WO2023223567A1

WO2023223567A1 - Centrifugal separation device

Info

Publication number: WO2023223567A1
Application number: PCT/JP2022/021035
Authority: WO
Inventors: 信介羽島; 正浩大竹; 勝青山
Original assignee: 巴工業株式会社
Priority date: 2022-05-20
Filing date: 2022-05-20
Publication date: 2023-11-23

Abstract

[Problem] To provide a centrifugal separation device that is able to suppress the generation of vibration when the rotation of a bowl decelerates during, for example, a stopping operation. [Solution] This centrifugal separation device comprises: a bowl that comprises a solid matter discharge port and a separated liquid discharge port, performs solid-liquid separation of solid matter from a liquid by applying a centrifugal force to a processing liquid supplied thereinside, and discharges the separated liquid from the separated liquid discharge port; a screw conveyor that is disposed inside the bowl rotates while having a relative speed difference with the bowl, and conveys the solid matter to the solid matter discharge port; and a liquid drain nozzle that comprises an inflow hole which forms a flow path in a direction that crosses or is oblique to a rotary shaft of the bowl, the leading end of the inflow hole being positioned further toward the rotary shaft side than a sedimentation layer of the solid matter formed on the bowl inner circumferential surface due to normal operations.

Description

centrifugal separator

The present invention relates to a centrifugal separator equipped with a bowl that applies centrifugal force to a processing liquid supplied therein to separate solid and liquid.

A centrifugal separator called a decanter is known as a device that separates a processing liquid containing solids into solid and liquid. FIG. 4 schematically shows the basic structure of the decanter. A so-called vertical decanter 10 includes a bowl 11 that rotates around a vertical axis and a screw conveyor 12. Although not shown, a horizontal decanter in which a bowl 11 and a screw conveyor 12 rotate around a horizontal axis is also known.

The bowl 11 is a rotary processing container formed into a cylindrical shape. The screw conveyor 12 is a rotary conveying means for conveying the solid matter separated within the bowl 11. A feed tube 13 for supplying the processing liquid is inserted into the screw conveyor 12. The processing liquid discharged from the tip of the feed tube 13 is supplied into the bowl 11 through a supply hole 14 formed on the outer peripheral surface of the screw conveyor 12 using centrifugal force.

In such a configuration, centrifugal force is applied to the processing liquid in the bowl 11 by supplying the processing liquid into the bowl 11 and rotating the bowl 11 at a predetermined rotational speed. The solids in the liquid separated by the action of centrifugal force are conveyed toward the lower end of the bowl 11 by the screw conveyor 12, and are separated from the liquid at the conical portion of the bowl 11. The solids are then discharged from the solids outlet 15. On the other hand, the separated liquid from which the solids have been separated overflows from the separated liquid outlet 16 and is discharged by continuously supplying the processing liquid to the bowl 11.

For example, when the apparatus is stopped after the normal operation of centrifuging the processing liquid, the supply of the processing liquid is stopped and the rotational speed of the bowl 11 is reduced. However, if this stop operation is performed with liquid remaining in the bowl 11, the remaining liquid becomes an unbalanced element in the rotation, resulting in excessive vibration during deceleration. As a result, damage to the device may occur. This excessive vibration is likely to occur in the vertical decanter 1.

Japanese Patent Application Publication No. 49-78262 Japanese Patent Application Publication No. 55-22397

The present invention has been made based on the above circumstances, and its purpose is to provide a centrifugal separator that can suppress the generation of vibrations when the rotational speed of the bowl is reduced, such as during stopped operation. Our goal is to provide the following.

