DE3536717C2 - Multi-chamber fluid bed device - Google Patents

Description

The invention relates to a multi-chamber fluidized bed device for converting UO ₃ or U ₃ O ₈ to UF ₆ with increased efficiency and simple structure.

A fluid bed based device of a gas-solid system forms a fluid bed by fluidizing solid particles with a  Fluidizing gas and performs the gas-solid reaction by placing the fluidized particles in contact with get a reaction gas. Such a Vorrich tung is widely used in industrial applications. However, should with the Vorrich mentioned above several different reactions continuously Lich carried out, so it is necessary to do the pre direction to multiply. There are two systems for this available, namely a multi-tower system, which more than two separate devices, and one chamber system, which covers the inner area of an a cell device multiplied. The latter system aims to increase its efficiency through multiplication the same reaction by drying and cooling to improve the particles (anonym; Chem. Eng. 63, 116 (1956)), but since the system is not a function of the Kon trolls of particle reaction and particle transfer shows, it cannot reali different reactions sieren. In contrast, the multi-tower system in general to perform various reactions by Ver multiplication used (C.D. Harringting et al; Uranium Production Technology, D. Van Nostrand Company, INC P550-501 (1959)). However, with the multi-tower system Fluid bed reaction device is multiplied, so will be the opportunity to transfer particles between the Towers increased so that many pipes to the Trans fer of particles, pumps for transfer and delivery systems are required. Therefore, the structure of the Device and operating system not only complex and the design of the device, the manufacture of the Components and the operation of the device are kom  plicated, but the multi-tower system is also regarding its cost disadvantageous.

DE-AS 10 46 577 relates to a lock for Fluidized bed reactors, with the two different Reaction zones are separated very closely from one another should. The individual reaction zones with the same Reaction conditions are not divided into sub-zones, whereby the composition, flow rate and temperature are not freely selectable and optimal over the entire fluid bed Conditions cannot be set for each section can.

US 2,419,245 describes a conversion method of Hydrocarbons at high temperature in the presence of solid heterogeneous catalysts in lighter products, especially gasoline with a high octane number. For The catalyst is regenerated by a reactor that can be provided with vertical baffles under oxidation passed through the regeneration gases.

US 2 895 906 describes an apparatus for the implementation catalytic reactions in a fluidized Solids conversion system. To do this, a lot of material to be converted with fluidized solids in brought into contact with a unitary device in which both the conversion and regeneration stages in one be carried out in the individual chamber corresponding reaction zones by interacting inner Baffles are divided.

A method for producing uranium hexafluoride is disclosed in US 3,010,784. For this purpose, higher-valent uranium oxides in the form of a fluidized bed containing hydrogen-containing gas are first reduced to UO ₂ in at least two different stages. Subsequently, the UO _{2 is} converted into UF ₄ in a fluidized bed with an HF-containing gas and further with an F ₂ -containing gas to UF ₆ .

The inventors have paid attention to the fact that, in accordance with the above-mentioned multi-chamber system, the reaction efficiency can be improved even if the reactions are the same, and they have worked to provide a multi-chamber fluidized bed apparatus for converting UO ₃ or to create U ₃ O ₈ in UF ₆ , which enables different reactions to be carried out and which enables the efficiency of the device to be improved and the operating system to be simplified by eliminating the above-mentioned disadvantages of conventional multi-chamber systems.

As a result, the inventors found that a multi-chamber fluid bed apparatus for converting UO ₃ or U ₃ O ₈ to UF _{6 of} the above-mentioned type can be obtained by ensuring the regulatory conditions for the reaction of the particles and the amount of the particle transfer, with which the present invention was realized.

The invention has for its object to provide a Mehrkam mer fluidized bed device for converting UO ₃ or U ₃ O ₈ to UF ₆ , which che has an improved efficiency. In addition, a multi-chamber fluid bed reaction device is to be created by the invention, which has a simple construction by simplifying the operating system.

