JPS597495B2 - centrifuge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a centrifugal separator, and particularly to a centrifugal separator that can increase the pressure of exhaust gas while maintaining high gas separation performance.

FIG. 1 shows a centrifugal separator that has been used in the past, and is of an axial center feed/scoop extraction type. In other words, the centrifugal separator shown in the same figure is the scoop countercurrent method proposed by Mr. Jitzpe.
Of the two scoops installed on the fixed shaft inside the rotating body,
One is isolated in a separate upper chamber, and the other is inserted near the lower end of the separation cylinder. In this centrifuge,
If gas is fed into the rotating cylinder from a fixed shaft, the gas will eventually start rotating at almost the same speed as the rotating cylinder, but in the vicinity of the scoop in the separation cylinder, the rotation speed will decrease due to the resistance of this scoop. However, the pressure gradient is gentler than the radial distribution of gas pressure near the upper end plate. This situation is shown on the left side of Figure 4, and if you compare the radial distribution of pressure a shown in this figure with There is. Therefore, an axial flow called a scoop counterflow as shown on the right side of Fig. 4 is generated, and light gas and heavy gas are separated in this flow. The advantage of using a scoop as described above is that depending on the opening radius of the scoop in the rotary cylinder, a gas pressure close to the pressure at that position can be obtained, and for UF6 gas, approximately 5 torr can be expected.

This pressure level allows for easy gas piping in plants using multiple centrifuges. Furthermore, the use of a scoop has the advantage of reducing friction loss in areas where the circumferential speed of the rotating body is high. However, when a scoop is used as described above, the scoop reduces the rotational speed inside the rotating shell, which reduces the separation power and kills the ability of the rotating shell to operate at its full material strength. In addition, the flow inside the rotary barrel is agitated by the scoop, which causes a decrease in separation efficiency.

Furthermore, for the structure shown in Figure 1, the work of assembling the scoop,
This method has disadvantages in terms of workability, such as a complicated relationship with the dynamic balancing work of the rotating body, and also has the limitation that a magnetic bearing must be used as the upper bearing. The centrifugal separator shown in FIG. 2 uses an end plate feeding method and an end plate extraction method, which is called the inner periphery feeding method (Enriching Method) among BEAMS countercurrent methods. In this method, the pressure of the gas extracted from the end plate is
Because it is necessary to reduce the friction loss at the end plate,
The pressure is increased by the diffuser outside the end plate atmosphere by utilizing the gas discharge flow rate. The centrifugal separator shown in FIG. 3 is of a both-end plate feed/both-end plate extraction type.

In the centrifugal separator shown in FIGS. 2 and 3 above, the gas in the rotary motion rotates at the same rotation speed as the rotary drum and flows in the axial direction.

In this method, there is no disturbance due to a scoop or the like, so high separation efficiency is obtained. It has been found that the flow system shown in Figure 2 can theoretically increase the separation efficiency by reducing the feed flow rate and increasing the proportion of concentrated gas taken out of that flow rate [Atomic Energy Society of Japan. Magazine VO
l. l7, NO. 2 (1975) 604, BEAMS Counterflow Centrifugal Separation Characteristics, (1) Three Representative Methods] Due to the low feed flow rate, this type has a low axial flow velocity in the cylinder and a weak internal circulation force. In fact, separation performance is not stabilized because it is susceptible to thermal convection caused by uneven temperature distribution in the axial and radial directions of the rotating body.

In order to increase efficiency, it is possible to get closer to theoretical calculations by forcibly cooling or adjusting the temperature from outside the rotating body, but this is meaningless if energy is consumed. . In the flow system shown in Figure 3, it is theoretically clear that the separation efficiency can be increased by increasing the feed flow rate (said academic journal), and this has also been proven in practice, with extreme temperature distribution. It has also been found that if there is no difference, the separation power will not be affected.

In this method, the gas feed is carried out from opposite end plates, so it is easy to increase the flow rate to twice that of the method shown in Figure 2, and because the flow rate is large, there is no strain on the flow inside the cylinder. This can be said to be the reason for achieving stable and high efficiency. The disadvantage of using the external circulation countercurrent type as shown in Figures 2 and 3 above is that it is necessary to lower the gas discharge pressure in order to reduce the friction loss on the side of the end plate. This may result in the diameter of the gas piping between the centrifuges becoming thicker, or in taking care of the pressure loss of the flow meter installed in the piping. In order to achieve this, the feed pressure has to be extremely reduced, which imposes dimensional constraints on the design and results in unnecessarily enlarging a portion of the rotating body.

