JP3974462B2 - Rotary kiln for uranium dioxide production - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses gaseous uranium hexafluoride (UF ₆ ) and water vapor as raw materials to produce solid UO ₂ F ₂ (uranyl fluoride) by these reactions at a high temperature. The present invention relates to a rotary kiln for producing uranium dioxide (UO ₂ ) by producing UO ₃ by reaction with water vapor and reacting the produced UO ₃ with hydrogen gas.
[0002]
[Prior art]
A rotary kiln is a facility used to sinter, incinerate, or calcinate an object to be processed and take it out as a solid material. A cylindrical kiln main body provided rotatably, an inlet hood provided at one end thereof, and the like And an outlet hood provided at the end. The inside of the kiln body is brought to a high temperature state by a heating means, and supplies the object to be processed through the inlet hood, and heat-processes the supplied object to be processed while sending it to the outlet side. Is discharged through the outlet hood.
[0003]
This type of rotary kiln is also used in foreign countries to produce uranium dioxide powder, which is a raw material for nuclear fuel pellets. As a rotary kiln for producing uranium dioxide, for example, the one described in JP-T-8-500057 is known. The rotary kiln described in the publication includes an inlet device, a kiln body, and an outlet device. In the inlet device, a reaction gas inlet nozzle having a double tube structure is provided so as to coincide with the axial center of the kiln main body, and gaseous uranium hexafluoride and water vapor are supplied from the reaction gas inlet nozzle to the inlet device. Erupted inside. The ejected uranium hexafluoride and water vapor react in the inlet device to produce uranyl fluoride. On the other hand, the outlet device is provided with means for introducing water vapor and hydrogen into the kiln body, and uranyl fluoride produced in the inlet device enters the kiln body, where the water vapor and hydrogen are mixed. In reaction with the gas mixture, the uranium dioxide powder is finally released from the outlet device.
[0004]
In addition, a gas discharge pipe for discharging excess gas generated in the kiln main body is provided on the outer peripheral surface of the inlet device, but the uranyl fluoride generated in the inlet device is a fine particle and is In order to prevent uranyl chloride from being discharged from the gas discharge pipe, a cylindrical filter is provided in the inlet device.
[0005]
[Problems to be solved by the invention]
However, in the conventional rotary kiln described above, it can be said that the reaction conditions for generating uranyl fluoride from uranium hexafluoride and the reaction conditions for generating uranium dioxide from uranyl fluoride are sufficiently optimized. There wasn't.
[0006]
For example, uranyl fluoride produced by the reaction of uranium hexafluoride and water vapor is very fine with a particle size of 1 μm or less, and is easy to float in the rotary kiln, and is a gas release pipe together with the gas produced in the rotary kiln. Head to. And, uranyl fluoride heading to the gas discharge pipe is captured by the filter, but the captured uranyl fluoride is not used for the reaction in the next stage, which is a factor of reducing the utilization efficiency of uranyl fluoride. It was. In addition, since uranyl fluoride trapped in the filter may cause clogging of the filter, if the amount of uranyl fluoride trapped in the filter increases, the frequency of replacement of the filter increases, resulting in the availability of the rotary kiln. This also causes a problem of lowering.
[0008]
As described above, in the conventional rotary kiln, the reaction conditions for obtaining uranium dioxide from uranium hexafluoride are not sufficiently optimized. The production efficiency will be reduced. In order to optimize the reaction conditions for obtaining uranium dioxide from uranium hexafluoride, there is a method of strictly controlling the amount of substance to be supplied, reaction temperature, reaction time, etc. In a rotary kiln that is performed continuously throughout the stages, it is difficult to manage them, and the configuration of the rotary kiln itself is complicated.