This object is achieved by a multi-chamber fluid bed device for converting UO ₃ or U ₃ O ₈ to UF ₆ ,
with first chambers ( 1 , 2 ) for converting U ₃ O ₈ or UO ₃ into UO ₂ , second chambers ( 7 A, 7 B, 7 C, 8 ) for converting UO ₂ into UF ₄ , and third chambers ( 13 , 14 ) for converting UF ₄ to UF ₆ , wherein the plurality of chambers are formed by partitioning by means of partitions;
a fluidized bed in which the starting material is successively transported from the first chamber ( 1 ) to the third chambers ( 14 );
with wind boxes ( 1 a, 2 a, 7 a- 8 a, 13 a, 14 a), which are each assigned to the first ( 1 , 2 ), second ( 7 A- 8 ) and third ( 13 , 14 ) chambers, wherein supply nozzles (1 b-14 b) are provided for the fluidized gas, which supply hydrogen gas to the first chambers, HF gas to the second chambers and fluorine gas to third chambers, and the partition walls alternately from the bottom of the fluidized bed to a point below the surface or extend from the roof of the reaction device to a point below the surface of the fluidized bed;

Particle transfer regulation chambers ( 3-6 ) with inert gas supply between the first chambers ( 1 , 2 ) and the second chambers ( 7 A- 8 ) and further particle transfer regulation chambers ( 9-12 ) between the second chambers ( 7 A- 8 ) and the third chambers ( 13 , 14 ), whereby a gas lock is formed for each different reaction gas; and finally with
Solid gas separation sections in each of the first ( 16 , 17 ), second ( 19 A, 19 B) and third ( 22 ) chambers.

As described above, is fiction the various reactions can be carried out Lich by the fluid bed area and the wind box area for the supply of a fluidizing gas in a multiple chamber divided and the operating system (Amount of reaction gas, gas temperature, etc.) in each Chamber can be made freely selectable, after which the training a fluidized bed, a moving bed or one Fixed bed in each chamber is made possible by the height the partition chosen appropriately and the regulation the particle reaction and the particle transfer Regulation of a flow rate of the feed gas fold is made, the particles formed by  Arrangement of a gas-particle separator in each Chamber can be effectively recovered.

The invention is then based on the drawings explained in more detail. Show it:

Figure 1 is a schematic elevation of a preferred embodiment of a multi-chamber fluid bed device according to the invention, in which uranium oxide is converted to UF ₆ .

Fig. 2 (a) is a schematic elevation of the fluid bed device in which the partition is arranged in Anla ge with the base surface of the fluid bed;

Fig. 2 (b) is a schematic elevation of the fluid bed device in which the partition is disposed over a gap that opens above the base surface of the fluid bed;

Fig. 2 (c) is a schematic elevation of the fluidized bed device, which unites the partition of Figure 2 (a) and that of Figure 2 (b).

Fig. 3 (a), (b), (c), (d) are schematic plan views of an arrangement of apparatus which illustrates the great freedom in the arrangement of the inventive apparatus;

Fig. 4 is a schematic plan view of a fluidized bed device in block design, which can be expanded both horizontally and vertically; and

Fig. 5 is a schematic plan view of a fluid bed device with recirculation, in which the particles are circulated again.

The invention will now be explained in more detail where, for example, the multi-chamber device according to the invention is compared with the usual multi-tower system for an application, in which uranium oxide is converted to UF ₆ and, as a game example of the reaction device according to the invention, a multi-chamber device in Block construction was selected.

Referring to FIG. 1 1-14 represent the chambers a multi-chamber fluidized bed area is (and in some cases a part of a moving bed or a fixed bed), the Kam numbers 1 a- 14 a provide the wind box portion for supplying fluidizing gas respectively to the Chamber 1-14 and nozzles 1 b- 14 b supply the chambers 1-14 with fluidizing gas.

Of the chambers 1-14 , the chambers 1-2 have the task of reducing U ₃ O ₈ or UO ₃ to UO ₂ , and the chambers 3-6 serve to cool and store the particles, to seal the gas and to regulate the particle transfer . The chambers 7-8 have the task of converting UO ₂ to UF ₄ , and the chambers 9-12 are used for cooling and storing particles, for gas sealing and for regulating particle transfer. Chambers 13-14 are used to convert UF ₄ to UF ₆ . The raw material U ₃ O ₈ or UO ₃ is fed via a raw material feed line 15 to the chamber 1 , in which U ₃ O ₈ or UO ₃ by means of water gas which contained in the fluidizing gas supplied via the nozzle 16 and the wind box 1 a is reduced to UO ₂ . If in chamber 1 the UO ₂ particles, which form the fluidized bed, increase the height of the fluidized bed according to the supplied amount of raw material from a uranium composition, they pass from chamber 1 to chamber 2 mainly under the pressure of the fluidized bed the lower gap of the partition.

In chamber 2 , remaining U ₃ O ₈ or UO ₃ in the unreacted state of chamber 1 is almost completely converted to UO ₂ using hydrogen gas. The hydrogen gas for reduction is contained in the fluidization gas supplied via the wind box 3 a and the nozzle 3 b releases the hydrogen gas remaining under the UO ₂ particles and at the same time prevents the entry of hydrogen gas into the subsequent chamber by means of a gas seal. The chamber 4 and the chamber 5 are used for cooling and storing the particles, nitrogen gas being supplied via the nozzle 4 b, the wind box 4 a, and 5 a and the nozzle 5 b. The fluidized bed is formed in the chamber 4 , while a fluidized bed or moving bed is produced in the chamber 5 . The chamber 5 and the chamber 6 also have the task of regulating the transfer of particles. The regulation of the transfer amount of the particles is done by the amount of gas that is supplied to the chamber 5 and the chamber 6 .

By regulating the amount of the nitrogen gas chamber 6 fed to the height changes of the fluid bed in the chamber 6 and the amount of particles further flows to the chamber 7 A. The amount of the particles which passes from the chamber 5 into the chamber 6 is determined by the relation of the bed height in the chamber 5 , the amount of the nitrogen gas supplied to the chamber 5 and the amount of the nitrogen gas supplied to the chamber 6 . Finally, when the amount of nitrogen gas supplied to the chamber 6 is caused to drop below a limit of the flow rate (speed at the initial fluidization), the fluidization is stopped to form a fixed bed in the chamber 6 and the transfer of particles to the chamber 7 A is stopped. As a result, the chamber 5 and the chamber 6 are caused to perform a function of the particle storage and chamber 6 performs the function of a gas seal. As in chamber 7 , HF gas is used, the nitrogen gas supplied to chamber 6 preventing the HF gas from entering the adjacent chambers. In chambers 7 A, 7 B, 7 C and in chamber 8 , UO _{2 is} converted to UF ₄ with HF gas. HF gas is supplied as part of the fluidizing gas via 7 Ab, 7 Aa and 8 b, 8 a. The complete conversion of UO ₂ to UF ₄ follows somewhat slowly and careful monitoring of the operating conditions is necessary, it being known that according to the reaction of the initial phase and depending on the end phase, a change in the reaction conditions is effective to the progress of the reaction to push ahead effectively. Starting from this point, the fluidized bed area is formed in this reaction area as a multi-area to change the operating conditions alternately in each area and the chamber is divided into 7 A, 7 B, 7 C and 8 , so that the temperature of each chamber and the composition of the supplied HF gas can be freely selected. The chambers 9-12 have a similar function to the chambers 3-6 and the HF gas remaining in the chamber 9 under the particles is expelled and prevented from entering and entering chamber 1 by means of gas sealing. The chambers 10 and 11 have the task of cooling and storing the particles and at the same time regulating the particle transfer. Chamber 12 is used for gas sealing against the HF gas used in chamber 13 or in chamber 14 and also for regulating the particle transfer in conjunction with chamber 11 . A fluidized bed, a moving bed or a fixed bed are formed in chamber 11 , while a fluidized bed or fixed bed is formed in chamber 12 .

The chambers 13 and 14 have the task of converting UF ₄ into UF ₆ using F ₂ gas which is supplied as a fluidizing gas via 13 b, 13 a and 14 b, 14 a. In the UF ₆ conversion process, it is important to increase the operational efficiency of the expensive F ₂ gas as much as possible, since this is directly linked to the reduction in production costs. For this purpose, it is necessary to monitor the quantitative relationship between UF ₄ and the F ₂ gas supplied to the reaction chamber, and as a result, the task of quantitative regulation of the particle transfer is of considerable importance.

In the chambers 13 and 14 , aluminum oxide or CaF ₂ particles are used as the fluidization medium. The UF ₄ particles supplied to the chamber 13 react with the F ₂ gas when fluidizing with the fluidizing medium to form UF ₆ , and unreacted UF ₄ particles enter the chamber 14 . In the chamber 14, the unreacted UF ₄ particles react again with F ₂ gas to form UF ₆ , but the unreacted UF ₄ remains partly here to be returned to the chamber 13 . Thus, between the chamber 13 and the chamber 14 UF circulated ₄ particles with the fluidizing medium and quantitative change of more than 13 b and 13 a supplied F ₂ gas and the 14 b, 14 a supplied F ₂ gas, the The degree of utilization of the F ₂ gas may be higher than in the case of a single fluid bed.

In a gas-particle separation area 16-22 , the particles accompanied by the gas of the fluidized bed are separated from the gas, and the separation area is divided by particle and gas parts, each divided separation area being equipped with a gas-particle separation filter. The gas-particle separation regions 16 and 17 have a common exhaust line, however, are separated in the chambers 1 and 2 to a mixture of part surfaces to avoid the chambers 1 and 2. FIG. The gas-particle separation area 18 is independent because the greater part of the gas consists of nitrogen gas.

In the gas-particle separation area 19 A, 19 B and 20 , the main constituent of the gas is HF gas and steam, but in view of the difference in the reaction conditions, in particular the difference in the HF gas concentration in each chamber of the gas particles - Separation area divided into three sections, in each of which post-treatment is possible. The gas-particle separation area is designed similarly to the separation area 18 . The gas-particle separation region 22 supplied gas is a gas mixture of UF ₆ gas, remaining F ₂ gas and nitrogen gas. The gas mixture is separated in the gas separation area 22 and fed to a cold trap for the recovery of the UF ₆ , as well as a cleaning reaction line to increase the extent of the usability of the remaining F ₂ gas.

In the device according to the invention due to the essentially horizontal particle transfer fers the height of the device be low and for the Particle transfer is not a special device required. Therefore, the device can be extremely compact be fanned. A multiple arrangement for improvement the efficiency of the fluid bed device can be easily carried out by the number of cams mern is increased and the efficiency of the Reaction process can be easily improved by the Be drive conditions must be changed carefully because the Operating conditions are freely selectable in each chamber.

In the device according to the invention, the multiple arrangement in the conversion range from UO ₂ to UF _{4 is} a good example of this.

Finally, the device according to the invention exists mainly from a fluid bed process ren, but - as explained above - next to the moving bed a moving bed and a fixed bed can be easily realized by the amount of gas supplied is changed and the device has consequently for example the advantage that they immediately for a Ver driving can be used, in which a verb efficiency of the reaction is expected, in which a fluidized bed process and moving bed process can be combined.

There are two for arranging the partition in each chamber Procedures in place, d. H. a process in which  the partition in contact with the base area of the flow bed is arranged and the other method, at wel chem the partition is placed over a gap that opens above the base of the fluidized bed.

In a conventional multi-chamber fluidized bed device according to FIGS. 2 (a) and 2 (b), only one of these two types of partition walls is used as a partition. In the system of Fig. 2 (a), in which the partition is arranged in contact with the base surface of the fluidized bed, the problem arises that when coarse particles are present in the particle mixture, these coarse particles remain in the base region of the fluidized bed and do not flow over the partition, resulting in the formation of the fluidized bed on the coarse particle layer. In the system of Fig. 2 (b), in which the partition is placed over a gap that opens above the base surface of the fluidized bed, there is no such problem as that of Fig. 2 (a), but the probability becomes short Conclusion of particles between the chambers larger, which is undesirable for the course of the reaction. In contrast, these problems can be avoided by connecting the two systems according to FIG. 2 (c) and, at the same time, the efficiency of the reaction can be increased, since the flow of the particles approaches a piston flow. Furthermore, by combining these two systems, a combination of the fluidized bed and the moving bed can be achieved, which is not possible with the known systems. In this game Ausführungsbei a fluidized bed device is shown in block construction as a physical unit. However, if different types of materials are used and it is difficult or not economical to bring them into a physical unit or uneven thermal expansions occur due to extremely different temperatures between the chambers, so that it is difficult to control the operating conditions, so it becomes difficult to achieve physical unity by connecting several types of reaction devices, and these difficulties can be avoided without changing the spirit of the invention.

