JP2004028463A - Rotary kiln for producing uranium dioxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase efficiency of a reaction until uranium dioxide is produced from uranium hexafluoride in a simple constitution. <P>SOLUTION: This rotary kiln 1 has a kiln body 2 of which one end has an inlet hood 3 and the other end has an outlet hood 4. The inlet hood 3 is provided with an inlet side supply pipe 5 for supplying gaseous uranium hexafluoride and water vapor into the kiln body 2. The outlet hood 3 is provided with an outlet side supply pipe 6 for supplying water vapor and hydrogen into the kiln body 2. The inlet side supply pipe 5 has a double pipe structure having an inner pipe for supplying the uranium hexafluoride and an outer pipe for supplying the water vapor, and the water vapor is supplied as spiral flow into the kiln body 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to gaseous uranium hexafluoride (UF) ₆ ) And steam as raw materials, and these reactions at a high temperature produce a solid UO ₂ F ₂ (Uranyl fluoride), which is further reacted with steam to produce UO ₃ Generated, and the generated UO ₃ With hydrogen gas to produce uranium dioxide (UO ₂ ) For manufacturing rotary kilns.
[0002]
[Prior art]
A rotary kiln is a facility used to bake, incinerate or calcine an object to be processed and remove it as a solid.The rotary kiln has a cylindrical kiln body rotatably provided, an inlet hood provided at one end thereof, and other components. And an outlet hood provided at the end. The inside of the kiln main body is heated to a high temperature state by a heating means, into which an object to be processed is supplied through an inlet hood, and the supplied object to be processed is heated while being sent to an outlet side. Is discharged through an outlet hood.
[0003]
Rotary kilns of this type are also used in foreign countries to produce uranium dioxide powder, which is the raw material for nuclear fuel pellets. As a rotary kiln for producing uranium dioxide, for example, a rotary kiln 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 pipe structure is provided so as to coincide with the axis of the kiln body, and gaseous uranium hexafluoride and water vapor are supplied from the reaction gas inlet nozzle to the inlet device. Squirted into. The jetted uranium hexafluoride and steam react in the inlet device to generate uranyl fluoride. On the other hand, the outlet device is provided with a means for introducing steam and hydrogen into the kiln body, and uranyl fluoride generated in the inlet device enters the kiln body, where steam and hydrogen are mixed. After reacting with the gas mixture, uranium dioxide powder is finally released from the outlet device.
[0004]
In addition, a gas discharge pipe for discharging extra gas generated in the kiln body is provided on the outer peripheral surface of the inlet device, but uranyl fluoride generated in the inlet device is fine particles, A tubular filter is provided in the inlet device to prevent uranyl iodide from being discharged from the gas discharge pipe.
[0005]
[Problems to be solved by the invention]
However, in the conventional rotary kiln described above, the reaction conditions for producing uranyl fluoride from uranium hexafluoride and the reaction conditions for producing uranium dioxide from uranyl fluoride can be said to be sufficiently optimized. Did not.
[0006]
For example, uranyl fluoride produced by the reaction between uranium hexafluoride and water vapor has a very fine particle size of 1 μm or less, easily floats in a rotary kiln, and a gas discharge pipe together with gas generated in the rotary kiln. Head to. Then, uranyl fluoride headed to the gas discharge pipe is captured by the filter, but the captured uranyl fluoride is not used for the reaction in the next step, which is a factor that reduces the use efficiency of uranyl fluoride. Was. In addition, uranyl fluoride trapped in the filter causes 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 an increase in the operating rate of the rotary kiln. Is also reduced.
[0007]
Further, to obtain uranium dioxide from uranium hexafluoride, it is necessary to go through a plurality of stages, but since the space for the reaction from the inlet device to the outlet device is a substantially continuous space, it is not necessarily required that each At the stage of the reaction, a necessary substance is not supplied to a necessary portion.
[0008]
As described above, in the conventional rotary kiln, the reaction conditions for obtaining uranium dioxide from uranium hexafluoride are not sufficiently optimized. This leads to a decrease in production efficiency. In order to optimize the reaction conditions for obtaining uranium dioxide from uranium hexafluoride, there is also a method of strictly controlling the amount of the substance to be supplied, the reaction temperature, the reaction time, and the like. In a rotary kiln that is performed continuously over stages, it is difficult to manage them, and the configuration of the rotary kiln itself becomes complicated.
