JPS6056560B2 - microwave melting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave melting device for melting powder and granular materials such as incinerated ash using microwaves.

In recent years, incineration ash, which is a powdery material, has been used as a treatment method for waste such as urban garbage discharged from households, incineration ash after sewage treatment, plating sludge containing heavy metals, and incineration ash containing radioactive waste. A method has been developed to melt and solidify waste materials using microwaves.

In other words, the composition of these incinerated ash and other wastes is approximately 51,005
3%, CaO24.8%, MgO9.3%, Al2O3
6.2% Na. 04.3%, Fe2O3 and 2O account for 2.4%, and SiO2 accounts for more than half, so 14
When the temperature rises to around 00℃, it becomes vitrified, and harmful substances such as heavy metals and radioactive substances mixed in the form of oxides are strongly captured in the glass in the form of intermediate oxides and modified oxides, preventing harmful substances from flowing out. There is no need to worry about this, and the volume of waste can be significantly reduced to 1110 to 115 by vitrification.

Moreover, these granular materials have poor thermal conductivity, so external heating has low thermal efficiency and requires strong insulation, whereas microwave heating can heat from the inside, making it possible to heat efficiently and with high thermal conductivity. This is because there is an advantage that surrounding objects to be heated, which are poorly heated, can be used as a heat insulating material.
An example of a cross-sectional view of a conventional microwave melting device is shown in FIG.

In Fig. 1, 1 is a resonant melting furnace formed of a rectangular waveguide that can only propagate the fundamental wave, 2 is a microwave inlet, 3 is a resonance adjustment tool, 4 is a heated material inlet, 5 is a screw feeder, 6 is a hopper, 7 is a gas exhaust port, 8 is a melt outlet, 9
1 is a melted material, 10 is an object to be heated, and 11 is a closed end portion of a rectangular waveguide whose one end is closed with a metal plate to constitute the melting furnace 1. With this device, microwaves are introduced while the object to be heated 10 is introduced into the resonant melting furnace 1, and the resonance adjuster 3 is adjusted to resonate within the melting furnace 1, so that the microwaves are transmitted to the microwave generator (
(not shown) so that the reflection does not occur. As a result, the object to be heated is heated and the melted material 9 is discharged from the molten material outlet 8, and the object to be heated is continuously charged and melted one after another, and the gas generated during melting is exhausted. Air is exhausted from the port 7. The heated material inlet 4 and the gas exhaust port 7 are formed with microwave-blocking dimensions to prevent microwaves from leaking outside, but depending on the internal situation, the heated material at the tip of the screw feeder There is a drawback that seizure occurs at the input port 4 and microwave discharge occurs at the gas exhaust port 7, and in that case, the microwave introduction must be temporarily stopped or the microwave power introduced must be reduced. be. The biggest drawback of these conventional devices is that they do not have a mechanism to raise the temperature of the melt outlet 8, so the operation of the device may be temporarily stopped, or due to some accident the melt 9 may become stuck at the outlet 8. If the discharge port 8 is blocked, the solid matter must be mechanically destroyed to open the discharge port 8, which impedes intermittent operation and is a major hindrance to unmanned operation. The purpose of the present invention is to solve these drawbacks and provide a microwave melting device that can prevent baking and microwave discharge at the heating material inlet. At least the terminal end side of the resonant melting furnace was
The melting furnace is tilted at an angle smaller than 0, and the side wall located at the bottom of the tilted melting furnace is melted. It is equipped with a material discharge port, and will be explained below with reference to the drawings.

Fig. 2 is a sectional view showing one embodiment of the present invention, Fig. 3 is a perspective view of the main parts thereof, and 1 to 11 indicate the same parts as in Fig. 1. ! 1 is a rectangular waveguide capable of propagating only the fundamental wave, bent at the E plane, and the resonance adjustment tool 3 is piston-shaped.

