JPS6328279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave melting and solidification apparatus for treating radioactive waste containing metals. For more details,
The present invention relates to a microwave melting and solidifying device for treating radioactive waste containing metal, which is equipped with an in-furnace cleaning device.

Waste containing radioactive materials or waste contaminated with radioactive materials discharged from nuclear facilities is dangerous to handle, and if the radioactive materials have a long half-life, they require long-term isolation and storage. There is a strong demand for volume reduction treatment from the viewpoint of work safety, saving of storage container/storage space, etc.
Volume reduction methods include incineration in the case of combustible materials, mechanical methods such as cutting and crushing in the case of non-combustible materials, and melting and solidification treatment methods in which the material to be treated is heated and melted and then cooled to solidify. . In particular, the melting method is the best in terms of volume reduction effect, as the material to be processed becomes extremely dense after melting and solidifying.Moreover, recently, a method using a microwave melting furnace as a means for heating and melting has been put into practical use. It's coming.

The method of heating and melting by microwave irradiation utilizes the dielectric heating phenomenon of the substance itself due to the molecular movement and intermolecular bond resistance of the constituent molecules of the dielectric solid object, and is not compatible with other forms such as radiant heat or heat transfer. It has the advantage that it is possible to uniformly and efficiently heat and melt the object to be processed, and that the melting process can be performed at any speed or speed by adjusting the power applied to the microwave.

When operating a microwave melting furnace, a material to be processed is charged into a melting furnace main body, and microwaves are introduced from a microwave oscillator into the main furnace through a waveguide to perform melting. In this case, a tuner held by a sleeve mechanism made of Teflon or the like is moved up and down depending on the molten metal level of the material to be processed in the crucible, thereby matching the wavelength of the microwave and performing the melting operation. exist.

In such a melting furnace using microwaves, due to the convection phenomenon caused by radiant heat from the surface of the melt or the air feeding operation, the supplied material to be processed and fumes and dust caused by evaporation during melting blow up and adhere to the inner wall of the furnace. A considerable amount is generated during long-term operation. These deposits are mainly composed of evaporative cooling substances, most of which are Na ₂ SO ₄ , NaCl, KCl, or salts such as B ₂ O ₃ or Na ₂ B ₂ O ₇ added as a fluxing agent.
If such deposits adhere to the inside of the furnace, (1) the salts tend to absorb moisture from the air and deliquesce easily, which accelerates corrosion of the furnace walls; (2)
Microwaves are absorbed by deposits, and the effective irradiation rate of microwaves irradiated to the object to be processed in the crucible decreases.(3) Discharge phenomena are more likely to occur using deposits as discharge points.(4) When a tuner is present, there are various operational problems such as deposits getting caught in the sleeve mechanism and making smooth movement of the tuner difficult.

In addition, during volume reduction treatment using microwave melting, metals and other good electrical conductors are only heated due to reflection of microwaves or partial surface current flow, but do not melt and solidify metal objects. It's impossible.

In view of the above problems, the present inventors have conducted research on a microwave melting and solidifying device that can easily melt and solidify metal objects together with metal oxides and that can easily remove deposits inside the furnace. As a result, the present invention was completed.

That is, the present invention consists of an upper furnace body and a lower furnace body that can be attached to and detached from the upper furnace body. In the melting furnace,
In addition to being equipped with a metal object supply device and an incinerated ash supply device, a cleaning device having a cleaning head that can move forward and backward and rotate with respect to the upper furnace body is installed below the upper furnace body, and is capable of melting and solidifying metal objects. The present invention provides a microwave melting and solidification apparatus for radioactive waste, which allows easy removal of deposits inside the reactor.

In order to treat metals with the apparatus of the present invention, metal oxide complexes such as incineration ash (2CaO・Al ₂ O ₃・SiO ₂ ,
3CaO・Al ₂ O ₃ , etc.), single metal oxides (Fe ₂ O ₃ , ZnO, etc.), or mixtures thereof (Al ₂ O ₃ +
CaO + B ₂ O ₃ , Fe ₂ O ₃ + ZnO + CaO, etc.) (hereinafter simply referred to as metal oxides) are continuously dropped into a metal crucible, for example, and melted while being irradiated with microwaves, and metal objects are placed inside the crucible. A method is adopted in which the metal oxide is supplied and contained in a molten metal oxide. There are two possible methods for this: one is to mix these metal objects with metal oxides and feed them into the furnace, or the other is to separate the metal objects from the metal oxides and feed them into the furnace separately. It was discovered that metal objects can be treated using microwaves using either method. Above all, it is better to separate the metal oxides and metal objects and feed them into the furnace through separate systems, which allows for quantitative supply, and also allows the metal objects to be evenly separated and contained in the resulting solidification. There is an advantage that a solidified product can be obtained. Here, we will mainly discuss the case where metal objects are separated and supplied.

The metal objects to be processed in the apparatus of the present invention include metal objects such as nails, metal pipes, metal plates, and metal pieces that are contaminated with radioactive materials discharged from nuclear facilities, as well as combustible objects that are contaminated with radioactive materials. It is mixed into the industrial waste, which is then incinerated together, and mixed into the incineration ash.