[0009]
Therefore, an object of the present invention is to provide a rotary kiln capable of improving the efficiency of the reaction from uranium hexafluoride 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 is a kiln body having an inlet hood at one end and an outlet hood at the other end, and gaseous uranium hexafluoride from the inlet hood side. And an inlet supply pipe for supplying steam and steam from the outlet hood, and an outlet supply pipe for supplying hydrogen and steam from the outlet hood. In the rotary kiln for obtaining solid uranium dioxide from the outlet hood, supply from the inlet 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 a reaction between uranium hexafluoride and steam supplied from the inlet side supply pipe into the kiln body, and at least one of uranium hexafluoride and steam is formed as a swirling flow. As it is supplied, the generated uranyl fluoride also swirls with the flow. As a result, uranyl fluoride moves to the inner wall surface of the kiln body to cause a situation in which the particle diameter of uranyl fluoride tends to grow, and the amount of uranyl fluoride traveling toward the inlet hood decreases. 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 swirling flow can be generated with a very simple configuration.
[0012]
In the above invention, in order to prevent the uranium compound generated in the kiln body from entering the inlet hood, a plate-shaped filter may be provided on the end surface of the kiln body on the inlet hood side. In this case, an inlet-side supply pipe is provided through the center of the filter, and a scraper that scrapes uranium compounds attached to the surface of the filter is fixed to the inlet-side supply pipe, thereby utilizing the rotation of the kiln body. The uranium compound from the filter. As described above, the particle size of the uranium compound (uranyl fluoride) generated by the reaction between the steam supplied from the inlet side supply pipe and uranium hexafluoride increases, and the amount of the uranium compound heading toward the inlet hood decreases. Since the number is reduced, clogging of the filter is suppressed.
[0013]
A second 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 an inlet for supplying gaseous uranium hexafluoride and water vapor from the inlet hood side. A rotary kiln that includes a supply pipe for supplying hydrogen and water vapor from the outlet hood side and obtains solid uranium dioxide from the outlet hood, wherein the inside of the kiln body is subjected to a first reaction by a partition plate. A chamber and a second reaction chamber, wherein the first reaction chamber and the second reaction chamber communicate with each other by a gap formed by an inner surface of the kiln body and an outer edge of the partition plate. And
[0014]
According to the present invention, by dividing the inside of the kiln body into the first reaction chamber and the second reaction chamber, the movement of uranium hexafluoride supplied from the inlet side supply pipe to the outlet hood side, and the outlet side The movement of hydrogen supplied from the supply pipe to the inlet hood side is suppressed. That is, a substance necessary for the reaction is supplied to a necessary place. Further, since the first reaction chamber and the second reaction chamber communicate with each other through a gap formed between the inner surface of the kiln body and the outer edge of the partition plate, the first reaction of the uranium compound generated in the kiln body is performed. The transfer from the chamber to the second reaction chamber is not hindered. As a result, the reaction between uranium hexafluoride and water vapor, the reaction between uranyl fluoride generated by this reaction and water vapor, and the reaction between uranium trioxide generated by this reaction and hydrogen are efficiently performed. Moreover, this is achieved with a very simple configuration in which the partition plate is installed in the kiln body.
[0015]
A third aspect of the rotary kiln of the present invention is a kiln body provided with an inlet hood at one end and an outlet hood at the other end, and an inlet for supplying gaseous uranium hexafluoride and water vapor from the inlet hood side. A rotary kiln that includes a side supply pipe and an outlet side supply pipe that supplies hydrogen and water vapor from the outlet hood side, and wherein the water vapor is supplied to the outlet side supply pipe in a rotary kiln that obtains solid uranium dioxide from the outlet hood It has a double pipe structure of an inner pipe and an outer pipe to which the hydrogen is supplied, while the steam is injected from the tip of the inner pipe, and the hydrogen is formed on a peripheral surface of the outer pipe. It is characterized by being ejected from the ejection port of (1).