[0009]
Accordingly, an object of the present invention is to provide a rotary kiln capable of improving the efficiency of the reaction from the generation of uranium dioxide to uranium dioxide with a simpler configuration.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the rotary kiln of the present invention includes a kiln body provided with an inlet hood at one end and an outlet hood at the other end, and gaseous uranium hexafluoride from the inlet hood side. In a rotary kiln for obtaining solid uranium dioxide from the outlet hood, an inlet-side supply pipe for supplying water and steam and an outlet-side supply pipe for supplying hydrogen and steam from the outlet hood side are supplied from the inlet-side supply pipe. At least one of uranium hexafluoride and water vapor is supplied to the kiln body as a swirling flow.
[0011]
According to the present invention, uranyl fluoride is generated by the reaction of uranium hexafluoride and water vapor supplied from the inlet side supply pipe into the kiln main body, and at least one of uranium hexafluoride and water vapor is swirled. Since it is supplied, the generated uranyl fluoride also swirls with the flow. As a result, the uranyl fluoride moves to the inner wall surface of the kiln main body and causes a situation in which the particle diameter of the uranyl fluoride is easily grown, and the amount of uranyl fluoride toward the inlet hood is reduced. As a result, more uranyl fluoride can be deposited inside the kiln body, and the utilization efficiency of uranyl fluoride reacting with hydrogen and water vapor supplied from the outlet hood side is improved. Such a swirl flow can be generated with a very simple configuration.
[0012]
In said invention, in order to prevent the uranium compound produced | generated in the kiln main body from invading into an inlet hood, a plate-shaped filter can also be provided in the end surface by the side of the inlet hood of a kiln main body. In this case, an inlet-side supply pipe is provided through the center of the filter, and a scraper that scrapes off uranium compounds adhering to the surface of the filter is fixed to the inlet-side supply pipe. The uranium compound can be scraped off from the filter. As described above, the particle diameter of the uranium compound (uranyl fluoride) generated by the reaction between the water vapor supplied from the inlet side supply pipe and uranium hexafluoride increases, and the amount of the uranium compound toward the inlet hood is increased. Since it decreases, clogging of the filter is suppressed.
[0017]
Contact name herein, "water vapor" means a vaporous water, including saturated steam and heated water vapor or the like.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a view showing a structure of a rotary kiln according to an embodiment of the present invention.
[0020]
As shown in FIG. 1, the rotary kiln 1 is used for conversion to an oxide, more specifically, powdery uranium dioxide (UO ₂ ) is produced from gaseous uranium hexafluoride (UF ₆ ) as a raw material. And a cylindrical kiln main body 2 supported on a roller 7 so as to be rotatable about a substantially horizontal axis, and an inlet hood 3 provided at one end of the kiln main body 2. And an outlet hood 4 provided at the other end.
[0021]
A gear 13 is provided on the outer peripheral surface of the kiln main body 2 on the inlet hood 3 side, and the kiln main body 2 is rotated by transmitting a driving force by a driving means (not shown) to the gear 13. Further, outside the kiln body 2, an external heating furnace 14 provided with heating means such as an electric heater is provided. The external heating furnace 14 is for setting the temperature inside the kiln main body 2 to a predetermined temperature suitable for the reaction. In particular, in the present embodiment, uranium dioxide is generated through a plurality of stages of reaction in the process from the inlet hood 3 side to the outlet hood 4 side. Therefore, the temperature in the kiln body 2 is set to a temperature suitable for the reaction at each stage. Therefore, the external heating furnace 14 is divided into a plurality of blocks 14a to 14c along the axial direction of the kiln body 2, and the temperature can be controlled independently for each of the blocks 14a to 14c. It has become. Inside the kiln body 2, thermometers (not shown) inserted from the ends of the kiln body 2 are installed at positions corresponding to the blocks 14a to 14c of the external heating furnace 14, respectively. The temperature control for each 14c is performed based on the temperature measurement results by these thermometers.
[0022]
In the present embodiment, the external heating furnace 14 is divided into the three blocks 14a to 14c. However, the number of blocks is not limited to this, and may be appropriately set in consideration of the accuracy of temperature control. If the number of blocks is increased, the production cost of the rotary kiln increases due to the complexity of the configuration of the external heating furnace 14 and the increase in the number of parts, but the temperature control accuracy increases.
