processed using microwaves and a waveguide section that transmits microwaves to this heating section, it is made of a material that absorbs little microwaves. gas ejection means having a large number of gas ejection openings for ejecting gas toward the heating section is provided on the waveguide section or the upper part of the heating section, and a gas supply means for supplying gas to the gas ejection means. A microwave heater characterized by being provided with.