[0016]
In this rotary kiln, uranyl fluoride is generated by a reaction between steam supplied from an inlet-side supply pipe and uranium hexafluoride, and uranium trioxide is produced by a reaction between the uranyl fluoride and steam supplied from an outlet-side supply pipe. Is generated, and uranium dioxide is finally generated by a reaction between the uranium trioxide and hydrogen supplied from the outlet side supply pipe. According to this invention, the outlet side supply pipe has a double pipe structure, in which steam is injected from the tip of the inner pipe, and hydrogen is injected from the injection port formed on the peripheral surface of the outer pipe. Thereby, the water vapor injected from the inner pipe of the outlet side supply pipe comes into contact with uranyl fluoride generated by the reaction between the water vapor and uranium hexafluoride first, and then the uranyl fluoride and the water vapor The hydrogen injected from the outer pipe of the outlet side supply pipe comes into contact with the uranium trioxide generated by the above reaction preferentially, so that the reaction from uranyl fluoride to uranium dioxide is efficiently performed. In addition, this can be achieved with a very simple structure in which a jet port is formed on the outer peripheral surface of the outer tube with respect to the double tube structure.
[0017]
In the above invention, uranium trioxide is deposited on the bottom of the kiln main body, and therefore, in order to effectively inject hydrogen into such uranium trioxide, the injection port must be connected to the outer tube. It is desirable to form it on the lower side. Furthermore, considering the movement of uranium trioxide due to the rotation of the kiln body, the injection port is arranged such that the center of the hydrogen injection range is located downstream of the kiln body in the rotational direction below the rotation center of the kiln body. More preferably, it is formed.
In addition, in this specification, "steam" means water in a vapor state, and includes saturated steam, heated steam, and the like.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a diagram showing a structure of a rotary kiln according to one embodiment of the present invention.
[0020]
As shown in FIG. 1, a rotary kiln 1 is used for conversion to oxides, more specifically, gaseous uranium hexafluoride (UF). ₆ Uranium dioxide (UO) as raw material ₂ The kiln body 2 is provided at one end of the kiln body 2 and a cylindrical kiln body 2 supported on the roller 7 so as to be rotatable about a substantially horizontal axis. 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 entrance hood 3 side, and the kiln main body 2 is rotated by transmitting a driving force from a driving unit (not shown) to the gear 13. 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 adjusting the temperature inside the kiln body 2 to a predetermined temperature suitable for the reaction. In particular, in the present embodiment, uranium dioxide is generated through a multi-step 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 for each step. 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. Has become. Inside the kiln body 2, thermometers (not shown) inserted from 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 obtained by these thermometers.
[0022]
In the present embodiment, the external heating furnace 14 is divided into three blocks 14a to 14c, but 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-shaped filter 15 for preventing uranium compounds generated in the kiln body 2 from entering the inlet hood 3 is fixed to an end surface of the kiln body 2 on the side of the inlet hood 3. The end surface of the kiln body 2 on the side of the entrance hood 3 is closed. The filter 15 may be any filter that is commonly used in this type of rotary kiln. Further, inside the kiln main body 2, a partition plate 9 for partitioning the inside of the kiln main body 2 into a first reaction chamber 2a and a second reaction chamber 2b in order from the entrance hood 3 side is provided. Due to the external heating furnace 14 described above, the first reaction chamber 2a is converted into a gaseous UF. ₆ The temperature is set to 300 ° C. or higher, which is suitable for the reaction between water and steam, and the second reaction chamber 2b contains uranyl fluoride (UO) generated by the reaction in the first reaction chamber 2a. ₂ F ₂ ) And steam, and the uranium trioxide (UO) produced by this reaction ₃ ) Is set at a temperature of 450 to 800 ° C. suitable for the reaction between hydrogen and hydrogen.
[0024]
The partition plate 9 regulates 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. Not something. That is, as shown in FIG. 3, the partition plate 9 has an outer diameter slightly smaller than the cross section of the kiln main body 2, and the kiln main body 2 is covered with the appropriate fixing member 9 a over the entire outer edge of the partition plate 9. It is supported inside the kiln main body 2 so that a gap is formed between the inner wall surface and 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, and the UO generated in the kiln body 2 ₂ F ₂ Etc. are made to flow easily to the outlet hood 4 side. The angle of the downward slope of the kiln body 2 is set in consideration of the size and fluidity of the generated particles, and is not limited to 2 to 3 degrees.
