JPS6045933B2 - Fluidized bed reaction method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a fluidized bed reaction method, and more specifically, to an improvement in a fluidized bed reaction apparatus that handles radioactive materials.

Uranyl nitrate and plutonium nitrate are mixed in a fluidized bed reaction vessel (
It is known that oxides of uranium and plutonium can be produced by direct and continuous thermal decomposition (denitrification) using a column.

In addition to equipment design, this method requires particularly sufficient process control to enable smooth operation. It is important to maintain the average particle size of the particles that precipitate and grow, some of which are continuously discharged as products, and some of which are taken out as seed particles for the next reaction, to below 400 μm (Japanese Patent Laid-Open No. 55 -7527).

If the average particle size of oxide particles becomes abnormally large, it will have a negative effect on the flow state and heat transfer, and if left untreated, not only will the flow stop and the operation will be stopped.
The reaction vessel (tower) must be disassembled and cleaned, which consumes a great deal of labor and time. In order to avoid the worst situation of decomposing and cleaning the tower as described above, periodically sample the oxide particles and check their average particle size, and check if the particle size has grown beyond a certain limit. It is necessary to interrupt the operation immediately when a trend is observed, and in this way, it is possible to restart the operation only by replacing the seed particles.

In conventional methods and equipment, in the event of a planned interruption of operation (completion of one operating unit), the oxide particles recovered as a product or the oxide particles recovered from the sampling line are taken into a separate container and then collected. Transfer to a reaction vessel (tower) was performed manually.

When the material to be treated is radioactive, such manual operations are undesirable or difficult. A similar problem also occurred when the seed particles were replaced. The present invention provides a novel operating method and apparatus that overcomes this difficulty.

According to the present invention, a fluidized bed is formed by introducing seed particles (usually reaction product powder) and a fluidizing gas into the lower part of the fluidized bed reaction zone, and a reactant (gas or atomized liquid) is added to a portion of the zone. A fluidized bed reaction system in which the zone is heated if necessary, most of the product is removed from the top of the fluidized bed as an overflow, and a portion is removed from the bottom of the fluidized bed as a test sample or next seed particle. A vacuum suction system is connected to the lower part of the fluidized bed, a solid-gas separation means is interposed in the middle of this system, a powder receiving means is provided to the solid-gas separation means via a powder discharge path, and the powder is By providing a system for returning the powder from the body receiving means to the reaction zone, the product powder is taken out from the reaction zone by vacuum absorption at any time, and the powder is separated by the solid-gas separation means. A fluidized bed reaction method is provided, which is characterized in that the fluidized bed reaction zone is transferred to a fluidized bed reaction zone as needed.

According to another aspect of the invention, a fluidized bed is formed by introducing seed particles (usually reaction product powder) and a fluidizing gas into the lower part of the fluidized bed reaction zone, and a part of the zone is filled with reactants. (gas or atomized liquid), heating the zone if necessary, removing most of the product as an overflow from the top of the fluidized bed and a portion from the bottom of the fluidized bed as a test sample or subsequent seed particles. It is an apparatus for carrying out a fluidized bed reaction consisting of an inlet for fluidizing gas at the bottom, an inlet for the reactant above it, an overflow outlet for the powder produced above it, and an outlet for the produced powder above it. A fluidized bed reaction tower equipped with a gas outlet with an offshore filter at the top and heating means if necessary; a vacuum suction pipe connected to the lower end of the fluidized bed forming part of the tower; a gas separator; a piping system leading to a suction source connected to the solid-gas separator; a powder receiver connected to the solid-gas separator; and a piping system for returning the powder from the powder receiver to the reaction tower. An apparatus is provided which is characterized in that:

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 illustrates the concept of the method and apparatus of the present invention. The reaction tower 1 has a dispersion plate 11, a fluidizing gas inlet 12, and a valve 14 at the bottom.
A sample extraction pipe system 13 is provided, and above it, a reactant inlet 17 and a product discharge pipe system 18 due to overflow are provided,
A filter 15 and an outlet 16 for fluidizing gas and reaction product gas are provided at the top.

(The heating device is not shown for convenience.) Such fluidized bed reaction towers are known, one example of which is disclosed in, for example, JP-A-55-752.
7 is explained in detail. In addition to these, the apparatus of the present invention has a suction pipe system 2 (21 and 22) are provided.

This pipe system is usually provided with an on-off valve 22 and a valve 23 for opening/closing and regulating pressure. The solid-gas separator 4 is essentially the same as the gas separator 15 in the upper part of the reaction column and has a filter 41 and is preferably equipped with a valve 45 to prevent clogging of the filter. A blow tube system 44 is provided.