[0023]
A plate-like filter 15 for preventing the uranium compound generated in the kiln body 2 from entering the inlet hood 3 is fixed to the end face of the kiln body 2 on the inlet hood 3 side. The end face of the kiln body 2 on the inlet hood 3 side is closed. The filter 15 may be a filter that is usually used in this type of rotary kiln. Furthermore, a partition plate 9 that divides the inside of the kiln main body 2 into a first reaction chamber 2a and a second reaction chamber 2b in order from the inlet hood 3 side is installed inside the kiln main body 2. By the external heating furnace 14 described above, the first reaction chamber 2a is set to a temperature of 300 ° C. or more suitable for the reaction between gaseous UF ₆ and water vapor, and the second reaction chamber 2b is the first reaction chamber 2a. A temperature of 450 to 800 ° C. suitable for the reaction of water vapor with uranyl fluoride (UO ₂ F ₂ ) produced by the reaction of and the reaction of uranium trioxide (UO ₃ ) produced by this reaction with hydrogen Set to
[0024]
The partition plate 9 restricts the free movement of gas between the first reaction chamber 2a and the second reaction chamber 2b, and completely partitions the first reaction chamber 2a and the second reaction chamber 2b. It is not a thing. That is, as shown in FIG. 3, the partition plate 9 has an outer diameter that is slightly smaller than the cross section of the kiln body 2, and the kiln body 2 is spread over the entire outer edge of the partition plate 9 by an appropriate fixing member 9 a. The kiln body 2 is supported so that a gap is formed with the inner wall surface.
[0025]
The kiln body 2 is installed so as to have a downward slope of 2 to 3 degrees toward the outlet hood 4 side so that UO ₂ F _{2 and the} like generated in the kiln body 2 can easily flow to the outlet hood 4 side. Yes. The angle of the downward slope of the kiln main body 2 is set in consideration of the size and fluidity of the particles to be generated, and is not limited to 2 to 3 degrees.
[0026]
Since the kiln main body 2 is provided so as to be rotatable with respect to the inlet hood 3 and the outlet hood 4, the connecting portion between the inlet hood 3 and the kiln main body 2 and the connecting portion between the outlet hood 4 and the kiln main body 2 are provided. In order to prevent gas leakage from this portion, sealing means 17a and 17b are provided. Each of the sealing means 17a and 17b has two seal rings that are spaced apart from each other in the axial direction of the kiln body 2, and more effectively prevents gas leakage through the sealing means 17a and 17b. Therefore, nitrogen gas is injected into the space between the seal rings.
[0027]
The inlet hood 3 has an inlet-side supply pipe 5 for supplying gaseous UF ₆ and water vapor into the first reaction chamber 2 a of the kiln body 2, and an exhaust gas outlet 18 for discharging gas generated in the kiln body 2. And are provided. The inlet-side supply pipe 5 passes through the central portion of the inlet hood 3 and the filter 15 and is disposed on the central axis of the kiln main body 2 with the tip end facing the kiln main body 2. A scraper 16 for removing deposits adhering to the surface of the filter 15 is fixed to the tip of the inlet side supply pipe 5. The scraper 16 rubs the surface of the filter as the filter 15 rotates with the rotation of the kiln body 2, and thereby the deposits are scraped off from the surface of the filter 15.
[0028]
The outlet hood 4 has an exhaust gas outlet 19 for discharging the gas generated in the kiln body 2 and an outlet 8 for discharging the solid final product obtained by the reaction in the kiln body 2. Is provided. Further, the outlet hood 4 is provided with an outlet side supply pipe 6 for supplying hydrogen and water vapor into the second reaction chamber 2 b of the kiln body 2 so as to penetrate the outlet hood 4.