Furthermore, the end plate friction loss must be greater than that in the scoop method, and therefore the separation performance is greatly affected by heat. As mentioned above, the conventional centrifugal separator with a shaft-centered feed and scoop extraction method can achieve high exhaust gas pressure, but the separation efficiency is poor, while the centrifuge with an end plate feed and end plate extraction method has a poor separation efficiency. is good, but has the drawback of low exhaust gas pressure. This invention was made in view of the above, and its purpose is to provide a centrifugal separator that can increase the pressure of exhaust gas while maintaining high gas separation performance.

The centrifugal separator of the present invention, which achieves the above object, is a centrifugal separator of both end plate feed and both end plate extraction type, and is provided with a scoop chamber separate from the accumulation chamber at a position closer to the end than the end plate, and The accumulation chamber and the scoop chamber are communicated with each other at a position closer to the circumferential side thereof, and a scoop for gas discharge is guided into the scoop chamber from an end side of the scoop chamber and is opened in the scoop chamber. Become.

Next, an embodiment of the centrifugal separator of the present invention will be described in detail with reference to the drawings.

In the figure, reference numeral 1 denotes a rotary cylinder, 2 an upper end plate, and 3 a lower end plate.Each end plate 2, 3 has a blade attached thereto which functions as a feed pump. A large number of outflow ports of the feed pump into the rotary barrel 1 in the upper end plate 2 are selected at one radial position between approximately 50 and 80% of the inner diameter of the barrel, and are provided in a centrally symmetrical manner. A shielding plate 4 is installed adjacent to the upper side of the lower end plate 3 in the longitudinal direction of the rotary cylinder 1 and has an inner diameter that is open all the way around, with approximately the same radius as the in-cylinder outlet provided in the upper end plate 2. It is worn.

A communication path 6 communicates near the outer diameter between the accumulation chamber 5 composed of the lower end plate 3 and the shielding plate 4 and the scoop chamber 7 provided at a position closer to the end than the end plate. tied together. The scoop chamber 7 is arranged at the lower part of the lower end plate 3, and the outer wall for forming the scoop chamber 7 consists of a disk part and a cylindrical part, and the outer diameter of the disk is connected to the rotating body 1. It is kept airtight. Further, the cylindrical portion communicates with and is integrated with the inner diameter of the disc portion. The inner and outer diameters of the cylindrical part are machined smoothly and precisely, and serve as the rotating surfaces of the molecular pump. Further, a rotor member such as a hysteresis motor is attached to this disk portion. A ring is fitted around the outer circumference of the shaft of the feed pump on the end plate.
The outer diameter of the ring is machined to form a molecular pump. The structure of the feed pump includes, for example, the type shown in Japanese Patent Laid-Open No. 49-64796.

Considering the gas pressure in the scoop chamber 7, C in Fig. 4
The scoop 10 is opened at a location where the pressure is high, and the exhaust gas is guided to the outside of the machine.

The plan of the molecular pump 11 inserted between the outer diameter of the feed pump and the inner diameter of the cylinder attached to the scoop chamber wall is as follows:
Feed pump inlet pressure? It is well-recognized.

The pressure is empirically determined to be 0.5 torr or less. The procedure for inserting the scoop 10 into the scoop chamber 7 will be explained with reference to FIG.

First, using a pipe-shaped scoop 10 having approximately the same radius as the average radius of the ring of the molecular pump 11, after assembling the rotating body 1 to the casing with one end at approximately the average radius of the ring, from the outside to the position indicated by the two-dot chain line. Raise it up and secure it to the stationary part of the centrifuge. The dimensions of the scoop 10 are determined so that the opening does not touch the outer periphery of the scoop chamber, and a stopper is provided for safety. Note that it is possible for several scoops 10 to be placed in one scoop chamber. This mechanism can be similarly adopted for the upper and lower end plates. Next, gas flow in the centrifugal separator having the above structure will be explained.

As seen from the top of FIG. 5, the gas to be separated is introduced into the upper decompression chamber 13 from the upper feeder 12 with a throttle, and is introduced into the rotary cylinder 1 from a predetermined radius position by the feed pump on the end plate.
It flows out parallel to the axis toward the lower end plate 3. This gas enters the accumulation chamber 5 through the inner diameter hole of the shielding plate 4, and enters the communication path 6.
The liquid is guided to the scoop chamber 7 through a scoop 10 at the bottom and discharged to the outside of the machine. On the other hand, as seen from the bottom in FIG. Let it flow.

This gas is guided into the scoop chamber 8 through a gap provided almost at the outer diameter of the upper end plate 2 while exchanging isotopes in a direction opposite to the inner peripheral gas flow flowing out from the upper end plate.
It is discharged from the machine through scoop 10. The gas flow method in the rotating body 1 described above is called non-circulation counterflow. What's good about this separation performance? However, by adding the ability to discharge gas under high pressure using a scoop, stable self-sufficiency and
A centrifugal separator with stable separation performance is established. The centrifugal separator of the present invention is configured as described above, and therefore, while maintaining high separation performance, the centrifugal separator of the present invention can increase the pressure of the exhaust gas and the outer surface of the end plate. It becomes possible to reduce the friction loss at In other words, since the accumulation chamber and the scoop are separate rooms, even if the inside of the scoop chamber is stirred by the scoop, the influence of the agitation does not reach the accumulation chamber or the inside of the rotating barrel, and the non-circulating countercurrent flow inside the separation barrel is prevented. This is because it can be maintained in a state free from the influence of stirring. In addition, since the accumulation chamber and the scoop chamber are communicated with each other at a position closer to the circumferential side, among the exhaust gas introduced into the accumulation chamber, the exhaust gas closer to the circumferential side that is pressurized by centrifugal force is Since the gas is guided into the scoop chamber and extracted by the scoop, it is possible to further increase the pressure of the exhaust gas. Moreover, in the conventional centrifugal separator of the axis-centered feed scoop extraction method, the rotary barrel and the upper and lower end plates are usually assembled, and the 1 and 2
After performing the next balancing, it is necessary to disassemble it, insert the gas evacuation scoop, and reassemble it, but in this device, the gas evacuation scoop is guided into the scoop chamber from the end side of the scoop chamber. Since the opening is opened into the scoop chamber, after the above-mentioned balancing is completed, it becomes possible to attach the gas exhaust scoop from the end side of the scoop chamber without disassembling it. As described above, although the BEAMS non-circulating countercurrent centrifuge shown in Fig. 3 has excellent separation performance, it has traditionally been avoided by plant planners due to its high volumetric flow rate. This is an excellent uranium centrifugal separation plant that uses scoop extraction in combination with a centrifugal separator that enables high-pressure piping and requires less driving power. Further, when the scoop is configured as shown in FIGS. 5 and 6, it is not necessary to provide the scoop inside the rotary cylinder, and as a result, the assembly process can be greatly simplified.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a scoop countercurrent type centrifugal separator, where F indicates a gas feed, P indicates a concentrated gas, and w indicates a depleted gas. FIG. 2 is an explanatory diagram of a beams counterflow type internal feed type centrifugal separator with end plates removed, and the symbols F, P, and W are the same as in FIG. 1. FIG. 3 is an explanatory diagram of a BEAMS countercurrent type non-circulation type centrifugal separator, and the symbols F, P, and W are the same as in FIG. 1. Figure 4 is a graph showing the pressure distribution inside the scoop countercurrent type centrifuge during operation, where Pr represents the pressure, R represents the radius, and a represents the pressure distribution of the atmosphere with the scoop inside the separation barrel. b shows the pressure distribution on the side without the scoop in the separation barrel, and c shows the pressure distribution in the scoop chamber. FIG. 5 is an explanatory diagram of a centrifugal separator according to the present invention, which employs a non-circulation system and a scoop extraction method among beams counterflow. FIG. 6 is a cross-sectional projection view taken along the line X--X in FIG. 5, showing a procedure for assembling the scoop, and showing the transition from point A1 to point A2. DESCRIPTION OF SYMBOLS 1... Rotating cylinder, 2... Upper end plate, 3... Lower end plate, 4... Shielding plate, 5... Accumulation chamber, 6... Communication path, 7... Lower scoop Chamber, 8... Upper scoop chamber,
9... Motor member, 10... Scoob, 11...
Molecular pump, 12... Upper feedstock, 13... Upper reduced pressure chamber, 14... Lower reduced pressure chamber, 15... Lower reduced pressure chamber, 16... Vacuum chamber.

Claims (1)

[Claims] 1 A centrifugal separator with both end plate feeding and both end plate extraction methods, in which a scoop chamber, which is separate from the accumulation chamber, is provided at a position closer to the end than the end plate, and the accumulation chamber and scoop chamber are separated from each other near the periphery thereof. A centrifugal separator characterized in that the scoop for gas discharge is guided into the scoop chamber from an end side of the scoop chamber and opened in the scoop chamber.