Electric heating – Microwave heating – Waveguide applicator
Patent
1995-03-08
1997-01-28
Leung, Philip H.
Electric heating
Microwave heating
Waveguide applicator
219687, 219701, 588900, 588247, 110250, H05B 680
Patent
active
055975046
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a microwave refining and melting furnace for the treatment of solid products and dissolved products.
The particular field of the invention is that of the reprocessing of industrial or nuclear waste.
2. Prior Art
French patent application FR-A-2 671 392 describes a microwave melting furnace for the treatment of fluid products such as industrial waste. Said furnace has an upper furnace body, a lower furnace body, means for supplying the products to be treated located in the upper furnace body and a crucible located in the lower furnace body. In order to prevent the crucible from overflowing, said furnace has means for detecting the upper level of the material to be treated and fed into the crucible and a control member for stopping the means for supplying the products to be treated by a detection signal from detection means.
This furnace permits the heat treatment of waste by drying, calcining and melting, but does not make it possible to check the effective obtaining of the melting of the treated waste. Therefore a product may be treated with this apparatus without it being meltable and said apparatus does not behave in a systematic manner like a melting furnace. This configuration does not make it possible to guarantee the complete degassing of the products as a result of the absence of a check on the state of the material.
The apparatus makes it necessary for the operators to work in stages with stoppage of the microwave power. The consequence of such a discontinuous method can be the formation of treated product layers and therefore the production of non-homogeneous and non-monolithic packs. Moreover, this treatment procedure does not permit the refining of products. Finally, the level check in said apparatus does not make it possible to continuously check the filling of the reception member with treated materials.
A publication by C. Shibata and M. Tamai in the journal J1 and entitled "Microwave power and electromagnetic energy", vol. 25, no. 2, 1990 describes a melting furnace, the waveguide of which is inclined at its end, thus forming a constant volume melting vessel. Such a configuration of the guide does not permit the treatment in thin layer form of the product, because the latter is introduced directly into the melting vessel. The design of this inclined furnace also does not permit a continuous, thin layer flow of molten products.
Therefore, this furnace suffers from the same operating disadvantages as the furnace described in FR-A-2 671 392.
Moreover, the movement of material and microwave flows take place in a countercurrent manner, so that the introduced products are not exposed to the high power zone located level with the overflow lock.
However, the energy requirement is very high at the introduction point, because it is at the latter that the drying, calcining and melting operations take place.
Finally, there is always a retention of material within the guide and disassembly is necessary in order to tap the apparatus hold-up.
French patent application FR-A-2 674 939 describes a microwave melting furnace for vitrification and densification of materials. This furnace is equipped with two vertical parts respectively surmounted by a supply means and a wave reflecting buffer. The two vertical parts are connected by a horizontal melting vessel. The materials to be melted and the microwaves are introduced by the first vertical part. The melting vessel has a constant cross-section as a result of a horizontal upper wall in order to assist the microwave power distribution over the surface of the molten bath. The second part can be provided with a piston permitting the regulation of the return of the non-absorbed microwaves.
The design of this melting furnace does not make it possible to refine the molten products by the action of the microwave electromagnetic field. The flowing products undergo thermal quenching because there is no device for the reception and controlled temperature refining of the molten products. Thermal quenching af
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Berson Xavier
Bertrand Eric
Vivet Alain
Commissariat a l''Energie Atomique
Leung Philip H.
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