Further, 12 indicates the upper surface of the melt, a is the H-plane dimension of the rectangular waveguide, b is the E-plane dimension, and θ is the inclination angle of the closed end 11 of the melting furnace 1 with respect to the horizontal plane. In the apparatus shown in FIG. 2, when the object to be heated 10 is introduced while microwaves are introduced and the resonance adjusting tool 3 adjusts the microwave to resonate, the object to be heated 10 is heated and melted. In this case, these materials to be heated 10, including incinerated ash, generally have the properties of an insulator near normal temperature, and when the temperature rises to 700°C or higher, the resistance value decreases rapidly, and when the temperature rises to about 1400°C, the resistance value decreases to several Ω. -0, which is sufficiently small compared to the impedance of the waveguide. Therefore, when these heated objects 10 are heated with microwaves, they are first heated by dielectric heating, and when the resistance value decreases, they are heated by high frequency current flowing through the surface. Since the molten material 9 melted in the melting furnace 1 is in a viscous liquid state, the molten material surface 12 becomes horizontal, and the molten material 9 that is melted one after another is discharged from the molten material outlet 8 and forms a horizontal surface determined by the position of the outlet 8. form. This molten material surface 12 has a very small resistance value as described above, so it can be regarded as a metal surface, and the melting furnace 1 appears to have a molten material surface 12.
The upper part is partitioned. If the resonance adjustment tool 3 is adjusted in this state to cause resonance, the position of the molten material surface 12 will remain constant thereafter, so there is no need to perform resonance adjustment. Next, in order to explain the microwave resonance region formed by this melting surface 12, a simplified cross-sectional view is shown in FIG. 4a. Fourth
In figure a. ABCD shows a cross section taken parallel to the H plane of the melting furnace 1, B and C show the closed end 11, E shows the melt outlet 8, and F and G show the melt surface 12 and the melting furnace 1, respectively. Indicates the position of the microwave shielding wall. That is, FG
When the dimension of λ becomes less than half of the introduced microwave wavelength λ, the microwave will no longer propagate deeper than that, so the limit position is expressed as FG. As a result, AEFG
The region formed by D is the microwave resonance region, and the EFGC
The area formed by B becomes a microwave blocking area. In addition, since the high-frequency current flows only on the surface of the material and does not penetrate into the interior, there is no microwave at all in the EFGCB region, and the temperature of the molten material that is first melted at the bottom of the melting furnace 1 decreases and becomes glass-like. It becomes a solid substance. If this situation is strictly illustrated, it will be as shown in FIG. 4b, where 13 is a solid substance, and FIGS. 2 and 3 are conceptual illustrations of a molten substance. If the microwave resonance region AEFGD is completely resonant and in a resonant state, from point F to (λV/4+n・λ
y/2) (n is O or a positive integer, λq is the tube wavelength), the current reaches its maximum and the melt reaches its highest temperature.

