JPS6241389B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous heating device using microwaves.

Generally, in a heating device such as a heating dryer or a decomposition furnace, a method is adopted in which hot air is generated using a gas or an electric heater, and the moisture of the object to be heated is evaporated by this hot air.

However, the heating device has a problem in that it requires a certain amount of preparation time to generate hot air, and it takes a long time to process the object to be heated.

For this reason, heating devices using microwaves have recently been proposed. That is, this type of microwave heating device is configured so that microwaves are generated simultaneously with the operation of the heating device, and the microwaves are uniformly transmitted through the object to be heated and are contained in the object to be heated. It generates heat due to dielectric loss of substances such as water and salts, and dries or thermally decomposes.

Therefore, it has the effect of significantly shortening the processing time, but on the other hand, the heating chamber has to be of a closed structure due to problems of loss and danger due to leakage of microwaves. Therefore, when there is a large amount of objects to be heated, it becomes troublesome to carry the objects into the heating chamber and take them out, which results in a disadvantage that the processing time is long.

The present invention solves the drawbacks of the various conventional heating devices described above, and includes a rotating drum having a shaft connected to a driving device, and a heating chamber having a discharge pipe provided surrounding the rotating drum. , a device for supplying microwaves into the heating chamber; a device for attaching a heated object in a thin film form to the surface of the rotating drum; and a device for attaching the solid heated object obtained by heating to the surface of the rotating drum. This is a continuous microwave heating device consisting of a scraping device.

Embodiments of the present invention will be described below with reference to the drawings.

In Figs. 1 to 4, reference numeral 1 denotes a rotating drum, which has a shaft 3 connected to a drive device 2 such as a motor with a speed reducer, and the shaft 3 is supported by a bearing by a support device (not shown).

A heating chamber 4 has a plurality of microwave generators 5 and an exhaust pipe 6 having a blower (not shown), and the heating chamber 4 is composed of a ceiling wall 7, side walls 8, and a bottom wall 10 having a sealing member 9 to be described later. At the same time, an opening 11 is provided in the bottom wall 11. The sealing member 9 is provided with a plurality of slit-like grooves 12, as shown in detail in FIG.
is formed. The gap D between the surface of the rotating drum 1 and the side surface of the end of the seal member 9 is selected to be the minimum necessary. 14, the object to be heated B is placed in the liquid receiving tank 1.
5, and a valve 16 is provided on the way. Reference numeral 17 denotes a scraping device for scraping off the solid object to be heated B' adhering to the surface of the rotating drum 1. As shown in FIG. The blade part a is pressed against the rotating drum 1 by its own weight or by a pressing device such as a spring (not shown).
is in close contact with the surface of the chute part b.
is the angle of inclination θ that is larger than the angle of repose of the solid heated object B′
It is arranged so that it has. A receiving tank 18 is connected to the lower end of this chute portion b. 19 is a liquid film detector.

In this configuration, the object to be heated B supplied from the supply pipe 14 into the liquid receiving tank 15 adheres in the form of a liquid film to the surface of the rotating drum 1 which is rotated in the direction of arrow A by the drive device 2. Since the thickness of this liquid film differs depending on the viscosity of the object to be heated, this state is detected by the detector 19 and the output of the drive device 2 and/or the microwave generator 5 is controlled to control the solid object to be heated. The quality of B' is maintained. The object to be heated B that has adhered to the surface of the rotating drum 1 in the form of a liquid film is sent into the heating chamber 4, where it is dried or thermally decomposed and becomes a solid object to be heated B'. After leaving the heating chamber 4, it is scraped. It is collected in a receiving tank 18 by a collection device 17.

Steam or cracked gas generated within the heating chamber 4 is suctioned and discharged through the exhaust pipe 6, thereby maintaining a negative pressure within the heating chamber 4.

FIG. 5 shows a second embodiment, in which when the thickness of the thin film-shaped heated object B attached to the rotating drum 1 is insufficient for microwave heating, the microwave passes through the thin film. It is configured as follows. The rotating drum 1 is made of a microwave transparent material such as quartz, heat-resistant glass, ceramic, etc., and a bottom wall 10' and a sealing member 9 are also provided inside the rotating drum 1.

According to this embodiment, since the microwaves pass through the thin film of the object to be heated attached to the rotating drum 1, even if the object to be heated cannot be heated sufficiently in the embodiments shown in FIGS. Can be heat treated.

7 to 9 show preferred examples in which the present invention is applied to a spent nuclear fuel reprocessing device, and the same reference numerals as in FIG. 1 indicate the same names.

The process of reprocessing spent nuclear fuel includes a uranium and plutonium recovery process (conversion process), and one of these methods is the direct denitrification method. In this method, spent nuclear fuel is immersed in nitric acid to create a nitric acid solution containing uranium, plutonium, etc. The solution is chemically treated to remove impurities, then heated and thermally decomposed to form powdered uranium and plutonium. The purpose is to collect This uranium and plutonium recovery process can be broadly divided into an evaporation process, a temperature raising process, and a denitration reaction process.

Furthermore, taking as an example the case where a nitric acid solution containing uranium, plutonium, and nitric acid is heat-treated, in the evaporation process, the water and nitric acid in the solution evaporate, and crystals of uranyl nitrate and plutonium nitrate crystallize. put out

The crystals crystallized in such a state are heated and heated in a temperature raising step to evaporate adhering water between crystal particles or water of crystallization.

The crystals that have undergone this temperature raising step are thermally decomposed in the denitrification reaction step, releasing NOx gas, and producing uranium oxide and plutonium oxide as a foam cake shaped like Carmela oxide. The products are then crushed to recover powdered uranium and plutonium, respectively. FIG. 6 shows the temperature change inside the heating chamber in this example.

In this way, when processing spent nuclear fuel,
Three steps are required: evaporation, temperature rise, and denitrification reaction.
If this process were to be carried out using a heating device using a general gas or electric heater, the problem would be that the device would be large and temperature control would not be easy, resulting in an inefficient process.

The present invention can be effectively carried out in the above-mentioned process, and in particular, by attaching an intermediate treatment product of spent nuclear fuel, which is a material to be heated, to the surface of a rotating drum in the form of a thin film,
Each of the above steps is carried out by irradiating microwaves while rotating this.

7 and 8, the heating device is made of a microwave transparent material, such as quartz, heat-resistant glass,
A liquid receiving tank 15 is provided below the rotating drum 1 made of a material such as porcelain, and the object to be heated B is supplied to the liquid receiving tank 15 through a supply pipe 14.

The upper half of the rotating drum 1 includes a ceiling wall 7 and a bottom wall 10.
a and 10d, radially partitioned by partition walls 10b and 10c to form an evaporation chamber E, a heating chamber H, and a denitrification reaction chamber C.
Furthermore, a bottom wall 10 is formed in the upper half of the inner side of the rotating drum 1 on an extension line of the bottom wall and the partition wall.
a', 10d' and partition walls 10b' and 10c' are provided to form chambers E', H' and C', respectively.

Microwaves generated by the microwave generator 5a are supplied to the evaporation chamber E through the waveguide 20a, and similarly, microwaves generated by the microwave generators 5b and 5c are supplied to the heating chamber H and the denitrification reaction chamber C. It is supplied through wave tubes 20b and 20c.

Furthermore, an evaporation chamber E, a heating chamber H, and a denitrification reaction chamber C
are provided with exhaust pipes 6 each having a blower (not shown), as well as a heating chamber H and a denitrification reaction chamber c.
is provided with a detector 20 such as a thermometer or an illuminance meter. The signals from the detector 20 are used to control the microwave generators 5b and 5c, respectively. 9a, 9a', 9b, 9b', 9c,
Seal members 9c', 9d, and 9d' are provided at the tips of the bottom plate and the partition wall so as to sandwich the inner and outer surfaces of the rotating drum 1. Reference numerals 19a and 19b are thickness gauges that measure the thickness of the object to be heated adhering to the rotating drum 1 using transmitted light or the like.

The rotating drum 1 is driven at a predetermined speed by a drive device 2 such as a motor with a speed reducer.

FIG. 9 is a diagram showing the rotating drum bearing part and the drum side wall part, in which the side wall 8 includes the ceiling wall 7 and the partition wall 1.
0b sealing member 9b is connected, and the shaft 2 is connected to the center.
1 is extended, and the rotating drum 1 is supported via a bearing 22 provided therein.

The rotating drum 1 has a drum part 23 made of a microwave-transparent material sealed and supported by a side plate 24, and a cylindrical part 25 protruding from the side plate 24 supported by a shaft 21 via the bearing 22. There is.

As can be seen from FIG. 9, the rotating drum 1 is rotatably supported in a sealed chamber, and is constructed so that even if harmful gases are generated, they will not leak outside.

In this embodiment, a thin film of a nitric acid solution containing uranium and plutonium, which is an intermediate treatment for spent nuclear fuel, is deposited on the surface of the rotating drum 1. The feature is that this is configured to be processed using microwaves, but the following points should be kept in mind when operating the device.

As a means for forming a thin film on the rotating drum 1,
In addition to the method of immersing a part of the rotating drum 1 in the object to be heated as in the above embodiment, the coating may be applied using a spray. Furthermore, two rotating drums 1 are arranged in parallel, the object to be heated is stored in the recesses formed in the upper parts of the two rotating drums 1, and the rotating drums 1 are rotated outward from each other. However, thin films can still be formed. Further, it is preferable to adjust the degree of immersion of the liquid supplied from the supply pipe 14 to make the liquid film uniform, and to obtain a state suitable for the series of processing steps described above.

In addition, evaporation chamber E, warming chamber H, and denitrification reaction chamber C
The area in which the rotating drum 1 is exposed is designed in consideration of the conditions shown in FIG.

During operation of the device, the intermediate treatment liquid for spent nuclear fuel is supplied from the supply pipe 14 into the liquid receiving tank 15, and as the rotating drum 1 rotates, it is deposited in a thin film on the surface of the rotating drum 1. Heat treatment using microwaves is carried out in greenhouse H and denitrification reaction chamber C, respectively, and eventually thermal decomposition occurs in denitrification reaction chamber C.
NOx gas is released, and uranium oxide and plutonium oxide form a carmela-like foam cake, which is scraped off by a scraping device 17 and collected in a receiving tank 19.

In the present invention, the object to be heated is attached in the form of a thin film to the surface of a rotating drum, and the object to be heated is continuously irradiated with microwaves. Moreover, not only continuous processing but also large-scale and homogeneous processing becomes possible.

Furthermore, since the intensity of the microwave, the properties of the object to be heated, the speed of the rotating drum, etc. can be controlled depending on the processing status of the object to be heated, appropriate processing can be carried out.

When processing spent nuclear fuel, it is necessary to improve the quality of the product by ensuring uniformity in the firing of the heated material, but in the present invention, since it is processed in the form of a thin film, the homogeneity is significantly improved. Further, since thin films are continuously formed and continuously fired, operating conditions are always constant, and a plurality of different processing steps can be carried out efficiently.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, and FIG. 1 is a schematic front cross-sectional view of a heating device using microwaves, and FIG.
The figure is a side view, FIG. 3 is a side sectional view of the sealing member,
FIG. 4 is a perspective view of the scraping device, FIG. 5 is a schematic front sectional view of the heating device according to the second embodiment, and FIG. 6 is a graph showing the relationship between spent nuclear fuel processing temperature and time.
FIG. 7 is a schematic front view of a heating device for a spent nuclear fuel processing apparatus, FIG. 8 is a side view of the same, and FIG. 9 is a sectional view showing details of a bearing portion and a drum side wall portion. 1... Rotating drum, 2... Drive device, 3...
Shaft, 4...Heating chamber, 5...Microwave generator, 6
...Exhaust pipe, 7...Ceiling wall, 8...Side wall, 9...
Seal member, 10... bottom plate, 12... slit groove, 13... recess, 14... supply pipe, 15... liquid receiving tank, 17... scraping device, 18... receiving tank, 19...
...film detector, 20...detector.

Claims (1)

[Claims] 1. A rotating drum having a shaft connected to a drive device, a heating chamber having an exhaust pipe provided surrounding the rotating drum, a device for supplying microwaves into the heating chamber, and a device that covers the surface of the rotating drum. A continuous microwave heating device comprising a device for attaching a heated object in the form of a thin film, and a device for scraping off a solid heated object obtained by heating from the surface of the rotating drum.