JPH045507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to centrifugal separators, including centrifugal clarifiers, centrifugal extractors, and the like.

[Technical background of the invention]

In a nuclear fuel reprocessing plant, spent nuclear fuel is dissolved in nitric acid, U (uranium) and Pu (plutonium) are extracted from the solution using a centrifugal extractor, and these are recycled and used. Since the insoluble residue present in the solution is harmful in the extraction process of U and Pu, it is necessary to remove it using a centrifugal clarifier prior to extraction.

As the above-mentioned centrifugal clarifier, a circular centrifugal clarifier shown in FIG. 1 is suitable from the viewpoint of clarification performance. In this figure, a bearing box 2 is provided on the upper surface of a shielding slab 1, and a rotating shaft 5 is supported by bearings 3 and 4 within this bearing box 2. The shaft 5 hangs below the slab, and a cylindrical bowl 7 disposed within a casing 6 is fixed to its lower end. In addition, 6a in the figure
8 is a drain, 8 is a receiver, 9 is a discharge pipe, 10 is a liquid supply pipe, 11 is a cleaning nozzle, 12 is an extraction hole, and 13 is a motor.

[Problems with background technology]

In order to improve the performance of the centrifugal clarifier configured as described above, particularly its clarity, it is necessary to increase the peripheral speed of the bowl 7. Also, although omitted in Figure 1,
It is necessary to provide a seal between the slab 1 and the rotating shaft 5. For this reason, the rotating shaft 5 is made thicker to make it subcritical so that the lower critical speed of the rotating shaft is not exceeded.

By doing the above, the earthquake resistance of the centrifugal clarifier can be improved, but on the other hand, the bearing 3,
4's DN value (diameter x rotational speed) is high, and at the same time the thrust load on the bearing is also large, which has the disadvantage of shortening the bearing life.

Although the above explanation has been made using a centrifugal clarifier as an example, similar problems exist in centrifugal extractors as well.

[Purpose of the invention]

The present invention was made based on the above-mentioned circumstances, and an object of the present invention is to obtain a centrifuge with high durability and earthquake resistance.

[Summary of the invention]

In the present invention, a cylindrical cavity concentric with the rotating shaft is provided at the upper end of the rotating shaft, and a fixed shaft is suspended from the upper surface of the bearing plate in this cavity concentrically with the rotating shaft, and is placed between the cavity and the fixed shaft. The rotating shaft is supported by a bearing, and the rotor of the motor, which is shaped like an annular plate, is attached to the upper end of the rotating shaft, and the stator of the motor, which is also shaped like an annular plate, is attached to the inner surface of the upper plate of the bearing box. The above object is achieved by driving and driving.

[Embodiments of the invention]

FIG. 2, in which the same parts as in FIG. 1 are given the same reference numerals, shows an embodiment of the present invention. A cylindrical cavity 20 is concentrically provided at the upper end of the rotating shaft 5, extending from the upper end surface to near the upper surface of the shielding slab 1. The lower end portion of the cavity 20 is a small diameter portion 21 . Also,
A fixed shaft 22 is suspended from the inner surface of the upper plate of the bearing box 2 within the cavity 20 and coaxially with the rotating shaft 5 . A flange 23 is provided at the lower end of the fixed shaft 22, the upper surface of which is located at the upper end position of the small diameter portion 21, and the lower surface of the cavity 20 is brought into contact with this flange, so that the outer peripheral surface is in contact with the peripheral surface of the cavity 20, and the inner periphery is in contact with the flange. Lower bearings 24 are provided with surfaces respectively engaging the fixed shafts 22 . Further, a cylindrical spacer 25 is engaged with the cavity 20, with a length extending from the upper surface of the lower bearing 24 to near the upper end of the cavity, and having a thickness equal to the difference between the diameter of the cavity 20 and the diameter of the small diameter portion 21. The lower surface of the upper part of the cavity 20 is in contact with the upper end of the spacer 25, and the outer periphery of the cavity 20 is
Upper bearings 26 are provided with their inner peripheries engaged with the fixed shafts 22, respectively. Note that each bearing has fixing members 27 and 28 passing through the fixed shaft 22 in the radial direction.
It is fixed by.