The gist of the present invention is as follows.
(1) The centrifugal separator of the present invention is equipped with a solid matter discharge port and a separated liquid discharge port, and applies centrifugal force to the liquid to be treated supplied inside to separate the solids in the liquid into solid and liquid. a bowl for discharging the solids from the separated liquid discharge port; a screw conveyor disposed within the bowl and rotating at a relative speed with the bowl to convey the solids to the solids discharge port; The inflow hole is provided with a flow path formed in a direction perpendicular or oblique to the rotation axis of the bowl, and the inflow hole is located closer to the rotation axis than the deposited layer of solid matter formed on the inner peripheral surface of the bowl during normal operation. A liquid draining nozzle in which a tip portion is located.
(2) In the liquid draining nozzle, when the opening diameter of the inflow hole is D and the flow path length of the inflow hole is L, L/D is 1.4 or less.
(3) The centrifugal separator is a vertical centrifuge in which the rotation axis of the bowl is arranged in the vertical direction.
(4) Furthermore, the centrifugal separator of the present invention is provided with a solid matter discharge port and a separated liquid discharge port, and applies centrifugal force to the liquid to be treated supplied inside to separate solid matter in the liquid from solid to liquid; a bowl for discharging the separated liquid from the separated liquid outlet; and a screw conveyor arranged in the bowl and rotating at a relative speed with respect to the bowl to convey the solids to the solids outlet. , a liquid draining nozzle whose tip portion protrudes inward from the inner circumferential surface of the bowl, and discharges residual liquid in the bowl before the rotational frequency of the bowl, which is decelerated during stop operation, passes a primary resonance point; It is characterized by having the following.

According to the centrifugal separator of the present invention, since the liquid draining nozzle is provided, the liquid can be drained while the bowl is rotating, so that the remaining liquid in the bowl can be prevented from becoming an unbalanced element in the rotation, and, for example, Even if the rotational speed of the bowl is reduced during stopped operation, excessive vibration can be suppressed from occurring. In addition, the liquid draining nozzle is equipped with an inflow hole with a flow path formed in a direction perpendicular to or diagonally to the rotation axis of the bowl, and is located closer to the rotation axis than the solid deposit layer formed on the inner peripheral surface of the bowl during normal operation. By locating the tip of the inflow hole, it is possible to prevent the inflow hole from being blocked by solid matter.

Furthermore, when the inflow hole is oriented perpendicularly or obliquely to the rotation axis of the bowl, the centrifugal force acts more directly on it than when the inlet hole is oriented parallel to the rotation axis of the bowl, facilitating the removal of liquid from inside the bowl. be done. As a result, the time required for stop operation can be shortened.

FIG. 1 is a block diagram of a decanter according to a preferred embodiment of the present invention. It is a partial sectional view of the above-mentioned decanter. It is a sectional view, a front view, and a back view of the liquid draining nozzle of the above-mentioned decanter. It is an explanatory view showing the main composition of a decanter.

Hereinafter, a centrifugal separator according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. However, the technical scope of the present invention is not interpreted to be limited in any way by the embodiments described below.

FIG. 1 shows a vertical decanter 1 as an example of a centrifugal separator. The decanter 1 includes a bowl 2 that is a rotating container that applies centrifugal force to the processing liquid to separate solid and liquid. In the case of a vertical decanter 1, a rotating shaft is arranged in the vertical direction, and the bowl 2 is arranged so as to rotate, for example, around a vertical axis. A casing 3, which is an exterior body housing the bowl 2, forms a process space for centrifugation. The process pressure during normal operation for centrifugation varies depending on, for example, the type of processing liquid. In the case of high pressure or reduced pressure, the casing 3 is designed to be a pressure vessel.

The drive device that rotates the bowl 2 is, for example, a drive motor 31 placed outside the casing 3. For example, the driving force of the drive motor 31 is transmitted to a pulley 34 on the bowl 2 side through an endless rotating belt 33 that spans a pulley 32. The drive motor 31 rotates the bowl 2 at a predetermined rotational speed. As a preferable example, the rotation speed is controlled by controlling the output of the drive motor 31 using an inverter. The design value of the rotational speed of the bowl 2 is set, for example, within a range of 800 to 8000 rpm, depending on the size of the bowl 2, the type of processing liquid, and the like.