In the arrangement according to FIG. 2 (a), in which the partition is arranged in contact with the base surface of the fluidized bed, coarse particles that are mixed in the particles remain in the base position of the fluid bed and do not flow over the partition away, so that the difficulty arises that a fluidized bed forms there. In the arrangement of Fig. 2 (b), in which the partition is disposed over a gap that opens above the base surface of the fluidized bed, such a difficulty as shown in Fig. 2 (a) is not created, but is Particles are more likely to short-circuit, which is undesirable for the course of the reaction.

In contrast, by connecting the two arrangements this difficulty can be avoided and at the same time the particle flow approaches a piston flow, which increases the efficiency of the reaction according to FIG. 2 (c). Furthermore, the combination of the two arrangements results in a combination of a fluidized bed and a moving bed, which is not possible with the known arrangement.

FIGS. 3 (a), (b), (c), (d) each show an order to a fluidized bed apparatus according to the invention in block construction. Furthermore, according to FIG. 4, by using a system in which a fluidized bed constructed in block form is expanded vertically and horizontally, a series of processes can be realized by horizontal expansion and an effortlessly increasing process capacity of the device by its vertical expansion. Thus, the modular design of the fluidized bed device can overcome the shortcomings of the known fluidized bed device, which cannot be easily expanded. According to Fig. 5, in which the chambers 80-83 are tightly together, the present invention can Vorrich tung as a fluidized bed device, be constructed in a single construction.

The present invention realizes the results listed below by using the arrangement described above.

• (1) In the device according to the invention if the particles are roughly horizontal, so that the height of the device can be reduced and since no special facility to promote the Particle is required, the device can be in their structure can be simplified.
• (2) In the device according to the invention a multiplication of the device in more than two Chambers possible and the operating system of each chamber is freely selectable, so that the reaction efficiency of the Device can be improved by the operation system is changed carefully in each case.  
• (3) By gas sealing the reaction gas can its undesirable influence avoided and the same the yield of particles can be increased at an early stage.
• (4) The freedom in the arrangement of the device is extremely great, as shown in FIG. 3.
• (5) If the arrangement of each chamber is made similar to that of Fig. 5, the device can also be used as a recirculating fluidized bed device which circulates the particles.
• (6) If a fluid bed device in Block construction used, a number of Ver be carried out by moving the device in horizontal direction is expanded and the procedure Capacity of the device can be increased stab can be increased by placing the device in vertical Direction is expanded.
• (7) In the device according to the invention with two chambers, if UF _{4 is converted} into UF ₆ , the amount of F ₂ gas supplied to the two chambers can be regulated in each case and as a result the F ₂ gas can be used more than in one Fluid bed device that has only one chamber.

Claims (1)

Horizontal multi-chamber fluid bed device for converting UO ₃ or U ₃ O ₈ to UF ₆ , with
first chambers ( 1 , 2 ) for converting U ₃ O ₈ or UO ₃ into UO ₂ , second chambers ( 7 A, 7 B, 7 C, 8 ) for converting UO ₂ into UF ₄ and third chambers ( 13 , 14 ) for converting UF ₄ to UF ₆ , wherein the plurality of chambers are formed by dividing by means of partitions;
a fluidized bed in which the starting material is successively transported from the first chamber ( 1 ) to the third chambers ( 14 );
Wind boxes ( 1 a, 2 a, 7 a- 8 a, 13 a, 14 a), which are each assigned to the first ( 1 , 2 ), second ( 7 A- 8 ) and third ( 13 , 14 ) chambers, in which Feed nozzles ( 1 b - 14 b) are provided for the fluidized gas, which supply hydrogen gas to the first chambers, HF gas to the second chambers and fluorine gas to the third chambers, and the partition walls alternately from the bottom of the fluidized bed to a point below the surface or range from the roof of the reaction device to a point below the surface of the fluidized bed;
Particle transfer regulation chambers ( 3-6 ) with inert gas supply between the first chambers ( 1 , 2 ) and the second chambers ( 7 A- 8 ) and further particle transfer regulation chambers ( 9-12 ) between the second chambers ( 7 A- 8 ) and the third chambers ( 13 , 14 ), whereby a gas lock is formed for each different reaction gas; and finally with
Solid gas separation sections in each of the first ( 16 , 17 ), second ( 19 A, 19 B) and third ( 22 ) chambers.