[0026]
Since the kiln body 2 is provided rotatably with respect to the inlet hood 3 and the outlet hood 4, a connecting portion between the inlet hood 3 and the kiln body 2 and a connecting portion between the outlet hood 4 and the kiln body 2 are provided. In order to prevent leakage of gas from this portion, sealing means 17a and 17b are provided. Each of the seal means 17a and 17b has two seal rings arranged at an interval in the axial direction of the kiln body 2, and more effectively prevents gas leakage through the seal means 17a and 17b. Therefore, a configuration is adopted in which nitrogen gas is injected into the space between the seal rings.
[0027]
In the inlet hood 3, gaseous UF is introduced into the first reaction chamber 2 a of the kiln body 2. ₆ An inlet-side supply pipe 5 for supplying steam and steam, and an exhaust gas outlet 18 for discharging gas generated in the kiln body 2 are provided. The inlet-side supply pipe 5 penetrates the inlet hood 3 and the center of the filter 15, and is installed on the central axis of the kiln main body 2 with its front end facing the inside of the kiln main body 2. At the end of the inlet side supply pipe 5, a scraper 16 for removing extraneous matter adhering to the surface of the filter 15 is fixed. The scraper 16 rubs the surface of the filter as the filter 15 rotates with the rotation of the kiln main body 2, whereby 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 gas generated in the kiln body 2 and an outlet 8 for discharging a solid end 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 steam into the second reaction chamber 2 b of the kiln body 2, passing through 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 jetted from the tip of the inner pipe 63, specifically, from the tip of the inner pipe 63 and a plurality of injection ports formed around the inner pipe 63 near the tip of the inner pipe 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 is a gaseous UF. ₆ Has a double pipe structure having an inner pipe 51 for injecting water and an outer pipe 52 for injecting water vapor. Inclined blades 53 for generating a swirling flow with respect to the central axis of the inlet side supply pipe 5 are provided. 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 form a ring whose diameter gradually decreases toward the distal end. Are formed. For this reason, the UF ₆ Is injected while diffusing in a donut shape. On the other hand, the outer pipe 52 has a tapered shape, and water vapor is injected from the UF injected from the inner pipe 51. ₆ It is injected to collide with. Thereby, UF ₆ Is performed.
[0032]
UF from inlet side supply pipe 5 ₆ The two are swiftly mixed by the collision of the two with the injection of water and steam, and the following reaction occurs in the first reaction chamber 2a.
UF ₆ + 2H ₂ O → UO ₂ F ₂ + 4HF
By UO ₂ F ₂ Is generated.
[0033]
UO generated in the first reaction chamber 2a ₂ F ₂ Is a fine solid having a particle size of 1 μm or less and tends to float in the first reaction chamber 2a. However, with the above-described configuration of the inlet-side supply pipe 5, the steam injected from the inlet-side supply pipe 5 is injected while rotating 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 In the kiln main body 2 along with the flow, it turns around the central axis of the kiln main body 2. As a result, the generated UO ₂ F ₂ Can easily move to the inner wall surface of the first reaction chamber 2a, and the UO ₂ F ₂ Are likely 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. UO ₂ F ₂ Are bonded to each other to form UO ₂ F ₂ Has a large particle size. As a result, UO ₂ F ₂ Is easily separated from water vapor and generated gas components, and the UO heading toward the exhaust gas outlet 18 of the inlet hood 3 ₂ F ₂ The amount of is reduced.
[0034]
As described above, the UO heading to the exhaust gas outlet 18 ₂ F ₂ More UO by reducing the amount of ₂ F ₂ Can be deposited on the bottom of the kiln body 2 and more UO ₂ F ₂ Can be used for the reaction in the second reaction chamber 2b. Also, the UO heading to the exhaust gas outlet 18 ₂ F ₂ Is reduced, the UO adhering to the filter 15 is reduced. ₂ F ₂ Can be reduced. Deposits adhering to the filter 15 can be removed by the scraper 16. ₂ F ₂ By reducing the amount of clogging, clogging of the filter 15 can be more effectively suppressed for a long period of time. In addition, according to the above-mentioned inlet side supply pipe, the application of the swirling flow causes the UO ₂ F ₂ Can be made larger than before, but as described above, UO ₂ F ₂ The clogging of the filter 15 can also be suppressed by increasing the particle size of ₂ F ₂ Can be easily removed by the scraper 16.