A shaft 4 that rotates the bowl 2 is supported by a bearing mechanism 41 placed at the top of the casing 3. The bearing mechanism 41 is supported by a vibration prevention device 41b based on the casing 3 through a support member 41a arranged around the bearing mechanism 41. In the vertical type decanter 1, since the bowl 2 rotates while being suspended on the bearing mechanism 41, the rotation axis may become misaligned due to vibration. Therefore, a vibration prevention device 41b is provided to absorb vibrations generated during centrifugal separation (=during normal operation). The vibration prevention device 41b is, for example, an isolator, and is configured to absorb vibrations using elastic force of rubber or the like.

The bowl 2 has a cylindrical upper side and a conical lower side. Further, the upper opening of the cylindrical portion is sealed with a bowl top 20 which is a disc-shaped member, and a separated liquid discharge port 20a is formed in the bowl top 20. Preferably, a plurality of separated liquid discharge ports 20a are formed at intervals, for example, on a concentric circle centered on the rotation axis of the bowl.

During normal operation, the cylindrical part of the bowl 2 becomes a pool part that holds the processing liquid due to the action of centrifugal force, and the conical part becomes a beach part from which solids are separated from the liquid. Furthermore, in the illustrated example, a ring dam 21 serving as a weir is placed in front of the bowl top 20 to raise the liquid level formed during normal operation and increase the amount of liquid held. In this configuration, when the processing liquid is continuously supplied into the bowl 2, the separated liquid, which is the liquid from which solids have been separated, overflows from the ring dam 21 and is discharged from the bowl 2 through the separated liquid outlet 20a. be done. The discharged separated liquid is received by a gutter-like liquid receiving part 35 formed on the inner peripheral surface of the casing 3, and is further discharged to the outside of the apparatus through a discharge port 36 communicating with the liquid receiving part 35. On the other hand, the solid matter discharge port 22 is formed on the tip side of the conical portion of the bowl 2.

A screw conveyor 5 that conveys the solids is rotatably arranged within the bowl 2. More specifically, as an example of forming a speed difference, when the bowl 2 and the screw conveyor 5 are connected via a gear box 6, which is a speed difference generating device, and the bowl 2 is rotated by the drive motor 31, the screw conveyor 5 moves to the bowl 2. It is configured to rotate at a relative speed to the rotation of. Thereby, the solid material can be conveyed by the conveyor flight 51 spirally formed in the body of the screw conveyor 5. During normal operation, the solid matter separated into solid and liquid in the bowl 2 by the action of centrifugal force is conveyed downward by the screw conveyor 5. The solids are separated from the liquid at the beach portion of the conical bowl 2 and are discharged from the solids discharge port 22.

The feed tube 23, which is an example of a supply nozzle, is inserted through an opening formed at the lower end of the screw conveyor 5 so as not to contact the screw conveyor 5. A base end 23a of the feed tube 23 is connected to a processing liquid supply source such as a pump, for example. Then, the processing liquid is discharged from the tip of the feed tube 23 and supplied to the buffer chamber 52 formed within the screw conveyor 5. The processing liquid is discharged from the liquid supply hole 53 formed on the outer circumferential surface by the centrifugal force of the rotating screw conveyor 5 and is supplied into the bowl 2 .

The feed tube 23 has, for example, a double pipe structure. The inner pipe is used as a supply path for processing liquid, and the outer pipe is used as a supply path for cleaning liquid. The cleaning liquid supply path is connected to the cleaning liquid supply nozzle 24 and further connected to a cleaning liquid supply source such as a pump.

Next, the liquid draining mechanism inside the bowl 2 will be explained. FIG. 2 is an enlarged view of a portion where the liquid draining nozzle 7 of FIG. 1 is arranged. The liquid draining nozzle 7 is a nozzle that discharges liquid from the bowl 2 by using centrifugal force during stopped operation, for example, and therefore, during normal operation, the bowl 2 communicates with a pool holding liquid by the action of centrifugal force. There is. The liquid discharged from the liquid drain nozzle 7 is received by the liquid receiving part 35 in the same manner as the separated liquid, and is discharged to the outside of the apparatus through the discharge port 36.