[0029]
The outlet side supply pipe 6 has a double pipe structure of an outer pipe 62 and an inner pipe 63. Hydrogen is injected from a plurality of injection ports 61 formed on the peripheral wall of the outer tube 62. The water vapor is injected from the tip of the inner tube 63, specifically, the tip of the inner tube 63 and a plurality of injection ports formed around the inner tube 63 near the tip of the inner tube 63. The injection port 61 is provided on the lower wall surface of the outer tube 62 so as to inject hydrogen toward the uranium compound deposited on the bottom of the kiln body 2.
[0030]
Here, the inlet side supply pipe 5 will be described with reference to FIG.
[0031]
As shown in FIG. 2, the inlet side supply pipe 5 has a double pipe structure having an inner pipe 51 for injecting gaseous UF ₆ and an outer pipe 52 for injecting water vapor. 5 is provided with an inclined blade 53 for generating a swirling flow with respect to the central axis of the inlet side supply pipe 5 between the inner pipe 51 and the outer pipe 52. In addition, a dispersion 54 is provided at the center of the inner pipe 51 at the distal end of the inlet side supply pipe 5, and the dispersion 54 and the inner pipe 51 allow the diameter to gradually decrease toward the distal end. An inclined passage is formed. Therefore, UF ₆ from the inner tube 51 is injected while diffusing becomes a donut shape. On the other hand, the outer tube 52 has a tapered shape, and water vapor is injected so as to collide with the UF ₆ injected from the inner tube 51. Accordingly, atomization of UF ₆ is performed.
[0032]
Both of them collide by injection of UF ₆ and water vapor from the inlet side supply pipe 5, so that both are quickly mixed. In the first reaction chamber 2 a, the following reaction UF ₆ + 2H ₂ O → UO ₂ F ₂ + 4HF
As a result, UO ₂ F ₂ is generated.
[0033]
UO ₂ F ₂ produced in the first reaction chamber 2a is a fine solid having a particle size of 1 μm or less and tends to float in the first reaction chamber 2a. However, since the inlet-side supply pipe 5 is configured as described above, the water vapor injected from the inlet-side supply pipe 5 is injected while being swung by the action of the inclined blades 53, so that the UF injected from the inner pipe 51. ₆ and the generated UO ₂ F ₂ also rotate around the central axis of the kiln body 2 in the kiln body 2 in accordance with the flow. As a result, the generated UO ₂ F ₂ easily moves to the inner wall surface of the first reaction chamber 2a, and the UO ₂ F ₂ particles tend to be bonded to each other. This is the same even when the inlet side supply pipe 35 shown in FIGS. 5 and 6 is used. When the particles of UO ₂ F ₂ are bonded to each other, the particle diameter of UO ₂ F ₂ is increased. As a result, UO ₂ F ₂ is easily separated from water vapor and generated gas components, and the amount of UO ₂ F ₂ toward the exhaust gas outlet 18 of the inlet hood 3 is reduced.
[0034]
As described above, by reducing the amount of UO ₂ F ₂ toward the exhaust gas outlet 18, more UO ₂ F ₂ can be deposited on the bottom of the kiln body 2, and more UO ₂ F ₂ can be deposited. It can be used for the reaction in the second reaction chamber 2b. Moreover, the amount of UO ₂ F ₂ adhering to the filter 15 can be reduced by reducing the amount of UO ₂ F ₂ toward the exhaust gas outlet 18. Deposits adhering to the filter 15 can be removed by the scraper 16, but by reducing the amount of UO ₂ F ₂ adhering to the filter 15 in this way, the clogging of the filter 15 can be further prevented over a long period. It can be effectively suppressed. Incidentally, according to the inlet-side supply pipe mentioned above, but the particle size of UO ₂ F ₂ by the application of the swirling flow can be increased as compared with the conventional particle size of the thus UO ₂ F ₂ is increased Also, the clogging of the filter 15 can be suppressed, and UO ₂ F ₂ adhering to the filter 15 can be easily removed by the scraper 16.