Now, if EF and DG are parallel, λy will always be constant, and E
Although it is easy to calculate the position of point E where F becomes (λy/4+n・λy/2), EF. As is clear from the figure, 15DG is not parallel, and λy changes as a function of location, so it cannot be easily calculated, and when determined experimentally, the wavelength λ = 3
2.8cm (f=915MHz) microwave, a=2
4.8c71. ．． When using a melting furnace with b=12.4 cm, when n=0, θ=60. , when n=1, O=22 furnace, when n=2, θ=12.5n, when n=3, θ=9.
8=, and if these angles are set, the outlet 8 can be provided at the highest temperature point of the molten material 9. It goes without saying that if the wavelength λ and the dimensions A and b are changed, the discharge port 8 will be the highest temperature point unless the inclination angle θ is also changed. The discharge port 8 set in this way reaches the maximum current point when the molten material surface 12 coincides with this position, but the microwave is introduced while adjusting with the resonance adjustment tool 3 when the melt is not melted at all. Then, melting starts from the strong electric field of the melting furnace 1, the molten material 9 accumulates at the bottom, and the molten material surface 12 gradually rises and reaches the position of the discharge port 8, which is the highest temperature point. Therefore, even if the discharge port 8 is closed, it opens immediately and the position of the molten material surface 12 becomes constant, and there is no need for resonance adjustment thereafter. By setting the discharge port 8 at the maximum current point in this way, even if solid matter is formed at the discharge port 8 during intermittent operation, operation can be resumed without having to remove the solid matter from the outside. There is an advantage. As described above, according to the present invention, the melting furnace 1 is separated into the microwave resonance region and the microwave blocking region by the molten material surface 12. If it is provided on the pipe wall, there is no possibility that microwave discharge or burning will occur at these inlets or at the tip of the screw feeder 5. Furthermore, FIG. 5 is a simplified perspective view of another embodiment of the present invention in which a circular waveguide capable of propagating only the TELL mode, which is the fundamental mode, is used as the melting furnace. In the case of a circular waveguide, the radius R when microwaves are blocked
c is Rc=λ●ρNm/2π (λ: microwave wavelength, ρ
Nm: Root of the Betzel function, which varies depending on the propagation mode, and is 1.841 in the TELL mode. ), and FG=LO when microwave is cut off in Figure 5 is L.
c=? . =λ・ρNm/ml. Therefore, in a melting furnace in which only the TELL mode can propagate (for example, a melting furnace with a radius of 12.5 cm, in this case ρNm = 1.841), the input = 32.
If a microwave of 8 cm (f = 915 MHz) is used, LO = 19.2 cm, points F and G at this time are the microwave cutoff positions, and the dimension of EF is (λy/4+n
- Setting the inclination angle so that it becomes λy/2) is the same as in the case of a rectangular waveguide. In the above embodiment, only the fundamental wave can be propagated in both the rectangular and circular cases.However, even in the case of a large melting furnace where higher-order modes can also be propagated, in the case of a rectangle, both the E plane and the H plane have complicated slopes. However, if the angle is determined experimentally, the angle can be set so that the position of the discharge port is the maximum current point.

As explained above, according to the present invention, at least the terminal end of the microwave melting furnace is inclined and the melt outlet is provided in the side wall located below the end, so that the melting surface can be used as an electrical shielding plate. As a result, a microwave-blocking area can be formed in the melting furnace, and if a heating material inlet is provided on the wall of the melting furnace in the blocking area, baking and electrical discharge caused by microwaves can be prevented. It is possible to prevent interruptions in melting operations and accidents caused by this process, which is extremely effective in terms of maintenance and safety, as well as in terms of service life.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional microwave melting device, Fig. 2 is a sectional view of a microwave melting device which is an embodiment of the present invention, Fig. 3 is a perspective view of the main part of Fig. 2, and Fig. 4 is a sectional view of a conventional microwave melting device. Figure a is a simplified sectional view of the main part of Figure 2 for explaining the present invention, and Figure 4 b is a simplified sectional view of the main part of Figure 2.
FIG. 5 is a simplified sectional view showing the actual state of the melt shown in FIG. 5, and FIG. 5 is a perspective view for explaining another embodiment of the present invention. 1...Melting furnace, 2...Microwave inlet, 3...Resonance adjustment tool, 4...Things to be heated inlet, 7... ...Gas exhaust port, 8...
Melt outlet.

Claims (1)

[Claims] 1. One end of a rectangular or circular tubular body made of metal, which is equipped with a microwave inlet, a resonance adjuster, a heated material inlet, and a molten material outlet, is closed with a metal plate. In the microwave melting apparatus, the tube axis of at least one end of the tubular body closed by the metal plate is inclined at an angle of less than 90° with respect to a horizontal plane, and the melt outlet is opened at the tip of the inclined tubular body. A shielding area for the introduced microwave is provided on the lower side wall and is surrounded by a horizontal plane formed at the position of the melt discharge port and the inclined tubular body on the horizontal plane. Microwave melting characterized in that the object to be heated input port is provided on the wall surface of the tubular body in a portion corresponding to the dimension, and the microwave inlet is provided in a portion of the tubular body other than the portion corresponding to the dimension of the cutoff region. Device. 2. The microwave melting apparatus according to claim 1, wherein the melt discharge port is set so that the current reaches a maximum point in a steady state where the melt is continuously discharged.