[0035]
UO adhering to the filter 15 ₂ F ₂ Is removed by the scraper 16, but if the filter 15 becomes clogged with time, the nitrogen gas may be intermittently supplied from the upstream side of the filter 15 (the left side of the filter 15 in FIG. 1). It is effective for removing extraneous matter.
[0036]
In the present embodiment, an example in which a swirl flow is generated in the first reaction chamber 2a by the structure of the inlet-side supply pipe 5 itself has been described. However, as shown in FIGS. May be provided to generate a swirling flow. 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 point-symmetric with respect to the rotation center of the kiln main body 32. Are located in The distal end of each inlet-side supply pipe 35 is bent in a direction opposite to the rotation direction of the kiln body 32. For this reason, the UF ₆ And steam are injected in the circumferential direction of the kiln body 32, thereby ₆ And the steam is supplied into the kiln main body 32 as a swirling flow. In each of the structure shown in FIG. 1 and the structures shown in FIGS. ₂ F ₂ Generated in order to prevent the ₂ F ₂ The swirling flow is given to the inner wall surface of the kiln body, and the configuration is extremely simple. UO generated in this way ₂ F ₂ In order to give swirling flow to the inlet, the inlet side supply pipe is ₆ There is no particular limitation as long as at least one of steam and steam can be supplied into the kiln body as a swirling flow. UF ₆ The means for supplying water and water vapor is not limited to the above-described means, but may be a gaseous UF. ₆ Any means may be used as long as the mixture is sufficiently mixed with water vapor and a sufficient reaction is performed as a result of the mixing.
[0037]
Further, in the present embodiment, the filter 15 is formed in a plate shape, and is provided on the end face of the kiln body 2, and a scraper 16 for scraping off the deposits attached to the filter 15 is fixed to the distal end portion of the inlet side supply pipe 5. The removal of the deposits attached to the surface of the kiln 15 is automatically performed using the rotation of the kiln body 2. This makes it possible to remove the deposits on the filter 15 with a very simple configuration that does not require a driving source for driving the scraper 16, and since the filter 15 is plate-shaped, its manufacture is also easy. .
[0038]
Referring again to FIG. 1, as described above, the first reaction chamber 2 a is separated from the second reaction chamber 2 b 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 depends on the UF to be supplied. ₆ The optimum temperature is appropriately selected and set according to the properties (purity, etc.) of the water and the amount of water vapor. Further, since the first reaction chamber 2a is separated from the second reaction chamber 2b by the partition plate 9, the first reaction chamber 2a is not diluted by the hydrogen and steam supplied to the second reaction chamber 2b, and is not diluted by the first reaction chamber 2a. Supplied UF ₆ And the concentration of water vapor is maintained, the atmosphere in the first reaction chamber 2a is changed to UO ₂ F ₂ Can be maintained in a condition in which is easily generated. Moreover, this can be achieved with a very simple configuration in which the kiln body 2 is partitioned by the partition plate 9.
[0039]
UO generated in the first reaction chamber 2a ₂ F ₂ Is deposited on the bottom of the first reaction chamber 2a, and is gradually transferred to the outlet hood 4 side with the rotation of the kiln body 2 because the kiln body 2 is installed at a downward slope toward the outlet hood 4. You. Here, since a gap is provided between the partition plate 9 and the kiln body 2 as shown in FIG. 3, the UO generated in the first reaction chamber 2a is formed. ₂ F ₂ Moves to the second reaction chamber 2b through this gap.