[0035]
UO ₂ F ₂ adhering to the filter 15 is removed by the scraper 16, but when the filter 15 becomes clogged over time, nitrogen is introduced from the upstream side of the filter 15 (left side of the filter 15 in FIG. 1). Supplying gas intermittently is also effective for removing the deposits.
[0036]
In the present embodiment, an example in which a swirling flow is generated in the first reaction chamber 2a by the structure of the inlet side supply pipe 5 itself has been shown. However, as shown in FIGS. Thus, a swirling flow may be generated. In the example shown in FIGS. 5 and 6, each inlet-side supply pipe 35 has a double pipe structure, and the peripheral portion of the kiln main body 32 is symmetric with respect to the rotation center of the kiln main body 32. Is arranged. Further, the distal end portion of each inlet-side supply pipe 35 is bent in the direction opposite to the rotation direction of the kiln main body 32. Therefore, UF ₆ and steam from the inlet-side supply pipe 35 is injected in the circumferential direction of the kiln body 32, thereby being supplied into the kiln body 32 UF ₆ and steam as swirling flow. In both cases of the structure shown in FIG. 1 and the structures shown in FIGS. 5 and 6, in order to prevent UO ₂ F ₂ from moving toward the filter 15, a swirl flow is given to the generated UO ₂ F ₂ , and the kiln is It is directed to the inner wall surface of the main body, and its configuration is very simple. In order to give a swirl flow to the UO ₂ F ₂ generated in this way, the inlet side supply pipe is particularly capable of supplying at least one of UF ₆ and water vapor as a swirl flow into the kiln body. It is not limited. The means for supplying UF ₆ and water vapor is not limited to the above-mentioned means, and means that sufficient reaction is performed as a result of sufficient mixing of gaseous UF ₆ and water vapor. I just need it.
[0037]
In the present embodiment, the filter 15 is plate-shaped and provided on the end surface of the kiln main body 2, and a scraper 16 that scrapes off deposits attached to the filter 15 is fixed to the tip of the inlet-side supply pipe 5. The removal of the deposits adhering to the surface of 15 is automatically performed using the rotation of the kiln body 2. As a result, the deposits on the filter 15 can be removed with a very simple configuration that does not require a drive source for driving the scraper 16, and the filter 15 is plate-shaped, so that its manufacture is also easy. .
[0038]
Referring to FIG. 1 again, as described above, the first reaction chamber 2a is partitioned from the second reaction chamber 2b by the partition plate 9, and the internal temperature is about 300 to 400 ° C. which is the optimum temperature for the reaction. Is controlled. The temperature of the first reaction chamber 2a is appropriately selected and set depending on the properties (purity, etc.) of UF _{6 to be} supplied and the amount of water vapor. Further, since the first reaction chamber 2a is partitioned from the second reaction chamber 2b by the partition plate 9, the first reaction chamber 2a is not diluted with hydrogen and water vapor supplied to the second reaction chamber 2b. Since the concentration of the supplied UF ₆ and water vapor is maintained, the atmosphere in the first reaction chamber 2a can be maintained in a condition where UO ₂ F ₂ is easily generated. Moreover, this is achieved with a very simple configuration in which the kiln body 2 is partitioned by the partition plate 9.
[0039]
The UO ₂ F ₂ generated in the first reaction chamber 2a is deposited on the bottom of the first reaction chamber 2a, and the kiln body 2 is installed with a downward slope toward the outlet hood 4. With rotation, it is gradually transferred to the outlet hood 4 side. Here, since a gap is provided between the partition plate 9 and the kiln body 2 as shown in FIG. 3, the UO ₂ F ₂ generated in the first reaction chamber 2a passes through this gap. Move to the second reaction chamber 2b.