As described above, the decanter 1 has a structure in which the separated liquid outlet 20a is formed in the bowl top 20 and the separated liquid is discharged by overflow, so that ) cannot be drained from there. Further, when a ring dam 21 serving as a weir is provided, a liquid level is formed up to at least the upper end of the ring dam 21. It is undesirable to allow the liquid held in the bowl 2 to fall into the water because it will mix with the separated solids. Therefore, this embodiment has a configuration in which a liquid draining nozzle 7 that can drain liquid while the bowl 2 is rotated is provided. In addition, the code|symbol 21a in a figure is a sealing material.

Although such a liquid draining nozzle 7 that communicates the inside and outside of the bowl 2 can drain the liquid inside the bowl 2 during stop operation, the liquid inside the bowl 2 also flows out from the nozzle during normal operation. Therefore, for example, in order to prevent the solid-liquid separation efficiency from decreasing too much, under normal operating conditions, the flow rate Q2 from the liquid removal nozzle 7 is sufficiently small compared to the flow rate Q1 of the processing liquid supplied to the bowl 2, and the internal fluid It is desirable to design the nozzle so that the time during which centrifugal force acts on the centrifugal force (centrifugal residence time) is not affected, for example, as a guideline, Q2 is one-tenth or less of Q1. Note that, as will be described in detail later, the drain nozzle 7 can be prevented from being clogged with deposits, and as a result, there is an advantage in that the influence on the throughput Q1 can be set to a minimum. A plurality of liquid draining nozzles 7 can be provided. In this case, the total amount of outflow from each nozzle is used as the outflow amount Q2. In addition, when providing a plurality of liquid draining nozzles 7, it is preferable to arrange them so that the entire circumference of the bowl 2 may be equally divided. For example, when two draining nozzles 7 are provided, they are arranged opposite to each other on the diameter line of the bowl 2.

As an example, if the inner diameter of bowl 2 is 400 mm, the amount of liquid held in bowl 2 is 30 L (liters), the rotation speed of bowl 2 during normal operation is 4000 rpm, and the flow rate of processing liquid is 150 L/min, the design value is , the flow rate from the liquid removal nozzle 7 is set to 3 L/min (=1.5 L/min x 2 units). In this case, if the supply of processing liquid is stopped after the end of the normal operation and the rotational speed of the bowl 2 is maintained at 4000 rpm, which is the same as the normal operation, the liquid in the bowl 2 can be drained in 10 minutes after starting the stop operation. It becomes a calculation.

The liquid draining nozzle 7 is an elongated tubular nozzle that has a flow path formed therein that penetrates in the longitudinal direction. However, the structure of the tip is important to prevent it from being blocked by solid matter. This is because if the drain nozzle 7 is made thinner in order to suppress the amount of outflow during normal operation, the tip of the nozzle becomes more likely to become clogged with solid matter during normal operation. As a result of actual tests, it has been concluded that the position of the nozzle tip in the bowl 2, the shape and orientation of the tip are important in order to prevent clogging with solid matter during normal operation. The reason is detailed below.

First, the position of the nozzle tip inside the bowl 2 will be explained. During normal operation, in the bowl 2 that rotates at high speed, solid matter settles on the inner peripheral surface of the bowl due to the action of centrifugal force, and some of the solid matter adheres to and accumulates on the surface of the bowl 2. If the processing liquid contains solid matter that tends to accumulate on the surface of the bowl 2, the tip of the liquid removal nozzle 7 is likely to become clogged during normal operation. If the draining nozzle 7 is clogged with solid matter, the liquid in the bowl 2 cannot be drained during stopped operation, resulting in excessive vibration.

Therefore, the tip of the inflow hole 70 of the draining nozzle 7 is arranged so as to be located above (on the rotation axis side of the bowl) the layer of solid matter deposited on the inner circumferential surface of the bowl during normal operation. As a preferable example, the distal end portion is arranged so as to protrude from the inner circumferential surface of the bowl 2 toward the inside of the bowl 2 . The thickness of the deposited layer is preferably measured, for example, by opening the bowl 2 after normal operation. Alternatively, it is estimated by simulation or the like. Even if the tip of the inflow hole 70 is placed in a part where there is no conveyor flight 51, as in the example shown in the figure, the solid state in the solution is Disassembly studies of actual equipment have revealed that substances take a fixed form of accumulation in environments where there are no significant changes in processing conditions. Therefore, if the actual or estimated thickness of the deposited layer is known, the position of the tip may be fixed. Furthermore, when the conveyor flight 51 is disposed on the upper side as in the example shown in the figure, there is less accumulation of solid matter and it is difficult to block the conveyor flight. Furthermore, since it is close to the separated liquid outlet 20a, it has the advantage of being easy to recover together with the separated liquid.