On the other hand, metal oxides are obtained by incinerating various combustible wastes discharged from nuclear facilities, or are impurities in heat insulation materials made of glass fibers and asbestos fibers. Its main ingredients are
These include CaO, MgO, _SiO2 , _{Al2O3 ,} etc.

Next, a specific example of the device of the present invention is shown in FIG.
The explanation will be based on the drawings.

As shown in FIG. 1, the melting and solidifying apparatus of the present invention comprises an upper furnace body 1, which together constitute the apparatus main body;
Consisting of a lower furnace body 2 and an in-furnace cleaning device 3 attached to the lower furnace body 2, the upper furnace body 1
The incinerated ash supply system is equipped with an incinerated ash hopper 8 that communicates with the inside of the furnace via a microwave waveguide 4 connected to a microwave oscillator (not shown), a tuner 5, an exhaust pipe 6, and a screw conveyor 7. It has a device 9 and a metal object supply device 10. The metal object supply device 1
0 has a metal object hopper 12 that communicates with the upper furnace body 1 via a supply pipe 11, and the metal object hopper 12 is connected to a vibrating feeder 13 and is rotated by a push-up rod 14. A weighing machine 16 having a weighing tray 15 therein opens via a damper 17.

Further, the lower furnace body 2 is raised and lowered by a lift mechanism 19 placed on a trolley 18.
, a cylindrical rotating container 21 that is rotatably housed in the rotating container, and a metal crucible 22 that is housed in the rotating container and rotates together with the crucible. Mounted as possible.

Furthermore, the furnace cleaning device 3 is equipped with a trolley 18.
an outer cylinder 27 having a connecting rod 24 attached to the connecting rod 24, a power cylinder 25 disposed on the opposite side of the connecting rod 24, and a lifting motor 26 provided on a side surface; An inner cylinder 28 that moves up and down the inner surface of the outer cylinder 27 by means of a cleaning head 30 that is housed inside the inner cylinder 28 and has a brush 29 on the top, and a rotary lifting motor 3 at the lower end.
1 is attached to the rotating shaft 32. Note that a suction blower 34 is provided on the side surface of the outer cylinder 27 with a filter 33 interposed therebetween.

To carry out melting using the apparatus of the present invention, the lower furnace body 2 is attached to the upper furnace body 1 via the flange 23, as shown in FIG. In the melting process, the incinerated ash A is first transferred from the incinerated ash hopper 8 to the metal crucible 22 in the furnace via the screw conveyor 7.
and irradiated with microwaves to form molten slag. On the other hand, the metal object M is supplied from the vibrating feeder 13 and weighed in advance on the weighing tray 15, and once the microwave irradiation is interrupted, the metal object M is placed on the push-up rod 1.
4, the slag is dropped from the open damper 17 through the metal hopper 12 and the supply pipe 11 onto the slag in the crucible 22. Next, the incinerated ash A is reintroduced by the conveyor 7 to form a predetermined layer on the metal object, and then microwaves are irradiated to restart melting. By repeating this operation, the throughput of one melting process can be increased.

In addition, since the solidification device of the present invention can supply a certain amount of metal objects at once, the metal objects can be supplied without stopping microwave irradiation during the continuous supply and melting of incinerated ash. It is also possible.

Further, according to the apparatus of the present invention, other foreign objects such as glass pieces, concrete pieces, SiC ceramic filters, porcelain pieces, etc. can also be treated in the same manner without being turned into powder, but in the form of lumps.

Next, after the melting process is completed, in order to clean the inside of the furnace, move the trolley 18 (to the right in the figure) to the furnace directly below the upper furnace body 1, as shown in Figure 2 (the lower furnace body is omitted). The inner cleaning device 3 is positioned, and the lifting motor 26 and rotary lifting motor 31 are driven to rotate and raise the cleaning head 30, inserting it into the upper furnace body 1, and cleaning the furnace wall with the brush 29. When cleaning is completed, the cleaning head 30 is lowered and removed from the upper furnace body 1, and a new crucible is placed on the lower furnace body 2 and returned to its original position (see Fig. 1). Upper furnace body 1 through
and the lower furnace body 2 in preparation for the next melting.

According to the present invention, a metal object supply device is provided, and a cleaning device having a cleaning head that can move forward and backward into the furnace and rotate is also provided, so that even when metal objects are included, the objects to be processed can be removed. It can be easily and stably melted and solidified, and it can be done automatically, safely, and without scattering the deposits inside the furnace outside the system.
It can be removed reliably and without requiring a large number of man-hours.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a specific example of the apparatus of the present invention, and FIG. 2 is a schematic diagram illustrating a cleaning operation of the apparatus of the present invention. The main symbols in the figure are as follows. 1...
Upper furnace body, 2... Lower furnace body, 3... Cleaning device, 9... Incineration ash supply device, 10... Metal material supply device, 22... Crucible, 30... Cleaning head.

Claims (1)

[Claims] 1. A microwave melting furnace consisting of an upper furnace body and a lower furnace body that can be attached to and detached from the upper furnace body, which irradiates microwaves to a workpiece loaded in a crucible in the lower furnace body to heat and melt the workpiece, A method for handling radioactive waste, characterized in that a metal material supply device and an incineration ash supply device are attached, and a cleaning device having a cleaning head that can move forward and backward and rotate with respect to the upper furnace body is arranged below the upper furnace body. Microwave melting and solidification equipment.