[0040]
As the size of the gap between the partition plate 9 and the kiln body 2, an optimal value is appropriately selected according to the amount of UF ₆ to be processed. When the variation width of the UF ₆ to be processed is large, a partition plate that can change the gap with the kiln body 2 may be used. Further, the gap between the partition plate 9 and the kiln body 2 need not be provided over the entire circumference of the partition plate 9. This is because the gap always passes through the bottom of the kiln main body 2 during one rotation of the kiln main body 2 even when the gap is provided only partially, and at this time, the UO ₂ F ₂ is used as the first. This is because the reaction chamber 2a can be moved to the second reaction chamber 2b. However, in order to move UO ₂ F ₂ more smoothly, it is desirable to provide a gap over the entire circumference of the partition plate 9.
[0041]
UO ₂ F ₂ moved to the second reaction chamber 2b reacts with water vapor injected from the inner pipe 63 of the outlet side supply pipe 6, and the following reaction formula UO ₂ F ₂ + H ₂ O → UO ₃ + 2HF
As a result, UO ₃ is generated. The generated UO ₃ further reacts with hydrogen injected from the injection port 61 of the outlet side supply pipe 6 by the transfer accompanying the rotation of the kiln main body 2, and the following reaction formula UO ₃ + H ₂ → UO ₂ + H ₂ O
As a result, the final product uranium dioxide (UO ₂ ) is produced. The generated UO ₂ is discharged from the outlet 8 of the outlet hood 4.
[0042]
Thus, in the second reaction chamber 2b, UO ₂ F ₂ generated in the first reaction chamber 2a becomes UO ₂ through a two-stage reaction. Here, since the outlet side supply pipe 6 is configured to inject water vapor from its tip and inject H ₂ from the peripheral surface injection port 61, the transfer direction of the uranium compound in the second reaction chamber 2b. , H ₂ O is preferentially supplied on the upstream side and H ₂ is preferentially supplied on the downstream side. As a result, the first stage reaction with H ₂ O and the second stage reaction with H ₂ can be efficiently performed with a simple configuration. As a result, UO ₂ can be efficiently converted from UO ₂ F _2. Obtainable.
[0043]
Further, as shown in FIGS. 1 and 4, a plurality of injection ports 61 are formed in the axial direction and the circumferential direction of the outlet side supply pipe 6, respectively. Therefore, hydrogen is efficiently injected to UO ₃ accumulated at the bottom of the second reaction chamber 2b of the kiln main body 2 and supplied so that the reaction between UO ₃ and hydrogen occurs optimally. The number and distribution density of the injection ports 61 are appropriately set according to the amount of uranium compound (UO ₃ ) accumulated in the second reaction chamber 2b so that the uranium compound deposited can be effectively injected. .
[0044]
Here, in consideration of the position of the uranium compound in the kiln body 2 during the operation of the rotary kiln 1, that is, during the rotation of the kiln body 2, the uranium compound is actually caused by friction between the inner wall surface of the kiln body 2 and the uranium compound. As shown also in FIG. 4, it exists in the position which shifted | deviated to the downstream with respect to the rotation direction of the kiln main body 2 rather than right under the rotation center of the kiln main body 2. FIG.
[0045]
Therefore, in this embodiment, the center C of the hydrogen injection range in the rotation direction of the kiln body 2 is the rotation of the kiln body 2 so that hydrogen effectively contacts the rotating uranium compound of the kiln body 2. The injection port 61 is provided so as to be downstream by a predetermined angle with respect to the rotational direction of the kiln main body 2 from directly below the center. This angle is appropriately determined according to the particle size and amount of the uranium compound to be produced. As a result, the region where the uranium compound and hydrogen come into contact increases, and the amount of hydrogen that is wasted is reduced, so that the reaction between hydrogen and the uranium compound can be performed efficiently. Moreover, it is preferable that each injection port 61 has a structure in which hydrogen is injected in a broad manner so that the injected hydrogen can contact the uranium compound as uniformly as possible.
[0046]
The temperature suitable for the reaction between UO ₂ F ₂ and H ₂ O and the reaction between UO ₃ and H ₂ is 450 to 800 ° C., and this temperature is determined for each block 14 a to 14 c of the external heating furnace 14. Measured and controlled by a thermometer equipped with a uranium adhesion prevention function. Each set temperature is determined for each of the blocks 14a to 14c so that the reaction is optimally performed. Generally, the temperature is set so as to increase in steps of approximately 100 ° C. from the first reaction chamber 2a side.
[0047]
Further, as seen in the above reaction, in the second reaction chamber 2b, HF was generated when UO ₃ was generated, and was further supplied from the outlet side supply pipe 6 into the second reaction chamber 2b. Unreacted hydrogen is also present. As described above, the gas components in the second reaction chamber 2b include hydrogen fluoride gas (HF) that is corrosive gas, hydrogen gas (H ₂ ) that is flammable gas, water vapor (H ₂ O), and the like. It is. Moreover, the temperature of the second reaction chamber 2b is as high as 800 ° C., and the kiln main body 2 is in a situation where corrosion due to corrosive gas is likely to occur. Therefore, it is difficult to select the material of the kiln body 2, and conventionally, a monel alloy or nickel has been used. However, since there are reports that these materials also corrode, as a result of extensive studies by the present inventors, the material of the kiln main body 2 and the thermometer installed in the kiln main body 2 is Inconel (for example, Inconel). 600, Inconel 625, etc.), Monel, Ni Hastelloy (eg Hastelloy B, Hastelloy C, etc.), stainless steel have been found suitable. Therefore, in this embodiment, Inconel 600 is used as a material of at least a portion of the kiln main body 2 and the thermometer installed therein that is exposed to the internal space of the kiln main body 2.
[0048]
Although the circular shape generally used may be sufficient as the cross-sectional shape of the kiln main body 2, as shown in FIG.3 and FIG.4, it is desirable to set it as a polygon (in the example shown in figure). If the cross section is circular, the accumulated uranium compound slips as it is when the kiln body 2 is rotated, and the replacement of the surface layer with the inner layer is not performed smoothly. Although it becomes difficult, it becomes easy to interchange a surface layer and an internal layer by making it a polygon, and reaction of a uranium compound is performed rapidly.
[0049]
The exhaust hood 4 is provided with an exhaust gas outlet 19, and the exhaust gas outlet 19 is provided with a valve, and the amount of exhaust gas from the exhaust gas outlet 19 is adjusted to adjust the first reaction chamber 2 a and the second reaction chamber. The pressure balance with 2b is adjusted so that the pressure in the second reaction chamber 2b is higher than the pressure in the first reaction chamber 2a. This suppresses unreacted UF ₆ in the first reaction chamber 2a from flowing into the second reaction chamber 2b. Each of the first reaction chamber 2a and the second reaction chamber 2b is provided with a pressure sensor (not shown). Based on the detection results of these pressure sensors, the valve provided at the exhaust gas outlet 19 is opened and closed. By controlling the above, the pressure in the second reaction chamber 2b is adjusted.
[0050]
In addition, the removal of the deposit | attachment adhering to the inner surface of the kiln main body 2 can use the hammering system which gives an impact to the kiln main body 2 from the exterior, and drops an deposit | attachment with the vibration at that time.
[0051]
Further, as described above, thermometers (not shown) are installed in the kiln main body 2 at positions corresponding to the blocks 14a to 14c of the external heating furnace 14, respectively. In addition, since the deposits are also generated in the accessory devices installed inside the kiln main body 2, it is necessary to remove these deposits. Therefore, in this embodiment, a double pipe (not shown) is installed inside the kiln main body 2, and an accessory device is installed in the inner pipe of the double pipe. And a double pipe is vibrated by flowing a high-pressure nitrogen gas from between an inner pipe and an outer pipe every fixed time, and this makes it possible to drop deposits. The installation position and number of double pipes are determined according to the installation position and number of attached devices. In addition, it is preferable that the important tip of the accessory device installed in the inner tube is protruded by about 10 mm from the tip of the outer tube in order to eliminate the influence of the outer tube.