As an example, when the distance H1 from the inner peripheral surface of the bowl 2 to the tip of the conveyor flight 51 is 1.7 mm, and the thickness H2 of the deposited layer formed during normal operation is 0.5 mm, inflow from the inner peripheral surface of the bowl 2 The distance H3 to the tip of the hole 70 is 1.7 mm. In this case, distance H3 is also the same as distance H1. That is, it is at the same position as the tip of the conveyor flight 51.

Next, the shape of the nozzle tip will be explained. In particular, as shown in FIG. 3(a), the tip of the liquid draining nozzle 7 has a ratio of L/D=1.4, where the opening diameter of the inflow hole 70 is D and the flow path length of the inflow hole 70 is L. It has been confirmed that the thinner structure shown below is highly effective in preventing blockages. The inflow hole 70 is preferably a circular through hole. In the case of a circular through hole, the diameter φ (=D) is preferably 1 mm. In this case, the channel length L is set to 1.4 mm or less. However, the size of the diameter φ (=D) is not limited, and may be 2.5 mm or less, although it depends on the size of the bowl 2, for example. Further, the shape of the inflow hole 70 does not necessarily have to be circular, and may be other shapes such as a polygon, for example.

The inflow hole 70 communicates with the enlarged diameter portion 71 in the longitudinal direction within the nozzle, and further communicates with a flow path 72 formed to the base end side. The expanded diameter portion 71 expands to a diameter of 2.3 mm, for example. The length of the flow path 72 is, for example, 32.2 mm. Moreover, the code|symbol 73 is a hexagonal hole. The liquid removal nozzle 7 has a small-diameter inflow hole 70 formed at its tip, but the flow path from there is enlarged, so that the liquid can flow smoothly inside the nozzle and be discharged from the end. Such a liquid draining nozzle 7 is formed by processing a round bar member, for example.

Here, L/D=1.4 or less is a preferable value derived from the results of actually conducted tests. The value of L/D increases in two ways: when the opening diameter D is made small, and when the flow path length L is made long. In the former case, blockage by solid objects is likely to occur. In the latter case, the farther the expanded diameter portion 71 is, the greater the liquid resistance becomes and the liquid in the nozzle does not flow smoothly. In some cases, it may induce blockage of solid objects. Since the drain nozzle 7 can be prevented from being blocked by deposits, there is an advantage that the influence on the flow rate can be set to a minimum.

Next, the orientation of the nozzle will be explained. The liquid draining nozzle 7 is disposed in a direction perpendicular or oblique to the rotation axis (for example, rotation center axis) of the bowl 2. As a preferable example, in FIG. 2, the tip of the liquid draining nozzle 7 is arranged in an oblique direction facing downward. In plan view, it is along the diameter line of the bowl 2. When the liquid draining nozzle 7 is arranged in an oblique direction, the angle θ with respect to the axis R perpendicular to the rotation axis is set to be 60 degrees or less, especially as shown in FIG. 3(b). In the illustrated example, the angle θ is 50 degrees. When set within this range, centrifugal force acts directly on the inflow hole 70 at the tip of the nozzle, promoting discharge from the drain nozzle 7 during stopped operation. Note that the liquid draining nozzle 7 may be arranged in an oblique direction with the tip of the liquid draining nozzle 7 facing upward. Further, it does not necessarily have to be along the diameter line in plan view. For example, it may be arranged obliquely in the direction opposite to the direction of rotation of the bowl 2.