[0040]
The size of the gap between the partition plate 9 and the kiln body 2 depends on the UF to be treated. ₆ The optimal value is appropriately selected according to the amount of UF to be processed ₆ If the fluctuation width of the kiln 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 does not need to be provided over the entire circumference of the partition plate 9. This is because even when the gap is provided only at one position, the gap always passes through the bottom of the kiln body 2 during one rotation of the kiln body 2, and at this time, the UO ₂ F ₂ From the first reaction chamber 2a to the second reaction chamber 2b. However, UO ₂ F ₂ It is desirable to provide a gap over the entire periphery of the partition plate 9 in order to move the partition more smoothly.
[0041]
UO moved to the second reaction chamber 2b ₂ F ₂ Reacts with the 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
By UO ₃ Is generated. UO generated ₃ Further reacts with the hydrogen injected from the injection port 61 of the outlet side supply pipe 6 by the transfer accompanying the rotation of the kiln body 2, and the following reaction formula
UO ₃ + H ₂ → UO ₂ + H ₂ O
Uranium dioxide (UO) ₂ ) Is generated. UO generated ₂ Is discharged from the outlet 8 of the outlet hood 4.
[0042]
Thus, in the second reaction chamber 2b, the UO generated in the first reaction chamber 2a ₂ F ₂ However, after a two-step reaction, UO ₂ It becomes. Here, the outlet side supply pipe 6 injects water vapor from its tip, and H is injected from the injection port 61 on the peripheral surface. ₂ , The transport direction of the uranium compound in the second reaction chamber 2b is H on the upstream side. ₂ O is H on the downstream side ₂ Are supplied preferentially. As a result, H ₂ First stage reaction with O and H ₂ Can be efficiently performed with a simple configuration by the simple configuration, and as a result, the UO ₂ F ₂ From UO ₂ Can be obtained efficiently.
[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, the hydrogen is accumulated on the bottom of the second reaction chamber 2b of the kiln body 2 in UO. ₃ Sprayed efficiently to the UO ₃ And hydrogen are supplied in such a manner that the reaction between hydrogen and hydrogen occurs optimally. The number and the distribution density of the injection ports 61 are determined by the uranium compound (UO) deposited in the second reaction chamber 2b. ₃ ) Is set as appropriate so that the deposited uranium compound can be effectively jetted.
[0044]
Here, considering the position of the uranium compound in the kiln main body 2 during the operation of the rotary kiln 1, that is, the rotation of the kiln main body 2, the friction between the inner wall surface of the kiln main body 2 and the uranium compound actually causes the uranium compound to actually move. As shown in FIG. 4, exists at a position shifted to the downstream side in the rotation direction of the kiln body 2 from immediately below the rotation center of the kiln body 2.
[0045]
Thus, in the present embodiment, the center C of the hydrogen injection range in the rotation direction of the kiln body 2 is set so that the hydrogen contacts the uranium compound during the rotation of the kiln body 2 effectively. The injection port 61 is provided so as to be downstream of the kiln body 2 by a predetermined angle with respect to the rotation direction of the kiln body 2 directly below the center. This angle is appropriately determined according to the particle size and amount of the uranium compound to be produced. Thereby, the area where the uranium compound contacts the hydrogen increases, and the amount of the hydrogen that is wasted is reduced, whereby the reaction between the hydrogen and the uranium compound can be performed efficiently. In addition, it is preferable that each injection port 61 has a structure in which hydrogen is injected with a wide spread so that the injected hydrogen can contact the uranium compound as uniformly as possible.
[0046]
UO above ₂ F ₂ And H ₂ Reaction with O, and UO ₃ And H ₂ The temperature suitable for the reaction with is 450 to 800 ° C., and this temperature is measured and controlled for each of the blocks 14 a to 14 c of the external heating furnace 14 by a thermometer having a uranium adhesion preventing 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 about 100 ° C. from the first reaction chamber 2a side.
[0047]
Further, as seen in the above reaction, UO ₃ Is generated when HF is generated, and unreacted hydrogen supplied from the outlet side supply pipe 6 also exists in the second reaction chamber 2b. As described above, the gas components in the second reaction chamber 2b include hydrogen fluoride gas (HF) as a corrosive gas and hydrogen gas (H ₂ ), Water vapor (H ₂ O) and the like. Moreover, the temperature of the second reaction chamber 2b is as high as 800 ° C., and the kiln body 2 is in a state where corrosion by 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 is a report that these materials are also corroded, the inventors of the present invention have conducted intensive studies and found that the materials of the kiln body 2 and the thermometer installed in the kiln body 2 are Inconel (for example, Inconel). 600, Inconel 625, etc.), Monel, Ni Hastelloy (eg, Hastelloy B, Hastelloy C, etc.), and stainless steel were found to be suitable. Therefore, in the present embodiment, Inconel 600 is used as a material of at least a portion of the kiln body 2 and a thermometer installed therein that is exposed to the internal space of the kiln body 2.
[0048]
The cross-sectional shape of the kiln body 2 may be a generally used circular shape, but is desirably a polygon (a hexagon in the illustrated example) as shown in FIGS. If the cross section is circular, the deposited uranium compound slides as it is when the kiln body 2 is rotated, and the replacement of the surface layer with the internal layer is not performed smoothly, so that the reaction of the internal layer is performed. Although it becomes difficult, the surface layer and the inner layer are easily replaced by the polygon, and the reaction of the uranium compound is promptly performed.
[0049]
The outlet hood 4 is provided with an exhaust gas outlet 19, and a valve is provided at the exhaust gas outlet 19 to adjust the amount of exhaust gas from the exhaust gas outlet 19 so that the first reaction chamber 2a and the second reaction chamber 2 The pressure balance with the second reaction chamber 2b is adjusted such that the pressure in the second reaction chamber 2b is higher than the pressure in the first reaction chamber 2a. Thereby, unreacted UF in the first reaction chamber 2a ₆ Is suppressed from flowing into the second reaction chamber 2b. In addition, a pressure sensor (not shown) is provided in each of the first reaction chamber 2a and the second reaction chamber 2b, and a valve provided at the exhaust gas outlet 19 is opened and closed based on the detection results of these pressure sensors. Is controlled, the pressure of the second reaction chamber 2b is adjusted.
[0050]
It should be noted that a hammering method in which an adhering substance attached to the inner surface of the kiln main body 2 is removed by applying an impact to the kiln main body 2 from the outside and dropping the adhering substance by vibration at that time can be used.
[0051]
Further, as described above, thermometers (not shown) are installed inside the kiln body 2 at positions corresponding to the blocks 14a to 14c of the external heating furnace 14, respectively. In addition, since attached matter is also generated in the attached equipment installed inside the kiln body 2, it is necessary to remove these attached matter. For this purpose, in the present embodiment, a double pipe (not shown) is installed inside the kiln main body 2 and an accessory device is installed inside the inner pipe of the double pipe. Then, the double pipe is vibrated by flowing a high-pressure nitrogen gas from the inner pipe and the outer pipe at regular intervals, whereby the deposits can be removed. The installation position and number of double pipes are determined according to the installation position and number of accessory devices. In addition, it is preferable that the important distal end of the attached device installed on the inner pipe is protruded by about 10 mm from the distal end of the outer pipe in order to eliminate the influence of the outer pipe.
[0052]
【The invention's effect】
According to the present invention as described above, the following effects can be obtained.
[0053]
In a rotary kiln that supplies at least one of uranium hexafluoride and steam supplied from the inlet-side supply pipe as a swirling flow, the rotary kiln simply generates a swirling flow, and is formed by a reaction between uranium hexafluoride and steam. As the particle size of uranyl fluoride increases, the amount of uranyl fluoride flowing to the inlet hood decreases, 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-shaped filter can be provided on the end surface of the kiln body on the inlet hood side.However, by providing an inlet-side supply pipe through the center of the filter and fixing the scraper to the inlet-side supply pipe. In addition, clogging of the filter can be suppressed.
[0054]
In addition, a rotary kiln in which the inside of the kiln body is divided into a first reaction chamber and a second reaction chamber by a partition plate, and an outlet side supply pipe having a double pipe structure, in which steam is injected from the tip of the inner pipe to form an outer pipe, 2. Description of the Related Art In a rotary kiln that injects hydrogen from a plurality of injection ports formed on a peripheral surface, substances necessary for various reactions in the kiln body are preferentially supplied to necessary parts while having a simple configuration. Therefore, the reaction in the kiln body can be efficiently performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of a rotary kiln according to one embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a structure of a distal end portion of an inlet side supply pipe shown in FIG.
FIG. 3 is a sectional view taken along line XX of the rotary kiln shown in FIG.
FIG. 4 is a sectional view taken along line YY of the rotary kiln shown in FIG.
FIG. 5 is a longitudinal sectional view of a kiln body and an inlet hood for explaining another example of an inlet side supply pipe applicable to the present invention.
FIG. 6 is a cross-sectional view of a kiln main body viewed from an outlet hood side for explaining another example of an inlet side supply pipe applicable to the present invention.
[Explanation of symbols]
1 rotary kiln
2,32 kiln body
2a First reaction chamber
2b Second reaction chamber
3 Entrance hood
4 Exit hood
5,35 Inlet supply pipe
6 Outlet side supply pipe
7 Laura
8 outlet
9 Partition plate
9a Fixing member
13 gears
14 External heating furnace
15 Filter
16 Scraper
17a, 17b sealing means
18,19 Exhaust gas outlet
51 Inner tube
52 outer tube
53 Inclined blade
54 dispersion
61 injection port
62 outer tube
63 inner tube

Claims (9)

A kiln body provided with an inlet hood at one end and an outlet hood at the other end, an inlet supply pipe for supplying gaseous uranium hexafluoride and steam from the inlet hood side, and hydrogen from the outlet hood side And an outlet-side supply pipe for supplying steam, in a rotary kiln for obtaining solid uranium dioxide from the outlet hood,
A rotary kiln, wherein at least one of uranium hexafluoride and steam supplied from the inlet-side supply pipe is supplied to the kiln body as a swirling flow. The inlet-side supply pipe has a double pipe structure of an inner pipe and an outer pipe, which is installed on a central axis of the kiln body with a front end portion facing the inside of the kiln body, and The rotary kiln according to claim 1, wherein uranium is diffused from a tip of the inner tube and supplied into the kiln body, and the steam is supplied into the kiln body as a swirling flow from a tip of the outer tube. A plate-shaped filter for preventing uranium compounds generated in the kiln body from entering the inlet hood is provided on an end surface of the kiln body on the side of the inlet hood. 3. The rotary kiln according to claim 1, wherein the rotary kiln is fixed by penetrating a pipe, and a scraper that scrapes off a uranium compound attached to a surface of the filter is fixed to the inlet-side supply pipe. 4. The rotary kiln according to claim 1, wherein the inlet-side supply pipe gives the swirling flow by injecting the uranium hexafluoride and steam in a circumferential direction of the kiln body. A kiln body provided with an inlet hood at one end and an outlet hood at the other end, an inlet supply pipe for supplying gaseous uranium hexafluoride and steam from the inlet hood side, and hydrogen from the outlet hood side And an outlet-side supply pipe for supplying steam, in a rotary kiln for obtaining solid uranium dioxide from the outlet hood,
The inside of the kiln main body is partitioned into a first reaction chamber and a second reaction chamber by a partition plate, and the first reaction chamber and the second reaction chamber are formed by an inner surface of the kiln main body and an outer edge of the partition plate. A rotary kiln characterized in that it is communicated by a gap formed by: The rotary kiln according to claim 5, wherein the partition plate is supported in the kiln body by a support member such that the gap is formed around the entire circumference of the partition plate. A kiln body provided with an inlet hood at one end and an outlet hood at the other end, an inlet supply pipe for supplying gaseous uranium hexafluoride and steam from the inlet hood side, and hydrogen from the outlet hood side And an outlet-side supply pipe for supplying steam, in a rotary kiln for obtaining solid uranium dioxide from the outlet hood,
The outlet side supply pipe has a double pipe structure of an inner pipe to which the steam is supplied and an outer pipe to which the hydrogen is supplied, and the steam is injected from a tip of the inner pipe, A rotary kiln wherein hydrogen is injected from a plurality of injection ports formed on a peripheral surface of the outer tube. The rotary kiln according to claim 7, wherein the injection port is formed below the outer tube. 9. The rotary kiln according to claim 8, wherein the injection port is formed such that a center of a hydrogen injection range is located downstream of a position directly below a rotation center of the kiln main body in a rotational direction of the kiln main body.

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