[0052]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0053]
In a rotary kiln that supplies at least one of uranium hexafluoride and water vapor supplied from the inlet side supply pipe as a swirling flow, it is generated by the reaction of uranium hexafluoride and water vapor with a simple configuration that only generates swirling flow. The particle size of uranyl fluoride to be increased is increased, the amount of uranyl fluoride directed to the inlet hood is reduced, and the amount of uranyl fluoride deposited in the kiln body can be increased. The utilization efficiency of uranyl fluoride used for the reaction can be improved. In this case, a plate-like filter can be provided on the end face of the kiln body on the inlet hood side, but the inlet side supply pipe is provided through the center of the filter, and the scraper is fixed to the inlet side supply pipe. Filter clogging can be suppressed.
[0054]
In addition, the rotary kiln in which the inside of the kiln main body is divided into a first reaction chamber and a second reaction chamber by a partition plate, and the outlet side supply pipe has a double pipe structure, water vapor is jetted from the tip of the inner pipe, and the outer pipe In a rotary kiln that injects hydrogen from a plurality of injection ports formed on the peripheral surface, materials necessary for various reactions in the kiln body are preferentially supplied to the necessary locations even with a simple configuration. Therefore, the reaction in the kiln body can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a view showing a structure of a rotary kiln according to an embodiment of the present invention.
2 is a longitudinal sectional view showing a structure of a distal end portion of an inlet side supply pipe shown in FIG.
3 is a cross-sectional view of the rotary kiln shown in FIG. 1 taken along line XX.
4 is a cross-sectional view of the rotary kiln shown in FIG. 1 taken along line YY.
FIG. 5 is a longitudinal sectional view of a kiln main body and an inlet hood for explaining another example of the inlet side supply pipe applicable to the present invention.
FIG. 6 is a cross-sectional view of the kiln body viewed from the outlet hood side for explaining another example of the inlet side supply pipe applicable to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotary kiln 2,32 Kiln main body 2a 1st reaction chamber 2b 2nd reaction chamber 3 Inlet hood 4 Outlet hood 5,35 Inlet side supply pipe 6 Outlet side supply pipe 7 Roller 8 Outlet 9 Partition plate 9a Fixing member 13 Gear 14 Outside Heat furnace 15 Filter 16 Scraper 17a, 17b Sealing means 18, 19 Exhaust gas outlet 51 Inner pipe 52 Outer pipe 53 Inclined blade 54 Dispersion 61 Outlet 62 Outer pipe 63 Inner pipe

Claims (4)

A kiln body provided with an inlet hood at one end and an outlet hood at the other end, an inlet side supply pipe for supplying gaseous uranium hexafluoride and water vapor from the inlet hood side, and hydrogen from the outlet hood side And a rotary kiln for obtaining solid uranium dioxide from the outlet hood,
At least one of uranium hexafluoride and water vapor supplied from the inlet side supply pipe is supplied to the kiln main body as a swirling flow.   The inlet side supply pipe has a double pipe structure of an inner pipe and an outer pipe installed on a central axis of the kiln body with a tip portion facing the inside of the kiln body, and the hexafluoride 2. The rotary kiln according to claim 1, wherein uranium is diffused from the tip of the inner pipe and supplied into the kiln main body, and the water vapor is supplied into the kiln main body as a swirling flow from the tip of the outer pipe.   A plate-like filter for preventing the uranium compound generated in the kiln main body from entering the inlet hood is provided on the end surface of the kiln main body on the inlet hood side. The rotary kiln according to claim 1 or 2, wherein a scraper for scraping off uranium compounds adhering to the surface of the filter is fixed to the inlet side supply pipe.   The rotary kiln according to claim 1, wherein the inlet side supply pipe gives the swirl flow by injecting the uranium hexafluoride and water vapor in a circumferential direction of the kiln body.

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