A circular motor mounting plate 29 is concentrically attached to the upper end of the rotating shaft 5, and a ring plate-shaped motor rotor 30 is concentrically attached to the upper surface of this motor mounting plate. Furthermore, a ring plate-shaped motor stator 31 is attached to the inner surface of the upper plate of the bearing box 2 .

Furthermore, a seal cylinder 32 that concentrically surrounds the rotating shaft 5 is provided on the upper surface of the shielding slab 1, and a rotating ring 33 that rotates integrally with the seal cylinder 32 is provided at the upper end of the rotating shaft 5.
is installed. A large diameter portion 34 is provided on the inner peripheral surface of the seal cylinder 32, and a circumferential protrusion 35 is provided on the axially intermediate portion of the outer periphery of the rotating ring 33.
The seal parts 36 and 37 of the mechanical seal are the protrusions 3
5, the lower end and the upper end are in sliding contact with the fixing rings 38 and 39, which are arranged and fixed in the large diameter part 34, and the upper end and the lower end are in sliding contact with the fixing rings 38 and 39, which are arranged and fixed in the large diameter part 34, respectively. Since the seal portions 36 and 37 have springs built in at both ends thereof, they are sealed by the above-described structure.

A bowl is fixed to the lower end of the rotating shaft 5 in the same manner as shown in FIG. 1, thereby constructing a centrifugal clarifier.

The centrifugal clarifier is driven by a motor composed of a stator 31 and a rotor 30. Therefore, the rotating shaft 5
The vibration during rotation is caused by the fixed shaft 2 fixed to the bearing box 2.
2 through upper and lower bearings 26 and 24.

If we pay attention to the transverse vibration of the rotating shaft 5, its frequency _S-1 is: However, l: Length of the rotating shaft E: Longitudinal elastic modulus of the rotating shaft I: Cross-sectional moment of inertia about the principal axis perpendicular to the vibration direction A: Cross-sectional area γ: Weight of unit volume g: Gravitational acceleration λ: Boundary conditions and vibration type Therefore, in the present invention, the length l of the rotating shaft 5 can be made small by using the above-mentioned support structure.

Therefore, it can be seen from the above equation (1) that the critical speed of the rotating shaft 5 can be increased.

Furthermore, the distance between the lower bearing 24 and the portion of the rotating shaft 5 below the shielding slab 1 where vibration is a problem can be reduced, and the vibration value of the portion of the rotating shaft 5 below the shielding slab 1 can be reduced. I can do it.

Furthermore, the rotating shaft 5 is attached to the fixed shaft 22 with bearings 24, 2.
6, the bearings 24 and 26 can be made small in diameter even if the rotating shaft 5 is made thicker.
The ND value can be reduced. Therefore, the thrust load on the bearing can be reduced, and the life of the bearing can be extended.

〔Effect of the invention〕

As described above, according to the present invention, since the critical speed can be increased, it is possible to provide a centrifuge with stable performance even when the circumferential speed is increased. Furthermore, since the life of the bearing is extended, the centrifugal separator can be easily maintained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a conventional centrifugal separator, and FIG. 2 is a sectional view of essential parts of an embodiment of the present invention. 1... Shielding slab, 2... Bearing box, 5... Rotating shaft, 6... Casing, 7... Bowl, 20...
Cavity, 22... Fixed shaft, 24... Lower bearing, 26
... Upper bearing, 30 ... Rotor, 31 ... Stator, 32 ... Seal cylinder, 33 ... Rotating ring, 36,
37...Seal part.

Claims (1)

[Claims] 1 In a device having a rotating shaft that passes through a shielding slab and has a bowl fixed to the lower end, a bearing box is provided on the upper surface of the slab, and a cylindrical cavity extending from the upper end surface to the vicinity of the upper surface of the shielding slab is concentrically formed in the rotating shaft. A fixed shaft that hangs concentrically with the rotating shaft in the cavity is attached to the inner surface of the upper plate of the bearing box, the rotating shaft is supported by the fixed shaft via a bearing, and a ring plate is attached to the upper end of the rotating shaft. A centrifugal separator characterized in that a rotor of the motor is shaped like a circular plate, and a stator of the motor that is shaped like an annular plate is attached to the inner surface of the upper surface plate of the bearing box.