Further, the liquid draining nozzle 7 is not necessarily entirely linear. That is, the liquid draining nozzle 7 mentioned here does not exclude, for example, one bent in a dogleg shape or curved halfway. It is sufficient that at least the flow path length L of the inflow hole 70 is arranged in a direction perpendicular to the rotation axis of the bowl 2 or in an oblique direction.

The liquid draining nozzle 7 is arranged so that its tip is located between the ring dam 21 and the conveyor flight 51, as shown in FIG. This area is close to the separated liquid discharge port 21a and is a position where the nozzle tip does not interfere with the rotating conveyor flight 51.

Next, an example of control in which the decanter 1 having the above-described configuration performs centrifugation and then stops the centrifugation will be described. To start a normal operation for performing centrifugation, the drive motor 31 is first started and the rotation of the bowl 2 is accelerated until it reaches a predetermined rotational speed. When the bowl 2 is rotated by the drive motor 31, the driving force is transmitted to the screw conveyor 5 through the gear box 6, which is a differential speed generator, and the screw conveyor 5 rotates at a differential speed relative to the rotating bowl 2. . As an example, the rotational speed of the bowl 2 is set to 4000 rpm, and the differential speed is set to 10 min ^-1 .

The processing liquid is discharged from the feed tube 23 and supplied into the bowl 2 through the liquid discharge hole 53. The types of treatment liquid and solid matter are not particularly limited. The processing liquid supplied into the bowl 2 forms a liquid pool on the beach part of the bowl 2 due to the action of centrifugal force, and solid matter in the liquid settles to the inner peripheral surface of the bowl 2 due to the action of the centrifugal force. solid-liquid separation is performed. The processing liquid is continuously supplied, whereby the separated liquid overflows from the upper end of the ring dam 21 and is discharged from the separated liquid outlet 20a. At this time, the liquid in the bowl 2 also flows out from the liquid draining nozzle 7 due to the action of centrifugal force. The separated liquid from the separated liquid outlet 20a and the liquid flowing from the liquid draining nozzle 7 are discharged toward the inner peripheral surface of the casing 3 by the action of centrifugal force, and are received by the liquid receiving portion 35. Thereafter, it is discharged from the apparatus through the discharge port 36.

On the other hand, the solids separated into solid and liquid by centrifugal force in the bowl 2 are conveyed toward the lower side of the bowl 2 by the screw conveyor 5, and are separated from the liquid at the conical beach part of the bowl 2 and solidified. The material is discharged from the material discharge port 22. The solid matter is discharged from the lower side of the casing 3.

For example, when the solid-liquid separation of the planned amount of treated liquid is completed, the normal operation is ended and the operation is shifted to a stopped operation. In the stop operation, for example, the supply of the processing liquid is stopped and the bowl 2 continues to rotate, thereby draining the remaining liquid in the bowl 2 from the liquid draining nozzle 7. When supplying the cleaning liquid into the bowl 2, the cleaning liquid is discharged from the liquid draining nozzle 7 by rotating the bowl 2. When the liquid in the bowl 2 is drained by such liquid draining operation, the rotational speed of the bowl 2 is reduced and the apparatus is stopped. The bowl 2 may be decelerated by lowering the output of the drive motor 31 using an inverter, or by stopping the drive motor 31 and allowing it to decelerate naturally. As described above, since the speed of draining the liquid in the bowl 2 can be determined by calculation, the draining time may be set using a timer, for example. Furthermore, the rotational speed of the bowl 2 during draining does not have to be the same as during normal operation. For example, the vehicle may be driven at a constant speed slower than normal operation, or at a reduced speed. However, for the following reasons, it is desirable not to reduce the rotational speed to the band of the primary resonance point where excessive vibration may occur until the liquid draining process is finished. The rotation speed may be controlled automatically by the control unit or may be controlled manually.