Further, it is preferable that the solid-gas separator 4 is provided with a vibrator 42 . The solid-gas separator 4 is connected to the powder receiver 5 by a line having a valve 43, which in turn communicates with the reaction column by a line having a valve 51 and opening into the reaction column at 52.

Connected to this pipe system, a further powder receiver 6 is preferably provided, which includes a hopper 62 for introducing the powder and a valve 6.
1 and a discharge valve 63.

To carry out a fluidized bed reaction, the reaction tower is first charged with seed particles, fluidized gas is introduced, heated, and the reactants are introduced into the inlet 1.
7 and continue the reaction.

A suitable example of the operating method is, for example, the previously mentioned JP-A-55-
7527, etc., so there is no need to specifically describe it here. A feature of the method of the present invention is that when a single operation is completed, the suction blower 3 is operated and the valve 23 is used to provide an appropriate suction force, thereby transferring the produced powder from the reaction tower to the solid-gas separator 4. Here, the produced powder is collected and stored appropriately in the powder receiver 5, and seed particles (relatively small product powder) are charged into another powder receiver. Once operations begin, samples are taken from the sample extraction system at any time to monitor the particle size and other characteristics of the product. Powder receiver 5 at the end of planned operations
The resulting powder is then transferred to a reaction vessel and the next operation begins.
When the average particle size of the produced particles exceeds a certain limit, new seed particles are charged and a new operation is started. Second
The figure shows a specific example of the device according to the invention.

This specific example is a device that handles uranium alone. Naturally, when handling plutonium, due to criticality control constraints, the inner diameter of the solid-gas separator and receiver should be 76T! U
Although it is necessary to keep the amount below TL, since the plutonium denitrification reaction tower is also small for the same reason, the amount of powder to be transferred is also 10k9 or less. Therefore, even if the transfer device is made smaller, it will have a sufficient effect on improving the operation. The transfer device is composed of a solid-gas separator 4, a receiver 5, and a second receiver 6.

The solid-gas separator 4 has a straight pipe with an inner diameter of 158Tr$L1 and a total height of 7
Made of 007T0n stainless steel, solid-gas separation filter 41. It consists of a powder suction pipe 21, a blowback gas inlet 4, a male gas exhaust pipe 22, an inner cylinder 46, and an exciter 42. The solid-gas separation filter 41 is a stainless steel copper filter with an outer diameter of 36TT0!11 and a length of 230 wun, and four filters are installed therein, and the blowback gas injection time and injection interval can be set using a timer. The powder suction pipe 21 has an inner diameter of 2
2Tm! The Rtl gas exhaust pipe 22 has an inner diameter of 28W1! ! It is l. Both receptors 5 and 6 are made of stainless steel, have an inner diameter of 20 cm, and a total height of 600 mm. , effective capacity 15e. Receptor 5 is a receptacle for the transferred powder, and pneumatically actuated valve 4
3 to the solid-gas separator 4, and to the outside of the system via an air-operated valve 51 and an air-operated valve 53, and to the reaction tower via an air-operated valve 54. On the other hand, the second receptor 6 is for the new seed particles and the pneumatically actuated valve 6
A hopper 62 for filling seed particles is provided through 1,
It is connected to the reaction column via an air-operated valve 63. Further, the receiver 6 is maintained at approximately 300'C by a heating furnace 64. The transfer device is housed in the glove box in order to prevent scattering of radioactive materials when supplying new seed particles from the hopper 62 or extracting powder that cannot be reused as seed particles as it is out of the system.

Next, an example of operation will be shown.

Example 1 Approximately 8k9 seed particles of uranium trioxide with an average particle size of 200μ were charged into the fluidized bed reaction tower, air was introduced at a pressure of 4kg/d to form a fluidized bed, and a uranyl nitrate solution was sprayed to form a An operation to obtain uranium trioxide by thermal decomposition at 300°C was started.

After 2 gT1 from the start of the operation, the operation was systematically terminated and the product particles were extracted. The procedure and conditions in this case are as follows.Heat the fluidized bed is stopped, the air flow rate for forming the fluidized bed is reduced by 1k9/Cr?L, and the suction blower 3 shown in FIG. Start the shaker 42, adjust the pressure to about -400CkInH20 by the valve 23,
The blowback system 44 to prevent clogging is started (compressed air injection time 0.2 times, same pressure 5k9/CdGl same injection interval 3 times 2 times), valves 43 and 22 are opened, and the powder F is pumped into the pipe system. From 21, it was extracted into a receiver 5 via a solid-gas separator 4.

At this time, the time required for extraction was about 5 minutes, and the weight of the product particles extracted was 7.6k9. In the conventional method, it took about 1 piece to extract, and the amount extracted was about 7k9. Example 2 Approximately 30k9 seed particles of uranium trioxide with an average particle size of 200μ were charged into the fluidized bed reactor, air was introduced at a pressure of 4k9/d to form a fluidized bed, and a uranyl nitrate solution was sprayed.
In an operation to obtain uranium trioxide through thermal decomposition at approximately 320°C, the average particle size of the product particles grew to 450μ after 5 minutes from the start of operation, so the product particles were extracted and new seed particles were supplied. The procedures and conditions in this case are as follows.

The amount of heating of the fluidized bed is reduced, and the amount of air for fluidized bed formation is reduced to approximately 1
k9/d, the suction blower 3 and the vibrator 42 shown in FIG.
hH20 and started the blowback system 44 to prevent clogging (compressed air injection time 0 seconds, same pressure 7K9).
/CrlGl injection interval of 30 seconds), valves 43 and 22 were opened, and product particles F were extracted from pipe system 21 through solid-gas separator 4 into a receiver.

At this time, the time required for extraction was approximately 1 particle, and the weight of the product particles extracted was 28.7k9. Immediately after the extraction operation was completed, new seed particles preheated to about 300° C., which had been prepared in advance in the receiver 6, were supplied to the column, and the operation was resumed.

The time required to resume operation was approximately 40 minutes, which was approximately 112 minutes compared to the conventional method. In addition, regarding the amount withdrawn, about 10% remained in the column in the conventional method, but the residual amount in this example was reduced to about 5%. The device of the invention can be designed compactly and can be designed to be remotely operated inside a shield. Therefore, the problem of worker radiation exposure is eliminated and operational efficiency is greatly improved.
Although the present invention has been described with reference to uranium compounds for convenience, it will be obvious to those skilled in the art that plutonium compounds can be used as is, as long as critical constraints on device dimensions are observed and radiation shielding considerations are taken. .

Although the present invention is primarily intended for the handling of radioactive materials, it is also applicable to non-radioactive general materials such as aluminum nitrate, which is converted into aluminum oxide using a fluidized bed reactor. It is also self-evident that it can also be used for handling.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the concept of the method of the present invention.

Claims (1)

[Claims] 1 A fluidized bed is formed by introducing seed particles (usually reaction product powder) and a fluidizing gas into the lower part of a fluidized bed reaction zone, and a reactant (gas or spray) is introduced into a part of the zone. fluidized bed), heating the zone if necessary, removing most of the product as an overflow from the top of the fluidized bed, and a portion from the bottom of the fluidized bed as a test sample or subsequent seed particles. In the reaction method, a vacuum suction system is connected to the lower part of the fluidized bed, a solid-gas separation means is interposed in the middle of the system, and a powder receiving means is provided to the solid-gas separation means via a powder discharge path, By providing a system for returning the powder from the powder receiving means to the reaction zone, the product powder is taken out from the reaction zone by vacuum suction at any time, and the powder is separated by the solid-gas separation means. A fluidized bed reaction method characterized in that the fluidized bed reaction zone is transferred to a fluidized bed reaction zone at any time. 2. The method according to claim 1, wherein the reactant and the product are radioactive substances. 3. The method according to claim 2, wherein the reactant is uranyl nitrate and/or plutonium nitrate. 4 introducing seed particles (usually reaction product powder) and a fluidizing gas into the lower part of the fluidized bed reaction zone to form a fluidized bed, and introducing a reactant (gas or atomized liquid) into a portion of the zone; If necessary, the zone is heated to carry out a fluidized bed reaction consisting of removing most of the product as an overflow from the top of the fluidized bed and a portion from the bottom of the fluidized bed as a test sample or subsequent seed particles. The device is equipped with an inlet for fluidizing gas at the bottom, an inlet for the reactant above it, an overflow outlet for the produced powder above it, and a gas outlet with a filter at the top. , a fluidized bed reaction tower having a heating means if necessary; a vacuum suction pipe connected to the lower end of the fluidized bed forming section of the tower; a solid-gas separator connected to the pipe; connected to the solid-gas separator An apparatus characterized in that it is equipped with a pipe system leading to a suction source where the powder is removed; a powder receiver connected to the solid-gas separator; and a pipe system returning the powder from the powder receiver to the reaction column. 5. The apparatus according to claim 4, wherein the solid-gas separator is equipped with blowback means for recovering from clogging of the filter. 6. The apparatus according to claim 4 or 5, further comprising a receptor for new seed particles connected to the pipe system connecting the powder receptor to the reaction tower. Featured device.