That is, one of the purposes of increasing the amount of liquid held in the bowl 2 is to improve the throughput of the decanter 1. However, during a stop operation in which the device is stopped, this retained liquid becomes a cause of excessive vibration. Excessive vibration occurs when the rotation of the bowl 2 is decelerated with an unbalanced element such as residual liquid, and the rotational frequency is amplified when passing through the primary resonance point of the device (decanter 1). Confirmed on actual machine. Although vibrations generated during normal operation are absorbed by the vibration prevention device 41b, it is difficult to absorb excessive vibrations amplified by resonance. Although it depends on the size of the bowl 2 and the type of processing liquid, the band of the primary resonance point, which is the resonance point of the decanter 1 as a device, is 400 to 800 rpm (that is, a frequency of 10 Hz ± 3Hz), and resonance does not occur during normal operation, for example, when rotating at 4000 rpm. The band of the primary resonance point can be determined by actually operating the device and measuring the vibration.

According to the decanter of this embodiment, by providing the liquid draining nozzle 7, a preferred example of which is described in detail, the interior of the decanter can be drained by continuing to rotate the bowl 2 after normal operation. Therefore, it is possible to pass through the primary resonance point after removing the unbalanced rotational element of the residual liquid, and it is possible to suppress the occurrence of excessive vibration.

Furthermore, by appropriately setting the position, shape, and orientation of the nozzle tip in the bowl 2 based on the above-mentioned reasons, it is possible to prevent the drain nozzle 7 from clogging during normal operation. As a result, the problem of not being able to drain the liquid during stopped operation can be prevented. It is desirable to finish draining the liquid from the liquid draining nozzle 7 before the rotational frequency of the bowl 2, which is decelerated during stopped operation, passes through the primary resonance point. Note that if the tip of the inflow hole 70 of the liquid draining nozzle 7 is set above the deposited layer (on the rotating shaft side), the liquid will remain below the tip (on the inner peripheral surface side of the bowl), but the amount of liquid will be Very little.

Note that a horizontal type decanter, in which both sides of the bowl 2 are supported by two shafts, is less prone to excessive vibration than a vertical type, in which the rotating shaft is supported by one shaft. It is also possible to apply it to

Although the present invention has been described in detail in accordance with specific embodiments, various substitutions, modifications, changes, etc. in form and details may be made to the present invention as defined by the claims. It will be apparent to those of ordinary skill in the art that anything may be done without departing from the spirit and scope.

1 Decanter 2 Bowl 20a Separated liquid discharge port 22 Solid matter discharge port 3 Casing 31 Drive motor 4 Shaft 5 Screw conveyor 51 Conveyor flight 7 Liquid removal nozzle 70 Inflow hole 71 Expanded diameter part 72 Channel

Claims

a bowl that is equipped with a solid matter discharge port and a separated liquid discharge port, applies centrifugal force to the processing liquid supplied therein to separate solid matter in the liquid from solid to liquid, and discharges the separated liquid from the separated liquid discharge port;
a screw conveyor disposed within the bowl and rotating at a differential speed relative to the bowl to convey the solids to the solids discharge port;
The inflow hole has a flow path formed in a direction perpendicular or oblique to the rotation axis of the bowl, and the inflow hole is closer to the rotation axis than the solid matter deposit layer formed on the inner peripheral surface of the bowl during normal operation. A centrifugal separator characterized by comprising: a liquid draining nozzle in which a tip of the liquid draining nozzle is located;
2. The liquid draining nozzle according to claim 1, wherein when the opening diameter of the inflow hole is D and the flow path length of the inflow hole is L, L/D is 1.4 or less. Centrifugal separator.
The centrifugal separator according to claim 1, wherein the centrifugal separator is a vertical separator in which the rotation axis of the bowl is arranged in the vertical direction.
a bowl that is equipped with a solid matter discharge port and a separated liquid discharge port, applies centrifugal force to the processing liquid supplied therein to separate solid matter in the liquid from solid to liquid, and discharges the separated liquid from the separated liquid discharge port;
a screw conveyor disposed within the bowl and rotating at a differential speed relative to the bowl to convey the solids to the solids discharge port;
a liquid draining nozzle whose tip protrudes inward from an inner circumferential surface of the bowl and discharges residual liquid in the bowl before the rotational frequency of the bowl, which is decelerated during stop operation, passes a primary resonance point; A centrifugal separator characterized by comprising: